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We examine a natural extension of D-term inflation and construct a successful model. General type of the D-term potential is shown to produce successful inflation with appropriate COBE normalization. The effect of the dilaton shift at the inflation period is taken into account.
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arxiv:hep-ph/9705448
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The ensemble of light-cone Fock wavefunctions $\{\psi_{n/H}(x_i,\vec k_{\perp i},\lambda_i)\}$ provides a conceptual basis for representing physical hadrons and nuclei in terms of their fundamental quark and gluon degrees of freedom. A number of applications of the light-cone formalism to QCD phenomenology are briefly reviewed, such as the origin of Regge behavior of polarized structure functions, the high momentum transfer behavior of exclusive reactions, the color transparency properties of diffractive vector meson photoproduction, and the behavior of quark distributions at large $x_{bj}$. The light-cone formalism illuminates novel features of hadron physics, such as the intrinsic gluon and heavy quark distributions, the quark - antiquark asymmetry of the intrinsic heavy quark sea, and the importance of rearrangement mechanisms in heavy quarkonium decay. I also discuss the potential for measuring the shape of the valence light-cone Fock wavefunction of hadrons and photons in nuclear diffractive multi-jet production.
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arxiv:hep-ph/9706236
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We show that the two scenarios able to explain the HERA anomaly --- a new leptoquark coupling or a new contact interaction --- predict new contributions to atomic parity violation. These corrections are sufficiently large and different that a feasible reduction in the dominant atomic theory uncertainty could give some hint in favour of one of the two scenarios.
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arxiv:hep-ph/9706298
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We reanalyse $\bar p p$ and $pp$ high energy data of the elastic scattering above $\sqrt{s}=5$ GeV on the total cross-section $\sigma_{tot}$ and on the forward $\rho$-ratio for various models of Pomeron, utilizing two methods. The first one is based on analytic amplitudes, the other one relies on assumptions for $\sigma_{tot}$ and on dispersion relation for $\rho$. We argue that it is not possible, from fitting only existing data for forward scattering, to select a definite asymptotic growth with the energy of $\sigma_{tot}$. We find equivalent fits to the data together with a logarithmic Pomeron giving a behavior $\sigma_{tot} \propto \ln ^\gamma s$, $\gamma\in [0.5,2.20]$ and with a supercritical Pomeron giving a behavior $\sigma_{tot} \propto s^\epsilon $, $\epsilon\in [0.01,0.10]$.
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arxiv:hep-ph/9706306
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We present an approach that generalizes in a natural way the perturbative QCD formalism developed by Brodsky and Lepage for the study of exclusive hadronic processes to the case of $L\neq 0$ mesons. As an application of our approach we consider here the production of meson pairs, involving tensor and pseudotensor mesons, in photon-photon collisions.
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arxiv:hep-ph/9706349
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We give a survey of recent development and applications of the chiral quark soliton model (also called the Nambu-Jona-Lasinio soliton model) with $N_f$=2 and $N_f$=3 quark flavors for the structure of baryons. The model is an effective chiral quark model obtained from the instanton liquid model of the quantum chromodynamics. Mesons appear as quark-antiquark excitations and baryons arise as non-topological solitons with three valence quarks and a polarized Dirac sea. In this model, a wide variety of observables of baryons is considered.
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arxiv:hep-ph/9706461
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We consider possible mechanical masses that could appear in supersymmetry, other than by direct Higgs coupling to fermions and we speculate that the existence of such a type of mass would allow one to have the Higgs mass of the $u$ quark zero, and the Higgs mass of the $d$ quark (at 1 \gev) of $\approx 1 \to 2 MeV$, thus solving at the same time the strong CP problem and arranging the grand unification prediction $m_{\mu}/m_{e} = m_{s, Higgs}/m_{d, Higgs}.$ One possible mechanism for this is related to, but not identical with the quark condensate. Here a mass is generated which is the same for all quarks, and which adds to the Higgs type mass. Unfortunately, the numerical value of the generated mass falls short of the desired value (some 5 MeV) by orders of magnitude. An alternate mechanism, through Higgs-induced left-right couplings in the squark sector may produce masses of the correct order of magnitude if the mixing angles are diferent in the squark and quark sectors. To get the desired result for the $u$ quark mass, we need a stop component mixing of 1/20 for the $LR$ $\tilde{u}$ squark coupling, so the strong CP problem may still be solved. For the $d$ mass, this mechanism is not really sufficient to solve the grand unification mass ratio problem.
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arxiv:hep-ph/9706483
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We review the origin of soft supersymmetry-breaking terms in N=1 supergravity models of particle physics. We first consider general formulae for those terms in general models with a hidden sector breaking supersymmetry at an intermediate energy scale. The results for some simple models are given. We then consider the results obtained in some simple superstring models in which particular assumptions about the origin of supersymmetry breaking are made. These are models in which the seed of supersymmetry breaking is assumed to be originated in the dilaton/moduli sector of the theory.
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arxiv:hep-ph/9707209
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We investigate numerical solution of Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) Q^2 evolution equations for longitudinally polarized structure functions. Flavor nonsinglet and singlet equations with next-to-leading-order $\alpha_s$ corrections are studied. A brute-force method is employed. Dividing the variables x and Q^2 into small steps, we simply solve the integrodifferential equations. Numerical results indicate that accuracy is better than 1% in the region 10^{-5}<x<0.8 if more than two-hundred Q^2 steps and more than one-thousand x steps are taken. Our evolution results are compared with polarized experimental data of the spin asymmetry A_1 by the SLAC-E130, SLAC-E143, EMC, and SMC collaborations. The comparison indicates that we cannot assume A_1 is independent of Q^2. We provide a FORTRAN program for the Q^2 evolution and devolution of polarized nonsinglet-quark, singlet-quark, Delta q_i+ Delta q-bar_i, and gluon distributions (and corresponding structure functions).
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arxiv:hep-ph/9707220
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Preliminary results are presented on the gluon density obtained from a QCD analysis of ZEUS and NMC F2 structure function data. Also given is an estimate of the experimental error on the positron-proton NC Born cross-section at large x and Q2.
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arxiv:hep-ph/9707289
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Meson-baryon couplings between positive and negative parity baryons are investigated using two point correlation functions in the soft meson limit. We find that the pi NN^* coupling vanishes due to chiral symmetry, while the eta NN^* coupling remains finite. We perform an analysis based on the algebraic method for SU(2) and SU(3) chiral symmetry, and find that baryon axial charges play an essential role for vanishing coupling constants.
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arxiv:hep-ph/9707307
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The jet shape is a simple measure of how widely a jet's energy is spread. At present jet shape distributions have only been calculated to leading order in perturbative QCD. In this paper we consider how much these predictions should be affected by higher order perturbative corrections, by resummation of enhanced corrections to all orders, and by (power-suppressed) non-perturbative corrections. We also show that current cone-type jet definitions are not infrared safe for final states with more than three partons. Unless this situation is rectified by using improved definitions, hadron collider experiments will never be able to study the internal properties of jets with the quantitative accuracy already achieved in $e^+e^-$ annihilation.
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arxiv:hep-ph/9707338
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We derive the character of neutrino oscillations that results from a model of equivalence principle violation suggested recently by Damour and Polyakov as a plausible consequence of string theory. In this model neutrino oscillations will take place through interaction with a long range scalar field of gravitational origin even if the neutrinos are degenerate in mass. The energy dependence of the oscillation length is identical to that in the conventional mass mixing mechanism. This possibility further highlghts the independence of and need for more exacting direct neutrino mass measurements together with a next generation of neutrinoless double beta decay experiments.
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arxiv:hep-ph/9707407
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A review of the basic principles of baryogenesis is given. Baryogenesis in heavy particle decays as well as electroweak, SUSY-condensate, and spontaneous baryogenesis are discussed. The models of abundant creation of antimatter in the universe are briefly reviewed.
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arxiv:hep-ph/9707419
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The HERA data on inelastic lepton proton scattering for values of the Bjorken scaling variable x < 0.05 are confronted with predictions based on Generalized Vector Dominance. Good agreement between theory and experiment is found over the full kinematic range of the squared four-momentum-transfer, Q^2, from Q^2 = 0 (photoproduction) to Q^2 < 350 GeV^2.
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arxiv:hep-ph/9707447
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In a first step, we explore the discovery and analysis potentials of the HERA collider, with and without polarized beams, in the search for electron-quark compositeness in the neutral current channel. Then we study the parity violating effects, for jet production in polarized $pp$ collisions at RHIC, which could be due to the presence of quark subconstituents or new massive gauge bosons. We emphasize that the measurement of spin asymmetries in such a polarized context could give some crucial informations on the chiral structure of these hypothetical new interactions.
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arxiv:hep-ph/9707470
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We review the loop effects of the low energy supersymmetry. The global success of the Standard Model rises two related questions: how strongly the mass scales of the superpartners are constrained and can they be, nevertheless, indirectly seen in precision measurements. The bulk of the electroweak data is well screened from supersymmetric loop effects, due to the structure of the theory, even with superpartners generically light, $O(M_Z)$. The only exception are the left-handed squarks of the third generation which have to be $\simgt O(300$ GeV) to maintain the success of the SM. The other superpartners can still be light, at their present experimental mass limits, and would manifest themselves through virtual corrections to the small number of observables such as $R_b, b \to s\gamma, K^0-\bar K^0$ and $B^0-\bar B^0$ mixing and a few more for large $tan\beta$. Those effects require still higher experimental precision to be detectable.
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arxiv:hep-ph/9707497
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Factorization, in the sense defined for inclusive hard scattering, is discussed for diffractive hard scattering. A factorization theorem similar to its inclusive counterpart is presented for diffractive DIS. For hadron-hadron diffractive hard scattering, in contrast to its inclusive counterpart, the expected breakdown of factorization is discussed. Cross section estimates are given from a simple field theory model for non-factorizing double-pomeron-exchange (DPE) dijet production with and without account for Sudakov suppression.
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arxiv:hep-ph/9707499
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We show that the perturbation series for quarkonia energies diverges at large orders. This results in a perturbative ambiguity in the energy that scales as e^(-1/a*Lambda) where a is the Bohr radius of quarkonium and Lambda is the QCD scale parameter. This ambiguity is associated with a nonperturbative contribution to the energy from distances of order 1/Lambda and greater. This contribution is separate from that of the gluon condensate.
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arxiv:hep-ph/9707525
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I discuss some general aspects of diagonalizing the quark mass matrices and list all possible parametrizations of the Cabibbo-Kobayashi-Maskawa matrix (CKM) in terms of three rotation angles and a phase. I systematically study the relation between the rotations needed to diagonalize the Yukawa matrices and various parametrizations of the CKM.
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arxiv:hep-ph/9708216
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We present a brief discussion of the general form of the amplitude that describes the two-pion photoproduction process. We outline an effective Lagrangian method that we are using to calculate this amplitude, and comment briefly on a few aspects of the calculation.
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arxiv:hep-ph/9708236
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Every nonsingular fermion mass matrix, by an appropriate unitary transformation of right-chiral fields, is equivalent to a triangular matrix. Using the freedom in choosing bases of right-chiral fields in the minimal standard model, reduction to triangular form reduces the well-known ambiguities in reconstructing a mass matrix to trivial phase redefinitions. Furthermore, diagonalization of the quark mass sectors can be shifted to one charge sector only, without loosing the concise and economic triangular form. The corresponding effective triangular mass matrix is reconstructed, up to trivial phases, from the moduli of the CKM matrix elements, and vice versa, in a unique way. A new formula for the parametrization independent CP-measure in terms of observables is derived and discussed.
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arxiv:hep-ph/9708247
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We present a general formalism for simplifying manipulations of spin indices of massless and massive spinors and vectors in Feynman diagrams. The formalism is based on covariantly reducing the number of field components in the action in favor of chiral/self-dual fields. In this paper we concentrate on calculational simplifications involving fermions in gauge theories by eliminating half of the components of Dirac spinors. Some results are: (1) We find reference momenta for massless fermions analogous to those used for external gauge bosons. (2) Many of the known supersymmetry identities (tree and one-loop) are seen in a simple manner from the graphs. (3) Manipulations with external line factrs for massive fermions are unnecessary. (4) Some of the simplifications for nearly maximally helicity violating gluonic amplitudes are built into the Feynman rules.
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arxiv:hep-ph/9708251
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$J/\psi$ production cross section considering the contributions of both color-singlet and color-octet $c\bar c$ channels is calculated. The result is used to study the suppression of $J/\psi$ in nuclear collisions. With absorption cross sections for $(c \bar c)_8$ $\sigma_{abs}^8\simeq 11mb $ and $(c \bar c)_1$ $\sigma_{abs}^1\simeq 0mb $ the p-A and A-B data except for Pb-Pb can be explained. Possible explanations of additional suppression in Pb-Pb are discussed.
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arxiv:hep-ph/9708258
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The odderon singularity is studied in perturbative QCD in the framework of the Bartels-Kwieci\'nski-Praszalowicz (BKP) equation. Arguments for the odderon intercept being exactly equal to unity are given. Besides, a variational method based on a complete system of one-gluon functions is presented. For the odderon, the highest intercept calculated by this method is $1-(N_c\alpha_{s}/\pi) 0.45$. Comparison to other calculations is shown.
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arxiv:hep-ph/9708296
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In this paper, we construct a supersymmetric composite axion (c-axion) model based on the gauge group $SU(N)\times SU(M)$, which is one possible physical application of the N=1 duality. The dual of SU(M) is interpreted as the color gauge group. We illustrate the existence of c-axion for the case of one dual quark in the dual gauge group $SU(\tilde M)$.
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arxiv:hep-ph/9708307
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We compute the first two moments of the final hadronic invariant mass in inclusive semileptonic B decay, in the presence of a cut on the charged lepton energy. These moments may be measured directly by experiments at the Upsilon(4S) using the neutrino reconstruction technique, which requires such a cut. Measurement of these moments will place constraints on the nonperturbative parameters \bar\Lambda and \lambda_1, which are relevant for extracting the quark masses m_b and m_c, as well as the CKM angle V_cb. We include terms of order \alpha_s^2\beta_0 and 1/m_b^3 in the operator product expansion, and use the latter to estimate the theoretical uncertainty in the extraction of \bar\Lambda and \lambda_1.
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arxiv:hep-ph/9708327
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If supersymmetry is discovered at future colliders, what can we learn? While our appreciation of the variety of possible supersymmetric models has grown tremendously in recent years, most attempts to answer this question have been in the context of some simple and highly restrictive framework, such as minimal supergravity. In this talk I describe new probes of phenomena that are generic in models beyond the minimal framework. These include tests of supersymmetric flavor and CP violation and probes of kinematically inaccessible superparticle sectors through ``super-oblique corrections.'' Such probes have wide applicability to distinguishing models, from gravity- and gauge-mediated theories to hybrid models and models with flavor symmetries. Examples of measurements at LEP II, the LHC, and the NLC are given.
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arxiv:hep-ph/9708361
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It is shown that there exist nine different ways to describe the flavor mixing, in terms of three rotation angles and one CP-violating phase, within the standard electroweak theory of six quarks. For the assignment of the complex phase there essentially exists a continuum of possibilities, if one allows the phase to appear in more than four elements of the mixing matrix. If the phase is restricted to four elements, the phase assignment is uniquely defined. If one imposes the constraint that the phase disappears in a natural way in the chiral limit in which the masses of the u and d quarks are turned off, only three of the nine parametrizations are acceptable. In particular the ``standard'' parametrization advocated by the Particle Data Group is not permitted. One parametrization, in which the CP-violating phase is restricted to the light quark sector, stands up as the most favorable description of the flavor mixing.
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arxiv:hep-ph/9708366
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We study the $q \bar{q}$ relativistic interaction starting from the Feynman-Schwinger representation of the gauge-invariant quark-antiquark Green function. We focus on the one-body limit and discuss the obtained non-perturbative interaction kernel of the Dirac equation.
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arxiv:hep-ph/9708371
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The Fermilab top quark analysis is heavily dependent on the assumption of standard model backgrounds only. In the light gluino scenario, the stop quarks lie near the top in mass and their decays can influence the resulting top quark mass by an amount that is not small relative to the currently quoted errors. Several slight anomalies in the top quark analysis find a natural explanation in the light gluino case.
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arxiv:hep-ph/9708405
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The order - \alpha radiative corrections to the differential decay rate of polarized orthopositronium are obtained. Their influences on the three photons coincidence rate as a function of positronium polarization is considered.
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arxiv:hep-ph/9708450
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Motivated by cosmological considerations, and by the atmospheric and solar neutrino flux deficits, we consider the scenario in which the three Standard Model neutrinos are endowed with a nearly equal Majorana mass in the eV range. Combined constraints coming from (1) direct search for electron neutrino mass, (2) absence of neutrinoless double beta decay, and (3) unsuppressed electron neutrino flux in present reactor experiments, imply a quite well specified pattern of neutrino masses and mixing angles. We discuss the experimental tests of the model and comment on the features of this scenario.
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arxiv:hep-ph/9708483
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New interactions appearing at a scale $\Lambda$ larger than the weak interaction scale v can affect physical processes at energies below $\Lambda$ through non-renormalizable $SU(3)\times SU(2)\times U(1)_y$ invariant operators added to the standard model Lagrangian. In this article we investigate the effect of flavor conserving contact interactions on the total cross-section for the process $e^+e^-\to HZ$ at $\sqs =500$ Gev. We find that for $\Lambda\approx 2.5 $ Tev, which is consistent with LEP and SLD asymmetry measurements on Z peak as well as theoretical estimates, these operators can increase the total cross-section by a factor of 3 relative to the SM for intermediate mass higgs boson.
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arxiv:hep-ph/9709217
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After some general remarks on non-perturbative QCD I present shortly models which lead to a color-electric flux tube formation. The implications of such a flux tube formation especially on high energy scattering are discussed.
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arxiv:hep-ph/9709222
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In this talk we discuss rare B decays (b -> s gamma, b -> s g, b -> s l^+ l^-), B-\bar{B} oscillations and CP violation in B physics in the context of low-energy SUSY. We outline the variety of predictions that arise according to the choice of the SUSY extension ranging from what we call the "minimal" version of the MSSM to models without flavour universality or with broken R-parity. In particular, we provide a model-independent parameterization of the SUSY FCNC and CP-violating effects which is useful in tackling the problem in generic low-energy SUSY. We show how rare B decays and CP violation in B-decay amplitudes may be complementary to direct SUSY searches at colliders, in particular for what concerns extensions of the most restrictive version of the MSSM.
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arxiv:hep-ph/9709244
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It is shown that in the Effective Standard Model new phenomena can arise due to the presence of small instanton configurations. The chief result is that under certain conditions new hidden coupling constants could exist in the model. In the Electroweak sector that might result in the possibility of observing B+L violating processes due to a highly non perturbative contribution to the holy grail function. The same phenomenon might occur in the QCD sector of the theory and could be observed in the DIS experiments at HERA.
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arxiv:hep-ph/9709276
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We show that an effective field theory that includes non-standard couplings between the electroweak gauge bosons and the top and bottom quarks may yield negative contributions to both the S and T oblique radiative electroweak parameters. We find that that such an effective field theory provides a better fit to data than the standard model (the chi-squared per degree of freedom is half as large). We examine in some detail an illustrative model where the exchange of heavy scalars produces the correct type of non-standard couplings.
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arxiv:hep-ph/9709297
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A Lagrangian of electroweak interactions without Higgs is used to study the contributions of quarks and leptons to the masses of the W and the Z bosons. It is shown that the $SU(2)\times U(1)$ symmetry is broken by both fermion masses and axial-vector components of the intermediate bosons. The masses of the W and the Z bosons are obtained to be (m^{2}_{W}={1\over2}g^{2}m^{2}_{t}) and (m^{2}_{Z}=\rho m^{2}_{W}/cos^{2}\theta_{W}) with (\rho\simeq 1). Two fixed gauge fixing terms for W and Z boson fields are derived respectively. A coupling between photon and Z boson is predicted. Massive neutrinos are required.
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arxiv:hep-ph/9709332
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The comparison of $J/\psi$ photoproduction data in the inelastic region with theoretical predictions based on the NRQCD approach has remained somewhat ambiguous and controversial, in particular at large values of the inelasticity variable $z$. We study the polar and azimuthal decay angular distribution of $J/\psi$ mesons as functions of $z$ and transverse momentum $p_t$. Future measurements of decay angular distributions at the HERA $ep$ collider will provide a new test of theoretical approaches to factorisation between perturbation theory and quarkonium bound-state dynamics and shed light on the colour-octet production fraction in various regions of $z$ and $p_t$.
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arxiv:hep-ph/9709376
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It has been argued that the observations of cosmic particles with energies in excess of $10^8$ TeV represent a puzzle. Its solution requires new astrophysics or new particle physics. We show that the latter is unlikely given that the scale associated with a new particle physics threshold must be of order 1 GeV, not TeV and above, in order to resolve the problem. In most cases such new physics should have been revealed by accelerator experiments. We examine the possibility that the highest energy cosmic rays are initiated by non-standard interactions of neutrinos in the atmosphere. We show that proposals in this direction either violate s-wave unitarity or fall short of producing a sizeable effect by several orders of magnitude.
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arxiv:hep-ph/9709399
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It is shown that, at a 500 GeV LC, a number of different theoretical models would be unambigously identified by their virtual effects. Negative limits in case of no signal identification are also derived.
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arxiv:hep-ph/9709403
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The low-energy two neutrino-two photon interactions in the presence of homogeneous magnetic field are studied. The cross sections in external magnetic field are shown to be larger than in vacuum by factor $\sim (m_W /m_e) ^4(B/B_c) ^2$. The energy-loss rate due to the process $\gamma \gamma \to \nu \bar{\nu}$ in magnetic field is obtained.
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arxiv:hep-ph/9709420
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We study charged Higgs boson production at future electron-proton colliders in the framework of the Minimal Supersymmetric Standard Model. We focus our attention to the case of single-top production and decay through the channel $t\to bH^\pm$ and of vector-scalar fusion via $W^{\pm*} \Phi^*\to H^\pm$ (where $\Phi=H,h$ and $A$). We consider the signature $H^\pm\to \tau\nu_\tau$ and compare it to the irreducible background from Standard Model interactions. For $M_{H^\pm}<m_t$, the $H^\pm$ signal is accessible through lepton universality breaking if $M_A<100-120$ GeV at both low and large values of $\tan\beta$. Furthermore, although the bulk of the production cross section comes from single-top events, a sizable contribution due to vector-scalar-scalar interactions should be observable at large $\tan\beta$, this possibly offering some insights into the structure of the scalar sector of the theory. The possibility of the CERN collider running in the LEPXLHC mode is considered in detail
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arxiv:hep-ph/9709458
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Lattice attempts to compute the leptonic decay constants of heavy-light pseudoscalar mesons are described. I give a short historical overview of such attempts and then discuss some current calculations. I focus on three of the most important sources of systematic error: the extrapolation to the continuum, the chiral extrapolation in light quark mass, and the effects of quenching. I briefly discuss the ``bag parameters'' $B_B$ and $B_{B_s}$, and then conclude with my expectations of the precision in decay constants and bag parameters that will be possible in the next few years.
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arxiv:hep-ph/9709460
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We describe in some detail the present features of an automatic loop calculation program as well as the integration techniques that go into it. The program, called XLOOPS 1.0, allows one to calculate massive one- and two-loop Feynman diagrams in the Standard Model including their tensor structure. UV divergences in UV divergent integrals are explicitly computed in dimensional regularization. One-loop integrals are calculated analytically in d \neq 4 dimensions whereas two-loop integrals are reduced to two-fold integral representations which the program evaluates numerically. We discuss Higgs decay at the two-loop level as a first application of the novel integration techniques that are incorporated into XLOOPS.
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arxiv:hep-ph/9709490
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A proof is given that hard-scattering factorization is valid for deep-inelastic processes which are diffractive or which have some other condition imposed on the final state in the target fragmentation region.
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arxiv:hep-ph/9709499
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By model independent way scalar and pseudoscalar neutral Higgs boson production with photon in the tree process $\mu^+\mu^- \to H^0 \gamma$ are considered.For the Standard Model and Minimal Supersymmetric Standard Model cases numerical estimates are obtained.The model independent flavour changing Higgs bosons production in the tree processes $e^+e^-,\mu^+e^- \to H^0_{fc} \gamma$ is also considered.
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arxiv:hep-ph/9709501
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A brief summary of the experimental results presented at the conference is given.
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arxiv:hep-ph/9709504
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We discuss long-baseline neutrino oscillations in the framework of the two 4-neutrino schemes which can accommodate all existing neutrino oscillation data. Negative results of short-baseline reactor and accelerator experiments allow to obtain rather strong bounds on the long-baseline nu_e->nu_e and nu_mu->nu_e transition probabilities. We consider in detail matter effects and show that the vacuum bounds are not substantially modified. We also comment on corresponding bounds in 3-neutrino scenarios.
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arxiv:hep-ph/9710209
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This theoretical review is intended to give non-theorists a flavor of the ideas driving the current efforts to experimentally find supersymmetry. We discuss the main reasons behind the expectation that supersymmetry may be "just around the corner" and may be discovered in the near future. We use simple quantum-mechanical examples to illustrate the concept---and the power---of supersymmetry, the possible ways to break supersymmetry, and the dynamical generation of small scales. We then describe how this theoretical machinery helps shape our perception of what physics beyond the electroweak scale might be.
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arxiv:hep-ph/9710274
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In the present paper the two and three point functions which occur at the study of the various physical processes are considered. The investigation has dan in the framework of the perturbative theory at the one loop level. The general and asymptotic expressions for these functions are obtained.
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arxiv:hep-ph/9710283
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A critical assessment is given of the theoretical uncertainty in the predicted cross-sections for large-angle Bhabha scattering at LEP 1, with or without t-channel subtraction. To this end a detailed comparison is presented of the results obtained with the programs ALIBABA and TOPAZ0. Differences in the implementation of the radiative corrections and the effect of missing higher-order terms are critically discussed.
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arxiv:hep-ph/9710376
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A review of the soft supersymmetry-breaking parameters and the $\mu$ term arising in superstring models is performed paying special attention to their phenomenological implications. In particular, the violation of the scalar mass universality which may lead to dangerous flavor changing neutral current phenomena and the existence of charge and color breaking minima are discussed. Finally, quadratically-divergent loop effects by pure supergravity interactions on soft parameters and the $\mu$ term are also reviewed and applied to superstring models. They provide several new sources of the $\mu$ term, naturally of order the weak scale, but also may lead to non--universal soft terms.
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arxiv:hep-ph/9710388
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It has been recently shown that the observed baryon number may originate at the electroweak phase transition, provided that the Higgs boson and the lightest stop are sufficiently light. In this work, we perform a detailed analysis, including all dominant two-loop finite temperature corrections to the Higgs effective potential, as well as the non-trivial effects proceeding from the mixing in the stop sector, to define the region of parameter space for which electroweak baryogenesis can happen. The limits on the stop and Higgs masses are obtained by taking into account the experimental bounds on these quantities, as well as those coming from the requirement of avoiding dangerous color breaking minima. We find for the Higgs mass $m_h \simlt 105$ GeV, while the stop mass may be close to the present experimental bound and must be smaller than, or of order of, the top quark mass. These results provide a very strong motivation for further non-perturbative analysis of the electroweak phase transition, as well as for the search for Higgs and stop particles at the LEP and Tevatron colliders.
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arxiv:hep-ph/9710401
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We look at effective fields defined in the heavy-quark effective theory as operator-valued generalized functions on Minkowski space-time to be averaged with physically suitable smoothing functions (Gaussians of typical width the hadronic size) leading to operator-valued distributions in Hilbert space. One-heavy-quark states are thus represented by normalizable wave packets displaying a particle-like behaviour at the characteristic hadronic time ${\Lambda}_{QCD}^{-1}$. We examine some consequences relative to the average kinetic energy of heavy quarks in hadrons to avoid inconsistences within this formalism.
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arxiv:hep-ph/9710408
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In the context of HERA with polarized lepton and proton beams, we explore the sensitivity of the collider to contact interactions. We emphasize that the measurement of longitudinal spin asymmetries in such a polarized context could give some crucial informations on the chiral structure of these hypothetical new interactions.
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arxiv:hep-ph/9710423
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Assuming that the string inspired, universal sum rules for soft supersymmetry-breaking terms, which have been recently found both in a wide class of four-dimensional superstrings and in supersymmertic gauge-Yukawa unified gauge models, are satisfied above and at the grand unification scale, we investigate theirlow energy consequences and derive sum rules in the superpartner spectrum of the minimal supersymmetric standard model.
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arxiv:hep-ph/9710453
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I review the ways that have been proposed to measure the quark transversity distribution in the nucleon. I then explain a proposal, developed by Xuemin Jin, Jian Tang and myself, to measure transversity through the final state interaction between two mesons ($\pi\pi$, $K \bar K$, or $\pi K$) produced in the current fragmentation region in deep inelastic scattering on a transversely polarized nucleon.
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arxiv:hep-ph/9710465
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Using the dipole picture describing the $1/N_C$ limit of QCD at small $x$ and the conformal invariance properties of the BFKL kernel in transverse coordinate space, we show that the 1->p dipole densities can be expressed in terms of dual Shapiro-Virasoro amplitudes B_{2p+2} and their generalization including non-zero conformal spins. We discuss the possibility of an effective closed string theory of interacting QCD dipoles.
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arxiv:hep-ph/9710483
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We present calculations of several pp scattering cross sections with potential applications at the LHC. Significantly large rates for momentum fraction, x, as low as 10^-7 are obtained, allowing for possible extraction of quark and gluon densities in the proton and nuclei down to these small x values provided a detector with good acceptance at maximal rapidities is used.
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arxiv:hep-ph/9710490
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We recall the definitions and the basic properties of the transversity distributions $h^{q,\bar q}_1(x,Q^2)$ and the corresponding nucleon tensor charges $\delta q(Q^2)$. We briefly comment on different estimates from several phenomenological models and on the future possible measurements with the polarized $pp$ collider at RHIC-BNL. Recent works on the $Q^2$-evolution of $h^{q,\bar q}_1(x,Q^2)$ are also discussed and their implications on a very useful positivity bound.
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arxiv:hep-ph/9710530
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The present status of Unified Theories is summarized with special emphasis on their possible experimental tests. Outline: i) Unification of couplings; ii) Where can a positive signal come from? iii) HERA anomaly and Unification; iv) Recent progress in model building; v) Flavour and Unification.
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arxiv:hep-ph/9711232
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The exchange charge density operators that correspond to the Fermi-invariant decomposition of quark-quark interactions have been constructed. Their effect on the electromagnetic charge radii of the nucleons, in combination with that of the relativistic corrections to the single-quark operator, has been studied with a constituent quark model with a spin and flavor dependent hyperfine and a linear confining interaction, which gives a quantitative description of the spectra for the light and strange baryons. The model gives proton and neutron charge radii in approximate agreement with the empirical results assuming reasonable values for the radii of the constituent quarks.
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arxiv:hep-ph/9711252
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We explore the possibility of using CP violation in B decays to detect the presence of physics beyond the Standard Model. We first study the possibility of new physics in the $B-\bar B$ mixing amplitude. We discuss a construction to extract information about the phase and magnitude of the new physics contribution, as well as the CKM parameters in a model independent way. We point out the difficulty of carrying through this program induced by hadronic uncertainties and discrete ambiguities, and suggest additional measurements to overcome these problems. We then study the possibility of new physics contributions to the B meson decay amplitudes. We emphasize the sensitivity of the $B\to \phi K_S$ decay to these new contributions, and explain how this sensitivity can be quantified using experimental data on SU(3) related decays. Finally, we analyse a number of models where the B decay amplitudes are modified.
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arxiv:hep-ph/9711265
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HQET lagrangian up to $1/m^3$ terms is discussed. Consequences of reparameterization invariance are considered. Results for the chromomagnetic interaction coefficient at two loops, and in all orders in the large--$\beta_1$ approximation, are presented.
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arxiv:hep-ph/9711269
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We study the cooling (heating) of a glue-parton gas due to production (destruction) of particles and determine the associated production of entropy. We incorporate sharing of the system energy among a changing number of particles. We find that the entropy of an evolving glue-parton gas changes in an insignificant range once the initial high temperature state has been formed, despite a great change in particle number and temperature.
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arxiv:hep-ph/9711346
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We investigate the possibility of preheating in hybrid inflation. This scenario involves at least two scalar fields, the inflaton field $\phi$, and the symmetry breaking field $\sigma$. We found that the behavior of these fields after inflation, as well as the possibility of preheating (particle production due to parametric resonance), depends crucially on the ratio of the coupling constant $\lambda$ (self-interaction of the field $\sigma$) to the coupling constant $g^2$ (interaction of $\phi$ and $\sigma$). For $\lambda \gg g^2$, the oscillations of the field $\sigma$ soon after inflation become very small, and all the energy is concentrated in the oscillating field $\phi$. For $\lambda \sim g^2$ both fields $\sigma$ and $\phi$ oscillate in a rather chaotic way, but eventually their motion stabilizes, and parametric resonance with production of $\chi$ particles becomes possible. For $\lambda \ll g^2$ the oscillations of the field $\phi$ soon after inflation become very small, and all the energy is concentrated in the oscillating field $\sigma$. Preheating can be efficient if the effective masses of the fields $\phi$ and $\sigma$ are much greater than the Hubble constant, or if these fields are coupled to other light scalar (or vector) fields $\chi$. In the recently proposed hybrid models with a second stage of inflation after the phase transition, both preheating and usual reheating are inefficient. Therefore for a very long time the universe remains in a state with vanishing pressure. As a result, density contrasts generated during the phase transition in these models can grow and collapse to form primordial black holes. Under certain conditions, most of the energy density after inflation will be stored in small black holes, which will later evaporate and reheat the universe.
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arxiv:hep-ph/9711360
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We investigate the possibility to identify photon-gluon fusion (PGF) events in polarised deep inelastic ep scattering, assuming the kinematics of the HERA collider, by a pair of charged high p_t particles. In a Monte Carlo study we find possible selection criteria and show the expected measurable asymmetries. We discuss the sensitivity to $\Delta G(x)$ and compare the result to the one obtained using di-jets to tag PGF events.
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arxiv:hep-ph/9711382
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The study of the scattering at high energy of the gauge bosons W and Z, in particular longitudinally polarized W and Z, can clarify the mechanism of spontaneous symmetry breaking in the Standard Model of the electroweak interactions. Different models of strong electroweak sector, based on the effective lagrangian approach are briefly reviewed. They include models with no resonance, with scalar resonance, additional vector and axial-vector resonances. The effective Lagrangians are derived from the chiral symmetry of the symmetry breaking sector. Limits on these models from existing measurements, mainly LEP and Tevatron, are considered. We study also direct and indirect effects of the new interactions at high energy future e^+e^- linear colliders, through WW scattering and the direct production of these new vector gauge bosons.
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arxiv:hep-ph/9711385
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We study the effect of including flavor changing neutral currents (FCNC) in the analysis of the neutrino signal of a supernova burst. When we include the effect of the FCNC which are beyond the standard model (SM) in the study of the MSW resonant conversion, we obtain dramatic changes in the \Delta m^2-sin^2(2\theta) probability contours for neutrino detection.
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arxiv:hep-ph/9711424
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A Higgs boson in the intermediate mass range is considered. An effective Lagrangian approach is used in order to evaluate the top-induced QCD corrections of order $\alpha_s^3$ to the decay into light quarks and $O(\alpha_s^4)$ corrections to the gluonic decay mode. The connection to the decoupling relations for $\alpha_s$ and the light quark masses is discussed.
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arxiv:hep-ph/9711465
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We present a simple isospin invariant parametrization for $(B \to K\pi)$ decay amplitudes which consistently includes CP violation and (quasi-elastic) hadronic final states interactions. We find that the observed $(B \to K\pi)$ decays do not lead to a significant bound on the angle $\gamma$ of the unitarity triangle. On the other hand, we claim that a sizeable CP violation asymmetry in $(B^{\pm} \to K\pi^{\pm})$ rates is by no means excluded.
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arxiv:hep-ph/9711469
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We review the available constraints on the low energy supersymmetry. The bulk of the electroweak data is well screened from supersymmetric loop effects, due to the structure of the theory, even with superpartners generically light, ${\cal O}(M_Z)$. The only exception are the left-handed squarks of the third generation which have to be $\simgt {\cal O}(300$ GeV) to maintain the success of the SM in describing the precision data. The other superpartners can still be light, at their present experimental mass limits. As an application of the derived constraints (supplemented by the requirement of ``naturalness'') we discuss the predictions for the mass of the lighter MSSM Higgs boson in specific scanarios of supersymmetry breaking.
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arxiv:hep-ph/9711470
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A generic class of string theories predicts the existence of light moduli fields, and they are expected to have masses $m_\phi$ comparable to the gravitino mass $m_{3/2}$ which is in a range of $10^{-2}$keV--1GeV in gauge-mediated supersymmetry breaking theories. Such light fields with weak interactions suppressed by the Planck scale can not avoid some stringent cosmological constraints, that is, they suffer from `cosmological moduli problems'. We show that all the gravitino mass region $10^{-2}$keV $\lesssim m_{3/2} \lesssim$ 1GeV is excluded by the constraints even if we incorporate a late-time mini-inflation (thermal inflation). However, a modification of the original thermal inflation model enables the region $10^{-2}$keV $\lesssim m_{3/2} \lesssim$ 500keV to survive the constraints. It is also stressed that the moduli can be dark matter in our universe for the mass region $10^{-2}$keV $\lesssim m_\phi \lesssim$ 100keV.
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arxiv:hep-ph/9711501
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The problem if existing neutrinos are Dirac or Majorana particles is considered in a very pedagogical way. After a few historical remarks we recall the theoretical description of neutral spin 1/2 particles, emphasizing the difference between chirality and helicity which is important in our discussion. Next we describe the properties of neutrinos in the cases when their interactions are given by the standard model and by its extensions (massive neutrinos, right-handed currents, electromagnetic neutrino interaction, interaction with scalar particles). Various processes where the different nature of neutrinos could in principle be visible are reviewed. We clear up misunderstandings which have appeared in last suggestions how to distinguish both types of neutrinos.
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arxiv:hep-ph/9711506
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We consider the Minimal Supergravity Model with universality of scalar and gaugino masses plus an extra bilinear term in the superpotential which breaks R-Parity and lepton number. We explicitly check the consistency of this model with the radiative breaking of the electroweak symmetry. A neutrino mass is radiatively induced, and large Higgs-Lepton mixings are compatible with its experimental bound. We also study briefly the lightest Higgs mass. This one-parameter extension of SUGRA-MSSM is the simplest way of introducing R-parity violation.
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arxiv:hep-ph/9712213
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The combined effect of neutrino flavor oscillations and neutrino magnetic moment on neutrino-electron scattering is discussed. It is shown, that if the tau neutrino has a (large) magnetic moment and can oscillate into a neutrino of another flavor it can be used for a sensitive search for $\nu_{\mu}(\nu_{e}) \to \nu_{\tau}$ neutrino oscillations and the tau neutrino magnetic moment in neutrino -electron scattering experiments. The combined limits on the mixing angles and the tau neutrino magnetic moment $sin^{2}2\theta_{\mu\tau}\times \mu_{\nu_{\tau}}^{2} < 1.1 \times 10^{-18}\mu_{B}^{2}$ and $sin^{2}2\theta_{e\tau}\times \mu_{\nu_{\tau}}^{2} < 2.3 \times 10^{-18}\mu_{B}^{2}$ for $\Delta m^{2} > 10~ eV^{2}$ are presented based on results of a study of the neutrino-electron elastic scattering at LAMPF. For $\nu_{\mu}\to \nu_{\tau}$ oscillations, this would results in sensitive limit of $sin^{2}2\theta_{\mu\tau} < 4 \times 10^{-6}$, assuming the tau neutrino magnetic moment being equal to the present experimental limit of $5.4 \times 10^{-7} \mu_{B}$. The tau neutrino magnetic moment would be constrained to $\mu_{\nu_{\tau}} < 1.0 \times 10^{-8} \mu_{B}$, assuming the existence of $\nu_{\mu}\to \nu_{\tau}$ oscillations with the mixing angle $sin^{2}2\theta_{\mu\tau}$ equal to the present experimental limit of 0.01 for $\Delta m^{2} > 10~ eV^{2}$.\ Under similar assumptions the corresponding limits for $\nu_{e}\to \nu_{\tau}$ oscillations could be set to $sin^{2}2\theta_{e\tau} < 8 \times 10^{-6}$ and $\mu_{\nu_{\tau}} < 3.9 \times 10^{-9}\mu_{B}$.
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arxiv:hep-ph/9712220
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This contribution to the XXVII Symposium on Multiparticle Dynamics held in Frascati, Italy, September, 1997 consists of the following subject matter: (1) Introductory generalities. (2) Brief mention of some of the contributions to the meeting. (3) More extended discussion of a few specialized topics. (4) Discussion of the FELIX initiative for a QCD detector at the LHC.
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arxiv:hep-ph/9712240
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We present a relativistic quark model for baryons, based on the Bethe-Salpeter equation in instantaneous approximation. Confinement is implemented by an interaction kernel which essentially is a linearly rising potential with a spin-dependence chosen such as to minimize spin-orbit effects. The fine structure of the baryon spectrum follows from an effective quark-interaction based on instanton effects. Results for the spectra of all baryons build from u,d,s-quarks are presented. In particular it is found, that the present relativistic setup can account for the low position of Roper-like resonances in all sectors.
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arxiv:hep-ph/9712246
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The success of the quantum level predictions of the Standard Model on the $Z$ boson properties, on $\mw$ and on $\mt$, which makes use of the muon lifetime as an input, implies a stringent constraint on new physics contributions to the $V-A$ charged-current interactions among leptons. Observed unitarity of the CKM matrix elements then implies constraints on non-standard contributions to the lepton-quark charged-current interactions. By using the recent electroweak data as inputs, we find the 95%~CL limits for the corresponding contact interactions: $\Lambda_{CC,+}^{\ell\ell}>7.5$ TeV and $\Lambda_{CC,-}^{\ell\ell}>10.2$ TeV for the purely leptonic terms, and $\Lambda_{CC,+}^{\ell q}>5.8$ TeV and $\Lambda_{CC,-}^{\ell q}>10.1$~TeV for the lepton-quark contact interactions.
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arxiv:hep-ph/9712260
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We show that because of the milder GIM suppression, the four-quark dipenguin operator contributes to the short distance piece of the D^0-\bar D^0 mixing amplitude at the same order of magnitude as the box diagram. In addition, we put an upper bound \Delta m_D^{LDR} \leq 5 \times \Delta m_D^{box} on a long-distance resonant contribution induced by the penguin mixing.
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arxiv:hep-ph/9712279
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In some cases, an important example being at finite temperature, extreme infrared, collinear, or light-cone behaviour may cause the usual loop expansion to break down. For some of these cases higher order ladder graphs can become important. In an earlier paper it was shown that, given a particular relation between a vertex and a self-energy function, the resummation of the ladder graphs simplifies significantly when other types of graphs are included in a consistent effective expansion. In this paper we show that this assumed relation is valid for a large class of vertex and self-energy functions at finite temperature.
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arxiv:hep-ph/9712280
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We propose a nonspectator mechanism in which eta' is produced by two gluon fusion as the underlying process to explain the inclusive B-> X_s eta' as well as the exclusive B -> K^(*) eta' decays.
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arxiv:hep-ph/9712296
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We show that in supersymmetric unified theories such as SO(10), implementation of the see-saw mechanism for neutrino masses introduces a new set of color triplet fields and thereby a new source of d=5 proton decay operators. For neutrino masses in a plausible range, these operators are found to have the right strength to yield observable, but not yet excluded, proton decay rates. The flavor structure of the new operators is distinctive. Proton decay modes into a charged lepton, such as l^+ \pi^0, l^+ K^0 and l^+ \eta where l = e or \mu, can become prominent, even for low or moderate values of tan(\beta) < 10, along with the \nu K^+ and \nu \pi^+ modes. A distinctive feature is the charged lepton modes involving an e^+ and/or a \mu^+ with the ratio \Gamma(l^+ K^0):\Gamma(l^+ \pi^0) = 2:1.
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arxiv:hep-ph/9712307
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We discuss the SM Higgs discovery potential of the LHC in the channel pp->H+jet->gamma+gamma+jet when the jet is observed at sufficiently high Pt and a small rapidity to be reliably identified. We calculate all the signal subprocesses and the irreducible background with realistic kinematical cuts. The reducible QCD background is also estimated. We conclude that the channel gamma+gamma+jet can give about 120-200 signal events for Higgs mass MH=100-140 GeV at the integrated luminosity of 30 inverse fb. This signal rate should be compared with only 330-600 events for the irreducible background per two-photon invariant mass interval of 2 GeV. We estimate the QCD reducible background at the level of 20% of the irreducible one. Thus, one may hope that the Higgs boson can be discovered already during the LHC operation at a low luminosity. At a high luminosity the observation of several hundreds of high Pt Higgs bosons in this channel will be possible with significance higher than 15 for L=100 inverse fb.
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arxiv:hep-ph/9712335
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Conventional jet algorithms are based on a deterministic view of the underlying hard scattering process. Each outgoing parton from the hard scattering is associated with a hard, well separated jet. This approach is very successful because it allows quantitative predictions using lowest order perturbation theory. However, beyond leading order in the coupling constant, when quantum fluctuations are included, deterministic jet algorithms will become problematic precisely because they attempt to describe an inherently stochastic quantum process using deterministic, classical language. This demands a shift in the way we view jet algorithms. We make a first attempt at constructing more probabilistic jet algorithms that reflect the properties of the underlying hard scattering and explore the basic properties and problems of such an approach.
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arxiv:hep-ph/9712355
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The new precise LEP measurements of alphas and the electroweak mixing angle as well as the new LEP II mass limits for supersymmetric particles and new calculations for the radiative (penguin) decay of the b-quark into sgamma allow a further restriction in the parameter space of the Constrained Minimal Supersymmetric Standard Model (CMSSM).
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arxiv:hep-ph/9712376
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Methods to make precision measurements of SUSY masses and parameters at the CERN Large Hadron Collider are described.
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arxiv:hep-ph/9712402
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We investigate numerical solution of the Dokshitzer-Gribov-Lipatov-Altarelli- Parisi (DGLAP) Q^2 evolution equation for the transversity distribution Delta_T q or the structure function h_1. The leading-order (LO) and next-to- leading-order (NLO) evolution equations are studied. The renormalization scheme is MS or overline{MS} in the NLO case. Dividing the variables x and Q^2 into small steps, we solve the integrodifferential equations by the Euler method in the variable Q^2 and by the Simpson method in the variable x. Numerical results indicate that accuracy is better than 1% in the region 10^{-5}<x<0.8 if more than fifty Q^2 steps and more than five hundred x steps are taken. We provide a FORTRAN program for the Q^2 evolution and devolution of the transversity distribution Delta_T q or h_1. Using the program, we show the LO and NLO evolution results of the valence-quark distribution Delta_T u_v + Delta_T d_v, the singlet distribution sum_i (Delta_T q_i + Delta_T qbar_i), and the flavor asymmetric distribution Delta_T ubar - Delta_T dbar.They are also compared with the longitudinal evolution results.
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arxiv:hep-ph/9712410
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The inelasticity in nucleus-nucleus collisions at high energies is calculated in the framework of geometrical multichain model. The very fast increase of the inelasticity is found as a result of a second-stage cascading process. The same behaviour is expected for all the models using the wounded nucleon idea. The simple formula for the number of wounded nucleons inside colliding nuclei does not need to be exact.
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arxiv:hep-ph/9712416
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We consider two body decays of B meson into a light vector (V) and a pseudoscalar (P) meson. The constraint obtained from the $B\to P P$ modes on the parameter space of the input parameters is imposed also on $B\to V P$ modes. In particular we constrain $\xi\equiv (1/N_c)$ for those modes from recently measured $B\to \omega K, \phi K$ and are able to get a satisfactory pictures for all modes where data exists. Modes that should be seen shortly and those with possibly large CP asymmetries are identified.
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arxiv:hep-ph/9712445
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Since the x dependence of the axial-anomaly effect in inclusive polarized deep inelastic scattering is fixed, the transformation from the $\bar{MS}$ scheme to different factorization schemes are not arbitrary. If the quark spin distribution is demanded to be anomaly-free so that it does not evolve with $Q^2$ and hard gluons contribute to the first moment of $g_1(x)$, then all the moments of coefficient and splitting functions are fixed by perturbative QCD for a given $\gamma_5$ prescription, contrary to the commonly used Adler-Bardeen (AB) or AB-like scheme. It is urged that, in order to correctly demonstrate the effect of factorization scheme dependence, the QCD analysis of polarized structure functions in next-to-leading order should be performed, besides the $\bar{MS}$ scheme, in the chiral-invariant factorization scheme in which the axial anomaly resides in the gluon coefficient function, instead of the less consistent and ambiguous AB scheme.
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arxiv:hep-ph/9712473
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It has recently been shown how to break SO(10) down to the Standard Model in a realistic way with only one adjoint Higgs. The expectation value of this adjoint must point in the B-L direction. This has consequences for the possible form of the quark and lepton mass matrices. These consequences are explored in this paper, and it is found that one is naturally led to consider a particular form for the masses of the heavier generations. This form implies typically that there should be large (nearly maximal) mixing of the mu- and tau-neutrinos. An explanation that does not involve large tan beta also emerges for the fact that b and tau are light compared to the top quark.
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arxiv:hep-ph/9712488
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The phenomenological sum-rule-based approach is used to discuss the quark composition dependence of some static and quasi-static electroweak characteristics of nucleons.The role of nonvalence degrees of freedom, the nucleon sea partons and/or peripheral meson currents, is shown to be important to select and make use of the relevant symmetry parametrization of hadron observables. With our preferable universal value of the SU(3)-symmetry parameter $\alpha_{D}=D/F+D=.58$, taken for both magnetic moments and axial-vector constants entering into the semi-leptonic baryon decays, we obtain the following values for moments $\Delta q$ of the spin-dependent structure function of the proton: $\Delta u \simeq .84(.82), \Delta d \simeq -.42(-.44), \Delta s=-.22 \pm .05 (-.10 \pm .03)$, where the values in parentheses correspond to the widely used "standard" value of $\alpha^{axial}_{D}=.63$. The estimations of the strange sea contributions to the nucleon magnetic moments and rms are also presented.
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arxiv:hep-ph/9712511
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The differential cross section dsigma/dt of elastic photoproduction of J/Psi at different gamma p center of mass energies W are used to determine the properties of the exchanged trajectory in the reaction gamma p --> J/Psi p. In the region |t| < 1 GeV^2, the resulting trajectory is alpha(t) = (1.153 \pm 0.027) + (-0.001 \pm 0.072)t. The vanishing value of the slope of the trajectory is an experimental evidence for no shrinkage and thus for the perturbative nature of the exchange.
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arxiv:hep-ph/9712519
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We discuss possibilities to investigate the effects of CP (and T) violation in the lepton sector in neutrino oscillation experiments. We consider the effects of CP violation in the framework of two schemes of mixing of four massive neutrinos that can accommodate the results of all neutrino oscillation experiments. Using the constraints on the mixing parameters that follow from the results of short-baseline neutrino oscillation experiments, we derive rather strong upper bounds on the effects of CP violation in nu_mu<->nu_e transitions in long-baseline neutrino oscillation experiments. We show that the effects of CP violation in nu_mu<->nu_tau transitions in long-baseline oscillation experiments can be as large as is allowed by the unitarity of the mixing matrix. The matter effects, which complicate the problem of searching for CP violation in long-baseline experiments, are discussed in detail. We consider the T-odd asymmetries whose measurement could allow to reveal T and CP violation in the lepton sector independently from matter effects.
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arxiv:hep-ph/9712537
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Analytic formulae are derived for the complete photon energy spectrum due to QED corrections to fermion pair production in case of a limited angular acceptance for the final state fermions. After a numerical integration over the energy of non-observed photons, this corresponds to typical experimental conditions at LEP/SLC.
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arxiv:hep-ph/9801209
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We demonstrate the existence of global monopole and vortex configurations whose core exhibits a phase structure. We determine the critical values of parameters for which the transition from the symmetric to the non-symmetric phase occurs and discuss the novel dynamics implied by the non-symmetric cores for defect interactions. We model phase transitions in the core of global embedded topological defects by identifying the relevant parameters with the vacuum expectation value of a dynamical scalar field. Finally, we argue that superheavy defects that undergo a core phase transition in the very early universe provide a novel realization for topological inflation.
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arxiv:hep-ph/9801232
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Motivated by the experimental measurement of the decay rate, $\Gamma$, and the longitudinal polarization, $P_L$, in the Cabibbo favored decay $D_s^+\to \phi {\rho}^{+}$, we have studied theoretical prediction within the context of factorization approximation invoking several form factors models. We were able to obtain agreement with experiment for both $\Gamma$ and $P_L$ by using experimentally measured values of the form factors $A_1^{D_s\phi}(0)$, $A_2^{D_s\phi}(0)$ and $V^{D_s\phi}(0)$ in the semi-leptonic decay $D_s^+\to \phi l^{+}\nu_{l}$. We have also included in our calculation the effect of the final state interaction ($fsi$) by working with the partial waves amplitudes $S$, $P$ and $D$. Numerical calculation shows that the decay amplitude is dominated by $S$ wave, and that the polarization is sensitive to the interference between $S$ and $D$ waves. The range of the phase difference $\delta_{SD} = \delta_S - \delta_D$ accommodated by experimental error in $P_L$ is large.
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arxiv:hep-ph/9801239
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