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We investigate $e^+ e^- \to t\bar t$ by taking into account wave function distortion effects in the near-threshold region and interpolating the correction factor to the high-energy perturbative QCD region. The strong color attraction between the color singlet $t$ and $\bar t$ enhances the cross section over the tree level results near threshold. The rise of the cross section near the threshold is smoothed by the effects of the large top width and below-threshold resonances. The reliability of the prediction is well assessed by comparing with experimental $R$ ratios for lighter quark production at lower energies. The cross sections obtained here using the reported values of the top mass, can be used directly for New Linear Collider (NLC) projections.
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arxiv:hep-ph/9501218
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In this talk I briefly explain the concept of the structure function of a photon (the best known boson). Then I review some of the current experimental evidence which confirms the existence of `strong' interactions of photon suggested by this idea. I end by pointing out how the photon `structure' has important implications for the interactions of high energy photons and hence for the design of the next generation of the high energy $e^+e^-$ (linear) colliders which are absolutely essential for locating the missing links in our knowledge of fundamental particles and interactions among them.
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arxiv:hep-ph/9501235
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We reexamine radiative corrections to $\pi_{l2}$ and $K_{l2}$ decays. We perform a matching calculation, including vector and axial vector resonances as explicit degrees of freedom in the long distance part. By considering the dependence on the matching scale and on the hadronic parameters, and by comparing with model independent estimates, we scrutinize the model dependence of the results. For the pseudoscalar meson decay constants, we extract the values f_pi = (92.1 \pm 0.3) MeV and f_K = (112.4 \pm 0.9) MeV. For the ratios R_pi and R_K of the electronic and muonic decay modes, we predict R_pi = (1.2354 \pm 0.0002) 10^{-4} and R_K = (2.472 \pm 0.001) 10^{-5}.
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arxiv:hep-ph/9501286
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Predictions for angular correlations between an arbitrary number of partons are derived in the high energy limit. The quantities considered depend on angles and primary energy through a single variable $\epsilon$ which implies certain scaling properties and relations between quite different observables. These asymptotic predictions derived in the double log approximation of QCD are checked against Monte Carlo calculations at the parton and hadron level.
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arxiv:hep-ph/9501326
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A simple model for the photoproduction of kaons off protons with a lambda hyperon in the final state is presented. In a quark model, the interaction is modelled by the pair-creation of the (anti-) strange quarks in the final state which recombine with the three quarks of the proton to form the lambda and kaon. The calculated scattering cross sections for photon energies up to $E_\gamma = 1.9 \; \mbox{GeV}$ are compared to experiment. The pair-creation process is found to have a significant contribution to the total cross section.
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arxiv:hep-ph/9501342
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We show that the factorization assumption in colour-suppressed $B$ meson decays is not ruled out by experimental data on $B \ra K(K^*) + J/\Psi(\Psi^{'})$. The problem previously pointed out might be due to an inadequate choice of hadronic form factors. Within the Isgur-Wise SU(2) heavy flavour symmetry framework, we search for possible $q^2$-dependences of form factors that satisfy both the large longitudinal polarization $\rho_L$ observed in $B \ra K^* + J/\Psi$ and the relatively small ratio of rates $R_{J/\Psi} = \Gamma(B \ra K^* + J/\Psi)/\Gamma(B \ra K + J/\Psi)$. We find out that the puzzle could be essentially understood if the $A_1(q^2)$ form factor is frankly decreasing (instead of being almost constant or increasing as commonly assumed). Of course, the possibility of understanding experimental data is not necessarily a proof of factorization.
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arxiv:hep-ph/9501360
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We show that a particular ``universal'' form for the soft-breaking couplings in a softly broken $N=1$ supersymmetric gauge theory is renormalisation-group invariant through two loops, provided we impose one simple condition on the dimensionless couplings. The universal form for the trilinear couplings and mass terms is identical to that found in popular derivations of the soft-breaking terms from strings or supergravity.
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arxiv:hep-ph/9501395
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In our recent paper (hep-ph/9501348) we argued that the Bjorken variable $x$ in deep inelastic scattering cannot be interpreted as the light cone momentum fraction $\xi$ even in the Bjorken limit and in zero order of the perturbation theory. The purpose of the present paper is to qualitatively explain this fact using only a few simplest kinematical relations.
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arxiv:hep-ph/9502236
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Both Cabibbo allowed and doubly forbidden transitions contribute coherently to $D\rightarrow K_{S,L}+\pi 's$ decays. This leads to several intriguing and even quantitatively significant consequences, among them: (i) A difference between $\Gamma (D^+\rightarrow K_S \pi ^+)$ and $\Gamma (D^+\rightarrow K_L \pi ^+)$ and between $\Gamma (D^0\rightarrow K_S \pi ^0)$ and $\Gamma (D^0\rightarrow K_L \pi ^0)$ of roughly 10\% ; similarly $\Gamma (D^+\rightarrow [K_S\pi ^0]_{K^*} \pi ^+) \neq \frac{1}{4}\Gamma (D^+\rightarrow [K^-\pi ^+]_{K^*} \pi ^+)$, and more generally $\Gamma (D\rightarrow \bar K^0+\pi 's) \neq 2\Gamma (D\rightarrow K_S+\pi 's)$. (ii) A change in the relative phase between the isospin 3/2 and 1/2 amplitudes as extracted from the observed branching ratios for $D^+\rightarrow K_S\pi ^+$, $D^0\rightarrow K_S\pi ^0 ,\, K^-\pi ^+$. (iii) If New Physics intervenes to provide the required {\em weak} phase, then CP asymmetries of up to a few per cent can arise in $D^+\rightarrow K_S\pi ^+$ vs. $D^-\rightarrow K_S\pi ^-$, $D^0\rightarrow K_S\pi ^0$ vs. $\bar D^0\rightarrow K_S\pi ^0$, $D^+\rightarrow [K_S\pi ^0]_{K^*}\pi ^+$ vs. $D^-\rightarrow [K_S\pi ^0]_{K^*}\pi ^-$, etc.; an asymmetry of the same size, but opposite in sign occurs when the $K_S$ is replaced by a $K_L$ in the final state.
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arxiv:hep-ph/9502238
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I discuss in this talk the physics of the $Q^2$ dependence of the $G_1(x,Q^2)$ structure function sum rule. For $Q^2>3$ GeV$^2$, the $Q^2$ variation is controlled by pure QCD radiative corrections. For $0.5<Q^2<3$ GeV$^2$, the twist-four contribution becomes significant, but stays perturbative. For $Q^2$ below $\sim 0.05$, the sum rule is determined by low-energy theorems. The rapid change of the sum rule between 0.05 and 0.5 GeV$^2$ signals the transition between parton and hadron degrees of freedom.
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arxiv:hep-ph/9502288
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In the Nambu--Jona-Lasinio model baryons are either considered as quark-diquark-composites or the soliton configurations of the model are interpreted as baryons. As a first step towards constructing a hybrid model, which possesses a dynamical interplay between both pictures, the Bethe-Salpeter equation for diquarks in the background of a soliton configuration is solved. The presence of the soliton causes a significant reduction of the resulting bound state eigenenergy of the diquark. As a consequence a unit baryon number configuration may be constructed with a mass lower than the energy of the soliton. An estimate of the influence of the diquark on the meson fields indicates a small decrease of the extension of the soliton due to diquark correlations.
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arxiv:hep-ph/9502328
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We consider the Strongly-Coupled Standard Model (Abbott-Farhi model) including an isotriplet of W' vector bosons. First we calculate the corrections to the low-energy theory, which can be effectively summarized in terms of the parameters S, T and U. Then we use high- precision electroweak measurements to constrain the mass and couplings of the W'. The W' couplings are restricted to be unnaturally small, and we conclude that this model is no longer compelling as a theory of the electroweak interactions.
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arxiv:hep-ph/9502331
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We discuss the low-energy analysis of models involving quarks and four-fermion couplings. The relation with QCD and with other models of mesons and meson plus quarks at low energies is discussed. A short description of how the heat-kernel expansion can be used to get regularization independent information, is given. The anomaly within this class of models and a physical prescription to obtain the correct flavour anomaly while keeping as much of the VMD aspects as possible is discussed. The major part is the discussion within this framework of the order $p^4$ action and of two and some three-point functions to all orders in momenta and quark masses. Some results on hadronic matrix elements are given.
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arxiv:hep-ph/9502335
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Leptons, quarks and gauge bosons are assumed to be described by local field theory. Stringent bounds on nonlocal scale can be derived from the high- presision LEP measurements. We find a bound on nonlocal scale $\Lambda_{nl} > 1020\: Gev$, C.L.95\% from LEP data.
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arxiv:hep-ph/9503220
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The presence of the $(B+L)$-conserving decay modes $n \to K^+ e^-,$ $n \to K^+ \mu^-,$ $p \to K^+ e^- \pi^+$ and $p \to K^+ \mu^- \pi^+$ is shown to be a characteristic feature of a class of models with explicit breaking of $R$-parity. These modes dominate over the $(B-L)$-conserving ones in certain regions of the parameter space; the impact of this scenario for nucleon decay search at the Super-Kamiokande is discussed.
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arxiv:hep-ph/9503227
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We present improved Coulomb correction formulae for Bose-Einstein correlations including also exchange term and use them to calculate appropriate correction factors for several source functions. It is found that Coulomb correction to the exchange function in the Bose-Einstein correlations cannot be neglected.
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arxiv:hep-ph/9503232
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We discuss some applications of the effective quantum field theory to the description of the physics beyond the Standard Model. We consider two different examples. In the first one we derive, at the one-loop level, an effective lagrangian for an extension of the Standard Model with a charged scalar singlet by ``integrating out'' the heavy scalar. In the second example we illustrate the use of general effective theories at the loop level.
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arxiv:hep-ph/9503257
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We solve a unified integral equation to obtain the $x, Q_T$ and $Q$ dependence of the gluon distribution of a proton in the small $x$ regime; where $x$ and $Q_T$ are the longitudinal momentum fraction and the transverse momentum of the gluon probed at a scale $Q$. The equation generates a gluon with a steep $x^{- \lambda}$ behaviour, with $\lambda \sim 0.5$, and a $Q_T$ distribution which broadens as $x$ decreases. We compare our solutions with, on the one hand, those that we obtain using the double-leading-logarithm approximation to Altarelli-Parisi evolution and, on the other hand, to those that we determine from the BFKL equation.
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arxiv:hep-ph/9503266
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The theoretical motivations, experimental searches/hints, and implications of neutrino mass are surveyed.
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arxiv:hep-ph/9503327
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I show that a cosmological baryon asymmetry generated at the GUT scale is in general safe against washout due to sphalerons and generic $B$- or $L$-violating effects. This result is mainly due to the (almost) conserved number of right-handed electrons at high temperatures $T \gsim {\cal O}(10) $ TeV, but also the mass corrections, in particular the thermal masses of leptons act as the protector of the primordial baryon asymmetry.
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arxiv:hep-ph/9503335
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We analyze the impact of using $b$-tagged samples in studying non-Abelian effects due to QCD in $e^+e^-\ar 4$jet events at $\sqrt s=M_{Z^0}$, using angular variable analyses and comparisons with $e^+e^-\ar 3 \mbox{jet}\gamma$ events. We find that QCD effects are largely enhanced in $b$-quark samples with respect to `unflavoured' ones, where energy-ordering is used to distinguish between gluon and quark jets. We show that the $b$-quark mass influences the angular distributions significantly and should not be neglected
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arxiv:hep-ph/9503354
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Despite the many empirical successes of QCD, there are a number of intriguing experimental anomalies that have been observed in heavy flavor hadroproduction, in measurements of azimuthal correlations in deep inelastic processes, and in measurements of spin correlations in hadronic reactions. Such phenomena point to color coherence and multiparton correlations in the hadron wavefunctions and physics beyond standard leading twist factorization. Two new high precision tests of QCD and the Standard Model are discussed: classical polarized photoabsorption sum rules, which are sensitive to anomalous couplings and composite structure, and commensurate scale relations, which relate physical observables to each other without scale or scheme ambiguity. The relationship of anomalous couplings to composite structure is also discussed.
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arxiv:hep-ph/9503391
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We obtain a generalization of the Low theorem for non-Abelian boson emission in collision of scalar and gauge vector particles and its extension to high energy collisions for small transverse momenta of produced particles. We demonstrate that in the case of particles with spin the direct extension the Low formula to high energy is in contradiction with the correct amplitude factorization behavior. Consideration of different kinematical regions and use of methods of dual models allows us to separate contributions of intermediate excited states and standard spin corrections in the Low formulae. We show that the amplitude factorization occurs at high energy due to the contribution of the intermediate states which is additional to the gluon production amplitude for the scalar particle collision.
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arxiv:hep-ph/9503428
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We critically reexamine the precision tests of the standard model by coupling the current world average value of $M_W$ with the recent LEP electroweak data with the aid of a modified ZFITTER program to include the dominant two-loop and QCD-EW mixed terms. The results show a clear evidence of nonvanishing electroweak radiative corrections. The recent CDF $m_t$ is a solution of the minimal $\chi^2$-fits to the recent LEP data set and $M_W=80.23(18)~$ GeV but with a heavy Higgs scalar, i.e., $m_t=179~$ GeV and $m_H=300~$ GeV. We discuss how sensitive $m_t$ and $m_H$ are depending on the exact value of $M_W$ even within the present uncertainty, as well as on $\alpha_s$ and $\alpha (M_Z)$. We show how the future improvements on $M_W$ can discriminate different values of $m_t$ and $m_H$ from the electroweak data and provide a crucial and decisive test for the standard model.
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arxiv:hep-ph/9503478
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The discovery potential and diagnostic abilities of proposed future colliders for new heavy neutral ($Z'$) and charged ($W'$) gauge bosons are summarized. Typical bounds achievable on $M_{Z',W'}$ at the TEVATRON, DI-TEVATRON, LHC, 500 GeV NLC, and 1 TeV NLC are $\sim$1~TeV, $\sim$2~TeV, $\sim$4~TeV, 1--3~TeV, and 2--6~TeV, respectively. For $M_{Z'} \sim$1 TeV the LHC will have the capability to determine the magnitude of normalized $Z'$ quark and lepton couplings to around $10-20\%$, while the NLC would allow for determination of the couplings (including their signs) with a factor of 2 larger error-bars, provided heavy flavor tagging and longitudinal polarization of the electron beam is available.
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arxiv:hep-ph/9504216
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Inelastic photoproduction of $J/\psi$ particles at high energies is one of the processes to determine the gluon distribution in the nucleon. The QCD radiative corrections to the color-singlet model of this reaction have recently been calculated. They are large at moderate photon energies, but decrease with increasing energies. I compare the cross section and the ${J/\psi}$ energy spectrum with the available fixed-target photoproduction data. Predictions for the HERA energy range are given which demonstrate the sensitivity of the result to the parametrization of the gluon distribution in the small-$x$ region. (Talk presented at the Workshop on "Heavy Quark Physics", Bad Honnef, FRG, Dec. 1994)
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arxiv:hep-ph/9504255
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We compute the particle currents induced on a bubble wall background at finite temperature in a model with CP violation in the Higgs sector. Using a field theory approach we show that fermionic currents arise at one loop, so that a suppression factor ${\cal O}(h_t \phi/\pi T)^2$ with respect to previous computations is found. The contributions to the Higgs currents are also derived and their relevancy for the spontaneous baryogenesis mechanism is discussed.
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arxiv:hep-ph/9504265
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Lattice QCD is the only non-perturbative method based uniquely on the first principles of QCD. After a very simple introduction to the principles of lattice QCD, I discuss its present limitations and the type of processes it can deal with. Then I present some striking results in the light and heavy quarks sectors. Finally I try to guess the prospects.
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arxiv:hep-ph/9504271
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Bound states of heavy quarks are considered. Using the path integral formalism we are able to rederive, in a gauge invariant way, the Leutwyler-Voloshin short distance analysis as well as a long distance linear potential. At all distances we describe the states in terms of nonperturbative field correlators, and we include radiative corrections at short and intermediate distances. For intermediate distance states (particularly $b\bar {b}$ with $n=2$) our results improve, qualitatively and quantitatively, standard analyses, thanks mostly to being able to take into account the finiteness of the correlation time.
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arxiv:hep-ph/9504273
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Weakly-interacting massive particles (WIMPs) annihilating in the center of the Sun or the Earth may give rise to energetic neutrinos which might be discovered by astronomical neutrino detectors. The angular distribution of the neutrino-induced muons is considered in detail via Monte Carlo simulations. It is shown that large underground \v{C}erenkov neutrino telescopes might be able to extract the WIMP mass from the width of the muon angular distribution.
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arxiv:hep-ph/9504283
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By applying the Ward identity found by Weinberg two new relations of the amplitude of $a_{1}\rightarrow\rho\pi$ with other physical quantities have been found.
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arxiv:hep-ph/9504305
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With $\mu\to e\gamma$ decay forbidden by multiplicative lepton number conservation, we study muonium--antimuonium transitions induced by neutral scalar bosons. Pseudoscalars do not induce conversion for triplet muonium, while for singlet muonium, pseudoscalar and scalar contributions add constructively. This is in contrast to the usual case of doubly charged scalar exchange, where the conversion rate is the same for both singlet and triplet muonium. Complementary to muonium conversion studies, high energy $\mu^+e^- \to \mu^- e^+$ and $e^-e^- \to \mu^- \mu^-$ collisions could reveal spectacular resonance peaks for the cases of neutral and doubly charged scalars, respectively.
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arxiv:hep-ph/9504311
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We use classical or large Nc QCD to describe the mesons (pion, rho, omega) coming from proton-antiproton annihilation at rest as classical fields, which we then quantize as coherent states. This treatment gives a nearly parameter free account of the pion branching ratios in annihilation.
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arxiv:hep-ph/9504362
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In the underlying Planck scale theory we introduce a certain type of discrete symmetry, which potentially brings the stability of the weak-scale hierarchy under control. Under the discrete symmetry the $\mu $-problem and the tadpole problem can be solved simultaneously without relying on some fine-tuning of parameters. Instead, it is required that doublet Higgs and color-triplet Higgs fields reside in different irreducible representations of the gauge symmetry group at the Planck scale and that they have distinct charges of the discrete symmetry group.
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arxiv:hep-ph/9504368
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It is shown that one can fit the available data on the a0(980), f0(980), f0(1300) and K*0(1430) mesons as a distorted 0++ qq bar nonet using very few (5-6) parameters and an improved version of the unitarized quark model. This includes all light two-pseudoscalar thresholds, constraints from Adler zeroes, flavour symmetric couplings, unitarity and physically acceptable analyticity. The parameters include a bare uu bar or dd bar mass, an over-all coupling constant, a cutoff and a strange quark mass of 100 MeV, which is in accord with expectations from the quark model. It is found that in particular for the a0(980) and f0(980) the KK bar component in the wave function is large, i.e., for a large fraction of the time the qq bar state is transformed into a virtual KK bar pair. This KK bar component, together with a similar component of eta' pi for the a0(980) , and eta eta, eta eta' and eta' eta' components for the f0(980), causes the substantial shift to a lower mass than what is naively expected from the qq bar component alone. Mass, width and mixing parameters, including sheet and pole positions, of the four resonances are given, with a detailed pedagogical discussion of their meaning.
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arxiv:hep-ph/9504372
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The flavor changing and CP violating phenomena predicted in supersymmetric unified theories as a consequence of the large top quark Yukawa coupling, are investigated in the quark sector and compared with related phenomena in the lepton sector, considered previously. In particular we study $\varepsilon_K$, $\varepsilon_K'/\varepsilon_K$, $\Delta m_B$, $b\to s\gamma$, the neutron electric dipole moment, $d_n$, and CP violation in neutral $B$ meson decays, both in minimal~SU(5) and~SO(10) theories. The leptonic signals are generically shown to provide more significant tests of quark-lepton unification. Nevertheless, mostly in the~SO(10) case, a variety of hadronic signals is also possible, with interesting correlations among them.
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arxiv:hep-ph/9504373
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We show that a simple scaling model of very forward particle production, consistent with accelerator and air shower data, can describe all features of the very high-energy interactions recorded with emulsion chambers. This is somewhat surprising after numerous claims that the same data implied large scaling violations or new dynamics. Interestingly, we cannot describe some of the Centauro events, suggesting that these events are anomalous independently of their well-advertised unusual features such as the absence of neutral secondaries.
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arxiv:hep-ph/9504391
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Three--loop contributions to massive QED vacuum polarization are evaluated by a combination of analytical and numerical techniques. The first three Taylor coefficients, at small $q^2$, are obtained analytically, using $d$\/--dimensional recurrence relations. Combining these with analytical input at threshold, and at large $q^2$, an accurate Pad\'e approximation is obtained, for all $q^2$. Inserting this in the one--loop diagram for the muon anomalous magnetic moment, we find reasonable agreement with four--loop, single--electron--loop, muon--anomaly contributions, recently re--evaluated by Kinoshita, using 8--dimensional Monte--Carlo integration. We believe that our new method is at least two orders of magnitude more accurate than the Monte--Carlo approach, whose uncertainties appear to have been underestimated, by a factor of 6.
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arxiv:hep-ph/9504398
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We review algorithmic methods for two-loop calculations in HQET, and the analogous methods for on-shell QCD, needed for matching HQET to QCD.
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arxiv:hep-ph/9504400
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We study the effects of QCD corrections to the process $e^+e^-\rightarrow t\bar t+X\rightarrow b\ell^+\nu \bar b\ell^-\bar \nu+X$ above threshold. We show how to treat consistently to ${\cal O}(\alpha_s)$ the gluon radiation in both the production and the decay of the top quarks, while maintaining all angular correlations in the event. At this order there is an ambiguity in the event reconstruction whenever a real gluon occurs in the final state. We study the effects of this ambiguity on the top mass and helicity angle distributions. For a top mass of 175 GeV and collider energy of 400 GeV the gluon radiation is emitted predominantly in the decay of the top quarks.
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arxiv:hep-ph/9504434
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In models with a non-minimal Higgs sector, the lightest scalar state may be a neutral CP-even Higgs boson, whose properties are nearly identical to those of the minimal Higgs boson of the Standard Model. In such a scenario, the other Higgs scalars are significantly heavier than $m_Z$; their effects rapidly decouple from the low-energy theory. The decoupling limit of the most general CP-conserving two-Higgs doublet model is formulated. Detection of evidence for a non-minimal Higgs sector in the decoupling limit presents a formidable challenge for Higgs searches at future colliders.
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arxiv:hep-ph/9505240
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I give a short review of the relation of infrared renormalons in QCD and higher twist effects, with the emphasis on possible applications. In particular, I present estimates of renormalon-induced uncertainties in deep inelastic sum rules and explain how the renormalons can potentially be used to unravel the structure of nonperturbative effects in complicated situations and to indicate possible systematic sources of large perturbative corrections.
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arxiv:hep-ph/9505317
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We propose a new parametrisation of the Cabibbo-Kobayashi-Maskawa Matrix in which the approximations of the standard parametrisation, $|V_{cb}|\approx s_{23}$, $|V_{us}|\approx s_{12}$, are promoted to exact results.
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arxiv:hep-ph/9505362
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The problem of clusters growth in quark-hadron phase transition in heavy-ion collision is investigated by cellular automata. The system is found to exhibit self-organized criticality with the distribution of cluster sizes having universal scaling behavior.
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arxiv:hep-ph/9505376
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We analyze the capability of prompt photon production in pp and pp(bar) collisions to constrain the gluon distribution of the proton, considering data from fixed-target experiments as well as collider measurements. Combined fits are performed to these large-p_T direct gamma cross sections and lepton-proton deep-inelastic scattering data in the framework of next-to-leading order perturbative QCD. Special attention is paid to theoretical uncertainties originating from the scale dependence of the results and from the fragmentation contribution to the prompt photon cross section.
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arxiv:hep-ph/9505404
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Starting from the multi-Regge effective action for high-energy scattering in QCD a $t$-channel approach can be developed which is similar to the approach by White based on general Regge arguments. The BFKL kernel of reggeized gluon interaction, contributions to the $2 \rightarrow 4 $ reggeized gluon vertex function and the one-loop correction to the BFKL kernel are considered. The conditions are discussed under which this approach can provide a simple estimante of the next-to-leading logarithmic corrections to the BFKL perturbative pomeron intercept.
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arxiv:hep-ph/9505421
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We analyze the role played by the gauge invariance for the existence of Dirac monopole. To this end, we consider the electrodynamics with massive photon and ask if the magnetic charge can be introduced there. We show that the derivation of the Dirac quantization condition based on the angular momentum algebra cannot be generalized to the case of massive electrodynamics. Possible implications of this result are briefly discussed.
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arxiv:hep-ph/9505445
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This talk is dedicated to honor the memory of Professor S.N. Bose. I survey the crucial roles played by Bose-Fermi symmetry in all recent attempts at higher unification, which include the ideas of (i) the conventional approach to grand unification; (ii) the preonic approach; and (iii) superstrings.
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arxiv:hep-ph/9506211
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We study the $\eta \to 2 \gamma$ decay using an extended three-flavor Nambu-Jona-Lasinio model that includes the 't~Hooft instanton induced interaction. The $\eta$ meson mass and the $\eta \to 2 \gamma$ decay width are reproduced simultaneously with a rather strong instanton induced interaction. The calculated $\eta$ decay constant is $f_\eta = 2.23 f_\pi$ and it suggests that the $\eta$ meson is no longer the Goldstone boson.
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arxiv:hep-ph/9506254
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Assuming that a horizontal abelian (gauge) symmetry is at the origin of texture zeros in the fermion mass matrices we show how realistic mass patterns can be generated in the presence of scalar fields whose vacuum expectation value breaks the extra $U(1)$ symmetry. In the simplest scenario with just one pair of singlet fields and under the assumption of L-R symmetry one obtains quark mass matrices {\it \`a la Fritzsch}. The $U(1)$ symmetry can be made anomaly free by the Green-Schwarz mechanism in which case the canonical unification of the gauge couplings emerges as its byproduct. The generation of neutrino masses requires either two extra heavy scalar (Higgs) fields to determine the texture structure of the righthanded neutrino mass matrix or the latter will contain a hierarchy of scales.
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arxiv:hep-ph/9506301
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We introduce a way of implementing Wilson renormalization within the context of the theory of effective Hamiltonians. Our renormalization scheme involves manipulations at the level of the generalized $G$--matrix and is independent of any specific kinematics. We show how to calculate the beta function within this context and exhibit our method using simple scale--invariant quantum mechanical systems.
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arxiv:hep-ph/9506320
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The strange vector form factors are evaluated for $Q^2=0$ and $Q^2=1\ \mbox{GeV}^2$ in the framework of the SU(3) chiral quark-soliton model (or semi-bosonized SU(3) Nambu-Jona-Lasinio model). The rotational $1/N_c$ and $m_s$ corrections are taken into account up to linear order. The mean-square strange radius $\langle r^{2}\rangle^{Sachs}_{s}=-0.35\; \mbox{fm}^2$ and the strange magnetic moment $\mu_s = -0.44\;\mu_N$ are obtained. The results are compared with several different models.
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arxiv:hep-ph/9506344
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I present some comments on the partonic interpretation of the HERA data on the proton structure function. The effects of the resummation of the leading and next-to-leading $\ln x$-contributions are discussed. A new factorization scheme, in which these resummation effects are absorbed into a steep redefinition of the gluon density, is introduced and its (possible) interpretation and phenomenological relevance are suggested.
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arxiv:hep-ph/9506357
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Within quantum mechanics model we study the problem of resummation of an asymptotic perturbation series for bound state parameters via optimization of the perturbative expansion. A possible application of the method to the positronium lifetime calculation is also briefly considered.
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arxiv:hep-ph/9506370
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A simple model-independent formula for cross-section asymmetries $A$ in fermion-pair production is derived, which may be used for the analysis of LEP~1 data, $A = \sum_n A_n (s - M_Z^2)^n$. The coefficient $A_0$ depends on the $Z$ boson exchange, $A_1$ additionally on the $\gamma Z$ interference, while the higher-order contributions are practically redundant. QED corrections are taken into account, and relations to other approaches are indicated.
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arxiv:hep-ph/9506382
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Tunneling in quantum field theory is well understood in the case of a single scalar field. However, in theories with spontaneous symmetry breaking, one has to take into account the additional zero modes which appear due to the Goldstone phenomenon. We calculate the false vacuum decay rate in this case. The result may differ significantly from the tunneling rates in the absence of symmetry breaking.
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arxiv:hep-ph/9506386
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We study the effect of the diagonal extended technicolor(ETC) gauge boson on the oblique correction parameters. It is shown that in the $T$ parameter is unacceptably large when the $Zbb$ vertex correction and $S$ parameter are consistent with the experiments in the ETC model.
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arxiv:hep-ph/9506411
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We demonstrate that the non-trivial CP-violating structure of QCD vacuum can lead to an observable effect in $e^+e^-\to q\bar q\to 2$-jet annihilation. We find that the sign of the jet handedness correlation can be opposite to that predicted by factorization of $q~\bar q$ fragmentation and CP-conjugation of the two jets. A simple model estimation of the handedness correlation magnitude is given.
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arxiv:hep-ph/9506412
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The cross--section for two--photon events with (at least) two independent partonic scatters is estimated, for LEP energies as well as a 500 GeV ``photon collider". This results in events with (at least) four central (mini--)jets. Such events might be found in existing data, and should be clearly seen at the second stage of LEP.
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arxiv:hep-ph/9506453
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We present the results of an analysis of the data of reactor and accelerator neutrino oscillation experiments in the framework of a model with mixing of three massive neutrino fields and a neutrino mass hierarchy. The results of the LSND experiment are commented. Taking into account future long-baseline neutrino oscillation experiments, we have also analyzed the atmospheric neutrino data in the framework of the model.
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arxiv:hep-ph/9507226
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We consider thermal properties of the susy singlet majoron model. We compute the critical temperature $T_c$ and the subsequent reheating temperature $T_{\rm RH}$ for $R$-parity breaking. Succesful baryogenesis constrains the parameter space via the requirements that $T_c$ and $T_{\rm RH}$ are lower than the electroweak phase transition temperature. A further constraint is provided by requiring that the gauge singlet should be kinematically allowed to decay, in order not to have a matter dominated universe at the time of nucleosynthesis. We have made a detailed study of the parameter space and find an upper limit for the susy breaking scalar mass $\mm\lsim 750~(900)$ GeV if $\gluino=100~(1000)$ GeV, which is valid except for certain special values of the singlet sector parameters.
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arxiv:hep-ph/9507227
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We study left-right symmetric quark mass matrices whose up- and down-sectors have the same structure. This type of realistic mass matrices are derived from orbifold models. We cannot derive some of them by using an extra U(1) symmetry.
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arxiv:hep-ph/9507244
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We give a preliminary report of a new quark mass matrix model basing on a $SU(5)\otimes SU(5)\otimes Q_{12}$ symmetry embedding into a fully gauged $SU(5)\otimes SU(5)\otimes SU(2)$.~\cite{fk} The two $SU(5)$'s contain the standard SUSY $SU(5)$ as a diagonal subgroup, while the $Q_{12}$ or $SU(2)$ is horizontal. Starting by assuming a judiciously-chosen set of chiral supermultiplets, and a pattern of spontaneous symmetry breaking, we obtain the low-energy chiral fermions together with a spectrum of superheavy fermions at two different scales. The latter mediate Froggatt-Nielsen tree graphs that give rise to a phenomenologically viable effective quark mass matrix texture. The model is the first example of a nontrivial combination of supersymmetry without R-parity, gauged nonabelian horizontal symmetry and unification/anti-unification. It is expected to have some very interesting features in SUSY-GUT phenomenology.
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arxiv:hep-ph/9507313
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We study a new $K\rightarrow\pi\pi$ decay channel with gluons in intermediate state which is normally neglected within the factorization framework. Both short-distance and long-distance parts of the amplitude are calculated. The chiral Lagrangian approach is used for obtaining the long-distance contribution. The nonperturbative contribution gives an additional enhancement to $K\rightarrow\pi\pi$ decay amplitude with $\Delta I=1/2$. A sizable violation of factorization in the $p^4$ order of chiral perturbation theory is found.
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arxiv:hep-ph/9507316
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Neutrinos can undergo flavor--oscillations if they possess flavor--dependent couplings to the surrounding gravitational field (the VEP mechanism). The neutrino fields can be massless, in accord with the Minimal Standard Model, but at the expense of the Einstein Equivalence Principle. We show that it is possible to explain the observed Solar Neutrino data from the various experiments using the VEP solution in a realistic three--generation framework, and further note how the three--flavor model can offer larger allowed regions of parameter space over the two--flavor models.
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arxiv:hep-ph/9507355
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The cross-section for $\gamma\gamma\to t \bar t$ with arbitrary polarized photons is calculated within the electroweak Standard Model including the complete virtual and soft-photonic $O(\alpha)$ corrections. We present a detailed numerical discussion of the radiative corrections with particular emphasis on the purely weak corrections. These are usually of the order of 1--10\% for energies up to 1 TeV. For unpolarized or equally polarized photons they reach almost 10\% close to threshold. The large corrections cannot be traced back to a universal origin like the running of $\alpha$ or the $\rho$-parameter. Apart from the energy region around the Higgs resonance $(\gamma\gamma\to H^*\to t\bar t)$ the weak corrections are widely independent of the Higgs-boson mass.
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arxiv:hep-ph/9507372
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In the absence of any additional assumption it is natural to conjecture that sizeable flavour-mixing mass entries, $\Delta m^2$, may appear in the mass matrices of the scalars of the MSSM, i.e. $\Delta m^2\sim O(m^2)$. This flavour violation can still be reconciled with the experiment if the gaugino mass, $M_{1/2}$, is large enough, leading to a {\em gaugino dominance} framework (i.e. $M_{1/2}^2\gg m^2$), which permits a remarkably model--independent analysis. We study this possibility focussing our attention on the $\mu\rightarrow e,\gamma$ decay. In this way we obtain very strong and general constraints, in particular $\frac{M_{1/2}^2}{\Delta m}\simgt 34\ {\rm TeV}$. On the other hand, we show that our analysis and results remain valid for values of $m^2$ much larger than $\Delta m^2$, namely for $\frac{\Delta m^2}{m^2}\simgt \frac{m^2} {10\ {\rm TeV^2}}$, thus extending enormously their scope of application. Finally, we discuss the implications for superstring scenarios.
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arxiv:hep-ph/9507377
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We calculate the three gauge-boson production in the Standard Model at Fermilab Tevatron energies. At $\sqrt s=2$ TeV in $p\bar p$ collisions, the cross sections for the triple gauge-boson production are typically of order 10 femtobarns (fb). For the pure leptonic final states from the gauge-boson decays and with some minimal cuts on final state photons, the cross sections for $p \bar p \rightarrow W^\pm \gamma\gamma, Z\gamma\gamma$ and $W^+W^- \gamma$ processes are of order a few fb, resulting in a few dozen clean leptonic events for an integrated luminosity of 10 fb$^{-1}$. The pure leptonic modes from other gauge-boson channels give significantly smaller rate. Especially, the trilepton modes from $W^+W^-W^\pm$ and $t \bar t W^\pm \rightarrow W^+W^-W^\pm$ yield a cross section of order 0.1 fb if there is no significant Higgs boson contribution. For a Higgs boson with $m_H^{} \simeq 2M_Z^{}$, the triple massive-gauge-boson production rate could be enhanced by a factor of $4-6$.
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arxiv:hep-ph/9507409
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We consider a modification of the standard electroweak model with the third quark generation and the $\tau$-lepton in vector representations of $SU(2)\otimes U(1)_Y$ electroweak symmetry. This is a new way to implement right-handed currents which are controlled by the usual Fermi constant, $G_F$, the weak mixing angle, $\sin\theta_W$, and also by the right-handed mixing matrices which survive when the Lagrangian density is written in terms of the mass eigenstates. In this case there are also new CP violation phases.
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arxiv:hep-ph/9507448
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The present CORE 2.1 (COmpendium of RElations, Version 2.1) contains various formulas and relations used in the practical calculations in the Standard Model. The properties of the Pauli, Dirac, Gell--Mann matrices, wave functions of free fermions and gauge bosons are considered. We present the full Lagrangian of the Standard Model and the corresponding Feynman rules. The method of the evaluation of the Feynman (loop) integrals and calculations in non-covariant gauges is considered. We discuss in brief the relativistic kinematic and present a large number of the matrix elements of the various processes in the Standard Model.
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arxiv:hep-ph/9507456
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The scattering of pions on a dibaryon configuration is analyzed within the $SU(2)$ Skyrme model. It is shown that this model leads to a low-lying $(J^P,I)= (0^-,2)$ resonance. The possibility that this resonance corresponds to one proposed recently in the context of double charge exchange pion scattering on nuclei is discussed. Given the setup used in those experiments we also show that a resonance with isospin assignment $I=0$ cannot be excited according to the description presented here.
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arxiv:hep-ph/9507459
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New distributions are presented which allow di-photon + jet events to be clearly separated into three classes of events based on the $p_{T}$ of the final state particles and their separation $R$ = $\sqrt{(\Delta y)^{2} + (\Delta \phi)^{2}}$. The analysis used can easily be extended to the case of di-jet + photon.
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arxiv:hep-ph/9507468
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We study the effect of a magnetic field on the strage quark matter and apply to strange star. We found that the strange star becomes more compact in presence of strong magnetic field.
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arxiv:hep-ph/9508251
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Predictions for the angular distribution of massive quarks and leptons are presented, including QCD and QED corrections. Recent results for the fermionic part of the two-loop corrections to the electromagnetic form factors are combined with the BLM scale fixing prescription. Two distinctly different scales arise as arguments of $\alpha_s(\mu^2)$ near threshold: the relative momentum of the quarks governing the soft gluon exchange responsible for the Coulomb potential, and a large momentum scale approximately equal to twice the quark mass for the corrections induced by transverse gluons. Numerical predictions for charmed, bottom, and top quarks are given. One obtains a direct determination of $\alpha_V(Q^2)$, the coupling in the heavy quark potential, which can be compared with lattice gauge theory predictions. The corresponding QED results for $\tau$ pair production allow for a measurement of the magnetic moment of the $\tau$ and could be tested at a future $\tau$-charm factory.
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arxiv:hep-ph/9508274
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The diffractive process $\gamma^*(Q^2) p\to V+X$ (where $V= \rho^0, \omega , \phi$ are the vector mesons, consisted of light quarks, $X$ represents the hadrons to that a proton dissociates) is studied. We consider the region of large momentum transfers, $|t|>>\Lambda^2_{QCD}$, and large energies, s. In the leading log approximation of perturbative QCD ( using BFKL equation ) the asymptotic behaviour of the cross section in the limit $s\to\infty , s>>|t|, Q^2$ is obtained. We compare the results derived from BFKL equation with that obtained in the lowest order of QCD (two--gluon exchange in the $t$- channel). The possibility to investigate these reactions at HERA is discussed.
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arxiv:hep-ph/9508319
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Due to a rapid change of the entropy density $s(T)$ across the critical temperature $T_c$ of the QCD phase transition, the pressure $P(T)$ and the energy density $e(T)$ above $T_c$ generally deviate from their Stefan-Boltzmann values. We shall demonstrate this both analytically and numerically for a general class of $s(T)$ consistent with thermodynamical constraints and make a qualitative comparison of the result with the lattice QCD data. Quantities related to $ds(T)/dT$ such as the specific heat and sound velocity are also discussed.
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arxiv:hep-ph/9508360
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Within the framework of a dynamical and physically transparent model developed earlier, we study the time evolution of various quark flavours in the baryon-free region in ultrarelativistic heavy ion collisions. We show that even under optimistic conditions, the quark-gluon system fails to achieve chemical equilibrium.
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arxiv:hep-ph/9508385
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In the limit of an infinite number of colors, an analytic expression for the quark condensate in $QCD_{1+1}$ is derived as a function of the quark mass and the gauge coupling constant. For zero quark mass, a nonvanishing quark condensate is obtained. Nevertheless, it is shown that there is no phase transition as a function of the quark mass. It is furthermore shown that the expansion of $\langle 0 | \overline{\psi}\psi |0\rangle$ in the gauge coupling has zero radius of convergence but that the perturbation series is Borel summable with finite radius of convergence. The nonanalytic behavior $\langle 0 | \overline{\psi}\psi |0\rangle \stackrel{m_q\rightarrow0}{\sim} - N_C \sqrt{G^2}$ can only be obtained by summing the perturbation series to infinite order. The sum-rule calculation is based on masses and coupling constants calculated from 't Hooft's solution to $QCD_{1+1}$ which employs LF quantization and is thus based on a trivial vacuum. Nevertheless the chiral condensate remains nonvanishing in the chiral limit which is yet another example that seemingly trivial LF vacua are {\it not} in conflict with QCD sum-rule results.
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arxiv:hep-ph/9509226
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QCD sum rules are used to calculate the contribution of short-distance single-quark transition $s\rightarrow d \gamma$, to the amplitudes of the hyperon radiative decay, $\Omega^-\rightarrow \Xi^-\gamma$. We re-evaluate the Wilson coefficient of the effective operator responsible for this transition. We obtain a branching ratio which is comparable to the unitarity limit.
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arxiv:hep-ph/9509297
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It is shown that a constant magnetic field in 3+1 and 2+1 dimensions is a strong catalyst of dynamical chiral symmetry breaking, leading to the generation of a fermion dynamical mass even at the weakest attractive interaction between fermions. The essence of this effect is the dimensional reduction $D\to D-2$ in the dynamics of fermion pairing in a magnetic field. The effect is illustrated in the Nambu--Jona--Lasinio (NJL) model and QED. In the NJL model in a magnetic field, the low--energy effective action and the spectrum of long wavelength collective excitations are derived. In QED (in ladder and improved ladder approximations) the dynamical mass of fermions (energy gap in the fermion spectrum) is determined. Possible applications of this effect and its extension to inhomogeneous field configurations are discussed.
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arxiv:hep-ph/9509320
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In terms of an effective chiral theory of mesons it is shown quantitatively that in the limit of $m_{q}=0$, the masses of $\rho$, $\omega$, $K^{*}(892)$, $m_{\phi}$, $a_{1}$, $f_{1}(1286)$, $K_{1}(1400)$, and $f_{1}(1510)$ mesons originate from dynamical chiral symmetry breaking.
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arxiv:hep-ph/9509368
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We use heavy vector meson $SU(2)_L \times SU(2)_R$ chiral perturbation theory to predict differential decay distributions for $\tau \rightarrow \rho \pi \nu_\tau$ and $\tau \rightarrow K^* \pi \nu_\tau$ in the kinematic region where $p_V \cdot p_\pi/m_V$ (here $V = \rho$ or $K^*$) is much smaller than the chiral symmetry breaking scale. Using the large number of colors limit we also predict the rate for $\tau \rightarrow \omega \pi \nu_\tau$ in this region (now $V = \omega$). Comparing our prediction with experimental data, we determine one of the coupling constants in the heavy vector meson chiral Lagrangian.
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arxiv:hep-ph/9509414
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The QCD corrections for the box diagrams are revisited for the case of a heavy top quark with $\mt = 174 \GeV$. We resolve first a longstanding discrepancy between two methods of calculation by showing that they give the same results when the threshold factors are treated correctly. Using this observation we refine our earlier results and derive formulae valid for the $K$- and $B$-meson systems. Our formulae are given in terms of integrals to be evaluated numerically, as well as approximate analytical formulae. These calculations include the evolution above $\MW$ which has been neglected by other authors.
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arxiv:hep-ph/9509420
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It is suggested that virtual gluon-clusters exist in nucleon, and that such colorless and colored objects manifest themselves in the small $x_B$ region of inelastic lepton-nucleon scattering processes. The relationship between the space-time properties of such clusters and the striking features observed in these scattering processes is discussed. A phase-space model is used to show how quantitative results can be obtained in such an approach. The results of this model-calculation are in reasonable agreement with the existing data. Further experiments are suggested.
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arxiv:hep-ph/9509422
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Numerical calculations for the production of $P$-wave levels of $B_c$ quarkonium in $\gamma\gamma$ collisions are performed in the leading $O(\alpha_s^2\alpha_{em}^2)$ order of perturbation theory. The total cross-section of $P$-wave state production is about 10 \% of that for the $S$-wave levels. The contribution of fragmentation component ($6+6$ diagrams) is low, and the basic contribution is determined by the recombination mechanism ($8$ Feynman diagrams). The gauge invariant term of the $\bar b\to B_c$ fragmentation ($6$ diagrams) quite accurately reproduces the result of the fragmentation model, whereas there is a strong deviation of the $c\to B_c$ fragmentation term from the predictions of the fragmentation model.
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arxiv:hep-ph/9510238
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A review of the present knowledge on polarized parton distributions is given. The effects of perturbative evolution on these distributions are discussed qualitatively and a comparison of various recent parametrizations is made.
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arxiv:hep-ph/9510243
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I review the prospects for measuring the properties of the top quark at the Tevatron, with an integrated luminosity of 2 fb$^{-1}$ or more, and at LHC in the early running at instantaneous luminosities of $10^{32}-10^{33}~cm^{-2}~s^{-1}$.
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arxiv:hep-ph/9510274
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The following aspects of hadronic final states in deep inelastic lepton scattering are reviewed: measuring $alpha_s$ from multi-jet production rates and event shapes; alternative jet algorithms for DIS; power-suppressed corrections to event shapes; comparing jet fragmentation in $e^+e^-$ annihilation and DIS; final states in the BFKL and CCFM formulations of small-$x$ dynamics; exotic (instanton-induced) final states.
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arxiv:hep-ph/9510283
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The relativistic fermion-antifermion bound state vector potential of constraint theory is calculated, in perturbation theory, by means of the Lippmann-Schwinger type equation that relates it to the scattering amplitude. Leading contributions of n-photon exchange diagrams are calculated in an approximation scheme that adapts eikonal approximation to the bound state problem. They produce terms proportional, in three-dimensional x-space, to $(\alpha/r)^n$. The series of leading contributions is summed.
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arxiv:hep-ph/9510302
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The special role played by singly polarized high-energy hadron-hadron collisions in Spin Physics is discussed: In such processes, the measured and the calculated quantities can be and have been directly compared with each other --- without data-extrapolation and without sum rules. It is in this kind of processes, where significant asymmetries (up to 30-40\%) have been observed. It is also in this kind of processes, where the obtained data and the predictions of the conventional theories dramatically disagree with each other. Attempts to understand the existing data are briefly summarized. Predictions for further experiments are presented.
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arxiv:hep-ph/9510336
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In the Nambu--Jona-Lasinio (NJL-) model baryons are considered either as quark-diquark-composites or as soliton configurations of mesons. The construction of a hybrid model, which possesses a dynamical interplay between both pictures, is presented. The Bethe-Salpeter equation for diquarks and the Faddeev equation for diquark-quark bound states in the background of a soliton configuration is solved.
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arxiv:hep-ph/9510382
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I summarize the results of the complete one--loop chiral perturbation theory calculation performed recently. It is shown that it allows to accurately pin down the isospin two, S--wave $\pi \pi$ scattering length $a_0^2$. On the other hand, interesting resonance physics makes a precise determination of $a_0^0$ very difficult.
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arxiv:hep-ph/9510390
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It is shown that single and double spin asymmetries in polarized diffractive $Q \bar Q$ production depend strongly on the spin structure of the quark-pomeron vertex. They can be studied in future spin experiments at HERA.
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arxiv:hep-ph/9510405
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An introduction to the minimal supersymmetric Standard Model (MSSM) is given. The motivation for ``low-energy'' supersymmetry is reviewed, and the structure of the MSSM is outlined. In its most general form, the MSSM can be viewed as a low-energy effective theory parametrized by a set of arbitrary soft-supersymmetry-breaking parameters. A variety of techniques for reducing the parameter freedom of the MSSM are surveyed. The search for supersymmetry below and above the threshold for supersymmetric particle production presents a challenging task for experimentalists at present and future colliders.
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arxiv:hep-ph/9510412
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In this paper, we develop a weak-coupling treatment of nonperturbative QCD to heavy hadrons on the light-front. First, we present a derivation of quark confining interaction in light-front QCD for heavy quark systems, based on the recently developed light-front similarity renormalization group approach and the light-front heavy quark effective theory. The resulting effective light-front QCD Hamiltonian $H_\lambda$ at a low-energy cutoff $\lambda$ manifests the coexistence of a confining potential and a Coulomb potential. A clear light-front picture of quark confinement emerges. Using this low energy QCD Hamiltonian $H_\lambda$, we study heavy hadron bound state equations in the framework of a recently proposed possible weak-coupling treatment of non-perturbative QCD. Light-front heavy hadron bound states with definite spin and parity are constructed and the general structure of the corresponding wavefunctions is explored. A Gaussian-type wavefunction ansatz is used to solve the light-front quarkonium bound state equation. We find that the effective coupling constant determined from the quarkonium bound state equation can be arbitrarily small so that the weak-coupling treatment to heavy hadron bound states in light-front QCD is explicitly achieved. Finally, the scale dependence of the effective coupling constant is analytically calculated and the similarity renormalization group $\beta$ function is determined, from which the running coupling constant in small momentum transfer is given qualitatively by $\overline{\alpha}(Q^2) \sim {\Lambda_{QCD}^2 \over Q^2}$. Such a running coupling constant is the basic assumption in the successful Richardson $Q\overline{Q}$ potential that ensures the existence of a linear confining potential at large distance, but now can be obtained from light-front QCD.
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arxiv:hep-ph/9510428
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We discuss possible symmetries of effective theories describing spinless and spin 1 bosons, mainly to concentrate on an intriguing phenomenological possibility: that of a hardly noticeable strong electroweak sector at relatively low energies. Specifically, a model with both vector and axial vector strong interacting bosons may possess a discrete symmetry imposing degeneracy of the two sets of bosons (degenerate BESS model). In such a case its effects at low energies become almost invisible and the model easily passes all low energy precision tests. The reason lies essentially in the fact that the model automatically satisfies decoupling, contrary to models with only vectors. For large mass of the degenerate spin one bosons the model becomes identical at the classical level to the standard model taken in the limit of infinite Higgs mass. For these reasons we have thought it worthwhile to fully develop the model, together with its possible generalizations, and to study the expected phenomenology. For instance, just because of its invisibility at low energy, it is conceivable that degenerate BESS has low mass spin one states and gives quite visible signals at existing or forthcoming accelerators.
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arxiv:hep-ph/9510431
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We extract information on the fluxes of Be and CNO neutrinos directly from solar neutrino experiments, with minimal assumptions about solar models. Next we compare these results with solar models, both standard and non standard ones. Finally we discuss the expectations for Borexino, both in the case of standard and non standard neutrinos.
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arxiv:hep-ph/9511286
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The instanton contribution to the quark distribution functions in the nucleon is estimated. It is shown, that taking into account the instanton induced interaction between quarks allows to explain the anomalous violation of the Ellis-Jaffe and Gottfried sum rules. The spin-dependent structure functions $g_1^p(x)$, $g_1^n(x)$, $g_1^d(x)$ are calculated in the framework of the instanton model of the QCD vacuum.
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arxiv:hep-ph/9511299
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We demonstrate that detection of the heavier minimal supersymmetric model CP-even Higgs boson $H^0$ will be possible at the LHC via its $H^0\to h^0h^0\to 4b$ and/or $H^0\to A^0A^0\to 4b$ decay channels for significant portions of the $( m_{A^0},\tan\beta)$ model parameter space. At low $ m_{A^0}$ ($\lsim 60\gev$), {\it both} the $H^0\to A^0A^0\to 4b$ and $H^0\to h^0h^0\to 4b$ modes yield a viable signal for most $\tan\beta$ values; viability for the $h^0h^0$ channel extends up to $\mhh\sim 2\mt$ when the model parameter $\tan\beta$ is not large. At the Tevatron, the $h^0h^0$ and $A^0A^0$ channels are both potentially viable at low $ m_{A^0}$ for sufficiently good $b$-tagging efficiency and purity.
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arxiv:hep-ph/9511319
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We have found in numerical simulations that the chaoticity of the classical hamiltonian lattice SU(2) gauge theory is reduced in the presence of static charges at the same total energy. The transition from strongly to weakly chaotic behavior is rather sudden at a critical charge strength.
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arxiv:hep-ph/9511354
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