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arxiv:hep-ph/9511359
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A computer study is performed to estimate the influence of the small-$k_T$ region in the BFKL evolution equation. We consider the small-x region of the deep inelastic structure function $F_2$ and show that the magnitude of the small-$k_T$ region depends on $Q^2$ and $x_B$. We suggest that the width of the $\log k_T^2$-distribution in the final state may serve as an additional footprint of BFKL dynamics. For diffractive dissociation it is shown that the contribution of the infrared region is large - even for large $Q^2$. This contribution becomes smaller only if restrictions on the final state are imposed.
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arxiv:hep-ph/9511399
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We present a detailed discussion of the particle spectrum of the Non-Minimal Supersymmetric Standard Model (NMSSM), containing two Higgs doublets and a singlet, in the limit $\tan\beta \simeq m_t/m_b$. This is compared with the corresponding particle spectrum of the Minimal Supersymmetric Standard Model (MSSM). In this limit the singlet vacuum expectation value is forced to be large, of the order of $10$ TeV, and the singlet decouples from the lightest scalar Higgs boson and the neutralinos. With the exception of the lightest Higgs boson, the particle spectrum in the model turns out to be heavy. The radiatively corrected lightest Higgs boson mass is in the neighbourhood of $\sim 130$ GeV.
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arxiv:hep-ph/9511415
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$D^0-\bar{D}^0$ mixing leads to the mass and width differences in the mass eigenstates of $D^0$ and $\bar{D}^0$ mesons (measured by parameters $x^{~}_D$ and $y^{~}_D$ respectively), but their magnitudes cannot be reliably predicted by the standard model. We show that it is possible to separately determine $x^{~}_D$ and $y^{~}_D$ through {\it time-integrated} measurements of the dilepton events of coherent $D^0\bar{D}^0$ decays on the $\psi(4.14)$ resonance at a $\tau$-charm factory.
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arxiv:hep-ph/9512217
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The algebraic content of chiral symmetry constrains the strong interactions of mesons containing a single heavy quark. We show that the S-wave single-pion transition amplitudes of all heavy meson states are determined as a consequence of the participation of these states in reducible multiplets of unbroken $SU(2)_L\times SU(2)_R$. We find this representation content by making use of phenomenologically inspired Lie-algebraic sum rules, together with QCD constraints on the heavy meson spectrum in the heavy quark limit. For example, the transition amplitude for the process $P^*\rightarrow P\pi$, where $P$ is a $D$ or a $B$ meson, is predicted to vanish. We also consider the Kaon system in light of our general conclusions for $I=\oneh$ states.
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arxiv:hep-ph/9512228
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We discuss the potential for making precision measurements of $M_W$ and $M_T$ at a muon collider and the motivations for each measurement. A comparison is made with the precision measurements expected at other facilities. The measurement of the top quark decay width is also discussed.
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arxiv:hep-ph/9512260
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The theoretical status of perturbative QED and QCD corrections to deep inelastic scattering is reviewed.
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arxiv:hep-ph/9512272
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It has now become possible to observe appreciable numbers of hadronically produced lepton pairs in mass ranges where the contributions of the photon and $Z^0$ are comparable. Consequently, in the reaction $p \bar p \to \ell^- \ell^+ + \ldots$, substantial forward-backward asymmetries can be seen. These asymmetries provide a test of the electroweak theory in a new regime of energies, and can serve as diagnostics for any new neutral vector bosons coupling both to quarks and to charged lepton pairs.
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arxiv:hep-ph/9512299
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The influence of strong and electroweak penguin amplitudes in $B/ \bar B \rightarrow \pi^+\pi^-$ is investigated in connection with the determination of the unitarity triangle angle $\alpha$ of the CKM matrix. A relation between the observable asymmetry, the angle $\alpha$, and the penguin amplitude is established. A model calculation of the penguin amplitude shows that the CP asymmetry in $B^{0}\rightarrow \pi^{+}\pi^{-}$ decays is only mildly influenced by the penguin amplitudes. Experimental limits on pure penguin and penguin dominated processes are consistent with the model. This information also suggests in a rather model independent way that penguin amplitudes will not be a serious complicating factor in the determination of $\alpha$ from the $\pi^{+}\pi^{-}$ time dependent asymmetry.
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arxiv:hep-ph/9512341
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The elastic and inelastic high--energy small--angle electron--positron scattering is considered. All radiative corrections to the cross--section with the relative accuracy $\delta\sigma/ \sigma = 0.1 \% $ are explicitly taken into account. According to the generalized eikonal representation for the elastic amplitude, in higher orders only diagrams with one exchanged photon may be considered. Single photon emission with radiative corrections and next--to--leading two--photon and pair production diagrams are evaluated, together with leading three--loop corrections. All contributions have been calculated analytically. We integrate the calculated distributions over typical for LEP~1 experiments intervals of angles and energies. To the leading approximation, the results are shown to be described in terms of kernels of electron structure functions. Some numerical results are presented. PACS numbers 12.15.Lk, 12.20.--m, 12.20.Ds, 13.40.--f
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arxiv:hep-ph/9512344
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We use the BLM scale-fixing prescription to derive a renormalization-scheme invariant relation between the coefficient function for the Bjorken sum rule for polarized deep inelastic scattering and the $R$-ratio for the $e^+e^-$ annihilation cross section. This relation provides a generalization of the Crewther relation to non-conformally invariant gauge theories. The derived relations allow one to calculate unambiguously without renormalization scale or scheme ambiguity the effective charges of the polarized Bjorken and the Gross-Llewellen Smith sum rules from the experimental value for the effective charge associated with $R$-ratio. Present data are consistent with the generalized Crewther relations, but measurements at higher precision and energies will be needed to decisively test these fundamental relations in QCD.
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arxiv:hep-ph/9512367
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We consider the twist-3 gluon contribution to the transverse spin structure function $g_2$.We find that the Burkhardt-Cottingham sum rule is satisfied. The additional {\it nonlocal} operators appear in the moments of g2 which were absent in previous analysis of Bukhvostov, Kuraev and Lipatov.
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arxiv:hep-ph/9512377
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A constituent quark model is developed for an arbitrary light- cone direction \omega. Form factors are obtained from free one-body electromagnetic current matrix elements. They are found to be \omega- independent for spin-0 mesons, the nucleon and \Lambda hyperon, while there is \omega-dependence for spin-1 systems like the deuteron.
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arxiv:hep-ph/9512382
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We consider resonant neutrino conversions in magnetised matter, such as a degenerate electron gas. We show how magnetisation effects caused by axial vector interactions of neutrinos with the charged leptons in the medium can induce a new type of resonant neutrino conversion which may occur even in situations where the MSW effect does not occur, such as the case of degenerate or inverted neutrino mass spectra. Our new resonance may simultaneously affect anti-neutrino $\bar{\nu_a} \leftrightarrow \bar{\nu}_b$ as well as neutrino $\nu_{a} \leftrightarrow \nu_b$ flavour conversions, and therefore it may substantially affect supernova neutrino energy spectra. Using SN1987A data we conclude that only laboratory experiments with long baseline such as ICARUS or MINOS are likely to find neutrino oscillations due to their sensitivity to small $\Delta m^2$. We also comment on the possibility of resonant conversions induced by Majorana neutrino transition moments and mention the case of sterile neutrinos $\nu_s$.
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arxiv:hep-ph/9512390
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It is proposed to use the pinch technique (PT) to obtain the gauge-independent thermal $\beta$ function $\beta_T$ in a hot Yang-Mills gas. Calculations of the thermal $\beta$ function are performed at one-loop level in four different gauges, (i) the background field method with an arbitrary gauge parameter, (ii) the Feynman gauge, (iii) the Coulomb gauge, and (iv) the temporal axial gauge. When the pinch contributions to the gluon self-energy are included, the same result is derived for $\beta_T$ in all four cases.
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arxiv:hep-ph/9512434
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We describe heavy baryons as bound states of a quark and a diquark. For this purpose we derive the Faddeev equation for baryons containing a single heavy quark from a Nambu-Jona-Lasinio type of model which is appropriately extended to include also heavy quarks. The latter are treated in the heavy mass limit. The heavy baryon Faddeev equation is then solved using a static approximation for the exchanged quark.
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arxiv:hep-ph/9601257
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Recent refinements of the phenomenology of Higgs bosons in the Standard Model and the Minimal Supersymmetric Standard Model are reviewed.
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arxiv:hep-ph/9601330
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The Donnachie-Landshoff fit of total cross sections has now become a standard reference for models of total, elastic and diffractive cross-sections. Adopting their philosophy that simple-pole exchanges should account for all data to present energies, we assess the uncertainties on their fits. Our best estimate for the pomeron intercept is $1.096^{+0.012}_{-0.009}$, but several models have a good chi square for intercepts in the range [1.07,1.11].
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arxiv:hep-ph/9601336
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We calculate $O(\alpha_s)$ corrections to inclusive and isolated double prompt photon production, both for the unpolarized case, and for longitudinal polarization of the incoming hadrons. The calculation is performed using purely analytical techniques for the inclusive case, and a combination of analytical and Monte Carlo techniques to perform the phase space integration in the isolated case. A brief phenomenological study is made of the process $pp\rightarrow \gamma \gamma X$ at CMS energies appropriate for the RHIC heavy ion collider.
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arxiv:hep-ph/9601350
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We analyze the capability of charm production in deep-inelastic ep scattering at HERA to constrain the gluon distribution g(y,\mu^2) of the proton. The dependence of the theoretical predictions for the charm structure function F_2^c on the mass factorization scale \mu and the charm mass is investigated. F_2^c seems to be well suited for a rather clean and local gluon measurement at small momentum fractions y.
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arxiv:hep-ph/9601352
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We obtain the low-energy effective theory from string models with anomalous $U(1)$ symmetry. The feature of soft supersymmetry breaking scalar masses and some phenomenological implications are discussed. We show that it is, in general, difficult to keep the degeneracy and the positivity of squared soft scalar masses at the Planck scale.
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arxiv:hep-ph/9601365
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The leading order coefficients of the beta-function of QCD are computed in a large N_f expansion. They are in agreement with the three loop MSbar calculation. The method involves computing the anomalous dimension of the operator (G^2_{mu nu})^2 at the d-dimensional fixed point in the non-abelian Thirring model to which QCD is equaivalent in this limit. The effect the O(1/N_f) corrections have on the location of the infrared stable fixed point for a range of N_f is also examined.
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arxiv:hep-ph/9602214
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We suggest a method of determination of the pion structure function down to x \simeq 10^{-4} based on semi-exclusive deep inelastic scattering off protons. The idea is to exploit the nonperturbative \pi N$ and \pi\Delta Fock components of the nucleon, which contribute significantly to deep inelastic scattering and dominate the fragmentation of protons into fast neutrons and deltas. The intrinsic factorization properties of the semi-exclusive cross section give a good test for the validity of this approach.
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arxiv:hep-ph/9602229
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Using the O(4) linear $\sigma$ model, we address the topic of non-equilibrium relaxation of an inhomogeneous initial configuration due to quantum and thermal fluctuations. The space-time evolution of an inhomogeneous fluctuation of the condensate in the isoscalar channel decaying via the emission of pions in the medium is studied within the context of disoriented chiral condensates. We use out of equilibrium closed time path methods in field theory combined with the amplitude expansion. We give explicit expressions for the asymptotic space-time evolution of an initial inhomogeneous configuration including the contribution of thresholds at zero and non-zero temperature. At non-zero temperature we find new relaxational processes due to thermal cuts that have no counterpart in the homogeneous case. Within the one-loop approximation, we find that the space time evolution of such inhomogeneous configuration out of equilibrium is effectively described in terms of a rapidity dependent temperature $T(\vartheta)=T/\cosh[\vartheta]$ as well as a rapidity dependent decay rate $\Gamma(\vartheta, T(\vartheta))$. This rate is to be interpreted as the production minus absorption rate of pions in the medium and approaches the zero temperature value at large rapidities. An initial configuration localized on a bounded region spreads and decays in spherical waves with slower relaxational dynamics at large rapidity.
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arxiv:hep-ph/9602232
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The 1/m corrections to heavy baryon masses are calculated from the QCD sum rules within the framework of the heavy quark effective theory. Numerical results for the heavy baryons are obtained. The implications of the results are discussed.
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arxiv:hep-ph/9602242
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We develop the pQCD description of the diffraction dissociation (DD) of longitudinal photons. We demonstrate that the longitudinal diffractive structure function does not factor into the flux of pomerons and the partonic structure function of the pomeron, thus defying the usually assumed Regge factorization. In contrast to DD of the transverse photons, DD of the longitudinal photons is strongly peaked at $\beta =1$. We comment on duality properties of DD in deep inelastic scattering.
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arxiv:hep-ph/9602246
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The perturbative QCD corrections to the nonleptonic decay rate of the $b$ quark are discussed. By considering the limit where the final charmed quarks are slow, it is argued that the coefficients of the $\alpha_s^2$ terms, corresponding to next-to-next-to-leading order in the standard renormalization group expansion in $\ln (m_W/m_b)$, are naturally large. The large coefficients arise from the final-state gluon exchange between quarks and are associated with the region of rather low momenta, which may further enhance the phenomenological significance of these terms.
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arxiv:hep-ph/9602256
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We study the system of multi color-flux-tubes in terms of the dual Ginzburg -Landau theory. We consider two ideal cases, where the directions of all the color-flux-tubes are the same in one case and alternative in the other case for neighboring flux-tubes. We formulate the system of multi color-flux -tubes by regarding it as the system of two color-flux-tubes penetrating through a two dimensional sphere surface. We find the multi flux-tube configuration becomes uniform above some critical flux-tube number density $\rho_c = 1.3 \sim 1.7 {\rm fm}^{-2}$. On the other hand, the inhomogeneity on the color electric distribution appears when the flux-tube density is smaller than $\rho_c$. We discuss the relation between the inhomogeneity in the color-electric distribution and the flux-tube number density in the multi-flux-tube system created during the QGP formation process in the ultra-relativistic heavy-ion collision.
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arxiv:hep-ph/9602412
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We have calculated inclusive one-- and two--jet production in photon--photon collisions superimposing direct, single resolved and double resolved cross sections for center of mass energies of the LEP1, LEP2 and NLC range. The direct and single resolved cross sections are calculated up to next--to--leading order. The double resolved two--jet cross section is calculated only in LO with a $k$ factor estimated from the NLO one--jet cross section. Various differential cross sections as functions of transverse momenta and rapidities of the jets are evaluated.
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arxiv:hep-ph/9602418
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In this brief report we adress spontaneous symmetry breaking in a finite-temperature scalar meson plasma. We calculate the in-medium averaged thermal $\sigma-\sigma$ scattering crossection and the related shear viscosity $\eta(T)$ and mean-free-path $L(T)$. Our results suggest that slightly below the critical temperature there is a 30 percent peak in the crossection leading to equivalent dips in $\eta(T)$ and $L(T)$. We discuss the relevance of this observation.
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arxiv:hep-ph/9602427
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We calculate the supersymmetric QCD corrections in order $\alpha_s$ to the cross section $e^+ e^- \to \sq_i \bar\sq_j$ $(i,j = 1, 2)$ within the Minimal Supersymmetric Standard Model. We pay particular attention to the case of the left--right squark mixing and to the renormalization of the mixing angle. The corrections due to gluino exchange turn out to be smaller than those due to gluon exchange, but they can be significant at higher energies even for a gluino mass of a few hundred GeV.
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arxiv:hep-ph/9603206
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A recent global analysis of direct photon production at hadron collider and fixed target experiments has noted a disturbing trend of disagreement between next-to-leading-order (NLO) calculations and data. The conjecture has been made that the discrepancy is due to explicit multiple parton emission effects which are not accounted for in the theoretical calculations. We investigate this problem by merging a NLO calculation of direct photon production with extra multiple parton emissions via the parton shower (PS) algorithm. Our calculation maintains the integrity of the underlying NLO calculation while avoiding ambiguities due to double counting of multiple parton emissions. We find that the NLO+PS calculation can account for much of the theory/CDF data discrepancy at $\sqrt{s}=1.8$ TeV. It can also account for much of the theory/UA2 discrepancy if a very large virtuality is assumed to initiate the initial state parton shower. For lower energy data sets ({\it e.g.} $\sqrt{s}< 63$ GeV), NLO+PS calculations alone cannot account for the data/theory discrepancy, so that some additional non-perturbative $k_T$ smearing is needed.
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arxiv:hep-ph/9603209
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The QCD structure of the electron is defined and calculated. The leading order splitting functions are extracted, showing an important contribution from $\gamma$-$Z$ interference. Leading logarithmic QCD evolution equations are constructed and solved in the asymptotic region where log$^2$ behaviour of the parton densities is observed. Corrections to the naive evolution procedure are demonstrated. Possible applications with clear manifestation of 'resolved' photon and weak bosons are discussed.
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arxiv:hep-ph/9603284
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We show that the Gottfried and the Bjorken integrals have the same nonperturbative evolution, which is related to the gluon polarization in the proton.
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arxiv:hep-ph/9603286
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We study the decay $B_c \rightarrow D_s^* \gamma$. There are two mechanisms contributing to the process. One proceeds through the short distance $b{\rightarrow}s\gamma$ transition and the other occurs through weak annihilation accompanied by a photon emission.The electromagnetic penguin contribution is estimated by perturbative QCD and found to be $4.68\times10^{-18}$ GeV. In particular, we find the contribution of the weak annihilation is $6.25\times10^{-18}GeV$ which is in the same order as that of the electromagnetic penguin. The total decay rate $\Gamma(B_c \rightarrow D_s^* \gamma)$ is predicted to be $1.45\times10^{-17}GeV$ and the branching ratio $Br(B_c \rightarrow D_s^* \gamma)$ is predicted to be $2.98\times 10^{-5}$ for $\tau_{B_c}=1.35ps$. The the decays $B_c \rightarrow D_s^* \gamma$ can be well studied at LHC in the near future.
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arxiv:hep-ph/9603291
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It is unlikely to reach at high temperatures the state which is used as the starting point of DCC formation in the quenched approximation. The chiral symmetry is restored in the linear sigma model by Goldstone modes (pions), because such isospin-p-wave states carry more entropy. In this paper we estimate this effect of isospin-angular motion in the mean field approximation assuming equipartition of the energy.
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arxiv:hep-ph/9603299
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We study the semileptonic branching fraction of $B$-meson into higher resonance of charmed meson $D^{**}$ by using the Bjorken sum rule and the heavy quark effective theory(HQET). This sum rule and the current experiment of $B$-meson semileptonic decay into $D$ and $D^*$ predict that the branching ratio into $D^{**}l\nu_l$ is about 1.7\%. This predicted value is larger than the value obtained by the various theoretical hadron models based on the HQET.
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arxiv:hep-ph/9603355
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In recent studies it has become increasingly clear that presence of infinitely many instability bands of the parametric resonance plays crucial roles in the phenomenon of particle production under periodic classical field oscillation. We extend previous works to a general class of models including both the Yukawa and the quartic type of couplings of the classical field to quantum bose fields. Decay rate from the $n-$th band is derived in the small amplitude limit using the functional Schr$\stackrel{..}{{\rm o}}$dinger picture. It is then shown that this analytic result of the decay rate can also be derived as the zero momentum limit of a physical process, $n$ particles that comprise the classical homogeneous field decaying simultaneously into 2 bose particles. The latter approach uses ordinary perturbation theory, hence the former result is a novel resummation of many perturbative amplitudes, which usually becomes complicated for a large $n$ order.
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arxiv:hep-ph/9603356
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The rise with energy of the neutrino--nucleon cross section implies that at energies above few TeV the Earth is becoming opaque to cosmic neutrinos. The neutrinos interact with the nucleons through the weak charged current, resulting into absorption, and the weak neutral current, which provides a redistribution of the neutrino energy. We Mellin transform the neutrino transport equation and find its exact solution in the moment space. A simple analytical formula is provided, which describes accurately the neutrino spectrum, after the neutrinos have traversed the Earth. The effect of the weak neutral current is most prominent for an initial flat neutrino spectrum and we find that at low energies (around 1 TeV) the neutrino intensity is even enhanced.
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arxiv:hep-ph/9603382
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We present and study the results for the standard model process $e^+e^-\to \nu\bar{\nu}b\bar{b}$ at c.m energies 150$\leq \sqrt{s} (GeV) \leq $ 240 and for Higgs boson masses $80 GeV \leq m_H \leq 120 GeV$, obtained from all tree-level diagrams and including the most important radiative corrections. The $\sqrt{s}$ dependence and the interference properties of the Higgs boson contribution and of various coherent background contributions to the total cross section are examined. The effect of the QED initial state radiative corrections is estimated. The important differential distributions for the Higgs boson and the background components are studied, providing information usefull for choosing cuts in Higgs searches. We also examine the effect of a minimal set of cuts and evaluate the importance of the WW fusion for detecting a higher mass Higgs boson at LEPII.
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arxiv:hep-ph/9603383
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We consider interactions of fermions with the domain wall bubbles produced during the first order phase transitions. New exact solution of Dirac equations and reflection coefficient are obtained.
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arxiv:hep-ph/9603395
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Taking into account the mixing effects between left- and right-handed top-squarks, we calculate the genuine supersymmetric eletroweak correction to top quark production at the Tevatron in the minimal supersymmetric model. The analytic expressions of the corrections to both the parton level cross section and the total hadronic cross section are presented. Some numerical examples are also given to show the size of the corrections.
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arxiv:hep-ph/9603442
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New physics can be searched for in deep inelastic scattering experiments. New phenomena, like additional production mechanisms for heavy quarks, manifest themselves through production and decays of short-lived hadrons, which give additional muons in their decays. Muons from decays of light mesons can then be a severe background, especially at fixed target experiments. In order to make a first estimate of such a background a simple analytic method is here developed and applied on the muon scattering experiment NMC.
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arxiv:hep-ph/9604291
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Evolution of structure functions is studied in a chiral potential model which incorporates the pion as the chiral symmetry restoring field. Evolution equations for the quark and pion densities are derived in the lowest order at large $Q^2$. The splitting function for quark emission from point-like pion is flavor-dependent. This is shown to lead to nontrivial evolution of the nonsinglet moments in the next order which is consistent with the observed departure from the Gottfried sum rule.
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arxiv:hep-ph/9604292
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Final state interactions in the $S$--wave $\pi\pi$ system (I=0,2) are re-examined on the basis of the Omn\`es-Mus\-khe\-li\-shvili equation and the coupled channel formalism. The contributions to the pion scalar form factor from $\rho$ and $f_2(1270)$ exchange in the $t$--channel and from the $f_0(980)$ $s$--channel resonance are separately evaluated and the role of the nontrivial polynomial in the Omn\`es function in a coupled channel situation is elucidated. Applications are made to $K\to \pi\pi$ and $pp\to pp\pi\pi$. It is found that the contribution from the $f_0$ resonance to the form-factor is strongly reduced by a nearby zero.
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arxiv:hep-ph/9604310
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I outline a perturbative QCD approach to the analysis of the deeply virtual Compton scattering process $\gamma^* p \to \gamma p'$ in the limit of vanishing momentum transfer $t= (p' - p)^2$. The DVCS amplitude in this limit exhibits a scaling behaviour described by a two-argument distributions $F(x,y)$ which specify the fractions of the initial momentum $p$ and the momentum transfer $r \equiv p'-p$ carried by the constituents of the nucleon.The kernel $R(x,y;\xi,\eta)$ governing the evolution of the non-forward distributions $F(x,y)$ has a remarkable property: it produces the GLAPD evolution kernel $P(x/\xi)$ when integrated over $y$ and reduces to the Brodsky-Lepage evolution kernel $V(y,\eta)$ after the $x$-integration. This property is used to construct the solution of the one-loop evolution equation for the flavour non-singlet part of the non-forward quark distribution.
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arxiv:hep-ph/9604317
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(1) A simple transversity analysis permits one to separate the P-even and P-odd partial waves in such decays as $B_s \to J/\psi \phi$ and $B \to J/\psi K^*$. This method is relevant to the separation of contributions of CP-even and CP-odd final states in $B_s$ decays, and hence to the measurement of a possible lifetime difference between mass eigenstates. (2) The enhancement $\Delta \Gamma (\Lambda_b)$ of the $\Lambda_b$ decay rate due to four-fermion processes is calculated in terms of the $\Sigma_b^* - \Sigma_b$ hyperfine splitting, the $B^* - B$ hyperfine splitting, and the $B$ meson decay constant $f_B$. Despite a relatively large hyperfine splitting observed by the DELPHI Collaboration, the mechanism falls far short of being able to explain the observed enhancement.
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arxiv:hep-ph/9604319
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We consider the possibility of having a large branching ratio for the decay $b\to s g$ coming from an enhanced Wilson coefficient of the chromomagnetic dipole operator. We show that values of $BR(b\to s g)$ up to $\sim 10\%$ or more are compatible with the constraints coming from the CLEO experimental results on $BR(B\to X_s\gamma)$ and $BR(B\to X_s\phi)$. Such large values can reconcile the predictions of both the semileptonic branching ratio and the charm counting with the present experimental results. We also discuss a supersymmetric model with gluino-mediated flavour violations, which can account for such large values of $BR(b\to s g)$.
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arxiv:hep-ph/9604438
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The tensor charges of the nucleon are calculated in the framework of the SU(3) chiral quark soliton model. The rotational $1/N_c$ and strange quark mass corrections are taken into account up to linear order. We obtain the following numerical values of the tensor charges: $\delta u=1.12$, $\delta d=-0.42$, and $\delta s=-0.008$. In contrast to the axial charges, the tensor charges in our model are closer to those of the nonrelativistic quark model, in particular, the net number of the transversely polarized strange quarks in a transversely polarized nucleon $\delta s$ is compatible with zero.
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arxiv:hep-ph/9604442
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As the excitement surrounding the heavy top quark discovery subsides, while the expectation for LEP II physics gathers, it is a good time to sit back and reflect on whether energy regions available to us have been fully explored. We emphasize that a loophole exists where heavy quarks, perhaps the actual top quark itself, could still be hidden below $M_W$. This would typically involve scalar induced decays of the heavy quark, and could be realized in models with more than one Higgs doublet, e.g. MSSM. We illustrate such mechanisms with two Higgs doublet models, the addition of singlet quarks, as well as reconsidering a fourth family of quarks and leptons. Curiously, the present $R_b$--$R_c$ problem may be a harbinger of such scenarios. Given that LEP-II would be running soon, and in view of the large amount of data that the Tevatron has collected, we urge our experimental colleagues to conduct a critical analysis.
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arxiv:hep-ph/9605203
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We review the latest information that is available about the parton distributions of the proton, paying particular attention to the determination of the gluon. We briefly describe the various processes that have been advocated to be a measure of the gluon. We discuss the importance of the gluon to the description of the structure function F2 at small x, with emphasis on the ln 1/x resummations.
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arxiv:hep-ph/9605271
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A relativistic generalisation of a well-known method for approximating the dynamics of topological defects in condensed matter is constructed, and applied to the evolution of domain walls in a cosmological context. It is shown that there are self-similar ``scaling'' solutions, for which one can in principle calculate many quantities of interest without recourse to numerical simulations. Here, the area density in the scaling regime is calculated in various backgrounds. Remarkably good agreement with numerical simulations is obtained.
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arxiv:hep-ph/9605332
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The production mechanisms and decay modes of the heavy neutral and charged Higgs bosons in the Minimal Supersymmetric Standard Model are investigated at future $e^+ e^-$ colliders in the TeV energy regime. We generate supersymmetric particle spectra by requiring the MSSM Higgs potential to produce correct radiative electroweak symmetry breaking, and we assume a common scalar mass $m_0$, gaugino mass $m_{1/2}$ and trilinear coupling $A$, as well as gauge and Yukawa coupling unification at the Grand Unification scale. Particular emphasis is put on the low $\tb$ solution in this scenario where decays of the Higgs bosons to Standard Model particles compete with decays to supersymmetric charginos/neutralinos as well as sfermions. In the high $\tb$ case, the supersymmetric spectrum is either too heavy or the supersymmetric decay modes are suppressed, since the Higgs bosons decay almost exclusively into $b$ and $\tau$ pairs. The main production mechanisms for the heavy Higgs particles are the associated $AH$ production and $H^+H^-$ pair production with cross sections of the order of a few fb.
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arxiv:hep-ph/9605339
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The next-to-next-to-leading order (NNLO) non-singlet QCD analysis of the experimental data of the CCFR collaboration for the $xF_3$ and $F_2$ structure functions of the deep-inelastic scattering of neutrinos and antineutrinos on the nucleon by means of the Jacobi polinomial expansion method is made. The target mass corrections are also taken into account. We demonstrate that the NNLO corrections have the important: they are decreasing the difference between the values of $\alpha_s(M_Z)$, extracted from the NLO fit of $xF_3$ data and from the NLO non-singlet fit of the combined $xF_3$ and $F_2$ CCFR data. The obtained NNLO results for $\alpha_s(M_Z)$ are :$\alpha_s(M_Z)=0.109 \pm 0.003(stat) \pm 0.005(syst) \pm 0.003 (theor)$ (from $xF_3$ data) and $\alpha_s(M_Z)=0.111\pm 0.002 (stat) \pm 0.003 (syst) \pm 0.003 (theor)$ (from the combined $xF_3$ and $F_2$ data). We also estimate the values of the order $O(\alpha_s^2)$-corrections to the Gottfried sum rule.
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arxiv:hep-ph/9605367
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Resummation of large infrared logarithms in perturbation theory can, in certain circumstances, enhance the sensitivity to small gluon momenta and introduce spurious nonperturbative contributions. In particular, different procedures -- equivalent in perturbation theory -- to organize this resummation can differ by $1/Q$ power corrections. The question arises whether one can formulate resummation procedures that are explicitly consistent with the infrared behaviour of finite-order Feynman diagrams. We explain how this problem can be treated and resolved in Drell-Yan (lepton pair) production and briefly discuss more complicated cases, such as top quark production and event shape variables in the $e^+e^-$ annihilation.
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arxiv:hep-ph/9605375
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We provide high-energy approximations for all one-loop scalar 3- and 4-point functions and the corresponding tensor integrals that appear in scattering processes with four external on-shell particles. Our expressions are valid if all kinematical invariants are much larger than the internal and external masses. They contain all leading-order terms of the integrals.
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arxiv:hep-ph/9605420
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An important issue in the direct reconstruction method of determining the $W$ mass from $q\bar q Q\bar Q$ events at LEP2 concerns the impact of the relatively unknown QCD interconnection effects. It has been suggested that a study of `short string' states, in which colour singlet states are formed from $q \bar Q $ and $Q\bar q$ pairs with small phase--space separation, could shed important light on this issue. We show that such configurations can also be generated by conventional background $e^+e^-\ar 4$~parton processes, in particular QCD $q \bar q g g$ and $q \bar q Q \bar Q$ and non--resonant electroweak $q \bar q Q \bar Q$ production. We study the colour and kinematic structure of these background contributions, and estimate the event rate to be expected at LEP2. We find that the QCD processes are heavily suppressed, but that non--resonant $q \bar q Q \bar Q$ production may be comparable in rate to the expected `short string' signal from $W^+W^-$ production.
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arxiv:hep-ph/9605449
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In the light gluino variant of the minimal supersymmetric model gluino pairs can be readily produced in collider experiments even if the squarks are arbitrarily heavy. This enhances the jet transverse energy distributions. In addition the slower running of the strong coupling constant in the presence of light gluinos leads to a further enhancement at higher transverse energies relative to the standard $QCD$ expectations. Finally, the enhanced squark gluino production would lead to a Jacobian peak in the $E_T$ distribution at about $M_{\tilde Q}/2$. These effects are of about the right magnitude to explain anomalies observed by the $CDF$ and $D0$ collaborations.
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arxiv:hep-ph/9605463
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We consider restrictions imposed on the (electromagnetic or weak) current operator by its commutation relations with the representation operators of the Poincare group and show that the nonperturbative part of the current operator contributes to deep inelastic scattering even in leading order in $1/Q$ where $Q$ is the magnitude of the momentum transfer. Some consequences of this result are discussed.
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arxiv:hep-ph/9606204
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We explore the sensitivity to a non vanishing neutrino mass offered by dynamical observables, i.e., branching ratios and polarizations. The longitudinal polarization in the C.M. frame decreases by a 4% for $D^+ \rightarrow \tau^+ \nu_\tau$ and $m_{\nu_\tau}=24$ MeV. Taking advantage of the fact that the polarization is a Lorentz variant quantity, we study the polarization effects in a boosted frame. By means of a neutrino beam, produced by a high velocity boosted parent able to flip the neutrino helicity, we find that an enhanced left-handed neutrino deficit, induced by a Wigner rotation, appears.
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arxiv:hep-ph/9606218
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We have considered the penguin interaction contribution to $K \rightarrow 2 \pi$ decays. In particular, we have investigated the effect of the momentum dependence of the penguin coefficient. Our analysis is performed within the Chiral Quark Model where quarks are coupled to the pseudoscalar mesons, which means that hadronic matrix elements can be calculated in terms of quark loop diagrams. We have inserted the momentum dependent penguin coefficient into the relevant quark loop diagrams for $K \rightarrow \pi$. We discuss two possible prescriptions for performing the calculations, and conclude that the momentum dependence of the penguin coefficient increases the amplitude by 10-20 $\%$. In any case, the (CP-conserving) penguin contribution is very sensitive to the values chosen for the involved parameters.
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arxiv:hep-ph/9606245
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Recent results on the entirely analytic calculation of second order corrections to massive quark pair production vertices induced by light quark flavours are reviewed. Based on the method presented in this talk the second order effects of the insertion of any massless one-loop vacuum polarization into the gluon line of the first order diagrams can be determined. The behaviour of the corrections at threshold for vector and axial-vector current induced massive quark production is discussed.
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arxiv:hep-ph/9606288
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The twist three contributions to the $Q^2$-evolution of the spin-dependent structure function $g_2(x)$ are considered in the non-local operator product approach. Starting from the perturbative expansion of the T-product of two electromagnetic currents, we introduce the nonlocal light-cone expansion proved by Anikin and Zavialov and determine the physical relevant set of light-ray operators of twist three. Using the equations of motion we show the equivalence of these operators to the Shuryak-Vainshtein operators plus the mass operator, and we determine their evolution kernels using the light-cone gauge with the Leibbrandt-Mandelstam prescription. The result of Balitsky and Braun for the twist three evolution kernel (nonsinglet case) is confirmed.
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arxiv:hep-ph/9606320
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It is demonstrated that in simple soliton models essential features of the electro-magnetic nucleon form factors observed over three orders of magnitude in momentum transfer $t$ are naturally reproduced. The analysis shows that three basic ingredients are required: an extended object, partial coupling to vector mesons, and relativistic recoil corrections. We use for the extended object the standard skyrmion, one vector meson propagator for both isospin channels, and the relativistic boost to the Breit frame. Continuation to timelike $t$ leads to quite stable results for the spectral functions in the regime from the 2- or 3-pion threshold to about two rho masses. Especially the onset of the continuous part of the spectral functions at threshold can be reliably determined and there are strong analogies to the results imposed on dispersion theoretic approaches by the unitarity constraint.
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arxiv:hep-ph/9606336
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We show that inflation which is dominated by the D-term density avoids the `slow-roll' problem of inflation in supergravity. Such an inflationary scenario can naturally emerge in theories with non-anomalous or anomalous U(1) gauge symmetry. In the latter case the scale of inflation is fixed by the Green--Schwarz mechanism of anomaly cancellation. The crucial point is that the (super)gravity-mediated curvature of all the scalar fields (and, in particular, of the inflaton), which in the standard F-dominated case is of the order of the Hubble parameter, is absent in the D-term inflation case. The curvature of moduli and of all other flat directions during such an inflation crucially depends on their gauge charges.
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arxiv:hep-ph/9606342
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We study the coupling arising via perturbative QCD of zero 4-momentum Higgs bosons to light quarks inside the nucleon. Qualitative comparison with the results obtained from one-loop-order low energy theorems for the Higgs-nucleon interaction suggests the existence of a dynamical light-quark mass which falls off with momentum. Quantitative comparison leads to an estimate of $\alpha_s$ at very low $q^2$ quite near unity.
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arxiv:hep-ph/9606352
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We review recent experimental results on lifetimes and hadronic decays of hadrons that contain $c$ and $b$ quarks. The theoretical implications of these results are also considered. An understanding of hadronic decays of heavy quarks is required to interpret the CP violating asymmetries in $B$ decays that will be observed in experiments planned for the near future.
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arxiv:hep-ph/9606354
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A new analysis of S-wave production amplitudes for the reaction $\pi^- p_{\uparrow} \rightarrow \pi^+ \pi^- n$ on a transversely polarized target is performed. It is based on the results obtained by the CERN-Cracow -Munich collaboration in the pion-pion energy range from 600 MeV to 1600 MeV at 17.2 GeV/c $\pi^-$ momentum. Energy-independent separation of the S-wave pseudoscalar amplitude ($\pi$ exchange) from the pseudovector amplitude ($a_{1}$ exchange) is carried out using assumptions much weaker than those in all previous analyses. We show that, especially around 1000 MeV and around 1500 MeV, the $a_{1}$ exchange amplitude cannot be neglected. The scalar-isoscalar $\pi\pi$ phase shifts are calculated using fairly weak assumptions. Below the $K\overline{K}$ threshold we find two solutions for the $\pi-\pi$ phase shifts, for which the phases increase slower with the effective $\pi-\pi$ mass than the P-wave phases. Both solutions are consistent with a broad $f_{0}(500)$ but only one is similar to the well-known "down" solution. We find also the third solution (with a somewhat puzzling behavior of inelasticity) which exhibits a narrow $f_{0}(750)$ claimed by Svec. All the solutions undergo a rapid change at the $K\overline{K}$ threshold. Above 1420 MeV the phase shifts increase with energy faster than those obtained without the polarized-target data. This phase behavior as well as an increase of the modulus of the $a_{1}$-exchange amplitude can be due to the presence of the $f_{0}(1500)$.
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arxiv:hep-ph/9606362
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The HERA data at large $Q^2$ and small-$x$ investigate large distances on the light-cone. At such large distances the scattered quarks can maintain their colour identity by polarizing the vacuum as they transfer energy to it. We calculate the probability for the creation of quark-antiquark pairs from the polarized QCD vacuum and their contribution to the structure function.
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arxiv:hep-ph/9606373
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The two-loop electroweak radiative corrections to the muon's anomalous magnetic moment, $a_\mu\equiv (g_\mu-2)/2$, are presented. We obtain an overall 22.6\% reduction in the electroweak contribution $a_\mu^{\rm EW}$ from $195\times 10^{-11}$ to $151(4)\times 10^{-11}$. Implications for the full standard model prediction and an upcoming high precision measurement of $a_\mu$ are briefly discussed. Some aspects of the calculations are discussed in detail.
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arxiv:hep-ph/9606393
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We argue that the mass of the inflaton can be much smaller than the Hubble constant in supergravity models in which inflation is driven by D--terms and not F--terms. We investigate a supergravity toy model which leads to hybrid inflation due to an anomalous D--term. We show that the slow--roll condition can be satisfied and the correct magnitude for density perturbations can be obtained for some choice of model parameters. The kind of model considered can naturally arise in some string derived supergravity models.
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arxiv:hep-ph/9606423
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We study color fluctuations in the quark-gluon plasma produced at the early stage of nucleus-nucleus collision at RHIC or LHC. The fluctuating color current, which flows along the beam, can be very {\it large} due to the strong anisotropy of the parton momentum distribution. A specific fluctuation, which splits the parton system into the current filaments parallel to the beam direction, is argued to grow exponentially. The physical mechanism responsible for the phenomenon, which is known as a filamentation instability, is discussed.
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arxiv:hep-ph/9606442
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We re-examine resonant massless-neutrino conversions in a dense medium induced by flavour changing neutral current (FCNC) interactions. We show how the observed $\bar\nu_e$ energy spectra from SN1987a and the supernova $r$-process nucleosynthesis provide constraints on supersymmetric models with $R$ parity violation, which are much more stringent than those obtained from the laboratory. We also suggest that resonant massless-neutrino conversions may play a positive role in supernova shock reheating. Finally, we examine the constraints on explicit $R$-parity-violating FCNCs in the presence of non-zero neutrino masses in the eV range, as indicated by present hot dark matter observations.
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arxiv:hep-ph/9606445
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We consider inflaton decay to final state bosons with self-interactions of moderate strength. We find that such final state self-interactions qualitatively alter the reheat dynamics. In the case of narrow-band resonance decay, where a quantitative analysis is possible, we show that these final state interactions regulate the decay rate. The phenomenon of parametric amplification is then effectively suppressed, and does not drastically enhance the decay rate and reheat temperature. Detailed applications of our results to realistic classes of inflationary models will be considered elsewhere.
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arxiv:hep-ph/9606463
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We present some recent advances in the computational study of baryon number violation in high energy electroweak collisions. We examine classically allowed processes above the sphaleron barrier and, using a stochastic search procedure, we explore the topology changing region in the energy and particle number plane. Finding topology changing classical solutions with small incident particle number would be an indication that baryon number violation becomes unsuppressed in high energy collisions. Starting with a topology changing solution of approximately 50 incoming particles, our Monte-Carlo procedure has produced other topology changing solutions with 40% lower incident particle numbers, with energies up to one and a half times the sphaleron energy. While these solutions still involve a rather large number of incident particles, we have nonetheless demonstrated that our search procedure is effective in reducing the particle number while ensuring topology change. Taking advantage of more powerful computational resources, we plan to extend the search to still higher energies.
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arxiv:hep-ph/9606479
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We present the calculation of the elastic and inelastic high--energy small--angle electron--positron scattering with a {\it per mille} accuracy. PACS numbers 12.15.Lk, 12.20.--m, 12.20.Ds, 13.40.--f
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arxiv:hep-ph/9607228
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We present a complete analysis of the Heavy Quark Effective Theory Lagrangian at order $1/m^2$ in the leading logarithmic approximation, including effects induced by spectator quarks. At this order new correction terms appear in the effective Lagrangian, as four-quark operators containing both heavy and light quark fields. We compute the coefficients of these operators to one-loop order and in the leading-logarithmic approximation. Two of them break the heavy quark spin symmetry and we estimate their contribution to the hyperfine splitting of the heavy mesons in the factorization approximation. We find that they make a positive contribution to the hyperfine splitting of about 10% of the measured splitting in the charm case and of up to 5% in the bottom case.
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arxiv:hep-ph/9607233
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We investigate the existence of anomalous Higgs boson couplings, $H\gamma\gamma$ and $HZ\gamma$, through the analysis of the process $e^+ e^- \to \gamma\gamma\gamma$ at LEP2 energies. We suggest some kinematical cuts to improve the signal to background ratio and determine the capability of LEP2 to impose bounds on those couplings by looking for a Higgs boson signal in this reaction.
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arxiv:hep-ph/9607241
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We extend the Standard Model gauge group by a a gauged $U(1)_R$ R-Symmetry or a gauged $U(1)'$. The requirement of cancellation of anomalies is very constraining but can be achieved by adding three or four hidden-sector fields which are Standrad Model singlets. The $U(1)_R$ or $U(1)'$ quantum numbers of these singlets are usually large producing a non-renormalisable superpotential with a high power in the singelt fields. We have minimized the supergravity scalar potential and have found solutions where the vacuum expectation values of all hidden-sector singlet fields are less than the Planck mass $<{z_m}>=O(M_{Pl}/10)$. This produces the small supersymmetry scale of order the weak scale from only the Planck scale. The mu problem is simultaneously solved in this manner.
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arxiv:hep-ph/9607261
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The heavy quark effective field theory Lagrangian is renormalized to order 1/m^2. Our technique eliminates operators that vanish by the equation of motion by continuously redefining the heavy quark fields during renormalization. It is consequently only necessary to calculate the running of the operators that do not vanish by the equation of motion. Our results are found to be consistent with reparameterization invariance.
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arxiv:hep-ph/9607272
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We compute complete tree level matrix elements for $gg , q \bar q \rightarrow b \bar b W^+W^-$. We analyze the irreducible backgrounds to top signal at the Tevatron and at the LHC. Their contribution to the total cross section is about $5 \%$ at the LHC, due to single resonant channels. Several distributions with contributions from signal and backgrounds are presented.
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arxiv:hep-ph/9607288
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The constraints imposed by the requirement that the scalar potential of supersymmetric theories does not have unbounded directions and charge or color breaking minima deeper than the usual electroweak breaking minimum (EWM) are significantly relaxed if one just allows for a metastable EWM but with a sufficiently long lifetime. For this to be acceptable one needs however to explain how the vacuum state reaches this metastable configuration in the first place. We discuss the implications for this issue of the inflaton induced scalar masses, of the supersymmetry breaking effects generated during the preheating stage as well as of the thermal corrections to the scalar potential which appear after reheating. We show that their combined effects may efficiently drive the scalar fields to the origin, allowing them to then evolve naturally towards the EWM.
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arxiv:hep-ph/9607403
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We investigate the imaginary parts of the nucleon electromagnetic and axial form factors close to threshold in the framework of heavy baryon chiral perturbation theory. For the isovector electromagnetic form factors, we recover the well known strong enhancement near threshold. For the isoscalar ones, we show that there is no visible enhancement due to the three--pion continuum. This justifies the use of vector meson poles only in dispersion--theoretical calculations. We also calculate the imaginary part of the nucleon isovector axial form factor and show that it is small in the threshold region.
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arxiv:hep-ph/9607428
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I address the phenomenology of CPT violation in the neutral kaon system under the assumption that it originates from Planck scale physics. This assumption opens the door to a new set of CPT violating parameters whose phenomenology is distinct from the $\Delta$ parameter usually considered in the Hamiltonian. The origin of these parameters reflects a possible departure from a $S$-matrix evolution. Existing bounds on CPT violation are near the expected range based on naive dimensional analysis. This provides a strong incentive to pursue the quest of CPT violation in near-future kaon experiments. (Talk given at the Workshop on K Physics, Orsay, France, May 30 - June 4, 1996.)
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arxiv:hep-ph/9607435
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We predict a nonvanishing baryon asymmetry of the proton sea at low $x$. It is expected to be about $7\%$ and nearly $x$-independent at $x < 0.5 \times 10^{-3}$. The asymmetry arises from the baryon-antibaryon component of the Pomeron, rather than from the valence quarks of the proton, which are wide believed carriers of baryon number. Experimental study of $x$-distribution of the baryon asymmetry of the proton sea can be performed in $ep$ or $\gamma p$ interactions at HERA, where $x\sim 10^{-5}$ are reachable, smaller than at any of existing or planned proton colliders.
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arxiv:hep-ph/9607486
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In Skyrme-type models, the leading term of the low-energy photoproduction amplitude is identical to the standard expression and independent of the number of flavors considered, but subleading terms are not.
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arxiv:hep-ph/9608268
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The transition constant for the hadronic decay $\omega \rightarrow \rho\pi$ is investigated by means of QCD sum rules in external axial field. The obtained value for $g_{\omega\rho\pi}$ is about 16 GeV${}^{-1}$ that is in a good agreement with experimental data.
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arxiv:hep-ph/9608331
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We review and update the effects of physics beyond the standard model on CP asymmetries in B decays. These asymmetries can be significantly altered if there are important new-physics contributions to \bqbqbar mixing. This same new physics will therefore also contribute to rare, flavor-changing B decays. Through a study of such decays, we show that it is possible to partially distinguish the different models of new physics.
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arxiv:hep-ph/9608430
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A simple mixing scheme describing the $f_0(1500)$ and the $f_0(1700)$ as mixed states of a $\bar s s$ meson and a digluonium is reconsidered at the light of new experimental data.
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arxiv:hep-ph/9608451
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Presented at the Meeting of the Division of Particles and Fields, August 1996, in Minneapolis. The work presented here is based upon a recent paper (hep-ph/9608413) done in collaboration with Oscar F. Hernandez, Ivan Maksymyk, and Helene Nadeau. The NRQCD predictions for the polarization of the J/psi produced in b->J/psi+X, as well as the helicity-summed production rate are presented.
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arxiv:hep-ph/9608457
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We present a systematic study of the leading twist structure functions of the deuteron, F_2^D, b_{1,2}^D and g_1^D in a fully relativistic approach. Our study is based on a realistic Bethe-Salpeter amplitude for the deuteron, which is obtained as a solution to the homogeneous Bethe-Salpeter equation with a realistic NN kernel. Particular effort is made to connect the structure functions to the densities of the appropriate charges and currents. This allows for a systematic comparison between the relativistic and nonrelativistic calculations, by analysing the same densities in both approaches. Thus, the sources of the relativistic effects in the structure functions are understood and clearly distinguished from variations caused by the differences in the model parameters. We present both the formalism and extensive numerical calculations for all steps of our analysis. We find that the nonrelativistic and relativistic calculations are qualitatively very much alike. However, three main features systematically distinguish a consistent relativistic approach from the nonrelativistic one: (i) the binding effects are larger, (ii) the effect of Fermi motion at high $x$ is stronger and (iii) the relativistic description of the structure functions b_{1,2}^D is fully consistent, unlike the nonrelativistic approach, which is internally inconsistent and violates the fundamental sum rules.
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arxiv:hep-ph/9608459
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We do a systematic analysis of the question of calculability of CKM matrix elements in terms of quark mass ratios, within the framework of the hypothesis of universality of strength for Yukawa couplings (USY), where all Yukawa couplings have equal moduli, and the flavor dependence is only in their phases. We use the fact that the limit $m_u=m_d=0$ is specially simple in USY, to construct the various ans\"atze. It is shown that the experimentally observed CKM matrix can be obtained within USY ans\"atze corresponding to simple relations among phases of Yukawa couplings. Within USY, one finds a natural explanation why Cabibbo mixing is significantly larger than the other CKM mixings. In the most successful of the USY ans\"atze, one obtains in leading order: $|V_{us}|=\sqrt{m_d/{m_s}}$ ; $ |V_{cb}|=\sqrt{2}(m_s/m_b)$ $ |V_{ub}|= (1/\sqrt{2})\sqrt{m_dm_s/m_b^2}$ ; $|V_{td}|= 3|V_{ub}|$. We study the behavior of this USY ansatz under the renormalization group.
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arxiv:hep-ph/9608477
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Phenomenological CP-violating parameters in decays of neutral B-mesons are discussed. Special attention is given to the degree of their measurability. We emphasize important role of the sign of $\Delta m_B$ and suggest how it could be determined experimentally.
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arxiv:hep-ph/9608478
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We investigate to what extent the oscillation or conversion of neutrinos enhances the expected event rate of the supernova relic neutrino background (SRN) at the Super-Kamiokande detector (SK). The SRN \bar\nu_e's can be almost completely exchanged with \nu_\mu-like neutrinos by the MSW oscillation under the inverse mass hierarchy with \Delta m^2 ~ 10^{-8}--10^5 [eV^2], or by the magnetic moment of Majorana neutrinos with \mu_\nu >~ 10^{-12} \mu_B and \Delta m^2 ~ 10^{-4}--10^0 [eV^2]. In the standard calculation of the SRN flux, the event rate of the SRN \bar\nu_e's at the SK in the observable energy range of 15--40 MeV can be enhanced from 1.2 yr^{-1} to 2.4 yr^{-1} if all \bar\nu_e's are exchanged with \nu_\mu-like neutrinos. The enhancement is prominent especially in the high energy range (\gtilde 25 MeV). In the astrophysically optimistic calculation, the event rate becomes as high as 9.4 yr^{-1}. Because the theoretical upper bound of the SRN events without oscillation is about 5 yr^{-1} taking account of the various astrophysical uncertainties, we might have to resort to the neutrino oscillation if more than 5 events in a year, as well as a significantly harder spectrum, were observed in the SK.
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arxiv:hep-ph/9609241
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We present prospects and requirements for the study at HERA of hard photon processes which generate high $p_T$ photons in the final state, and processes which generate Drell-Yan lepton pairs.
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arxiv:hep-ph/9609273
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Correction to the $b\rightarrow s\gamma$ branching ratio in the multiscale walking technicolor model (MWTCM) is examined. For the original MWTCM, the correction is too large to explain the recent CLEO data. We show that if topcolor is further introduced, the branching ratio in the topcolor assisted MWTCM can be in agreement with the CLEO data for a certain range of the parameters.
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arxiv:hep-ph/9609283
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We show that both the multiplicity distribution and the ratio of factorial cumulants over factorial moments for 2-jet events in e+e- annihilation at the Z^0 peak can be well reproduced by the weighted superposition of two negative binomial distributions, associated to the contribution of $b\bar b$ and light flavoured events respectively. The negative binomial distribution is then suggested to describe the multiplicity distribution of 2-jet events with fixed flavour.
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arxiv:hep-ph/9609306
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Some results of a calculation of electroweak radiative corrections to $W$ and $Z$ boson production in hadronic collisions are presented.
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arxiv:hep-ph/9609315
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We investigate the connection between the NSVZ and the DRED forms of the gauge $\beta$-function in an $N=1$ supersymmetric gauge theory. We construct a coupling constant redefinition that relates the two forms up to four loops. By abelian calculations, we are able to infer the complete non-abelian form of $\beta_g^{(3)DRED}$, and also $\beta_g^{(4)DRED}$ except for one undetermined parameter.
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arxiv:hep-ph/9609325
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The electroweak equivalence theorem quantitatively connects the physical amplitudes of longitudinal massive gauge bosons to those of the corresponding ``unphysical'' would-be Goldstone bosons. Its precise form depends on both the gauge fixing condition and the renormalization scheme. Our previous modification-free schemes have applied to a broad class of $R_\xi$ gauges including 't Hooft-Feynman gauge but excluding Landau gauge. In this paper we construct a new renormalization scheme in which the radiative modification factor, $C_{mod}^a$, is equal to unity for all $R_\xi$-gauges, including both 't Hooft-Feynman and Landau gauges. This scheme makes $C_{mod}^a$ equal to unity by specifying a convenient subtraction condition for the would-be Goldstone boson wavefunction renormalization constant $Z_{\phi^a}$. We build the new scheme for both the standard model and the effective Lagrangian formulated electroweak theories (with either linearly or non-linearly realized symmetry breaking sector). Based upon these, a new prescription, called ``divided equivalence theorem'', is further proposed for extending the high energy region applicable to the equivalence theorem.
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arxiv:hep-ph/9609326
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