Showing papers on "Up quark published in 1994"
TL;DR: It is shown that no precise definition of the pole mass can be given in the full theory once non-perturbative effects are included.
Abstract: The key quantity of the heavy quark theory is the quark mass mQ. Since quarks are unobservable one can suggest different definitions of mQ. One of the most popular choices is the pole quark mass routinely used in perturbative calculations and in some analyses based on heavy quark expansions. We show that no precise definition of the pole mass can be given in the full theory once non-perturbative effects are included. Any definition of this
345 citations
TL;DR: In this paper, the couplings of a charged scalar H i ± to up quarks, down quarks and charged leptons depend on three new complex parameters, X i, Y i, and Z i, respectively.
227 citations
TL;DR: In this article, the authors analyzed the implications of the infrared quasi fixed point solution for the top quark mass in the Minimal Supersymmetric Standard Model (MSM) and showed that the solution could explain in a natural way the relatively large value of the top qark mass and, if confirmed experimentally, may be suggestive of the onset of nonperturbative physics at very high energy scales.
81 citations
TL;DR: In this article, the authors calculate the valence distribution of down quarks and up quarks in the proton and the neutron, taking into account the major sources of charge symmetry violation, including the effect of the mass difference of u and d quarks on the bag wave function, and the masses of the intermediate diquark states.
Abstract: We calculate the valence distribution of down quarks in the proton and up quarks in the neutron (the ‘minority’ quark distributions), taking into consideration the major sources of charge symmetry violation, including the effect of the mass difference of the u and d quarks on the bag wave function, and the masses of the intermediate diquark states. The relative difference of the distributions can be as large as 10% for intermediate values of Bjorken x.
58 citations
TL;DR: In this paper, the quark-meson coupling model was extended to incorporate the δ meson and the Nolen-Schiffer anomaly and isospin symmetry breaking in nuclear matter.
50 citations
TL;DR: In this paper, a QCD-based interpretation of heavy quark fragmentation is presented, which utilizes the heavy-quark mass expansion and can reliably extract mass independent parameters characterizing the fragmentation function.
41 citations
TL;DR: In this article, a hybrid Monte Carlo algorithm was used to generate lattice configurations for heavy quark couplings on a 163 x 24 lattice, and the shape of the resulting potential was well described by the superposition of a term proportional to 1/R and a linear confinement potential.
38 citations
01 Jan 1994
TL;DR: Dual QCD is used to derive an effective potential to order (quark mass)-2 for a constituent quark and antiquark, and the use of these potentials are extended to heavy-light quark-antiquark systems through use of the Salpeter equation and the Dirac equation.
36 citations
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TL;DR: In this article, the authors show that an anomaly free horizontal symmetry can naturally lead to a massless up quark and to a corresponding accidental anomalous symmetry, and conclude that this possiblity is still open and can solve the strong CP problem.
Abstract: We reconsider the massless up quark solution of the strong CP problem We show that an anomaly free horizontal symmetry can naturally lead to a massless up quark and to a corresponding accidental anomalous symmetry Reviewing the controversy about the phenomenological viability of $m_u=0$ we conclude that this possiblity is still open and can solve the strong CP problem To appear in the Proceedings of The Yukawa Couplings and the Origins of Mass Workshop
29 citations
TL;DR: In this paper, the authors compare plane-wave, coordinate-space and moment methods for evaluating OPE coefficients of light-quark and gluon condensates, and show that these three methods yield equivalent contributions to two-current correlation functions regardless of the gauge chosen for external gluons fields in the coordinate space approach.
Abstract: We compare plane-wave, coordinate-space and moment methods for evaluating operator-product expansion (OPE) coefficients of the light-quark and gluon condensates. Equivalence of these methods for quark condensate contributions is proven to all orders in the quark mass parameterm. The three methods are also shown to yield equivalent gluon condensate contributions to two-current correlation functions, regardless of the gauge chosen for external gluon fields in the coordinate space approach. An improved method for evaluating quarkcondensate OPE coefficients is presented for several (two-current) correlation functions. Gauge-dependent Green functions are also discussed. It is shown that contradictory expressions for the gluon-condensate contribution to the quark propagator occurring from the plane-wave and coordinate-space approaches yield identical relations between the heavy-quark and gluon condensates, as anticipated from the gauge invariance of the heavy-quark expansion.
27 citations
01 Mar 1994
TL;DR: In this paper, it was shown that an anomaly free horizontal symmetry can naturally lead to a massless up quark and to a corresponding accidental anomalous symmetry and that this possiblity is still open and can solve the strong CP problem.
Abstract: We reconsider the massless up quark solution of the strong CP problem. We show that an anomaly free horizontal symmetry can naturally lead to a massless up quark and to a corresponding accidental anomalous symmetry. Reviewing the controversy about the phenomenological viability of $m_u=0$ we conclude that this possiblity is still open and can solve the strong CP problem. To appear in the Proceedings of The Yukawa Couplings and the Origins of Mass Workshop.
TL;DR: In this article, the authors proposed to use Fermi-Dirac distributions for quark and antiquark partons to obtain a fair description of the dependence of the very recent NMC data on the proton and neutron structure functions.
Abstract: We propose to use Fermi-Dirac distributions for quark and antiquark partons. It allows a fair description of thex-dependence of the very recent NMC data on the proton and neutron structure functionsF
2
(x) andF
2
(x) atQ
2=4 GeV2, as well as the CCFR antiquark distribution
$$x\bar q(x)$$
. We show that one can also use a corresponding Bose-Einstein expression to describe consistently the gluon distribution. The Pauli exclusion principle, which has been identified to explain the flavor asymmetry of the light-quark sea of the proton, is advocated to guide us for making a simple construction of the polarized parton distributions. We predict the spin dependent structure functionsg
1
(x) andg
1
(x) in good agreement with EMC and SLAC data. The quark distributions involve some parameters whose values support well the hypothesis that the violation of the quark parton model sum rules is a consequence of the Pauli principle.
TL;DR: In this paper, the authors derived the bulk viscosity of quark matter from the dominant reactionu + s ↔d + u by taking the effect of temperature and quark-gluon coupling perturbatively to first order in the chemical composition of the quark mass.
Abstract: We rederive the bulk viscosity of strange quark matter from the dominant reactionu + s ↔d + u by taking the effect of temperature and quark-gluon coupling perturbatively to first order in the chemical composition of the quark matter. We also calculate the contribution from the β-decay processes s(d) →u + e + ¯v andu + e → s(d)+ v and show that this contribution has different temperature dependence and can even be larger than the contribution from the former reaction at temperatures of the order of the electron Fermi energy.
TL;DR: In this article, the quark distributions for the ground state of doubly-magic nuclei, i.e. 4He, 16O and 40Ca, were calculated using the non-relativistic quark model of the nucleons and considering quark exchange between at most two nucleons.
Abstract: Using the non-relativistic quark model of the nucleons and considering the quark exchange between at most two nucleons, we calculate the quark distributions for the ground state of the doubly-magic nuclei, i.e. 4He, 16O and 40Ca. We take into the account the effect of two-body nucleon correlations which depend on spin, isospin, total angular momentum, tensor operators and the relative and centre-of-mass coordinates of two nucleons. The harmonic-oscillator wavefunctions are used as the uncorrelated states and a local density approximation is performed to convert the infinite nuclear-matter correlation functions to finite ones. The result is compared with results due to Catara and Sambataro (1992).
Journal Article•
TL;DR: In this article, the spin dependence of the potential between heavy quarks in full lattice QCD, including the effects of light quark loops, was investigated, and it was shown that long-range scalar confinement supplemented by a Coulomb force at short distances.
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TL;DR: In this article, the linear sigma model was used to describe quark-pion interactions, and the effects of transverse quark polarizations appeared in the correlation between the two leading pions in a jet produced by the fragmentation of a quark.
Abstract: Using the linear sigma model to describe quark--pion interactions, we compute polarization asymmetries in quark fragmentation. We show that the effects of transverse quark polarizations appear in the correlation between the two leading pions in a jet produced by the fragmentation of a quark. Such asymmetries provide a window to the nature of chiral symmetry breaking in QCD.
TL;DR: In this article, the implications of a vector-like quark, especially a down-type vector like quark in the case of the neutral Higgs in the calculation were investigated.
Abstract: We study the implications of a vector-like quark, especially a down-type vector-like quark in $b \rightarrow s(d) \gamma$ including the neutral Higgs in the calculation. After analyzing some possible constraints for the mixing, the contribution may be significant for the $b \rightarrow d \gamma$, but not for the $b \rightarrow s \gamma$. We also find that the FCNC among ordinary quarks vanishes for a special form of down-type quark mass matrix.
TL;DR: In this article, it was shown that the D-meson, whose light quark is the initial-pion valence quark and whose charmed quark was produced in annihilation of the first hadrons, is really a leading meson in reactions like $\pi^-p -> DX$.
Abstract: It is shown that the D--meson, whose light quark is the initial-pion valence quark and whose charmed quark is produced in annihilation of valence quarks and has got a large enough momentum, is really a leading meson in reactions like $\pi^- p -> DX$. If such annihilation of valence quarks from initial hadrons is impossible there must be no distinct leading effect.
TL;DR: The robust character of the Standard Model is confirmed in this paper by examining its geometrical basis in three equivalent internal symmetry spaces: the unitary plane, the quaternion space, and the real space.
Abstract: The robust character of the Standard Model is confirmed. Examination of its geometrical basis in three equivalent internal symmetry spaces-the unitary planeC
2, the quaternion spaceQ, and the real spaceR
4—as well as the real spaceR
3 uncovers mathematical properties that predict the physical properties of leptons and quarks. The finite rotational subgroups of the gauge groupSU(2)
L
×U(1)
Y
generate exactly three lepton families and four quark families and reveal how quarks and leptons are related. Among the physical properties explained are the mass ratios of the six leptons and eight quarks, the origin of the left-handed preference by the weak interaction, the geometrical source of color symmetry, and the zero neutrino masses. The (u, d) and (c, s) quark families team together to satisfy the triangle anomaly cancellation with the electron family, while the other families pair one-to-one for cancellation. The spontaneously broken symmetry is discrete and needs no Higgs mechanism. Predictions include all massless neutrinos, the top quark at 160 GeV/c
2, theb′ quark at 80 GeV/c
2, and thet′ quark at 2600 GeV/c
2.
TL;DR: In this article, it was shown that the Heavy Quark Effective Theory is renormalizable perturbatively and there exist renormalization schemes in which the infinite quark mass limit of any QCD Green function is exactly given by the corresponding Green function of the heavy quark effective theory.
TL;DR: In this article, the suppression of the lightest generation fermion mass terms in realistic superstring standard-like models in the free fermionic formulation was discussed, and it was shown that the suppression is a consequence of horizontal symmetries that arise due to the Z 2 ×Z 2 orbifold compactification.
TL;DR: In this paper, a non-relativistic QCD approach was used to measure the excitation energies for a heavy Q Q system on a 243 × 48 lattice at β = 6.2.
TL;DR: In this article, a preliminary computation of the Isgur-Wise universal form factor using a lattice formulation of the Heavy Quark Effective Theory (HQET) is described and compared with the recent data from ARGUS and CLEO on B -> D*lv decay.
Abstract: A preliminary computation of the Isgur-Wise universal form factor using a lattice formulation of the Heavy Quark Effective Theory (HQET) is described and compared with the recent data from ARGUS and CLEO on B -> D*lv decay.
TL;DR: In this article, the authors discuss the possibility that a narrow peak found recently in the ( pi +, pi -) reaction at Tpi =50 MeV could be a signal from an NN-decoupled dibaryon with quantum numbers JP, T=0-, 0.
Abstract: We discuss the possibility that a narrow peak found recently in the ( pi +, pi -) reaction at Tpi =50 MeV could be a signal from an NN-decoupled dibaryon with quantum numbers JP, T=0-, 0. We classify the possible six-quark states with the given quantum numbers in the framework of the nonrelativistic constituent quark model. The 'mass' of the lowest possible state (s5p) is calculated with and without chiral interactions.
TL;DR: In this paper, the authors investigated the self-energy of quarks for various models which are inspired by the Nambu-Jona-Lasinio (NIL) model.
Abstract: The self-energy of quarks is investigated for various models which are inspired by the Nambu-Jona-Lasinio (NIL) model. Including, beyond the Hartree-Fock approximation, terms up to second order in the quark interaction, the real and imaginary parts of scalar and vector components of the self-energy are discussed. The second-order contributions depend on the energy and momentum of the quark under consideration. This leads to solutions of the Dirac equation which are significantly different from those of a free quark or a quark with constant effective mass, as obtained in the Hartree-Fock approximation.
TL;DR: In this article, the authors summarize the motivations for and the status of the calculation of the $W +$ heavy quark production process in $p \bar p$ colliders to Next-to-Leading Order in QCD.
Abstract: We summarize the motivations for and the status of the calculation of the $W +$ heavy quark production process in $p \bar p$ colliders to Next-to-Leading Order in QCD. This process can be used to constrain the strange quark distribution function at high $Q^2$ at the Tevatron, and also to study the bottom content of $W+1$~jet events. In addition, when crossed, the calculation essentially describes the single top quark production process to Next-to-Leading Order in QCD.
TL;DR: In this article, the authors considered the MIT bag model of stable quark matter consisting of u, d, and s quarks and electrons and showed that the binding energy of the models depends essentially on the quark-gluon interaction constant αc.
Abstract: In the framework of the MIT bag model we consider absolutely stable strange quark matter consisting of u, d, and s quarks and electrons. For a realistic range of parameters of the quark bag we compute the threshold density for the appearance of strange quark matter that is realized on the surface of self-sustaining strange stars. On the basis of twelve calculated equations of state we give a detailed study of the series of configurations of strange stars consistent with the best known observational data. We show that the binding energy of the models depends essentially on the quark-gluon interaction constant αc.
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TL;DR: In this article, the authors studied the valence approximation in lattice QCD of hadrons where the cloud quarks and antiquarks are deleted by truncating the backward time propagation (Z graphs) in the connected insertions.
Abstract: We study the valence approximation in lattice QCD of hadrons where the cloud quarks and antiquarks are deleted by truncating the backward time propagation (Z graphs) in the connected insertions. Whereas, the sea quarks are eliminated via the quenched approximation and in the disconnected insertions. It is shown that the ratios of isovector to isoscalar matrix elements in the nucleon reproduce the SU(6) quark model predictions in a lattice QCD calculation. We also discuss how the hadron masses are affected.
TL;DR: The first evidence for the top quark at the Tevatron may indicate a cross section higher than the QCD expectation as mentioned in this paper, and the possibility that isosinglet heavy quarks may contribute to the signal and discuss ways of testing this possibility.