Search results for "Quark model"
showing 10 items of 207 documents
Comments on "Neutron-proton mass difference in the chiral solitonic bag model"
1990
It is pointed out that the topological soliton bag is incompletely quantized in the papers of Durgut, Pak, and Yilmaz and of Wittman and Woloshyn, leading to results on the neutron-proton mass difference and other phenomena that are not implied by the model. The purpose of this paper is to clarify how and where their scheme goes wrong and to propose an alternative consistent scheme of quantization.
Quark-model study of the hadron structure and the hadron-hadron interaction
2011
Recent results of hadron spectroscopy and hadron-hadron interaction within a quark model framework are reviewed. Higher order Fock space components are considered based on new experimental data on low-energy hadron phenomenology. The purpose of this study is to obtain a coherent description of the low-energy hadron phenomenology to constrain QCD phenomenological models and try to learn about low-energy realizations of the theory.
The lowest-lying baryon masses in covariant SU(3)-flavor chiral perturbation theory
2010
We present an analysis of the baryon-octet and -decuplet masses using covariant SU(3)-flavor chiral perturbation theory up to next-to-leading order. Besides the description of the physical masses we address the problem of the lattice QCD extrapolation. Using the PACS-CS Collaboration data we show that a good description of the lattice points can be achieved at next-to-leading order with the covariant loop amplitudes and phenomenologically determined values for the meson-baryon couplings. Moreover, the extrapolation to the physical point up to this order is found to be better than the linear one given at leading-order by the Gell-Mann-Okubo approach. The importance that a reliable combinatio…
Model calculations of the Sivers function satisfying the Burkardt sum rule
2009
9 pages, 4 figures.-- ISI article identifier:000266408300028.-- ArXiv pre-print avaible at:http://arxiv.org/abs/0811.1191
Identifying spin and parity of charmonia in flight with lattice QCD
2019
The spectrum of charmonium resonances contains a number of unanticipated states along with several conventional quark-model excitations. The hadrons of different quantum numbers $J^P$ appear in a fairly narrow energy band, where $J^P$ refers to the spin-parity of a hadron at rest. This poses a challenge for Lattice QCD studies of (coupled-channel) meson-meson scattering aimed at the determination of scattering amplitudes and resonance pole positions. A wealth of information for this purpose can be obtained from the lattice spectra in frames with nonzero total momentum. These are particularly dense since hadrons with different $J^P$ contribute to any given lattice irreducible representation.…
Strong magnetic fields in a nonlocal Polyakov chiral quark model
2018
We study the behavior of strongly interacting matter under an external constant magnetic field in the context of nonlocal chiral quark models that incorporate a coupling to the Polyakov loop. We find that at zero temperature the behavior of the quark condensates shows the expected magnetic catalysis effect, our predictions being in good quantitative agreement with lattice QCD results. On the other hand when the analysis is extended to the case of finite temperature our results show that nonlocal models naturally lead to the Inverse Magnetic Catalysis effect for both the chiral restoration and deconfinement transition temperatures.
Quark-model description of the NN*(1440) potential
2001
We derive a $NN^*$(1440) potential from a non-relativistic quark-quark interaction and a chiral quark cluster model for the baryons. By making use of the Born-Oppenheimer approximation we examine the most important features of this interaction in comparison to those obtained from meson-exchange models.
Two-loop calculation of the anomalous dimension of the axial current with static heavy quarks
1992
Abstract A method to perform two-loop calculations in Eichten's effective field theory for heavy quarks is developed. The anomalous dimension of the axial current for static heavy quarks is calculated at two loops. For N = 3, we get γ A (2) = − 1 36 [ 127 2 +28ξ(2)−5N f ] . This result is very important to understand completely the physical significance of the lattice measurement of the decay constant of the B meson. The two-loop correction generated by γ A (2) turns out to be small, less than 1% for four quark flavours, so that the value of the decay constant of the B meson does not need in practice renormalization group improvement. As extra results, the self-energy renormalization consta…
Constituent quarks and parton distributions
1997
Abstract The high energy parton distribution when evolved to a low energy scale appears to indicate that a valence picture of hadron structure arises. We have developed a formalism based on a laboratory partonic description which connects the parton distributions with the momentum distributions of a quark model. The formalism uses Next to Leading Order evolution and has been defined to produce the right support for the parton distributions. In this scheme we have analyzed the polarized and unpolarized data and shown that well-known Quark Models lead to a qualitative description of the data. However, if one aims at a quantitative agreement, these conventional low energy models have to be cha…
S-4 model for quarks and leptons with maximal atmospheric angle
2010
We consider a model for quark and lepton masses and mixings based on S-4 flavor symmetry. The model contains six Higgs doublets where three of them give mass to the leptons, and the other three gives mass to the quarks. Charged fermion and quark masses arise from renormalizable interactions while neutrino Majorana masses are generated through effective dimension five Weinberg operator. From the study of the minimization of the scalar potential we found a residual mu tau symmetry in the neutrino sector predicting zero reactor angle and maximal atmospheric angle and for the quark sector we found a four-zero texture. We give a fit of the mass hierarchies and mixing angles in the quark sector.