Baryon Mass Splitting in a Boson-Fermion Model

We study the weak interaction axial form factors of the octet baryons, within the covariant spectator quark model, focusing on the dependence of four-momentum transfer squared, Q 2 . In our model the axial form factors GA(Q 2 ) (axial-vector form factor) and GP (Q 2 ) (induced pseudoscalar form factor), are calculated based on the constituent quark axial form factors and the octet baryon wave functions. The quark axial current is parametrized by the two constituent quark form factors, the axial-vector form factor g q A (Q 2 ), and the induced pseudoscalar form factor g q P (Q 2 ). The baryon wave functions are composed of a dominant S-state and a P -state mixture for the relative angular momentum of the quarks. First, we study in detail the nucleon case. We assume that the quark axial-vector form factor g q A (Q 2 ) has the same function form as that of the quark electromagnetic isovector form factor. The remaining parameters of the model, the P -state mixture and the Q 2 -dependence of g q P (Q 2 ), are determined by a fit to the nucleon axial form factor data obtained by lattice QCD simulations with large pion masses. In this lattice QCD regime the meson cloud effects are small, and the physics associated with the valence quarks can be better calibrated. Once the valence quark model is calibrated, we extend the model to the physical regime, and use the low Q 2 experimental data to estimate the meson cloud contributions for GA(Q 2 ) and GP (Q 2 ). Using the calibrated quark axial form factors, and the generalization of the nucleon wave function for the other octet baryon members, we make predictions for all the possible weak interaction axial form factors GA(Q 2 ) and GP (Q 2 ) of the octet baryons. The results are compared with the corresponding experimental data for GA(0), and with the estimates of baryon-meson models based on SU (6) symmetry.

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“…[98]. Previous works had shown that an S-state quark-diquark system is a good approximation for the nucleon [117][118][119].…”

Section: Methodsmentioning

confidence: 99%

Axial form factors of the octet baryons in a covariant quark model

Ramalho

Tsushima

2016

Phys. Rev. D

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“…The idea of diquarks [24][25][26] has been widely used in hadron physics for describing the mass spectrum, electromagnetic properties, and many other properties of hadrons (for a review, see, for example, Ref. [27]), although the properties and even the existence of diquarks are still under debate [28].…”

Section: Introductionmentioning

confidence: 99%

Ratios of heavy baryons to heavy mesons in relativistic nucleus-nucleus collisions

et al. 2009

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Heavy baryon/meson ratios c /D 0 and b /B 0 in relativistic heavy ion collisions are studied in the quark coalescence model. For heavy baryons, we include production from coalescence of heavy quarks with free light quarks as well as with bounded light diquarks that might exist in the strongly coupled quark-gluon plasma produced in these collisions. Including the contribution from decays of heavy hadron resonances and also that due to fragmentation of heavy quarks that are left in the system after coalescence, the resulting c /D 0 and b /B 0 ratios in midrapidity (|y| 0.5) from central Au + Au collisions at √ s NN = 200 GeV are about a factor of five and ten, respectively, larger than those given by the thermal model, and about a factor of ten and twelve, respectively, larger than corresponding ratios in the PYTHIA model for pp collisions. These ratios are reduced by a factor of about 1.6 if there are no diquarks in the quark-gluon plasma. The transverse momentum dependence of the heavy baryon/meson ratios is found to be sensitive to the heavy quark mass, with the b /B 0 ratio being much flatter than the c /D 0 ratio. The latter peaks at the transverse momentum p T

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“…There has in fact been a long history of somewhat phenomenological applications of the quark-diquark approach to the calculation of baryon properties. Initial studies were by Ida and Kobayashi (1966) and by Lichtenberg and Tassie (1967). A literature compilation is available (Skytt and Fredriksson 1988), as well as reviews by Lichtenberg (1988) and Fredriksson (1988).…”

Section: Hadronic Lawsmentioning

confidence: 99%