44,043 research outputs found
Electrical Neutrality and Symmetry Restoring Phase Transitions at High Density in a Two-Flavor Nambu-Jona-Lasinio Model
A general research on chiral symmetry restoring phase transitions at zero
temperature and finite chemical potentials under electrical neutrality
condition has been conducted in a Nambu-Jona-Lasinio model to describe
two-flavor normal quark matter. Depending on that , the ratio of
dynamical quark mass in vacuum and the 3D momentum cutoff in the loop
integrals, is less or greater than 0.413, the phase transition will be second
or first order. A complete phase diagram of quark chemical potential versus
is given. With the electrical neutrality constraint, the region where
second order phase transition happens will be wider than the one without
electrical neutrality limitation. The results also show that, for the value of
from QCD phenomenology, the phase transition must be first order.Comment: 9 pages, 1 figur
Semileptonic decays of meson to S-wave charmonium states in the perturbative QCD approach
Inspired by the recent measurement of the ratio of branching fractions
to and final states at the LHCb
detector, we study the semileptonic decays of meson to the S-wave ground
and radially excited 2S and 3S charmonium states with the perturbative QCD
approach. After evaluating the form factors for the transitions , where and denote pseudoscalar and vector S-wave charmonia,
respectively, we calculate the branching ratios for all these semileptonic
decays. The theoretical uncertainty of hadronic input parameters are reduced by
utilizing the light-cone wave function for meson. It is found that the
predicted branching ratios range from up to and could be
measured by the future LHCb experiment. Our prediction for the ratio of
branching fractions is in good
agreement with the data. For decays, the relative
contributions of the longitudinal and transverse polarization are discussed in
different momentum transfer squared regions. These predictions will be tested
on the ongoing and forthcoming experiments.Comment: 12 pages, 3 figures, 5 table
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