111 research outputs found
Cumulants of the chiral order parameter at lower RHIC energies
We study cumulants of the chiral order parameter as function of beam energy
as a possible signal for the presence of a critical end point and first-order
phase transition in the QCD phase diagram. We model the expansion of a
heavy-ion collision by a fluid dynamic expansion coupled to the explicit
propagation of the chiral order parameter sigma via a Langevin equation. We
evolve the medium until a parametrized freeze-out condition is met where we
calculate event-by-event fluctuations and cumulants of sigma which are expected
to follow the trend of net-proton number cumulants. We emphasize the role of a
nonequilibrium first-order phase transition: The presence of an unstable phase
causes the well-known bending of the trajectories in the space of temperature
and baryochemical potential. For these cases at lower beam energies, the system
crosses the freeze-out line more than once, allowing us to calculate a range of
cumulants for each initial condition which are overall enhanced for the second
hit of the freeze-out line. We thus find not only the critical end point but
also the phase transition of the underlying model clearly reflected in the
cumulants. The impact of volume fluctuations is demonstrated to play a
measurable role for fluid dynamical evolutions that last significantly long.Comment: 14 pages, 4 figures, ICNFP 2021. arXiv admin note: text overlap with
arXiv:2204.0028
Resonances in the Compact Pentaquark Picture
resonances are studied in the approach of quark model and group theory.
It is found that there are totally 17 possible pentaquark states with the quark
contents ( are and quarks; is quark) in the
compact pentaquark picture, where the hidden heavy pentaquark states may take
the color singlet-singlet () and color
octet-octet () configurations. The
partial decay widths of hidden heavy pentaquark states are calculated for all
possible decay channels. The results show that the is the dominant
decay channel for both the spin and pentaquark states, and indicate
that the may not be a compact pentaquark state while
and could be the spin- and spin-
pentaquark states, respectively.Comment: 6 pages, 2 figure
Determination of parameters of a potential model for tetraquark study by studying all S-wave mesons
The masses of low-lying S-wave mesons are evaluated in a constituent quark
model (CQM) where the Cornell-like potential and one-gluon exchange spin-spin
interaction are employed. To make the model applicable to both the light and
heavy quark sectors, we introduce mass-dependent coupling coefficients. There
are four free parameters in the model, which are determined by comparing the
theoretical results with experimental data. The established model with one set
of parameters may be applied to study higher excited meson states as well as
multiquark systems in both the light and heavy quark sectors
states in the mixture of molecular and pentaquark pictures
We systematically study hidden charm pentaquark states in the constituent
quark model with a general Hamiltonian for multiquark systems, considering the
coupling between the molecular states and the
compact pentaquark states by the one-gluon exchange hyperfine
interaction. The ground state hidden-charm pentaquark mass spectra and the
strong decay widths are calculated. This work suggests that ,
and resonances might be mainly ,
and hadronic molecules respectively,
and might include sizable pentaquark components
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