We study the dependence of the normalized moments of the net-proton multiplicity distributions on the definition of centrality in relativistic nuclear collisions at a beam energy of s NN = 7.7 GeV . ...Using the ultra relativistic quantum molecular dynamics model as event generator we find that the centrality definition has a large effect on the extracted cumulant ratios. Furthermore we find that the finite efficiency for the determination of the centrality introduces an additional systematic uncertainty. Finally, we quantitatively investigate the effects of event-pile up and other possible spurious effects which may change the measured proton number. We find that pile-up alone is not sufficient to describe the data and show that a random double counting of events, adding significantly to the measured proton number, affects mainly the higher order cumulants in most central collisions.
We study pentaquark states of both light q4 q and hidden heavy q3 QQ (q = u, d, s quark in SU(3) flavor symmetry; Q = c, b quark) systems with a general group theory approach in the constituent quark ...model, and the spectrum of light baryon resonances in the ansatz that the l = 1 baryon states may consist of the q3 as well as q4 q pentaquark component. The model is fitted to ground state baryons and light baryon resonances which are believed to be normal three-quark states. The work reveals that the N (1535) 1/2 − and N (1520)3/2 − may consist of a large q4 q component while the N (1895) 1/2 − and N (1875) 3/2 − are respectively their partners, and the N+ (1685) might be a q4 q state. By the way, a new set of color-spin-flavor-spatial wave function for q3QQ systems in the compact pentaquark picture are constructed systematically for studying hidden charm pentaquark states.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Abstract
We investigate the impact of a first-order chiral phase transition and critical point on hadron multiplicity ratios. We model the dynamical expansion of the hot and dense matter created in a ...heavy ion collision with a Bjorken hydrodynamics expansion coupled to the explicit evolution of the chiral order parameter at center-of-mass energies from 2 to 7 GeV. Hereby, the chiral dynamics is implemented using a Langevin equation including dissipation and noise. We find a strong enhancement of the entropy-per-baryon S/A at lowest energies which is created at the non-equilibrium first-order phase transition. By mapping the initial and final S/A to a hadron resonance gas, we can quantify the shift of hadron multiplicity ratios.
Abstract
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.
The meson cloud distributions in r-space are extracted from the nucleon electromagnetic and axial form factors which are derived in the perturbative chiral quark model. The theoretical results ...indicate that the magnetic charge and axial charge distributions of the three-quark core have the similar distributions in r-space, the magnetic charge distributions of the meson cloud and three-quark core are more or less in the same region and peak at distances of around 0.4 fm, which is in good agreement with the finding of works in the framework of chiral perturbation theory, but the axial charge meson cloud distributes mainly inside the three-quark core.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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The charge form factor and charge radius of neutron are investigated in the perturbative chiral quark model (PCQM) with considering both the ground and excited states in the quark propagator. A ...Cornell-like potential is extracted in accordance with the predetermined ground state quark wave function, and the excited quark states are derived by solving the Dirac equation with the extracted PCQM potential numerically. The study reveals that the contributions of the excited quark states are considerably influential in the charge form factor and charge radius of neutron as expected, and the total results are significantly improved and increased by nearly four times by including the excited states in the quark propagator. The theoretical PCQM results are found, including the ground and excited quark propagators, in good agreement with the recent lattice QCD values at pion mass of about 130MeV.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
An open system consists of the decay of the excited states of two two-level atoms due to the stimulated emission of photons is studied in a quantum operator formalism, the approach of Kraus ...operators. We have constructed in the work the Kraus operators which will be applied to derive the time evolution of the density matrix for analyzing the stability of the entanglement of two qubits system.
Jiangmen Undergroud Neutrino Observatory (JUNO) is a reactor antineutrino experiment with the main purpose for determining the neutrino mass hierarchy by precisely measuring the energy spectrum of ...nuclear reactor electron antineutrinos. The JUNO central detector consists of 20 kilotons an organic liquid scintillator filling the spherical CD or acrylic sphere whose diameter is 35.4 meters, surrounded by a water pool, approximately 18, 000 20″ and 25, 000 3″ photomultiplier tubes (PMTs) on the inner CD truss and 2,400 20″ Veto-PMT on the outer CD truss. The PMTs are very sensitive to external magnetic fields, the earth magnetic field (EMF) passing through the PMTs without any shielding would largely reduce the efficiency of the PMTs. In order to minimize the effect of EMF inside the detector, JUNO has been planing to use the DC coils to shield EMF, aiming at the residual EMF to less than 10 % on PMT areas.
The electromagnetic properties of baryon octet are studied in the perturbative chiral quark model (PCQM). The relativistic quark wave function is extracted by fitting the theoretical results of the ...proton charge form factor to experimental data and the predetermined quark wave function is applied to study the electromagnetic form factors of other octet baryons as well as magnetic moments, charge and magnetic radii. The PCQM results are found, based on the predetermined quark wave function, in good agreement with experimental data.
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