Nuclear Theory·nucl-th

Tuesday·November 24, 2015

10 papers—7 primary·3 cross-listed

08
Searching for minimum in dependence of squared speed-of-sound on collision energy
Fu-Hu Liu🇨🇳 · Li-Na Gao🇨🇳 · Roy A. Lacey🇺🇸
Experimental results of the rapidity distributions of negatively charged pions produced in proton-proton ( $p$ - $p$ ) and beryllium-beryllium (Be-Be) collisions at different beam momentums, measured by the NA61/SHINE Collaboration at the super proton synchrotron (SPS), are described by a revised (three-source) Landau hydrodynamic model. The squared speed-of-sound parameter $c_{s}^{2}$ is then extracted from the width of rapidity distribution. There is a local minimum (knee point) which indicates a softest point in the equation of state (EoS) appearing at about 40 $A$ GeV/ $c$ (or 8.8 GeV) in $c_{s}^{2}$ excitation function [the dependence of $c_{s}^{2}$ on incident beam momentum (or center-of-mass energy)]. This knee point should be related to the searching for the onset of quark deconfinement and the critical point of quark-gluon plasma (QGP) phase transition.
↳ hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2016)·5 citations
09
Vector Meson Masses from Hidden Local Symmetry in Constant Magnetic Field
Mamiya Kawaguchi🇯🇵 · Shinya Matsuzaki🇯🇵
We discuss the magnetic responses of vector meson masses based on the hidden local symmetry (HLS) model in constant magnetic field, described by the lightest two-flavor system including the pion, rho and omega mesons in the spectrum. The effective masses influenced under the magnetic field are evaluated in a way of the derivative/chiral expansion established in the HLS model. At the leading order O(p^2) the g-factor of the charged rho meson is fixed to be 2, implying that the rho meson at this order is treated just like a point-like spin-1 particle. Beyond the leading order, one finds anomalous magnetic interactions of the charged rho meson, involving the anomalous magnetic moment, which give corrections to the effective mass. It is then suggested that up to O(p^4) the charged rho meson tends to become massless. Of interest is that nontrivial magnetic-dependence of neutral mesons emerges to give rise to the significant mixing among neutral mesons. Consequently, it leads to the dramatic enhancement of the omega meson mass, which is testable in future lattice simulations. Corrections from terms beyond O(p^4) are also addressed.
↳ hep-phhep-latnucl-thPRD(2016)·39 citations
10
Excited Baryon Structure Using Exclusive Reactions with CLAS12
Daniel S. Carman (for the CLAS Collaboration)🇺🇸
Studying excited nucleon structure through exclusive electroproduction reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. Electrocouplings for $N^{*}$ states in the mass range below 1.8~GeV have been determined from analyses of CLAS $π N$ , $η N$ , and $π π N$ data. This work made it clear that consistency of independent analyses of exclusive channels with different couplings and non-resonant backgrounds but the same $N^{*}$ electro-excitation amplitudes, is essential to have confidence in the extracted results. In terms of hadronic coupling, many high-lying $N^{*}$ states preferentially decay through the $π π N$ channel instead of $π N$ . Data from the $K Y$ channels will therefore be critical to provide an independent analysis to compare the extracted electrocouplings for the high-lying $N^{*}$ states against those determined from the $π N$ and $π π N$ channels. A program to study excited $N^{*}$ decays to non-strange and strange exclusive final states using CLAS12 will measure differential cross sections to be used as input to extract the $γ_{v} N N^{*}$ transition form factors for the most prominent $N^{*}$ states in the range of invariant energy $W$ up 3~GeV in the virtually unexplored domain of momentum transfers $Q^{2}$ up to 12~GeV $^{2}$ .
↳ nucl-exnucl-thAIP Conf.Proc.(2016)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Searching for minimum in dependence of squared speed-of-sound on collision energy

Vector Meson Masses from Hidden Local Symmetry in Constant Magnetic Field

Excited Baryon Structure Using Exclusive Reactions with CLAS12

Affiliations