Nuclear Theory·nucl-th

Friday·December 8, 2017

10 papers—5 primary·5 cross-listed

01
Color superconductivity and charge neutrality in Yukawa theory
Mark G. Alford🇺🇸 · Kamal Pangeni🇺🇸 · Andreas Windisch🇺🇸
It is generally believed that when Cooper pairing occurs between two different species of fermions, their Fermi surfaces become locked together so that the resultant state remains 'neutral', with equal number densities of the two species, even when subjected to a chemical potential that couples to the difference in number densities. This belief is based on mean-field calculations in models with a zero-range interaction, where the anomalous self-energy is independent of energy and momentum. Following up on an early report of a deviation from neutrality in a Dyson-Schwinger calculation of color-flavor-locked quark matter, we investigate the neutrality of a two-species condensate using a Yukawa model which has a finite-range interaction. In a mean field calculation we obtain the full energy-momentum dependence of the self energy and find that the energy dependence leads to a population imbalance in the Cooper-paired phase when it is stressed by a species-dependent chemical potential. This gives some support to the suggestion that the color-flavor-locked phase of quark matter might not be an insulator.
nucl-thhep-phPRL(2018)·10 citations
02
The effect of the fluctuating proton size on the study of chiral magnetic effect in proton-nucleus collisions
Dmitri Kharzeev🇺🇸 · Zhoudunming Tu🇺🇸 · Aobo Zhang🇺🇸 · Wei Li🇺🇸
High energy proton-nucleus (pA) collisions provide an important constraint on the study of the chiral magnetic effect in QCD matter. Naively, in pA collisions one expects no correlation between the orientation of event plane as reconstructed from the azimuthal distribution of produced hadrons and the orientation of magnetic field. If this is the case, any charge-dependent hadron correlations can only result from the background. Nevertheless, in this paper we point out that in high multiplicity pA collisions a correlation between the magnetic field and the event plane can appear. This is because triggering on the high hadron multiplicity amounts to selecting Fock components of the incident proton with a large number of partons that are expected to have a transverse size much larger than the average proton size. We introduce the effect of the fluctuating proton size in the Monte Carlo Glauber model and evaluate the resulting correlation between the magnetic field and the second-order event plane in both pA and nucleus-nucleus (AA) collisions. The fluctuating proton size is found to result in a significant correlation between magnetic field and the event plane in pA collisions, even though the magnitude of the correlation is still much smaller than in AA collisions. This result opens a possibility of studying the chiral magnetic effect in small systems.
nucl-thhep-phnucl-exPRC(2018)·9 citations
03
Systematics of strong nuclear amplification of gluon saturation from exclusive vector meson production in high energy electron-nucleus collisions
Heikki Mäntysaari🇫🇮 · Raju Venugopalan🇺🇸
We show that gluon saturation gives rise to a strong modification of the scaling in both the nuclear mass number $A$ and the virtuality $Q^{2}$ of the vector meson production cross-section in exclusive deep-inelastic scattering off nuclei. We present qualitative analytic expressions for how the scaling exponents are modified as well as quantitative predictions that can be tested at an Electron-Ion Collider.
nucl-thhep-phPLB(2018)·44 citations
04
Repulsion and absorption of the $Σ$ -nucleus potential for $Σ^{-}$ - $^{5}$ He in the $^{6}$ Li( $π^{-}$ , $K^{+}$ ) reaction
Toru Harada · Ryotaro Honda · Yoshiharu Hirabayashi
We study phenomenologically inclusive spectra of the $^{6}$ Li( $π^{-}$ , $K^{+}$ ) reaction at 1.2 GeV/ $c$ within a distorted-wave impulse approximation with the optimal Fermi-averaging $π^{-} p \to K^{+} Σ^{-}$ $t$ matrix. We attempt to clarify the property of a $Σ$ -nucleus potential for $Σ^{-}$ - $^{5}$ He by comparing the calculated spectra with the data of the J-PARC E10 experiment. The result shows that the repulsive and absorptive components of the $Σ^{-}$ - $^{5}$ He potential provide the ability to explain the data of the continuum spectra in $Σ$ and $Λ$ regions; the strengths of $V_{Σ} ≃$ +30 MeV and $W_{Σ} ≃$ $-$ 26 MeV are favored within the Woods-Saxon potential, consistent with analyses for heavier nuclei. Effects of the size and potential range for $Σ^{-}$ - $^{5}$ He in the neutron excess of $(N - Z) / (N + Z) =$ 0.2 are also discussed.
nucl-thPRC(2018)·14 citations
05
Some aspects of global Lambda polarization in heavy-ion collisions
Xiao-Liang Xia🇨🇳 · Hui Li🇨🇳 · Qun Wang🇨🇳
Large orbital angular momentum can be generated in non-central heavy-ion collisions, and part of it is expected to be converted into final particle's polarization due to the spin-orbit coupling. Within the framework of A Multi-Phase Transport (AMPT) model, we studied the vorticity-induced polarization of $Λ$ hyperons at the midrapidity region $∣ η ∣ < 1$ in Au-Au collisions at energies $s_{N N} = 7.7 \sim 200$ GeV. Our results show that the global polarization decreases with the collisional energies and is consistent with the recent STAR measurements. This behavior can be understood by less asymmetry of participant matter in the midrapidity region due to faster expansion of fireball at higher energies. As another evidence, we discuss how much the angular momentum is deposited in different rapidity region. The result supports our asymmetry argument.
nucl-thhep-phPoS(2018)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Color superconductivity and charge neutrality in Yukawa theory

The effect of the fluctuating proton size on the study of chiral magnetic effect in proton-nucleus collisions

Systematics of strong nuclear amplification of gluon saturation from exclusive vector meson production in high energy electron-nucleus collisions

Repulsion and absorption of the Σ-nucleus potential for Σ−-5He in the 6Li(π−, K+) reaction

Some aspects of global Lambda polarization in heavy-ion collisions

Affiliations

Repulsion and absorption of the $Σ$ -nucleus potential for $Σ^{-}$ - $^{5}$ He in the $^{6}$ Li( $π^{-}$ , $K^{+}$ ) reaction