Nuclear Theory·nucl-th

Friday·September 14, 2018

8 papers—5 primary·3 cross-listed

01
Hydrodynamic fluctuations of entropy in one-dimensionally expanding system
Tetsufumi Hirano🇯🇵 · Ryuichi Kurita🇯🇵 · Koichi Murase🇯🇵
The fluctuation-dissipation relation tells that dissipation always accompanies with thermal fluctuations. Relativistic fluctuating hydrodynamics is used to study the effects of the thermal fluctuations in the hydrodynamic expansion of the quark-gluon plasma created in the high-energy nuclear collisions. We show that the thermal noise obeys the steady-state fluctuation theorem when (i) the time scales of the evolution of thermodynamic quantities are sufficiently longer than the relaxation time, and (ii) the thermal fluctuations of temperature are sufficiently small. The steady-state fluctuation theorem describes the distribution of the entropy which can be related to the multiplicity observed in high-energy nuclear collisions. As a consequence, we propose an upper bound to the multiplicity fluctuations which is useful to test the initial state models. We also numerically investigate breaking of the steady-state fluctuation theorem due to the non-vanishing relaxation time in real nuclear collisions.
nucl-thcond-mat.stat-mechhep-phnucl-exNPA(2019)·20 citations
02
Broken mirror symmetry in $^{36}$ S and $^{36}$ Ca
J.J. Valiente-Dobón · A. Poves · A. Gadea · B. Fernández-Domínguez
Shape coexistence is an ubiquitous phenomenon in the neutron-rich nuclei belonging to (or sitting at the shores of) the $N = 20$ Island of Inversion (IoI). Exact isospin symmetry predicts the same behaviour for their mirrors and the existence of a proton-rich IoI around $Z = 20$ , centred in the (surely unbound) nucleus $^{32}$ Ca. In this article we show that in $^{36}$ Ca and $^{36}$ S, Coulomb effects break dramatically the mirror symmetry in the excitation energies, due to the different structures of the intruder and normal states. The Mirror Energy Difference (MED) of their 2 $^{+}$ states is known to be very large at -246 keV. We reproduce this value and predict the first excited state in $^{36}$ Ca to be a 0 $^{+}$ at 2.7 MeV, 250 keV below the first 2 $^{+}$ . In its mirror $^{36}$ S the 0 $^{+}$ lies at 55 keV above the 2 $^{+}$ measured at 3.291 MeV. Our calculations predict a huge MED of -720 keV, that we dub "Colossal" Mirror Energy Difference (CMED). A possible reaction mechanism to access the 0 $_{2}^{+}$ in $^{36}$ Ca will be discussed. In addition, we theoretically address the MED's of the $A = 34$ $T = 3$ and $A = 32$ $T = 4$ mirrors.
nucl-thPRC(2018)·14 citations
03
Cluster-Daughter Overlap as a New Probe of Alpha-Cluster Formation in Medium-Mass and Heavy Even-Even Nuclei
Dong Bai🇨🇳 · Zhongzhou Ren🇨🇳
We study the possibility to use the cluster-daughter overlap as a new probe of alpha-cluster formation in medium-mass and heavy even-even nuclei. We introduce a dimensionless parameter $O$ , which is the ratio between the root-mean-square (rms) intercluster separation and the sum of rms point radii of the daughter nucleus and the alpha particle, to measure the degree of the cluster-daughter overlap quantitatively. By using this parameter, a large (small) cluster-daughter overlap between the alpha cluster and daughter nucleus corresponds to a small (large) $O$ value. The alpha-cluster formation is shown explicitly, in the framework of the quartetting wave function approach, to be suppressed when the $O$ parameter is small, and be favored when the $O$ parameter is large. We then use this $O$ parameter to explore systematically the landscape of alpha-cluster formation probabilities in medium-mass and heavy even-even nuclei, with $O$ being calculated from experimentally measured charge radii. The trends of alpha-cluster formation probabilities are found to be generally consistent with previous studies. The effects of various shell closures on the alpha-cluster formation are identified, along with some hints on a possible subshell structure at $N = 106$ along the Hg and Pb isotopic chains. The study here could be a useful complement to the traditional route to probe alpha-cluster formation in medium-mass and heavy even-even nuclei using alpha-decay data. Especially, it would be helpful in the cases where the target nucleus is stable against alpha decay or alpha-decay data are currently not available.
nucl-thPLB(2018)·11 citations
04
On the eikonal approach to nuclear diffraction dissociation
Angela Bonaccorso · David M. Brink
The study of nuclear breakup of halo and weakly bound particles has been one of the key ingredients in the understanding of exotic nuclei during the last thirty years. One of the most used methods to analyse data, in particular absolute breakup cross sections, has been the eikonal approximation. Here we revise critically the formalisms used for calculating the diffraction dissociation part of nuclear breakup and show that there is a formula that can be applied to breakup on any target, while a most commonly used formula must be restricted to light targets as it contains also the effect of Coulomb breakup calculated to first order in the sudden approximation which is well known for not being accurate.
nucl-thnucl-exEPJA(2018)·3 citations
05
Investigation of spatial manifestation of $α$ clusters in $^{16}$ O via $α$ -transfer reactions
Tokuro Fukui · Yoshiko Kanada-En'yo · Kazuyuki Ogata · Tadahiro Suhara · Yasutaka Taniguchi
Recently, we have determined surface distributions of $α$ clusters in the ground state of $^{20} Ne$ from $α$ -transfer cross sections, without investigating the properties of its excited states. In this paper we extend our comprehension of $α$ -cluster structures in excited states of nuclei through reaction studies. In particular we focus on $^{16} O$ , for which attention has been paid to advances of structure theory and assignment regarding $4^{+}$ -resonance states. We study the surface manifestation of the $α$ -cluster states in both the ground and excited states of $^{16} O$ from the analysis of the $α$ -transfer reaction $^{12} C (^{6} Li, d)^{16} O$ . The $α$ -transfer reaction is described by the distorted-wave Born approximation. We test two microscopic wave functions as an input of reaction calculations. Then a phenomenological potential model is introduced to clarify the correspondence between cluster-wave functions and transfer-cross sections. Surface peaks of the $α$ -wave function of $^{16} O (0^{+})$ are sensitively probed by transfer-cross sections at forward angles, while it remains unclear how we trace the surface behavior of $^{16} O (4^{+})$ from the cross sections. We are able to specify that the $α$ -cluster structure in the $0_{1}^{+}$ and $0_{2}^{+}$ states prominently manifests itself at the radii $\sim 4$ and $\sim 4.5$ ~fm, respectively. It is remarkable that the $4_{1}^{+}$ state has the $^{12} C + α$ -cluster component with the surface peak at the radius $\sim 4$ or outer, whereas the $^{12} C + α$ -cluster component in the $4_{2}^{+}$ state is found not to be dominant. The $4_{2}^{+}$ state is difficult to be interpreted by a simple potential model assuming the $^{12} C + α$ configuration only.
nucl-thNPA(2019)·15 citations
06
Superstatistics and the effective QCD phase diagram
Alejandro Ayala🇲🇽 · Martin Hentschinski🇲🇽 · Luis Alberto Hernandez🇲🇽 · Marcelo Loewe🇨🇱 · Renato Zamora🇨🇱
We study the effect of a partially thermalized scenario for chiral symmetry restoration at finite temperature and quark chemical potential, and in particular for the position of the critical end point in an effective description of the QCD phase diagram. We show that these effects produce the critical end point to be displaced towards larger values of temperature and lower values of the quark chemical potential as compared to the case when the system can be regarded as completely thermalized. We conclude that these effects may be important for relativistic heavy ion collisions where the number of subsystems making the whole interaction volume can be linked to the finite number of participants in the reaction.
↳ hep-phnucl-thPRD(2018)·26 citations
07
Effect of centrality bin width corrections on two-particle number and transverse momentum differential correlation functions
Victor Gonzalez🇪🇸 · Ana Marin🇩🇪 · Pedro Ladron de Guevara🇪🇸 · Jinjin Pan🇺🇸 · Sumit Basu🇺🇸 · Claude Pruneau🇺🇸
Two-particle number and transverse momentum differential correlation functions are powerful tools for unveiling the detailed dynamics and particle production mechanisms involved in relativistic heavy-ion collisions. Measurements of transverse momentum correlators $P_{2}$ and $G_{2}$ , in particular, provide added information not readily accessible with better known number correlation functions $R_{2}$ . However, it is found that the $R_{2}$ and $G_{2}$ correlators are somewhat sensitive to the details of the experimental procedure used to measure them. They exhibit, in particular, a dependence on the collision centrality bin width, which may have a rather detrimental impact on their physical interpretation. A technique to correct these correlators for collision centrality bin-width averaging is presented. The technique is based on the hypothesis that the shape of single- and pair- probability densities vary slower with collision centrality than the corresponding integrated yields. The technique is tested with Pb-Pb simulations based on the HIJING and ultrarelativistic quantum molecular dynamics models and shown to enable a precision better than 1% for particles in the kinematic range $0.2 \leq p_{T} \leq 2.0$ GeV/ $c$ .
↳ physics.data-anhep-exhep-phnucl-ex+1PRC(2019)·6 citations
08
Nonperturbative strange-quark sea from lattice QCD, light-front holography, and meson-baryon fluctuation models
Raza Sabbir Sufian🇺🇸 · Tianbo Liu🇺🇸 · Guy F. de Téramond🇨🇷 · Hans Günter Dosch🇩🇪 · Stanley J. Brodsky🇺🇸 · Alexandre Deur🇺🇸 · Mohammad T. Islam🇺🇸 · Bo-Qiang Ma🇨🇳
We demonstrate that a nonzero strangeness contribution to the spacelike electromagnetic form factor of the nucleon is evidence for a strange-antistrange asymmetry in the nucleon's light-front wave function, thus implying different nonperturbative contributions to the strange and antistrange quark distribution functions. A recent lattice QCD calculation of the nucleon strange quark form factor predicts that the strange quark distribution is more centralized in coordinate space than the antistrange quark distribution, and thus the strange quark distribution is more spread out in light-front momentum space. We show that the lattice prediction implies that the difference between the strange and antistrange parton distribution functions, $s (x) - s ˉ (x)$ , is negative at small- $x$ and positive at large- $x$ . We also evaluate the strange quark form factor and $s (x) - s ˉ (x)$ using a baryon-meson fluctuation model and a novel nonperturbative model based on light-front holographic QCD. This procedure leads to a Veneziano-like expression of the form factor, which depends exclusively on the twist of the hadron and the properties of the Regge trajectory of the vector meson which couples to the quark current in the hadron. The holographic structure of the model allows us to introduce unambiguously quark masses in the form factors and quark distributions preserving the hard scattering counting rule at large- $Q^{2}$ and the inclusive counting rule at large- $x$ . Quark masses modify the Regge intercept which governs the small- $x$ behavior of quark distributions, therefore modifying their small- $x$ singular behavior. Both nonperturbative approaches provide descriptions of the strange-antistrange asymmetry and intrinsic strangeness in the nucleon consistent with the lattice QCD result.
↳ hep-phhep-exhep-latnucl-thPRD(2018)·44 citations

Affiliations

first authorsco-authorsvia INSPIRE