Nuclear Theory·nucl-th

Thursday·November 17, 2016

10 papers—5 primary·5 cross-listed

01
Recent progress in anisotropic hydrodynamics
Michael Strickland🇺🇸
The quark-gluon plasma created in a relativistic heavy-ion collisions possesses a sizable pressure anisotropy in the local rest frame at very early times after the initial nuclear impact and this anisotropy only slowly relaxes as the system evolves. In a kinetic theory picture, this translates into the existence of sizable momentum-space anisotropies in the underlying partonic distribution functions, <p_L^2> << <p_T^2>. In such cases, it is better to reorganize the hydrodynamical expansion by taking into account momentum-space anisotropies at leading-order in the expansion instead of as a perturbative correction to an isotropic distribution. The resulting anisotropic hydrodynamics framework has been shown to more accurately describe the dynamics of rapidly expanding systems such as the quark-gluon plasma. In this proceedings contribution, I review the basic ideas of anisotropic hydrodynamics, recent progress, and present a few preliminary phenomenological predictions for identified particle spectra and elliptic flow.
nucl-thhep-phEPJ Web Conf.(2017)·9 citations
02
Dynamics of semi-superfluid fluxtubes in color-flavor locked quark matter
Mark G. Alford🇺🇸 · Andreas Windisch🇺🇸
At very high densities, as for example in the core of a neutron star, matter may appear in the color-flavor locked (CFL) phase, which is a superfluid. This phase features topologically stable vortex solutions, which arise in a spinning superfluid as localized configurations carrying quanta of angular momentum. Despite the topological stability of these vortices they are not the lowest energy state of the system at neutron star densities and decay into triplets of semi-superfluid fluxtubes. In these proceedings we report on the progress of our numerical study in the Ginzburg-Landau approach, where we investigate lattices of semi-superfluid fluxtubes. The fluxtubes are obtained through controlled decay of global vortex configurations in the presence of a gauge field. Understanding the dynamics of semi-superfluid string configurations is important in the context of angular momentum transfer from a quark matter core of a neutron star beyond the core boundary, since not vortex-, but fluxtube pinning seems to be the relevant mechanism in this scenario.
nucl-thastro-ph.HEhep-phEPJ Web Conf.(2017)·0 citations
03
Neutrino-nucleon scattering in supernova matter from the virial expansion
C.J. Horowitz🇺🇸 · O. L. Caballero🇨🇦 · Zidu Lin🇺🇸 · Evan O'Connor🇺🇸 · A. Schwenk🇩🇪
We generalize our virial approach to study the neutral current neutrino response of nuclear matter at low densities. In the long-wavelength limit, the virial expansion makes model-independent predictions for neutrino-nucleon scattering rates and the density S_V and spin S_A responses. We find S_A is significantly reduced from one even at low densities. We provide a simple fit S_A^f(n,T,Y_p) of the axial response as a function of density n, temperature T and proton fraction Y_p. This fit reproduces our model independent virial results at low densities and reproduces the Burrows and Sawyer random phase approximation (RPA) results at high densities. Our fit can be incorporated into supernova simulations in a straight forward manner. Preliminary one dimensional supernova simulations suggest that the reduction in the axial response may enhance neutrino heating rates in the gain region during the accretion phase of a core-collapse supernovae.
nucl-thastro-ph.HEPRC(2017)·99 citations
04
Investigating the NCQ scaling of elliptic flow at LHC with a multiphase transport model
Liang Zheng🇨🇳 · Hui Li🇨🇳 · Hong Qin🇨🇳 · Qi-Ye Shou🇨🇳 · Zhong-Bao Yin🇨🇳
The number of constituent quark (NCQ) scaling behavior of elliptic flow has been systematically studied at the LHC energy within the framework of a multiphase transport model (AMPT) in this work. We find that the parameters used to generate the initial states and the collision centrality are important for the existence of NCQ scaling even when hadronic rescattering contribution is off in Pb-Pb collisions of $s_{N N} = 2.76$ TeV. By turning on the hadron rescattering process, the hadronic evolution impacts are also found to be significant. Extending the analysis to Pb-Pb collsions of $s_{N N} = 5.02$ TeV, one would observe similar qualitative features.
nucl-thnucl-exEPJA(2017)·13 citations
05
From gluon topology to chiral anomaly: Emergent phenomena in quark-gluon plasma
Jinfeng Liao🇺🇸
Heavy-ion collision experiments at RHIC and the LHC have found a new emergent phase of QCD, a strongly coupled quark-gluon plasma (sQGP) that is distinctively different from either the low temperature hadron phase or the very high temperature weakly coupled plasma phase. Highly nontrivial emergent phenomena occur in such sQGP and two examples will be discussed in this contribution: the magnetic component of sQGP that stems from topologically nontrivial configurations in the gluon sector; and the anomalous chiral transport that arises as macroscopic manifestation of microscopic chiral anomaly in the quark sector. For both examples, their important roles in explaining pertinent heavy-ion data will be emphasized.
nucl-thhep-phhep-thnucl-exJ.Phys.Conf.Ser.(2017)·1 citation
06
Cross section line shape of $e^{+} e^{-} \to χ_{c 0} ω$ around the $Y (4260)$ mass region
Martin Cleven🇪🇸 · Qiang Zhao🇨🇳
We demonstrate that the recent measurement of the cross section line shapes of $e^{+} e^{-} \to χ_{c 0} ω$ can be naturally explained by the molecular picture for $Y (4260)$ where the $Y (4260)$ is treated as a hadronic molecule dominated by $D ˉ D_{1} (2420) + c . c .$ This result is consistent with properties extracted for $Y (4260)$ as the $D ˉ D_{1} (2420) + c . c .$ molecular state in other reactions such as $e^{+} e^{-} \to J / ψ π π$ , $h_{c} π π$ , $D ˉ D^{*} π + c . c .$ , and $γ X (3872)$ .
↳ hep-phhep-exnucl-thPLB(2017)·25 citations
07
Beyond WIMPs: the Quark (Anti) Nugget Dark Matter
Ariel Zhitnitsky🇨🇦
We review a testable dark matter (DM) model outside of the standard WIMP paradigm. The model is unique in a sense that the observed ratio $Ω_{dark} ≃ Ω_{visible}$ for visible and dark matter densities finds its natural explanation as a result of their common QCD origin when both types of matter (DM and visible) are formed during the QCD transition and both are proportional to single dimensional parameter of the system, $Λ_{QCD}$ . We argue that the charge separation effect also inevitably occurs during the same QCD transition in the presence of the $C P$ odd axion field $a (x)$ . It leads to preferential formation of one species of nuggets on the scales of the visible Universe where the axion field $a (x)$ is coherent. A natural outcome of this preferential evolution is that only one type of the visible baryons (not anti- baryons) remain in the system after the nuggets complete their formation. Unlike conventional WIMP dark matter candidates, the nuggets and anti-nuggets are strongly interacting but macroscopically large objects. The rare events of annihilation of the anti-nuggets with visible matter lead to a number of observable effects. We argue that the relative intensities for a number of measured excesses of emission from the centre of galaxy (covering more than 11 orders of magnitude) are determined by standard and well established physics. At the same time the absolute intensity of emission is determined by a single new fundamental parameter of the theory, the axion mass, $1 0^{- 6} eV ≲ m_{a} ≲ 1 0^{- 3} eV$ . Finally, we comment on implications of these studies for the axion search experiments, including microwave cavity and the Orpheus experiments.
↳ hep-phastro-ph.COnucl-thEPJ Web Conf.(2017)·4 citations
08
Estimation of Stopped Protons at Energies Relevant for a Beam Energy Scan at the BNL Relativistic Heavy-Ion Collider
Dhananjaya Thakur🇮🇳 · Sunil Jakhar🇮🇳 · Prakhar Garg🇮🇳 · Raghunath Sahoo (Indian Institute of Technology Indore, India)🇮🇳
The recent net-proton fluctuation results of the STAR (Solenoidal Tracker At RHIC) experiment from beam energy scan (BES) program at the BNL Relativistic Heavy Ion Collider (RHIC) have drawn much attention to exploring the QCD critical point and the nature of deconfinement phase transition. There has been much speculation that the non-monotonic behavior of $κ σ^{2}$ of the produced protons around $s_{NN}$ = 19.6 GeV in the STAR results may be due to the existence of QCD critical point. However, the experimentally measured proton distributions contain protons from heavy resonance decays, from baryon stopping and from direct production processes. These proton distributions are used to estimate the net-proton number fluctuation. Because it is difficult to disentangle the protons from the above-mentioned sources, it is better to devise a method which will account for the directly produced baryons (protons) to study the dynamical fluctuation at different center-of-mass energies. This is because, it is assumed that any associated criticality in the system could affect the particle production mechanism and hence the dynamical fluctuation in various conserved numbers. In the present work, we demonstrate a method to estimate the number of stopped protons at RHIC BES energies for central $0 - 5%$ \auau collisions within STAR acceptance and discuss its implications on the net-proton fluctuation results.
↳ nucl-exhep-exhep-phnucl-thPRC(2017)·10 citations
09
Rearrangement of valence neutrons in the neutrinoless double- $β$ decay of $^{136}$ Xe
S. V. Szwec🇬🇧 · B. P. Kay🇺🇸 · T. E. Cocolios🇬🇧 · J. P. Entwisle🇬🇧 · S. J. Freeman🇬🇧 · L. P. Gaffney🇬🇧 · V. Guimarães🇧🇷 · F. Hammache🇫🇷 · P. P. McKee🇬🇧 · E. Parr🇬🇧 · C. Portail🇫🇷 · J. P. Schiffer🇺🇸 and 4 other authors
A quantitative description of the change in ground-state neutron occupancies between $^{136}$ Xe and $^{136}$ Ba, the initial and final state in the neutrinoless double- $β$ decay of $^{136}$ Xe, has been extracted from precision measurements of the cross sections of single-neutron adding and -removing reactions. Comparisons are made to recent theoretical calculations of the same properties using various nuclear-structure models. These are the same calculations used to determine the magnitude of the nuclear matrix elements for the process, which at present disagree with each other by factors of 2 or 3. The experimental neutron occupancies show some disagreement with the theoretical calculations.
↳ nucl-exnucl-thPRC(2016)·30 citations
10
Phases of dense matter with holographic instantons
Florian Preis🇦🇹 · Andreas Schmitt🇬🇧
We discuss nuclear matter and the transition to quark matter in the decompactified limit of the Sakai-Sugimoto model. Nuclear matter is included through instantons on the flavor branes of the model. Our approximation is based on the flat-space solution, but we allow for a dynamical instanton width and deformation and compute the energetically preferred number of instanton layers in the bulk as a function of the baryon chemical potential. We determine the regions in parameter space where the binding energy of nuclear matter is like in QCD, and compute the phase diagram in the plane of temperature and chemical potential.
↳ hep-phhep-thnucl-thEPJ Web Conf.(2017)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE