Tue·Dec 15, 2020Tuesday·December 15, 2020

1. 01*

   Flow-plane decorrelations in heavy-ion collisions with multiple-plane cumulants

   Zhiwan Xu🇺🇸 · Xiatong Wu🇺🇸 · Caleb Sword🇺🇸 · Gang Wang🇺🇸 · Sergei A. Voloshin🇺🇸 · Huan Zhong Huang🇺🇸

   The azimuthal correlations between local flow planes at different (pseudo)rapidities ($\eta$) may reveal important details of the initial nuclear matter density distributions in heavy-ion collisions. Extensive experimental measurements of a factorization ratio ($r_2$) and its derivative ($F_2$) have shown evidence of the longitudinal flow-plane decorrelation. However, nonflow effects also affect this observable and prevent a quantitative understanding of the phenomenon. In this paper, to distinguish decorrelation and nonflow effects, we propose a new cumulant observable, $T_2$, which largely suppresses nonflow. The technique sensitivity to different initial-state scenarios and nonflow effects are tested with a simple Monte Carlo model, and in the end, the method is applied to events simulated by a multiphase transport model (AMPT) for Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV. We also emphasize that a distinct decorrelation signal requires not only the right sign of an observable, but also its proper dependence on the $\eta$-window of the reference flow plane, to be consistent with the pertinent decorrelation picture.

   nucl-exhep-exPRC(2022)·12 citations
2. 02*

   Symmetry energy investigation with pion production from Sn+Sn systems

   G. Jhang🇺🇸 · J. Estee🇺🇸 · J. Barney🇺🇸 · G. Cerizza🇺🇸 · M. Kaneko🇯🇵 · J. W. Lee🇰🇷 · W. G. Lynch🇺🇸 · T. Isobe🇯🇵 · M. Kurata-Nishimura · T. Murakami🇯🇵 · C. Y .Tsang🇺🇸 · M. B. Tsang🇺🇸 and 68 other authors

   In the past two decades, pions created in the high density regions of heavy ion collisions have been predicted to be sensitive at high densities to the symmetry energy term in the nuclear equation of state, a property that is key to our understanding of neutron stars. In a new experiment designed to study the symmetry energy, the multiplicities of negatively and positively charged pions have been measured with high accuracy for central ${}^{132}$Sn+${}^{124}$Sn, ${}^{112}$Sn+${}^{124}$Sn, and ${}^{108}$Sn+${}^{112}$Sn collisions at $E/A=270\mathrm{MeV}$ with the S$\pi$RIT Time Projection Chamber. While the uncertainties of individual pion multiplicities are measured to 4\%, those of the charged pion multiplicity ratios are measured to 2\%. We compare these data to predictions from seven major transport models. The calculations reproduce qualitatively the dependence of the multiplicities and their ratios on the total neutron to proton number in the colliding systems. However, the predictions of the transport models from different codes differ too much to allow extraction of reliable constraints on the symmetry energy from the data. This finding may explain previous contradictory conclusions on symmetry energy constraints obtained from pion data in Au+Au system. These new results call for better understanding of the differences among transport codes, and new observables that are more sensitive to the density dependence of the symmetry energy.

   nucl-exnucl-thPLB(2021)·69 citations
3. 03*

   Comparison of transverse single-spin asymmetries for forward ${\pi }^0$ production in polarized $pp$, $p\mathrm{Al}$ and $p\mathrm{Au}$ collisions at nucleon pair c.m. energy $\sqrt{s_{\mathrm{NN}}}=200$ GeV

   STAR Collaboration: J. Adam🇺🇸 · L. Adamczyk🇵🇱 · J. R. Adams🇺🇸 · J. K. Adkins🇺🇸 · G. Agakishiev🇷🇺 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · I. Alekseev🇷🇺 · D. M. Anderson🇺🇸 · A. Aparin🇷🇺 · E. C. Aschenauer🇺🇸 · M. U. Ashraf🇨🇳 and 359 other authors

   The STAR Collaboration reports a measurement of the transverse single-spin asymmetries, $A_N$, for neutral pions produced in polarized proton collisions with protons ($pp$), with aluminum nuclei ($p\mathrm{Al}$) and with gold nuclei ($p\mathrm{Au}$) at a nucleon-nucleon center-of-mass energy of 200 GeV. Neutral pions are observed in the forward direction relative to the transversely polarized proton beam, in the pseudo-rapidity region $2.7<\eta <3.8$. Results are presented for ${\pi }^0$s observed in the STAR FMS electromagnetic calorimeter in narrow Feynman x ($x_F$) and transverse momentum ($p_T$) bins, spanning the range $0.17<x_F<0.81$ and $1.7<p_T<6.0$ GeV/$c$. For fixed $x_F<0.47$, the asymmetries are found to rise with increasing transverse momentum. For larger $x_F$, the asymmetry flattens or falls as $p_T$ increases. Parametrizing the ratio $r(A)\equiv A_N(pA)/A_N(pp)=A^P$ over the kinematic range, the ratio $r(A)$ is found to depend only weakly on $A$, with $⟨P⟩=-0.027\pm 0.005$. No significant difference in $P$ is observed between the low-$p_T$ region, $p_T<2.5$ GeV/$c$, where gluon saturation effects may play a role, and the high-$p_T$ region, $p_T>2.5$ GeV/$c$. It is further observed that the value of $A_N$ is significantly larger for events with a large-$p_T$ isolated ${\pi }^0$ than for events with a non-isolated ${\pi }^0$ accompanied by additional jet-like fragments. The nuclear dependence $r(A)$ is similar for isolated and non-isolated ${\pi }^0$ events.

   nucl-exhep-exPRD(2021)·20 citations
4. 04*

   Elliptic ($v_2$) and triangular ($v_3$) anisotropic flow of identified hadrons from the STAR Beam EnergyScan program

   P. Parfenov (for the STAR Collaboration)🇷🇺

   Elliptic ($v_2$) and triangular ($v_3$) anisotropic flow coefficients for inclusive and identified charged hadrons (~${\pi }^{\pm }$, $K^{\pm }$, $p$, $\bar{p}$~) at midrapidity in Au+Au collisions, measured by the STAR experiment in the Beam Energy Scan (BES) at the Relativistic Heavy Ion Collider at $\sqrt{s_{NN}}$ = $11.5$ - $62.4$ GeV, are presented. We observe that the triangular flow signal ($v_3$) of identified hadrons exhibits similar trends as first observed for $v_2$ in Au+Au collisions, i.e. (i) mass ordering at low transverse momenta, $p_T<2$ GeV/c, (ii) meson/baryon splitting at intermediate $p_T$, $2<p_T<4$ GeV/c, and (iii) difference in flow signal of protons and antiprotons. New measurements of $v_3$ excitation function could serve as constraints to test different models and to aid new information about the temperature dependence of the transport properties of the strongly interacting matter.

   ↳ hep-exnucl-exJ.Phys.Conf.Ser.(2020)·5 citations
5. 05*

   The comparison of methods for anisotropic flow measurements with the MPD Experiment at NICA

   P. Parfenov🇷🇺 · A. Taranenko🇷🇺 · D. Idrisov🇷🇺 · V. B. Luong🇷🇺 · N. Geraksiev🇧🇬 · A. Demanov🇷🇺 · A. Povarov🇷🇺 · V. Kireyeu🇷🇺 · A. Truttse🇷🇺 · E. Volodihin (for the MPD Collaboration)🇷🇺

   The anisotropic collective flow is one of the key observables to study the properties of dense matter created in heavy-ion collisions. The performance of Multi-Purpose Detector (MPD) at NICA collider for directed and elliptic flow measurements is studied with Monte-Carlo simulations of heavy-ion collisions at energies $\sqrt{s_{NN}}$ = 4 - 11 GeV.

   ↳ hep-exnucl-ex4 citations
6. 06*

   Gravity Resonance Spectroscopy and Dark Energy Symmetron Fields

   Tobias Jenke🇫🇷 · Joachim Bosina🇦🇹 · Jakob Micko🇫🇷 · Mario Pitschmann🇦🇹 · Rene Sedmik🇦🇹 · Hartmut Abele🇦🇹

   Spectroscopic methods allow to measure energy differences with unrivaled precision. In the case of gravity resonance spectroscopy, energy differences of different gravitational states are measured without recourse to the electromagnetic interaction. This provides a very pure and background free look at gravitation and topics related to the central problem of dark energy and dark matter at short distances. In this article we analyse the effect of additional dark energy scalar symmetron fields, a leading candidate for a screened dark energy field, and place limits in a large volume of parameter space.

   ↳ hep-phnucl-exEur.Phys.J.ST(2021)·30 citations
7. 07*

   How Silicon and Boron Dopants Govern the Cryogenic Scintillation Properties of N-type GaAs

   Stephen Derenzo🇺🇸 · Edith Bourret🇺🇸 · Christiane Frank-Rotsch🇩🇪 · Stephen Hanrahan🇺🇸 · Maurice Garcia-Sciveresa🇺🇸

   This paper is the first report describing how the concentrations of silicon and boron govern the cryogenic scintillation properties of n-type GaAs. It shows that valence band holes are promptly trapped on radiative centers and then combine radiatively with silicon donor band electrons at rates that increase with the density of free carriers. It also presents the range of silicon and boron concentrations needed for efficient light emission under X-ray excitation, which along with its low band gap and apparent absence of afterglow, make scintillating GaAs suitable for the detection of rare, low-energy electronic excitations from interacting dark matter particles. A total of 29 samples from four different suppliers were studied. Luminosities and timing responses were measured for the four principal emission bands centered at 860, 930, 1070, and 1335 nm, and for the total emissions. Excitation pulses of 40 kVp X-rays were provided by a light-excited X-ray tube driven by an ultra-fast laser. Scintillation emissions from 800 to 1350 nm were measured using an InGaAs photomultiplier. Within the concentration ranges of free carriers from 2 x 10^16/cm3 to 6 x 10^17/cm3 and boron from 1.5 x 10^18/cm3 to 6 x 10^18/cm3, nine samples have luminosities > 70 photons/keV and two have luminosities > 110 photons/keV. Other samples in that range have lower luminosities due to higher concentrations of non-radiative centers. The decay times decrease by typically a factor of ten with increasing free carrier concentrations from 10^17/cm3 to 2 x 10^18/cm3.

   ↳ cond-mat.mtrl-scinucl-exNucl.Instrum.Meth.A(2021)·9 citations
8. 08*

   Global $\Lambda$ polarization in moderately relativistic nuclear collisions

   Yu. B. Ivanov🇷🇺

   Predictions for the global polarization of $\Lambda$ hyperons in Au+Au collisions at moderately relativistic collision energies, 2.4 $\le \sqrt{s_{NN}}\le$ 11 GeV, are made. These are based on the thermodynamic approach to the global polarization incorporated into the model of the three-fluid dynamics. Centrality dependence of the polarization is studied. It is predicted that the polarization reaches a maximum or a plateau (depending on the equation of state and centrality) at $\sqrt{s_{NN}}\approx$ 3 GeV. It is found that the global polarization increases with increasing width of the rapidity window around the midrapidity.

   ↳ nucl-thhep-phnucl-exPRC(2021)·54 citations
9. 09*

   Coupling dynamical and statistical mechanisms for baryonic cluster production in nucleus collisions of intermediate and high energies

   A.S. Botvina🇩🇪 · N. Buyukcizmeci🇹🇷 · M. Bleicher🇩🇪

   Central nucleus-nucleus collisions produce many new baryons and the nuclear clusters can be formed from these species. The phenomenological coalescence models were sufficiently good for description of light nuclei yields in a very broad range of collision energies. We demonstrate that in reality the coalescence process can be considered as 1) the formation of primary diluted excited baryon clusters and 2) their following statistical decay leading to the final cold fragment production. We argue that the formation of such excited systems from the interacting baryons is a natural consequence of the nuclear interaction at subnuclear densities resulting in the nuclear liquid-gas type phase transition in finite systems. In this way one can provide a consistent interpretation of the experimental fragment yields (FOPI data) including the important collision energy dependence in relativistic ion reactions. We investigate the regularities of this new kind of fragment production, for example, their yield, isospin, and kinetic energy characteristics. A generalization of such a clusterization mechanism for hypernuclear matter is suggested. The isotope yields and particle correlations should be adequate for studying these phenomena.

   ↳ nucl-thnucl-exPRC(2021)·21 citations
10. 10*

    Get on the BAND Wagon: A Bayesian Framework for Quantifying Model Uncertainties in Nuclear Dynamics

    D.R. Phillips🇺🇸 · R.J. Furnstahl🇺🇸 · U. Heinz🇺🇸 · T. Maiti🇺🇸 · W. Nazarewicz🇺🇸 · F.M. Nunes🇺🇸 · M. Plumlee🇺🇸 · M.T. Pratola🇺🇸 · S. Pratt🇺🇸 · F.G. Viens🇺🇸 · S.M. Wild🇺🇸

    We describe the Bayesian Analysis of Nuclear Dynamics (BAND) framework, a cyberinfrastructure that we are developing which will unify the treatment of nuclear models, experimental data, and associated uncertainties. We overview the statistical principles and nuclear-physics contexts underlying the BAND toolset, with an emphasis on Bayesian methodology's ability to leverage insight from multiple models. In order to facilitate understanding of these tools we provide a simple and accessible example of the BAND framework's application. Four case studies are presented to highlight how elements of the framework will enable progress on complex, far-ranging problems in nuclear physics. By collecting notation and terminology, providing illustrative examples, and giving an overview of the associated techniques, this paper aims to open paths through which the nuclear physics and statistics communities can contribute to and build upon the BAND framework.

    ↳ nucl-thnucl-exphysics.data-anJ.Phys.G(2021)·102 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.