Tue·Sep 17, 2019Tuesday·September 17, 2019

1. 01*

   Study of $R_{\mathrm{AA}}$ and $v_2$ of non-strange D mesons and D-jet production in Pb-Pb collisions with ALICE

   Fabrizio Grosa (for the ALICE Collaboration)🇮🇹

   Heavy quarks are sensitive probes of the colour-deconfined medium formed in ultra-relativistic heavy-ion collisions, the Quark-Gluon Plasma (QGP). The ALICE Collaboration measured the production of ${\mathrm{D}}^0$, ${\mathrm{D}}^{+}$, and ${\mathrm{D}}^{\ast +}$ mesons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. The properties of the in-medium energy loss are investigated via the measurement of the nuclear modification factor ($R_{\mathrm{AA}}$) of non-strange D mesons. The modification of the D-meson transverse momentum ($p_{\mathrm{T}}$) distributions inside the jet is studied via the measurement of the D-meson tagged jet $R_{\mathrm{AA}}$ in central Pb-Pb collisions. In mid-central collisions, the measurement of the D-meson elliptic flow ($v_2$) at low and intermediate $p_{\mathrm{T}}$ gives insight into the participation of the charm quark in the collective motion of the system, while at high $p_{\mathrm{T}}$ it constrains the path-length dependence of the energy loss. The coupling of the charm quark to the light quarks in the underlying medium is further investigated with the application of the event-shape engineering (ESE) technique to D-meson elliptic flow.

   nucl-exPoS(2020)·0 citations
2. 02*

   Probing the role of proton cross-shell excitations in 70Ni using nucleon knockout reactions

   B. Elman · A. Gade🇺🇸 · R. V. F. Janssens🇺🇸 · A. D. Ayangeakaa🇺🇸 · D. Bazin🇺🇸 · J. Belarge · P. C. Bender🇨🇦 · B. A. Brown🇺🇸 · C. M. Campbell🇺🇸 · M. P. Carpenter🇺🇸 · H. L. Crawford🇺🇸 · B. P. Crider🇺🇸 and 12 other authors

   The neutron-rich Ni isotopes have attracted attention in recent years due to the occurrence of shape or configuration coexistence. We report on the difference in population of excited final states in 70Ni following gamma-ray tagged one-proton, one-neutron, and two-proton knockout from 71Cu, 71Ni, and 72Zn rare-isotope beams, respectively. Using variations observed in the relative transition intensities, signaling the changed population of specific final states in the different reactions, the role of neutron and proton configurations in excited states of 70Ni is probed schematically, with the goal of identifying those that carry, as leading configuration, proton excitations across the Z = 28 shell closure. Such states are suggested in the literature to form a collective structure associated with prolate deformation. Adding to the body of knowledge for 70Ni, 29 new transitions are reported, of which 15 are placed in its level scheme.

   nucl-exPRC(2019)·5 citations
3. 03*

   Testing claims of the GW170817 binary neutron star inspiral affecting $\beta$-decay rates

   P.A. Breur🇳🇱 · J.C.P.Y. Nobelen · L. Baudis🇨🇭 · A. Brown🇨🇭 · A.P. Colijn🇳🇱 · R. Dressler🇨🇭 · R.F. Lang🇺🇸 · A. Massafferri🇧🇷 · C. Pumar · C. Reuter🇺🇸 · D. Schumann · M. Schumann🇩🇪 · S. Towers · R. Perci

   On August 17, 2017, the first gravitational wave signal from a binary neutron star inspiral (GW170817) was detected by Advanced LIGO and Advanced VIRGO. Here we present radioactive $\beta$-decay rates of three independent sources ${}^{44}$Ti, ${}^{60}$Co and ${}^{137}$Cs, monitored during the same period by a precision experiment designed to investigate the decay of long-lived radioactive sources. We do not find any significant correlations between decay rates in a 5\,h time interval following the GW170817 observation. This contradicts a previous claim published in this journal of an observed 2.5$\sigma$ Pearson Correlation between fluctuations in the number of observed decays from two $\beta$-decaying isotopes (${}^{32}$Si and ${}^{36}$Cl) in the same time interval. By correcting for the choice of an arbitrary time interval, we find no evidence of a correlation above 1.5$\sigma$ confidence. In addition, we argue that such analyses on correlations in arbitrary time intervals should always correct for the so-called Look-Elsewhere effect by quoting the global significance.

   nucl-exstat.OTAstropart.Phys.(2020)·4 citations
4. 04*

   Constraining the ${}^{12}$C+${}^{12}$C astrophysical S-factors with the ${}^{12}$C+${}^{13}$C measurements at very low energies

   N.T. Zhang🇨🇳 · X.Y. Wang🇨🇳 · H. Chen🇺🇸 · Z.J. Chen · W.P. Lin🇨🇳 · W.Y. Xin · S.W. Xu🇨🇳 · D. Tudor · A.I. Chilug · I.C. Stefanescu · M. Straticiuc🇷🇴 · I. Burducea and 15 other authors

   We use an underground counting lab with an extremely low background to perform an activity measurement for the ${}^{12}$C+${}^{13}$C system with energies down to $E{}_{c.m.}$=2.323 MeV, at which the ${}^{12}$C(${}^{13}$C,$p$)${}^{24}$Na cross section is found to be 0.22(7) nb. The ${}^{12}$C+${}^{13}$C fusion cross section is derived with a statistical model calibrated using experimental data. Our new result of the ${}^{12}$C+${}^{13}$C fusion cross section is the first decisive evidence in the carbon isotope systems which rules out the existence of the astrophysical S-factor maximum predicted by the phenomenological hindrance model, while confirming the rising trend of the S-factor towards lower energies predicted by other models, such as CC-M3Y+Rep, DC-TDHF, KNS, SPP and ESW. After normalizing the model predictions with our data, a more reliable upper limit is established for the ${}^{12}$C+${}^{12}$C fusion cross sections at stellar energies.

   nucl-exnucl-thPLB(2020)·41 citations
5. 05*

   Energy Dependence of Light Nuclei ($d$, $t$) Production at STAR

   Dingwei Zhang🇨🇳

   In high-energy nuclear collisions, the production of light nuclei is sensitive to the temperature and phase-space density of the system at freeze-out. In addition, the phase transition from QGP to the hadronic phase will lead to large baryon density fluctuation, which will be reflected in the light nuclei production. For example, the ratio of proton ($N(p)$) and triton ($N(t)$) to deuteron ($N(d)$) yields, which is defined as $N(t)$$\cdot$$N(p)$/$N^2(d)$, may be used as a sensitive observable to search for the QCD critical point. In this paper, we will report the energy dependence of light nuclei ($d$, $t$) production in Au+Au collisions at $\sqrt{s_{NN}}$ =7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV measured by the STAR experiment at RHIC. We will present the beam energy dependence for the coalescence parameter $B_2(d)$ and $B_3(t)$, particle ratios ($d/p$, $t/p$, and $t/d$), and the yield ratio of $N(t)$$\cdot$$N(p)$/$N^2(d)$. Their physics implications will be discussed.

   nucl-exhep-exJPS Conf.Proc.(2020)·23 citations
6. 06*

   Symmetry energy of super-dense neutron-rich matter from integrating barotropic pressures in neutron stars and heavy-ion reactions

   Bao-An Li🇺🇸 · Wen-Jie Xie🇺🇸

   Within the minimum model of neutron stars (NS) consisting of neutrons, protons and electrons, a new approach is proposed for inferring the symmetry energy of super-dense neutron-rich nucleonic matter above twice the saturation density ${\rho }_0$ of nuclear matter directly from integrating iteratively barotropic pressures in both neutron stars and heavy-ion reactions. Simultaneously, the proton fraction of NSs at $\beta$ equilibrium is extracted as a function of baryon density from the same procedure. An application of this approach using the NS pressure from GW170817 and the pressure in cold symmetric nuclear matter (SNM) extracted earlier by analyzing nuclear collective flow data in relativistic heavy-ion collisions provides a useful constraining band for the symmetry energy above $2{\rho }_0$.

   ↳ nucl-thastro-ph.HEastro-ph.SRnucl-exPLB(2020)·7 citations
7. 07*

   Monte Carlo variations as a tool to assess nuclear physics uncertainties in nucleosynthesis studies

   T. Rauscher🇨🇭

   The propagation of uncertainties in reaction cross sections and rates of neutron-, proton-, and $\alpha$-induced reactions into the final isotopic abundances obtained in nucleosynthesis models is an important issue in studies of nucleosynthesis and Galactic Chemical Evolution. We developed a Monte Carlo method to allow large-scale postprocessing studies of the impact of nuclear uncertainties on nucleosynthesis. Temperature-dependent rate uncertainties combining realistic experimental and theoretical uncertainties are used. The importance of contributions of cross sections of reactions on excited states of the nuclear targets, which have weights different from from the thermal Boltzmann population factors, is explained. From detailed statistical analyses of the Monte Carlo data uncertainties in the final abundances are derived as probability density distributions. Furthermore, based on rate and abundance correlations an automated procedure identifies the most important reactions in complex flow patterns from superposition of many zones or tracers. The method already has been applied to a number of nucleosynthesis processes.

   ↳ astro-ph.HEnucl-exnucl-thJ.Phys.Conf.Ser.(2020)·3 citations
8. 08*

   Effects of $P_{\mathrm{tot}}$ gates and velocity gates on light-particle momentum correlation in intermediate-energy heavy-ion collisions

   Ting-Ting Wang🇨🇳 · Yu-Gang Ma🇨🇳 · Zheng-Qiao Zhang🇨🇳

   Momentum correlation functions at small relative momenta are calculated for light particles $\left(n,p,d,t\right)$ emitted from ${}^{197}$Au + ${}^{197}$Au collisions at different impact parameters and beam energies within the framework of the isospin-dependent quantum molecular dynamics model complemented by the $Lednick\acute{y}$ and $Lyuboshitz$ analytical method. We first make sure our model is able to reproduce the FOPI data of proton-proton momentum correlation in a wide energy range from 0.4$A$ GeV to 1.5$A$ GeV. Then we explore more physics insights through the emission times and momentum correlations among different light particles. The specific emphasize is the effects of total pair momentum among different light particles, impact parameters and in-medium nucleon-nucleon cross section. Both two-deuteron and two-triton correlation functions are anti-correlation due to the final state interaction, and they are affected by in-medium nucleon-nucleon cross section for the higher total momentum of the particle pairs, but not for the lower ones. In addition, impact parameter and in-medium nucleon-nucleon cross section dependences of the emission source radii are extracted by fitting the momentum correlation functions. The results indicate that momentum correlation functions gating with total pair momentum is stronger for the smaller in-medium nucleon-nucleon cross section factor $\left(\eta \right)$ or impact parameter $\left(b\right)$. Non-identical particle correlations ($np,pd,pt,$ and $dt$) are also investigated by the velocity-gated correlation functions which can give information of the particles' emission sequence, and the result indicates that heavier ones $\left(deuteron/triton\right)$ are, one the average, emitted earlier than protons, in the small relative momentum region.

   ↳ nucl-thnucl-exPRC(2019)·15 citations
9. 09*

   Study of the lateral distribution functions of electron and muon bundles using Trasgo detectors

   A. Álvarez-Díaz🇪🇸 · P. Cabanelas🇪🇸 · Y. Fontenla🇪🇸 · J.A. Garzón🇪🇸

   Some of the main features of the new generation Trasgo detectors are their capability in measuring the incoming direction and the arrival time of secondary cosmic particles. They also offer the identification capability between muon and electrons and a rough calorimetry for electrons. Using ground-based stations, these properties allow for the development of new tools for the measurement of primary cosmic ray fluxes. In order to verify and quantify the suitability of Trasgo detectors, whether a single one or arrays of them, to provide reliable information of the properties (mass, energy, incoming direction) of primary cosmic rays we have started an initiative for the systematic study of the 'lateral distributions' displayed by electrons and muons, or by bundles of those particles, using MonteCarlo simulations. In a first approach, electrons and muons were produced in vertical showers from primary H, He, C and Fe nuclei, and with incoming energies limited to a maximum of 10${}^{15}$ eV per nucleon. This choice represents a significant component of all secondary particles, which can be measured on Earth's surface. The lateral distributions study has been done at the two locations of Santiago de Compostela (Spain) and Livingston Island (Antarctica), where Trasgo detectors are either in operation, or will be operative in the near future.

   ↳ astro-ph.IMnucl-exPoS(2020)·1 citation
10. 10*

    New Results from the Cosmic-Ray Program of the NA61/SHINE facility at the CERN SPS

    Michael Unger · NA61 Collaboration

    The NA61/SHINE experiment at the SPS accelerator at CERN is a unique facility for the study of hadronic interactions at fixed target energies. The data collected with NA61/SHINE is relevant for a broad range of topics in cosmic-ray physics including ultrahigh-energy air showers and the production of secondary nuclei and anti-particles in the Galaxy. Here we present an update of the measurement of the momentum spectra of anti-protons produced in ${\pi }^{-}$+C interactions at 158 and 350 GeV/c and discuss their relevance for the understanding of muons in air showers initiated by ultrahigh-energy cosmic rays. Furthermore, we report the first results from a three-day pilot run aimed at investigating the capability of our experiment to measure nuclear fragmentation cross sections for the understanding of the propagation of cosmic rays in the Galaxy. We present a preliminary measurement of the production cross section of Boron in C+p interactions at 13.5 AGeV/c and discuss prospects for future data taking to provide the comprehensive and accurate reaction database of nuclear fragmentation needed in the era of high-precision measurements of Galactic cosmic rays.

    ↳ astro-ph.HEnucl-exPoS(2020)·19 citations
11. 11*

    Improvement of heavy flavor productions in a multi-phase transport model updated with modern nPDFs

    L. Zheng🇨🇳 · C. Zhang🇨🇳 · S.S. Shi🇨🇳 · Z.W. Lin🇺🇸

    Recently we have updated a multi-phase transport (AMPT) model with modern parton distribution functions of nuclei (nPDFs). Here we study open charm production in the updated AMPT model and compare to the experimental data from $pp$ and $AA$ collisions over a wide range of collision energies. Besides the update of nPDFs, we have removed the transverse momentum cutoff on initial heavy quark productions and also included the resultant heavy flavor cross section into the total minijet cross section in the initial condition as described by the HIJING model. We show that the AMPT model with these updates provides a much better description of the yields and transverse momentum spectra of various open charm hadrons in comparison with the experimental data. This lays the foundation for further heavy flavor studies within the transport model approach.

    ↳ nucl-thhep-phnucl-exPRC(2020)·21 citations
12. 12*

    $S$-factor and scattering-parameter extractions from ${}^3\mathrm{He}+{}^4\mathrm{He}\to {}^7\mathrm{Be}+\gamma$

    Xilin Zhang🇺🇸 · Kenneth M. Nollett · D. R. Phillips🇺🇸

    Previous studies of the reaction ${}^3\mathrm{He}+{}^4\mathrm{He}\to {}^7\mathrm{Be}+\gamma$ have focused on providing the best central value and error bar for the $S$ factor at solar energies. Measurements of this capture reaction, the ${}^3\mathrm{He}$-${}^4\mathrm{He}$ scattering phase shifts, as well as properties of ${}^7\mathrm{Be}$, have been used to constrain employed theoretical models. Here we show that much more information than was previously appreciated can be extracted from angle-integrated capture data alone. We use the next-to-leading-order (NLO) amplitude in an effective field theory (EFT) for the reaction to perform the extrapolation. At this order the EFT describes the reaction using an s-wave scattering length and effective range, the asymptotic properties of the final bound states, and short-distance contributions to the $E1$ capture amplitude. We extract the multi-dimensional posterior of all these parameters via a Bayesian analysis. We find that properties of the ${}^7\mathrm{Be}$ ground and excited states are well constrained. The total $S$ factor $S(0)=0.578_{-0.016}^{+0.015}$ keV~b, while the branching ratio for excited- to ground-state capture at zero energy, $Br(0)=0.406_{-0.011}^{+0.013}$, both at 68\% degree of belief. This $S(0)$ is broadly consistent with other recent evaluations, including the previously recommended value $S(0)=0.56\pm 0.03$ eV b, but has a smaller error bar. We also find significant constraints on the scattering parameters, and we obtain constraints on the $S(E)$'s angular dependence. The path forward seems to lie with better measurements of the scattering phase shift and $S(E)$'s angular dependence, together with better understanding of the asymptotic normalization coefficients of the ${}^7$Be bound states' wave functions. Data on these could further reduce $S(0)$'s uncertainty.

    ↳ nucl-thastro-ph.SRnucl-exJ.Phys.G(2020)·39 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.