Thu·Jul 19, 2018Thursday·July 19, 2018

1. 01*

   Shape coexistence and isospin symmetry in $A=70$ nuclei: Spectroscopy of the $T_z=-1$ nucleus ${}^{70}$Kr

   K. Wimmer🇯🇵 · W. Korten🇫🇷 · T. Arici🇩🇪 · P. Doornenbal🇯🇵 · P. Aguilera🇨🇱 · A. Algora🇪🇸 · T. Ando🇯🇵 · H. Baba🇯🇵 · B. Blank🇫🇷 · A. Boso🇮🇹 · S. Chen🇯🇵 · A. Corsi🇫🇷 and 22 other authors

   Excited states in the $T_z=-1$ nucleus ${}^{70}$Kr have been populated using inelastic scattering of a radioactive ${}^{70}$Kr beam as well as one- and two-neutron removal reactions from ${}^{71,72}$Kr at intermediate beam energies. The level scheme of ${}^{70}$Kr was constructed from the observed $\gamma$-ray transitions and coincidences. Tentative spin and parity assignments were made based on comparison with the mirror nucleus ${}^{70}$Se. A second $2^{+}$ state and a candidate for the corresponding $4_2^{+}$ state suggest shape coexistence in ${}^{70}$Kr.

   nucl-exPLB(2018)·24 citations
2. 02*

   Recent results for STAR $\sqrt{s_{NN}}=4.9$ GeV Al+Au and $\sqrt{s_{NN}}=4.5$ GeV Au+Au Fixed-Target Collisions

   Yang Wu (for the STAR collaboration)🇺🇸

   We present recent results from Al(beam)+Au(target) collisions at $\sqrt{s_{NN}}=4.9$ GeV and Au+Au collisions at $\sqrt{s_{NN}}=4.5$\kern 0.16667em GeV from the STAR fixed-target (FXT) program. We report transverse mass spectra of protons, $K_S^0$ and $\Lambda$, rapidity density distributions of ${\pi }^{\pm }$, $K_S^0$ and $\Lambda$, directed flow of protons, ${\pi }^{\pm }$, $K_S^0$ and $\Lambda$, and elliptic flow of protons and ${\pi }^{\pm }$. These are the first measurements of pion directed and elliptic flow in this energy range at RHIC. Pion and proton elliptic flow show mass ordering. Measurements are compared with the published results from AGS and RHIC. These results demonstrate that STAR has good performance in the FXT configuration. The implications of these results for future STAR FXT runs are discussed.

   nucl-exNPA(2019)·17 citations
3. 03*

   Medium modification of the shape of small-radius jets in central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$

   ALICE Collaboration

   We present the measurement of a new set of jet shape observables for track-based jets in central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. The set of jet shapes includes the first radial moment or angularity, $g$; the momentum dispersion, $p_{\mathrm{T}}D$; and the difference between the leading and sub-leading constituent track transverse momentum, $LeSub$. These observables provide complementary information on the jet fragmentation and can constrain different aspects of the theoretical description of jet-medium interactions. The jet shapes were measured for a small resolution parameter $R=0.2$ and were fully corrected to particle level. The observed jet shape modifications indicate that in-medium fragmentation is harder and more collimated than vacuum fragmentation as obtained by PYTHIA calculations, which were validated with the measurements of the jet shapes in proton-proton collisions at $\sqrt{s}=7$ TeV. The comparison of the measured distributions to templates for quark and gluon-initiated jets indicates that in-medium fragmentation resembles that of quark jets in vacuum. We further argue that the observed modifications are not consistent with a totally coherent energy loss picture where the jet loses energy as a single colour charge, suggesting that the medium resolves the jet structure at the angular scales probed by our measurements ($R=0.2$). Furthermore, we observe that small-$R$ jets can help to isolate purely energy loss effects from other effects that contribute to the modifications of the jet shower in medium such as the correlated background or medium response.

   nucl-exhep-exJHEP(2018)·86 citations
4. 04*

   Light Yield of Perovskite Nanocrystal-Doped Liquid Scintillator

   D. Gooding🇺🇸 · J. Gruszko🇺🇸 · C. Grant🇺🇸 · B. Naranjo🇺🇸 · L. Winslow🇺🇸

   Liquid scintillators doped with metals are needed for a variety of measurements in nuclear and particle physics. Nanoparticles provide a mechanism to dope the scintillator and their unique optical properties could be used to enhance detection capabilities. We present here the first study of lead-based perovskite nanoparticles for this application. Perovskites are an attractive choice due to the versatility of their crystal structure and their ease of synthesis.

   ↳ physics.ins-dethep-exnucl-ex4 citations
5. 05*

   Nuclear and neutron matter equations of state from high-quality potentials up to fifth order of the chiral expansion

   F. Sammarruca🇺🇸 · L. E. Marcucci🇮🇹 · L. Coraggio🇮🇹 · J. W. Holt🇺🇸 · N. Itaco🇮🇹 · R. Machleidt🇺🇸

   We present predictions for the equation of state of symmetric nuclear and pure neutron matter based on recent high-quality nucleon-nucleon potentials from leading order to fifth order in the chiral expansion. We include as well the next-to-next-to-leading order (N2LO) chiral three-nucleon force whose low-energy constants cD and cE are fitted to the binding energies of 3H and 3He as well as the \b{eta}-decay lifetime of 3H. The ground state energy per particle is computed in the particle- particle ladder approximation up to a few times saturation density. Due to the soft character of the interactions, uncertainties due to the convergence in many-body perturbation theory are small. We find that nuclear matter saturation is reproduced quantitatively at N3LO and N4LO, and therefore we encourage the application of these interactions in finite nuclei, where the description of ground- state energies and charge radii of medium-mass nuclei may be improved.

   ↳ nucl-thnucl-ex37 citations
6. 06*

   Effects of the initialization of nucleon momentum in heavy-ion collisions at medium energies

   Zu-Xing Yang🇨🇳 · Xiao-Hua Fan🇨🇳 · Gao-Chan Yong🇨🇳 · Wei Zuo🇨🇳

   Based on the Isospin-dependent transport model Boltzmann-Uehling-Uhlenbeck (IBUU), effects of the difference of the high momentum tails (HMTs) of nucleon momentum distribution in colliding nuclei on some isospin-sensitive observables are studied in the ${}^{197}\mathrm{Au}{+}^{197}\mathrm{Au}$ reactions at incident beam energy of 400 MeV/nucleon. It is found that the nucleon transverse and elliptic flows, the free neutron to proton ratio at low momenta are all less sensitive to the specific form of the HMT, while the free neutron to proton ratio at high momenta and the yields of ${\pi }^{-}$ and ${\pi }^{+}$ as well as the ${\pi }^{-}/{\pi }^{+}$ ratio around the Coulomb peak are sensitive to the specific form of the HMT. Combining the present studies with the experimental measurements at rare-isotope reaction facilities worldwide, one may get more insights into the nuclear short-range correlations in heavy nuclei or nuclear matter.

   ↳ nucl-thnucl-exPRC(2018)·14 citations
7. 07*

   From in-Medium Color Forces to Transport Properties of QGP

   Shuai Y.F. Liu🇺🇸 · Ralf Rapp🇺🇸

   A thermodynamic quantum many-body $T$-matrix approach is employed to study the spectral and transport properties of the quark-gluon plasma at moderate temperatures where nonperturbative effects are essential. For the partonic two-body interaction we utilize a QCD-inspired Hamiltonian whose color forces are motivated by the heavy-quark (HQ) limit including remnants of the confining force, and augmented by relativistic corrections. We solve the in-medium parton propagators and $T$-matrices selfconsistently and resum the skeleton diagrams for the equation of state (EoS) to all orders thereby accounting for the dynamical formation of two-body bound states. Two types solutions for the in-medium potential are found in when fitting to lattice-QCD data for the EoS, HQ free energy and quarkonium correlators: a weakly-coupled scenario (WCS) with a (real part of the) potential close to the free energy, resulting in moderately broadened spectral functions and weak bound states near $T_c$, and a strongly-coupled scenario (SCS), with a much stronger potential which produces large imaginary parts ("melting" the parton spectral functions) and generates strong bound states near $T_c$. We calculate pertinent transport coefficients (specific shear viscosity and HQ diffusion coefficient) and argue that their constraints from heavy-ion phenomenology unambiguously favor the strongly-coupled scenario.

   ↳ nucl-thhep-latnucl-exNPA(2019)·2 citations
8. 08*

   Higher moment fluctuations of identified particle distributions from ALICE

   Nirbhay Kumar Behera (for the ALICE Collaboration)🇰🇷

   Cumulants of conserved charges fluctuations are regarded as a potential tool to study the criticality in the QCD phase diagram and to determine the freeze-out parameters in a model-independent way. At LHC energies, the measurements of the ratio of the net-baryon (net-proton) cumulants can be used to test the lattice QCD predictions. In this work, we present the first measurements of cumulants of the net-proton number distributions up to $4^{th}$ order in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 and 5.02 TeV as a function of collision centrality. We compare our cumulant ratios results with the STAR experiment net-proton results measured in the first phase of the Beam Energy Scan program at RHIC. The results can be used to obtain the chemical freeze-out parameters at LHC.

   ↳ hep-exnucl-exNPA(2019)·14 citations
9. 09*

   Proton Isovector Helicity Distribution on the Lattice at Physical Pion Mass

   Huey-Wen Lin🇺🇸 · Jiunn-Wei Chen🇹🇼 · Xiangdong Ji🇺🇸 · Luchang Jin🇺🇸 · Ruizi Li🇺🇸 · Yu-Sheng Liu🇨🇳 · Yi-Bo Yang🇺🇸 · Jian-Hui Zhang🇩🇪 · Yong Zhao🇺🇸

   We present a state-of-the-art calculation of the isovector quark helicity Bjorken-$x$ distribution in the proton using lattice-QCD ensembles at the physical pion mass. We compute quasi-distributions at proton momenta $P_z\in \{2.2,2.6,3.0\}$~GeV on the lattice, and match them systematically to the physical parton distribution using large-momentum effective theory (LaMET). We reach an unprecedented precision through high statistics in simulations, large-momentum proton matrix elements, and control of excited-state contamination. The resulting distribution with combined statistical and systematic errors is in agreement with the latest phenomenological analysis of the spin-dependent experimental data; in particular, $\Delta \bar{u}(x)>\Delta \bar{d}(x)$.

   ↳ hep-lathep-exhep-phnucl-ex+1PRL(2018)·137 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.