Wed·Aug 5, 2015Wednesday·August 5, 2015

1. 01*

   Toward precision mass measurements of neutron-rich nuclei relevant to $r$-process nucleosynthesis

   B. H. Sun🇨🇳 · Yu.A. Litvinov🇩🇪 · I. Tanihata🇨🇳 · Y. H. Zhang🇨🇳

   The open question of where, when, and how the heavy elements beyond iron enrich our Universe has triggered a new era in nuclear physics studies.\ Of all the relevant nuclear physics inputs, the mass of very neutron-rich nuclides is a key quantity for revealing the origin of heavy elements beyond iron.\ Although the precise determination of this property is a great challenge, enormous progress has been made in recent decades, and it has contributed significantly to both nuclear structure and astrophysical nucleosynthesis studies.\ In this review, we first survey our present knowledge of the nuclear mass surface, emphasizing the importance of nuclear mass precision in $r$-process calculations.\ We then discuss recent progress in various methods of nuclear mass measurement with a few selected examples.\ For each method, we focus on recent breakthroughs and discuss possible ways of improving the weighing of $r$-process nuclides.

   nucl-exhep-exnucl-thFront.Phys.(Beijing)(2015)·20 citations
2. 02*

   Breaking of axial symmetry in excited heavy nuclei as identified in Giant Dipole Resonance data

   Eckart Grosse🇩🇪 · Arnd R. Junghans🇩🇪 · Ralph Massarczyk🇺🇸

   A recent theoretical prediction of a breaking of axial symmetry in quasi all heavy nuclei is confronted to a new critical analysis of photon strength functions of nuclei in the valley of stability. For the photon strength in the isovector giant dipole resonance (IVGDR) regime a parameterization of GDR shapes by the sum of three Lorentzians (TLO) is extrapolated to energies below and above the IVGDR. The impact of non-GDR modes adding to the low energy slope of photon strength is discussed including recent data on photon scattering and other radiative processes. These are shown to be concentrated in energy regions where various model calculations predict intermediate collective strength; thus they are obviously separate from the IVGDR tail. The triple Lorentzian (TLO) ansatz for giant dipole resonances is normalized in accordance to the dipole sum rule. The nuclear droplet model with surface dissipation accounts well for positions and widths without local, nuclide specific, parameters. Very few and only global parameters are needed when a breaking of axial symmetry already in the valley of stability is admitted and hence a reliable prediction for electric dipole strength functions also outside of it is expected.

   nucl-exastro-ph.SRnucl-thEPJA(2017)·16 citations
3. 03*

   Bridging Soft-Hard Transport Properties of Quark-Gluon Plasmas with CUJET3.0

   Jiechen Xu🇺🇸 · Jinfeng Liao🇺🇸 · Miklos Gyulassy🇺🇸

   A new model of jet quenching in nuclear collisions, CUJET3.0, is constructed by generalizing the perturbative QCD based CUJET2.0 model to include two complementary non-perturbative features of the QCD confinement cross-over phase transition near $T_c\approx 160$ MeV: (1) the suppression of quark and gluon degrees of freedom and (2) the emergence of chromo-magnetic monopole degrees of freedom. Such a semi-Quark-Gluon-Monopole Plasma (sQGMP) microscopic scenario is tested by comparing predictions of the leading hadron nuclear modification factors, $R_{AA}^h(p_T>10GeV/c,\sqrt{s})$, and their azimuthal elliptic asymmetry $v_2^h(p_T>10GeV/c,\sqrt{s})$ with available data on $h=\pi ,D,B$ jet fragments from nuclear collisions at RHIC($\sqrt{s}=0.2$ ATeV) and LHC($\sqrt{s}$=2.76 ATeV). The sQGMP model is shown to solve the long standing $R_{AA}$ vs $v_2$ puzzle by predicting a maximum of the jet quenching parameter field $\hat{q}(E,T)/T^3$ near $T_c$. The consistency of jet quenching with observed bulk perfect fluidity is demonstrated by extrapolating the sQGMP $\hat{q}$ down to thermal energy $E\sim 3T$ scales and showing that the sQGMP shear viscosity to entropy density ratio $\eta /s\approx T^3/\hat{q}$ falls close to the unitarity bound, $1/4\pi$, in the range $(1-2)T_c$. Detailed comparisons of CUJET2.0 and CUJET3.0 reveal that the remarkably different $\hat{q}(T)$ could be consistent with the same $R_{AA}$ data and could only be distinguished by anisotropy observables. These findings demonstrate clearly the inadequacy of focusing on the jet path averaged quantity $<\hat{q}>$ as the only relevant medium property to characterize jet quenching, and point to the crucial roles of other essential factors, such as the chromo electric and magnetic composites of the plasma, the screening masses and the running couplings at multiple scales that all strongly influence jet energy loss.

   ↳ hep-phnucl-exnucl-thJHEP(2016)·162 citations
4. 04*

   Measurement of the centrality dependence of the charged-particle pseudorapidity distribution in proton--lead collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=5.02$ TeV with the ATLAS detector

   ATLAS Collaboration

   The centrality dependence of the mean charged-particle multiplicity as a function of pseudorapidity is measured in approximately 1 $\mu$b${}^{-1}$ of proton--lead collisions at a nucleon--nucleon centre-of-mass energy of $\sqrt{s_{{}_{\mathrm{NN}}}}=5.02$ TeV using the ATLAS detector at the Large Hadron Collider. Charged particles with absolute pseudorapidity less than 2.7 are reconstructed using the ATLAS pixel detector. The $p$+Pb collision centrality is characterised by the total transverse energy measured in the Pb-going direction of the forward calorimeter. The charged-particle pseudorapidity distributions are found to vary strongly with centrality, with an increasing asymmetry between the proton-going and Pb-going directions as the collisions become more central. Three different estimations of the number of nucleons participating in the $p$+Pb collision have been carried out using the Glauber model as well as two Glauber--Gribov inspired extensions to the Glauber model. Charged-particle multiplicities per participant pair are found to vary differently for these three models, highlighting the importance of including colour fluctuations in nucleon--nucleon collisions in the modelling of the initial state of $p$+Pb collisions.

   ↳ hep-exnucl-exEPJC(2016)·117 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.