Wed·Mar 16, 2016Wednesday·March 16, 2016

1. 01*

   Shape coexistence and the role of axial asymmetry in ${}^{72}$Ge

   A.D. Ayangeakaa🇺🇸 · R.V.F. Janssens🇺🇸 · C.Y. Wu🇺🇸 · J.M. Allmond🇺🇸 · J.L. Wood🇺🇸 · S. Zhu🇺🇸 · M. Albers🇺🇸 · S. Almaras-Calderon🇺🇸 · B. Bucher🇺🇸 · M.P. Carpenter🇺🇸 · C.J. Chiara🇺🇸 · D. Cline🇺🇸 and 13 other authors

   The quadrupole collectivity of low-lying states and the anomalous behavior of the $0_2^{+}$ and $2_3^{+}$ levels in ${}^{72}$Ge are investigated via projectile multi-step Coulomb excitation with GRETINA and CHICO-2. A total of forty six $E2$ and $M1$ matrix elements connecting fourteen low-lying levels were determined using the least-squares search code, gosia. Evidence for triaxiality and shape coexistence, based on the model-independent shape invariants deduced from the Kumar-Cline sum rule, is presented. These are interpreted using a simple two-state mixing model as well as multistate mixing calculations carried out within the framework of the triaxial rotor model. The results represent a significant milestone towards the understanding of the unusual structure of this nucleus.

   nucl-exnucl-thPLB(2016)·73 citations
2. 02*

   Measurement of transverse energy at midrapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV

   ALICE Collaboration

   We report the transverse energy ($E_{\mathrm{T}}$) measured with ALICE at midrapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV as a function of centrality. The transverse energy was measured using identified single particle tracks. The measurement was cross checked using the electromagnetic calorimeters and the transverse momentum distributions of identified particles previously reported by ALICE. The results are compared to theoretical models as well as to results from other experiments. The mean $E_{\mathrm{T}}$ per unit pseudorapidity ($\eta$), $⟨$d$E_{\mathrm{T}}/$d$\eta ⟩$, in 0-5% central collisions is 1737 $\pm$ 6(stat.) $\pm$ 97(sys.) GeV. We find a similar centrality dependence of the shape of $⟨$d$E_{\mathrm{T}}/$d$\eta ⟩$ as a function of the number of participating nucleons to that seen at lower energies. The growth in $⟨$d$E_{\mathrm{T}}/$d$\eta ⟩$ at the LHC $\sqrt{s_{\mathrm{NN}}}$ exceeds extrapolations of low energy data. We observe a nearly linear scaling of $⟨$d$E_{\mathrm{T}}/$d$\eta ⟩$ with the number of quark participants. With the canonical assumption of a 1 fm/$c$ formation time, we estimate that the energy density in 0-5% central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV is 12.3 $\pm$ 1.0 GeV/fm${}^3$\xspace and that the energy density at the most central 80 fm${}^2$ of the collision is at least 21.5 $\pm$ 1.7 GeV/fm${}^3$. This is roughly 2.3 times that observed in 0-5% central Au-Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV.

   nucl-exhep-exPRC(2016)·119 citations
3. 03*

   Photon bremsstrahlung from quark jet via transverse and longitudinal scatterings: single versus multiple scatterings

   Le Zhang🇨🇳 · De-Fu Hou🇨🇳 · Guang-You Qin🇨🇳

   We study the production of jet-bremsstrahlung photons through the scattering with the constituents of a dense nuclear matter within the framework of deep-inelastic scattering off a large nucleus. Applying a gradient expansion up to the second order for the exchanged three-dimensional momentum between jet and medium, we derive the single photon bremsstrahlung spectrum with the inclusion of the contributions from the transverse broadening as well as the longitudinal drag and diffusion of the hard parton's momentum. We also compare the medium-induced photon radiation spectra for single scattering and from the resummation of multiple scatterings. It is found that the coupling between different scatterings can give additional contribution to medium-induced photon radiation, while for small momentum exchange, the leading contribution from the drag and diffusions to the photon emission spectra remain the same for single and multiple scatterings.

   ↳ hep-phnucl-exnucl-thPRC(2016)·5 citations
4. 04*

   Empirical Parameterization of Nucleon-Nucleon Elastic Scattering Amplitude at High Beam Momenta for Glauber Calculations and Monte Carlo Simulations

   V. Uzhinsky🇷🇺 · A. Galoyan🇷🇺 · Q. Hu🇨🇳 · J. Ritman🇩🇪 · H. Xu🇨🇳

   A parameterization of the nucleon-nucleon elastic scattering amplitude is needed for future experiments with nucleon and nuclear beams in the beam momentum range of 2 -- 50 GeV/c/nucleon. There are many parameterizations of the amplitude at $P_{lab}>$ 25--50 GeV/c, and at $P_{lab}\le$ 5 GeV/c. Our paper is aimed to cover the range between 5 -- 50 GeV/c. The amplitude is used in Glauber calculations of various cross sections and Monte Carlo simulations of nucleon-nucleon scatterings. Usually, the differential nucleon-nucleon elastic scattering cross sections are described by an exponential expression. Corresponding experimental data on $pp$ interactions at $|t|>$ 0.005 (GeV/c)${}^2$ and $|t|\le$ 0.125 (GeV/c)${}^2$ have been fit. We propose formulae to approximate the beam momentum dependence of these parameters in the momentum range considered. The same was done for $np$ interactions at $|t|\le$ 0.5 (GeV/c)${}^2$. Expressions for the momentum dependence of the total and elastic cross sections, and the ratio of real to imaginary parts of the amplitude at zero momentum transfer are also given for $pp$ and $np$ collisions. These results are sufficient for a first approximation of the Glauber calculations. For more exact calculations we fit the data at $|t|>$ 0.005 (GeV/c)${}^2$ without restrictions on the maximum value of $|t|$ using an expression based on two coherent exponential. The parameters of the fits are found for the beam momentum range 2 -- 50 GeV/c.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2016)·1 citation

* 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.