Fri·Apr 19, 2019Friday·April 19, 2019

1. 01*

   A Scintillator Attenuation Spectrometer For Intense Gamma-Rays

   Edison Liang · Kevin Qinyuan Zheng · Kelly Yao · Willie Lo · Hannah Hasson · Aileen Zhang🇺🇸 · Matthew Burns · Wai-Hoi Wong · Yuxuan Zhang · Andriy Dashko · Hernan Quevedo🇲🇽 · Todd Ditmire · Gillis Dyer

   A new type of compact high resolution high sensitivity gamma ray spectrometer for short pulse intense 250 keV to 50 MeV gamma rays has been developed by combining the principles of scintillators and attenuation spectrometers. The first prototype of this scintillator attenuation spectrometer or SAS was tested successfully in Trident laser experiments at LANL. Later versions have been used extensively in the Texas Petawatt laser experiments in Austin TX, and more recently in OMEGAEP laser experiments at LLE, Rochester, NY. The SAS is particularly useful for high repetition rate laser applications. Here we give a concise description of the design principles, capabilities and sample preliminary results of the SAS.

   ↳ physics.ins-detnucl-exphysics.acc-phRev.Sci.Instrum.(2022)·2 citations
2. 02*

   Two-particle angular correlations in heavy ion collisions from a multiphase transport model

   Liu-Yao Zhang🇨🇳 · Jin-Hui Chen🇨🇳 · Zi-Wei Lin🇺🇸 · Yu-Gang Ma🇨🇳 · Song Zhang🇨🇳

   We extend our earlier study on two-particle angular correlations in $pp$ collisions at low transverse momentum ($p_T$) to $p$-Pb, Pb-Pb and Au-Au collisions at RHIC and LHC energies. We mainly use the string melting version of a multiphase transport model with improved quark coalescence for this study. We start from the analysis of ${\pi }^{\pm }$, $K^{\pm }$ and $p$($\bar{p}$) $p_T$ and rapidity distributions at different centralities. We then focus on two-particle angular correlations in $p$-Pb collisions at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}=5.02$ TeV and Pb-Pb collisions at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}=2.76$ TeV. For $p$-Pb collisions, a near side depression in the angular correlation is observed for low $p_T$ proton pairs and $\Lambda$ pairs but not for pion pairs or kaon pairs, similar to our earlier finding for $pp$ collisions at $\sqrt{\mathrm{s}}=7$ TeV. This is also the case for very low multiplicity Pb-Pb and Au-Au collisions. We also find that parton interactions and the improved quark coalescence are mainly responsible for the depression feature in baryon pair angular correlations. However, no such baryon-baryon anti-correlations are observed in Pb-Pb and Au-Au collisions at higher multiplicities. Therefore our results suggest that low $p_T$ baryon-baryon angular anti-correlations have a strong multiplicity dependence.

   ↳ nucl-thhep-phnucl-exPRC(2019)·19 citations
3. 03*

   Emergence of hydrodynamical behavior in expanding quark-gluon plasmas

   Jean-Paul Blaizot🇫🇷 · Li Yan🇨🇳

   We use a set of simple angular moments to solve the Boltzmann equation in the relaxation time approximation for a boost invariant longitudinally expanding gluonic plasma. The transition from the free streaming regime at early time to the hydrodynamic regime at late time is well captured by the first two-moments, corresponding to the monopole and quadrupole components of the momentum distribution, or equivalently to the energy density and the difference between the longitudinal and the transverse pressures. We relate this property to the existence of fixed points in the infinite hierarchy of equations satisfied by the moments. These fixed points are already present in the two-moment truncations and are only moderately affected by the coupling to higher moments. Collisions contribute to a damping of all the non trivial moments. At late time, when the hydrodynamic regime is entered, only the monopole and quadrupole moments are significant and remain strongly coupled, the decay of the quadrupole moment being delayed by the expansion, causing in turn a delay in the full isotropization of the system. The two-moment truncation contains second order viscous hydrodynamics, in its various variants, and third order hydrodynamics, together with explicit values of the relevant transport coefficients, can be easily obtained from the three-moment truncation.

   ↳ nucl-thhep-phnucl-exAnnals Phys.(2020)·76 citations
4. 04*

   Excitation of the electric pygmy dipole resonance by inelastic electron scattering

   V.Yu. Ponomarev🇩🇪 · D.H. Jakubassa-Amundsen · A. Richter🇩🇪 · J. Wambach🇮🇹

   To complete earlier studies of the properties of the electric pygmy dipole resonance (PDR) obtained in various nuclear reactions, the excitation of the 1${}^{-}$ states in ${}^{140}$Ce by $(e,e^{\prime })$ scattering for momentum transfers $q=0.1-1.2$~fm${}^{-1}$ is calculated within the plane-wave and distorted-wave Born approximations. The excited states of the nucleus are described within the Quasiparticle Random Phase Approximation (QRPA), but also within the Quasiparticle-Phonon Model (QPM) by accounting for the coupling to complex configurations. It is demonstrated that the excitation mechanism of the PDR states in $(e,e^{\prime })$ reactions is predominantly of transversal nature for scattering angles ${\theta }_e\approx 90^o-180^o$. Being thus mediated by the convection and spin nuclear currents, the $(e,e^{\prime })$ like the $(\gamma ,{\gamma }^{\prime })$ reaction, may provide additional information to the one obtained from Coulomb- and hadronic excitations of the PDR in $(p,p^{\prime })$, $(\alpha ,{\alpha }^{\prime })$, and heavy-ion scattering reactions. The calculations predict that the $(e,e^{\prime })$ cross sections for the strongest individual PDR states are in general about three orders of magnitude smaller as compared to the one of the lowest $2_1^{+}$ state for the studied kinematics, but that they may become dominant at extreme backward angles.

   ↳ nucl-thnucl-exEPJA(2019)·4 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.