Mon·Aug 14, 2017Monday·August 14, 2017

1. 01*

   Rapidity correlations in the RHIC Beam Energy Scan Data

   Sedigheh Jowzaee (for the STAR Collaboration)🇺🇸

   A pair-normalized two-particle covariance versus the rapidity of the two particles, called R${}_2$, was originally studied in ISR and FNAL data in the 1970's. This variable has recently seen renewed interest for the study of the dynamics of heavy-ion collisions in the longitudinal direction. These rapidity correlations can be decomposed into a basis set of Legendre polynomials with prefactors $⟨a_{mn}⟩$, which can be considered the rapidity analog of the decomposition of azimuthal anisotropies into a set of cosine functions with prefactors v${}_{\mathrm{n}}$. The $⟨a_{mn}⟩$ values have been suggested to be sensitive to the number of particle emitting sources, baryon stopping, viscosities, and critical behavior. The rapidity correlations have been measured by the STAR collaboration as a function of the beam energy for 0-5% central Au$+$Au collisions with beam energies ranging from 7.7 to 200 $\mathrm{GeV}$. The experimental results and comparisons to the UrQMD model are presented.

   nucl-exhep-exNPA(2017)·2 citations
2. 02*

   Measurement of prompt D${}^0$ meson azimuthal anisotropy in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}=$5.02 TeV

   CMS Collaboration

   The prompt D${}^0$ meson azimuthal anisotropy coefficients, $v_2$ and $v_3$, are measured at midrapidity ($|y|<1.0$) in PbPb collisions at a center-of-mass energy $\sqrt{s_{\mathrm{NN}}}=$5.02 TeV per nucleon pair with data collected by the CMS experiment. The measurement is performed in the transverse momentum ($p_{\mathrm{T}}$) range of 1 to 40 GeV/c, for central and midcentral collisions. The $v_2$ coefficient is found to be positive throughout the $p_{\mathrm{T}}$ range studied. The first measurement of the prompt D${}^0$ meson $v_3$ coefficient is performed, and values up to 0.07 are observed for $p_{\mathrm{T}}$ around 4 GeV/c. Compared to measurements of charged particles, a similar $p_{\mathrm{T}}$ dependence, but smaller magnitude for $p_{\mathrm{T}}<$6 GeV/c, is found for prompt D${}^0$ meson $v_2$ and $v_3$ coefficients. The results are consistent with the presence of collective motion of charm quarks at low $p_{\mathrm{T}}$ and a path length dependence of charm quark energy loss at high $p_{\mathrm{T}}$, thereby providing new constraints on the theoretical description of the interactions between charm quarks and the quark-gluon plasma.

   nucl-exPRL(2018)·191 citations
3. 03*

   Pygmy and core polarization dipole modes in ${}^{206}$Pb: connecting nuclear structure to stellar nucleosynthesis

   A.P. Tonchev🇺🇸 · N. Tsoneva🇩🇪 · C. Bhatia🇮🇳 · C.W. Arnold🇺🇸 · S. Goriely🇧🇪 · S.L. Hammond🇺🇸 · J.H. Kelley🇺🇸 · E. Kwan🇺🇸 · H. Lenske🇩🇪 · J. Piekarewicz🇺🇸 · R. Raut🇮🇳 · G. Rusev🇺🇸 · T. Shizuma🇯🇵 · W. Tornow🇺🇸

   A high-resolution study of the electromagnetic response of ${}^{206}$Pb below the neutron separation energy is performed using a ($\vec{\gamma }$,${\gamma }^{\prime }$) experiment at the HI$\vec{\gamma }$S facility. Nuclear resonance fluorescence with 100% linearly polarized photon beams is used to measure spins, parities, branching ratios, and decay widths of excited states in ${}^{206}$Pb from $4.9$ to $8.1$MeV. The extracted $\Sigma$$B$(E1)$\uparrow$ and $\Sigma$$B$(M1)$\uparrow$ values for the total electric and magnetic dipole strength below the neutron separation energy are 0.9$\pm$0.2e${}^2$fm${}^2$ and 8.3$\pm$2.0${\mu }_N^2$, respectively. These measurements are found to be in very good agreement with the predictions from an energy-density functional (EDF) plus quasiparticle phonon model (QPM). Such a detailed theoretical analysis allows to separate the pygmy dipole resonance from both the tail of the giant dipole resonance and multi-phonon excitations. Combined with earlier photonuclear experiments above the neutron separation energy, one extracts a value for the electric dipole polarizability of ${}^{206}$Pb of ${\alpha }_D=122\pm 10$mb/MeV. When compared to predictions from both the EDF+QPM and accurately calibrated relativistic EDFs, one deduces a range for the neutron-skin thickness of $R_{\mathrm{skin}}^{206}=0.12$-$0.19$fm and a corresponding range for the slope of the symmetry energy of $L=48$-$60$MeV. This newly obtained information is also used to estimate the Maxwellian-averaged radiative cross section ${}^{205}$Pb(n,$\gamma$)${}^{206}$Pb at 30keV to be $\sigma =130\pm 25$mb. The astrophysical impact of this measurement--on both the s-process in stellar nucleosynthesis and on the equation of state of neutron-rich matter--is discussed.

   nucl-exnucl-thPLB(2017)·50 citations
4. 04*

   On the nucleons motion in the nucleus as being due to realistic inter-nucleonic forces

   Yuriy Lyakhno

   This paper deals with the possible motion of nucleons in the nucleus, which is due to realistic inter-nucleonic forces. This approach provides new or more substantiated conclusions about the nuclear structure than those based on the effective interaction of nucleons, while the shell model of the nucleus may lead to questionable conclusions regarding the nuclear structure and nuclear reaction mechanisms.

   ↳ nucl-thnucl-ex0 citations
5. 05*

   Measurement of multi-particle azimuthal correlations with the subevent cumulant method in $pp$ and $p$+Pb collisions with the ATLAS detector at the LHC

   ATLAS Collaboration

   A detailed study of multi-particle azimuthal correlations is presented using $pp$ data at $\sqrt{s}=5.02$ and 13 TeV, and $p$+Pb data at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV, recorded with the ATLAS detector at the LHC. The azimuthal correlations are probed using four-particle cumulants $c_n\{4\}$ and flow coefficients $v_n\{4\}=(-c_n\{4\}{)}^{1/4}$ for $n=2$ and 3, with the goal of extracting long-range multi-particle azimuthal correlation signals and suppressing the short-range correlations. The values of $c_n\{4\}$ are obtained as a function of the average number of charged particles per event, $⟨N_{\mathrm{ch}}⟩$, using the recently proposed two-subevent and three-subevent cumulant methods, and compared with results obtained with the standard cumulant method. The three-subevent method is found to be least sensitive to short-range correlations, which originate mostly from jets with a positive contribution to $c_n\{4\}$. The three-subevent method gives a negative $c_2\{4\}$, and therefore a well-defined $v_2\{4\}$, nearly independent of $⟨N_{\mathrm{ch}}⟩$, which provides direct evidence that the long-range multi-particle azimuthal correlations persist to events with low multiplicity. Furthermore, $v_2\{4\}$ is found to be smaller than the $v_2\{2\}$ measured using the two-particle correlation method, as expected for long-range collective behavior. Finally, the measured values of $v_2\{4\}$ and $v_2\{2\}$ are used to estimate the number of sources relevant for the initial eccentricity in the collision geometry.

   ↳ hep-exnucl-exPRC(2018)·160 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.