Mon·Jul 20, 2015Monday·July 20, 2015

1. 01*

   Preliminary Results on the Experimental Investigation of the Structure Functions of Bound Nucleons

   A. Bodek🇺🇸

   We present preliminary results on an experimental study of the nuclear modification of the longitudinal (${\sigma }_L$) and transverse (${\sigma }_T$) structure functions of nucleons bound in nuclear targets. The origin of these modifications (commonly referred as as the EMC effect) is not fully understood. Our measurements of R= ${\sigma }_L/{\sigma }_T$ for nuclei ($R_A$) and for deuterium ($R_D$) indicate that nuclear modifications of the structure functions of bound nucleons are different for the longitudinal and transverse structure functions, and that contrary to expectation from several theoretical models, $R_A<R_D$.

   nucl-exhep-exPoS(2015)·1 citation
2. 02*

   Isospin splitting of nucleon effective mass from giant resonances in ${}^{208}$Pb

   Zhen Zhang🇨🇳 · Lie-Wen Chen🇨🇳

   Based on mean field calculations with Skyrme interactions, we extract a constraint on the isovector effective mass in nuclear matter at saturation density ${\rho }_0$, i.e., $m_v^{\ast }({\rho }_0)=(0.77\pm 0.03)m$ by combining the experimental data of the centroid energy of the isovector giant dipole resonance (IVGDR) and the electric dipole polarizability ${\alpha }_{\mathrm{D}}$ in ${}^{208}$Pb. Meanwhile, the isoscalar effective mass at ${\rho }_0$ is determined to be $m_s^{\ast }({\rho }_0)=(0.91\pm 0.05)m$ by analyzing the measured excitation energy of the isoscalar giant quadrupole resonance (ISGQR) in ${}^{208}$Pb. From the constrained $m_s^{\ast }({\rho }_0)$ and $m_v^{\ast }({\rho }_0)$, we obtain the isospin splitting of nucleon effective mass in asymmetric nuclear matter of isospin asymmetry $\delta$ at ${\rho }_0$ as $[m_n^{\ast }({\rho }_0,\delta )-m_p^{\ast }({\rho }_0,\delta )]/m=\Delta m_1^{\ast }({\rho }_0)\delta +O({\delta }^3)$ with the linear isospin splitting coefficient $\Delta m_1^{\ast }({\rho }_0)=0.33\pm 0.16$. We notice that using the recently corrected data on the ${\alpha }_{\mathrm{D}}$ in ${}^{208}$Pb with the contribution of the quasideuteron effect subtracted slightly enhances the isovector effective mass to $m_v^{\ast }({\rho }_0)=(0.80\pm 0.03)m$ and reduces the linear isospin splitting coefficient to $\Delta m_1^{\ast }({\rho }_0)=0.27\pm 0.15$. Furthermore, the constraints on $m_v^{\ast }(\rho )$, $m_s^{\ast }(\rho )$ and $\Delta m_1^{\ast }(\rho )$ at other densities are obtained from the similar analyses and we find that the $\Delta m_1^{\ast }(\rho )$ increases with the density.

   ↳ nucl-thastro-ph.SRhep-phnucl-exPRC(2016)·51 citations
3. 03*

   Elliptic flow difference of charged pions in heavy-ion collisions

   Yoshitaka Hatta🇯🇵 · Akihiko Monnai🇺🇸 · Bo-Wen Xiao🇨🇳

   Recently, the STAR collaboration at RHIC has presented experimental evidence for the correlation between the elliptic flow difference of charged pions and charge asymmetry as a possible signal of the chiral magnetic wave. We demonstrate that the STAR results can be understood within the standard viscous hydrodynamics.

   ↳ hep-phnucl-exnucl-thNPA(2016)·43 citations
4. 04*

   Nucleon and pion structure with lattice QCD simulations at physical value of the pion mass

   A. Abdel-Rehim (Cyprus Inst.)🇨🇾 · C. Alexandrou (Cyprus Inst. & Univ. of Cyprus)🇨🇾 · M. Constantinou (Cyprus Inst. & Univ. of Cyprus)🇨🇾 · P. Dimopoulos (Fermi Center & Rome Tor Vergata)🇮🇹 · R. Frezzotti (INFN & Rome Tor Vergata)🇮🇹 · K. Hadjiyiannakou (Univ. of Cyprus & Cyprus Inst.)🇨🇾 · K. Jansen (DESY)🇩🇪 · Ch. Kallidonis (Cyprus Inst.)🇨🇾 · B. Kostrzewa (Humboldt Univ. & DESY)🇩🇪 · G. Koutsou (Cyprus Inst.)🇨🇾 · M. Mangin-Brinet (Grenoble)🇫🇷 · M. Oehm (Bonn Univ.)🇩🇪 and 3 other authors

   We present results on the nucleon scalar, axial and tensor charges as well as on the momentum fraction, and the helicity and transversity moments. The pion momentum fraction is also presented. The computation of these key observables is carried out using lattice QCD simulations at a physical value of the pion mass. The evaluation is based on gauge configurations generated with two degenerate sea quarks of twisted mass fermions with a clover term. We investigate excited states contributions with the nucleon quantum numbers by analyzing three sink-source time separations. We find that, for the scalar charge, excited states contribute significantly and to a less degree to the nucleon momentum fraction and helicity moment. Our analysis yields a value for the nucleon axial charge agrees with the experimental value and we predict a value of 1.027(62) in the $\overline{\text{MS}}$ scheme at 2 GeV for the isovector nucleon tensor charge directly at the physical point. The pion momentum fraction is found to be $⟨x{⟩}_{u-d}^{{\pi }^{\pm }}=0.214(15){(}_{-9}^{+12})$ in the $\overline{\mathrm{MS}}$ at 2 GeV.

   ↳ hep-lathep-phnucl-exnucl-thPRD(2015)·175 citations
5. 05*

   Probing the properties of event-by-event distributions in Hanbury-Brown--Twiss radii

   Christopher Plumberg🇺🇸 · Ulrich Heinz🇺🇸

   Hanbury-Brown--Twiss interferometry is a technique which yields effective widths (i.e., "HBT radii") of homogeneity regions in the fireballs produced in heavy ion collisions. Because the initial conditions of these collisions are stochastically fluctuating, the measured HBT radii also exhibit variation on an event-by-event basis. However, HBT measurements have, to date, been performed only on an ensemble-averaged basis, due to inherent limitations of finite particle statistics. In this paper, we show that experimental measurements to date are best characterized theoretically as weighted averages of the event-by-event HBT radii, and we propose a new method for extracting experimentally both the arithmetic mean and the variance of the event-by-event distribution of HBT radii. We demonstrate the extraction of the mean and variance of this distribution for a particular ensemble of numerically generated events, and offer some ideas to extend and generalize the method to enable measurement of higher moments of the HBT distribution as well.

   ↳ nucl-thnucl-exPRC(2015)·13 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.