Fri·Nov 18, 2016Friday·November 18, 2016

1. 01*

   Recent results on collective effects in small systems from PHENIX at RHIC

   Sarah Campbell (for the PHENIX Collaboration)🇺🇸

   Collisions of simple systems, such as $p$+$p$, or $p$+Nucleus have been used as benchmarks for our understanding of heavy ion collsions, since it was assumed they would be free of the effects from hot nuclear matter. Recently long range correlations and anisotropies of momentum spectra have been seen in such collisions, challenging this assumption. Such phenomena have been understood to be the result of the collective motion, which can best be described by hydrodynamics, whose initial conditions are set by the geometry of the colliding systems, together with their fluctuations. This talk will discuss the recent results from the PHENIX experiment at RHIC using a variety of colliding species ($p$+Au, $d$+Au, ${}^3$He+Au) that give a better understanding of the origin of the observed correlations and anisotropies, thus providing insight as to whether a quark gluon plasma is formed in these simple systems.

   nucl-exPoS(2016)·0 citations
2. 02*

   Accessing transverse nucleon and gluon distributions in heavy nuclei using coherent vector meson photoproduction at high energies in ion ultraperipheral collisions

   V. Guzey (St. Petersburg, INP)🇷🇺 · M. Strikman (Penn State U.)🇺🇸 · M. Zhalov (St. Petersburg, INP)🇷🇺

   By using the theoretical approaches describing well the available data on $t$-integrated coherent photoproduction of light and heavy vector mesons in Pb-Pb ultraperipheral collisions (UPCs) at the Large Hadron Collider (LHC) in Run 1, we calculate the momentum transfer distributions for this process for $\rho$ and $J/\psi$ vector mesons in the kinematics of Run 2 at the LHC. We demonstrate that nuclear shadowing not only suppresses the absolute value of the cross sections, but also shifts the momentum transfer distributions toward smaller values of the momentum transfer $|t|$. This result can be interpreted as a broadening in the impact parameter space of the effective nucleon density in nuclei by 14\% in the case of $\rho$ and the nuclear gluon distribution by $5-11$\% in the case of $J/\psi$.

   ↳ hep-phhep-exnucl-exPRC(2017)·59 citations
3. 03*

   Two-Photon-Exchange Effects and $\Delta (1232)$ Deformation

   Hai-Qing Zhou🇨🇳 · Shin Nan Yang🇹🇼

   The two-photon-exchange (TPE) contribution in $ep\to ep{\pi }^0$ with $W=M_{\Delta }$ and small $Q^2$ is calculated and its corrections to the ratios of electromagnetic transition form factors $R_{EM}=E_{1+}^{(3/2)}/M_{1+}^{(3/2)}$ and $R_{SM}=S_{1+}^{(3/2)}/M_{1+}^{(3/2)}$, are analysed. A simple hadronic model is used to estimate the TPE amplitude. Two phenomenological models, MAID2007 and SAID, are used to approximate the full $ep\to ep{\pi }^0$ cross sections which contain both the TPE and the one-photon-exchange (OPE) contributions. The genuine the OPE amplitude is then extracted from an integral equation by iteration. We find that the TPE contribution is not sensitive to whether MAID or SAID is used as input in the region with $Q^2<2$ GeV${}^2$. It gives small correction to $R_{EM}$ while for $R_{SM}$, the correction is about -10\% at small $ϵ$ and about $1\%$ at large $ϵ$ for $Q^2\approx 2.5$ GeV${}^2$. The large correction from TPE at small $ϵ$ must be included in the analysis to get a reliable extraction of $R_{SM}$.

   ↳ nucl-thnucl-exJPS Conf.Proc.(2017)·13 citations
4. 04*

   Measurement of ${\sigma }_{\mathrm{ABS}}$ and ${\sigma }_{\mathrm{CX}}$ of ${\pi }^{+}$ on carbon by DUET

   E. S. Pinzon Guerra🇨🇦 · S. Bhadra🇨🇦 · S. Berkman🇨🇦 · C. Cao🇺🇸 · P. de Perio🇺🇸 · Y. Hayato🇯🇵 · K. Ieki🇯🇵 · M. Ikeda🇯🇵 · Y. Kanazawa🇯🇵 · J. Kim🇰🇷 · P. Kitching🇨🇦 · K. Mahn🇺🇸 and 10 other authors

   The DUET Collaboration reports on the measurements of the absorption (${\sigma }_{\mathrm{ABS}}$) and charge exchange (${\sigma }_{\mathrm{CX}}$) cross sections of positively charged pions on carbon nuclei for the momentum range 201.6 MeV$/c$ to 295.1 MeV$/c$. The uncertainties on the absorption and charge exchange cross sections are $\sim$9.5\% and $\sim$18\%, respectively. The results are in good agreement with previous experiments. A covariance matrix correlating the 5 ${\sigma }_{\mathrm{ABS}}$ and 5 ${\sigma }_{\mathrm{CX}}$ measured data points is also reported

   ↳ hep-exnucl-exphysics.ins-detPRC(2017)·41 citations
5. 05*

   Squeezed back-to-back correlations of $\varphi \varphi$ in Au+Au and d+Au collisions at the Relativistic Heavy Ion Collider energies

   Yong Zhang🇨🇳 · Wei-Ning Zhang🇨🇳

   We investigate the squeezed back-to-back correlations (BBC) of $\varphi \varphi$, caused by the mass modification of the particles in the source medium, in the heavy-ion collisions of Au+Au and d+Au at the Relativistic Heavy Ion Collider (RHIC) energies. The BBC functions are calculated using the modified masses extracted from experimental data and the source space-time distributions provided by the viscous hydrodynamic code VISH2+1. Our investigations indicate that the BBC of $\varphi \varphi$ may perhaps be observed in the collisions of d+Au and the peripheral collisions of Au+Au at the RHIC. We suggest to measure the BBC experimentally for understanding the mass modifications of the $\varphi$ meson in the collisions.

   ↳ nucl-thnucl-ex1 citation
6. 06*

   Concentration of the velocity distribution of pulsed neutron beams

   Masaaki Kitaguchi🇯🇵 · Yoshihisa Iwashita🇯🇵 · Hirohiko M. Shimizu🇯🇵

   The velocity of neutrons from a pulsed neutron source is well-defined as a function of their arrival time. Electromagnetic neutron accelerator/decelerator synchronized with the neutron time-of-flight is capable of selectively changing the neutron velocity and concentrating the velocity distribution. Possible enhancement of the neutron intensity at a specific neutron velocity by orders of magnitude is discussed together with an experimental design.

   ↳ physics.ins-dethep-exnucl-exphysics.acc-phPTEP(2017)·0 citations
7. 07*

   In-Medium Pion Valence Distribution Amplitude

   K. Tsushima (Cruzeiro do Sul U.)🇧🇷 · J. P. B. C de Melo (Cruzeiro do Sul U.)🇧🇷

   After a brief review of the quark-based model for nuclear matter, and some pion properties in medium presented in our previous works, we report new results for the pion valence wave function as well as the valence distribution amplitude in medium, which are presented in our recent article. We find that both the in-medium pion valence distribution and the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.

   ↳ nucl-thhep-exhep-phnucl-exFew Body Syst.(2017)·3 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.