Mon·May 7, 2018Monday·May 7, 2018

1. 01*

   Resonance-like coherent production of a pion pair in the reaction $pd\to pd\pi \pi$ in the GeV region

   V.I. Komarov (1)🇷🇺 · D. Tsirkov (1)🇷🇺 · T. Azaryan (1)🇷🇺 · Z. Bagdasarian (2,3)🇩🇪 · B. Baimurzinova (4,5)🇷🇺 · S. Barsov (6)🇷🇺 · S. Dymov (1,2)🇩🇪 · R. Gebel (2)🇩🇪 · M. Hartmann (2)🇩🇪 · A. Kacharava (2)🇩🇪 · A. Khoukaz (7)🇩🇪 · A. Kulikov (1)🇷🇺 and 18 other authors

   The reaction $p+d\to p+d+X$ was studied at 0.8-2.0 GeV proton beam energies with the ANKE magnetic spectrometer at the COSY synchrotron storage ring. The proton-deuteron pairs emerging with high momenta, 0.6-1.8 GeV/$c$, were detected at small angles with respect to the proton beam. Distribution over the reaction missing mass $M_x$ reveals a local enhancement near the threshold of the pion pair production specific for the so-called ABC effect. The enhancement has a structure of a narrow bump placed above a smooth continuum. The invariant mass of the $d\pi \pi$ system in this enhancement region exhibits a resonance-like peak at $M_{d\pi \pi }\approx 2.36$ GeV/$c^2$ with the width $\Gamma \approx 0.10$ GeV/$c^2$. A possible interpretation of these features is discussed.

   nucl-exEPJA(2018)·8 citations
2. 02*

   Anisotropic flow in Xe-Xe collisions at $\sqrt{{\mathbf{s}}_{\mathrm{NN}}}=5.44$ TeV

   ALICE Collaboration

   The first measurements of anisotropic flow coefficients $v_{\mathrm{n}}$ for mid-rapidity charged particles in Xe-Xe collisions at $\sqrt{s_{\mathrm{NN}}}=5.44$ TeV are presented. Comparing these measurements to those from Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV, $v_2$ is found to be suppressed for mid-central collisions at the same centrality, and enhanced for central collisions. The values of $v_3$ are generally larger in Xe-Xe than in Pb-Pb at a given centrality. These observations are consistent with expectations from hydrodynamic predictions. When both $v_2$ and $v_3$ are divided by their corresponding eccentricities for a variety of initial state models, they generally scale with transverse density when comparing Xe-Xe and Pb-Pb, with some deviations observed in central Xe-Xe and Pb-Pb collisions. These results assist in placing strong constraints on both the initial state geometry and medium response for relativistic heavy-ion collisions.

   nucl-exPLB(2018)·181 citations
3. 03*

   Single-spin asymmetry of $J/\psi$ production in $p$$+$$p$, $p$$+$Al, and $p$$+$Au collisions with transversely polarized proton beams at $\sqrt{s_{{}_{NN}}}=200$ GeV

   C. Aidala · Y. Akiba · M. Alfred · V. Andrieux · N. Apadula · H. Asano · B. Azmoun · V. Babintsev · A. Bagoly · N.S. Bandara · K.N. Barish · S. Bathe and 282 other authors

   We report the transverse single-spin asymmetries of $J/\psi$ production at forward and backward rapidity, $1.2<|y|<2.2$, as a function of $J/\psi$ transverse momentum ($p_T$) and Feynman-$x$ ($x_F$). The data analyzed were recorded by the PHENIX experiment at the Relativistic Heavy Ion Collider in 2015 from $p$$+$$p$, $p$$+$Al, and $p$$+$Au collisions with transversely polarized proton beams at $\sqrt{s_{{}_{NN}}}=200$ GeV. At this collision energy, single-spin asymmetries for heavy-flavor particle production of $p$$+$$p$ collisions provide access to the spin-dependent gluon distribution and higher-twist correlation functions inside the nucleon, such as the gluon Qiu-Sterman and trigluon correlation functions. Proton+nucleus collisions offer an excellent opportunity to study nuclear effects on the correlation functions. The data indicate negative asymmetries at the two-standard-deviation level in the $p$$+$Au data for $p_T<2$ GeV/$c$ at both forward and backward rapidity, while in $p$$+$$p$ and $p$$+$Al collisions the asymmetries are consistent with zero within the range of experimental uncertainties.

   ↳ hep-exnucl-exPRD(2018)·35 citations
4. 04*

   On the performance of Zero Degree Calorimeters in detecting multinucleon events

   Uliana Dmitrieva (1 and 2) · Igor Pshenichnov (2) · ((1) Moscow Institute for Physics and Technology, Moscow Region, Russia, (2) Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia)

   The facilities designed to study collisions of relativistic nuclei, such as the MPD at NICA (JINR), STAR at RHIC (BNL), ALICE, ATLAS and CMS at the LHC (CERN), are equipped with pairs of hadronic Zero Degree Calorimeters (ZDC) to detect forward nucleons at the both sides of the interaction point and estimate the collision centrality. The energy deposited in a ZDC fluctuates from one event to another, but on average it is proportional to the number of absorbed nucleons. Forward nucleons are also emitted in electromagnetic dissociation (EMD) of nuclei in ultraperipheral collisions, and they are used to monitor the luminosity. As known, ZDC energy spectra are specific to each facility, because they are affected by the ZDC acceptance, and the ZDC energy resolution depends on the beam energy. In this work a simple combinatorial model leading to handy formulas has been proposed to connect the numbers of emitted and detected forward nucleons taking into account a limited ZDC acceptance. The ZDC energy spectra from the EMD with the emission of one, two, three and four forward neutrons and protons have been modeled for collision energies of NICA and the LHC. The case of a rather small ZDC acceptance has been investigated and a possibility to measure the inclusive nucleon emission cross section has been demonstrated.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2018)·7 citations
5. 05*

   Statistical hadron-gas treatment of systems created in proton-proton interactions at CERN SPS

   V. V. Begun🇵🇱 · V. Vovchenko🇩🇪 · M. I. Gorenstein🇺🇦 · H. Stoecker🇩🇪

   We analyze the newest data from the NA61/SHINE collaboration which, in addition to previous results on pions and kaons, include mean multiplicities of $p$, $\Lambda$, and $\varphi$-mesons produced in inelastic proton-proton (p+p) interactions at $\sqrt{s_{NN}}=6.3-17.3$~GeV. The canonical ensemble formulation of the ideal hadron resonance gas (HRG) model is used with exact conservation of net baryon number $B=2$, electric charge $Q=2$, and strangeness $S=0$. The chemical freeze-out parameters in p+p interactions are obtained and compared to those in central nucleus-nucleus collisions. Several features of p+p interactions at the CERN SPS within a statistical model are studied: 1) the inclusion of the $\varphi$-meson yields in thermal fits worsens significantly the fit quality; 2) the data show large event-by-event multiplicity fluctuations in inelastic p+p interactions which can not be explained by a single fireball described by a statistical model; 3) the fits within the canonical ensemble formulation of HRG do not give any improvement over the fits within the grand canonical ensemble formulation, i.e., there are no indications for existence of a single statistical system in p+p inelastic interactions in the considered energy range.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2018)·17 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.