Tue·Apr 14, 2020Tuesday·April 14, 2020

1. 01*

   First measurement of direct photoproduction of the $a_2(1320{)}^0$ meson on the proton

   A. Celentano · M. Battaglieri · R. De Vita · L. Marsicano · V. Mathieu · A. Pilloni · A. Szczepaniak (for the CLAS collaboration)

   We present the first measurement of the exclusive reaction $\gamma p\to a_2(1320{)}^{0}p$ in the photon energy range $3.5$-$5.5$ GeV and four-momentum transfer squared $0.2<-t<2.0$ GeV${}^2$. Data were collected with the CEBAF Large Acceptance Spectrometer at the Thomas Jefferson National Accelerator Facility. The neutral $a_2$ resonance was detected by measuring the reaction $\gamma p\to {\pi }^0\eta p$ and reconstructing the ${\pi }^0\eta$ invariant mass. The differential cross section $d\sigma /dt$ was extracted at different beam energies in each $-t$ bin. The most prominent feature of the differential cross section is a dip at $-t\simeq 0.55$ GeV${}^2$. This can be well described in the framework of Regge phenomenology, where the exchange degeneracy hypothesis predicts a zero in the reaction amplitude for this value of the four-momentum transfer.

   nucl-exhep-exnucl-thPRC(2020)·12 citations
2. 02*

   How EIC can help us to understand heavy-ion collisions

   Yoshitaka Hatta🇺🇸

   I give a brief overview of the science cases of the Electron-Ion Collider (EIC) with a particular emphasis on the connections to the physics of ultrarelativistic heavy-ion collisions.

   ↳ hep-phnucl-exnucl-thNPA(2021)·4 citations
3. 03*

   Extracting the magnitude of magnetic field at freeze-out in heavy-ion collisions

   Kun Xu🇨🇳 · Shuzhe Shi🇨🇦 · Hui Zhang🇨🇳 · Defu Hou🇨🇳 · Jinfeng Liao🇺🇸 · Mei Huang🇨🇳

   A strong magnetic field influences significantly the masses of the charged light mesons. For example, the mass of charged pion increases with the magnetic field increasing. We propose this mechanism as a possible way to extract the magnitude of magnetic field at freeze-out in heavy ion collisions and thus help constrain its lifetime which is currently a major open question to resolve. Specifically we show that the ratio between the yield of charged pions and that of charged rhos is very sensitive to the magnetic field value at freeze-out. By using a viscous-hydrodynamic framework (iEBE-VISHNU) to simulate heavy ion collisions and implementing magnetic-field-dependent meson masses, we compute their yields and predict the dependence of such ratio on the magnetic field. We suggest to use this ratio of charged rho yield over charged pion yield as an experimental observable to extract the possible magnetic field at freeze-out in heavy ion collisions.

   ↳ hep-phnucl-exPLB(2020)·21 citations
4. 04*

   Classical excluded volumes of loosely bound light (anti)nuclei and their chemical freeze-out in heavy ion collisions

   B. E. Grinyuk🇺🇦 · K. A. Bugaev🇺🇦 · V. V. Sagun🇺🇦 · O. I. Ivanytskyi🇺🇦 · D. L. Borisyuk🇺🇦 · A. S. Zhokhin🇺🇦 · G. M. Zinovjev🇺🇦 · D. B. Blaschke🇵🇱 · L. V. Bravina🇳🇴 · E. E. Zabrodin🇳🇴 · E. G. Nikonov🇷🇺 · G. Farrar🇺🇸 and 3 other authors

   From the analysis of light (anti)nuclei multiplicities that were measured recently by the ALICE collaboration in Pb+Pb collisions at the center-of-mass collision energy $\sqrt{s_{NN}}=2.76$ TeV there arose a highly non-trivial question about the excluded volume of composite particles. Surprisingly, the hadron resonance gas model (HRGM) is able to perfectly describe the light (anti)nuclei multiplicities under various assumptions. Thus, one can consider the (anti)nuclei with a vanishing hard-core radius (as the point-like particles) or with the hard-core radius of proton, but the fit quality is the same for these assumptions. It is clear, however, that such assumptions are unphysical. Hence we obtain a formula for the classical excluded volume of loosely bound light nuclei consisting of A baryons. To implement a new formula into the HRGM we have to modify the induced surface tension concept to treat the hadrons and (anti)nuclei on the same footing. We perform a simultaneous analysis of hadronic and (anti)nuclei multiplicities measured by the ALICE collaboration. The HRGM with the induced surface tension allows us to verify different assumptions on the values of hard-core radii and different scenarios of chemical freeze-out of light (anti)nuclei. It is shown that the unprecedentedly high quality of fit ${\chi }_{tot}^2/dof\simeq 0.769$ is achieved, if the chemical freeze-out temperature of hadrons is about $T_h=150$ MeV, while the one for all (anti)nuclei is $T_A=174-175.2$ MeV.

   ↳ hep-phnucl-exnucl-thIJMPE(2020)·7 citations
5. 05*

   Momentum-dependent potential and collective flows within the relativistic quantum molecular dynamics approach based on relativistic mean-field theory

   Yasushi Nara🇯🇵 · Tomoyuki Maruyama🇯🇵 · Horst Stoecker🇩🇪

   Relativistic quantum molecular dynamics based on the relativistic mean field theory (RQMD.RMF) is extended by including momentum-dependent potential. The equation of state (EoS) dependence of the directed and the elliptic flow of protons in the beam energy range of $2.3<\sqrt{s_{NN}}<20$ GeV is examined. It is found that the directed flow depends strongly on the optical potential at high energies,$\sqrt{s_{NN}}>3$ GeV, where no information is available experimentally. The correlation between effective mass at saturation density and the optical potential is found: smaller values of effective mass require smaller strengths of the optical potential to describe the directed flow data.This correlation can also be seen in the beam energy dependence of the elliptic flow at $\sqrt{s_{NN}}>3$ GeV, although its effect is rather weak. On the other hand, stiff EoS is required to describe the elliptic flow at lower energies.Experimental constraints on the optical potential from $pA$ collisions will provide important information on the EoS at high energies.The proton directed and the elliptic flow are well described in the RQMD.RMF model from $\sqrt{s_{NN}}=2.3$ to 8.8 GeV. In contrast,to reproduce the collapse of the directed flow above 10 GeV, pressure has to be reduced, which indicates a softening of the EoS around $\sqrt{s_{NN}}=10$ GeV.

   ↳ nucl-thhep-phnucl-exPRC(2020)·69 citations
6. 06*

   A simple method to prepare deuterated targets for experiments relevant to nuclear astrophysics

   Tanmoy Bar · Chinmay Basu

   In this work, a simple and efficient thin ($50-350\mu g/c{m}^2$) deuterated polyethylene target preparation method is described. The method of easy removal of thin targets from casting surface without using any cryogenic freezing has been described. The difference in thermal expansion properties is used to separate films from glass slides. 3-$\alpha$ radioactive source is used to measure the target thickness. The material property of the prepared targets is verified by Attenuated total reflection (ATR) method.

   ↳ physics.ins-detnucl-exRev.Sci.Instrum.(2020)·1 citation

* 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.