Thu·Apr 14, 2016Thursday·April 14, 2016

1. 01*

   Theoretical study of photoproduction of ${\eta }^{\prime }N$ bound state on deuteron target with forward proton emission

   Takayasu Sekihara (Osaka U., Res. Ctr. Nucl. Phys.)🇯🇵 · Shuntaro Sakai (Kyoto U.)🇯🇵 · Daisuke Jido (Tokyo Metropolitan U.)🇯🇵

   Possibilities of observing a signal of an ${\eta }^{\prime }n$ bound state are investigated by considering photoproductions of the $\eta$ and ${\eta }^{\prime }$ mesons on a deuteron target with forward proton emission. For this purpose, we take the ${\eta }^{\prime }n$ interaction from the linear sigma model with a coupling to $\eta n$, in which an $s$-wave ${\eta }^{\prime }n$ bound state can be dynamically generated, and we fix the $\gamma p\to \eta p$ and ${\eta }^{\prime }p$ scattering amplitudes so as to reproduce the experimental cross sections with forward proton emission. By using these $\gamma p\to {\eta }^{(\prime )}p$ and ${\eta }^{(\prime )}n\to {\eta }^{(\prime )}n$ amplitudes, we calculate cross sections of the $\gamma d\to \eta np$ and ${\eta }^{\prime }np$ reactions with forward proton emission in single and ${\eta }^{(\prime )}$-exchange double scattering processes. As a result, we find that the signal of the ${\eta }^{\prime }n$ bound state can be seen below the ${\eta }^{\prime }n$ threshold in the $\eta n$ invariant mass spectrum of the $\gamma d\to \eta np$ reaction and is comparable with the contribution from the quasifree ${\eta }^{\prime }$ production above the ${\eta }^{\prime }n$ threshold. We also discuss the behavior of the signal of the ${\eta }^{\prime }n$ bound state in several experimental conditions and model parameters.

   ↳ nucl-thhep-phnucl-exPRC(2016)·4 citations
2. 02*

   Vector-boson production in p--Pb collisions with ALICE at the LHC

   Kgotlaesele Johnson Senosi (for the ALICE collaboration)🇿🇦

   ALICE (A Large Ion Collider Experiment) is designed and optimized to study ultra-relativistic heavy-ion collisions at the LHC, in which a hot and dense, strongly-interacting medium is created. Vector bosons (W and Z) are produced in hard scattering processes and interact weakly with the medium formed in heavy-ion collisions. Thus, they present a suitable reference for processes which are heavily affected by the medium. In proton-nucleus collisions their production can be used to study the modification of parton distribution functions in the nucleus and to test the validity of binary-collision scaling for hard processes. The production of W and Z bosons is studied in p--Pb collisions at a centre-of-mass energy of $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with the ALICE muon spectrometer at forward ($2.03<y_{\text{cms}}^{\mu }<3.53$) and backward ($-4.46<y_{\text{cms}}^{\mu }<-2.96$) rapidity. W bosons are studied via the inclusive single muon differential $p_{\mathrm{T}}$ spectrum whereas the Z-boson signal is observed in the invariant mass distribution of unlike-sign muon pairs as a peak around the Z-boson mass. In this presentation the measured cross sections of W and Z bosons and the W-boson yield per centrality interval will be discussed. The cross-sections are compared to theoretical calculations.

   ↳ hep-exnucl-ex1 citation
3. 03*

   Mean-field instabilities and cluster formation in nuclear reactions

   M. Colonna🇮🇹 · P. Napolitani🇫🇷 · V. Baran🇷🇴

   We review recent results on intermediate mass cluster production in heavy ion collisions at Fermi energy and in spallation reactions. Our studies are based on modern transport theories, employing effective interactions for the nuclear mean-field and incorporating two-body correlations and fluctuations. Namely we will consider the Stochastic Mean Field (SMF) approach and the recently developed Boltzmann-Langevin One Body (BLOB) model. We focus on cluster production emerging from the possible occurrence of low-density mean-field instabilities in heavy ion reactions. Within such a framework, the respective role of one and two-body effects, in the two models considered, will be carefully analysed. We will discuss, in particular, fragment production in central and semi-peripheral heavy ion collisions, which is the object of many recent experimental investigations. Moreover, in the context of spallation reactions, we will show how thermal expansion may trigger the development of mean-field instabilities, leading to a cluster formation process which competes with important re-aggregation effects.

   ↳ nucl-thnucl-ex5 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.