Wed·Jun 24, 2015Wednesday·June 24, 2015

1. 01*

   Event shape sorting

   Renata Kopecna🇨🇿 · Boris Tomasik🇸🇰

   We propose a novel method for sorting events of multiparticle production according to the azimuthal anisotropy of their momentum distribution. Although the method is quite general, we advocate its use in analysis of ultra-relativistic heavy-ion collisions where large number of hadrons is produced. The advantage of our method is that it can automatically sort out samples of events with histograms that indicate similar distributions of hadrons. It takes into account the whole measured histograms with all orders of anisotropy instead of a specific observable (e.g. $v_2$, $v_3$, $q_2$). It can be used for more exclusive experimental studies of flow anisotropies which are then more easily compared to theoretical calculations. It may also be useful in the construction of mixed-events background for correlation studies as it allows to select events with similar momentum distribution.

   ↳ nucl-thhep-phnucl-exphysics.data-anEPJA(2016)·10 citations
2. 02*

   Effects of a $N^{\ast }$ resonance with hidden charm in the ${\pi }^{-}p\to D^{-}{\Sigma }_c^{+}$ reaction near threshold

   E. J. Garzon🇪🇸 · Ju-Jun Xie🇨🇳

   We study the effect of a hidden charm nuclear excited state $N_{c\bar{c}}^{\ast }$ in the ${\pi }^{-}p\to D^{-}{\Sigma }_c^{+}$ reaction near threshold using an effective Lagrangian approach. We calculate the background contribution of the $t$ and $u$ channels by the $D^{\ast 0}$ vector meson exchange and ${\Sigma }_c^{++}$ intermediate state, respectively. We show that the consideration of a $N_{c\bar{c}}^{\ast }$ resonance provides an enhancement of the total cross section close to the reaction threshold. We also evaluate the differential cross section for different energies and we study the angle dependence. It is expected that our model calculations will be tested in future experiments.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2015)·44 citations
3. 03*

   Dynamical effects of spin-dependent interactions in low- and intermediate-energy heavy-ion reactions

   Jun Xu🇨🇳 · Bao-An Li🇺🇸 · Wen-Qing Shen🇨🇳 · Yin Xia🇨🇳

   It is well known that non-central nuclear forces, such as the spin-orbital coupling and the tensor force, play important roles in understanding many interesting features of nuclear structures. However, their dynamical effects in nuclear reactions are poorly known since only the spin-averaged observables are normally studied both experimentally and theoretically. Realizing that spin-sensitive observables in nuclear reactions may carry useful information about the in-medium properties of non-central nuclear interactions, besides earlier studies using the time-dependent Hartree-Fock approach to understand effects of spin-orbital coupling on the threshold energy and spin polarization in fusion reactions, some efforts have been made recently to explore dynamical effects of non-central nuclear forces in intermediate-energy heavy-ion collisions using transport models. The focuses of these studies have been on investigating signatures of the density and isospin dependence of the form factor in the spin-dependent single-nucleon potential. Interestingly, some useful probes were identified in the model studies while so far there is still no data to compare with. In this brief review, we summarize the main physics motivations as well as the recent progress in understanding the spin dynamics and identifying spin-sensitive observables in heavy-ion reactions at intermediate energies. We hope the interesting, important, and new physics potentials identified in the spin dynamics of heavy-ion collisions will stimulate more experimental work in this direction.

   ↳ nucl-thnucl-exFront.Phys.(Beijing)(2015)·7 citations
4. 04*

   Designing an upgrade of the Medley setup for light-ion production and fission cross-section measurements

   Kaj Jansson🇸🇪 · Cecilia Gustavsson🇸🇪 · Ali Al-Adili · Anders Hjalmarsson🇸🇪 · Erik Andersson-Sundén · Alexander V. Prokofiev🇸🇪 · Diego Tarrío🇪🇸 · Stephan Pomp🇸🇪

   Measurements of neutron-induced fission cross sections and light-ion production are planned in the energy range 1-40 MeV at the upcoming Neutrons For Science (NFS) facility. In order to prepare our detector setup for the neutron beam with continuous energy spectrum, a simulation software was written using the Geant4 toolkit for both measurement situations. The neutron energy range around 20 MeV is troublesome when it comes to the cross sections used by Geant4 since data-driven cross sections are only available below 20 MeV but not above, where they are based on semi-empirical models. Several customisations were made to the standard classes in Geant4 in order to produce consistent results over the whole simulated energy range. Expected uncertainties are reported for both types of measurements. The simulations have shown that a simultaneous precision measurement of the three standard cross sections H(n,n), ${}^{235}$U(n,f) and ${}^{238}$U(n,f) relative to each other is feasible using a triple layered target. As high resolution timing detectors for fission fragments we plan to use Parallel Plate Avalanche Counters (PPACs). The simulation results have put some restrictions on the design of these detectors as well as on the target design. This study suggests a fissile target no thicker than 2 micrometers (1.7 mg/cm${}^2$) and a PPAC foil thickness preferably less than 1 micrometer. We also comment on the usability of Geant4 for simulation studies of neutron reactions in this energy range.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2015)·0 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.