Wed·Jul 11, 2018Wednesday·July 11, 2018

1. 01*

   HBT radii : Comparative studies on collision systems and beam energies

   Debasish Das🇮🇳

   Two-particle Hanbury-Brown-Twiss (HBT) interferometry is an important probe for understanding the space-time structure of particle emission sources in high energy heavy ion collisions. We present the comparative studies of HBT radii in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 17.3 GeV with Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 19.6 GeV. To further our understanding for this specific energy regime we also compare the HBT radii for Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 19.6 GeV with Cu+Cu collisions at $\sqrt{s_{\mathrm{NN}}}$ = 22.4 GeV. We have found interesting similarity in the $R_{\mathrm{out}}/R_{\mathrm{side}}$ ratio with $m_{\mathrm{T}}$ across the collision systems while comparing the data for this specific energy zone which is interesting as it acts as a bridge from SPS energy regime to the RHIC energy domain.

   nucl-exhep-exAdv.High Energy Phys.(2018)·2 citations
2. 02*

   Extraction of the Specific Shear Viscosity of Hot Hadron Gas

   Zhidong Yang🇺🇸 · Rainer J. Fries🇺🇸

   We extract the specific shear viscosity $\eta /s$ of nuclear matter for various temperatures and chemical potentials in the hadronic phase using data taken in high energy nuclear collisions. We use a blastwave parameterization of the final state of nuclear collisions, including non-equilibrium deformations of particle distributions due to shear stress in the Navier-Stokes approximation. We fit spectra and elliptic flow of identified hadrons for a variety of collision energies and impact parameters at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). The systems analyzed cover a temperature range from about 110 to 140 MeV and vary in their chemical potentials for stable hadrons. We attempt to assign meaningful systematic uncertainties to our results. This work is complementary to efforts using viscous fluid dynamics to extract the specific shear viscosity of quark gluon plasma at higher temperatures. We put our work in context with existing theoretical calculations of the specific shear viscosity.

   ↳ nucl-thhep-phnucl-ex4 citations
3. 03*

   Theoretical study of the capture of stable ${}^{39}$K and neutron-rich radioactive ${}^{46}$K by ${}^{181}$Ta

   Bing Wang🇨🇳 · Wei-Juan Zhao🇨🇳 · En-Guang Zhao🇨🇳 · Shan-Gui Zhou🇨🇳

   The empirical coupled-channel (ECC) model and the universal fusion function (UFF) prescription are used to analyse the data of capture cross sections for reactions ${}^{39}$K$+{}^{181}$Ta and ${}^{46}$K$+{}^{181}$Ta reported recently by A. Wakhle {\it et al.} [Phys. Rev. C 97, 021602(R) (2018)]. The results of the ECC model are in good agreement with the data of ${}^{39}$K$+{}^{181}$Ta while, for ${}^{46}$K$+{}^{181}$Ta, the predictions of the ECC model overestimate the above-barrier capture cross sections. Comparing the reduced data of these two reactions, it is found that the above-barrier cross sections of ${}^{39}$K$+{}^{181}$Ta are consistent with the UFF and are larger than those of ${}^{46}$K$+{}^{181}$Ta. This implies that the capture cross sections of ${}^{46}$K$+{}^{181}$Ta are suppressed at energies above the Coulomb barrier. Furthermore, at sub-barrier energies, the reduced calculated capture cross sections of ${}^{39}$K$+{}^{181}$Ta are a little larger than those of ${}^{46}$K$+{}^{181}$Ta, which is owing to the coupling to the positive $Q$-value two-neutron transfer channel.

   ↳ nucl-thnucl-exPRC(2018)·9 citations
4. 04*

   Automatic trajectory recognition in Active Target Time Projection Chambers data by means of hierarchical clustering

   Christoph Dalitz · Yassid Ayyad🇯🇵 · Jens Wilberg · Lukas Aymans · Daniel Bazin🇺🇸 · Wolfgang Mittig🇺🇸

   The automatic reconstruction of three-dimensional particle tracks from Active Target Time Projection Chambers data can be a challenging task, especially in the presence of noise. In this article, we propose a non-parametric algorithm that is based on the idea of clustering point triplets instead of the original points. We define an appropriate distance measure on point triplets and then apply a single-link hierarchical clustering on the triplets. Compared to parametric approaches like RANSAC or the Hough transform, the new algorithm has the advantage of potentially finding trajectories even of shapes that are not known beforehand. This feature is particularly important in low-energy nuclear physics experiments with Active Targets operating inside a magnetic field. The algorithm has been validated using data from experiments performed with the Active Target Time Projection Chamber developed at the National Superconducting Cyclotron Laboratory (NSCL).The results demonstrate the capability of the algorithm to identify and isolate particle tracks that describe non-analytical trajectories. For curved tracks, the vertex detection recall was 86\% and the precision 94\%. For straight tracks, the vertex detection recall was 96\% and the precision 98\%. In the case of a test set containing only straight linear tracks, the algorithm performed better than an iterative Hough transform.

   ↳ physics.ins-detnucl-exstat.MLComput.Phys.Commun.(2019)·8 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.