Wed·Aug 29, 2018Wednesday·August 29, 2018

1. 01*

   Study of charged particle multiplicity, average transverse momentum and azimuthal anisotropy in Xe+Xe collisions at $\sqrt{s_{NN}}$ = 5.44 TeV using AMPT model

   Sourav Kundu🇮🇳 · Dukhishyam Mallick🇮🇳 · Bedangadas Mohanty🇮🇳

   We have studied the average charged particle density ($<$dN${}_{ch}$/d$\eta$$>$), transverse momentum ($p_{\mathrm{T}}$) spectra, $<$$p_{\mathrm{T}}$$>$ and azimuthal anisotropies of inclusive charged particles produced in Xe+Xe collisions at $\sqrt{s_{NN}}$ = 5.44 TeV using A Multiphase Transport Model (AMPT), which includes the deformation of Xe${}^{129}$ nucleus. Calculations have been performed with the string melting version of AMPT model and compared with the recent measurements from the ALICE experiment. The model results over predict the measured $<$dN${}_{ch}$/d$\eta$$>$ for central collisions, agree with the data for mid-central collisions and under predict the measurements for peripheral collisions. The centrality dependence of $<$$p_{\mathrm{T}}$$>$ of charged particles measured in ALICE is not reproduced by the model results. The calculated elliptic flow ($v_2$) from AMPT model overpredicts the ALICE measurements in central collisions but are consistent with the data in mid central collisions. We find that the model shows a mild centrality dependence of triangular flow and overestimates the ALICE measurements. Within the model framework, we have also studied various collision configurations of Xe nuclei such as body-body, tip-tip, side-side and random. We find a strong dependence of the above observable on the collision configurations.

   nucl-exhep-exnucl-thEPJA(2019)·8 citations
2. 02*

   Impact of a cryogenic baffle system on the suppression of radon-induced background in the KATRIN Pre-Spectrometer

   S. Goerhardt🇩🇪 · J. Bonn🇩🇪 · L. Bornschein🇩🇪 · G. Drexlin🇩🇪 · F.M. Fraenkle🇩🇪 · R. Gumbsheimer🇩🇪 · S. Mertens🇩🇪 · F.R. Mueller🇩🇪 · T. Thuemmler🇩🇪 · N. Wandkowsky🇺🇸 · C. Weinheimer🇩🇪 · J. Wolf🇩🇪

   The KATRIN experiment will determine the effective electron anti-neutrino mass with a sensitivity of 200 meV/c${}^2$ at 90% CL. The energy analysis of tritium $\beta$-decay electrons will be performed by a tandem setup of electrostatic retarding spectrometers which have to be operated at very low background levels of $<10^{-2}$ counts per second. This benchmark rate can be exceeded by background processes resulting from the emanation of single ${}^{219,220}$Rn atoms from the inner spectrometer surface and an array of non-evaporable getter strips used as main vacuum pump. Here we report on a the impact of a cryogenic technique to reduce this radon-induced background in electrostatic spectrometers. It is based on installing a liquid nitrogen cooled copper baffle in the spectrometer pump port to block the direct line of sight between the getter pump, which is the main source of ${}^{219}$Rn, and the sensitive flux tube volume. This cold surface traps a large fraction of emanated radon atoms in a region outside of the active flux tube, preventing background there. We outline important baffle design criteria to maximize the efficiency for the adsorption of radon atoms, describe the baffle implemented at the KATIRN Pre-Spectrometer test set-up, and report on its initial performance in suppressing radon-induced background.

   ↳ physics.ins-detastro-ph.IMnucl-exJINST(2018)·18 citations
3. 03*

   Two-photon exchange correction to the Lamb shift and hyperfine splitting of S levels

   Oleksandr Tomalak🇩🇪

   We evaluate the two-photon exchange corrections to the Lamb shift and hyperfine splitting of S states in electronic hydrogen relying on modern experimental data and present the two-photon exchange on a neutron inside the electronic and muonic atoms. These results are relevant for the precise extraction of the isotope shift as well as in the analysis of the ground state hyperfine splitting in usual and muonic hydrogen.

   ↳ hep-phnucl-exnucl-thphysics.atom-phEPJA(2019)·49 citations
4. 04*

   Binding-energy independence of reduced spectroscopic strengths derived from (p, 2p) and (p, pn) reactions with nitrogen and oxygen isotopes

   M. Gómez-Ramos🇪🇸 · A.M. Moro🇪🇸

   A campaign of intermediate energy (300-450 MeV/u) proton-induced nucleon knockout measurements in inverse kinematics has been recently undertaken at the R 3 B/LAND setup at GSI. We present a systematic theoretical analysis of these data with the aim of studying the quenching of the single-particle strengths and its binding-energy dependence. For that, the measured semi-inclusive (p, 2p) and (p, pn) cross sections are compared with theoretical predictions based on single-particle cross sections derived from a novel coupled-channels formalism and shell-model spectroscopic factors. A systematic reduction of about 20-30% is found, with a very limited dependence on proton-neutron asymmetry.

   ↳ nucl-thnucl-exPLB(2018)·54 citations
5. 05*

   Mass-dependence of pseudoscalar meson elastic form factors

   Muyang Chen🇨🇳 · Minghui Ding🇨🇳 · Lei Chang🇨🇳 · Craig D. Roberts🇺🇸

   A continuum approach to quark-antiquark bound-states is used to determine the electromagnetic form factors of pion-like mesons with masses $m_{0^{-}}/\mathrm{GeV}=0.14$, $0.47$, $0.69$, $0.83$ on a spacelike domain that extends to $Q^2\lesssim 10$GeV${}^2$. The results enable direct comparisons with contemporary lattice-QCD calculations of heavy-pion form factors at large values of momentum transfer and aid in understanding them. They also reveal, inter alia, that the form factor of the physical pion provides the best opportunity for verification of the factorised hard-scattering formula relevant to this class of exclusive processes and that this capacity diminishes steadily as the meson mass increases.

   ↳ nucl-thhep-lathep-phnucl-exPRD(2018)·56 citations
6. 06*

   A Facility for Production and Laser Cooling of Cesium Isotopes and Isomers

   Alexandros Giatzoglou · Tanapoom Poomaradee · Ilkka Pohjalainen🇫🇮 · Sami Rinta-Antila🇫🇮 · Iain D. Moore · Philip M. Walker🇬🇧 · Luca Marmugi · Ferruccio Renzoni

   We report on the design, installation, and test of an experimental facility for the production of ultra-cold atomic isotopes and isomers of cesium. The setup covers a broad span of mass numbers and nuclear isomers, allowing one to directly compare chains of isotopes and isotope/isomer pairs. Cesium nuclei are produced by fission or fusion-evaporation reactions using primary proton beams from a 130 MeV cyclotron impinging upon a suitable target. The species of interest is ejected from the target in ionic form, electrostatically accelerated, mass separated, and routed to a science chamber. Here, ions are neutralized by implantation in a thin foil, and extracted by thermal diffusion. A neutral vapor at room temperature is thus formed and trapped in a magneto-optical trap. Real-time fluorescence imaging and destructive absorption imaging provide information on the number of trapped atoms, their density, and their temperature. Tests with a dedicated beam of ${}^{133}$Cs${}^{+}$ ions at 30 keV energy confirm neutralization, evaporation, and laser cooling to 150 $\mu$K, with an average atomic density of 10${}^{10}$ cm${}^{-3}$. Availability of cold and dense atomic samples of Cs isotopes and isomers opens new avenues for high-precision measurements of isotopic and isomeric shifts thereby gaining deeper insight into the nuclear structure, as well as for sensitive measurements of isotopes' concentration ratios in trace quantities. The facility also constitutes the core for future experiments of many-body physics with nuclear isomers.

   ↳ physics.ins-detnucl-exphysics.atom-phNucl.Instrum.Meth.A(2018)·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.