Tue·Nov 10, 2015Tuesday·November 10, 2015

1. 01*

   Broad levels in ${}^{17}$O and their relevance for the astrophysical s-process

   Thomas Faestermann🇩🇪 · Peter Mohr🇭🇺 · Ralf Hertenberger🇩🇪 · Hans-Friedrich Wirth

   Levels in ${}^{17}$O affect the astrophysical s-process in two opposite ways. The neutron production is enhanced by resonances in the ${}^{13}$C($\alpha$,$n$)${}^{16}$O reaction at excitation energies around 7 MeV in ${}^{17}$O, and the number of available neutrons is reduced by low-lying resonances in the ${}^{16}$O($n$,$\gamma$)${}^{17}$O reaction corresponding to levels in ${}^{17}$O with excitation energies of $4-5$ MeV. The present work uses the ${}^{19}$F($d$,$\alpha$)${}^{17}$O reaction to determine absolute widths of the relevant levels in ${}^{17}$O. The results improve the uncertainties of the previously adopted values and resolve a discrepancy between recent studies for the $1/2^{+}$ level close to the threshold of the ${}^{13}$C($\alpha$,$n$)${}^{16}$O reaction. In addition, improved excitation energies and widths are provided for several states in ${}^{17}$O up to excitation energies close to 8 MeV.

   nucl-exPRC(2015)·33 citations
2. 02*

   Measurement of scintillation and ionization yield with high-pressure gaseous mixtures of Xe and TMA for improved neutrinoless double beta decay and dark matter searches

   Y. Nakajima🇺🇸 · A. Goldshmidt🇺🇸 · H. S. Matis🇺🇸 · T. Miller🇺🇸 · D. R. Nygren🇺🇸 · C. A. B. Oliveira🇺🇸 · J. Renner🇪🇸

   The gaseous Xenon(Xe) time projection chamber (TPC) is an attractive detector technique for neutrinoless double beta decay and WIMP dark matter searches. While it is less dense compared to Liquid Xe detectors, it has intrinsic advantages in tracking capability and better energy resolution. The performance of gaseous Xe can be further improved by molecular additives such as trimethylamine(TMA), which is expected to (1) cool down the ionization electrons, (2) convert Xe excitation energy to TMA ionizations through Penning transfer, and (3) produce scintillation and electroluminescence light in a more easily detectable wavelength (300 nm). In order to test the feasibility of the performance improvements with TMA, we made the first direct measurement of Penning and fluorescence transfer efficiency with gaseous mixtures of Xe and TMA. While we observed a Penning transfer efficiency up to ~35%, we found strong suppression of primary scintillation light with TMA. We also found that the primary scintillation light with Xe and TMA mixture can be well characterized by ~3% fluorescence transfer from Xe to TMA, with further suppression due to TMA self-quenching. No evidence of the scintillation light produced by recombination of TMA ions was found. This strong suppression of scintillation light makes dark matter searches quite challenging, while the possibility of improved neutrinoless double beta decay searches remains open. This work has been carried out within the context of the NEXT collaboration.

   ↳ physics.ins-dethep-exnucl-exJINST(2016)·9 citations
3. 03*

   Status and prospects of Di-jet production in high-energy polarized proton-proton collisions at RHIC at s**(1/2) = 200-GeV

   STAR Collaboration (Bernd Surrow (MIT) for the collaboration)

   The STAR experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) is carrying out a spin physics program colliding transversely or longitudinally polarized proton beams at = 200-500 GeV to gain deeper insigh t into the spin structure and dynamics of the proton. These studies provide fundamental insight into Quantum Chromodynamics (QCD). One of the main objectives is the determination of the polarized gluon distribution function, g, through the measurement of the longitudinal double-spin asymmetry, ALL, for various processes. Inclusive hadron and jet production from polarized pp collision data collected so far at = 200 GeV using the STAR detector at RHIC have placed important constraints on g. Di-jet producti on provides direct access to the initial parton kinematics at leading order (LO) QCD and thus provides sensitivity to the Bjorken-x dependence of g. The status of the mid-rapidity di-jet cross section analysis from the 2005 RHIC run and the longitudinal d ouble-spin asymmetry at mid-rapidity for the 2006 data sample are discussed in these proceedings. Projections on future di-jet measurements at STAR are provided.

   ↳ hep-exnucl-exAIP Conf.Proc.(2009)·0 citations
4. 04*

   Development of Water $\check{C}$erenkov Detector for On-line Proton Rejection in ${\Xi }^{-}$ Hypernuclear Spectroscopy via the $(K^{-},K^{+})$ Reaction

   T. Gogami🇯🇵 · N. Amano🇯🇵 · S. Kanatsuki🇯🇵 · T. Nagae🇯🇵 · K. Takenaka🇯🇵

   The missing mass spectroscopy of ${\Xi }^{-}$ hypernuclei with the $(K^{-},K^{+})$ reaction is planned to be performed at the J-PARC K1.8 beam line by using a new magnetic spectrometer, Strangeness $-2$ Spectrometer (S-2S). A $\check{C}$cerenkov detector with a radiation medium of pure water (refractive index of 1.33) is designed to be used for on-line proton rejection for a momentum range of 1.2 to 1.6 GeV/$c$ in S-2S. Prototype water $\check{C}$erenkov detectors were developed and tested with positron beams and cosmic rays to estimate their proton-rejection capability. We achieved an average number of photoelectrons of greater than 200 with the latest prototype for cosmic rays, which was stable during an expected beam time of one month. The performance of the prototype in the cosmic-ray test was well reproduced with a Monte Carlo simulation in which some input parameters were adjusted. Based on the Monte Carlo simulation, we expect to achieve $>90\%$ proton-rejection efficiency while maintaining $>95\%$ $K^{+}$ survival ratio in the whole S-2S acceptance. The performance satisfies the requirements to conduct the spectroscopic study of ${\Xi }^{-}$ hypernuclei at J-PARC.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2016)·5 citations
5. 05*

   Nuclear isospin asymmetry in $\alpha$ decays of heavy nuclei

   Eunkyoung Shin · Yeunhwan Lim🇺🇸 · Chang Ho Hyun🇰🇷 · Yongseok Oh🇰🇷

   The effects of nuclear isospin asymmetry on $\alpha$ decay lifetimes of heavy nuclei are investigated within various phenomenological models of nuclear potential for the $\alpha$ particle. We consider the widely used simple square well potential and Woods-Saxon potential, and modify them by including an isospin asymmetry term. We then suggest a model for the potential of the $\alpha$ particle motivated by a microscopic phenomenological approach of the Skyrme force model, which naturally introduce the isospin dependent form of the nuclear potential for the $\alpha$ particle. The empirical $\alpha$ decay lifetime formula of Viola and Seaborg is also modified to include isospin asymmetry effects. The obtained $\alpha$ decay half-lives are in good agreement with the experimental data and we find that including the nuclear isospin effects somehow improves the theoretical results for $\alpha$ decay half-lives. The implications of these results are discussed and the predictions on the $\alpha$ decay lifetimes of superheavy elements are also presented.

   ↳ nucl-thnucl-exPRC(2016)·45 citations
6. 06*

   Observables and initial conditions for rotating and expanding fireballs with spheroidal symmetry

   T. Csorgo🇭🇺 · M.I. Nagy🇭🇺 · I. F. Barna🇭🇺

   Utilizing a recently found class of exact, analytic rotating solutions of non-relativistic fireball hydrodynamics, we calculate analytically the single-particle spectra, the elliptic flows and two-particle Bose-Einstein correlation functions for rotating and expanding fireballs with spheroidal symmetry. We demonstrate, that rotation generates final state momentum anisotropies even for a spatially symmetric, spherical initial geometry of the fireball. The mass dependence of the effective temperatures, as well as the HBT radius parameters and the elliptic flow are shown to be sensitive not only to radial flow effects but also to the magnitude of the initial angular momentum.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2016)·12 citations
7. 07*

   Production of strange particles in charged jets in Pb--Pb and p--Pb collisions measured with ALICE

   Vít Kučera (for the ALICE Collaboration)🇨🇿

   Measurements of spectra of identified particles produced in jets represent an important tool for understanding the interplay of various hadronisation mechanisms which contribute to particle production in the hot and dense medium created in ultra-relativistic heavy-ion collisions. In this contribution, we present the measurements of the pT spectra of {\Lambda} baryons and K0S mesons produced in charged jets in Pb--Pb collisions at sqrt(sNN) = 2.76 TeV and in p--Pb collisions at sqrt(sNN) = 5.02 TeV. The results are obtained with the ALICE detector at the LHC, exploiting the excellent particle identification capabilities of this experiment. Baryon-to-meson ratios of the spectra of strange particles associated with jets are studied in central collisions and are compared with the inclusive ratios.

   ↳ hep-exnucl-exNucl.Part.Phys.Proc.(2016)·6 citations
8. 08*

   ALICE TPC upgrade for High-Rate operations

   Saikat Biswas (for the ALICE Collaboration)🇮🇳

   A new type of Time Projection Chamber (TPC) has been proposed for the upgrade of the ALICE (A Large Ion Collider Experiment at CERN) so as to cater to the high luminosity environment expected at the Large Hadron Collider (LHC) facility in future. This device will rely on the intrinsic ion back flow (IBF) suppression of Micro-Pattern Gas Detectors (MPGD) based technology in particular the Gas Electron Multiplier (GEM). GEM is to minimise the space charge effect in the main drift volume and thus will not require the standard gating grid and the resulting intrinsic dead time. It will thus be possible to read all minimum bias Pb--Pb events that the Large Hadron Collider (LHC) will deliver at the anticipated peak interaction rate of 50 kHz for the high luminosity heavy-ion era in Run 3. New read-out electronics will send the continuous data stream to a new online farm at rates up to 1~TByte/s. The new read-out chambers will consist of stacks of 4 GEM foils combining different hole pitches. In addition to a low ion back flow ($<$ 1\%) other important requirements are good energy resolution (better than 12\% (sigma) for ${}^{55}$Fe X-rays) and operational stability.

   ↳ physics.ins-dethep-exnucl-exPoS(2017)·6 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.