Thu·Jul 2, 2009Thursday·July 2, 2009

1. 01*

   PHENIX Measurements of Azimuthal Anisotropy for ${\pi }^0$ Production at High $p_T$ in Au+Au Collisions at $\sqrt{s_{NN}}=200$GeV

   Rui Wei (for the PHENIX Collaboration)🇺🇸

   An improved measurement of $v_2$ for ${\pi }^0$ in a broad range of $p_T$ and centrality is presented. By combining $v_2$ with the $R_{AA}$, we provide new insights on jet-medium interactions. We show that current pQCD energy loss models cannot describe the suppression of the ${\pi }^0$ as a function of the angle with respect to the reaction plane. Our result could help to resolve the factor of 4 differences in the predicted transport coefficients among these models. Alternatively, it may suggest that non-perturbative effects associated with the strongly coupled QGP are important, and new theoretical developments are needed to fully understand the jet medium interactions.

   nucl-exNPA(2009)·13 citations
2. 02*

   Search for long-lived isomeric states in neutron-deficient thorium isotopes

   J. Lachner🇩🇪 · I. Dillmann🇩🇪 · T. Faestermann🇩🇪 · G. Korschinek🇩🇪 · M. Poutivtsev🇩🇪 · G. Rugel🇩🇪

   The discovery of naturally occurring long-lived isomeric states (t_1/2 > 10^8 yr) in the neutron-deficient isotopes 211,213,217,218Th [A. Marinov et al., Phys. Rev. C 76, 021303(R) (2007)] was reexamined using accelerator mass spectrometry (AMS). Because AMS does not suffer from molecular isobaric background in the detection system, it is an extremely sensitive technique. Despite our up to two orders of magnitude higher sensitivity we cannot confirm the discoveries of neutron-deficient thorium isotopes and provide upper limits for their abundances.

   nucl-exPRC(2008)·13 citations
3. 03*

   The CTOF measurements and Monte Carlo analyses of neutron spectra for backward direction from iron target irradiated by protons with energies from 400 to 1200 MeV

   I. L. Azhgirey🇷🇺 · V. I. Belyakov-Bodin🇷🇺 · I. I. Degtyarev🇷🇺 · S. G. Mashnik🇺🇸 · F. X. Gallmeier🇺🇸 · W. Lu🇺🇸

   A calorimetric-time-of-flight (CTOF) technique was used for real-time, high-precision measurement of neutron spectrum at the angle of 175 degrees from the initial proton beam direction, which hits a face plane of a cylindrical iron target of 20 cm in diameter and 25 cm thick. A comparison was performed between the neutron spectra predicted by the MARS and the MCNPX code systems and measured by experiments for 0.4-, 0.6-, 0.8-, 1.0-, and 1.2-GeV protons.

   nucl-exNucl.Instrum.Meth.B(2009)·4 citations
4. 04*

   Photon-jet coincidence measurements in polarized pp collisions at sqrt{s}=200 GeV with the STAR Endcap Calorimeter

   Ilya Selyuzhenkov (for the STAR Collaboration)🇩🇪

   Recent inclusive measurements with polarized proton-proton collisions at RHIC provide significant constraints on the polarized gluon distribution, Delta g(x), integrated over the gluon momentum range 0.02 < x < 0.3. Di-jet and photon-jet coincidence measurements will allow to study the x-dependence of Delta g(x). In this report we present the status of photon-jet coincidence studies for photons detected at forward pseudorapidity, 1.08<eta<2, using the STAR Endcap Calorimeter.

   nucl-exAIP Conf.Proc.(2009)·0 citations
5. 05*

   Global analysis of J/psi suppression in cold nuclear matter

   Vi-Nham Tram (LBL, Berkeley)🇺🇸 · Francois Arleo (Annecy, LAPTH)🇫🇷

   Interpreting the J/psi suppression reported in nucleus--nucleus collisions at SPS and RHIC requires the quantitative understanding of cold nuclear matter effects, such as the inelastic rescattering of J/psi states in nuclei or the nuclear modification of parton densities. With respect to our former Glauber analysis, we include in the present work the new PHENIX d--Au measurements, and analyze as well all existing data using the EPS08 nuclear parton densities recently released. The largest suppression reported in the new PHENIX analysis leads in turn to an increase of sigma from 3.5 +/- 0.3 mb to 5.4 +/- 2.5 mb using proton PDF. The stronger x-dependence of the G^{A}/G^p ratio in EPS08 as compared to e.g. EKS98 shifts the cross section towards larger values at fixed target energies (x_2 ~ 0.1) while decreasing somehow the value extracted at RHIC (x_2 ~10^{-2}).

   ↳ hep-phnucl-exnucl-thEPJC(2009)·14 citations
6. 06*

   Production of Radioactive Isotopes through Cosmic Muon Spallation in KamLAND

   The KamLAND Collaboration

   Radioactive isotopes produced through cosmic muon spallation are a background for rare-event detection in $\nu$ detectors, double-$\beta$-decay experiments, and dark-matter searches. Understanding the nature of cosmogenic backgrounds is particularly important for future experiments aiming to determine the pep and CNO solar neutrino fluxes, for which the background is dominated by the spallation production of ${}^{11}$C. Data from the Kamioka liquid-scintillator antineutrino detector (KamLAND) provides valuable information for better understanding these backgrounds, especially in liquid scintillators, and for checking estimates from current simulations based upon MUSIC, FLUKA, and GEANT4. Using the time correlation between detected muons and neutron captures, the neutron production yield in the KamLAND liquid scintillator is measured to be $(2.8\pm 0.3)\times 10^{-4}{\mu }^{-1}{g}^{-1}c{m}^2$. For other isotopes, the production yield is determined from the observed time correlation related to known isotope lifetimes. We find some yields are inconsistent with extrapolations based on an accelerator muon beam experiment.

   ↳ hep-exastro-ph.SRnucl-exPRC(2010)·293 citations
7. 07*

   Determination of the stellar (n,gamma) cross section of 40Ca with accelerator mass spectrometry

   I. Dillmann🇩🇪 · C. Domingo-Pardo🇩🇪 · M. Heil🇩🇪 · F. Käppeler🇩🇪 · A. Wallner🇦🇹 · O. Forstner🇦🇹 · R. Golser🇦🇹 · W. Kutschera🇦🇹 · A. Priller🇦🇹 · P. Steier🇦🇹 · A. Mengoni🇦🇹 · R. Gallino🇮🇹 · M. Paul🇮🇱 · C. Vockenhuber🇨🇦

   The stellar (n,gamma) cross section of 40Ca at kT=25 keV has been measured with a combination of the activation technique and accelerator mass spectrometry (AMS). This combination is required when direct off-line counting of the produced activity is compromised by the long half-life and/or missing gamma-ray transitions. The neutron activations were performed at the Karlsruhe Van de Graaff accelerator using the quasistellar neutron spectrum of kT=25 keV produced by the 7Li(p,n)7Be reaction. The subsequent AMS measurements were carried out at the Vienna Environmental Research Accelerator (VERA) with a 3 MV tandem accelerator. The doubly magic 40Ca is a bottle-neck isotope in incomplete silicon burning, and its neutron capture cross section determines the amount of leakage, thus impacting on the eventual production of iron group elements. Because of its high abundance, 40Ca can also play a secondary role as "neutron poison" for the s-process. Previous determinations of this value at stellar energies were based on time-of-flight measurements. Our method uses an independent approach, and yields for the Maxwellian-averaged cross section at kT=30 keV a value of <sigma>30 keV= 5.73+/-0.34 mb.

   ↳ astro-ph.SRastro-ph.IMnucl-exPRC(2009)·16 citations
8. 08*

   Solving the stellar 62Ni problem with AMS

   I. Dillmann🇩🇪 · T. Faestermann🇩🇪 · G. Korschinek🇩🇪 · J. Lachner🇩🇪 · M. Maiti🇮🇳 · M. Poutivtsev🇩🇪 · G. Rugel🇩🇪 · S. Walter · F. Käppeler🇩🇪 · M. Erhard🇩🇪 · A.R. Junghans🇩🇪 · C. Nair🇩🇪 · R. Schwengner🇩🇪 · A. Wagner🇩🇪

   An accurate knowledge of the neutron capture cross sections of 62,63Ni is crucial since both isotopes take key positions which affect the whole reaction flow in the weak s process up to A=90. No experimental value for the 63Ni(n,gamma) cross section exists so far, and until recently the experimental values for 62Ni(n,gamma) at stellar temperatures (kT=30 keV) ranged between 12 and 37 mb. This latter discrepancy could now be solved by two activations with following AMS using the GAMS setup at the Munich tandem accelerator which are also in perfect agreement with a recent time-of-flight measurement. The resulting (preliminary) Maxwellian cross section at kT=30 keV was determined to be <sigma>30keV = 23.4 +/- 4.6 mb. Additionally, we have measured the 64Ni(gamma,n)63Ni cross section close to threshold. Photoactivations at 13.5 MeV, 11.4 MeV and 10.3 MeV were carried out with the ELBE accelerator at Forschungszentrum Dresden-Rossendorf. A first AMS measurement of the sample activated at 13.5 MeV revealed a cross section smaller by more than a factor of 2 compared to NON-SMOKER predictions.

   ↳ astro-ph.SRastro-ph.IMnucl-exNucl.Instrum.Meth.B(2010)·19 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.