Wed·Jul 22, 2009Wednesday·July 22, 2009

1. 01*

   Exploring Jet Properties in p-p Collisions at 200 GeV with STAR

   Helen Caines (for the STAR Collaboration)🇺🇸

   The mechanisms underlying hadronization are not well understood, both in vacuum and in hot QCD matter. Precise characterization of jet fragmentation to hadrons in p-p collisions will help elucidate the fundamental process of hadronization, and will serve as essential reference to measure the modification of hadronization in heavy ion collisions. We present measurements of fragmentation functions for unidentified particles in jets produced in p-p collisions at 200 GeV using the STAR detector at RHIC. The results from different jet reconstruction algorithms are compared, including variations of the resolution parameter. It is found that the results are largely insensitive to details of the jet-finding algorithm at RHIC energies. Particle production inside and outside of these reconstructed jets will be compared to improve our understanding of the hadronization mechanisms for soft and hard particles in p-p events at RHIC energies.

   nucl-exNPA(2009)·22 citations
2. 02*

   Looking forward for Color Glass Condensate signatures

   Ermes Braidot (for the STAR collaboration)🇳🇱

   Forward ${\pi }^0$ production has been measured at STAR with the new Forward Meson Spectrometer (FMS) from p+p and d+Au collisions during the 2008 RHIC run. We present the first FMS results of azimuthal correlation involving a forward ${\pi }^0$ produced in p+p and d+Au collisions to search for the onset of gluon density saturation, expected to occur at small momentum fractions.

   nucl-exhep-exNPA(2009)·11 citations
3. 03*

   Deep sub-threshold ${\Xi }^{-}$ production in Ar+KCl reactions at 1.76A GeV

   G. Agakishiev · A. Balanda · R. Bassini · D. Belver · A. V. Belyaev · A. Blanco · M. Böhmer · J. L. Boyard · P. Braun-Munzinger · P. Cabanelas · E. Castro · S. Chernenko and 92 other authors

   We report first results on a deep sub-threshold production of the doubly strange hyperon ${\Xi }^{-}$ in a heavy-ion reaction. At a beam energy of 1.76A GeV the reaction Ar+KCl was studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. A high-statistics and high-purity $\Lambda$ sample was collected, allowing for the investigation of the decay channel ${\Xi }^{-}\to \Lambda {\pi }^{-}$. The deduced ${\Xi }^{-}/(\Lambda +{\Sigma }^0)$ production ratio of $(5.6\pm 1.2_{-1.7}^{+1.8})\cdot 10^{-3}$ is significantly larger than available model predictions.

   nucl-exPRL(2009)·99 citations
4. 04*

   Preparation for heavy-flavour measurements with ALICE at the LHC

   A. Dainese (INFN Padova) (for the ALICE Collaboration)🇮🇹

   ALICE will study nucleus-nucleus and proton-proton collisions at the LHC. The main goal of the experiment is to investigate the properties of QCD matter at the extreme energy densities that will be reached in Pb-Pb collisions. Heavy quarks (charm and beauty) are regarded as powerful tools for this study. After briefly reviewing the ALICE heavy-flavour program, we will describe the preparation for the first measurements to be performed with pp collisions.

   nucl-exNPA(2009)·2 citations
5. 05*

   J/psi production in p-A collisions at 158 and 400 GeV: recent results from the NA60 experiment

   E. Scomparin (for the NA60 collaboration)🇮🇹

   The NA60 experiment has studied muon pair production in p-A and In-In collisions at the CERN SPS. We present new results on nuclear effects on J/psi production in p-A at 158 GeV, the same energy used for collecting A-A data at the SPS. We then compare nuclear effects with previous results from fixed target experiments, and with the results obtained from a p-A data sample taken by NA60 at 400 GeV. Based on the 158 GeV results, we calculate the expected J/psi suppression in In-In and Pb-Pb collisions due to cold nuclear matter effects, and we extract a new estimate for the anomalous suppression at SPS energies. Finally, we show preliminary results on J/psi polarization in p-A collisions.

   nucl-exNPA(2009)·36 citations
6. 06*

   Precise electromagnetic tests of ab-initio calculations of light nuclei: States in ${}^{10}$Be

   E.A. McCutchan🇺🇸 · C.J. Lister🇺🇸 · R.B. Wiringa🇺🇸 · Steven C. Pieper🇺🇸 · D. Seweryniak🇺🇸 · J.P. Greene🇺🇸 · M.P. Carpenter🇺🇸 · C.J. Chiara🇺🇸 · R.V.F. Janssens🇺🇸 · T.L. Khoo🇺🇸 · T. Lauritsen🇺🇸 · I. Stefanescu🇧🇪 · S. Zhu🇺🇸

   In order to test {\it ab-initio} calculations of light nuclei, we have remeasured lifetimes in ${}^{10}$Be using the Doppler Shift Attenuation Method (DSAM) following the ${}^7$Li(${}^7$Li,$\alpha$)${}^{10}$Be reaction at 8 and 10 MeV. The new experiments significantly reduce systematic uncertainties in the DSAM technique. The J${}^{\pi }$ = $2_1^{+}$ state at 3.37 MeV has $\tau$ = 205$\pm$(5)${}_{stat}\pm$(7)${}_{sys}$ fs corresponding to a $B$($E2\downarrow$) of 9.2(3) $e^2$fm${}^4$ in broad agreement with many calculations. The J${}^{\pi }$ = $2_2^{+}$ state at 5.96 MeV was found to have a $B$($E2\downarrow$) of 0.11(2) $e^2$fm${}^4$ and provides a more discriminating test of nuclear models. New Green's Function Monte Carlo (GFMC) calculations for these states and transitions with a number of Hamiltonians are also reported and compared to experiment.

   nucl-exPRL(2009)·37 citations
7. 07*

   Inclusive Dielectron Production in Ar+KCl Collisions at 1.76 AGeV studied with HADES

   The HADES Collaboration: F.Krizek · G.Agakishiev · A.Balanda · G.Bellia · D.Belver · A.Belyaev · A.Blanco · M.Boehmer · J.L.Boyard · P.Braun-Munzinger · P.Cabanelas · E.Castro and 100 other authors

   Results of the HADES measurement of inclusive dielectron production in Ar+KCl collisions at a kinetic beam energy of 1.76 AGeV are presented. For the first time, high mass resolution spectroscopy was performed. The invariant mass spectrum of dielectrons is compared with predictions of UrQMD and HSD transport codes.

   nucl-exNPA(2009)·8 citations
8. 08*

   Unexpected impact of D waves in low-energy neutral pion photoproduction from the proton and the extraction of multipoles

   C. Fernandez-Ramirez🇺🇸 · A.M. Bernstein🇺🇸 · T.W. Donnelly (Center for Theoretical Physics, Laboratory for Nuclear Science, Massachusetts Institute of Technology)🇺🇸

   Contributions of $D$ waves to physical observables for neutral pion photoproduction from the proton in the near-threshold region are studied and means to isolate them are proposed. Various approaches to describe the multipoles are employed --a phenomenological one, a unitary one, and heavy baryon chiral perturbation theory. The results of these approaches are compared and found to yield essentially the same answers. $D$ waves are seen to enter together with $S$ waves in a way that any means which attempt to obtain the $E_{0+}$ multipole accurately must rely on knowledge of $D$ waves and that consequently the latter cannot be dismissed in analyses of low-energy pion photoproduction. It is shown that $D$ waves have a significant impact on double-polarization observables that can be measured. This importance of $D$ waves is due to the soft nature of the $S$ wave and is a direct consequence of chiral symmetry and the Nambu--Goldstone nature of the pion. $F$-wave contributions are shown to be negligible in the near-threshold region.

   ↳ nucl-thnucl-exPRC(2009)·30 citations
9. 09*

   Parton Propagation and Fragmentation in QCD Matter

   Alberto Accardi (Hampton U. & Jefferson Lab) · Francois Arleo (Annecy, LAPTH) · William K. Brooks (Santa Maria U., Valparaiso) · David D'Enterria (CERN & MIT, LNS) Valeria Muccifora (Frascati)

   We review recent progress in the study of parton propagation, interaction and fragmentation in both cold and hot strongly interacting matter. Experimental highlights on high-energy hadron production in deep inelastic lepton-nucleus scattering, proton-nucleus and heavy-ion collisions, as well as Drell-Yan processes in hadron-nucleus collisions are presented. The existing theoretical frameworks for describing the in-medium interaction of energetic partons and the space-time evolution of their fragmentation into hadrons are discussed and confronted to experimental data. We conclude with a list of theoretical and experimental open issues, and a brief description of future relevant experiments and facilities.

   ↳ nucl-thhep-exhep-phnucl-exRiv.Nuovo Cim.(2009)·135 citations
10. 10*

    UV Degradation of the Optical Properties of Acrylic for Neutrino and Dark Matter Experiments

    Bryce Littlejohn🇺🇸 · K. M. Heeger🇺🇸 · T. Wise🇺🇸 · E. Gettrust🇺🇸 · M. Lyman🇺🇸

    UV-transmitting (UVT) acrylic is a commonly used light-propagating material in neutrino and dark matter detectors as it has low intrinsic radioactivity and exhibits low absorption in the detectors' light producing regions, from 350 nm to 500 nm. Degradation of optical transmittance in this region lowers light yields in the detector, which can affect energy reconstruction, resolution, and experimental sensitivities. We examine transmittance loss as a result of short- and long-term UV exposure for a variety of UVT acrylic samples from a number of acrylic manufacturers. Significant degradation peaking at 343 nm was observed in some UVT acrylics with as little as three hours of direct sunlight, while others exhibited softer degradation peaking at 310 nm over many days of exposure to sunlight. Based on their measured degradation results, safe time limits for indoor and outdoor UV exposure of UVT acrylic are formulated.

    ↳ physics.ins-detnucl-exJINST(2009)·12 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.