Tue·Jul 12, 2011Tuesday·July 12, 2011

1. 01*

   Centrality and pT dependence of charged particle RAA in PbPb collisions at sqrt(sNN) = 2.76 TeV

   Andre S. Yoon · for CMS Collaboration

   The transverse momentum pT spectra of charged particles is measured by CMS as a function of collision centrality in PbPb collisions at sqrt(sNN) = 2.76 TeV. The results are compared to a pp reference spectrum, constructed by interpolation between sqrt(s) = 0.9 and 7 TeV measurements. The nuclear modification factor RAA is constructed by dividing the PbPb pT spectrum, normalized to the number of binary collisions (Ncoll), by the pp spectrum. Measured RAA in 0-5% centrality bin is compared to several theoretical predictions.

   nucl-exhep-ex6 citations
2. 02*

   Bulk Properties of Pb-Pb collisions at sqrt(sNN) = 2.76 TeV measured by ALICE

   Alberica Toia (for the ALICE Collaboration)🇺🇸

   Global variables, such as the charged particle multiplicity and the transverse energy are important observables to characterize Relativistic Heavy Ion collisions and to constrain model calculations. The charged particle multiplicity dNch/deta and transverse energy dET/deta are measured at sqrt(sNN) = 2.76 TeV in Pb-Pb collisions as a function of centrality and in pp collisions. The fraction of inelastic cross section seen by the ALICE detector is calculated either using a Glauber model or the data corrected by simulations of nuclear and electromagnetic processes, or data collected with a minimum bias interaction trigger. The centrality, defined by the number of nucleons participating in the collision, is obtained, via the Glauber model, by relating the multiplicity distributions of various detectors in the ALICE Central Barrel and their correlation with the spectator energy measured by the Zero-Degree Calorimeters. The results are compared to corresponding results obtained at the significantly lower energies of the BNL AGS, the CERN SPS, and the BNL RHIC, and with models based on different mechanisms for particle production in nuclear collisions. Particular emphasis will be given to a discussion on systematic studies of the dependence of the centrality determination on the details of the Glauber model, and the validity of the Glauber model at unprecedented collision energies.

   nucl-exJ.Phys.G(2011)·101 citations
3. 03*

   Measurement of the electromagnetic dissociation cross section of Pb nuclei at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV

   C. Oppedisano · the ALICE Collaboration

   Electromagnetic dissociation of heavy nuclei in ultra-peripheral interactions at high energies can be used to monitor the beam luminosity at colliders. In ALICE neutrons emitted by the excited nuclei close to beam rapidity are detected by the Zero Degree Calorimeters (ZDCs), providing a precise measurement of the event rate. During the 2010 Pb run, a dedicated data taking was performed triggering on electromagnetic processes with the ZDCs. These data, combined with the results from a Van der Meer scan, allowed to measure the electromagnetic dissociation cross-section of Pb nuclei at $\sqrt{s_{\mathrm{NN}}}$~=~2.76~TeV. Experimental results on various cross-sections are presented together with a comparison to the available predictions.

   nucl-exhep-exJ.Phys.G(2011)·8 citations
4. 04*

   The Next Decade of Physics with PHENIX

   Anne Sickles (for the PHENIX Collaboration)🇺🇸

   The first decade of RHIC physics and the first heavy ion running at the LHC have produced a wealth of data and discoveries. It is timely to now evaluate what has been learned and ask what compelling new questions have been raised. In this talk, several key unanswered questions about the properties of the strongly coupled quark gluon plasma and the distribution of partons inside nucleons and nuclei will be discussed along with how they can be addressed experimentally. The PHENIX Collaboration has developed a plan for upgrading the experiment in order to address these new questions. The current status of these plans will be presented.

   nucl-exJ.Phys.G(2011)·1 citation
5. 05*

   Correlations of Electrons from Heavy Flavor Decay with Hadrons in Au+Au and p+p Collisions

   Anne M. Sickles (for the PHENIX Collaboration)🇺🇸

   Measurements of electrons from the decay of open-heavy flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled p+p collisions. These measurements indicate that charm and bottom quarks interact with the hot-dense matter produced in heavy-ion collisions much more than expected. Here we extend these studies to two-particle correlations where one particle is an electron from the decay of a heavy-flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interactions between heavy quarks and the matter, such as whether the modifcation of the away-side-jet shape seen in hadron-hadron correlations is present when the trigger particle is from heavy-meson decay and whether the overall level of away-side-jet suppression is consistent. We statistically subtract correlations of electrons arising from background sources from the inclusive electron-hadron correlations and obtain two-particle azimuthal correlations at $\sqrt{s_{NN}}$ =200 GeV between electrons from heavy-flavor decay with charged hadrons in p+p and also first results in Au+Au collisions. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to p+p collisions.

   nucl-exJ.Phys.Conf.Ser.(2011)·0 citations
6. 06*

   Quasi-free photoproduction of eta-mesons off the deuteron

   I. Jaegle🇨🇭 · B. Krusche🇨🇭 · A.V. Anisovich🇩🇪 · J.C.S. Bacelar🇳🇱 · B. Bantes🇩🇪 · O. Bartholomy🇩🇪 · D.E. Bayadilov🇩🇪 · R. Beck🇩🇪 · Y.A. Beloglazov🇷🇺 · R. Castelijns🇳🇱 · V. Crede🇺🇸 · M. Dieterle🇨🇭 and 60 other authors

   Precise data for quasi-free photoproduction of $\eta$ mesons off the deuteron have been measured at the Bonn ELSA accelerator with the combined Crystal Barrel/TAPS detector for incident photon energies up to 2.5 GeV. The $\eta$-mesons have been detected in coincidence with recoil protons and neutrons. Possible nuclear effects like Fermi motion and re-scattering can be studied via a comparison of the quasi-free reaction off the bound proton to $\eta$-production off the free proton. No significant effects beyond the folding of the free cross section with the momentum distribution of the bound protons have been found. These Fermi motion effects can be removed by an analysis using the invariant mass of the $\eta$-nucleon pairs reconstructed from the final state four-momenta of the particles. The total cross section for quasi-free $\eta$-photoproduction off the neutron reveals even without correction for Fermi motion a pronounced bump-like structure around 1 GeV of incident photon energy, which is not observed for the proton. This structure is even narrower in the invariant mass spectrum of the $\eta$-neutron pairs. Position and width of the peak in the invariant mass spectrum are $W\approx 1665$ MeV and FWHM $\Gamma \approx 25$ MeV. The data are compared to the results of different models.

   nucl-exEPJA(2011)·93 citations
7. 07*

   The high-lying ${}^6$Li levels at excitation energy around 21 MeV

   Orest Povoroznyk (1)🇺🇦 · Olga K. Gorpinich (1)🇺🇦 · Olexiy O. Jachmenjov (1)🇺🇦 · Hanna V.Mokhnach (1)🇺🇦 · Oleg Ponkratenko (1) · Giuseppe Mandaglio (2 and 3)🇮🇹 · Francesca Curciarello (2 and 3)🇮🇹 · Veronica De Leo (2 and 3) · Giovanni Fazio (2 and 3)🇮🇹 · Giorgio Giardina (2 and 3) ((1) Institute for Nuclear Research, National Academy of Science of Ukraine, Kiev, Ukraine (2) Dipartimento di Fisica dell'Università di Messina, Italy, (3) Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Italy)🇮🇹

   The ${}^3$H+${}^3$He cluster structure in ${}^6$Li was investigated by the ${}^3$H($\alpha$,${}^3$H ${}^3$He)n kinematically complete experiment at the incident energy $E_{\alpha }$ = 67.2 MeV. We have observed two resonances at $E_x^{\ast }$ = 21.30 and 21.90 MeV which are consistent with the ${}^3$He(${}^3$H, $\gamma$)${}^6$Li analysis in the Ajzenberg-Selove compilation. Our data are compared with the previous experimental data and the RGM and CSRGM calculations.

   nucl-exJ.Phys.Soc.Jap.(2011)·6 citations
8. 08*

   Octet baryon electromagnetic form factors in a relativistic quark model

   G. Ramalho🇵🇹 · K. Tsushima🇦🇺

   We study the octet baryon electromagnetic properties by applying the covariant spectator quark model, and provide covariant parametrization that can be used to study baryon electromagnetic reactions. While we use the lattice QCD data in the large pion mass regime (small pion cloud effects) to determine the parameters of the model in the valence quark sector, we use the nucleon physical and octet baryon magnetic moment data to parameterize the pion cloud contributions. The valence quark contributions for the octet baryon electromagnetic form factors are estimated by extrapolating the lattice parametrization in the large pion mass regime to the physical regime. As for the pion cloud contributions, we parameterize them in a covariant, phenomenological manner, combined with SU(3) symmetry. We also discuss the impact of the pion cloud effects on the octet baryon electromagnetic form factors and their radii.

   ↳ hep-phhep-exhep-latnucl-ex+1PRD(2011)·54 citations
9. 09*

   Gas dynamics in high-luminosity polarized He-3 targets using diffusion and convection

   P. A. M. Dolph (1)🇺🇸 · J. Singh (1,2)🇺🇸 · T. Averett (3)🇺🇸 · A. Kelleher (3,4)🇺🇸 · K. E. Mooney (1)🇺🇸 · V. Nelyubin (1)🇺🇸 · W. A. Tobias (1)🇺🇸 · B. Wojtsekhowski (5)🇺🇸 · G. D. Cates (1) ((1) University of Virginia, Charlottesville, VA, (2) Argonne National Lab, Argonne, IL (3) College of William and Mary, Williamsburg, VA, (4) Massachusetts Institute of Technology, Cambridge, MA, (5) Thomas Jefferson National Accelerator Facility, Newport News, VA)🇺🇸

   The dynamics of the movement of gas is discussed for two-chambered polarized He-3 target cells of the sort that have been used successfully for many electron scattering experiments. A detailed analysis is presented showing that diffusion is a limiting factor in target performance, particularly as these targets are run at increasingly high luminosities. Measurements are presented on a new prototype polarized He-3 target cell in which the movement of gas is due largely to convection instead of diffusion. NMR tagging techniques have been used to visualize the gas flow, showing velocities along a cylindrically-shaped target of between 5-80 cm/min. The new target design addresses one of the principle obstacles to running polarized He-3 targets at substantially higher luminosities while simultaneously providing new flexibility in target geometry.

   ↳ physics.ins-dethep-exnucl-exPRC(2011)·15 citations
10. 10*

    Jet quenching via jet collimation

    J. Casalderrey-Solana🇨🇭 · J. G. Milhano🇵🇹 · U. Wiedemann🇨🇭

    The strong modifications of dijet properties in heavy ion collisions measured by ATLAS and CMS provide important constraints on the dynamical mechanisms underlying jet quenching. In this work, we show that the transport of soft gluons away from the jet cone - jet collimation - can account for the observed dijet asymmetry with values of $\hat{q}L$ that lie in the expected order of magnitude. Further, we show that the energy loss attained through this mechanism results in a very mild distortion of the azimuthal angle dijet distribution.

    ↳ hep-phnucl-exnucl-thJ.Phys.G(2011)·27 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.