Wed·Jul 13, 2011Wednesday·July 13, 2011

1. 01*

   Photoproduction of Neutral Pions off Protons

   The CBELSA/TAPS Collaboration: V. Crede🇺🇸 · N. Sparks🇺🇸 · A. Wilson🇺🇸 · A.V. Anisovich🇩🇪 · J.C.S. Bacelar🇳🇱 · R. Bantes🇩🇪 · O. Bartholomy🇩🇪 · D. Bayadilov🇩🇪 · R. Beck🇩🇪 · Y.A. Beloglazov🇷🇺 · R. Castelijns🇳🇱 · H. Dutz🇩🇪 and 49 other authors

   Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector in the reaction $\gamma p\to p{\pi }^0$ for photon energies between 0.85 and 2.50 GeV. The ${\pi }^0$ mesons are observed in their dominant neutral decay mode: ${\pi }^0\to \gamma \gamma$. For the first time, the differential cross sections cover the very forward region, ${\theta }_{c.m.}<60^{\circ }$. A partial-wave analysis of these data within the Bonn-Gatchina framework observes the high-mass resonances $G_{17}$(2190), $D_{13}$(2080), and $D_{15}$(2070).

   nucl-exhep-exhep-phPRC(2011)·36 citations
2. 02*

   Recent Heavy Ion Results with the ATLAS Detector at the LHC

   Peter Steinberg · ATLAS Collaboration

   Results are presented from the ATLAS collaboration from the 2010 LHC heavy ion run, during which nearly 10 inverse microbarns of luminosity were delivered. Soft physics results include charged particle multiplicities and collective flow. The charged particle multiplicity, which tracks initial state entropy production, increases by a factor of two relative to the top RHIC energy, with a centrality dependence very similar to that already measured at RHIC. Measurements of elliptic flow out to large transverse momentum also show similar results to what was measured at RHIC, but no significant pseudorapidity dependence. Extensions of these measurements to higher harmonics have also been made, and can be used to explain structures in the two-particle correlation functions that had long been attributed to jet-medium interactions. New hard probe measurements include single muons, jets and high $p_T$ hadrons. Single muons at high momentum are used to extract the yield of $W^{\pm }$ bosons and are found to be consistent within statistical uncertainties with binary collision scaling. Conversely, jets are found to be suppressed in central events by a factor of two relative to peripheral events, with no significant dependence on the jet energy. Fragmentation functions are also found to be the same in central and peripheral events. Finally, charged hadrons have been measured out to 30 GeV, and their centrality dependence relative to peripheral events is similar to that found for jets.

   nucl-exhep-exJ.Phys.G(2011)·41 citations
3. 03*

   Ridge correlation structure in high multiplicity pp collisions with CMS

   Dragos Velicanu (for the CMS collaboration)🇺🇸

   Results on two-particle angular correlations are presented in proton-proton collisions at center of mass energies of 7 TeV, over a broad range of pseudorapidity and azimuthal angle. In very high multiplicity events at 7 TeV, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate $p_{\mathrm{T}}$ of 1--3 GeV/c, in the kinematic region $2.0<|\Delta \eta |<4.8$ and small $\Delta \varphi$. This structure, which has not been observed in pp collisions before, is similar to what is known as the "ridge" in heavy ion collisions. It is not predicted by commonly used proton-proton Monte Carlo models and is not seen in lower multiplicity pp collisions. Updated studies of this new effect as a function of particle transverse momentum, rapidity and event characteristics are shown.

   nucl-exJ.Phys.G(2011)·40 citations
4. 04*

   Isolated photon production in $\sqrt{s_{NN}}$ = 2.76 TeV PbPb collisions as a function of transverse energy and reaction centrality

   Yongsun Kim (for the CMS collaboration)🇺🇸

   In studies of the dense medium produced in ultra-relativistic heavy ion collisions, photons are important hard probes, since they are not expected to be modified by the medium. The measurement of isolated prompt photon production in PbPb collisions provides a test of perturbative quantum chromodynamics (pQCD) and the information to constrain the nuclear parton distribution functions. CMS has shown photon purity measurement capabilities in pp collisions using the shower shape templates. In PbPb co llisions at CMS, this technique was applied for the first time in heavy ion collisions. We report the first measurement of the transverse momentum spectra of isolated photons with pT from 20 GeV/c to 80 GeV/c in PbPb collisions at $\sqrt{s_{NN}}$ =2.76 TeV. The centrality dependence of the nuclear modification factor is also reported by comparing the result to the photon spectrum of pp reference which is computed from NLO calculations.

   nucl-exJ.Phys.G(2011)·3 citations
5. 05*

   NA49/NA61: results and plans on beam energy and system size scan at the CERN SPS

   M. Gazdzicki (for the NA49 and NA61/SHINE Collaborations)🇩🇪

   This paper presents results and plans of the NA49 and NA61/SHINE experiments at the CERN Super Proton Synchrotron concerning the study of relativistic nucleus-nucleus interactions. First, the NA49 evidence for the energy threshold of creating quark-gluon plasma, the onset of deconfinement, in central lead-lead collisions around 30A GeV is reviewed. Then the status of the NA61/SHINE systematic study of properties of the onset of deconfinement is presented. Second, the search for the critical point of strongly interacting matter undertaken by both experiments is discussed. NA49 measured large fluctuations at the top SPS energy, 158A GeV, in collisions of light and medium size nuclei. They seem to indicate that the critical point exists and is located close to baryonic chemical potential of about 250 MeV. The NA61/SHINE beam energy and system size scan started in 2009 will provide evidence for the existence of the critical point or refute the interpretation of the NA49 fluctuation data in terms of the critical point.

   nucl-exJ.Phys.G(2011)·37 citations
6. 06*

   Nuclear modification factors from the CMS experiment

   Yen-Jie Lee (for the CMS collaboration)🇺🇸

   We report the measurements of nuclear modification factors of the Z bosons, isolated photons and charged particles in $\sqrt{s_{NN}}$ = 2.76 TeV PbPb collisions with the CMS detector. The nuclear modification factors are constructed by dividing the PbPb $p_T$ spectra, normalized to the number of binary collisions, by the pp references. No modifications are observed in isolated photon and Z boson production with respected to the pp references while large suppression is observed in the charged particles.

   ↳ hep-exnucl-exJ.Phys.G(2011)·28 citations
7. 07*

   TITAN's Digital RFQ Ion Beam Cooler and Buncher, Operation and Performance

   T. Brunner · M.J. Smith · M. Brodeur · S. Ettenauer · A.T. Gallant · V.V. Simon · A. Chaudhuri A. Lapierre · E. Mané · R. Ringle · M.C. Simon · J.A. Vaz · P. Delheij and 3 other authors

   We present a description of the Radio Frequency Quadrupole (RFQ) ion trap built as part of the TITAN facility. It consists of a gas-filled, segmented, linear Paul trap and is the first stage of the TITAN setup with the purpose of cooling and bunching radioactive ion beams delivered from ISAC-TRIUMF. This is the first such device to be driven digitally, i.e., using a high voltage ($V_{pp}=400\mathrm{V}$), wide bandwidth ($0.2<f<1.2\mathrm{MHz}$) square-wave as compared to the typical sinusoidal wave form. Results from the commissioning of the device as well as systematic studies with stable and radioactive ions are presented including efficiency measurements with stable ${}^{133}$Cs and radioactive ${}^{124,126}$Cs. A novel and unique mode of operation of this device is also demonstrated where the cooled ion bunches are extracted in reverse mode, i.e., in the same direction as previously injected.

   ↳ physics.acc-phnucl-exNucl.Instrum.Meth.A(2012)·86 citations
8. 08*

   Nuclear astrophysics: the unfinished quest for the origin of the elements

   Jordi Jose (UPC Barcelona)🇪🇸 · Christian Iliadis (UNC Chapel Hill)🇺🇸

   Half a century has passed since the foundation of nuclear astrophysics. Since then, this discipline has reached its maturity. Today, nuclear astrophysics constitutes a multidisciplinary crucible of knowledge that combines the achievements in theoretical astrophysics, observational astronomy, cosmochemistry and nuclear physics. New tools and developments have revolutionized our understanding of the origin of the elements: supercomputers have provided astrophysicists with the required computational capabilities to study the evolution of stars in a multidimensional framework; the emergence of high-energy astrophysics with space-borne observatories has opened new windows to observe the Universe, from a novel panchromatic perspective; cosmochemists have isolated tiny pieces of stardust embedded in primitive meteorites, giving clues on the processes operating in stars as well as on the way matter condenses to form solids; and nuclear physicists have measured reactions near stellar energies, through the combined efforts using stable and radioactive ion beam facilities. This review provides comprehensive insight into the nuclear history of the Universe and related topics: starting from the Big Bang, when the ashes from the primordial explosion were transformed to hydrogen, helium, and few trace elements, to the rich variety of nucleosynthesis mechanisms and sites in the Universe. Particular attention is paid to the hydrostatic processes governing the evolution of low-mass stars, red giants and asymptotic giant-branch stars, as well as to the explosive nucleosynthesis occurring in core-collapse and thermonuclear supernovae, gamma-ray bursts, classical novae, X-ray bursts, superbursts, and stellar mergers.

   ↳ astro-ph.SRnucl-exnucl-thRept.Prog.Phys.(2011)·47 citations
9. 09*

   Nonparametric Regression using the Concept of Minimum Energy

   Mike Williams🇬🇧

   It has recently been shown that an unbinned distance-based statistic, the energy, can be used to construct an extremely powerful nonparametric multivariate two sample goodness-of-fit test. An extension to this method that makes it possible to perform nonparametric regression using multiple multivariate data sets is presented in this paper. The technique, which is based on the concept of minimizing the energy of the system, permits determination of parameters of interest without the need for parametric expressions of the parent distributions of the data sets. The application and performance of this new method is discussed in the context of some simple example analyses.

   ↳ physics.data-anhep-exnucl-exJINST(2011)·1 citation
10. 10*

    Kaon and hyperon production in antiproton-induced reactions on nuclei

    A.B. Larionov🇩🇪 · T. Gaitanos🇩🇪 · U. Mosel🇩🇪

    We study the strangeness production in antiproton-nucleus collisions at the beam momenta from 200 MeV/c to 15 GeV/c within the Giessen Botzmann-Uehling-Uhlenbeck (GiBUU) transport model. The GiBUU model contains a very detailed description of the underlying antinucleon-nucleon cross sections, in-particular, of the strangeness production channels. We compare our calculations with the bubble chamber data on \Lambda- and K^0_S-production in antiproton-nucleus collisions and with the earlier intranuclear cascade calculations. The contributions of the various partial channels to the hyperon production are reported and systematic differences with experiment are discussed. The possible formation of the bound \Lambda- and \Lambda\Lambda-nucleus systems is also considered. Finally, the results on the \Xi-hyperon production are presented in view of the forthcoming experiments with antiproton beams at FAIR.

    ↳ nucl-thhep-phnucl-exPRC(2012)·35 citations
11. 11*

    A proposed search for a fourth neutrino with a PBq antineutrino source

    Michel Cribier🇫🇷 · Maximilien Fechner🇫🇷 · Thierry Lasserre🇫🇷 · Alain Letourneau🇫🇷 · David Lhuillier🇫🇷 · Guillaume Mention🇫🇷 · Davide Franco🇫🇷 · Vasily Kornoukhov🇷🇺 · Stefan Schoenert🇩🇪

    Several observed anomalies in neutrino oscillation data can be explained by a hypothetical fourth neutrino separated from the three standard neutrinos by a squared mass difference of a few eV^2. We show that this hypothesis can be tested with a PBq (ten kilocurie scale) 144Ce or 106Ru antineutrino beta-source deployed at the center of a large low background liquid scintillator detector. In particular, the compact size of such a source could yield an energy-dependent oscillating pattern in event spatial distribution that would unabiguously determine neutrino mass differences and mixing angles.

    ↳ hep-exnucl-exPRL(2011)·91 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.