Mon·Jul 11, 2011Monday·July 11, 2011

1. 01*

   Measurement of elliptic and higher order flow from ATLAS experiment at the LHC

   Jiangyong Jia (for the ATLAS Collaboration)🇺🇸

   We present a differential measurement of the azimuthal anisotropy of charged hadron production in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}$=2.76 TeV. This azimuthal anisotropy is expanded into a Fourier series in azimuthal angle, where the coefficient for each term, $v_n$, characterizes the magnitude of the anisotropy at a particular angular scale. We extract $v_2-v_6$ via a discrete Fourier analysis of the two-particle $\Delta \varphi -\Delta \eta$ correlation with a large $\Delta \eta$ gap ($|\Delta \eta |>2$), and via an event plane method based on the Forward Calorimeter. Significant $v_2-v_6$ values are observed over a broad range in $\text{pT}$, $\eta$ and centrality, and they are found to be consistent between the two methods in the transverse momentum region $\text{pT}<3-4$ GeV. This suggests that the measured $v_2-v_6$ obtained from two-particle correlations at low $\text{pT}$ with a large $\Delta \eta$ gap are consistent with the collective response of the system to the initial state geometry fluctuations, and is not the result of jet fragmentation or resonance decay.

   nucl-exJ.Phys.G(2011)·65 citations
2. 02*

   Neutron experiments to search for new spin-dependent interactions

   Yu.N. Pokotilovski (JINR, Dubna, Russia)🇷🇺

   The consideration is presented of possible neutron experiments to search for new short-range spin-dependent forces. The spin-dependent nucleon-nucleon interaction between neutron and nuclei may cause different effects: phase shift of a neutron wave in neutron interferometers of different kind, in particular of the Lloyd mirror configuration, neutron spin rotation in the pseudo-magnetic field, and transverse deflection of polarized neutron beam by a slab of substance. Estimates of sensitivity of these experiments are performed.

   nucl-exhep-phJETP Lett.(2011)·7 citations
3. 03*

   Energy dependence of the freeze out eccentricity from the azimuthal dependence of HBT at STAR

   Christopher Anson (for the STAR collaboration)🇺🇸

   Non-central heavy ion collisions create an out-of-plane-extended participant zone that expands toward a more round state as the system evolves. The recent RHIC Beam Energy Scan at sqrt{s_{NN}} of 7.7, 11.5, and 39 GeV provide an opportunity to explore the energy dependence of the freeze out eccentricity. The new low energy data from STAR complements high statistics data sets at sqrt{s_{NN}} of 62.4 and 200 GeV. Hanbury-Brown-Twiss (HBT) interferometry allows to determine the size of pion emitting source regions. The dependence of the HBT radius parameters on azimuthal angle relative to the reaction plane have been extracted. These dependencies can be related to the freeze out eccentricity. The new results from STAR are consistent with a monotonically decreasing freeze out eccentricity and constrain any minimum, suggested by previously available data, to lie in the range between 11.5 and 39 GeV. Of several models UrQMD appears to best predict the STAR and AGS data.

   nucl-exhep-exJ.Phys.G(2011)·9 citations
4. 04*

   New results on event-by-event ratio fluctuations in Pb+Pb collisions at CERN SPS energies

   Tim Schuster (for the NA49 collaboration)🇩🇪

   Event-by-event fluctuations of produced particle multiplicities are believed to be sensitive to a deconfinement phase transition and the critical point of strongly interacting matter. The NA49 collaboration has conducted a systematic study of various fluctuation observables. In this contribution, recent results on hadron ratio fluctuations in central Pb+Pb collisions at sqrt(s_NN) = 6.3 to 17.3 GeV are reported. These results are complemented by the centrality dependence of hadron ratio fluctuations at sqrt(s_NN) = 17.3 GeV. A universal scaling was found, describing the energy and centrality dependence of the (K++ K-)/({\pi}++ {\pi}-) and (p + pbar)/({\pi}++ {\pi}-) ratio fluctuations purely by a change in the observed average hadron multiplicities. This scaling is broken for the fluctuations of the (K+ + K-)/(p + pbar) and K+/p ratios, possibly hinting at a change in the baryon number-strangeness correlation.

   nucl-exJ.Phys.G(2011)·9 citations
5. 05*

   First direct mass-measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He

   M. Brodeur🇨🇦 · T. Brunner🇨🇦 · C. Champagne🇨🇦 · S. Ettenauer🇨🇦 · M. J. Smith🇨🇦 · A. Lapierre🇨🇦 · R. Ringle🇨🇦 · V. L. Ryjkov🇨🇦 · S. Bacca🇨🇦 · P. Delheij🇨🇦 · G. W. F. Drake🇨🇦 · D. Lunney🇫🇷 · A. Schwenk🇩🇪 · J. Dilling🇨🇦

   The first direct mass-measurement of ${}^6$He has been performed with the TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the mass of ${}^8$He was determined with improved precision over our previous measurement. The obtained masses are $m$(${}^6$He) = 6.018 885 883(57) u and $m$(${}^8$He) = 8.033 934 44(11) u. The ${}^6$He value shows a deviation from the literature of 4$\sigma$. With these new mass values and the previously measured atomic isotope shifts we obtain charge radii of 2.060(8) fm and 1.959(16) fm for ${}^6$He and ${}^8$He respectively. We present a detailed comparison to nuclear theory for ${}^6$He, including new hyperspherical harmonics results. A correlation plot of the point-proton radius with the two-neutron separation energy demonstrates clearly the importance of three-nucleon forces.

   nucl-exPRL(2012)·112 citations
6. 06*

   Particle Identification in the ALICE Experiment

   Alexander Kalweit (for the ALICE collaboration)🇩🇪

   The particle identification capabilities of the ALICE experiment are unique among the four major LHC experiments. The working principles and excellent performance of the central barrel detectors in a high-multiplicity environment are presented as well as two physics examples: the extraction of transverse momentum spectra of charged pions, kaons, protons, and the observation of the anti-4He-nucleus.

   ↳ hep-exnucl-exJ.Phys.G(2011)·35 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.