Nuclear Experiment·nucl-ex

Mon·Aug 4, 2014Monday·August 4, 2014

9 papers—4 primary·5 cross-listed·reconstructed*

01*
Collective phenomena in high-energy nuclear collisions
Jiangyong Jia🇺🇸
I review experimental studies of collective phenomena in $\pA$ and A+A collisions presented in the Quark Matter 2014 conference.
nucl-exnucl-thNPA(2014)·1 citation
02*
Azimuthally differential pion femtoscopy in Pb-Pb collisions at 2.76 TeV with ALICE at the LHC
Vera Loggins (for the ALICE Collaboration)🇺🇸
Femtoscopy of non-central heavy ion collisions provides access to information on the geometry of the effective pion-emitting source. In particular, the source shape can be studied by measuring femtoscopic radii as a function of the pion emission angle relative to the collision symmetry planes. We present the results of azimuthally differential femtoscopy of Pb-Pb collisions at $s_{N N} = 2.76$ TeV at the LHC relative to the second harmonic event plane. We observe a clear oscillation of the extracted radii as a function of the emission angle. We find that $R_{s i d e}$ and $R_{o u t}$ oscillate out of phase for all centralities and pion transverse momenta. The relative amplitude of $R_{s i d e}$ oscillation decreases in more central collisions, but remains positive, which indicates that the source remains out-of-plane extended qualitatively similar to what was observed at RHIC energies. We compare our results to existing hydrodynamical and transport model calculations.
nucl-exhep-exNPA(2014)·8 citations
03*
Production of light flavour hadrons at intermediate and high pT in pp, p-Pb and Pb-Pb collisions measured with ALICE
Michael Linus Knichel (for the ALICE Collaboration)🇩🇪
Light flavour transverse momentum spectra at intermediate and high pT provide an important baseline for the measurement of perturbative QCD processes in pp, for the evaluation of initial state effects in p-Pb, and for investigating the suppression from parton energy loss in Pb-Pb collisions. The measurement of the nuclear modification factor RpPb for inclusive charged particles is extended up to 50 GeV/c in pT compared to our previous measurement and remains consistent with unity up the largest momenta. Results on RpPb of charged pions, kaons and protons that cover up to 14 GeV/c in pT are presented and compared to RpPb of inclusive charged particles. On the production of charged pions, kaons, and protons up to pT = 20 GeV/c in Pb-Pb collisions final results for RAA are presented.
nucl-exhep-exNPA(2014)·10 citations
04*
Experimental Results on p(d)+A Collisions at RHIC and the LHC
Anne M. Sickles🇺🇸
Recent experimental results at both the LHC and RHIC show evidence for hydrodynamic behavior in proton-nucleus and deuteron- nucleus collisions (p+A). This unexpected finding has prompted new measurements in p+A collisions in order to understand whether similar matter is created in A+A and p+A collisions or whether some another explanation is needed. In this proceedings, we will discuss the new experimental data and its interpretation within the context of heavy ion collisions.
nucl-exNPA(2014)·4 citations
05*
Event-by-event direct photon anisotropic flow in relativistic heavy-ion collisions
Chun Shen🇺🇸 · Jean-Francois Paquet🇨🇦 · Jia Liu🇺🇸 · Gabriel Denicol🇨🇦 · Ulrich Heinz🇺🇸 · Charles Gale🇨🇦
We consider directly emitted and hadronic decay photons from event-by-event hydrodynamic simulations. We compute the direct photon anisotropic flow coefficients and compare with recent experimental measurements. We find that it is crucial to include the photon multiplicity as a weighting factor in the definition of $v_{n}^{γ}$ . We also investigate the sensitivity of the direct photon spectrum and elliptic flow to the theoretical uncertainty of the photon emission rate in the quark-hadron transition region and to the pre-equilibrium dynamics of relativistic heavy-ion collisions.
↳ nucl-thhep-phnucl-exNPA(2014)·17 citations
06*
Study of the characteristics of GEM detectors for the future FAIR experiment CBM
S. Biswas🇩🇪 · A. Abuhoza🇩🇪 · U. Frankenfeld🇩🇪 · J. Hehner🇩🇪 · C.J. Schmidt🇩🇪 · H.R. Schmidt🇩🇪 · M.Traeger🇩🇪 · S.Colafranceschi🇨🇭 · A.Marinov🇨🇭 · A.Sharma🇨🇭
Characteristics of triple GEM detector have been studied systematically. The variation of the effective gain and energy resolution of GEM with variation of the applied voltage has been measured with Fe55 X-ray source for different gas mixtures and with different gas flow rates. Long-term test of the GEM has also been performed.
↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2013)·13 citations
07*
Light flavor hadron spectra at low $p_{T}$ and search for collective phenomena in high multiplicity pp, p-Pb and Pb-Pb collisions measured with the ALICE experiment
C. Andrei (for the ALICE Collaboration)🇷🇴
Comprehensive results on transverse momentum distributions and their ratios for identified light flavor hadrons ( $π$ , K, p) at low $p_{T}$ and mid-rapidity as a function of charged particle multiplicity are reported for pp collisions at 7 TeV. Particle mass dependent hardening of the spectral shapes in Pb-Pb collisions at 2.76 TeV were attributed to hydrodynamical flow and quantitatively parameterized with Boltzmann-Gibbs Blast Wave fits. In this contribution, we investigate the existence of collective phenomena in small systems: pp, p-Pb and peripheral Pb-Pb where similar patterns are observed in multiplicity dependent studies.
↳ hep-exnucl-exNPA(2014)·18 citations
08*
What the collective flow excitation function can tell about the quark-gluon plasma
Jussi Auvinen🇩🇪 · Jan Steinheimer🇩🇪 · Hannah Petersen🇩🇪
Recent STAR data from the RHIC beam energy scan (BES) show that the midrapidity slope dv1/dy of the directed flow v1 of net-protons changes sign twice within the collision energy range 7.7 - 39 GeV. To investigate this phenomenon, we study the collision energy dependence of v1 utilizing a Boltzmann + hydrodynamics hybrid model. Calculations with dynamically evolved initial and final state show no qualitative difference between an equation of state with a cross-over and one with a first-order phase transition, in contrast to earlier pure fluid predictions. Furthermore, our analysis of the elliptic flow v2 shows that pre-equilibrium transport dynamics are partially compensating for the diminished elliptic flow production in the hydrodynamical phase at lower energies, which leads to a qualitative agreement with STAR BES results in midcentral collisions. No compensation from transport is found in our model for integrated v3, which decreases from approx 0.02 at sqrt(sNN) = 27 GeV to approx 0.005 at sqrt(sNN) = 7.7 GeV in midcentral collisions.
↳ nucl-thnucl-exNPA(2014)·1 citation
09*
The Proton Radius from Bayesian Inference
Krzysztof M. Graczyk🇵🇱 · Cezary Juszczak🇵🇱
The methods of Bayesian statistics are used to extract the value of the proton radius from the elastic $e p$ scattering data in a model independent way. To achieve that goal a large number of parametrizations (equivalent to neural network schemes) are considered and ranked by their conditional probability $P (parametrization ∣ data)$ instead of using the minimal error criterion. As a result the most probable proton radii values ( $r_{E}^{p} = 0.899 \pm 0.003$ fm, $r_{M}^{p} = 0.879 \pm 0.007$ fm) are obtained and systematic error due to freedom in the choice of parametrization is estimated. Correcting the data for the two photon exchange effect turns out to be important to obtain the agreement between the $r_{E}^{p}$ and $r_{M}^{p}$ values. The results disagree with recent muonic atom measurements.
↳ hep-phnucl-exnucl-thPRC(2014)·39 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.