Thu·Dec 31, 2015Thursday·December 31, 2015

1. 01*

   Direct-photon+hadron correlations to study parton energy loss with the STAR experiment

   Nihar Ranjan Sahoo (STAR collaboration)🇺🇸

   We report new results of ${\gamma }_{dir}$+hadron and ${\pi }^0$+hadron azimuthal correlations as a measure of the away-side jet-like correlated yields in central Au+Au and p+p collisions at $\sqrt{s_{NN}}$ = 200 GeV in the STAR experiment from years 2011 and 2009 of data taking, respectively. The charged-hadron per-trigger yields at mid-rapidity $(|\eta |<1)$ and for transverse momenta $p_T^{assoc}>1.2$ ~GeV/$c$ associated with ${\gamma }_{dir}$~ and ${\pi }^0$~(for triggers $|\eta |<$0.9, 12 $<p_T^{trig}<$ 20 GeV/$c$) in central Au+Au collisions are compared with p+p collisions. The $z_T$ ($=\frac{p_T^{assoc}}{p_T^{trig}}$) dependence, now extending down to $z_T$=0.1, of the suppression of the away-side associated yields is presented. We observed that the suppression of away-side associated yields tends to vanish at lower \zT. The dependence of the suppression on both $p_T^{assoc}$ and $p_T^{trig}$ is also discussed. Finally, these results are compared with various model predictions.

   nucl-exhep-exhep-phnucl-thNPA(2016)·3 citations
2. 02*

   Measurements of jet quenching with semi-inclusive charged jet distributions in $Au+Au$ collisions at $\sqrt{s_{NN}}$=200 GeV

   P. M. Jacobs🇺🇸 · A. Schmah (STAR Collaboration)🇺🇸

   We report measurements of jet quenching in $Au+Au$ collisions at $\sqrt{s_{NN}}$=200 GeV, based on the semi-inclusive distribution of reconstructed charged particle jets recoiling from a high $p_T$ hadron trigger. Jets are reconstructed with the anti-k${}_T$ algorithm ($R$=0.2 to 0.5), with low IR-cutoff of track constituents ($p_T>0.2$ GeV/c). Uncorrelated background is corrected using a novel mixed-event technique, with no fragmentation bias imposed by the correction procedure on the accepted recoil jet population. Corrected recoil jet distributions, reported in the range $0<p_{T,jet}^{ch}<30$ GeV/c, are used to measure jet yield suppression, jet energy loss, and intra-jet broadening. The first search for QCD Molière scattering of jets in hot QCD matter at RHIC is reported.

   nucl-exhep-exhep-phNPA(2016)·25 citations
3. 03*

   Multipion Bose-Einstein correlations in pp, p-Pb, and Pb-Pb collisions at the LHC

   ALICE Collaboration

   Three- and four-pion Bose-Einstein correlations are presented in pp, p-Pb, and Pb-Pb collisions at the LHC. We compare our measured four-pion correlations to the expectation derived from two- and three-pion measurements. Such a comparison provides a method to search for coherent pion emission. We also present mixed-charge correlations in order to demonstrate the effectiveness of several analysis procedures such as Coulomb corrections. Same-charge four-pion correlations in pp and p-Pb appear consistent with the expectations from three-pion measurements. However, the presence of non-negligible background correlations in both systems prevent a conclusive statement. In Pb-Pb collisions, we observe a significant suppression of three- and four-pion Bose-Einstein correlations compared to expectations from two-pion measurements. There appears to be no centrality dependence of the suppression within the 0-50% centrality interval. The origin of the suppression is not clear. However, by postulating either coherent pion emission or large multibody Coulomb effects, the suppression may be explained.

   nucl-exhep-exPRC(2016)·48 citations
4. 04*

   New State of Nuclear Matter: Nearly Perfect Fluid of Quarks and Gluons in Heavy Ion Collisions at RHIC Energies

   Rachid Nouicer🇺🇸

   This article reviews several important results from RHIC experiments and discusses their implications. They were obtained in a unique environment for studying QCD matter at temperatures and densities that exceed the limits wherein hadrons can exist as individual entities and raises to prominence the quark-gluon degrees of freedom. These findings are supported by major experimental observations via measuring of the bulk properties of particle production, particle ratios and chemical freeze-out conditions, and elliptic flow; followed by hard probe measurements. The results reveal that a dense, strongly-interacting medium is created in central Au+Au collisions at 200 GeV at RHIC. This revelation of a new state of nuclear matter has also been observed in measurements at the LHC. Further, the IP-Glasma model coupled with viscous hydrodynamic models, which assumes the formation of a QGP, reproduces well the experimental flow results from Au+Au at 200 GeV. This implies that the fluctuations in the initial geometry state are important and the created medium behaves as a nearly perfect liquid of nuclear matter because it has an extraordinarily low ratio of shear viscosity to entropy density. However, these discoveries are far from being fully understood. Furthermore, recent experimental results from RHIC and LHC in small p+A, d+Au and He+A collision systems provide brand new insight into the role of initial and final state effects. These have proven to be interesting and more surprising than originally anticipated; and could conceivably shed new light in our understanding of collective behavior in heavy-ion physics. Accordingly, the focus of the experiments at both facilities RHIC and the LHC is on detailed exploration of the properties of this new state of nuclear matter, the QGP.

   nucl-exEur.Phys.J.Plus(2016)·33 citations
5. 05*

   Beam-Energy and Centrality Dependence of Directed Flow of Identified Particles

   Prashanth Shanmuganathan (for the STAR Collaboration)🇺🇸

   These proceedings present directed flow ($v_1$) measurements in Au+Au collisions from STAR's Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider, for $p$, $\bar{p}$, $\Lambda$, $\bar{\Lambda }$, $K^{\pm }$, $K_S^0$ and ${\pi }^{\pm }$. At intermediate centrality, protons show a minimum in directed flow slope, $d{v}_1/dy{|}_{y\le 0.8}$, as a function of beam energy. Proton $d{v}_1/dy$ changes sign near 10 GeV, and the directed flow for $\Lambda$ is consistent with the proton result. The directed flow slope for net protons shows a clear minimum at 14.5 GeV and becomes positive at beam energies below 10 GeV and above 30 GeV. New results for net-kaon directed flow slope resemble net protons from high energy down to 14.5 GeV, but remain negative at lower energies. The slope $d{v}_1/dy$ shows a strong centrality dependence, especially for $p$ and $\Lambda$ at the lower beam energies. Available model calculations are in poor agreement.

   nucl-exhep-exNPA(2016)·17 citations
6. 06*

   D mesons in a magnetic field

   Philipp Gubler🇮🇹 · Koichi Hattori🇯🇵 · Su Houng Lee🇰🇷 · Makoto Oka🇯🇵 · Sho Ozaki🇯🇵 · Kei Suzuki🇯🇵

   We investigate the mass spectra of open heavy flavor mesons in an external constant magnetic field within QCD sum rules. Spectral ansätze on the phenomenological side are proposed in order to properly take into account mixing effects between the pseudoscalar and vector channels, and the Landau levels of charged mesons. The operator product expansion is implemented up to dimension-5 operators. As a result, we find for neutral D mesons a significant positive mass shift that goes beyond simple mixing effects. In contrast, charged D mesons are further subject to Landau level effects, which together with the mixing effects almost completely saturate the mass shifts obtained in our sum rule analysis.

   ↳ hep-phhep-latnucl-exnucl-thPRD(2016)·89 citations
7. 07*

   The R_AA and v_2 of muons from heavy-quark decays in Pb+Pb collisions at sqrt(s_NN)=2.76 TeV with the ATLAS detector

   Alexander Milov (for the ATLAS Collaboration)🇮🇱

   The ATLAS experiment measures the production of muons coming from the decays of heavy flavour particles in the kinematic interval 4<p_T<14 GeV and |eta|<1. The measurement is performed in sqrt(s) = 2.76 TeV pp collisions and over the centrality range of 0-60% in sqrt(s_NN) = 2.76 TeV Pb+Pb collisions. The heavy flavour muon differential cross-sections and per-event yields are measured in pp and Pb+Pb collisions, respectively. The nuclear modification factor measured in 0-10% most central collisions is observed to be approximately equal to 0.4 and independent of p_T within uncertainties, which indicates suppressed production of heavy flavour muons in Pb+Pb collisions. The muon yields are also measured as a function of the azimuthal angle with respect to the event plane. Fourier coefficients associated with the second harmonic modulation vary slowly with p_T and show a systematic variation with centrality that is characteristic of other elliptic anisotropy measurements.

   ↳ nucl-thnucl-exNPA(2016)·2 citations
8. 08*

   Dual Position Sensitive MWPC for tracking reaction products at VAMOS++

   Marine Vandebrouck🇫🇷 · Antoine Lemasson🇫🇷 · Maurycy Rejmund🇫🇷 · Georges Fremont🇫🇷 · Julien Pancin🇫🇷 · Alahari Navin🇫🇷 · Caterina Michelagnoli🇫🇷 · Johan Goupil🇫🇷 · Charles Spitaels🇫🇷 · Bertrand Jacquot🇫🇷

   The characteristics and performance of a Dual Position Sensitive Multi-Wire Proportional Counter (DPS-MWPC) used to measure the scattering angle, interaction position on the target and the velocity of reaction products, detected in the VAMOS++ magnetic spectrometer, are reported. The detector consists of a pair of position sensitive low pressure MWPCs and provides both fast timing signals, along with the two-dimensional position coordinates required to define the trajectory of the reaction products. A time-of-flight resolution of 305(11) ps (FWHM) was measured. The measured resolutions (FWHM) were 2.5(3) mrad and 560(70) {\mu}m for the scattering angle and the interaction point at the target respectively. The subsequent improvement of the Doppler correction of the energy of the gamma-rays, detected in the gamma-ray tracking array AGATA in coincidence with isotopically identified ions in VAMOS++, is also discussed.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2016)·44 citations
9. 09*

   CALDER: cryogenic light detector for rare events search

   L. Pagnanini · E. S. Battistelli · F. Bellini · M. Calvo · L. Cardani · N. Casali · M. G. Castellano · I. Colantoni · A. Coppolecchia · C. Cosmelli · A. Cruciani · P. De Bernardis and 6 other authors

   The CALDER project aims at developing cryogenic light detectors with high sensitivity to UV and visible light, to be used for particle tagging in massive bolometers. Indeed the sensitivity of CUORE can be increased by a factor of 3, thanks to the reduction of the $\alpha$-background, obtained by detecting the Cherenkov light (100 eV) emitted by $\beta /\gamma$ events. Currently used light detectors have not the features required to address this task, so we decided to develop a new light detector using Kinetic Inductance Detector as a sensor. This approach is very challenging and requires an intensive R$\&$D to be satisfied. The first results of this activity are shown in the following.

   ↳ physics.ins-dethep-exnucl-exPoS(2015)·1 citation
10. 10*

    Reconstruction of Energy Spectra of Neutrino Beams Independent of Nuclear Effects: Prospects for Current Experiments

    X.-G. Lu🇬🇧

    The energy spectrum of a neutrino beam in the few-GeV region is free of uncertainties from nuclear effects when reconstructed via neutrino-hydrogen interactions. On a multinuclear (hydrogen containing) target such interactions can be extracted using transverse kinematic imbalance. We discuss the prospects of this technique for current experiments.

    ↳ hep-exnucl-exphysics.ins-detJPS Conf.Proc.(2016)·5 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.