Mon·Sep 28, 2015Monday·September 28, 2015

1. 01*

   Measurement of the equilibrium charge state distributions of Ni, Co, and Cu beams in Mo at 2 MeV/u: review and evaluation of the relevant semi-empirical models

   P. Gastis · G. Perdikakis🇺🇸 · D. Robertson · R. Almus · T. Anderson🇺🇸 · W. Bauder · P. Collon · W. Lu🇺🇸 · K. Ostdiek · M. Skulski

   Equilibrium charge state distributions of stable 60Ni, 59Co, and 63Cu beams passing through a 1um thick Mo foil were measured at beam energies of 1.84 MeV/u, 2.09 MeV/u, and 2.11 MeV/u respectively. A 1-D position sensitive Parallel Grid Avalanche Counter detector (PGAC) was used at the exit of a spectrograph magnet, enabling us to measure the intensity of several charge states simultaneously. The number of charge states measured for each beam constituted more than 99% of the total equilibrium charge state distribution for that elements. Currently, little experimental data exists for equilibrium charge state distributions for heavy ions with 19<Zp,Zt<54 (Zp and Zt, are the projectile's and target's atomic numbers respectively). Hence the success of the semi-empirical models in predicting typical characteristics of equilibrium CSDs (mean charge states and distribution widths), has not been thoroughly tested at the energy region of interest. A number of semi-empirical models from the literature were evaluated in this study, regarding their ability to reproduce the characteristics of the measured charge state distributions. The evaluated models were selected from the literature based on whether they are suitable for the given range of atomic numbers and on their frequent use by the nuclear physics community. Finally, an attempt was made to combine model predictions for the mean charge state, the distribution width and the distribution shape, to come up with a more reliable model. We discuss this new "combinatorial" prescription and compare its results with our experimental data and with calculations using the other semi-empirical models studied in this work.

   nucl-exNucl.Instrum.Meth.B(2016)·1 citation
2. 02*

   Measurement of electrons from heavy-flavour hadron decays in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV

   ALICE Collaboration

   The production of electrons from heavy-flavour hadron decays was measured as a function of transverse momentum ($p_{\mathrm{T}}$) in minimum-bias p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with ALICE at the LHC. The measurement covers the $p_{\mathrm{T}}$ interval $0.5<p_{\mathrm{T}}<12$ GeV/$c$ and the rapidity range $-1.06<y_{\mathrm{cms}}<0.14$ in the centre-of-mass reference frame. The contribution of electrons from background sources was subtracted using an invariant mass approach. The nuclear modification factor $R_{\mathrm{pPb}}$ was calculated by comparing the $p_{\mathrm{T}}$-differential invariant cross section in p-Pb collisions to a pp reference at the same centre-of-mass energy, which was obtained by interpolating measurements at $\sqrt{s}=2.76$ TeV and $\sqrt{s}=7$ TeV. The $R_{\mathrm{pPb}}$ is consistent with unity within uncertainties of about 25%, which become larger for $p_{\mathrm{T}}$ below 1 GeV/$c$. The measurement shows that heavy-flavour production is consistent with binary scaling, so that a suppression in the high-$p_{\mathrm{T}}$ yield in Pb-Pb collisions has to be attributed to effects induced by the hot medium produced in the final state. The data in p-Pb collisions are described by recent model calculations that include cold nuclear matter effects.

   nucl-exhep-exPLB(2016)·95 citations
3. 03*

   Charged-particle multiplicities in proton-proton collisions at $\sqrt{s}$ = 0.9 to 8 TeV

   ALICE Collaboration

   A detailed study of pseudorapidity densities and multiplicity distributions of primary charged particles produced in proton-proton collisions, at $\sqrt{s}=$ 0.9, 2.36, 2.76, 7 and 8 TeV, in the pseudorapidity range $|\eta |<2$, was carried out using the ALICE detector. Measurements were obtained for three event classes: inelastic, non-single diffractive and events with at least one charged particle in the pseudorapidity interval $|\eta |<1$. The use of an improved track-counting algorithm combined with ALICE's measurements of diffractive processes allows a higher precision compared to our previous publications. A KNO scaling study was performed in the pseudorapidity intervals $|\eta |<$ 0.5, 1.0 and 1.5. The data are compared to other experimental results and to models as implemented in Monte Carlo event generators PHOJET and recent tunes of PYTHIA6, PYTHIA8 and EPOS.

   nucl-exhep-exEPJC(2017)·201 citations
4. 04*

   Centrality dependence of elliptic flow of multi-strange hadrons in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV

   Shusu Shi (for the STAR collaboration)🇨🇳

   We present recent results of the mid-rapidity elliptic flow ($v_2$) for multi-strange hadrons and the $\varphi$ meson as a function of centrality in Au + Au collisions at the center of mass energy $\sqrt{s_{NN}}$ = 200 GeV. The transverse momentum dependence of $\varphi$ and $\Omega$ $v_2$ is similar to that of pion and proton, indicating that the heavier strange ($s$) quark flows as strongly as the lighter up ($u$) and down ($d$) quarks. These observations constitute a clear piece of evidence for the development of partonic collectivity in heavy-ion collisions at the top RHIC energy. In addition, the mass ordering of $v_2$ breaks between the $\varphi$ and proton at low transverse momenta in the 0-30\% centrality bin, possibly due to the effect of late hadronic interactions on the proton $v_2$.

   nucl-exJ.Phys.Conf.Ser.(2016)·1 citation
5. 05*

   STAR Overview of Hard Probe Observables

   Li Yi (for the STAR Collaboration)🇺🇸

   Parton energy loss, quarkonium sequential melting and particle production from electromagnetic interactions are tools to study Quark Gluon Plasma properties. The STAR detector, with large acceptance at mid-rapidity, excellent particle identification and wide transverse momentum coverage, is able to study these probes in details. In Hard Probes 2015, the STAR collaboration reported measurements of reconstructed jets, heavy-flavor physics, di-lepton production and the performance of new detectors in seven presentations and one poster. Given the rich results from STAR, this overview report will focus on a few selected results on jets and ${\rm Y}$ measurements in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$GeV, $J/\psi$ production in $p$+$p$ collisions at $\sqrt{s_{\mathrm{NN}}}=500$GeV, and the di-electron spectrum in the low mass region from the Beam Energy Scan - Phase I.

   nucl-exNucl.Part.Phys.Proc.(2016)·1 citation
6. 06*

   Azimuthally anisotropic emission of low-momentum direct photons in Au$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV

   A. Adare · S. Afanasiev · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · H. Al-Bataineh · J. Alexander · M. Alfred · H. Al-Ta'ani · A. Angerami · K. Aoki and 541 other authors

   The PHENIX experiment at the Relativistic Heavy Ion Collider has measured 2nd and 3rd order Fourier coefficients of the azimuthal distributions of direct photons emitted at midrapidity in Au$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV for various collision centralities. Combining two different analysis techniques, results were obtained in the transverse momentum range of $0.4<p_T<4.0$ GeV/$c$. At low $p_T$ the second-order coefficients, $v_2$, are similar to the ones observed in hadrons. Third order coefficients, $v_3$, are nonzero and almost independent of centrality. These new results on $v_2$ and $v_3$, combined with previously published results on yields, are compared to model calculations that provide yields and asymmetries in the same framework. Those models are challenged to explain simultaneously the observed large yield and large azimuthal anisotropies.

   nucl-exPRC(2016)·163 citations
7. 07*

   Light fragments from (C + Be) interactions at 0.6 GeV/nucleon

   B. M. Abramov🇷🇺 · P. N. Alekseev🇷🇺 · Yu. A. Borodin🇷🇺 · S. A. Bulychjov🇷🇺 · I. A. Dukhovskoy🇷🇺 · A. I. Khanov🇺🇸 · A. P. Krutenkova🇷🇺 · V. V. Kulikov🇷🇺 · M. A. Martemianov · S. G. Mashnik🇺🇸 · M. A. Matsyuk🇷🇺 · E. N. Turdakina🇷🇺 · P. I. Zarubin🇷🇺

   Nuclear fragments emitted at 3.5 degrees in 12C fragmentation at 0.6 GeV/nucleon have been measured. The spectra obtained are used for testing the predictions of four ion-ion interaction models: INCL++, BC, LAQGSM03.03 and QMD as well as for the comparison with the analytical parametrization in the framework of thermodynamical picture of fragmentation.

   nucl-exEPJ Web Conf.(2016)·2 citations
8. 08*

   Measurements of directed, elliptic, and triangular flow in Cu$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV

   A. Adare · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · J. Alexander · M. Alfred · K. Aoki · N. Apadula · H. Asano · E.T. Atomssa · T.C. Awes and 393 other authors

   Measurements of anisotropic flow Fourier coefficients ($v_n$) for inclusive charged particles and identified hadrons ${\pi }^{\pm }$, $K^{\pm }$, $p$, and $\bar{p}$ produced at midrapidity in Cu+Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV are presented. The data were collected in 2012 by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). The particle azimuthal distributions with respect to different order symmetry planes ${\Psi }_n$, for $n$~=~1, 2, and 3 are studied as a function of transverse momentum $p_T$ over a broad range of collisions centralities. Mass ordering, as expected from hydrodynamic flow, is observed for all three harmonics. The charged-particle results are compared to hydrodynamical and transport model calculations. We also compare these Cu$+$Au results with those in Cu$+$Cu and Au$+$Au collisions at the same $\sqrt{s_{{}_{NN}}}$, and find that the $v_2$ and $v_3$, as a function of transverse momentum, follow a common scaling with $1/({\epsilon }_n{N}_{\mathrm{part}}^{1/3})$.

   nucl-exPRC(2016)·48 citations
9. 09*

   Search of Neutrinoless Double Beta Decay with the GERDA Experiment

   Giovanni Benato (for the GERDA Collaboration)🇨🇭

   The Gerda experiment designed to search for the neutrinoless double beta decay in 76Ge has successfully completed the first data collection. No signal excess is found, and a lower limit on the half life of the process is set, with T1/2 > 2.1x10^25 yr (90% CL). After a review of the experimental setup and of the main Phase I results, the hardware upgrade for Gerda Phase II is described, and the physics reach of the new data collection is reported.

   nucl-exphysics.ins-det6 citations
10. 10*

    Quark Hadron Duality - Recent Jefferson Lab Results

    Ioana Niculescu🇺🇸

    The duality between the partonic and hadronic descriptions of electron--nucleon scattering is a remarkable feature of nuclear interactions. When averaged over appropriate energy intervals the cross section at low energy which is dominated by nucleon resonances resembles the smooth behavior expected from perturbative QCD. Recent Jefferson Lab results indicate that quark-hadron duality is present in a variety of observables, not just the proton F2 structure function. An overview of recent results, especially local quark-hadron duality on the neutron, are presented here.

    nucl-exhep-ph3 citations
11. 11*

    Radiative energy loss and radiative p_T-broadening of high-energy partons in QCD matter

    Bin Wu🇫🇷

    I give a self-contained review on radiative p_T-broadening and radiative energy loss of high-energy partons in QCD matter. The typical p_T^2 of high-energy partons receives a double logarithmic correction due to the recoiling effect of medium-induced gluon radiation. Such a double logarithmic term, averaged over the path length of the partons, can be taken as the radiative correction to the jet quenching parameter qhat and hence contributes to radiative energy loss. This has also been confirmed by detailed calculations of energy loss by radiating two gluons.

    ↳ hep-phhep-exnucl-exnucl-thNucl.Part.Phys.Proc.(2016)·3 citations
12. 12*

    Undersaturation of quarks at early stages of relativistic nuclear collisions: the hot glue initial scenario and its observable signatures

    H. Stoecker🇩🇪 · M. Beitel🇩🇪 · T.S. Biró🇭🇺 · L.P. Csernai🇳🇴 · K. Gallmeister🇩🇪 · M.I. Gorenstein🇺🇦 · C. Greiner🇩🇪 · I.N. Mishustin🇩🇪 · M. Panero🇮🇹 · S. Raha🇮🇳 · L.M. Satarov🇩🇪 · S. Schramm🇩🇪 and 8 other authors

    The early stage of high multiplicity nuclear collisions is represented by a nearly quarkless, hot, deconfined pure gluon plasma. This new scenario should be characterized by a suppression of high $p_T$ photons and dileptons as well as by reduced baryon to meson ratios. We present the numerical results for central Pb+Pb collisions at the LHC energies by using the ideal Bjorken hydrodynamics with time-dependent quark fugacity. It is shown that about 25\% of final total entropy is generated during the hydrodynamic evolution of chemically undersaturated quark-gluon plasma.

    ↳ hep-phhep-exhep-latnucl-ex+1Astron.Nachr.(2015)·17 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.