Fri·Jan 4, 2019Friday·January 4, 2019

1. 01*

   Measurements of the fluctuations of identified particles in ALICE at the LHC

   Alice Ohlson (for the ALICE Collaboration)🇩🇪

   The event-by-event fluctuations of identified particles in ultrarelativistic nucleus-nucleus collisions give information about the state of matter created in these collisions as well as the phase diagram of nuclear matter. In this proceedings, we present the latest results from ALICE on the centrality and pseudorapidity dependence of net-proton fluctuations, which are closely related to net-baryon fluctuations, as well as net-kaon and net-pion fluctuations. The effects of volume fluctuations and global baryon conservation on these observables are discussed. Furthermore, the correlated fluctuations between different particle species, quantified by the observable ${\nu }_{dyn}$, are also shown as functions of multiplicity and collision energy and are compared with Monte Carlo models. These measurements are performed in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV using the novel Identity Method and take advantage of the excellent particle identification capabilities of ALICE.

   nucl-exhep-exPoS(2018)·5 citations
2. 02*

   Collective behavior in small systems

   Alice Ohlson🇩🇪

   The presence of correlations between particles significantly separated in pseudorapidity in proton-proton and proton-nucleus collisions has raised questions about whether collective effects are observed in small collision systems as well as in heavy-ion collisions. The quantification of these long-range correlations by $v_n$ coefficients is of particular interest. A selection of the latest $v_n$ measurements is presented, including results from the recent $d$+Au beam energy scan at RHIC where a significant non-zero $v_2$ is measured down to low center-of-mass energies ($\sqrt{s_{\mathrm{NN}}}$ = 39 GeV). Results from a collision system scan - comprising $p$+Au, $d$+Au, and ${}^3$He+Au collisions - are also shown to address the role of the initial nuclear geometry in the final state anisotropy. Finally, the challenge of measuring multi-particle cumulants, particularly $c_2\{4\}$, in $p$+$p$ collisions is discussed, and new methods for reducing the effects of non-flow are shown to produce a more robust measurement of $v_2\{4\}$ in $p$+$p$ collisions.

   nucl-exhep-exNPA(2017)·4 citations
3. 03*

   Correlations, multiplicity distributions, and the ridge in pp and p-Pb collisions

   Alice Ohlson (for the ALICE Collaboration)🇩🇪

   Measurements made by the ALICE Collaboration of single- and two-particle distributions in high-energy pp and p-Pb collisions are used to characterize the interactions in small collision systems, tune models of particle production in QCD, and serve as a baseline for heavy-ion observables. The measurements of charged-particle multiplicity density, $⟨d{N}_{ch}/d\eta ⟩$, and multiplicity distributions are shown in pp and p-Pb collisions, including data from the top center-of-mass energy achieved at the Large Hadron Collider (LHC), $\sqrt{s}$ = 13 TeV. Two-particle angular correlations in p-Pb collisions are studied in detail to investigate long-range correlations in pseudorapidity which are reminiscent of structures previously thought unique to heavy-ion collisions.

   nucl-exhep-exEPJ Web Conf.(2017)·0 citations
4. 04*

   Investigating correlated fluctuations of conserved charges with net-$\Lambda$ fluctuations in Pb-Pb collisions at ALICE

   Alice Ohlson (for the ALICE Collaboration)🇩🇪

   Event-by-event fluctuations of conserved charges - such as electric charge, strangeness, and baryon number - in ultrarelativistic heavy-ion collisions provide insight into the properties of the quark-gluon plasma and the QCD phase diagram. They can be related to the higher moments of the multiplicity distributions of identified particles, such as the $\Lambda$ baryon which carries both strangeness and baryon number and is thus of particular interest. We present the first measurement of net-$\Lambda$ fluctuations in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV as a function of centrality and the pseudorapidity acceptance of the measurement. The results are compared to expectations of the effects of global baryon number conservation as well as to predictions from the HIJING Monte Carlo event generator. In this analysis the Identity Method is applied in a novel way to account for the combinatoric background in the invariant mass distribution.

   nucl-exhep-exNPA(2019)·4 citations
5. 05*

   Ridges in p-A (and pp) collisions

   Alice Ohlson🇨🇭

   Correlations between particles separated by several units of pseudorapidity were discovered in high-multiplicity pp and p-Pb collisions at the LHC. These long-range structures observed in two-particle correlation functions are reminiscent of features seen in Pb-Pb collisions, where they are often viewed as a signature of collective behavior and the formation of a quark-gluon plasma (QGP). Therefore, the discovery of these `ridges' in small systems has implications for the study of collectivity in small systems as well as in heavy-ion collisions. The ridges in pp and p-Pb collisions have been studied in the ALICE, ATLAS, CMS, and LHCb experiments to characterize the $p_{\mathrm{T}}$-, $\eta$-, and multiplicity-dependences of the ridge yield, as well as its particle composition.

   nucl-exhep-ex3 citations
6. 06*

   Collision Energy Dependence of $p_{\mathrm{t}}$ Correlations in Au+Au Collisions at RHIC

   STAR Collaboration: J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson · R. Aoyama · A. Aparin · D. Arkhipkin and 330 other authors

   We present two-particle $p_{\mathrm{t}}$ correlations as a function of event centrality for Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV at the Relativistic Heavy Ion Collider using the STAR detector. These results are compared to previous measurements from CERES at the Super Proton Synchrotron and from ALICE at the Large Hadron Collider. The data are compared with UrQMD model calculations and with a model based on a Boltzmann-Langevin approach incorporating effects from thermalization. The relative dynamical correlations for Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV show a power law dependence on the number of participant nucleons and agree with the results for Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$ from ALICE. As the collision energy is lowered from $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV to 7.7 GeV, the centrality dependence of the relative dynamical correlations departs from the power law behavior observed at the higher collision energies. In central collisions, the relative dynamical correlations increase with collision energy up to $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV in contrast to previous measurements that showed little dependence on the collision energy.

   nucl-exPRC(2019)·50 citations
7. 07*

   R-matrix method and the nonlocal nucleon optical potential

   Doan Thi Loan🇻🇳 · Nguyen Hoang Phuc🇻🇳 · Dao T. Khoa🇻🇳

   The calculable R-matrix method is applied to solve the Schrödinger equation in the optical model (OM) analysis of the elastic nucleon-nucleus scattering using a nonlocal nucleon optical potential (OP). The phenomenological nonlocal nucleon OP proposed by Perey and Buck (PB), and the two recent versions of the PB parametrization were used in the present OM study of the elastic nucleon scattering on ${}^{27}$Al, ${}^{40}$Ca, ${}^{48}$Ca, ${}^{90}$Zr, and ${}^{208}$Pb targets at different energies. The comparison of the OM results given by the calculable $R$-matrix method with those given by other methods confirms that the calculable $R$-matrix method is an efficient tool for the OM study of the elastic nucleon-nucleus scattering using a nonlocal nucleon OP.

   ↳ nucl-thnucl-exCommun.in Phys.(2018)·3 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.