Fri·Jan 1, 2016Friday·January 1, 2016

1. 01*

   Indications for a critical point in the phase diagram for hot and dense nuclear matter

   Roy A. Lacey (Depts. of Chemistry and Physics, Stony Brook University)🇺🇸

   Two-pion interferometry measurements are studied for a broad range of collision centralities in Au+Au (Root_s = 7.7 - 200 GeV) and Pb+Pb (Root_s = 2.76 TeV) collisions. They indicate non-monotonic excitation functions for the Gaussian emission source radii difference [(R_out)^2 - (R_side)^2], suggestive of reaction trajectories which spend a fair amount of time near a "soft point" in the equation of state (EOS) that coincides with the critical end point (CEP). A Finite-Size Scaling (FSS) analysis of these excitation functions, provides further validation tests for the CEP. It also indicates a second order phase transition at the CEP, and the values T^{cep} ~ 165 MeV and mu_B^{cep} ~ 95 MeV for its location in the (T, mu_B)-plane of the phase diagram. The static critical exponents (nu ~ 0.66 and gamma ~ 1.2) extracted via the same FSS analysis, place this CEP in the 3D Ising model universality class. A Dynamic Finite-Size Scaling analysis of the excitation functions, gives the estimate z ~ 0.87 for the dynamic critical exponent, suggesting that the associated critical expansion dynamics is dominated by the hydrodynamic sound mode.

   nucl-exhep-exnucl-thNPA(2016)·14 citations
2. 02*

   Study of the bulk properties of the system formed in Au+Au collisions at $\sqrt{s_{NN}}$ = 14.5 GeV using the STAR detector at RHIC

   Vipul Bairathi (STAR collaboration)🇮🇳

   We present the first measurements of the transverse momentum spectra and azimuthal anisotropy of the identified hadrons (${\pi }^{+}$, ${\pi }^{-}$, $K^{+}$, $K^{-}$, $p(\bar{p})$, $K_s^0$, $\Lambda (\bar{\Lambda })$ and $\varphi$) at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}$ = 14.5 GeV for various collision centralities. These measurements are compared to corresponding results from other BES energies. The bulk properties of the system, like the chemical and kinetic freeze-out conditions and the collectivity extracted from the measured yields of the produced particles are presented. The difference between baryon and anti-baryon elliptic flow for minimum bias collisions previously reported by STAR is also observed in the new data taken at $\sqrt{s_{NN}}$ = 14.5 GeV. Furthermore, the new data at 14.5 GeV are consistent with the trend established by the results at lower and higher beam energies. The energy and centrality dependence of the baryon chemical potential (${\mu }_B$), radial flow velocity ($⟨\beta ⟩$), and chemical and kinetic freeze-out temperatures are discussed systematically.

   nucl-exhep-exNPA(2016)·9 citations
3. 03*

   Exploring the QCD Phase Structure with Beam Energy Scan in Heavy-ion Collisions

   Xiaofeng Luo🇨🇳

   Beam energy scan programs in heavy-ion collisions aim to explore the QCD phase structure at high baryon density. Sensitive observables are applied to probe the signatures of the QCD phase transition and critical point in heavy-ion collisions at RHIC and SPS. Intriguing structures, such as dip, peak and oscillation, have been observed in the energy dependence of various observables. In this paper, an overview is given and corresponding physics implications will be discussed for the experimental highlights from the beam energy scan programs at the STAR, PHENIX and NA61/SHINE experiments. Furthermore, the beam energy scan phase II at RHIC (2019-2020) and other future experimental facilities for studying the physics at low energies will be also discussed.

   nucl-exhep-exhep-latnucl-thNPA(2016)·147 citations
4. 04*

   Centrality and pseudorapidity dependence of the transverse energy flow in pPb collisions at sqrt(s_NN) = 5.02 TeV

   Christopher Bruner🇺🇸 · Michael Murray (for the CMS Collaboration)🇺🇸

   The almost hermetic coverage of CMS is used to measure the distribution of transverse energy as a function of pseudo-rapidity for pPb collisions at $\sqrt{s_{NN}}=5.02$ TeV. For minimum bias collisions $(1/N)d{E}_T/d\eta$ reaches 23 GeV which implies an $E_T$ per participant pair comparable to that of peripheral PbPb collisions at $\sqrt{s_{NN}}=2.76$ TeV. The centrality dependence of transverse energy production has been studied using centrality measures defined in three different angular regions. There is a strong auto-correlation between $(1/N)d{E}_T/d\eta$ and the $\eta$ range used to define centrality %both for data and the EPOS-LHC and HIJING event generators. The centrality dependence of the data is much stronger for $\eta$ values on the lead side than the proton side and shows significant differences from that predicted by either event generator.

   nucl-exNPA(2016)·1 citation
5. 05*

   PHENIX results on fluctuations and Bose-Einstein correlations in Au+Au collisions from the RHIC Beam Energy Scan

   Prakhar Garg (PHENIX Collaboration)🇮🇳

   The RHIC Beam Energy Scan focuses on mapping the QCD phase diagram and pinpointing the location of a possible critical end point. Bose-Einstein correlations and event-by-event fluctuations of conserved quantities, measured as a function of centrality and collision energy, are promising tools in these studies. Recent lattice QCD and statistical thermal model calculations predict that higher-order cumulants of the fluctuations are sensitive indicators of the phase transition. Products of these cumulants can be used to extract the freeze-out parameters (1) and to locate the critical point (2). Two-pion interferometry measurements are predicted to be sensitive to potential softening of the equation of state and prolonged emission duration close to the critical point (3). We present recent PHENIX results on fluctuations of net-charge using high-order cumulants and their products in Au+Au collisions at \sqsn = 7.7 - 200 GeV, and measurement of two-pion correlation functions and emission-source radii in Cu+Cu and Au+Au collisions at several beam energies. The extracted source radii are compared to previous measurements at RHIC and LHC in order to study energy dependence of the specific quantities sensitive to expansion velocity and emission duration. Implications for the search of a critical point and baryon chemical potentials at various collision energies are discussed.

   nucl-exNPA(2016)·1 citation
6. 06*

   Overview of recent results from the STAR experiment

   Mustafa Mustafa (STAR Collaboration)🇺🇸

   The Solenoidal Tracker at RHIC (STAR) experiment utilizes its excellent mid-rapidity tracking and particle identification capabilities to study the emergent properties of Quantum Chromodynamics (QCD). The STAR heavy-ion program at vanishingly small baryon density is aimed to address questions about the quantitative properties of the strongly-interacting Quark Gluon Plasma (QGP) matter created in high energy collisions ($\eta /s$, $\hat{q}$, chirality, transport parameters, heavy quark diffusion coefficients ...). At finite baryon density, the questions concern the phases of nuclear matter (the QCD phase diagram) and the nature of the phase transition, namely: what is the onset collision energy for the formation of QGP? What is the nature of phase transition in heavy-ion collisions? Are there two phase transition regions? If yes, where is the critical point situated? At Quark Matter 2015, the STAR collaboration has presented a wealth of new experimental results which address these questions. In these proceedings I highlight a few of those results.

   nucl-exNPA(2016)·7 citations
7. 07*

   Two-photon exchange correction to muon-proton elastic scattering at low momentum transfer

   O. Tomalak🇩🇪 · M. Vanderhaeghen (JGU Mainz)🇩🇪

   We evaluate the two-photon exchange (TPE) correction to the muon-proton elastic scattering at small momentum transfer. Besides the elastic (nucleon) intermediate state contribution, which is calculated exactly, we account for the inelastic intermediate states by expressing the TPE process approximately through the forward doubly virtual Compton scattering. The input in our evaluation is given by the unpolarized proton structure functions and by one subtraction function. For the latter, we provide an explicit evaluation based on a Regge fit of high-energy proton structure function data. It is found that, for the kinematics of the forthcoming muon-proton elastic scattering data of the MUSE experiment, the elastic TPE contribution dominates, and the size of the inelastic TPE contributions is within the anticipated error of the forthcoming data.

   ↳ hep-phnucl-exnucl-thEPJC(2016)·48 citations
8. 08*

   Devices for high precision x-ray beam intensity monitoring on BSRF

   LI Hua-Peng · Kun Tang · Yi-Dong Zhao · Lei Zheng · Shu-Hu Liu · Xiao-Liang Zhao · Ya-Shuai Zhao🇨🇳

   Synchrotron radiation with the characteristic of high brilliance, high level of polarization, high collimation, low emittance and wide tunability in energy has been used as a standard source in metrology(1, 2). For a decade, lots of calibration work have been done on 4B7A in Beijing Synchrotron Radiation Facility (BSRF) (3, 4). For the calibration process, a high-precision online monitor is indispensable. To control the uncertainty under 0.1%, we studied different sizes parallel ion chambers with rare-gas and used different collecting methods to monitor the x-ray intensity of the beamline. Two methods to collect the signal of the ion chambers: reading the current directly with electrometer or signal amplification to collect the counts were compared.

   ↳ physics.ins-detnucl-ex0 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.