Fri·Apr 21, 2017Friday·April 21, 2017

1. 01*

   Production of identified and unidentified charged hadrons in Pb--Pb collisions at \sqrt{s_{\rm NN}}~5.02~TeV

   Nicolò Jacazio (for the ALICE Collaboration)🇮🇹

   In late 2015, the ALICE collaboration recorded data from Pb--Pb collisions at the unprecedented energy of \sqrt{s_{\rm NN}}~5.02~TeV. The transverse-momentum ($p_{\mathrm{T}}$) spectra of pions, kaons and protons are presented. The evolution of the particle ratios as a function of collision energy and centrality is discussed. The ratio between $p_{\mathrm{T}}$-integrated particle yields are measured and compared to different collision energies as well as smaller collision systems. For the study of energy loss mechanisms in the QCD medium at high transverse momenta, the nuclear modification factors ($R_{AA}$) are computed and compared with results obtained at lower energy.

   nucl-exNPA(2017)·23 citations
2. 02*

   Measurements of charmonium production in p$+$p, p$+$Au, and Au$+$Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$~=~200~GeV with the STAR experiment

   Takahito Todoroki (for the STAR Collaboration)🇺🇸

   We present the first results from the STAR MTD of mid-rapidity charmonium measurements via the di-muon decay channel in p$+$p, p$+$Au, and Au$+$Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$~GeV at RHIC. The inclusive $J/\psi$ production cross section in p$+$p collisions can be described by the Non-Relativistic QCD (NRQCD) formalism coupled with the color glass condensate effective theory (CGC) at low transverse momentum ($p_T$) and next-to-leading order NRQCD at high $p_T$. The nuclear modification factor in p$+$Au collisions for inclusive $J/\psi$ is below unity at low $p_T$ and consistent with unity at high $p_T$, which can be described by calculations including both nuclear PDF and nuclear absorption effects. The double ratio of inclusive $J/\psi$ and $\psi (2S)$ production rates for $0<p_T<10$~GeV/$c$ at mid-rapidity between p$+$p and p$+$Au collisions is measured to be 1.37~$\pm$~0.42~$\pm$~0.19. The nuclear modification factor in Au$+$Au collisions for inclusive $J/\psi$ shows significant $J/\psi$ suppression at high $p_T$ in central collisions and can be qualitatively described by transport models including dissociation and regeneration contributions.

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

   Extraction of the Neutron Electric Form Factor from Measurements of Inclusive Double Spin Asymmetries

   V. Sulkosky🇺🇸 · G. Jin🇺🇸 · E. Long🇺🇸 · Y. W. Zhang🇺🇸 · M. Mihovilovic🇸🇮 · A. Kelleher🇺🇸 · B. Anderson🇺🇸 · D.W. Higinbotham🇺🇸 · S. Sirca🇸🇮 · K. Allada🇺🇸 · J.R.M. Annand🇬🇧 · T. Averett🇺🇸 and 80 other authors

   $[Background]$ Measurements of the neutron charge form factor, $G_E^n$, are challenging due to the fact that the neutron has no net charge. In addition, measurements of the neutron form factors must use nuclear targets which require accurately accounting for nuclear effects. Extracting $G_E^n$ with different targets and techniques provides an important test of our handling of these effects. $[Purpose]$ The goal of the measurement was to use an inclusive asymmetry measurement technique to extract the neutron charge form factor at a four-momentum transfer of $1(GeV/c{)}^2$. This technique has very different systematic uncertainties than traditional exclusive measurements and thus serves as an independent check of whether nuclear effects have been taken into account correctly. $[Method]$ The inclusive quasi-elastic reaction ${}^3\overrightarrow{\mathrm{He}}(\overrightarrow{e},e^{\prime })$ was measured at Jefferson Lab. The neutron electric form factor, $G_E^n$, was extracted at $Q^2=0.98(GeV/c{)}^2$ from ratios of electron-polarization asymmetries measured for two orthogonal target spin orientations. This $Q^2$ is high enough that the sensitivity to $G_E^n$ is not overwhelmed by the neutron magnetic contribution, and yet low enough that explicit neutron detection is not required to suppress pion production. $[Results]$ The neutron electric form factor, $G_E^n$, was determined to be $0.0414\pm 0.0077(stat)\pm 0.0022(syst)$; providing the first high precision inclusive extraction of the neutron's charge form factor. $[Conclusions]$ The use of the inclusive quasi-elastic ${}^3\overrightarrow{\mathrm{He}}(\overrightarrow{e},e^{\prime })$ with a four-momentum transfer near $1(GeV/c{)}^2$ has been used to provide a unique measurement of $G_E^n$. This new result provides a systematically independent validation of the exclusive extraction technique results.

   nucl-exPRC(2017)·12 citations
4. 04*

   Physics with ions at the Future Circular Collider

   David d'Enterria🇨🇭 · L. Apolinario🇵🇹 · N. Armesto🇪🇸 · A. Dainese🇮🇹 · J. Jowett🇨🇭 · J.P. Lansberg🇫🇷 · S. Masciocchi🇩🇪 · G. Milhano🇨🇭 · C. Roland🇨🇭 · C.A. Salgado🇪🇸 · M. Schaumann🇨🇭 · M. van Leeuwen🇨🇭 · U.A. Wiedemann🇨🇭

   The unique physics opportunities accessible with nuclear collisions at the CERN Future Circular Collider (FCC) are summarized. Lead-lead (PbPb) and proton-lead (pPb) collisions at $\sqrt{s_{NN}}$ = 39 and 63 TeV respectively with ${\mathcal{L}}_{int}$ = 33 nb${}^{-1}$ and 8 pb${}^{-1}$ monthly integrated luminosities, will provide unprecedented experimental conditions to study quark-gluon matter at temperatures $\mathcal{O}$(1 GeV). The following topics are succinctly discussed: (i) charm-quark densities thrice larger than at the LHC, leading to direct heavy-quark impact in the bulk QGP properties, (ii) quarkonia, including ${\rm Y}(1S)$, melting at temperatures up to five times above the QCD critical temperature, (iii) access to initial-state nuclear parton distributions (nPDF) at fractional momenta as low as $x\approx 10^{-7}$, (iv) availability of $5\cdot 10^5$ top-quark pairs per run to study the high-$x$ gluon nPDF and the energy loss properties of boosted colour-antennas, (v) study of possible Higgs boson suppression in the QGP, and (vi) high-luminosity $\gamma \gamma$ (ultraperipheral) collisions at c.m. energies up to 1 TeV.

   ↳ hep-exhep-phnucl-exnucl-thNPA(2017)·10 citations
5. 05*

   The QCD Equation of state and critical end-point estimates at $\mathcal{O}({\mu }_B^6)$

   Sayantan Sharma · for Bielefeld-BNL-CCNU collaboration

   We present results for the QCD Equation of State at non-zero chemical potentials corresponding to the conserved charges in QCD using Taylor expansion upto sixth order in the baryon number, electric charge and strangeness chemical potentials. The latter two are constrained by the strangeness neutrality and a fixed electric charge to baryon number ratio. In our calculations, we use the Highly Improved Staggered Quarks (HISQ) discretization scheme at physical quark masses and at different values of the lattice spacings to control lattice cut-off effects. Furthermore we calculate the pressure along lines of constant energy density, which serve as proxies for the freeze-out conditions and discuss their dependence on ${\mu }_B$ , which is necessary for hydrodynamic modelling near freezeout. We also provide an estimate of the radius of convergence of the Taylor series from the 6th order coefficients which provides a new constraint on the location of the critical end-point in the T-${\mu }_B$ plane of the QCD phase diagram.

   ↳ hep-lathep-phnucl-exnucl-thNPA(2017)·9 citations
6. 06*

   Nuclear final-state interactions in deep inelastic scattering off the lightest nuclei

   W. Cosyn🇧🇪 · M. Sargsian🇺🇸

   We review recent progress in studies of nuclear final-state interactions in deep inelastic scattering (DIS) off the lightest nuclei tagged by a recoil nucleon. These processes hold a lot of potential for resolving the outstanding issues related to the dynamics of hadronization in QCD. Within the minimal Fock component framework, valid at large Bjorken $x$, the main features of the theoretical approach based on the virtual nucleon approximation are elaborated. In this approach, the strong final-state interaction of the DIS products with the nuclear fragments is described by an effective eikonal amplitude, whose parameters can be extracted from the analysis of semi-inclusive DIS off the deuteron target. The extraction of the $Q^2$ and $W$ mass dependences of these parameters gives a new observable in studying the QCD structure of DIS final states. Another important feature of tagged DIS off the lightest nuclei is the possibility of performing pole extrapolation with a high degree of accuracy. Such extrapolation allows an extraction of the neutron structure function in a model independent way due to suppression of the final-state interaction in the on-shell limit of the struck nucleon propagator. We review the first application of the pole extrapolation to recent experimental data. Finally, we outline the extension of the framework to inclusive DIS, including a polarized deuteron target as well as its application to the tagged DIS reactions for future experiments at fixed target and collider energies.

   ↳ nucl-thhep-phnucl-exIJMPE(2017)·18 citations
7. 07*

   Calibration of the Space-borne Compton Polarimeter POLAR flight model with 100% polarized X-ray beams

   H.L. Xiao · W. Hajdas🇨🇭 · P. Socha · R. Marcinkowski · B.B. Wu🇨🇳 · T.W. Bao · J.Y. Chai🇮🇹 · Y.W. Dong🇨🇳 · M.N. Kong · L. Li🇺🇸 · Z.H. Li · J.T. Liu and 23 other authors

   POLAR is space-borne detector designed for a precise measurement of gamma-ray polarization of the prompt emissions of Gamma-Ray Bursts in the energy range 50 keV - 500 keV. POLAR is a compact Compton polarimeter consisting of 40$\times$ 40 plastic scintillator bars read out by 25 multi-anode PMTs. In May 2015, we performed a series of tests of the POLAR flight model with 100\% polarized x-rays beams at the European Synchrotron Radiation Facility beam-line ID11 aming to study thresholds, crosstalk between channels and responses of POLAR flight model to polarized X-ray beams. In this paper we present the data analysis method and some analysis results. According the results, POLAR FM has good polarimetric capabilities.

   ↳ physics.ins-detastro-ph.IMnucl-ex1 citation
8. 08*

   Azimuthally differential pion femtoscopy relative to the second and third harmonic in Pb-Pb 2.76 TeV collision from ALICE

   Mohammad Saleh (for the ALICE Collaboration)🇺🇸

   Azimuthally differential femtoscopic measurements, being sensitive to spatio-temporal characteristics of the source as well as to the collective velocity fields at freeze-out, provide very important information on the nature and dynamics of the system evolution. While the HBT radii modulations relative to the second harmonic event plane reflect mostly the spatial geometry of the source, the third harmonic results are mostly defined by the velocity fields. Radii variations with respect to the third harmonic event plane unambiguously signal a collective expansion and anisotropy in the flow fields. Event shape engineering (ESE) is a technique proposed to select events corresponding to a particular shape. Azimuthally differential HBT combined with ESE allows for a detailed analysis of the relation between initial geometry, anisotropic flow and the deformation of source shape. We present azimuthally differential pion femtoscopy with respect to second and third harmonic event planes as a function of the pion transverse momentum for different collision centralities in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV. All these results are compared to existing models. The effects of the selection of the events with high elliptic or triangular flow are also presented.

   ↳ hep-exnucl-exNPA(2017)·2 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.