Fri·Aug 5, 2016Friday·August 5, 2016

1. 01*

   Effects of Longitudinal Asymmetry in Heavy-Ion Collisions

   Rashmi Raniwala (University of Rajasthan)🇮🇳 · Sudhir Raniwala (University of Rajasthan)🇮🇳 · Constantin Loizides (LBNL)🇺🇸

   In collisions of identical nuclei at a given impact parameter, the number of nucleons participating in the overlap region of each nucleus can be unequal due to nuclear density fluctuations. The asymmetry due to the unequal number of participating nucleons, referred to as longitudinal asymmetry, causes a shift in the center of mass rapidity of the participant zone. The information of the event asymmetry allows us to isolate and study the effect of longitudinal asymmetry on rapidity distribution of final state particles. In a Monte Carlo Glauber model the average rapidity-shift is found to be almost linearly related to the asymmetry. Using toy models, as well as Monte Carlo data for Pb-Pb collisions at 2.76 TeV generated with HIJING, two different versions of AMPT and DPMJET models, we demonstrate that the effect of asymmetry on final state rapidity distribution can be quantitatively related to the average rapidity shift via a third-order polynomial with a dominantly linear term. The coefficients of the polynomial are proportional to the rapidity shift with the dependence being sensitive to the details of the rapidity distribution.Experimental estimates of the spectator asymmetry through the measurement of spectator nucleons in a Zero Degree Calorimeter may hence be used to further constrain the initial conditions in ultra-relativistic heavy-ion collisions.

   nucl-exnucl-thPRC(2018)·11 citations
2. 02*

   Study of the pd(dp) -> 3He pi pi reactions close to threshold

   F. Bellemann · A. Berg🇺🇸 · J. Bisplinghoff🇩🇪 · G. Bohlscheid · J. Ernst · C. Henrich · F. Hinterberger🇩🇪 · R. Ibald · R. Jahn🇩🇪 · R. Joosten🇩🇪 · K. Kilian🇩🇪 · A. Kozela🇵🇱 and 10 other authors

   New experimental data on the pd -> 3He pi+ pi- reaction obtained with the COSY-MOMO detector below the three-pion threshold are presented. The reaction was also studied in inverse kinematics with a deuteron beam and the higher counting rates achieved were especially important at low excess energies. The comparison of these data with inclusive pd -> 3He+X rates allowed estimates also to be made of pi0 pi0 production. The results confirm our earlier findings that close to threshold there is no enhancement at low excitation energies in the pi+ pi- system, where the data seem largely suppressed compared to phase space. Possible explanations for this behavior, such as strong p- waves in the pi+pi- -system or the influence of two-step processes, are explored.

   nucl-exnucl-thPRC(2016)·1 citation
3. 03*

   News from strong interactions program of the NA61/SHINE experiment

   Katarzyna Grebieszkow (for the NA61/SHINE Collaboration)🇵🇱

   The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. This is performed by a two dimensional phase diagram ($T-{\mu }_B$) scan of measurements of particle spectra and fluctuations in proton-proton, proton-nucleus and nucleus-nucleus interactions as a function of collision energy and system size. In this contribution new NA61/SHINE results on negative pion production, as well as transverse momentum and multiplicity fluctuations in Ar+Sc collisions are presented. Moreover, the latest results on higher order moments of net-charge multiplicity distribution in p+p collisions are also discussed. The Ar+Sc results are compared to NA61 p+p and Be+Be data, as well as to NA49 $A+A$ results.

   nucl-exhep-exActa Phys.Polon.Supp.(2017)·4 citations
4. 04*

   Probing Gluon Helicity with Dijets from $\sqrt{s}$ = 510 GeV Polarized Proton Collisions at STAR

   Suvarna Ramachandran🇺🇸

   The production of jets in polarized proton collisions at STAR is dominated by quark-gluon and gluon-gluon scattering processes. The dijet longitudinal double-spin asymmetry $(A_{LL})$ is sensitive to the helicity distributions and may be used to extract information about the gluon helicity contribution $\Delta g(x,Q^2)$ to the spin of the proton. Previous STAR jet measurements at $\sqrt{s}$ = 200 GeV show evidence of polarized gluons for gluon momentum fractions above 0.05. The measurement of dijet $A_{LL}$ at $\sqrt{s}$ = 510 GeV will extend the current constraints on $\Delta g(x,Q^2)$ to lower gluon momentum fractions and allow for the reconstruction of the partonic kinematics at leading order. These proceedings present preliminary results from the dijet $A_{LL}$ measurement from $\sim 50p{b}^{-1}$ of $\sim 50\%$ polarized proton data taken during the 2012 RHIC run.

   ↳ hep-exnucl-exPoS(2016)·4 citations
5. 05*

   Photoproduction of the scalar mesons $f_0(500)$ and $f_0(980)$ off the nucleon

   Je-Hee Lee🇰🇷 · Hyun-Chul Kim🇰🇷 · Sang-Ho Kim🇰🇷 · Hui-Young Ryu🇰🇷 · Byung-Geel Yu🇰🇷

   We investigate photoproduction of the scalar mesona off the nucleon, using the effective Lagrangians and the Regge approach. We first study $f_0(980)$ photoproduction, replacing the Feynman propagator with the Regge ones for the $\rho$-meson exchange in the $t$-channel. The model parameters are fixed by reproducing the experimental data on the differential cross section. We then apply the same method to $f_0(500)$ or $\sigma$ photoproduction with the same parameters for the Regge propagator. Since the threshold energy of the $f_0(500)$ production is rather low, $N^{\ast }$ resonances, which can decay into the nucleon and two pions in the isoscalar and scalar state, can come into play in the $s$-channel. To examine the effects of the $N^{\ast }$ resonances, we set up two models to look into the respective contribution of the $N^{\ast }$ resonances. We find that in particular $N^{\ast }(1440)$ and $N^{\ast }(1680)$ play important roles in $f_0(500)$ photoproduction. We discuss the physical implications of the present results.

   ↳ hep-phhep-exnucl-exnucl-thPTEP(2017)·5 citations
6. 06*

   The detector calibration system for the CUORE cryogenic bolometer array

   J. S. Cushman🇺🇸 · A. Dally🇺🇸 · C. J. Davis🇺🇸 · L. Ejzak🇺🇸 · D. Lenz🇺🇸 · K. E. Lim🇺🇸 · K. M. Heeger🇺🇸 · R. H. Maruyama🇺🇸 · A. Nucciotti🇮🇹 · S. Sangiorgio🇺🇸 · T. Wise🇺🇸

   The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton-scale cryogenic experiment designed to search for neutrinoless double-beta decay of ${}^{130}$Te and other rare events. The CUORE detector consists of 988 TeO${}_2$ bolometers operated underground at 10 mK in a dilution refrigerator at the Laboratori Nazionali del Gran Sasso. Candidate events are identified through a precise measurement of their energy. The absolute energy response of the detectors is established by the regular calibration of each individual bolometer using gamma sources. The close-packed configuration of the CUORE bolometer array combined with the extensive shielding surrounding the detectors requires the placement of calibration sources within the array itself. The CUORE Detector Calibration System is designed to insert radioactive sources into and remove them from the cryostat while respecting the stringent heat load, radiopurity, and operational requirements of the experiment. This paper describes the design, commissioning, and performance of this novel source calibration deployment system for ultra-low-temperature environments.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2017)·25 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.