Tue·Sep 20, 2016Tuesday·September 20, 2016

1. 01*

   Measurement of inclusive jet cross sections in pp and PbPb collisions at sqrt(s[NN]) = 2.76 TeV

   CMS Collaboration

   Inclusive jet spectra from pp and PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV, collected with the CMS detector at the LHC, are presented. Jets are reconstructed with three different distance parameters (R = 0.2, 0.3, and 0.4) for transverse momentum (pT) greater than 70 GeV and pseudorapidity abs(eta) < 2. Next-to-leading-order quantum chromodynamic calculations with non-perturbative corrections are found to over-predict jet production cross sections in pp for small distance parameters. The jet nuclear modification factors for PbPb compared to pp collisions, show a steady decrease from peripheral to central events, along with a weak dependence on the jet pT. They are found to be independent of the distance parameter in the measured kinematic range.

   nucl-exhep-exPRC(2017)·235 citations
2. 02*

   Recent Heavy Flavor Results Utilizing the FVTX in PHENIX at RHIC

   Xuan Li (for the PHENIX Collaboration)🇺🇸

   Heavy flavor and quarkona production are important hard probes to test the Quantum Chromodynamics (QCD) and measure the properties of the Quark Gluon Plasma (QGP) created in high energy heavy ion collisions. The new PHENIX mid- and forward-rapidity silicon vertex detectors provide precise Distance of Closest Approach (DCA) determination, allowing charm and bottom yields identification, and improve di-muon mass resolution for charmonia studies. The relative $\psi (2S)$ over $J/\psi$(1S) yields measured in $p$+$p$, $p$+Al and $p$+Au data at $\sqrt{s}=$200 GeV help us to understand final state effects on the charmonia production. Direct access to B-meson production has been enabled via measurements of non-prompt $J/\psi \to {\mu }^{+}+{\mu }^{-}$ in $p$+$p$ collisions at $\sqrt{s}=510$ GeV and Cu+Au collisions at $\sqrt{s}=200$ GeV. The fraction of B-meson decays in J/$\psi$ yields in the $p$+$p$ measurement agrees with higher energy results from Tevatron and LHC. This fraction is enhanced in Cu+Au collisions suggesting the B-meson yield is not modified by the medium whereas J/$\psi$ is strongly suppressed.

   nucl-exhep-exJ.Phys.Conf.Ser.(2017)·1 citation
3. 03*

   Experimental results on chiral magnetic and vortical effects

   Gang Wang🇺🇸 · Liwen Wen🇺🇸

   Various novel transport phenomena in chiral systems result from the interplay of quantum anomalies with magnetic field and vorticity in high-energy heavy-ion collisions, and could survive the expansion of the fireball and be detected in experiments. Among them are the chiral magnetic effect, the chiral vortical effect and the chiral magnetic wave, the experimental searches for which have aroused extensive interest. The goal of this review is to describe the current status of experimental studies at Relativistic Heavy Ion Collider at BNL and the Large Hadron Collider at CERN, and to outline the future work in experiment needed to eliminate the existing uncertainties in the interpretation of the data.

   nucl-exhep-exAdv.High Energy Phys.(2017)·6 citations
4. 04*

   Experimental study of the astrophysical gamma-process reaction 124Xe(alpha,gamma)128Ba

   Z. Halász🇭🇺 · E. Somorjai🇭🇺 · Gy. Gyürky🇭🇺 · Z. Elekes🇭🇺 · Zs. Fülöp🇭🇺 · T. Szücs🇩🇪 · G.G. Kiss🇭🇺 · N. Szegedi · T. Rauscher🇬🇧 · J. Görres🇺🇸 · M. Wiescher🇺🇸

   The synthesis of heavy, proton rich isotopes in the astrophysical gamma-process proceeds through photodisintegration reactions. For the improved understanding of the process, the rates of the involved nuclear reactions must be known. The reaction 128Ba(g,a)124Xe was found to affect the abundance of the p nucleus 124Xe. Since the stellar rate for this reaction cannot be determined by a measurement directly, the aim of the present work was to measure the cross section of the inverse 124Xe(a,g)128Ba reaction and to compare the results with statistical model predictions. Of great importance is the fact that data below the (a,n) threshold was obtained. Studying simultaneously the 124Xe(a,n)127Ba reaction channel at higher energy allowed to further identify the source of a discrepancy between data and prediction. The 124Xe + alpha cross sections were measured with the activation method using a thin window 124Xe gas cell. The studied energy range was between E = 11 and 15 MeV close above the astrophysically relevant energy range. The obtained cross sections are compared with statistical model calculations. The experimental cross sections are smaller than standard predictions previously used in astrophysical calculations. As dominating source of the difference, the theoretical alpha width was identified. The experimental data suggest an alpha width lower by at least a factor of 0.125 in the astrophysical energy range. An upper limit for the 128Ba(g,a)124Xe stellar rate was inferred from our measurement. The impact of this rate was studied in two different models for core-collapse supernova explosions of 25 solar mass stars. A significant contribution to the 124Xe abundance via this reaction path would only be possible when the rate was increased above the previous standard value. Since the experimental data rule this out, they also demonstrate the closure of this production path.

   nucl-exastro-ph.SRPRC(2024)·14 citations
5. 05*

   Nuclear modification factor of charged particles and light-flavour hadrons in p--Pb collisions measured by ALICE

   Gyula Bencedi (for the ALICE Collaboration)🇲🇽

   The hot and dense strongly interacting Quark-Gluon Plasma (sQGP) created in ultra-relativistic heavy-ion collisions can be probed by studying high-$p_{\mathrm{T}}$ particle production and parton energy loss. Similar measurements performed in p-Pb collisions may help in determining whether initial or final state nuclear effects play a role in the observed suppression of hadron production at high-$p_{\mathrm{T}}$ in Pb--Pb collisions. By examining the nuclear modification factors through the comparison of identified hadron yields in different collision systems one can gain insight into particle production mechanisms and nuclear effects.

   nucl-ex7 citations
6. 06*

   Cumulants and nonlinear response of high $p_T$ harmonic flow at $\sqrt{s_{NN}}=5.02$ TeV

   Jacquelyn Noronha-Hostler🇺🇸 · Barbara Betz🇩🇪 · Miklos Gyulassy🇺🇸 · Matthew Luzum🇧🇷 · Jorge Noronha🇧🇷 · Israel Portillo🇺🇸 · Claudia Ratti🇺🇸

   Event-by-event fluctuations caused by quantum mechanical fluctuations in the wave function of colliding nuclei in ultrarelativistic heavy ion collisions were recently shown to be necessary for the simultaneous description of $R_{AA}$ as well as the elliptic and triangular flow harmonics at high $p_T$ in PbPb collisions at the Large Hadron Collider. In fact, the presence of a finite triangular flow as well as cumulants of the flow harmonic distribution that differ from the mean are only possible when these event-by-event fluctuations are considered. In this paper we combine event-by-event viscous hydrodynamics and jet quenching to make predictions for high $p_T$ $R_{AA}$, $v_2\{2\}$, $v_3\{2\}$, and $v_2\{4\}$ in PbPb collisions at $\sqrt{s_{NN}}=5.02$ TeV. With an order of magnitude larger statistics we find that high $p_T$ elliptic flow does not scale linearly with the soft elliptical flow, as originally thought, but has deviations from perfectly linear scaling. A new experimental observable, which involves the difference between the ratio of harmonic flow cumulants at high and low $p_T$, is proposed to investigate the fluctuations of high $p_T$ flow harmonics and measure this nonlinear response. By varying the path length dependence of the energy loss and the viscosity of the evolving medium we find that $R_{AA}(p_T)$ and $v_2\{2\}(p_T)$ strongly depend on the choice for the path length dependence of the energy loss, which can be constrained using the new LHC run 2 data.

   ↳ nucl-thhep-phnucl-exPRC(2017)·86 citations
7. 07*

   The novel properties of SF${}_6$ for directional dark matter experiments

   N. S. Phan🇺🇸 · R. Lafler🇺🇸 · R. J. Lauer🇺🇸 · E. R. Lee🇺🇸 · D. Loomba🇺🇸 · J. A. J. Matthews🇺🇸 · E. H. Miller🇺🇸

   SF${}_6$ is an inert and electronegative gas that has a long history of use in high voltage insulation and numerous other industrial applications. Although SF${}_6$ is used as a trace component to introduce stability in tracking chambers, its highly electronegative properties have limited its use in tracking detectors. In this work we present a series of measurements with SF${}_6$ as the primary gas in a low pressure Time Projection Chamber (TPC), with a thick GEM used as the avalanche and readout device. The first results of an ${}^{55}$Fe energy spectrum in SF${}_6$ are presented. Measurements of the mobility and longitudinal diffusion confirm the negative ion drift of SF${}_6$. However, the observed waveforms have a peculiar but interesting structure that indicates multiple drift species and a dependence on the reduced field ($E/p$), as well as on the level of water vapor contamination. The discovery of a distinct secondary peak in the waveform, together with its identification and use for fiducializing events in the TPC, are also presented. Our measurements demonstrate that SF${}_6$ is an ideal gas for directional dark matter detection. In particular, the high fluorine content is desirable for spin-dependent sensitivity, negative ion drift ensures low diffusion over large drift distances, and the multiple species of charge carriers allow for full detector fiducialization.

   ↳ physics.ins-dethep-exnucl-exphysics.app-phJINST(2017)·62 citations
8. 08*

   Centrality dependence of chemical freeze-out parameters from net-proton and net-charge fluctuations using hadron resonance gas model

   Rama Prasad Adak🇮🇳 · Supriya Das🇮🇳 · Sanjay K. Ghosh🇮🇳 · Rajarshi Ray🇮🇳 · Subhasis Samanta🇮🇳

   We estimate chemical freeze-out parameters in HRG and EVHRG model by fitting the experimental information of net-proton and net-charge fluctuations measured in Au + Au collisions by the STAR collaboration at RHIC. We observe that chemical freeze-out parameters obtained from lower and higher order fluctuations are though almost same for $\sqrt{s_{NN}}>27$ GeV, tend to deviate from each other at lower $\sqrt{s_{NN}}$. Moreover, these separations increase with decrease of $\sqrt{s_{NN}}$ and for a fixed $\sqrt{s_{NN}}$ increase towards central collisions. Furthermore, we observe an approximate scaling behaviour of $({\mu }_B/T)/({\mu }_B/T{)}_{central}$ with $(N_{part})/(N_{part}{)}_{central}$ for the parameters estimated from lower order fluctuations for 11.5 GeV $\le \sqrt{s_{NN}}\le$ 200 GeV. Scaling is violated for the parameters estimated from higher order fluctuations for $\sqrt{s_{NN}}=11.5$ and 19.6 GeV. It is observed that the chemical freeze-out parameter, which can describe ${\sigma }^2/M$ of net-proton very well in all energies and centralities, can not describe the $s\sigma$ equally well and vice versa.

   ↳ nucl-thhep-phnucl-exPRC(2017)·24 citations
9. 09*

   Predictions on the alpha decay chains of superheavy nuclei with Z =121 within the range 290 $\le$ A $\le$ 339

   K. P. Santhosh🇮🇳 · C. Nithya

   A systematic study on the alpha decay half lives of various isotopes of superheavy element \textit{Z} = 121 within the range 290 $\le$ A $\le$ 339 is presented for the first time using Coulomb and proximity potential model for deformed nuclei (CPPMDN). The calculated $\alpha$ decay half lives of the isotopes within our formalism match well with the values computed using Viola-Seaborg systematic, Universal curve of Poenaru et al., and the analytical formula of Royer. In our study by comparing the $\alpha$ decay half lives with the spontaneous fission half lives, we have predicted $2\alpha$ chain from ${}^{309,311,312}$121, $3\alpha$ chain from ${}^{310}$121 and $1\alpha$ chain from ${}^{313,314}$121. Clearly our study shows that the isotopes of superheavy element \textit{Z} = 121 within the mass range 309 $\le$ A $\le$ 314 will survive fission and can be synthesized and detected in the laboratory via alpha decay. We hope that our predictions will provide a new guide to future experiments.

   ↳ nucl-thnucl-exIJMPE(2016)·8 citations
10. 10*

    Feasibility of observing the {\alpha} decay chains from isotopes of SHN with Z = 128, Z = 126, Z = 124 and Z = 122

    K. P. Santhosh🇮🇳 · B. Priyanka · C. Nithya

    Taking the Coulomb and proximity potential model for deformed nuclei (CPPMDN) as the interacting potential for the post-scission region, the alpha decay properties of 34 isotopes of the superheavy nuclei with Z = 128 within the range 306 $\le$ A $\le$ 339 have been studied, considering both the parent and daughter nuclei to be deformed. The manuscript also deals with the decay properties of the isotopes of Z = 126 (within 288 $\le$ A $\le$ 339), Z = 124 (within 284 $\le$A $\le$ 339) and Z = 122 (within 280 $\le$ A $\le$ 339). The alpha decay half lives thus evaluated has been compared with the values evaluated using other theoretical models and it was seen that, our theoretical alpha decay half lives matches well with these values. Through the present study, we have underlined and have established the fact that, among the 192 isotopes considered in the present study, only those isotopes ${}^{321-324,328-335}$128, ${}^{318-320,323-327}$126, ${}^{305-308,315-322}$124 and ${}^{298-307,311-314}$122 can be synthesized and detected through alpha decay in laboratory. As the alpha decay half lives of these superheavy isotopes lie within the experimental limits, we hope these predictions, on the decay modes of these unknown nuclei, to pave the way for the future experiments. The proton separation energy calculations on ${}^{306-339}$128, ${}^{288-336}$126, ${}^{284-339}$124 and ${}^{280-339}$122 superheavy nuclei have also been done and the study revealed the probable proton emitters among these nuclei.

    ↳ nucl-thnucl-exNPA(2016)·26 citations
11. 11*

    Mini-Proceedings, 18th meeting of the Working Group on Radiative Corrections and MC Generators for Low Energies

    H. Czyż · S. Eidelman · F. Ignatov · A. Keshavarzi · A. Kupsc · V. E. Lyubovitskij · P. Masjuan · A. Nyffeler · G. Pancheri · E. Tomasi-Gustafsson · G. Venanzoni

    The mini-proceedings of the 18${}^{\mathrm{th}}$ Meeting of the "Working Group on Radiative Corrections and MonteCarlo Generators for Low Energies" held in Frascati, 19${}^{\mathrm{th}}$ - 20${}^{\mathrm{st}}$ May, are presented. These meetings, started in 2006, have as aim to bring together experimentalists and theoreticians working in the fields of meson transition form factors, hadronic contributions to the anomalous magnetic moment of the leptons, and the effective fine structure constant. The development of MonteCarlo generators and Radiative Corrections for precision $e^{+}{e}^{-}$ and $\tau$-lepton physics are also covered, with emphasis on meson production. At this workshop, a documentary entitled {\it Bruno Touschek with AdA in Orsay} commemorating the first observation of electron-positron collisions in a laboratory was also presented. With this edition, the working group reaches 10 years of continuous activities.

    ↳ hep-phhep-exnucl-exnucl-th0 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.