Mon·Sep 21, 2015Monday·September 21, 2015

1. 01*

   Forward $J/\psi$ production in U$+$U collisions at $\sqrt{s_{NN}}$=193 GeV

   A. Adare · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · J. Alexander · M. Alfred · K. Aoki · N. Apadula · H. Asano · E.T. Atomssa · T.C. Awes and 393 other authors

   The invariant yields for $J/\psi$ production at forward rapidity $(1.2<|y|<2.2)$ in U$+$U collisions at $\sqrt{s_{{}_{NN}}}$=193 GeV have been measured as a function of collision centrality. The invariant yields and nuclear-modification factor $R_{AA}$ are presented and compared with those from Au$+$Au collisions in the same rapidity range. Additionally, the direct ratio of the invariant yields from U$+$U and Au$+$Au collisions within the same centrality class is presented, and used to investigate the role of $c\bar{c}$ coalescence. Two different parameterizations of the deformed Woods-Saxon distribution were used in Glauber calculations to determine the values of the number of nucleon-nucleon collisions in each centrality class, $N_{\mathrm{coll}}$, and these were found to give significantly different $N_{\mathrm{coll}}$ values. Results using $N_{\mathrm{coll}}$ values from both deformed Woods-Saxon distributions are presented. The measured ratios show that the $J/\psi$ suppression, relative to binary collision scaling, is similar in U$+$U and Au$+$Au for peripheral and midcentral collisions, but that $J/\psi$ show less suppression for the most central U$+$U collisions. The results are consistent with a picture in which, for central collisions, increase in the $J/\psi$ yield due to $c\bar{c}$ coalescence becomes more important than the decrease in yield due to increased energy density. For midcentral collisions, the conclusions about the balance between $c\bar{c}$ coalescence and suppression depend on which deformed Woods-Saxon distribution is used to determine $N_{\mathrm{coll}}$.

   nucl-exPRC(2016)·22 citations
2. 02*

   New Results from the Studies of the $N(1440)1/2^{+}$, $N(1520)3/2^{-}$, and $\Delta (1620)1/2^{-}$ Resonances in Exclusive $ep\to e^{\prime }{p}^{\prime }{\pi }^{+}{\pi }^{-}$ Electroproduction with the CLAS Detector

   V.I.Mokeev🇺🇸 · V.D.Burkert🇺🇸 · D.S.Carman🇺🇸 · L.Elouadrhiri🇺🇸 · G.V.Fedotov🇺🇸 · E.N.Golovatch🇷🇺 · R.W.Gothe🇺🇸 · K.Hicks🇺🇸 · B.S.Ishkhanov🇷🇺 · E.L.Isupov🇷🇺 · Iu.Skorodumina🇺🇸

   The transition helicity amplitudes from the proton ground state to the $N(1440)1/2^{+}$, $N(1520)3/2^{-}$, and $\Delta (1620)1/2^{-}$ resonances (${\gamma }_{v}p{N}^{\ast }$ electrocouplings) were determined from the analysis of nine independent one-fold differential ${\pi }^{+}{\pi }^{-}p$ electroproduction cross sections off a proton target, taken with CLAS at photon virtualities 0.5 GeV${}^2$ $<Q^2<$ 1.5 GeV${}^2$. The phenomenological reaction model employed for separation of the resonant and non-resonant contributions to this exclusive channel was further developed. The $N(1440)1/2^{+}$, $N(1520)3/2^{-}$, and $\Delta (1620)1/2^{-}$ electrocouplings were obtained from the resonant amplitudes of charged double-pion electroproduction off the proton in the aforementioned area of photon virtualities for the first time. Consistent results on ${\gamma }_{v}p{N}^{\ast }$ electrocouplings available from independent analyses of several $W$-intervals with different non-resonant contributions offer clear evidence for the reliable extraction of these fundamental quantities. These studies also improved the knowledge on hadronic branching ratios for the $N(1440)1/2^{+}$, $N(1520)3/2^{-}$, and $\Delta (1620)1/2^{-}$ decays to the $\pi \Delta$ and $\rho N$ final states. These new results provide a substantial impact on the QCD-based approaches that describe the $N^{\ast }$ structure and demonstrate the capability to explore fundamental ingredients of the non-perturbative strong interaction that are behind the excited nucleon state formation.

   nucl-exhep-phPRC(2016)·117 citations
3. 03*

   Evaluation of the strength of electron-proton scattering data for determining the proton charge radius

   M. Horbatsch🇨🇦 · E.A. Hessels🇨🇦

   Precisely measured electron-proton elastic scattering cross sections [Phys. Rev. Lett. {\bf 105}, 242002 (2010)] are reanalyzed to evaluate their strength for determining the rms charge radius ($R_{\mathrm{E}}$) of the proton. More than half of the cross sections at lowest $Q^2$ are fit using two single-parameter form-factor models, with the first based on a dipole parametrization, and the second on a linear fit to a conformal-mapping variable. These low-$Q^2$ fits extrapolate the slope of the form factor to $Q^2$=0 and determine $R_{\mathrm{E}}$ values of approximately 0.84 and 0.89~fm, respectively. Fits spanning all $Q^2$, in which the single constants are replaced with cubic splines at larger $Q^2$, lead to similar results for $R_{\mathrm{E}}$. We conclude that the scattering data is consistent with $R_{\mathrm{E}}$ ranging from at least 0.84 to 0.89~fm, and therefore cannot resolve the discrepancy between determinations of $R_{\mathrm{E}}$ made using muonic and electronic hydrogen-atom spectroscopy.

   nucl-exhep-phphysics.atom-phPRC(2016)·52 citations
4. 04*

   Bottomonium production in heavy-ion collisions at STAR

   Robert Vertesi (for the STAR Collaboration)🇨🇿

   Bottomonium measurements provide unique insight into hot and cold nuclear matter effects present in the medium that is formed in high-energy heavy-ion collisions. Recent STAR results show that in $\sqrt{s_{NN}}$ = 200 GeV central Au+Au collisions the ${\rm Y}$(1S) state is suppressed more than if only cold nuclear matter effects were present, and the excited state yields are consistent with a complete suppression. In 2012, STAR also collected 263.4 $\mu$b${}^{-1}$ high-energy-electron triggered data in U+U collisions at $\sqrt{s_{NN}}$= 193 GeV. Central U+U collisions, with an estimated 20% higher energy density than in central Au+Au data, extend the ${\rm Y}$(1S+2S+3S) and Upsilon(1S) nuclear modification trends observed in Au+Au towards higher number of participant nucleons, and confirm the suppression of the ${\rm Y}$(1S) state. We see a hint with 1.8 sigma significance that the ${\rm Y}$(2S+3S) excited states are not completely suppressed in U+U collisions. These data support the sequential in-medium quarkonium dissociation picture and favor models with a strong $q\bar{q}$ binding.

   ↳ hep-exnucl-exNucl.Part.Phys.Proc.(2016)·6 citations
5. 05*

   Blast wave fits with resonances to $p_t$ spectra from nuclear collisions at the LHC

   Ivan Melo🇸🇰 · Boris Tomasik🇸🇰

   We report our results for the freeze-out temperature and transverse flow profile obtained from fits to hadronic spectra measured by the ALICE collaboration. The influence of resonance decays is important and cannot be simply accounted for without the inclusion of their decays into the fits.

   ↳ nucl-thnucl-exJ.Phys.Conf.Ser.(2016)·5 citations
6. 06*

   Influence of vibrational excitation on surface diffuseness of inter-nuclear potential: study through heavy-ion quasi-elastic scattering at deep subbarrier energies

   Gurpreet Kaur🇮🇳 · B.R. Behera🇮🇳 · A. Jhingan · P. Sugathan🇧🇪 · K. Hagino🇯🇵

   We discuss the role of channel coupling in the surface properties of an inter-nuclear potential for heavy-ion reactions. To this end, we analyze the experimental quasi-elastic cross sections for the ${}^{12}$C + ${}^{105,106}$Pd and ${}^{13}$C + ${}^{105,106}$Pd systems using the coupled-channels approach by including the vibrational excitations in the target nuclei. While earlier studies have reported a negligible influence of vibrational excitation on the surface diffuseness parameter for spherical systems, we find a significant effect for the C+Pd systems. Our systematic study also reveals influence of transfer couplings on the surface diffuseness parameter.

   ↳ nucl-thnucl-exPRC(2015)·1 citation

* 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.