Tue·Oct 11, 2011Tuesday·October 11, 2011

1. 01*

   Evidence for $\alpha$-particle condensation in nuclei from the Hoyle state deexcitation

   Ad. R. Raduta🇷🇴 · B. Borderie🇫🇷 · E. Geraci🇮🇹 · N. Le Neindre🇫🇷 · P. Napolitani🇫🇷 · M. F. Rivet🇫🇷 · R. Alba🇮🇹 · F. Amorini🇮🇹 · G. Cardella🇮🇹 · M. Chatterjee🇮🇳 · E. De Filippo🇮🇹 · D. Guinet🇫🇷 and 14 other authors

   The fragmentation of quasi-projectiles from the nuclear reaction ${}^{40}$Ca+${}^{12}$C at 25 MeV/nucleon was used to produce excited states candidates to $\alpha$-particle condensation. Complete kinematic characterization of individual decay events, made possible by a high-granularity 4$\pi$ charged particle multi-detector, reveals that 7.5$\pm$4.0% of the particle decays of the Hoyle state correspond to direct decays in three equal-energy $\alpha$-particles.

   nucl-exPLB(2011)·93 citations
2. 02*

   First experimental determination of the charge radius of ${}^{74}$Rb and its application in tests of the unitarity of the CKM matrix

   E. Mané🇨🇦 · A. Voss🇨🇦 · J. A. Behr🇨🇦 · J. Billowes🇬🇧 · T. Brunner🇨🇦 · F. Buchinger🇬🇧 · J. E. Crawford🇬🇧 · J. Dilling🇨🇦 · S. Ettenauer🇨🇦 · C. D. P. Levy🇨🇦 · O. Shelbaya🇬🇧 · M. R. Pearson🇨🇦

   Collinear-laser spectroscopy with bunched-beams technique was used for the study of neutron deficient Rb isotopes, out to ${}^{74}$Rb ($N=Z=37$) at TRIUMF. The measured hyperfine coupling constants of ${}^{76,78m}$Rb were in agreement with literature values. The nuclear spin of ${}^{75}$Rb was confirmed to be $I=3/2$, and its hyperfine coupling constants were measured for the first time. The mean-square charge radius of ${}^{74}$Rb was determined for the first time. This result has improved the isospin symmetry breaking correction term used to calculate the $\mathcal{F}t$ value, with implications for tests of the unitarity of the Cabibbo-Kobayashi-Maskawa matrix.

   nucl-exPRL(2011)·32 citations
3. 03*

   First Results with Heavy-Ion Collisions at LHC from ALICE

   Domenico Elia (for the ALICE Collaboration)🇮🇹

   In November 2010 the ALICE experiment at CERN has collected the first Pb--Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV produced by the LHC. A first characterization of the hot and dense state of matter produced in this new energy domain became available shortly after the run. In this paper we present the results on charged-particle multiplicity, Bose-Einstein correlations, elliptic flow and their dependence on the collision centrality. Results from first measurements of strange and identified particle production and suppression of high-momentum hadrons with respect to $pp$ collisions are also reported.

   nucl-exhep-exAIP Conf.Proc.(2012)·1 citation
4. 04*

   Jets and Jet-like Correlations at RHIC

   Helen Caines🇺🇸

   I present an overview of some of the recent results on jets and jet-like correlation measurements from the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory. Jets are produced in the initial hard scatterings of an event and can therefore be exploited as probes of the hot and dense medium produced in heavy-ion collisions. Previous RHIC results indicate that this medium, the Quark Gluon Plasma (sQGP), is strongly coupled, with partonic degrees of freedom. High pT colored partons passing through the sQGP are therefore believed to suffer energy loss via induced gluon radiation and elastic collisions, before exiting the medium and fragmenting in vacuum. Jet reconstruction and high pT correlation studies allow us to investigate how the partons interact with the medium and how the medium responds to the partons moving through it. By comparing measurements from pp and d-Au to those in Au-Au collisions at sqrt{s_{NN}} = 200 GeV we aim to disentangle cold nuclear matter effects from those of the hot and dense sQGP.

   nucl-exhep-ex4 citations
5. 05*

   Fragmentation of ${}^7$Li Relativistic Nuclei on a Proton into the ${}^3$H+${}^4$He Channel

   N. G. Peresadko🇷🇺 · Yu. A. Alexandrov🇷🇺 · S. G. Gerasimov🇷🇺 · V. A. Dronov🇷🇺 · V. G. Larionova🇷🇺 · A. V. Pisetskaya🇷🇺 · A. I. Malakhov🇷🇺 · E. I. Tamm🇷🇺 · V. N. Fetisov🇷🇺 · S. P. Kharlamov🇷🇺 · L. N. Shesterkina🇷🇺

   In a track nuclear photoemulsion exposed to a beamof ${}^7$Li nuclei accelerated to a momentum of 3 GeV/$c$ per nucleon at the synchrophasotron of the Joint Institute for Nuclear Research (JINR, Dubna), 13 events in which ${}^7$Li nuclei interacting with protons break up into ${}^3$H and ${}^4$He fragments were detected among 3730 inelastic-interaction events. For this fragmentation channel, the cross section was found to be $8\pm 2$ mb. The average value of the fragment total transverse momentum was $214\pm 5$ MeV/$c$. This value exceedsmarkedly the average value of the transverse-momentumtransfer in the coherent dissociation of ${}^7$Li nuclei on track-emulsion nuclei ($166\pm 5$ MeV/$c$). The recoil-proton transverse momentum was on average 98% of the total proton momentum. The longitudinal-momentum distribution of protons was characterized by a variance of 16 MeV/$c$ and a mean value of $37\pm 2$ MeV/$c$.

   nucl-exPhys.Atom.Nucl.(2010)·4 citations
6. 06*

   Ab initio calculation of the Hoyle state and a new look at clustering in nuclei

   Ulf-G. Meißner🇩🇪

   I present an ab initio calculation of the spectrum of carbon-12, including also the famous Hoyle state. Its structure is discussed and a new interpretation of clustering in nuclear physics is given.

   ↳ nucl-thhep-latnucl-exJ.Phys.Conf.Ser.(2012)·2 citations
7. 07*

   Open Heavy Flavor Production in p-p and Pb-Pb collisions as seen by ALICE at the LHC

   Z. Conesa del Valle (for the ALICE Collaboration)🇨🇭

   Charm and beauty production are probed with the ALICE experiment at the LHC by studying the single lepton transverse momentum distribution (electrons at mid-rapidity, muons at large-rapidities) and D mesons reconstructed in their hadronic decays. The differential production cross sections in proton proton interactions show a good agreement with perturbative QCD calculations at both sqrt(s) = 2.76 and 7 TeV. The measurements in lead lead reactions at sqrt(s_{NN})= 2.76 TeV evidence a reduction (or suppression) of the production rate at intermediate and high pt in the most central collisions with respect to the rate in proton proton interactions.

   ↳ hep-exnucl-exAIP Conf.Proc.(2012)·9 citations
8. 08*

   Parton Energy Loss and Modified Beam Quark Distribution Functions in Drell-Yan Process in p+A Collisions

   Hongxi Xing🇨🇳 · Yun Guo🇨🇳 · Enke Wang🇨🇳 · Xin-Nian Wang🇨🇳

   Within the framework of generalized collinear factorization in perturbative QCD (pQCD), we study the effect of initial multiple parton scattering and induced parton energy loss in Drell-Yan (DY) process in proton-nucleus collisions. We express the contribution from multiple parton scattering and induced gluon radiation to the DY dilepton spectra in terms of nuclear modified effective beam quark distribution functions. The modification depends on the quark transport parameter in nuclear medium. This is similar to the final-state multiple parton scattering in deeply inelastic scattering (DIS) off large nuclei and leads to the suppression of the Drell-Yan cross section in $p+A$ relative to $p+p$ collisions. With the value of quark transport parameter determined from the nuclear modification of single-inclusive DIS hadron spectra as measured by the HERMES experiment, we calculate DY spectra in $p+A$ collisions and find the nuclear suppression due to beam parton energy loss negligible at the Fermilab energy $E_{\mathrm{lab}}$=800 GeV in the kinematic region as covered by the E866 experiment. Most of the observed nuclear suppression of DY spectra in E866 experiment can be described well by parton shadowing in target nuclei as given by the EPS08 parameterization. The effect of beam parton energy loss, however, becomes significant for DY lepton pairs with large beam parton momentum fraction $x^{\prime }$ or small target parton momentum fraction $x$. We also predict the DY cross section in $p+A$ collisions at lower beam proton energy $E_{\mathrm{lab}}$=120 GeV and show significant suppression due to initial state parton energy loss at moderately large $x^{\prime }$ where the effect of parton shadowing is very small.

   ↳ hep-phnucl-exnucl-thNPA(2012)·40 citations
9. 09*

   Type Ia supernovae and the ^{12}C+^{12}C reaction rate

   E. Bravo🇪🇸 · L. Piersanti · I. Domínguez🇲🇽 · O. Straniero🇮🇹 · J. Isern · J.A. Escartín

   The experimental determination of the cross-section of the ^{12}C+^{12}C reaction has never been made at astrophysically relevant energies (E<2 MeV). The profusion of resonances throughout the measured energy range has led to speculation that there is an unknown resonance at E\sim1.5 MeV possibly as strong as the one measured for the resonance at 2.14 MeV. We study the implications that such a resonance would have for the physics of SNIa, paying special attention to the phases that go from the crossing of the ignition curve to the dynamical event. We use one-dimensional hydrostatic and hydrodynamic codes to follow the evolution of accreting white dwarfs until they grow close to the Chandrasekhar mass and explode as SNIa. In our simulations, we account for a low-energy resonance by exploring the parameter space allowed by experimental data. A change in the ^{12}C+^{12}C rate similar to the one explored here would have profound consequences for the physical conditions in the SNIa explosion, namely the central density, neutronization, thermal profile, mass of the convective core, location of the runaway hot spot, or time elapsed since crossing the ignition curve. For instance, with the largest resonance strength we use, the time elapsed since crossing the ignition curve to the supernova event is shorter by a factor ten than for models using the standard rate of ^{12}C+^{12}C, and the runaway temperature is reduced from \sim8.14\times10^{8} K to \sim4.26\times10^{8} K. On the other hand, a resonance at 1.5 MeV, with a strength ten thousand times smaller than the one measured at 2.14 MeV, but with an {\alpha}/p yield ratio substantially different from 1 would have a sizeable impact on the degree of neutronization of matter during carbon simmering. We conclude that a robust understanding of the links between SNIa properties and their progenitors will not be attained until the ^{12}C+^{12}C reaction rate is measured at energies \sim1.5 MeV.

   ↳ astro-ph.SRnucl-exAstron.Astrophys.(2011)·27 citations
10. 10*

    Electron Cooling Performance at IMP Facility

    Yang Xiaodong

    The ion beam of 58Ni19+ with the energy of 6.39MeV/u was accumulated in the main ring of HIRFL-CSR with the help of electron cooling. The related angle between ion and electron beams in the horizontal and vertical planes was intentionally created by the steering coils in the cooling section after maximized the accumulated ion beam in the ring. The radial electron intensity distribution was changed by the ratio of potentials of grid electrode and anode of the electron gun, the different electron beam profiles were formed from solid to hollow in the experiments. In these conditions, the maximum accumulated ion beam intensity in the 10 seconds was measured, the lifetime of ion beam was measured, simultaneously the momentum spread of the ion beam varying with particle number was measured during the ion beam decay, furthermore, and the power coefficient was derived from these data. In additional, the momentum spread in the case of constant particle number was plotted with the angle and electron beam profile. The oscillation and shift of the central frequency of the ion beam were observed during the experiments. The upgrade and improvement in the CSRm cooler and the progress in the CSRe cooler were presented. These results were useful to attempt the crystal beam forming investigation in the CSR.

    ↳ physics.acc-phnucl-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.