Thu·Nov 26, 2015Thursday·November 26, 2015

1. 01*

   Participant and spectator scaling of spectator fragments in Au+Au and Cu+Cu collisions at sqrt(sNN) = 19.6 and 22.4 GeV

   B. Alver · B. B. Back · M. D. Baker · M. Ballintijn · D. S. Barton · R. R. Betts · A. A. Bickley · R. Bindel · A. Budzanowski · W. Busza · A. Carroll · Z. Chai and 70 other authors

   Spectator fragments resulting from relativistic heavy ion collisions, consisting of single protons and neutrons along with groups of stable nuclear fragments up to Nitrogen (Z=7), are measured in PHOBOS. These fragments are observed in Au+Au (sqrt(sNN)=19.6 GeV) and Cu+Cu (22.4 GeV) collisions at high pseudorapidity ($\eta$). The dominant multiply-charged fragment is the tightly bound Helium ($\alpha$), with Lithium, Beryllium, and Boron all clearly seen as a function of collision centrality and pseudorapidity. We observe that in Cu+Cu collisions, it becomes much more favorable for the $\alpha$ fragments to be released than Lithium. The yields of fragments approximately scale with the number of spectator nucleons, independent of the colliding ion. The shapes of the pseudorapidity distributions of fragments indicate that the average deflection of the fragments away from the beam direction increases for more central collisions. A detailed comparison of the shapes for $\alpha$ and Lithium fragments indicates that the centrality dependence of the deflections favors a scaling with the number of participants in the collision.

   nucl-exPRC(2016)·11 citations
2. 02*

   Mass of astrophysically relevant ${}^{31}$Cl and the breakdown of the isobaric multiplet mass equation

   A. Kankainen🇫🇮 · L. Canete · T. Eronen🇫🇮 · J. Hakala🇫🇮 · A. Jokinen · J. Koponen🇫🇮 · I.D. Moore🇫🇮 · D. Nesterenko · J. Reinikainen🇫🇮 · S. Rinta-Antila🇫🇮 · A. Voss · J. Äystö🇫🇮

   The mass of ${}^{31}$Cl has been measured with the JYFLTRAP double Penning trap mass spectrometer at the Ion-Guide Isotope Separator On-Line (IGISOL) facility. The determined mass-excess value, -7034.7(34) keV, is 15 times more precise than in the Atomic Mass Evaluation 2012. The quadratic form of the isobaric multiplet mass equation for the T=3/2 quartet at A=31 fails (${\chi }_n^2$=11.6) and a non-zero cubic term, d=-3.5(11) keV, is obtained when the new mass value is adopted. ${}^{31}$Cl has been found to be less proton-bound with a proton separation energy of $S_p$=265(4) keV. Energies for the excited states in ${}^{31}$Cl and the photodisintegration rate on ${}^{31}$Cl have been determined with significantly improved precision using the new $S_p$ value. The improved photodisintegration rate helps to constrain astrophysical conditions where ${}^{30}$S can act as a waiting point in the rapid proton capture process in type I x-ray bursts.

   nucl-exPRC(2016)·18 citations
3. 03*

   R&D on GEM Detectors for Forward Tracking at a Future Electron-Ion Collider

   Aiwu Zhang🇺🇸 · Vallary Bhopatkar🇺🇸 · Marcus Hohlmann🇺🇸 · Xinzhan Bai🇺🇸 · Kondo Gnanvo🇺🇸 · Nilanga K. Liyanage🇺🇸 · Matt Posik🇺🇸 · Bernd Surrow🇺🇸

   We report the status of R&D on large triple-GEM detectors for a forward tracker (FT) in an experiment at a future Electron Ion Collider (EIC) that will improve our understanding of QCD. We have designed a detector prototype specifically targeted for the EIC-FT, which has a trapezoidal shape with 30.1 degrees opening angle. We are investigating different detector assembly techniques and signal readout technologies, but have designed a common GEM foil to minimize NRE cost for foil production. The assembly techniques comprise either a purely mechanical method including foil stretching as pioneered by CMS but with certain modifications, or gluing foils to frames that are then assembled mechanically, or gluing foils to frames that are then glued together. The first two assembly techniques allow for re-opening chambers so that a GEM foil can be replaced if it is damaged. For readout technologies, we are pursuing a cost-effective one-dimensional readout with wide zigzag strips that maintains reasonable spatial resolution, as well two-dimensional readouts - one with stereo-angle (u-v) strips and another with r-phi strips. In addition, we aim at an overall low-mass detector design to facilitate good energy resolution for electrons scattered at low momenta. We present design for GEM foils and other detector parts, which we plan to entirely acquire from U.S. companies.

   ↳ physics.ins-dethep-exnucl-ex3 citations
4. 04*

   Further evidence for a dynamically generated secondary bow in ${}^{13}$C+${}^{12}$C rainbow scattering

   S. Ohkubo🇯🇵 · Y. Hirabayashi🇯🇵 · A. A. Ogloblin

   The existence of a secondary bow is confirmed for 13C+12C nuclear rainbow scattering in addition to the 16O+12C system. This is found by studying the experimental angular distribution of 13C+12C scattering at the incident 13C energy $E_L$=250 MeV with an extended double folding (EDF) model that describes all the diagonal and off-diagonal coupling potentials derived from the microscopic wave functions for 12C using a density-dependent nucleon-nucleon force. The Airy minimum at \theta\approx$70$^\circ$, which is not reproduced by a conventional folding potential, is revealed to be a secondary bow generated dynamically by a coupling to the excited state 2+ (4.44 MeV) of 12C. The essential importance of the quadruple {\it Y2} term (reorientation term) of potential of the excited state 2+ of 12C for the emergence of a secondary bow is found. The mechanism of the secondary bow is intuitively explained by showing how the trajectories are refracted dynamically into the classically forbidden angular region beyond the rainbow angle of the primary rainbow.

   ↳ nucl-thnucl-exPRC(2015)·13 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.