Mon·Nov 16, 2015Monday·November 16, 2015

1. 01*

   Strong Multi-step Interference Effects in 12C(d,p) to the 9/2+ State in 13C

   N. Keeley🇫🇷 · K. W. Kemper🇺🇸 · K. Rusek🇫🇷

   The population of the 9.50 MeV 9/2+ resonance in 13C by single neutron transfer reactions is expected to be dominated by the two-step route through the 12C 2+ (4.44 MeV) state, with another possible contribution via the strongly excited 3- (9.64 MeV) resonance in 12C. However, we find that a good description of the angular distribution for population of this state via the 12C(d,p)13C reaction is only possible when both direct 0+ x g_9/2 and two-step (via the 4.44 MeV 12C 2+ state) 2+ x d_5/2 paths are included in a coupled reaction channel calculation. While the calculated angular distribution is almost insensitive to the presence of the two-step path via the 9.64 MeV 12C 3- resonance, despite a much greater contribution to the wave function from the 3- x f_7/2 configuration, its inclusion is required to fit the details of the experimental angular distribution. The very large interference between the various components of the calculations, even when these are small, arises through the ``kinematic'' effect associated with the different transfer routes.

   nucl-exnucl-thPRC(2015)·5 citations
2. 02*

   Chiral Magnetic and Vortical Effects in High-Energy Nuclear Collisions --- A Status Report

   D. E. Kharzeev🇺🇸 · J. Liao🇺🇸 · S. A. Voloshin🇺🇸 · G. Wang🇺🇸

   The interplay of quantum anomalies with magnetic field and vorticity results in a variety of novel non-dissipative transport phenomena in systems with chiral fermions, including the quark-gluon plasma. Among them is the Chiral Magnetic Effect (CME) -- the generation of electric current along an external magnetic field induced by chirality imbalance. Because the chirality imbalance is related to the global topology of gauge fields, the CME current is topologically protected and hence non-dissipative even in the presence of strong interactions. As a result, the CME and related quantum phenomena affect the hydrodynamical and transport behavior of strongly coupled quark-gluon plasma, and can be studied in relativistic heavy ion collisions where strong magnetic fields are created by the colliding ions. Evidence for the CME and related phenomena has been reported by the STAR Collaboration at Relativistic Heavy Ion Collider at BNL, and by the ALICE Collaboration at the Large Hadron Collider at CERN. The goal of the present review is to provide an elementary introduction into the physics of anomalous chiral effects, to describe the current status of experimental studies in heavy ion physics, and to outline the future work, both in experiment and theory, needed to eliminate the existing uncertainties in the interpretation of the data.

   ↳ hep-phcond-mat.str-elhep-thnucl-ex+1PPNP(2016)·837 citations
3. 03*

   Analysis of recent CLAS data on ${\Sigma }^{\ast }(1385)$ photoproduction off a neutron target

   Xiao-Yun Wang🇨🇳 · Jun He🇨🇳 · Helmut Haberzettl🇺🇸

   Based on recent experimental data obtained by the CLAS Collaboration, the $\Sigma (1385)$ photoproduction off a neutron target at laboratory photon energies $E_{\gamma }$ up to 2.5\,GeV is investigated in an effective Lagrangian approach including $s$-, $u$-, and $t$-channel Born-term contributions. The present calculation does not take into account any explicit $s$-channel baryon-resonance contributions, however, in the spirit of duality, we include $t$-channel exchanges of mesonic Regge trajectories. The onset of the Regge regime is controlled by smoothly interpolating between Feynman-type single-meson exchanges and full-fledged Regge-trajectory exchanges. Gauge invariance broken by the Regge treatment is fully restored by introducing contact-type interaction currents that result from the implementation of \textit{local} gauge invariance in terms of generalized Ward-Takahashi identities. The cross sections for the $\gamma n\to K^{+}{\Sigma }^{\ast }(1385{)}^{-}$ reaction are calculated and compared with experimental results from the CLAS and LEPS collaborations. Despite its simplicity, the present theoretical approach provides a good description of the main features of the data. However, the parameters fitted to the data show that the gauge-invariance-restoring contact term plays a large role which may point to large contributions from final-state interactions.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2016)·23 citations
4. 04*

   Evaluation of Peak-Fitting Software for Gamma Spectrum Analysis

   Guilherme S. Zahn · Frederico A. Genezini · Maurício Moralles

   In all applications of gamma-ray spectroscopy, one of the most important and delicate parts of the data analysis is the fitting of the gamma-ray spectra, where information as the number of counts, the position of the centroid and the width, for instance, are associated with each peak of each spectrum. There's a huge choice of computer programs that perform this type of analysis, and the most commonly used in routine work are the ones that automatically locate and fit the peaks; this fit can be made in several different ways -- the most common ways are to fit a Gaussian function to each peak or simply to integrate the area under the peak, but some software go far beyond and include several small corrections to the simple Gaussian peak function, in order to compensate for secondary effects. In this work several gamma-ray spectroscopy software are compared in the task of finding and fitting the gamma-ray peaks in spectra taken with standard sources of ${}^{137}$Cs, ${}^{60}$Co, ${}^{133}$Ba and ${}^{152}$Eu. The results show that all of the automatic software can be properly used in the task of finding and fitting peaks, with the exception of GammaVision; also, it was possible to verify that the automatic peak-fitting software did perform as well as -- and sometimes even better than -- a manual peak-fitting software.

   ↳ physics.ins-detnucl-ex1 citation
5. 05*

   On $\gamma N\to \gamma \rho N^{\prime }$ at large $\gamma \rho$ invariant mass

   R. Boussarie🇫🇷 · B. Pire🇫🇷 · L. Szymanowski🇵🇱 · S. Wallon🇫🇷

   Photoproduction of a pair of particles with large invariant mass is a natural extension of collinear QCD factorization theorems which have been much studied for deeply virtual Compton scattering and deeply virtual meson production. We consider the case where the wide angle Compton scattering subprocess $\gamma (q\bar{q})\to \gamma \rho$ factorizes from generalized parton distribution. At dominant twist, separating the transverse (respectively longitudinal) polarization of the $\rho$ meson allows one to get access to chiral-odd (respectively chiral-even) GPDs. This opens a new way to the extraction of these elusive transversity GPDs.

   ↳ hep-phhep-exnucl-exnucl-th2 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.