Thu·Apr 21, 2016Thursday·April 21, 2016

1. 01*

   Integral measurement of the ${}^{12}$C(n,p)${}^{12}$B reaction up to 10 GeV

   P. Žugec🇭🇷 · N. Colonna🇮🇹 · D. Bosnar🇭🇷 · A. Ventura🇮🇹 · A. Mengoni🇮🇹 · S. Altstadt🇩🇪 · J. Andrzejewski🇵🇱 · L. Audouin🇫🇷 · M. Barbagallo🇮🇹 · V. Bécares🇪🇸 · F. Bečvář🇨🇿 · F. Belloni🇧🇪 and 93 other authors

   The integral measurement of the ${}^{12}$C(n,p)${}^{12}$B reaction was performed at the neutron time of flight facility n_TOF at CERN. The total number of ${}^{12}$B nuclei produced per neutron pulse of the n_TOF beam was determined using the activation technique in combination with a time of flight technique. The cross section is integrated over the n_TOF neutron energy spectrum from reaction threshold at 13.6 MeV to 10 GeV. Having been measured up to 1 GeV on basis of the ${}^{235}$U(n,f) reaction, the neutron energy spectrum above 200 MeV has been reevaluated due to the recent extension of the cross section reference for this particular reaction, which is otherwise considered a standard up to 200 MeV. The results from the dedicated GEANT4 simulations have been used to evaluate the neutron flux from 1 GeV up to 10 GeV. The experimental results related to the ${}^{12}$C(n,p)${}^{12}$B reaction are compared with the evaluated cross sections from major libraries and with the predictions of different GEANT4 models, which mostly underestimate the ${}^{12}$B production. On the contrary, a good reproduction of the integral cross section derived from measurements is obtained with TALYS-1.6 calculations, with optimized parameters.

   nucl-exEPJA(2016)·12 citations
2. 02*

   Determination of the Neutron-Capture Rate of 17C for the R-process Nucleosynthesis

   M. Heine · S. Typel · M.-R. Wu · T. Adachi · Y. Aksyutina · J. Alcantara · S. Altstadt · H. Alvarez-Pol · N. Ashwood · T. Aumann · V. Avdeichikov · M. Barr and 115 other authors

   With the R${}^3$B-LAND setup at GSI we have measured exclusive relative-energy spectra of the Coulomb dissociation of ${}^{18}$C at a projectile energy around 425~AMeV on a lead target, which are needed to determine the radiative neutron-capture cross sections of ${}^{17}$C into the ground state of ${}^{18}$C. Those data have been used to constrain theoretical calculations for transitions populating excited states in ${}^{18}$C. This allowed to derive the astrophysical cross section ${\sigma }_{\mathrm{n}\gamma }^{\ast }$ accounting for the thermal population of ${}^{17}$C target states in astrophysical scenarios. The experimentally verified capture rate is significantly lower than those of previously obtained Hauser-Feshbach estimations at temperatures $T_9\le 1$~GK. Network simulations with updated neutron-capture rates and hydrodynamics according to the neutrino-driven wind model as well as the neutron-star merger scenario reveal no pronounced influence of neutron capture of ${}^{17}$C on the production of second- and third-peak elements in contrast to earlier sensitivity studies.

   nucl-exastro-ph.SRPRC(2017)·15 citations
3. 03*

   The Impact of New Polarization Data from Bonn, Mainz and Jefferson Laboratory on $\gamma p\to \pi N$ Multipoles

   A.V. Anisovich R. Beck · M. Döring · M. Gottschall · J. Hartmann · V. Kashevarov · E. Klempt · Ulf-G. Meißner · V. Nikonov · M. Ostrick · D. Rönchen · A. Sarantsev · I. Strakovsky and 5 other authors

   New data on pion-photoproduction off the proton have been included in the partial wave analyses Bonn-Gatchina and SAID and in the dynamical coupled-channel approach Jülich-Bonn. All reproduce the recent new data well: the double polarization data for E, G, H, P and T in $\gamma p\to {\pi }^{0}p$ from ELSA, the beam asymmetry $\Sigma$ for $\gamma p\to {\pi }^{0}p$ and ${\pi }^{+}n$ from Jefferson Laboratory, and the precise new differential cross section and beam asymmetry data $\Sigma$ for $\gamma p\to {\pi }^{0}p$ from MAMI. The new fit results for the multipoles are compared with predictions not taking into account the new data. The mutual agreement is improved considerably but still far from being perfect.

   ↳ nucl-thnucl-exEPJA(2016)·85 citations
4. 04*

   Photoproduction of hidden-charm states in the $\gamma p\to {\bar{D}}^{\ast 0}{\Lambda }_c^{+}$ reaction near threshold

   Yin Huang🇨🇳 · Ju-Jun Xie🇨🇳 · Jun He🇨🇳 · Xurong Chen🇨🇳 · Hong-Fei Zhang🇨🇳

   We report on a theoretical study of the hidden charm $N_{c\bar{c}}^{\ast }$ states in the $\gamma p\to {\bar{D}}^{\ast 0}{\Lambda }_c^{+}$ reaction near threshold within an effective Lagrangian approach. In addition to the contributions from the $s$-channel nucleon pole, the $t$-channel $D^0$ exchange, the $u$-channel ${\Lambda }_c^{+}$ exchange and the contact term, we study the contributions from the $N_{c\bar{c}}^{\ast }$ states with spin-parity $J^P=1/2^{-}$ and $3/2^{-}$. The total and differential cross sections of the $\gamma p\to {\bar{D}}^{\ast 0}Lambd{a}_c^{+}$ reaction are predicted. It is found that the contributions of these $N_{c\bar{c}}^{\ast }$ states give clear peak structures in the total cross sections. Thus, this reaction is another new platform to study the hidden-charm states. It is expected that our model calculation may be tested by the future experiments.

   ↳ nucl-thhep-phnucl-exCPC(2016)·38 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.