Thu·Feb 16, 2017Thursday·February 16, 2017

1. 01*

   Neutron spectroscopy of ${}^{26}$Mg states: constraining the stellar neutron source ${}^{22}$Ne($\alpha ,n$)${}^{25}$Mg

   C. Massimi · The n_TOF Collaboration

   This work reports on accurate, high-resolution measurements of the ${}^{25}$Mg($n,\gamma$)${}^{26}$Mg and ${}^{25}$Mg($n,tot$) cross sections in the neutron energy range from thermal to about 300 keV, leading to a significantly improved ${}^{25}$Mg($n,\gamma$)${}^{26}$Mg parametrization. The relevant resonances for $n{+}^{25}$Mg were characterized from a combined R-matrix analysis of the experimental data. This resulted in an unambiguous spin/parity assignment of the corresponding excited states in ${}^{26}$Mg. With this information experimental upper limits of the reaction rates for ${}^{22}$Ne($\alpha ,n$)${}^{25}$Mg and ${}^{22}$Ne($\alpha ,\gamma$)${}^{26}$Mg were established, potentially leading to a significantly higher ($\alpha ,n$)/($\alpha ,\gamma$) ratio than previously evaluated. The impact of these results have been studied for stellar models in the mass range 2 to 25 $M_{\odot }$.

   nucl-exPLB(2017)·37 citations
2. 02*

   Generalized TMDs and the exclusive double Drell-Yan process

   Shohini Bhattacharya🇺🇸 · Andreas Metz🇺🇸 · Jian Zhou🇨🇳

   Generalized transverse momentum dependent parton distributions (GTMDs) are the most general parton correlation functions of hadrons. By considering the exclusive double Drell-Yan process it is shown for the first time how quark GTMDs can be measured. Specific GTMDs can be addressed by means of polarization observables.

   ↳ hep-phhep-exnucl-exPLB(2017)·105 citations
3. 03*

   Quark model study of the $\pi N\to \pi N$ reactions up to the $N(1440)$ resonance region

   Kai-Lei Wang🇨🇳 · Li-Ye Xiao🇨🇳 · Xian-Hui Zhong🇨🇳

   A combined analysis of the reactions ${\pi }^{+}p\to {\pi }^{+}p$, ${\pi }^{-}p\to {\pi }^{-}p$ and ${\pi }^{-}p\to {\pi }^{0}n$ is carried out with a chiral quark model. The observations are reasonably described from the $\Delta (1232)$ resonance region up to the $N(1440)$ resonance region. Besides the $\Delta (1232)P_{33}$, a confirmed role of $N(1440)P_{11}$ is found in the polarizations of the ${\pi }^{-}p\to {\pi }^{-}p$ and ${\pi }^{-}p\to {\pi }^{0}n$ reactions. It is found that the $N(1440)N\pi$ and $\Delta (1232)N\pi$ couplings are about $1.7$ and $4.8$ times larger than the expectations from the simple quark model, respectively, which may suggest the unusual property of $N(1440)P_{11}$ and deficiency of the simple quark model in the description of $N(1440)P_{11}$ and $\Delta (1232)P_{33}$. The $t$- and $u$-channel backgrounds have notable contributions to the ${\pi }^{+}p\to {\pi }^{+}p$ reaction, while in the ${\pi }^{-}p\to {\pi }^{-}p,{\pi }^{0}n$ reactions, the $s$-channel nucleon and $t$- and $u$-channel backgrounds play crucial roles.

   ↳ nucl-thhep-phnucl-exPRC(2017)·5 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.