Fri·Sep 5, 2014Friday·September 5, 2014

1. 01*

   A new study of ${}^{25}$Mg($\alpha$,n)${}^{28}$Si angular distributions at $E_{\alpha }$ = 3 - 5 MeV

   A. Caciolli · T. Marchi · R. Depalo · S. Appannababu · N. Blasi · C. Broggini · M. Cinausero · G. Collazuol · M. Degerlier · D. Fabris · F. Gramegna · M. Leone and 6 other authors

   The observation of ${}^{26}$Al gives us the proof of active nucleosynthesis in the Milky Way. However the identification of the main producers of ${}^{26}$Al is still a matter of debate. Many sites have been proposed, but our poor knowledge of the nuclear processes involved introduces high uncertainties. In particular, the limited accuracy on the ${}^{25}$Mg($\alpha$,n)${}^{28}$Si reaction cross section has been identified as the main source of nuclear uncertainty in the production of ${}^{26}$Al in C/Ne explosive burning in massive stars, which has been suggested to be the main source of ${}^{26}$Al in the Galaxy. We studied this reaction through neutron spectroscopy at the CN Van de Graaff accelerator of the Legnaro National Laboratories. Thanks to this technique we are able to discriminate the ($\alpha$,n) events from possible contamination arising from parasitic reactions. In particular, we measured the neutron angular distributions at 5 different beam energies (between 3 and 5 MeV) in the \ang{17.5}-\ang{106} laboratory system angular range. The presented results disagree with the assumptions introduced in the analysis of a previous experiment.

   nucl-exastro-ph.SREPJA(2014)·5 citations
2. 02*

   Breakdown of the Isobaric Multiplet Mass Equation for the A = 20 and 21 Multiplets

   A. T. Gallant🇨🇦 · M. Brodeur🇺🇸 · C. Andreoiu🇨🇦 · A. Bader🇨🇦 · A. Chaudhuri🇨🇦 · U. Chowdhury🇨🇦 · A. Grossheim🇨🇦 · R. Klawitter🇨🇦 · A. A. Kwiatkowski🇨🇦 · K. G. Leach🇨🇦 · A. Lennarz🇨🇦 · T. D. Macdonald🇨🇦 and 12 other authors

   Using the Penning trap mass spectrometer TITAN, we performed the first direct mass measurements of 20,21Mg, isotopes that are the most proton-rich members of the A = 20 and A = 21 isospin multiplets. These measurements were possible through the use of a unique ion-guide laser ion source, a development that suppressed isobaric contamination by six orders of magnitude. Compared to the latest atomic mass evaluation, we find that the mass of 21Mg is in good agreement but that the mass of 20Mg deviates by 3{\sigma}. These measurements reduce the uncertainties in the masses of 20,21Mg by 15 and 22 times, respectively, resulting in a significant departure from the expected behavior of the isobaric multiplet mass equation in both the A = 20 and A = 21 multiplets. This presents a challenge to shell model calculations using either the isospin non-conserving USDA/B Hamiltonians or isospin non-conserving interactions based on chiral two- and three-nucleon forces.

   nucl-exPRL(2014)·42 citations
3. 03*

   Transverse momentum broadening in semi-inclusive deep inelastic scattering at next-to-leading order

   Zhong-Bo Kang🇺🇸 · Enke Wang🇨🇳 · Xin-Nian Wang🇨🇳 · Hongxi Xing🇺🇸

   Within the framework of higher-twist collinear factorization, transverse momentum broadening for the final hadrons in semi-inclusive deeply inelastic $e+A$ collisions is studied at the next-to-leading order (NLO) in perturbative QCD. Through explicit calculations of real and virtual corrections at twist-4, the transverse-momentum-weighted differential cross section due to double scattering is shown to factorize at NLO and can be expressed as a convolution of twist-4 nuclear parton correlation functions, the usual twist-2 fragmentation functions and hard parts which are finite and free of any divergences. A QCD evolution equation is also derived for the renormalized twist-4 quark-gluon correlation function which can be applied to future phenomenological studies of transverse momentum broadening and jet quenching at NLO.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2016)·37 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.