Fri·Oct 16, 2015Friday·October 16, 2015

1. 01*

   Discovery of ${}^{34g,m}$Cl$(p,\gamma {)}^{35}$Ar resonances activated at classical nova temperatures

   C. Fry🇺🇸 · C. Wrede🇺🇸 · S. Bishop🇯🇵 · B. A. Brown🇺🇸 · A. A. Chen🇨🇦 · T. Faestermann🇩🇪 · R. Hertenberger🇩🇪 · A. Parikh🇪🇸 · D. Pérez-Loureiro🇺🇸 · H.-F. Wirth🇩🇪 · A. García · R. Ortez🇺🇸

   Background: The thermonuclear ${}^{34g,m}$Cl($p,\gamma$)${}^{35}$Ar reaction rates are unknown due to a lack of experimental nuclear physics data. Uncertainties in these rates translate to uncertainties in ${}^{34}$S production in models of classical novae on oxygen-neon white dwarfs. ${}^{34}$S abundances have the potential to aid in the classification of presolar grains. Purpose: Determine resonance energies for the ${}^{34g,m}$Cl($p,\gamma$)${}^{35}$Ar reactions within the region of astrophyical interest for classical novae to a precision of a few keV as an essential first step toward constraining their thermonuclear reaction rates. Method: ${}^{35}$Ar excited states were populated by the ${}^{36}$Ar($d,t$)${}^{35}$Ar reaction at $E$(d)=22~MeV and reaction products were momentum analyzed by a high resolution quadrupole-dipole-dipole-dipole (Q3D) magnetic spectrograph. Results: Seventeen new ${}^{35}$Ar levels have been detected at a statistically significant level in the region $E_x\approx$~5.9-6.7~MeV ($E_r$ \textless~800~ keV) and their excitation energies have been determined to typical uncertainties of 3~keV. The uncertainties for five previously known levels have also been reduced substantially. The measured level density was compared to those calculated using the WBMB Hamiltonian within the $sd-pf$ model space. Conclusions: Most of the resonances in the region of astrophyical interest have likely been discovered and their energies have been determined, but the resonance strengths are still unknown, and experimentally constraining the ${}^{34g,m}$Cl($p,\gamma$)${}^{35}$Ar reaction rates will require further experiments.

   nucl-exPRC(2015)·12 citations
2. 02*

   Study of ${}^{26}$Mg through 1p pick up reaction ${}^{27}$Al(d,${}^3$He)

   Vishal Srivastava🇮🇳 · C. Bhattacharya🇮🇳 · T. K. Rana🇮🇳 · S. Manna🇮🇳 · S. Kundu🇮🇳 · S. Bhattacharya🇮🇳 · K. Banerjee🇮🇳 · P. Roy🇮🇳 · R. Pandey🇮🇳 · G. Mukherjee🇮🇳 · T. K. Ghosh🇮🇳 · J. K. Meena🇮🇳 and 8 other authors

   The even-even nucleus ${}^{26}$Mg has been studied through the reaction ${}^{27}$Al(d,${}^3$He) at 25 MeV beam energy. The spectroscopic factors have been extracted upto 7.50 MeV excitation energy using local, zero range distorted wave Born approximation. The comparison of the spectroscopic factors have been done with previously reported values using the same reaction probe. The extracted spectroscopic factors for different excited states were found to be in good agreement with the previously reported values for the same. The present results were also compared with the predictions from shell model as well as rotational model. The analog states of ${}^{26}$Al and ${}^{26}$Mg were found to be in good agreement.

   nucl-exPRC(2016)·9 citations
3. 03*

   Deeply virtual Compton scattering at Jefferson Laboratory

   Angela Biselli🇺🇸

   The generalized parton distributions (GPDs) have emerged as a universal tool to describe hadrons in terms of their elementary constituents, the quarks and the gluons. Deeply virtual Compton scattering (DVCS) on a proton or neutron ($N$), $eN\to e^{\prime }{N}^{\prime }\gamma$, is the process more directly interpretable in terms of GPDs. The amplitudes of DVCS and Bethe-Heitler, the process where a photon is emitted by either the incident or scattered electron, can be accessed via cross-section measurements or exploiting their interference which gives rise to spin asymmetries. Spin asymmetries, cross sections and cross-section differences can be connected to different combinations of the four leading-twist GPDs ($H$, $E$, $\tilde{H}$, $\tilde{E}$) for each quark flavors, depending on the observable and on the type of target. This paper gives an overview of recent experimental results obtained for DVCS at Jefferson Laboratory in the halls A and B. Several experiments have been done extracting DVCS observables over large kinematics regions. Multiple measurements with overlapping kinematic regions allow to perform a quasi-model independent extraction of the Compton form factors, which are GPDs integrals, revealing a 3D image of the nucleon.

   nucl-ex1 citation
4. 04*

   Electroweak Measurements of Neutron Densities in PREX and CREX at JLab, USA

   Robert Michaels🇺🇸

   Measurement of the parity-violating electron scattering asymmetry from ${}^{208}$Pb has demonstrated a new opportunity at Jefferson Lab to measure the weak charge distribution and hence pin down the neutron radius in nuclei in a relatively clean and model-independent way. This is because the Z boson of the weak interaction couples primarily to neutrons. We will describe the PREX and CREX experiments on ${}^{208}$Pb and ${}^{48}$Ca respectively. PREX-I ran in 2010, and CREX and a second run of PREX are currently in preparation.

   nucl-ex4 citations
5. 05*

   Addendum to "Determination of $\gamma$-ray widths in ${}^{15}$N using nuclear resonance fluorescence''

   Tamás Szücs🇩🇪 · Peter Mohr🇭🇺

   The determination of absolute widths of two observed levels above the proton threshold in ${}^{15}$N has been improved by a combined analysis of our recent ${}^{15}$N($\gamma$,${\gamma }^{\prime }$)${}^{15}$N${}^{\ast }$ photon scattering data, resonance strengths $\omega \gamma$ of the ${}^{14}$C($p$,$\gamma$)${}^{15}$N reaction, and $\gamma$-ray branchings $b_{\gamma ,i}$ in ${}^{15}$N. The revised data are compared to the adopted values, and some inconsistencies in the adopted values are illustrated.

   nucl-exPRC(2015)·1 citation
6. 06*

   Pairing reentrance in warm rotating ${}^{104}$Pd nucleus

   N. Quang Hung🇻🇳 · N. Dinh Dang · B.K. Agrawal🇮🇳 · V.M. Datar🇮🇳 · A. Mitra · D. R. Chakrabarty🇮🇳

   Pairing reentrance phenomenon in the warm rotating ${}^{104}$Pd nucleus is studied within the Bardeen-Cooper-Schrieffer (BCS)-based approach (the FTBCS1). The theory takes into account the effect of quasiparticle number fluctuations on the pairing field at finite temperature and angular momentum within the pairing model plus noncollective rotation along the symmetry axis. The numerical calculations for the pairing gaps and nuclear level densities (NLD), of which an anomalous enhancement has been experimentally observed at low excitation energy $E^{\ast }$ and high angular momentum $J$, show that the pairing reentrance is seen in the behavior of pairing gap obtained within the FTBCS1 at low $E$ and high $J$. This leads to the enhancement of the FTBCS1 level densities, in good agreement with the experimental observation. This agreement indicates that the observed enhancement of the NLD might be the first experimental detection of the pairing reentrance in a finite nucleus.

   ↳ nucl-thnucl-ex0 citations
7. 07*

   Pion Photo- and Electroproduction and the Chiral MAID Interface

   M. Hilt🇩🇪 · B. C. Lehnhart🇩🇪 · S. Scherer🇩🇪 · L. Tiator🇩🇪

   We discuss the extended on-mass-shell scheme for manifestly Lorentz-invariant baryon chiral perturbation theory. We present a calculation of pion photo- and electroproduction up to and including order $q^4$. The low-energy constants have been fixed by fitting experimental data in all available reaction channels. Our results can be accessed via a web interface, the so-called chiral MAID (http://www.kph.uni-mainz.de/MAID/chiralmaid/).

   ↳ nucl-thhep-phnucl-exJPS Conf.Proc.(2016)·1 citation

* 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.