Wed·Jul 26, 2017Wednesday·July 26, 2017

1. 01*

   Precision mass measurements of magnesium isotopes and implications on the validity of the Isobaric Mass Multiplet Equation

   M. Brodeur🇺🇸 · A.A. Kwiatkowski🇨🇦 · O.M. Drozdowski🇨🇦 · C. Andreoiu🇨🇦 · D. Burdette🇺🇸 · A. Chaudhuri🇨🇦 · U. Chowdhury🇨🇦 · A.T. Gallant🇨🇦 · A. Grossheim🇨🇦 · G. Gwinner🇨🇦 · H. Heggen🇨🇦 · J.D. Holt🇨🇦 and 12 other authors

   If the mass excess of neutron-deficient nuclei and their neutron-rich mirror partners are both known, it can be shown that deviations of the Isobaric Mass Multiplet Equation (IMME) in the form of a cubic term can be probed. Such a cubic term was probed by using the atomic mass of neutron-rich magnesium isotopes measured using the TITAN Penning trap and the recently measured proton-separation energies of ${}^{29}$Cl and ${}^{30}$Ar. The atomic mass of ${}^{27}$Mg was found to be within 1.6$\sigma$ of the value stated in the Atomic Mass Evaluation. The atomic masses of ${}^{28,29}$Mg were measured to be both within 1$\sigma$, while being 8 and 34 times more precise, respectively. Using the ${}^{29}$Mg mass excess and previous measurements of ${}^{29}$Cl we uncovered a cubic coefficient of $d$ = 28(7) keV, which is the largest known cubic coefficient of the IMME. This departure, however, could also be caused by experimental data with unknown systematic errors. Hence there is a need to confirm the mass excess of ${}^{28}$S and the one-neutron separation energy of ${}^{29}$Cl, which have both come from a single measurement. Finally, our results were compared to ab initio calculations from the valence-space in-medium similarity renormalization group, resulting in a good agreement.

   nucl-exPRC(2017)·14 citations
2. 02*

   Technical Supplement to "Polarization Transfer Observables in Elastic Electron-Proton Scattering at Q${}^2$ = 2.5, 5.2, 6.8, and 8.5 GeV${}^2$"

   A. J. R. Puckett🇺🇸 · E. J. Brash🇺🇸 · M. K. Jones🇺🇸 · W. Luo🇨🇳 · M. Meziane🇺🇸 · L. Pentchev🇺🇸 · C. F. Perdrisat🇺🇸 · V. Punjabi🇺🇸 · F. R. Wesselmann🇺🇸 · A. Ahmidouch🇺🇸 · I. Albayrak🇺🇸 · K. A. Aniol🇺🇸 and 94 other authors

   The GEp-III and GEp-2$\gamma$ experiments, carried out in Jefferson Lab's Hall C from 2007-2008, consisted of measurements of polarization transfer in elastic electron-proton scattering at momentum transfers of $Q^2=2.5,5.2,6.8,$ and $8.54$ GeV${}^2$. These measurements were carried out to improve knowledge of the proton electromagnetic form factor ratio $R={\mu }_p{G}_E^p/G_M^p$ at large values of $Q^2$ and to search for effects beyond the Born approximation in polarization transfer observables at $Q^2=2.5$ GeV${}^2$. The final results of both experiments were reported in a recent archival publication. A full reanalysis of the data from both experiments was carried out in order to reduce the systematic and, for the GEp-2$\gamma$ experiment, statistical uncertainties. This technical note provides additional details of the final analysis omitted from the main publication, including the final evaluation of the systematic uncertainties.

   nucl-exhep-exNucl.Instrum.Meth.A(2018)·2 citations
3. 03*

   LUNA: Status and Prospects

   C.Broggini🇮🇹 · D.Bemmerer🇩🇪 · A.Caciolli🇮🇹 · D.Trezzi🇮🇹

   The essential ingredients of nuclear astrophysics are the thermonuclear reactions which shape the life and death of stars and which are responsible for the synthesis of the chemical elements in the Universe. Deep underground in the Gran Sasso Laboratory the cross sections of the key reactions responsible for the hydrogen burning in stars have been measured with two accelerators of 50 and 400 kV voltage right down to the energies of astrophysical interest. As a matter of fact, the main advantage of the underground laboratory is the reduction of the background. Such a reduction has allowed, for the first time, to measure relevant cross sections at the Gamow energy. The qualifying features of underground nuclear astrophysics are exhaustively reviewed before discussing the current LUNA program which is mainly devoted to the study of the Big-Bang nucleosynthesis and of the synthesis of the light elements in AGB stars and classical novae. The main results obtained during the study of reactions relevant to the Sun are also reviewed and their influence on our understanding of the properties of the neutrino, of the Sun and of the Universe itself is discussed. Finally, the future of LUNA during the next decade is outlined. It will be mainly focused on the study of the nuclear burning stages after hydrogen burning: helium and carbon burning. All this will be accomplished thanks to a new 3.5 MV accelerator able to deliver high current beams of proton, helium and carbon which will start running under Gran Sasso in 2019. In particular, we will discuss the first phase of the scientific case of the 3.5 MV accelerator focused on the study of ${}^{12}$C+${}^{12}$C and of the two reactions which generate free neutrons inside stars: ${}^{13}$C($\alpha$,n)${}^{16}$O and ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg.

   nucl-exastro-ph.SRPPNP(2018)·92 citations
4. 04*

   Effective proton-neutron interaction near the drip line from unbound states in ${}^{25,26}$F

   M. Vandebrouck🇫🇷 · A. Lepailleur🇫🇷 · O. Sorlin🇫🇷 · T. Aumann🇩🇪 · C. Caesar🇩🇪 · M. Holl🇩🇪 · V. Panin🇩🇪 · F. Wamers🇩🇪 · S.R. Stroberg🇨🇦 · J.D. Holt🇨🇦 · F. De Oliveira Santos🇫🇷 · H. Alvarez-Pol🇪🇸 and 98 other authors

   Background: Odd-odd nuclei, around doubly closed shells, have been extensively used to study proton-neutron interactions. However, the evolution of these interactions as a function of the binding energy, ultimately when nuclei become unbound, is poorly known. The ${}^{26}$F nucleus, composed of a deeply bound $\pi 0d\_5/2$ proton and an unbound $\nu 0d\_3/2$ neutron on top of an ${}^{24}$O core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a $J^{\pi }=1^{+}\_1-4^{+}\_1$ multiplet, whose energies must be determined to study the influence of the proximity of the continuum on the corresponding proton-neutron interaction. The $J^{\pi }=1^{+}\_1,2^{+}\_1,4^{+}\_1$ bound states have been determined, and only a clear identification of the $J^{\pi }=3^{+}\_1$ is missing.Purpose: We wish to complete the study of the $J^{\pi }=1^{+}\_1-4^{+}\_1$ multiplet in ${}^{26}$F, by studying the energy and width of the $J^{\pi }=3^{+}\_1$ unbound state. The method was firstly validated by the study of unbound states in ${}^{25}$F, for which resonances were already observed in a previous experiment.Method: Radioactive beams of ${}^{26}$Ne and ${}^{27}$Ne, produced at about $440A$\,MeV by the FRagment Separator at the GSI facility, were used to populate unbound states in ${}^{25}$F and ${}^{26}$F via one-proton knockout reactions on a CH$\_2$ target, located at the object focal point of the R${}^3$B/LAND setup. The detection of emitted $\gamma$-rays and neutrons, added to the reconstruction of the momentum vector of the $A-1$ nuclei, allowed the determination of the energy of three unbound states in ${}^{25}$F and two in ${}^{26}$F. Results: Based on its width and decay properties, the first unbound state in ${}^{25}$F is proposed to be a $J^{\pi }=1/2^{-}$ arising from a $p\_1/2$ proton-hole state. In ${}^{26}$F, the first resonance at 323(33)~keV is proposed to be the $J^{\pi }=3^{+}\_1$ member of the $J^{\pi }=1^{+}\_1-4^{+}\_1$ multiplet. Energies of observed states in ${}^{25,26}$F have been compared to calculations using the independent-particle shell model, a phenomenological shell-model, and the ab initio valence-space in-medium similarity renormalization group method.Conclusions: The deduced effective proton-neutron interaction is weakened by about 30-40\% in comparison to the models, pointing to the need of implementing the role of the continuum in theoretical descriptions, or to a wrong determination of the atomic mass of ${}^{26}$F.

   nucl-exPRC(2017)·19 citations
5. 05*

   Analysis of the Daya Bay Reactor Antineutrino Flux Changes with Fuel Burnup

   Anna Hayes🇺🇸 · Gerard Jungman🇺🇸 · Libby McCutchan🇺🇸 · Alejandro Sonzogni🇺🇸 · Gerry Garvey🇺🇸 · Xiaobao Wang🇨🇳

   We investigate the recent Daya Bay results on the changes in the antineutrino flux and spectrum with the burnup of the reactor fuel. We find that the discrepancy between current model predictions and the Daya Bay results can be traced to the original measured ${}^{235}$U/${}^{239}$Pu ratio of the fission beta spectra that were used as a base for the expected antineutrino fluxes. An analysis of the antineutrino spectra that is based on a summation over all fission fragment beta-decays, using nuclear database input, explains all of the features seen in the Daya Bay evolution data. However, this summation method still predicts an anomaly. Thus, we conclude that there is currently not enough information to use the antineutrino flux changes to rule out the possible existence of sterile neutrinos.

   ↳ nucl-thhep-exhep-phnucl-exPRL(2018)·53 citations
6. 06*

   Measurements of Hadron Production in Pion-Carbon Interactions with NA61/SHINE at the CERN SPS

   Raul R. Prado (for the NA61/SHINE Collaboration)🇧🇷

   NA61/SHINE is a fixed target experiment designed to study hadron-proton, hadron-nucleus and nucleus-nucleus interactions at the CERN Super-Proton-Synchrotron. In this proceeding we present results on spectra of identified hadrons produced in pion-carbon production interactions, which are of fundamental importance to improve the extensive air shower modeling, and hence the interpretation of ultra-high-energy-cosmic-rays measurements. In particular, our measurements of (anti)baryons and ${\rho }^0$ production in pion-carbon interactions can contribute to improve the predictions of muon production by air shower simulations using hadronic interaction models. In this contribution we discuss the data analysis and the results from pion-carbon collisions recorded at beam momenta of 158 and 350 GeV/c. The preliminary spectra of $K^{\pm }$ and $p$($\bar{p}$) are shown, as well as a comparison to predictions of hadronic interaction models used in air shower simulations. Additionally, we present final results on the production of ${\rho }^0$, $\omega$ and $K^{0\ast }$ resonances.

   ↳ hep-exastro-ph.HEnucl-exPoS(2018)·14 citations
7. 07*

   A tin-loaded liquid scintillator approach for the 2 neutrino double-beta decay measurement of Sn-124

   O. Chkvorets🇨🇦 · C. Kraus🇨🇦 · J. Kuettler🇩🇪 · V. Lozza🇵🇹 · B. von Krosigk🇨🇦 · K. Zuber🇩🇪

   A new experiment based on tin-loaded scintillator is proposed to measure the 2nu double beta decay half-life of Sn-124 for the first time. Measurements of long term stabilitiy and optical properties of the produced scintillator are presented. In addition a sophisticated estimation of the background due to cosmic ray spallation on tin has been performed. It is shown that such a measurement is feasible and can reach half-lives of 10^22 years, thus covering all current theoretical predictions for this decay mode.

   ↳ physics.ins-detnucl-ex1 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.