Nuclear Experiment·nucl-ex
8 papers—6 primary·2 cross-listed·reconstructed*
V.L. Kashevarov (A2 Collaboration at MAMI)🇷🇺
Preliminary data for target and beam-target asymmetry for the reaction obtained at the MAMI accelerator are presented. The data are compared to different theoretical predictions.
M. Pomorski · M. Pfützner🇬🇧 · W. Dominik🇵🇱 · R. Grzywacz🇺🇸 · A. Stolz · T. Baumann🇺🇸 · J.S. Berryman🇺🇸 · H. Czyrkowski · R. Dąbrowski · A. Fijałkowska · T. Ginter🇺🇸 · J. Johnson and 12 other authors
Results of decay spectroscopy on nuclei in vicinity of the doubly magic 48Ni are presented. The measurements were performed with a Time Projection Chamber with optical readout which records tracks of ions and protons in the gaseous volume. Six decays of 48Ni including four events of two-proton ground-state radioactivity were recorded. An advanced reconstruction procedure yielded the 2p decay energy for 48Ni of Q2p = 1.29(4) MeV. In addition, the energy spectra of \b{eta}-delayed protons emitted in the decays of 44Cr and 46Fe, as well as half-lives and branching ratios were determined. The results were found to be consistent with the previous measurements made with Si detectors. A new proton line in the decay of 44Cr corresponding to the decay energy of 760 keV is reported. The first evidence for the \b{eta}2p decay of 46 Fe, based on one clear event, is shown.
Nihar Ranjan Sahoo (the STAR Collaboration)🇺🇸
Event-by-event fluctuations of global observables in relativistic heavy-ion collisions are studied as probes for the QCD phase transition and as tools to search for critical phenomena near the phase boundary. Dynamical fluctuations in mean transverse momentum, identified particle ratios and conserved quantities (such as net-charge, net-baryon) are expected to provide signatures of a de-confined state of matter. Non-monotonic behavior in the higher-moments of conserved quantities as a function of beam energy and collision centrality are proposed as signatures of the QCD critical point. To study the QCD phase transition and locate the critical point, the STAR experiment at RHIC has collected a large amount of data for Au+Au collisions from ~GeV in the RHIC Beam Energy Scan (BES) program. We present the recent beam energy scan results on dynamical fluctuations of particle ratios and two-particle transverse momentum correlations at mid-rapidity. Higher-moments of the net-charge and net-proton multiplicity distributions as a function of beam energy will be presented. We give a summary of what has been learnt so far and future prospectives for the BES-II program.
Ingo Sick🇨🇭 · Dirk Trautmann🇨🇭
The standard procedure of extracting the proton root-mean-square radii from models for the Sachs form factors and fitted to elastic electron-proton scattering data %has a serious flaw. is more uncertain than traditionally assumed. The extrapolation of , from the region covered by data to momentum transfer where the -radius is obtained, often depends on uncontrolled properties of the parameterization used. Only when ensuring that the corresponding densities have a physical behavior at large radii can reliable -radii be determined.
Jan Glorius🇩🇪 · Kerstin Sonnabend🇩🇪 · Joachim Goerres🇺🇸 · Daniel Robertson🇺🇸 · Michael Knoerzer · Antonios Kontos🇺🇸 · Thomas Rauscher🇬🇧 · René Reifarth🇩🇪 · Anne Sauerwein🇩🇪 · Edward Stech · Wanpeng Tan🇺🇸 · Tanija Thomas🇺🇸 · Michael Wiescher🇺🇸
Background: Optical potentials are crucial ingredients for the prediction of nuclear reaction rates needed in simulations of the astrophysical \gamma-process. Associated uncertainties are particularly large for reactions involving \alpha-particles. This includes (\gamma,\alpha) reactions which are of special importance in the \gamma-process. Purpose: The measurement of (\alpha,n) reactions allows for an optimization of currently used \alpha-nucleus potentials. The reactions 165Ho(\alpha,n) and 166Er(\alpha,n) probe the optical model in a mass region where \gamma-process calculations exhibit an underproduction of p nuclei which is not yet understood. Method: To investigate the energy-dependent cross sections of the reactions 165Ho(\alpha,n) and 166Er(\alpha,n) close to the reaction threshold, self-supporting metallic foils were irradiated with \alpha-particles using the FN tandem Van de Graaff accelerator at University of Notre Dame. The induced activity was determined afterwards by monitoring the specific \beta-decay channels. Results: Hauser-Feshbach predictions with a widely used global \alpha-potential describe the data well at energies where the cross sections are almost exclusively sensitive to the \alpha-widths. Increasing discrepancies appear towards the reaction threshold at lower energy. Conclusions: The tested global \alpha-potential is suitable at energies above 14 MeV, while a modification seems necessary close to the reaction threshold. Since the \gamma- and neutron width show non-negligible impact on the predictions, complementary data are required to judge whether or not the discrepancies found can to be solely assigned to the \alpha-width.
P.D.Shidling🇺🇸 · D. Melconian🇺🇸 · S. Behling · B. Fenker🇺🇸 · J.C. Hardy🇺🇸 · V.E. Iacob🇺🇸 · E. McCleskey🇺🇸 · M. McCleskey · M. Mehlman🇺🇸 · H.I. Park🇺🇸 · B.T. Roeder🇺🇸
The half-life of \tsups{37}K has been measured to be , a value nearly an order of magnitude more precise than the best previously reported. The decay of \tsups{37}K occurs mainly via a superallowed branch to the ground-state of its mirror, \tsups{37}Ar. This transition has been used recently, together with similar transitions from four other nuclei, as an alternative test of CVC and method for determining , but the precision of its value was limited by the relatively large half-life uncertainty. Our result corrects that situation. Another motivation for improving the value was to determine the standard-model prediction for the -decay correlation parameters, which will be compared to those currently being measured by the \trinat{} collaboration at \triumf. The new value, , is now limited in precision by the ground-state branching ratio.
L. S. Song🇨🇳 · J. M. Yao🇯🇵 · P. Ring🇩🇪 · J. Meng🇨🇳
Neutrinoless double- () decay is related to many fundamental concepts in nuclear and particle physics beyond the standard model. Currently there are many experiments searching for this weak process. An accurate knowledge of the nuclear matrix element for the decay is essential for determining the effective neutrino mass once this process is eventually measured. We report the first full relativistic description of the decay matrix element based on a state-of-the-art nuclear structure model. We adopt the full relativistic transition operators which are derived with the charge-changing nucleonic currents composed of the vector coupling, axial-vector coupling, pseudoscalar coupling, and weak-magnetism coupling terms. The wave functions for the initial and final nuclei are determined by the multireference covariant density functional theory (MR-CDFT) based on the point-coupling functional PC-PK1. The low-energy spectra and electric quadrupole transitions in Nd and its daughter nucleus Sm are well reproduced by the MR-CDFT calculations. The decay matrix elements for both the and decays of Nd are evaluated. The effects of particle number projection, static and dynamic deformations, and the full relativistic structure of the transition operators on the matrix elements are studied in detail. The resulting decay matrix element for the transition is , which gives the most optimistic prediction for the next generation of experiments searching for the decay in Nd.
Wim Cosyn🇧🇪 · Misak Sargsian🇺🇸
Deep-inelastic scattering (DIS) from a tensor polarized deuteron is sensitive to possible non-nucleonic components of the deuteron wave function. To accurately estimate the size of the nucleonic contribution, final-state interactions (FSIs) need to be accounted for in calculations. We outline a model that, based on the diffractive nature of the effective hadron-nucleon interaction, uses the generalized eikonal approximation to model the FSIs in the resonance region, taking into account the proton-neutron component of the deuteron. The calculation uses a factorized model with a basis of three resonances with mass GeV as the relevant set of effective hadron states entering the final-state interaction amplitude for inclusive DIS. We present results for the tensor asymmetry observable for kinematics accessible in experiments at Jefferson Lab and Hermes. For inclusive DIS, sizeable effects are found when including FSIs for Bjorken , but the overall size of remains small. For tagged spectator DIS, FSIs effects are largest at spectator momenta around 300 MeV and for forward spectator angles.
* 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.