Tue·Oct 3, 2017Tuesday·October 3, 2017

1. 01*

   Dipole and quadrupole moments of ${}^{73-78}$Cu as a test of the robustness of the $Z=28$ shell closure near ${}^{78}$Ni

   R. P. de Groote🇧🇪 · J. Billowes🇬🇧 · C. L. Binnersley🇬🇧 · M. L. Bissell🇬🇧 · T. E. Cocolios🇧🇪 · T. Day Goodacre🇨🇭 · G. J. Farooq-Smith🇧🇪 · D. V. Fedorov🇷🇺 · K. T. Flanagan🇬🇧 · S. Franchoo🇫🇷 · R. F. Garcia Ruiz🇬🇧 · Á. Koszorús🇧🇪 and 12 other authors

   Nuclear spins and precise values of the magnetic dipole and electric quadrupole moments of the ground-states of neutron-rich ${}^{76-78}$Cu isotopes were measured using the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at ISOLDE, CERN. The nuclear moments of the less exotic ${}^{73,75}$Cu isotopes were re-measured with similar precision, yielding values that are consistent with earlier measurements. The moments of the odd-odd isotopes, and ${}_{29}^{78}$Cu ($N=49$) in particular, are used to investigate excitations of the assumed doubly-magic ${}^{78}$Ni core through comparisons with large-scale shell-model calculations. Despite the narrowing of the $Z=28$ shell gap between $N\sim 45$ and $N=50$, the magicity of $Z=28$ and $N=50$ is restored towards ${}^{78}$Ni. This is due to weakened dynamical correlations, as clearly probed by the present moment measurements.

   nucl-exPRC(2017)·50 citations
2. 02*

   $\varphi$ photoproduction on the proton at $E_{\gamma }$ = 1.5 - 2.9 GeV

   K. Mizutani🇯🇵 · M. Niiyama🇯🇵 · T. Nakano🇯🇵 · M. Yosoi🇯🇵 · Y. Nozawa🇯🇵 · D. S. Ahn🇯🇵 · J. K. Ahn🇰🇷 · W. C. Chang🇹🇼 · J. Y. Chen🇹🇼 · S. Daté🇯🇵 · W. Gohn🇺🇸 · H. Hamano🇯🇵 and 44 other authors

   Differential cross sections at $t=t_{\text{min}}$ and decay asymmetries for the $\gamma p\to \varphi p$ reaction have been measured using linearly polarized photons in the range 1.5 to 2.9 GeV. These cross sections were used to determine the Pomeron strength factor. The cross sections and decay asymmetries are consistently described by the $t$-channel Pomeron and pseudoscalar exchange model in the $E_{\gamma }$ region above 2.37 GeV. In the lower energy region, an excess over the model prediction is observed in the energy dependence of the differential cross sections at $t=t_{\text{min}}$. This observation suggests that additional processes or interference effects between Pomeron exchange and other processes appear near the threshold region.

   nucl-exPRC(2017)·27 citations
3. 03*

   Measurement of hyper triton lifetime in Au + Au collisions at the Relativistic Heavy-Ion Collider

   The STAR Collaboration

   A precise measurement of the hypertriton lifetime is presented. In this letter, the mesonic decay modes ${}_{\mathrm{\Lambda }}^3\mathrm{H}{\to }^3\mathrm{He}+{\pi }^{-}$ and ${}_{\mathrm{\Lambda }}^3\mathrm{H}\to \mathrm{d}+\mathrm{p}+{\pi }^{-}$ are used to reconstruct the hypertriton from Au+Au collision data collected by the STAR collaboration at RHIC. A minimum ${\chi }^2$ estimation is used to determine the lifetime of $\tau =142_{-21}^{+24}(stat.)\pm 31(syst.)$ ps. This lifetime is about 50\% shorter than the lifetime $\tau =263\pm 2$ ps of a free $\Lambda$, indicating strong hyperon-nucleon interaction in the hypernucleus system. The branching ratios of the mesonic decay channels are also determined to satisfy B.R.${}_{{(}^3\mathrm{He}+{\pi }^{-})}/$(B.R.${}_{{(}^3\mathrm{He}+{\pi }^{-})}+$B.R.${}_{(d+p+{\pi }^{-})})$ = $0.32\pm 0.05(stat.)\pm 0.08(syst.)$. Our ratio result favors the assignment $J({}_{\mathrm{\Lambda }}^3\mathrm{H})$ = $\frac{1}{2}$ over $J({}_{\mathrm{\Lambda }}^3\mathrm{H})$ = $\frac{3}{2}$. These measurements will help to constrain models of hyperon-baryon interactions.

   nucl-exPRC(2018)·97 citations
4. 04*

   Revealing Fine Structure in the Antineutrino Spectra From a Nuclear Reactor

   A. A. Sonzogni🇺🇸 · M. Nino🇺🇸 · E. A. McCutchan🇺🇸

   We calculate the Inverse Beta Decay (IBD) antineutrino spectrum generated by nuclear reactors using the summation method to understand deviations from the smooth Huber-Mueller model due to the decay of individual fission products, showing that plotting the ratio of two adjacent spectra points can effectively reveal these deviations. We obtained that for binning energies of 0.1 MeV or lower, abrupt changes in the spectra due to the jagged nature of the individual antineutrino spectra could be observed for highly precise experiments. Surprisingly, our calculations also reveal a peak-like feature in the adjacent points ratio plot at 4.5 MeV even with a 0.25 MeV binning interval, which we find is present in the IBD Daya Bay spectrum published in 2016. We show that this 4.5 MeV feature is caused by the contributions of just four fission products, 95Y, 98,101N and 102Tc. This would be the first evidence of the decay of a few fission products in the IBD antineutrino spectrum from a nuclear reactor.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2018)·40 citations
5. 05*

   Correlated Prompt Fission Data in Transport Simulations

   P. Talou🇺🇸 · R. Vogt🇺🇸 · J. Randrup🇺🇸 · M.E. Rising · S.A. Pozzi🇮🇹 · J. Verbeke · M.T. Andrews · S.D. Clarke · P. Jaffke🇺🇸 · M. Jandel · T. Kawano🇺🇸 · M.J. Marcath and 6 other authors

   Detailed information on the fission process can be inferred from the observation, modeling and theoretical understanding of prompt fission neutron and $\gamma$-ray~observables. Beyond simple average quantities, the study of distributions and correlations in prompt data, e.g., multiplicity-dependent neutron and \gray~spectra, angular distributions of the emitted particles, $n$-$n$, $n$-$\gamma$, and $\gamma$-$\gamma$~correlations, can place stringent constraints on fission models and parameters that would otherwise be free to be tuned separately to represent individual fission observables. The FREYA~and CGMF~codes have been developed to follow the sequential emissions of prompt neutrons and $\gamma$-rays~from the initial excited fission fragments produced right after scission. Both codes implement Monte Carlo techniques to sample initial fission fragment configurations in mass, charge and kinetic energy and sample probabilities of neutron and $\gamma$~emission at each stage of the decay. This approach naturally leads to using simple but powerful statistical techniques to infer distributions and correlations among many observables and model parameters. The comparison of model calculations with experimental data provides a rich arena for testing various nuclear physics models such as those related to the nuclear structure and level densities of neutron-rich nuclei, the $\gamma$-ray~strength functions of dipole and quadrupole transitions, the mechanism for dividing the excitation energy between the two nascent fragments near scission, and the mechanisms behind the production of angular momentum in the fragments, etc. Beyond the obvious interest from a fundamental physics point of view, such studies are also important for addressing data needs in various nuclear applications. (See text for full abstract.)

   ↳ nucl-thnucl-exEPJA(2018)·46 citations
6. 06*

   Peeling off neutron skins from neutron-rich nuclei: Constraints on the symmetry energy from neutron-removal cross sections

   T. Aumann🇩🇪 · C.A. Bertulani🇺🇸 · F. Schindler🇩🇪 · S. Typel🇩🇪

   An experimentally constrained equation of state of neutron-rich matter is fundamental for the physics of nuclei and the astrophysics of neutron stars, mergers, core-collapse supernova explosions and the synthesis of heavy elements. To this end, we investigate the potential of constraining the density dependence of the symmetry energy close to saturation density through measurements of neutron-removal cross sections in high-energy nuclear collisions of a few hundreds MeV/nucleon to GeV/nucleon. We show that the sensitivity of the total neutron-removal cross section is high enough so that the required accuracy can be reached experimentally with the recent developments of new detection techniques. We quantify two crucial points to minimize the model dependence of the approach and to reach the required accuracy: the contribution to the cross section from inelastic scattering has to be measured separately in order to allow a direct comparison of experimental cross sections to theoretical cross sections based on density functional theory and eikonal theory. The accuracy of the reaction model should be investigated and quantified by the energy and target dependence of various nucleon-removal cross sections. Our calculations explore the dependence of neutron-removal cross sections on the neutron skin of medium-heavy neutron-rich nuclei, and we demonstrate that the slope parameter L of the symmetry energy could be constrained down to +/-10 MeV by such a measurement with a 2% accuracy of the measured and calculated cross sections.

   ↳ nucl-thnucl-exPRL(2017)·58 citations
7. 07*

   Charmonium Coherent Photoproduction and Hadroproduction with Effects of Quark Gluon Plasma

   Wei Shi · Wangmei Zha🇨🇳 · Baoyi Chen🇨🇳

   We study the charmonium coherent photoproduction and hadroproduction consistently with modifications from both cold and hot nuclear matters. The strong electromagnetic fields from fast moving nucleus interact with the other target nucleus, producing abundant charmonium in the extremely low transverse momentum region $p_T<0.1$ GeV/c. This results in significative enhancement of $J/\psi$ nuclear modification factor in semi-central and peripheral collisions. In the middle $p_T$ region such as $p_T<3\sim 5$ GeV/c, $J/\psi$ final yield is dominated by the combination process of single charm and anti-charm quarks moving in the deconfined matter, $c+\bar{c}\to J/\psi +g$. In the higher $p_T$ region, $J/\psi$ production are mainly from parton initial hard scatterings at the beginning of nucleus-nucleus collisions and decay of B hadrons. We include all of these production mechanisms and explain the experimental data well in different colliding centralities and transverse momentum regions.

   ↳ nucl-thnucl-exPLB(2018)·41 citations
8. 08*

   Elliptic flow coefficients from transverse momentum conservation

   Adam Bzdak🇵🇱 · Guo-Liang Ma🇨🇳

   We calculate the $k$-particle ($k=2,4,6,8$) azimuthal cumulants resulting from the conservation of transverse momentum. We find that $c_2\{k\}>0$ and depending on the transverse momenta, $c_2\{k\}$ can reach substantial values even for a relatively large number of particles. The impact of our results on the understanding of the onset of collectivity in small systems is emphasized.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2018)·11 citations
9. 09*

   New Search for Mirror Neutrons at HFIR

   L. J. Broussard · K. M. Bailey · W. B. Bailey · J. L. Barrow · B. Chance · C. Crawford · L. Crow · L. DeBeer-Schmitt · N. Fomin · M. Frost · A. Galindo-Uribarri · F. X. Gallmeier and 13 other authors

   The theory of mirror matter predicts a hidden sector made up of a copy of the Standard Model particles and interactions but with opposite parity. If mirror matter interacts with ordinary matter, there could be experimentally accessible implications in the form of neutral particle oscillations. Direct searches for neutron oscillations into mirror neutrons in a controlled magnetic field have previously been performed using ultracold neutrons in storage/disappearance measurements, with some inconclusive results consistent with characteristic oscillation time of $\tau$$\sim$10~s. Here we describe a proposed disappearance and regeneration experiment in which the neutron oscillates to and from a mirror neutron state. An experiment performed using the existing General Purpose-Small Angle Neutron Scattering instrument at the High Flux Isotope Reactor at Oak Ridge National Laboratory could have the sensitivity to exclude up to $\tau$$<$15~s in 1 week of beamtime and at low cost.

   ↳ hep-exnucl-exphysics.ins-det23 citations
10. 10*

    Unfolding Neutron Spectrum with Markov Chain Monte Carlo at MIT Research Reactor with He-3 Neutral Current Detectors

    A. F. Leder🇺🇸 · A. J. Anderson🇺🇸 · J. Billard🇫🇷 · E. Figueroa-Feliciano🇺🇸 · J. A. Formaggio🇺🇸 · C. Hasselkus🇺🇸 · E. Newman🇺🇸 · K. Palladino🇺🇸 · M. Phuthi🇺🇸 · L. Winslow🇺🇸 · L. Zhang🇺🇸

    The Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering using dark-matter-style detectors with sub-keV thresholds placed near a neutrino source, such as the MIT (research) Reactor (MITR), which operates at 5.5 MW generating approximately 2.2e18 neutrinos/second in its core. Currently, Ricochet is characterizing the backgrounds at MITR, the main component of which comes in the form of neutrons emitted from the core simultaneous with the neutrino signal. To characterize this background, we wrapped Bonner cylinders around a He-3 thermal neutron detector, whose data was then unfolded via a Markov Chain Monte Carlo (MCMC) to produce a neutron energy spectrum across several orders of magnitude. We discuss the resulting spectrum and its implications for deploying Ricochet at the MITR site as well as the feasibility of reducing this background level via the addition of polyethylene shielding around the detector setup.

    ↳ physics.ins-dethep-exnucl-exJINST(2018)·8 citations
11. 11*

    $\gamma$-ray Spectroscopy using a Binned Likelihood Approach

    J. R. Dermigny · C. Iliadis🇺🇸 · M. Q. Buckner · K. J. Kelly🇺🇸

    The measurement of a reaction cross section from a pulse height spectrum is a ubiquitous problem in experimental nuclear physics. In $\gamma$-ray spectroscopy, this is accomplished frequently by measuring the intensity of full-energy primary transition peaks and correcting the intensities for experimental artifacts, such as detection efficiencies and angular correlations. Implicit in this procedure is the assumption that full-energy peaks do not overlap with any secondary peaks, escape peaks, or environmental backgrounds. However, for complex $\gamma$-ray cascades, this is often not the case. Furthermore, this technique is difficult to adapt for coincidence spectroscopy, where intensities depend not only on the detection efficiency, but also the detailed decay scheme. We present a method that incorporates the intensities of the entire spectrum (e.g., primary and secondary transition peaks, escape peaks, Compton continua, etc.) into a statistical model, where the transition intensities and branching ratios can be determined using Bayesian statistical inference. This new method provides an elegant solution to the difficulties associated with analyzing coincidence spectra. We describe it in detail and examine its efficacy in the analysis of ${}^{18}$O(p,$\gamma$)${}^{19}$F and ${}^{25}$Mg(p,$\gamma$)${}^{26}$Al resonance data. For the ${}^{18}$O(p,$\gamma$)${}^{19}$F reaction, the measured branching ratios improve upon the literature values, with a factor of 4 reduction in the uncertainties.

    ↳ physics.data-annucl-exNucl.Instrum.Meth.A(2016)·11 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.