Wed·Jun 12, 2019Wednesday·June 12, 2019

1. 01*

   Photoproduction Reactions and Non-Strange Baryon Spectroscopy

   David G. Ireland🇬🇧 · Eugene Pasyuk🇺🇸 · Igor Strakovsky🇺🇸

   We review the last two decades of using photon beams to measure the production of mesons, and in particular the information that can be obtained on the spectrum of light, non-strange baryons. This is a compendium of experimental results, which should be used as a complement to theoretical reviews of the subject. Lists of data sets are given, together with a comprehensive set of references. An indication of the impact of the data is presented with a summary of the results.

   nucl-exhep-exhep-phPPNP(2020)·68 citations
2. 02*

   Decay spectroscopy of ${}^{50}$Sc and ${}^{50m}$Sc to ${}^{50}$Ti

   M. Bowry · C.E. Jones · A.B. Garnsworthy · G.C. Ball🇨🇦 · S. Cruz🇨🇦 · S. Georges🇨🇦 · G. Hackman🇨🇦 · J.D. Holt🇨🇦 · J. Measures🇨🇦 · B. Olaizola🇨🇦 · H.P. Patel🇨🇦 · C.J. Pearson🇨🇦 · C.E. Svensson🇨🇦

   The $\beta$ decay of the isomeric and ground state of ${}^{50}$Sc to the semi-magic nucleus ${}_{22}^{50}$Ti${}_{28}$ has been studied using a ${}^{50}$Ca beam delivered to the GRIFFIN $\gamma$-ray spectrometer at the TRIUMF-ISAC facility. $\beta$-decay branching ratios are reported to 16 excited states with a total of 38 $\gamma$-ray transitions linking them. These new data significantly expands the information available over previous studies. Relative intensities are measured to less than 0.001$\%$ that of the strongest transition with the majority of $\gamma$-ray transitions observed here in $\beta$ decay for the first time. The data are compared to shell-model calculations utilizing both phenomenologically-derived interactions employed in the $pf$ shell as well as a state-of-the-art, $abinitio$ based interaction built in the valence-space in-medium similarity renormalization group framework.

   nucl-exPRC(2021)·0 citations
3. 03*

   Determining the average prompt-fission-neutron multiplicity for ${}^{239}$Pu($n$,$f$) via a ${}^{240}$Pu($\alpha$,${\alpha }^{\prime }f$) surrogate reaction

   B. S. Wang🇺🇸 · J. T. Burke · O. A. Akindele🇺🇸 · R. J. Casperson🇺🇸 · R. O. Hughes · J. D. Koglin · K. Kolos · E. B. Norman🇺🇸 · S. Ota🇯🇵 · A. Saastamoinen🇺🇸

   The average prompt-fission-neutron multiplicity $\bar{\nu }$ is of significance in the areas of nuclear theory, nuclear nonproliferation, and nuclear energy. In this work, the surrogate-reaction method has been used for the first time to indirectly determine $\bar{\nu }$ for ${}^{239}$Pu($n$,$f$) via ${}^{240}$Pu($\alpha$,${\alpha }^{\prime }f$) reactions. A ${}^{240}$Pu target was bombarded with a beam of 53.9-MeV $\alpha$ particles. Scattered $\alpha$ particles, fission products, and neutrons were measured with the NeutronSTARS detector array. Values of $\bar{\nu }$ were obtained for a continuous range of equivalent incident neutron energies between 0.25--26.25~MeV, and the results agree well with direct neutron measurements.

   nucl-exPRC(2019)·7 citations
4. 04*

   Longitudinal Wobbling Motion in ${}^{187}$Au

   N. Sensharma · U. Garg🇺🇸 · Q. B. Chen🇩🇪 · S. Frauendorf🇺🇸 · D. P. Burdette🇺🇸 · J. L. Cozzi · K. B. Howard🇺🇸 · S. Zhu🇺🇸 · M. P. Carpenter🇺🇸 · P. Copp🇺🇸 · F. G. Kondev🇺🇸 · T. Lauritsen🇺🇸 and 10 other authors

   The rare phenomenon of nuclear wobbling motion has been investigated for the nucleus ${}^{187}$Au. A longitudinal wobbling-bands pair has been identified and clearly distinguished from the associated signature-partner band on the basis of angular distribution measurements. Theoretical calculations in the framework of the Particle Rotor Model (PRM) are found to agree well with the experimental observations. This is the first experimental evidence for longitudinal wobbling bands where the expected signature partner band has also been identified, and establishes this exotic collective mode as a general phenomenon over the nuclear chart.

   nucl-exnucl-thPRL(2020)·63 citations
5. 05*

   Study of multi-neutron emission in the $\beta$-decay of ${}^{11}$Li

   F. Delaunay🇫🇷 · N. L. Achouri🇫🇷 · A. Algora🇪🇸 · M. Assié🇫🇷 · J. Balibrea🇪🇸 · K. Banerjee🇮🇳 · C. Bhattacharya🇮🇳 · M. J. G. Borge🇨🇭 · D. Cano-Ott🇪🇸 · B. Fernández-Domínguez🇪🇸 · L. M. Fraile🇪🇸 · J. Gibelin🇫🇷 and 15 other authors

   The kinematics of two-neutron emission following the $\beta$-decay of ${}^{11}$Li was investigated for the first time by detecting the two neutrons in coincidence and by measuring their angle and energy. An array of liquid-scintillator neutron detectors was used to reject cosmic-ray and $\gamma$-ray backgrounds by pulse-shape discrimination. Cross-talk events in which two detectors are fired by a single neutron were rejected using a filter tested on the $\beta$-1n emitter ${}^9$Li. A large cross-talk rejection rate is obtained ($>95\%$) over most of the energy range of interest. Application to ${}^{11}$Li data leads to a significant number of events interpreted as $\beta$-2n decay. A discrete neutron line at $\approx$ 2 MeV indicates sequential two-neutron emission, possibly from the unbound state at 10.6 MeV excitation energy in ${}^{11}$Be.

   nucl-exNuovo Cim.C(2019)·4 citations
6. 06*

   Jet sub-structure and parton shower evolution in p+p and Au+Au collisions at STAR

   Raghav Kunnawalkam Elayavalli (for the STAR Collaboration)🇺🇸

   Recent measurements of jet structure modifications at RHIC and LHC highlight the importance of differential measurements to study the nature of jet quenching. Since these jet structure observables are intimately dependent on parton evolution in both the angular and energy scales, measurements are needed to disentangle these two scales in order to probe the medium at different length scales to study its characteristic properties such as the coherence length. To that effect, the STAR collaboration presents fully unfolded results of jet sub-structure observables designed to extract fundamental quantities related to the parton shower via the SoftDrop shared momentum fraction, the groomed jet radius, and the jet Mass in p+p collisions at 200 GeV as a function of jet transverse momenta. We also showcase the first measurement of iterative softdrop groomed observables for first, second and third splits with an initiator prong transverse momenta ranging from 20-25 GeV. In comparing the un-corrected data to our simulation, we are able to look at snapshots of the jet clustering history leading towards an understand of the time evolution of the parton shower. Having established the p+p baseline, we present the first measurement of the jet's inherent angular structure in Au+Au collisions at 200 GeV via an experimentally robust observable the opening angle between the two leading sub-jets (${\theta }_{SJ}$). In Au+Au collisions at STAR, we utilize a specific di-jet selection as introduced in our previous momentum imbalance ($A_J$) measurement and measure both the $A_J$ and the recoil jet spectra differentially as a function of the angular classes based on the ${\theta }_{SJ}$ observable. With such measurements, we probe the medium response to jets at a particular resolution scale and find no significant differences in quenching for jets of different angular scales as given by ${\theta }_{SJ}$.

   nucl-exPoS(2020)·2 citations
7. 07*

   NoMoS: An $R\times B$ Drift Momentum Spectrometer for Beta Decay Studies

   Daniel Moser🇦🇹 · Hartmut Abele🇦🇹 · Joachim Bosina🇦🇹 · Harald Fillunger🇦🇹 · Torsten Soldner🇫🇷 · Xiangzun Wang🇦🇹 · Johann Zmeskal🇦🇹 · Gertrud Konrad🇦🇹

   The beta decay of the free neutron provides several probes to test the Standard Model of particle physics as well as to search for extensions thereof. Hence, multiple experiments investigating the decay have already been performed, are under way or are being prepared. These measure the mean lifetime, angular correlation coefficients or various spectra of the charged decay products (proton and electron). NoMoS, the Neutron decay prOducts MOmentum Spectrometer, presents a novel method of momentum spectroscopy: it utilizes the $R\times B$ drift effect to disperse charged particles dependent on their momentum in an uniformly curved magnetic field. This spectrometer is designed to precisely measure momentum spectra and angular correlation coefficients in free neutron beta decay to test the Standard Model and to search for new physics beyond. With NoMoS, we aim to measure inter alia the electron-antineutrino correlation coefficient $a$ and the Fierz interference term $b$ with an ultimate precision of $\Delta a/a<0.3\%$ and $\Delta b<10^{-3}$ respectively. In this paper, we present the measurement principles, discuss measurement uncertainties and systematics, and give a status update.

   ↳ physics.ins-detnucl-exEPJ Web Conf.(2019)·7 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.