Fri·Jan 29, 2021Friday·January 29, 2021

1. 01*

   Spectroscopy of ${}^{33}$Mg with knockout reactions

   D. Bazin🇺🇸 · N. Aoi🇯🇵 · H. Baba🇯🇵 · J. Chen🇺🇸 · H. Crawford🇺🇸 · P. Doornenbal🇯🇵 · P. Fallon🇺🇸 · K. Li🇯🇵 · J. Lee🇨🇳 · M. Matsushita🇯🇵 · T. Motobayashi🇯🇵 · H. Sakurai🇯🇵 and 7 other authors

   The structure of ${}^{33}$Mg was investigated by means of two knockout reactions, one-neutron removal from ${}^{34}$Mg and one-proton removal from ${}^{34}$Al. Using comparative analysis of the population of observed excited states in the residual ${}^{33}$Mg, the nature of these states can be deciphered. In addition, the long-standing controversy about the parity of the ${}^{33}$Mg ground state is resolved using momentum distribution analysis, showing a clear signature for negative parity. Partial cross section measurements are compared with the results of eikonal reaction theory combined with large-scale shell model calculations of this complex nucleus located in the island of inversion, where configuration mixing plays a major role.

   nucl-exPRC(2021)·12 citations
2. 02*

   Testing isospin symmetry breaking in ab initio nuclear theory

   M. S. Martin🇨🇦 · S. R. Stroberg🇺🇸 · J. D. Holt🇨🇦 · K. G. Leach🇺🇸

   In this work we present the first steps towards benchmarking isospin symmetry breaking in ab initio nuclear theory for calculations of superallowed Fermi $\beta$-decay. Using the valence-space in-medium similarity renormalization group, we calculate b and c coefficients of the isobaric multiplet mass equation, starting from two different Hamiltonians constructed from chiral effective field theory. We compare results to experimental measurements for all T=1 isobaric analogue triplets of relevance to superallowed $\beta$-decay for masses A=10 to A=74 and find an overall agreement within approximately 250 keV of experimental data for both b and c coefficients. A greater level of accuracy, however, is obtained by a phenomenological Skyrme interaction or a classical charged-sphere estimate. Finally, we show that evolution of the valence-space operator does not meaningfully improve the quality of the coefficients with respect to experimental data, which indicates that higher-order many-body effects are likely not responsible for the observed discrepancies.

   ↳ nucl-thnucl-exPRC(2021)·32 citations
3. 03*

   PANDA Phase One

   G. Barucca · F. Davì · G. Lancioni · P. Mengucci · L. Montalto · P. P. Natali · N. Paone · D. Rinaldi · L. Scalise · B. Krusche · M. Steinacher · Z. Liu and 413 other authors

   The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future antiProton ANnihilations at DArmstadt (PANDA or $\overline{\mathrm{P}}$ANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton-nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model, e.g. through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the \textit{Phase One} setup. The physics programme that is achievable during Phase One is outlined in this paper.

   ↳ hep-exnucl-exEPJA(2021)·102 citations
4. 04*

   A Comparative Study of Straight-Strip and Zigzag-Interleaved Anode Patterns for MPGD Readouts

   C.Perez-Lara🇺🇸 · S. Aune🇫🇷 · B. Azmoun🇺🇸 · K. Dehmelt🇺🇸 · A. Deshpande🇺🇸 · W. Fan🇺🇸 · P. Garg🇺🇸 · T. K. Hemmick🇺🇸 · M. Kebbiri🇫🇷 · A. Kiselev🇺🇸 · I. Mandjavidze🇫🇷 · M. L. Purschke🇺🇸 and 3 other authors

   Due to their simplicity and versatility of design, straight strip or rectangular pad anode structures are frequently employed with micro-pattern gas detectors to reconstruct high precision space points for various tracking applications. The particle impact point is typically determined by interpolating the charge collected by several neighboring pads. However, to effectively extract the inherent positional information, the lateral spacing of the straight pads must be significantly smaller than the extent of the charge cloud. In contrast, highly interleaved anode patterns, such as zigzags, can adequately sample the charge with a pitch comparable to the size of the charge cloud or even larger. This has the considerable advantage of providing the same performance while requiring far fewer instrumented channels. Additionally, the geometric parameters defining such zigzag structures may be tuned to provide a uniform detector response without the need for so-called pad response functions, while simultaneously maintaining excellent position resolution. We have measured the position resolution of a variety of zigzag shaped anode patterns optimized for various MPGDs, including GEM, Micromegas, and micro-RWELL and compared this performance to the same detectors equipped with straight pads of varying pitch. We report on the performance results of each readout structure, evaluated under identical conditions in a test beam.

   ↳ physics.ins-dethep-exnucl-exIEEE Trans.Nucl.Sci.(2021)·9 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.