Wed·Oct 30, 2019Wednesday·October 30, 2019

1. 01*

   Superallowed $0^{+}\to 0^{+}$ $\beta$ decay of $T=2$ ${}^{20}$Mg: $Q_{\text{EC}}$ value and $\beta \gamma$ branching

   B. E. Glassman (Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · D. Pérez-Loureiro (National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · C. Wrede (Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · J. M. Allen (Department of Physics, University of Notre Dame)🇺🇸 · D. W. Bardayan (Department of Physics, University of Notre Dame)🇺🇸 · M. B. Bennett (Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · B. A. Brown (Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · K. A. Chipps (Oak Ridge National Laboratory and Department of Physics and Astronomy, University of Tennesssee)🇺🇸 · M. Febbraro (Oak Ridge National Laboratory and Department of Physics and Astronomy, University of Tennesssee)🇺🇸 · C. Fry (Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University)🇺🇸 · M. R. Hall (Department of Physics, University of Notre Dame and Oak Ridge National Laboratory)🇺🇸 · O. Hall (Department of Physics, University of Notre Dame) and 9 other authors

   \textbf{Background}: Superallowed $0^{+}\to 0^{+}$ $\beta$ decays of isospin $T=2$ nuclides can be used to test theoretical isospin symmetry breaking corrections applied to extract the CKM matrix element $V_{ud}$ from $T=0,1$ decays by measuring precise $ft$ values and also to search for scalar currents using the $\beta -\nu$ angular correlation. Key ingredients include the $Q_{\text{EC}}$ value and branching of the superallowed transition and the half life of the parent. \textbf{Purpose}: To determine a precise experimental $Q_{\text{EC}}$ value for the superallowed $0^{+}\to 0^{+}$ $\beta$ decay of $T=2$ ${}^{20}$Mg and the intensity of ${}^{20}$Mg $\beta$-delayed $\gamma$ rays through the isobaric analog state in ${}^{20}$Na. \textbf{Method}: A beam of ${}^{20}$Mg was produced using the in-flight method and implanted into a plastic scintillator surrounded by an array of high-purity germanium detectors used to detect $\beta$-delayed $\gamma$ rays. The high-resolution $\gamma$-ray spectrum was analyzed to measure the $\gamma$-ray energies and intensities. \textbf{Results}: The intensity of ${}^{20}$Mg $\beta$-delayed $\gamma$ rays through the isobaric analog state in ${}^{20}$Na was measured to be $(1.60\pm 0.04_{\text{stat}}\pm 0.15_{\text{syst}}\pm 0.15_{\text{theo}})\times 10^{-4}$, where the uncertainties are statistical, systematic, and theoretical, respectively. The $Q_{\text{EC}}$ value for the superallowed transition was determined to be $4128.7\pm 2.2$ keV based on the measured excitation energy of $6498.4\pm 0.2_{\text{stat}}\pm 0.4_{\text{syst}}$ keV and literature values for the ground-state masses of ${}^{20}$Na and ${}^{20}$Mg. \textbf{Conclusions}: The $\beta$-delayed $\gamma$-decay branch and $Q_{\text{EC}}$ value are now sufficiently precise to match or exceed the sensitivity required for current low-energy tests of the standard model.

   nucl-exhep-exnucl-th0 citations
2. 02*

   $Z$ boson production in Pb+Pb collisions at $\sqrt{s_{\text{NN}}}$= 5.02 TeV measured by the ATLAS experiment

   ATLAS Collaboration

   The production yield of $Z$ bosons is measured in the electron and muon decay channels in Pb+Pb collisions at $\sqrt{s_{\text{NN}}}$ = 5.02 TeV with the ATLAS detector. Data from the 2015 LHC run corresponding to an integrated luminosity of 0.49 ${\text{nb}}^{-1}$ are used for the analysis. The $Z$ boson yield, normalised by the total total number of minimum-bias events and the mean nuclear thickness function, is measured as a function of dilepton rapidity and event centrality. The measurements in Pb+Pb collisions are compared with similar measurements made in proton$-$proton collisions at the same centre-of-mass energy. The nuclear modification factor is found to be consistent with unity for all centrality intervals. The results are compared with theoretical predictions obtained at next-to-leading order using nucleon and nuclear parton distribution functions. The normalised $Z$ boson yields in Pb+Pb collisions lie 1$-3$$\sigma$ above the predictions. The nuclear modification factor measured as a function of rapidity agrees with unity and is consistent with a next-to-leading-order QCD calculation including the isospin effect.

   nucl-exhep-exPLB(2020)·67 citations
3. 03*

   Performance evaluation of a silicon strip detector for positrons/electrons from a pulsed a muon beam

   T. Aoyagi🇯🇵 · Y. Honda🇯🇵 · H. Ikeda🇯🇵 · M. Ikeno🇯🇵 · K. Kawagoe🇯🇵 · T. Kohriki🇯🇵 · T. Kume🇯🇵 · T. Mibe🇯🇵 · K. Namba🇯🇵 · S. Nishimura🇯🇵 · N. Saito🇯🇵 · O. Sasaki🇯🇵 and 17 other authors

   A high-intensity pulsed muon beam is becoming available at the at the Japan Proton Accelerator Research Complex (J-PARC). Many experiments to study fundamental physics using this high-intensity muon beam are proposed. An experiment to measure the muon magnetic moment anomaly ($g-2$) and the muon electric dipole moment (EDM) is one of these experiments and it requires a tracking detector for positrons from muon decay. Fine segmentation is required in a detector to tolerate the high rate of positrons. The time resolution is required to be much better than the muon anomalous spin precession period while a buffer depth of a front-end electronics needs to be much longer than the accelerated muon lifetime. Requirements of this detector also meet requirements of a measurement of the muonium hyperfine structure interval at the J-PARC and another experiment to measure the proton charge radius at Tohoku University. We have developed a single-sided silicon strip sensor with a 190 $\mu$m pitch, a front-end electronics with a sampling rate of 200 MHz and a buffer memory depth of 8192, and a data acquisition system based on DAQ-Middleware for the J-PARC muon $g-2$/EDM experiment. We have fabricated detector modules consisting of this sensor and the front-end electronics. Performance of fabricated detector modules was evaluated at a laboratory and a beam test using the positron beam at Tohoku University. The detector is confirmed to satisfy all requirements of the experiments except for the time walk, which will be solved by the next version of a front-end electronics.

   ↳ physics.ins-dethep-exnucl-exJINST(2020)·14 citations
4. 04*

   Beam Test of the PIN-diode Readout Units with Electron Energies from 5 to 40 GeV at CERN SPS

   Chengbo Li🇨🇳 · Xiaomei Li🇨🇳 · Qiuying Meng🇨🇳 · Jing Zhou🇨🇳 · Shuhua Zhou🇨🇳 · Jian Yuan🇨🇳

   The Chinese large-area violet-light-sensitive silicon photodiode PIN is one of the candidates of the lead tungstate crystal detector readout component of the photon spectrometer in the large heavy ion collision experiment. The PIN diode was assembled with the lead tungstate crystal and the low-noise preamplifier into a complete detector unit. The beam test was carried out on the SPS accelerator at CERN. The energy resolution was measured with the electron beam energy ranging from 5 to 40 GeV. The summation correction method was discussed, and an excellent linearity of the nominal beam energy versus the peak position of the detector was obtained, which showed the punch-through effect can be ignored.

   ↳ physics.ins-dethep-exnucl-exEPJA(2020)·0 citations
5. 05*

   A New Theory Framework for the Electroweak Radiative Corrections in $K_{l3}$ Decays

   Chien-Yeah Seng🇩🇪 · Daniel Galviz🇩🇪 · Ulf-G. Meißner🇩🇪

   We propose a new theory framework to study the electroweak radiative corrections in $K_{l3}$ decays by combining the classic current algebra approach with the modern effective field theory. Under this framework, the most important $\mathcal{O}(G_F\alpha )$ radiative corrections are described by a single tensor $T^{\mu \nu }$ involving the time-ordered product between the charged weak current and the electromagnetic current, and all remaining pieces are calculable order-by-order in Chiral Perturbation Theory. We further point out a special advantage in the $K_{l3}^0$ channel that it suffers the least impact from the poorly-constrained low-energy constants. This finding may serve as a basis for a more precise extraction of the matrix element $V_{us}$ in the future.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2020)·37 citations
6. 06*

   Spectroscopy of short-lived radioactive molecules: A sensitive laboratory for new physics

   R.F. Garcia Ruiz🇨🇭 · R. Berger🇩🇪 · J. Billowes🇬🇧 · C.L. Binnersley🇬🇧 · M.L. Bissell🇬🇧 · A.A. Breier🇩🇪 · A.J. Brinson🇺🇸 · K. Chrysalidis🇨🇭 · T. Cocolios🇧🇪 · B. Cooper🇬🇧 · K.T. Flanagan🇬🇧 · T.F. Giesen🇩🇪 and 15 other authors

   The study of molecular systems provides exceptional opportunities for the exploration of the fundamental laws of nature and for the search for physics beyond the Standard Model of particle physics. Measurements of molecules composed of naturally occurring nuclei have provided the most stringent upper bounds to the electron electric dipole moment to date, and offer a route to investigate the violation of fundamental symmetries with unprecedented sensitivity. Radioactive molecules - where one or more of their atoms possesses a radioactive nucleus - can contain heavy and deformed nuclei, offering superior sensitivity for EDM measurements as well as for other symmetry-violating effects. Radium monofluoride, RaF, is of particular interest as it is predicted to have an appropriate electronic structure for direct laser cooling. Furthermore, some Ra isotopes are known to be octupole deformed, thereby resulting in a large enhancement of their symmetry-violating nuclear moments. Until now,however, no experimental measurements of RaF have been performed, and their study is impeded by major experimental challenges, as no stable isotopes of radium exist. Here, we present a novel experimental approach to study short-lived radioactive molecules using the highly sensitive collinear resonance ionisation method. With this technique we have measured, for the first time, the energetically low-lying electronic states for each of the isotopically pure RaF molecules at the ISOLDE-CERN. Our results provide strong evidence of the existence of a suitable laser-cooling scheme for these molecules and constitute a pivotal step towards high-precision studies in these systems. Our findings open up new opportunities in the synthesis, manipulation and study of short-lived radioactive molecules, which will have a direct impact in many-body physics, astrophysics, nuclear structure, and fundamental physics research.

   ↳ nucl-thhep-phhep-thnucl-exNature(2020)·98 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.