Mon·May 27, 2019Monday·May 27, 2019

1. 01*

   Undetected Electron Backscattering in PERKEO III

   Christoph Roick · Heiko Saul · Hartmut Abele🇦🇹 · Bastian Märkisch🇩🇪

   The beta asymmetry in neutron beta decay is used to determine the ratio of axial-vector coupling to vector coupling most precisely. In electron spectroscopy, backscattering of electrons from detectors can be a major source of systematic error. We present the determination of the correction for undetected backscattering for electron detection with the instrument PERKEO III. For the electron asymmetry, undetected backscattering leads to a fractional correction of $5\times 10^{-4}$, i.e. a change by 40% of the total systematic uncertainty.

   nucl-exEPJ Web Conf.(2019)·6 citations
2. 02*

   Pairing-quadrupole interplay in the neutron-deficient tin nuclei: first lifetime measurements of low-lying states in ${}^{106,108}$Sn

   M. Siciliano🇮🇹 · J.J. Valiente-Dobón🇮🇹 · A. Goasduff🇮🇹 · F. Nowacki🇫🇷 · A.P. Zuker🇫🇷 · D. Bazzacco🇮🇹 · A. Lopez-Martens🇫🇷 · E. Clément🇫🇷 · G. Benzoni🇮🇹 · T. Braunroth🇩🇪 · N. Cieplicka-Oryńczak🇮🇹 · F.C.L. Crespi and 58 other authors

   The lifetimes of the low-lying excited states $2^{+}$ and $4^{+}$ have been directly measured in the neutron-deficient ${}^{106,108}$Sn isotopes. The nuclei were populated via a deep-inelastic reaction and the lifetime measurement was performed employing a differential plunger device. The emitted $\gamma$ rays were detected by the AGATA array, while the reaction products were uniquely identified by the VAMOS++ magnetic spectrometer. Large-Scale Shell-Model calculations with realistic forces indicate that, independently of the pairing content of the interaction, the quadrupole force is dominant in the $B(E2;2_1^{+}\to 0_{g.s.}^{+})$ values and it describes well the experimental pattern for ${}^{104-114}$Sn; the $B(E2;4_1^{+}\to 2_1^{+})$ values, measured here for the first time, depend critically on a delicate pairing-quadrupole balance, disclosed by the very precise results in ${}^{108}$Sn. This result provides insight in the hitherto unexplained $B(E2;4_1^{+}\to 2_1^{+})/B(E2;2_1^{+}\to 0_{g.s.}^{+})<1$ anomaly.

   nucl-exPLB(2020)·35 citations
3. 03*

   Branching ratios in the $\beta$ decay of ${}^{16}$N

   O. S. Kirsebom · E. R. Christensen (for the IS605 Collaboration)🇩🇰

   In this brief note, we present the results of an experiment performed at the ISOLDE Decay Station at CERN in which several of the branching ratios in the $\beta$ decay of ${}^{16}$N were determined with high precision and accuracy.

   nucl-ex0 citations
4. 04*

   Correlations of azimuthal anisotropy Fourier harmonics with subevent cumulants in pPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 8.16 TeV

   CMS Collaboration

   Event-by-event correlations of azimuthal anisotropy Fourier coefficients ($v_n$) in 8.16 TeV pPb collision data, collected by the CMS experiment at the LHC, are extracted using a subevent four-particle cumulant technique. Each combination of four charged particles are selected from either two, three, or four distinct subevent regions of a pseudorapidity range from $-$2.4 to 2.4 of the CMS tracker, and with transverse momentum between 0.3 and 3.0 GeV. Using the subevent cumulant technique, correlations between $v_n$ of different orders are measured as functions of particle multiplicity and compared to the standard cumulant method without subevents over a wide event multiplicity range. At high multiplicity, the $v_2$ and $v_3$ coefficients exhibit an anticorrelation; this behavior is observed consistently using various methods. The $v_2$ and $v_4$ correlation strength is found to depend on the number of subevents used in the calculation. As the event multiplicity decreases, the results from different subevent methods diverge because of different contributions of non-collective or few-particle correlations. Correlations extracted with the four-subevent method exhibit a tendency to diminish monotonically toward the lowest multiplicity region (about 20 charged tracks) investigated. These findings extend previous studies to a significantly lower event multiplicity range and establish the evidence for the onset of long-range collective multiparticle correlations in small system collisions.

   ↳ hep-exnucl-exPRC(2021)·15 citations
5. 05*

   Relic neutrino detection through angular correlations in inverse $\beta$-decay

   Evgeny Akhmedov🇩🇪

   Neutrino capture on beta-decaying nuclei is currently the only known potentially viable method of detection of cosmic background neutrinos. It is based on the idea of separation of the spectra of electrons or positrons produced in captures of relic neutrinos on unstable nuclei from those from the usual $\beta$-decay and requires very high energy resolution of the detector, comparable to the neutrino mass. In this paper we suggest an alternative method of discrimination between neutrino capture and $\beta$-decay, based on periodic variations of angular correlations in inverse beta decay transitions induced by relic neutrino capture. The time variations are expected to arise due to the peculiar motion of the Sun with respect to the C$\nu$B rest frame and the rotation of the Earth about its axis and can be observed in experiments with both polarized and unpolarized nuclear targets. The main advantage of the suggested method is that it does not depend crucially on the energy resolution of detection of the produced $\beta$-particles and can be operative even if this resolution exceeds the largest neutrino mass.

   ↳ hep-phastro-ph.COhep-exnucl-exJCAP(2019)·21 citations
6. 06*

   Design of the Magnet System of the Neutron Decay Facility PERC

   Xiangzun Wang🇦🇹 · Carmen Ziener🇩🇪 · Hartmut Abele🇦🇹 · Stefan Bodmaier🇩🇪 · Dirk Dubbers🇩🇪 · Jaqueline Erhart🇦🇹 · Alexander Hollering🇩🇪 · Erwin Jericha🇦🇹 · Jens Klenke🇩🇪 · Harald Fillunger🇦🇹 · Werner Heil🇩🇪 · Christine Klauser🇦🇹 and 18 other authors

   The PERC (Proton and Electron Radiation Channel) facility is currently under construction at the research reactor FRM II, Garching. It will serve as an intense and clean source of electrons and protons from neutron beta decay for precision studies. It aims to contribute to the determination of the Cabibbo-Kobayashi-Maskawa quark-mixing element $V_{ud}$ from neutron decay data and to search for new physics via new effective couplings. PERC's central component is a 12m long superconducting magnet system. It hosts an 8m long decay region in a uniform field. An additional high-field region selects the phase space of electrons and protons which can reach the detectors and largely improves systematic uncertainties. We discuss the design of the magnet system and the resulting properties of the magnetic field.

   ↳ physics.ins-detnucl-exEPJ Web Conf.(2019)·22 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.