Fri·Mar 26, 2021Friday·March 26, 2021

1. 01*

   Complete set of bound negative-parity states in the neutron-rich 18N nucleus

   S. Ziliani🇮🇹 · M. Ciemała🇵🇱 · F. C. L. Crespi🇮🇹 · S. Leoni🇮🇹 · B. Fornal🇵🇱 · T. Suzuki🇯🇵 · T. Otsuka🇯🇵 · A. Maj🇵🇱 · P. Bednarczyk🇵🇱 · G. Benzoni🇮🇹 · A. Bracco🇮🇹 · C. Boiano🇮🇹 and 45 other authors

   High-resolution gamma-ray spectroscopy of 18N is performed with the Advanced GAmma Tracking Array AGATA, following deep-inelastic processes induced by an 18O beam on a 181Ta target. Six states are newly identified, which together with the three known excitations exhaust all negative-parity excited states expected in 18N below the neutron threshold. Spin and parities are proposed for all located states on the basis of decay branchings and comparison with large-scale shell-model calculations performed in the p-sd space, with the YSOX interaction. Of particular interest is the location of the 0^-_1 and 1^-_2 excitations, which provide strong constrains for cross-shell p-sd matrix elements based on realistic interactions, and help to simultaneously reproduce the ground and first-excited states in 16N and 18N, for the first time. Understanding the 18N structure may also have significant impact on neutron-capture cross-section calculations in r-process modeling including light neutron-rich nuclei.

   nucl-exPRC(2021)·11 citations
2. 02*

   Probable observation of the nuclear Cooper pair mean square radius in superfluid nuclei

   R. A. Broglia🇩🇰 · F. Barranco🇪🇸 · G. Potel🇺🇸 · E. Vigezzi🇮🇹

   The phenomenon of low-temperature superconductivity is intimately associated with the condensation of weakly bound, very extended, strongly overlapping Cooper pairs, and systematic experimental studies of the associated mean square radius (coherence length) have been made. While the extension of BCS theory to the atomic nucleus has been successful beyond expectation, to our knowledge, no measurement of the nuclear coherence length (expected to be much larger than nuclear dimensions) has been reported in the literature. Recent studies of Cooper pair transfer across a Josephson-like junction, transiently established in a heavy ion collision between superfluid nuclei, have likely changed the situation, providing the experimental input for a quantitative estimate of the nuclear coherence length, as well as the basis for a nuclear analogue of the (ac) Josephson effect.

   ↳ nucl-thnucl-ex0 citations
3. 03*

   Calibration of the GERDA experiment

   GERDA collaboration: M. Agostini🇬🇧 · G. R. Araujo🇨🇭 · A. M. Bakalyarov🇷🇺 · M. Balata🇮🇹 · I. Barabanov🇷🇺 · L. Baudis🇨🇭 · C. Bauer🇩🇪 · E. Bellotti🇮🇹 · S. Belogurov🇷🇺 · A. Bettini🇮🇹 · L. Bezrukov🇷🇺 · V. Biancacci🇮🇹 and 99 other authors

   The GERmanium Detector Array (GERDA) collaboration searched for neutrinoless double-$\beta$ decay in ${}^{76}$Ge with an array of about 40 high-purity isotopically-enriched germanium detectors. The experimental signature of the decay is a monoenergetic signal at Q${}_{\beta \beta }$ = 2039.061(7)keV in the measured summed energy spectrum of the two emitted electrons. Both the energy reconstruction and resolution of the germanium detectors are crucial to separate a potential signal from various backgrounds, such as neutrino-accompanied double-$\beta$ decays allowed by the Standard Model. The energy resolution and stability were determined and monitored as a function of time using data from regular ${}^{228}$Th calibrations. In this work, we describe the calibration process and associated data analysis of the full GERDA dataset, tailored to preserve the excellent resolution of the individual germanium detectors when combining data over several years.

   ↳ physics.ins-detnucl-exEPJC(2021)·23 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.