Thu·Nov 22, 2018Thursday·November 22, 2018

1. 01*

   How Robust is the N = 34 Subshell Closure? First Spectroscopy of ${}^{52}$Ar

   H. N. Liu🇫🇷 · A. Obertelli🇫🇷 · P. Doornenbal🇯🇵 · C. A. Bertulani🇺🇸 · G. Hagen🇺🇸 · J. D. Holt🇨🇦 · G. R. Jansen🇺🇸 · T. D. Morris🇺🇸 · A. Schwenk🇩🇪 · R. Stroberg🇨🇦 · N. Achouri🇫🇷 · H. Baba🇯🇵 and 68 other authors

   The first $\gamma$-ray spectroscopy of ${}^{52}$Ar, with the neutron number N = 34, was measured using the ${}^{53}$K(p,2p) one-proton removal reaction at $\sim$210 MeV/u at the RIBF facility. The 2${}_1^{+}$ excitation energy is found at 1656(18) keV, the highest among the Ar isotopes with N $>$ 20. This result is the first experimental signature of the persistence of the N = 34 subshell closure beyond ${}^{54}$Ca, i.e., below the magic proton number Z = 20. Shell-model calculations with phenomenological and chiral-effective-field-theory interactions both reproduce the measured 2${}_1^{+}$ systematics of neutron-rich Ar isotopes, and support a N = 34 subshell closure in ${}^{52}$Ar.

   nucl-exnucl-thPRL(2019)·92 citations
2. 02*

   The NUMEN project: NUclear Matrix Elements for Neutrinoless double beta decay

   F. Cappuzzello · C. Agodi · M. Cavallaro · D. Carbone · S. Tudisco · D. Lo Presti · J. R. B. Oliveira · P. Finocchiaro · M. Colonna · D. Rifuggiato · L. Calabretta · D. Calvo and 59 other authors

   The article describes the main achievements of the NUMEN project together with an updated and detailed overview of the related R&D activities and theoretical developments. NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave-functions in the two types of processes and the formal similarity of the transition operators. First experimental results obtained at the INFN-LNS laboratory for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV, give encouraging indication on the capability of the proposed technique to access relevant quantitative information. The two major aspects for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer. The former is used for the acceleration of the required high resolution and low emittance heavy ion beams and the latter is the large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the experimental resolution and sensitivity required for the accurate measurement of the DCE cross sections at forward angles. However, the tiny values of such cross sections and the resolution requirements demand beam intensities much larger than manageable with the present facility. The on-going upgrade of the INFN-LNS facilities in this perspective is part of the NUMEN project and will be discussed in the article.

   nucl-exphysics.ins-detEPJA(2018)·188 citations
3. 03*

   Effect of Siegert's Theorem on Low-Energy Neutrino-Nucleus Interactions

   A.C. Hayes🇺🇸 · J.L. Friar🇺🇸

   We examine the importance of conserving the vector current in calculating low-energy neutrino-nucleus interactions by implicitly invoking Siegert's Theorem in describing the vector transverse electric current. We find that at low neutrino energies (E? <50 MeV), Siegert's Theorem can change neutrino cross sections for normal-parity non-spin-flip excitations by about a factor of two.The same is true of muon capture rates. At higher neutrino energies the effect of Siegert's Theorem diminishes, and by about 100 MeV the effect is very small.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2018)·2 citations
4. 04*

   First measurement of a long-lived ${\pi }^{+}{\pi }^{-}$ atom lifetime

   B.Adeva🇪🇸 · L.Afanasyev🇷🇺 · A.Anania🇮🇹 · S.Aogaki🇷🇴 · A.Benelli🇨🇭 · V.Brekhovskikh🇷🇺 · T.Cechak🇨🇿 · M.Chiba🇯🇵 · P.V.Chliapnikov🇷🇺 · P.Doskarova🇨🇿 · D.Drijard🇨🇭 · A.Dudarev🇷🇺 and 47 other authors

   The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogen-like ${\pi }^{+}{\pi }^{-}$ atoms, produced by protons hitting a beryllium target. A part of these atoms crossed the gap of 96~mm and got broken up in the 2.1~\textmu{}m thick platinum foil. Analysing the observed number of atomic pairs, $n_A^L={436_{-61}^{+157}|}_{\mathrm{tot}}$, the lifetime of the 2$p$ state is found to be ${\tau }_{2p}=({0.45_{-0.30}^{+1.08}|}_{\mathrm{tot}})\cdot 10^{-11}$s, not contradicting the corresponding QED $2p$ state lifetime ${\tau }_{2p}^{\mathrm{QED}}=1.17\cdot 10^{-11}$s. This lifetime value is three orders of magnitude larger than our previously measured value of the ${\pi }^{+}{\pi }^{-}$ atom ground state lifetime $\tau =({3.15_{-0.26}^{+0.28}|}_{\mathrm{tot}})\cdot 10^{-15}$s. Further studies of long-lived ${\pi }^{+}{\pi }^{-}$ atoms will allow to measure energy differences between $p$ and $s$ atomic states and so to determine $\pi \pi$ scattering lengths with the aim to check QCD predictions.

   ↳ hep-exnucl-exPRL(2019)·10 citations
5. 05*

   Model-independent femtoscopic Levy imaging for elastic proton-proton scattering

   T. Csorgo🇭🇺 · R. Pasechnik🇸🇪 · A. Ster🇭🇺

   A model independent Levy expansion method is introduced to describe nearly Levy shaped squared moduli of Fourier transforms. We apply this method to precisely characterize the most recent elastic scattering data of proton-proton collisions at $\sqrt{s}=13$ TeV. The results reveal a substructure of protons, which is found to be significantly larger and darker in high energy proton-proton collisions at the TeV scale, as compared to a rather faint and apparently overlooked sub-structure, that we also identify in elastic proton-proton scattering at the ISR energy range of $\sqrt{s}=23-62$ GeV.

   ↳ hep-phhep-exnucl-exnucl-th+1Phys.Part.Nucl.(2020)·8 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.