Wed·Apr 24, 2019Wednesday·April 24, 2019

1. 01*

   An alternative approach to populate and study the ${}^{229}$Th nuclear clock isomer

   M. Verlinde🇧🇪 · S. Kraemer🇧🇪 · J. Moens🇧🇪 · K. Chrysaldis🇨🇭 · J.G. Correia🇵🇹 · S. Cottenier🇧🇪 · H. De Witte🇧🇪 · D.V. Fedorov🇷🇺 · V.N Fedosseev🇨🇭 · R. Ferrer🇧🇪 · L.M. Fraile🇪🇸 · S. Geldhof🇫🇮 and 15 other authors

   A new approach to observe the radiative decay of the ${}^{229}$Th nuclear isomer, and to determine its energy and radiative lifetime, is presented. Situated at a uniquely low excitation energy, this nuclear state might be a key ingredient for the development of a nuclear clock, a nuclear laser and the search for time variations of the fundamental constants. The isomer's $\gamma$ decay towards the ground state will be studied with a high-resolution VUV spectrometer after its production by the $\beta$ decay of ${}^{229}$Ac. The novel production method presents a number of advantages asserting its competitive nature with respect to the commonly used ${}^{233}$U $\alpha$-decay recoil source. In this paper, a feasibility analysis of this new concept, and an experimental investigation of its key ingredients, using a pure ${}^{229}$Ac ion beam produced at the ISOLDE radioactive beam facility, is reported.

   nucl-exPRC(2019)·26 citations
2. 02*

   Background Model of the CUPID-0 Experiment

   O. Azzolini🇮🇹 · J. W. Beeman🇺🇸 · F. Bellini🇮🇹 · M. Beretta🇮🇹 · M. Biassoni🇮🇹 · C. Brofferio🇮🇹 · C. Bucci🇮🇹 · S. Capelli🇮🇹 · L. Cardani🇮🇹 · P. Carniti🇮🇹 · N. Casali🇮🇹 · D. Chiesa🇮🇹 and 32 other authors

   CUPID-0 is the first large mass array of enriched Zn${}^{82}$Se scintillating low temperature calorimeters, operated at LNGS since 2017. During its first scientific runs, CUPID-0 collected an exposure of 9.95 kg yr. Thanks to the excellent rejection of $\alpha$ particles, we attained the lowest background ever measured with thermal detectors in the energy region where we search for the signature of ${}^{82}$Se neutrinoless double beta decay. In this work we develop a model to reconstruct the CUPID-0 background over the whole energy range of experimental data. We identify the background sources exploiting their distinctive signatures and we assess their extremely low contribution (down to $\sim 10^{-4}$ counts/(keV kg yr)) in the region of interest for ${}^{82}$Se neutrinoless double beta decay search. This result represents a crucial step towards the comprehension of the background in experiments based on scintillating calorimeters and in next generation projects such as CUPID.

   nucl-exphysics.ins-detEPJC(2019)·71 citations
3. 03*

   Disentangle contributions to small-system collectivity via scans of light nucleus-nucleus collisions

   Shengli Huang🇺🇸 · Zhenyu Chen🇺🇸 · Jiangyong Jia🇺🇸 · Wei Li🇺🇸

   The observation of multi-particle azimuthal correlations in high-energy small-system collisions has led to intense debate on its origin and the possible coexistence from two competing theoretical scenarios: one based on initial-state intrinsic momentum anisotropy (ISM), and the other based on final-state collective response to the collision geometry (FSM). To complement the previous scan of asymmetric collision systems ($p$+Au, $d$+Au and He+Au), we propose a scan of small symmetric collision systems at RHIC, such as C+C, O+O, Al+Al and Ar+Ar $\sqrt{s_{\mathrm{NN}}}=0.2$ TeV, to provide further insights in disentangling contributions from these two scenarios. These symmetric small systems have the advantage of providing a better controlled initial geometry dominated by the average shape of the overlap region, as opposed to fluctuation-driven geometries in asymmetric systems. A transport model is employed to investigate the expected geometry response in the FSM scenario. Different trends of elliptic flow with increasing charge particle multiplicity are observed between symmetric and asymmetric systems, while triangular flow appears to show a similar behavior. Furthermore, a comparison of O+O collisions at $\sqrt{s_{\mathrm{NN}}}=0.2$ TeV and at $\sqrt{s_{\mathrm{NN}}}=2.76-7$ TeV, as proposed at the LHC, provides a unique opportunity to disentangle the collision geometry effects at nucleon level from those arising from subnucleon fluctuations.

   nucl-exhep-phnucl-thPRC(2020)·46 citations
4. 04*

   Precision measurement of the proton charge radius in electron proton scattering

   A. Vorobyev🇷🇺

   This report presents a project of an experiment for precision studies of the elastic electron proton scattering in the low momentum transfer region. The project is based on an innovative experimental method which allows for detection of recoil protons in a hydrogen "active target". The goal of the experiment is to measure the $ep$ elastic scattering differential cross section in the $Q^2$ range from 0.001 GeV${}^2$ to 0.04 GeV${}^2$ with 0.1% relative and 0.2% absolute precision and to determine the proton charge radius with a sub-percent precision. The important advantages of the proposed experiment are low radiative corrections, inherent to the recoil proton method, and absolute measurements of the differential cross sections. The experiment will be performed in the 720 MeV electron beam of the Mainz electron accelerator MAMI. This accelerator can provide an electron beam with optimal for this experiment parameters. The Proposal was approved by the MAMI Program Advisory Committee, and a special Agreement aimed at realization of this experiment was signed between Petersburg Nuclear Physics Institute and Institute of Nuclear Physics of the Mainz University. Also, scientists from the following institutes will participate in this project: GSI Centre for Heavy Ion Research, Germany; Joint Institute for Nuclear Research, Russia; William and Mary College, USA; Mount Allison University, Canada; University of Regina, Canada; Saint Mary's University, Canada. The first measurements should be started in 2020.

   nucl-exhep-exPhys.Part.Nucl.Lett.(2019)·13 citations
5. 05*

   Measurement of the $K^{+}\to {\mu }^{+}{\nu }_{\mu }\gamma$ decay form factors in the OKA experiment

   V.I. Kravtsov🇷🇺 · V.A. Duk🇷🇺 · S.N. Filippov🇷🇺 · E.N. Gushchin🇷🇺 · A.A. Khudyakov🇷🇺 · Yu.G. Kudenko🇷🇺 · A.Yu. Polyarush🇷🇺 · S.A. Akimenko🇷🇺 · A.V. Artamonov🇷🇺 · A.M. Blik🇷🇺 · V.S. Burtovoy🇷🇺 · S.V. Donskov🇷🇺 and 27 other authors

   A precise measurement of the vector and axial-vector form factors difference $F_V-F_A$ in the $K^{+}\to {\mu }^{+}{\nu }_{\mu }\gamma$ decay is presented. About 95K events of $K^{+}\to {\mu }^{+}{\nu }_{\mu }\gamma$ are selected in the OKA experiment. The result is $F_V-F_A=0.134\pm 0.021(stat)\pm 0.027(syst)$. Both errors are smaller than in the previous $F_V-F_A$ measurements.

   ↳ hep-exnucl-exEPJC(2019)·11 citations
6. 06*

   Triply-heavy baryons in a constituent quark model

   Gang Yang🇨🇳 · Jialun Ping🇨🇳 · Pablo G. Ortega🇪🇸 · Jorge Segovia🇪🇸

   A constituent quark model, which has recently been successfully applied to the study of heavy quarkonium properties such as its spectrum but also a diverse array of observables related with their electromagnetic, strong and weak decays and reactions, is used herein to compute ground- and excited-state masses of $QQQ$-baryons containing either $c$- or $b$-quarks. Considering the lack of experimental information about the spectra of triply-heavy baryons, we believe that our computation could help on finding new states, since it is expected that phenomenological quark models describe triply-heavy baryons to a similar degree of accuracy as heavy quarkonia. The quark model parameters previously used to describe $c\bar{c}$ and $b\bar{b}$ properties have not been modified for this analysis. The non-relativistic three-body bound-state problem is solved by means of the Gaußian expansion method which provides enough accuracy and simplifies the subsequent evaluation of the matrix elements. Several low-lying states with quantum numbers $J^P={\frac{1}{2}}^{\pm }$, ${\frac{3}{2}}^{\pm }$, ${\frac{5}{2}}^{\pm }$ and ${\frac{7}{2}}^{+}$ are reported. We compare our results with those predicted by many other theoretical formalisms. There is a general trend of agreement about the mass of the ground state in each sector of triply-heavy baryons; however, the situation is more puzzling for the excited states and thus appropriate comments on the most relevant features of our comparison are given.

   ↳ hep-phhep-exhep-latnucl-ex+1CPC(2020)·77 citations
7. 07*

   Primordial non-Gaussianity in heavy-ion collisions

   Rajeev S. Bhalerao🇮🇳 · Giuliano Giacalone🇫🇷 · Jean-Yves Ollitrault🇫🇷

   We show that experimental data on cumulants of anisotropic flow in heavy-ion collisions probe the non-Gaussian statistics of the energy density field created right after the collision. We carry out a perturbative expansion of the initial anisotropies of the system in terms of its density fluctuations. We argue that the correlation between the magnitudes of elliptic flow and triangular flow, dubbed $sc(3,2)$, is generically of the same sign and order of magnitude as the kurtosis of triangular flow in a hydrodynamic picture. The experimental observation that these quantities are negative implies that the distribution of energy around a given point has positive skew.

   ↳ nucl-thhep-phnucl-exPRC(2019)·14 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.