Mon·Jun 13, 2022Monday·June 13, 2022

1. 01*

   Observation of $\tau$ lepton pair production in ultraperipheral lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   CMS Collaboration

   We present an observation of photon-photon production of $\tau$ lepton pairs in ultraperipheral lead-lead collisions. The measurement is based on a data sample with an integrated luminosity of 404 $\mu$b${}^{-1}$ collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The $\gamma \gamma$ $\to$ ${\tau }^{+}{\tau }^{-}$ process is observed for $\tau \tau$ events with a muon and three charged hadrons in the final state. The measured fiducial cross section is $\sigma (\gamma \gamma$ $\to$ ${\tau }^{+}{\tau }^{-})$ = 4.8 $\pm$ 0.6 (stat) $\pm$ 0.5 (syst) $\mu$b, in agreement with leading-order QED predictions. Using $\sigma (\gamma \gamma$ $\to$ ${\tau }^{+}{\tau }^{-})$, we estimate a model-dependent value of the anomalous magnetic moment of the $\tau$ lepton of $a_{\tau }$ = 0.001 ${}_{-0.089}^{+0.055}$.

   nucl-exhep-exPRL(2023)·92 citations
2. 02*

   Renormalization group evolution of optical potentials: explorations using a toy model

   M. A. Hisham · R. J. Furnstahl🇺🇸 · A. J. Tropiano🇺🇸

   To take full advantage of experimental facilities such as FRIB for applications to nuclear astrophysics, nuclear structure, and explorations of neutrinos and fundamental symmetries, we need a better understanding of the interplay of reaction and structure theory. The renormalization group (RG) is the natural tool for maintaining a consistent treatment of reaction and structure. Here we make a first study of RG for optical potentials, which are important ingredients for direct reactions. To simplify the analysis, we use a pedagogical one-dimensional model and evolve toward low RG resolution using the similarity RG (or SRG). We show how SRG decoupling at low resolution carries over to the optical potential and enhances perturbative approximations, and how induced SRG nonlocality compares to the nonlocality of the optical potential. We discuss the results in the larger context of consistent SRG evolution of operators and wave functions in the analysis of direct reactions.

   ↳ nucl-thnucl-exPRC(2022)·7 citations
3. 03*

   Final Result on the Neutrinoless Double Beta Decay of ${}^{82}$Se with CUPID-0

   O. Azzolini🇮🇹 · J. W. Beeman🇺🇸 · F. Bellini🇮🇹 · M. Beretta🇮🇹 · M. Biassoni🇮🇹 · C. Brofferio🇮🇹 · C. Bucci🇮🇹 · S. Capelli🇮🇹 · V. Caracciolo🇮🇹 · L. Cardani🇮🇹 · P. Carniti🇮🇹 · N. Casali🇮🇹 and 36 other authors

   CUPID-0, an array of Zn${}^{82}$Se cryogenic calorimeters, was the first medium-scale demonstrator of the scintillating bolometers technology. The first project phase (March 2017 - December 2018) allowed the most stringent limit on the neutrinoless double beta decay half-life of the isotope of interest, ${}^{82}$Se, to be set. After a six months long detector upgrade, CUPID-0 began its second and last phase (June 2019 - February 2020). In this letter, we describe the search for neutrinoless double beta decay of ${}^{82}$Se with a total exposure (phase I + II) of 8.82 kg$\times$yr of isotope. We set a limit on the half-life of ${}^{82}$Se to the ground state of ${}^{82}$Kr of T${}_{1/2}^{0\nu }$(${}^{82}$Se)$>$ 4.6$\times {10}^{24}$ yr (90\% credible interval), corresponding to an effective Majorana neutrino mass m${}_{\beta \beta }<$ (263 -- 545) meV. We also set the most stringent lower limits on the neutrinoless decays of ${}^{82}$Se to the 0${}_1^{+}$, 2${}_1^{+}$ and 2${}_2^{+}$ excited states of ${}^{82}$Kr, finding 1.8$\times$10${}^{23}$ yr, 3.0$\times$10${}^{23}$ yr, 3.2$\times$10${}^{23}$ yr (90$\%$ credible interval) respectively.

   ↳ hep-exnucl-exphysics.ins-detPRL(2022)·100 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.