Mon·Nov 22, 2021Monday·November 22, 2021

1. 01*

   Jet energy spectrum and substructure in $e^{+}{e}^{-}$ collisions at 91.2 GeV with ALEPH Archived Data

   Yi Chen (1)🇺🇸 · Anthony Badea (2)🇺🇸 · Austin Baty (3)🇺🇸 · Paoti Chang (4)🇹🇼 · Yang-Ting Chien (5)🇺🇸 · Gian Michele Innocenti (6)🇨🇭 · Marcello Maggi (7)🇮🇹 · Christopher McGinn (8)🇺🇸 · Dennis V. Perepelitsa (8)🇺🇸 · Michael Peters (1)🇺🇸 · Tzu-An Sheng (1)🇺🇸 · Jesse Thaler (1)🇺🇸 · Yen-Jie Lee (1) ((1) Massachusetts Institute of Technology, (2) Harvard University, (3) Rice University, (4) National Taiwan University, (5) Georgia State University, (6) CERN, (7) INFN Sezione di Bari, (8) University of Colorado)🇺🇸

   The first measurements of energy spectra and substructure of anti-$k_T$ jets in hadronic $Z^0$ decays in $e^{+}{e}^{-}$ collisions are presented. The archived $e^{+}{e}^{-}$ annihilation data at a center-of-mass energy of 91.2 GeV were collected with the ALEPH detector at LEP in 1994. In addition to inclusive jet and leading dijet energy spectra, various jet substructure observables are analyzed as a function of jet energy which includes groomed and ungroomed jet mass to jet energy ratios, groomed momentum sharing, and groomed jet radius. The results are compared with perturbative QCD calculations and predictions from the SHERPA, HERWIG v7.1.5, PYTHIA 6, PYTHIA 8, and PYQUEN event generators. The jet energy spectra agree with perturbative QCD calculations which include the treatment of logarithms of the jet radius and threshold logarithms. None of the event generators give a fully satisfactory description of the data.

   ↳ hep-exnucl-exJHEP(2022)·40 citations
2. 02*

   Towards testing the magnetic moment of the tau at one part per million

   Andreas Crivellin🇨🇭 · Martin Hoferichter🇨🇭 · J. Michael Roney🇨🇦

   If physics beyond the Standard Model (BSM) explains the $4.2\sigma$ difference between the Standard-Model and measured muon anomalous magnetic moment, $a_{\mu }$, minimal flavor violation predicts a shift in the analog quantity for the $\tau$ lepton, $a_{\tau }$, at the $10^{-6}$ level, and even larger effects are possible in generic BSM scenarios such as leptoquarks. We show that this produces equivalent BSM deviations in the Pauli form factor, $F_2(s)$, at $s=(10\text{GeV}{)}^2$, and report the first complete two-loop prediction of $\text{Re}{F}_2^{\text{eff}}(100{\text{GeV}}^2)=-268.77(50)\times 10^{-6}$ for resonant $\tau$-pair production in $e^{+}{e}^{-}\to {\rm Y}(nS)\to$ ${\tau }^{+}{\tau }^{-}$, $n=1,2,3$. $\text{Re}{F}_2^{\text{eff}}$ can be measured from $e^{-}$-helicity-dependent transverse and longitudinal asymmetries in $\tau$-pair events, which requires a longitudinally polarized $e^{-}$ beam. We discuss how Belle II asymmetry measurements could probe $a_{\tau }^{\text{BSM}}$ at $10^{-6}$, assuming such a polarization upgrade of the SuperKEKB $e^{+}{e}^{-}$ collider, and conclude by outlining the next steps to be taken in theory and experiment along this new avenue for exploring realistic BSM effects in $a_{\tau }$.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2022)·66 citations
3. 03*

   The ${}^3$He BF${}_3$ Giant Barrel (HeBGB) Neutron Detector

   K. Brandenburg🇲🇽 · G. Hamad🇺🇸 · Z. Meisel🇺🇸 · C. R. Brune🇺🇸 · D. E. Carter · T. Danley🇺🇸 · J. Derkin🇺🇸 · Y. Jones-Alberty🇲🇽 · B. Kenady · T. N. Massey🇺🇸 · S. Paneru🇺🇸 · M. Saxena🇺🇸 and 3 other authors

   $(\alpha ,n)$ reactions play an important role in nuclear astrophysics and applications and are an important background source in neutrino and dark matter detectors. Measurements of total $(\alpha ,n)$ cross sections employing direct neutron detection often have a considerable systematic uncertainty associated with the energy-dependent neutron detection efficiency and the unknown initial neutron energy distribution. The ${}^3\mathrm{He}{\mathrm{BF}}_3$ Giant Barrel (HeBGB) neutron detector was built at the Edwards Accelerator Laboratory at Ohio University to overcome this challenge. HeBGB offers a near-constant neutron detection efficiency of ($7.5\pm 1.2$) \% over the neutron energy range 0.01 MeV -- 9.00 MeV, removing a significant source of systematic uncertainty present in earlier $(\alpha ,n)$ cross section measurements.

   ↳ physics.ins-detnucl-exJINST(2022)·10 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.