Tue·Mar 24, 2020Tuesday·March 24, 2020

1. 01*

   The observation of vibrating pear shapes in radon nuclei: update

   P.A. Butler🇬🇧 · L.P. Gaffney🇬🇧 · P. Spagnoletti🇬🇧 · J. Konki🇨🇭 · M. Scheck🇬🇧 · J.F. Smith🇬🇧 · K. Abrahams🇿🇦 · M. Bowry🇨🇦 · J. Cederkäll🇸🇪 · T. Chupp🇺🇸 · G. De Angelis🇮🇹 · H. De Witte🇧🇪 and 32 other authors

   There is a large body of evidence that atomic nuclei can undergo octupole distortion and assume the shape of a pear. This phenomenon is important for measurements of electric-dipole moments of atoms, which would indicate CP violation and hence probe physics beyond the standard model of particle physics. Isotopes of both radon and radium have been identified as candidates for such measurements. Here, we have observed the low-lying quantum states in ${}^{224}$Rn and ${}^{226}$Rn by accelerating beams of these radioactive nuclei. We report here additional states not assigned in our 2019 publication. We show that radon isotopes undergo octupole vibrations but do not possess static pear-shapes in their ground states. We conclude that radon atoms provide less favourable conditions for the enhancement of a measurable atomic electric-dipole moment.

   nucl-exhep-phnucl-thphysics.atom-phNature Commun.(2019)·50 citations
2. 02*

   Experimental identification of the $T=1$, $J^{\pi }=6^{+}$ state of ${}^{54}$Co and isospin symmetry in $A=54$ studied via one-nucleon knockout reactions

   M. Spieker🇺🇸 · D. Weisshaar🇺🇸 · A. Gade🇺🇸 · B. A. Brown🇺🇸 · P. Adrich🇵🇱 · D. Bazin🇺🇸 · M. A. Bentley · J. R. Brown🇬🇧 · C. M. Campbell🇺🇸 · C. Aa. Diget🇬🇧 · B. Elman · T. Glasmacher and 6 other authors

   New experimental data obtained from $\gamma$-ray tagged one-neutron and one-proton knockout from ${}^{55}$Co is presented. A candidate for the sought-after $T=1,T_z=0,J^{\pi }=6^{+}$ state in ${}^{54}$Co is proposed based on a comparison to the new data on ${}^{54}$Fe, the corresponding observables predicted by large-scale-shell-model (LSSM) calculations in the full $fp$-model space employing charge-dependent contributions, and isospin-symmetry arguments. Furthermore, possible isospin-symmetry breaking in the $A=54$, $T=1$ triplet is studied by calculating the experimental $c$ coefficients of the isobaric mass multiplet equation (IMME) up to the maximum possible spin $J=6$ expected for the $(1f_{7/2}{)}^{-2}$ two-hole configuration relative to the doubly-magic nucleus ${}^{56}$Ni. The experimental quantities are compared to the theoretically predicted $c$ coefficients from LSSM calculations using two-body matrix elements obtained from a realistic chiral effective field theory potential at next-to-next-to-next-to-leading order (N${}^3$LO).

   nucl-exnucl-thPRC(2019)·3 citations
3. 03*

   Four-jet production via double parton scattering in $pA$ collisions at the LHC

   B. Blok (Technion)🇮🇱 · F.A. Ceccopieri (Technion)🇮🇱

   We present predictions for the double parton scattering (DPS) four-jet production cross sections in $pA$ collisions at the LHC. Relying on the experimental capabilities to correlate centrality with impact parameter $B$ of the proton-nucleus collision, we discuss a strategy to extract the double parton scattering contributions in $pA$ collisions, which gives direct access to double parton distribution in the nucleon. We show that the production cross sections via DPS of four jets, out of which two may be light- or heavy-quark jets, are large enough to allow the method to be used already with data accumulated in 2016 $pA$ run.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2020)·3 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.