Mon·Nov 30, 2020Monday·November 30, 2020

1. 01*

   Overview of the latest jet physics results from ALICE

   James Mulligan🇺🇸

   We overview recent jet measurements in pp and Pb-Pb collisions with the ALICE detector. ALICE reconstructs jets at midrapidity using the anti-$k_{\mathrm{T}}$ algorithm, including both charged particle jets from the ALICE tracking detectors, and full jets from the combination of the ALICE electromagnetic calorimeter with the tracking system. We focus on inclusive and semi-inclusive jet measurements as well as jet substructure measurements, including a variety of groomed and ungroomed observables. In pp collisions, these results test pQCD techniques at $p_{\mathrm{T},\mathrm{jet}}<140$ GeV$/c$ in a low pileup environment, and can constrain models of non-perturbative effects. In Pb-Pb collisions, these measurements test models of jet quenching in the quark-gluon plasma, and can be used to constrain the properties of high temperature QCD matter.

   nucl-exhep-exPoS(2021)·4 citations
2. 02*

   Characterization of cubic Li${}_2$${}^{100}$MoO${}_4$ crystals for the CUPID experiment

   A. Armatol · E. Armengaud · W. Armstrong · C. Augier · F. T. Avignone III · O. Azzolini · A. Barabash · G. Bari · A. Barresi · D. Baudin · F. Bellini · G. Benato and 160 other authors

   The CUPID Collaboration is designing a tonne-scale, background-free detector to search for double beta decay with sufficient sensitivity to fully explore the parameter space corresponding to the inverted neutrino mass hierarchy scenario. One of the CUPID demonstrators, CUPID-Mo, has proved the potential of enriched Li${}_2$${}^{100}$MoO${}_4$ crystals as suitable detectors for neutrinoless double beta decay search. In this work, we characterised cubic crystals that, compared to the cylindrical crystals used by CUPID-Mo, are more appealing for the construction of tightly packed arrays. We measured an average energy resolution of (6.7$\pm$0.6) keV FWHM in the region of interest, approaching the CUPID target of 5 keV FWHM. We assessed the identification of $\alpha$ particles with and without a reflecting foil that enhances the scintillation light collection efficiency, proving that the baseline design of CUPID already ensures a complete suppression of this $\alpha$-induced background contribution. We also used the collected data to validate a Monte Carlo simulation modelling the light collection efficiency, which will enable further optimisations of the detector.

   ↳ physics.ins-detnucl-exEPJC(2021)·39 citations
3. 03*

   Triaxial rigidity of ${}^{166}$Er and its Bohr-model realization

   Yusuke Tsunoda🇯🇵 · Takaharu Otsuka🇯🇵

   The triaxial nature of low-lying rotational bands of ${}^{166}$Er is presented from the viewpoint of the Bohr Hamiltonian and from that of many-fermion calculations by the Monte Carlo shell model and the constrained Hartree-Fock method with projections. A recently proposed novel picture of those bands suggests definite triaxial shapes of those bands, in contrast to the traditional view with the prolate ground-state band and the $\gamma$-vibrational excited band. Excitation level energies and E2 transitions can be described well by the Bohr Hamiltonian and by the many-fermion approaches, where rather rigid triaxiality plays vital roles, although certain fluctuations occur in shell-model wave functions. Based on the potential energy surfaces with the projections, we show how the triaxial rigidity appears and what the softness of the triaxiality implies. The excitation to the so-called double $\gamma$-phonon state is discussed briefly.

   ↳ nucl-thnucl-exPRC(2021)·28 citations
4. 04*

   Bose-Einstein momentum correlations at fixed multiplicities: Lessons from an exactly solvable thermal model for $pp$ collisions at the LHC

   M.D. Adzhymambetov🇺🇦 · S.V. Akkelin🇺🇦 · Yu.M. Sinyukov🇺🇦

   Two-particle momentum correlations of $N$ identical bosons are studied in the quantum canonical ensemble. We define the latter as a properly selected subensemble of events associated with the grand canonical ensemble which is characterized by a constant temperature and a harmonic-trap chemical potential. The merits of this toy model are that it can be solved exactly, and that it demonstrates some interesting features revealed recently in small systems created in $p+p$ collisions at the LHC. We find that partial coherence can be observed in particle emission from completely thermal ensembles of events if instead of inclusive measurements one studies the two-boson distribution functions related to the events with particle numbers selected in some fixed multiplicity bins. The corresponding coherence effects increase with the multiplicity.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2021)·2 citations
5. 05*

   The Impact of New d(p,\gamma)He3 Rates on Big Bang Nucleosynthesis

   Tsung-Han Yeh🇺🇸 · Keith A. Olive🇺🇸 · Brian D. Fields🇺🇸

   We consider the effect on Big Bang Nucleosynthesis (BBN) of new measurements of the $d(p,\gamma ){}^3$He cross section by the LUNA Collaboration. These have an important effect on the primordial abundance of D/H which is also sensitive to the baryon density at the time of BBN. We have re-evaluated the thermal rate for this reaction, using a world average of cross section data, which we describe with model-independent polynomials; our results are in good agreement with a similar analysis by LUNA. We then perform a full likelihood analysis combining BBN and Planck cosmic microwave background (CMB) likelihood chains using the new rate combined with previous measurements and compare with the results using previous rates. Concordance between BBN and CMB measurements of the anisotropy spectrum using the old rates was excellent. The predicted deuterium abundance at the Planck value of the baryon density was $(D/H{)}_{\mathrm{BBN}+\mathrm{CMB}}^{\mathrm{old}}=(2.57\pm 0.13)\times 10^{-5}$ which can be compared with the value determined from quasar absorption systems $(D/H{)}_{\mathrm{obs}}=(2.55\pm 0.03)\times 10^{-5}$. Using the new rates we find $(D/H{)}_{\mathrm{BBN}+\mathrm{CMB}}=(2.51\pm 0.11)\times 10^{-5}$. We thus find consistency among BBN theory, deuterium and ${}^4$He observations, and the CMB, when using reaction rates fit in our data-driven approach. We also find that the new reaction data tightens the constraints on the number of relativistic degrees of freedom during BBN, giving the effective number of light neutrino species $N_{\nu }=2.880\pm 0.144$ in good agreement with the Standard Model of particle physics. Finally, we note that the observed deuterium abundance continues to be more precise than the BBN+CMB prediction, whose error budget is now dominated by $d(d,n){}^3$He and $d(d,p){}^3\mathrm{H}$.

   ↳ astro-ph.COhep-phnucl-exJCAP(2021)·114 citations
6. 06*

   Progress in the Glauber model at collider energies

   David d'Enterria🇨🇭 · Constantin Loizides🇺🇸

   We review the theoretical and experimental progress in the Glauber model of multiple nucleon and/or parton scatterings, after the last 10--15 years of operation with proton and nuclear beams at the CERN Large Hadron Collider (LHC) and with various light and heavy colliding ions at the BNL Relativistic Heavy Ion Collider (RHIC). The main developments and the state-of-the-art of the field are summarized. These encompass measurements of the inclusive inelastic proton and nuclear cross sections, advances in the description of the proton and nuclear density profiles and their fluctuations, inclusion of subnucleonic degrees of freedom, experimental procedures and issues related to the determination of the collision centrality, validation of the binary scaling prescription for hard scattering cross sections, and constraints on transport properties of quark-gluon matter from varying initial-state conditions in relativistic hydrodynamics calculations. These advances confirm the validity and usefulness of the Glauber formalism for quantitative studies of QCD matter produced in high-energy collisions of systems, from protons to uranium nuclei, of vastly different size.

   ↳ hep-phhep-exnucl-exnucl-thAnn.Rev.Nucl.Part.Sci.(2021)·138 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.