Fri·Nov 13, 2020Friday·November 13, 2020

1. 01*

   ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ production and baryon-to-meson ratios in pp and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV at the LHC

   ALICE Collaboration

   The prompt production of the charm baryon ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ and the ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}/{\mathrm{D}}^0$ production ratios were measured at midrapidity with the ALICE detector in pp and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$TeV. These new measurements show a clear decrease of the ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}/{\mathrm{D}}^0$ ratio with increasing transverse momentum ($p_{\mathrm{T}}$) in both collision systems in the range $2<p_{\mathrm{T}}<12$ GeV/$c$, exhibiting similarities with the light-flavour baryon-to-meson ratios $\mathrm{p}/\pi$ and $\Lambda /{\mathrm{K}}_{\mathrm{S}}^0$. At low $p_{\mathrm{T}}$, predictions that include additional colour-reconnection mechanisms beyond the leading-colour approximation; assume the existence of additional higher-mass charm-baryon states; or include hadronisation via coalescence can describe the data, while predictions driven by charm-quark fragmentation processes measured in ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ and ${\mathrm{e}}^{-}\mathrm{p}$ collisions significantly underestimate the data. The results presented in this letter provide significant evidence that the established assumption of universality (colliding-system independence) of parton-to-hadron fragmentation is not sufficient to describe charm-baryon production in hadronic collisions at LHC energies.

   nucl-exhep-exPRL(2021)·144 citations
2. 02*

   ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ production in pp and in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV

   ALICE Collaboration

   The production cross section of prompt ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ charm baryons was measured with the ALICE detector at the LHC at midrapidity in proton-proton (pp) and proton-lead (p-Pb) collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. The ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ and $\overline{\mathrm{\Lambda }}{}_{\mathrm{c}}^{-}$ baryons were reconstructed in the hadronic decay channels ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}\to \mathrm{p}{\mathrm{K}}^{-}{\pi }^{+}$ and ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}\to \mathrm{p}{\mathrm{K}}_{\mathrm{S}}^0$ and respective charge conjugates. The measured differential cross sections as a function of transverse momentum ($p_{\mathrm{T}}$) and the $p_{\mathrm{T}}$-integrated ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ production cross section in pp and in p-Pb collisions are presented. The ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ nuclear modification factor ($R_{\mathrm{pPb}}$), calculated from the cross sections in pp and in p-Pb collisions, is presented and compared with the $R_{\mathrm{pPb}}$ of D mesons. The ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}/{\mathrm{D}}^0$ ratio is also presented and compared with the light-flavour baryon-to-meson ratios p$/\pi$ and $\Lambda /{\mathrm{K}}_{\mathrm{S}}^0$, and measurements from other LHC experiments. The results are compared to predictions from model calculations and Monte Carlo event generators.

   nucl-exhep-exPRC(2021)·117 citations
3. 03*

   Space-based Measurements of Neutron Lifetime: Approaches to Resolving the Neutron Lifetime Anomaly

   David J. Lawrence🇺🇸 · Jack T. Wilson🇺🇸 · Patrick N. Peplowski🇺🇸

   Free neutrons have a measured lifetime of 880 s, but disagreement between existing laboratory measurements of ~10 s have persisted over many years. This uncertainty has implications for multiple physics disciplines, including standard-model particle physics and Big-Bang nucleosynthesis. Space-based neutron lifetime measurements have been shown to be feasible using existing data taken at Venus and the Moon, although the uncertainties for these measurements of tens of seconds prevent addressing the current lifetime discrepancy. We investigate the implementation of a dedicated space-based experiment that could provide a competitive and independent lifetime measurement. We considered a variety of scenarios, including measurements made from orbit about the Earth, Moon, and Venus, as well as on the surface of the Moon. For a standard-sized neutron detector, a measurement with three-second statistical precision can be obtained from Venus orbit in less than a day; a one-second statistical precision can be obtained from Venus orbit in less than a week. Similarly precise measurements in Earth orbit and on the lunar surface can be acquired in less than 40 days (three-second precision) and ~300 days (one-second precision). Systematic uncertainties that affect a space-based neutron lifetime measurement are investigated, and the feasibility of developing such an experiment is discussed.

   nucl-exastro-ph.EPastro-ph.IMNucl.Instrum.Meth.A(2021)·14 citations
4. 04*

   Low-lying single-particle structure of 17C and the N = 14 sub-shell closure

   X. Pereira-López🇫🇷 · B. Fernández-Domínguez🇪🇸 · F. Delaunay🇫🇷 · N.L. Achouri🇫🇷 · N.A. Orr🇫🇷 · W.N. Catford🇬🇧 · M. Assié🇫🇷 · S. Bailey🇬🇧 · B. Bastin🇫🇷 · Y. Blumenfeld🇫🇷 · R. Borcea🇷🇴 · M. Caamaño🇪🇸 and 49 other authors

   The first investigation of the single-particle structure of the bound states of 17C, via the d(16C, p) transfer reaction, has been undertaken. The measured angular distributions confirm the spin-parity assignments of 1/2+ and 5/2+ for the excited states located at 217 and 335 keV, respectively. The spectroscopic factors deduced for these states exhibit a marked single-particle character, in agreement with shell model and particle-core model calculations, and combined with their near degeneracy in energy provide clear evidence for the absence of the N = 14 sub-shell closure. The very small spectroscopic factor found for the 3/2+ ground state is consistent with theoretical predictions and indicates that the {\nu}1d3/2 strength is carried by unbound states. With a dominant l = 0 valence neutron configuration and a very low separation energy, the 1/2+ excited state is a one-neutron halo candidate.

   nucl-exPLB(2020)·19 citations
5. 05*

   Search for decays of the ${}^9$B nucleus and Hoyle state in ${}^{14}$N nucleus dissociation

   E. Mitsova · A.A. Zaitsev🇷🇺 · D.A. Aretemenkov · N.K. Kornegrutsa · V.V. Rusakova🇷🇺 · R. Stanoeva🇧🇬 · P.I. Zarubin🇷🇺 · I.G. Zarubina🇷🇺

   First results of an analysis to determine contribution of decays of the unstable ${}^8$Be and ${}^9$B nuclei and the Hoyle 3$\alpha$-state to dissociation of ${}^{14}$N $\to$ 3He (+H) are presented. As the research material, layers of nuclear track emulsion longitudinally exposed to 2.9 $A$ GeV/$c$ ${}^{14}$N nuclei with at the JINR Nuclotron. Under the assumption that the He and H fragments retain momentum per nucleon of the primary nucleus, these unstable states are identified by the invariant mass calculated from the emission angles of the fragments.

   nucl-exPhys.Part.Nucl.(2022)·4 citations
6. 06*

   Open heavy-flavour production from small to large collision systems with ALICE at the LHC

   Luuk Vermunt (for the ALICE Collaboration)🇳🇱

   Heavy quarks are effective probes to study the properties of the quark-gluon plasma (QGP) produced in ultra-relativistic heavy-ion collisions. In this contribution, the latest results on open heavy-flavour production in pp and Pb-Pb collisions measured by the ALICE Collaboration will be discussed. Measurements of open heavy-flavour production in Pb-Pb collisions allow for testing the mechanisms of heavy-quark transport and energy loss in the medium. In addition, measurements of the elliptic ($v_2$) and triangular ($v_3$) flow coefficients of heavy-flavour particles give insights into the participation of heavy quarks in the collective motion of the medium, the path-length dependence of their in-medium energy loss, and recombination effects during the hadronisation. Finally, the directed flow ($v_1$) of open heavy-flavour particles is sensitive to the unprecedentedly strong magnetic fields present in the early stages of the collision, and so measurements of its charge dependence are key to constraining the electrical conductivity of the QGP. In small hadronic systems like pp, open heavy-flavour production provides the baseline for the investigation of hot-medium effects in heavy-ion collisions, as well as tests of perturbative quantum chromodynamic calculations.

   nucl-exPoS(2021)·4 citations
7. 07*

   Higher order conserved charge fluctuations inside the mixed phase

   Roman V. Poberezhnyuk🇺🇦 · Oleh Savchuk🇩🇪 · Mark I. Gorenstein🇺🇦 · Volodymyr Vovchenko🇺🇸 · Horst Stoecker🇩🇪

   General formulas are presented for higher order cumulants of the conserved charge statistical fluctuations inside the mixed phase. As a particular example the van der Waals model in the grand canonical ensemble is used. The higher order measures of the conserved charge fluctuations up to the hyperkurtosis are calculated in a vicinity of the critical point (CP). The analysis includes both the mixed phase region and the pure phases on the phase diagram. It is shown that even-order fluctuation measures, e.g. scaled variance, kurtosis, and hyperkurtosis, have only positive values in the mixed phase, and go to infinity at the CP. For odd-order measures, such as skewness and hyperskewness, the regions of positive and negative values are found near the left and right binodals, respectively. The obtained results are discussed in a context of the event-by-event fluctuation measurements in heavy-ion collisions.

   ↳ hep-phnucl-exnucl-thPRC(2021)·10 citations
8. 08*

   Performance of The Advanced GAmma Tracking Array at GANIL

   J. Ljungvall (1)🇫🇷 · R.M. Pérez-Vidal (2)🇪🇸 · A. Lopez-Martens (1)🇫🇷 · C. Michelagnoli (3 and 4)🇫🇷 · E. Clément (3)🇫🇷 · J. Dudouet (1 and 5)🇫🇷 · A. Gadea (2)🇪🇸 · H. Hess (6)🇩🇪 · A. Korichi (1)🇫🇷 · M. Labiche (7)🇬🇧 · N. Lalović (8)🇸🇪 · H. J. Li (3)🇫🇷 · F. Recchia (9 and 10) ((1) CSNSM Université Paris-Sud CNRS/IN2P3 Université Paris-Saclay 91405 Orsay France, (2) Instituto de Física Corpuscular CSIC - Universidad de Valencia E-46980 Paterna Valencia Spain, (3) GANIL CEA/DRF-CNRS/IN2P3 BP 55027 14076 Caen cedex 5 France, (4) Institut Laue-Langevin B.P. 156 F-38042 Grenoble cedex 9 France, (5) Institut de Physique Nucléaire de Lyon, Université de Lyon Université Lyon 1 CNRS-IN2P3 F-69622 Villeurbanne France, (6) IKP University of Cologne D-50937 Cologne Germany, (7) STFC Daresbury Laboratory Daresbury Warrington WA4 4AD United Kingdom, (8) Department of Physics Lund University SE-22100 Lund Sweden, (9) INFN Sezione di Padova I-35131 Padova Italy, (10) Dipartimento di Fisica e Astronomia dell'Università di Padova I-35131 Padova Italy)🇮🇹

   The performance of the Advanced GAmma Tracking Array (AGATA) at GANIL is discussed, on the basis of the analysis of source and in-beam data taken with up to 30 segmented crystals. Data processing is described in detail. The performance of individual detectors are shown. The efficiency of the individual detectors as well as the efficiency after $\gamma$-ray tracking are discussed. Recent developments of $\gamma$-ray tracking are also presented. The experimentally achieved peak-to-total is compared with simulations showing the impact of back-scattered $\gamma$ rays on the peak-to-total in a $\gamma$-ray tracking array. An estimate of the achieved position resolution using the Doppler broadening of in-beam data is also given. Angular correlations from source measurements are shown together with different methods to take into account the effects of $\gamma$-ray tracking on the normalization of the angular correlations.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2020)·12 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.