Thu·Sep 14, 2017Thursday·September 14, 2017

1. 01*

   New results on Initial State and Quarkonia with ALICE

   Giuseppe Trombetta (for the ALICE Collaboration)🇮🇹

   The study of quarkonia in heavy-ion collisions has been the subject of intense experimental and theoretical effort, ever since their production was predicted to be sensitive to the formation of a deconfined state of strongly-interacting matter, known as the Quark-Gluon Plasma (QGP). In p-Pb collisions, Cold Nuclear Matter (CNM) effects, such as nuclear shadowing or partonic energy loss, are expected to influence quarkonium production. The study of such system is therefore crucial to shed light on the mechanisms taking place at the initial-state of quarkonium production, and to disentangle the cold and hot nuclear effects envisioned in Pb-Pb collisions. The ALICE experiment at the LHC, is capable of reconstructing J/$\psi$, $\psi$(2S) and ${\rm Y}$ states at forward rapidity through their ${\mu }^{+}{\mu }^{-}$ decay channel, as well as J/$\psi$ at central rapidity through their $e^{+}{e}^{-}$ decay channel, down to zero transverse momentum. A review of the main ALICE findings from the measurements of the inclusive quarkonium yields in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV, collected during the LHC Run I period, as well as more recent results from J/$\psi$ measurements in p-Pb at $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV, from LHC Run II period, will be presented in this paper.

   nucl-ex3 citations
2. 02*

   Prompt photon production and photon-jet correlations at the LHC

   M. Klasen🇩🇪 · C. Klein-Bösing🇩🇪 · H. Poppenborg🇩🇪

   Next-to-leading order predictions matched to parton showers are compared with recent ATLAS data on inclusive photon production and CMS data on associated photon and jet production in pp and pPb collisions at different centre-of-mass energies of the LHC. We find good agreement and, as expected, considerably reduced scale uncertainties compared to previous theoretical calculations. Predictions are made for the ratio of inclusive photons over decay photons $R_{\gamma }$, an important quantity to evaluate the significance of additional photon sources, e.g. thermal radiation from a Quark-Gluon-Plasma, and for distributions in the parton momentum fraction in lead ions $x_{\mathrm{Pb}}^{\mathrm{obs}}$, that could be determined by ALICE, ATLAS, CMS and LHCb in ongoing analyses of photon+jet production in pPb collisions at $\sqrt{s_{NN}}=5.02$ TeV. These data should have an important impact on the determination of nuclear effects such as shadowing at low $x$.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2018)·33 citations
3. 03*

   Thermonuclear ${}^{19}$F($p$,${\alpha }_0$)${}^{16}$O reaction rate

   J.J. He · I. Lombardo · D. Dell'Aquila🇫🇷 · Y. Xu · L.Y. Zhang · W.P. Liu

   The thermonuclear ${}^{19}$F($p$,${\alpha }_0$)${}^{16}$O reaction rate in a temperature region of 0.007--10 GK has been derived by re-evaluating the available experimental data, together with the low-energy theoretical $R$-matrix extrapolations. Our new rate deviates up to about 30\% compared to the previous ones, although all rates are consistent within the uncertainties. At very low temperature (e.g. 0.01 GK) our reaction rate is about 20\% smaller than the most recently published rate, because of a difference in the low energy extrapolated $S$-factor and a more accurate estimate of the reduced mass entering in the calculation of the reaction rate. At temperatures above $\sim$1 GK, our rate is smaller, for instance, by about 20\% around 1.75 GK, because we have re-evaluated in a meticulous way the previous data (Isoya et al., Nucl. Phys. 7, 116 (1958)). The present interpretation is supported by the direct experimental data. The uncertainties of the present evaluated rate are estimated to be about 20\% in the temperature region below 0.2 GK, which are mainly caused by the lack of low-energy experimental data and the large uncertainties of the existing data. The asymptotic giant branch (AGB) star evolves at temperatures below 0.2 GK, where the ${}^{19}$F($p$,$\alpha$)${}^{16}$O reaction may play a very important role. However, the current accuracy of the reaction rate is insufficient to help to describe, in a careful way, for the fluorine overabundances phenomenon observed in AGB stars. Precise cross section (or $S$ factor) data in the low energy region are therefore mandatory for astrophysical nucleosynthesis studies.

   ↳ astro-ph.SRnucl-exnucl-thCPC(2018)·27 citations
4. 04*

   Central and peripheral interactions of hadrons

   I.M. Dremin🇷🇺 · V.A. Nechitailo🇷🇺 · S.N. White🇨🇭

   Surprisingly enough, the ratio of elastic to inelastic cross sections of proton interactions increases with energy in the interval correspond- ing to ISR - LHC (i.e. from 10 GeV to 10 TeV). That leads to special features of their spatial interaction region at these and higher ener- gies. Within the framework of some phenomenological models, we show how the particular ranges of the transferred momenta measured in elastic scattering experiments expose the spatial features of the in- elastic interaction region according to the unitarity condition. The difference between their predictions at higher energies is discussed. The notion of central and peripheral collisions of hadrons is treated in terms of the impact parameters description. It is shown that the shape of the differential cross section in the diffraction cone is mostly determined by collisions with intermediate impact parameters. Elastic scattering at very small transferred momenta is sensitive to peripheral processes with large impact parameters. The role of central collisions in formation of the diffraction cone is less significant.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2017)·9 citations
5. 05*

   Jet Substructure at the Large Hadron Collider: A Review of Recent Advances in Theory and Machine Learning

   Andrew J. Larkoski🇺🇸 · Ian Moult🇺🇸 · Benjamin Nachman🇺🇸

   Jet substructure has emerged to play a central role at the Large Hadron Collider (LHC), where it has provided numerous innovative new ways to search for new physics and to probe the Standard Model in extreme regions of phase space. In this article we provide a comprehensive review of state of the art theoretical and machine learning developments in jet substructure. This article is meant both as a pedagogical introduction, covering the key physical principles underlying the calculation of jet substructure observables, the development of new observables, and cutting edge machine learning techniques for jet substructure, as well as a comprehensive reference for experts. We hope that it will prove a useful introduction to the exciting and rapidly developing field of jet substructure at the LHC.

   ↳ hep-phhep-exnucl-exnucl-thPhys.Rept.(2020)·682 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.