Tue·Jul 31, 2018Tuesday·July 31, 2018

1. 01*

   Multiplicity dependence of light-flavor hadron production in pp collisions at $\sqrt{s}$ = 7 TeV

   ALICE Collaboration

   Comprehensive results on the production of unidentified charged particles, ${\pi }^{\pm }$, ${\mathrm{K}}^{\pm }$, ${\mathrm{K}}_{\mathrm{S}}^0$, $\mathrm{K}$*(892)${}^0$, $\mathrm{p}$, $\overline{\mathrm{p}}$, $\varphi$(1020), $\Lambda$, $\overline{\Lambda }$, ${\Xi }^{-}$, ${\overline{\Xi }}^{+}$, ${\Omega }^{-}$ and ${\overline{\Omega }}^{+}$ hadrons in proton-proton (pp) collisions at $\sqrt{s}$ = 7 TeV at midrapidity ($|y|<0.5$) as a function of charged-particle multiplicity density are presented. In order to avoid auto-correlation biases, the actual transverse momentum ($p_{\mathrm{T}}$) spectra of the particles under study and the event activity are measured in different rapidity windows. In the highest multiplicity class, the charged-particle density reaches about 3.5 times the value measured in inelastic collisions. While the yield of protons normalized to pions remains approximately constant as a function of multiplicity, the corresponding ratios of strange hadrons to pions show a significant enhancement that increases with increasing strangeness content. Furthermore, all identified particle to pion ratios are shown to depend solely on charged-particle multiplicity density, regardless of system type and collision energy. The evolution of the spectral shapes with multiplicity and hadron mass shows patterns that are similar to those observed in p-Pb and Pb-Pb collisions at LHC energies. The obtained $p_{\mathrm{T}}$ distributions and yields are compared to expectations from QCD-based pp event generators as well as to predictions from thermal and hydrodynamic models. These comparisons indicate that traces of a collective, equilibrated system are already present in high-multiplicity pp collisions.

   nucl-exhep-exPRC(2019)·295 citations
2. 02*

   Energy dependence of $\varphi$(1020) production at mid-rapidity in pp collisions with ALICE at the LHC

   Sushanta Tripathy (for the ALICE collaboration)🇮🇳

   Hadronic resonances are unique tools to investigate the interplay of re-scattering and regeneration effects during the hadronization phase in heavy-ion collisions. Measurements in small collision systems provide a necessary baseline for heavy-ion data, help to tune pQCD inspired event generators and give insight into the search for the onset of collective effects. As the $\varphi$ meson has a longer lifetime compared to other resonances, it is expected that its production would be much less affected by regeneration and re-scattering processes. We report on measurements of $\varphi$ meson production in minimum bias pp collisions at different beam energies and as a function of charged particle multiplicity with the ALICE detector at the LHC. The results include the transverse momentum $(p_{\mathrm{T}})$ distributions of $\varphi$ as well as the particle yield ratios. Finally, we have also studied the $\varphi$ effective strangeness content by comparing our results to theoretical calculations.

   ↳ hep-exnucl-exNPA(2019)·22 citations
3. 03*

   Energy and system dependence of nuclear modification factors of inclusive charged particles and identified light hadrons measured in p--Pb, Xe--Xe and Pb--Pb collisions with ALICE

   Daiki Sekihata (for the ALICE Collaboration)🇯🇵

   We report recent ALICE results on primary charged particle and neutral meson production in pp, p--Pb, Pb--Pb and Xe--Xe collisions at LHC energies. In this article, measurements of the nuclear modification factors $R_{\mathrm{AA}}$ of primary charged particles and of light neutral mesons in Pb--Pb, in Xe--Xe and in p--Pb collisions in a wide $p_{\mathrm{T}}$ range and different centrality classes are discussed. We compare the nuclear modification factors obtained for different collision systems as a function of transverse momentum, collision centrality as well as charged particle multiplicity ($\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta$). We also present comparison of experimental results to model calculations.

   ↳ hep-exnucl-exNPA(2019)·16 citations
4. 04*

   Angular distributions in electroweak pion production off nucleons: odd parity hadron terms, strong relative phases and model dependence

   J.E. Sobczyk🇪🇸 · E. Hernández🇪🇸 · S.X. Nakamura🇧🇷 · J. Nieves🇪🇸 · T. Sato🇯🇵

   The study of pion production in nuclei is important for signal and background determinations in current and future neutrino oscillation experiments. The first step, however, is to understand the pion production reactions at the free nucleon level. We present an exhaustive study of the charged-current and neutral-current neutrino and antineutrino pion production off nucleons, paying a special attention to the angular distributions of the outgoing pion. We show, using general arguments, that parity violation and time-reversal odd correlations in the weak differential cross sections are generated from the interference between different contributions to the hadronic current that are not relatively real. Next, we present a detailed comparison of three, state of the art, microscopic models for electroweak pion production off nucleons, and we also confront their predictions with polarized electron data, as a test of the vector content of these models. We also illustrate the importance of carrying out a comprehensive test at the level of outgoing pion angular distributions, going beyond comparisons done for partially integrated cross sections, where model differences cancel to a certain extent. Finally, we observe that all charged and neutral current distributions show sizable anisotropies, and identify channels for which parity violating effects are clearly visible. Based on the above results, we conclude that the use of isotropic distributions for the pions in the center of mass of the final pion-nucleon system, as assumed by some of the Monte Carlo event generators, needs to be improved by incorporating the findings of microscopic calculations.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2018)·40 citations
5. 05*

   Uncertainties in the production of p nuclides in SN Ia determined by Monte Carlo variations

   T. Rauscher🇬🇧 · N. Nishimura🇬🇧 · R. Hirschi🇬🇧 · A. St.J. Murphy🇬🇧 · G. Cescutti · C. Travaglio

   Several thousand tracers from a 2D model of a thermonuclear supernova were used in a Monte Carlo post-processing approach to determine p-nuclide abundance uncertainties originating from nuclear physics uncertainties in the reaction rates.

   ↳ astro-ph.HEnucl-exSpringer Proc.Phys.(2019)·0 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.