476 research outputs found
Heavy Ion Physics Highlights from ATLAS
No full textAn overview of the ATLAS results from Pb+Pb collisions at √sNN = 2.76 TeV will be presented. The results for hard probes include both single jet and di-jet measurements, W and Z bosons, photons, and high pT charged tracks. Taken together these results provide a compelling picture of the interaction of hard particles in the dense QCD medium. Additionally, ATLAS has measured properties of the bulk particle production including charged particle multiplicity and extensive measurements of the azimuthal particle distributions and correlations. Results shown will be from the ∼ 10 inverse µb−1 of minimum bias recorded in the 2010 LHC heavy ion run, as well as from ∼ 0.15 nb−1 sampled in the 2011 LHC heavy ion run
Study of correlations between neutral bosons and jets in lead-lead collisions at 2.76 TeV with the ATLAS detector
No full textThe correlations of jets with neutral bosons is a particularly powerful tool to probe the underlying physics of jet quenching. To gain insight into the physics of this process we can study Z-jet and gamma-jet correlations. Because the Z and photons do not directly couple to the strong force, in a jet+boson event the unmodified bosons allow us to access the modification of the opposite side jet; unlike dijet events, where both jets potentially lose energy, these bosons provide an excellent calibration of the energy of the recoil jet. The jets are measured in the same calorimeter, over a range of jet radii, and benefit from the detailed information about the shower profile. The ATLAS experiment has measured jet correlations with both direct photons as well as with Z bosons via dilepton channels in Pb+Pb collisions with =2.76 TeV in a data sample of nearly 0.15 nb of integrated luminosity. The measurement of these correlations will be presented
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Hate crimes in cyberspace /
No full textThe author examines the controversies surrounding cyber-harassment, arguing that it should be considered a matter for civil rights law and that social norms of decency and civility must be leveraged to stop it. --Publisher's description.In an in-depth investigation of a problem that is too often trivialized by lawmakers and the media, Citron exposes the startling extent of personal cyber-attacks and proposes practical, lawful ways to prevent and punish online harassment. She reveals the serious emotional, professional, and financial harms incurred by victims. Persistent online attacks disproportionately target women and frequently include detailed fantasies of rape as well as reputation-ruining lies and sexually explicit photographs
Hate crimes in cyberspace /
No full textThe author examines the controversies surrounding cyber-harassment, arguing that it should be considered a matter for civil rights law and that social norms of decency and civility must be leveraged to stop it. --Publisher's description.In an in-depth investigation of a problem that is too often trivialized by lawmakers and the media, Citron exposes the startling extent of personal cyber-attacks and proposes practical, lawful ways to prevent and punish online harassment. She reveals the serious emotional, professional, and financial harms incurred by victims. Persistent online attacks disproportionately target women and frequently include detailed fantasies of rape as well as reputation-ruining lies and sexually explicit photographs
boson production in 5.02 TeV pp, p+Pb and Pb+Pb collisions with ATLAS
No full text bosons are short lived and do not participate in the strong interaction. Thus their production yields, observed via dilepton decay channels in proton-lead and lead-lead collisions, provide direct tests of both binary collision scaling and the nuclear modification of parton distribution functions (nPDF). Proton-lead collisions further provide a relatively clean environment for benchmarking nPDFs. The ATLAS detector has a broad acceptance in the muon and electron channels, with excellent performance even in the high occupancy environment of central heavy-ion collisions. ATLAS has recorded 0.49 nb of lead-lead data at a center-of-mass energy of 5.02 TeV per nucleon pair. Z production yields are expected to increase by a factor of eight relative to the available Run 1 data at 2.76 TeV. In addition the data can be compared directly to the 29 nb of proton-lead data collected in Run 1. In this talk, Z yields, are presented differentially in rapidity and as a function of centrality in lead-lead and proton-lead collisions.Z bosons are short lived and do not participate in the strong interaction. Thus their production yields, observed via dilepton decay channels in proton-lead and lead-lead collisions, provide direct tests of both binary collision scaling and the nuclear modification of parton distribution functions (nPDF). Proton-lead collisions further provide a relatively clean environment for benchmarking nuclear parton distribution functions (PDF). The ATLAS detector has a broad acceptance in the muon and electron channels, with excellent performance even in the high occupancy environment of central heavy-ion collisions. In this talk, Z yields, are presented differentially in rapidity and as a function of centrality in lead-lead and proton-lead collisions
Heavy Ion Physics with ATLAS
No full textAn overview of the ATLAS results from Pb+Pb collisions at √sNN = 2.76 TeV will be presented. The results for hard probes include both single jet and di-jet measure- ments, W and Z bosons, photons, and high pT charged tracks. Taken together these re- sults provide a compelling picture of the interaction of hard particles in the dense QCD medium. Additionally, ATLAS has measured properties of the bulk particle production including charged particle multiplicity and extensive measurements of the azimuthal par- ticle distributions and correlations. Results shown will be from the ∼ 10 inverse μb−1 of minimum bias recorded in the 2010 LHC heavy ion run, as well as from ∼ 0.15 nb−1 sampled in the 2011 LHC heavy ion run
(nS) meson production in Pb+Pb and collisions with ATLAS
No full textMeasurements of bottomonium states in heavy-ion collisions provide a powerful tool to study both initial-state effects on heavy-quark production and final-state interactions between heavy quarks and the quark-gluon plasma (QGP). The ATLAS experiment at LHC has measured the production of bottomonium states (1S), (2S), and (3S), in Pb+Pb and collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The data correspond to integrated luminosities of 1.38 nb of Pb+Pb data collected in 2018, 0.44 nb of Pb+Pb data collected in 2015, and 0.26 fb of pp data collected in 2017. The final ATLAS result on the production of three bottomonium states will be reported. The measurement in Pb+Pb collisions is compared to that in collisions to extract the nuclear modification factor, , as a function of event centrality, and rapidity, and compared to several theoretical models. We will also present a new measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states with the inclusive-charged particle yields. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV data. A description of the technical challenges associated with a heavy-ion style analysis in high-pileup data will be shown, as well as the results and their physics implications
Upsilon - underlying event correlations in pp collisions at ATLAS
No full textThis talk presents a new measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states with the inclusive charged particle yields in 13 TeV pp collisions. These correlations, and in particular their comparison between excited and ground state Upsilons meson, lead to surprising conclusions about heavy quarkonium production and hadronization. Measurements of charged particles in events with different Upsilon states are studied in intervals of Upsilon momentum. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV pp data. This measurement benefits from novel application of statistical techniques to remove the combinatorial and pileup backgrounds leading to increased sensitivity. A description of the technical challenges associated with an inclusive hadron analysis in high-pileup pp data will be shown, as well as the results and their physics implications
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