Feasibility of Beauty Baryon Polarization Measurement in Lambda0 J/psi Decay Channel by Atlas-LHC

The possibility of beauty baryon polarization measurement by cascade decay angular distribution analysis in the channel Lambda0 J/psi --> p pi- l+ l- is demonstrated. The error analysis shows that in the proposed LHC experiment ATLAS at the luminosity $10^{4} pb^{-1}$ the polarization can be measured with the statistical precision better than $\delta=0.010$ for Lambda_b0 and $\delta=0.17$ for Xi_b0.Comment: 12 pages (LaTeX + AMS-LaTeX) and 3 figures in postscript (uuencoded, compressed tar file included at the end of the paper), PRA-HEP-94/

Backgrounds for rare muonic B-meson decays in ATLAS

The work gives an overview of expected exclusive backgrounds for rare muonic B-meson decays in ATLAS. Based on theoretical calculations and a modelling in Generators, followed by phase space cuts according to fiducial detector volume and trigger acceptance, the authors classify all possible backgrounds according to their importance and select those requiring full detector simulation. The most importat background comes from $B_d^0 \to \pi^- \mu^+ \nu_{\mu}$, when a charged pion decays in a detector volume producing a secondary muon. Similar mechanism would lead to a background comming from B-mesons decaying to two charged hadrons. Another important background is from $B^+ \to \mu^+\mu^-l^+ \nu$.This note gives an overview of expected exclusive backgrounds for rare muonic B–meson decays at ATLAS from the theoretical point of view. The goal of this work is to show which of backgrounds are most important for further full detector simulation. It is shown that the most important noncombinatorial background comes from $B_d^0 \to \pi^- \mu^+ \nu_{\mu}$ fake rate. Another important BG sources are $B^+ \to \mu^+\mu^-\ell^+ \nu_{\ell}, B_c^+ \to J/\psi (\mu^+ \mu^-) \ell \nu_{\ell}$ and two-body hadronic B–meson decays

Bottom Production

We review the prospects for bottom production physics at the LHC.Comment: 74 pages, Latex, 71 figures, to appear in the Report of the ``1999 CERN Workshop on SM physics (and more) at the LHC'', P. Nason, G. Ridolfi, O. Schneider G.F. Tartarelli, P. Vikas (conveners

Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Standalone vertex finding in the ATLAS muon spectrometer

A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at √s = 7 TeV collected with the ATLAS detector at the LHC during 2011