Rubin-LSST

Abstract:

Since 2009, the CMS experiment at LHC has provided intensive training on the use of Physics Analysis Tools (PAT), a collection of common analysis tools designed to share expertise and maximize productivity in the physics analysis. More than ten one-week courses preceded by prerequisite studies have been organized and the feedback from the participants has been carefully analyzed. This note describes how the training team designs, maintains and improves the course contents based on the feedback, the evolving analysis practices and the software development.

Abstract:

This paper presents measurements of the polarization ofW bosons in top quark decays, derived from tt̄ events with missing transverse momentum, one charged lepton and at least four jets, or two charged leptons and at least two jets. Data from pp collisions at a centre-of-mass energy of 7 TeV were collected with the ATLAS experiment at the LHC and correspond to an integrated luminosity of 1.04 fb-1. The measured fractions of longitudinally, left- and right-handed polarization are F0 = 0.67 ± 0.07, FL = 0.32 ± 0.04 and FR = 0.01 ± 0.05, in agreement with the Standard Model predictions. As the polarization of the W bosons in top quark decays is sensitive to the Wtb vertex Lorentz structure and couplings, the measurements were used to set limits on anomalous contributions to the Wtb couplings. © CERN.

Abstract:

The production of b jets in association with a Z/γ*boson is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy of 7TeV and recorded by the CMS detector. The inclusive cross section for Z/γ*+b-jet production is measured in a sample corresponding to an integrated luminosity of 2.2 fb-1. The Z/γ*+b-jet cross section with Z/γ*→ℓℓ (where ℓ ℓ = ee or μ μ) for events with the invariant mass 60 < Mℓ ℓ < 120 GeV, at least one b jet at the hadron level with pT > 25 GeV and |η|< 2:1, and a separation between the leptons and the jets of ΔR > 0:5 is found to be 5:84±0:08 (stat:) ±0:72 (syst:) -0:55+0:25 (theory) pb. The kinematic properties of the events are also studied and found to be in agreement with the predictions made by the MadGraph event generator with the parton shower and the hadronisation performed by pythia.

Abstract:

A measurement of the inclusive cross section for the process pp → bb̄X → μμX′ at √ s = 7TeV is presented, based on a data sample corresponding to an integrated luminosity of 27.9 pb-1 collected by the CMS experiment at the LHC. By selecting pairs of muons each with pseudorapidity |η| < 2:1, the value σ(pp → bb̄X → μμX′) = 26:4 ± 0:1 (stat.) ±2:4 (syst.) ±1:1 (lumi.) nb is obtained for muons with transverse momentum pT > 4 GeV, and 5:12±0:03 (stat.) ±0:48 (syst.) ±0:20 (lumi.) nb for pT > 6 GeV. These results are compared to QCD predictions at leading and next-to-leading orders.

Abstract:

The inclusive production cross sections for forward jets, as well for jets in dijet events with at least one jet emitted at central and the other at forward pseudorapidities, are measured in the range of transverse momenta pT = 35-150 GeV/c in proton-proton collisions at √ s = 7TeV by the CMS experiment at the LHC. Forward jets are measured within pseudorapidities 3.2 < |η| < 4.7, and central jets within the |η| < 2:8 range. The differential cross sections d2sigma;/dpT dη are compared to predictions from three approaches in perturbative quantum chromodynamics: (i) next-to-leading-order calculations obtained with and without matching to parton-shower Monte Carlo simulations, (ii) pythia and herwig parton-shower event generators with different tunes of parameters, and (iii) cascade and hej models, including different non-collinear corrections to standard single-parton radiation. The single-jet inclusive forward jet spectrum is well described by all models, but not all predictions are consistent with the spectra observed for the forward-central dijet events. Copyright CERN.