Determination of jet energy calibration and transverse momentum resolution in CMS

Abstract

Measurements of the jet energy calibration and transverse momentum resolution in CMS are presented, performed with a data sample collected in proton-proton collisions at a centreof-mass energy of 7 TeV, corresponding to an integrated luminosity of 36 pb −1. The transverse momentum balance in dijet and γ/Z+jets events is used to measure the jet energy response in the CMS detector, as well as the transverse momentum resolution. The results are presented for three different methods to reconstruct jets: a calorimeter-based approach, the "Jet-Plus-Track" approach, which improves the measurement of calorimeter jets by exploiting the associated tracks, and the "Particle Flow" approach, which attempts to reconstruct individually each particle in the event, prior to the jet clustering, based on information from all relevant subdetectors. KEYWORDS: Si microstrip and pad detectors; Calorimeter methods; Detector modelling and simulations I (interaction of radiation with matter, interaction of photons with matter, interaction of hadrons with matter, etc) ARXIV EPRINT: 1107.4277

Measurement of jet fragmentation into charged particles in pp and PbPb collisions at $ \sqrt{{{s_{\mathrm{NN}}}}} = 2.76 $ TeV

“…In all cases the reconstructed jet momenta are corrected to final-state stable particle (lifetime τ with cτ > 10 mm) level using factors derived from PYTHIA 6.422 [28] (tune D6T [29,30], CTEQ6L1 PDFs [31]) pp simulations at √ s = 2.76 TeV [32]. The uncertainty in the corrected jet energy scale is about 3% for pp events, resulting in a per-bin jet-yield uncertainty of ±15%.…”

Measurement of the top-quark mass in $\mathrm{t}\overline{\mathrm{t}}$ events with dilepton final states in pp collisions at $\sqrt{s}=7\ \mbox{TeV}$

“…Jets are reconstructed by the anti-k T jet clustering algorithm [25] with a distance parameter R = 0.5. Jet energy corrections are applied to all the jets in data and simulation [26]. The E miss T vector is calculated using all reconstructed particles.…”

“…The uncertainty of the overall jet energy scale (JES) is the dominant source of uncertainty on m t . The JES is known with an uncertainty of 1-3%, depending on the p T and η of the jet [26]. Even in a high-pileup regime such as the one observed throughout the 2011 data taking period, the JES uncertainty is mostly dominated by the uncertainties on the absolute scale, initial-and finalstate radiation, and corrections arising from the fragmentation and single-particle response in the calorimeter.…”

“…The jet p T , the E miss T direction, and the p tt z are varied independently according to their resolutions in order to scan the kinematic phase space consistent with the tt system. The jet p T resolution is obtained from the data [26]; the p tt z description, that is minimally dependent on m t , is taken from simulation. The solution with the lowest invariant mass of the tt system is accepted if the mass difference between the top quark and antiquark masses is less than 3 GeV.…”

Search for hadronic resonances at CMS

“…CMS applies the particle-flow technique to reconstruct jets [1,8]. The particle-flow event reconstruction consists in reconstructing and identifying muons, electrons, photons, charged hadrons and neutral hadrons with an optimized combination of all subdetector information.…”