The differential charged jet cross sections, jet fragmentation distributions, and jet shapes are measured in minimum bias proton-proton collisions at centre-of-mass energy $\sqrt{s}=7$ TeV using the ALICE detector at the LHC. Jets are reconstructed from charged particle momenta in the mid-rapidity region using the sequential recombination $k_{\rm T}$ and anti-$k_{\rm T}$ as well as the SISCone jet finding algorithms with several resolution parameters in the range $R=0.2$ to $0.6$. Differential jet production cross sections measured with the three jet finders are in agreement in the transverse momentum ($p_{\rm T}$) interval $20<p_{\rm T}^{\rm jet,ch}<100$ GeV/$c$. They are also consistent with prior measurements carried out at the LHC by the ATLAS collaboration. The jet charged particle multiplicity rises monotonically with increasing jet $p_{\rm T}$, in qualitative agreement with prior observations at lower energies. The transverse profiles of leading jets are investigated using radial momentum density distributions as well as distributions of the average radius containing 80% ($\langle R_{\rm 80} \rangle$) of the reconstructed jet $p_{\rm T}$. The fragmentation of leading jets with $R=0.4$ using scaled $p_{\rm T}$ spectra of the jet constituents is studied. The measurements are compared to model calculations from event generators (PYTHIA, PHOJET, HERWIG). The measured radial density distributions and $\langle R_{\rm 80} \rangle$ distributions are well described by the PYTHIA model (tune Perugia-2011). The fragmentation distributions are better described by HERWIG.
Measured charged jet differential cross sections for INEL proton-proton collisions at $\sqrt{s}$ = 7 TeV.
Measured charged jet differential cross sections for INEL proton-proton collisions at $\sqrt{s}$ = 7 TeV.
Measured charged jet differential cross sections for INEL proton-proton collisions at $\sqrt{s}$ = 7 TeV.
The jet fragmentation function and transverse profile for jets with 25 GeV < ptJet < 500 GeV and etaJet<1.2 produced in proton-proton collisions with a center-of-mass energy of 7 TeV are presented. The measurement is performed using data with an integrated luminosity of 36 pb^-1. Jets are reconstructed and their momentum measured using calorimetric information. The momenta of the charged particle constituents are measured using the tracking system. The distributions corrected for detector effects are compared with various Monte Carlo event generators and generator tunes. Several of these choices show good agreement with the measured fragmentation function. None of these choices reproduce both the transverse profile and fragmentation function over the full kinematic range of the measurement.
Charged particle fragmentation function in the jet-Pt range 25 TO 40 GeV.
Charged particle fragmentation function in the jet-Pt range 40 TO 60 GeV.
Charged particle fragmentation function in the jet-Pt range 60 TO 80 GeV.
The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb^-1. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta.
Inclusive double differential b-jet cross section as a function of PT for the |rapidity| range 0.0-0.3 from the lifetime-based analysis.
Inclusive double differential b-jet cross section as a function of PT for the |rapidity| range 0.3-0.8 from the lifetime-based analysis.
Inclusive double differential b-jet cross section as a function of PT for the |rapidity| range 0.8-1.2 from the lifetime-based analysis.
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