Abstract
*************Double-differential three-jet production cross-sections are measured in proton–proton collisions at a centre-of-mass energy of sqrt{s} = 7mathrm ,TeV{} using the ATLAS detector at the large hadron collider. The measurements are presented as a function of the three-jet mass (m_{jjj}), in bins of the sum of the absolute rapidity separations between the three leading jets (left| Y^{*}right| ). Invariant masses extending up to 5 TeV are reached for 8< left| Y^{*}right| < 10. These measurements use a sample of data recorded using the ATLAS detector in 2011, which corresponds to an integrated luminosity of 4.51~text{ fb }^{-1}. Jets are identified using the anti-k_{t} algorithm with two different jet radius parameters, R=0.4 and R=0.6. The dominant uncertainty in these measurements comes from the jet energy scale. Next-to-leading-order QCD calculations corrected to account for non-perturbative effects are compared to the measurements. Good agreement is found between the data and the theoretical predictions based on most of the available sets of parton distribution functions, over the full kinematic range, covering almost seven orders of magnitude in the measured cross-section values.
Highlights
The ATLAS Collaboration has measured the inclusive jet cross-sections at 7 TeV [2] and at 2.76 TeV [3] centre-ofmass energies in pp collisions for jets defined by the antikt algorithm [4] with two jet radius parameters, R = 0.4 and R = 0.6
The analysis presented in this paper tests the description of multi-jet events in next-to-leading-order (NLO) quantum chromodynamics (QCD) and uses two different values of jet radius parameter, R = 0.4 and R = 0.6, since three-jet crosssections depend on the jet radius even at leading order (LO) in the perturbative expansion
Total experimental uncertainties
Summary
Recent inclusive jet [5] and dijet [6] crosssection measurements at 7 TeV centre-of-mass energy in pp collisions have exploited improved jet energy calibration procedures [7] leading to smaller systematic uncertainties compared to those achieved in Refs. Similar measurements at 7 TeV centre-of-mass energy in pp collisions [8,9] have been carried out by the CMS Collaboration These measurements test perturbative QCD (pQCD) at very short distances and have provided constraints on the gluon momentum distribution within protons at large momentum fraction. Theoretical predictions of the multi-jet cross-sections in pp collisions at 7 TeV centre-of-mass energy have been tested in Refs. Measurements of double-differential threejet production cross-sections are presented as a function of the three-jet mass (m j j j ) and the sum of absolute rapidity separation between the three leading jets (|Y ∗|).
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