CERN-EP-2016-183
arXiv:1608.01857
JHEP 1611 (2016) 110

by: Aaboud, Morad (Oujda U.) et al.

Abstract:
Inclusive four-jet events produced in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV are analysed for the presence of hard double-parton scattering using data corresponding to an integrated luminosity of 37.3 pb$^{−1}$, collected with the ATLAS detector at the LHC. The contribution of hard double-parton scattering to the production of four-jet events is extracted using an artificial neural network, assuming that hard double-parton scattering can be approximated by an uncorrelated overlaying of dijet events. For events containing at least four jets with transverse momentum p$_{T}$ ≥ 20 GeV and pseudorapidity |η| ≤ 4.4, and at least one having p$_{T}$ ≥ 42.5 GeV, the contribution of hard double-parton scattering is estimated to be f$_{DPS}$ = 0.092$_{− 0.011}^{+ 0.005}$ (stat.)$_{− 0.037}^{+ 0.033}$ (syst.). After combining this measurement with those of the inclusive dijet and four-jet cross-sections in the appropriate phase space regions, the effective cross-section, σ$_{eff}$ , was determined to be σ$_{eff}$ = 14. 9$_{− 1.0}^{+ 1.2}$ (stat.)$_{− 3.8}^{+ 5.1}$ (syst.) mb. This result is consistent within the quoted uncertainties with previous measurements of σ$_{eff}$ , performed at centre-of-mass energies between 63 GeV and 8 TeV using various final states, and it corresponds to 21$_{− 6}^{+ 7}$  % of the total inelastic cross-section measured at $\sqrt{s}=7$ TeV. The distributions of the observables sensitive to the contribution of hard double-parton scattering, corrected for detector effects, are also provided.