Abstract
This Letter describes a model-agnostic search for pairs of jets (dijets) produced by resonant and non-resonant phenomena beyond the Standard Model in 3.6 fb$^{-1}$ of proton-proton collisions with a centre-of-mass energy of $\sqrt{s}=13$ TeV recorded by the ATLAS detector at the Large Hadron Collider. The distribution of the invariant mass of the two leading jets is examined for local excesses above a data-derived estimate of the smoothly falling prediction of the Standard Model. The data are also compared to a Monte Carlo simulation of Standard Model angular distributions derived from the rapidity of the two jets. No evidence of anomalous phenomena is observed in the data, which are used to exclude, at 95% CL, quantum black holes with threshold masses below 8.3 TeV, 8.1 TeV, or 5.3 TeV in three different benchmark scenarios; resonance masses below 5.2 TeV for excited quarks, 2.6 TeV in a $W^\prime$ model, a range of masses starting from $m_{Z^\prime}=1.5$ TeV and couplings from $g_q = 0.2$ in a $Z^\prime$ model; and contact interactions with a compositeness scale below 12.0 TeV and 17.5 TeV respectively for destructive and constructive interference between the new interaction and QCD processes. These results significantly extend the ATLAS limits obtained from 8 TeV data. Gaussian-shaped contributions to the mass distribution are also excluded if the effective cross-section exceeds values ranging from approximately 50-300 fb for masses below 2 TeV to 2-20 fb for masses above 4 TeV.
Highlights
IntroductionThe total production rates for two-jet (dijet) beyond the Standard Model (BSM) signals can be large, allowing searches for anomalous dijet production to test for such signals with a relatively small data sample, even at masses that constitute significant fractions of the total hadron collision energy
The centre-of-mass energy of proton–proton collisions at t√he Large Hadro√n Collider (LHC) at CERN has been increased from s = 8 TeV to s = 13 TeV, opening a new energy regime to observation.New particles produced in LHC collisions must interact with the constituent partons of the proton
No evidence of phenomena beyond the Standard Model was uncovered in this search using dijet events in 3.6 fb−√1 of proton– proton collisions with a centre-of-mass energy of s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider
Summary
The total production rates for two-jet (dijet) BSM signals can be large, allowing searches for anomalous dijet production to test for such signals with a relatively small data sample, even at masses that constitute significant fractions of the total hadron collision energy. A momentum imbalance between the two partons boosts the centre-of-mass frame of the collision relative to the laboratory frame along the z direction by yB = ln (x1/x2)/2 = ( y3 + y4)/2, where yB is the rapidity of the boosted centre-ofmass frame, x1 and x2 are the fractions of the proton momentum carried by each parton and y3 and y4 are the rapidities of the outgoing partons in the detector frame.
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