Abstract
This Letter describes a model-independent search for the production of new resonances in photon+jet (γ+jet) events using 20 fb−1 of proton–proton LHC data recorded with the ATLAS detector at a centre-of-mass energy of s=8 TeV. The γ+jet mass distribution is compared to a background model fit from data; no significant deviation from the background-only hypothesis is found. Limits are set at 95% credibility level on generic Gaussian-shaped signals and two benchmark phenomena beyond the Standard Model: non-thermal quantum black holes and excited quarks. Non-thermal quantum black holes are excluded below masses of 4.6 TeV and excited quarks are excluded below masses of 3.5 TeV.
Highlights
Several exotic production mechanisms have been proposed that produce massive photon + jet (γ + jet) final states
The γ + jet search is sensitive to new resonances in the region between 426 GeV and 1 TeV, where the statistics of dijet searches are limited by the higher hadronic trigger thresholds
20.3 fb−1 of pp collision data, collected dist√ribution measured at s = 8 TeV by the in AT
Summary
Several exotic production mechanisms have been proposed that produce massive photon + jet (γ + jet) final states. The present Letter describes a model-independent search for s-channel γ + jet production, improved over the earlier search It presents the first limits on QBHs decaying to the γ + jet final state and places new limits both on excited quarks and on generic Gaussianshaped sources which describe other narrow resonant signals such as topological pions. Sensitivity to such signals has been improved compared to the previous search through a combination of an order-of-magnitude√larger data sample (20.3 fb−1), a higher centre-of-mass energy ( s = 8 TeV), reduced background uncertainties, and improved selection criteria at high invariant mass. Factorization and renormalization scale uncertainties are not used for either signal type, for comparison with earlier analyses [18,28,29]
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