| Search for new physics in the exclusive Photon+MET channel in RunII |
The photon plus missing transverse energy signal is comparatively rare in the Standard Model. The production is dominated by the higher-order electroweak Z+gamma process. This signature is a sensitive place to search for new high-energy invisible particles because photons, radiated by incoming partons in a collision, can be the only tag available to us in the detection of such processes. Photons are also good candidates to be produced in the decay chains of new particles and appear in such popular models as Large Extra Dimensions, anomalous Z+gamma couplings, heavy right-handed neutrinos ... .Authors:
One model of new physics that can produce such a signature is the compactified Large Extra Dimensions (LED) model of Arkani-Hamed, Dimopoulos, and Dvali (ADD). In such a model, gravitons are produced directly in processes such as qqbar->gamma+G, where G is the emitted graviton. The emitted graviton will be undetected, leaving the final state quark to produce a photon. We optimize the cut on the photon Et to gain best sensitivity for the ADD model.
This generic search for new physics is based on ~2.0 fb-1 of data collected with the w_notrack trigger (photon Et> 18 GeV and MET > 18 GeV) using kinematic cuts of photon Et > 50 GeV and MET > 50 GeV. The optimization for the ADD model yields photon Et > 90 GeV. We find an upper limit of 14.3 events from new physics, which is equivalent to an upper limit on cross-section of 14.4 +/- 1.5 fb-1 for beyond the Standard Model processes.
M Goncharov, V Krutelyov, R Culbertson, A Pronko
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