Abstract
Results are presented from a search for new physics in final states containing a photon and missing transverse momentum. The data correspond to an integrated luminosity of 19.6 inverse femtobarns collected in proton-proton collisions at sqrt(s) = 8 TeV with the CMS experiment at the CERN LHC. No deviation from the standard model predictions is observed for these final states. New, improved limits are set on dark matter production and on parameters of models with large extra dimensions. In particular, the first limits from the LHC on branon production are found and significantly extend previous limits from LEP and the Tevatron. An upper limit of 14.0 fb on the cross section is set at the 95% confidence level for events with a monophoton final state with photon transverse momentum greater than 145 GeV and missing transverse momentum greater than 140 GeV.
Highlights
The production of events containing photons with large transverse momentum and having large missing transverse momentum at the CERN LHC is sensitive to physics beyond the standard model (SM)
In this Letter we investigate three possible extensions of the SM: a model incorporating pair production of dark matter (DM) particles, and two models with extra spatial dimensions, as described below
Various processes are contracted into an effective field theory (EFT) [2,3,4,5], assuming M much larger than the momentum transfer scale Q (i.e. M Q ) and a contact interaction scale given by −2 = gχ gq M−2, where gχ and gq are the mediator couplings to χ and to quarks, respectively
Summary
The production of events containing photons with large transverse momentum and having large missing transverse momentum at the CERN LHC is sensitive to physics beyond the standard model (SM). Various processes are contracted into an effective field theory (EFT) [2,3,4,5], assuming M much larger than the momentum transfer scale Q (i.e. M Q ) and a contact interaction scale given by −2 = gχ gq M−2, where gχ and gq are the mediator couplings to χ and to quarks, respectively Using this formalism, results from searches at the LHC can be related to limits for direct searches sensitive to χ -nucleon scattering [5]. MD is of the same order as the electroweak scale (MEW ∼ 102 GeV), the large value of MPl can be interpreted as being a consequence of large-volume (∼Rn) suppression from extra dimensional space This model predicts a sizable cross section for the process qq → γ G, where G is a graviton that escapes detection, and motivates the search for events with a single γ and missing transverse momentum. Other backgrounds include Wγ → νγ (where is an undetected charged lepton), W → eν (where the electron is misidentified as a photon), γ + jet, QCD multijet (with a jet misidentified as a photon), Zγ → γ , and diphoton events, as well as backgrounds from beam halo
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