Search for new physics in final states with low transverse energy photon and missing transverse energy in proton-proton collisions at $\sqrt{s} = 8$ TeV

Abstract

A search for new physics in the γ+ET final state is performed using pp collision data corresponding to an integrated luminosity of 7.3 fb-1 collected at √s = 8 TeV using low threshold triggers in a phase space region defined by ET > 45 GeV and E-slashT > 40 GeV. The data are also examined using optimized selections for maximum sensitivity to an exotic (gravitino/neutralino) decay of the Higgs boson predicted in a low-scale SUSY breaking scenario. The results are found to be compatible with the Standard Model hypothesis. These results are the first limits on this model from collider searches. Furthermore, proton-proton collision events containing high-energy photon and missing transverse momentum have been investigated. No deviations from the standard model have been observed using the √s = 8 TeV data set corresponding to 19.6 fb-1 of integrated luminosity. Further constraints are set on χ production and translated into upper limits on vector and axial-vector contributions to the χ-nucleon scattering cross section. For Mχ = 10 GeV, the χ-nucleon cross section is constrained to be 2.6 x 10-39 cm2 (9.6 x 10-41 cm2) for a spin-independent (spin-dependent) interaction at 90% confidence level. In addition the most stringent limits to datemore » are obtained on the effective Planck scale in the ADD model with large spatial extra dimensions and on the brane tension scale in the branon model.« less