Search for dark matter candidates and large extra dimensions in events with a jet and missing transverse momentum with the ATLAS detector

Abstract

A search for new phenomena in events with a high-energy jet and large missing transverse momentum is performed using data from proton-proton collisions at √ s = 7 TeV with the ATLAS experiment at the Large Hadron Collider. Four kinematic regions are explored using a dataset corresponding to an integrated luminosity of 4.7 fb −1 . No excess of events beyond expectations from Standard Model processes is observed, and limits are set on large extra dimensions and the pair production of dark matter particles. Keywords: Hadron-Hadron ScatteringArXiv ePrint: 1210.4491Open Access, Copyright CERN, for the benefit of the ATLAS collaboration 6 Results and interpretation 17 6.1 Large extra dimensions 18 6.2 WIMP pair production 22 Summary 27The ATLAS collaboration 35 IntroductionEvent topologies with a single jet with large transverse energy and large missing transverse momentum, referred to as monojets in the following, are important final states for searches for new phenomena beyond the Standard Model (SM) at a hadron collider. The primary SM process that results in a true monojet final state is Z-boson production in association with a jet, where the Z boson decays to two neutrinos. A further important reducible contribution to this final state consists of events that include a W boson and a jet, where the charged lepton from the W -boson decay is not reconstructed. Phenomenological scenarios beyond the Standard Model (BSM) that result in a monojet final state include supersymmetry [1][2][3][4][5][6][7][8][9][10][11] and large extra dimensions (LED) [12]. A model-independent treatment of the production of dark matter (DM) particles at the Large Hadron Collider (LHC) has been proposed recently, where DM particles are pair-produced in association with a jet [13][14][15]. In the following, a search for an excess of monojet events over SM expectations is performed. The results are interpreted in a framework of LED and DM particle pair production. They are based on a dataset of 4.7 fb −1 of proton-proton -1 -JHEP04 (2013) Models of large extra spatial dimensions have been proposed to remove the hierarchy problem [22][23][24][25] by addressing the weakness of gravity relative to all other forces. One popular model of LED that is often used to interpret the results of monojet searches at particle colliders is that of Arkani-Hamed, Dimopoulos, Dvali (ADD) [12]. In this model, gravity propagates in the (4 + n)-dimensional bulk of space-time, while the SM fields are confined to four dimensions. The large observed difference between the characteristic mass scale of gravity (the Planck mass) and the electroweak scale (as characterised by the W -boson mass) is the result of the four-dimensional interpretation of the Planck scale, M Pl = 1.2 × 10 19 GeV, which is related to the fundamental (4 + n)-dimensional Planck scale (M D ) by M P l 2 = 8π M D 2+n R n , where n and R are the number and size of the extra dimensions, respectively. An appropriate choice of R for a given n results in a value of M D close to the electroweak s...

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