Abstract:The ATLAS detector at the Large Hadron Collider is used to search for highmass resonances decaying to an electron-positron pair or a muon-antimuon pair. The search is sensitive to heavy neutral Z ′ gauge bosons, Randall-Sundrum gravitons, Z * bosons, techni-mesons, Kaluza-Klein Z/γ bosons, and bosons predicted by Torsion models. Results are presented based on an analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9 fb −1 in the e + e − channel and 5.0 fb −1 in the µ + µ − channel. A Z ′ boson with Standard Model-like couplings is excluded at 95% confidence level for masses below 2.22 TeV. A Randall-Sundrum graviton with coupling k /M Pl = 0.1 is excluded at 95% confidence level for masses below 2.16 TeV. Limits on the other models are also presented, including Technicolor and Minimal Z ′ Models.
Keywords: Hadron-Hadron ScatteringOpen Access, Copyright CERN, for the benefit of the ATLAS collaboration doi:10.1007/JHEP11(2012)138 10 Limits on spin-1 SSM and E 6 Z ′ bosons 13
JHEP11(2012)13811 Limits on spin-1 Z * bosons 1512 Limits on spin-2 Randall-Sundrum gravitons 1513 Limits on Torsion models 16
Limits on Technicolor 1715 Limits on spin-1 Kaluza-Klein S 1 /Z 2 bosons 2116 Limits on Minimal Z ′ bosons 22
Conclusions 23The ATLAS collaboration 30
IntroductionSearches for new resonances decaying to a dilepton final state have had a long and successful history. These channels contributed to the discovery of the quarkonium resonances J/ψ and Υ, as well as the discovery of the Z boson. Various models beyond the Standard Model (SM) contain additional bosons which can decay into dileptons, providing a fully -1 -
JHEP11(2012)138reconstructable final state with small, well-understood backgrounds. In this article, data collected by the ATLAS experiment at the LHC are used to search for new resonances decaying into dielectron and dimuon final states. The Sequential Standard Model (SSM) [1] defines the Z ′ SSM couplings to SM fermions to be the same as the SM Z boson couplings and is often used in the literature as a benchmark model. A number of models predict additional neutral vector gauge bosons. One class postulates larger symmetry groups in which the SM gauge group is embedded. This is usually motivated by gauge unification or restoration of left-right symmetry, which is violated by the weak interaction. In one scheme, the SM gauge group derives from the E 6 group which, upon symmetry-breaking via the SU(5) subgroup, results in two additional U(1) gauge groups named U(1) χ and U(1) ψ with associated gauge bosons Z ′ χ and Z ′ ψ that can mix [1,2]. In the Minimal Z ′ Models [3,4], the phenomenology is controlled by only two effective coupling constants in addition to the Z ′ boson mass. This parameterization encompasses many models, including a left-right symmetric model [5,6] and the pure (B-L) model [7], where B (L) is the baryon (lepton) number, and B-L is the conserved quantum number.A second set of models is motivated by various solutions to the hiera...