Background and signal estimation for a low mass Higgs boson at the LHC

The discovery of the Higgs boson(s) is the major goal of the LHC which will start taking data in 2008. In this work a data driven extraction of the background and statistical signal significance in the H→ZZ→4ℓ decay channel is presented. The background for Higgs masses as low as 130 GeV can be extracted with an error of 20%, using a sideband measurement from a single 30 fb^-1 experiment. The predicted background distribution is best described by a double asymmetric Gaussian. An analytic formula is introduced which provides an accurate p-value that a Higgs discovery claim is consistent with a background fluctuation. The formula can be used in a single real measurement at LHC using as input the measured background and the profile likelihood asymmetric errors of this measurement. The method presented here can be applied to the general case of extrapolating from a signal-free data region to a candidate signal region. This is the case of supersymmetry searches at the LHC. PACS  14.80.Bn; 06.20.Dk