Searches for the Higgs Boson in CMS

The CMS potential for the Higgs boson discovery is discussed in the framework of the Standard Model (SM) and its Minimal Supersymmetric extension (MSSM). Imperial College, London, UK


Introduction
The Large Hadron Collider (LHC) is designed to collide two counter rotating beams of protons or heavy ions. Proton-proton collisions are foreseen at an energy of 7 TeV per beam with a planned start-up in 2007. The Compact Muon Solenoid (CMS) is one of the two general purpose detectors that will be installed on the collider. One of its main challenges is the discovery of the Higgs boson. In this report, the CMS potential for the Higgs boson discovery is discussed in the framework of the Standard Model (SM) and its Minimal Supersymmetric extension (MSSM). More details can be found in [1].

Discovery Potential for the Standard Model Higgs Boson
The main production mechanism for the Higgs boson at 14 TeV is the gluon-gluon fusion and the WW/ZZ fusion. For low Higgs boson masses (below 130 GeV/c¦ ), the most promising channel for discovery is the H § which will allow a very fast discovery. For very high Higgs boson masses (above 500 GeV/c¦ ) the cross section for the qq § qqH production process is large and the decay channels were found to yield the highest sensitivity even though the large backgrounds and the large Higgs boson width make the discovery much more difficult compared to the lower Higgs boson masses.
The statistical significance expected for 30 fb3 r q of integrated luminosity can be seen in Figure 1 when all channels are combined.

Discovery Potential for the MSSM Higgs Bosons
In the MSSM there are five Higgs bosons: two CP-even Higgs boson mass eigenstates h,H, a charged Higgs boson pair Hs and a CP-odd neutral pseudoscalar A. At tree-level the Higgs boson sector is determined by two parameters. A common choice is the ratio of vacuum expectation values of the two doublets t c u 1 v =u ¦ /u q and the mass of the pseudoscalar Higgs boson Mw . Radiative corrections modify the predictions of the model significantly: the mass of the lightest higgs boson at tree level is predicted to be below M9 which is already excluded by LEP [2] but after corrections its mass may rise up to 135 GeV/c¦ . Several MSSM Higgs boson scenarios have been proposed depending on different choices of the soft SUSY breaking parameters. For the results presented in this report the SUSY parameters are fixed to the values used in the LEP studies [3].
In the large Mw limit (Mw y x M9 ), the so-called decoupling region, the heavy Higgs bosons (H, A, Hs ) are almost degenerate in mass. The lighter Higgs boson h is SM-like, so its production cross sections and decay partial widths are very close to those of the SM Higgs boson. The discovery potential for the lighter scalar Higgs boson h can be seen in Figure 2 for 30 fb3 r q of integrated luminosity.   decay channel in the production, by suppressing the backgrounds with an isolated lepton from the accompanying W decay. The discovery potential for the Hs Higgs bosons can be seen in Figure 4 for 30 fb3 r q of integrated luminosity.