SM Higgs decay to dimuons Ashok Kumar, Suman Beri Panjab University – Chandigarh INDIA-CMS meet March 3-5, 2005 Chandigarh

➢ LHC is well suited for direct observation of a Higgs boson or other remnants of EW breaking and fermion mass generation. ➢ One needs to study as many properties and decay channels of the Higgs-like resonance as possible – not only at a LC but also at LHC and even higher energy colliders – to finally claim understanding of the mechanism of EW symmetry breaking sector. ➢ SM Higgs : the fits to all LEP, SLC and tevatron precision measurements yield an indirect prediction for the SM Higgs m H = GeV and a 95% CL upper limit of 219 GeV. The Lower bound for the Higgs boson mass from LEP is GeV. Overview

➢ The low mass region is most probable to find the Higgs boson, as indicated by theoretical and experimental limits, but it is the harder to explore at LHC. ➢ For m H ≤ 130 GeV the H->gg, H -> bbar and H -> tau tau decay channels can provide a 5 sigma discovery with integrated luminosties exceeding 60 fb -1 and even lower luminosites if the channels are combined. ➢ For m H ≥ 140 GeV the predominent decay channels are H- > WW (*) and H-> ZZ (*). ➢ H -> W + W - is the main decay channel if the m H is about 170 GeV. ➢ H -> ZZ (*) -> 4 ĺ ( ĺ= e,µ) has the cleanest experimental signature, specially in the four-muon channel, for this reason called the “golden” channel at LHC. Low and High Mass Higgs Boson

H -> µ + µ - relevance ➢ H -> µ + µ - has been considered inaccessible due to very small branching fraction ~ ➢ Higgs boson couple to SM particles proportional to their masses. ➢ Higgs muon has Yukawa couplings not only to the third generation quarks and leptons but also to the lighter fermions. ➢ H~µµ couplings can be found using this channel only even if the 5 sigma discovery limit may not be reached.

What people worked so far..... ➢ Ritva et. al :- Worked on discovery potential for m H = 120 GeV. For inclusive channel S/B = 0.4 % (Statistical significance 1.1 for 300 fb -1 ), 40 % for WBF(Statistical significance 1.12 for 60 fb -1 ) was observed. ➢ T.Plehn et. al :- Extraction of Muon – Yukawa couplings to about 10 % level is possible at 200 TeV vLHC (WBF). ➢ T. Han et. al :- Feasibility of this channel at 300 fb -1 for 110 GeV < m H < 140 GeV in both channels at 3. 15% accuracy in coupling determination assuming SM-like h~ttbar, h~bbbar couplings. ➢ M. Battaglia et. al :- Determination of the muon Yukawa coupling at high energy e + e - linear colliders.

Events generated and cuts used ➢ 10k events simulated using ORCA 8_7_1 with new DST's. ➢ The signal selection is based on the identification of two isolated oppositely charged muons coming from a common vertex. ➢ Luminosity 30 fb -1 ➢ Events in dataset 9998 ➢ Isolated muons 5350 Cuts Used :- ➢ muonIsolCone (∆R iso ) 0.4 ➢ muonPt 20 GeV ➢ MuonIsolPt 1 ➢ Eta 2.5

pT,eta of two isolated muons

Invariant mass of isolated muons

Future Plan ➢ Requested datasets for gg and WBF production channels at CERN are ready with new DST's with m H = 120 GeV. ➢ We will go for detail study of the h -> µµ channel including the backgrounds (DY, qqbar etc). ➢ Try to see discovery potential but main focus on muon-Yukawa couplings (using CMSOO softwares).