An Exploration of H->aa->4mu Andy Haas Columbia University DZero Higgs Meeting May 1, 2008

Where's the Higgs? EW variables sensitive to mH via radiative corrections mH<97 GeV (at 95% CL) (leptonic only) LEP II: mH>114.4 GeV

Where's the Higgs? Maybe the Higgs is light after all, but decays to something other than bb! The coupling to bb is not very big. Any new light state could have a large Higgs branching ratio! A natural candidate is the NMSSM. Extra singlet, the “a”, mixes with h. BR h→aa can easily be 90%. mH<97 GeV (at 95% CL) (leptonic only) LEP II: mH>114.4 GeV

Where's the Higgs? ~10% BR H->bb 2.3σ

h->aa->?? If a→ττ, limit is weak (86 GeV). (ma<2mb) If a→cc/ss, we're screwed. (ma<2mτ) What about a→µµ? (ma<2ms) LEP II: mH>114.4 GeV

a->mumu? HyperCP experiment at Fermilab (data from 1999) reported in 2005 evidence for See this nice Moriond summary: http://arxiv.org/abs/hep-ex/0606038v1 SM BR expected to be between 1.6 – 9 x 10-8, so could just be SM. But strange Mµµ distribution!

h->aa->4mu If Ma is just above 2Mµ the muons will be extremely collinear !!! 2 tracks are visible

h->aa->4mu A very distinct signature Would have been overlooked since - often only one muon is reconstructed per collinear muon pair - muon fails standard track isolation Analysis would have to specifically look for muons which had a collinear partner track (and still good calorimeter isolation) Two pairs in the same event would be a smoking gun Some theorists have thought about it: http://arxiv.org/abs/hep-ph/0611270v3

h->aa->4mu Selections Start with 1210 MC events (mh=100 GeV) 680 have 2 muons, pT>10 GeV, Mµµ >10 GeV (no opposite-sign requirement!) Track Isolation > 5 GeV Cal Isoation < 2 GeV

h->aa->4mu Selections 298/1210 events pass all selections 25% acceptance sigma(h)=0.5-2pb (120-80 GeV) ~125-500 events dR between muons > 1 N tracks in iso cone < 3 M_mumu > 15 GeV

Let's look at the data!

h->aa->4mu in Data p17 2MuHighPt skim, 1.1/fb 6 events! But, none very clean. None with just 2 tracks in each cone. (10% acceptance for that.) Look at QCD sample, reverse calorimeter isolation cut on one side... > 2 GeV ~20-25% of jets have <3 tracks

h->aa->4mu QCD 92 events pass all cuts except the Ntrk requirements Expect 92*.25=23 events with one side with <3 tracks, observe 28 Expect 23*.20=4.6 events with both sides with <3 tracks, observe 6 Expect 92*.1*.1=0.92 events with both sides with <3 tracks, observe 0

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Conclusions 6 events

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