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

2. 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

3. 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

4. Where's the Higgs?
~10% BR
H->bb
2.3σ

5. 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

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

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

9. 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:

10. 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

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

12. Let's look at the data!

13. 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

14. 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

15. Event Displays

16. Event Displays

17. Event Displays

18. Event Displays

19. Event Displays

20. Event Displays

21. Conclusions
6 events

22. Backup