1. Searches for Non-SM Higgs at the Tevatron
Thomas Wright
University of Michigan
on behalf of the CDF and DØ Collaborations
This talk: neutral MSSM Higgs searches
More exotic Higgs to follow (M. Mulhearn)
XLIIIth Rencontres de Moriond
QCD and High Energy Interactions
March 8-15, 2008

2. Higgs in the MSSM
In the standard model, one complex doublet = four scalar fields
Three turn into W/Z mass  one physical scalar
Minimal Supersymmetric Standard Model (MSSM) requires two doublets
One couples only to up-type fermions, the other only to down-type
Ratio of VEV’s - “tanb”
Eight scalar fields – three for W/Z mass = five physical scalars
Three neutral (h, H, A), two charged (H±)
Properties of the Higgs sector largely determined by two parameters:
mA : mass of pseudoscalar
tanb : ratio of VEV’s
Higher-order effects introduce other SUSY parameters (benchmark scenarios, see Carena et al., hep-ph/ )
Typically, mh < mA < mH , and mH± ~ mA
For tanb near 1, h is SM-like and light – SM Higgs limits apply
Larger tanb and light mA shows more interesting behavior

3. Higgs at High tanb b 0 b 0
Processes involving bottom quarks (down-type) can be enhanced (goes like tan2b) Boost from femtobarns to picobarns
Could be observable at Tevatron!
f0 = h/H/A
via top loop
H = SM Higgs
here, H = A or h/H

4. Higgs at High tanb Neutral sector simplifies at high tanb
A and h/H become degenerate
Other scalar SM-like, low cross section
Only need to search for a single mass peak (f)
For the A and its twin h/H, at high tanb decays into bb (90%) and tt (10%) dominate
So, for example, won’t see enhancement in HWW* channel
CDF and DØ are searching in both of these decay modes

5. The    Channel th ID t cone
Unique final state – can look for inclusive f production
Main backgrounds: Z  tt, W+jets, dibosons
One tau decays leptonically: e/m (CDF) or m (DØ) (plus n’s)
pT > 10 GeV/c (CDF), 15 GeV/c (DØ)
Other tau hadronic (both) (and nt)
One or three tracks (Sqtrk = ±1), opposite to lepton
CDF : isolation 30°, shrinking t cone (10°  3°)
DØ : three types (p±, p±p0, 3-prong), NN score
No electron veto (allows em)
pT > 15 GeV/c (1-prong), 20 GeV/c (3-prong)
Also tt  em (CDF), pT > 10, 6 GeV/c
Reject non-tt background
Lepton and missing energy inconsistent with W
HT cut (CDF) or kinematic NN (DØ)
th ID
t cone
isolation
Multiple neutrinos  can’t reconstruct tt mass very well

6. CDF tt Results Moriond 2007, CDF 1 fb-1
mvis (GeV/c2)
Last year at this time, CDF had a >2s excess around 160 GeV/c2 (<2s over all mf)
Updated Fall 2007 with an additional 0.8 fb-1 of data
No excess in e/m + thad channel after update
mvis (GeV/c2)

7. CDF tt Results No apparent excess in em channel either
Set s x BR limits
mvis (GeV/c2)
mvis (GeV/c2)

8. DØ tt Results Visible mass (like CDF)
Just one input to search NN, along with lepton, tau kinematics
Do not see any excess (as was the case last winter)
Set s x BR limits

9. MSSM Interpretation DØ btt 340 pb-1
Interpret s x BR limits as limits on tanb vs mA in MSSM benchmark scenarios
More data and analysis improvements on the way
Project missing momentum onto t axes for boosted Higgs (improve mtt)
Split into b-tagged and untagged samples (already demonstrated by DØ)
Updated results from DØ in tt and btt channels coming soon!

10. too much background The fbb Channel 0 b b 0
Dawson, Jackson, Reina, Wackeroth hep-ph/
b quark pT >20 GeV/c, |h|<2 b 0
too much background b 0
with fbb, 3b total
Inclusive H  bb is too hard due to QCD background
Require one additional bottom quark jet besides the two from Higgs decay
“3b” channel best compromise between signal and background rates

11. B-Jet Identification CDF CDF : displaced vertices with Lxy/s cut
Vertex mass separation
DØ : combine vertex properties and displaced track info with NN
Tag to h beyond 2 DØ

12. DØ 3b Channel Result with 0.9 fb-1 (2006), update coming soon!
Search uses invariant mass of the two leading jets m01 in triple-tagged events
Derive background shape from double-tagged sample
Correct for kinematic bias of third jet tag
Normalize background to data in sideband region, look inside the signal window
No excess observed, set limits on s x BR
mH = 120

13. CDF 3b Channel New result for Moriond QCD 2008, using 1.9 fb-1
Search in mass of two lead jets m12
Backgrounds are events with two true b-tags, and a b/c/fake tag
Characteristic m12 spectra for each
Start from bb+jet sample (corrected double-tags), weight events by flavor hypothesis
Correct bbb and bcb shapes for double/triple-tag selection bias
Largest systematic error
Fit the observed m12 spectrum with the backgrounds and a Higgs shape

14. CDF 3b Channel
Improve prediction of total background m12 using tag properties
Invariant mass of tracks in each vertex mj
m1+m2 : bbb+bbx / bcb+bqb
m3 : bbx / bbb+bcb+bqb
Unstack into 1D variable “xtags” for plotting/fitting
Fits are 2D – m12 vs xtags
Four backgrounds
Higgs signal template

15. CDF 3b Results No significant excess observed Set limits on s x BR
Background systematics limiting improvement at low mH
Focus of the next round

16. MSSM Interpretation Interpret in MSSM scenarios
Include effect of Higgs width (~20% for tanb = 100)
Lose sensitivity (lower S/B)
Lowers event yield
Best limits obtained in scenarios with m < 0 (loop enhancements)

17. Summary CDF and DØ are looking hard for neutral MSSM Higgs bosons
Lots of progress but no discovery as of yet
Techniques are well-advanced but still room for improvement
Taus: split samples to improve mtt and S/B with b-tagging
3b: background shape systematics (CDF)
DØ updates on all three channels (tt, btt, 3b) coming soon
Combination of experiments/channels is planned
Results today use 1-2 fb-1, expect 5-6 by 2009 (7 by 2010?)
Could probe down to tanb in the 20’s with full Run II samples
Or, with the right mA and tanb, make a discovery!

18. Backup Material

19. Charged Higgs
CDF : use dilepton, l+jets (single and double-tagged), and lepton+tau s’s
Consider H+  tn, cs, t*b, W+bb
Map out allowed and excluded regions in mH+ vs tanb using CPsuperH and CDF simulation to predict effects on top s’s
Search in top decays
t  H+b
DØ : ration of cross sections l+jets/dilepton
BR(t  H+b) < 95% CL (for H+  cs)

20. CDF tt Projections