1. g g s High Mass Higgs at the Tevatron
Matthew Herndon, University of Wisconsin Madison
Higgs Days 2012

2. The Higgs Boson
SM postulates a mechanism of electroweak symmetry breaking via the Higgs mechanism
Interaction with the Higgs field results in masses for the W and Z vector bosons,
Possible mass terms for the fermions
Also expect and observable quanta of the field: Higgs boson
Directly testable hypothesis by searching for the Higgs boson
A primary goal of the Tevatron and LHC
Now directly testable by measuring Higgs properties!

3. The Higgs Boson Where to concentrate you search
One answer: where your experiment excels
Higgs decay to pairs of mass vector bosons with leptonic decays
Where the data says to look(just before final analyses)
SM LEP Direct search: mH > 114GeV
SM (Tevatron) indirect constraint: mH < 152GeV
LHC: < mH < 129
LHC: Look around 125 GeV
Some Hints that optimizing the analysis at low mass was called for.

4. Tevatron Performance Over 10 fb-1!
Enough data to make an impact at low mass
9.7/fb used in analysis

5. Tevatron Higgs History
After LP 2007 we had predicted expected preface enhancements and extrapolated to 10fb-1
Improvement factors based on studies in data
Expectation: 3σ evidence for Higgs possible at 115GeV
125 was a harder mass.
Needed to exceed the expectations

6. SM Higgs Production and Decay
High mass: HWWll decay available (ZZ used - contribution small)
Takes advantage of large ggH production cross section
Alternative production mechanisms
WHWWW, ZHZWW, VBF: qqHqq->WWjj
Significant contribution in events with 1, 2 or more jets and same sign leptons, three leptons events. Helps at low mass

7. Analysis Technique Expanded acceptance
Expanded lepton acceptance in areas with weak/no dedicated lepton Id
Multiple analysis channels beyond HWW: HZZ, HWW (lepton + jets), VH (same sign, trilepton, extra jets) and VBF (extra jets)
Analyze specific event topologies
Isolate subsets of signal/background processes for optimal discrimination
Optimize inputs to discriminants as a function of mass
Use of jet kinematics to find vector bosons and identify VBF events
Control regions
Check modeling of primary backgrounds
Measure background cross sections where possible: Z, WW, WZ, ttbar
Apply advanced techniques
Add only order 10-20% sensitivity to the analysis but needed in regions where the spin correlation is not enough such as at low mass

8. SM Higgs: HWW HWWll - signature: Two high pT leptons and MET
The most powerful analysis channel
Primary backgrounds: WW and top in di-lepton decay channel
Excellent physics based discriminants H μ+ ν W- W+ e-
Spin correlation: Charged leptons
go in the same direction

9. CDF WW 2+ Jet Analysis Signals Analysis improvements 25% imrpvement
VHVWWl+l- MET jj analysis, VHB HWW + forward jets, ggHWW jj
Analysis improvements
Implementation of MCs with good 2+ jets modeling for backgrounds
Use of jets kinematics:
Energy and rapidity
Use of dijet variables
mass, delta rapidity
Optimization of variables
as a function of mH
25% imrpvement

10. CDF HWW Search As sensitive as individual Hbb searches as low mass
Combination of CDF H  WW searches
UW contribution
HWW Channels:
Exp. Limit σ/σH per channel and combined
Exp. Limit 125
Exp. Limit 165
ggH: 0 Jets
6.68
1.41
ggH, VH, VBF: 2+ Jets
7.83
1.89
ggH: 1 Jet
9.11
1.83
Low mll
11.1
2.86 SS
11.7
3.93
Trilepton
11.6
4.07
Combined
3.08
0.69
Like WH -> WWW like sign dilepton
ttH -> ttbb
As sensitive as individual Hbb searches as low mass
most sensitive analysis for mH > 128GeV
Observed limit 2.98

11. DØ HWWll Search
ll – signature subdivided by jet topology & lepton charge
Further subdivided by lepton flavor
BDT for DY suppression
Example: HWWeμ + MET
High purity channel
Exp limit – most powerful single Tevatron channel

12. DØ H: ljj ljj(jj): lepton + jets signature
HWWljj, VHljjjj, WHlnubb
High and low mass analysis at once
At high mass takes advantage of large Wjj branching ratio
Classifies events by number and type of b tag
BDT based discriminant

13. DØ HWW Search
Combination of DØ H  WW searches
HWW Channels:
Exp. Limit σ/σH per channel and combined
Exp. Limit 125
Exp. Limit 165
H: eμ
5.22
1.19
H: ee, μμ
6.89
6.76
1.59
1.64
gg->H Combined
3.59
0.81
VH: SS leptons
11.6
5.89
VH: tri leptons
11.1
6.64
H: l+jets
----
4.56
Combined
0.72
Like WH -> WWW like sign dilepton
ttH -> ttbb
hWW combined sensitivity more powerful that any of the low mass H analysis
Observed limit 4.56

14. Tevatron Higgs Combination
Exclusion driven by HWW
No interesting WW signal observed
Obs. Exclusion GeV

15. Conclusions LHC has observed a boson with mass ~125 GeV!
What we have measured so far almost certainly means it plays a part in electroweak symmetry breaking.
The Tevatron experiments have achieved sensitivity to the SM Higgs boson production cross section at high and low mass
The sensitivity of the CDF and DØ high mass searches make them a primary element of the Tevatron search at mass around 125 GeV
We exclude at 95% C.L. the production of a SM Higgs boson of GeV
The observed data in HWW is compatible with a SM Higgs boson but not constraining