# Presentation: 726572

## Search for a SM Higgs Bosonin the WW Dilepton Decay Channel with 200/pb CDF II Data

- Shan-Huei Chuang
- UW−Madison
- for the CDF Collaboration
**2004 PHENOMENOLOGY SYMPOSIUM  **
- Madison WI
- April 27 2004

## Why Do Higgs? And ggh0WW*? 

-  Electroweak symmetry
-     breaking dynamics?
-  Mass generation of
-     electroweak gauge
-     bosons and fermions?
-  Indication of the scale of
-     new physics where the
-     Standard Model will fail?

**HIGGS**

-  TeVatron provides an opportunity with pp collision.

- major leading-order production mechanism

- dominant decay mode in high mass region

- Shan-Huei Chuang @ PHENO 04

- 04/27/2004

## How to Approach Higgs?

**SPIN-ZERO**

-  parity conservation
-    spin conservation
- makes two distinctive higgs features:
-  small dilepton angular separation
-  small dilepton invariant mass

- tendency of
- collinearity

- in the rest frame of the higgs boson

- l−(spin -1⁄2, left-handed)

- l+(spin 1⁄2, right-handed)

- ν(spin -1⁄2, left-handed)

- Shan-Huei Chuang @ PHENO 04

- 04/27/2004

## Event Selection 

- Select events that have
- “well-detected” two electron/mμons, each with Et > 20 GeV
- missing Et > 25 GeV
- no jets with Et > 15 GeV and |η| < 2.5
- ΔΦ(missing Et,
-           closest lepton or jet) > 20°
-       for missing Et < 50 GeV
- not 76 < MZee/μμ < 106 GeV
- opposite lepton charge signs
- dilepton invariant mass Mll < 1⁄2MH
- Use a binned maximum likelihood method                                          on the ∆Φll distribution of selected events
- Extract the 95% CL σ·BR(ggh0WW) limit

****

- Shan-Huei Chuang @ PHENO 04

- 04/27/2004

## Signal Acceptance

| MH | Mll Cut (GeV) | ee          (%) | eμ          (%) | μμ         (%) | ee+eμ+μμ (%) |
| --- | --- | --- | --- | --- | --- |
| 140 | 55.0 | 0.030±0.001 | 0.060±0.001 | 0.034±0.001 | 0.124±0.002 |
| 150 | 57.5 | 0.055±0.002 | 0.110±0.002 | 0.063±0.002 | 0.228±0.003 |
| 160 | 62.5 | 0.093±0.002 | 0.196±0.003 | 0.113±0.002 | 0.402±0.004 |
| 170 | 70.0 | 0.115±0.003 | 0.230±0.004 | 0.131±0.003 | 0.476±0.005 |
| 180 | 80.0 | 0.110±0.003 | 0.219±0.003 | 0.119±0.002 | 0.449±0.005 |

- MC study shows the tendency of
- small HWW* dilepton invariant
- mass, which is not a property of
- other SM background processes.

- SM ggHWW* signal acceptance
- in each dilepton channel for each higgs mass

- Shan-Huei Chuang @ PHENO 04

- 04/27/2004

## Signal and Background Expectations

| SM MH (GeV) | 180 |
| --- | --- |
| Mll cut (GeV) | 80.0 |
| ttbar | 0.02 ± 0.01 |
| ZZ | 0.06 ± 0.01 |
| WZ | 0.18 ± 0.02 |
| DY ττ | 0.03 ± 0.01 |
| DY μμ | 0.43 ± 0.19 |
| DY ee | 0.87 ± 0.44 |
| fakes | 0.81 ± 0.25 |
| WW | 6.49 ± 0.76 |
| total bg  | 8.90 ± 0.98 |
| HWW | 0.17 ± 0.02 |
| data | 8 |

- Shan-Huei Chuang @ PHENO 04

- 04/27/2004

## Dilepton ΔΦ Distribution

- Shan-Huei Chuang @ PHENO 04

- 04/27/2004

## Limit on σ·BR(ggHWW*) as a fun-ction of Higgs Mass at √ŝ = 1.96 TeV

| SM Higgs Mass (GeV) | 140  | 150 | 160 | 170 | 180 |
| --- | --- | --- | --- | --- | --- |
| σ(ggh0) (pb) | 0.45 | 0.36 | 0.30 | 0.25 | 0.21 |
| BR (H  WW*) | 0.48 | 0.68 | 0.90 | 0.97 | 0.94 |
| Integrated Luminosity (pb-1) | 184 ± 11 |  |  |  |  |
| Total Acceptance (%) | 0.124±0.012 | 0.228±0.023 | 0.402±0.040 | 0.476±0.048 | 0.449±0.045 |
| Expected Signal (event) | 0.10 ± 0.01 | 0.15 ± 0.02 | 0.22 ± 0.03 | 0.22 ± 0.03 | 0.17 ± 0.02 |
| WW Background (event) | 3.51 ± 0.41 | 3.82 ± 0.45 | 4.45 ± 0.52 | 5.38 ± 0.63 | 6.49 ± 0.76 |
| Other Background (event) | 0.68 ± 0.16 | 0.90 ± 0.24 | 1.34 ± 0.35 | 1.91 ± 0.47 | 2.40 ± 0.55 |
| 95% CL Limit − Counting (pb) | 18.4 | 9.8 | 6.2 | 8.2 | 8.8 |
| Expected Limit − ΔΦ-fitting | 18.1 | 9.8 | 6.0 | 7.4 | 8.0 |
| 95% CL Limit − ΔΦ-fitting (pb) | 17.8 | 9.4 | 5.6 | 5.6 | 6.4 |

- BR(Wlv)2 included

- Limit on σ·BR(ggHWW*) as a fun-ction of Higgs Mass at √ŝ = 1.96 TeV

- CDF Run II Preliminary, Lint ≈ 200 pb-1

- Shan-Huei Chuang @ PHENO 04

- 04/27/2004

## Conclusion

- We studied the production of ggh0WW*lvlv (l = {e,μ}) at TeVatron.
- We extracted 95% C.L. limits on higgs production at √ŝ = 1.96 TeV as a function of the higgs mass.
- Our results are good yet pre-liminary. We are making pro-gress on the optimization of our approach while waiting for data increase to advance the results.

- Shan-Huei Chuang @ PHENO 04

- 04/27/2004

## Backup

- Indirect searches:
-  For Mtop = 174.3** **±** **5.1 GeV,
-       log MH = 1.98+0.21−0.22
-       MH = 96+60−38 GeV
-       MH < 219 GeV @ 95% CL
-  For Mtop = 178 ± 4.3 GeV,
-       log MH = 2.07+0.20−0.21
-       MH = 117+67−45 GeV
-       MH < 251 GeV @ 95% CL
-  LARGE uncertainties!
- LEP2 direct searches:
-  MH > 114.4 GeV @ 95% CL

- Shan-Huei Chuang @ PHENO 04

- 04/27/2004