# Presentation: 660830

## Search for HWW(*) at DØ

*presented by*
**Per Jonsson**
**Imperial College London**
**On behalf of the D*****Ø****** ******Collaboration***

**2004 Phenomenology Symposium**
**University of Wisconsin, Madison, April 26-28 2004**

## Standard Model Higgs Production @ the Tevatron

- Production cross sections are small 1 - 0.1 pb depending on MH
- Gluon fusion, gg->H, dominates
- Light Higgs preferred by global fit
- MH < 251 GeV at 95% C.L.
- LEP limit from direct searches
- MH > 114.4 GeV at 95% C.L.

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Standard Model Higgs Decay Modes

**H->bb is dominant for M****H ****< 135 GeV**
**Strong interaction background overwhelm signatures with jets**
**WW branching fraction ~5% for low mass **
**Main search channel for M****H ****> 120 GeV**
**Look for the “clean” final states:              ****e********ee********and ******
**    **

- Why look for H->WW(*)?

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Cross Section Enhancement from Extra Generations

- Extra quark generations could increase production cross section significantly,
- Enhancement factor depends on Higgs and quark masses,
- A factor of 8.5 is expected for a 4th generation, m4=320 GeV.

- E. Arik et al, SN-ATLAS-2001-006

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Suppressed Couplings to b,

-    Occurs Beyond the SM in Top Color or Fermiophobic Higgs models, see talk by
-    A. Melnitchouk

- L. Brucher, R. Santos, hep-ph/9907434

- Increased H->WW(*) branching

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## The Upgraded DØ Detector

-  Completely new tracking system uses 2T magnetic field
-  Inner Si vertex detector (SMT) provides b-tagging capability
-  Excellent Run I calorimetry exploited in Run II
-  Upgraded 3-tier trigger and data acquisition system

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Data Samples

- Search for H->WW(*)  in the 3 leptonic channels:
-      eeeand 
- Data investigated correspond to integrated lumi. of
- ~ 180 (ee), 160 (e) and 150 () pb-1
- Collected between April 02 and September 03
- MC generated with Pythia passed through detailed detector simulation
- Rates normalized to NLO cross section values

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Event Signature-Spin Correlations

- Higgs Mass reconstruction not possible due to two neutrinos:
-        Missing ET
- Use spin correlations to suppress background.
-   The charged leptons tend to be collinear:
-         Small opening angle

- Experimental signature:
-  high pT l, small ll and large Missing ET

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Azimuthal Opening Angle: ll

- An example: e+e- final state C

- ain
- background

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Missing ET

- An example: e+e- final state C

- ain
- background

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Event Selection

- Event selection includes:
- Require two oppositely charged isolated leptons l = e, 
-  ee: pT(e1) > 12 GeV, pT(e2) > 8 GeV
-  epT(e) > 12 GeV, pT() > 8 GeV
-   pT(1) > 20 GeV, pT(2) > 10 GeV
- Missing ET greater than:  20 GeV (ee,e); 30 GeV (
- Removal of mass resonances:
- 12 GeV < m(e,e) < 80 GeV
- m GeV and m()- mZ| > 15 GeV
- Azimuthal opening angle: e,e)e
- Rejection of energetic jets:
- ee, e T1< 90 GeV or ET1 < 50 GeV, ET2 < 30 GeV
-  :  ET1 < 60 GeV, ET2 < 30 GeV

- Signal acceptance is ~ 0.02 – 0.2 depending on the Higgs mass/final state

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Invariant mass: mee and m

- Data vs. MC after preselection

- iggs of 160 GeV

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Missing ET

- ee

- 

- iggs of 160 GeV

- Data vs. MC after preselection

**D*****Ø *****Run II Preliminary**

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Opening Angle:e,e)

- After preselection

- After final selection

- iggs of 160 GeV

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Opening Angle: e,

- Good agreement between data and MC
- in all final states and variables examined

- fter preselection

- After final cut

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Event Counts

| Source |  ll’=ee     L=180 pb-1 | ll’=eL=160 pb-1 | ll’=L=150 pb-1 |
| --- | --- | --- | --- |
| tt->blbl’ | 0.06 ±0.01 | 0.13 ±0.01 | 0.03 ±0.003 |
| WZ->ll’+X | 0.04 ±0.01 | 0.11 ±0.01 |  |
| ->ee | 0.0 ±0.01 |  |  |
| QCD/W+jets | 1.24 ±0.07 | 0.34 ±0.02 | 0.02 ±0.02 |
| WW->ll’ | 1.17 ±0.02 | 2.51 ±0.05 | 1.28 ±0.03 |
| Z/->ee | 0.1 ±0.1 |  |  |
| Z/-> |  | 0.0 ±0.05 | 3.9 ±0.6 |
| Z/-> | 0.0 ±0.1 | 0.0 ±0.1 | 0 ±0 |
| Total Background | 2.7 ±0.4 | 3.1 ±0.3 | 5.3 ±0.6 |
| Data | 2 | 2 | 5 |
| Expected SM Signal MH=160 GeV  | 0.073 ±0.002 | 0.111 ±0.004 | 0.085 ±0.001 |

**D0 Run II Preliminary**

- Data in agreement with background expectations

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Limits

- Excluded cross section times
- Branching Ratio at 95% C.L.

- Combined Upper Limits on xBR between 6-40 pb

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Summary

- D***Ø*** has searched for H->WW(*) with ee, eand + MET signatures in 147-177 pb-1 of Run II data
- There are a total of 9 events with a background of 11.1
- Cross section limits for the combination of all channels have been calculated
- With L= ~1 fb-1 we will start to be sensitive to enhanced Higgs signals
- With L= ~ 10 fb-1 we will be sensitive to SM Higgs with MH=160 GeV

- Looking forward to more data!

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Tevatron: Current and Projected Performance

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Higgs Sensitivity Reach

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004

## Back-up Slides

## Opening Angle: ,

- fter preselection

- After final cut

- Per Jonsson                                                                             Imperial College London

- PHENO'04                                                                                  April 27 2004