# Presentation: 675398

## WH @ DØ

** ****	****	**
**	****     ****Introduction, Status and Prospects**

**WH @ D****Ø**

**	****               ****Gregorio Bernardi **
**	****  ****Hyunwoo Kim, Lars Sonnenschein**

## Evidence for a Light SM-like Higgs Boson

**Evidence for a Light SM-like Higgs Boson**

- Precision EW fit, Summer ’05

- but

- Fit **assumes **SM

**2003 Predictions:**
** ****1.5 – 2.5 fb****-1****/Exp. to exclude m****H****=115 GeV (if it’s not there!)**
** ****3 - 5 fb****-1****/Exp. to get 3******** Evidence if m****H****=115 GeV**

## SM Higgs Production and Decay

**SM Higgs Production and Decay**

**Production Cross-Sections**

**Decay Branching Ratios**

## SM Higgs Searches:  WHlbb

## First Run II Higgs Search - WH(e)

**For 115 GeV Higgs,  mass window cut**:** **
**0 data, 0.05 exp Higgs, 1.07 bckgd**
******95% CL limit on WH  of ****9.0 - 12.2 pb**** for m_Higgs of ****105-135**** ****GeV**
**Published Run II limit better than Run I ******** detector improvements**

**First Run II Higgs Search - WH(e)**

- But ...
- large difference with SM expectation
-   (factor 50 in sensitivity, factor 2500 in luminosity, i.e. 450 fb-1 would be needed ! )

## Comparison of WH published Results with Sensitivity Prospective Study

** ****The following factors are not included: **
** ****3 (leptons)  * 2 (experiments) * 2.5 (channels) * 1.8 (NN-selec) * 12 (lumi ******** 2fb****-1****) = 324 = 18****2**** **
**factor of ****18**** is not  included in WH sensitivity **
**Combining both factor 2.4*18 =43 ******** consistent with 50**

| 

Dijet mass window | DØ Analysis
(PRL ‘05)
174 pb-1
WH ebb
[85,135] | Prospective Study (‘03)  normalized to  174 pb-1 and to WH bbe
  [100,136] |    Ratio 

 Prospective
  DØ Analysis
R=0.72    |
| --- | --- | --- | --- |
| Dijet mass resolution  | 14 +/- 1 % | 10 % | R=0.71 |
| Signal events (S) | 0.049  | 0.145 | R=3.0 |
| Background evts (B) | 1. 07 | 1.76 | R=1.6 |
| S/B | 0.045   | 0.11 | R=2.4 |
| S/B | 0.046  | 0.082 | R=1.8 |

**Comparison of WH published Results ****with Sensitivity Prospective Study**

##  How to Reach “Expected” Sensitivity

**Step1: End of 2005 ******** Publications on 300-400 pb****-1**
**WH/ZH: Optimize b-tagging (Looser)**
**	****          ****Combine single and double tag**
**WH(e):  Include Phi-cracks****	**
**WH(********):  Combine single-******** and ********+jets trigger**
**ZH       :  Optimize Selection**

** ****How to Reach “Expected” Sensitivity**

## WH (e) : How limits are improved?

**Here also a factor 2 has been gained compared to the preliminary results.**
**Since the average WH/ZH missing sensitivity was a factor 3, these improvements reduce it to about  1.5**
**	****	****	**

**B-tagging optimized**
**Phi cracks included**

**Work in progress**

## Slide 9

## MC samples

## Data Samples and Triggers

## Selection Cuts

## Control Plots / Untagged

## Control Plots / Untagged

**Control Plots / Untagged**

## Control Plots /Single Tagged

**Control Plots /Single Tagged**

**m****inv**

**p****T****b**

## MTW  (ST)   and    Inv. Mass (DT)

## WH preliminary limit

## Single and Double Tags

## Conclusions

**e and mu analyses Pass2 are converging, finalizing strategies on b-tagging, and systematics.**
**e-mu combination limit is expected to be lower than 3-4 pb****-1 ****(i.e. a gain of 4 to 3 in sensitivity compared to the initial measurement, compare to an expected factor 2 due to lumi and e+mu). **
**P17 long term analyses are started: UTA (Venkat, e channel) and Paris (Lars, Jeremie Lellouch,GB) ******** first results summer 06.**