# Presentation: 210353

## ICHEP – Moscow – July 06  
Gregorio Bernardi, LPNHE-Paris 
for the CDF and DØ Collaboration

**Gregorio Bernardi, LPNHE-Paris**** **
**for the CDF and D****Ø**** Collaboration**

**Results on Higgs Searches **
**@  the Tevatron            **

**Layer 0 now      inserted and fully readout**

** ****Run IIb upgrade relevant for Higgs****           ****- Layer ****Ø ****for  DØ SMT**

**Excellent noise performance S/N=18!!**

**Luminosity**
**Introduction to Higgs **
**SM Higgs Searches at High mass**
**Combined CDF, D0 and CDF+D0 results.**
**Sensitivity Prospects**

## Tevatron Performance

**Tevatron Performance**

**85% Average Efficiency**

**Currently in shutdown:**
**Silicon and Trigger upgrades**

**Run I**
** ****Lumi**

**4-8 fb****-1 ****expected by end of 2009**

**This talk:**
**260- 1000 pb****-1**

- Dmitri Denisov, ICHEP04, August 21 2004

## SM Higgs Production and Decays 

**Dominant Decays**
****** ****bb     for M****H**** < 135 GeV**
****** ****WW********* for M****H**** > 135 GeV**

**Search strategy:**
**    ****M****H**** <135 GeV: ****associated production WH and ZH with H********bb decay**
**    ****Backgrounds: Wbb, Zbb, top, WZ,QCD****       ****complement with WWW********* & WW*******
**    ****M****H**** >135 GeV: ****gg ********H production with decay to WW*******
**    ****Backgrounds:  WW, DY, W/ZZ, tt, tW, ********    ****complement with WWW*******

- Decays

- mH (GeV/c2)

- Excluded

**Production cross section (m****H**** 115-180)**
****** ****in the 0.8-0.2   pb range for gg ******** H**
****** ****in the 0.2-0.03 pb range for WH  associated vector boson production**

- Dmitri Denisov, ICHEP04, August 21 2004

## SM “Heavy” Higgs: H  WW*  ll

**Search strategy:**
**      ******** ****2 high P****t****  leptons and missing E****t**
**      ******** ****WW comes from spin 0 Higgs:**
**leptons prefer to point in the same direction.**
** ****But Higgs mass peak cannot be reconstructed due to the presence of 2 ****************look for an excess**
**CDF and D****Ø already published on 0.3-0.4 fb****-1**

**H**

**4****th**** generation?**

**CDF**

- Dmitri Denisov, ICHEP04, August 21 2004

## H  WW*  ll

**WW production**

**H ******** WW* ******** l********l******

**Major backgrounds**

- DATA CORRESPOND TO LUMI: L ~ 950 pb-1 in H  WW*  ee and e                                                	                      L ~ 930 pb-1 in H  WW*  

** ****Selection Strategy:**
** ****Presection:****                               ****lepton ID, trigger, opposite charge leptons**
** ****Remove QCD and Z********l****+****l****-****:****       ****E****T**** > 20 GeV **
** ****Reject events with mismeasured jet energy**
** ****Higgs Mass Dependent Cuts:**** ****Invariant Mass (M****l+l-****); Min. Transverse Mass            ****	****	****	****            Sum of lepton p****T****l**** and E****T**** (********p****T****l**** + E****T****)**
** ****Anti tt(bar) cut:****                       H****T**** = ******** P****T****jet**** < 100 GeV**
** ****Spin correlation in WW pair:****  ****D********(l,l) < 2.0**

**Now measured at the Tevatron by both expts. in agreement with NLO calculation:12-13.5 pb**

- Dmitri Denisov, ICHEP04, August 21 2004

## H  WW*  ee / e/   (950-930 pb-1)

**e ******

**e e**

**Missing Transverse Energy  > 20 GeV Cut (to suppress Z/********* ******** l****+****l****-**** background) **

**e e**

**e ******

**H ******** WW* ******** ee / e********/********   ****(950-930 pb****-1****)**

****

****

- Dmitri Denisov, ICHEP04, August 21 2004

##  HWW* : final selection

**M****H****=160GeV (x10)**

- selections

****

******e******

**ee**

- Dmitri Denisov, ICHEP04, August 21 2004

## Results for HWW*

**We exclude 4****th**** generation models,  for which       m****H****=150-185 GeV **

**Results for H********WW***

- Dmitri Denisov, ICHEP04, August 21 2004

## Search for WHWWW* (2 like-sign leptons)

**Low BR, but  channel important in the “intermediate region”    125-145 GeV**

**Search**** for WH********WWW* ****(2 like-sign leptons)**

- Dmitri Denisov, ICHEP04, August 21 2004

##  WHWWW* (360-380 pb-1)

** ****WH********WWW* ****(360-380 pb****-1****)**

**Event preselection**
**    ****Same charge di-lepton from W’ ****(one from H********WW, the other from prompt W)**
**    ****Suppress SM backgrounds p****T**** (lepton)> 15 GeV,  |********| < 1.1/2.0**

- Dmitri Denisov, ICHEP04, August 21 2004

## Final Selection for WWW*

**Final Selection for W****WW***

**Topological Likelihood discriminant, built on 3 variables per channel**

- Dmitri Denisov, ICHEP04, August 21 2004

## Exclusion limit for WWW*

**Exclusion limit for WWW***

**Events after Topological Likelihood discriminant**

**Effect on global combination significant in the intermediate region (125-145 GeV)**

- Dmitri Denisov, ICHEP04, August 21 2004

## Combining Higgs boson Searches

**Combining Higgs boson Searches**

**	****D****Ø ****uses the CLs (LEP) Method**
**	****     **the CLS confidence interval is a normalization of CLS+B
- 	      CLS+B = signal + bkgd hypothesis,  CLB = bkgd only hypothesis
- 	         CLS = CLS+B/CLB :      CLS+B & CLB are defined using a “test statistic”
-     Test statistic used is the Log-Likelihood Ratio (LLR=-2 ln Q)
-     generated via Poisson statistics** ****(Q=e****-(s+b)****(s+b)****d****/e****-b****b****d****) s,b,d=sig.,bkd,data)**
**   ****Tevatron Higgs combination is done with both methods ******** they give results compatible within 10%.**

** ****CDF ****uses a Bayesian approach**

## Systematic Uncertainties @ CDF

**Systematic Uncertainties @ CDF**

- Dmitri Denisov, ICHEP04, August 21 2004

## Combined Higgs boson Search  @ CDF

**Combined Higgs boson Search  @ CDF**

**All low mass channels analyses use 1 fb****-1 ****of data !**
**WH (l********bb)**
**ZH  (********bb)**
**ZH (l****+****l****-**** bb)**
**For m****H**** =  115 GeV,   the 95%CL Limit/SM is 9 (expected) and 13(observed)     **

- Dmitri Denisov, ICHEP04, August 21 2004

## Combined Higgs boson Search  @

**  ****16 independent channels have been combined, taking into account correlated & uncorr. systematics**
**WH (e)  ST, DT**
**WH (********)  ST,DT**
**WH ( l ) ST DT**
**ZH  (********) ST,DT**
**ZH  (l****+****l****-****) DT**
**WWW  (ee,e********)**
**WW      (ee,e************)   ******** 1 fb-1, others 260-390 pb****-1****)**

**Combined Higgs boson Search  @**

**WH******** e********bb**

**With low statistics (0.3 fb****-1****)**
**Data/SM  = ~15 at 115 GeV**
**                   ****~   9 at 160 GeV**
**With higs statistics (1 fb****-1****)**
**Data/SM  = ~ 5 at 160 GeV**
**                   **

**Based on our first experiences with Data, can cdf+d****Ø**** reach exclusion  for a 115 GeV Higgs with 2 fb****-1**** as  early simulation studies were expecting ?**

- Dmitri Denisov, ICHEP04, August 21 2004

## Jet energy resolution  (recalibration + track-jet algorithm)
Subtract expected energy deposition in cal
Add the track momentum
Add the energy of out-of-cone tracks
Improve the jet energy resolution by ~20%

Use  improved calorimeter calibration
        Z bb to calibrate b-jet response

L1-cal Trigger  (DØ Upgrade)
Important for difficult channels  efficiency improvement (ZHbb, hbb)

Addition of SMT Layer 0 (Upgrade)
r@L1 = 2.7 cm  r@L0 = 1.6 cm                                          
 better impact parameter resolution
More redundancy in pattern                                          
Recognition for higher luminosity  reduce fake track
Keep functionality in case of degradation  of Layer 1 due to radiation damage
    further b-tag improvement (15%)
    improvement onHiggs sensitivity

**           ****New b-tagging tool **
**Combines various variables from the track based b-tagging tools in a Neural Network, ****trained on Monte Carlo**
**Performance measured on data**
**Substantial improvement in performance over constituent input b-taggers**
**Increase of 33% in efficiency for a fixed fake rate of 0.5 %**

**Jet energy resolution****  (recalibration + track-jet algorithm)**
**Subtract expected energy deposition in cal**
**Add the track momentum**
**Add the energy of out-of-cone tracks**
**Improve the jet energy resolution by ~20%**
**Use  improved calorimeter calibration**
**        ****Z******** bb to calibrate b-jet response**
** **
**L1-cal Trigger  ****(D****Ø**** Upgrade)**
**Important for difficult channels ******** efficiency improvement (ZH************bb, hbb)**
**Addition of SMT Layer 0 ****(Upgrade)**
**r@L1 = 2.7 cm ******** r@L0 = 1.6 cm                                          **
** ****better impact parameter resolution**
**More redundancy in pattern                                          **
**Recognition for higher luminosity  reduce fake track**
**Keep functionality in case of degradation  of Layer 1 due to radiation damage**
**   ******** ****further b-tag improvement ****(15%)**
**   ******** ****improvement onHiggs sensitivity**

- Dmitri Denisov, ICHEP04, August 21 2004

## Sensitivity Prospects extrapolated from 0.3 fb-1 results  

**Will 6X more lumi take our x-section factors of 15/9**** to 1??   ****Maybe..**** with analyses improvements under work in CDF and D****Ø**** ******** ****Close !!!!!**

**Ingredient****s (D****Ø)**

**Equiv Lumi**
**gain (@115)**

**Today ****with ~330 fb****-1**

**-**

**1****5                 ****   9**

**6.0**

**6.****1                 ****3.7**

**Combine ****D****Ø and**** CDF**

**2.0**

**NN b-Tagger****/L0**

**3.0**

**3.5**

**NN ****a****nalys****is selections**

**1.7**

**2.7                 ****2.8 **

**Dijet-mass resolution**

**1.****5**

**2.2**

**Increased Acceptance**

**1.2**

**2.0                 ****2.5**

**New channels**

**1.****2**

**1.9                 ****2.1**

**1.****7**

**Reduced Systematics**

**1.2**

**1.2                 ****1.5**

**At 160 GeV needs 4.5 fb****-1**
**               ****(2 fb****-1**** x1.5****2****)**

**At 115 GeV   needs 2.8 fb****-1**

**Xsec Factor****     ****Xs****ec ****Fact****or**

**m****H****=115 GeV****   ****  **** ****m****H****= 160 GeV****  **

**Sensitivity Prospects**** extrapolated from 0.3 fb****-1**** results  **

**Lumi = 2.0 fb-1**

******  ****95% CL exclusion for m****H****= 115-180 GeV with 6 fb****-1**

## Tevatron SM Higgs Combination

- Dmitri Denisov, ICHEP04, August 21 2004

## Conclusions

**First time with essentially complete result**
**Full impact of systematics uncertainties is included**
**Analyses have been steadily improving due to optimization, already close to the Prospective reports**
**Combined limit looks very promising**
**High mass region benefits a lot from H********WW********* type analyses (H and WH production), but low mass as well, as low as 120 GeV.**
**Our outlook for the future looks very interesting**
**LHC experiments will have to work hard to get the signal,  if the Higgs is light (<130 GeV), but Tevatron has insight also if it is close to 160 GeV. Barring accidents, the Tevatron could have evidence by 2009, if it’s there.**
**If the Higgs is light we might end-up combining with LHC!**

**SM Higgs Summary**

## Conclusions

**Will we soon understand better what’s going on in the Universe?**

**	****        ****if we get somewhere around   ****here****   the answer is ****YES! ****        ****So we’ll try hard !!!**

- Dmitri Denisov, ICHEP04, August 21 2004

## H  WW*  ee / e 950 pb-1

**e ******

**e e**

**Preselection: Trigger, ID, leptons of opposite charge: p****T****l1**** = 15 GeV; p****T****l2**** = 10 GeV**

**e e**

**e ******

**PRESELECTION (L ~ 950 pb****-1****):**

**H ******** WW* ******** ee / e******** 950 pb****-1**

- Dmitri Denisov, ICHEP04, August 21 2004

## 2 muons of opposite charge

Leading muon:      Pt > 15 GeV
Nex- to- leading muon: 
     Pt > 10 GeV

Cuts optimized for a Higgs mass of 160GeV  

**2 muons of opposite charge**
**Leading muon:      Pt > 15 GeV**
**Nex- to- leading muon: **
**     ****Pt > 10 GeV**
**Cuts optimized for a Higgs mass of 160GeV  **

****

****

****

****

**H ******** WW* ******** ******** 930 pb****-1**

- Dmitri Denisov, ICHEP04, August 21 2004