# Presentation: 939356

## Higgs Searches at the Tevatron

- Chris Tully
- Princeton
*On behalf of the CDF/D0 Collaborations*
**SUSY 2005**
**IPPP Durham, England, July 18-25, 2005**

## Low Energy Supersymmetry

- The Higgs Sector is vacuous without it...

**Stability of the Electroweak scale is as fundamental and as deserving a resolution as Classical E&M arguments were to the instability of atomic states posed over a 100 years ago.**

*We can only hope the answer will be equally far reaching... *

## Preferences from MW and mtop

- Preferences from MW and mtop

- Error on mtop no longer dominates
- W self-energy may be decisive once MW improves

**M****top**** = 172.7 ****± 2.9 GeV**
**New CDF/D0 Mass Combination**

## New Top Mass Combination

- This includes new preliminary measurements (based on 320 pb-1) from CDF/D0 which simultaneously fit the jet energy scale with the hadronic W mass constraint
- The correlated systematical error is of order ~1.7 GeV

## SUSY Guidance

- Lightest Higgs mass compatible with high tan region for wide range of stop mixing

- Heinemeyer,
- Weiglein

- qd,l–

- qd,l+

**h:**

**H:**

**A:**

**Use tan****β**** enhancement!**

**down-**
**type**

## Large b-Production

- But how well known...

**Use Leptonically Decaying Z’s **
**as a probe!**

## MSSM Higgs b(b) Search

**b(b)******** ****→ b(b)bb  ********=h/A or H/A**
- At least 3 b-tagged jets
- Data-derived background shape

**Leading**

- Submitted to PRL

- 260 pb-1

-  at 95% Excl.

## b(b) Limits: tan2β Enhancement

- b(b) Limits: tan2β Enhancement

**Enhancement depends on loop corrections (****Δ****b****)**** **
**and SUSY parameters:**

- 260 pb-1

## b(b) Projections

**CDF+**

**1 fb****-1**

**8 fb****-1**

**4 fb****-1**

**2 fb****-1**

**Tevatron will **
**probe below**

**!**

- Projection based on existing analysis:
- Doesn’t include proposed b-tag improvements

## Higgs Decays to -leptons

- -Identification Methods (CDF)

## h/H/A→ Search

- Visible Mass is the final search variable:

**tan********=30**

- H

## MSSM Higgs→ Search

**tan******** Exclusion Limits:**

**b(b)******

## Higgs→ Projections

- Higgs→ and b(b) will reach similar sensitivities at the same time

**Opens up exciting prospects for learning more about SUSY as y****b**** and y******** ****see different loop-corrections**

- Assumes several analysis
- improvements

- CDF+D0

## Charged Higgs from top quark decay

- Predicted to substantially modify top quark Branching Ratios at high and low tan
- Additional sensitivity in lepton +  channel

**m****H****+**** = 100 GeV**

**m****H****+**** = 140 GeV**

****

****

**cs**

**t*********b**

## H+ tan Exclusion

- H+ tan Exclusion

## Br(t→H+b) Exclusion for Br(H+→)=1

- Range of Exclusions Br<0.4 to Br<0.7 depending on MSSM parameters

- H+→cs Search in progress...

## Lightest Higgs Boson

- Lightest Higgs boson is SM-like for large *M**A*
- Given the difficulty of detecting the h→bb decay at the LHC, the Tevatron provides a potentially essential probe of this low mass channel

- (decoupling limit)

## Low Mass Higgs Search

**Maximum sensitivity requires a combination of CDF/D0 search channels:**
- WH→lbb, ZH→bb & llbb, WH→WWW*, H→WW

## lbb Search (CDF)

- 319 pb-1

## ebb Search (DØ)

- bb in Progress...

- Expect        0.14 ± 0.03    WH
-                  4.29 ± 1.03    Wbb
-                  5.73 ± 1.45    tt+other
- Total        10.2   ± 2.4 events
- Observe    **13**

- Tagged Sample
- ≥1 b-tag

- Double-Tagged
- Sample

## Missing Energy Channel (CDF)

- Two Control Regions:
- No Leptons + (ET, 2nd Jet)<0.4      (QCD H.F.)
- Min. 1 Lepton + (ET, 2nd Jet)>0.4  (Top, EWK, QCD)

- Control Region 1

-  **Large E****T**
-  **Two jets **
**     ****(one b-tagged)**

## Missing Energy Event (CDF)

**Second Jet E****T**** = 54.7 GeV  **

**Leading Jet E****T**** = 100.3 GeV**** **

**Double tagged event**
**Di-jet invariant mass = 82 GeV**

**Missing E****T**
**144.8 GeV**

## Missing Energy Channel (CDF)

| Selection cut | ZH 120 (288.9 pb-1) |
| --- | --- |
| Di-jet mass cut (100,140) | 0.1260.016 |

## Missing Energy Channel (DØ)

- Cross-efficiency important
- WH→lbb (lost l)
- ZH→bb
- 3x Larger WZ/ZZ Signal
- Similar dijet bb mass peak

## WH→WWW* (CDF)

- WH→WWW* (CDF)

**Vector p****T**** Sum**

**2****nd**** Lepton p****T**

**Fake Lepton Region**

**“****One Leg”**
**Photon**
**Conv.**

**0.03 SM Signal Expected**

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

**No Event**
**Seen**

**Same-Sign Dilepton Search**

## WH→WWW* (DØ)

- WWW*→l± l± + X
- Same-Sign Dileptons
- Important bridge across 130-160 GeV “Gap” from H→bb and inclusive H→WW
- Background from WZ→lll

- 363-384 pb-1

- CDF 194 pb-1

## H→WW (DØ)

**Leptons from Higgs tend to point in same direction**

**Apply ********ll********< 2**

******ll********< 2**

- WW cross section measured

- PRL 94, 151801 (2005)

- WW =13.8       (st.)       (sy.) ± 0.9 pb

- +4.3         +1.2

- –3.8         –0.9

## Overview of CDF/DØ SM Higgs Searches

## Prospects for SM Higgs Search

- Current analyses sensitivities are lower than used for projections, but differences appear to be recoverable

## Summary

- MSSM tan enhancement searches
- b(b)  &  Higgs→already sensitive to tan~50-60
- Plans to add b(b)→b(b)
- t→H+b, H+→ results  (Plans to add H+→cs)
- SM Higgs searches
- Full complement of search channels with first results
- Will be important to benchmark search sensitivity with WZ diboson production with Z→bb
- ~1 fb-1 to analyze by Fall

- Combine, combine, combine...

## Backup Plots & Tables

## Tevatron Performance

## SM Higgs Production Processes

## Z→bb (CDF)

## lbb Search (CDF)

## H→WW (DØ)

## Improvements to b-tagging

| Operating 
Point | ~ Fake Rate | ~ b Efficiency |
| --- | --- | --- |
| Tight | 0.25 % | 44 % |
| Medium | 0.5 % | 52 % |
| Loose | 1.0 % | 57 % |
| Loose2 | 2.0 % | 64 % |
| Loose3 | 3.0 % | 68 % |
| Loose4 | 4.0 % | 70 % |

**Analysis depends on strongly on b-tag**
**Neural Net b-tagging**

- DØ

## Z→ as a benchmark

**D****Ø**** Neural Network          ********-Selection**
**Variables:**
- Shower Profile
- Calorimeter Isolation
- Track Isolation
- Charged Momentum Frac
- Opening Angle
- Etc.
**3 Types:**
- -like
- -like
- Multi-prong

## Missing Energy Channel (DØ)

- Trigger on event w/ large *E*T & acoplanar jets
- Instrumental *E*T backgrounds (Data-driven estimation)
- Asymmetries computed:  Asym(*E*T,*H*T) and Asym( pTtrk,pT2trk)

**Data**

**Data in   signal region**

**Signal**

**Sidebands**

- Exponential

**Signal**

**Instr. Background**
**from Sidebands(Data)**

## Missing Energy Channel (DØ)

**No b-tag**

**Single b-tag**

**Double b-tag**

## H→WW (CDF)

**Cluster mass:**

- =184 pb-1