# Presentation: 811084

## Searches for Higgs and New Phenomena at CDF

**Searches for Higgs and New Phenomena at CDF**

**Song Ming Wang**
**University of Florida**
**On behalf of CDF Collaboration**

**The Tevatron Connection**
**June 24-25, 2005**

## Outline

- Detecting New Physics at CDF
- New CDF Results on the Searches for :
- New Phenomena w/ Leptons in Final States :
- High Mass Resonances
- SUSY in Multi-lepton Signature
- Extra Dimensions
- New Physics in MET+Jets
- Higgs
- Summary

## Searches for New Physics

***NEW PHYSICS !!!***

_**Need to look for distinctive signature to suppress SM background**_

- “searching for a needle in a hay stack” (western version)
- Or
- “searching for a needle in the ocean” (eastern version)

- _To search for New Physics is like :_

- Predicted rates for new physics are LOW !!!

## New Phenomena Searches at CDF

- New physics can manifest itself in several rare final state signatures of p-pbar collisions

## New Phenomena Searches at CDF

- Experimental Signatures

- New Phenomena

- W’, Z’
- Extra Dimensions
- Technicolor
- Leptoquarks
- Compositeness
- Excited leptons
- SUSY
- Higgs
- .

- Need good understanding of the SM final states to **DISCOVER** *New Phenomena*

## Measurement of Final State Objects with CDF

## Measurement of Final State Objects with CDF

- Electron ID :
- Coverage : ||<3.6
- ||<2 (w/ trk)
- ID eff. ~ 80-90%

- Photon ID :
- Coverage : ||<2.8
- ID eff. ~ 80%

## Measurement of Final State Objects with CDF

- Muon ID :
- Coverage : ||<1
- ID eff. ~ 90-100%

## Measurement of Final State Objects with CDF

- Tau ID :
- Narrow iso. cluster
- Low # tracks
-  0 identification
- Coverage : ||<1
- ID eff. ~ 46%

## Measurement of Final State Objects with CDF

- Jet ID :
- Cluster of CAL towers
- Coverage : ||<3.6

- Heavy Flavor Jet Tagging :
- Id HF jets via semi-leptonic decay
- Find soft lepton in jets
- Coverage : ||<1
- Id HF jets via finding displaced vertex
- Coverage : ||<1.5

## Run II Data Collected at CDF

- Tevatron has delivered ~1.05 fb-1 to CDF
- CDF has collected about ~0.85 fb-1 data
- Results shown today are based on data samples of ~0.2 – 0.4 fb-1

## New Results from CDF

| Topic | Analyses | L(pb-1) | Cover |
| --- | --- | --- | --- |
| High Mass | Z’ee, ,  | 200/450 | yes |
|  | W’e | 205 | yes |
| SUSY | Chargino/Neutralino in Trilepton | 346/224 | yes |
|  | Scalar Neutrino (RPV) | 344 | yes |
|  | Stop Pair Production (RPV) | 200 | no |
|  | Stop Pair Production (RPC) | 163 | no |
|  | Squark/Gluino Production | 254 | yes |
| Extra Dimension | ED in Multi-lepton | 88 | yes |
| Higgs | WHlbb | 319 | yes |
|  | WHWWW* | 194 | no |
|  |  | 310 | yes |

- Please visit:  http://www-cdf.fnal.gov/physics/exotic/exotic.html

## Search for High Mass Resonances w/ Leptons in Final States

## Searches in High Mass Di-Lepton

- Data samples ~ 200 pb-1
- Relatively “clean” channel
- Signature to explore many models
- Z’, SUSY(RPV), TC, RS graviton, ....
- Look for resonance in the mass spect., or enhancement in the cross section

**CDF Run II Preliminary (200 pb****-1****)**

- CC/CP/PP

- CC

##  *Br Limit in Search for Mass Bumps (ee+)

** *********Br Limit in Search for Mass Bumps (ee+********)**

- M(Z’,seq)>825 GeV
- M(E6,Z)>720 GeV

- M(G) > 710 GeV (k/MPl = 0.1)

- Limits at 95% C.L.

## New Results in High Mass Di-Electron Search

- New analysis use 448 pb-1 data sample (~2x the previous e+e- analysis)
- Look at both the M(ee) and decay angle cos* for signal of new physics

- New resonance could interfere with  and Z
- May observe the effect in AFB distribution
- Can observe evidence below the Z’ pole

## New Results in High Mass Di-Electron Search

**New Results in High Mass Di-Electron Search**

- Select events with 2 high Pt electrons
- Central-Central, or Central-Plug
- Good agreement between data and prediction for full mass region

|  | Data | Predicted |
| --- | --- | --- |
| M>200 GeV | 120 | 125  11stat |

- # Events in Signal Region

- CC/CP

## New Results in High Mass Di-Electron Search

## Limits in High Mass Di-Lepton Search

|  | CDF
e+e-
448 pb-1 | CDF
ee + 
~200 pb-1 | CDF

~200 pb-1 | DØ
ee
~200 pb-1 | LEP2 |
| --- | --- | --- | --- | --- | --- |
| Seq. Z’ | 845 GeV | 825 GeV | 394 GeV | 780 GeV | 1.8 TeV |
| E6 ZI | 625 GeV | 615 GeV |  | 575 GeV |  |
| E6 Z | 720 GeV | 675 GeV |  | 640 GeV | 673 GeV |
| E6 Z | 690 GeV | 690 GeV |  | 650 GeV | 481 GeV |
| E6 Z | 715 GeV | 720 GeV |  | 680 GeV | 434 GeV |

## Limits in High Mass Di-Lepton Search

**Limits in High Mass Di-Lepton Search**

- Previous analyses focused on specific Z’ models
*Carena*, *Daleo*, *Dobrescu*, and *Tait*
- Defines 4 general model classes (PRD 70:093009, 2004)
- B-*x*L, q+*x*u, 10+*x*5, d-*x*u
- Within each class, a Z’ model is defined by :
-  mass MZ’
-  strength gz
-  parameter *x*
- E6 motivated models :
- 10+*x*5 models :
- Z(*x*=-0.5, gz=0.344)
- Z(*x*=1, gz=0.272)
- Z(*x*=-3, gz=0.211)

- Comparing CDF to LEP2:
- CDF’s sensitivity relative to LEP2 depends on model and *x*
- B-*x*L : sensitivity similar to LEP2
- 10+*x*5 : better sensitivity than LEP2

- LEP2: excluded below line

## W’ Search in e Channel

**W’ Search in e******** Channel**

- W’ additional charged heavy vector boson
- Appears in theories based on ext. of gauge group of  SM
- Left-Right symmetry models
- Feature new gauge bosons, including a heavy right-handed W’
- Assume W’e , and  is light and stable
- Signature: high Pt e, high MET

**MC**

- MT (GeV/c2)

- highest MT event
- MT = 524 GeV/c2

- Et=244.90 GeV

## W’ Search in e Channel

-  => No evidence for W’
- Set limits on W’ production rate
- Use binned likelihood fitting method
- Two types of systematic are examined as function of MT:
- Event rate (dominant: PDF)
- Signal shape (dominant: elec energy scale)
-  *B(W’e) limit : ~50-100 fb for M(W’)>500 GeV at 95% CL

- Limit: M(W’SM )> 842 GeV/c2

- Run I results (with the same assumptions):
- M(W’SM )>  754 GeV/c2

- W’SM

- Limit

## Search for SUSY in Multi-Lepton Final States

## Searches for Chargino/Neutralino in Tri-Lepton

- Small contributions from SM processes in this signature
- Very clean, “Gold Plated” signature to find SUSY
- So far completed two channels:

- Pair production of chargino/neutralino can produce multi-lepton and Et in final state (assume R-parity conserved)

|  | High Pt | Low Pt |
| --- | --- | --- |
| Lepton 1 |  e: >20 GeV |  e: >10 GeV |
| Lepton 2 |  e: >8 GeV |  e: >5 GeV |
| Lepton 3 |  e/m: >5 GeV |  trk: >4 GeV |

- Both analyses require :
- MET > 15 GeV
-  *l*1, *l*2 not back-to-back => reduce DY
- Veto events in Z and low mass resonances regions

- Low Pt analysis has higher backgrounds, require additional cuts

## Searches for Chargino/Neutralino in Tri-Lepton

***E******T******Miss*****>15 GeV**

- High Pt: Final selection (No MET cut)

|  | “High Pt” | “Low Pt” |
| --- | --- | --- |
| mSugra | 0.5 | 0.5 |
| Exp. Bkg. | 0.16±0.07 | 0.36±0.27 |
| OBSERVED | 0 | 2 |

-  M0=100 GeV, M1/2=180 GeV
-  tan()=5, >0, A0=0

- To do :
- Include  channel (soon)
- Extend to forward region (elec)
- Combine results from all channels

- Low Pt: Final selection (No MET cut)

## Search for Scalar Neutrino (R-Parity Violation)

- Resonant slepton can be produced at Tevatron via ’ Rp coupling
- Slepton can decay to two leptons via  Rp coupling
- CDF search for        in the *e-* final state
- Selections :
- Electron : Et>20 GeV
- Muon : Pt>20 GeV
-  *e*, : opposite charged
- Relatively high acceptance in the region of interest
- Very clean signature
- Dominant background: Z

## Search for Scalar Neutrino (R-Parity Violation)

- After all cuts:

- Nobs=77, Nexpect=71.3±1.8(stat)
- For M(*e*)>100 GeV
- Nobs=5, Nexpect=8.0±1.1(stat)
- Backgrounds:
- Z, ttbar, Diboson

- Highest M(*e*) event :
- M(*e*) = 158 GeV
- Elec Et=59 GeV, Muon Pt=102 GeV

**200 GeV**

## Interpret x-section limit: 

**Search for Scalar Neutrino (R-Parity Violation)**

- Interpret x-section limit:
- For =0.05  ’ 311 =0. 16
- M>460 GeV
- Can set a limit in 2D ’ 311 vs M()

## Search for Universal Extra Dimension (UED)

**Search for Universal Extra Dimension (UED)**

- UED (Appelquist, Cheng, Dobrescu: Phys. Rev. D64, 035002 (2001) ) :
- All particles live in a (4+n) dimensional space. SM fields can propagate into the extra compact dimensions of size *R *(~TeV-1)
- 1st KK excitation of the SM particle undergoes cascade decays into its SM counterpart and the lightest KK particle (LKP)
- LKP: stable and interact weakly (like LSP in SUSY)
- Pair production of KK particles could results in final states with multiple leptons and MET
- Leptons are usually soft, due to cascade decays

- Q1, Z1,W1,L1,1   counterparts of    q,Z,W,*l*,

- In minimal UED (MUED) scenario:
- Has 3 free parameters (*R*, , mh)
-  *R* : size of extra dimensions
-   : radiation correction cut off
-  mh : SM Higgs mass

## Search for Universal Extra Dimension (UED)

- Nexpect=0.05±0.005, Nobs=0
- Nsignal=0.38 (*R*-1=350 GeV, R=20, mh=120 GeV)
- @ 95% CL, upper limit cross section for total KK production = 7.9 pb
****** ****R****-1 ****> 280 GeV**** (********R=20, m****h****=120 GeV)**

**Search for Universal Extra Dimension (UED)**

- CDF searched for UED using Run 1 data (87.5 pb-1), requiring at least three leptons
- SM backgrounds :
-  bb-bar/cc-bar, tt-bar,WZ, ZZ
-  DY, WW
- Selections:
- 3 leptons (*e*,) (Et(pt) > 11,5,5 GeV)
- At least one pair e+e-, +-
- Leptons not back-to-back (reduce DY)
- Remove resonances, bb/cc
- Lepton isolated, MET>15 GeV
- Consider only “non-” channels
- Large fraction of  BG with “” signature from bb/cc

-  real multi-lepton

-  di-lepton + fake

- Before Iso+MET cuts

- (arbitrary unit)

## Search for New Physics in MET+Jets

## Search for Squarks/Gluino in MET+Jets

- Light colored sparticles(        ) can be copiously pair produced at Tevatron

- Decays of         may produce multiple jets and large Et  (if Rp is conserved)

- CDF performs direct search for              using Et + jets data sample (~254 pb-1)
- Challenging analysis:
- Signal is buried under enormous QCD multi-jet background
- Missing energy mis-measurements
- Jet energy mis-measured
- Non-collision backgrounds (beam halo, hot towers..)

## Search for Squarks/Gluino in MET+Jets

**Search for Squarks/Gluino in MET+Jets**

- All cuts, except MET cut

- ~

- ~

- Selection:
- 3 jets (125, 75, 25 GeV)
- MET>165 GeV, HT>350 GeV
- MET not aligned w/ jets
- No charged leptons (reduce EW BG)
- Nobs=3,  Nexpect(SM)=4.2±1.1
- Expect ~0.7-4.8 SUSY events in SUSY space explored ( M(q,g)~380 GeV )

- Scan parameter space, will set limit soon

## Search for the Higgs Boson

## Searches for SM Higgs

- CDF search for SM Higgs in several channels :

|  |  |
| --- | --- |
|  |  |

- 1st results soon

- NEW updated results from
- Selection:
- High pt lepton data (L=319 pb-1)
- One high pt central *e* or , large MET (MET>20 GeV)
- 2 jets (at least one is tagged as b-jet)
- Veto events w/ >1 lepton (suppress ttbar)

## Searches for SM Higgs

**Searches for SM Higgs**

- This analysis

## MSSM Higgs

**MSSM Higgs******

- Higgs production rate in MSSM can be much larger than in SM at high tan
- Coupling of Higgs to down-type fermions are enhanced by factor of tan
- 

- (ppH/A/h)tan2

- Br(bb)~90%
-  gg,bbbb: need to overcome large QCD BG
- Br()~10%
-  gg,bb  overcome much smaller SM BG

- Promising channel at Tevatron

## Selections:

- Lepton (e/) pT>10 GeV
- Had. Tau pT>15 GeV
- HT (|PT(e/)|+|PT(h)|+|MET|)>50 GeV
- Anti-W cut
- Backgrounds:
- Z
- W+jets, QCD: jets faking 
-  ttbar, diboson, Zee/

## MSSM Higgs

- Good agreement between data and SM expectation in low mass region
- High mass events (m>120):
- Exp. SM = 8.4 ev, Obs. = 11
- Limit:
- Fit mass spectrum for (Bkg+Z+A)

## MSSM Higgs

- For <0
- Complementary to SUSY Higgs bbb(b) mode (from D)

- Interpret cross-section limit in terms of tan and mA:

- For >0:
-   channel extends to higher higgs mass and lower tan region than for <0

##  >0

**MSSM Higgs******

- Projection of the reach of this search in  to higher luminosity

- M. Carena et al., hep-ph/0202167:
- mhmax: =+200, A0=6MSUSY (we use MSUSY=1 TeV)
- Min mix: =+200, A0=0

** ********>0**

- CDF Run II Preliminary

## Summary

- CDF has an extensive program in searches for new physics at the Tevatron
- Exploring many exotic new phenomena (e.g. Extra Dimensions, Champs, Magnetic Monopoles, Stop, Sbottom .....)
- Systematic approach in several other searches
- Z’ (*ee*,,,....spin 0,1,2 ..)
- Higgs (different production and decays channels)
- Although have not yet make new discoveries w/ current analyzed data
- Have developed/sharpen our analysis tools
- Have entered the _**fb**__**-1**__** era**_ !
**VERY EAGER to look at these new data !!!**

## Search for Stop Quark in R-Parity Violation

**Search for Stop Quark in R-Parity Violation**

- If stop quark is light => can be pair produced at Tevatron
- If Rp is allowed, and ’3330, =>
- Assume Br(              ) = 100%

- Selection:
- 1 lepton (*e* or ), 1 hadronic tau
-  2 jets
- MT(*l*, MET) < 35 GeV (remove W background)

## Search for Stop Quark in MET+Jets

- Stop quark is often predicted to be light due to large top Yukawa coupling
- Depending on the stop’s mass w.r.t. other sparticles, assume BR(                  )=100%
- Signature :
- 2 jets + Large MET
- Tag charm jets with JetProb

- JetProb:
- Compute probability a jet originates from primary vertex (based on track impact parameter)

- All selection cuts applied, except tagging charm jets

## Search for Stop Quark in MET+Jets

|  | Exp. | Obs. |
| --- | --- | --- |
| Pre-tag | 105 ± 12 | 119 |
| Tag (silicon) | 8.3 ± 2.3 | 11 |

- No excess, set limit
- Benchmark assuming

## Search for Stop Quark in MET+Jets

|  | Exp. | Obs. |
| --- | --- | --- |
| Pre-tag | 105 ± 12 | 119 |
| Tag (silicon) | 8.3 ± 2.3 | 11 |

- No excess, set limit
- Benchmark assuming