# Presentation: 530810

## Discovery Potential through Searchesfor the CDF and DØ Collaborations

**Discovery Potential through Searches****for the CDF and DØ Collaborations**

- Beate Heinemann
- University of Liverpool
- P5 meeting, Fermilab, 09/12/2005

## CDF and DØ Detectors

- Multi-purpose detectors:
- Calorimeter coverage up to ||<3
- Full tracking coverage up to ||<1, limited up to ||<2.5
- Identify electrons/photons, muons, tau’s, jets
- precision vertexing and tracking, b-tagging
- High performance DAQ and trigger systems
- Have analysed about 300-600 pb-1
- data taken until September 2004-March 2005

## There are many open Questions...

- What is the origin of mass?
- Are there 3 generations? And if so, why?
- Why is there such a large mass hierarchy?
- Within fermion sector
- Between EWK and Planck scale
- What is cold dark matter?
- Is there a common single force?
- Are the fermions and bosons point-like? Or do they have substructure?
- Where has all the anti-matter gone?

## ...and about as many Models!

- Supersymmetry
- mSUGRA, GMSB, AMSB, R-parity violated or not,...
- Extended gauge theories
- Little Higgs
- Technicolor, topcolor
- Compositeness: excited fermions, preons
- Extra dimensions (ADD, Randall-Sundrum)
- ...

-  All of which predict new particles to be discovered
-  None of which may be true

## Selected a Few Analyses

- Chosen the following topics because particularly well motivated theoretically:
- Standard Model Higgs Boson
- SUSY:
- Higgs bosons
- Charginos/neutralinos +squarks/gluinos
- Rare decays
- But remember, we are experimentalists!
- So, we keep an open eye as much as we can
- We may find the unexpected which would be most exciting for our field

## Standard Model Higgs Boson

-  Only Standard Model particle not seen as yet:
- understanding of electroweak symmetry breaking
-  Precision data prefer light SM Higgs:
-  SUSY (MSSM) requires mh<136 GeV/c2
-  Studies in 1999 and 2003 predicted Tevatron reach:
- 1.5-2.5 fb-1: 95%CL exclusion at mH=115 GeV/c2
- 3-5 fb-1          : 3 evidence at mH=115 GeV/c2

- LEP
- excluded

- Luminosity (fb-1)

## Some Recent Results by CDF and DØ

-  Low Mass, mH<140 GeV/c2:
- -dominant decay into bb (~90%)
- -Search for peak in bb mass spectrum
- High mass, mH>140 GeV/c2:
- -Dominant decay into WW (~90%)
- -Examine angular distributions of leptons

## Current Higgs Search Results

- Current results from DØ and CDF:
- WH->lbb, ZH->bb
- WW->ll, WWW->l±l± + X
- Combination of current CDF analyses   (L=300 pb-1):
- upper limit 20 times larger than SM prediction at 115 GeV/c2
- Will gain
- factor √2 from combination of CDF and D0
- factor √(L/300 pb-1)  with increasing luminosity
- factor 5 missing with L=2 fb-1
- Are the 1999 and 2003 studies credible given the current performance?

**Can we close the gap?**

- L≈300 pb-1

- Combination of CDF analyses

## Can we close the Gap?

|  | Luminosity equivalent=(S/√B)2 |  |  |
| --- | --- | --- | --- |
| Improvement | WH->lvbb | ZH->vvbb | ZH->llbb |
| mass resolution | 1.7 | 1.7 | 1.7 |
| Continuous b-tag (NN) | 1.5 | 1.5 | 1.5 |
| Forward b-tag | 1.1 | 1.1 | 1.1 |
| Forward leptons | 1.3 | 1.0 | 1.6 |
| Track-only leptons | 1.4 | 1.0 | 1.6 |
| NN selection | 1.75 | 1.75 | 1.0 |
| WH signal in ZH | 1.0 | 2.7 | 1.0 |
| Product of above | 8.9 | 13.3 | 7.2 |
| CDF+DØ combination | 2.0 | 2.0 | 2.0 |
| All combined | 17.8 | 26.6 | 14.4 |

- Assume current analyses as starting point
- Scale current systematic uncertainties by 1/√L
- Reevaluated all improvements using latest knowledge

- See talks by
- G. Blazey and
- Y.-K. Kim

- Expect factor ~10 improvements and CDF+DØ combination:
- => Need 2.5 fb-1 for 95%C.L. exclusion of 115 GeV Higgs

## Neural Net Selection

- Neural Net:
- NN analysis done for ZHllbb
- 16 input variables
- Improves S/√B by factor 1.44
- Mass cut : 10020 GeV:
- Signal **** =53.7%
- Background **** =15.8%
- NN cut >0.6
- Signal ****=77.5%
- Background ****=15.4%
- Equivalent lumi=(S/√B)2=2
- 1.75 from 2003 HSWG study is achievable:
- Even gained factor 4 in (S/√B)2 in single top NN analysis!
- see talk by J. Hobbs

## Higgs at Tevatron: Conclusions

- Confirmed previous studies with run 2 data experience
- Syst. uncertainties increase required  luminosity by 40%
- 95% C.L. exclusion:
- ∫Ldt =2-2.5 fb-1: probe LEP excess at mH=115 GeV/c2
- ∫Ldt =4.0 fb-1: up to mH=130 GeV/c2
- ∫Ldt =8.0 fb-1: up to mH=135 GeV/c2
- 3 evidence:
- ∫Ldt ≈5.0 fb-1: for mH=115 GeV/c2

- mH=115 GeV/c2

- 68% of all experiments

- 95% of all experiments

- based on Run 2 analyses

- based on pre-Run 2 analyses

- Severely constrains MSSM

- mH=115 GeV/c2

## All numbers given so far were 
a 50% probability of an experiment achieving discovery or exclusion
We perform 1 experiment
Could get statistically lucky or unlucky (mH=115 GeV/c2):
with L=1 fb-1:
5% chance for 3 evidence
0% chance for 5 discovery
with L=4 fb-1:
35% chance for 3 evidence
2% chance for 5 discovery
with L=8 fb-1:
75% chance for 3 evidence
10% chance for 5 discovery

- a 50% probability of an experiment achieving discovery or exclusion
- We perform 1 experiment
- Could get statistically lucky or unlucky (mH=115 GeV/c2):
- with L=1 fb-1:
- 5% chance for 3 evidence
- 0% chance for 5 discovery
- with L=4 fb-1:
- 35% chance for 3 evidence
- 2% chance for 5 discovery
- with L=8 fb-1:
- 75% chance for 3 evidence
- 10% chance for 5 discovery

- “God Does Not Play Dice” (with the Physicist)?

- mH=115 GeV/c2

## Supersymmetry

- Addresses many questions and problems in SM:
- Elegant solution to hierarchy problem (mW<<mPl)
- Achieves unification of gauge theories at GUT scale
- Predicts a natural candidate for cold dark matter
- if R-parity is conserved
- More than 100 parameters:
- Rich phenomenology => many different signatures
- Experimental status:
- No evidence found:
- Stringent direct limits on sleptons and gauginos set by LEP: e.g. m( )>103.5 GeV/c2
- Consistent with measurements of DMh2 , (g-2) , bs and  electroweak precision data

## Higgs: Abb and A

- Higgs: Abb and A

- Supersymmetry (MSSM):
- 2 Higgs doublets => 5 Higgs bosons: h, H, A, H±
- High tan:
- A degenerate in mass with h or H
- Cross sections enhanced with tan2 due to enhanced coupling to down-type quarks
- Decay into either  or bb:
- BR(A ) ≈ 10%, BR(A bb) ≈ 90%
- Exact values depend on SUSY parameter space
- Experimentally:
- pp  Ab+X  bbb+X
- pp  A+X   +X

- C. Balazs, J.L.Diaz-Cruz, H.J.He, T.Tait and C.P. Yuan, PRD 59, 055016 (1999)
- M.Carena, S.Mrenna and C.Wagner, PRD 60, 075010 (1999)
- M.Carena, S.Mrenna and C.Wagner, PRD 62, 055008 (2000)

## MSSM Higgs: Present and Future

- First results in Run 2:
- Probe tan>50-60 at low mA
- Channels complementary: different sensitivity to radiative corrections
- Will close gap to LEP with increasing datasets
- For tan=40≈mtop/mb :
- L=1fb-1: mA<170 GeV/c2 @95%CL
- L=4 fb-1: mA<225 GeV/c2 @95%CL
- L=8 fb-1: mA<240 GeV/c2 @95%CL
- Simultaneous analysis of both decay channels will be crucial to know what it is

******<0**

## Discovery potential 
L=2 fb-1 vs L=8 fb-1: 
improves reach by ~10 units in tan

- L=2 fb-1 vs L=8 fb-1:
- improves reach by ~10 units in tan

- MSSM Higgs: Evidence/Discovery?

## SUSY Trileptons

- “Golden” Trilepton Signature
- Chargino-neutralino production
- Low SM backgrounds
- 3 leptons and large Missing ET:
- Neutralino  is LSP
- Recent analysis of electroweak precision and WMAP data (J. Ellis, S. Heinemeyer, K. Olive, G. Weiglein: hep-ph/0411216)
- Preference for “light SUSY”
- Chargino mass around 200 GeV/c2
- Current DØ analysis:
- 2 l (l=e,) + isolated track or ±±
- Et +topological cuts
- Analysis most sensitive at low tan
- BG expectation: 2.9±0.8 events
- Observed: 3 events

- M(chargino)

## Trileptons: Present and Future

- NowxBR<0.2-0.3 pb
- 3l-max scenario:
- Sleptons light
- Optimistic mSUGRA
- Large m0 scenario:
- Sleptons heavy
- Pessimistic mSUGRA
- Current data probe optimistic scenario
- Future:
- Cross section limit 0.05-0.01 pb
- L=1 fb-1: probe chargino masses up to 100-170 GeV/c2
- L=8 fb-1: probe chargino masses up to 150-240 GeV/c2

- Preferred by precision data

## Squarks and Gluinos

- Search for Missing Et+jets:
- Strong production => Large production cross sections
- Data consistent with SM background
- Currently excluding masses up to 350 GeV for squarks and gluinos
- Future:
- L=2 fb-1:  reach up to 400 GeV
- L=8 fb-1:  reach up to 450 GeV
- Could improve with further reoptimisation of cuts
- Not sensitive to stop quarks
- ....and they are special

## A Light Stop Quark?

- Stop mass “low” due to large mass and large Yukawa coupling of top quark
- Baryogenesis prefers light stop quark and Higgs boson
- m(t)<165 GeV/c2
- Several decay channels:
- t  0c
- t  lb
- t  ±b  lb or t  0t  0lb
- Depends on masses of  0, ±, t,  
- Light stop reach :
- L=1 fb-1:  m(t)<160 GeV/c2
- L=4 fb-1:  m(t)<180 GeV/c2

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## Rare Decay: Bs

- SM rate heavily suppressed:
- SUSY rate may be enhanced:
- Related to Dark Matter cross section (in one of 3 cosmologically interesting regions)
- Recently gained a lot of attention when interpreting WMAP data

- (Buchalla & Buras, Misiak & Urban)

- (Babu, Kolda: hep-ph/9909476+ many more)

- S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033

## Current limits at 90% C.L.: 
Fierce Competition:
CDF (L=171 pb-1): BR < 5.8 x 10-7
DØ   (L=240 pb-1): BR < 4.1 x 10-7
DØ   (L=300 pb-1): BR < 3.0 x 10-7
CDF (L=364 pb-1): BR < 1.6 x 10-7
Friendly combination:
CDF+DØ:                  BR < 1.2 x 10-7
Projected reach (CDF+DØ):
Exclusion at 90% C.L.:
L=1 fb-1: BR < 6.4 x 10-8 
L=4 fb-1: BR < 2.8 x 10-8 
L=8 fb-1: BR < 2.0 x 10-8 
Discovery at 5: 
L=1 fb-1: BR = 2.1 x10-7
L=4 fb-1: BR = 9.9 x10-8
L=8 fb-1: BR = 6.7 x10-8

- Current limits at 90% C.L.:
- Fierce Competition:
- CDF (L=171 pb-1): BR < 5.8 x 10-7
- DØ   (L=240 pb-1): BR < 4.1 x 10-7
- DØ   (L=300 pb-1): BR < 3.0 x 10-7
- CDF (L=364 pb-1): BR < 1.6 x 10-7
- Friendly combination:
- CDF+DØ:                  BR < 1.2 x 10-7
- Projected reach (CDF+DØ):
- Exclusion at 90% C.L.:
- L=1 fb-1: BR < 6.4 x 10-8
- L=4 fb-1: BR < 2.8 x 10-8
- L=8 fb-1: BR < 2.0 x 10-8
- Discovery at 5:
- L=1 fb-1: BR = 2.1 x10-7
- L=4 fb-1: BR = 9.9 x10-8
- L=8 fb-1: BR = 6.7 x10-8

- Rare Decay: Bs

- (this assumes no improvements to analyses)

## Impact of Bs Limits: Now 

- Starting to constrain MSSM parameter space

- R. Dermisek, S. Raby, L. Roszkowski,
- R. Ruiz de Austri, hep-ph/0507233

- S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033

**Consistent with WMAP data**

## Impact of Bs Limits: L=8 fb-1 

- Will severely constrain parameter space
- “Tevatron can rule out 29% of parameter space allowed by WMAP data within mSUGRA.” B. Allanach, C. Lester, hep-ph/0507283

- R. Dermisek, S. Raby, L. Roszkowski,
- R. Ruiz de Austri, hep-ph/0507233

- S. Baek, Y.G.Kim, P. Ko, hep-ph/0406033

## 1 vs 4 vs 8 fb-1What difference does it make?

|  |  Ldt = 1 fb-1 |  Ldt = 4 fb-1 |  Ldt = 8 fb-1 |
| --- | --- | --- | --- |
| SM Higgs: 95% C.L. excl. | mH <100 GeV/c2 | mH <130 GeV/c2 | mH <135 GeV/c2 |
| mH=115 GeV/c2: 3 evidence | 5% chance | 35% chance | 75% chance |
| mH=115 GeV/c2: 5 discovery | 0% chance | 2% chance | 10% chance |
| MSSM A, tan=40: 95%CL excl | mA<170 GeV | mA<225 GeV | mA<240 GeV |
| MSSM A @140 GeV: 5 disc. | tan=70 | tan=60 | tan=55 |
| 3leptons (3l-max): 95%CL excl | m(±) < 170 GeV | m(±) < 200 GeV | m(±) < 230 GeV |
| 3leptons (large m0): 95%CL excl. | m(±) <100 GeV | m(±) < 135 GeV | m(±) < 150 GeV |
| Gluinos: 95% C.L. excl. | - | M<420 GeV | M<450 GeV |
| Stop quarks: 95% C.L. excl. | M(t)<160 GeV | M(t)<180 GeV | M(t)<185 GeV |
| Bs: 95% C.L. excl.  | BR<6.4 x 10-8 | BR<2.8 x 10-8 | BR<2.0 x 10-8 |
| Bs: 5 discovery | BR=21.0x 10-8 | BR=9.9 x 10-8 | BR=6.7 x 10-8 |
| Z’ discovery, e.g. E6 model | M=720 GeV | M=820 GeV | M=870 GeV |
| LED: 95% C.L. excl. | M<1.8 TeV | M<2.15 TeV | M<2.35 TeV |

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## However ...We Are Experimentalists!

## And So Much More!!! (e.g. CDF)

- Published/Submitted:
- H++->ee,,e
- H++, stable double charged particle
- Excited electrons
- GMSB: +MET
- LQ->vvqq
- Magnetic monopoles
- MSSM Higgs: A->
- LQ, 1st gen.
- Z’->ee, 
- Bs->
- Other (no result yet):
- Photon+MET (LED+GMSB)
- Like-sign dileptons
- Dileptons at large qT
- 4-leptons
- Bs ->
- Excited muons and taus
- tt+Higgs
- GMSB Stop: +2jet+MEt
- Lepton-flavor violating Higgs
- MSSM Higgs: A+b ->bb+b
- Excited quarks
- Dijet mass resonance
- Syst. Scan of high pT data

- Preliminary results:
- 4th generation quarks: b’, t’
- Diphoton resonance
- W’->ev
- SM Higgs
- Charged Higgs
- Vector LQ, 3rd gen.
- LQ, 2nd gen.
- Gluino->sbottom+bottom
- Squark/gluino->jets+MET
- Stop: 2 decay modes
- RPV stop quark
- RPV sneutrino
- Trileptons
- monojets
- lepton+gamma+X
- Ditop resonance
- High Et jets
- CHAMPs: CHArged Massive Particles
- Longlived particle decaying to Z+X

- Blue: shown here
- Black: not shown here

- (similar at DØ)

## About 1/6 of Run 2 Search Results

- leptoquarks

- W’->ev

- RPV SUSY

- GMSB SUSY

- High ET jets

- Extra Dimensions

- Long-lived Z parent

- sbottom

- Magnetic monopoles

- long-lived particle

- Ditop resonance

- Monojets

## Conclusions

- Discovery potential:
- Predictions based on Run 2 analysis experience
- Standard Model Higgs
- L=2.5 fb-1: Probe LEP excess at mH=115 GeV/c2
- L=4-8 fb-1: significant exclusion or evidence
- Tevatron competitive with LHC until experiments complete analysis of L≈5 fb-1
- SUSY
- Higgs, Trileptons, squarks/gluinos, Bs+-
- Tevatron less competitive with LHC experiments
- How exactly depends on model parameters and type
- Many other models (Z’, Extra Dimensions, etc.)
- We are explorers
- Model independent searches for signatures
- Don’t know whether any theory is right!
- We may find the unexpected
- Every 1-2 weeks a “blind box” is opened and an exciting surprise may show up!

## Backup Slides

## LHC Higgs Discovery Potential

- Very fast for high mass, e.g. 160 GeV/c2:
- L=500 pb-1 in hWW channel
- Harder at low mass => zoom into low mass region

- F. Gianotti, LP2005:
- “the LHC experiments may collect several fb-1 by end of 2008.“

## LHC: Low Mass Region

- mH=115 GeV/c2
- Three channels contribute, each with about 2-3:
- H->, ttH->ttbb, qqH->qq
- Combining those three channels:
- Require L≈10 fb-1 for 5 discovery with single experiment at mH=115 GeV/c2
- Tevatron results competitive until at least 5 fb-1 have been analysed by both LHC experiments

## Any Hints in the Current Data?

- Not significant but, e.g.
- Gluino candidate event at HT=660 GeV
- 2 excess in ditop mass spectrum at 500 GeV
- 1.5 excess in Higgs ditau search
- Only more data can tell...

## Z ́ Discovery Reach

- Z ́e+e- with mZ ́=1 TeV/c2 and SM couplings:
- LHC (F. Gianotti, M. Mangano, hep-ph/0504221) :
-  5 discovery with ∫Ldt=70 pb-1
- Tevatron:
- 95% CL exclusion with ∫Ldt=1 fb-1
- 3 discovery with ∫Ldt=1.3 fb-1
- 5 discovery with ∫Ldt=1.5 fb-1

- LHC projections (from M. Mangano)

## Z ́ Discovery

- Several models inspired by E6 theories

## Higgs: Systematic Uncertainties

- Width of bands shows difference between:
- Assume current systematic uncertainties improve with 1/√L
- No systematic uncertainties
- Factor 1.4 difference in luminosity between those assumptions
- Main systematic uncertainties determined by data statistics, e.g.:
- Wbb and Wc background normalisation (currently 40%)
- mistags

**5******** discovery**
**3******** evidence**
**95% CL exclusion**

## WH Signal in ZHbb Analysis

- This is easy!
- Got factor 2.1 with current analysis (CDF):
- S/√B increases: 0.062 => 0.091
- Luminosity factor=(S/√B)2=2.1
- DØ observe factor 1.6
- Remarks:
- ZHbb analysis:
- vetoes against isolated tracks, electrons and muons
- Exact factor depends on veto cuts
- Cross-talk with lepton and track-only selections
- being further optimised with global view on all analyses
- Assume factor 2.7 with optimal lepton selection/vetoes

|  | CDF  | DØ |
| --- | --- | --- |
| ZH signal | 0.13 | 0.065 |
| WH signal | 0.06 | 0.018 |
| Background | 4.4 | 2.2 |
| S(ZH)/√B | 0.062 | 0.043 |
| S(ZH+WH)/√B | 0.091 | 0.055 |

## Higgs: Mass Resolution

- Current value:
- CDF 17%, DØ 14%
- HSWG result: 10.4%
- How do we get there?
- Combine track and calorimeter information: 2%
- Expand cone size (CDF): 2%
- Specific corrections for b-jets: 1-2%
- Fancy algorithms (“hyperball”): 1-2%
- 1% in mass corresponds to 10% in luminosity

## Higgs: NN B-tagging

- Neural Net b-tagging
- first versions available in both experiments
- DØ achieve 25% improvement now by cutting on NN output
- Exploit full distribution:
- better statistical power
- Best events count most
- e.g. Factor 1.2
- simply combining single and double tag samples
- Factor 1.5 is likely achievable

- CDF

- DØ

## Higgs: Lepton Selection

- Forward leptons:
- Assume gain of factor 1.3
- Current analyses use only up to ||<1.1
- Available improvements:
- CDF:
- Forward electrons used already by other analyses, e.g. W charge asymmetry
- Up to ||<2.8
- Central electrons and muons: recently improved efficiency by ~5%
- Factor 1.34 in acceptance
- D0:
- Estimate 50% gain from trigger, lepton ID and using electrons near cracks

## Improvement 5: Track Lepton

- Track leptons: 1.4
- Catch one-prong tau-decay
- Catch region with poor muon/calorimeter instrumentation
- Depends on how well we identify electrons and muons
- CDF already uses them in top dilepton selection:
- Signal: 17.2->21.7 events
- 25% signal increase
- Can also do full tau ID:
- See later MSSM higgs search
- Tau ID:
- Cut based: ****≈45%
- NN based: ****≈ 80%
- Not yet evaluated potential

- Factor 1.4 reasonable

## WHebb in DØ

- Improvements:
- Forward leptons: 26%
- B-tagging: 40%
- Trigger+ID: 30%
- Mass resolution: 40%
- Total:
- Factor 1.85 in S/√B
- Luminosity equivalent: 3.4

|  | now | future(*) |
| --- | --- | --- |
| Mass resolution | 14% | 10% |
| Signal | 0.12 | 0.48 |
| Background | 2.37 | 5.79 |
| S/√B | 0.08 | 0.20 |

- (*) 2003 HSWG study without NN
- assumption, scaled to L=382 pb-1

## Does the NN Create a Mass Bias?

- WH NN from Run I:
- Avoids using variables correlated with mass
- Expected limit improved from 13 pb to 10 pb => luminosity equivalent is (13/10)2=1.7
- Background shape not biased towards higgs mass
- Better discrimination when mass used in NN (~2)
- But will we believe the pure NN output?
- Can test this with other channels, e.g. WW->jjlv

## How does the Higgs Signal look like?

- Will first observe WZ:
- excellent calibration channel
- tests validity of procedure

## LHC: Higgs at 115 GeV/c2

- from F. Gianotti, LP 2005

## LHC: Higgs at 115 GeV/c2

- from F. Gianotti, LP 2005

## D0: Rare Decays

## SUSY at the LHC

- Will generally be found fast!
- But SUSY comes in very many flavours
- Hints from the Tevatron would help on search priorities, e.g.
- tan large:
- 3rd generation important    (’s, b’s)
- R-parity is violated
- No ET
- GMSB models:
- Photons important
- Split-SUSY:
- Stable charged hadrons
- Can setup triggers accordingly