# Presentation: 042324

## Carsten Rott, Purdue University

- for the CDF Collaboration
- Tsukuba, Japan, 2004

- Searches for the Supersymmetric Partner of the Bottom Quark

## Sbottom Searches

**CDF Run I**

******0**** Mass (GeV/c****2****)   **

**Sbottom Mass (GeV/c****2****)**

- LEP Limits
- 92GeV/c2 for m>10GeV/c2

**Direct Sbottom Search**

- Sbottom could be light due to large mass splitting between the eigenstates (large tan)

- Assume:

- R-parity conservation which leads to stable undetectable neutralino

- m46GeV/c2

## Sbottom Quark Production at the Tevatron

**Sbottom Quark Production at the Tevatron**

- Direct Sbottom production:

- Gluino-pair production:

- Large production
- cross section

- 2pb

- 2pb

## Sbottom Quarks from Gluino Decays Signature 

**Sbottom Quarks from Gluino Decays Signature**

- Motivation
-  Large cross section
-  Very distinctive signature
-  Accessible at Tevatron

-    4 b jets +

- Sbottom quarks could be pair produced at the Tevatron or in a scenario where the gluino is heavier than the sbottom, through decays of gluinos.
- Consider here search for second case, it yields a richer signature

- Assume:

##  at CDF 

-  at CDF

-      caused by particles escaping detection or by detector mis-measurement

- Real

-  limited detector coverage
-  reconstruction
-  cosmics

- Fake

- Events

- from non-detectable

## B-Tagging at CDF 

- B hadrons fly macroscopic distance:
-                    with

- B-Tagging at CDF

- b-jets are identified using a secondary vertex tagging algorithm.
- Tracks with large impact parameter     are selected and a vertex fitting algorithm is used to reconstruct a displaced vertex.

- primary vertex

- Lxy

- secondary vertex

- B-tagging Efficiency per Jet

- d0

- d0

- Can be detected using CDFs Silicon Vertex Detector

- b-jet Et [GeV]

## Search Strategy

- Event kinematics depend on the mass differences:
- M=m(gluino)-m(sbottom)  / m=m(sbottom)-m(neutralino)
- Assume fixed neutralino mass (60GeV/c2), m is large and consider different gluino/sbottom mass scenarios:
- M – large -> b from gluino energetic
-                      boosted -> moderate
-                      3rd b-jet energetic

- M – small -> b from sbottom decay energetic
-                      not boosted -> larger
-                      3rd b-jet non-energetic

- Perform separate two analyses: Excl. single tagged / Inclusive double tagged

##  Backgrounds 

**QCD**
**W/Z+jets**
**Diboson**
**Top**

- Fake tag rate parameterization from data +
- QCD HF MC
- MC simulation
- MC simulation
- MC simulation

-  Backgrounds

-  QCD heavy flavor production
-  mismeasured jet energy
-  semileptonic b-decay
-  large
-  mismeasured jet energy
-  neutrinos
-  neutrinos
-   small
-  b-jets
-  neutrinos
-  very similar signature !

-  (      ,jets) cuts
-  isolated lepton veto
-  b-tag requirement
-  isolated lepton veto
-  b-tag requirement
-  isolated lepton veto

- Event selection cuts

-  Inclusive three jets Pt>15GeV ||<2
-      > 35GeV
-  (     ,1-3jet) > 40O
-  Heavy flavor tags

- Use     cut and lepton veto/requirement to define signal and control regions

## ??

- Define three control regions, based on     and lepton requirement to provide cross-check for background predictions.

- Signal and Control Regions

**Control regions in agreement with SM predictions**

**QCD**** dominated**

**Top**** dominated**

*??*

## Control Regions

-    :                          35-50GeV   35-50GeV     >50GeV
- Lepton:                        yes              no               yes
- W/Z+jets/Diboson   3.9±0.8       11.0±1.2         9.6±1.2
- Top                          11.7±0.2        8.2±0.1       35.2±0.3
- QCD-multijet          19.2±4.1     129.6±17.3     10.9±4.5
- Total background    34.8±4.2    148.8±17.3     55.7±4.7
- Data                             36               121               63

- Comparison of standard model background predictions for inclusive single tagged events is in agreement with data

- Dominant systematics:
- Tagging efficiency
-  Energy scale

- Statistical errors

## Signal Expectations

- Optimal sensitivity:     >80GeV

- Similar signal acceptance for exclusive single tagged events and inclusive double tagged events

| Expected  Signal | Acceptance | Expected events |
| --- | --- | --- |
| SingleTagged | 7.7% | 24.3 |
| DoubleTagged | 9.0% | 28.6 |

- Large signal acceptance + small SM background

|  | Exclusive Single B-Tag | Inclusive Double B-Tag |
| --- | --- | --- |
| EWK | 5.66±0.76±1.72 | 0.61±0.21±0.19 |
| TOP | 6.18±0.12±1.42 | 1.84±0.06±0.46 |

| QCD | 4.57±1.64±0.57 | 0.18±0.08±0.05 |
| --- | --- | --- |
| Predicted | 16.41±1.81±3.15 | 2.63±0.23±0.66 |
| Observed |          ??  |          ?? |

- stat  syst

- Expect 28.6 signal events

## Results

- Expected 16.4±3.7
- Observed     21** **

- Use 156pb-1 of data taken 2002-2003

- Perform counting experiment

- Expected  2.6±0.7
- Observed      4

## Sbottom Searches

- B-tagged

- B-tagged

**MET=86.4GeV**

- Primary Vertex

- Secondary Vertex

- Double tagged event in signal region

| Et |  |  | Tag |
| --- | --- | --- | --- |
| 85.3GeV | 0.02 | 4.99 | 1 |
| 51.6GeV | 0.84 | 5.97 | 1 |
| 30.0GeV | -0.83 | 1.42 | 0 |

## Cross Section Limit 

- Cross Section Limit

- Now translate upper limit cross section to exclusion plane

- Upper limit on signal events

- M(gluino,sbottom) = 60GeV/c2

- Incl. Double Tag

- Excl. Single Tag

- Excl. single tag: Exclude 20.6 signal events at 95%C.L.
- Incl. double tag: Exclude 8.7 signal events at 95% C.L.

## Gluino/Sbottom Exclusion Plane

- Exclude new parameter space
- Obtain larger exclusion limit using inclusive double tagged events, due to better background suppression by similar signal acceptance
- Similar limits expected also for also for larger neutralino mass scenarios

- Exclusive single tag analysis more sensitive for nearly mass degenerated scenario

## Conclusions

-  Heavy flavor jets and       exciting combination to look for new physics
-  Performed search for sbottom quarks from gluino decays
-  No excess found and new exclusion limit was set
-   Vastly exceed Run I limits
-  Searches beyond the standard model are ongoing ...
-  http://www-cdf.fnal.gov/physics/exotic/run2/gluino-sbottom-2003/bless_plots.html

## Gluino/Sbottom Exclusion Plane

**Gluino production allows significant extension of the best limits at high mass Sbottom and low mass neutralinos**