# Presentation: 930800

## Supersymmetry Searches at the Tevatron

*Chris Hays, Oxford University*
- for the CDF and DØ Collaborations
- SUSY '08
- Seoul, Korea
- June 17, 2008

## Supersymmetry

-   New parameters: 105

-   Possible mass hierarchies: O(1028)

-   New particles: 32

-   Discovering a new symmetry of nature: Priceless

- C. Hays, SUSY '08

- June 16, 2008

## Discovering Supersymmetry

-  *Search for generic sparticle production*
-  Probe large regions of parameter space
-  Use constrained models to interpret results
-  *Search for sparticles with unusual properties*
-  Small mass differences or couplings
-  Requires specialized analysis
-  *Search all data independent of models*
-  Maximally probe the parameter space
-  Some cost in sensitivity

**Strategies**

- C. Hays, SUSY '08

- June 16, 2008

## Discovering Supersymmetry at the Tevatron

***  ******s***** = 1.96 TeV pp collisions**
**Sensitivity to ****≲ ****400 GeV sparticles**
**(c.f. LEP ****≲ ****100 GeV)**

**√**

**> 4 fb****-1**** delivered per experiment**

**CDF**

**DØ**

- C. Hays, SUSY '08

- June 16, 2008

## Discovering Supersymmetry

-  *Search for generic sparticle production*
-  Probe large regions of parameter space
-  Use constrained models to interpret results
-  *Search for sparticles with unusual properties*
-  Small mass differences or couplings
-  Requires specialized analysis
-  *Search all data independent of models*
-  Maximally probe the parameter space
-  Some cost in sensitivity

**Strategies**

- C. Hays, SUSY '08

- June 16, 2008

## Generic Sparticle Searches

-  *Focus on production with highest cross sections*
-  Small masses or large couplings
-  *Lightest sparticles*
-  Charginos, neutralinos
-  Stop quarks, staus
-  *Strong production*
-  Squarks and gluinos
-  *Final states depend *
*	** **on sparticle mass *
*	** **hierarchy*
*Interpret results using a reference model*
- mSUGRA most common (5 parameters)

***Feldman, Liu, Nath***
***PRL 99, 251802 (2007)***

***Barger et al.***
***arXiv:hep-ph/0003154***

- 0%        5%       10%     15%     20%     25%

***tan************ = 4 ***
***m******0****** = 100 GeV***
***m******1/2****** = 150 GeV***
***A******0****** = 300 GeV***
********* ******> 0 ***

- C. Hays, SUSY '08

- June 16, 2008

## Chargino & Neutralino Production 

- CDF and DØ data consistent with background predictions

-  *Search for ****2**0****1**±** production in final states with three charged leptons and missing transverse momentum (p**T**)*
- Three identified *e*/ or two *e*/and one *e*// track
-  Requires substantial branching ratio to *e*/
-  Most sensitive at low tan = <*H**u*> / <*H**d*>

- C. Hays, SUSY '08

- June 16, 2008

## Chargino & Neutralino Production 

- DØ sets chargino mass limit of 145 GeV in a particular SUGRA-inspired model

-  CDF* sets limits in m**0**-m**1/2** mSUGRA plane*
- Limits depend on relative neutralino-slepton masses
-  m2 > mslepton increases branching ratio to *e*/
-  m2 ≈ mslepton reduces acceptance to lowest-*p**T* lepton

- pb

***S. Dube, today 5:10***

- C. Hays, SUSY '08

- June 16, 2008

## Squark & Gluino Production 

* **Search for squark and gluino production in final states with 2, 3, or 4 jets plus p**T*
-  2 jets + *p**T *:  qq → qq1010  (mq < mg)
-  3 jets + *p**T *:  qg → qqq1010 (mq  mg)
-  4 jets + *p**T *:  gg → qqqq1010  (mq > mg)

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- CDF and DØ data consistent with background predictions

- C. Hays, SUSY '08

- June 16, 2008

## Squark & Gluino Production 

* **Set limits in m**q**-m**g** and **m**0**-m**1/2** mSUGRA planes*

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***DØ Collaboration,***
***PLB 660, 449 (2008)***

***S. ******_x001a_******M. Wang, today 4:30***

- C. Hays, SUSY '08

- June 16, 2008

## Squark Production 

* **Squarks can also decay to charginos and neutralinos*
- Large branching ratio to taus at high tan

- 2 jets +  + *p**T* search:

***tan************ = 15 ***
***A******0****** = -2m******0****** ***
********* ******< 0 ***

- C. Hays, SUSY '08

- June 16, 2008

## Gluino Production 

* **Search for gluino pair-production in final states with 4 b-jets plus p**T*
-  Improves sensitivity when *m**sbottom* < *m**gluino** (large tan****)*

*m**gluino **- m**sbottom* = 70 GeV

*m**gluino **- m**sbottom* = 20 GeV

- C. Hays, SUSY '08

- June 16, 2008

## Stop Production

* **Final state depends on stop-****±**/LSP mass difference*
-  2 *c*-jets + *p**T *:  *tt* → *cc*1010
-  *l**+**l**-* + *bb* + *p**T *:  *tt* → *Wb****Wb*** (*m**t* > *m**w** + m**b** + m***)
- 		              *tt* → ***1******1**∓**bb* (*m**t* > *m**b* +* m****1*)

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- 2 *c*-jets + *p**T* search:

***DØ Collaboration, arXiv:0803.2263 ***

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- C. Hays, SUSY '08

- June 16, 2008

## Stop Production

* **Dilepton final state can be enhanced if chargino decays to slepton or sneutrino*
*e.g.* 50% branching ratio for tan = 15

*l**+**l**-* + 2 *b*-jets + *p**T* search (*tt* → ***1******1**∓**bb*):

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- C. Hays, SUSY '08

- June 16, 2008

## Stop Production

*e*** + 2 *b*-jets + *p**T* search (*tt* → *llbb***):

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*Stop can decay to lb**** through a chargino  *
*** **escapes detection as the LSP*

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***P. Calfayan, today 4:50***

- C. Hays, SUSY '08

- June 16, 2008

## Discovering Supersymmetry

-  *Search for generic sparticle production*
-  Probe large regions of parameter space
-  Use constrained models to interpret results
-  *Search for sparticles with unusual properties*
-  Small mass differences or couplings
-  Requires specialized analysis
-  *Search all data independent of models*
-  Maximally probe the parameter space
-  Some cost in sensitivity

**Strategies**

- C. Hays, SUSY '08

- June 16, 2008

## Specialized Sparticle Searches

-  *Particles with long lifetimes*
-  Result from small mass differences or couplings
-  Common in GMSB and split supersymmetry
-  Searches use specialized timing systems
-  *R-parity-violating couplings*
-  Leads to unstable LSP
-  No dark matter candidate
-  Consistent with experimental constraints
-  *Enhancement of rare SM processes*
-  Search for indirect evidence of supersymmetry

- C. Hays, SUSY '08

- June 16, 2008

## GMSB Gaugino Production

*CDF search for ****1**0** with >1 ns lifetime in **** + j +* *p**T **:*

*Gauginos cascade to photons, taus and gravitinos*
*Gravitino with O(keV) mass is dark matter candidate*
******* **can have O(10 ns) lifetime*

***CDF Collaboration, PRL 99, 121801 (2007), arXiv:0804.1043 ***

- C. Hays, SUSY '08

- June 16, 2008

## GMSB Gaugino Production

*DØ search for ****1**0** with short lifetime in **** +* *p**T **:*

*CDF and DØ use "SPS 8" model line as a reference*
*One parameter:  energy scale **** that determines scale of supersymmetry breaking*

***DØ Collaboration, PLB 659, 856 (2008) ***

***E. Nagy, today 5:30***

- C. Hays, SUSY '08

- June 16, 2008

## Long-Lived Stop Production

* **Stop decay length larger than detector if m**t** < m**** + m**c*
-  Signature is slow heavy charged particle (CHAMP)

- CDF search using timing from
- time-of-flight system and tracking chamber:

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***Also sensitive to long-lived stau production***

- 

- C. Hays, SUSY '08

- June 16, 2008

## Long-Lived Gluino Production

* **Split supersymmetry predicts gluino with long lifetime*
- Results in "*R*-hadron" that ionizes and stops in the detector
- Number of stopped gluinos depends on neutral to charged *R*-hadron cross section

- DØ search for single jet and no *pp* collision:

***DØ Collaboration, PRL 99, 131801 (2007) ***

***0.3 mb   3 mb        30 mb***

- C. Hays, SUSY '08

- June 16, 2008

## Resonant Sneutrino Production

* **Resonant sparticle production allowed if R-parity violated*
*R*-parity-violating couplings:

- DØ search for sneutrino in *e* decay:

***DØ Collaboration, arXiv:0711.3207***

- C. Hays, SUSY '08

- June 16, 2008

## Bs →  Branching Ratio

* **Sparticle exchange can significantly increase BR(B**s** → ****)*
*Enhancement factor of tan**6**** over SM BR of 3.5 **** 10**-9*

- CDF: BR(*B**s* → ) < 5.8 10-8
- DØ: BR(*B**s* → ) < 9.3  10-8

***CDF Collaboration, ***
***PRL 100, 101802 (2008)***

- C. Hays, SUSY '08

- June 16, 2008

## Discovering Supersymmetry

-  *Search for generic sparticle production*
-  Probe large regions of parameter space
-  Use constrained models to interpret results
-  *Search for sparticles with unusual properties*
-  Small mass differences or couplings
-  Requires specialized analysis
-  *Search all data independent of models*
-  Maximally probe the parameter space
-  Some cost in sensitivity

**Strategies**

- C. Hays, SUSY '08

- June 16, 2008

## CDF Global Search

-  *_x0003_**Cannot cover all possible parameter space with targeted searches*
-  Search all data with objects above threshold
-  *e*, , , , *b*, quark or gluon jet, *p**T*
-  Procedure:
- Develop global SM prediction using combination
- 	of MC, detector simulation, and data-based corrections
- Compare normalization and shapes of 399 final states
- Search final states for mass resonances
- Judiciously combine final states and search for excesses at large object  *p**T*

***S. Xie, Friday 2:40***

- C. Hays, SUSY '08

- June 16, 2008

## CDF Global Search Results

-  *_x0003_**Shape and bump discrepancies dominantly due to mismodelling of jet separation*
- No significant discrepancy at high  *p**T*
- Expect 8% of similar experiments
- 	to see SM fluctuation as significant
- 	as that observed

- C. Hays, SUSY '08

- June 16, 2008

## Tevatron experiments broadly probing for supersymmetry
Covering likeliest scenarios, unusual scenarios, unconsidered scenarios

Supersymmetry not (yet) discovered
Expect factor of ~3 more data to analyze by end of Run II 

- Covering likeliest scenarios, unusual scenarios, unconsidered scenarios
- Supersymmetry not (yet) discovered
- Expect factor of ~3 more data to analyze by end of Run II

*Summary*

| Sparticle | Scenario | Mass Limit (GeV) |
| --- | --- | --- |
| Neutralino | NLSP in GMSB | ~125 |
| Chargino | mSUGRA at low tan | ~150 |
| Stop | Short (long) lifetime | ~150 (~250) |
| Sneutrino | RPV couplings ~ 0.01 | ~250 |
| Sbottom | Br(g → b) = 100% | ~300 |
| Squark & Gluino | mSUGRA at low tan | ~400 |

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- C. Hays, SUSY '08

- June 16, 2008