# Presentation: 009953

## Status of SUSY searches

- Jean-François Grivaz
- LAL – Orsay
- Physics at LHC – Vienna 2004

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## What this talk will not be:

-  an introduction to SUSY (you are all experts)
-  a discussion of cosmological implications (my own inability)
-  a comprehensive review (half-an-hour)

- What it will address:
-  the LEP legacy (no experimental details)
-  recent results from the Tevatron

- In which framework ?
-  mostly “standard” SUSY, i.e.(C)MSSM / mSUGRA
-  some GMSB (clean and simple)
-  no RPV (too many equally acceptable scenarios, no DM)
- 	 [Apologies to our HERA colleagues]

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Standard SUSY:

-  The MSSM with some unification conditions
-  R-parity conservation
-  Neutralino LSP

- At LEP:
-  All sparticles democratically produced (not the gluino...)
-  Search for the next-to-lightest one(s) and express the results
-    in a model-independent (or moderately dependent) way
-  Combine the results within some constrained framework

- At the Tevatron:
-  Colored sparticles (squarks and gluinos) have the largest
-   production cross sections, but backgrounds are also large
-  Electroweak gauginos have small cross sections,
-   but benefit from clean signatures (will win in the end...)
-  Hard to get away from highly constrained models

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## A simple case at LEP: smuons

-  Pair production only via s-channel /Z exchange
-     ms = 1st parameter
-  Assume sR is NLSP
-    (sL is heavier in typical unified models,
-     and would have larger cross section)
-    Only decay mode: sR  
-     m = 2nd parameter
-  Signature = acoplanar pair of muons
-    Well controlled background:WW  
-  With gaugino mass unification,
-   cascade decays (sR  ’ with ’) can be taken into account

- Other sleptons are more model dependent:
-  Staus because of L-R mixing (Z-s1-s1 coupling may vanish)
-  Selectrons because of t-channel neutralino exchange

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Another simple case at LEP: stops

-  Squarks are more efficiently searched
-   at the Tevatron but...
-  st1 could be (very) light because of
-   renormalization and mixing effects
-   (both due to large topYukawa)
-  For st1 NLSP, st1  c (loop decay)
-   Window for LEP at small/moderate
-      st1   mass difference
-    Search in acoplanar jet topology
-    Needed dedicated generator because of
-     competing decay and hadronization times
-  For very small mass differences, specific searches have been
-   performed for stop-hadrons with macroscopic decay lengths,
-   and for (quasi) stable stops

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Charginos and neutralinos at LEP (I)

- Chargino pair production (neutralino pair or associated production)
- involves s-channel /Z exchange, which depends on the field content,
- as well as t-channel sneutrino (selectron) exchange.
-  First assume heavy sleptons  s-channel only  decays to W* ( Z*)
-  Charginos are then fully described in terms of M2,  and tan
-  Neutralinos need M1 in addition:
-   Assume unification (M1~M2/2)

- Search extended to very small + mass differences
- (ISR tagging, stable charged particles)
- Applies to the deep higgsino region, or in AMSB models (M1~M2)

- Direct and indirect
-       mass limits

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Charginos and neutralinos at LEP (II)

- The impact of light sleptons:
-  Reduced chargino cross section (negative interference)
-  Enhanced neutralino production (positive interference)
-  Invisible decay modes: ’   sL
-    or l sL with small  sLmass difference  (the “corridor”)
-  Use slepton searches and
-       assume scalar mass unification

- For m0 and tan given, a slepton
- mass limit gives a constraint on M2

-  Robust chargino mass limit

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## The LSP mass limit at LEP

-  There is no absolute neutralino-LSP mass limit from LEP
-   (ee vanishes for a pure photino and heavy selectrons)
-  Indirect limits have been
-   obtained under the assumption
-   of gaugino mass universality
-  For large slepton masses:
-    ~ m/2 (52 GeV) at large tan,
-    somewhat lower otherwise
-  For low slepton masses, scalar
-   mass universality is also needed
-   (The limit is set in the “corridor”)
-  And finally Higgs searches are
-    used at low tan ...

- The impact of stau mixing has recently been investigated: no loophole

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## On the LEP Higgs constraints

-  Assume scalar (sfermions only) and gaugino mass unifications
-   (mA and  remain free parameters, compared to mSUGRA)
-  m0, tan and M2  masses of stL and stR
-  maximal impact of stop mixing + large mA  mh-max
-  for large mA, h is SM-like  compare to SM-Higgs limit
-  This provides an upper limit on M2, given m0 and tan,
-     which is most constraining at low m0 and low tan

-  However, configurations exist for mh  SM-Higgs limit, which
-    are not excluded by SM-Higgs searches (e.g. h  bb vanishes)
-  Need to supplement SM-Higgs searches by other ones:
-    hA, HH, invisible, flavor independent + SUSY particles
-   Perform a parameter scan (with dichotomies as appropriate)
-   Result: the SM-Higgs limit is robust,
-     and hence was adequately used to set the LSP mass limit

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## mSUGRA at LEP

-  Compared to the previous LSP-mass analysis,
-    mA and  are no longer free parameters,
-    A0 controls all sfermion mixings

- Excluded by...

- the Z width

- theory

- chargino

- Higgs

- slepton

- stable particle

- ... searches

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## A bit of GMSB at LEP

-  In GMSB, the LSP is a (very light) gravitino G
-  The phenomenology depends mostly on the nature
-   (and lifetime) of the NLSP:

- Interpretations within mGMSB are available

- CDF Run I

- A slepton, preferably
- a stau: s1   G

- A neutralino:    G

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## GMSB at the Tevatron (I)

- Inclusive searches for   Missing ET by both CDF / DØ

-  Photon ET  13 / 20 GeV
-  Missing ET > 45 / 40 GeV
-  Mild topological cuts

- Main backgrounds:
-  EM-jets (or real QCD photons)
-   + fake Missing ET
-  electron + photon
-   + real Missing ET
- All determined from the data

- Photon = electron without track

- CDF : 0 vs 0.6 expected
- DØ   : 1 vs 2.5 expected

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## GMSB at the Tevatron (II)

- Interpretation within mGMSB
- with:
-  N = 1
-  Mmessenger = 2,
-    0,
-  tan = 15 (CDF)
-   or 5 (DØ, aka “Snowmass slope”)
- Signal dominated by chargino-
- neutralino production

- World best limit:
- m  105 GeV

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Trileptons at the Tevatron (I)

-  Arise from chargino-neutralino
-    associated production
-  Clean signature but:
-    - low cross sections ( BR)
-    - soft leptons
-    - taus (at large tan)
-  Needs large integrated luminosity
-  Combine various final states

- (Also decays via W/Z exchange)

- DØ analysis based on 145  175 pb1
- Combines eel, el and same sign dimuon final states
- Addresses “just beyond LEP” mSUGRA

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Trileptons at the Tevatron (II)

- Two isolated (rather soft) e or 
- Require some Missing ET
-  channel-dependent cuts (e.g. anti Z)
-  Two same sign muons, or
-  An isolated third track (no e or  ID)
- Main backgrounds: WW, WZ, W, a bit of bb
- Altogether: 2 events observed vs 0.9  0.5 expected

- Substantial improvement
- wrt Run I
- Should soon probe virgin
- mSUGRA territory

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Stop and sbottom at the Tevatron

- CDF has searched for charged massive particles in 53 pb1
-  appear as slow moving  (TOF) high pT muons
-  result interpreted for (meta)stable stop
-  mstop108 GeV (isolated) or 95 GeV (non-isolated)

- CDF has searched for sbottoms
-   in gluino decays (156 pb1)
-  assumes sb1 much lighter than
-   all other squarks (large tan)
-  gluino  sb1 b
-    4 b-jets + Missing ET
-   for gluino pairs
-  the selection requires at least
-   one b-tag, no isolated lepton

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Generic squarks at the Tevatron (I)

- Strong production of:
-  sq-sqbar
-  sq-sq
-  sq-gl
-  gl-gl

- In 85pb1, DØ has searched
- along the “minimum sq-mass
- line” of mSUGRA:
- very low m0 (25 GeV),
- (tan = 3, A0 = 0,   0),
- scan over m1/2

-  Mostly sq-sqbar with sq  q   Acoplanar jets + Missing ET

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Generic squarks at the Tevatron (II)

- Main selection cuts:
-  at least two high pT jets
-  isolated lepton veto
-  Missing ET should not be
-   along or opposite to a jet
-  Sum of jet pT  275 GeV
-  Missing ET  175 GeV

- Main backgrounds left:
-  (Z  ) + jets
-  (W ) + jets
- QCD negligible

- 4 events selected
- vs
- 2.7 + 2.3  1.5
- expected

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Generic squarks at the Tevatron (III)

- Slight improvement over CDF-Run I
- along that “minimum sq-mass line”:
- (msq  292 GeV and mgl  333 GeV)

- How relevant are the Tevatron
- results on squarks and gluinos ?
- LEP slepton and chargino limits  much tighter constraints
- on m0 and m1/2 within mSUGRA (or even MSSM with unification)
- The Tevatron should consider models with smaller M3/M2 ratios:
- not unnatural in GUTs (e.g. M3/M2 ~ 1 if SUSY breaking by a **75**)
- or in string inspired models

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Bs   at the Tevatron

- In SM, tiny BR ~ 3.5 109 (and 25 times smaller for Bd)
- But in SUSY, a (tan)6 factor could lead to an enhancement
- by as much as three orders of magnitude

- CDF BR limit (95% CL): 7.5 10-7 (Previous best: CDF Run I < 2.6 10-6)
- DØ: sensitivity study, but the box hasn’t yet been opened...
- Close to getting relevant

- Select dimuons originating from displaced vertices, and look inside a mass window:

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz

## Conclusions

- As of today, the main constraints on (RPC-) SUSY
- from accelerator searches remain those established by LEP:
- Slepton and chargino masses > 100 GeV

- The Tevatron already entered new GMSB territory:
- NLSP neutralino mass > 105 GeV

- Trilepton searches should provide relevant results very soon

- Squark and gluino searches are well underway
- (awaiting adequate interpretation)

- But...

- Bs   is about to probe large tan SUSY

- ...and the Tevatron luminosity is steadily increasing...

- Physics at LHC - Vienna 2004

- Jean-Francois Grivaz