1. Search for R-parity Violation at DØ
on behalf of the DØ collaboration
Frédéric Déliot
CEA-Saclay, France

2. Search for R-parity Violation at DØ
introduction
the TeVatron and the DØ experiment
R-parity violation
pair production + R̸p LSP decay
dilepton signal via ’ 
trilepton signal via 
top decays via ’ or ’’ 
sparticule resonant production
resonant slepton production 
resonant stop production 
: new results included
11/06/01
SUSY'01 - F. Déliot

3. integrated luminosity
The TeVatron
Run
duration
center of mass energy
integrated luminosity
RunI
1.8 TeV
~ 0.13 fb-1
RunIIa
2.TeV
2 fb-1
RunIIb
15 fb-1
CDF DØ MI
Tevatron
RunII: 2 new accelerators:
(3.3 km ring)
Main injector (injector to the TeVatron, p̅ production)
recycler (p̅ recycling ring)
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SUSY'01 - F. Déliot

4. Forward mini- drift chambers
The DØ Detector
muon chambers
toroid
tracking system
calorimeter
Central scintillators
Forward scintillators
Shielding
Solenoid,
Tracking system
Forward mini- drift chambers
DØ upgrade for RunII:
new tracking system (Si tracker, fiber tracker)
central solenoid
preshower
new forward muon system
DØ in RunI:
central detector (drift chambers, transition radiation detector)
no central magnetic field
compact and hermetic Ar-U calorimeter
muon system with iron toroid

5. R-parity discrete quantum number:
R = (-1)3B+L+2S, B: baryon nb, L: lepton nb, S spin
R = +1 for SM particle
R = -1 for SUSY particule
R parity violation terms compatible with all superpotential symmetries:
WR̸p=ijkLiLjEck+ ’ijkLiQjDck + ’’ijkUciDcjDck
45 new Yukawa couplings
can not be excluded theoretically L̸ B̸
11/06/01
SUSY'01 - F. Déliot

6. R-parity Violation experimental consequences of R̸p :
B and/or L violation
LSP can decay with or without displaced vertices
sparticules can be produced resonantly
usual search hypothesis:
mSUGRA with ̃01 as LSP and R̸p
similarly to Yukawa couplings hierarchy, only one R̸p coupling dominates
if R̸p coupling large enough, resonant production
otherwise pair production + R̸p does not affect branching ratios except for LSP decay
11/06/01
SUSY'01 - F. Déliot

7. Limits on R-parity Violation Couplings
Dreiner, hep-ph/ Ledroit, Sajot, GDR-S-008
indirect limits via low energy processes
(assuming a single dominant R̸p):
neutrinoless double-beta decay
charged-current universality constraints
e-- universality
-e scattering
AFB
atomic parity violation
2  limits
for m̃ = 100GeV
ijk ijk
ijk ʹijk
ijk ʹijk
ijk ʺijk * * * *

8. Pair Production: Dielectron Channel
DØ, PRL 83 (99) 4476
All pair production processes considered
dominant coupling: one of the six ’1jk (j=1,2; k=1,2,3)
LSP decay to 1 electron and 2 jets (close to its production)
channel:  2 electrons +  4 jets
background: Drell Yann, tt̅, Zee+…, misidentification of jets as electrons q ~ e
1o q’ ’
RunI Results:
Lint= 99  4.4 pb-1
Events observed: 2
Expected Bkg: 1.8  0.2  0.3 e ~ q
1o q’ ’
11/06/01
SUSY'01 - F. Déliot

9. ’1jk : Dielectron Channel in Run I
A0=0, < 0, tan  = 2
A0=0, < 0, tan  = 6
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SUSY'01 - F. Déliot

10. Dielectron Channel in RunII
A0=0, < 0, tan  = 2
Lint= 2 fb-1 , s̅=2 TeV
Scenario I: extrapolation from RunI
Scenario II: electrons misidentification reduced by a factor 2 due to central magnetic field
Mg̃  500 GeV
Mq̃  400 GeV
11/06/01
SUSY'01 - F. Déliot

11. Pair Production: Dimuon Channel
DØ, preliminary
All pair production processes considered
dominant coupling:
same analysis as previously with a dominant ’2jk
channel:  2 muons +  4 jets
background: Drell Yann, tt̅, Z+jets, Z, WW q ~ 
1o q’
’2jk
Run I Results:
Lint=  4 pb-1
Events observed: 0
Expected Bkg: 0.18   0.02  ~ q
1o q’
’2jk
11/06/01
SUSY'01 - F. Déliot

12. ’2jk : Dimuon Channel RunI RunII, 2 fb-1 A0=0, < 0, tan  = 2
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SUSY'01 - F. Déliot

13. Pair Production: Multilepton Channel
DØ, PRL 80 (98) 1592
dominant coupling: 121 ,122 or 233
LSP decay to 2 charged leptons and a neutrino
channel: reinterpretation of search for ̃1 ̃20 production
4 different final states:  eee,  ee,  e,   + E̸t
background: Drell Yann, tt̅, Zee+…, misidentification of jets as electrons e ~ e
1o
121
Run I Results:
eee
ee
e

Lint
97.8 5.2
93.1 4.9
78.3 4.1
Obs evts
Bkg
0.34 0.07
0.61 0.36
0.11 0.04
0.20 0.04   ~ 
1o
233

14. ijk : Multilepton Channel in Run I
dLSP >1 cm
dLSP <1 cm
dLSP <1 cm
11/06/01
SUSY'01 - F. Déliot

15. Top Decay via R̸p dominant coupling: ’’331
Abraham et al., PRD 63 (01) 34011
dominant coupling: ’’331
pp  tt̅ with one t  bd̃01 (̃01 decays outside the detector) and t̅  Wb̅  lb̅
channel: 1 lepton, 3 jets with 2 b-tagged + E̸t
background: tt̅, Wbbj
Sbottom Mass (GeV)
5.00
2.00
1.00
0.50
0.20
0.10
0.05
’’331 b̅
1o ~ d̅ b̃ t
RunII:
s̅=2 TeV, Lint = 2 fb-1 d̅
1o ~ b̅ d̃ t

16. Top Decay via R̸p dominant coupling: ’333
Han et al., PLB 476 (00) 79
dominant coupling: ’333
pp  tt̅ with one t  b̃01 (̃01 decays in or outside the detector)
channel: same signal as H+ b: detection optimized for SM tt̅ analysis  disappearance experiment
background: tt̅, W+jets t ̃ b
1o ~
t̃1 t  b
1o ~ b̃ t b 
long lived LSP
Indirect 2  limit
for m̃ = 100 GeV:
’333 =0.58
for M̃ = 70 GeV,
’333 < 0.94 at 95 % CL
RunII (2fb-1): ’333 < 0.38

17. Resonant Production
at hadronic colliders, resonant production via ’ or ’’
via ’: resonant slepton production (̃,̃)
via ’’: resonant squark production (t̃)
generally assumed that those sparticles decay via Rp conserved couplings
cascade to LSP which decays into the detector or outside the detector depending on the dominant coupling considered
11/06/01
SUSY'01 - F. Déliot

18. Resonant Slepton Production
Déliot et al., EPJ C 19 (01) 155
dominant coupling: ’
chargino or neutralino singly produced
4 possible channels:
(̃) in pb
’211=0.09, < 0, tan  = 2
(̃) in pb m0 m0 M2 M2

19. Resonant Production: Dimuon Channel
DØ, preliminary
dominant coupling: ’211
resonant ̃ or ̃ production
channel:  2 muons +  2 jets
background: tt̅, Z+2jets, WW+jets p
1o ~  L _
1o ~
 u d
1- ~
l - l
W -
1o d
1- ~ +  _
Run I Results:
Lint= 94  5 pb-1
Events observed: 5
Expected Bkg: 5.34  0.07
1o ~
 u d
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SUSY'01 - F. Déliot

20. Resonant ’211 : Dimuon Channel in Run I
A0=0, < 0, tan  = 2
s̅=1.8 TeV
Exclusion contours at 95% CL down to ’211 =0.07
and m0 200 GeV
m1/2  220 GeV
Indirect 2  limit
for m̃ = 100 GeV:
’211 =0.06
11/06/01
SUSY'01 - F. Déliot

21. Resonant ’211 in RunII: Trilepton Channel
Déliot et al., EPJ C 19 (01) 155
search for trilepton channel via resonant sneutrino production
s̅=2 TeV, A0=0, < 0, tan  = 1.5
11/06/01
SUSY'01 - F. Déliot

22. RunII Trilepton Channel: Mass Reconstruction
allow mass reconstructions:
simulation: M̃01=77.7 GeV, M̃+1=158.3 GeV, M̃=236 GeV
2 jets and softer muon: M̃01=71 GeV (9)
Lint = 10fb-1
’211 = 0.09
11/06/01
SUSY'01 - F. Déliot

23. Resonant ’211 in RunII: Dimuon Channel
search for dimuon channel via resonant smuon production
Lint = 2fb-1, ’211 =0.05
A0=0, < 0, tan  = 1.5
Lint = 10fb-1
’211 =0.05
11/06/01
SUSY'01 - F. Déliot

24. Resonant Squark Production
Berger et al., PRD 63 (01)
dominant coupling: ’’3jk
resonant stop production, decay to: b ̃+1 and ̃01 decays outside the detector
channel: 1 b-tagged jet, 1 e or 1  + E̸t
background: Wc, Wj with c or j that mimics a b, Wbb̅, Wcc̅, single top via Wg
1+ ~ l l W
1o d
1+ ~ b t s
11/06/01
SUSY'01 - F. Déliot

25. Resonant ’’3jk in Run I for Mt̃ = 255 GeV,
s̅=1.8 TeV, Lint = 110pb-1
for Mt̃ = 255 GeV,
’’312 < 0.08 at 95 % CL
Indirect 2  limit
for m̃ = 100 GeV:
’’312 =0.50
11/06/01
SUSY'01 - F. Déliot

26. Resonant ’’3jk in RunII
s̅=2 TeV, Lint = 2 fb-1
11/06/01
SUSY'01 - F. Déliot

27. Conclusion DØ searches for R-parity violation in RunI:
large number of R̸p couplings explored
 No sign of R̸p SUSY found
DØ RunII will provide a wide range of improved coupling limits and a great discovery potential:
 20  more luminosity (2003)
10% more energy
improved detectors
 large increase on R̸p coupling and mass sensitivity
11/06/01
SUSY'01 - F. Déliot