lep searches in r-parity violation scenarios
DESCRIPTION
LEP searches in R-parity Violation scenarios. Theodora D. Papadopoulou NTU Athens. July 25 - Amsterdam ICHEP 2002. Outline. Introduction RPV Superpotential Decays via trilinear RPV Couplings Search strategies Review of Updated Analyses Results - PowerPoint PPT PresentationTRANSCRIPT
LEP searches in R-parity Violation scenarios
Theodora D. Papadopoulou
NTU Athens
July 25 - Amsterdam ICHEP 2002
ICHEP 2002 Th. D. Papadopoulou2
Outline
• Introduction
• RPV Superpotential
• Decays via trilinear RPV Couplings
• Search strategies
• Review of Updated Analyses Results
• Exclusion plots and limits
• Summary
• Conclusion
• As an Epilogue
ICHEP 2002 Th. D. Papadopoulou3
Introduction
• What is Rp and why go beyond ?
a discrete multiplicative symmetry in SUSY models connected to matter parity
R p = 1 for SM particles
R p = -1 for SUSY particles
o SUSY particles produced in pairs
o LSP is stable
o experimental signature of SUSY E T miss
fast proton decay is suppressed
ICHEP 2002 Th. D. Papadopoulou4
RpV Superpotential
kjikjikjikjikjikji DDUDQLELL W
• Rp can be explicitly broken by trilinear terms in the superpotential
o single sparticle production via a ΔL 0 or a ΔB 0 operator
o Unstable LSP !
o Signature of multilepton or multijet events in excessfast proton decay is suppressed if Lepton and Baryon number Violating Couplings are not simultaneously present
0L 0L 0B
9 Couplings )( ji 27 Couplings 9 Couplings )( kj
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Decays via trilinear RPV Couplings
Decay topologies
9 λijk + 27 λ´ijk + 9 λ´´ijk = 45 new couplings
Hierarchies in RpV Couplings expected ( as for Yukawa Couplings generating fermion masses)
• direct decays
multileptons - multijets
• indirect decays
ICHEP 2002 Th. D. Papadopoulou6
LSP Decay Length
Decay Length of
01
~5
~
4~
2
1
100
1
m
GeV
GeV
mL f
• LEP analyses are sensitive only if the LSP has a negligible lifetime ( L < 1 cm )
GeVmx 10~
~ 10 –5 < λ < 10 –2 up to 1
Displaced Vertices < λ < indirect SM bounds
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Search strategies
Suppose one Coupling λi j k
(´ ´´) 0
Consider that many channels have to be combined
Optimize Signal selection on various topologies
--with sequential cuts : ALEPH, OPAL, L3, DELPHI
--using lepton identification and lepton isolation criteria
-- with neural network methods : DELPHI
-- using jet algorithm, b tagging
Calculate signal reconstruction efficiency
-- optimization on different mass combinations depending on the decays and the kinematics
If no significant deviation from the SM, set 95 % CL limits on:
*cross-sections * couplings and sparticle masses * exclusion plots in the MSSM
regions
)ELL(
)DLQ , ELL(
)DDU(
) DDU , DLQ (
ICHEP 2002 Th. D. Papadopoulou8
Theoretical Framework of searches
Minimal SUSY scenario :
• Topologies predicted in a Constrained MSSM =>
• gaugino mass unification ( M1 0.5 M2 ) at EW scale
• Mass universality at GUT scale =>
• Trilinear terms are set to 0 => Ab,t,τ = 0
• Μixing angles for stop and sbottom =>
Bounds on RpV Couplings at EW scale:
λ : ~ 5. 10-2 λ´ : ~ 2. 10-2 (131) up to 0.56 (232)
λ´´: ~ 0.5 up to ~1.23 (except λ´´112 = λ´´121~ O(10-9), λ´´131 = λ´´113=10-4 )
( for a sparticle mass of 100 GeV/c2 )
CMSSMCMSSM
μ, tanβ, m0 μ, tanβ, m0
bt ~~ ,
ICHEP 2002 Th. D. Papadopoulou9
LEP 2 Data
• LEP 2 : 5 years of data taking
Ecm up to 209 GeV ~ 714 pb-1 per experiment
Year Ecm <L/Exp>
GeV pb-1
1996 161-172 ~ 20
1997 183 ~ 551998 189 ~170 1999 192-202 ~230 2000 204-209 ~227
• Backgrounds :
* Four fermions (ZZW+W-)
f f ( γ )
γ γ
• Signal :
generated using
SUSYGEN 2.2 (3.0 )
No evidence for a significant signal observed in all the RpV searchesMANY LIMITS (at 95 % ) are derived
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Single sneutrino production
• Resonant sneutrino production
probes masses up to Ecm
~,~
• Single gaugino production
Analysis of final states : 3 topologies
2 leptons and Emiss
4 or 6 leptons (with or without Emiss)
leptons + jets
• Couplings λ121 , λ131
2kji
limits on λ 1. – 3. 10-3
DELPHI
for tanβ=1.5 or 30.
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Single sneutrino production
• single sneutrino production : ~,~,~
e kj le ~ALEPH
• Couplings λ1jk and λ231
• multi – lepton final states
( direct / indirect )
6 analyses
Upper limits on λ~ 7. 10-3 - 3. 10-2 ( for a sneutrino mass of 100 GeV/c2 )
ICHEP 2002 Th. D. Papadopoulou12
Gaugino pair production
λ
2, 4 and 6 leptons (+ Emiss)
λ´ 2, 4 jets +lepton(s)
(+ Emiss)
λ´´multijets + leptons
(+ Emiss)
• Final states
• indirect decay is the dominant decay channel in almost all the MSSM parameter space
~
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Limits from Gaugino searches
• Limits in MSSM parameter space Scans in μ , Μ2
for different values of m0
and tanβ
DELPHI
λλ
λ´ λ´´
λ
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Gaugino mass limits
λ
λ´´
• Μass limits at 95 % CL in GeV/c2
λ λ´ λ´´
L 40.2 — 39.9
D 39.5 — 38.0
L 84.0 — 80.0
L 107.2 — 107.2
A 103 103 103 D 103 102.5
L 103.0 — 102.7
01
~
02
~03
~
1~
A D L O
λ
DELPHI
DELPHI
NEW
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slepton pair production
• Direct decay :
• Indirect decay :
fermionsllee 4~~
fermionsllee 8~~ 01
01 ~,~,~e
λλ´´
μ=200 GeV/c2, tanβ=1.5, BR=1
~
ALEPHDELPHI
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slepton pair production
• MSSM exclusion contours,
at 95 % C.L.
• Cross-section upper limits, at 95 % C.L.
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Sneutrino pair production
~,~,~e
• Direct decay :
• Indirect decay :fermionsee 4
~~ )2(8~~ 0
10
1 fermionsee
Excluded cross-section ( 4 jets )
~~ Excluded contour , at 95% CLfor for indirect decays ~,~
ALEPH DELPHI
λ
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Squark pair production
• Direct decays :
=> => 4 fermions
• Indirect decays :
=> => 8 fermions
qq~~
01
01
λ´´
ΜSSM
Exclusion contours,at 95% CL
ICHEP 2002 Th. D. Papadopoulou19
Squark pair production
bt~
,~• Mixing : qRqL ttt ~~1 sin~cos~~
λλ´´
0~ 56t
0~ 68b
Mixing angle for vanishing coupling to Z for => σ min
• Exclusion contours at 95% CL
bt~
,~
1
~b
1~t
ΑLEPHDELPHI
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Single top production
)()(
)()(
ucbluctee
ucbqquctee
• Analysis with neural network method
• b tagging used
λ´
pb11.0limitupper
( σ upper limit at 95 % CL )
DELPHI Preliminary
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LSP Mass Limit with RpV
01
~• production cross-section of
vrs mass in all μ , all M2 tanβ(2-4),
m0(200-500) GeV/c2
01
~
• Limits are set at 95 % CL
via a dominant Coupling
λ133 or λ´311 or λ´´223
60.2 44.2 42.2 (GeV/c2)
LSP
Mass limits
ALEPH PRELIMINARY
DDU DLQ ELL
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New lower mass Limits (GeV/c2 ) ADLO
sfermion λ (dd) λ´(dd) λ´´(dd) λ (id) λ´(id) λ´´(id)
96 69 (89) (89) 96 96 79 99 95 93 92 94 96 92
87 61 (74) (81)(77) 86 96 87 92 90 90 87 85 86 87
87 61 (74) (76) 75 95 86 90 90 76 - - 75 -
100 95 90 90 99 98 99 95 98 91 88 88 99 -
90 65 76 79 75 7089 78 81 85
78 - 65 70 -
- 65 76 75 70 89 78 81 85 78 - 65 70 -
- - - (97) - (91) (85) (71.5) (87)
- - - - - (90) (80) (71.5) (78)
- - - -(82.5)
80 (87)- - 79 (87)
- - - -(77 )
56 (86)- - 55 (86)
~
)~(~LR ee
)~(,~LR
e~
~
t~
b~
)~( Lt
)~
( Lb
)~(~LR uu
)~
(~
LR dd
)~(~LR
ICHEP 2002 Th. D. Papadopoulou23
Conclusions
• RpV has inspired new interesting scenarios of SUSY searches
• RpC and RpV are two complementary ways of SUSY searches
• Searches for SUSY with RpV performed by all LEP collaborations ( ADLO) in …many channels ….
• No evidence for SUSY with RpV so far at LEP
• Limits on SUSY particles and RpV Couplings are set at 95% CL
• Limits from RpV searches are comparable with the RpC ones!
ICHEP 2002 Th. D. Papadopoulou24
As an Epilogue
….. Many papers and … many searches on SUSY !
….. but there is NO evidence up to now
SUSY with RpV
predicts very clear signatures especially for couplings
with
all hopes are shifted
towards future colliders !
),(0 DLQELLL