sanjay k swain, slac babar collaboration 27 th july 2007
DESCRIPTION
t -decays in B-factories. Sanjay K Swain, SLAC BABAR Collaboration 27 th July 2007. SUSY07 @ Karlsruhe. Outline. Introduction t l g ( l = e, m ) t l K s t l P 0 (P 0 = p 0 ,h,h ’) t lll / l hh (h = K, p ) t L h Conclusion. - PowerPoint PPT PresentationTRANSCRIPT
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Sanjay K Swain, SLAC BABAR Collaboration 27th July 2007
Outline• Introduction• l (l = e, )• lKs
• lP0 (P0 =’)• lll / lhh (h = K, )• h• Conclusion
-decays in B-factories
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Lepton Flavor Violation (LFV) in -decays • In the minimal Standard Model, the lepton flavor is conserved for each generation
e.g is not allowed LLL = 1 L =0 L 1 L = -1 but L = 0
• But neutrino oscillation implies:
e => Lepton Flavor is violated
• The LFV in neutral sector induces LFV in charged lepton sector
ee-
Le =1 L L L = Le + L + L
But B) M
Mw2
2
Mw ~ 1011 eV
M2 ~ 10-3 eV2
~ 10-54
Lee-Shrock, Phys. Rev. D 16, 1444 (1977)
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New physics phenomena in -decays
Things would be completely if we replace
Now B) MMx
2
M and Mx have different (higher) mass scale~~
2
The slepton have same lepton numbers and do have mixing
~ ~
The branching fraction can be enhanced significantly
1.
2.
2
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KEKB at KEK
BelleBaBar
9GeV (e) 3.1GeV (e+)peak luminosity:
1.121034cm2s1
8GeV (e)3.5GeV (e+) peak luminosity:
1.711034cm2s1
PEP-II at SLAC
B-factories
Two asymmetric energy B-factories
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PEP-IIfor BaBar
July 2006
KEKBfor Belle
KEKB + PEP-II
710/fb (Jan 07)710/fb (Jan 07)
391/fb (Jan 07)391/fb (Jan 07)
Integrated Luminosity
more than 1 billion (109) -pairs
Cross Section 1.05 nb 0.92 nb
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-decay topology
e+e-
electron/muon
Signal side
Tag side
tag
missing
• Two hemispheres thrust (separated in space)
• Signal side: neutrino-less 1-prong decay electron / muon (all the particles are fully reconstructed)
• Tag side: 1-prong or 3-prong e
MEC : beam energy constrained mass
E: energy difference E - Ebeam
Sometimes, variables used are Eand M = Mrec – M
Signal MC
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-1.0 0.51.5
2.0M
ec (
Gev
/c2 )
E (Gev) 0.0
±3 blinded region
±2 signal region
For lthe expected background in the signal box is obtained by fitting the sidebands of MEC distribution from the ±2 band in E where as
for lP0, the background is obtained by 2D un-binned maximum likelihood fit to un-blinded region in MEC and E.
We look for the expected and observed backgroundin the neighboring regions to validate the fit
Analysis methodology
GSB: E[-1.0, 0.5] and MEC[1.5,2.0]
For lP0: -0.8
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Results from l
Efficiency=2.99%
BF (e ) < 12 x10-8
Efficiency=5.07%
BF ( < 4.5 x 10-8
Efficiency=(4.7±0.3)%
BF (e ) < 11 x10-8
Efficiency=(7.42±0.65)%
BF ( < 6.8 x 10-
8
PRL 96, 041801 (2006)
PRL 95, 041802 (2006)
ar-Xiv:0705.0650 [hep-ex]
Signal MC
Data
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MSSM with seesaw:
Results from land impact on new physics
tan<vu>
<vd>
Vu,d are VEVs of neutral higgs coupledto up-type or down-type fermion fields
S. Banerjee (Tau06)Nucl. Phys. Proc.Suppl. 169, 199 (2007)
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lKs (l= e or ) BELLE used 281 fb-1 data
B (eKs ) < 5.6 x 10-8
@90% CL
B (Ks ) < 4.9 x 10-8
In R-parity violating SUSY scenario , ’, ’’ ( with 45 couplings)
2. This result can be used to constrain new physics scale in dimension-six fermionic effective operator involving flavor violation motivated by neutrino oscillations
1.
lower bounds on axial-vector and pseudo-scalar operators: 36.2TeV and 37.2 TeV
PLB 639, 159 (2006)
decays lKs via tree level scalar neutrino exchange by ’ coupling
Signal MC
Data
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Signal box(±2 in E and MEC)
Shaded regioncovers 68% ofsignal MC
Total expected events = 3.1
Total observed events = 2
lP0 (P0 = ’)
Using 339 fb-1 data, the upper limit is (1 - 6 ) x 10-7
Data
PRL 98, 061803 (2007)
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401
fb-1
data
These improved upper limit can be used to constrain the parameters of Heavy Dirac neutrino model.
Branching fractions of different modes are evaluated in terms of Model Parameters: ye and y
Using lye 0.17 and y@ 90% C.L
lP0 (P0 = ’)
PLB 648, 341 (2007)
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The left plot shows the Exclusion regions in the mA and tan plane bydifferent experiments
New result from BABAR
Competitive with the direct Higgs searches at CDF and D0
(@ 95% C.L.)
Constraining new physics using result
M.Sher, PRD 66, 057301 (2002)
CDF: pp H fb_
D0: pp H bbfb _
_
fb-1S.Banerjee (Tau 06) Nucl. Phys. Proc. Suppl. 169, 199 (2007)]
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376 fb-1 BABAR data used
Total expected events = 4.2Total observed events = 6
90% of the selected MC events
Signal box
lll ( l = e or )
Upper limits ~ ( 4 – 8) x 10-8
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lhh’ and lV0
Belle used 158 fb-1 datah (h’) K or V0 K
These improved upper limit can be used to constrain the parameters of Heavy Diracneutrino model.
Using lye2 < 0.24 and y
@ 90% C.L
Constraint the energy scale of dimension-six fermionic effective operator
uu,dd 29.4TeV, ss 24.8 TeV and ds 26.8 TeV
1.
2
Signal Box
Decay modes used:
[ e, ] x [ +-, --, +K-,K+-,K--,K-K+,K-K-,
0, k*0, K*0, ] _
22 decay modes
The upper limit varies (1.6 - 8.0) X 10-7
VectorPLB 640, 138 (2006)
(including modes violating total lepton number)
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• The baryon asymmetry of the universe Baryon number violation (Sakharov condition)
• For lepton -> baryon + meson decays, the angular momentum conservation requires, (B-L) = 0 or 2
The following decays modes used in this analysis: (237 fb-1)
Lepton and baryon number violating -decay
(hep-ex: 0607040)
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• If LFV is discovered in near future, it is possible that LFV-inducing particles will be produced directly at high energy. The LFV effects from real particles production may then also be seen at colliders
• Further probe into the LFV using more data can put constraint on different theoretical models.
• None of the lepton flavor violating processes has been observed yet.
• For l, the best upper limit is ~ 4.5 X 10-8
• For lP0, the best upper limits are ~ (1-9) X 10-8
• For lKS, the upper limits are ~ 5 X 10-8
• For lll (hh’), the upper limits are ~ (1 - 8) X 10-8
Summary