PowerPoint プレゼンテーション

Tauonic B decays in the MSSM
arXiv : hep-ph/0409228
YITP : 2005.1.13
Hideo Itoh (Ibaraki univ., KEK)
in collaboration with
S.Komine(KEK), Y.Okada(KEK,SOKENDAI)
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0: Overview of the physics of the B and SuperB Factory
The current experiments
Asymmetric B factory experiments(1999～)
KEKB(KEK) : Belle experiment (～340fb-1)
PEPⅡ(SLAC) : BaBar experiment (～250fb-1)
The first purpose of the B factories
Precise test of the CKM picture
It succeeded!
for the CPV
Ex.
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The history of the integrated luminosity
2004 summer
2003 summer
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What is the next purpose of the B factories?
We look for deviation from the SM:
Correction from new physics beyond the SM
We need more Luminosity and far precise test.
In particular:
Processes of the final state including
more than two neutrinos
tauonic B decays : B→Dτν, B→τν
To identify these processes, we have to accumlate
more luminosity.
Necessity of the SuperB
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Motivation of the SuperB Factory
(Letter of Intent for KEK Super B Factory, hep-ex/0406071)
SuperB Factory : Goal of the luminosity is 50-100 times more
than the current achieved luminosity.
・SuperB is focused on studies for new physics (NP).
・LHC may find NP, but the information from LHC are not
enough to distinguish between NP models.
・SuperB provides much information for the NP models
from following measurements.
LC
- New CP phase
LHC
- LFV (τ→μγ, τ→eγ,…)
- Tauonic B decays
EDM
LFV
- etc…
B physics
These results are useful to
K physics
Muon g-2
combine with the LHC results.
Charm physics
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(Okada san)
KEKB Upgrade Scenario
Lpeak (cm-2s1)
Lint
1.4x1034
280 fb-1
5x1034
1 ab-1
Super-KEKB
(major upgrade)
5x1035
10 ab-1
5x109 BB
/year !!
& also t+t-
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1. Introduction
Two types of the SUSY effects on B physics
1. For the FCNC processes (b→sγ, Bs→μμ, B→φKs…)
Ex.)
SM (loop)
SUSY (loop)
2. For the Tauonic B decays (B→Dτν, B→τν)
Ex.)
SM (tree)
SUSY (tree)
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Important features of the tauonic B decays
・Charged Higgs boson can contribute to the decay
amplitude at the tree level in the MSSM.
・At least two neutrinos are present in the final state
in the signal side.
Full-reconstruction is required for
the B decay in the opposite side.
It is difficult to probe the tauonic B decays.
However we may probe the charged Higgs effects on
the B physics if we can probe the tauonic B decays.
Full-reconstruction efficiency is 10-3.
So we need more and more luminosity to probe the tauonic B decays.
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SM prediction and current experimental results
The branching ratio of the tauonic B decays at the SM
・B→Dτν : 8×10-3
・B→τν : 9×10-5
・B→Dτνis larger branching ratio.
There is no experimental data.
We have not probed B→Dτνat both B factories.
・B→τνis smaller branching ratio due to helicity suppression.
Experimental data
- Upper bound from Belle : 2.9×10-4
- Upper bound from BaBar : 3.3×10-4
These processes are important target of the SuperB Factory.
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The b→c(u)τυ processes in the MSSM
Contributing diagrams
SUSY corrections
Also there are SUSY corrections to the Yukawa couplings
SUSY correction to yd is induced due to 1-loop diagrams.
(K.S.Babu & C.Kolda, M.Carena, et al)
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This correction affects the branching ratios
for some other processes too.
Ex. BS→μμ (A.Dedes & Pilaftsis, et al)
b→sγ (G.Degrassi & P.Gambino & G.F.Giudice, et al)
…
We study B￫Dτν and B￫τν in MSSM
・Assume the Minimal Flavor Violation case
Explain later・・・
・SUSY correction to H±-c (u )-b and H±-τ-ν vertex
・Correlation between b￫sγ, Bs￫μ+μ- and tauonic
B decays.
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2: Formalism (A.Dedes & A.Pilaftsis)
Framework: MSSM with MFV and large tanβ
Tree level Yukawa couplings have the same structure
as that of the superpotential.
Different types of the tree level Yukawa couplings
are induced by SUSY effects through 1-loop diagram.
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MSSM with Minimal Flavor Violation (MFV)
Minimal Flavor Violation
Squarks have the same flavor structure as one of the quarks.
In other words, the flavor changing source is only the KM matrix.
・Not MFV case
The large deviation from SM is possible generally.
Because there are many flavor mixing parameters.
・MFV case
The large deviation from SM is possible for large tanβ.
tanβ is the ratio of the two vacuum expectation values
of the neutral Higgs.
This assumption comes from mSUGRA, GMSB, AMSB ・・・.
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Under the Minimal Flavor Violation
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Under the Minimal Flavor Violation
Loop function
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SUSY corrections to the charged Higgs couplings
Charged Higgs coupling including SUSY correction :
(“
“ denotes a diagonal matrix.)
For the correction to the down-type Yukawa coupling
The SUSY corrections at b→u,c are given by
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In Minimal Flavor Violation case
・gluino-sbottom contribution
・higgsino-stop contribution
Higgsino contribution becomes too small
in comparison with gluino contribution.
at MFV
For the correction to the lepton Yukawa coupling
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These SUSY corrections appear via the following combina
-tion of the parameters in the branching ratio formulas.
SUSY effects are absorbed into
the value of tanβ. I will explain later.
If there are no SUSY corrections (Ex. 2HDM case)
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Intuitively, these SUSY corrections become the vertex correction like below.
2HDM
SUSY
Also we can see the following results.
In MFV case
B→Dτν
B→τν
There is a correlation between the tauonic B decays at MFV!
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SUSY parameters for
the tauonic B decays at MFV
・Tree-level charged Higgs effect depends on the following parameters.
・The SUSY corrections to the Yukawa couplings depend on the follow
-ing parameters with tanβ.
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3: Numerical results
The SUSY correction matrix elements
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3: Numerical results
The SUSY correction matrix elements
At above parameter space, the SUSY correction to the
lepton Yukawa coupling becomes sizable in comparison
with the down-type Yukawa’s one.
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Branching ratio for B￫Dτν and B￫τν at tanβ = 50
B￫Dτν
B￫τν
μ = -400GeV
μ = 400GeV
μ = -400GeV
μ = 400GeV
SM
No SUSY cor. case
SM
No SUSY correction case
μ is the higgsino mass parameter.
The SUSY corrections drastically contribute to the branching ratio.
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The correlation of the two processes as a function of
Theoretical uncertainties :
・Vertical error :
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5
20
15
10
SM
・Horizontal error :
・SuperKEKB : 5ab-1
Sensitivity to
reach to 11
In MFV, SUSY effect can be absorbed into an effective tanβ.
The correlation itself is the same as the 2HDM,
and so one cannot distinguish them.
It is thus interesting to compare it with other experiments.
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Effect on other process: b￫sγ
Au=Ad=-100GeV
no SUSY corr.
Au=Ad=-100GeV
Au=Ad=100GeV
no SUSY corr.
Au=Ad=100GeV
Au and Ad are trilinear scalar couplings
・Charged Higgs and chargino-stop diagrams contribute.
・For μ<0 case, fine-tuning of parameters is necessary.
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Effect on other process: Bs￫μ+μUpper bound from exp.
Au=Ad=-100GeV
Au=Ad=100GeV
Au=Ad=-100GeV
Upper bound from exp.
・SM prediction : 3.4×10-9
・Receive the large SUSY corrections
・μ<0 case is strongly restricted by b￫sγ
Au=Ad=100GeV
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4. Summary
MSSM with MFV at large tanβ : B￫Dτν and B￫τν
Receive large correction via SUSY loops.
The correlation between Br[B￫Dτν] and Br[B￫τν] in MFV
SUSY loop effect
absorbed into the effective tanβ
Correlation is same as the 2HDM
Important to compare : measurements of Br[B￫Dτν] and Br[B￫τν]
(SuperB Factory )
: measurements of tanβ (LHC )
Ex. ・heavy Higgs direct production
・chargino/neutralino mixing
・stau decay
b￫sγ and Bs￫μ+μ- : receive large correction generally
in the same parameter space
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