Transcript PowerPoint プレゼンテーション

Tauonic, Radiative & Electroweak
B Decays at Super-B
Toru Iijima
Nagoya University
November 9, 2005
“Flavour in the era of the LHC” workshop @ CERN
Based on results and studies by Belle
Letter of Intent for KEK Super B Factory ( KEK Report 2004-4 )
Physics at Super B Factory ( hep-ex/0406071 )
cf) SLAC-R-709, “The Discovery Potential of a Super B Factory”
Proceedings of the 2003 SLAC Workshops
Physics Targets at Super-B



CP violation
B   K 0 , K 0 , K  K  K 0
Precise CKM
1 , 1 , 1, | Vub |, | Vtd |
Search for new origin of
flavor mixing and CPV.
Figure by Dr.Hayasaka (Nagoya Univ.)
Rare decays
FCNC decays
b  s , s , s etc.
This talk
Tauonic decays
b  ct , t etc.

t decays
Lepton flavor violation
t   etc.
Using O(1010) B and t (~100 x now)
2
Tauonic B Decays
Charged Higgs contribution to B decays
 Leptonic: Bt 
mb tan   mu cot 
mt tan 
b
u
Br(SM)
~ 9 x 10-5
H/W
t
 Semileptonic: BD t 
mb tan   mc cot 
c
b
H/W

mt tan 
t
t
Br(SM)
~ 8 x 10-3
B
( B  Dt vt )
( B  Dv )
Decay amplitude  mb mt tan 2 
Tauonic decay is the most sensitive
3 !
Bt  (within the SM)
 Proceed via W annihilation in the SM.
 Branching fraction is given by
 Provide information of fB|Vub|
– |Vub| from BXu l 
– Br(Bt)/Dmd
fB
|Vub| / |Vtd|
cf) Lattice (d~16%)
 Expected branching fraction
| Vub | (3.67  0.47) 103
f B  (0.196  0.032) GeV
Br ( B  t )  (9.3  3.9) 105
4
Full Reconstruction Method
 Fully reconstruct one of the B’s to tag
– B production
– B flavor/charge
– B momentum
B
e
(8GeV)
e+(3.5GeV)
Υ(4S)
p
B
Decays of interests
BXu l ,
BK  
BDt, t
full (0.1~0.3%)
reconstruction
BDp etc.
Single B meson beam in offline !
Powerful tools for B decays w/ neutrinos
5
Fully Reconstructed Sample
 Belle (253fb-1): 275M BB  2.5x105 B0B0 + 4.2x105 B+B-
6
Bt  Status (Belle LP05/EPS05)
 NBB (produced) = 275M
 NB+B- (full recon.)
= 4.0 x 105 (purity 0.55)
 Searched t decay modes
t     , e
t   p  , p p 0 , p p p 
Obtained Eresidual
– Cover 81% of the t decay
 Event selection
– Residual ECL energy
Eresidual  0.3 GeV
– Total net charge
etc.
Q  0
i
i
See K.Ikado’s talk at EPS05
and hep-ex/0507034
7
Cont’d
 Overall
–
–
–
–
Signal efficiency = 33.7 %
Expected signal = 13.5 (SM)
Background est. = 31.4
N observed = 39
Br ( B  t )  1.8 104 (90%CL)
Upper limit calculated by M.L. fit.
tp-  mode has the best S/N ~1.
8
Prospect
 Will soon reach the SM.
– 3s evidence at ~700 fb-1
– 5s discovery at ~2 ab-1
 Expected precision
at Super-B
– 13% at 5 ab-1
– 7% at 50 ab-1
 Search with D(*) l  tag will help.
(BaBar 232M BB, hep-ex/0507069)
– Tag eff ~ 1.75 x 10-3
– Signal selection eff. ~31%
– Similar S/N to Belle
Br ( B  t )  2.8 104 (90%CL)
9
Impact to Charged Higgs

H  effects to branching fraction
rH
tan/mH
90%CL excluded region
at present
95% CL excluded region
at 5ab-1 (if Bobs = BSM)
10
BD t  (MC studies)
 Use fully reconstructed samples.
 T decay modes
t     , e , p  ,  
 Analysis cuts;
– Reject events w/ p, KL
– Reject D(*) t  contamination
mD0  mD0  142  10 MeV/c 2
– No remaining charged or p0 tracks
– ECL residual energy
Eresidual  100MeV
– Angle between two ’s
Signal
BG
1.0  cos  0.8
– Missing mass
pB  pD  p
2
 1.2 (GeV / c 2 ) 2
11
Cont’d

Signal selection efficiency
D 0t  (e  t e ) t
D 0t  (   t e ) t

10.2%
2.6%
D 0t  (p  t ) t
26.1%
13.3%
D 0t  (   t ) t
Expectation at 5 / 50 ab-1 for B+ decay
5ab-1
Mode
Nsig
Nbkg
D0t  ( t )t
280
550
D t (h t )t
620
3600
0 

50ab-1
S
12.7
dB/B
7.9%
Nsig
Nbkg
2800
5500
6200
36000
S
dB/B
40.3
2.5%
5s observation possible at 1ab-1

Major background source
Missing charged and  tracks from BD(*) l  X (incl. slow p)
12
Constraint to Charged Higgs
 Once branching fraction is measured, we can constrain R.
MW
R
tan 
MH
M.Tanaka,
Z.Phys. C67 (1995) 321
Form factor error
 can be determined experimentally
by B semiletonic decays
R  11 at 5ab-1
13
Cont’d
Constraint
From bs
Present limit
From Bt 
14
bs/sl+l Possible to search for NP in theoretically clean way.


, Z
t
W

s
b
W

Effective Hamiltonian for bs
4G F * 10
H eff  
VtsVtb  Ci (  )O(  )
2
i 1
 Many observables;
Branching fractions
Mixing indcued CPV
Direct CPV
Forward-backward asym.
Ratio of exclusive modes
s



t
b
–
–
–
–
–

W
b
W
t
s
|C7| by BXs,
Sign of C7, C9, C10 by BXsll
M(H+) > 350 GeV already
in TYPE II 2HDM
15
Measurement of B(BXsl+l-)
 Semi-inclusive technique
M. Iwasaki et al. submitted to PRD, hep-ex/0503044
140/fb data
– Xs is reconstructed from K+
or Ks + 0-4p (at most one p0
is allowed)
– MXs < 2.0 GeV
 Electron or muon pair
– Mll>0.2GeV
– Charmonium veto
Wrong flavor
MXs
q2
Theoretical prediction by Ali et al.
16
Constraints on Ci from B(BXsl+l-)
P.Gambino, U.Haisch and M.Misiak PRL 94 061803 (2005)
 Clean prediction for B(BXsll) with 1<q2<6GeV2 is available.
– Combine Belle and Babar results
– Sign of C7 flipped case with SM C9 and C10 value is unlikely.
BF
Belle
Babar
WA
SM
C7 = -C7SM
q2>(2m)2
4.11±1.1
5.6±2.0
4.5±1.0
4.4±0.7
8.8±0.7
1<q2<6GeV2
1.5±0.6
1.8±0.9
1.60±0.5 1.57±0.16
C10NP
C7
SM
C10NP
C7 = -C7SM
3.30±0.25
Donut : 90% CL
allowed region
SM
C9NP
17
BK*ll FB Asymmetry
 Good electroweak probe for bs loop.

q2
distribution has different pattern
depending on sign(C7).

, Z
AFB   C10* ( sC9eff ( s )  r ( s )C7 ) 
W
sb

Forward
B
l

AFB
l
q2 (GeV 2 )
W
W
s
t
Backward
B

K*



t
b

l
K*
l
q0(the point w/ AFB=0) is
sensitive for New Physics
SM; q02=(4.2±0.6)GeV2
18
 357fb-1 (386M BB)
 N(K*ll)=114+-14 (purity 44%)
 Unbinned M.L. fit to d2/dsd(cos)
– 8 event categories
• Signal + 3 cross-feed + 4 bkg.
– Ali et al’s form factor
– Fix |A7| to SM
– Float A9/A7 and A10/A7
A10/A7
AFB: Belle Summer ‘05
A10/A7
ＳＭ
A9/A7
A9/A7
 Results;
w/negative A7 (SM like)
w/positive A7
Sign of A9A10 is negative !
See Hep-ex/0508009 &
A.Ishikawa’s talk at EPS05
19
Prospect at Super-B
1000 pseudo experiments w/ SM input values
Expected precision @ 5ab-1
dC9 ~ 11%
dC10 ~14%
d q02/q02 ~11%
5% at 50ab-1
20
Radiative Decays





Inclusive Br(bs)
BK* isospin asymmetry (D+-)
Mixing induced CPV
Direct CPV in BXs
BXd 
|C7|, SF for |Vub|
sign of C7
Summary by M.Nakao
1st Super-B workshop
at Hawaii
21

BXs CP Asymmetry
 Sensitive to NP.
 Theoretically clean.
 Standard Model “~Zero”.
– Gamma is polarized, and
the final state is almost
flavor specific.
– Helicity flip of 
suppressed by ~ms/mb
 Time dependent CPV requires
vertex reconstruction with Ks
p+pVertex recon. Eff.
51% (SVD2)
40% (SVD1)
t
b
mb
ms
b
b
s L
C7
s
W
ms
mb
s R
p p
Ks trajectory
B vertex
IP profile


s x  100m, s y  5m, s z  3mm,
Possible at e+e- B-factory
22
B0KSp0 tCPV: Belle Summer ‘05
 386MBB
Atwood, Gershon, Hazumi, Soni,
PRD71, 076003 (2005)
 M(Ksp0) < 1.8GeV/c2
– NP effect is independent of the resonance structure.
 Two M(Ksp0) regions(MR1:0.8-1.0GeV/c2 / MR2: <1.8GeV/c2)
 70+-11 (45+-11) events in MR1(2).
Result
S= +0.08 ±0.41 ±0.10
A= +0.12±0.27±0.10
Good tag (0.5<r<1.0)
Present Belle
(stat./syst.)
Acpmix(BK*, K*Ksp0) 0.41 / 0.10
Acpdir(BXs)
0.051 / 0.038
5ab-1
50ab-1
0.14
0.04
0.011
0.005
23
Acp(BXs) vs SUSY models
5ab-1
50ab-1
Mixing CPV
U(2)
tan=30
mSUGURA
tan=30
Acpmix
Acpdir
Direct CPV
mSUGURA
tan=30
SU(5)+R
tan=30
SU(5)+R
tan=30
degenerate
SU(5)+R
tan=30
non-degenerate
degenerate
mg (GeV )
U(2)
tan=30
SU(5)+R
tan=30
non-degenerate
mg (GeV )
T. Goto, Y.Okada, Y.Shimizu,T.Shindou, M.Tanaka
hep-ph/0306093, also in SuperKEKB LoI
24
Summary
 Tauonic, Radiative and Electroweak B decays are
of great importance to probe new physics.
 We are starting to measure Bt, Dt, AFB(K*ll),
ACP(Kp0) etc. at the current B factories.
Hot topics in the coming years !
 For precise measurements, we need Super-B !
Expected precision (5ab-150ab-1);
–
–
–
–
Br(tv):
Br(Dt):
q02 of AFB(K*ll):
ACP(Kp0) tCPV:
13%7%
7.9%2.5%
11%5%
0.140.04
25
Backup Slides
26
CPV in bs and SUSY Scenario
 Different SUSY breaking scenario can be distinguished in
Acpmix(Ks) - Acpmix(K*0) correlation.
Expected precision at 5ab-1
Correlation of other ovservables are also useful.
Acpdir(Xs), AFB(Xsll), Br(t), CKM
27
28
29