1. Akimasa Ishikawa (Tohoku University)
bsg Exclusive Decays
Akimasa Ishikawa
(Tohoku University)

2. Evidence for bsg
CLEO found an evidence for bsg process using exclusive BK*(892)g decays in 1993 with only 1.38fb-1 data on Y(4S).
More than 20 years has passed from the evidence and now….

3. Now we are here
Now we (Babar and Belle) have more than 800 times larger data of 1144fb-1 (433fb-1+711fb-1) on Y(4S) than data with which CLEO found an evidence for bsg.
Further, LHCb collected 3fb-1 at 7TeV and 8TeV at pp collisions.
sbb = 7.7mb for pTbb > 5GeV and 2.5 < h < 4.0 at 7TeV
Copious numbers of B hadrons are available.

4. Ideal tool to search for new physics
Exclusive bsg decays can be used to measure
Branching fraction (BF)
Fragmentation of Xs
Direct CP Violation (ACP)
To Search for New phase
Time dependent CP Violation (SCP)
For B0fCPg modes
to search for right handed current/new phase
CPV is suppressed by O(ms/mb)
Isospin Violation (D0+ or AI)
Spectator dependent operator
Up-Down Asymmetry (AUD)
For BK1gKppg
To search for right handed current
New physics makes |AUD| value smaller than the SM
Photon Polarization from conversion (no groups measure yet)

5. Observed Exclusive Decays
Now we observed
BK*(892)g in 1993
BK2*(1430)g in 2000
BKfg in 2004
BKhg in 2005
BK1(1270)g in 2005
BpLg in 2007
BKh’g in 2010
Only 40% are exclusively known!

6. Direct CPV
In the SM, bsg process is dominated by single EW penguin diagram, and further weak phase in Vts is suppressed by O(l2), so direct CPV in bsg is small.
E.g. ACP(BK*(892)g) = -0.6±0.4%
If new physics contribution to bsg has sizable amplitude and weak (+strong) phase, direct CPV could appear.
Is the difference of direct CPV btw B0 and B+ interesting/sensitive NP also for exclusive decays?
Benzke, Lee, Neuber and Paz propose it for inclusive decays as a sensitive probe for new physics.
Matsumori, Sanda, Keum

7. Direct CPV in BK*(892)g LHCb reported ACP with 1fb-1
Only with K*0K+p-
W.A. consistent with null asymmetry predicted in the SM
-0.6±0.4 %
exp error 3times larger than theo
LHCb 1fb-1  3fb-1
Belle 78fb-1  711fb-1
Matsumori, Sanda, Keum
ACP B0 B+ B
Babar 347fb-1
-1.6±2.2±0.7 %
1.8±2.8±0.7 %
-0.3±1.7±0.7 %
Belle 78fb-1
n.a.
-1.5±4.5±1.2 %
LHCb 1fb-1
0.8±1.7±0.9 %
Average
0.7±1.9 %
1.8±2.9 %
0.1±1.3 %

8. Isospin Violation Isospin Violation can be calculated in the SM.
+5.0 ~ +10 %
+2.7±0.8 %
If new physics has isospin breaking contributions, such as spectator dependent diagrams, D0- could be deviated from the SM value
Even sign of Isospin Violation flips
Kagan, Neubert
Matsumori, Sanda, Keum

9. Isospin Violation in BK*(892)g
Babar and Belle measured isospin violation
thanks to high reconstruction efficiency for Ks and p0 involved modes at e+e- machine
Consistent with SM Predictions
+5.0 ~ +10 %
+2.7±0.8 %
Kagan, Neubert
Matsumori, Sanda, Keum
D0-
Babar 347fb-1
6.6±2.1±2.2 %
Belle 78fb-1
1.2±4.4±2.6 %
Average
5.2±2.6 %

10. Time dependent CPV
In the SM, photon emitted from b is predominantly left handed. Time dependent CPV in BfCPg is small due to small interference
If new physics has right handed current, time dependent CPV emerges by interference.
Gluon emission bsgg processes make SSM larger than naive calculation??
Atwood, Gronau, Soni
Atwood, Gershon, Hazumi, Soni
SSM ~ O(0.1)
Grinstein, Grossman, Ligeti, Pirjol
Grinstein, Pirjol
Matsumori, Sanda
Ball, Zwicky

11. Time Dependent CPV in BKhg
Preliminary
Time Dependent CPV in BKhg
711fb-1
Recently Belle reported measurement of time dependent CPV in BKhg with full data
Measured values are out of physical boundary but consistent with null CPV.
SM prediction

12. Summary of time dependent CP Violation
Four decay modes are used to search for time dependent CPV.
fCP = Ksp0(K*0), Ksh, Ksr, Ksf
All are consistent with null with stat errors.
fCP
Babar
Belle
Ksp0 (K*0)
427fb-1
495 fb-1
Ksh
711 fb-1
Ksr
n.a.
605 fb-1
Ksf

13. Up Down Asymmetry
Gronau, Grossman, Pirjol, Ryd
Polarization of photon can be extracted from the BK1g(Kpp)g process by measuring up down asymmetry (photon polarization from K1 polarization).
Angle q btw photon and normal vector to K1 decay plane.
Interference btw rK and K*p generates imaginary part.
 modes involving p0 gives larger AUD
Need theoretical calculation of the amplitudes

14. Up Down Asymmetry in BKppg
LHCb observed AUD with 3fb-1 in BK+p-p+g
With 13876±153 signal events
Measure AUD with 4 bins of MKpp
No resonance separation
5.2s significance from null polarization
No interpretation to photon polarization yet

15. Given title is bsg exclusive decays but I would add bdg
bdg Exclusive Decays
Given title is bsg exclusive decays but I would add bdg

16. bdg Decays The bdg is suppressed by Vtd
About 30 times smaller than bsg ( |Vtd/Vts|2 )
Need very good PID detector and EM Calorimeter
The observables to search for NP are the same as the bsg but NP contribution could be different.
Branching fraction (BF)
Direct CP Violation (ACP)
Time dependent CP Violation (SCP)
Isospin Violation (Dr)
Up-Down Asymmetry (AUD)
Photon Polarization from conversion (no groups measure yet)

17. Observation of bdg
Belle had observed bdg process using exclusive B(r, w)g with 357fb-1 data in 2006

18. |Vtd/Vts|, ACP and Dr
|Vtd/Vts| can be measured from the ratio of BF of B (r,w)g and BK*g
Consistent with the SM
Direct CPV in Br+g consistent with null
Dr Isospin Violation large?
2~3s deviation %
- 10±6 %
- 5.4±3.9 % if f3 = 60deg
- 4.6±7 %
Ali, Lunghi
Lyon, Zwicky
Ball, Jones, Zwicky
Beneke, Feldmann, Seidel
|Vtd/Vts|
ACP(B+r+g) Dr
Babar 423fb-1
n.a.
Belle 605fb-1
Average

19. Time Dependent CPV in B0r0g
Only Belle had measured time dependent CPV in B0r0g
48±14 signal events are used for fits.
Though signal yield is smaller than B0Ksp0g, fraction of events used for time dependent fit is larger thanks to easier vertex reconstruction with r0p+p-
The results are consistent with null asymmetry

20. Summary
Many studies of bsg are performed in more than 20 years to search for new physics.
No hint of new physics yet.
New window bdg was opened since 2006.
A hint in Isospin Asymmetry??
Some analyses in bsg and all analyses in bdg are still statistical error dominant
Need higher luminosity experiments
 Belle II and LHCb upgrade
Some theoretical predictions are different btw groups.
Isospin violation
Time dependent CPV
Hope the predictions improved in coming several years.

21. backup

22. CCP = - ACP