1. EW Penguin & Leptonic B decays
Youngjoon Kwon
Overview
Prologue: Introduction & History
Modes w/ 0 n’s
Modes w/ 1 n’s
Modes w/ ≥2 n’s
Summary & Prospects

2. Physics Goals of B-factories
Establish CP violation in B decays and
over-constrain the SM picture of CP violation
any inconsistency?
Measure fundamental parameters of SM
10 (out of 18, not counting neutrino masses, yet) parameters are related with quark flavors
CKM triangle parameters; angles & sides
Search for rare / forbidden decays and
explore new physics effects
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

3. Motivation for Rare B decays
SM is a very good approximation to reality.
i.e., for most processes
Need to consider processes where is small in order to be sensitive to new physics.
(Ex.) processes dominated by penguin loops
Compare Nature (exp.) with SM prediction for those sensitive processes
Find New Physics or learn new lessons
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

4. First penguin observation
History 1
EM Penguins
First penguin observation
CLEO, PRL 1993

5. First EW Penguin observation
History 2
Electroweak Penguins
First EW Penguin observation
by Belle, PRL 2002

6. Contents 0n final states Full recon. of signals
B  l+l-
B  Xs l+l-
1n final states n-recon. using (E,p)miss
B  l n
B  l n g
Final states w/ ≥2n Full recon. of “other B”
B  tn
B  K(*) nn, “nothing”

7. Similar penguins, rotated by 90o
zero-n modes – straightforward by full-recon. of signal B – hermeticity is still used to suppress Xln backgr.
EW penguin, mostly
Similar penguins, rotated by 90o

8. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Overview
penguins (g, Z) and W-box contribute
sensitive to C9, C10 & sgn(C7)
( |C7| from bsg)
rich structure
q2 distribution
Forward-Backward asymmetry
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

9. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Overview
AFB K* l+ l-
Ali et al. PRD (2000) SM q2 B
: measured in the l+l- frame
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

10. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Inclusive
First measured by Belle: PRL (2003) w/ 60fb-1
pseudo-reconstruction of the Xs system
combine K  or KS with (0~4)p (n(p0)≤1)
L-fit Mbc for signal yield
peaking background component
J/y, y(2S): vetoed by m(l+l-)
B  Xs p+p- is subtracted, weighted by fake rate
combinatorial backgr. comp.
mostly from double-semilept. B decays + some from conti.
suppressed by combining variables into a likelihood ratio
Fitted (Mbc) using shapes from Xsem
Beam-constrained mass:
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

11. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
NBB=89M
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

12. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
NBB=152M
3210 Xse+e-
369 Xsm+m-
6814 Xsl+l-
Xse+m-
control sample
5.8s significance
Belle-Conf-0414
 then, extrapolated
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

13. Differential distributionsK K*
K, K* states are clearly seen / consistent w/ SM
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

14. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Exclusive B  K(*) l+ l-
first observed by Belle in 2001 (29/fb)
first >3s evidence by BaBar (81/fb)
first observed by Belle in 2003 (140/fb)
Main backgrounds
B  J/yK(*), etc.  veto!
B  K*g (conversion), B  K*p0
 m(e+e-) > 0.14 GeV
combinatorial
from semileptonic, continuum
B  K(*) p+p- (pm fake ~2%)2
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

15. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
B  K(*) l+ l- update
NBB=273M
NBB=123M
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

16. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
BF(B  K(*) l+ l-)
Belle-Conf-0415
[Note]
NNLO by Ali, et al.
is assumed to compensate for q2=0 pole for K*e+e-
factor 0.75 & SM values from Ali, et al.
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

17. more than just BF for B  K(*)l+l-
rich structure: sensitive to C9, C10 & sgn(C7)
q2 distribution
Forward-Backward asymmetry
Ratio of BF’s (ee vs. mm)
Kl+l- : sensitive to H0 in 2HDM (=1 in SM)
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

18. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
q2 for B  K(*)l+l-
dq2 /q2 ~ 0.6%
Yellow bands show ranges of theoretical predictions.
Both results are consistent with the SM prediction.
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

19. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Belle-Conf-0415
AFB (q2) for B  K(*)l+l-
Raw AFB in each q2 region is extracted from Mbc fit.
Dotted lines indicate charmonium veto windows.
Kll has no asymmetry, hence a good control sample.
Curves (not fitted lines!) show theory including exp’tal efficiency.
Both are in agreement with data.
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

20. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Leptonic decays
Highly suppressed in the SM
by CKM & GIM
SM: BF(Bs(d)m+m-)= 3.5x10-9 (1.0x10-10)
New physics potential
Tree: SUSY w/ RPV
Loop: MSSM, mSugra, 2HDM, etc.
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

21. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Belle/BaBar
NBB=85M
NBB=123M
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

22. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
CDF/D0
These limits start to restrict SUSY SO(10) models
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

23. W-annihilation; crucial for fB
one-n modes
W-annihilation; crucial for fB
Not as clean, but could be
interesting/useful
A missing neutrino in the final state,
 full recon. of signal B is not possible
Use hermeticity and neutrino mass constraint
 (E,p)miss for neutrino 4-momentum

24. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)

25. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)

26. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Belle/BaBar
BaBar, PRL (2004)
Belle, prelim.
Belle-Conf-0429
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

27. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)

28. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Belle
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

29. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)

30. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Belle
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

31. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Belle-Conf-0429
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

32. Searches for these modes use
modes with ≥2 n’s
Belle/BaBar
BaBar
Searches for these modes use
full reconstruction of the other B

33. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)

34. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)

35. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
B  t n Belle
(for example)
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

36. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)

37. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Belle-Conf-0428
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

38. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
B  t n BaBar
Two methods for kinematic tagging
a. Hadronic full-recon tag high purity
NBB=89M
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

39. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
B  t n BaBar
b. semileptonic partial-recon tag high stat
- some ambiguity, trading purity for statistics
- require in the physical region
NBB=124M
combining the two methods,
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

40. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
B  K n n
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

41. B  “invisible” (nn), nng
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)

42. FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.)
Summary
Electroweak penguin decays B  Xs l+l-
Firmly established in both exclusive & inclusive measurements
Measurements (BF, q2, m(Xs)) are consistent with SM
First attempt to measure AFB as a function of q2 in exclusive modes, K l+l- & K* l+l-  consistent with SM
Much improved limits in the leptonic B decays
Approach w/in 1 order of mag. to SM for B  ln(g), tn
2 orders of mag. to SM for B  l+l-
Limits for other exotic modes: B  (nothing)(X)
FPCP 2004, Oct , 2004, Youngjoon Kwon (Yonsei Univ.)