EW Penguin & Leptonic B decays

EW Penguin & Leptonic EW Penguin & Leptonic BB decays decays

Prologue: Introduction & History Modes w/ 0 ’s Modes w/ 1 ’s Modes w/ ≥2 ’s Summary & Prospects

Youngjoon Kwon

OverviewOverview

FPCP 2004, Oct. 4 - 9, 2004, Youngjoon Kwon (Yonsei Univ.) 2

Physics Goals of B-factoriesPhysics 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


Motivation for Rare Motivation for Rare BB decays 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

NPSMordinary AA

SMA

EMEM PenguinsPenguins

*KB First penguin observationCLEO, PRL 1993

History 1

Electroweak PenguinsElectroweak Penguins

lKlB First EW Penguin observationby Belle, PRL 2002

History 2

ContentsContents

0 final states Full recon. of signals B l+l- B Xs l+l-

1 final states -recon. using (E,p)miss

B l B l

Final states w/ ≥2Full recon. of “other B” B B K(*) , “nothing”

zero-zero- modes modes– straightforward by full-recon. of signal B– hermeticity is still used to suppress Xl backgr.

llXB sEW penguin, mostly

llBSimilar penguins, rotated by 90o


penguins (, Z) and W-box contribute sensitive to C9, C10 & sgn(C7)

( |C7| from bs) rich structure

– q2 distribution– Forward-Backward asymmetry

llXB s OverviewOverview


llXB s OverviewOverview

7 7eff eff

SMC C

SM

AFB K* l+ l-

q2

Ali et al. PRD (2000)

Bl

Bl

l

Bl : measured in the l+l- frame

0cos0cos

0cos0cosFB

BlBl

BlBlA


InclusiveInclusive llXB s

First measured by Belle: PRL (2003) w/ 60fb-1

– pseudo-reconstruction of the Xs system• combine K or KS with (0~4) (n(0)≤1)

• L-fit Mbc for signal yield

– peaking background component• J, (2S): vetoed by m(l+l-)

• B Xs +- 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 Xse

Beam-constrained mass:22

CMbc )()2( ipEM


llXBXB

eeXB

s

s

s

NBB=89M


674.070.0

673.069.0

680.076.0

10]83.011.4[ )(10]05.113.4[ )(10]30.104.4[ )(

llXBBXBB

eeXBB

s

s

s

GeV 2.0)( llm

NBB=152M

3210 Xsee 369 Xs

6814 Xsll

Xse

control sample 5.8 significance

GeV 1.2)( sXm then, extrapolated

%9.2)eff.( %6.2)eff.(

ee

Belle-Conf-0414


KK*

llXB s Differential distributionsDifferential distributions

K, K* states are clearly seen / consistent w/ SM


Exclusive Exclusive B B K K(*)(*) l l++ ll

first observed by Belle in 2001 (29/fb)first >3 evidence by BaBar (81/fb)first observed by Belle in 2003 (140/fb)

Main backgroundsB J/K(*), etc. veto! B K* conversion), B K*

m(ee) > 0.14 GeV

combinatorial from semileptonic, continuum

B K(*) fake

lKlB llKB *


B B K K(*)(*) l l++ llupdateupdate

73.3

9.2*

74.13.1

100.18.8 )(104.05.6 )(

llKBBlKlBB

73.2

2.2*

775.070.0

104.09.05.16 )(1002.027.050.5 )(

llKBBlKlBB

NBB=123M

NBB=273M


BF(BF(B B K K(*)(*) l l++ ll))

is assumed to compensate for q2=0 pole for K*ee

factor 0.75 & SM values from Ali, et al.

[Note]

73.3

9.2*

74.13.1

100.18.8 )(104.05.6 )(

llKBBlKlBB

73.2

2.2*

775.070.0

104.09.05.16 )(1002.027.050.5 )(

llKBBlKlBB

7*

7

109.39.11 )( 102.15.3 )( :SM

llKBBlKlBB

NNLO by Ali, et al.

Belle-Conf-0415


more than just BF for more than just BF for B B K K(*)(*)ll++ll

rich structure: sensitive to C9, C10 & sgn(C7)– q2 distribution– Forward-Backward asymmetry

Ratio of BF’s (ee vs. )– Kl+l- : sensitive to H0 in 2HDM (=1 in SM)


qq22 for for B B K K(*)(*)ll++ll

q2 /q2 ~ 0.6% Yellow bands show ranges of theoretical

predictions. Both results are consistent with the SM

prediction.


AAFB FB ((qq22) for ) for B B K K(*)(*)ll++ll

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.

Belle-Conf-0415


Leptonic decaysLeptonic decays llB sd )(

Highly suppressed in the SM– by CKM & GIM

– SM: BF(Bs(d))= 3.5x10-9 (1.0x10-

10)

New physics potential– Tree: SUSY w/ RPV– Loop: MSSM, mSugra, 2HDM, etc.


llB0Belle/BaBarBelle/BaBar

NBB=123M

80

80

80

1071 )(1061 )(

1091 )(

eBBBB

eeBB

NBB=85M


llB sd )(

CDF/D0CDF/D0

These limits start to restrict SUSY SO(10) models

one-one- modes modes

lB W-annihilation; crucial for fB

Not as clean, but could be interesting/useful lB

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




lB Belle/BaBarBelle/BaBar

6

6

100.2 106.6

BBF BaBar, PRL (2004)

Belle, prelim.Belle-Conf-0429



lB BelleBelle



lB BelleBelle


Belle-Conf-0429

modes with modes with ≥≥2 2 ’s’s

B KB , ,

Belle/BaBar

BaBar

Searches for these modes use full reconstruction of the other B




B B BelleBelle

(for example)



Belle-Conf-0428


B B BaBarBaBar Two methods for kinematic tagging

a. Hadronic full-recon tag high purity

4102.4 BBF NBB=89M


b. semileptonic partial-recon tag high stat

- some ambiguity, trading purity for statistics- require in the physical region

B B BaBarBaBar

22beam

22beam

,2

2cos (*)

BDl

DlBDllDB

mEp

mmEE

lDB (*),cos

4103.4 BBFNBB=124M

4103.3 BBF

combining the two methods,


B B K K


B B “invisible” ( “invisible” (), ),


SummarySummary 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

l(), 2 orders of mag. to SM for B

l+l-

– Limits for other exotic modes: B (nothing)(X)

Documents

EW Penguin & Leptonic B decays