1 Physics in Collision, June 27-29, 2004, Youngjoon Kwon Rare B decays Introduction Hadronic...

Physics in Collision, June 27-29, 2004, Youngjoon Kwon 1

Rare B decaysRare B decays

Introduction Hadronic two-body states

- non-factorizable processes Radiative & EW penguins Special subject: B DsJ X

Youngjoon KwonYonsei University

OverviewOverview

Physics Goals in B-Physics Goals in B-factoriesfactories

Establish CP violation in B decaysand 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– Belle, in particular, measures CKM triangle

parameters; angles & sides

Search for rare/forbidden decays and explore new physics effects

The major players in B The major players in B physicsphysics

Clean environment of Clean environment of B-factoriesB-factories

Energy difference:

Beam-constrained mass:

222 )()( iCMbc pEM

2CMi EEE

B-factory with a clean B-factory with a clean initial stateinitial state

Kinematically clean environment of B production and decays

Provides an excellent laboratory to search for new particles & measure their properties– For example, B K X(3872), K c(2S)

““Rare B decays”Rare B decays” b c W* is the dominant B decay process others are suppressed due to

– CKM suppression: b u

– Loop effect (“penguin”): b s, b d

Motivation for Rare B Motivation for Rare B decaysdecays

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.– e.g. processes dominated by penguin loops

Compare Nature (exp.) with SM prediction for those sensitive processes

Find New Physics or learn new lessons

NPSMordinary AA

Where to look forWhere to look for – – two starting pointstwo starting points

CPV in Ks– Do we understand penguins?

• Radiative, EW• BF, ACP

as an ingredient for ()– Do we understand the strong-

interaction part?• QCDF, pQCD• Color-suppressed modes

0 0A A

Let’s start with charmless 2-meson modes and see what we can learn!

22, 1 sin 2( )A S A 22, 1 sin 2( )A S A

Charmless 2-meson Charmless 2-meson final statesfinal states

Observables– BF– ACP

– polarization, etc.

Experimental concerns– continuum background – hadron ID: Cherenkov + dE/dx + TOF

on interpretation– isospin, SU(3)– Final state re-scattering

Discrimination of and Discrimination of and ContinuumContinuum

Combine into a Fisher (or NN)

Signalu,d,s,cbackground

Fisher Discriminant

sMonte Carlo

B produced (almost) at rest in Y(4S) frame

Isotropic B Jetty Continuum

cleanest modes Both tree & penguin processes

can lead to direct CPV

may provide some info. on 2() & 3()but complicated, due to hadronic effects

KKKB , ,

610)2.06.07.1( BF610)3.06.01.2( BF

T/P ratio?T/P ratio?

K0+ +0

3* ~ udubVV

~*tstbVV

Mode CKM (fdecay)2 Ratio Exp Ratio BF (10-6)

K0+ 1 1 1 1 19.6

K*0+ 1 1.85 1.85 0.65 12.7

+0 2 0.66 0.03 0.27 5.3

+0 2 1.71 0.085 0.46 9.1

+0 2 2.9 0.145 1.35 26.4

AACPCP in in

Belle result (152 million BB)-

Comparison w/ theory: Comparison w/ theory: BF & AcpBF & Acp

Mode BFExp

(10-6)

BF pQCD

(10-6)

ACP Expt

ACP pQCD

ACP QCDF

K+- 18.2 ± 0.8 13 – 19 -9 ± 3† -13 – -22 +5 ± 10

K0+ 19.6 ± 1.5 14 – 26 -1 ± 6 -0.6 – -1.5 0 ± 1

K+0 12.8 ± 1.1 8 – 14 0 ± 7 -10 – -17 +7 ± 10

K00 11.2 ± 1.4 8 – 14 3 ± 37 -3 ± 4

+- 4.55 ± 0.44 6 – 11 16 – 30 -6 ± 13

+0 5.3 ± 0.8 2.7 – 4.8 -7 ± 14 0 -2 ± 5

00 1.90 ± 0.47 0.33 – 0.65 45 ± 60

Longitudinal pol. in B Longitudinal pol. in B → → V VV V

fL = L /

100% Pol CP evenExpect: fL ~ 1 – O(M2

V/M2B)

B0 + -

NS = 93 ±22±9BaBar [> 5]

Cos(1) MES

B B (Belle) (Belle)

B B → → and and K K** [[BaBar BaBar && BelleBelle]]

(Errors approximated) BF (10-6) ACP % Long. Poln %

B0→ ρ0 ρ0 < 2.1 (90 % CL)

B0→ ρ+ ρ- 27 ± 7 ± 6 99 ± 7 ± 3

B+→ ρ+ ρ0

22.5 ± 5.7 ± 5.8

31.7 ± 7.1 ± 6.7

-19 ± 23 ± 3

0 ± 22 ± 3

97 ± 7 ± 4

95 ± 11 ± 2

B+→ ρ0 K*+ 10.6 ± 3.0 ± 2.4 20 ± 32 ± 4 96 ± 15 ± 4

• CP asymmetries are consistent with zero

• Longituidnal polarization is ~1 as expected

CP even

Grossman-Quinn Grossman-Quinn bound :bound :

Grossman Quinn boundPRD 58 (1998) 017504

BF give model-independentlimits to the CP angle

)()(sin

BBFEff

)%90(55.045.055.4

45.09.1)(sin 2 CLEff

)%90(10.0827

1.2)(sin 2 CLEff

| - Eff| < 50o () and < 20o () at 90% CL

+ - is dominantly longitudinal polarised, CP-even final state

00000 , B

A concern on G-Q A concern on G-Q bound bound fromfrom

modifications from final-state interactions non-resonant background

Let’s consider a few decay modes potentially sensitive to FSI !

Not directly accessible through the spectator process Sensitive to W-exchange, or final state rescattering

potential for generating large theory uncertainty

in extracting CKM angle 3 from hadronic B decays Wide range of predictions: (0.3 ~ 6)x10-5

KDB s0

BF is consistent with p-QCD calculation, but in the upper edge of prediction

Similar FSI amplitudes – enhanced by (uu)/(ss) – should exist for color-suppressed modes such as D0 0, etc.

KDB s0

6.4 significance!

Color-suppressed B decaysColor-suppressed B decays

5.0 8.06.0 7.07.2

5.04.01.3

4.00.2

3.04.19.08.0

5.04.0

8.01.3

5.08.13.11.1

4.03.0

4.00.19.2

consistently larger thanthe factorization model

FSI re-scattering / W-exchange?

Color-suppressed B Color-suppressed B decaysdecays

Where to look forWhere to look for – – two starting pointstwo starting points

CPV in Ks– Do we understand penguins?

• Radiative & EW• BF, ACP

as an ingredient for ()– Do we understand the strong-interaction part?

• QCDF, pQCD• Color-suppressed modes

Now, let’s move on to look at the situationin the penguin sector!

B B K K(*)(*)

• Dominated by a single process (penguin) Expect similar BF for all modes

• Note: BF(B+) < 4x10-7 [90% CL] If large, it might indicate a large FSI • Longitudinal polarisation (expected) ~1

B B K K** angular angular distributionsdistributions

B B K K(*)(*) summary summary

Mode BF (10-6) ACP (%) Polarisation %

K0 7.6 ± 1.4 9.0 ± 2.2

K+ 10.0 ± 1.0 9.4 ± 1.3 4 ± 9 1 ± 13

K*0 11.2 ± 1.5 10.0 ± 1.8 4 ± 12 7 ± 16 65 ± 7 43 ± 10

K*+ 12.7 ± 2.4 6.7 ± 2.2 16 ± 17 -13 ± 31 46 ± 12

BaBar Belle

New physics, in penguin?(Y. Grossman hep-ph/0310229)

Or, something new to learnin phenomenology?

BF(BBF(B±±KK±±) at CDF) at CDF

• BR(B±K±) /BR(B±J/K±) = 0.0068 ±0.0021 (stat.) ± 0.0007 (syst.)

Using PDG 2002 for BR(B±J/K±):

• BR(B±K±) = (6.9 ± 2.1 (stat.) ± 0.8 (syst.)) x 10-6

powerful vertex trigger makes CDF a contender

Electroweak PenguinsElectroweak Penguins

*KB First penguin observationCLEO, PRL 1993

Branching Branching FractionsFractions

(x 10-6)

EE spectrum in B spectrum in B X Xs s

EE in B in B X Xs s

CLEOCLEO

EE in B in B X Xs s (Belle) (Belle)

EE in B in B X Xs s

(Belle)(Belle)

Signal selection is optimized formax. significance in 1.8 ~ 1.9 GeV

CP asymmetry in B CP asymmetry in B X Xss CP asymmetry is expexted to be small (<1%) in SM some non-SM models allow large (~10%) ACP without changing the BF possible contamination from Xd (ACP can be large) but negligible in our measurement

CP asymmetry in B CP asymmetry in B X Xss

rawCPCP DAA

AACPCP(B (B X Xss Belle Belle

GeV) 1.2( 030.0050.0002.0)(

096.0)(093.0 sbACP

9.252.393 N 9.250.392 N 6.98.520 N

tagged as 0, BB 0, BB ambiguous

AACPCP(B (B X Xss BaBar BaBar

015.0050.0025.0)( sbACP

11.0)(06.0 sbACP

AACPCP(B (B Xs Xs Summary Summary

Exclusive: B Exclusive: B K K**

B B K* K* asymmetries asymmetries

012.0044.0015.0

CP asymmetry SM << 0.01

KBBKBB

026.0044.0012.0

Isospin asymmetry SM << (5~10)%

Exclusive B Exclusive B X Xdd

td* /1

)( :SM

Exclusive B Exclusive B X Xdd

Standard Model predictions for BF’s

Prior measurements (in 10-6)

653.046.0

10)(1.58

10)18.0(0.49 ,10)34.0(0.90

Ali & Parkhomenko (2001)

Bosch & Buchalla (2001)

1.0 4.4 9.2 1.2 2.6 17 2.1 2.7 13

CLEO Belle BaBar

Excl. B Excl. B X Xdd

unbinned 2D max. likelihood fit to E and Mbc

Fit region: |E| < 0.3 GeV

5.2 < Mbc < 5.3 GeV

B B X Xdd fitting fitting

)(2)(2

017.0083.1with 0

B B X Xdd fitting fitting (projections)(projections)

Exclusive: B Exclusive: B X Xdd

observed yield 280 749 197

signal yield 6.3 15.2 5.9signal

efficiency(%) 5.0 0.3 5.9 0.4 4.7 0.5

significance 3.5 incluing syst. err.Branching

Fraction 66.0

5.0 101.08.1

000 BBB

Semileptonic Semileptonic PenguinsPenguins

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

( |C7| from bs) rich structure

– q2 distribution

– Forward-Backward asymmetry

InclusiveInclusive llXB s

llXBXB

678.073.0

674.070.0

684.079.0

10]84.039.4[ )(10]06.131.4[ )(10]32.145.4[ )(

llXBBXBB

GeV 2.0)( llm

72 signal events6.2 significance

updated (preliminary)

Main features Main features of of

Result is consistent with SM for both Xse+e & Xs+

– BF, m(l+ l), m(Xs)

– Kaon yield in m(Xs) & exclusive BKl+ l

Will remain interesting with even more statistics – BF is sensitive to Wilson coefficients C7, C9 & C10

– Detailed internal distributions m(l+ l), AFB are sensitive to new physics

llXB s

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++ ll updateupdate

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. [caution] available SM predicted values vary by factor ~2

[Note]

74.13.1

100.18.8 )(104.05.6 )(

llKBBlKlBB

70.19.0

102.08.05.11 )(101.03.08.4 )(

llKBBlKlBB

109.39.11 )( 102.15.3 )( :SM

llKBBlKlBB

DDsJsJ in B decays in B decays

Observations of Observations of DDsJsJ

BaBar (Apr. 2003 PRL)– Discovery of a new resonance at 2317 MeV

in CLEO (May 2003 PRD)

– another resonance at 2459 MeV in

What’s so strange …?What’s so strange …? Surprisingly low mass compared to the

potential model expectations– below D(*) K threshold => narrow!

The masses are practically equal to those of similar states in the cu system:

Observed in the isospin-violating mode

Need to determine the quantum #’s and the BF’s

a potential model a potential model predictionprediction

Isgur & WisePRL 66, 1130 (1991)

on the other hand...on the other hand...

Prior to the DsJ observations,

there were theoretical papers that suggested:– Nowak, Rho, & Zahed, PRD 48, 4370 (1993)

– Bardeen & Hill, PRD 49, 409 (1994)

In the HQ limit,the j=1/2, 0+, 1+ states could be thought ofas the chiral partners of Ds and Ds*

the masses could be light

DDsJsJ(2457) : new decays ( (2457) : new decays ( ) )

• 1st observation

08.013.055.0

)2457(

)2457(0*

DDsJsJ(2457) : new decays ( (2457) : new decays ( ) )

• 1st observation

02.004.014.0

)2457(

)2457(0*

BD DsJ(2317)

DsJ(2317)Ds

BD DsJ(2457)

DsJ(2457)D*s

BD DsJ(2457)

DsJ(2457) Ds

DDsJsJ production in B production in B decaysdecays

B(B D DsJ(2317)) x B(DsJ(2317) Ds ) = (8.52.02.6)x 10-4

B(B D DsJ(2457)) x B(DsJ(2457) Ds*) = (17.84.25.3) x 10-4

B(B D DsJ(2457)) x B(DsJ(2457) Ds ) = (6.71.32.0) x 10-4

DDsJsJ(2457) (2457) DDss decay decay

0.55 0.13 0.08 (continuum) 0.38 0.11 0.04 (B decays)

Consistent with 1+ hypothesis, 0+, 2+ are excluded

in B DDsJ decays

0*)2457(

)2457(

spin-parity of spin-parity of DDsJsJ(2317)(2317)

B DDsJ is observed high J is not likely

All evidence favors JP = 0+ assignment

spin-parity of spin-parity of DDsJsJ(2457)(2457)

B DDsJ is observed high J is not likely

All evidence favors JP = 1+ assignment

SummarySummary

Physics in the B-factories is getting really interesting!!

Rare B decays are excellent places to search for new physics and/or learn new things

ACP(B0K)=-0.090.03 B(B0)=(1.9 0.5)x10-6 fL(BK*)~0.5 « 1 color-suppressed decays

Great progresses in the EW penguin processes

Precise BF, ACP & E in B Xs B K(*)l+l- established; Xs l+l- improved

Discover/understand new states : DsJ spin-parity

1 Physics in Collision, June 27-29, 2004, Youngjoon Kwon Rare B decays Introduction Hadronic...

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