Physics from B Decays: Lifetimes, Mixing, CP-Violating Asymmetries and Rare Hadronic Decays

Physics from B Decays: Lifetimes, Mixing,

CP-Violating Asymmetriesand Rare Hadronic Decays

Patricia BurchatStanford University

Some of the Highlights …

DPF, May 27, 2002 Patricia Burchat, Stanford 2

Outline

• The B Factory Experiments

• B lifetimes and mixing• Time-dependent CP-

violating asymmetries• CP charge asymmetries• B hadronic decay rates

Motivation for measurements.

How well have we measured these properties?

What have we learned?


The B Factory ExperimentsBABAR/PEP-II• peak luminosity:

– 4.6 x 1033cm-2s-1 (~5 BB/s)

• max lumi/24h: 303 pb-1

• total recorded lumi to date: ~90 fb-1 recorded (~10% off-peak)

• 4.5-month shutdown starts July 1, 2002

Belle/KEK-B• peak luminosity:

– 7.2 x 1033cm-2s-1 (~8 BB/s)• max lumi/24h: 388 pb-1

• total recorded lumi to date: ~80 fb-1 recorded (~10% off-peak)

• 2-month shutdown starts July 1, 2002

c.f. integrated luminosity for

•Argus (1983-1987): ~100 pb-

1

•CLEO (1981-2000): ~16 fb-1


The Unitarity Triangles

u

c

t

d s b

apply unitarity constraint to pairs of columns

d•s* = 0

s•b* = 0

d•b* = 0

(K system)

(Bs system)

(Bd system)

These three triangles (and the three triangles corresponding to the rows) all have the same area. A nonzero area is a measure of CP violation and is an invariant of the CKM matrix.


The Unitarity Triangle

u

c

t

d s b

apply unitarity constraint to these two columns

Vub*Vud Vtb

*Vtd

Orientation of triangle has no physical significance. Only relative angle between sides is significant.

Vcb*Vcd


The Unitarity Triangle

u

c

t

d s b

apply unitarity constraint to these two columns

(1,0)

(,)

(0,0)

Vub*Vud

Vcb*Vcd

Vtb*Vtd

Vcb*Vcd


We are sensitive to CP-violating CKM phases through interference between two decays with known (or unknown) CP-conserving relative phases.

Meson mixing provides a source of error-free non-CKM phase shift by 90o ( i ): |B0 (t) cos(m t/2) |B0 – i sin(m t/2) |B0 exp(2i, where the CKM angle is associated with the mixing box diagram.

Interference between two decay diagrams (e.g., tree and penguin amplitudes with different CKM phases) can lead to CP-violating asymmetries but interpretation depends on relative strong phase.


The Asymmetric-Energy B Factories

z

(4S)

e -

B0 / B0

B0 / B0

e +

z ~ 255 m for PEP-II: 9.0 GeV on 3.1 GeV

~ 200 m for KEKB: 8.0 GeV on 3.5 GeV

e ±, ±, K± tag

+

—


t distributions with NO experimental effects

dN exp(–|t|/B) ( 1 ± cos(mt) )B Mixing

B0 B0 or B0 B0

B0 B0 or B0 B0

Flavor states sorted by mixing status

dN exp(–|t|/B) ( 1 ± sin2 sin(mt) )CP violation

CP states sorted by B tag flavor

Btag= B0Btag= B0


Decay Time Difference (reco-tag) (ps)

UnMixedMixed

0

10

20

30

40

50

60

-8 -6 -4 -2 0 2 4 6 8Decay Time Difference (reco-tag) (ps)

UnMixedMixed

0

10

20

30

40

50

60

-8 -6 -4 -2 0 2 4 6 8

perfect flavor tagging and time resolution

realistic mistag and finite time resolution

Unmixed – Mixed

Unmixed + Mixed ~ (1 – 2)

~ mdAsymmetry (1 – 2) cos(md t)


Increase in precision of B lifetimes and mixing

frequency

PDG2000

PDG2002

B0 Mixing Frequency ( x 1012 ps-1)

0.472 0.017

0.489 0.009

18 measurements

+3 B Factory +1 LEP

CKM/CP III and FP VIII

B0 Lifetime ( x 10-12 ps)

1.548 0.032

1.542 0.016

+3 B Factory +2 LEP

12 measurements

Ratio of B+ to B0 Lifetime

1.060 0.029

1.083 0.017

10 measurements

+2 B Factory +1 LEP

Flavor Session V: U. Nierste (theory)


Prospects for future lifetime and mixing measurements

•many preliminary lifetime and mixing results.•systematic uncertainties dominated by t resolution function and, for mixing, knowledge of the lifetime.•measure mixing and lifetime simultaneously

•expect <1% uncertainty on Bd mixing in a few years.•measure .•test assumptions of CP/T/CPT symmetries.

Flavor Session VIII, T. Meyer


sin2

Vtb*Vtd

Vcb*Vcd


Charmonium modes used for measuring sin2

Both BABAR and Belle use six charmonium modes:

• B J/ Ks0, Ks

0 +-, 00

• B J/ KL0

• B (2S) Ks0

• B c1 Ks0

• B J/ K*0, K*0 Ks0

• B c Ks0

b

d d

c

s

c

B0

, c, c

KS,L

One dominant decay

amplitude theoretically clean!

CKM/CP Session V, S. Olsen

Belle has observed a 6 signal that is most likely the not-well-established c(2S) charmonium state in B0 c(2S) Ks

0 and B+ c(2S) K+


sin2 data samples in BABAR

J/ Ks (Ks +-)

J/ Ks (Ks 00)

J/ K*0 (K*0 Ks0)

c1 Ks

(2s) Ks

J/ KL

Bflav

Mixing sample


42 fb-1 (44 M BB) 1772 events (78% purity) 1550 evts with t meas’t

effective tagging efficiency: =(27.0 1.2)%

sin2 = 0.82 0.12 0.05 || = 1.06 0.09 (stat)

Belle

CKM/CP Session I, Wang, Vahnsen

hep-ex/0205020hep-ex/0205020


56 fb-1 (62 M BB) 1850 tagged events with t (79% purity; 68% tagging

)

effective tagging efficiency:

=(25.1 0.8)%

sin2 = 0.75 0.09 0.04 || = 0.92 0.06 0.02

BABAR

hep-ex/0203007hep-ex/0203007

471 events

524 events

CKM/CP Session I, Rahatlou, Lange


Constraints on upper vertex of Unitarity Triangle from all measurements EXCEPT

sin2

Regions of >5% CL

A. Hööcker, H. Lacker, S. Laplace, F. Le Diberder, Eur. Phys. Jour. C21 (2001) 225, [hep-ph/0104062]


World Average sin2 = 0.78 0.08

The Standard Model (and the CKM paradigm, in particular) wins again … at least at the current level of experimental precision, in this decay mode.


CKM/CP Session I, J. Albert

Measurement of “sin2” in bccd decays: D*D*+ and D*D+

D*D*

Ntag = 76Purity = 80%

• Weak phase for tree decay is same as for bccs but watch out for penguins!

• D*D* is vector-vector decay (L=0,1,2) so mix of CP=+1 and –1.

• Fit for Sf and Cf (no penguin assumptions).

D*D*

S = -0.05 0.45 0.05C = 0.12 0.30 0.05

CP asymmetries in D* D+

have also been studied in BABAR.

b

d d

cd

c

D(*)-b

d d

d

c

c

t

B0

D(*)+B0

D(*)-

D(*)+


Future sin2 studies:B0 Ks

Pure penguin!

• time-dependent asymmetries in B0 Ks measures sin2.

• direct charge asymmetries in B+ K+ sensitive to new physics.

b

d d

s

s

s

B0

K0

t

b

d d

s

s

s

B0

K0

t


B K

BABAR K+

111±12 evts

BABAR K0

40±8 evts

~60M BB pairs

Flavor Session VI: A. Telnov

Branching Fractions (10-6) (stat. and syst. errors added in quadrature and symmetrized)

CLEO, Belle, BABAR

K+ 5.5±2.0, 11.2±2.4, 9.2±1.3

K0 <12, 8.9±3.2, 8.7±1.8

K*+ <23, <36, 9.7±4.2

K*0 11.5±4.4, 13.0±6.1, 9.2±1.3

+ < 5, 0.56

B(K) slightly favors pQCD over QCDf.

CP asymmetries also measured: consistent with 0.


“sin2”

Vub*Vud Vtb

*Vtd


CP Violation in B0 +-

b

d d

ud

u

+

-b

d d

d

u

u -

+

t

B0

B0

|P/T| and relative phase are unknown but can, in principle, be determined from an isospin analysis that requires measuring BF for B0+-, B0+-, B±±0, B000, and B000

CKM/CP Session II, N. Sinha (theory)


Expectations/Prejudices…• Measure coefficients for

both sinmt and cosmt terms (S and C).

• S and Care determined by , , |P/T|, and . Assume

22

3021

28.0/

26

)97(

TP

cf. Gronau and Rosner, Phys. Rev. D65, 093012 (2002) CKM/CP Session I, Wang,

Vahnsen


Sππ= -0.01 ± 0.37 ± 0.07Cππ= -0.02 ± 0.29 ± 0.07

~60M BB pairs

BABAR

qq and K background

CKM/CP Session II: Olsen, Sumisawa

B0 tags

B0 tags Belle

Sππ= -1.21 +0.38 -0.27

+0.16-0.13

Cππ= -Aππ=-0.94 +0.25 -0.31 ± 0.07

B0 tags

bkgdsubtracted

~44M BB pairs

B0 tags


Interpretation

BABAR

Belle


Other studies of “sin2”Belle B0 ’ KS

• Penguin mediated.• Sensitive to new physics.• sin2 = 0.29 ± 0.54 ± 0.07

Many other studies of B (’)K (*) are being aggressively pursued.

Challenge to theoretical models to explain relative rates.


sin2

Vub*Vud

Vcb*Vcd


Charmless Two-Body Decays

In decays such as B K , interference between the Tree and Penguin amplitudes can lead to CP asymmetries that depend on AND the strong phase difference. Also, ratios of BF for various and K decay modes are sensitive to the angle .

Goal: Measure CP asymmetries AND branching fractions for all charmless two-body final states.


World average two-body results from CLEO, Belle, BABAR

CKM/CP Sessions I, M. Bona, II: B. Casey

+- 5.2±0.6 C, S

+0 4.9±1.1 (Belle 3.5/BABAR 5.2)

00 < 5.2, 5.6, 3.4

K+- 18.6±1.1

K+0 11.5±1.3

K0- 17.9±1.7

K00 8.9±2.3

K+ K- < 1.9, 0.5, 1.1

K0 K0 < 13, 13, 7.3

Branching Fraction (10-6) CP Asymmetry

+ 0.46 ± 0.15 ± 0.02 - 0.17 ± 0.10 ± 0.02

incompatible at 3.3 level


Charmless Three-Body B Decays: why are they interesting?

Sensitive to same weak phases as charmless 2-body decays.

Dalitz plot analyses of 3-body decays can (eventually) be used to help disentangle relative strong phases.

Already being done in charm decays.

A long way to go in B physics, but we’re starting…

Charm Session I, D. Asner


All B+K+h+h-, B0Ksh+h- and BKsKsh modes being studied by Belle

Flavor Session I, N. Gabyshev

>4 signals in six of eleven 3-body modes being studied.

Studying resonance substructure.

Belle B+K++-

237±23 events

K*(892)0 + and f0(980) K+ observed.


3-body branching fractions

Branching Fractions (10-6)

Belle BABAR

+ +- <15

K++ - 55.6 ± 5.8 ± 7.7 59.2 ± 4.7 ± 4.9

K+ K+ K- 35.3 ± 3.7 ± 4.5 34.7 ± 2.0 ± 1.7

K+ K± ± no signal no signal


B D(CP)K decays: why are they interesting?

)(21000 DDD

)()()(2000

KDBAKDBAKDBA

1||)(0 ieAKDBA

ii eeAKDBA 2||)( 0 Potential for measuring CKM angle :

Determine through amplitude relationships (up to discrete ambiguities): Gronau & Wiler; Dunietz (1991).

b

u u

cs

u

B-D0

K-b

u u

c

s

u

B-

D0

K-


B-D

Dfl

DCP

+

DCP-

B-D KCP charge asymmetries in B D(CP)K from Belle and BABAR:

ACP+ = + 0.29 ± 0.26

ACP+ = + 0.16 ± 0.27

Afl = - 0.044 ± 0.059 (stat)

Afl = + 0.003 ± 0.096

ACP- = - 0.22 ± 0.24

E (GeV) Flavor Session V, G. Mancinelli


Many highlights in hadronic B decays not covered here . . .

B D(*)+ -: potential for measuring sin(2+); See CLEO analysis of strong phase between I = 1/2 and 3/2.

Analysis of partially-reconstructed hadronic decays.

B Ds(*)+ - (Vub suppressed); help in interpretation of B D(*)+

Color-suppressed B decays (e.g., B D(*)0X0)

B D(*)D(*) (BF, ang analysis)

B baryons

Flavor Session V, T. Pedlar

Flavor Session V, T. Orimoto

FP Session I: Fang Fang (Belle); Cheng (theory)

Flavor Session V, M. Krishnamurthy, VI: C.S.Kim; CKM/CP Sesion III: Y. Zheng


Summary With the rapidly increasing data samples from the B

Factories, many new decay modes are becoming available for

1. time-dependent CP asymmetry measurements (sensitive to and );

2. direct CP asymmetry measurements (sensitive to and );

3. branching fraction and resonant substructure measurements that are crucial for the interpretation of many of the CP asymmetries.

is in agreement with SM predictions; too early to interpret results on .

The summer conferences and the Fall papers will continue to bring many interesting new results to interpret as the B Factory experiments “catch up” on their analyses.

Documents

Physics from B Decays: Lifetimes, Mixing, CP-Violating Asymmetries and Rare Hadronic Decays