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BaBar & Belle: Results and Prospects

Claudio CampagnariUniversity of California

Santa Barbara

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Physics Program at the B-Factories

• Comprehensive investigation of CKM structure of SM– CP-Violation (CPV) a key ingredient

• CPV from just one phase in SM

– Other measurements very important too

• Rare B-meson decay (but also D, )– Sensitive to new particles in loops– Indirect signature of new physics?

• B (and D and ) decay dynamics

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Today:

Concentrate (mostly) on measurements related to

the unitarity triangle

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B-factories and the unitarity triangle

B0 J/ Ks, D*D*,…

B0 , ,..

B,DK,D*,…

B-mixingB(,)

BulB(,,)l

BclBD(*)l

Both angles and sides of U.T. are accessible through measurements at the B-factories

Both angles and sides of U.T. are accessible through measurements at the B-factories

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Outline• BaBar and Belle

– Luminosity, present and future

• Lifetimes and mixing• Sin2 results• Working towards sin2• Comments on • Vub

• Conclusions

Note: averages from Heavy Flavor Averaging Group(unless otherwise specified)

Note: averages from Heavy Flavor Averaging Group(unless otherwise specified)

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B-factories performance

Belle: 132 fb-1

Record lumi: 9.5 1033

BaBar: 117 fb-1

Record lumi: 5.2 1033Note: 100 fb-1

~ 108 106 BB pairs

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B-factories prospects

• Luminosities are improving– PEPII up to ~ 2 to 4 1034 cm-2 sec-1

– KEKB perhaps as high as 1035

• Detectors need modest upgrades to cope

• Should have ~500 fb-1 by 2005-2006, 1000-2000 fb-1 by end of decade– Now have ~ 100 fb-1 per expt

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Mixing and lifetimesResults based on large samples of

– Fully or partially reco. hadronic decays– Fully or partially reco. D* l – Dileptons

8K events

12K events29 fb-1

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t Distributions Lifetimes

t = proper time differencebetween the decay times of the two B-mesons

t = proper time differencebetween the decay times of the two B-mesons

t resolution of ~ same order of magnitude as lifetime

t resolution of ~ same order of magnitude as lifetime

0 = 1.554 0.030 0.019 psec- = 1.695 0.026 0.015 psec

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Adding Tagging Information

md = 0.516 0.016 0.010 ps -130 fb-1

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Lifetimes results summary

• Belle and BaBar now dominate world averages• Improvement by x2 over pre B-factory era• Order 1% uncertainty on lifetimes and ratio

• Belle and BaBar now dominate world averages• Improvement by x2 over pre B-factory era• Order 1% uncertainty on lifetimes and ratio

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} LEP+CDF0.497§0.014 ps-1

} BaBar + Belle0.502§0.006 ps-1

World Average0.502§0.006 ps-1

Dominated by BaBar & Belle

Partial averagesfrom F. RongaCKM Workshop03

Mixing results summary

3% precision!

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Mixing and Lifetimes - Prospects

• Hard, precision measurements• Many are based on only a fraction of

the available dataset– Statistical uncertainties still significantroom for improvement

Theoretical uncertainties limiting factor in ability to extract clean CKM information

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The measurements of mixing and lifetimesprovide the foundations for the

time dependent CPV measurements that follow

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General time-dependent formalism

Interfering amplitudes with different CP-violating (weak) phases can give a non-zero CP asymmetry. For B0 ! fCP:

Then, when one of the interfering amplitudes is B-mixing

with

S C

Only one decay amplitude (or all decay amp. same CKM phase):C=0 and S gives clean CKM phase information

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Sin2 in b ! c c s

• Golden modes:– clean theory– “relatively easy” experiment

• Tree and leading penguin have same phase • sinmt coeff. measures sin2 cleanly• Not just J/ KS:

– Also ’ KS, c1 KS, c KS (CP=-1)

– J/ KL (CP=+1)

– J/ K*0 (Mixed CP)

b

d

d

W cc

s

0B /J

0K

0K0Bb

dW

s

d

c

cg

u,c,t

/J

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1.6K events

~500 signal ev.

Event Samples

Clean ~2K KS sample

+~ 500 KL events

with ~ 60% purity

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t distributions and asymmetries

CP=-1 CP=+1

Events with KS Events with KL

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Summary of sin2 in b ccs

7.5% precision

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Fit for cosmt coefficient, extract ||

5% precisionconsistent with ||=1(as expected in SM)

5% precisionconsistent with ||=1(as expected in SM)

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Sin2 from other modes

• b ! ccd– D(*) D(*) and J/ 0

• penguins with different phases can be important

• b ! s (penguin)– KS, ’ KS etc

• sensitive to new physics in the b!s penguin

Results from these modes are very much statistics limited

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J/ 0

~ 40 evD*D*

~ 130 ev

KS

~ 36 ev ‘ KS

~ 150 ev

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B0 ! J/ 0b

d

d

W cc

d

0B /J

0 0Bb

dW

d

d

c

cg

u,c,t

/J

0

S = - sin2 if no penguin C = 0 if no penguin

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B0 ! D*D*

• Vector-Vector final state: could have CP even and odd components

• Both BaBar and Belle measure mostly CP even

• BaBar fits S and CS = -0.32 § 0.43 § 0.13C = +0.02 § 0.25 § 0.09

b

d d

Wccd )(D

)(D0B

0Bt,c,ub

dd

W

d

)(D

c

cg

)(D

S = sin2 if no penguin

C = 0 if no penguin

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b ! s modes

Bb

d,u

W

ss

sg

Kd,u

bW

s

s

sg

u,c,t

Kd,u d,u

B

B ! KS B ! KS

B ! ‘ KS B ! ‘ KS

• Same CKM structure as J/ KS

• u-penguin down by ~1/50• Expect S=sin2 to 5%

• Same CKM structure as J/ KS

• u-penguin down by ~1/50• Expect S=sin2 to 5%

• Like KS but also u-tree• Still, S~sin2

• Like KS but also u-tree• Still, S~sin2

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bs penguin: S coefficient (sin2)

bs penguin average

0.18 0.20

~ 2.5 from ccs modes

bs penguin average

0.18 0.20

~ 2.5 from ccs modes

Expectation from J/KS

‘

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Sin2 prospects

• Sin2 in b ccs is already a precision measurement– But still statistically limited– Will be improved

• Measurements in other modes will improve as luminosity– Maybe faster, as techniques improve

• Improved results in the b s modes will be particularly interesting!

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Sin2• In the absence of penguins, sin2 from

B0 ! + - asymmetry• BR of B0 ! K+ - and B+ ! + 0 tell us that

interference between P and T is large• In principle isospin analysis of +-, +0,

and 00 allows for clean extraction of • In practice 00 very hard

b

d d

ud

u

+

-

B0

b

d d

d

u

u -

+

t

B0

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B ! hh Branching Ratios (x 10-6)

Averages from J. Olsen, CKM Workshop 2003

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Time dependent fits to +-

78 fb-1

~ 106 events 84 fb-1

~ 160 events

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+ - Fit Results

Belle rules out CP conservation (C=S=0) at 99.93% C.L.BaBar is still consistent with C=S=0The discrepancy is at ~ 2-2.5 level

Belle rules out CP conservation (C=S=0) at 99.93% C.L.BaBar is still consistent with C=S=0The discrepancy is at ~ 2-2.5 level

S C

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Sin2 from • from full, time dependent, tagged,

Dalitz plot analysis of +-0

• Hard analysis• For starters, BaBar

– Quasi two body analysis, only +- and - + – Also +K- and -K+

– BF(B0K)= (7.31.31.3) 10-6

– BF(B0)= (22.61.82.2) 10-6

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~ 430 events

ACP = -0.18 § 0.08 § 0.03 Ã time integrated termC = 0.36 § 0.18 § 0.04S = 0.19 § 0.24 § 0.03

• 2 CPV effect• first step towards full Dalitz analysis

B

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Sin2- Prospects

• Clean extraction without theoretical assumptions will be hard

• If B0 0 0 very small, bounds on sin2 could become quite useful

• We will most likely see CPV (maybe we are already seeing it)– but we will have a hard time

disentangling the weak phases

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What can we say about ?

• B ! vs K– From tree-penguin interference– Needs some theo assumptions

• B ! DK– Theoretically clean– Interference between bu(cd) and bc(ud)

• B D(*) D(*)D(*)a1 – Theoretically clean– Sin(2+)

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B DK

B - b

u

u

u

sc

D 0

B - b

s

D0

u c

Information on through interference in final states common to D0 and D0 (e.g. , KK..)

Several variants on the market• prospects look a little brighter, as color suppression not as large as previously thought

Measurements of various BR done or in progress

First asymmetry measurements

u u

Vub ~ ei

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from B DK, an example

D is CP-odd or CP-even neutral D combination

with strong phase

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DK D

D K+K-, +-

D KS0, Ks, KS , KS , KS ‘

no usefulconstraints yet

no usefulconstraints yet

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- Prospects• Many methods, many theoretically clean• Problems:

– Need a lot of luminosity!– Often methods have ambiguities

• , + 45o, + 90o, etc.

• Will need to combine many channels• It will be a long and arduous journey

• We are taking the first steps– Many more B D(*)K(*) modes have been/are being

measured

• Not sure where we will end up– But it should be fun

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Vub from b u l

Two complementary approaches• Reconstructed exclusive states

– B l B l B l B l – Theoretical uncertainties– Lattice could eventually come to the

rescue• Inclusive b u l

– Theoretically cleaner– Experimenters make cuts into phase

spaceintroduce theoretical uncertainties

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Vub: Exclusive Decays

• Branching ratios: BaBar, Belle, Cleo

• General agreement

• Working to combine into single Vub

• Typical individual measurement

|Vub| ~ 20%

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Exclusive Branching Ratios

Compilation from Gibbons, CKM Workshop 2003Compilation from Gibbons, CKM Workshop 2003

x 10-4

x 10-4

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E(lepton)

M2(X) E(X)

q2(l)

From Muheim, CKM Workshop 2003:Blue lines indicate bc l regionsFrom Muheim, CKM Workshop 2003:Blue lines indicate bc l regions

Inclusive decays: b u l

X=hadronic systin bX l

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b u l : new expt. technique

• Fully reconstruct one B• Then look only at what’s left

– Reduce combinatorics– Know momentum vector of recoil

• Important for kinematic reconstruction

– Reduce continuum

Brecoil

BrecoD* Y(4S) l

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S/B~0.3

MES [GeV]

Leptonpl>1.0 GeV/cS/B ~ 2.5

• B D(*) n• Efficiency only 0.4%• But statistics are OK• M(X) reconstruction• Belle, similar technique with B D(*) l

• B D(*) n• Efficiency only 0.4%• But statistics are OK• M(X) reconstruction• Belle, similar technique with B D(*) l

MX < 1.55 GeV

Signal167 ± 21events

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b u l inclusive: summary

•Individual measurements in agreement• ~ 15-20% uncertainty each• improvement on LEP

•Individual measurements in agreement• ~ 15-20% uncertainty each• improvement on LEP

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Vub Summary

• Much progress is being made• Very active area, both theory and

experiment• Lattice improvements soon• Want to go well below 10%

uncertainty for Unitarity Triangle constraints

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Conclusions• The B-factories have gone

through a very successful first three years

• Today I showed you only a small fraction of their physics program, there is much more

• We are looking forward to increases in luminosity, eventually x10-20 more data

• The SM is still alive and well, but we’ll continue poking at it

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THE END