# Presentation: 367560

## BaBar & Belle: Results and Prospects

- Claudio Campagnari
- University of California
- Santa Barbara

## 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

## Today:Concentrate (mostly) on measurements related to the unitarity triangle

## B-factories and the unitarity triangle

****

****

****

****

****

****

**B****0**** ******** J/******** K****s****, D*********D*********,...**

**B****0**** ******** ********, ********,..**

**B************,DK,D*************,...**

**B-mixing**
**B********(********,********)******

**B********ul******
**B********(********,********,********)l******

**B********cl******
**B********D****(*)****l******

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

## 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)

## B-factories performance

## 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

## Mixing and lifetimes

- Results based on large samples of
- Fully or partially reco. hadronic decays
- Fully or partially reco. D* l ****
- Dileptons

- 29 fb-1

## t Distributions  Lifetimes

- t = proper time difference
- between the decay times of the
- two B-mesons

- t resolution of ~ same order
- of magnitude as lifetime

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

## Adding Tagging Information

- md = 0.516  0.016  0.010 ps -1

- 30 fb-1

## 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

## Mixing results summary

- }

-     LEP+CDF
- 0.497§0.014 ps-1

**}**

- BaBar + Belle
- 0.502§0.006 ps-1

- World Average
- 0.502§0.006 ps-1
- Dominated by BaBar & Belle

- _Mixing results summary_

- 3% precision!

## Mixing and Lifetimes - Prospects

- Hard, precision measurements
- Many are based on only a fraction of the available dataset
- Statistical uncertainties still significant
- room for improvement
- Theoretical uncertainties limiting factor in ability to extract clean CKM information

## The measurements of mixing and lifetimes

- provide the foundations for the
- time dependent CPV measurements that follow

## General time-dependent formalism

- _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

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

## Sin2 in b ! c c s

- Golden modes:
- clean theory
- “relatively easy” experiment
- Tree and leading penguin have same phase
- sinmt  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)

## Event Samples

- 1.6K events

- ~500 signal ev.

- _Event Samples_
- Clean ~2K KS sample
- +
- ~ 500 KL events
- with ~ 60% purity

## t distributions and asymmetries

- CP=-1

- CP=+1

## Slide 19

## Summary of sin2 in b  ccs

- 7.5% precision

## Fit for cosmt coefficient, extract ||

- 5% precision
- consistent with |****|=1
- (as expected in SM)

## Sin2 from other modes

- _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

##  J/ 0

-  J/ 0
-  ~ 40 ev

- D*D*
-  ~ 130 ev

-  KS
-  ~ 36 ev

- ‘ KS
-  ~ 150 ev

## B0 ! J/ 0

- _B__0__ __**!**__ J/____ ____0_

## 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 C

- S = -0.32 **§** 0.43 **§** 0.13
- C = +0.02 **§** 0.25 **§** 0.09

## b ! s modes

- B **!**  KS

- B **!** ‘ KS

-  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

## bs penguin: S coefficient (sin2)

- bs penguin average
-  0.18  0.20
- ~ 2.5  from ccs modes

## 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!

## 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 00 allows for clean extraction of 
- In practice 00 very hard

## B ! hh Branching Ratios (x 10-6)

- _B __**!**__ hh Branching Ratios (x 10__-6__)_

- Averages from J. Olsen, CKM Workshop 2003

## Time dependent fits to +-

- 78 fb-1
- ~  106 events

- 84 fb-1
- ~ 160 events

## + - Fit Results

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

## 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(B0K)= (7.31.31.3) 10-6
- BF(B0)= (22.61.82.2) 10-6

## B   

- ~ 430 events

- ACP = -0.18 **§** 0.08 **§** 0.03  **Ã** time integrated term
- C    = 0.36 **§** 0.18  **§** 0.04
- S    = 0.19 **§** 0.24 **§** 0.03

-  2 CPV effect
-  first step towards full
-    Dalitz analysis

- _B ____ ____ ___

## 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

## What can we say about ?

- B **!**  vs K
- From tree-penguin interference
- Needs some theo assumptions
- B **!** DK
- Theoretically clean
- Interference between bu(cd) and bc(ud)
- B D(*) D(*)D(*)a1
- Theoretically clean
- Sin(2+)

## B  DK

- 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

- Vub ~ ei

##  from B  DK, an example

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

- with

- strong phase

## DK

- D

- D  K+K-, +-

- D  KS0, Ks,
-   KS , KS , KS ‘

- no useful
- constraints yet

## - 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

## 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 space
- introduce theoretical uncertainties

## Vub: Exclusive Decays

- Branching ratios: BaBar, Belle, Cleo
- General agreement
- Working to combine into single Vub
- Typical individual measurement
- ****|Vub| ~ 20%

## Exclusive Branching Ratios 

- x 10-4

- x 10-4

## Inclusive decays: b  u l 

- From Muheim, CKM Workshop 2003:
- Blue lines indicate bc l  regions

- _Inclusive decays: b ____ u l ___

- X=hadronic syst
- in bX l 

## 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

**B****recoil**

****

**B****reco**

***D****

****

**Y(4S)**

***l****** ***

##  B  D(*) n

-  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

- Signal
- 167 ± 21
- events

## b  u l  inclusive: summary

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

## 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

## 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

## THE END