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Searching for New Physics at the B factories:

Measurements of sin2b at BaBar

Gabriella Sciolla

Massachusetts Institute of Technology

Representing the BaBar Collaboration

Beauty 2005 - Assisi, June 20-24, 2005

- BaBar detector
- 4p collider detector

- PEP-II asymmetricBfactory
- 9.0 GeV e- beam
- 3.1 GeV e+ beam

- Peak luminosity
- 9.1 x 1033cm-2s-1

- Integrated luminosity
- Delivered: >268 fb-1

e+

e+

Most results in this talk are

based on 227 M BB events

Measurements of sin(2b) at BaBar

(r,h)

a

b

g

(0,0)

(1,0)

Two ways of looking for New Physics:

- Compare measurement of sides and angles
- Measure angles in channels with different sensitivity to New Physics

Measurements of sin(2b) at BaBar

- Charmonium modes:
- J/ψKS, ψ(2S)KS, χc1KS, ηcKS
- J/ψKL
- J/ψK*0 (K*0 → KS π0)

- Open-charm modes:
- D*+ D*−,D*+ D−, D+ D−

- Penguin-dominated modes:
- φK0, K+K−KS,KSKSKS
- η′KS
- KSπ0, ωKS,f0(980)KS

Measurements of sin(2b) at BaBar

mixing

decay

(hf)

- When only one diagram contributes to the final state:
- Example: B0 J/YKS:

Measurements of sin(2b) at BaBar

e+

Flavor tagging

Q=(30.5 0.5)%

Exclusive B

reconstruction

Dz~bgc Dt

Precise Dt determination

.

e-

B0

e-

U(4S)

m+

B0

p+

p-

m-

Measurements of sin(2b) at BaBar

Phys. Rev. Lett. 94, 161803 (2005)

- Theoretically clean
- Experimentally clean
- Relatively large BF (~10-4)

CP sample:

mES[GeV]

DE [MeV]

Measurements of sin(2b) at BaBar

Phys. Rev. Lett. 94, 161803 (2005)

The golden mode for sin2b:CP fit in B charmonium K0

Unbinned maximum likelihood fit to Dt distribution

CP=-1

CP=+1

sin(2b) = 0.722 ± 0.040stat ± 0.023syst

Measurements of sin(2b) at BaBar

cos(2β)<0

- Compare sides and angles
- Both BaBar and Belle results used

- Ambiguity resolved measuring sign(cos2b) in B0J/YK*
- cos(2b)=-0.68 excluded at 86.6%CL[PRD 71 (2005)032005]

- Excellent agreement with constraints from the sides
- Another SM triumph?
.

- Another SM triumph?

cos(2β)>0

SM test #2:

Compare b in various channels

Measurements of sin(2b) at BaBar

Measurements of angles NOT included in fit

- Tree measures sin2b from bccd transitions
- Penguin expected to be small in SM (< few %)
- D*D*: as large as Db = 0.6 [Grossman and Worah, 1997]

u,c,t

New Physics could have large effects

Measurements of sin(2b) at BaBar

New

BaBar

Preliminary

- Vector-vector final state:
- CP-even and CP-odd admixture

- Transversity analysis measures fCP-even

CCP+ = +0.06 ± 0.17 ± 0.03

-SCP+ = 0.75 ± 0.25 ± 0.03

fCP+ = (87.54.4 0.7)%

In good agreement with SM

Measurements of sin(2b) at BaBar

hep-ex/0505092

Updated

Updated

New

Measurements of sin(2b) at BaBar

Decays dominated by gluonic penguin diagrams

- The typical example: B0fKS
- No tree level contributions
- In SM, top quark dominates the loop: C~0; S~sin2b

- Impact of New Physics could be significant
- New particles could participate in the loop new CPV phases

- Low branching fractions
- Measure ACP in as many bsqq penguins as possible!
- φ K0, K+ K− KS,η′ KS, KS π0, KS KS KS, ω KS,f0(980) KS

- Measure ACP in as many bsqq penguins as possible!

NP

SM

Measurements of sin(2b) at BaBar

Phys. Rev. D 71, 091102(R) (2005)

Combined fKS and fKL fit:

Measurements of sin(2b) at BaBar

Phys. Rev. D 71, 091102(R) (2005)

- For non resonant B0K+K-KS decays, hCP = 2 feven- 1
- feven measured from angular moment analysis of the K+K- system

Measurements of sin(2b) at BaBar

hep-ex/0502013 (accepted by PRL)

- Theoretically clean
- Penguin dominated CP=+1 eigenstate

- Experimentally challenging
- B decay vertex uses KS pseudo-particles and beam spot constraint

Measurements of sin(2b) at BaBar

Phys. Rev. Lett. 94, 191802 (2005)

- Relative large BF ~ 6 x 10-5
- Theoretically less clean than fKS
- Tree diagram possible
… but Cabibbo and color suppressed…

- |DS| =|SYK-SPenguin|~ 0.01QCDFact 0.1SU(3)

- Tree diagram possible

Sη′Ks = 0.30± 0.14±0.02

Cη′Ks = −0.21±0.10±0.02

Measurements of sin(2b) at BaBar

hep-ex/0503011 hep-ex/0408095

hep-ex/0503018

- B0p0KS:
- dominated by
- tree contribution are non negligible (DS ~ 0.1 – 0.2)
- Experimental challenge: BCP decay vertex reconstruction (sDt~1ps)

- B0f0KS:
- In SM dominated by

- B0wKS:
- In SM dominated by
- But tree can be relatively large

Measurements of sin(2b) at BaBar

- Although each
- measurement is
- compatible with J/YKS,
- a trend is visible
- h’KS has the most
- significant shift
- (~2.9 s if theory
- uncertainties neglected)
- … but statistical errors are
- still large…

Measurements of sin(2b) at BaBar

Statistical fluctuation or

first signs of New Physics?

- Average of BaBar
- and Belle results
- Boxes are SM expected
- ranges for -hfSf from
- Beneke, hep-ph/0505075
- Shift still significant…

SJ/Y- Spenguins > 3 s

Measurements of sin(2b) at BaBar

- Precision measurements of sin2b in many different channels are a powerful probe for New Physics
- B0 charmonium K0: our calibration point (ssin2b ~ 0.04)
- B0 open charm: no smoking guns so far
- B0 penguin modes: intriguing shifts observed

- New Physics or statistical fluctuations?
- Time and data will tell…

- Goals for BaBar luminosity
- Summer 2006: 500 fb-1
- Summer 2008: 1 ab-1

Measurements of sin(2b) at BaBar

Measurements of sin(2b) at BaBar

- D*+D*- is not a CP eigenstate
- sum of L=0, 2 (CP even) and L=1 (CP odd)

- CP odd fraction Rdetermined by transversity analysis

Measurements of sin(2b) at BaBar

SM expectations

- D+D-
- D*D

Measurements of sin(2b) at BaBar

Measurements of sin(2b) at BaBar

hep-ex/0503011

- In SM these decays are dominated by
- tree contribution are non negligible
- DS ~ 0.1 in model dependent QCD calculations
- DS ~ 0.2 in SU(3)

- tree contribution are non negligible
- Experimentally challenging
- BCP decay vtx from KS and beam spot
- KS tracks with > 3 SVT: sDt~1ps

- Unbinned max likelihood fit:

Nsig = 300 ± 23

Measurements of sin(2b) at BaBar

hep-ex/0408095

hep-ex/0503018

B0 f0KSdominated by b sss

B0 ωKS : dominated by b → sdd

Tree contamination can be relatively large

Measurements of sin(2b) at BaBar

Results presented at Moriond 2005

BaBar

Preliminary

- Vector-vector final state:
- CP-even and CP-odd admixture

- Transversity analysis measures fodd
- fodd = (12.54.4 0.7)%

CCP+ = +0.04 ± 0.14 ± 0.02

-SCP+ = 0.65 ± 0.26 +0.09-0.07 ± 0.04

Good agreement with SM

Measurements of sin(2b) at BaBar

Measurements of sin(2b) at BaBar