princeton university, department of physics jadwin hall, washington rd

Princeton University, Department of PhysicsJadwin Hall, Washington Rd.

Princeton, NJ 08542-0708, U.S.A.

E-mail: [email protected]

XXXIII International Conference on High Energy Physics Moscow, Russia

Session 8: CP violation, Rare decays, CKM Friday, July 28, 2006, 10:06

Alexandre V. Telnov

Princeton University

for the BaBar Collaboration

Measurements of the CP angle Measurements of the CP angle

with the BaBar experimentwith the BaBar experiment

Alexandre V. Telnov (Princeton University) Measurements of the CP angle with the BaBar experiment 2

Current BaBar dataset: 347 million BB pairs (±1.1%)_

Theoretical and experimental introduction to the CKM angle

New BaBar results; their interpretation and implications for :

B → +−, ±0 , 00

B → 00, ±0, +−

B0 → ()0

Summary and outlook

OutlineOutline


g

u

u

,d

,d

W

0Bd

b

Penguin

Measuring Measuring

ACP(t) in decay to a CP eigenstate at the tree level :duub

Measure

SM)(in arg 180*

*

ubud

tbtd

VV

VV

Penguins: ACP (t ) sin(2eff); eff = Δdirect ACP ≠ 0

0B ,

,

uu

d

d

Wb

d

Tree


Isospin analysis in Isospin analysis in B B → → , , ρρρρ

A2

1A

~

2

1

00 ~ AA

00~A

00A

2

)(~

)(

)(~

)(

)(~

)(

00

00

00000

00000

0

0

BAA

BAA

BAA

BAA

BAA

BAA

In B → ρρ, there are 3 such relations (one for each polarization)

M. Gronau, D. London, Phys. Rev. Lett. 65, 3381 (1990)

PeTeA

PeTeAii

hh

iihh

~

21)22sin( CS

000

000

~~

2

1~2

1

AAA

AAA

)(~

)( 00 hhBAhhBA

Neglecting EW penguins, ±0 is a pure tree mode, and so the two triangles share a common side:

4-fold ambiguity in 2Δ : either triangle can flip up or down

6 unknowns, 6 observables in (there is no vertex to measure S00)5 observables in (or 7, when both C00 and S00 are measured)


TheThe BB00 → → ++−− analysisanalysis

Simultaneous ML fit to B0 → +−, K+−, +K−, K+K−

Using DIRC Cherenkov angle to separate pions and kaons Additional / K / KK separation from ΔE

Also measure AK+− : see talk by Emanuele Di Marco at 12:12 today

DIRC: 144 quartz bars 0.84 x 4π coverage; 97% eff. @ 3 GeV/c

12 σ /K separation at 1.5 GeV/c, 2 σ at 4.5 GeV/cCalibration sample: B− → −D0, D0 → +K−


New New BaBarBaBar results: results: BB00 → → ++−− (1)

signalbackground

mES

mES

Δt Δt

M. Pivk and F. R. Le Diberder, “sPlot: a statistical tool to unfold data distributions,”

Nucl. Instrum. Meth. A 555, 356 (2005) [arXiv:physics/0402083].

B0 tags

B0 tags_

asymmetry

BaBar-CONF-06/039

N+− = 675 ± 42

sPlot:Builds a histogram of x excluding it from the Maximum-Likelihood fit, assigning a weight to each event, keeping all signal events, getting rid of all background events, and keeping track of the statistical errors in each x bin


New New BaBarBaBar results: results: BB00 → → ++−− (2)

BaBar has observed a 3.63.6 σσ evidence for CP violation in B0 → +−

SS = = −0.53 −0.53 ±± 0.14 0.14 ±± 0.020.02

CC = = −0.16 −0.16 ±± 0.11 0.11 ±± 0.030.03

(S,C) = (0.0, 0.0) is excluded at a confidence level of 0.99970 (3.6 σ)

BaBar-CONF-06/039


TheThe B B → → ±±00, , 00 00 analysisanalysis

Simultaneous fit to B0 → +0, K+0 (using DIRC Cherenkov angle to separate pions and kaons)

B0 → 00: branching fraction and time-integrated direct CP asymmetry

new: in addition to 0 → , we use merged 0 and → e+e− conversions

10% efficiency increase per 0 (4% from merged 0

, 6% from conversions)

merged 0 :

the two photons are too close to one another in the EMC to be reconstructed individually; can be recovered using

,

where S is the second EMC moment of the merged 0 →

The control sample: →

)( 00022

SSEM

→ e+e− conversions: result from interactions with detector elements

beam pipebeam pipe

inner SVT layersinner SVT layersDCH inner wallDCH inner wall

SVT outer layersSVT outer layers


New New BaBarBaBar results: results: B B → → ±±00, , 00 00

mES ±0 mES 00

N00 = 140 ± 25N±0 = 572 ± 53

CC0000 = = −0.33 −0.33 ±± 0.36 0.36 ±± 0.080.08

BrBr0000 = = (1.48 (1.48 ±± 0.26 0.26 ±± 0.12) 0.12)

1010−−66BrBr±±00 = = (5.12 (5.12 ±± 0.47 0.47 ±± 0.29) 0.29)

1010−−66

B± → ±0 background

BaBar-CONF-06/039

sPlot


Here is one of the possible solutions to the Gronau-London isospin triangle in B → according to the

central values of the latest BaBar results:

An interpretation An interpretation of the new of the new B B → → resultsresults

ΔΔ

This is a frequentist interpretation: we use only the B → isospin-triangle relations in arriving at these constraints on Δ = − eff

and on itself

|Δ | < 41º at 90% C.L.

BaBar-CONF-06/039

= 0 excluded at 1−C.L. = 4.4 10−5

near 0 can be disfavored by additional experimental information


B B → → angular analysisangular analysis

DSA3

2

3

1 :alLongitudin 0

PDSA

PDSA

2

1

6

1

3

1 :Transverse

2

1

6

1

3

1 :Transverse

1

1

pure CP = +1

transverse is not a CP eigenstate

“helicity frame”

B → is a vector-vector state; angular analysis is required to determine CP content:

Fortunately, the fraction fL of the helicity-zero state in B → decays is very close to 1:

Heavy Flavor Averaging Group, April 2006 update: http://www.slac.stanford.edu/xorg/hfag/rare/winter06/polar/index.html

fL(B0 → +−)WA= 0.967+0.023

−0.028

fL(B± → ±0)WA= 0.96 ± 0.06


ΔΕmES 0f0

00

New New BaBarBaBar results: results:

Incremental improvements in the event selection and the analysis techniqueResults are statistically consistent with the previous BaBar analyses

N00 = 98+32 ± 22−31

Br00 = (1.16 +0.37 ± 0.27) 10−6−0.36

fL(B0 → 00)= 0.86+0.11 ± 0.05−0.13

3.03.0 evidence forevidence for BB00 → → 0000

The systematic error is dominated by interference with B0 → a± (1260) and by PDF parameter uncertainties

1

BaBar-CONF-06/027

hep-ex/0603050,accepted by PRLBr (B0 → a± (1260)

) Br (a± (1260) →

±

± ) = (16.6 ± 1.9 ± 1.5)

10−61 1

Br (B0 → 0f0 ) Br ( f0 → +

−) < 0.68 10−6 (at 90%

C.L.)Br (B0 → f0 f0) Br 2( f0 → +

−) < 0.33 10−6 (at 90%

C.L.)

Also measure:


New New BaBarBaBar results: results: BB±± → → ±±00

ΔΕ

Br±0 = (16.8 ± 2.2 ± 2.3) 10−6The systematic error is dominated by modeling of backgrounds, signal misreconstruction, and by statistical PDF uncertainties

mES

continuum + BB backgrounds

N±0 = 390 ± 49 BABARpreliminary BABAR

preliminary

Based on 232 million BB pairs; BaBar-PUB-06/052 _

Phys. Rev. Lett. 91, 221801 (2003)Phys. Rev. Lett. 91, 171802 (2003)

PDG 2004: (26 ± 6) 10−6

Belle: (31.7 ± 7.1+3.8) 10−6

Previous BaBar : (22.5+5.7 ± 5.8 ) 10−6−6.7

−5.4

}+0

00+−/√2“before”:

old ±0 WA

isospin prediction

fL(B± → ±0) = 0.905 ± 0.042+0.023

−0.027

The new BaBar measurement in B± → ±0 allows the isospin triangle to close


Br (B0 → a± ) Br (a± → +

−

± ) < 30 10−6 (90%

C.L.)1 1

B0 tags

B0 tags_

asymmetry

Δt (ps)

New New BaBarBaBar results: results: BB00 → → ++−−

N+− = 615 ± 57

fL(B0 → +−) = 0.977 ± 0.024+0.015

−0.013

Slong = −0.19 ± 0.21+0.05

−0.07Br +− = (23.5 ± 2.2 ± 4.1)

10−6 Clong = −0.07 ± 0.15 ± 0.06

dominated by self-crossfeed

distributions for the highest-purity tagged events

mES sum of backgrounds

ΔΕ

m±0 helicity

BaBar-CONF-06/016

BABARpreliminary

reduced systematics thanks to hep-ex/0605024,accepted by PRD


As datasets increase, determination of both C and S will become possible in B0 →00,

leading to an improvement in the precision of the the isospin analysis

BaBar-CONF-06/27, BaBar-CONF-06/016

An interpretation An interpretation of the new of the new B B → → resultsresults

This is a frequentist interpretation: we use only the B → branching fractions, polarization fractions and isospin-triangle relations in

arriving at these constraints on Δ = − eff and

ΔΔ

|Δ | < 21º at 90% C.L.

|Δ | < 18º at 68% C.L.

BABARpreliminary

[74, 117]º at 68.3% C.L.

BABARpreliminary

Due to the new B0 →00 BF result, the constraint on from B → has become less stringent


BB00 → → (())00: : Dalitz-plot analysisDalitz-plot analysisBaBar-CONF-06/037 and references therein

0B

0B

is not a CP eigenstate

An isospin-pentagon analysis method exists but is not fruitful

Time-dependent Dalitz-plot analysis assuming isospin symmetry,

measuring 26 coefficients of the bilinear form factors

00

−

+−

The (1450) and (1700) resonances are also included in this analysis

Interference in the corners of the Dalitz plot provides information on strong phases between resonances

)(~

)(~

)(~

)(~

)()()()(

000

00

000

00

AfAfAfBA

AfAfAfBA

A. Snyder and H. Quinn, Phys. Rev. D, 48, 2139 (1993)

0

+

0

+

Monte Carlo


New New BaBarBaBar results: results: BB00 → → (())00 (1)

mES

Δt/(Δt)

BaBar-CONF-06/037

ΔΕ

NN output

m' '

data

projection of the fit result

signal misreconstructionexpected B backgroundcontinuum background

minimum of the three di-pion invariant masses


New New BaBarBaBar results: results: BB00 → → (())00 (2)

S = 0.01 ± 0.12 ± 0.028

C = 0.154 ± 0.090 ± 0.037

ΔS = 0.06 ± 0.13 ± 0.029

ΔC = 0.377 ± 0.091 ± 0.021

parameters from the quasi-two-body description of B → :

a more physically intuitive way to represent direct-CP quantities:

A = −0.142 ± 0.041 ± 0.015

A = 0.03 ± 0.07 ± 0.03+−

A = −0.38+0.15 ± 0.07−0.16

−+

BaBar-CONF-06/037

For results on Direct CP Violation, attend talk by Emanuele Di Marco at 12:12 today


An interpretation An interpretation of the new of the new BB00 → → (())00 resultsresults

++ −−[5, 63]º

at 68.3% C.L.

[75, 152]º at 68.3% C.L.

no constraint at 2σ level

BaBar-CONF-06/037

+ − = arg(A+*A−) :the relative phase between the amplitudes of

B0 → −+ and B0 → +−

The constraint on from B0 → ()0 is relatively weak – but free from ambiguities!


Recap of new resultsRecap of new results

Br (B0 → a± (1260) ) Br (a± (1260) →

±

± ) = (16.6 ± 1.9 ± 1.5)

10−61 1

Br (B0 → a± ) Br (a± → +

−

± ) < 30 10−6 (90%

C.L.)1 1

Br00 = (1.16 +0.37 ± 0.27) 10−6

First evidence, at 3.0−0.36

fL(B0 → 00)= 0.86+0.11 ± 0.05−0.13

Br±0 = (16.8 ± 2.2 ± 2.3) 10−6 fL(B± → ±0) = 0.905 ± 0.042+0.023

−0.027

S = −0.53 ± 0.14 ± 0.02C = −0.16 ± 0.11 ± 0.03

CP violation at 3.6

Br±0 = (5.12 ± 0.47 ± 0.29) 10−6

Br00 = (1.48 ± 0.26 ± 0.12) 10−6

C00 = −0.33 ± 0.36 ± 0.08

fL(B0 → +−) = 0.977 ± 0.024+0.015

−0.013

Br +− = (23.5 ± 2.2 ± 4.1) 10−6

BB00 → → (())00:: see page 18see page 18

Slong = −0.19 ± 0.21+0.05

−0.07

Clong = −0.07 ± 0.15 ± 0.06


CKM fitno in fit

169.7°

[164, 176]º at 68.3% C.L.

Global fits for the value ofGlobal fits for the value of

CKMfitter Group (J. Charles et al.), Eur. Phys. J. C41, 1-131 (2005), [hep-ph/0406184], updated results and plots available at http://ckmfitter.in2p3.fr

M. Ciuchini, G. D'Agostini, E. Franco, V. Lubicz, G. Martinelli, F. Parodi, P. Roudeau, A. Stocchi, JHEP 0107 (2001) 013 [hep-ph/0012308],

updated results and plots available at http://utfit.roma1.infn.it

Please see talks by S. T'Jampens (CKMfitter) and V. Vagnoni (UTfit) for detailsPlease see talks by S. T'Jampens (CKMfitter) and V. Vagnoni (UTfit) for details

97.5°

[86, 114]º at 68.3% C.L.

Two interpretations currently exist that convert the B → , , measurements to constraints on :

CKMfitter talk: 17:30 tomorrow UTfit talk: 17:48 tomorrow


Summary and outlookSummary and outlook

The ability of existing B-meson factories to measure the angle with a precision

of a few degrees crucially depends on the developments in measuring the

branching fractions and CP parameters in B0 → 00 and B0 → 00

The BaBar experiment has observed evidence of

• Time-dependent CP violation in B0 → +−

• The decay process B0 → 00

and improved the precision of other measurements related to the extraction of .

The extraction of depends significantly on the statistical and theoretical treatment;

The larger of the CKMfitter and UTfit 68.3% C.L. intervals is [86, 114]º (CKMfitter)

princeton university, department of physics jadwin hall, washington rd

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