Guillaume Thérin LPNHE – Paris Lausanne

18th November 2005 Guillaume Thérin 1Lausanne – measurements with

Guillaume ThérinLPNHE – Paris

Lausanne

BaBar Measurements of

detector at SLACwith


• Theoretical context– CP violation– Standard model

• PEPII and BaBar B-Factory

• Direct measurements of – B- D(*)K(*)- method (ADS, GLW, GGSZ)

• Direct measurements of sin(2)– B0 D(*)-+, D(*)-+,

• B0 D(*)0K(*)0

• Combinations of the results with CKMFitter

Outline


Theoretical context


• The CKM matrix elements Vij describe the electroweak coupling strength of the W to quarks• The CKM mechanism introduces quark flavour mixing

CP violation in the Standard Model

The phase changes sign under CP.

Transition amplitude violates CP if Vub ≠ Vub*, i.e. if Vub has a non-zero phase

=CP

Complex phases in Vij are the origin of SM CP violation


Structure of the CKM matrix

– Mixing is weak Magnitude of elements strongly ranked (leading to ~diagonal form)

• 3 particle generations and unitary CKM matrix: 4 parameters (3 real + 1 im.)

= arg( V*ub/ Vcb ) (Wolf.)

Unitarity Triangle

/3

/2

/1

VtdVtb*

VudVub* VcdVcb

*

()

VcdVcb*)(

1)1(21

)(214

23

22

32

AiAA

iA

Wolfenstein :

•Measuring SM CP violation Measure complex phase of CKM elements

• 3 real par. A, λ (= sin Cabibbo = 0.22) and ρ

• 1 imaginary par. iη (responsable of CP violation)

() ()


http://ckmfitter.in2p3.fr

• CP violation studies established:

Experimental Constraints on the Unitarity Triangle

• Before the B-factories, constraints came from kaons, B oscillations and |Vub/Vcb|• B-factories can be used to over-constrain the triangle and so to test the SM

• sin(2) = 0.685 ± 0.032• experimental contraints on • (this talk) harder to measure

• The SM test consists of comparing 2 kinds of measurements :

• P (new physics)• B decays in charmless 2-bodies (envolving amplitudes with penguins)

charmonium

bcus,bucsbcud,bucdbcus,bucs

• st (Standard Model), • B- D(*)K(*)- (GLW, ADS, GGSZ)• B0 D(*), D0K(*)0 ( or sin(2))• Bs Ds K(*)0 (probably at LHC)


PEPII / BaBar, Experimental apparatus


3.1 GeV9 GeV

0 0

(4 )

(50% ,50% )

e e S BBB B B B

The PEP-II B factory - Specifications

BB threshold

(4S)

• Produces B0B0 and B+B- pairs via Y(4s) resonance (10.58 GeV)

• Asymmetric beam energies•Low energy beam 3.1 GeV•High energy beam 9.0 GeV

• Clean environment~28% of all hadronic interactions are BB


RUN1

RUN2

RUN5

RUN3

Most analyses are based on 232.106 BB pairs

RUN4

Trickle injection:w/o trickle injection top-off every 30-40 min

continuous filling with trickle injectionmore stable machine, +35% more lumi

The PEP-II B factory - Performance

• PEP-II top lumi: 1.x1034 cm-2s-1 (~10 BB pairs per second)

• Integrated luminosity• PEP-II delivered: 311 fb-1

• BaBar recorded: 299 fb-1 on-peak+off-peak data• Most analyses use 211fb-1 of on-peak data

Records:

18th November 2005 Guillaume Thérin 10Lausanne – measurements withBABAR Collaboration : 11 countries and ~590 physicists !

Solenoid : 1.5T

ElectroMagnetic Calorimeter :6580 CsI crystals (Tl)E)/E = (2.32 E–1/4 1.85)%

Support tube

Instrumented Flux Return :iron / RPCs [ → LSTs ]

The BaBar detector

Drift CHamber :40 layers(pT)/pT = (0.13 pT 0.45)%

Detector of Internally Reflected Cherenkov light : 144 quartz bars, 11000 PMsK/ > 2.5 (p < 4.3 GeV/c)

Silicon Vertex Tracker :5 layers of double-sided Silicium, vertex resolution of 60-120 m


Selecting B events for CP analysisB mesons identification

mES

E

**beamB EEE

e+ (3.1 GeV)

e- (9 GeV)

2*2*BbeamES pEm

b

udsc

Signal

)()4( MeVME Sbeam

isotropic

E*beam very well known

e+e- → uu, dd, ss, cc

e+e- → bb

-2 –1 0 1 2 3 4Fisher discrimnant

E*beam = E*Υ(4S) / 2

K/ separation with Cherenkov angle

Excellent separation between 1.5 and 4 GeV/c

Combinatorial e+e- qq bkg suppression

Jet-like

E*beam 2 mB>~


Constraining with B- D(*)K(*)- decays

Gronau-London-Wyler methodAtwood-Dunietz-Soni method

Giri-Grossman-Soffer-Zupan methodCombination

Introduction


B-bu

cu

su

D0

K*-Vcb

Vus

Constraining with B± → D(*) K(*)± decays

a a rB ei()

B-

b

usu

u

cD0

K*-

Vub

= arg( V*ub/ Vcb )

Favored decay b c

Strong phase CKM Angle

Suppressed decay b u

Ratio of the 2 amplitudes

rB ≈ 0.1-0.2

• D0 , D0 same f interference sensitive to :

f f

– Gronau-London-Wyler : CP eigenstates

– Atwood-Dunietz-Soni : DCSD D0 and CA D0 ex. : B- → (K+ -)D K-

Ks0

KsK+K-

+Ks

– Giri-Grossman-Soffer-Zupan : D0 → Ks

K+-Ks-

rD / rB ≈ 0.5

B(B- D(*)K(*)-) 5. 10-4

! rB, , different for DK*±, DK± and D*K± modes


Constraining with B- D(*)K(*)- decaysIntroduction

Atwood-Dunietz-Soni methodGiri-Grossman-Soffer-Zupan method

Combination

Gronau-London-Wyler method


GLW - Observables of the method - B± D(*) K±(*)

A(B+→D CP K

*- )

A(B- →DCP K*+)

A( B→D0K* )

Observables are:

non-CP modes ≈ flavour eigenstates

N(B+ → D K*+) ≠ N(B- → D K*-)

Direct CP violation:


A+ R+= - A- R-

• Extract the 3 unknowns (, rB, (*)B) for each mode from 4 observables a relation

between observables:

• 8-fold ambiguity in • Sensitivity on depends on rB

• D(*)K modes• suffer from bkg from D(*)0 (12x higher BF) need excellent /K separation

• D(*)K* modes • cleaner but lower BF and lower efficiency• need to consider D(*)Ks irreductible component

• Need to take into account dilution effect from opposite-sign CP D0 decays in fKS0

and KS0 (for instance D0a0KS

0)• D*K* need angular analysis -not realistic with current statistics

GLW - Characteristics of the method - B± D(*) K±(*)

Experience:

Theory:


• Event Shape Variables

• cos( of B momentum

• mES & E

• mass (D0)

• D0 helicity

D0B• mass (KS

0)

• distance of flight

• mass (K*)

• K* helicity

K*Ks

0

• 232 millions of charged B decays• Reconstructed BF of the order of 2.10-7 – 10-6

CP=+1 : KK, ,non-CP : K , K 0, K 3

D0• track PIDs

CP+, non-CP

• mass (KS0)

• distance of flight

CP- : K s0 X.

X = {}Ks0

• mass ()

• helicity

• dalitz angle

• track PIDs

• mass (0)0

• mass ()

• helicity

• track PIDs

GLW – Reconstruction and selection - B± D K±*

-

-

+


CP+ : 24 CP- : 25B+B-

B0B0

cc

uds

Signal

• Adding CP+ modes together (resp. CP- and non-CP)• Strategy : fit in one dimension in mes

• Use data in E and D0 mass sidebands to fix the background shape

• Hypothesis : common parameterisation for all modes (checked on MC)

D0 mass

E

mes

Gaussian G(rB = 0)

Argus function Ames

GLW – Distribution of the simulation and fit strategy - B± D K±*


GLW - Results of the fit for 232 millions of charged B - B± D K±*

m(D0) sidebands

E sidebands

B+non-CP CP+1 CP-1

SIGNAL REGION

B-

• One single Gaussian G• One single Argus A

• Simultaneous fit in mes for 3 regions :

– Signal– mD0 sidebands– E sidebands

PRD72,71103(2005)


• BD0K: 232M B± decays, D0KK, KS00

,0 KKDCP

000 SCP KD

KDB CP0

0CPDB

A 2 cut on C in these plots

• BD*0K: 123 B± decays, only D*0D00, D0KK, at the moment:

• Main background from kinematically similar B→D0 which has BF 12x larger– So the signal and this main background are fitted together

Kaon hypothesis

GLW - Results - B± D(*) K±

• Only CP+ modes

• 3D Fit(mes, E, C) without the kaon hypothesis

• 2D fit to E and the Cherenkov angle of the prompt track


GLW – Summary - B± D(*) K±(*)

No asymmetry seen All values compatible with 1 except for the DK* mode rB is bigger

than expected for this mode

1 0



Gronau-London-Wyler method


Atwood-Dunietz-Soni method


ADS - Method - B± D(*) K ±(*)

B-b

u

c

u

s

u

D0

K*-

B-

b

u

u

cD0

Cabibbo favoured bc amplitude

Cabibbo suppressed bu amplitude

s

u

s

u

u

d

u

d

u

s DK

rB =Cabibbo suppressed cd amplitude

Cabibbo favoured su amplituderD =

rD = 0.060±0.003Sensitivity: rD / rB ≈ 0.5

([ ] ) ([ ] ) 2 sin( )sin /([ ] ) ([ ] )ADS B D D B ADS

Br K K Br K KA r r RBr K K Br K K

2 2([ ] ) ([ ] ) 2 cos( )cos([ ] ) ([ ] )ADS D B B D D B

Br K K Br K KR r r r rBr K K Br K K

• Better sensitivity than GLW but lower BF •4-fold ambiguity in : need to measure at least two D decay modes to loose ambiguity between and the strong phase


mES (GeV/c²)

~90 events ~4 events

RS WS

WS B+

WS B-

• Cut same variables as GLW

• Some of them are put in a neural network

ADS – Results of the fit - B± [K ±]D K±(*)

±

B± [K± ]D K*±

±

B± [K ±]D K*±

±

B- [K+ -]D K*-

B+ [K- +]D K*-

PRD72,71104(2005)


1-C

L GLWADScombination

rB

[0,] & (D+)[0,2]

(deg)

1-C

L

(semi-log scale)

[75°,105°] (excluded @2 CL)

GLW+ADS – Interpretation - B± D K±*

EPJ,C41,1 (2005)• CkmFitter Frequentist approach to determine and rB

• Construction of Confidence Level plots

PRD72,71104(2005)


hep-ex/0504047

B-→D*[D0]K-

B-→D*[D]K-

B-→DK-

D*→D0/D ≠ in D* by

(r*B)²< (0.16)² * (Bayesian r*B²>0 & uniform, and D*)

PRD70,091503(2004)

0<D<2rD±1

51°<<66°

rB<0.23**

*

*

*

ADS – Results - B± [K ±]D(*) K±

±


ADS – Summary - B± D(*) K±(*)

• No signal peak was observed

• More sensitive than GLW but need more statistics to constrain

• Other non-CP modes to add and reduce ambiguities

0




CombinationGiri-Grossman-Soffer-Zupan method


Schematicview of the

interference

2m

2m2m

2m

0 D 0 D

Reconstruct BD(*)0K(*) with Cabibbo-allowed D0/D0KS

If D0/D0 Dalitz f(m+2,m-

2) is known (included charm phase shift D): ),(),()(),( 2222022

mmfeermmfKDBAmmM iiB

B

),(),()(),( 2222022

mmfeermmfKDBAmmM ii

BB

B:B+:

|M|2 =

ambiguity only 2-fold ( ↔ )Experimentally: BF[(B D0K)(D0 K0 )]=(2.20.4)10-5 High statisticOnly charged tracks in final state high efficiency/low bkg

)( BiBer

GGSZ – Dalitz Method - B± D(*) K±(*)2 0 2

2 0 2 ( ) ( )

S

S

m M Km M K


f(m2+,m2

-) extracted from high statistics tagged D0 events (from D*)

• D decay model described by coherent sum of Breit-Wigner amplitudes

• Dphase difference determined by model

•Not so good for s-wave. Need controversial and ’(1000) to reasonably describe the data

• Masses and widths fixed to PDG2004 values except for and ’ (fitted)

13 fitted resonances + NR term ++’2/dof3824/3022=1.27

DCS K*(892)

CA K*(892)

(770)

GGSZ – D0 KS Dalitz model f - B± D(*) K±(*)


Mode Signal events

B-DK− 282 ± 20

90 ± 11

B-D*[D]K− 44 ± 8

B-DK*−[K0S-] 42 ± 8

B-D*[D0] K−

DK- D*[D0]K- D*[D]K-

hep-ex/0504039

(mES>5.27 GeV/c²)

B-DK*−[K0S-]

GGSZ – Fit results - B± D(*) K±(*)


(deg

)

k.rsB

0<k<1 is an extra parameter with no assumption made on (K0

S-) under the K*- part

2 CL1 CL

GLW+ADS

1 1

2

GGSZ/GLW+ADS – Confidence regions - B± D K±*

(deg)

GGSZrB

More constraint with GLW/ADS for this mode than with GGSZ

(K0S-) under the K*- and K S-waves

accounted for in a model where strong phase are unknown (k=1)


7D Neyman Confidence Region:•rB(DK), rB(D*K), k.rsB

• B(DK), B(D*K), B(DK*)•

= 67°± 28°(stat.) ± 13°(syst. exp.) ± 11°(Dalitz model)

D0K- D*0K- D0K*-

(deg

)

k.rsB (<0.75 @ 2CL+and no assumption)

2 CL1 CL

GGSZ – Combined results - B± D(*) K±(*)

rBrB


(deg)

1-C

L

=

GLW+ADS+GGSZ - Combination - B± D(*) K±(*)

• Sensitivity for all methods depends on rB

GGSZ

GLW+ADS

B± D K*±

B± D* K±

B± D K±


Constraining sin( with B0 D(*) decays


CP violation in B0D(*)

• Large branching fraction for favoured decay (~3x 10-3)• Small BR for suppressed decay (~10-6)• Small CP violating amplitude

Favoured b c decay

*cb udV V A (*)

* i i iub cd rV V e A e e

Strong phasedifferenceCKM

angle

c0B

d

bu

d

*D

W +

Suppressed b u decay

Determines the sensitivityof the method

r(D(*)) ≡ r(*) =A(B0 → D(*)- +)

≈ 0.015 A(B0 → D(*)- +)

b

d

bc

d

0Bu

*D

0B

d+


Time-dependent decay rate distributions

• Measurements of S+ and S- determine 2+ and if r is an external input • Experiment : tag the flavour of the B with lepton and kaon categories combined in a neural network

Mixing-Decay interferenceP(B0 → D(*) ,t) 1 C cos(md t) + S sin(md t)

P(B0 → D(*) ,t) 1 C cos(md t) - S sin(md t)

∞ ±

±

±

±

±±

±

C = 1 – r2 1 + r2 ≈ 1

0Bcb

l+lepton tag

0Bc sb K+

kaon tag

(4s)Tag B

Reco BK+

+z

K+

t z/c

z

-s

-

neglecting terms in o(r2)S± ≈ 2r sin ( 2 ± ) , |S±| 0.03<~

±∞


Possible CP violation on the tag side

Potential competing CP violating effects in B decays used for flavour tagging

signal side

tag side

2 sin(2 )cos2 'sin(2 )cos '2cos(2 )( sin 'sin ')

a rb rc r r

2 sin(2 )cos

2 cos(2 )si0

nlep

ba r

c r

Lepton tagsKaon and other flavour tags

(*)

* i i iub cd rV V e A e e ’*

cb udV V A +

P(B0 → D(*) - ,t) 1 + C cos(md t) + sin(md t) [± 2r sin(2) + 2r’ sin(2’)]∞

Kaon tag : expect CP violation comparable to signal → Modified time distributions

0Bc sb K+

Observables a, b, c

c sK+

b0B u

PRD68, 034010


B0→D*: partial reconstruction results

• 18710 ± 270 lepton tags• 70580 ± 660 kaon tags

Lepton Tags

PreliminarySignalCombinatoric BBPeaking BBContinuum

D

*0 DBsoftD

0

X Find events with two pions and examine the missing mass mmiss

Lepton Tags

kaon Tags

Mea

n va

lue

ACP= N(B0 tag) - N(B0 tag) N(B0 tag) + N(B0 tag)

Preliminary

Preliminary

hep-ex/0504035


B0D(*),D full reconstruction results

*B D

*

0

DB

BB

rec

tag

*

0

DB

BB

rec

tag

*

0

DB

BB

rec

tag

background

*

0

DB

BB

rec

tag

Lepton tags, D* final state

B mode Yield Purity (%)

D 15635 135 85.5 0.3

D* 14554 126 93.0 0.2

D 8736 105 81.7 0.4

*B D

++0, D+K-++, Ks+ D*+ D0+ ,

D0 K-+,K-+0,K-+-+,Ks+-

- Reconstruct B0 candidate using full decay tree:


Determination of r

• Simultaneous determination of sin(2+) and r from time-evolution is not possible with current statistics Need r as an external input

• Estimate amplitude ratios from B0Ds(*)+- using SU(3) symmetry

0Bd

u

*SD

bc

0Bd

d

u

*D

bc

scsV cdVSU(3)

r(D) = 0.019 ± 0.004 r(D*) = 0.015 ± 0.006 r(D) = 0.003 ± 0.006

I. Dunietz, Phys. Lett. B 427, 179 (1998)

Assuming several hypotheses for SU(3) :• Assuming factorisation• Neglect exchange and annihilation diagrams

without any theoritical errors


|sin(2+)| > 0.64 @ 68 % C.L.|sin(2+)| > 0.42 @ 90 % C.L.

- Combine partial and fully reco results for the a and clep parameters

|2+| = 90o 43o

68 % 90 %

30% theoretical error on r 100% theoretical error on r

Interpretation of sin(2) assuming SU(3)Assign theoretical error on r(D*), r(D) and r(D)

Bayesian approachFrequentist approach (Feldman-Cousins)

90 % CL68 % CL

www.utfit.org


Conclusion


Conclusion

• Measuring at B-Factories: an impossible mission a few years ago

• GGSZ analyses give the best results• The GLW method eliminates

constraints close to 900

• All analyses are statistically limited or statistics are too low for most sensitive methods

GLW,ADS,GGSZ WA = (63+15

-12)º

|sin(2β+γ)| BaBar >0.64 (@ 68 %CL)

•B- D(*)K(*)- (GLW, ADS, GGSZ)

•B0 D(*)


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