Max Baak 1

Measurement of the Amplitude Ratio of Measurement of the Amplitude Ratio of B B0 0 J/J/ K K*0*0 to B to B0 0 J/J/ K K*0*0 (K (K++--) decays) decays

Max BaakNIKHEF, Amsterdam

For the BaBar Collaboration

APS MeetingPhiladelphia, 8 April 2003

Max Baak 2

Two simple conceptsTwo simple concepts

cs

c /J

0B d

b(*)0K

Wrong-flavor decay

d?

- B0 J/ K * 0

- B0 J/ K * 0

( )

( )

cs

c /J

0B d d

b(*)0K

Right-flavor decay

- B0 J/ K * 0

- B0 J/ K * 0( )

( )

s

s

d duu

0*K

K

s

s

d duu

0*K

K

To tag a K*, use charge of kaon and pion

1

2

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Can sin2ßCan sin2ßSS and sin2ßand sin2ßL L be different?be different?

• Time-dependent asymmetry for B0 J/ KS,L normally given by-

sin2ßS = sin2ßL

• Can sin2ßS and sin2ßL be different?

- SM corrections: (sin2ßS - sin2ßL) ~ 0.01

- Experimental limit: 0.02 ± 0.17

• How to find wrong-flavor decays if K0 and K0 mix into CP states? Use B0 J/ K*0 sample! Same quark-level process. Tag with

K*0 K+-.

S,L

S,L S,L/ ψ

S L SS,L

, ,L

( ( ) ) ( ( ) )( ) sin( )

( ( ) ) ( ( )sin(2β)

)B J K d

B t K B t Ka t m t

B t K B t K

sin2L = 0.723 0.158

sin2S = 0.741 0.067 Ob

serv

ed a

sym

met

ry

Grossman, Ligeti, KaganPhys.Lett.B538:327

BaBar

data

0 0 0 0/ , /B J K B J K

For different sin2ßS and sin2ßL, need non-zero wrong-flavor decay amplitudes (New Physics)

Max Baak 4

B B J/ J/ K K*0*0 time dependent analysis time dependent analysis

B0(t) J/K*0

B0

Initialstate

Flavor eigenstate

No wrong- flavor

decays

B0(t)B0

Initialstate

Flavor eigenstate J/K*0

a) unmixed b) mixed

B0

B0

With wrong- flavor

decays

J/K*0

Standard ModelWrong-flavor

2

2

1 | λ |1 | λ |

C

2

2Im λ1 | λ |

S

0 *

0 *

/

/

A B J Kqλp A B J K

0 *

0 *

/

/

A B J Kpλq A B J K

For final state J/ K*0

replace C -C , S -S .

Extract wrong-flavor to right-flavor amplitude-ratios and from time-dependent fit to B0/B0 J/ K*0 and B0/B0 J/ K*0

=0 C=1, S=0 (standard B0B0 mixing)

*04( / , ) e c [1 + )]os(t

unmix dedf J K m tt *0

4( / , ) e cos( ) [1 - ]dt

mixedf J m tK t b)

a) *04( / , ) e [1 cos( ) + sin ( )+ ]t

unmi de dx df J S mt tmK Ct *0

4( / , ) e [1 cos sin( )( ) -- ]tmixe dd dS mf J t tCt mK b)

a)

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BaBar DetectorBaBar Detector

Cerenkov Detector (DIRC)144 quartz bars

11000 PMs

1.5 T solenoid

Electromagnetic Calorimeter 6580 CsI(Tl) crystals

Drift Chamber40 stereo

layers

Silicon Vertex Tracker5 layers, double sided

strips

e+ (3.1 GeV)

e- (9 GeV)

SVT: 97% efficiency, 15 m z hit resolution (inner layers, perp. tracks)

SVT+DCH: (pT)/pT = 0.13 % pT + 0.45 % DIRC: K- separation 4.2 @ 3.0 GeV/c 2.5 @ 4.0 GeV/c EMC: E/E = 2.3 %E-1/4 1.9 %

z

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K-K- separation with Cerenkov Detector (DIRC) separation with Cerenkov Detector (DIRC)• Good kaon-pion separation essential to distinguish

between K*0K+- and K*0 K-+ • BaBar uses DIRC: Čerenkov light in quartz angle c handle on

particle ID

(c) 2.2 mrad

K/ separation

>9

Momentum range of K and from K* < 3 GeV

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Analysis TechniqueAnalysis Technique

Fully reconstruct B mesonin state J/K*0 or J/K*0

Determine flavor of other B meson BTAG (“tagging”)

Reconstruct vertex of BTAG and compute proper time difference t

(4s)

Tag Bz ~ 110 m Reco B

z ~ 65 mJ/

K*0zcB 260 m

K+

t z/c = 0.55

At time of BTAG decay,the 2 B’s are in opposite

flavor states

z

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t distribution of mixed and unmixed eventst distribution of mixed and unmixed events

Decay Time Difference (reco-tag) (ps)

UnMixedMixed

0

10

20

30

40

50

60

-8 -6 -4 -2 0 2 4 6 8

perfect flavor tagging & time

resolution

x

UnmixMi

1 cos( ) sin( )4

f (Δ t)Bd

d

| Δ t |

d

/τ

dB

e C ΔtΔm S Δtmτ

Δ

Decay Time Difference (reco-tag) (ps)

UnMixedMixed

0

10

20

30

40

50

60

-8 -6 -4 -2 0 2 4 6 8

realistic mis-tagging & finite time

resolution

UnmixMix

cos( ) sin( )f (Δ t) 1 1 2 Resolution4 d d

Bd

d

| Δ t |/τ

BΔC Δt S Δtm Δme

τ w

w

J/ K* pdf (similar for J/ K*)Bflav Mixing pdf

D(*) , , a1 sample (Bflav) determines mistag fraction w and resolution function

tmetf dB

t

mixingd

dB

cos211τ4

)(τ

||

, Resw

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Data Sample [1999-2002]: 82 fbData Sample [1999-2002]: 82 fb-1-1 on on (4s) (4s) ResonanceResonance

Sample Ntagged PurityJ/ K*0 860 96%J/ K*0 856 96%

3 cut on E applied

‘tight’ kaon selection

* *B beamE E E

2 2* *ES beam Bm = E - p

signal region

mES [GeV/c2]

E [M

eV]

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Likelihood FitLikelihood Fit• Combined unbinned maximum likelihood fit to t spectra

of B-flavor and J/K*0 and J/K*0 samples.• Analysis performed blind.

Fit ParametersC,S,C,S 4Mistag fractions for B0 and B0 tags 12Signal resolution function 8Empirical description of background t 24B lifetime fixed (PDG 2002 value) B = 1.542 psMixing Frequency fixed (PDG) md = 0.489 ps-1

48 total free parameters

All t parameters extracted from data Correct estimate of the error and correlations

tagged flavor sample

tagged J/K*

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]sin[]cos[1),(

]sin[]cos[1),(

]sin[]cos[1),(

]sin[]cos[1),(

0*

0*

0*

0*

tmStmCtKR

tmStmCtKR

tmStmCtKR

tmStmCtKR

mix

unmix

mix

unmix

(assuming C, C and S, S are of equal size)

mixed upon wrec

occasions

• Doubly mis-IDing both K+ and - for each other fakes a K*0 for a K*0 - From MC: double mis-ID rate wrec = 0.3 %

K-K- swapping swapping

]sin[]cos[)21(1),(

]sin[]cos[)21(1),(

]sin[]cos[)21(1),(

]sin[]cos[)21(1),(

0*

0*

0*

0*

tmStmCwtKR

tmStmCwtKR

tmStmCwtKR

tmStmCwtKR

recmix

recunmix

recmix

recunmix

• To lowest order sine terms not affected, but cosine terms are.

Coefficient C S C SSyst. Error 0.004 0.001 0.003 0.001

Determined using MC

WARNING! Fake wrong-flavor decays! Need to minimize this

effect• Effect of K- swapping on time-dependent decay distributions?

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ResultResult

Source Error C/C

Error S/S

Background description 0.019 0.017t resolution and detector effects

0.016 0.021

Signal mistag fractions 0.013 0.000md and B (PDG 2002) 0.004 0.006Monte Carlo statistics 0.015 0.016K swapping 0.004 0.001Tag-side DCKM decays 0.006 0.019Total 0.034 0.039

C = 1.045 ± 0.058 (stat) ± 0.034 (syst)S = -0.024 ± 0.094 (stat) ± 0.039 (syst)C = 0.966 ± 0.051 (stat) ± 0.034 (syst)S = 0.004 ± 0.090 (stat) ± 0.039 (syst)

See my next talk!t (ps)

a) unmixed

b) mixed

c) asymmetry

Asym

met

ryEn

tries

/ 0.

6 ps

Max Baak 13

ConclusionConclusion

• To be submitted to PRL.Assuming common wrong-flavor decay amplitudes for B0 J/ K*0 and B0 J/

K*0

2 2

2 2

1 | λ | 1 | λ |;1 | λ | 1 | λ |

C C

0 *0

0 *0

2

/

/

0.041 (90% )

0.20 (90% )

B J K

B J K

CL

CL

0 *0

0 *0

2

/

/

0.063 (90% )

0.25 (90% )

B J K

B J K

CL

CL

• No sign for wrong-flavor decays B0 J/ K*0 and B0 J/ K*0

• Using the relations:

1

2

3

Measured values Standard Model

0.17 (90% )CL

Max Baak 14

Backup SlidesBackup Slides

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Cerenkov Particle Identification System (DIRC)Cerenkov Particle Identification System (DIRC)• Good kaon-pion separation essential to

distinguish between K*0K+- and K*0

K-+ • DIRC: Čerenkov light in quartz

Transmitted by internal reflectionRings projected in standoff boxDetected by PMTsEssential for Kaon ID >2 GeV

K- separation > 4

for this analysis

Max Baak 16

B Flavor Tagging MethodsB Flavor Tagging Methods• In BaBar tagging is handled with Neural

Nets• Information used:Primary leptonSecondary leptonKaon(s)Soft pions from D* decaysFast charged tracks

0

0 *

0

0 0

,,

, s

B D lB D D K lB DX D K XB D X D D

l ,

K b c s

W W

l

Tagging category

Fraction of tagged events(%)

Wrong tag fraction w (%)

Q = (1-2w)2 (%)

Lepton 9.1 0.2 3.3 0.6 7.9 0.3

Kaon+Kpi 16.7 0.2 9.9 0.7 10.7 0.4

Kaon+Spi 19.8 0.3 20.9 0.8 6.7 0.4

Inclusive 20.0 0.3 31.6 0.9 0.9 0.2

ALL 65.6 0.5 28.1 0.7

Smallest mistag fraction

The errors on C,S,C,S

scale with quality Q

1Q

Mistag fraction w determined with flavor eigen-states sample Bflav (23.7k events,

purity 82%)