Summary of 2 measurements at Super KEKB

Hirokazu Ishino

Tokyo Institute of Technology

19 Dec., 2006

• current status

• 2 constraint with a 50ab-1 data sample

– • time-dependent Dalitz plot analysis

– • time-dependent CP violation (tCPV) parameter• isospin analysis including 00

– • tCPV parameter measurements and isospin analysis

• S00 measurement

• Summary

Contents

Notes

2• Almost all the measurement errors are

systematic dominant with 50ab-1 data.– except for 00, A00 and S00

• For the 2 constraints, we use the R-fit. – J. Charles et al., Eur. Phys. J. C 41, 1 (2005)

• Theoretical uncertainties are not taken into account.– will be summarized later.

Current Status

Dalitz+isospin

~10 degrees

00 B

B0→(

time-dependent Dalitz plot analysis involves cos(22)

27 parameter fit: one of the most complicate analyses!

B→systematic errors

by A. Kusaka in BNM

B→ errors

by A. Kusaka in BNM

2 constraints with B→at Super B factory

by A. Kusaka in BNM

B

Isospin relation

M. Gronau and D. London, PRL 65, 3381 (1990)

)22sin(1 22 AS

The cleanest method to extract 2

The measurements we need are branching fractions, CP asymmetry parameters and longitudinal polarization fraction in B→.

B→ measurements

HFAG2006

01.001.011.0)(

01.002.006.0)(

01.001.086.0)(

10)05.005.016.1()(

002.0002.0968.0)(

10)4.13.01.23()(

005.0005.0912.0)(

10)4.13.02.18()(

00

600

6

0

60

A

S

f

Br

f

Br

f

Br

L

L

L

Super B 2020(?)

B→systematic errors

• Branching fraction– PDF shapes, B.G. fractions, track , 0 – assume PDF and B.G. errors reduce to 1/10– assume track and 0 reduce to half: still

dominant• assign track = 1%, 0 = 2%

• CP asymmetries– assign 1% error to both A and S

• fL

– the current error: PDF shape and B.G. fractions– assume those are reduced to 1/10

2 constraint with B→at Super B factory

without asymmetries in B→00

We definitely need the asymmetries in B→00 for more constraints.

2

1

B0→asymmetries

• With 50ab-1 data, we assume– number of signal events: 5000– number of background events 22500

• assume the CP asymmetries of the main backgrounds such as continuum and a1 are well known.

• Toy MC using E and Mbc in the PDF

– (S)=0.10, (A)=0.08• Note: if we use LR (fisher discriminant), the error would be improved.• assume systematic error is much smaller than the statistics.

2 constraint with B→at Super B factory

2

1

dashed line: w/o 00 asymmetries

red solid line: w/ 00 asymmetries

9.02 @1

01.008.035.0)(

01.010.021.0)(00

00

A

S

0B

B→at Super B factory

01.003.016.0)(

01.001.037.0)(

01.001.066.0)(

10)05.002.031.1()(

10)17.004.07.5()(

10)10.002.021.5()(

00

600

6

60

A

A

S

Br

Br

Br

Super B 2020(?)

The ambiguity can be reduced if we measure the mixing-induced CP violation parameter S00 in

B0→00 decays

B0→vertexing

• We need B0→00 decay vertex position• Use 0 Dalitz decay

– 0→e+e−

– but small B.R. of ~1.2%• photon conversion

– reconstruct a photon from a e+e− pair– B vertex reconstruction with the same technique

as KS

– Conversion probability ~3% per photon in the current Belle silicon detectorreconstruct photon track

from an electron-positron pair

the photon track is extracted to the IP position.

• generate 1M Geant MC events with Belle detector– 2.2% 0 Dalitz decay– 11.3% photon conversion – 0.2% 0 Dalitz + photon conversion

• reconstruction– one 0 from 2, the other 0 from + e+e− pair

• e+e− pair either from IP or V0finder

– B candidates within |E|<0.3GeV, Mbc>5.26GeV/c2

– require at least two hits in Silicon Vertex Detector (SVD)– reconstruction efficiency 1.4%– estimated signal events with vertex info. : 920 w/ 50ab-1 data

• Backgrounds estimated from Geant MC samples– +0: 300– continuum events: 20000

B0→event selection

B0→event selection

continuum suppression variable

signal+0

continuum

E, Mbc and LR are used for the fit to the time-dependent CP parameters.

signal+0

continuum

Toy MC projection plots

~120m ~150m

B0→vertex resolution

z(CP,rec) - z(CP,gen) dz(CP-tag, rec) - dz(CP-tag, gen)

• Toy MC– # of signal =920– resolution function obtained from Geant MC

• previous page

– tagging efficiency 30%– B+→+0 300 events– e+e- →qq (q=u,d,s,c) continuum background:

20000 events.

• RMS of fitted S00

– S00 = 0.23

B0→Toy MC

2 constraint with B→at Super B factory

01.023.080.0)(

01.003.016.0)(

01.001.037.0)(

01.001.066.0)(

10)05.002.031.1()(

10)17.004.07.5()(

10)10.002.021.5()(

00

00

600

6

60

S

A

A

S

Br

Br

Br

w/ S00 w/o S00

32

Theoreticaluncertainties on2

@CKM06

Summary

• 2 constraints at Super B factory

– B→• systematic error dominant: the size of total

error is 1/5 of the current Belle measurement.

• 2 ~ 2◯

– B→• systematic error dominant other than B0→00

• 2 < 1◯

– B→• systematic error dominant other than S00

• 2 ~ 3◯

• Theoretical uncertainty ~3◯, comparable with the experimental uncertainties

Back up

B→a

first tCPV measurements

additional constraints on (2) in near future!