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!