1. Search for CP Violating Decays of theU(4S)
O. Tajima (KEK)
for Belle collaboration
EPS-HEP`07 , Manchester

2. Introduction CP violation !! f1 B0 Y(4S) _ B0 f2 x1 x2 xY(4S)= +1
xCP = - x1 x x2
In case of x1 = x2
xCP = -1
CP violation !!

3. Examples of CP-violating decays
J/yKS
x1=-1
J/yKL
x1=+1
x2=+1
xCP=-1
J/yKS
x1=-1
hCKS
cC1KS
y(2S)KS
x2=-1
xCP=-1
Y(4S)
xCP=+1 B0 _ B0
J/yKS
x2=-1
xCP=+1
xCP=-1
CP violation !!

4. Y(4S) CPV is well described by the SM
Br( Y(4S)  B0B0bar  f1 f2 ; x1=x2 )
= F * Br(Y(4S)  B0B0bar) * Br(B0f1) * Br(B0f2)
Suppression factor due to CP violation
F = x2/(1+x2) * (2 sin2f1)2
x = /
sin2f1 = /
= /- 0.05
DCPV effect is neglected
This is an another
method to measure
Mixing induced CPV
Details are described in Text-books etc.
I.Bigi, V.Khoze, N.Uraltsev and A.Sanda, “CP Violation” (ed. Jarlskog), p175;
L.Wolfenstein, Nucl. Phys. B246, 45 (1984);
M.B.Gavela et. al., Phys. Lett. B162, 197 (1985);
I.Bigi and A.Sanda, Phys. Lett. B194, 307 (1987).

5. Fully reconstruct both B0B0 decays
Brute Force method
Fully reconstruct both B0B0 decays _ m+
J/y m- B0
Y(4S)
Far from the 5s observation
even if we have Super-B factory,
50billion Y(4S) (~50ab-1) p+ KS p-
Full reconstruction _ B0 e+
J/y e- p+ KS p-
Full reconstruction
Only ~0.04 events/(0.5billion Y(4S)) are expected …
( 1billion Y(4S)  1ab-1 data at a B-factory)

6. An Idea to Hunt for Such Decays
Full reconstruction m+
J/y m- B0
Y(4S) p+ KS p- _ B0
Signal MC
J/y(l+l-)KS
J/y(any)KS p+ KS p-
J/y, hc
Partial reconstruction
About 40 times higher eff. than “brute force method”
1.1(0.6) inclusive-J/y(hc) events in 535 million Y(4S) decays

7. This technique can be demonstrated with B+B- data
Full reconstruction:
B- J/y(l+l-)K-, D0(K-p+, K-p+p-p+)p-
Partial reconstruction:
B+ hc K+ and J/y K+
Nsig = 206  57 events
532M Y(4S) decays

8. Generic B0 decays are background
Large recoil mass region (>3.3GeV)
is not used because of large BG
and CP conserving BG (cc0, cc2 …)
MC samples ( 36billion Y(4S) )
scaled to 535million Y(4S)
y(2S)
ccbar KS + BG
Generic B0 decays
cc1
Events/(0.04GeV/c2)
J/y hc
recoil mass (GeV/c2)
We do not have any peaking BG contribution
in MC samples, Mbc sideband data

9. Additional BG suppression
CP violating modes (CP eigenstate) are flavor non-specific
flavor tagging quality (r)
for signal MC
(J/yKS , hcKS ) r
No flavor
discrimination
Perfect flavor
flavor tagging quality (r)
for BG MC r
No flavor
discrimination
Perfect flavor
discrimination
Generic B0 decays (BG) contain flavor specific decays,
such as B0D(*)ln , D*pslow …

10. Demonstration with a control sample
Full reconstruction:
B0 D(*)-p+ and D*-r+
Partial reconstruction:
B0 hc KS and J/y KS
Signal extraction by 2-D fitting
Nsig = 35  16 events
532 million Y(4S) decays

11. Preliminary
Results with 535 million Y(4S) decays for Y(4S)  B0B0  J/yKS+J/y(hc)KS
Nsig = events (consistent with ZERO)
+3.6
With 30 billion Y(4S) (30ab-1),
such decays will be observed
with 5s significance
Br(Y(4S)B0B0J/yKS+J/y(hc)KS) < 4x10-7 (90%C.L.)
SM prediction : 1.4x10-7

12. Super B Factory at KEK L = 8x1035 cm-2s-1 x±y I± L a b*±y
q=30mrad.
b*y=3mm
L = 8x1035 cm-2s-1
L a I±
x±y
b*±y
More beam currents
4x higher than KEKB
More RF power
New IR design
b*±y x1/2 (63mm)
New Beam pipe
Crab crossing
Beam-beam para. x6
0.057 (KEKB)
 0.19 (sKEKB)
Damping ring
Linac upgrade

13. Prospects of Super-KEB
Observation of
CP violation in Y(4S) decay
Now, we are here

14. Physics in Super-KEKB
Discovery of Lepton Flavor Violation in tmg decays#
Search for New CP-Violating Phase in b g s with 1 degree precision
CKM Angle Measurements with 1 degree precision
Discovery of B g Knn
Discovery of New Right handed currents in bs transition#
Discovery of New Subatomic Particles
sin2qW with O(10-4) precision
SfKs < SJ/yKs is established#
New results with
U(5S), U(3S) etc.
|Vub| with 5% Precision
Discovery of B g Dtn
Discovery of B g mn
# SUSY GUT with
gluino mass = 600GeV,
tanb = 30
“Discovery” with
significance > 5s

15. Summary A new method to hunt for CP violation in Y(4S) decay
Y(4S)B0B0barJ/yKS+J/y(hc)KS
Partial (with Full) reconstruction technique
Using 535 million Y(4S) decays in Belle experiment,
we obtain an U.L. of 4x10-7 (90%CL) for Br of such decays (SM prediction 1.4x10-7)
A Super-B factory has sufficient potential for observation of such CP-violating decays
Preliminary

17. Systematic uncertainty for Br(Y(4S)B0B0J/yKS+J/y(hc)KS)
Source
(%)
Recoil mass distribution
20.5
r distribution
4.2
Reconstruction efficiency
5.7
Number of BBbar
1.3
Branching fraction of sub decays
10.9
Total
24.3
Obtained from B+B- control samples
Dominated by statistical fluctuation
 to be reduced with increasing stat.
Dominated with uncertainty of Br(B0  hc KS)