Selected topics from Belle
Something Unique at Belle and New
- EPR entanglement
- Y(3S) run: Dark Matter Search
- B  D*tn (New @FPCP07)
- Crab cavity study / Super-KEKB
Y.Sakai KEK
SLAC seminar 29-May-2007
1
KEKB / Belle
Mt. Tsukuba
KEKB
Belle
~1 km in diameter
Belle detector
8 GeV e- x 3.5 GeV e+
Ares RF
cavity
e+ source
Lpeak = 1.71x1034
Integ. Lum. ~700 fb-1
2
EPR Entanglement
EPR Paradox:
Quantum Mechanics:
Entangled state  non-separable wave function even for
far apart particles
can not be a “complete” theory
Local realistic theory with “hidden” parameters
3
Bell Inequality
Any Local realistic theory with “hidden” parameters
S = |E(a,b)-E(a’,b)| + |E(a,b’)+E(a’,b’)| < 2
(Belle-CHSH Inequality)
[Physics 1, 195(1964); PRL 23, 880(1969)]
Violation  Reject LRT, Confirm QM
Many experiments performed: violation ~established
• Entangled photons
• Entangled Be ions
[e.g. G.Weihs et al., PRL 81, 5039(1998)]
[e.g. M.A.Rowe et al., Nature 409, 791(2001)]
_
Also, attempts with K0K0 system
[CPLEAR, PLB 422, 339(1998)
KLOE, PLB 642, 315 (2006)]
4
Why Y(4S)  B0B0 System
_
• One of few coherent systems in HEP
• Highest energy scale (~10 GeV)
breakdown of QM at high energy ?
Bell Inequality Test : intrinsically impossible
• QM to violate B.I. ; x = Dm/G > 2.6  xd = 0.78
• Active measurement needed
 Flavor measurement via decay reconstruction = passive
[.A.Bertlmann et al., PL A332, 355(2004)]
Any way to test QM at Y(4S) ?
5
Flavor Asymmetry (as Dt)
Precisely measure Time-dependent decay rate
Compare with Non-QM model
_
_ _
QM:
Same Flavor (B0B0, B0B0): ∝ 1 + cos(DmDt)
Opposite Flavor (B0B0) : ∝ 1 - cos(DmDt)
OF-SF
AQM(Dt) =
OF+SF
= cos(DmDt)
6
Non-QM models
• Local Realism: Pompili & Selleri (PS)
(examples)
[EPJ C14,469(2004)]
_ _
“elements of reality” = Flavor & mass (BH,BL, BH,BL)
random jump of Flavor within pair
• Spontaneous & immediate Decoherence (SD)
[e.g. PR 49,393(1936)]
Note) Local realistic model with same A(Dt) as QM is possible [quant-ph/0703206]
7
Time-dependent Asymmetry
8
Analysis Method
B0  D*ln + Lepton-tag
~Same as Dm
measurement
( high quality
lepton-tag only)
[PRL,89,251,803(02),PRD 71,972003(05)]
• Background subtraction
• Unfolding [SVD method]
Fully corrected (= true) A(Dt)
 Direct comparison with (any) theories
 Quantitative Test for non-QM model
9
Signal Reconstruction
signal
background
152M BB
6718 OF
1847 SF
10
Results & fit with QM
Fully corrected A(Dt): fit with QM
[quant-ph/0702267,
submitted to PRL]
152M BB
c2 = 5.2 (11 dof)
Good !
[ fit including WA Dm = (0.496  0.014) ps-1 (excl. Belle/BaBar)]
11
Result: SD & PS
SD
c2 = 174
disfavored 13s
over QM
PS
152M BB
c2 = 31.3
disfavored 5.1s
over QM
Decoherence fraction: l = 0.029  0.057
12
Y(3S) Run
Dark Matter search:
Y(3S)  p+p- Y(1S) [ cc]
No sensitivity
DAMA NaI
3s
Region
WIMPs: good candidate
o% antimatter
13
B ( Y(1S)cc )
Wh2
@
W : relic density
h : Hubble constant
v : 1/20 ~ 1/25
0.1 pb ・ c
<s(ccSM) v >
= 0.113  WMAP
qc
_
qc
s(ccSM) ~ 18 pb
@ s(SM cc ),
q
c
_
q
c
G(U(1S)cc) = fU2MUs(bbcc)
B ( Y(1S)cc ) ~ 6x10-3
(mc<4.73GeV/c2 ~ mb)
PRD 72, 103508 (2005) “Invisible quarkonium decays as a sensitive probe of dark matter”
Presented by B. McElrath in BNM-I in KEK Sep, 2006
Previous Upper Limit : < 23x10-3 (90% CL) by ARGUS (1986)
14
Signal of Y(1S)  invisible
e+
e-
Y(3S)
fixed energy
p+
No signal left
in the detector
Y(1S)
Invisible
Y(3S)
p+p- recoil mass
forms a peak
p-
@ 9.46GeV/c2
== mY(1S)
M precoil
+ p
15
Y(3S) : best for Y(1S)invisible
No signal
in detector
Y(3S) runs : 2.9 fb-1
(Feb, 2006 : 4days)
s~7nb
No trigger issue
s~4nb
S/N~1/8
sISR~0.02nb
S/N <1/1000
Energy scan by CLEO
16
Special: Loose 2-track Trigger
ptH > 300 MeV c
ptL
> 170 MeV c
D > 30
Trigger eff.
89.8%
(f135)
Trig. effic.: monitored by
prescaled 1-track Trrig.
17
Control sample:
2.9
4901.9±71
signals
fb-1
Y(3S)p+p-Y(1S)[mm]
498K Y(3S)
 p+p- Y(1S)
11M Y(3S)
+
p
Y(3S)
p-
m+
~ Signal peak
U(1S)
m18
Background Suppression
p+
p-
~ Dominant : Two-photon process ~
Pion opening angle
in the CMS
Vector-sum of
transverse momenta
of 2 pions in the CMS
signal
BG
Maximum energy
deposit in the
calorimeter cluster
Fisher
signal
F < -0.7
reject
19
Backgrounds
Two-photon BG
recoil mass of p+p-
Y(1S) m+m-, e+e- … (outside of acceptance)
p
m
p
m
244 events predictedBr(Y(1S)invisible)=6x10-3
20
Results
Nsignal = 38 ± 39  0 consistent
B (Y(1S)invisible) < 2.5x10-3 (90%C.L.)
2.9 f b-1
at Y(3S)
Prediction is
disfavored
data
Fit
BG
Prediction
Br(Y(1S)invisble)=0.6%
[PRL 98,132001(07)]
21
Prospect
Disfavored by this result
at 90% C.L.
Theoretical prediction
continue with
current condition
_
Y(1S)  nn
With super-forward
calorimeter & m-detector
to reduce peaking BG
[Veto Y(1S)  l+l- ]
22
Another
DM search in B  K(*)nn
_
SM
SM: BF(BK nn) ~4 x 10-6
(Buchalla, Hiller, Isidori)
[PRD 63, 014015]
h
S
S
[e.g. C.Bird, PRL 93,201803(2004)]
Sensitive to New Physics
(in loop)
and
also Light Dark Matter
(mS < 2 GeV/c2)
Signature: K(*) + invisible
23
Experimental Method
n
Signature :
1 particle + invisible
B+
Residual ECL energy
EECL ~ 0
n
B-
Y(4S)
K+
535M BB
641K B 
Charged B
Tag-side:
Full reconstruction
B +  D (*)0 + p + /  + / a1+ / DS(*) +
D0p 0 / D0
Ds+
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Result
535M BB
FPCP07
1.6 < p* < 2.5 GeV/c
Nb = 20.0  4.0
Nobs = 10
B(B+  K+nn) < 1.4x10-5
@90% CL
25
Constraint on DM
26
Other B  h(*)nn modes
_
FPCP07
27
Other B  h(*)nn modes
_
UL
(@90%CL)
FPCP07
< 3.4x10-4
< 1.4x10-4
< 1.4x10-5
< 1.6x10-4
< 1.7x10-4
< 2.2x10-4
< 4.4x10-4
< 1.5x10-4
< 5.8x10-5
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B  D*tn
FPCP07
B decays including t  sensitive to Charged Higgs
Always involve > 2 n (Missing E): experimental challenge
• B  tn : First Evidence !
[Belle, PRL 97, 251802(2006)]
• B  D* tn : Lepton (t) polarization info.
Expected B ~ 1.4% in SM (large) [e.g. D.S.Hwang EPJ C14,271(2000)]
But, large background (D*(**)ln, D*X)
29
B0  D*-t+n :Reconstruction
Use detector Hermiticity
Full Recon. tag : excellent S/N, but very low efficiency
Signal side
Clean signature: D*+lepton
Sub-decay modes: D*-  D0pt  enn, D0  K+p-/K+p-p0
t  pn, D0  K+p-
_
_
_
(leptons are too soft : t  mnn not used)
Tag side
“Inclusive B” reconstruction
Sum all the residuals
SQ=0, no lepton, SNbaryon=0
-0.25 < DEtag < 0.05 GeV
Mtag = [Eb2 – ptag2]1/2
MC
30
Validity Check
Tag side “Inclusive” reconstruction
Control sample : B0  D*- p+
All tag-side cuts applied
31
Signal side: Bkg suppression
t  enn mode
_
Main background: B  D*e n
D*e n
D**e n
other B
continuum
signal
most powerful
32
Signal side: Bkg suppression
t  pn mode
Main background: Hadronic B, Continuum
•
•
•
•
•
•
M0 > 1.5
M2W – M2M – M2t + M2p > 0
Visible energy: Evis < 8.3 GeV
Pion energy: Ep > 0.6 GeV
No KL’s in the event : N(KL) = 0
Number of rejected tracks: Nbad < 4
(bad inpact parameters)
only two n’s  more kinematic constraint
equivalent to |cosn1n2 | < 1
33
Signal side: Bkg suppression
Before
MC
After Bkg. suppression
MC
tenn
_
MC
t  pn
MC
signal
other D*tn
modes
(B =1.4% assumed)
D*e/m n
D**e/m n
other B
c-continuum
uds-continuum
peaking part
treated as signal
34
Results
Extended ML fit: Signal = Crystal-Ball, Bkg = Argus + peaking
Shape params fixed to MC, peaking fixed to expectation
_
Ns=20
+6
-5
t(enn), D(K+p-p0)
_
t(enn), D(K+p-)
Ns=12
+6
-5
t(pn), D(K+p-)
Ns=30
+10
-9
Simultaneous fit: Ns=60 +12
-11 6.7s(> 5 w/ sys) First Observation !
B (B0  D*-t+n ) = (2.02
+0.40
-0.37
 0.36) %
35
Systematic Error
(*)
Total 18% for combined BF
(*) Peaking background
1.2 +1.6
-1.5
5.0 +2.6
-2.2
-1.0 +3.6
-3.2
36
Cross Checks
tenn
Mtag >5.27
signal
background
Mtag >5.275
tpn
Mtag <5.26
signal
Fit to signal side variable
other
D*tn
background
cosn1n2
cosn1n2
37
Checks: Look-back plots
Distribution of a variable in signal-box (“N-1” cuts)
data
signal
other D*tn
modes
background
38
B (B0  D*-t+n ) = (2.02
+0.40
-0.37
 0.36) %
• Consistent with SM estimations
• Need more precise measurements & updated SM predictions
to obtain useful NP constraint
First Step !
95%CL interval
(assume fL same)
B  D*t+n
B  Dt+n
B+  t+n
Super B Factory
[M.Tanaka Z.Phys. C67,321(1995)]
39
Prospects: H± sensitivity
Super B Factory
B g D- t +n
B g t +n
50ab-1
5ab-1
50ab-1
40
Crab Cavity Study
Crab Crossing  Head on collision
increase Luminosity by ~2
with Crab
w/o Crab
simulation by K.Ohmi
(strong-strong)
41
Crab cavity Installed
Jan-2007: Crab cavity installed (1/ring at Nikko area)
13-Feb-2007: Beam study started
Superconducting Crab Cavity
HER
LER
42
How works w/ 1 cavity/ring ?
IP
crab
cavity
2 cavities per ring
orbits of bunch head and tail
43
How works w/ 1 cavity/ring ?
bunch head
bunch tail
IP
crab
cavity
crab
cavity
1 cavity per ring
beam
beam
orbits of bunch head and tail
44
Observation of Crabbing !
Crab OFF
Crab ON
0°
＋180°
Crab ON
0°
＋180°
HER(1.43MV)
LER(0.9MV)
Horizontal
Streak camera
schematics
Hamamatsu C5680
45
Specific Luminosity
46
Plan / Goal
May-2007 (Golden week):
wormed-up once and cooled-down
14-May: Beam operation resumed
Study : performance at higher bunch current
& at higher total current
Beam-bean tune xy > 0.1
Important Step toward Super-KEKB
47
A few words on Super-KEKB
48
News
Consensus in J-HEP community
 Japanese HEP community reached the following agreement
in October 2006 after a long discussion.
 First priority is to realize ILC, and its R&D should be boosted.
On the other hand, flavour physics programs (SuperKEKB,
and K and n program at J-PARC) should be carried out as
physics programs before ILC (i.e., 2010’s).
[M.Yamauchi’s recent talk]
49
Recommendation by Belle-PAC
 The committee provided strong endorsement to
SuperKEKB in the meeting in April 2007.
 This is also an important support from the int’l community.
50
2006
2008
2010
2012
2014
2016
2018
2020
J-PARC n, n construction
J-PARC n, K experiment
J-PARC n, m experiment
PF upgrade
PF
Budget transfer
J-PARC R&D
upgrade
Budget transfer
ERL prototype
ERL construction
experiment
KEKB
Option 1
ILC R&D
Budget transfer
Budget transfer
ILC construction
KEKB
KEKB upgrade
ILC R&D
experiment
Option 1’
experiment
Budget transfer
ILC construction
experiment
51
Remarks
 2008 will be a critical timing for KEKB/SuperKEKB.
– J-PARC construction will be completed.
– Belle accumulates 1000/fb.
– PEP-II/BaBar will be shutdown.
 It is likely that KEK takes some decision soon.
– Machine: KEK + contributions from the world
– Detector: perfectly open to the new collaboration
 Hope to strengthen collaboration with Western SuperB.
Letter of Intent for Super-KEKB (Jan-2004)
Progress on Physics cases / Detector / Accelerator
Update of LOI in progress welcome to join !
52
Proposed schedule
Integrated luminosity (ab-1)
10
~1.5×1034
Lpeak
1.5 -
SuperKEKB
~8×1035
3×1034
8
6
2 yr shutdown
for upgrade
4
~10B BB and
t+t- every year
Crab cavity installation
Belle is here.
0.7ab-1
2
0
2000
2002
2004
2006
2008
2010
2012
2014
Calendar year
53
Summary
Diversity of Analyses & Data [Y(3S/5S)]
 EPR entanglement
Confirmed QM, disfavor PS, DS with >5s
 Light Dark Matter Search at Y(3S)
B (Y(1S)invisible) < 2.5x10-3 (90%C.L.) < Theory
_
Also, searched by B g K(*) n n
 B g D*- t +n : First Observation ! (5.2s)
 Crab Cavity installed : study in progress
step toward SuperKEKB
welcome to join !
54