Transcript Slajd 1
Highlights of the Belle Experiment
A.Bożek
NZ11
Precision tests of the Standard Model and New Physics
searches at the B-Factory
e+e-(4S) B0 B0 / B- B+
Selection of the most important Belle results
since last SAB review (2005):
B0 gh'K0 : first observation of time dependent CPV
in rare B decays;
B- t-nt : evidence for purely leptonic decay
(decay with missing energy);
New particles with charm;
First results from Bs ((5S) run).
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Highlights of the Belle Experiment SAB Review 2007
B0 (db)
B- (ub)
0
Bs (sb)
1
Physics analyses in Kraków
Rare B decays:
b s: B- f0(980)K- , B0 f0(980)K*0
B decays with missing energy:
b c t -nt: B0 D*- t+ nt
New particle searches :
Krakow’s Belle group
•5 PhD physicists
•3 electronics eng.
•3 PhD students
•1 diploma student
-Dsj(2700) in B- D0D0K- analysis
-Charmed baryons study
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B Factory Physics Program
• Studies of rare B, D and t decays with potential sensitivity to new physics;
• Precise tests of the most stringent Standard Model (SM) predictions,
e.g. unitarity relations between elements of the quark mixing matrix.
d
qi
W±
u
VCKM
Vij
qj
c
t
*
ud ub
V V
f2()
Unitarity Triangle
being overconstrained
f3()
at B factories
s
b
Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
Cabibbo-KobayashiMaskawa (CKM)
matrix
VtdVtb*
VudVub* VcdVcb* VtdVtb* 0
f1(b)
VcdVcb*
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Asymmetric ee- collider
13 countries,
57 institutes,
~400 collaborators
8GeV (e-) 3.5GeV (e+)
More than
milion BB pairs
per day
~710x106 BB pairs
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Time-dependent CP violation (tCPV)
“double-slit experiment” with particles and antiparticles
a flagship measurement at B-factories
Quantum interference between two diagrams
tree diagram
b
B0
d
c
c
s
d
box diagram + tree diagram
J/
+
KS
b
t
B0
d
d
B0
t
b
d
s
c
c
KS
J/
You need to “wait” ( Dt0) to have the box diagram contribution.
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B0 J/ K0
_
535 M BB pairs
0
B
_ tag
B0 tag
tCPV
Obtained precision is 1.3o
+sin2f1
f1(b)
sin2f1= 0.642 ±0.031 (stat) ±0.017 (syst)
hep-ex/0608039
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B decays with b g s transition
one of the best new physics probes
b ccs tree
_
c
B0
b
w
d
c
_
s
d
J/Y
K0
SM
?
sin 2f1 (b c) =
b sqq penguin
g
w
_
_
B0
b
sg
bt
g
d
s
s
_
s
d
f, h’...
K0
sin 2f1 (b s)
SUSY as an example
Extra CPV phase from New Physics
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tCPV in B0 g h'K0
Dt distribution and asymmetry
_
535M BB
First observation of tCPV
(5.6s) in a single b g s mode
sin2f1(b→s) = 0.64 0.10(stat) 0.04(syst)
PRL 98, 031802 (2007)
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f1 from b g s transition
B0
J/
K0…
Smaller than bgccs
in all of 9 modes
Naïve average of all modes
sin2f1(b→s) = 0.52 ± 0.05
2.6 s deviation
Theory tends to
predict positive
shifts
We need more statistics and more bs modes
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Motivation:
B0 f0(980)K*0
•
Not observed yet, expected BF ~10-6
•
Expected to be dominated by b s transitions
-mode with simple final state
•
In addition nature of f0(980) can be studied (candidate for
four quark state or other exotic combinations).
Started as a diploma work; can lead to an important
physics output in hot field.
Results should be published this year
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B decays with missing energy
B
e(8GeV)
e+(3.5GeV)
Υ(4S)
p
B
Decays of interests
BXu l n,
BK n n
BDtn, tn
fully reconstructed
second B
i.e. BDp
Method
•
Fully reconstruct one of the B’s to :
- tag BB events
– determine other B flavor/charge & momentum
Powerful tools to study B decays with neutrinos
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B+t+nt
B+ g D0 p+
K+ p- p+ p-
Missing momentum
B- g t -nt
e-nent
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The First Btn Evidence
Observation based on the residual energy in the electromagnetic
calorimeter not used in both B reconstruction.
Signal +
background
17.2 +5.3
- 4.7 events in the signal region.
Measured branching fraction:
+0.56
Br B tn ) 1.79 -0.49
Btn
+0.46
-0.51
) ×10
Background
PRL 97,251802 (2006)
Signal
Another „multi-neutrino” mode: B0 D*- t+ nt experimentally more difficult
analysis is carried on in Kraków, results are expected this year.
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-4
New particles, charm spectroscopy
B factories are an abundant source of other particles:
charmed mesons and baryons : e+e- cc, B decays, …
: e+e- t+t- ~700 M events
t lepton „factory”
New charmed mesons : new unresolved questions about charm spectroscopy
cD
s
s X(3872)
c
D
q
b
q
Belle
b
Charmonium type
2003
e
e
q
2004
BaBar
at slac B-factory
c
DsJ(2317)
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DsJ(2458)
„cs” type
c
cZ(3930)
,hc , X
c
s
q K
Y(3940)
2005
t
e
e
Y(4260)
t
Picture: R. Faccini, DOE review 2005
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New DsJ in B+→D0D0K+
Signalof B D0 D 0 K
N=399 40
Dalitz plot M(D0D0) vs M(D0K) differs from
3-body phase space
DsJ(2700)
sideband
new state
Nefficiency
182 30
11
M (2715 11-14
) MeV / c 2
36
(115 20-32
) MeV
J P 1-
hep-ex/0608031
Interpretation still open
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Conclusions and prospects
We are in high statistics era at B factories ( 1ab-1 ~109 BB)
- many interesting & unexpected results
38 papers in Phys.Rev.Lett. (with discovery status) during 2005/2006
- powerful tool to study rare and experimentally difficult B decays
that are not accessible in other environments
Good prospects for next generation experiment at Super B-Factory
SuperKEKB (50 ab-1 ~5*1010 BB)
New physics searches in rare B & t decays, that are not accessible on
hadron machines e.g:
BK n n, BDtn, BD*tn, BXs/Xu
t→m , t→e , …
solve the b s & other ~2.5s puzzles
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Future plans
Lpeak = 1.71034cm-2s-1
Ltot = 710 fb-1 (Dec. 2006)
world records !
~1010 BB/year !!
& similar number
of t+t-
Major upgrade of
KEKB & Belle detector
(>1yr shutdown)
We are here
Lpeak (cm-2s-1)
Lint
1.7x1034
700 fb-1
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5x1034
~1 ab-1
8x1035
~10 ab-1
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(5S) test runs
CLEO
PRL 54, 381 (1985)
1985: CESR (CLEO,CUSB) ~116 pb-1 at Y(5S)
2003: CESR (CLEO III) ~0.42 fb-1 at Y(5S)
2005: Belle, KEKB
(5S)
~ 1.86 fb-1 at Y(5S)
2006, June 9-31: Belle, KEKB ~21.7 fb-1 at Y(5S)
e+ e- -> Y(5S) -> BB, B*B, B*B*, BBp, BBpp, BsBs, Bs*Bs, Bs*Bs*
Bs -> Ds
+
p-
MC
BsBs , Bs*Bs , Bs*Bs*
sum of all Bs decay modes
5.408< MBC<5.429 GeV/c2
B s* B s *
Nev=20.0 ± 4.8
6.7 s
9 events in Bs* Bs*
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Hunting Rare Decays
• High luminosity
Evidence of Btn
• Good detector (PID, vertex…)
• Analysis techniques
Observation of bd
– qq background suppression
FB asymmetry in BK* l+l– Fully reconstructed tag
Direct CPV in B0K+pBeginning of B->fK0 saga
Observation of BK l+ lCPV in B decay
Success of B factories brought rare B decays in
leptonic and neutrino modes on the stage !
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Major Achievements Expected at
SuperKEKB
Case 2: New Physics with Extended Flavor Structure
Search for New CP-Violating Phase in b g s with 1 degree precision
Discovery of Lepton Flavor
Violation in t g m Decays#
CKM Angle Measurements with 1 degree precision
of B g Knn
Discovery of NewDiscovery
Right-Handed
Current in b g s Transitions #
Discovery of New Subatomic Particles
-4
Discoverysin
of2qNew
CP Violation
W with O(10 ) precision
0 Decays#
in B0 |Vub|
g fK
with 5% Precision
Discovery of B g Dtn
“Discovery” with
significance > 5s
# SUSY GUT with
gluino mass = 600GeV,
tanb = 30
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Observations with
U(5S), U(3S) etc.
Discovery of B g mn
Discovery of CP Violation in Charged B Decays
Discovery of Direct CP Violation in B0 g Kp Decays (2005)
Discovery of CP Violation in Neutral B Meson System (2001)
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Principle of tCPV measurement
CP-side
electron
(4S)
resonance
positron
_
B0
B1
B0
B2
nm
b = 0.425 (Belle)
Dz
b c
KS/L
D
0
p+
K
-
0.56 (BaBar)
Dt
m+
J/
m
Dz ~ 200mm
(Belle)
p
m+
Flavor tag and
vertex
reconstruction
1. Fully reconstruct one B-meson which decays to CP eigenstate
2. Tag-side determines its flavor (effective efficiency = 30%)
3.Andrzej
time
(Dt) is
measured from decay-vertex difference (Dz)
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tCPV in B0 decays
Vtd
+
Mixing-induced CPV
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e.g. for J/ Ks
S = -CPsin2f1 = +sin2f1
A=0
to a good approximation
Vtd
(CP : CP eigenvalue)
Direct CPV
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Update after
ICHEP2006 !
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Highlights of the Belle Experiment SAB Review 2007
K.Ulmer
23
Belle 2006:
tCPV in
_
0
B
g
0
fK
535M BB
“sin2f1” = 0.50 0.21(stat) 0.06(syst)
A
= 0.07 0.15(stat) 0.05(syst)
Dt distribution and asymmetry
Consistent with the SM (~1s lower)
The most precise measurement now
fKS and fKL combined
background subtracted
good tags
Dt g –Dt for fKL
unbinned fit
SM
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Highlights of the Belle Experiment SAB Review 2007
B0 D*- t+ nt search
•
•
•
•
•
Motivations:
BD(*)not observed yet
Decays with heavy fermions
enhancement of effects beyond SM
Many avaiable observables from decays
transverse or longitudinal polarisation
Semileptonic heavy quark decay –
clear theoretical situation:
good description of b quark in HQET
BG for BDdecay
Experimentally very difficult:
•At least 2n in decay chain
•Low effective Br: Effective Br for
decay chain ~ 10-4 – 10-5
need for more effective
reconstruction of Btag
or/and higher statistics
Results should be presented this year
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New DsJ in B+→D0D0K+
hep-ex/0608031
N=399 40
Dalitz plot M(D0D0) vs M(D0K) differs from
3-body phase space
sideband
DsJ(2700)
new state
efficiency
JP = 1 ψ(4160) reflection
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