Transcript Slide 1

Highlights from Belle
Jolanta Brodzicka
(NO1, Department of Leptonic Interactions)
SAB 2009
Plan
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CPV studies → Nobel Prize for Kobayashi and Maskawa
B decays with „missing energy”: New Physics probe
Ds meson spectroscopy
D0 -D0 mixing: charm highlight
Bs Physics: also possible at Belle
The Future
Belle experiment at KEKB
 KEKB: asymmetric e+e- collider
e+: 3.5 GeV  e-: 8.0 GeV
√s = 10.58 GeV = (4S) mass
e+e-  (4S) BB
 Operating since 1999
 Peak luminosity: 1.711034cm-2s-1
 1MBB/day
 Integ. luminosity: 860 fb-1 @ (4S)
 Upgrade to Super KEKB approved
 Super Belle collaboration formed
CPV studies: goal reached
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The Nobel Prize for Kobayashi and Maskawa: the crown of CPV studies
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K-M idea:
3rd quark family (b,t) introduced
 irreducible phase in quark mixing matrix (complex couplings between quarks)
 CP violation (in processes with interference sensitive to the complex phase)
u Vud
W+
d
VCKM
L ~ ( u c t )L γμ
Vud Vus Vub
d
Vcd Vcs Vcb
s W+μ
Vtd Vts Vtb
b
Vub Vtd: complex
L
• B-Factories have verified predictions of the K-M mechanism
 CPV in B system: observed in several processes
 Relations between CKM parameters: tested
CPV: observations, out of many
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K-M predicted two types of CPV violations: both observed
 Time dependent CPV. Golden mode: B0→J/ψKs
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B0 -B0 mixing: time dependent
ACP (t ) 
d
dt
d
dt
( B  fCP )  ddt ( B  fCP )
( B  fCP )  ddt ( B  fCP )
ACP(t) = S sin(mdt)
S= 0.642  0.031(stat)  0.017(syst)
 Direct CP violation: difference in decay rates for B0K+- andB0K-+
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B0 K
B0 K
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ACP 
( B  f )  ( B  f )
( B  f )  ( B  f )
ACP= -0.094  0.018(stat)  0.008 (syst)
Tests of Unitarity Triangle
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• VCKM is unitary matrix: VCKM V†CKM=1
 From unitarity relation:
Vud* Vub  Vcd* Vcb  Vtd*Vtb  0
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 Angles and sides of the Untarity Triangle: fundamental SM parameters
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Measure both angles and sides  UT over-constrained
ACP in B0J/K0  β
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ACP in B0, ,   
ACP in BD(*)K(*)  
semileptonic B decays
B -B oscillations
UT sides
Directly measured:
β = (21 ± 1)o
β = (24 ± 2)o
α = (92 ± 7)o
α = (92 ± 4)o
γ = (78 ±
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From UT sides:
12)o
consistency
γ = (64 ± 4)o
Confirmed: UT is a triangle (within ~10% accuracy)
Next step: any effects beyond KM mechanism?
2008
B decays with „missing energy”
beyond SM
amplitudes
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Theoretically clean (small hadronic effects)
Sensitive to New Physics: charged Higgs effects at tree level
Experimentally challenging: multiple neutrinos in final states
B0→D*-τ+ντ : highlight of B decays 2007
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Decay chain: B0→D*-τ+ντ D*→D0π D0 →Kπ, Kππ0 τ→eνeντ , πντ
Signal side
Tagging side
Signal yield: 60+12
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BF(B0→D*-τ+ν)=(2.02 +0.40
-0.37 (stat) ±0.37(syst)) 10
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First observation of exclusive semi-tauonic B decay
Analysis performed entirely in Krakow
Study continued: other channels B→Dτν, polarization analysis
Important topic at SuperB Factory
A. Matyja, M. Różańska et al.
PRL 98, 211803 (2007)
Ds spectroscopy
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Study of B+→ D0D0K+ Dalitz plot
Observation of new meson: DsJ(2700)+→D0K+
DsJ(2700)
On the PRL cover
M = 2708  9  11 MeV
Γ = 108  23 +36
-31 MeV
 JP=1-
M(D0K+)
Signal yield / 40 MeV
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cosθhel
Radial excitation of Ds* or L=2 orbital excitation?
Toward interpretation: resonances in D*K studied
DsJ(2700) ?
M(D*+Ks0)
J. Brodzicka, H. Pałka et al.
PRL 100, 092001 (2008)
D0 -D0 mixing : most unexpected result of 2007
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Mixing observed in K0 (1958), B0d (1987) and B0s (2006)
Unique for D0: only d,s,b quarks enter the box  mixing suppressed
Mixing governed by x and y
|x| ~ O(10-5)
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|x|, |y| ~ O(10-2)
New Physics can enlarge x and y
Mixing „modifies” decay time distribution
D1, D2 : mass eigenstates
D0, D0 : flavor eigenstates
 perform time dependent study of produced D0 andD0
• Measure D0 lifetime from its decay length
yCP from D0→K+K-,π+π•
D0→K+K- and π+π- : CP even eigenstates D1  τ=1/Γ1
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D0→K-π+ : not CP eigenstate  τ=f(1/Γ1 , 1/Γ2)
Lifetime difference between non-CP and CP eigenstates
 access to mixing
τ(K-π+)
yCP=
-1 = y
τ(K+K- or π+π-)
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if no CPV (in SM: CPV<10-3)
if yCP≠0  D0 - D0 mixing
Measured proper decay time distributions:
=
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t (fs)
t (fs)
yCP  (1.31 0.32  0.25)%
t (fs)
t (fs)
Significance:3.2σ
 First evidence for D0 mixing
A  (0.01 0.30  0.15)% no CPV found
Belle PRL 98, 211803 (2007)
D0 -D0 mixing: status
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World average mixing parameters from HFAG-charm
(all existing measurements included):
y= ( 0.73 ± 0.18 )%
x= ( 0.91 ± 0.26 )%
No mixing (x=0 and y=0)
excluded at ~7σ
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Statistics of SuperB Factory needed for precision measurements
and searches for New Physics effects
More than Bu,d at B-Factory: Bs physics
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KEKB increased beam energies: Y(4S)→Y(5S)
E(e+): 3.500 GeV → 3.595 GeV,
E(e-) : 7.996 GeV → 8.211 GeV
No modification of the detector, trigger, software
KEKB (Belle):
2005-2006: ~23 fb-1
2008-2009: ~80 fb-1
Y(4S)
Y(5S)
Y(6S)
World Y(5S) data:
1985:CESR (CLEO,CUSB): 0.1fb-1
2003:CESR (CLEO III): 0.4fb-1
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e+e-→Y(5S)→ BsBs, Bs*Bs,Bs*Bs*
 access to Bs (bs mesons )
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Advantages of Bs physics at B-Factory versus hadronic machines:
+ low background
+ final states with π0/γ
+ absolute BF measurements
(with BF ~20%)
Bs decays with first data
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Cabibbo favored decay: Bs→Ds+π- with 21.7 fb-1 (2.8M Bs )
Bs→Ds-π+
163  13 ev
M(Bs*)=5417.6  0.4  0.5 MeV
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BF(Bs→Ds+π-)=(3.41 +0.33+0.70
-0.31 -0.67 ) 10
Belle PRL 102, 021801 (2008)
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Rare decay: Bs→φγ (b→s electroweak penguin)
Bs →f
5.5 σ
BF(Bs→φγ)=(5.7 +1.8+1.2
) 10-5
-1.5 -1.1
First observation of rare Bs decay
Belle PRL 100, 121801 (2008)
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B-Factory competitive in Bs physics
Precision BF for normalization modes  callibration for LHCb
BF(Bs→ Ds+π-)  to reduce error of BF(Bs→μ+μ-)
Future: KEKB upgrade approved
Physics prospects for Super KEKB
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Krakow activity toward Super KEKB:
Physics analyses: important in physics program of SuperBelle
SVD and Pixel Detector
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B Physics in Department of Leptonic Interaction:
(Super)Belle and LHCb: lots of synergies
ab-1
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