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Results on CP Violation and CKM Unitary Triangle. B-Factories in the World. Data taking finished on Jun.30 th , 2010 ∫ L dt = 1052.79 fb⁻¹. Belle (Japan). BaBar (US). Data taking finished in Apr, 2008 ∫ L dt = 558 fb⁻¹. KEKB Accelerator. - PowerPoint PPT Presentation
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Takeo HiguchiInstitute of Particle and Nuclear Studies, KEK
The Belle Collaboration / The Belle II Collaboration
Results on CP Violationand
CKM Unitary Triangle
Workshop on Synergy betweenHigh Energy and High Luminosity
FrontiersJan.10,2011
Belle (Japan)
BaBar (US)
B-Factories in the World2
Accelerator Detector
Belle(Japan)
BaBar(US)
Data taking finished on Jun.30th, 2010∫ L dt = 1052.79 fb⁻¹
Data taking finished in Apr, 2008∫ L dt = 558 fb⁻¹
KEKB Accelerator
3km incircumference
KEK
3
Mt. Tsukuba
e⁻
e⁺
IR
e⁻ 8.0GeV
e⁺ 3.5GeV
World highest luminosity2.1x10³⁴cm⁻²s⁻¹
World highest integrated luminosity 1052.79 fb⁻¹
History of the integrated luminosity
Particle species
Particle species
Particle species
γ and e± energy
Charged particle momentumB decay positionSilicon Vertex Detector• Four detection layers.• Vertex resolution ~ 100 μm.
Time-of-Flight Counter• Plastic scintillation
counter.• K/π-ID of high range p.• Time resolution ~100 ps.
Aerogel Čerenkov Counter• Refractive index n=1.01-1.03.• K/π-ID of middle range p.
8.0GeV e⁻
3.5GeV e⁺
Belle Detector
KLμ Detector• Sandwich of 14 RPCs and 15 iron plates.• μ-ID with iron-punch-through power.• Return path of magnetic flux.
4
Electromagnetic Calorimeter• CsI (Tl) crystal.• Energy measurements of γ and e±.• @ 1 GeV.%6.1~EE
Central Drift Chamber• 8,400 sense wires along the beam direction.• Momentum resolution• PID with dE/dx measurement.• 1.5 T magnetic field.
%3.0)GeV(28.0~ tttcppp
• Dec.,1998 Detector constructionhad completed.
• Jan.,1999 Cosmic-ray eventtaking had started.
• Feb.,1999 The first e+-e– collision of KEKB.• May.,1999 The detector had been rolled in to the
IR.
• Jun.4th,1999 The first physics event.…
• 9:00am Jun.30th,2010Data taking finished.
History of Belle5
End Run Ceremony
• The e+/e– beams wereaborted by A. Suzuki, thedirector general of KEK.
• Collaborators’ snapshot at the run end:
6
I was here.
CKM Matrix and Unitarity Triangle
One of the unitarity conditions:
Wolfenstein Parameterization
KM ansatz: Irreducible complex phases (in Vub and Vtd inWolfenstein parameterization) cause the CP
violation.
iη
O ρ
Unitarity condition forms a untarity triangle in the complex plane.
(φ₁, φ₂, φ₃) = (β, α, γ)
7
B0-B0 Mixing and Mixing-Induced CPV
W Wt
t
b
d
d
b
B⁰ B⁰
Vtd
Vtd V*tb
V*tb
B⁰ and B⁰ mix with each other through a box diagram shown above._
B⁰ fCP
B⁰B⁰ fCP
phase == 0
phase difference = 2φ₁
_
Even if B⁰ and B⁰ decay to the same final state, the phase of the decayamplitude may differ depending on the B flavor at the decay time.
interference
_
_
__
_
CPV due to the interference is called“mixing-induced CP violation”.
8
2tdV
~ Vtd² ~ e⁻²iφ₁
CP Violation in Proper-Time Distribution
The e⁺-e⁻ collision produces a pair of B mesons through bb resonance.
S = 0.65A = 0.00
Btag = B0
Btag = B0_
Δt (ps)
The mixing-induced CP violation manifests itself in the signed time duration “Δt = tBCP – tBtag”, where• tBCP … time when one B decays to the CP eigenstate.• tBtag … time when the other B decays to the flavor-specific state.
9
BBbbee S
)4(
)cos
sin(14
),;(
tmA
tmSeAStP
d
dB
t B
Analysis Method10
e⁻8.0GeV e⁺ 3.5GeV
Silicon Vertex Detector
Silicon Vertex Detector
Silicon Vertex Detector
Silicon Vertex Detector
B⁰
B⁰_
Beam pipe
KS⁰
J/ψ
π⁺ ℓ⁺
ℓ⁻
π⁻
1. Reconstruct fCP (J/ψKS⁰ …)
π⁻
D⁺π⁺
π⁺K⁻
2. Determine the B meson flavor q opposite to the one decayed to fCP
3. Determine proper-time difference Δt of the two B mesons
Δt4. Determine S (= sin2φ₁)
using the event-by-event q and Δt
e⁺-e⁻collision
• The B⁰ J/ψK⁰ is mediated by b ccs tree transition.
• SM prediction: S = –ηCPsin2φ₁, A ≈ 0– Test of Kobayashi-Maskawa theory. Nobel prize in 2008– Check for a NP phase with very precise unitarity tests.
B⁰ J/ψK⁰: Golden Modes for φ₁
The decay diagram includesneither Vub nor Vtd. The φ₁ is accessible.
_
d
b_ c
csd
_WB⁰
K⁰
b ccs treeJ/ψ
_
_
11
B⁰ J/ψK⁰ ReconstructionEv
ents
/ 1
MeV
/c²
Even
ts /
50 M
eV/c
Nsig = 6512Purity = 59 %ηCP = +1
BCP mass (GeV/c²) BCP momentum in the cms (GeV/c)
+ data
MC: J/y KLX MC: signal
MC: J/y X MC: comb.
Nsig = 7482Purity = 97 %ηCP = –1
BCP J/ψKS⁰ BCP J/ψKL⁰
Gaussian Gaussian
peak @ 5.28 GeV/c²peak @ 0 GeV
ARGUS func.
cmsbeam
cms EEE B 2cms2cmsbeambc )()( BpEM
Event-by-event S/N isobtained from the model above.
Event-by-event S/N isobtained from an MC simulation.
12
535M BB_
slope
S and A from B J/ψK⁰ (535M BB)
(stat) (syst)
Phys. Rev. Lett. 98, 031802 (2007).
_
Dominant systematic error sources
13
014.0021.0018.0017.0031.0642.0
AS
Brec = J/ψKS⁰ + J/ψKL⁰
Dec.9,2010
S and A Update (772M BB)_
J/ψKL⁰
J/ψKS⁰ J/ψKL⁰ ψ(2S)KS⁰ χc1KS⁰ NBB
Signal yield (’10) 12727±115 10087±154 1981±46 943±33772 x 10⁶
Purity (’10) [%] 97 63 93 89
Signal yield (’06) 7484±87 6512±123 – –535 x 10⁶
Purity (’06) [%] 97 59 – –
from 772 x 10⁶ BB pairs = final Belle data sample
We have more yields than the NBB increase, for we have improved the track finding algorithm.
Belle preliminary
ccKS⁰
_ 14
_
Latest Status of S and A Measurements
• We are finalizing the S and A in bccs modes using the full data set.
• Preliminarily expected statistical sensitivity
Predicted by a signal-yield scale applied to the ICHEP2006 results.– The statistical uncertainties are getting close to the systematic
ones.
_
15
016.0,024.0 AS
bsqq Time-Dependent CP Violation
• Deviation of bsqq CP-violating parameter from bccs indicates NP in the penguin loop
_
d
b_ c
csd
_WB0
J/ψ
K⁰ d
b_ _
sssd
_gtB0
K⁰
φ, f₀…W
b ccs tree_
b sqq penguin_
S = sin2φ₁, A ≈ 0 S = sin2φ₁eff, A ≈ 0
In case of an extra CP phasefrom NP in the penguin loop
_
_ 16
02sin2sin)2(sin 1eff
11
_
Interference in B⁰KS⁰K⁺K⁻ Final State
• B⁰KS⁰K⁺K⁻ final state has several different paths.– Fit to the Dalitz plot is need for the correct CPV measurement.
φKS⁰f₀(980)KS⁰
Non-resonant
Dalitz-plot φKS⁰CP = –1 A₁
B⁰ KS⁰K⁺K⁻
f₀(980)KS⁰CP = +1
Others …
A₂
AN
Non-resonant
s₊ = M²(K⁺KS⁰)s₋
= M
²(K⁻
K S⁰)
Dalitz plot
17
N
ii ssAA
1
),(
Interference in B⁰KS⁰K⁺K⁻ Final State
• B⁰KS⁰K⁺K⁻ final state has several different paths.– Fit to the Dalitz plot is need for the correct CPV measurement.
φKS⁰CP = –1 A₁
B⁰ KS⁰K⁺K⁻
f₀(980)KS⁰CP = +1
Others …
A₂
AN
Non-resonant
Dalitz plot
B⁰
mixing_
B⁰-B⁰ mixing_
φKS⁰f₀(980)KS⁰
Non-resonant
Dalitz-plot
s₊ = M²(K⁺KS⁰)s₋
= M
²(K⁻
K S⁰)
18
Interference in B⁰KS⁰K⁺K⁻ Final State
• B⁰KS⁰K⁺K⁻ final state has several different paths.– Fit to the Dalitz plot is need for the correct CPV measurement.
φKS⁰CP = –1 A₁
B⁰ KS⁰K⁺K⁻
f₀(980)KS⁰CP = +1
Others …
A₂
AN
Non-resonant
B⁰-B⁰ mixingDalitz plot
B⁰
mixing_
+_
CPV measurement
φKS⁰f₀(980)KS⁰
Non-resonant
Dalitz-plot
s₊ = M²(K⁺KS⁰)s₋
= M
²(K⁻
K S⁰)
19
B⁰KS⁰K⁺K⁻ Reconstruction
• # of reconstructed events– Estimation by unbinned-maximum-
likelihood fit to the ΔE-Mbc distribution
• B⁰KS⁰K⁺K⁻ Nsig = 1176±51– Reconstruction efficiency ~16%
• Background– Continuum ~ 47%– Other B decays ~ 3%– Signal purity ~ 50%
signal
continuum
Mbc
ΔE
other B
from 657 x 10⁶ BB pairs_
20
CPV Measurement in B⁰KS⁰K⁺K⁻
• The (φ₁, A) are determined by an unbinned-ML fit onto the time-dependent Dalitz distribution.– The signal probability density function:
• Four parameter convergences from the fit
– They are statistically consistent with each other.– Which is the most preferable solution?
21
tmAAqtmAAqAAessqtP ddB
t B
sin)Im(2cos4
),;,(2222
sig
CPV Measurement in B⁰KS⁰K⁺K⁻
• Solution #1 is most preferred from an external information.
– The Br(f₀(980)π⁺π⁻)/Br(f₀(980)K⁺K⁻) favors solutions withlow f₀(980)KS⁰ fraction, when compared to the PDG.
– The Br(f₀(1500)π⁺π⁻)/Br(f₀(1500)K⁺K⁻) favors solutions withlow f₀(1500)KS⁰ fraction, when compared to the PDG.
Here, we assume fX as f₀(1500).
Intermediatestate-by-state fraction
22
CPV Measurement in B⁰KS⁰K⁺K⁻Y.Nakahama et al., Phys. Rev. D 82, 073011 (2010)
BG
The third error accounts for an uncertainty arises from Dalitz model.
SM prediction
[solution #1]
657 x 10⁶ BB pairs_
Only in the φmass region
Only in the φmass region
23
0SK
00 )980( SKf
)4.16.20.92.32(eff1
)0.44.30.93.31(eff1
02.010.020.004.0 CPA
09.011.029.030.0 CPA
CP Violation in bs Penguin
• Latest tension in between tree and penguin
– Sbc = SbsSM
– W.A.: Sbs = 0.64±0.04– W.A.: Sbc = 0.673±0.023
0.8σdeviation
B⁰ J/ψK⁰ (bc) B⁰ φK⁰, η’K⁰ (bs)
24
δ(Sbs) ~ 0.012 @ 50ab–1Prospect
Measurement of φ₂
• φ₂ can be measured using B⁰ π⁺π⁻, ρ⁺ρ⁻ decays.
d
b ud
ud
W π⁺, ρ⁺B⁰
π⁻, ρ⁻ d
b d
ud
gtW
uB⁰π⁺, ρ⁺
π⁻, ρ⁻_
__
_
__
If no penguin contribution …
In presence of penguin,(θ can be given from the isospin analysis.)
25
tree penguin
0),22sin(1 12 AAS
0,2sin 1 AS
Extraction of φ₂ from Isospin Analysis
Complex amplitude: A
S = …A = …
• B ππ branching fraction• B ππ DCPV parameters
Input
φ₂ can be solved
26
Amp(B⁰ π⁺π⁻)
Amp(B⁰ π⁺π⁻)
Amp(B⁺ π⁺π⁰)
Amp(B⁻ π⁻π⁰)
Amp(B⁰ π⁰π⁰)
Amp(B⁰ π⁰π⁰)
AA~
0A0~ A
00A00~A
_
_
00 ~ AA
00A2
2~ A
2A )22sin(1 12 AS
S and A from B⁰ π⁺π⁻, ρ⁺ρ⁻ (535M BB)_
B⁰ π⁺π⁻ B0 ρ⁺ρ⁻
27
05.008.055.004.010.061.0
AS
07.021.016.007.030.019.0
AS
H.Ishino et al.,Phys. Rev. Lett. 98, 211801 (2007)
A.Somov et al.,Phys. Rev. D 76, 011104(R) (2007)
Constraint on φ₂28
4.42.42 0.89
J.Charles et al. [CKMfitter Group], Eur. Phys. J. C41, 1 (2005).
Kπ Puzzle in B⁰/B⁺ CP Violation29
5.3σ deviation Hint of NP
T P
C PEW
PEW contribution to CPVis large due to NP…?
S.-W. Lin et al. (The Belle collaboration), Nature 452, 332 (2008).
Diagrams contributingto both B⁰ and B⁺
B⁰ K⁻π⁺ B⁰ K⁺π⁻
B⁻ K⁻π⁰ B⁺ K⁺π⁰
B⁰
B⁺
_
Diagrams contributingonly to B⁰ and B⁺
Kπ Puzzle in B⁰/B⁺ CP Violation30
Four precise measurements of CP-violating parameters related to the Kπ and the “sum rule” will give the answer.
0.14 ± 0.13 ± 0.06@ 600 fb⁻¹ (Belle)
CPV in K⁰π⁰ is statistically difficult to measure Need for SuperKEKB.
Significant deviation may be seen with 10 ab⁻¹ data.
50 ab⁻¹Present
Sum Rule
10ab–1 data may conclude the existence of NPProspect
Direct CP Violation in B⁺ J/ψK⁺
• Physics motivation
– The B⁺ J/ψK⁺ decay mediated by the bs u-penguin has a different weak phase from the tree.
– The interference between the tree and penguin can cause the direct CP violation in B⁺ J/ψK⁺.
Tree
Penguin
Belle –2.6±2.2±1.7Phys. Rev. D67, 032003 (2003)
BABAR +3.0±1.4±1.0Phys. Rev. Lett. 94, 141801 (2005)
D0 +0.75±0.61±0.30Phys. Rev. Lett. 100, 211802 (2008)
W/A +0.9±0.8 (PDG2009)
Previous measurementsof ACP(B⁺ J/ψK⁺) [%]
31
NEW!!
)()()()()(
KJBBrKJBBrKJBBrKJBBrKJBACP
• B± J/ψK± event reconstruction– B± candidates are reconstructed from J/ψ and K±.
• Raw asymmetry: ACPraw
– Measured raw asymmetry, which still includes K⁺/K⁻ charge asymmetry in detection, is: ACP
raw = (–0.33±0.50)% The “raw asymmetry” is obtained from yields of the B⁺ J/ψK⁺ and
the B⁻ J/ψK⁻ in a signal region.
Raw Asymmetry in B⁺ J/ψK⁺
Signal = single GaussianBackground = ARGUS BG
Peaking BG is negligibly small systematic uncertainty.
Yield: 41188±205Mean: 5279.28±0.01 MeV/c²Width: 2.69±0.01 MeV/c²ΔE region: |ΔE|< 40 MeV
772 x 10⁶ BB pair data_
K-π likelihood ratioFor K±(average), 80.5% K efficiency and 9.6% π fake rate.
32
6.0
LL
LRK
KK
• K⁺/K⁻ charge asymmetry in detection: AεK⁺
– The K+/K– charge asymmetry in detection arises due to Non-symmetric detector geometry, Different interaction rates in material of K⁺/K⁻, and Different KID efficiencies of K⁺/K⁻.
• The raw asymmetry ACPraw should be corrected for by the
K⁺/K⁻ charge asymmetry AεK⁺.
K⁺/K⁻ Charge Asymmetry33
K⁺/K⁻ Charge Asymmetry Estimation
• K⁺/K⁻ charge asymmetry estimation– The K⁺/K⁻ detection asymmetry is estimated using
the Ds⁺ φ[K⁺K⁻]π⁺ and D⁰K⁻π⁺, and their charge conjugate.
– Estimated K⁺/K⁻ charge asymmetryin detection (averaged over bins) is: Aε
K⁺ = (–0.43±0.07±0.17)%
assuming
The K⁺/K⁻ charge asymmetry depends on the cosθK
lab and pKlab. We bin the signal regions in
the (cosθKlab, pK
lab) plane into 10 boxes, and measure the charge asymmetry for each bin.
Each box corresponds toone of the 10 signal bins.
#1#10
Real data
34
KDD
DD
AAAA
AAA ss
00
FBrec
FBrec
KDD AAA s
0
FBrec
0
FBFBDD AA s
)()()()(
xNxNxNxNAx
34
CP Violation Measurement in B⁺ J/ψK⁺
• Fit result– From the sum of ACP
raw and AεK⁺, we preliminarily determine
– We observe no significant CP violation in B⁺ J/ψK⁺.
K.Sakai et al., Phys. Rev. D82, 091104(R) (2010).
772 x 10⁶ BB pairs_
35
)%22.050.076.0()(
KJBACP
35
Unitarity Triangle Opened?
• Unitarity triangle opened?
36
50ab–1 data may conclude the real unitarityProspect
Summary
• Following items have been presented:– Mixing-induced CPV (φ₁) measurement in b ccs– Mixing-induced CPV measurement in b sqq– Mixing-induced CPV (φ₂) measurement in B⁰ π⁺π⁻, ρ⁺ρ⁻ – Kπ Puzzle in B⁰/B⁺ CP violation– Direct CPV in B⁺ J/ψK⁺
– Prospect of unitarity check by Belle II
__
37
Backup Slides38
• Δt: proper-time difference of the two B mesons– The Δt is calculated from a Δz: displacement of
decay vertices of the two B mesons.
• Decay vertex reconstruction– Assume all decay tracks
goes through a commonpoint (vertex).
– Minimizes The Vi is the i-th inverse error matrix.
– RMS of the vertex resolutionis ~ 120 μm
Reconstruction of Δt
B
vertexdecay products
425.0)()(
c
tc
z
vertex
j-th track
i-th track
δhjδhi
Tzdd )tan,,,,( 0 h
jjTjii
Ti VV hhhh 2
tracks
39
Δt Resolution Function
• One of dominant systematic error sources to the S/A
• Convolution of the following 4 components– Detector resolution … modeled by σ and χ² of the vertex fit.– Secondary track effect of Btag decay … modeled by exponential.
Higher priority is given to the ℓ of the Btag D*ℓν decay.
– Effect from ... exactly calculated.
– “Outlier” component ... Gaussian with σ ~ 10τB⁰.
40
)(czt
ℓ
D*
Kπ
Btag
true vertex
primary tracks
secondary tracks
reconstructed vertex
Determination of Btag Flavor
• Memory lookup method– Assign flavor to Btag decay products track-by-track referring the
MC-generated lookup table– Combine the track-by-track flavors and get flavor of the event.– Determine Btag flavor (q:±1)
and its ambiguity (w: 0…1).
• Calibration of MC-originated w– The w is calibrated using B⁰-B⁰ mixing.
41
Btag = B0
unambiguousunambiguous no info.
Btag = B 0
–1 0 +1
_ r = q(1–2w)
tmwPPPPA dSFOF
SFOF
cos)21(chg
_
A chg
|Δt| (ps)
)()1(
)()sincos)(21(14
),;,(
bkgsig
sig
tPf
tRtmStmAwqefASqtP ddB
t B
Unbinned-Maximum Likelihood FitΔt resolutionwrong tagging probability
background contamination
background
CPV-parameter determination from the UML fit
wrong tagging probability
Btag = B⁰Btag = B⁰
_Btag = B⁰Btag = B⁰
_
42
Δt resolution
events all
1
2
),;,(),(0),(i
ii ASqtPASLASASL
B⁰KS⁰K⁺K⁻ CPV Systematic Uncertainty
• List of the systematic-uncertainty sources
for the solution #1
43
B⁺ J/ψK⁺ Reconstruction
• B± J/ψK± event reconstruction: J/ψ– J/ψ candidates are reconstructed from e⁺e⁻ or μ⁺μ⁻ pairs.
(Tightly identified lepton) + (tightly or loosely identified lepton).
Tightly identified edE/dx && EECL/p && ECL shower shape
Loosely identified edE/dx || EECL/p
Tightly identified μ# of penetrating iron plates && shower
Loosely identified μ EECL ≈ E deposit by MIP
e⁺e⁻ μ⁺μ⁻tight + loose tight + tight tight + loose tight + tight
2.947 < Mee < 3.133 GeV/c² 3.037 < Mμμ < 3.133 GeV/c²
44
B⁺ J/ψK⁺ CPV Systematic Uncertainty
• List of the systematic-uncertainty sources
4545
CP Violation Measurement in B⁺ J/ψK⁺
• List of bin-by-bin CP violation and charge asymmetry
46
SuperKEKB
SuperKEKB Accerelator
Installation ofdamping ring
SRBeam
[Beam Channel][SR Channel]
[NEG Pump]
Improvements in beam pipe Improvementsin the RF components
7.0GeV e⁻
4.0GeV e⁺
IR
x40 luminosity of KEKBL = 2x10³⁵cm⁻²s⁻¹
Better “squeezing” magnet
Belle II DetectorCentral drift chamber
Smaller cell, longer lever arm
2-layer DEPFET pixel4-layer DSSD
Electromagnetic calorimeterBarrel part: CsI(Tℓ)
Endcal part: pure CsI
Ring image Čerenkov counter
KLμ detectorBarrel part: RPC
Endcap part:scintillator + SiPM
Fast data acquisition systemIntelligent
hardware triggerLarger mass storage
system
Time-of-propagation counter