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18th November 2005 Guillaume Thérin 1Lausanne – measurements with
Guillaume ThérinLPNHE – Paris
Lausanne
BaBar Measurements of
detector at SLACwith
18th November 2005 Guillaume Thérin 2Lausanne – measurements with
• Theoretical context– CP violation
– Standard model
• PEPII and BaBar B-Factory
• Direct measurements of – B- D(*)K(*)- method (ADS, GLW, GGSZ)
• Direct measurements of sin(2)– B0 D(*)-+, D(*)-+,
• B0 D(*)0K(*)0
• Combinations of the results with CKMFitter
Outline
18th November 2005 Guillaume Thérin 4Lausanne – measurements with
• The CKM matrix elements Vij describe the electroweak coupling strength of the W to quarks
• The CKM mechanism introduces quark flavour mixing
CP violation in the Standard Model
The phase changes sign under CP.
Transition amplitude violates CP if Vub ≠ Vub*, i.e. if Vub has a non-zero phase
=CP
Complex phases in Vij are the origin of SM CP violation
18th November 2005 Guillaume Thérin 5Lausanne – measurements with
Structure of the CKM matrix
– Mixing is weak Magnitude of elements strongly ranked (leading to ~diagonal form)
• 3 particle generations and unitary CKM matrix: 4 parameters (3 real + 1 im.)
= arg( V*ub/ Vcb ) (Wolf.)
Unitarity Triangle
/3
/2
/1
VtdVtb*
VudVub* VcdVcb
*
()
VcdVcb*)(
1)1(
21
)(214
23
22
32
AiA
A
iA
Wolfenstein :
•Measuring SM CP violation Measure complex phase of CKM elements
• 3 real par. A, λ (= sin Cabibbo = 0.22) and ρ
• 1 imaginary par. iη (responsable of CP violation)
() ()
18th November 2005 Guillaume Thérin 6Lausanne – measurements with
http://ckmfitter.in2p3.fr
• CP violation studies established:
Experimental Constraints on the Unitarity Triangle
• Before the B-factories, constraints came from kaons, B oscillations and |Vub/Vcb|• B-factories can be used to over-constrain the triangle and so to test the SM
• sin(2) = 0.685 ± 0.032
• experimental contraints on • (this talk) harder to measure
• The SM test consists of comparing 2 kinds of measurements :
• P (new physics)• B decays in charmless 2-bodies (envolving amplitudes with penguins)
charmonium
bcus,bucs
bcud,bucd
bcus,bucs
• st (Standard Model),
• B- D(*)K(*)- (GLW, ADS, GGSZ)
• B0 D(*), D0K(*)0 ( or sin(2))
• Bs Ds K(*)0 (probably at LHC)
18th November 2005 Guillaume Thérin 7Lausanne – measurements with
PEPII / BaBar, Experimental apparatus
18th November 2005 Guillaume Thérin 8Lausanne – measurements with
3.1 GeV
9 GeV
0 0
(4 )
(50% ,50% )
e e S BB
B B B B
The PEP-II B factory - Specifications
BB threshold
(4S)
• Produces B0B0 and B+B- pairs via Y(4s) resonance (10.58 GeV)
• Asymmetric beam energies
•Low energy beam 3.1 GeV
•High energy beam 9.0 GeV
• Clean environment
~28% of all hadronic interactions are BB
18th November 2005 Guillaume Thérin 9Lausanne – measurements with
RUN1
RUN2
RUN5
RUN3
Most analyses are based on 232.106 BB pairs
RUN4
Trickle injection:w/o trickle injection top-off every 30-40 min
continuous filling with trickle injectionmore stable machine, +35% more lumi
The PEP-II B factory - Performance
• PEP-II top lumi: 1.x1034 cm-2s-1
(~10 BB pairs per second)
• Integrated luminosity• PEP-II delivered: 311 fb-1
• BaBar recorded: 299 fb-1 on-peak+off-peak data• Most analyses use 211fb-1 of on-peak data
Records:
18th November 2005 Guillaume Thérin 10Lausanne – measurements withBABAR Collaboration : 11 countries and ~590 physicists !
Solenoid : 1.5T
ElectroMagnetic Calorimeter :6580 CsI crystals (Tl)E)/E = (2.32 E–1/4 1.85)%
Support tube
Instrumented Flux Return :iron / RPCs [ → LSTs ]
The BaBar detector
Drift CHamber :40 layers(pT)/pT = (0.13 pT 0.45)%
Detector of Internally Reflected Cherenkov light : 144 quartz bars, 11000 PMsK/ > 2.5 (p < 4.3 GeV/c)
Silicon Vertex Tracker :5 layers of double-sided Silicium, vertex resolution of 60-120 m
18th November 2005 Guillaume Thérin 11Lausanne – measurements with
Selecting B events for CP analysisB mesons identification
mES
E
**beamB EEE
e+ (3.1 GeV)
e- (9 GeV)
2*2*BbeamES pEm
b
udsc
Signal
)()4( MeVME Sbeam
isotropic
E*beam very well known
e+e- → uu, dd, ss, cc
e+e- → bb
-2 –1 0 1 2 3 4Fisher discrimnant
E*beam = E*Υ(4S) / 2
K/ separation with Cherenkov angle
Excellent separation between 1.5 and 4 GeV/c
Combinatorial e+e- qq bkg suppression
Jet-like
E*beam 2 mB>~
18th November 2005 Guillaume Thérin 12Lausanne – measurements with
Constraining with B- D(*)K(*)- decays
Gronau-London-Wyler method
Atwood-Dunietz-Soni method
Giri-Grossman-Soffer-Zupan method
Combination
Introduction
18th November 2005 Guillaume Thérin 13Lausanne – measurements with
B-bu
cu
su
D0
K*-
Vcb
Vus
Constraining with B± → D(*) K(*)± decays
a a rB ei()
B-
b
usu
u
cD0
K*-
Vub
= arg( V*ub/ Vcb )
Favored decay b c
Strong phase CKM Angle
Suppressed decay b u
Ratio of the 2 amplitudes
rB ≈ 0.1-0.2
• D0 , D0 same f interference sensitive to :
f f
– Gronau-London-Wyler :
CP eigenstates
– Atwood-Dunietz-Soni :
DCSD D0 and CA D0 ex. : B- → (K+ -)D K-
Ks0
KsK+K-
+Ks
– Giri-Grossman-Soffer-Zupan :
D0 → Ks
K+-Ks-
rD / rB ≈ 0.5
B(B- D(*)K(*)-) 5. 10-4
! rB, , different for DK*±, DK± and D*K± modes
18th November 2005 Guillaume Thérin 14Lausanne – measurements with
Constraining with B- D(*)K(*)- decaysIntroduction
Atwood-Dunietz-Soni method
Giri-Grossman-Soffer-Zupan method
Combination
Gronau-London-Wyler method
18th November 2005 Guillaume Thérin 15Lausanne – measurements with
GLW - Observables of the method - B± D(*) K±(*)
A(B+→D CP K
*- )
A(B- →DCP K*+)
A( B→D0K* )
Observables are:
non-CP modes ≈ flavour eigenstates
N(B+ → D K*+) ≠ N(B- → D K*-)
Direct CP violation:
18th November 2005 Guillaume Thérin 16Lausanne – measurements with
A+ R+= - A- R-
• Extract the 3 unknowns (, rB, (*)B) for each mode from 4 observables a relation
between observables:
• 8-fold ambiguity in • Sensitivity on depends on rB
• D(*)K modes
• suffer from bkg from D(*)0 (12x higher BF) need excellent /K separation
• D(*)K* modes
• cleaner but lower BF and lower efficiency
• need to consider D(*)Ks irreductible component
• Need to take into account dilution effect from opposite-sign CP D0 decays in fKS0
and KS0 (for instance D0a0KS
0)
• D*K* need angular analysis -not realistic with current statistics
GLW - Characteristics of the method - B± D(*) K±(*)
Experience:
Theory:
18th November 2005 Guillaume Thérin 17Lausanne – measurements with
• Event Shape Variables
• cos( of B momentum
• mES & E
• mass (D0)
• D0 helicity
D0B• mass (KS
0)
• distance of flight
• mass (K*)
• K* helicity
K*Ks
0
• 232 millions of charged B decays
• Reconstructed BF of the order of 2.10-7 – 10-6
CP=+1 : KK, ,non-CP : K , K 0, K 3
D0• track PIDs
CP+, non-CP
• mass (KS0)
• distance of flight
CP- : K s0 X.
X = {}Ks0
• mass ()
• helicity
• dalitz angle
• track PIDs
• mass (0)0
• mass ()
• helicity
• track PIDs
GLW – Reconstruction and selection - B± D K±*
-
-
+
18th November 2005 Guillaume Thérin 18Lausanne – measurements with
CP+ : 24 CP- : 25B+B-
B0B0
cc
uds
Signal
• Adding CP+ modes together (resp. CP- and non-CP)
• Strategy : fit in one dimension in mes
• Use data in E and D0 mass sidebands to fix the background shape
• Hypothesis : common parameterisation for all modes (checked on MC)
D0 mass
E
mes
Gaussian G
(rB = 0)
Argus function Ames
GLW – Distribution of the simulation and fit strategy - B± D K±*
18th November 2005 Guillaume Thérin 19Lausanne – measurements with
GLW - Results of the fit for 232 millions of charged B - B± D K±*
m(D0) sidebands
E sidebands
B+non-CP CP+1 CP-1
SIGNAL REGION
B-
• One single Gaussian G• One single Argus A
• Simultaneous fit in mes for 3 regions :
– Signal
– mD0 sidebands
– E sidebands
PRD72,71103(2005)
18th November 2005 Guillaume Thérin 20Lausanne – measurements with
• BD0K: 232M B± decays, D0KK, KS00
,0 KKDCP
000 SCP KD
KDB CP0
0CPDB
A 2 cut on C in these plots
A 2 cut on C in these plots
• BD*0K: 123 B± decays, only D*0D00, D0KK, at the moment:
• Main background from kinematically similar B→D0 which has BF 12x larger– So the signal and this main background are fitted together
Kaon hypothesis Kaon hypothesis
GLW - Results - B± D(*) K±
• Only CP+ modes
• 3D Fit(mes, E, C) without the kaon hypothesis
• 2D fit to E and the Cherenkov angle of the prompt track
18th November 2005 Guillaume Thérin 21Lausanne – measurements with
GLW – Summary - B± D(*) K±(*)
No asymmetry seen All values compatible with 1 except for the DK* mode rB is bigger
than expected for this mode
1 0
18th November 2005 Guillaume Thérin 22Lausanne – measurements with
Constraining with B- D(*)K(*)- decaysIntroduction
Gronau-London-Wyler method
Giri-Grossman-Soffer-Zupan method
Combination
Atwood-Dunietz-Soni method
18th November 2005 Guillaume Thérin 23Lausanne – measurements with
ADS - Method - B± D(*) K ±(*)
B-b
u
c
u
s
u
D0
K*-
B-
b
u
u
cD0
Cabibbo favoured bc amplitude
Cabibbo suppressed bu amplitude
s
u
s
u
u
d
u
d
u
s DK
rB =Cabibbo suppressed cd amplitude
Cabibbo favoured su amplituderD =
rD = 0.060±0.003Sensitivity: rD / rB ≈ 0.5
([ ] ) ([ ] )2 sin( )sin /
([ ] ) ([ ] )ADS B D D B ADS
Br K K Br K KA r r R
Br K K Br K K
2 2([ ] ) ([ ] )2 cos( )cos
([ ] ) ([ ] )ADS D B B D D B
Br K K Br K KR r r r r
Br K K Br K K
• Better sensitivity than GLW but lower BF
•4-fold ambiguity in : need to measure at least two D decay modes to loose ambiguity between and the strong phase
18th November 2005 Guillaume Thérin 24Lausanne – measurements with
mES (GeV/c²)
~90 events ~4 events
RS WS
WS B+
WS B-
• Cut same variables as GLW
• Some of them are put in a neural network
ADS – Results of the fit - B± [K ±]D K±(*)
±
B± [K± ]D K*±
±
B± [K ±]D K*±
±
B- [K+ -]D K*-
B+ [K- +]D K*-
PRD72,71104(2005)
18th November 2005 Guillaume Thérin 25Lausanne – measurements with
1-C
L GLWADScombination
rB
[0,] & (D+)[0,2]
(deg)
1-C
L
(semi-log scale)
[75°,105°] (excluded @2 CL)
GLW+ADS – Interpretation - B± D K±*
EPJ,C41,1 (2005)• CkmFitter Frequentist approach to determine and rB
• Construction of Confidence Level plots
PRD72,71104(2005)
18th November 2005 Guillaume Thérin 26Lausanne – measurements with
hep-ex/0504047
B-→D*[D0]K-
B-→D*[D]K-
B-→DK-
D*→D0/D ≠ in D* by
(r*B)²< (0.16)² * (Bayesian r*B²>0 & uniform, and D*)
PRD70,091503(2004)
0<D<2rD±1
51°<<66°
rB<0.23*
*
*
*
*
ADS – Results - B± [K ±]D(*) K±
±
18th November 2005 Guillaume Thérin 27Lausanne – measurements with
ADS – Summary - B± D(*) K±(*)
• No signal peak was observed
• More sensitive than GLW but need more statistics to constrain
• Other non-CP modes to add and reduce ambiguities
0
18th November 2005 Guillaume Thérin 28Lausanne – measurements with
Constraining with B- D(*)K(*)- decaysIntroduction
Gronau-London-Wyler method
Atwood-Dunietz-Soni method
Combination
Giri-Grossman-Soffer-Zupan method
18th November 2005 Guillaume Thérin 29Lausanne – measurements with
Schematicview of the
interference
2m
2m2m
2m
0 D 0 D
Reconstruct BD(*)0K(*) with Cabibbo-allowed D0/D0KS
If D0/D0 Dalitz f(m+2,m-
2) is known (included charm phase shift D):
),(),()(),( 2222022
mmfeermmfKDBAmmM ii
BB
),(),()(),( 2222022
mmfeermmfKDBAmmM ii
BB
B:B+:
|M|2 =
ambiguity only 2-fold ( ↔ )Experimentally: BF[(B D0K)(D0 K0 )]=(2.20.4)10-5 High statisticOnly charged tracks in final state high efficiency/low bkg
)( BiBer
GGSZ – Dalitz Method - B± D(*) K±(*)2 0 2
2 0 2 ( ) ( )
S
S
m M Km M K
18th November 2005 Guillaume Thérin 30Lausanne – measurements with
f(m2+,m2
-) extracted from high statistics tagged D0 events (from D*)
• D decay model described by coherent sum of Breit-Wigner amplitudes
• Dphase difference determined by model
•Not so good for s-wave. Need controversial and ’(1000) to reasonably describe the data
• Masses and widths fixed to PDG2004 values except for and ’ (fitted)
13 fitted resonances + NR term ++’2/dof3824/3022=1.27
DCS K*(892)
CA K*(892)
(770)
GGSZ – D0 KS Dalitz model f - B± D(*) K±(*)
18th November 2005 Guillaume Thérin 31Lausanne – measurements with
Mode Signal
events
B-DK− 282 ± 20
90 ± 11
B-D*[D]K− 44 ± 8
B-DK*−[K0S-] 42 ± 8
B-D*[D0] K−
DK- D*[D0]K- D*[D]K-
hep-ex/0504039
(mES>5.27 GeV/c²)
B-DK*−[K0S-]
GGSZ – Fit results - B± D(*) K±(*)
18th November 2005 Guillaume Thérin 32Lausanne – measurements with
(deg)
k.rsB
0<k<1 is an extra parameter with no assumption made on (K0
S-) under the K*- part
2 CL
1 CL
GLW+ADS
1 1
2
GGSZ/GLW+ADS – Confidence regions - B± D K±*
(deg)
GGSZrB
More constraint with GLW/ADS for this mode than with GGSZ
(K0S-) under the K*- and K S-waves
accounted for in a model where strong phase are unknown (k=1)
18th November 2005 Guillaume Thérin 33Lausanne – measurements with
7D Neyman Confidence Region:
•rB(DK), rB(D*K), k.rsB
• B(DK), B(D*K), B(DK*)
•
= 67°± 28°(stat.) ± 13°(syst. exp.) ± 11°(Dalitz model)
D0K- D*0K- D0K*-
(deg)
k.rsB (<0.75 @ 2CL+
and no assumption)
2 CL
1 CL
GGSZ – Combined results - B± D(*) K±(*)
rBrB
18th November 2005 Guillaume Thérin 34Lausanne – measurements with
Constraining with B- D(*)K(*)- decaysIntroduction
Gronau-London-Wyler method
Atwood-Dunietz-Soni method
Giri-Grossman-Soffer-Zupan methodCombination
18th November 2005 Guillaume Thérin 35Lausanne – measurements with
(deg)
1-C
L
=
GLW+ADS+GGSZ - Combination - B± D(*) K±(*)
• Sensitivity for all methods depends on rB
GGSZ
GLW+ADS
B± D K*±
B± D* K±
B± D K±
18th November 2005 Guillaume Thérin 36Lausanne – measurements with
Constraining sin( with B0 D(*) decays
18th November 2005 Guillaume Thérin 37Lausanne – measurements with
CP violation in B0D(*)
• Large branching fraction for favoured decay (~3x 10-3)
• Small BR for suppressed decay (~10-6)
• Small CP violating amplitude
Favoured b c decay
*cb udV V A (*)
* i i iub cd rV V e A e e
Strong phasedifferenceCKM
angle
c0B
d
bu
d
*D
W +
Suppressed b u decay
Determines the sensitivityof the method
r(D(*)) ≡ r(*) =A(B0 → D(*)- +)
≈ 0.015 A(B0 → D(*)- +)
b
d
bc
d
0B
u
*D
0B
d+
18th November 2005 Guillaume Thérin 38Lausanne – measurements with
Time-dependent decay rate distributions
• Measurements of S+ and S- determine 2+ and if r is an external input • Experiment : tag the flavour of the B with lepton and kaon categories combined in a neural network
Mixing-Decay interferenceP(B0 → D(*) ,t) 1 C cos(md t) + S sin(md t)
P(B0 → D(*) ,t) 1 C cos(md t) - S sin(md t)
∞ ±
±
±
±
±±
±
C = 1 – r2 1 + r2
≈ 1
0Bcb
l+lepton tag
0Bc sb
K+
kaon tag
(4s)Tag B
Reco BK+
+
z
K+
t z/c
z
-s
-
neglecting terms
in o(r2)S± ≈ 2r sin ( 2 ± ) , |S±| 0.03<~±
∞
18th November 2005 Guillaume Thérin 39Lausanne – measurements with
Possible CP violation on the tag side
Potential competing CP violating effects in B decays used for flavour tagging
signal side
tag side
2 sin(2 )cos
2 'sin(2 )cos '
2cos(2 )( sin 'sin ')
a r
b r
c r r
2 sin(2 )cos
2 cos(2 )si
0
nlep
b
a r
c r
Lepton tagsKaon and other flavour tags
(*)
* i i iub cd rV V e A e e ’
*cb udV V A +
P(B0 → D(*) - ,t) 1 + C cos(md t) + sin(md t) [± 2r sin(2) + 2r’ sin(2’)]∞
Kaon tag : expect CP violation comparable to signal → Modified time distributions
0Bc sb
K+
Observables a, b, c
c sK+
b0Bu
PRD68, 034010
18th November 2005 Guillaume Thérin 40Lausanne – measurements with
B0→D*: partial reconstruction results
• 18710 ± 270 lepton tags
• 70580 ± 660 kaon tags
Lepton Tags
PreliminarySignal
Combinatoric BBPeaking BBContinuum
D
*0 DBsoftD
0
X Find events with two pions and examine the missing mass mmiss
Lepton Tags
kaon Tags
Mea
n va
lue
ACP= N(B0 tag) - N(B0 tag)
N(B0 tag) + N(B0 tag)
Preliminary
Preliminary
hep-ex/0504035
18th November 2005 Guillaume Thérin 41Lausanne – measurements with
B0D(*),D full reconstruction results
*B D
*
0
DB
BB
rec
tag
*
0
DB
BB
rec
tag
*
0
DB
BB
rec
tag
background
*
0
DB
BB
rec
tag
Lepton tags, D* final state
B mode Yield Purity (%)
D 15635 135 85.5 0.3
D* 14554 126 93.0 0.2
D 8736 105 81.7 0.4
*B D
++0, D+K-++, Ks+ D*+ D0+ ,
D0 K-+,K-+0,K-+-+,Ks+-
- Reconstruct B0 candidate using full decay tree:
18th November 2005 Guillaume Thérin 42Lausanne – measurements with
Determination of r
• Simultaneous determination of sin(2+) and r from time-evolution is not possible with current statistics Need r as an external input
• Estimate amplitude ratios from B0Ds(*)+- using SU(3) symmetry
0B
d
u
*SD
bc
0B
d
d
u
*D
bc
scsV cdVSU(3)
r(D) = 0.019 ± 0.004 r(D*) = 0.015 ± 0.006 r(D) = 0.003 ± 0.006
I. Dunietz, Phys. Lett. B 427, 179 (1998)
Assuming several hypotheses for SU(3) :
• Assuming factorisation
• Neglect exchange and annihilation diagrams
without any theoritical errors
18th November 2005 Guillaume Thérin 43Lausanne – measurements with
|sin(2+)| > 0.64 @ 68 % C.L.|sin(2+)| > 0.42 @ 90 % C.L.
- Combine partial and fully reco results for the a and clep parameters
|2+| = 90o 43o
68 % 90 %
30% theoretical error on r 100% theoretical error on r
Interpretation of sin(2) assuming SU(3)Assign theoretical error on r(D*), r(D) and r(D)
Bayesian approachFrequentist approach (Feldman-Cousins)
90 % CL
68 % CL
www.utfit.org
18th November 2005 Guillaume Thérin 45Lausanne – measurements with
Conclusion
• Measuring at B-Factories: an impossible mission a few years ago
• GGSZ analyses give the best results
• The GLW method eliminates constraints close to 900
• All analyses are statistically limited or statistics are too low for most sensitive methods
GLW,ADS,GGSZ WA = (63+15
-12)º
|sin(2β+γ)| BaBar >0.64 (@ 68 %CL)
•B- D(*)K(*)- (GLW, ADS, GGSZ)
•B0 D(*)