Recent Results from B A B AR
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Transcript of Recent Results from B A B AR
Recent Results from BABARP.-Fabrizio Salvatore
Royal Holloway College, University of LondonFor the BBAABBARAR Collaboration
Hadron Structure 2002, Herl’any
22-27 September 2002
Measurement of sin2Measurement of sin2eff
Future: and sin (2+
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 2
The search for CP violation with asymmetric e+e- collider
PEPII and the BaBar Experiment sin2 measurement:
The golden modes: b -> ccs The Cabibbo-suppressed modes: b -> ccd The pure penguin modes: b -> sss
sin2eff measurement: CP asymmetries in +- and K+-
+0 and 00 decay rates CP asymmetries in +- and +K-
Future:and sin(2 +) Asymmetry in B ->D0
(CP)K decay B0 ->D* (n) decays
Conclusions
Outline
--
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 3
Physics principles: CP violation in the SM
The only source of CP violation in the SM is the KM phase that appears in the CKM matrix
CP from complex component of Vub and
Vtd
Unitarity Triangle comes from the unitarity of the
matrix
1
2
3
, and constrained by CP asymmetries in B decays
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 4
Time-dependent CP violation from B0-B0 mixing
B0
B 0
fCP
BL ,H p B0 q B0 b
d
d
bu,c,t
u,c,t
top quark box introduces: Vtb Vtd*
f(t )e t /
41S f sin(mdt)C f cos(mdt)
md = mH - mL
W W
Cf 1 f
2
1 f2
Sf 2 Im f
1 f2
f qp
A(B0 fCP)
A(B0 fCP)
qp
~Vtd
Vtd*
f (B0 fCP)
f (B0 fCP)
Direct CP violation if multiple amplitudes with different phases
Purely CP violation in interference of decays with and without mixing
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 5
PEPII performancesPeak luminosity: 4.60 x 1033cm-2s-1
(exceeded design goal 3.0 x 1033)
PEP-II delivered 99 fb-1
BaBar recorded 94 fb-1
For sin2 and sin2 used:On peak 81 fb-1
88M BB pairsOff peak 10 fb-1
Peak luminosity: 4.60 x 1033cm-2s-1 (exceeded design goal 3.0 x 1033)
PEP-II delivered 99 fb-1
BaBar recorded 94 fb-1
For sin2 and sin2 used:On peak 81 fb-1
88M BB pairsOff peak 10 fb-1
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 6
BABAR Detector
SVT: 5 double side layers. 97% efficiency, 15 m z hit resolution (inner layers, perp. tracks)Momentum resolution (SVT+DCH): (pT)/pT = 0.13 % pT + 0.45 %
DIRC: 144 quartz bars. Provide K- separation 4.2 @ 3.0 GeV/c 2.5 @ 4.0 GeV/c EMC: 6580 CsI(Tl) crystals. Energy resolution: E/E = 2.3 %E-1/4 1.9 %
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 7
B0-B0 events at the (4S) resonance
Boost: = 0.55
Start the ClockCoherent BB pair
B0
B0
z
t z c
K-
Flavour tag and vertex reconstructi
on
Flavour tag and vertex reconstructi
on
Exclusive B meson and vertex reconstruction
Exclusive B meson and vertex reconstruction
KS
Z
Compute f+ (t)
+e-e
4S Btag
Brec
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 8
Vertexing and tagging algorithms
Brec vertex from charged Brec daughters
BTag vertex from: All charged tracks not in Brec,
constrain with Brec vertex, beam spot, and (4S) momentum
High efficiency: 95% Average z resolution ~ 180 m measured
from data)
Beam spot
Interaction Point
BREC Vertex
BREC daughters
BREC direction
BTAG directionTAG Vertex
TAG tracks, V0s
z
New tagging algorithm based on neural networks: inputs: leptons, K, slow (D* decay) and high-momentum tracks
5 mutually exclusive categories:
• Lepton - isolated high-momentum leptons;
• kaon I – high quality K, correlated K and slow • kaon II – low quality K or slow • Inclusive – unidentified leptons, low quality K, high-momentum tracks;
• Untagged Q = 28.1 + 0.7 % (~7% improvement)PRL87 (Aug01)
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 9
Tree level dominates and CP only from B 0-B 0 mixing
sin2 from charmonium states (b ccs)
)sin(2sinff
ff)(
-+
-+ tmtAd
fCP
f = f e-
i2f=±1
1)(
)(0
0
CP
CP
fBA
fBA
p
qfc
s
c
dd
bB0 K0
B0 -> J/ Ks
B0 -> (2S) Ks
B0 -> c1 Ks
B0 -> c Ks
f = -1
f = 1 B0 -> J/ KL
f = 1- 2RT B0 -> J/ K*0 (K*0 -> Ks 0)
RT = 16.0 + 3.5 % (PRL87)
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 10
Recent addition:B0 c Ks
where c K+K-
0 or
K+Ks -
Event yields and purity
Event Sample
Ntag Purity
J/ Ks(+-) 974 97%
J/ Ks(00) 170 89%
(2S) Ks 150 97%
c1 Ks 150 95%
c Ks 132 73%
Total (f = -1) 1506 92%
J/ KL 988 55%
J/ K*0 (Ks 0) 147 81%
All CP modes 2641 78%
Energy-substituted mass: 2cm2cmbeamES BpEm
Energy difference:cmbeam
cm0B
EEE
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 11
sin2 = 0.723 0.158
sin2 result
f =-1 f =+1
sin2 = 0.741 0.067 (stat) 0.033 (sys)
• Unbinned maximum likelihood fit: 34 parameters: sin2, mistag fract. (8), t resolution funct. (8), bkgnd (17) B = 1.542 ps, md = 0.489 ps-1 fixed (PDG 2002)
sin2 = 0.755 0.074
(hep-ex/0207042)
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 12
Asymmetry in b ccs modes with lepton tag
sin2 = 0.79 0.11
Golden mode (cc) Ks with lepton tag only
Ntagged = 220
Purity = 98%
Mistag fraction 3.3%
t 20% better than other tag categories
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 13
sin2 fit results by decay mode
Consistency of CP Channels: P(2) = 57%
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 14
Constraints in the () plane
One solution for is in excellent
agreement with measurements of unitarity triangle
apex
Method as in Höcker et al, Eur.Phys.J.C21:225-259,2001
= (1-2/2)
= (1-2/2)
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 15
Search for new physics in (cc)KS events
| f | = 0.948 0.051 (stat) 0.017
(syst)
Sf = 0.759 0.074 (stat) 0.032 (syst)
ACP (t) S f sin(mdt) C f cos(mdt)
Cf 1
f
2
1 f
2
Sf 2 Im
f
1 f
2
If another amplitude that
contributes with a
different phase:
In the measurement of sin2 we have assumed |f | = 1 (SM expectation)
Sf - f sin2 Cf 0
Fit |f| and Sf using the
clean (cc)Ks modes
(f =-1, Ntagged = 1506,
Purity = 92%):
Consistent with the Standard Model expectation of |f |=1 and nominal fit sin2 = 0.755 0.074 for (cc)Ks modes alone.
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 16
• B0 D*+D*-: same weak phase as b ccs (tree level);
small penguin contribution (<0.1 Tree);
not CP eigenstate (needs angular analysis)
The Cabibbo-suppressed modes (b ccd ) (I)
Ntagged= 102
Purity = 82%
B0
D* -
D* +
B0
D* -
D* +
Vcd
RT = 0.07+0.06+0.03
|+| = 0.98 0.25 (stat) 0.09 (syst)
Im(+) = 0.31 0.43 (stat) 0.10 (syst)
Im(+) measurement ~2.7 from BaBar sin2 in
charmonium, assuming no penguins.
+
Parameterize in terms of CP-odd () and CP-even (+) components and use:
| |= 1, Im( ) = -0.741
(hep-ex/0207072)
If penguins are negligible, then
Im(+) = - sin2
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 17
(hep-ex/0207058)
The Cabibbo-suppressed modes (b ccd) (II)
• B0 J/ 0 : also color-suppressed
Comparable tree and penguin
contribution ~ O(3)
Vcd
Tree: ~VcbVcd*
Penguin:~VcbVcd* +
VubVud*
Ntagged = 49 Purity = 59%f = + 1
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 18
Dominated by b sss gluonic penguins
sin2 from penguin mode B0 KS
|K| = 1 fixed
SK = -0.19 (stat) 0.09 (syst)
+0.52- 0.50
Small branching fraction O(10-5) Significant background from qq
continuum Using only K+K-
Ntagged = 66 Purity = 50%f = - 1
Cross check on B+ K +: SK = 0.26 0.27Analysis of B0 ’ KS in progress
If no new physics, SK = sin2
(hep-ex/0207070)
Same Weak phase as b ccs, but sensitive to new physics in loops
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 19
Interesting new measurements are being obtained on the open charm modes:
B 0D*+D*- (hep-ex/0207072)
and b penguin modes:B 0J/ 0 (hep-ex/0207058)
B 0 K0S (hep-ex/0207070)
Summary of sin2results
New measurement of sin2 from charmonium modes (88 x106 BB)
Submitted to PRL July 17, 2002(hep-ex/0207042)
Results have been improving by more than just luminosity gain
No hints of physics beyond the Standard Model yet, but lots of opportunities to challenge the theory with the increasing event statistics in BaBar
Million BB pairs
July 00
Feb 01
July 01Mar 02
July 02
sin2sin2 = 0.741 ± 0.067 (stat) ± 0.033 (syst) = 0.741 ± 0.067 (stat) ± 0.033 (syst)
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 20
sin2 from charmless B decays
Penguin contribution is non-negligible
measure sin2eff
mixing
*
*
ubud
ubud
VV
VV *
*
tdtb
tdtb
VV
VV
decay +
Tree (T)
Penguin (P)
)2sin(1
)sin(
eff2
/1
/12
CS
C
e ieieTP
ieieTPi
need BF from B -> +-, +0 and 00 and isospin analysis to obtain from eff
B0 +-
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 21
sin2 : B → , K, KK modes
• Small branching ratios (10-5-10-6)
lots of data needed
• Large background from continuum (qq)
events
use kinematic and topology of events to separate signal from
light-quark bg
i i
iii ppF2*** )cos(27.160.053.0
Fisher discriminant:
*
p*
• Ambiguity between and K
needs excellent particle ID (DIRC)
Data sample: 88M BB events
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 22
hypothesis
K hypothesis
K/ separation using the DIRC
• Double-gaussian PDFs built from the difference (c – c
exp)/s(c)
• K/ separation and PDF parameters measured using fully reconstructed
dataFor =85%: P(K->) = 1.7% P(->K) = 2.7 %
• Identification of h+h’- tracks as or K using the angle c measured in the
DIRC
KDDD 00* ,
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 23
Event yields and K asymmetry
sinsin
)()(
)()(00
00
T
P
KBBrKBBr
KBBrKBBrAK
CP
• Time-independent maximum likelihood fit to extract event yields and K asymmetry
no tagging or vertexing needed
Mode Yield BR (10-6) ACP(K)
B→ 157 + 19 4.7 + 0.6 + 0.2
B→ K 589 + 3017.9 + 0.9 + 0.7
-0.102 + 0.050 + 0.016
B→ KK 1 + 8< 0.6 (90% C.L.)
Direct CP
Preliminary
Submitted to Phys Rev (hep-ex/0207055)
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 24
mES and E distributionsPreliminary
Signal events are selected in the (mES,E) plane
same as for sin2 measurement
Bo -> Bo ->
K
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 25
1 p
s
Projection in sample of -selected events
qq+ K
S and C measurement
• Time-dependent unbinned maximum likelihood fit Same tagging and vertexing procedure as for sin2
)cos()sin(
)(00
00
tmCtmS
BNBN
BNBNtA
dd
tagtag
tagtag
S = 0.02 + 0.34 + 0.05
C = -0.30 + 0.25 + 0.04
Preliminary
Submitted to Phys Rev (hep-ex/0207055)
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 26
)(
)(21
1
1arccos22
0
00
2
BR
BR
Ceff
Extraction of from eff
Need to measure:
B+ ->+0, B0 ->00, B0 ->00
Grossman-Quinn bound
• Otherwise, put limit on BR(B0 ->00):
Isospin analysisGronau and London, Phys.Rev.Lett 65, 3381
(1991)
• B ->+-, +0 and 00 decays related by isospin
• (gluonic) penguins contribute only to I=0
• +0 has I=2 only tree amplitude only
(|AA)
2eff = 2 +
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 27
B+->+0 and B+->K+0 branching ratio
B+->+0 has pure tree amplitude and
no CP expected
• Usual charmless two-body analysis
• B0-> +- bg reduced by a
Fit region
ee→ qq
Mode Yield BR (10-6) ACP
B→
B→K
23211252122239
6.05.5 0.19.0
0.18.12 2.11.1
02.003.0 18.017.0
01.009.009.0
Simultaneous fit to /K
hep-ex/0207065
tight cut on E
Preliminary
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 28
B0->00 branching ratioPrelim
inary
B0->00 yield determined by unbinned ML fit:10
900 23
n
)%7.15.16(00
@ 90% CL
6000 106.3)( BBR
| – eff| < 510
Central value for BR:
66.03.0
7.06.0 10))()(6.1(
syststat
If BR as high as its central value, Grossman-Quinn bound not adequate isospin analysis is necessary
hep-ex/0207063
• Small signal expected
• Flavour tagging and event topology used to reduce qq bg
• B+->+0 bg reduced using a cut on m(+0) and E
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 29
B0->h: direct and indirect CP measurement
0000 and BBBB
CP
0
B
0
B
0B
0B
CP
BR = (28.9+5.4+4.3)x10-
6
)()(
)()(
hNhN
hNhN
NOT CP eigenstate
tmCCtmSSDD
Af dhhdhhh
CPh
tagBcossin
21)1(0
insensitive to CPK self
tagging
0 ,0 ,1 ,0 KKKK SSCC
Direct CP ACP and C = 0 Indirect CP S =
0
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 30
Event yields and charge asymmetry
Clear B0-> signal
• Maximum likelihood fit to extract yields and charge asymmetry:
2221
3433 147,413
KNN
background and qqBB
0.140.140.19 ( ) 0.11( )K
CPA stat syst 0.140.140.19 ( ) 0.11( )K
CPA stat syst
0.080.080.22 ( ) 0.07( )CPA stat syst 0.080.080.22 ( ) 0.07( )CPA stat syst
Preliminary
hep-ex/0207068
• Validation test: fit B and md using data
1-ps)09.051.0(
ps)12.059.1(
d
B
m
background and qqBB
B0/B0->
B0/B0->
B = (1.540 + 0.014) ps
md = (0.503 + 0.006) ps-1
World AverageWorld
Average
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 31
Time-dependent asymmetry
qqBB and
only BB
0.180.19
0.250.25
0.45 ( ) 0.09( )
0.16 ( ) 0.07( )
C stat syst
S stat syst
0.180.19
0.250.25
0.45 ( ) 0.09( )
0.16 ( ) 0.07( )
C stat syst
S stat syst
Preliminary
hep-ex/0207068
dominated by uncertainties on B
background components
expected ~0.4 (from naïve factorization)
sensitive to strong phase differences
0.190.20
0.250.25
0.38 ( ) 0.11( )
0.15 ( ) 0.05( )
C stat syst
S stat syst
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 32
Direct CP violation
Direct CP can be expressed using the asymmetries:
CAC
CACA
BNBN
BNBNA
CP
CPCP
1)()(
)()(00
00
CAC
CACA
BNBN
BNBNA
CP
CPCP
1)()(
)()(00
00
meson from spectator quark
meson from spectator quark
Using previous results and their correlations:
A+- = - 0.82+0.31(stat)+0.16(syst)
A-+ = - 0.11+0.16(stat)+0.09(syst)
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 33
Summary of sin2and direct CP violation results
• Charmless two-body decays: branching ratios and CP asymmetries in B0->+-, K+- and K+K- (hep-ex/0207055) no evidence for large direct or indirect CP violation in +
branching fractions needed to extract from eff computed:
upper limit on BR(B0->00) (hep-ex/0207063)
B+->+0 and K+0 branching ratios (hep-ex/0207065)
still too early for significant constraint:
• Charmless three-body decays: first CP asymmetry measurement for B0->and B0->K(hep-ex/0207068)
| – eff| < 510
0.180.19
0.250.25
0.45 ( ) 0.09( )
0.16 ( ) 0.07( )
C stat syst
S stat syst
0.180.19
0.250.25
0.45 ( ) 0.09( )
0.16 ( ) 0.07( )
C stat syst
S stat syst
A+- = - 0.82+0.31(stat)+0.16(syst)
A-+ = - 0.11+0.16(stat)+0.09(syst)
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 34
Future: and sin(2+) (I)
with B ->D0(CP)K with B ->D0
(CP)K
W+
B+
b
uu
u
s
c
K+
D0
Vus
Vcb*
Colour allowed
B+
b
uu
c
K+
D0
W+
u
sVcs
Vub*
Colour suppressed
1||)(0 ieAKDBA
ii eeAKDBA 2||)( 0
)( *uscbVV
)( *csubVV
)%20.035.031.8()(
)(0
0
DBBr
KDBBrR
0 00.090.070 0
( ) ( )0.17 0.23
( ) ( )
CP CPCP
CP CP
Br B D K Br B D KA
Br B D K Br B D K
data sample 75
fb-1
hep-ex/0207087
Preliminary
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 35
Future: and sin(2+) (II) Preliminary
B ->D*//a1
h+W+
B0
b
dd
u
d
c
D*-
Vud
Vcb*
Cabibbo allowed
W+
B0
b
dd
c
d
u
h-
Vcd
Vub*
Cabibbo suppressed D*+
Time evolution of B0->D*-h+ and B0->D*+h- related to sin(2+)
• For precise measurement, need many events
• D*a1 mode has the largest BR (~1.3%)
• use partial reconstruction:
Only the slow from D*->D0 decay and the //a1 (a1->0) are reconstructed
If only the D0 is missing, in the (4S) frame the B direction lies on the surface of a cone
Averaging over this surface, the missing mass mmiss can be defined
P*(,,a1)P*
P*D0
P*B
Signal: mmiss peaks to D0 mass
Bg events: broader distribution
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 36
B ->D*
t(ps)
Continuum
Comb. BB
Peak. BB
Signal
Nsig = 6971+241
First steps: B0 lifetime using D* and D* decays
B = 1.616+0.064(stat)+0.075(syst) pshep-ex/0203036
B = (1.540 + 0.014) ps
World AverageB = 1.510+0.040(stat)+0.038(syst)
ps hep-ex/0203038
Validation for the partial reconstruction technique
B ->D* Nsig = 5521+251
B extracted using an unbinned maximum
likelihood fit
data sample
20.7 fb-1
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 37
data sample
20.7 fb-1
PDG: (1.30+0.27)%
BF = (1.20+0.07+0.14)%
BF = (1.20+0.07+0.14)%
Signal yield: 18400+1200
Preliminary hep-ex/0207085
• data on-reso (off-reso subtr.)
signal+BB bg MC
BB bg MC only
D*a1 branching fraction measurement
• Continuum background rejected using a neural network technique
exploit the different topologies between qq events (jet structure) and B events (spherical)
• mmiss distribution obtained from off-reso data subtracted from that obtained on on-reso
• result fitted with a combination of:
BB Monte Carlo events
signal Monte Carlo events
B ->D*a1
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 38
Summary: B ->D0(CP)K and B0 ->D*(n)
Analyses just begun, still lot of work to do !
• B -> D0(CP)K mode:
ratio of branching fraction for B->D0K and B->D0 modes
first measurement of CP asymmetry in B->D(CP)
K (hep-ex/0207087)
• B -> D*(n) mode : B0 lifetime using D* and D* decays (hep-ex/0203038, hep-ex/0203036)
branching fraction of B0 -> D*a1 decay channel (hep-ex/0207085)
R= (8.31+0.35+0.20)%
ACP= (0.17+0.23 )+0.0
9
-0.07
BF = (1.20+0.07+0.14)%
B = (1.533+0.034+0.038) psCombined measurement:
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 39
Conclusions (I)
Extremely productive time for B physics with
BaBar !More still to
come !BUT
New measurement of sin2 from charmonium modes Submitted to PRL July 17, 2002
(hep-ex/0207042)sin2sin2 = 0.741 ± 0.067 (stat) ± 0.033 (syst) = 0.741 ± 0.067 (stat) ± 0.033 (syst)
First steps to analyze decay modes related to and sin(2+) first measurement of CP asymmetry in B->DK (hep-ex/0207087) B0 lifetime with D* and D* decays (hep-ex/0203038, hep-ex/0203036) branching fraction of B0->D*a1 decay (hep-ex/0207085)
No evidence for large direct or indirect CP violation in B0->+ Measurement of the branching ratios for B+-> +0,K+ (hep-ex/0207065)
Upper limit on BR(B0-> 00) and constraint on |-eff| (hep-ex/0207063)
CP asymmetry in B0/B0->+ decay (hep-ex/0207068)
(hep-ex/0207055)
BaBar and Belle’s sin2 results have convinced the physics community that CKM is the dominant
source of CP violation
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 40
Conclusions (II)
More exciting physics results are on their
way !
0
100
200
300
400
500
Year
Inte
gra
ted
Lu
mi [
fb-1
]
024681012141618
Pea
k L
um
i [10
**33
]Yearly Lumi
Cumulative Lumi
Peak Lumi
Yearly Lumi 2 23 40 70 95 110 70
Cumulative Lumi 2 25 65 135 230 340 410
Peak Lumi 1 2 5 7.5 10 12 17
1999 2000 2001 2002 2003 2004mid
2005A lot more to do with the 100 fb-1 of data already recorded and those still to come in the next run
starting this fall• higher precision in the sin2 measurement
• measurement of and better knowledge of |Vub| and |Vcb| rare decays (possibility to probe new physics) Charm physics (D0 mixing, CP, ….) tau results
• other very interesting physics results:
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 41
Tagging performance
Category Efficiency () Mistag Fr. () Mistag Q=(1-2)2
Lepton 9.1 0.2 3.3 0.6 -1.4 1.1 7.9 0.3
KPiorK 16.7 0.2 9.9 0.7 -1.1 1.1 10.7 0.4
KorPi 19.8 0.3 20.9 0.8 -4.2 1.1 6.7 0.4
Inclusive 20.0 0.3 31.6 0.9 -2.0 1.2 2.7 0.3
Total 65.6 0.5 28.1 0.7
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 42
Sources of Systematic Error
sin2Description of background events 0.017
CP content of background componentsBackground shape uncertainties
Composition and content of J/ KL background 0.015
t resolution and detector effects 0.017Silicon detector alignment uncertaintyt resolution model
Mistag differences between BCP and Bflav samples 0.012
Fit bias correction 0.010Fixed lifetime and oscillation frequency 0.005TOTAL 0.033
Steadily reducing systematic error: July 2002 = 0.033July 2001 = 0.05
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 43
sin2 in subsamples
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 44
Cross-check on data control samples
Observed no asymmetry as expected
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 45
CP composition of B0 D*+D*-
We measure CP odd fraction (corrected for acceptance) to be small:
R = 0.07 0.06 (stat) 0.03 (syst)
dd cos tr
34
1 R sin2 tr 32
R cos2 tr
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 46
The Cabibbo-suppressed modes (b ccd)
D* _
D+
D* _
B0
B0
D*+
D _
D*+
D _
D+
CPconjugation
strongphase
D*D 56 fb-1
Ntagged= 85Purity = 52%
S+- = -0.43 1.41 0.20
C+- = 0.53 0.74 0.13
S-+ = 0.38 0.88 0.05
C-+= 0.30 0.50 0.08Update to full data set in progress
• B0 D*+D- :
Not a CP eigenstate
• possible strong phase contributions;
• different decay time distributions for :
B0 D- D*+
B0 D*- D+
September 26, 2002 Fabrizio Salvatore, Royal Holloway College 47
Validation of tagging, vertexing and fit procedure
• Use B0 ->K events:
T=tag charge, Q=K charge
)cos()21(14
)(/
, tmwTQe
tf d
tK
QT
same sample as for CP asymmetries
B and md floating in the fit
B = (1.56 + 0.07) ps
md = (0.52 + 0.05) ps-1B = (1.540 + 0.014) ps
md = (0.503 + 0.006) ps-1
World Average
Projection in sample of -selected events