EPS, July 2003 1
Dalitz plot of D0 - + 0 (EPS-208)
Kinematic distributions in c e+ (EPS-138)
Decay rate of B0 K*(892)+ - (EPS-123)
Victor Pavlunin Purdue University
the CLEO collaborationEPS-2003, Aachen, Germany
Searches for CP asymmetries in the:
EPS, July 2003 2
CPV in decay (direct):
Time integrated asymmetries; but strong phases are hard to calculate.
CPV in mixing (indirect):
Time integrated asymmetries (e.g., like-sign di-lepton events); expected to be small in the
SM.
CPV in the interference between decays with and without mixing:
Time dependent analyses; avoid hadronic uncertainties in some important cases.
CP violation in the Standard Model
jijji
i dVuJ )1(2
15
,
In the SM, the origin of CPV resides in flavor changing quark transitions (VCKM):
1)(
)()(
)(
j
ij
j
ij
jj
jj
ea
ea
fPA
fPA
1
2
2,
1212
*12
*12
2
00
i
M
iM
p
qPqPpP
0)(Im)(Im A
A
p
qCP
EPS, July 2003 3
The CLEO II and II.V detector
Tracking system: SVX (3 layers) or Gas Vertex Detector, Vertex Detector, Drift Chamber (B=1.5T, Ar2+C2H6 or He2+C3H8)
(p/p ~ 0.6% for a 2 GeV track) Time of Flight system Scintillating plastic (t ~ 170ps) Crystal Calorimeter CsI crystals(E/E ~ 2% for a 2 GeV photon Muon chambers Proportional chambers at 3, 5 and 7 I
The size of the data sample is 13.7 fb-1.• 2/3 (1/3) is taken with CLEOII.V (CLEOII).• 2/3 (1/3) is taken ON (50 MeV OFF) (4S).
~10M of and ~18M of events. BBee ccee
EPS, July 2003 4
CPV studies at CLEO
Type of CPV Direct Mixing Interference
Bottom Yes Yes No
Charm Yes Yes Yes
All results reported today are on searches for direct CP asymmetries
CESR is a symmetric (5.3+5.3) GeV e+e – collider. On (4S),
B = B BcB is ~30 m,
D = DDcD is 120 - 320 m (assuming DD =1 ),
B < Vertex resolution < D
Time integrated asymmetries in B and D systems, and time dependent asymmetries in the D system are accessible.
EPS, July 2003 5
ACP in the Dalitz plot of D0 - +0 (EPS-208)
Interference of different intermediate resonances in the Dalitz plot makes amplitudes and phases of the resonances accessible. Expected contributions are from resonant decays through 0, + and -, as well as a non-resonant contribution.
ACP is predicted to be as large as 0.1% (F.Buccella et al., Phys.Lett.B 379, 249 (1996)).
E791 found strong evidence for (500) in D+ -+ + (PRL 86, 770 (2001)). Does (500) contribute in D0 - + 0?
EPS, July 2003 6
Event selection for D0 -+0 (CLEOII.V data only)
Standard criteria on charged tracks and 0’s
Constrain D0 and slow
to the beam spot
D0( - + 0) and D*+( - + 0 +slow):
1.841 GeV < M(D0) < 1.885 GeV -0.604MeV < Q – Qexpected < 0.691MeV,
where Q M(D*+) - M(D0) Xp P(D*+) / P(D*+) max > 0.7
D*+ D0 +slow , D0 - + 0 , 0 . The
sign of slow
determines the flavor of the D0.
Signal yield: 1.1K events in the signal box, of which ~20% are background.
EPS, July 2003 8
Fit to the Dalitz plot of D0 - + 0
The likelihood function has the form
The matrix element is parameterized as
ACP across the Dalitz plot is obtained as
backgroundsignal
D
N
mmBF
N
MmmFL
),()1(
),( 222
220000
000
00
0000
00
D
i
D
i
D
i
iNRD
MeaMeaMea
eaM NR
2222
22
22
00
00
00
/ dmdmdmdmMM
MMA
DD
DDCP
EPS, July 2003 9
All Preliminary
Results for ACP in D0 - + 0
Resonance Amplitude Phase Fit Fraction
+ 1.00 (fixed) 0 (fixed) 76.5±1.8±4.8
0 0.56±0.02±0.07
10±3±3 23.9±1.8±4.6
0.65±0.03±0.04
4±3±4 32.3±2.1±2.2
Non res 1.03±0.17±0.31
77±8±11 2.7±0.9±1.7
)(09.007.0 09.001.0 sysCPA
Systematic errors (on-going):Parameterization of efficiencies;Parameterization of background; Signal fraction; Event selection criteria.
Fit fraction of (500) is consistent with zero.
The results of a fit with no CPV assumed (systematic errors are
included):
The integrated ACP across the Dalitz plot:
EPS, July 2003 10
Form factor measurement and search for CPV in the decay c e+ (EPS-138)
In the heavy quark symmetry limit, particles with a heavy quark are subject to a larger symmetry group . The Lorentz structure of -type baryons is due to the polarization states of the heavy quark only (light quarks form a spin zero state). Due to this simplicity, the predictions of HQET for -type baryons are more reliable than for mesons.
Four kinematic variables describe the decay sequence c e+, p +: t = q2/q2
max , cos, cosW and . The four-fold decay rate has the form:
are helicity amplitudes containing the dependence on
the form factors.
SpinHQSULorentzG _)2(
WH
EPS, July 2003 11
Form factor predictions for c e+
Traditional parameterization of the hadronic current:
HQET implies relations among form factors and reduces their number to two:
In order to fit the data, the q2 dependence of
the form factors must be assumed. We follow the Korner-Kramer (KK) model (Phys.Lett. B 275,
495 (1992)) and assume the same dipole dependence for both form factors:
The fit is made for R = f2/f1 and Mpole .
EPS, July 2003 12
Yields and Estimation of kinematic variables
Event selection and background studies:
Estimation of kinematic variables (neutrino is missing):
kinematic constraints of the decay, the thrust vector of the event, the fragmentation function of c.
~3K of signal events and S/B=3.7
EPS, July 2003 13
ML fit for form factors in c e+ The fitting method used in the analysis was first suggested
in D.M.Schmidt, R.J.Morrison and M.S.Witherell, Nucl.Instr. and Methods A328 547 (1993), in the measurement of form factors in DK*l.
The following samples are used as separate components in the fit (10 different components): c e+ for CleoII/CleoII.V (2 components)
c e- for CleoII/CleoII.V (2 components)
c e+ (2 components) fake positron background (3 components with different
momentum ranges) fake background (1 component)
Simultaneous fit for R=f2/f1 and Mpole:
Major systematic errors Background shapes in 4D,
Feeddown from modes c Xe+ , X0, Background normalizations, Uncertainties intrinsic to the fitter
5.0t
5.0t
5.0t
5.0t
5.0t
5.0t
cos cos
Wcos Wcos
12 / ffR
GeVM
R
sysstatpole
sysstat
10.007.013.2
,04.005.031.0
M(Ds*(1-)) = 2.11 GeV
EPS, July 2003 14
The fit results correspond to
If CP is conserved then . Therefore, a CP violating parameter can be defined as .
Fitting the charge conjugate states separately for
and , and using the relation
we obtain
where correlations among systematic errors are taken into account.
All Preliminary
ACP in the kinematic distributions of c e+
Asysstat
cc
cc
cA 02.001.003.001.0
),( 22
AAOAAcc
cc
cc
cc
cc
cc
cA
)(02.0)(03.085.0
2
02/1
2
02/1
2
12/1
2
12/1
2
02/1
2
02/1
2
12/1
2
12/1
sysstat
HHHH
HHHHc
for <q2> = 0.67 GeV2.
c
c
EPS, July 2003 15
ACP in the decay rate of B0 K*(892)+ - (EPS-123)
In SU(3) symmetry limit:
Measuring and
allows the extraction of both and the strong phase, .
CLEO measured (PRL 89, 251801 (2002)):
This study extends the previous analysis and measures:
)(*0 ))892(( ieTPKBA)(*0
))892(( ieTPKBA)(~
22 AAB )(~ 22AAACP
665
* 10)216())892((
KBB
))892(())892((
))892(())892((*0*0
*0*0
KBBKBB
KBBKBBACP
EPS, July 2003 16
Event selection in B0 K*(892)+ -
Standard cut on tracks and showers
0’s: P( 0) > 1.0 GeV
Beam constrained mass:
B candidate energy:
GeVpEMGeV BbeamB 3.52.522
BbeamB
B
EEE
MeVE
,)300(200
Veto some b c background: B D, D K; B J/K0(or J/0), J/ +-
Example:
Suppress background: .
qqee
8.0)cos( sph
K*(892)+ is reconstructed in two submodes: K*(892)+ KS0+ and K*(892)+ K+ 0.
EPS, July 2003 17
UML fit for B0 K*(892)+ - and ACP
The likelihood function is given by
Variables (plot on the right): MB, EB, the Fisher discriminant, cos(B), dE/dx for the faster of the primary tracks (h- = - or K - ) and Dalitz plot variables.
Components: the signal, the continuum, the BBbar bckg, the B0 R*+h–, where h– is - or K-, R*+ can be any of the intermediate state resonances - K*(1430), (770), or f0(980); and non-resonant (phase space) decays.
The fit is made for fj’s and ’s, where
, for B0 K*(892)+ -
PDFs are functions of the event location in the Dalitz plot (plot of the right) and are derived from the off-resonance data, the D0 K-+ data and MC.
candidates
1
components
1
variables
1
)1(i j k
ijkj
j PAfL
j
h
j
h
j
h
j
hj
NN
NNA
jA
K*(892)+(KS0
-) -
)10( 4 OAA
CP
EPS, July 2003 18
Results for ACP in B0 K*(892)+ -
Fit to 30 free parameters (fj’s and ’s) Yield for B0 K*(892)+ -, K*(892)+ KS
0+:
Yield for B0 K*(892)+ -, K*(892)+ K+ 0: Combined significance 4.6.
Major systematic errors
Dalitz PDF shapes Fitting method Interference among intermediate resonances
Final results for ACP (Phys.Rev. D 68, 017101
(2003)):
jA
10.0
08.033.034.0
*0 26.0))892((
KBACP
C.L.%90at 78.0;31.0))892(( *0 KBACP
B0 K*(892)+ -
CPA
6.49.36.12
2.29.11.6
EPS, July 2003 19
SUMMARY
ACP in the Dalitz plot of D0 - + 0 (EPS-208): , No evidence for (500) is found.
Form Factors and Search for CPV in c e+ (EPS-138):
Charge Asymmetry in B K*(892)+ - (EPS-123):
)(09.007.0 09.001.0 sysCPA
GeVM
f
fR
sysstatpole
sysstat
10.007.013.2
,04.005.031.02
1
Asysstat
cc
cc
cA 02.001.003.001.0
10.0
08.033.034.0
*0 26.0))892((
KBACP
C.L.%90at 78.0;31.0))892(( *0 KBACP
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