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Limits on the Lifetime Difference DG of Neutral B Mesons and CP, T, and CPT Violation in B 0 B 0 mixing. Wouter Verkerke (UC Santa Barbara) for the BaBar collaboration. EPS2003 July 17-23 Aachen, Germany. -1 0 1 E (ps -1 ). - PowerPoint PPT Presentation
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Wouter Verkerke, UCSB
Limits on the Lifetime Difference of Neutral B Mesons andCP, T, and CPT Violation in B0B0 mixing
Wouter Verkerke (UC Santa Barbara) for the BaBar collaboration
EPS2003 July 17-23 Aachen, Germany
Wouter Verkerke, UCSB
-1 0 1 E (ps-1)
Introduction: Flavor mixing in the Bd system
• Mass states BL, BH superposition of B0 and B0 flavor states
• Properties of the system:
Oscillation frequency Well measured
Average life time Well measured
Life time difference NOT well measured
IfCPTholds
Wouter Verkerke, UCSB
Introduction: CP,T,CPT violation in B0B0 mixing
• Increasing statistics of B factories precision measurements: look at correction to ‘naïve’ mixing picture: CP/T/CPT violation in B0B0 mixing
SM:small1p
q 41051 p
q
CPT violation
CP/T violation
Life time difference SM: small
Usually assumed to be 0..
Locality CPT invariance (e.g SM: 0)
Violated in mixing if
Effect and magnitude on B decay rate measurement similarNeed combined analysis to disentangle effects
Best limit sofar: / < 18% (90% CL)
CP and T violation
CP and CPT violation
Violated in mixing if 0
1)
2)
3)
Eur. Phys. J. C 28 (2003) 155-173
Wouter Verkerke, UCSB
Coherent Time Evolution at the Y(4S)
B-Flavor Tagging
Exclusive B Meson
Reconstruction
Vertexing &Time DifferenceDetermination
PEP-II (SLAC)
Wouter Verkerke, UCSB
Time dependent B decay rates: naïve mixing picture
Exp. Decay Oscillations with frequency m
Differential event rate, as a function of the difference between the proper decay times of the two B mesons in the final state Assume = 0, no CP/T/CPT violation
)cos(11
))4(( || tmeffBBSYNtd
d trectag
ftag frec (unmixed) ftag = frec (mixed) Mixed – UnmixedMixed + Unmixed
Decay time distributions
Deca
y r
ate
Deca
y r
ate
Asy
mm
etr
y
-15 0 15 t (ps)
-15 0 15 t (ps)
-15 0 15 t (ps)
Wouter Verkerke, UCSB
Time dependent B decay rates allowing 0, CP/T/CPT violation
Full expression much more complicated…
New parameterization allows to test conventional assumptions on CP/T/CPT violation in mixing
=1 if =0
with
and
Allow 0
=1 w/o CP/CPT violation Absent w/o CP/CPT violation
Allow CP/CPT
violation
If z 0 Prob(B0 B0,t) Prob(B0 B0,t)
Wouter Verkerke, UCSB
Variation: B decay into CP eigenstates
Allow 0
complex CP-parameter characterizes interferencebetween mixing & decay
Different expression for coefficients C and S
Wouter Verkerke, UCSB
Effect of 0, CP/T/CPT violation on B decay rate
unmixed mixed
B0 B0
Flavor eigenstate sample
CP eigenstate sample
Sensitive to:|p/q|Im(z)m
(2nd order)
Sensitive to:Re(z)
CP
(1st order)
Naïve model& / = 20%& |q/p| = 0.9& Im(z) = 0.1
Naïve model& Re(z) = 0.2& / = 20%& |q/p| = 0.9
Effect of |q/p| opposite for B0/B0
Clearly a precision measurement, effects of detector performance not even yet included…
t-parityevenoddeven
t-parityevenoddodd
(Untagged eventsalso sensitive to /)
Wouter Verkerke, UCSB
The measurement – Data Samples
before tagging and vertexing cutsSamples of B decays to flavor-specific
final states
Samples of B decays to CP-eigenstates
with charmonium .
charge conjugate
decays are implied, unless specified
Nov 1999- June 2002 data 82 fb-1 on-peak – 88 million BB pairs
CP = +1
CP = -1
(31000 events)
(2600 events)
Wouter Verkerke, UCSB
The measurement – Fit Procedure
• Effects of (0, CPT violation) small be precise– Take %-level physics effects that can fake CP/CPT/ into account
– Accurate detector response modelling
– Simultaneous fit for |q/p|, /, m, Im(z), Re(z) and CP to time-dependence of CP and flavor eigenstates, including tagged and untagged events
Account for
– Possible direct CP violation in the CP eigenstate sample (CP)
– Correlation between reco B and tag B via interference between CKM-allowed and doubly-CKM suppressed decays
Account for
– Incorrect assignments of the flavour tagging algorithm (separate mistag fractions for B0 and B0bar)
– t resolution that is comparable to the B life time and asymmetric for positive and negative dt (triple Gaussian t resolution model)
– Account for possible asymmetries in detector response for positive and negative particles
FitModel Detector response(t, ftag, frec)
Wouter Verkerke, UCSB
Results – Limits on , search for CP,T,CPT violation in mixing
90% CL intervals
Mixing
CP & T violation
CPT & CP violation
Mixing
CP & T violation
S i m
u l t
a n
e o
u s
f
i t
Preliminary result
SM: 0
SM: 0
SM: -0.003
SM: |q/p|-1 510-4
Best limit so far <20%, big improvementEur. Phys. J. C 28 (2003) 155-173
Physics parameter correlations O(5%), largest correlation 17%
(Assuming CPT invariance – Consistent with above results)
Wouter Verkerke, UCSB
Results – Limits on , search for CP,T,CPT violation in mixing
Preliminary result
Also represented: constraint on indirect CPV using dilepton sample
Phys. Rev. Lett. 89 (2002) 201802
(CP/T violation)
(CP/C
PT v
iola
tion)
Wouter Verkerke, UCSB
Summary
• First simultaneous measurement of /, CP, T and CPT violation in the B0 system
– Hadronic data sample Nov 1999 – June 2002 (82 fb-1)
• Much improved limit on /– / < 20 % (90% C.L., PDG 2003 (DELPHI))
/ < 8% (90% C.L. this analysis)
• Measurement of CP and T violation (|q/p|) consistent with Standard Model expectation
– Also consistent with previous BaBar measurement using di-lepton events
• Strongest test of CPT invariance outside K0 system to date – BaBar (2003): Im(z) = 0.038 0.029 0.025
Re(z) = 0.014 0.035 0.034
– Belle di-Lepton (2002) Im(z) = -0.03 0.01 0.03Re(z) = 0.00 0.12 0.02
– OPAL Z bb (1997) Im(z) = 0.040 0.032 0.012
Wouter Verkerke, UCSB
(Backup slides)
Wouter Verkerke, UCSB
Correlations between physics parameters
Wouter Verkerke, UCSB
Summary of systematic uncertainties