BS Physics and mS

1
BS Physics?? and ?mS

• Iain Bertram
• Department of Physics
• Lancaster University
• PIC 06 July 7 2006

2
B0S Decays

• Have two eigenstates (H)eavy and (L)ight and
  assuming CP conservation

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Width Difference ??S

• ?12 is dominated by the decay b ?ccs
• in particular decays common to BS and anti-BS
• ??S
• CP-even final state ??S ?
• CP-odd final state ??S ?
• Latest results from Belle, CDF, DØ

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Bs ? J/? ? Decay

• Pseudoscalar ? Vector-Vector decay
• Three waves S, P, D,
• or A0, A, A-
• CP-even and CP-odd separated in angular
  distributions
• measure two lifetimes
• S, D (Parity, CP even)
• linear combination of A0, A
• P (Parity, CP odd)
• A-
• R- ? A-(t0) 2

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Bs ? J/? ? Decay

• Update to published result
• DØ (PRL 2005) used 1 angle, ?, 513 events
• This analysis 0.8 fb-1 3 angle ???????? analysis
  Nsignals 978 ? 45

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Angular Distributoin

• ?1?ArgA(0)A-(0) and ?2?ArgA0(0)A-(0) are
  CP-conserving strong phases
• No dependence on ?mt
• Correct for acceptances and kinematic cuts as
  well

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Fitting
Simultaneous fit to mass, proper decay length and
3 angles using an unbinned maximum
log-likelihood method

• 30 parameters 1 fsig signal
  fraction
• 2 signal mass,
  width
• 3 A? , A02-A2, 1 strong phase
• 1 c? c /?? , ?? (?L ?H) /2
• 1 ?? ? L - ?H
• 3 bkg mass (1 prompt, 2 long-lived)
• 1 ?(ct ) scale
• 6 bkg ct shape
• 4 bkg transversity (2 prmpt 2
  long-lived)
• 4 bkg angle f (2 prompt 2 long-lived)
• 2 bkg angle ? (1 prompt 1 long-lived)
• 2 bkg interference (1 prompt 1 bkg)

set df 0
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Fits
?
q
?
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Results

• With ?1 free and ?2 0, obtain ?? -0.9 0.7
• CP-violating angle ?? consistent within
  statistical uncertainty of 0.7.

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B0S ? KK- lifetime analysis
trigger bias

• Trigger bias for signal is extracted from
  detailed simulation.
• Procedure validated in unbiased B ? J/?X decays
  from di-muon trigger.
• Check that lifetime fits of samples with/without
  applying track-trigger cuts yield consistent
  results.
• Lifetime p.d.f for background is extracted from
  higher mass data sideband.

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B0S ? KK- Results 360 pb-1

• Fit to B0S ? KK-, B0d ? K?, ??
• B0S ? KK- predicted to by 95 CP-even

• Results in ?L 1.53 ?0.18(stat) ?0.02(syst) ps
• Combine with HFAG average of (?L2 ?H2)/ (?L
  ?H)

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B0S ? D()SD ()S?

• B0S ? DSDS??is pure CP-even (theory
  assumptions) Phys. Lett. B316 (1993) 567
• B0S ? DS()DS () ??inclusive, also CP-even at
  5 level

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B0S ? D()SD ()S?

• Branching Ratio measured in the decay mode

D?
DS? 15.2k

• Normalise to

With associated muon Look for additional ?

• Measure Ratio

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B0S ? D ()SD ()S?

• Use Br(DS???) from BaBar,
• combined with PDG Br(B0S ? ??DS()), Br(DS????)

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Bs? DS DS- (exclusive hadronic mode)

• 1st observation of fully reconstructed decay
• Next Extract ??S

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Belle Y(5S) Data - 1.86 fb-1 Jun 2005
Bs ? DS() DS()-
Bs ? DS??-
with 50 fb-1, expect B0S ? DS()DS () ??
(12?3). Just taken 20 fb-1 reconstruct in fall
9 events in BB
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Summary of ?S ??S

• Bs ? J/? ?DG 0.18 ? 0.09 ps?1?? 1/G
  1.520 ? 0.068 ps
• B0S ? KK-
• B0S ? DSDS?
• Theory ??S 0.097 ?0.03 ps-1(fBs/260 MeV)2
• Unofficial WA

R. Van Kooten hep-ex/0606005
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Oscillations - ?mS

• Combine with ?md
• ?md (QCD)Vtd
• ?ms (QCD)Vts
• QCD cancels in ratio

• Constrain Unitarity Triangle
• Look for inconsistancy

Vtd
Vub
?
?
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Measurement - ?mS

• Very fast oscillations
• 40 times faster than Bd oscillations
• Period 100 µm
• Resolution should be 25µm

• DØ Accepted for Publication in PRL
• hep-ex/0603029
• CDF Submitted to PRL
• hep-ex/0606027

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Proper Decay Length Resolution

• CDF
• the resolution does not degrade
  with PDL for
  hadronic modes
• sp/p 3-20 for semileptonic modes
• 10-20 improvement from L00
• DØ
• work on hadronic modes in progress
  
• L0 has been installed

First cosmic tracks with L0
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Calibrating the Proper Time Resolution _at_ CDF
trigger tracks

• utilize large prompt charm cross section
• construct B0-like topologies of prompt D-
  prompt track
• calibrate ct resolution by fitting for lifetime
  of B0-like objects

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Bs Proper Time Resolution _at_ CDF

• average uncertainty
• 26 ?m
• this information is used per candidate in the
  likelihood fit

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Vertex Resolution _at_ DØ

• Tune resolution using data
• Use J/??µµ events
• Clean sample ? can study tails
• Fit pull distribution for J/? Proper Decay
  Length with 2 Gaussians
• Resolution Scale Factor is 1.0 for 72 of the
  events and 1.8 for the rest
• Confirmed by Impact Parameter tuning procedure
  in MC

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Tagging the B Production Flavor
Reconstructed side
e,?
opposite side

• use muon, electron tagging, jet charge on
  opposite side
• use a combined same side and opposite side tag
  (CDF)
• particle ID based kaon tag on same side (CDF)

• Significance of the measurement
• e?efficiency of tagging
• D12w ? tagging dilution
  (w ? mistag rate)

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Tagging the B Production Flavor
Reconstructed side
e,?
opposite side

• use muon, electron tagging, jet charge on
  opposite side
• use a combined same side and opposite side tag
  (CDF)
• particle ID based kaon tag on same side (CDF)

• Significance of the measurement
• e?efficiency of tagging
• D12w ? tagging dilution (w
  ? mistag rate)

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Tagger Performance

• Calibrate OST using Bd sample Calibrate SST
  using tuned MC

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CDF Signal Sample for ?ms
Hadronic Modes 3600 events
Semileptonic Modes 37k events
D Mass
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µ?? sample _at_ DØ (1 fb-1)
Opposite-side flavor tagging
µD 7,422281
µD 1,51996
µDs 26,710560
µDs 5,601102
Tagging efficiency 20
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DØ Amplitude Scan

• Deviation of the amplitude at 19 ps-1
• 2.5s from 0
• 1.6s from 1

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DØ Log Likelihood Scan

• Resolution
• K-factor variation
• BR (Bs??DsX)
• VPDL model
• BR (Bs?DsDs)

Systematic
Have no sensitivity above 22 ps-1 Probability of
background fluctuation 3.8 (5 with syst.
uncertainties)
17 lt Dms lt 21 ps-1 _at_ 90 CL assuming Gaussian
errors Most probable value of Dms 19 ps-1
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CDF Combined Amplitude Scan
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Measurement of ?ms from CDF
-0.21
-0.21
?ms in 17.01, 17.84 ps-1 at 90 CL ?ms in
16.96, 17.91 ps-1 at 95 CL
Probability of background fluctuation 0.2
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Preliminary World Average
Tevatron Average significance of 3.3 sigma at
17.75 ps-1
World Average significance of 3.8 sigma at 17.5
ps-1
Preliminary CDF Result
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Results on ?ms - CKM Fitter

• DØ
• 17?21 ps-1 _at_ 90C.L.
• CDF
• 17 ps-1
• UT Fit
• 21.5 2.6 ps-1
• CKM Fit
• ps-1

New CKM Fit Preliminary CDF numbers
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CKM Fitter Comparisons
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??S and ?mS

• Updating from Phys. Lett. B 459, 631 (1999) by
  Nierste
• SM prediction

• Combination of Averages

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Conclusions

• First Measurement of ?ms
• expect significant improvement over next year
• Layer-0 at DØ - hadronic channels
• ??S well constrained by several measurements
• statistics will improve
• Significant Belle results
• LHC physics 2008
• Tevatron and Belle the leaders until 2009