the observation of b 0 s oscillations at the tevatron
DESCRIPTION
The Observation of B 0 s Oscillations at the Tevatron. Matthew Jones Purdue University / CDF. Fermion Masses. Gauge sector with massless fermions: Higgs sector: General Higgs-quark couplings: Spontaneous symmetry breaking:. diagonalize. CKM Sector of the Standard Model. - PowerPoint PPT PresentationTRANSCRIPT
June 2, 2006 CIPANP06 1
The Observation of B0s
Oscillations at the Tevatron
Matthew Jones
Purdue University/CDF
2
Fermion Masses• Gauge sector with massless fermions:
• Higgs sector:
• General Higgs-quark couplings:
• Spontaneous symmetry breaking:
diagonalize
3
• One of several explanations for CP violation observed in
• If this was the source of CP violation in the kaon system, then large effects should be observed in B decays.
CKM Sector of the Standard Model
4
The CKM Matrix
• Unitary 3x3 matrix 4 parameters:
• λ = 0.2272±0.0010 A = 0.809±0.014
• CP violation η≠0
• Need a precise determination of Vtd
Magnitude proportional to the area of this little square...
Already well measured
(most recent results from CKMFitter)
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(0,0)
The Unitary Triangle
• Try to over-constrain its shape:– ACP in B0J/ψK0
S: sin 2β=0.72±0.02
– Length of one side from
– Length of other side from Δmd/Δms...
(1,0)
(ρ,η)
6
Last Year’s Unitary Triangle
• Next strong constraint will come from Δms.
(0,0)
(1,0)
7
• Quark flavor eigenstates:
• Time dependence:
• CP eigenstates:
• Mass difference: Δm = MH – M L
Mixing
8
Time Evolution • QCD produces flavor eigenstates:
• Interference between CP eigenstates
• Decay identifies final quark flavor:
• Fit for Δms using this model, taking into account several experimental limitations.
9
Mixing
From lattice QCD
(hep-lat/0510113)
Δmd and masses are well measured
10
Contributions from New Physics?
• FCNC suppressed in Standard Model
• Contribution from new physics scenarios:
• Also affects
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Search for Bs Oscillations
• Four steps:– Reconstruct decays– Measure proper decay time precisely– Identify initial flavor state
– Is the data consistent with oscillations at a
given mixing frequency?
• Significance of an observation:
Statistical power reduced by efficiency and mistag fraction (εD2)
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(2003)
Amplitude Scans and Likelihood
Expect A=1 at true Δms
Significance from depth of log-likelihood ratio
13
Result from the DØ Experiment
• March 12, Moriond EW 2006
• Result from DØ: 17<Δms<21 ps-1 (90% CL)
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Result from the DØ Experiment
• March 12, Moriond EW 2006
• Result from DØ: 17<Δms<21 ps-1 (90% CL)
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The CDF Detector
Muon systems:CMP CMX CMU
SVX-IICOTTOF
Hadronic EM
Calorimeter
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Signal Reconstruction• Trigger on displaced tracks and look for:
3,700 fully reconstructed
53,000 partially reconstructed
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Limited number of patterns
Cut at |d0|>120 μm
Proper Decay Time• Proper decay time: ct = Lxy M/pT
• Impact parameter trigger lifetime bias
• Efficiency calculated using B Monte Carlo and an emulation of the trigger
• Checked using B+J/ψK+
lifetime resolution
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Lifetime Measurements
Still dominated by statistical uncertainty
World Averages: hep-ex/0603003
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Initial State Flavor Tagging
Two techniques used:• Opposite Side Tag
– QCD produces pairs – Look for decay products of
the other B hadron (eg, leptons)
– Combined effectiveness:
εD2 = 1.5%• Same Side Tag
Dsπ
B decay
primary vertex
D decaySa
me
Sid
eO
pp
osite
Sid
e
Other B decay
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Δmd=0.503±0.065 ps-1 (hadronic)
Δmd=0.497±0.032 ps-1 (semi-leptonic)
Δmd=0.507±0.004 ps-1 (World average)
Cross Checks with B0/B±
• Account for any difference between signal and calibration samples.
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Initial State Flavor Tagging
Two techniques used:• Opposite Side Tag
– QCD produces pairs – Look for decay products of
the other B hadron (eg, leptons)
– Combined effectiveness:
εD2 = 1.5%• Same Side Tag
– Look for particles produced in association with the Bs
Dsπ
B decay
primary vertex
D decaySa
me
Sid
eO
pp
osite
Sid
e
Other B decay
22
Same Side Kaon Tag• Local quark flavor
conservation in QCD
• Expect more kaons with Bs mesons
• Kaon charge identifies the initial Bs flavor
• A primary motivation for building TOF detector.
Original estimates based on Pythia (Lund string model):
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• Count charged kaons around B0, B+, Bs:
• Find more kaons produced in association with Bs
• Qualitative agreement with Monte Carlo
Same Side Kaon Tag
CDF Run II Preliminary
CDF Data
Pythia Monte Carlo
K± around B0/B± K± around Bs
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An Exciting Spring:
• March 12: DØ result released at Moriond• March 14: CDF unblinded an analysis
of about 1/3 of the hadronic decay data– Observed evidence for oscillations
• Next few weeks:– Validation of remaining data– Inclusion of semi-leptonic analysis– Establish criteria for quoting a limit or a
measurement
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Unblinded CDF Analysis
Released April 11, presented at FPCP 2006 on April 12.
evidence of oscillations
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Limit or Measurement?
• Probability of statistical fluctuation: 0.5%
• Measure
-6.06
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Constraints on CKM matrix
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• Already limited by input from Lattice QCD
• Contributes 2.9% to ξ
Future Prospects
(3.8%)
From JLQCD Collab. (hep-ph/0307039)
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Statistical uncertainty and extrapolation to small mq/ms
All other uncertainties
mq/ms=0.036
Lattice Input from HPQCD+MILChep-lat/0507015
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Constraints on New Physics
• Several different assumptions about flavor structure of SUSY models– Parameters in some models are constrained– Others are not...
• Correlated with other experimental results on FCNC
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Example: Impact on MFV Scenarios
(2006 CDF result)
(destructive ±/W± interference)
Theory error on
Lunghi, Porod, Vives: hep-ph/0605177
10
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Summary
• Unlikely to be a statistical fluctuation• Next improvements from lattice results...
• Long term future uncertainty: ~1%?• A milestone has been reached in the world-wide
heavy flavor physics program!– But there are still many more
measured to few % at CLEO-c and BES-III
33
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Fully Reconstructed Bs Yields in 1 fb-1
• All decays contribute but ones with larger S/B contribute more
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Semi-leptonic Lifetimes
• Correct for unreconstructed momentum
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Lepton-Ds Mass Distribution
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Lifetime Resolution
• Measure σct using “prompt B0s” decays:
φK+K-π+
prompt track
prompt Ds
error propagation scale factor
38
Lifetime Resolution
• Estimate σ*ct using
event-by-event error propagation
• Apply scale factor• Resolution is still
small compared with expected period of oscillations (100 μm)
(for Δms = 18 ps-
1)
39
Systematic Uncertainties on the Amplitude
• Small compared with statistical uncertainty
Hadronic Semi-leptonic
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Systematic Uncertainty on Δms
• Many ways to bias amplitude
• Much harder to bias Δms
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|Vtd| / |Vts| via Penguin Decays
• Compare Br(Bρ) with Br(BK*)• Small branching fractions• Recent result from Belle (hep-ex/0506079):
,s
,Vts*
42
Kaons affect SST on B0/B+
• B+ produced in association with π- or K-
• B0 produced in association with π- or K+
• Particle identification improves same side tag for B0 sample
• Agrees with Monte Carlo
43
Flavor Tagging Performance
• Rank opposite side tags (no correlations)• Assume same-side and opposite-side are
uncorrelated compute combined
Opposite side tags
(stat. error)
Same side (syst. error)
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Dilution Scale Factor Analysis
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Same Side Kaon Tag• Count K±, π±, p/p around B0, B+, Bs:
• Find more kaons produced in association with Bs
• Qualitative agreement with Monte Carlo
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Same Side Kaon Tag
• Compare predicted dilution on B+ and B0 samples
• Combine TOF+dE/dx• Re-weight Monte Carlo
to assess impact of:– production mechanisms– fragmentation functions– observed K/π around B– P-wave B mesons– TOF + dE/dx modeling– Luminosity
dependence
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• In context of Minimal Flavor Violation scenarios, limited by theory uncertainty
• Some constraints when considering single mass insertion parameters
• Weaker constraints with multiple mass insertions• These are only a few examples... see also
– Carena, et al.: hep-ph/0603106– Ball & Fleischer: hep-ph/0604249– But there are many others
Constraints on New Physics
Lunghi, Porod, Vives: hep-ph/0605177
Foster, Okumura, Roszkowski: hep-ph/0604121
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GFM Single Mass Insertion ParametersF
oste
r, O
kum
ura,
Ros
zkow
ski:
hep-
ph/0
6041
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