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Matter-Antimatter Transformations at 3 Trillion Hertz. Prof. Joseph Kroll University of Pennsylvania Fall 2006. Executive Summary (1). At the beginning of ‘06 this is what was known. at least 3.5 cycles per lifetime. Executive Summary (2). - PowerPoint PPT Presentation
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Matter-Antimatter Transformations at3 Trillion Hertz
Prof. Joseph Kroll
University of Pennsylvania
Fall 2006
Fall 2006 Colloquium
Joseph Kroll - University of Pennsylvania 2
Executive Summary (1)
At the beginning of ‘06 this is what was known
at least 3.5 cycles per lifetime
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Executive Summary (2)
Measure asymmetry A as a function of proper decay time t
“unmixed”: particle decays as particle
For a fixed value of ms, data should yieldAmplitude “A” is 1, at the true value of ms
Amplitude “A” is 0, otherwise
“mixed”: particle decays as antiparticle
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Start 2006: Published Results on ms
Results from LEP, SLD, CDF I ms > 14.5 ps-1 95% CL
see http://www.slac.stanford.edu/xorg/hfag/osc/winter_2004/index.html
Amplitude method:H-G. Moser, A. Roussarie,NIM A384 p. 491 (1997)
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March 2006: Result DØ Collaboration
17 < ms < 21 ps-1 @ 90% CL
1st reported direct experimental upper bound
Probability“Signal” israndom fluctuationis 5%
V. M. Abazov et al., Phys. Rev. Lett.Vol. 97, 021802 (2006)
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April 2006: Result from the CDF Collaboration
Probability“Signal” israndom fluctuationis 0.2%
Under signalhypothesis:measure ms
V. M. Abulencia et al., Phys. Rev. Lett.Vol. 97, 062003 (2006)
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Outline
• Neutral Weakly Decaying Mesons
• Neutral Meson Matter-Antimatter Transformations
• The Weak Interaction
• History of Flavor Oscillations (Mixing)
• B Physics at Hadron Colliders
• Outline of the Measurement Strategy
• Measuring B0s Oscillations at CDF
• Results & Outlook
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Quarks and Hadrons
Quarks: 3 Families
Hadrons: colorless combinations of quarks
Three colorsq q q
Mesons:
Baryons:
Aside: other exotic combinations predicted: e.g., Pentaquarks
Electric charge
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Weakly Decaying Neutral Mesons
Mass units: melectron = 0.511 MeV/c2, mproton = 0.938 GeV/c2
0.511 MeV/c2 = 9.11 £ 10-31 kg
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Neutral Meson Flavor Oscillations (Mixing)
Due to phase space suppression:K0
L very long-lived: 5.2£ 10-8 s(K0
S: 0.0090£ 10-8 s)
1954: over 50 years ago
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Long-Lived Neutral Kaon
Discovered by Ken Lande et al., (now at Penn) in 1956
Led to discovery of CP Violation in 1964 (Nobel Prize in 1980)BF(K0
L ! +-) = 0.2%Christenson, Cronin, Fitch, Turlay, Phys. Rev. Lett. 13, 138 (1964)
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Neutral Meson Mixing (Continued)
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Neutral B Meson Flavor Oscillations
= 1/ = 1.6 psec
Units: [m] = ~ ps-1. We use ~=1 and quote m in ps-1
To convert to eV multiply by 6.582£ 10-4
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The Weak Interaction: Leptons
Muon decay:
••
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Weak Interaction: Quarks & the Cabibbo Angle
Pion Decay:
Kaon Decay:
• •
• •
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The Cabibbo Angle: = sinC
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texpoint test
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The Flavor Parameters (CKM Matrix)
mass eigenstates ≠ weak eigen.
weak mass
related by Cabibbo-Kobayashi-Maskawa Matrix
V is unitary: VyV = 1 Measurements + Unitarity assuming 3 generations
PDG: S. Eidelman et al. Phys. Lett. B 592, 1 (2004) Ranges are 90% CL
These fundamental parameters must be measured
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Wolfenstein Parametrization Illustrates Hierarchy
Original reference: L. Wolfenstein, PRL, 51, p. 1945 (1983)Reference for this slide: A. Höcker et al., Eur. Phys. J. C21, p. 225 (2001); ibid, hep-ph/0406184
from hep-ph/0406184
Expand matrix in small parameter: = Vus = sinCabibbo» 0.2
3 £ 3 complex unitary matrix: 3 real & 1 imag. parameters ≡ 3 angles, 1 phase
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B Meson Decay – Predominantly to Charm
• }{
• }{
}
Semileptonic (not completely reconstructed – missing p)
Hadronic
phase space factor
Vcb = (41.3 § 1.5) £ 10-3
Small Vcb meansSmall Long (lifetime)
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Small Vcb Means Long B Lifetime
Nigel Lockyer (Penn), Bill Ford, Jim Jaros2006 APS Panofsky Prizesee also E. Fernandez et al. Phys. Rev. Lett. 51 1022 (1983)
Long B lifetime possible to see B0s particle-antiparticle transitions
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Neutral B Meson Flavor Oscillations
Flavor oscillations occur through2nd order weak interactions
e.g.
Same diagrams and formula for ms for Bs except replace “d” with “s”
All factors known well except “bag factor” £ “decay constant”
md = 0.507 § 0.005 ps-1 (1%) (PDG 2006) from Lattice QCD calculations – see Okamoto, hep-lat/0510113
From measurement of md derive |V*tbVtd|2
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B Meson Flavor Oscillations (cont)
If we measure ms then we would know the ratio ms/md
Many theoretical quantities cancel in this ratio, we are left with
Ratio measures |Vtd/Vts|This is why ms ishigh priority in Run II
Using measured md & B masses, expected |Vts/Vtd|
Predict ms » 18 ps-1
We know what to expect
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Why is this Interesting? Probe of New Physics
Supersymmetric particles 4th Generation
Additional virtual particlesincrease ms
Measured value can be usedto restrict parameters in models
e.g., Harnik et al. Phys. Rev. D 69 094024 (2004) e.g., W. Huo Eur. Phys. J. C 24 275 (2002)
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Tevatron Performance Key performance number isIntegrated Luminosity
Cross-section: [] = Area
Luminosity: [L] = 1/Area 1/time
Rate: [ L] = 1/time
Integrated Lum. [∫Ldt] = 1/Area
Number: ∫Ldt
Collison rate: 2.5 MHz
t quark production = 6pb
t quark rate @ 1032 cm-2s-1 = 0.6 mHz
Typical L = 1032 cm-2 s-1
Projected ∫Ldt = 4-8 fb-1
Barn: b = 10-24 cm2
pb = 10-36 cm2, pb-1 = 1036 cm-2
∫Ldt = 2 fb-1
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CDF II
Installation of Silicon Tracking Device Fall 2000
CDF rolls in to collision hall – Winter 2001
At the energy frontier at the Fermilab Tevatron (p-antip)
TOF Detector (Penn Electronics)
Penn COT Electronics
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Experimental Steps for Measuring Bs Mixing
1. Extract B0s signal – decay mode must identify b-flavor at decay (TTT)
Examples:
2. Measure decay time (t) in B rest frame (L = distance travelled) (L00)
3. Determine b-flavor at production “flavor tagging” (TOF)
“unmixed” means production and decay flavor are the same
“mixed” means flavor at production opposite flavor at decay
Flavor tag quantified by dilution D = 1 – 2w, w = mistag probability
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Schematic
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Event Display
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Measuring Bs Mixing (cont.)
4. Measure asymmetry
these formulas assume perfect resolution for t
Asymmetry is conceptual: actually perform likelihood fit to expected“unmixed” and “mixed” distributions
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Measurement of Oscillation
What about experimental issues?
“Rig
ht
Sig
n”
“Wro
ng
Sig
n”
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Realistic Effects
flavor tagging power,background
displacementresolution
momentumresolution
mis-tag rate 40% L) ~ 50 m p)/p = 5%
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All Effects Together
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1st Evidence: Time Integrated Mixing:
is the time integrated mixing probability
In principle, a measurement of determines m - 1st Bd mixing measurements were measurements - d = 0.187 § 0.003 (PDG 2004) - this does not work for Bs: s = 0.5 (the limit as x!1)
Inclusive measurements at hadron colliders yield
1987
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Discovery of Neutral B Flavor Oscillations
Implications: mtop>50 GeV/c2
Top quark is heavier than expectedEllis, Hagelin, Rudaz, Phys. Lett. B 192, 201 (1987)
UA1 1987: Evidence for B0 & B0s mixing
Followed up by observationof B0 mixing by ARGUS:H. Albrecht et al., (25 June 87) Phys. Lett. B 192, 245 (1987)
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State of the Art Measurement of md
B. Aubert et al.Phys. Rev. Lett.88, 221802 (2002)
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Measuring ms at CDF: Signal
Decay sequence
Four charged particles infinal state: K+ K- + -
Complete reconstruction: pB negligable
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Lifetime Measurement
production vertex25 m £ 25 m
Decay position
Decay time inB rest frame
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Decay Time Resolution
<t> = 86 £ 10-15 s¼ period for ms = 18 ps-1
Oscillation period for ms = 18 ps-1
Maximize sensitivity:use candidate specificdecay time resolution
Superior decay timeresolution gives CDFsensitivity at muchlarger values of ms
than previous experiments
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B Flavor Tagging
We quantify performance with efficiency and dilution D
= fraction of signal with flavor tag
D = 1-2w, w = probability that tag is incorrect (mistag)
Statistical error A on asymmetry A (N is number of signal)
statistical error scales with D2
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Same Side Flavor Tags
Based on correlation betweencharge of fragmentation particleand flavor of b in B meson
TOF Critical(dE/dx too)Both due to PENN
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Time of Flight Detector (TOF)
• 216 Scintillator bars, 2.8 m long, 4 £ 4 cm2
• located @ R=140 cm• read out both ends with fine mesh PMT (operates in 1.4 T B field – gain down ~ 400)• anticipated resolution TOF=100 ps• (limited by photostatistics)
Kaon ID for B physics
Measured quantities:s = distance travelledt = time of flightp = momentum
Derived quantities:v = s/tm = p/v
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Recent Penn CDF group Ph. D.s
Designed & built electronicsfor CDF TOF
Successfully defendsthesis on Charm mesonproduction cross-sections:First PRL from TevatronRun II
Chunhui Chennow PD at Maryland
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Recent Penn CDF Group Ph. D.s
Used TOF to measure types of particlesproduced in association with B mesons.
First such results from hadron collider
Crucial for B0s oscillations
Denys Usynin: Now at JP Morgan
Contributions to several TOFelectronic components & PMT assembly
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Kaons Produced in Vicinity of B’s
Larger fraction of Kaons near B0s compared to B0, B+, as expected
Ph. D. Thesis, Denys Usynin
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Contributions to CDF Trigger
Trigger selects in real time interesting collisionsCrucial for successful physics program
Kristian Hahn made major contributions to 2nd Level upgrade
Fritz Stabenau spentone year with us workingon 2nd Level upgrade
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Flavor Tagging Summary
Opposite-side tags: D2 = 1.5%
Same-side kaon tag: D2 = 4.0%
Same-side kaon tag increases effective statistics £ 4
Penn played the lead role in Run I CDF analysisto develop these tags: Ph. D. Thesis, Owen Long
Penn played the lead role in proposing and building TOFMeasured kaons near B’s: Ph. D. Thesis, Denys Usynin
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Results: Amplitude Scan
A/A = 3.5 Sensitivity25.3 ps-1
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Results: Amplitude Scan
A/A = 6.1 Sensitivity31.3 ps-1
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Measured Value of ms
- log(Likelihood) Hypothesis of A=1 compared to A=0
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Measured Value of ms
- log(Likelihood) Hypothesis of A=1 compared to A=0
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Significance: Probability of Fluctuation
Probability ofrandom fluctuationdetermined from data
Probability = 0.5%(2.8)
Below threshold toclaim “observation”Continue improvinganalysis to increasepotential significance
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Significance: Probability of Fluctuation
Probability ofrandom fluctuationdetermined from data
Probability = 8 £ 108(5.4)
Have exceededstandard thresholdto claim observation
28 of 350 millionrandom trialshave L < -17.26
-17.26
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Determination of |Vtd/Vts|
Previous best result: D. Mohapatra et al.(Belle Collaboration)PRL 96 221601 (2006)
CDF
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Summary of CDF Results on B0s Mixing
First direct measurement of ms
Precision: 2.4% Probability of random fluctuation: 0.5%
Most precise measurement of |Vtd/Vts|
All results are preliminary
( 2.76 THz, 0.011 eV)
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Some Final Words• Mixing in Neutral Kaons
– led to discovery of violation of combination of fundamental symmetry operations: C & P – CP Violation:necessary condition for matter antimatter asymmetry in Universe.
• Mixing in B0 mesons led to possibility of observing CP Violation in another system – validated that SM mechanism for CP Violation is dominant mechanism.
• The discovery of B0 mixing pointed to a much heavier top quark: – Results on B0
s mixing could point to heavier new particles.• Establishing B0
s mixing sets the stage for the next step: – measuring CP asymmetries in B0
s decays– could produce unambiguous signals of new physics.
• We are coming to the end of a long story: – a 20 year quest to measure ms
– a tremendous technical achievement– allows precise measurement of fundamental parameters
• Penn Physicists played a leadership role– in pioneering techniques in Run I– in establishing the measurement as a key goal for the Tevatron in Run II– in contributing to the critical detector elements– in playing a leading role in the data analysis
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Additional Slides for Reference
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Different Parameterizations of CKM Matrix
L. L. Chau, W. Y. Keung Phys. Rev. Lett. 53, p. 1802 (1984) - used by PDG
3 £ 3 complex unitary matrix: 3 real & 1 imag. parameters ≡ 3 angles, 1 phase
notation: cij´ cosij & sij´ sinij, i, j = 1st, 2nd, 3rd generation
Advantages of this parameterization:1. Satisfies unitarity exactly2. If ij= 0, generations i & j decouple3. If 13= 23= 0, 3rd generation decouples, 12 is Cabibbo angle4. Same formulation used for lepton mixing matrix U with (£ diag[ei1/2,ei2/2, 1])
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Wolfenstein Parametrization Illustrates Hierarchy
Original reference: L. Wolfenstein, PRL, 51, p. 1945 (1983)Reference for this slide: A. Höcker et al., Eur. Phys. J. C21, p. 225 (2001); ibid, hep-ph/0406184
valid to O(6) ¼ 0.01%, = Vus = sinCabibbo» 0.2
Define:
from hep-ph/0406184
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Example of Bs Oscillations
Example of Asymmetrywith lots of statisticsms = 20 ps-1
Illustrated are - tagging reduces statistics dilution reduces amplitude - decay length resolution damps amplitude further - momentum uncertainty damps amplitude more as decay time t increases
Large ms: Bs! Ds l no goodneed fully reconstructed decayse.g., Bs! Ds
Figures courtesy M. Jones (Penn/Purdue)
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Some More Detail
Aside:Total D2 ¼ 30%at the B factories
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Amplitude Scan
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The Unitarity Triangles
V is unitarity
geometric representation: triangle in complex plane
Im
ReVi1V*
k1
Vi2V*k2Vi3V*
k3
There are 6 triangles
Kaon UT
Beauty UT
flat
n.b. these triangles arerescaled by one of the sides
i = 1 is previous page
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The Beauty Unitary Triangle
of Chau & Keungparametrization is
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How Do Measurements Constrain Triangle?Figure courtesy of CKM Fitter group: ckmfitter.in2p3.fr – as were all of the formulas on previous slides
B0 flavor oscillations (md)constrains one side
How do B0s oscillations (ms)
fit in this picture?
Why is ms consideredone of the most important Run II measurements?
Aside: a key issue is to pickexperimental quantities thatcan be related to CKM para.without large theory errors
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