matter-antimatter transformations at 3 trillion hertz

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

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

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)

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)

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)

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

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

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

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

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)

Neutral Meson Mixing (Continued)

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

The Weak Interaction: Leptons

Muon decay:

••

Weak Interaction: Quarks & the Cabibbo Angle

Pion Decay:

Kaon Decay:

• •

The Cabibbo Angle: = sinC

texpoint test

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

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

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)

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

Neutral B Meson Flavor Oscillations

Flavor oscillations occur through2nd order weak interactions

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

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

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)

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

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

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

Schematic

Event Display

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

Measurement of Oscillation

What about experimental issues?

“Rig

“Wro

Realistic Effects

flavor tagging power,background

displacementresolution

momentumresolution

mis-tag rate 40% L) ~ 50 m p)/p = 5%

All Effects Together

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

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)

State of the Art Measurement of md

B. Aubert et al.Phys. Rev. Lett.88, 221802 (2002)

Measuring ms at CDF: Signal

Decay sequence

Four charged particles infinal state: K+ K- + -

Complete reconstruction: pB negligable

Lifetime Measurement

production vertex25 m £ 25 m

Decay position

Decay time inB rest frame

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

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

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

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

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

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

Kaons Produced in Vicinity of B’s

Larger fraction of Kaons near B0s compared to B0, B+, as expected

Ph. D. Thesis, Denys Usynin

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

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

Results: Amplitude Scan

A/A = 3.5 Sensitivity25.3 ps-1

Results: Amplitude Scan

A/A = 6.1 Sensitivity31.3 ps-1

Measured Value of ms

- log(Likelihood) Hypothesis of A=1 compared to A=0

Measured Value of ms

- log(Likelihood) Hypothesis of A=1 compared to A=0

Significance: Probability of Fluctuation

Probability ofrandom fluctuationdetermined from data

Probability = 0.5%(2.8)

Below threshold toclaim “observation”Continue improvinganalysis to increasepotential significance

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

Determination of |Vtd/Vts|

Previous best result: D. Mohapatra et al.(Belle Collaboration)PRL 96 221601 (2006)

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)

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

Additional Slides for Reference

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])

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

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)

Some More Detail

Aside:Total D2 ¼ 30%at the B factories

Amplitude Scan

The Unitarity Triangles

V is unitarity

geometric representation: triangle in complex plane

ReVi1V*

Vi2V*k2Vi3V*

There are 6 triangles

Kaon UT

Beauty UT

n.b. these triangles arerescaled by one of the sides

i = 1 is previous page

The Beauty Unitary Triangle

of Chau & Keungparametrization is

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

matter-antimatter transformations at 3 trillion hertz

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