Matter-Antimatter%20Oscillations

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Matter-Antimatter Oscillations

• Introduction to flavor physics
• Tevatron and CDF
• Bs Oscillations
• Conclusion

BEACH 04
J. Piedra
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The Standard Model

• What is the Standard Model?
• Comprehensive theory
• Explains the hundreds of common particles atoms
  - protons, neutrons and electrons
• Explains the interactions between them
• Basic building blocks
• 6 quarks up, down
• 6 leptons electrons
• Bosons force carrier particles
• All common matter particles are composites of the
  quarks and leptons and interact by exchange of
  the bosons

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If not the Standard Model, What?

• Standard Model predictions validated to high
  precision, however

• Gravity not a part of the SM
• What is the very high energy behaviour?
• At the beginning of the universe?
• Grand unification of forces?
• Dark Matter?
• Astronomical observations of indicate that there
  is more matter than we see
• Where is the Antimatter?
• Why is the observed universe mostly matter?

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Searches For New Physics

• How do you search for new physics at a collider?
• Direct searches for production of new particles
• Particle-antiparticle annihilation
• Example the top quark
• Indirect searches for evidence of new particles
• Within a complex process new particles can occur
  virtually

• Tevatron is at the energy frontier and
• a data volume frontier 2 billion events on
  tape
• So much data that we can look for some very
  unusual processes
• Where to look
• Many weak flavor physics processes are very low
  probability
• Look for enhancements from other low probability
  processes Non Standard Model

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A Little History

• Everything started with kaons
• Flavor physics is the study of quarks
• Our tool is the bound states of quarks
• Kaon Discovered using a cloud chamber in 1947 by
  Rochester and Butler
• Could decay to pions and had a very long
  lifetime 10-10 sec

• Bound state of up or down quarks with with a new
  particle the strange quark!
• Needed the weak force to understand its
  interactions
• Neutral kaons were some of the most interesting
  kaons

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Physics of Neutral Mesons

• New physics(at the time) of neutral particles and
  antiparticles
• K0 and K0
• Interacted differently with weak and strong
  force. Different eigenstates
• Strong force quark eigenstates K0 and K0
• Weak force mass and CP eigenstates K0S and K0L
• The Schrödinger equation
• H not diagonal
• K0 and K0 not mass eigenstates

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Physics of Neutral Mesons

• Treat the particle and anti-particle as one two
  state system (Gell-Mann, Pais)

• New states mass eigenstates
• Weak force mass and CP eigenstates K0S and K0L
• ?m 2M12 mass difference
• But weve seen this type of system before

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Classical Analogue

• Coupled spring system
• Start the system with one spring moving and over
  time it will evolve to a state where the other
  spring is moving.

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Oscillations

• Time dependence

• Given a pure K0 state at t 0

• Then at time t

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Why?

• The flavor changing weak interaction is necessary
  to get from K0
  to K0
• The weak force provides the coupling between the
  states that leads to the oscillations
• Also the CP eigenstates KS and KL are not changed
  by the weak force making them the weak force
  eigenstates

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Neutral Kaons
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CKM Physics

• Our knowledge of the flavor physics can be
  expressed in the CKM matrix
• Translation between strong and weak eigenstantes
• Sets magnitude of flavor changing decays Strange
  type kaons type type pions

• Several unitarity relationships to preserve
  probability
• b quark relationship the most interesting
• Largest CP violating parameter
• Best place to look for explanations for
  mater-antimatter asymmetry

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Bs and CKM Physics

• B quark unitarity relationship
• Can be expressed as triangle in the complex plane

• Mixing strength set by Vts parameter

Pierini, et al.,
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New Physics and the Bs Meson

• Look at processes that are suppressed in the SM
• Bs Oscillations a.k.a Mixing
• SM Loop level box diagram Extra weak vertices
  lead to a suppression
• Oscillation frequency can be calculated using
  electroweak SM physics and lattice QCD
• NP can enhance the oscillation process, higher
  frequencies
• Harnik et al., Phys. Rev. D 69 094024, 2004 -
  Barger et al., PL B596 229, 2004

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Neutral B Mesons

• The B0 and Bs meson
• Very interesting place to look for new physics(in
  our time) Higgs physics couples to mass so B
  mesons are interesting
• Same program Oscillations , CP violation

• First evidence for B meson oscillations How the
  Bs meson was found
• 1987 UA1 Integrated mixing measurement
• ? Compare charges of leptons from two B decays
  opposite(unmixed) same(mixed)
• 1987 Argus measured
  B0 meson mixing frequency
• UA1 and Argus measurements
  disagreed!

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Bs Oscillations

• With the first evidence of the Bs meson we knew
  it oscillated fast.
• How fast has been a challenge for a generation of
  experiments.

Amplitude method Fourier scan for the mixing
frequency
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The Rival DØ Results
Key Features Result
Sen 95CL 16.5ps-1
Sen ?A(_at_17.5ps-1) 0.7
A/?A 1.6
Prob. Fluctuation 8
Peak value ?ms 19ps-1
PRL 97, 021802 2006
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The Tevatron
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• 1.96TeV pp collider
• Excellent performance and improving each year
• Record peak luminosity in 2006 2.4x1032sec-1cm-2
• Average beam crossing 1.7MHz

• CDF Integrated Luminosity
• 1fb-1 with good run requirements through 2005
• All critical systems operating including silicon
• Doubled data in 2005, predicted to double again
  in 2006

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The CDF Detector

• CDF Tracker
• 8 layer , 90cm long, rL00 1.3 - 1.6cm, 1
  million channel solid state device!
• 96 layer drift chamber 44 to 132cm
• Dedicated systems for electron and muon finding
• Particle Identification
• Time of Flight
• dE/dx in drift chamber

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The Real CDF Detector
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The Trigger

• Hadron collider high production rate of B
  hadrons
• QCD Backgrounds 4 orders of magnitude higher
• The solution a displaced track trigger trigger
  on long B lifetime
• Find tracks of interest at 1.7MHz
• Read out and interpret our silicon detector at
  25KHz

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Bs Mixing Overview
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• Measurement of the rate of conversion from matter
  to antimatter Bs ? Bs
• Determine b meson flavor at production, how long
  it lived, and flavor at decay

to see if it changed!
tag
Bs
p(t)(1 D cos ?mst)
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Bs Mixing A Real Event

• CDF event display of a mixing event

Bs ? Ds-?, where Ds- ? ??-, ? ? KK-
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Bs Mixing Signals

• Fully reconstructed decays Bs ? Ds- ?(2?),
  where Ds- ?
  ??-, KK-, 3?
• Partially reco. hadronic decays Bs ? Ds-? and
  Bs ? Ds- ?, where Ds- ? Ds-
  ?, ? ? ??0/?
• Semileptonic decays Bs ? Ds-lX,
  where l e,?

Decay Candidates
Bs ? Ds?(2?) 5600
Bs ? Ds-?, Bs ? Ds- ? 3100
Bs ? DslX 61,500

• Identified using kinematic, lifetime and PID
  information
  

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More Signals
Decay Candidates
Bs ? Ds?(2?) 5600
Bs ? Ds-?, Bs ? Ds- ? 3100
Bs ? DslX 61,500
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Bs Mixing Flavor Tagging

• OST Opposite side tags Jet with b vertex, kaon
  and lepton tags
• SST Same side tag Kaon PID and kinematic
  information
• Employ two techniques to get maximum performance
• Identify situations in which tagger works best
  and weight these events more highly Example a
  high momentum lepton is more likely a lepton from
  semileptonic B decay and correctly identifies the
  flavor.
• Use situations in which multiple taggers give
  flavor information.
• Taggers calibrated in data where possible
• OST tags calibrated using B
• SST calibrated using MC and kaon finding
  performance validated in data

Tag Performance(?D2)
OST 1.8
SST 3.7(4.8)
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Bs Mixing Proper Time Resolution

• Measurement critically dependent on proper time
  resolution
• Full reconstructed events have excellent proper
  time resolution
• Semileptonic events have worse resolution
• Momentum necessary to convert from decay length
  to proper time

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Bs Mixing Results
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Example Improvement

• Including L00
• Silicon sensors mounted directly on the beam
  vacuum pipe as close as possible to interaction
  region - Sensors have to be radiation damage
  resistant
• Used CMS prototype sensors - half a dozen
  different types - donated for free
• Detector very difficult to calibrate for physics

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Bs Mixing Results
Key Features Result
Sen 95CL 25.8ps-1
Sen ?A(_at_17.5ps-1) 0.28
A/?A 3.7
Prob. Fluctuation 0.2
Peak value ?ms 17.3ps-1
PRL 97, 062003 2006

• Add PID to selection Many kaons in decay chains
• Take advantage of tagger correlations

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Bs Mixing Results
Key Features Result
Sen 95CL 31.3ps-1
Sen ?A(_at_17.5ps-1) 0.2
A/?A 6
Prob. Fluctuation 8x10-8
Peak value ?ms 17.75ps-1
Submitted to PRL
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Bs Mixing CKM Triangle
?ms 17.77 ? 0.10 (stat) ? 0.07 (syst) ps-1
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Bs Oscillations Conclusion

• 2 decade long quest to measure the Bs Oscillation
  frequency done
• Oscillations observed directly
  
  with gt5? significance

-0.18
?ms 17.77 ? 0.10 (stat) ? 0.07 (syst) ps-1
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Bs Results - New Physics

• Many new physics models that predict observable
  effects in flavor physics
• Consider a SUSY GFV model general rather than
  minimal flavor violation
• Makes predictions for Non Standard model BF(Bs ?
  µµ-) and ?ms
• Basically corrects quark mass terms with
  squark-gluino loop terms in a general way
• Size of effects depends on tan? and mA

hep-ph/0604121
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