Is It Interesting?

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Is It Interesting?

• Mike Strauss

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Outline

• Statistics and probability
• Experimental uncertainties
• Particle decays and invariant mass distributions
• Quarks to jets
• CDF W 2 Jet signal

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Enough Data?

• If you flip a coin ten times and there are 4
  heads and 6 tails, is the coin properly weighted?
• 21 probability
• (or 38 probability of 6)
• If you flip a coin 1000 times and there are 400
  heads and 600 tails, is the coin properly
  weighted?
• 4.6 10-9 probability
• (or 1.4 10-8 probability of 600)
• The conclusion depends on the amount of data
  available

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Statistics

• For a Gaussian (normal) distribution
• 1s deviation 32 probability
• 2s deviation 5 probability
• 3s deviation 0.3 probability
• 4s deviation 0.006 probability
• 5s deviation 0.00006 probability

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Experimental Uncertainties

• Uncertainties (not errors) come in two varieties
• Statistical
• Well defined based on the amount of data you have
• Some interesting experimental signals occur
  because of statistical fluctuations. These
  will disappear with more data
• Systematic
• Not as well defined but with general learned
  guidelines
• Some discoveries have occurred because
  systematic uncertainties were not fully accounted
  for. These tend to go away with a better
  understanding of apparatus, or because another
  experiment doesnt see the same effect.

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Particle Decay

• mP2 EP2 pP2
• mP2 (E1 E2)2 (p1 p2)2

Parent
Daughters

• EP E1 E2
• p p1 p2
• E2 p2c2 m2c4
• E2 p2 m2
• m2 E2 p2

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Discovering new particles Synopsis

• A new particle can be discovered by observing
  peaks in an energy distribution when plotting the
  invariant mass of chosen decay products.
• The peak must have enough statistical
  significance.
• We must understand our background shape to know
  the statistical significance of the peak.
• Other experiments should be able to verify new
  discoveries.

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Seeing quarks in the detector
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A 2 jet event
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CDF W 2 jet
?
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Latest CDF W 2 jet data
Options?
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Discussion?