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Is It Interesting?

This article explores the concepts of statistics and experimental uncertainties in particle physics, including topics such as particle decays, invariant mass distributions, quarks to jets, and the significance of experimental data. It also discusses how statistical and systematic uncertainties impact the interpretation of results.

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Is It Interesting?

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  1. Is It Interesting? Mike Strauss

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

  3. 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

  4. Statistics • For a Gaussian (normal) distribution • 1σ deviation: 32% probability • 2σ deviation: 5% probability • 3σ deviation: 0.3% probability • 4σ deviation: 0.006% probability • 5σ deviation: 0.00006% probability

  5. 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 doesn’t see the same effect.

  6. Particle Decay EP = E1 + E2 p = p1 + p2 E2 = p2c2 + m2c4 E2 = p2 + m2 m2 = E2 – p2 mP2 = EP2 – pP2 mP2 = (E1 + E2)2 – (p1 + p2)2 Parent Daughters

  7. 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.

  8. Seeing quarks in the detector Remember that quarks are always confined! q q As quarks leave a collision, they change into a ‘shotgun blast’ of particles called a ‘jet’ Hadronization 

  9. A 2 jet event

  10. CDF W + 2 jet ?

  11. Latest CDF W + 2 jet data Options?

  12. Discussion?

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