Current Statistical Issues in Particle Physics Louis Lyons Particle Physics Oxford U.K. Future of Statistical Theory Hyderabad December 2004

Current Statistical Issues in Particle Physics What is Particle Physics? What is Particle Physics data like? Typical analysis PHYSTAT Conferences Where we would like help

Typical Experiments Experiment Energy Beams # events Result LEP 200 GeV e+ e- 10 Z N = 2.987± BaBar/Belle 10 GeV e+ e- 10 BB CP-violation Tevatron 2000 GeV p anti-p “10 14 ” SUSY? LHC GeV p p (2007…) Higgs? Super-K ~3 GeV K  K 100 ν oscillations

K2K -from KEK to Kamioka- Long Baseline Neutrino Oscillation Experiment

CDF at Fermilab

Typical Analysis Parameter determination: dn/dt = 1/τ * exp(-t/ τ) Worry about backgrounds, t resolution, t-dependent efficiency 1) Reconstruct tracks 2) Select real events 3) Select wanted events 4) Extract t from L and v 5) Model signal and background 6) Likelihood fit for lifetime and statistical error 7) Estimate systematic error τ ± σ τ (stat) ± σ τ (syst)

Where we would like help Access to understood programs Multivariate analysis Cuts, Fisher, PCA, NN, SVM, Boosted Trees……. Confidence limits Nuisance parameters Unphysical values Coverage? Very small intervals Estimating signal significance S/ B Nuisance parameters Look elsewhere effect Goodness of fit Sparse multi-dimensional data Combining results Asymmetric errors Overlapping data samples