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± 0.008

• BaBar/Belle 10 GeV e+ e- 10 BB CP-violation

• Tevatron 2000 GeV p anti-p “1014” SUSY?

• LHC 14000 GeV p p (2007…) Higgs?

• Super-K ~3 GeV KK 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 ± στ (stat) ± στ (syst)

Where we would like helpAccess to understood programsMultivariate analysis Cuts, Fisher, PCA, NN, SVM, Boosted Trees…….Confidence limits Nuisance parameters Unphysical values Coverage? Very small intervalsEstimating signal significance S/ B Nuisance parameters Look elsewhere effectGoodness of fit Sparse multi-dimensional dataCombining results Asymmetric errors Overlapping data samples