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Study of Invariant Mass Spectrum in Particle Physics Experiments

This study aims to assess contributions from specific resonances in the spectral function and optimize signal event selection. Analysis includes background reduction techniques and future plans for unfolding detector effects.

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Study of Invariant Mass Spectrum in Particle Physics Experiments

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  1. 1. Motivation • spectral function → aμ , α Dominant uncertainty comes from experimentally determined hadronic loops: Mitchell Naisbit Manchester Jan2004

  2. 2. Motivation cont’d Recent results show discrepancy between and spectral functions Babar ideal to validate τ result.

  3. 3. Aim • Study ρ line shape → Assess contribution from ρ(1450) and ρ(1700) • Make a selection of signal events, maximising the efficiency and purity • Form invariant mass spectrum of the system.

  4. 4. Samples Produced using TauUser package 19 fb-1 of run 1, 2 and 3 data (124 fb-1) 60 M τ Events 130 M uds events small bhabha samples

  5. 5. Selection Procedure Selection for data and MC samples: Use 1-1 events and tag to reduce backgrounds Signal sideTag side • Truth-match to calculate ε and π: • particle ID • same mothers

  6. 6. Invariant Mass Spectrum ε = 9.6 % π = 55.1 % • τ background dominant, seen to be: • mostly a1 decays where 1 πo is lost • improperly reconstructed signal decays

  7. 7. Tag Invariant Mass Spectra e-tag = bhabha background, low uds μ-tag = no bhabha, low uds ρ-tag = uds background, no bhabha

  8. 8. Future Work • Running on the entire 124fb-1 sample: • Apply cuts to subtract remaining backgrounds and optimiseε and π • Unfold detector effects from invariant mass spectrum • Perform fits to spectrum to assess contributions from higher ρ resonances.

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