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Status and Plan for Particle ID

Status and Plan for Particle ID. Matthew Jones. May 27, 2004. Endpoint: Ability to perform likelihood based dE/dx analysis on tracks with p T > 400 MeV/c Work by many people: Stefano, Diego, Paola Squillacioti, Nicola Pounder, Mauro Donega, Vivek Tiwari, (and others!). Assumptions.

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Status and Plan for Particle ID

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  1. Status and Plan for Particle ID Matthew Jones May 27, 2004 • Endpoint: • Ability to perform likelihood based dE/dx analysis on tracks with pT > 400 MeV/c • Work by many people: • Stefano, Diego, Paola Squillacioti, Nicola Pounder, Mauro Donega, Vivek Tiwari, (and others!)

  2. Assumptions • Apply macroscopic corrections determined for pT > 2 GeV/c (Note 6932) • Separate universal curves for positive and negative tracks • Average over remaining non-uniformities for parameterization of resolution • We need to demonstrate/quantify to what extent this will work.

  3. Macroscopic Corrections • Correct , , time dependence for SVT tracks (pT > 2 GeV/c) • Universal curve fit for pT > 2 GeV/c using D*+D0+, D0K-+ • No constraint for  < 4:

  4. Constrain universal curve with TOF • TOF can easily identify low pT protons to constrain the low  region • Apply simultaneous fit to TOF + dE/dx to determine: • Parameters for universal curve • Parameters for the resolution • Include low pT conversions as an additional constraint

  5. Time-of-Flight analysis • Calculate ti = t – TOFi for mass i •  ti = ti – t0 is Gaussian with zero mean for correct mass hypothesis • Likelihood function: • Imbelishments: • Double Gaussian resolution function • Background parameterization

  6. dE/dx parameterization • Standard “CDF” parameterization: • Define Zi = log(dE/dxmeasured/dE/dxpredicted) • Zi is Gaussian distributed with resolution parameterized by:

  7. Example fit: • Reasonably good description at low pT… • Need to quantify this

  8. Example fit: • Momentum dependent particle fractions means that projections do not indicate goodness of fit:

  9. Momentum dependent fits • Example: K TOF   p dE/dx K p

  10. What about low momentum? • Indications that dE/dx is biased at lowest momenta by ~0.2 (~0.3 ns)

  11. Is there an XFT bias? • § from K0S might be biased • Similar effects seen with conversions • Try to understand this using other pure samples

  12. Cross checks with pure samples • People have looked at XFT and non-XFT biased samples. Stefano provided a compilation:

  13. Problems at low momentum? • Maybe macroscopic corrections shouldn’t be applied directly to low pT tracks:

  14. Work in progress • Make consistent comparisons of pure samples • Different estimators of <dE/dx> have different biases (eg. Gaussian/log-normal fits) • Macroscopic corrections for p<1 GeV/c • Corrections for pT>2 GeV/c might not apply • Can we generate low pT macroscopic corrections using, eg. D*+D0+? • More cross checks with pure samples

  15. Longer Term Work • We recognize that macroscopic corrections are not the ideal solution • We need to develop time-dependent and z-dependent wire-by-wire corrections • In principle, this should improve resolution and uniformity, reduce systematics • Time scale unclear – most effort devoted to tools for summer conferences

  16. Other TOF fit parameters TOF resolution scale factor is ~1 (essentially by construction) Hits limit – needs further attention

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