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Charged Particle Multiplicity in DIS

Charged Particle Multiplicity in DIS. QCD Group Review Meeting. M. Rosin, D. K çira, A. Savin, and L. Shcheglova University of Wisconsin Feb. 5, 2004. Motivation for the use of M eff as energy scale. Similarity of particle production at e+e- and ep colliders. W had.

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Charged Particle Multiplicity in DIS

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  1. Charged Particle Multiplicity in DIS QCD Group Review Meeting M. Rosin, D. Kçira, A. Savin, and L. Shcheglova University of Wisconsin Feb. 5, 2004

  2. Motivation for the use of Meff as energy scale Similarity of particle production at e+e- and ep colliders Whad • Similarity of Whad dependence on <nch> has been observed • A common Whad dependence on <nch> implies the production of secondary particles is similar in the different interactions • Study the dependence of <nch> of the observed part of the produced HFS on it’s total invariant mass, Meff Whad Meff Whad: HFS measured in full phase space Meff: HFS measured in the detector where the tracking efficiency is maximized

  3. 1996 & 1997 Data Selection • DIS Event Selection • Scattered positron found with E > 12 GeV • A reconstructed vertex with |Zvtx| < 50 cm • scattered positron position cut: |x| > 15 cm or |y| > 15cm (in RCAL) “Box cut” • 40 GeV < E-pz < 60 GeV • Track Selection • Tracks associated with primary vertex • || < 1.75 • pT > 150 MeV • Physics and Kinematic Requirement • 25 GeV2 < Q2 da < 1200 GeV2 • y el < 0.95 • y JB > 0.04 • 70 GeV < W < 260 GeV ( W2 = (q + p)2 )

  4. Monte Carlo Study Lab frame • Dependence of multiplicity on Meff is the same for restricted regions of phase space

  5. Comparison to 2nd analysis: Q2 2nd Analysis: Dorian Kçira • Small data sample • Gen level MC • Perfect agreement • Det level MC • Good agreement • Data • Some small disagreement

  6. Comparison to 2nd analysis: Meff • Small data sample • Gen level MC • Perfect agreement • Det level MC • Good agreement • Data • Some small disagreement

  7. Comparison to 2nd analysis: <nch> • Small data sample • Gen level MC • Perfect agreement • Det level MC • Good agreement • Data • Some small disagreement

  8. Comparison with second analysis • General agreement within statistical errors

  9. Uncorrelated systematics

  10. Trigger studies by L. Shcheglova Lydia has investigsated the possibility to go to lower Q2. Because of changing prescales for DIS01 and changing radius for DIS03, must use a weighting scheme Created a mixed sample of DIS01 & DIS03 to get agreement with MC The weighting scheme is described in detail here: http://amzeus.desy.de/~sumstine/trigger_study/weighting_foils.ps

  11. Results • Full 96 & 97 data sample • Same dependence as 1995 data

  12. Results of reweighting Good agreement between data and MC up to Q2 15 or 10 GeV2 Currently Q2 >25, but it should be possible to go lower

  13. Summary • MC studies • Started systematics • 2nd analysis is on the way; first look: general agreement • Trigger study by Lydia Shcheglova • Plans • Make preliminary • work on small differences between 1st and 2nd analysis • finish systematics

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