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Comments on some parameters related to particle-flow analysis - a reminder -

Comments on some parameters related to particle-flow analysis - a reminder -. Sandro Palestini. Measurement of jets is critical (e.g.: identify W/Z from invariant mass in decays to two jets) Two ILC experiments base the general detector design on the assumption of Particle-Flow-Analysis:

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Comments on some parameters related to particle-flow analysis - a reminder -

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  1. Comments on some parameters related to particle-flow analysis- a reminder - Sandro Palestini

  2. Measurement of jets is critical (e.g.: identify W/Z from invariant mass in decays to two jets) • Two ILC experiments base the general detector design on the assumption of Particle-Flow-Analysis: • Charged particles measured in solenoid • Tracks matched to e.m. and hadronic showers in calorimeter • Fine read-out segmentation transversally and longitudinally • Ideally, calorimeters energy measurement used only for neutral hadrons • Ultimate energy resolution is not needed in either e.m. and hadronic sections of the calorimeter • In practice, “confusion error” is relevant and becomes dominant at large jet energies

  3. Basic implication on detector parameters • Tracking detector (radius R) • Momentum measurement: • B∙R2 ~ sagitta∙(8Psin(θ)/0.3), to be compared to tracking resolution • Aspect ratio (radius/length) affects the area of resolution loss at small polar angle • Separation of jets as they enter the calorimeter • Scales as: k∙<α/√2>∙R/sin(θ) (+) B∙R2/sin(θ)∙(0.3/2P) along r∙φ for charged particles <α> is the average angle of jet particles to the jet axis, k ~0.1 describes the separation between particle near the jet axis • Compares to the combination of: • Molière-radius/hadronic-shower-width in calorimeters • transversal segmentation of calorimeter read-out

  4. ILC experiments (being revised?): • ILD: R=2m, B=3.5T, B∙R2 = 5.0 Tm2, aspect ratio: 2R/L~1.0 • SiD: R=1.2m, B=5T, B∙R2 = 7.0 Tm2, aspect ratio: 2R/L~0.8 and comparables parameters in calorimeter segmentation • <α> : rough estimate attempted from charged multiplicities in electron-positron colliders: (input data in blue) • Energy[Gev] 30100 200 500 • <Nch> 1321 26 32 • <Ntot> 20 32 39 48 • <Ep>[GeV]=E/<Ntot> 1.5 3.1 5.1 10. • <α>~0.8Gev/<Ep> .5 .25 .16 .08 <Ep> would not grow as fast as E, but still there is an important increase between ~100 and ~200 GeV, and above (and <α> decreases)

  5. In summary: • if particle flow is to be used at CLIC as expected at ILC, B-field and even more tracking radius (related to B∙R2 and also R) appear as leading design parameters • Assuming that ILD and SiD have approximately optimized their design for ILC, even limited increase in jet energies interesting for CLIC would suggest more challenging choices for these parameters. (Detailed studies are required to quantify these statements)

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