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Muon momentum scale calibration with J/y peak

Muon momentum scale calibration with J/y peak. PRELIMINARY: low statistics in data not final MC (low stat used). First pass on the data: many details to be investigated. Samples and cuts. Data (~15 nb -1 ):. May6 Re-Reco from 132440 to 134725 Onia-CS-V9 up to 135735

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Muon momentum scale calibration with J/y peak

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  1. Muon momentum scale calibration with J/y peak PRELIMINARY: low statistics in data not final MC (low stat used) First pass on the data: many details to be investigated

  2. Samples and cuts • Data (~15 nb-1): May6 Re-Reco from 132440 to 134725 Onia-CS-V9 up to 135735 Mu-CS-V1 up to 136086 (CMSSW_3_5_8_patch3) Mu-CS-V2 up to 136561 (max useful 136297) (CMSSW_3_6_1_patch2) BPH Json file applied • MC (~100 nb-1): Spring10 J/y prompt + ppMuMuX • Standard onia selection: global muon: nHits inner track > 11 tracker muon: nHits inner track > 11 pixelLayer >1 pixelLayer >1 d0<5 cm, |dZ|<20 cm d0<5 cm, |dZ|<20 cm chi2 < 5 chi2 < 20 TMLastStationAngTight Exclusive cathegories: glb-glb if any, otherwise glb-trk (inner track always used, also for glb muons) No trigger, no acceptance cuts

  3. Mass peak (nominal mass 3.0969 GeV) Fit: CrystalBall (to include FSR tail) + exponential for the background DATA: mean (3.092 ± 0.001) GeV MC: mean (3.0976 ± 0.0006) GeV sigma (43 ± 1) MeV sigma (37.3 ± 5) MeV Data have 5MeV bias and worse resolution (and larger background)… … BUT the pT, h distribution of J/y is quite different in data and MC (to be checked)

  4. Mass reso VS muon kinematics data data |h| 1.6 MC MC pT 1.4 GeV |h| 0 pT 4.6 GeV

  5. Mass scale VS muon kinematics MC (1.38 pb-1 Spring10 prompt J/y) • Also in MC we have scale bias • bias in the reco algorithm • approximated material budget in reconstruction • Gaussian fit in each pT, h bin: bias < 5 MeV • FSR not considered (→ CB with more stat) • bins are large: integration over different eta/pt distribution btw data and MC

  6. Inner VS global tracks GG+GT GG: inner tracks GG: global tracks No significative difference with this statistics

  7. peak+FSR convoluted with gaussian for resolution MuScle fit (FSR from fit of generated mass distribution) • Fit reconstructed mass profile with signal model + exponential background • ansatz functions for single muon scale and reso • compute m, s(m) (with error propagation) event by event • unbinned likelihood multiparameter fit → two muons can probe uncorrelated detector regions → correlation between different kinematic variables taken into account extract scale and resolution on single track as a function of muon kinematics a0 = 1.0019 ± 0.0008 2‰ effect a1 = (-4 ± 2)·10-4 GeV-1 1‰ at 3 GeV b0 = 1.66 ± 0.09 b1 = (5.8 ± 0.9)·10-3 b2 = (2.1 ± 0.2)·10-2 bad fit for high h parabola (to be checked with more stat) b3 = (3 ± 3)·10-2 b4 = 1.8 ± 0.3

  8. Mass after corrections Raw Calibrated m = 3.092 ± 0.001 m =3.094± 0.001

  9. Crystal Ball is an approximation • Model computed analytically: fit to the generated mass spectrum gaussian for the resolution 2D model mass VS s peak shift at high s • If you fit this model with Crystal Ball → 2MeV shift in the mean

  10. Resolution: PRELIMINARY • Resolution from MuScle fit • !! large uncertainties not plotted !! • hints of worse resolution in dat at high h(confirmed by plot in slide 4) DATA s(M) GeV • Width of gaussian fit in each f bin • sinusoidal shape (??) mu - mu + 42±1 MeV c0 45±1 MeV c1 -4±2 MeV -4±2 MeV c2 1.5±0.5 0.5±0.5

  11. Final aims • Commissioning: • measure pT resolution from data and compare with MC • measure scale bias in data → provide corrections → compare with expected effects from misaligment, magnetic field, material budget (tested in MC) • Usage in physics analyses: • onia ds/dpT measured with corrected momenta → remaining systematics due to correction uncertainty • systematics on onia acceptance due to different MC-data scale and resolution (full scale bias in MC + data uncertainty) used for systematics (difference in resolution between data and MC + data uncertainty) used for systematics • VBTF: extrapolation of results to Z

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