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MCP checks for the H-4l mass

MCP checks for the H-4l mass. Outline and work program. The problems: Higgs mass difference from the gg Possible single resonant peak mass shift (with low stat) M12 in the 2mu2e channel shifted MCP checks (to be finalized): Muon absolute mass scale Overall Momentum scale

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MCP checks for the H-4l mass

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  1. MCP checks for the H-4l mass

  2. Outline and work program • The problems: • Higgs mass difference from the gg • Possible single resonant peak mass shift (with low stat) • M12 in the 2mu2e channel shifted • MCP checks (to be finalized): • Muon absolute mass scale • Overall Momentum scale • Local misalignments • Per Event mass error • Work program

  3. The main problem Inconsistency between the two masses 2.7 s

  4. Other “features” in the H-4l analysis Fully relaxed analysis to increase stat: M34>0 All Pt>4 GeV Mass increased from 89.4 -> 90.4 For 2011 we have MC without cuts Mass DT = 91.0 ± 0.8 GeV Mass MC = 91.1 • Z-4 Leptons • Single resonant Distributions Apparent shift in the the single resonant mass spectra with standard analysis cuts Increasing stat Mass increased from 89.4 -> 90.4

  5. M12 Distributions Very good agreement on M12 with 4 mu Disagreement in tails of M12 for 2mu2e events

  6. M12 in 2mu2e events • Fit crystal-ball conv. BW • cbmean shift w.r.t. MC mass value • Diif = 0.8 ± 0.5

  7. MCP Checks: Absolute scale using Z events MC Data • Template fit of the Z mass (DT and MC) • Results given as Scale factors to be applied to the PDG mass value in different eta region. • To be finalized using Z in different Pt ranges Error on these numbers : Max 10-3

  8. Z reconstruction different Pt regions Data-MC agree at the level of about 100 MeV over the full Pt range Disclaimer this is NOT a measurement of the Z mass as in the previous page so we are NOT looking at agreement between PDG value and fit.

  9. MCP Checks: Mass scale vs Pt End Cap A • Reconstruct Z Mass for data and MC as a function of leading muon Pt • Plot difference DT-MC difference vs Pt for ID, MS and CB reconstruction • Mean difference < 0.2% stable over data taking period and Pt. • Same results on the other end cap and Barrel • To be done • Enlarge the Pt coverage to lower Pt. • Cross check the results with J/Psi and Y data. Standalone Combined ID

  10. MCP Checks: Pt scale vs Pt End Cap A Data [PT(SA)-PT(ID)]–MC[PT(SA)-PT(ID)] • Plot difference between DT and MC of the measured Pt in ID and MS and in ID and Cb • Difference 100 MeV for Sa-ID stable over data taking period and Pt. • Same results on the other end cap and on the barrel • To be done • Enlarge the Pt coverage to lower Pt. • Cross check the results with J/Psi and Y data. • Check charge dependent distributions Standalone Data [PT(CB)-PT(ID)]–MC[PT(CB)-PT(ID)] Combined

  11. Checks with J/Psi and Y • Different studies done with J/Psi and Y • Some small inconsistencies between them to be understood • General picture: • Also from J/Psi absolute scale of the CB muons is at the 0.2% level • J/psi Mass measured with SA muons shows a max 40 MeV discrepancy Y

  12. Local misalignment Studying curvature offsets as a function of detector region

  13. Effect of local misalignment • Select Z samples with positive muon and Z sample with negative muon going into the problematic region • Plot the quantity q(M(mm)-Mz) • Evident shift between the two distribution (about 1.5 GeV) • Due to the MS-ID Z misalignment (See next slides) • Both SA and ID measurement do not show this problem (CB only problem)

  14. Assessing the magnitude of the effect • Correct the effect in two ways: • Downweight the Z measurement in the MS covariance matrix • Correct ZME and ThetaME for the measured misalignment.

  15. Option 1: Downweight Z ME Bias greatly reduced proving that the effect is (mainly) given by the MS ID Z misalignment

  16. Option 2: Correct for Z and Theta Same result on Z mass Will check if there are other local effects: ex:Study width of Z mass vs eta and phi

  17. Effect of local misalignment and corrections The correction has no effect on the overall momentum scale and negligible effect on mass resolution

  18. Proposed systematics • Reprocessed the ZZ candidates with the Z and Theta corrections • One candidate moves by 1.7 GeV • The average of the distribution (simple average no weighting) moves by less than 300 MeV • Propose to use this method to assess the systematic error due to local misalignment.

  19. Per event mass error • Work started: • Retrive momentum error per muon using standard MCP resolution and smearing tool and propagate it in the Mass formula.

  20. Short term program • Finalize absolute mass scale measurement with Z also as function of pt • Determine the systematic error to be assigned to the absolute mass scale • Obtain coherency of results of J/PSI studies and between J/Psi and Z studies in the low Pt regime • Continue checking for local misalignment other than the Z and assess systematic error for the Z misalignment • Understand the per event error and the discrepancy on the mass error obtained in the “ standard analysis” and the first results from the analysis using per event errors.

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