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Z mass shift in MC release 17 Comparing release 16 and 17

Z mass shift in MC release 17 Comparing release 16 and 17. Peter Kluit Muon week 15 November MCP/MATF meeting 9 November 2011. Introduction. A Z mass shift has been reported in MCP in MC release 17 Several studies are ongoing: latest is from Nayanka Bolnet

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Z mass shift in MC release 17 Comparing release 16 and 17

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  1. Z mass shift in MC release 17Comparing release 16 and 17 Peter Kluit Muon week 15 November MCP/MATF meeting 9 November 2011

  2. Introduction A Z mass shift has been reported in MCP in MC release 17 Several studies are ongoing: latest is from Nayanka Bolnet See MATF 26 october https://indico.cern.ch/conferenceDisplay.py?confId=160046 Here I try to localize and pin down further the problem for the Muon Spectrometer (there is also an ID problem see 4 Nov ID Tracking weekly https://indico.cern.ch/conferenceDisplay.py?confId=161459) MC release 16 mc10_7TeV.106047.PythiaZmumu_no_filter.recon.ESD.e574_s933_s946_r1652 MC release 17 mc11_7TeV.106047.PythiaZmumu_no_filter.recon.ESD.e815_s1272_s1274_r2730 Z muon muons selection 2 MuidCB muons with pT > 20 GeV Truth matching uses the ID hit truth matching (p after FSR)

  3. The MC truth for Z mass: Fit is with Egge function: using the truth momentum for mass Conclusion: NO mass shift Rel16-17 at “generator” level < 5 MeV

  4. The CB resolution pTrue/p CB – 1 Fit is with double gaussian and common mean: Conclusion: dp/p shift Rel17 is -1.4 10-3 (q<0) (140 MeV@Z)

  5. The CB resolution pTrue/p CB – 1 Fit is with double gaussian and common mean: Conclusion: dp/p shift Rel17 is -1.8 10-3 (q>0) (180 MeV@Z)

  6. The SA resolution pTrue/p SA – 1 Fit is with double gaussian and common mean: Conclusion: dp/p shift Rel17 is -2.0 10-3 (q<0) (200 MeV@Z)

  7. The SA resolution pTrue/p SA – 1 Fit is with double gaussian and common mean: Conclusion: dp/p shift Rel17 is -1.8 10-3 (q<0) (180 MeV@Z)

  8. The ME resolution pTrue/p ME – 1track at Muon Entry Fit is with double gaussian and common mean: Conclusion: dp/p shift Rel17 is -4.0 10-3 (q<0) (400 MeV@Z)

  9. The ME resolution pTrue/p ME – 1track at Muon Entry Fit is with double gaussian and common mean: Conclusion: dp/p shift Rel17 is -4.0 10-3 (q<0) (400 MeV@Z)

  10. The ME resolution pTrue/p ME – 1track at Muon Entry: Eta dependence Momenta are shifted upward (so too high) by 200-600 MeV Note that this shift is localized: ONLY in the Muon System What happens between IP and Muon Entry?

  11. The Eloss between IP and Muon Entry in Simulation truth Very small changes in Eloss…and irrelevant for the shift reported on slide 10 Conclusion; the issue is in the simulation & reco of the Muon System

  12. The Eloss between the first and last hit in Muon System Small changes in Eloss ~ 50 MeV Cannot be the cause

  13. The ME resolution pTrue/p ME – 1track at Muon Entry Z prime sample release 17Dinos his sample Conclusion: dp/p shift Z prime Rel17 is ALSO -4.0 10-3 (q><0)

  14. The B field integral: between the first and last hit in Muon System Some observations: The Integrated Bfield used in the reconstruction looks very symmetric in rel 17 Checked logfiles in Dinos mc11 production: “asymmetric map is loaded”. I don’t understand this…. More symmetric than in rel 16 Changes wrt 16 are significant Maybe a B field issue?

  15. Conclusions • We have in mc 11 a major upward shift in the momentum in the Muon System of 200-700 MeV for Z’s. • NB: Release 16 is OK • For Z and Z prime the dp/p shift is similar -4 per mille. • A simple “Muon System E loss problem” is not very likely. • The cause can only be in the simulation & reconstruction in the Muon System. The generator is very similar. • Possible causes: • configuration problems that make that one picks up an inconsistent B field map e.g. • Or … a muon tracking precision problem in G4? • Or …

  16. Configuration issues? In the simulation a field map was used with current 20400: Thanks Laurent However we see during the reconstruction of the simulated data: Thanks Dinos, Felix and Niels: Py:AutoConfiguration WARNING BField current in input file differs from GEO version!! Field is configured due to GEO version Py:AutoConfiguration INFO Trying to guess magnetic field status from geometryVersion. Py:AutoConfiguration INFO Toroid current fm GEO PK 20500.000000 Py:AutoConfiguration INFO Toroid current from input file metadata PK 20500.000000 Note that this fits perfectly with the observations! But… in the reconstruction it looks like a current of 20400 is used. Puzzling!

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