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A more realistic photon simulation in Geanfi

A more realistic photon simulation in Geanfi. By: C.Bloise, M.Martini, S.Miscetti , M.Moulson, T.Spadaro. Motivations: A better description of shower simulation for photons and a “standard” recipe to recover the data-MC discrepancy needed to : - attain a 0.1% error on K s  0  0

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A more realistic photon simulation in Geanfi

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  1. A more realistic photon simulation in Geanfi By: C.Bloise, M.Martini, S.Miscetti, M.Moulson, T.Spadaro ... • Motivations: • A better description of shower simulation for photons and a “standard” • recipe to recover the data-MC discrepancy needed to : • - attain a 0.1% error on Ks00 • - measure rare Ks decays in neutral channels • - parametrize response /resolution for Kinematic Fitting • Four main tasks : • - selection of Machine background events • - insertion of Machine background events in MC data • - survey of existing data-MC discrepancy • - correction-adjustment of MC simulation Capri 24-5-03, Kloe Phys Workshop III S.Miscetti @ KPW3

  2. SELBKG & INSERT: basic ideas • Differences with last year bkg simulation (ACCELE + MBCKADD) • Use a unique selection sample ( ee   from FILFO) for evaluation of DCH, EMC, QCAL machine background • ( bias found in mbckadd where the usage of L3BHA events was • providing events already cleaned of out of time clusters ! ) • Study side-bands (early/late) of T-R/c to measure rate of accidental • events but extend the selection to the whole time spectrum & inserting • hits for the 3 detectors at the same time. All correlations preserved. • Closely follow the rate dependence along the run by selecting events • of “same machine activity” in groups of few pb-1. • The background is inserted in MC on a run by run basis. • Finally ... • BGG stream created! • Insertion in MC weighted with the effective cross section of BGG selector. S.Miscetti @ KPW3

  3. SELBKG : selection of golden events • Two clusters in • the barrel with: • TW ( 5 T, 1 ns) • Ecl > 480 MeV • Etot > 960 MeV • * cuts • z cuts • Vclu cut Etot (1+2) (MeV) Still a lot of mess in the “IN TIME” window T (ns) S.Miscetti @ KPW3

  4. SELBKG : looking for the machine bkg events Once “clean” clusters have been selected we look for all “residual” ones looking at all combinations of DRij vs DTij between the “clean” and “residual” clusters. R(cm) 3 categories • () • Flying clusters (shower fragments) • splitted clusters Fiducial region T (ns) S.Miscetti @ KPW3

  5. SELBKG : survey distributionsafter weighting tecnique • After golden clusters selection & restricting the search to the fiducial region: • pieces of collision remain in the c0,c1,c2 bands for single hits. • comparing the E vs cos plot • for early band and cj bands • a set of 2D weights is found. • Nice agreement found in all distributions after applying these 2D weights Early Times c0 c1 c2 bands 1 hit  1 hit S.Miscetti @ KPW3

  6. SELBKG : survey distributionsafter weighting tecnique II C0 C1 C1 C0 C2 C0,C1,C2 C0,C1,C2 C2 solid line (early-band) black dots (Cj bands) S.Miscetti @ KPW3

  7. INSERT: inserting BGG eventsinside MC events • SELBKG technique applied • to groups of few pb-1 to follow • closely the machine activity • along the run. • BGG stream DONE! • INSERT: • two bugs found in TSKT & • SmearT0 fixed last week: • now times can be negative • correction for att in EMC • and space2time relation for • DCH close to reality. • overlap between accidental and MC hits tested at first order both for tracking &clustering S.Miscetti @ KPW3

  8. INSERT: inserting BGG events inside MC events • Tests of insert bgg done with MC PRE-Production • T-R/c behaviour with • /without t0_finder: • enhancement  0 for bgg satisfying t0_finder ! • otherwise correctly bunched • Tests to be done for • post-production are: • energy slope • hits multeplicity • effects on Filfo • effect on rec.efficiency S.Miscetti @ KPW3

  9. Toward a more realistic MC description of EMC • EMC geometry closer to the real one (Barrel moved down inY of 1 cm) • Survey of existing data-MC discrepancy done! • Most of the checks based on  sample. Other tests in progress • with  & Bhabha’s samples. A lot of differences data-MC found. • Scale and Resolutions: • - Energy resolution • - Timing resolution • - Non linearity of response • - behaviour along cracks (  barrel , X EndCaps) • - behaviour along Y ( attenuation lengths EndCaps) • Shower shape • - X0 simulation • Light Yield • - Ea/Eb • - Efficiency ? S.Miscetti @ KPW3

  10. Energy response and resolution vs E Data MC 5.0%/(E/GeV) 5.7%/(E/GeV) • Energy scale is set better in data than in MC. Still contained below 1% • Non linearity better in data than MC (clufixene effect) • Stoc.term in resolution much better in MC S.Miscetti @ KPW3

  11. Energy response vs  MC DATA • Data show clear  -cracks + calib error around  = 0 S.Miscetti @ KPW3

  12. Energy response vs MOD(,15) • crack effect much more visible if shown vs mod(,15) S.Miscetti @ KPW3

  13. Energy response & resolution: no crack vs crack zone • As shown by profile there is a lowering in response in the crack. Integrating 1 degree • around the crack the effect is of  –2% in response (some energy dependence ?) • slightly worse resolution! S.Miscetti @ KPW3

  14. Reconstruction efficiency: no crack vs crack zone • No effect on efficiency • data MC differ up to 70 MeV S.Miscetti @ KPW3

  15. Energy response in EndCaps: dependence vs Y • Also on Endcaps cracks • are visible along X. • Moreover, there is a • miscalibration of response • along Y at a level of 3-4 % S.Miscetti @ KPW3

  16. Shower Shape: measurement of the decay length (data) • N(x) = N0 e(-x/)(1) • with x the EMC depth. • The distribution of the first • plane fired fit with (1) in bins • of as a function of E. • E dependence of cross • section as expected. • “plateau” region • E250 MeV • We derive •  = 1.5 cm • X0 = 7/9  1.2 cm (degrees) S.Miscetti @ KPW3

  17. Shower Shape: measurement of the decay length (MC) Following same description X0 1.5 cm (MC) MC composition: 23 cm with Pb/Sc slabs of 0.11 cm (400 m/700m) 1/X0 = Fpb/X0pb+Fsc/X0sc X0 = 1.53 cm Fs(Mip) = 24% Fs(e.m.) = 14.5% Great agreement! (degrees) Same exercize on data: 200 planes of 500 m Pb X0 = 1.2 cm EMC in MC too light! S.Miscetti @ KPW3

  18. Measurement of light yield (MC) • Two techniques used to get Npe • Gaussian fit to the distributions: • R = (Ea/Eb) • /S = (Ea-Eb)/(Ea+Eb) • for Barrel cells fired @ Z=0. (2./(1.2xE/MeV))  0.11 Assuming fluctuaction to be dominated by Poisson on Npe  v = (2/Npe) (2./(1.5xE/MeV))  0.12 • /S method more stable. • we get 1.2 pe/MeV in scint • @ calorimeter center. • In agreement with • light yield used in MC • 25pe*0.145*0.33 S.Miscetti @ KPW3

  19. Measurement of light yield (data) Using same technique on data sample we find Npe = 0.6-0.7/MeV i.e. 600-700 pe/GeV/side (2./(0.60xE/MeV))  0.12 • 50% of exp. light yield - 20% drop due to B-field • - estimated @ CRS using • time resolution and (scint) • - effect of light yield on • energy resolution small. • ( in operation we found less than extrapolating from CRS and TB ) (2./(0.65xE/MeV))  0.12 S.Miscetti @ KPW3

  20. Measurement of time resolution (data) • Usual numbers: • - stoc. term • 57 ps/sqrt(E/GeV) • - const.term • 140 ps • Stable since 1999 • on MC • - const.term  0 • - stoc.term • 50 ps/sqrt(E/GeV) • much more light in MC • still not a factor 2 T-R/c (ns) T(ns) E (MeV) S.Miscetti @ KPW3

  21. Summary review of information in our hands • Radiation length on data 1.26 cm ( vs 1.53 cm MC) • Light yield 0.6-0.7 pe/MeV (1.2 pe/MeV) • Sampling fraction used in MC for showers 14.5 % • Stoc.term of energy resolution lower in data than MC (5.7% vs 5.0 %) • Not recoverable only with difference in Npe • Stoc.term of time resolution 57ps (data) vs 50 ps(MC)  • missing description of holes and behaviour along Y • reconstruction efficiency data lower than MC S.Miscetti @ KPW3

  22. Adjustements done in MC and Reconstruction Geanfi simulation was adjusted in many steps varying : 1) X0lead thickness from 400 to 500 m 2) light yield lowered from 25 to 19 pe/MeV 3) adjusting sampling fraction in rec for each selectedX0 4) fastening the Time emission distribution and recalibrating MC T0s for each choice. 5) constant term of 140 ps add + • Two new routines in MC path: • EMCSIMULA: Adding holes • CLUADJUST called in clufixene • - fixing  calib-hole and attenuation lengths • - flagging clusters to be killed to simulate obs.efficiency (only ) S.Miscetti @ KPW3

  23. Comparison old vs new MC ( fo ) events • Barrel • Barrel holes • EndCaps Resolution OK, holes ok bug found on EndCap .. now fixed S.Miscetti @ KPW3

  24. Old vsNewMC:dependence along  S.Miscetti @ KPW3

  25. Old vsNewMC:dependence along X and Y S.Miscetti @ KPW3

  26. New MC: simulation of cluster efficiency for  S.Miscetti @ KPW3

  27. Conclusions • The new MC follows much more closely the details of cluster • reconstruction and shower development in the EMC: • energy and time resolution OK • Non linearity in response similar. • holes and other small details simulated • shower shape OK • inefficiency still a trouble. Forced imposing measured efficiency. • simulation of mach background OK for all detectors • (much more tests expected for post-mc production • Slopes, rates of accidentals ) • Much more testing also necessary on masses of neutral objects S.Miscetti @ KPW3 MC meeting LNF 23-1-03

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