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Neutral Current 98/99 e - p and 99/00 e + p

Neutral Current 98/99 e - p and 99/00 e + p. Outline. Chris Cormack Ricardo Gonçalo Alexander Kappes Kenneth Long Matthias Moritz Henning Schnurbusch Amaya Lopez-Duran Viani. Note on FPCHOT bug. Systematics studies. Update on 98/99 analysis. ZEUS Collaboration Meeting

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Neutral Current 98/99 e - p and 99/00 e + p

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  1. Neutral Current 98/99 e-p and 99/00 e+p Outline Chris Cormack Ricardo Gonçalo Alexander Kappes Kenneth Long Matthias Moritz Henning Schnurbusch Amaya Lopez-Duran Viani Note on FPCHOT bug Systematics studies Update on 98/99 analysis ZEUS Collaboration Meeting October 17th 2001 Collaboration Meeting 17 Oct. 2001

  2. Note on FPCHOT bug fix What to do: Routine CureMyCalDoc from Juan Terrón corrects the DATA/MC if it was affected. Routine is now in EAZE (since software release 2001a.1) and is called in the right place BUT be sure to use the latest version of RCALCORR - (version 63). So: 1) get the latest version of RCALCORR in: /afs/desy.de/group/zeus.zsmsm/ZEUSSysSoft/Released/zeus/ZeusUtil/phantom/v2001a.1/src/DetectorsUCAL/corrections/rcalcorr.fpp 2) set ZEUSRELEASE to “new” and recompile your EAZE job . How to be sure it was fixed: Look for: “ZAINIT: CureMyCalDoc is enabled for this EAZE job” in your log files. How to turn the bug fix OFF: Use control card: SPECIAL-CURECAL OFF if you want to be absolutely sure. But it’s safe to run CureMyCalDoc on un-corrupted data. To know more: Juan Terron’s talk on friday Collaboration Meeting 17 Oct. 2001

  3. Systematics studies • Calorimeter energy scale • Photoproduction Normalisation • Inelastic QED Compton • Electron energy smearing • Hadronisation and FCAL inner ring Collaboration Meeting 17 Oct. 2001

  4. Systematics studies - Calorimeter Energy Scales - Chris Cormack • Double Angle Method, used in Neutral Current analysis is sensitive to angular variations in the energy scale. • Need to Calibrate each individual Calorimeter section (EMC/HAC separately). • For DIS need to understand the CAL response in a wide range of PT ~ 5 to ~ 80 GeV • Two Methods Used • Diffractive Method • Allows the isolation of the hadronic energy deposits in each calorimeter. • Limited range in PT (peak at ~6 GeV, up to ~20 GeV). • Jets Method • Isolated Jets can be restricted to the BCAL. • Large range in PT can be Covered. • Calibrating the 2 Other Calorimeters not so simple. At present there are no tunings of the hadronic energy scales only factors as applied to data in RCALCOR A Priori Scale Factors (DATA): FCAL = 1.00 BCAL = 1.05 RCAL = 1.022 DATA and MC: 98/99/00 Dead material map Collaboration Meeting 17 Oct. 2001

  5. zMAX zMIN max Systematics studies - Energy scales • Typical properties of DIS events • Event not well contained in central detectors • Large Energy loss in beam pipe • EHAD dependence on beam pipe/FPC leakage • Almost Impossible to have complete hadronic containment in F/B/RCAL • The Solution: Use Diffractive Events • Standard DIS events with max< 3.4 • yJB > 0.01 and MX > 2 GeV - To ensure sufficient hadronic activity • Look at PT Balance PTH/PTDA • Check individual calorimeters • Study the energy response PTH/PTDA vs hadron Collaboration Meeting 17 Oct. 2001

  6.   Systematics studies - Energy scales Partial result from PTHAD/PTDA alone (no separation EMC/HAC) PTH = Hadronic PT from cells PTDA = EeDA sin e PTDA / PTTRUE Statistical Error 0.5 % F/B CAL 2% RCAL HADRON Acceptance reduction due to Q2cut Acceptance reduction due to max cut • =>Angular acceptance cuts: 0.05<  < 2.75 • Within the Acceptance PTDA unbiased Collaboration Meeting 17 Oct. 2001

  7. DATA Monte Carlo Systematics studies - Energy scales Now separate HAC and EMC scales For each CAL section plot PTHAD/PTDAas function of the EMC fraction and fit a straight line to the points. Take the intercept at EMC fraction=0 as HAC scale and at EMC fraction=1 as EMC scale. PT peaks at ~6 GeV & extends to ~20 GeV BCAL: constant offset! Only need to change factor Collaboration Meeting 17 Oct. 2001

  8. Systematics studies - Energy scales • Results from diffractive method • FCAL: No Need to Tune Factors -Values within Errors (1%) • BCAL: EMC (DATA) scaled up 1% 101% (+/- 1.0 %) • BCAL: HAC (DATA) scaled up 5% 105% (+/- 1.5 %) • RCAL: Scale factors Unchanged (+/- 2% (stat)) Collaboration Meeting 17 Oct. 2001

  9. Systematics studies - Energy scales: Jets method • Select Events with Jets • Standard NC DIS Event Selection • Jets Selected using Cone Algorithm - In BCAL • 1° < Jet < 2.2 ° >>---> BCAL||Jet - e | - 180| < 40  • >>---> jets back to back • Forward Energy Flow Resticted: • FCAL Energy Outside 2 Inner Rings < 20 GeV

  10. MC DATA DATA MC Systematics studies - Energy scales Linearity - Energy Response vs. PT Consistent with diffractive method Overall Total Hadronic Response off by 2-3% • FIT EMC/HAC Fractions • HAC 105% +/- 1.5% • EMC 101% +/- 1.0% After correction!!! Collaboration Meeting 17 Oct. 2001

  11. Systematics studies - Energy scales Studies of Calorimeter response to electrons - A.Lopez, M.Moritz After hadronic energy scale correction: Assigned errors of 1.5% for Ee<20GeV / 1% Ee>20GeV - No further correction necessary Collaboration Meeting 17 Oct. 2001

  12. Systematics studies - Energy scales Hadronic energy scale factors (diffractive meth) Factors to be applied to DATA Calorimeter response to electrons: Energy scale errors No E-scale correction Collaboration Meeting 17 Oct. 2001

  13. Systematics studies - Php. Normalization H.Schnurbusch, A.Kappes DIS cuts don’t reject all PhP Photoproduction cross section poorly known => use tagged photoproduction data to normalize PhP Monte Carlo • Selection cuts: • DST bit 12 • Q2DA > 120 GeV2 • Elumi- < 2 GeV (avoid bremstrahlung) • 5 GeV < Elumi-e < 15 GeV (acceptance) • ET > 30 GeV • |Z-vertex| < 50 cm • EelectronCAL > 10 GeV Used Lumi electron detector (35m tagger) to tag photoproduction events Collaboration Meeting 17 Oct. 2001

  14. Systematics studies - Php. normalization 1) Determine number of tagged events in data and MC 2) Correct tagged distribution in DATA for overlayed DIS events. 3) Determine correction factor for PhP cross section in MC from ratio of tagged events in MC/tagged events in data 4) Add correctly normalised PhP MC and DIS MC and compare to DIS data Collaboration Meeting 17 Oct. 2001

  15. Systematics studies - inelastic QED Compton M.Moritz • Question: • Can the QEDC flagged events in DIS MC describe the data? • Method: • Reject elastic QED Compton events • Select events with 2 Sinistra candidates (ecand, cand) • Take events with ecand has a track and cand doesn’t (cand must be within CTD acceptance) • Use cuts to extract high purity sample and see how well it is described by the Monte Carlo Collaboration Meeting 17 Oct. 2001

  16. Systematics studies - inelastic QED Compton • Cuts: • (cand) > 1 rad • |  (ecand) -  (cand)| > 2.5 rad • Only 1 good track in event • E(ecand) + E(cand) > 25 GeV Collaboration Meeting 17 Oct. 2001

  17. Results: - Purity - Efficiency - Data/MC nr. events ~ 1.05% (within stat. errors) Systematics studies - inelastic QED Compton • Conclusions: • High purity sample selected (most additional events flagged as ISR, question of definition in MC). • Cut on one good track only responsible for low efficiency but needed for high purity. • The selected MC sample reproduces the data selected with same method. Collaboration Meeting 17 Oct. 2001

  18. DATA Monte Carlo Eemeas./EeDA (2data-2MC) Systematics studies - Electron energy smearing - M.Moritz Energy resolution not well simulated in Monte Carlo: generally better resolution than in data => smear electron energy in MC Method: 1) Calculate Ee/EDA and plot in bins of Ee 2) Determine widths of DATA and MC distributions data and MC 3) Fit constant to (2data-2MC) (note: E ~ 0.18 E/E) BCAL E/E1/E Collaboration Meeting 17 Oct. 2001

  19. Systematics studies - Electron energy smearing • Analysis done separately for BCAL and RCAL (no stats in FCAL) • 0.030 used to smear Ee linearly:Ee= Eemeas (1+Gauss.(=0.03,=0)) BCAL Collaboration Meeting 17 Oct. 2001

  20.  e- ? Remnant H Systematics studies - Hadronic energy flow R.Goncalo Question: How well does the Monte Carlo describe the hadronisation? (Double angle relies on good reconstruction of H) Method: Define the Hadronic energy flow: average energy deposit per event in islands, calculated in bins of polar angle: Islands: remaining after CorAndCutenergy correction and backsplash cut. Cells corresponding to the electron were discarded Collaboration Meeting 17 Oct. 2001

  21. Systematics studies - Hadronic energy flow BCAL BCAL BCAL FCAL FCAL FCAL FCAL BCAL BCAL RCAL RCAL BCAL BCAL BCAL RCAL RCAL RCAL BCAL BCAL Ariadne (+CorAndCut) seem to describe the data well to first approximation Lepto (MEPS) a bit worse current jet current jet Proton remnant BUT... Collaboration Meeting 17 Oct. 2001

  22. Ariadne MEPS Systematics studies - Hadronic energy flow Superposition of current jet and remnant beampipe 1st IR Now plotting dE/dRFCAL: Energy flow in FCAL 10 cm radial bins remnant Jet in BCAL  Ariadne not good in 1st IR; MEPS closer to data but still not perfect jet Jet in BCAL Jet in BCAL Jet in BCAL Jet in BCAL Jet in BCAL Jet in BCAL Collaboration Meeting 17 Oct. 2001

  23. Systematics studies - Hadronic energy flow • The problem divided itself into: • 1st Inner Ring (remnant/very low y) • Hadronisation of the current jet • 1) First inner ring • Tried varying: • Intrinsic KT of proton (0.01-1.66 GeV, default 0.45 GeV) • KT of proton remnant (0.05-0.8 GeV, default 0.35 GeV) • No clear improvement, small local changes only. • Will find some way of quantifying systematic error for 1st IR. • 2) Hadronisation • Does the difference Ariadne/MEPS quantify our ignorance? Collaboration Meeting 17 Oct. 2001

  24. DATA Ariadne  |Ariadne-MEPS| Systematics studies - Hadronic energy flow Collaboration Meeting 17 Oct. 2001

  25. = Finalised = Understudy = To do Systematics Completion List for 98/99 and 99/00 Data Analyses

  26. Update on analyses results • 1998/99: • Comparison A. Kappes/A. Lopez • Extraction of xG3 and Sum rule Collaboration Meeting 17 Oct. 2001

  27. Comparison of e-p analyses A.Kappes & A.Lopez Collaboration Meeting 17 Oct. 2001

  28. -Z0 Z0 Extraction of xG3 and Sum rule - A.Lopez At LO: FL=0 Can also be written as a sum of terms for  exchange, -Z0 interference and Z0 exchange xF3 can be written in terms of new structure functions xG3 (-Z0 interference) and xH3(Z0 exchange) Can extract xG3 from xF3! Negligible (next slide) With: Collaboration Meeting 17 Oct. 2001

  29. Extraction of xG3 and Sum rule - theory... xG3 has little dependence on Q2 (curves are CTEQ5D) xG3 can be extracted from xF3 Collaboration Meeting 17 Oct. 2001

  30. Extraction of xG3 and Sum rule - extraction xF3 results: old bins - preliminary ZEUS measurement new bins Collaboration Meeting 17 Oct. 2001

  31. Extraction of xG3 and Sum rule - extraction Then extract xG3 in bins of x from xF3 measurement. Q2 dependence is negligible with respect to the statistical errors. Points with same x are combined for all Q2 values Neutrino data was corrected : Collaboration Meeting 17 Oct. 2001

  32. Extraction of xG3 and Sum rule - theory... For Charged Current: (GLS sum rule) (3 valence quarks in proton) For Neutral Current a similar rule can be found: At HERA not all phase space available=> Integral has implicit Q2 dependence ( xmin = xmin (Q2) ) @Q2 = 1500 GeV2 (CTEQ5D) Collaboration Meeting 17 Oct. 2001

  33. Extraction of xG3 and Sum rule - sum rule With our available phase space (theory): Result obtained in this analysis: Result obtained by H1: With polarized bems ZEUS will be able to extend xF3 and xG3 measurement to lower Q2and lower x Collaboration Meeting 17 Oct. 2001

  34. Neutral Current - Conclusions • The FPCHOT bug can now be corrected • Most systematics studies have been completed • Remaining systematics studies are progressing • 98/99 e-p analysis in very good shape - publication expected soon • 99/00 e+p analysis not too far behind e-p Collaboration Meeting 17 Oct. 2001

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