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

R. GoncaloCollaboration Meeting 17 Oct 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/v 2001a.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

R. GoncaloCollaboration Meeting 17 Oct Systematics studies Calorimeter energy scale Photoproduction Normalisation Inelastic QED Compton Electron energy smearing Hadronisation and FCAL inner ring

R. GoncaloCollaboration Meeting 17 Oct 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 P T ~ 5 to ~ 80 GeV Two Methods Used Diffractive Method Allows the isolation of the hadronic energy deposits in each calorimeter. Limited range in P T (peak at ~6 GeV, up to ~20 GeV). Jets Method Isolated Jets can be restricted to the BCAL. Large range in P T 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 = DATA and MC: 98/99/00 Dead material map

R. GoncaloCollaboration Meeting 17 Oct Systematics studies - Energy scales Typical properties of DIS events Event not well contained in central detectors Large Energy loss in beam pipe E HAD 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 y JB > 0.01 and M X > 2 GeV - To ensure sufficient hadronic activity Look at P T Balance P T H /P T DA Check individual calorimeters Study the energy response P T H /P T DA vs  hadron  max z MIN z MAX

R. GoncaloCollaboration Meeting 17 Oct P T H = Hadronic P T from cells P T DA = E e DA  sin  e Systematics studies - Energy scales Acceptance reduction due to  max cut Acceptance reduction due to Q 2 cut =>Angular acceptance cuts: 0.05<  < 2.75 Within the Acceptance P T DA unbiased  HADRON P T DA / P T TRUE Partial result from P T HAD /P T DA alone (no separation EMC/HAC) Statistical Error 0.5 % F/B CAL 2% RCAL 

R. GoncaloCollaboration Meeting 17 Oct Systematics studies - Energy scales Now separate HAC and EMC scales For each CAL section plot P T HAD /P T DA as 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. DATA Monte Carlo P T peaks at ~6 GeV & extends to ~20 GeV BCAL: constant offset! Only need to change factor

R. GoncaloCollaboration Meeting 17 Oct 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))

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

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

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

R. GoncaloCollaboration Meeting 17 Oct 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

R. GoncaloCollaboration Meeting 17 Oct 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 Q 2 DA > 120 GeV 2 E lumi-  < 2 GeV (avoid bremstrahlung) 5 GeV < E lumi-e < 15 GeV (acceptance) E T > 30 GeV |Z-vertex| < 50 cm E electron CAL > 10 GeV Used Lumi electron detector (35m tagger) to tag photoproduction events

R. GoncaloCollaboration Meeting 17 Oct 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

R. GoncaloCollaboration Meeting 17 Oct 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 (e cand,  cand ) Take events with e cand 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

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

R. GoncaloCollaboration Meeting 17 Oct Systematics studies - inelastic QED Compton Results: - Purity - Efficiency - Data/MC nr. events ~ 1.05% (within stat. errors) 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.

R. GoncaloCollaboration Meeting 17 Oct 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 E e /E DA and plot in bins of E e 2) Determine widths of DATA and MC distributions  data and  MC 3) Fit constant to  (  2 data -  2 MC ) (note:  E ~ 0.18 E/  E) DATA Monte Carlo  (  2 data -  2 MC )  Ee meas. /  Ee DA BCAL  E/E  1/  E

R. GoncaloCollaboration Meeting 17 Oct Systematics studies - Electron energy smearing Analysis done separately for BCAL and RCAL (no stats in FCAL) used to smear E e linearly: E e = E e meas (1+Gauss.(  =0.03,  =0)) BCAL

R. GoncaloCollaboration Meeting 17 Oct 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 CorAndCut energy correction and backsplash cut. Cells corresponding to the electron were discarded  e- Remnant  H ?

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

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

R. GoncaloCollaboration Meeting 17 Oct 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 K T of proton ( GeV, default 0.45 GeV) K T of proton remnant ( 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?

R. GoncaloCollaboration Meeting 17 Oct Systematics studies - Hadronic energy flow DATA Ariadne  |Ariadne-MEPS|

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

R. GoncaloCollaboration Meeting 17 Oct Update on analyses results 1998/99: Comparison A. Kappes/A. Lopez Extraction of xG 3 and Sum rule

R. GoncaloCollaboration Meeting 17 Oct Comparison of e - p analyses A.Kappes & A.Lopez

R. GoncaloCollaboration Meeting 17 Oct Extraction of xG 3 and Sum rule - A.Lopez Can also be written as a sum of terms for  exchange,  -Z 0 interference and Z 0 exchange At LO: F L =0 xF 3 can be written in terms of new structure functions xG 3 (  -Z 0 interference ) and xH 3 (Z 0 exchange)  -Z 0 Z 0 With: Negligible (next slide) Can extract xG 3 from xF 3 !

R. GoncaloCollaboration Meeting 17 Oct Extraction of xG 3 and Sum rule - theory... xG 3 has little dependence on Q 2 (curves are CTEQ5D) xG 3 can be extracted from xF 3

R. GoncaloCollaboration Meeting 17 Oct Extraction of xG 3 and Sum rule - extraction xF3 results: old bins - preliminary ZEUS measurement new bins

R. GoncaloCollaboration Meeting 17 Oct Extraction of xG 3 and Sum rule - extraction Then extract xG 3 in bins of x from xF 3 measurement. Q 2 dependence is negligible with respect to the statistical errors. Points with same x are combined for all Q 2 values Neutrino data was corrected :

R. GoncaloCollaboration Meeting 17 Oct Extraction of xG 3 and Sum rule - theory... For Charged Current: (GLS sum rule) For Neutral Current a similar rule can be found: (3 valence quarks in proton) At HERA not all phase space available => Integral has implicit Q 2 dependence ( x min = x min (Q 2 ) Q 2 = 1500 GeV 2 (CTEQ5D)

R. GoncaloCollaboration Meeting 17 Oct Extraction of xG 3 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 xF 3 and xG 3 measurement to lower Q 2 and lower x

R. GoncaloCollaboration Meeting 17 Oct 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