neutral current 98/99 e - p and 99/00 e + p

R. Goncalo Collaboration Meeting 17 Oct. 2001 1

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 17th 2001

Outline

Systematics studies

Update on 98/99 analysis

Note on FPCHOT bug


Note on FPCHOT bug fixWhat 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


Systematics studies

•Calorimeter energy scale

•Photoproduction Normalisation

•Inelastic QED Compton

•Electron energy smearing

•Hadronisation and FCAL inner ring


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


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/PT

DA

• Check individual calorimeters

• Study the energy response PTH/PT

DA vs hadron

max zMINzMAX


PTH = Hadronic PT from

cells PT

DA = EeDA sin e


Acceptance reduction due to max

cut

Acceptance reduction due to Q2

cut

=>Angular acceptance cuts: 0.05< < 2.75

•Within the Acceptance PTDA

unbiased

HADRON

PTD

A /

PTTR

UE

Partial result from PT

HAD/PTDA alone (no

separation EMC/HAC)

Statistical Error

0.5 % F/B CAL

2% RCAL

MC DATA

FCAL 0.866 0.86

BCAL 0.85 0.825

RCAL 0.8 0.8



Now separate HAC and EMC scales

For each CAL section plot PT

HAD/PTDA 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

HACEMC

EMC

EE

EnEMCfractio

PT peaks at ~6 GeV & extends to ~20 GeV

BCAL: constant offset!

Only need to change factor



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))

Title:

Creator:

Preview:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.

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

Systematics studies - Energy scales:

Jets method



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. PT

Consistent with diffractive method

DATA

MC

After correction!!!


Systematics studies - Energy scalesStudies of Calorimeter response

to electrons - A.Lopez, M.Moritz

Assigned errors of 1.5% for Ee<20GeV / 1% Ee>20GeV

- No further correction necessary

After hadronic energy scale correction:



CAL EMC error HAC Error

FCAL 1.00 0.015 1.00 0.01

BCAL 1.01 0.015 1.05 0.01

RCAL 1.00 0.02 1.00 0.02

Hadronic energy scale factors (diffractive meth)

Factors to be applied to DATA

98/ 99/ 00 Error

Ee < 20 GeV 1.5 %

Ee > 20 GeV 1.0 %

Calorimeter response to electrons: Energy scale errors

No E-scale correction


Systematics studies - Php. Normalization

H.Schnurbusch, A.KappesDIS 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


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


Systematics studies - inelastic QED Compton

M.MoritzQuestion:

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



Cuts:

(cand) > 1 rad

•| (ecand) - (cand)| > 2.5 rad

• Only 1 good track in event

•E(ecand) + E(cand) > 25 GeV



Results:- Purity

- Efficiency

- Data/MC nr. events ~ 1.05%

(within stat. errors)

%76).(

).(

sampleselectedMC

sampleselectedMCAll

dQEDCflagge

%50)_00/99(

).(

analysisMC

sampleselectedMCdQEDCflagge

dQEDCflagge

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.


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-2

MC)

(note: E ~ 0.18 E/E)

DATA

Monte Carlo

(2data-2

MC)

Eemeas./Ee

DA

BCAL

E/E1/E


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


Systematics studies - Hadronic energy flow

R.GoncaloQuestion:

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

Nevents

iiE

Nd

dE

1

)(1

e-

Rem

nan

t

H

?



current jetcurrent jet

Proton remnant

Ariadne (+CorAndCut) seem to describe the data well to first approximation

Lepto (MEPS) a bit worse

BUT...

FCAL BCALBCAL RCAL

BCAL BCAL BCAL

BCALBCAL

BCAL BCAL BCALFCALFCAL

FCAL RCAL

RCALRCALRCAL



Now plotting dE/dRFCAL:

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

Jet in BCAL Jet in BCAL Jet in BCAL

Jet in BCALJet in BCALJet in BCAL



The problem divided itself into: •1st Inner Ring (remnant/very low y)

•Hadronisation of the current jet

1) First inner ringTried 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) HadronisationDoes the difference Ariadne/MEPS quantify our ignorance?



DATA

Ariadne |Ariadne-MEPS|

Systematic Treatment, Status and ValuesAlignment The alignment uncertainty is given in a routine.

Energy scale (Electron) The energy scale for the BCAL/RCAL is to be set as follows:Scaling factors (after CALCOR in data)

Ee < 20 GeV :1.00 +/- 0.015 (1.5% uncertainty)Ee> 20 GeV: 1.00 +/- 0.01 (1% uncertainty)

Non-uniformity corrections The electron Energy systematic will be accounted for in terms of a resolution and scaleuncertainty

Energy scale (HAC) The individual factors for the separate calorimeter sections have been determined asfollows: The factors will be applied to the data:

FCAL EMC 1.00 +/- 0.015HAC 1.00 +/- 0.01

BCAL HAC 1.05 +/- 0.01EMC 1.01 +/- 0.015

RCAL HAC 1.00 +/- 0.02HAC 1.00 +/- 0.02

These factors should be applied directly to the CALTRU table.Backsplash (ZUFO vs

CorAndCut)For CorandCut the energy scale variation is to be applied as above. The systematic on theCorandCut method is to vary the amount of backplash, the latest version of CaC has the

new gamma_max parameters.Chimney/supercrack/RCAL

radiusThis cut includes the end of the BCAL (dead material description) the RCAL radius R >

175.0 cm and the Chimney – due to trigger discrepancies.The cut will remain for both the data and MC, the cut will be such that any cluster is

excluded if found in such a region.Electron finder eff. 1% global variation for all energies and angles (area for improvement ?)

Track matching efficiency 1% global variation for all energies and angles (area for improvement with greaterstatistics?)

RapGap bug fixed The RAPGAP fraction is reweighted by 50% and the acceptance recalculatedTypically gives 0.5% Error

PhP, normalisation andcheck of sample

The photoproduction normalisation will be fixed from the study, the systematic will bebased on the uncertainty of the normalisation of this sample

Pilot bunches study The pilot bunches are subtracted directly – there will be no need for a systematicVertex distribution The nominal vertex distribution is assigned a normalisation uncertainty which spans the

unbiased vertex distribution – the routines already exist for this procedure.Errror ~ 0.5%. The vertex z position needs to be shifted by +/- 4mm, also as part of this

error one must vary the electron track angle by +/- 1 milliradian< 0.5 % Uncertainty

Compton study The contribution of comptons to the cross sections needs to be determined, after the relativenormalisation of the process has been found, further cuts may be needed and an uncertainty

on the normalisation of the Compton background appliedComparison of electron

finder reconstructionmethods

No systematic will be assigned for this.

Trigger efficiency The trigger in the main part is well described, except for the regions we have decided tocut. Uncertainty < 0.5%

Higher Order EW terms A comparison of the higher order terms is nessecary to determine the “correctness” of theradiative corrections in DJANGOH, this is a theoretical uncertainty, this is typically 1%

globally for the whole Q2 RangeInner Ring Study This study will be done in conjunction with the Hadronic Energy Scale and Hadronisation

Systematic. A check on the average Energy will be performed and the variation of thisenergy with different fragmentation schemes.

Hadronisation systematic Energy flows – Pending the result of this study and the above study an error will beassigned.

Systematics Completion List for 98/99 and 99/00 Data Analyses

= Finalised= Understudy= To do


Update on analyses results

1998/99:

•Comparison A. Kappes/A. Lopez

•Extraction of xG3 and Sum rule


Comparison of e-p analyses

A.Kappes & A.Lopez


Extraction of xG3 and Sum rule - A.Lopez

2)1(1 yY ),(),(),(

2

.

)( 2223

224

2

2

2

QxFyQxxFYQxFYxQdQdx

ped NCL

NCNCNCBorn

Can also be written as a sum of terms for exchange, -Z0 interference and Z0 exchange

ZZZxQ 4

22

At LO: FL=0

22

2

22 cossin4

1

ZWWZ MQ

Q

xF3 can be written in terms of new structure functions xG3 (-Z0 interference ) and xH3 (Z0 exchange)

f ffff qxxqaexG )(23

f ffff qxxqvaxH )(23

-Z0

Z0

With:

32

32

3 2)( xHvaxGaqxxqQBxF ZeeZef fff

Negligible (next slide)

Can extract xG3 from xF3!


Extraction of xG3 and Sum rule - theory...

32 xHva Zee

3xGa Ze

xG3 has little dependence on Q2

(curves are CTEQ5D)

xG3 can be extracted from xF3

Zea

xFxG

3

3


Extraction of xG3 and Sum rule - extractionxF3 results:

old bins - preliminary ZEUS measurement

new bins


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

Zea

xFxG

3

3 Neutrino data was corrected : 55.0

1

21

1

3

2

3

3

V

V

V

V

CC

udud

xF

xG


Extraction of xG3 and Sum rule - theory...

For Charged Current:

(GLS sum rule)

31

0

3 CCxFx

dx

For Neutral Current a similar rule can be found:

3

52}{2

1

0

1

0

3 ff

fefff

fe NeadxqqeaxGx

dx

(3 valence quarks in proton)

At HERA not all phase space available => Integral has implicit Q2 dependence

( xmin = xmin (Q2) )

16.165.0

017.0

3 xGx

dx

@ Q2 = 1500 GeV2 (CTEQ5D)


Extraction of xG3 and Sum rule - sum rule

16.1)( 3

65.0

017.0

2 xGx

dxQJ

With our available phase space (theory):

.44.0

45.0.44.017.1)( 2 syststatQJ

Result obtained in this analysis:

.27.0.35.088.1)( 2 syststatQJ

Result obtained by H1: With polarized bems ZEUS will be able to extend xF3 and xG3 measurement to lower Q2 and lower x


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

neutral current 98/99 e - p and 99/00 e + p

Documents

hadronic energy scales

hadronic energy deposits

hadronic pt

fridaycollaboration

rcalcollaboration meeting

factors data

pt peak

wide range of pt