D.Cavalli, S. Resconi

Etmiss Reconstruction and Calibration in Athena

Workshop on Energy Calibration of the ATLAS calorimeters July 23, 2002

D.Cavalli, S. Resconi

Reconstruction & Calibration • Starting point : Etmiss reconstruction from all calorimeter cells Comparison of reconstructed Etmiss quantities per calorimeter and total between Athena and Atrecon • To have an Etmiss value “usable” for physics studies : Calibration Contribution of muons and eventually not full-simulated calorimeter regions• To evaluate Etmiss resolution : MC truth Etmiss Calculation of SumEt : ( Etmiss) SumEt • Calibration : Region Calibration , H1-Style Calibration Comparison with the refined calibration method applied

in ATLAS Physics Technical Design Report, TDR Calibration

D.Cavalli, S. Resconi

Next slide : • Comparison of not calibrated Etmiss_calo between

Athena and Atrecon : On a sample of TDR full simulated data (98_2): bbA - had m(A )=150 GeV , 665 evts

full simulation within || < 3 read with Atrecon: release 1.3.0 (atrecon-01-42-29) and Athena: release 3.1.0, used RecExample +

new MissingET package (now in current release ) No energy threshold applied (no noise added yet !!)

Ex(y)miss_calo = - Ex(y) performed on calo cells

Etmiss reconstruction from calorimeters :

D.Cavalli, S. Resconi

Athena - Atrecon Athena - Atrecon superimposed superimposed (!!) distributions of ETmiss in calos(!!) distributions of ETmiss in calos

PS BarrelPS Barrel EM BarrelEM Barrel

EM EndCapEM EndCap TileTile

HECHEC PS EndCapPS EndCap (only Athena histo)(only Athena histo)

11 22

33 44

55 77

D.Cavalli, S. Resconi

• Forward Calorimeter (Calo 6) has not been full simulated in this event sample

• Perfect agreement of Etmiss_calo reconstruction in Calorimeters between Athena and Atrecon (!!)

• PS EndCap contribution not included in Atrecon Etmiss routine (EMISREC) , so the total not calibrated reconstructed Etmiss is slightly different between Athena and Atrecon

Total Etmiss Total Etmiss |||<3|<3 Total Etmiss Total Etmiss |||<3|<3

AthenaAthena AtreconAtrecon

< > ~ 47.3< > ~ 47.3 < > ~ 46.9< > ~ 46.9

D.Cavalli, S. Resconi

(1) Calibration : a first rough method = Region Calibration

• 7 calibration constants : ( MissingETRegionCalib class)

are applied to the partial contributions from the calorimeters: Ex(y)miss_reg_calib += const( 17 ) Ex(y)miss_calo ( 17 ) Etmiss_reg_calib = sqrt (Exmiss_calib 2 + Eymiss_calib 2)

have been obtained minimizing Etmiss resolution of bbA • new calibrated quantities added to output CBNT • possibility to change default calibration constants in the JobOptions

Contributions implemented in the Athena MissingET package :

To obtain an Etmiss value “usable” for physics analysis

D.Cavalli, S. Resconi

AthenaAthena

Etmiss before calib Etmiss before calib |||<3|<3

Etmiss after calib Etmiss after calib |||<3|<3

Etmiss Resol. before calib Etmiss Resol. before calib |||<3|<3

Etmiss Resol. after calib Etmiss Resol. after calib |||<3|<3

~ 9~ 9

~ 5.4~ 5.4

< > ~ 47.3< > ~ 47.3

< > ~ 57< > ~ 57

- - -- - - =TRUTH =TRUTH EtmissEtmiss

D.Cavalli, S. Resconi

(2) Contribution of not full-simulated calorimeter regions :

when the full simulation is not performed till || = 5

accessing MC truth info

(3) Muon contribution :

accessing MC truth info (will substituted by

reconstructed muons when available in Athena)

(4) MC truth Etmiss :

to calculate directly from CBNT the Etmiss resolution

(5) Calculation of SumEt = ET calo cells within ||< 5 and

Calibration: SumEt_reg_calib += const( 17 ) SumEt_calo ( 17 )

Etmiss Resolution||<3 == ( Ex(y)miss Rec ||<3 - Ex(y)miss Truth ||<3 )

Ex(y)miss Truth= - px(y) of stable parts except neutrinos and ’s

To evaluate Etmiss resolution

( Etmiss ) SumEt

D.Cavalli, S. Resconi

All Etmiss MC truth quantities calculated in CBNT_MissingETtruth class in Athena MissingEt package :

• a separate CBNT algorithm for Etmiss MC truth quantities from the reconstructed ones• calculation of : “true” Etmiss : from neutrinos (no cut) Etmiss seen in calorimeters : from stable particles in calos (= no neutrinos , no ` s) for 2 -ranges : with |-range| < etafullsim with etafullsim < ||--range| < 5| < 5 etafullsim parameter = --range of full simulation,

set by the user in the JobOptions

truth muon contribution : from "measurable" muons with pt > 6 GeV and ||| | < = 2.5

D.Cavalli, S. Resconi

Etmiss quantities to be used in physics analysisEtmiss quantities to be used in physics analysis

Etmiss TruthEtmiss Truth (from neutrinos)(from neutrinos)Etmiss Calib + forward (p.l.) + Etmiss Calib + forward (p.l.) + (p.l.) (p.l.)

Final Etmiss ResolutionFinal Etmiss Resolution

~ 6.8~ 6.8

< > ~ 24.4< > ~ 24.4 < > ~ 25.3< > ~ 25.3

< > ~ 185< > ~ 185

SumET Calib + forward (p.l.)SumET Calib + forward (p.l.)

Etmiss to beEtmiss to beused forused for physicsphysics

Sumet to beSumet to beused forused for physicsphysics

D.Cavalli, S. Resconi

• comparing with the results published in the TDR, that have been

obtained with a more refined calibration method: (1) TDR Calibration • a slightly worse resolution has been obtained with this first rough

calibration method implemented in Athena: (2) Region Calibration • some promising results with an other calibration approach

implemented in Athena : (3) H1-Style calibration • comparison between those different approaches on a wider statistic

(preliminary results !!) More in details

final Etmiss Resolution = = ( Ex(y)miss Rec ||< 5 - Ex(y)miss Truth (no cut) )

takes into account also detector coverage

D.Cavalli, S. Resconi

(1) TDR Calibration :

• Results published in the ATLAS Physics Technical Design Report (TDR) have been obtained using different set of calibration constants for hadronic cluster cells, em cluster cells and cells outside clusters in each calorimeter region

• This means to: start from the identified objects (jets, e/ clusters, tau jets), and

calibrate all associated cells , calibrate cells outside clusters (using minimum bias events) sum all contributions at cell level to calculate final Etmiss…. If the identified objects are already correctly calibrated, in principle,

the final Etmiss is automatically calibrated too, only cells outside clusters contribution should be corrected …

• This refined calibration method can be applied only after cluster identification and calibration…more work needed to implement all that in Athena

D.Cavalli, S. Resconi

Etmiss Resolution = ( Ex(y)miss Rec ||< 5 - Ex(y)miss Truth (no cut) )SumEt = ET calo cells within ||< 5

Published in ATLAS physics TDR - 1999Published in ATLAS physics TDR - 1999

Etmiss Resolution = 0.46 SumEt

bbA evts

Noise addedEcell > 1.5 (Noise)

D.Cavalli, S. Resconi

(2) Region Calibration in Athena:

• is an approximation of the complete Etmiss calibration: the present constants are average constants for cells in em clusters,

hadronic clusters and outside clusters

• calibration constants depend on physics event type and energy (!!) : 3 sets of calibration constants have been provided for low, middle and high range of A masses

• users can calculate calibration constants for their own physics events using Etmiss truth quantities from CBNT

• This is a rough calibration method that has been implemented in Athena as first step to provide soon a “usable Etmiss” for

physics

D.Cavalli, S. Resconi

(3) H1-Style Calibration in Athena:

• First attempt to calibrate Etmiss with H1-Style calibration method in Athena

• Simple approach : used available weights tuned for jets (see next slide): • New calibration class in MissingET package (MissingETH1Calib class ) : apply H1 weights to all calorimeters cells entering in the Etmiss calculation 4 new calibrated quantities in output CBNT : Ex(y)miss_H1_calib, Etmiss_H1_calib, SumEt_H1_calib

D.Cavalli, S. Resconi

(3) H1-Style Calibration in Athena:

• H1 weights : from Table 1 of note “H1-Style Jet Calibration in Athena” , by H. Ma, F.E. Paige, S. Rajagopalan ( 3 May 2002 ): tuned for jets (JET35 sample, TDR geometry) depend on cell energy and Calorimeter region dependency is not yet taken into account, as first approximation

for the moment hardwired in the code (still to think how to

make them accessible from the jobOptions)

• Comparison between Etmiss Region Calibration and Etmiss H1-Style Calibration on 2 mass points :

m(A )=150, 800 GeV

preliminary results...

D.Cavalli, S. Resconi

m(A)=150 GeV

~ 5.4~ 5.4

~ 4.5~ 4.5

< > ~ 55.5< > ~ 55.5

< > ~ 57< > ~ 57

Etmiss after Etmiss after REGREG calib calib |||<3|<3

Etmiss after Etmiss after H1 H1 calib calib |||<3|<3

- - -- - - =TRUTH =TRUTH EtmissEtmiss Etmiss Resol. After Etmiss Resol. After REG REG calib calib |||<3|<3

Etmiss Resol. After Etmiss Resol. After H1 H1 calib calib |||<3|<3

Etmiss:Etmiss:<REG/truth> =<REG/truth> =

= 0.997= 0.997

Etmiss:Etmiss:<H1/truth> =<H1/truth> =

= 0.965= 0.965

D.Cavalli, S. Resconi

m(A)=800 GeV

~13.2~13.2

~11.4~11.4

< > ~103.2< > ~103.2

< > ~99.72< > ~99.72

Etmiss after Etmiss after REGREG calib calib |||<3|<3

Etmiss after Etmiss after H1H1 calib calib |||<3 |<3

Etmiss Resol. after Etmiss Resol. after REG REG calib calib |||<3|<3

Etmiss Resol. after Etmiss Resol. after H1 H1 calib calib |||<3|<3

Etmiss:Etmiss:<REG/truth> =<REG/truth> =

= 1.040= 1.040

Etmiss:Etmiss:<H1/truth> =<H1/truth> =

= 1.004= 1.004

- - -- - - =TRUTH =TRUTH EtmissEtmiss

D.Cavalli, S. Resconi

• Event samples : physics channels: bbA - had,

bbA had - had

A mass points : m(A )=150, 300, 450, 600, 800 GeV

total number of evts : ~ 5650

TDR full simulated data (98_2) within || < 3, read with

Athena: release 3.2.0, used RecExample + new

MissingET package

Preliminary comparison of these 2 new implemented calibration methods in Athena with

Atlas physics TDR results on a wider statistic

D.Cavalli, S. Resconi

Etmiss Resolution = ( Ex(y)miss Rec ||< 5 - Ex(y)miss Truth (no cut) )SumEt = ET calo cells within ||< 5

No Noise addition in Athena results No Noise addition in Athena results (not yet available) (not yet available) !! !!

REGION REGION + + TDRTDR calibration calibration H1-StyleH1-Style + + TDR TDR calibrationcalibration

D.Cavalli, S. Resconi

Added an event sample with e decays : physics channels: bbA e - had total number of evts : ~ 2500 (low statistic)

Red curve = all decay channels weighted

with the right decay BR: BR(bbA e - X) ~30 %

H1-StyleH1-Style + + TDR TDR calibrationcalibration

H1-StyleH1-StyleH1-StyleH1-Style

D.Cavalli, S. Resconi

H1-Style Calibration seems a very powerful and promising method to calibrate Etmiss :• Etmiss resolution “seems “ in nice agreement with TDR results (but...no noise added !)• Etmiss mean value in agreement with the Truth mean value within few % • H1-Style Calibration results to be refined : on more statistic with noise addition (when it will be available in Athena) : expected a worsening of the results (!!) re-tuning H1 weights (?) TDR Calibration to be implemented ...

WORK IN

PROGRESS...

H1-StyleH1-Style + + TDR TDR calibrationcalibration

Conclusions :

D.Cavalli, S. ResconiATLAS Software Week, May 30, 2002ATLAS Software Week, May 30, 2002

Fitted H1 weights for JetsFitted H1 weights for Jets

1.2411.2411.0521.0521.2061.2061.0411.0418=98=9

1.2021.2021.1041.1041.1281.1280.9640.96477

1.0781.0781.1351.1351.4511.4510.9840.98466

1.0001.0001.2231.2231.0791.0791.0431.04355

0.9220.9221.3551.3551.1651.1651.1371.13744

0.9500.9501.8941.8941.5001.5001.4231.42333

1.1631.1632.2302.2301.3931.3931.6451.64522

3.1233.1233.9993.9992.0002.0001.2031.2030=10=1

W(HEC)W(HEC)W(Tile)W(Tile)W(EM3)W(EM3)W(EM2)W(EM2)BinBin

Cryo term = 0.471* (EEM3 * ETile)Gap weight = 0.915

ET Bins = 1/32, 1/16, 1/8, … 16 GeV

From talk by Srini, ATLAS Software Week, May 30 2002