study of ecal resolution alexandr kozlinskiy budker institute of nuclear physics, novosibirsk

Study of ECAL resolution

Alexandr KozlinskiyBudker Institute of Nuclear Physics, Novosibirsk

Alexandr Kozlinskiy 2

Outline

1. Motivation2. Tools3. "Beam test conditions".4. Energy resolution.5. MC corrections6. Results7. Next step


1. MotivationResolution on beam test

Resolution on beam test gives:

MC of one module gives the same results.

E

MeV

EE

E 145%8.0

%4.9

Test beam results

11th Vienna Conference on Instrumentation"Calorimeters for collider experiments"( Andrey GOLUTVIN (ITEP Moscow) )


E

MeV

EE

E )12190()%05.062.1(

)%3.08.11(

MC of PGUN photons in DC04:

1. MotivationEnergy resolution DC04

σE/E

(%

)

1/√E (GeV1/2)

Olivier Deschampsresults for DC04

E

MeV

EE

E )5160()%02.034.1(

)%1.09.10(

E

MeV

EE

E )2595()%07.047.1(

)%4.04.10(

SPD hit

no SPD hit

no SPD, no PS


Why resolution become worse?

Experts say that SPD and PSshould not worsen resolution.

• Are there bugs in MC?• Or is it dead material before ECAL?

E

MeV

EE

E 145%8.0

%4.9

E

MeV

EE

E 190%6.1

%8.11

1. Motivation

Resolution parameters are important for understanding pools and fits.


We can try to recreate beam test conditions.

There are two ways to do it:1. remove all material before ECAL in MC. But it is to hard to debug.2. place particle just before ECAL. In this case however we have to take into account time of particle birth.

Of course we will not have the same conditions as in the beam test:there are many corrections in MC - noise, gain errors etc.

1. Motivation


2. Tools.

1. Gauss v25r72. Boole v12r103. Brunel v30r144. DaVinci v17r8

Standard particle gun was changed to make it possible to generate particle at any point in the detector with respect to time needed for this particle to fly from center of interaction to the initial vertex:

z

initialvertex

ECAL

particledirection

centerof

interaction

timecorrection


Vertex:381.5 mm, 383.2 mm, 12468 mm, +41.7 ns

( before ECAL inner zone )

• energy resolution• space resolution

3. "Beam test conditions"


Energy resolution

%100

sim

recsim

E

EE

Relative energy difference distributions for different energies of photon:13 points from 0.4 to 8 GeV of transverse energy.

So there are 13 histograms with 1000 events in each histogram.

Along x-axis:

185 GeV 166 GeV

92.3 GeV 55.4 GeVReconstructed energy is about 5% less then MC energy of photon.


Space resolution

mmE

P

E

P

rec

recy

sim

simy 12500

185 GeV 166 GeV

55.4 GeV92.3 GeV

Along x-axis:

Angle difference is multiplied by 12500 mm ( distance to ECAL from center of interaction ) to make mm units (space resolution).

The same 13 samples of events with different energies were used.

Space resolution alongY axis of detector isabout 1.5 mm.


We have many energy and space distributions for different energies of photon.

We can use 2 different functions to fit energy resolution:(with noise term) and (without noise term)

BE

A

E

C

E

E

B

E

A

E

E

Energy and Space resolution

1. 2.

Fits with functions 1 and 2 give very different results.


Energy and Space resolution

%0.1%5.9300

EE

MeV

E

E5 % difference from MC photon energy

mmE

mm

E

mmY 5.0

99

Here we see that fitwith noise term is betterthan without one.

Energy resolution is ingood agreement withbeam test.

The only difference isnoise term which can bedescribed by correctionsin Boole.


350 MeVThere should be no dependence of noise term from vertex z-position. So we fix it on 350 MeV.

4. Energy resolution dependence from vertex z-position

Here we see dependency of parameters A, B and C infrom vertex z-position.

Red points: C = 0 MeV ( fit without noise - function number 2 )

BE

A

E

C

E

E

There is visible difference for red and black points which shows that A and C parameters influence each other.


With fixed noise parameter: C = 350 MeV

C = 350 MeV, B = 1.0 %

1.0 %

Energy resolution dependence from vertex z-position

B parameter is very close to 1.0 %.We can try to fit energy resolution with fixed B and C parameters.

12 %


5. MC corrections

NoiseincoherentisecoherentNoGain

EnergygainErroradcValue 1

1) gain errors - 1 % 2) noise - about 1.5 channels

Boole: [CaloDigit::CaloDigitAlg algorithm v2r2]

Gauss: [GaussCalo::EcalSensDet algorithm v8r4]

gtimeBinniniformitylocalNonUntionbirkCorrechitEnergyhitEnergy

3) local nonuniformityno contribution

( time shifting of vertex )

LHCb ECAL uniformity of response

11th Vienna Conference on Instrumentation"Calorimeters for collider experiments"( Andrey GOLUTVIN (ITEP Moscow) )


Resolution dependence from gain errors

350 MeV

With removing of gain errors B term fall from 1.0 % to 0.6 %.

Fixing noise term on 350 MeV.

1.0 %

0.6 %

Resolution without gain errors correction in Boole.


C = 350 MeV

C = 350 MeV, B = 0.6 %

Resolution dependence from gain errors

0.6 %

Fixing B and C term on 0.6 % and 350 MeV respectively.


Resolution dependence from noise

200 MeV

Noise consist of 2 terms:coherent noise - 0.3 adcincoherent noise - 1.2 adc

Without noise C term fall to 200 MeV.We can say that 1.5 adc = 150 MeV.

To compare resolution dependencyto normal mode, let's fix C term on 200 MeV

Noise has fall to 200 MeV: it is the value of beam test


C = 200 MeV

C = 200 MeV, B = 1.0 %

Resolution dependence from noise

1.0 %

Fixing C term on 200 MeV and B term on 1.0 %.


Resolution dependence from nonuniformity

350 MeV

Local nonuniformity doesn't give any visible changes in parameters on this stage.

Let's fix C parameter as innormal mode.


Resolution dependence from nonuniformity

C = 350 MeV

C = 350 MeV, B = 1.0 %

1.0 %

And fix B parameter on 1.0 %.


no gain errorsC = 200 MeV, B = 1.0 %

no noiseC = 350 MeV, B = 0.6 %

normal modeC = 350 MeV, B = 1.0 %

no local nonuniformityC = 350 MeV, B = 1.0 %

Different modes with fixed B and C terms

Normal mode andmodes withoutnoise and gainerrors almostidentical.

While mode withoutlocal nonuformityhas slight betterresolution beforeECAL.

11.2 % 10.8 %


6. Results

1. We have the same resolution as in Beam Test when vertex is placed just before ECAL.

2. With full MC - the resolution is the same as before.

3. The main conclusion from plots on previous slide is that corrections in MC are right and main source of resolution worsening is dead material before ECAL.

Energy resolution:

Space resolution:

E

MeV

EE

E )30350()%1.00.1(

)%5.05.12(

E

mmmm

E

mmY

)725()1.03.0(

)312(

Resolution for inner ECAL area:

E

MeV

EE

E 145%8.0

%4.9

E

MeV

EE

E 300%0.1

%5.9

E

MeV

EE

E )12190()%05.062.1(

)%3.08.11(


7. Next step

Irina's effect.

adc

There will be new correctionto the adc value for hits which willbe added soon (Irina's effect).

This effect has probability about 1 %and value about 15-20 adc.

probability: 1 %

study of ecal resolution alexandr kozlinskiy budker institute of nuclear physics, novosibirsk

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