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Study of ECAL resolution Alexandr Kozlinskiy Budker Institute of Nuclear Physics, Novosibirsk

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- Motivation
- Tools
- "Beam test conditions".
- Energy resolution.
- MC corrections
- Results
- Next step

Alexandr Kozlinskiy

Resolution on beam test

11th Vienna Conference on Instrumentation

"Calorimeters for collider experiments"

( Andrey GOLUTVIN (ITEP Moscow) )

- Resolution on beam test gives:
- MC of one module gives the same results.

Test beam results

Alexandr Kozlinskiy

Energy resolution DC04

Olivier Deschamps

results for DC04

SPD hit

MC of PGUN photons in DC04:

no SPD hit

no SPD, no PS

σE/E (%)

1/√E (GeV1/2)

Alexandr Kozlinskiy

Resolution parameters are important for understanding pools and fits.

- Why resolution become worse?
- Experts say that SPD and PS
- should not worsen resolution.
- Are there bugs in MC?
- Or is it dead material before ECAL?

Alexandr Kozlinskiy

- 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.

Alexandr Kozlinskiy

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:

- Gauss v25r7
- Boole v12r10
- Brunel v30r14
- DaVinci v17r8

ECAL

particle

direction

initial

vertex

time

correction

center

of

interaction

z

Alexandr Kozlinskiy

Vertex:

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

( before ECAL inner zone )

- energy resolution
- space resolution

Alexandr Kozlinskiy

- 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.

166 GeV

185 GeV

Along x-axis:

92.3 GeV

55.4 GeV

Reconstructed energy is about 5% less then MC energy of photon.

Alexandr Kozlinskiy

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.

166 GeV

185 GeV

Along x-axis:

92.3 GeV

55.4 GeV

Space resolution along

Y axis of detector is

about 1.5 mm.

Alexandr Kozlinskiy

- 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)

1.

2.

Fits with functions 1 and 2 give very different results.

Alexandr Kozlinskiy

Here we see that fit

with noise term is better

than without one.

Energy resolution is in

good agreement with

beam test.

The only difference is

noise term which can be

described by corrections

in Boole.

5 % difference from MC photon energy

Alexandr Kozlinskiy

4. Energy resolution dependence from vertex z-position

Here we see dependency of parameters A, B and C in

from vertex z-position.

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

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

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

350 MeV

Alexandr Kozlinskiy

Energy resolution dependence from vertex z-position

With fixed noise parameter: C = 350 MeV

12 %

1.0 %

C = 350 MeV, B = 1.0 %

B parameter is very close to 1.0 %.

We can try to fit energy resolution with fixed B and C parameters.

Alexandr Kozlinskiy

Gauss: [GaussCalo::EcalSensDet algorithm v8r4]

3) local nonuniformity

LHCb ECAL uniformity of response

no contribution

( time shifting of vertex )

11th Vienna Conference on Instrumentation

"Calorimeters for collider experiments"

( Andrey GOLUTVIN (ITEP Moscow) )

Boole: [CaloDigit::CaloDigitAlg algorithm v2r2]

1) gain errors - 1 %

2) noise - about 1.5 channels

Alexandr Kozlinskiy

Resolution dependence from gain errors

Resolution without gain errors correction in Boole.

1.0 %

0.6 %

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

350 MeV

Fixing noise term on 350 MeV.

Alexandr Kozlinskiy

Resolution dependence from gain errors

C = 350 MeV

0.6 %

C = 350 MeV, B = 0.6 %

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

Alexandr Kozlinskiy

Resolution dependence from noise

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

Noise has fall to 200 MeV:

it is the value of beam test

Without noise C term fall to 200 MeV.

We can say that 1.5 adc = 150 MeV.

200 MeV

To compare resolution dependency

to normal mode, let\'s fix C term on 200 MeV

Alexandr Kozlinskiy

Resolution dependence from noise

C = 200 MeV

1.0 %

C = 200 MeV, B = 1.0 %

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

Alexandr Kozlinskiy

Resolution dependence from nonuniformity

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

350 MeV

Let\'s fix C parameter as in

normal mode.

Alexandr Kozlinskiy

Resolution dependence from nonuniformity

C = 350 MeV

1.0 %

C = 350 MeV, B = 1.0 %

And fix B parameter on 1.0 %.

Alexandr Kozlinskiy

Different modes with fixed B and C terms

no local nonuniformity

C = 350 MeV, B = 1.0 %

normal mode

C = 350 MeV, B = 1.0 %

11.2 %

10.8 %

Normal mode and

modes without

noise and gain

errors almost

identical.

While mode without

local nonuformity

has slight better

resolution before

ECAL.

no noise

C = 350 MeV, B = 0.6 %

no gain errors

C = 200 MeV, B = 1.0 %

Alexandr Kozlinskiy

Resolution for inner ECAL area:

Energy resolution:

Space resolution:

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.

Alexandr Kozlinskiy

Irina\'s effect.

There will be new correction

to the adc value for hits which will

be added soon (Irina\'s effect).

This effect has probability about 1 %

and value about 15-20 adc.

probability: 1 %

adc

Alexandr Kozlinskiy

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