ecal status & studies

ECAL status & studies

Irina Machikhiliyan, 10.10.2012

Tech. stop activities (Sept 2012)Latest Monitoring system repair (tech stop Sept 2012):

One noisy LED group C107 ( 2 LEDs, 32 detector cells)

CELL O 16/46 (LED C107.1) CELL O 23/49 (LED C107.2)

Peak R.M.S. Peak R.M.S.

Run Number Tech. Stop 17-21 Sep, cabling repair

LED Spectrum

Run 127001(2 Sept)

Run 129805(4 Oct)


Also: LED intensity tuning for two LEDs (two cells were in saturation)

Relative ECAL adjustment on the basis of raw occupancies


ECAL occupancies: definition


OCC = Nentries(adc_reading > threshold) / NentriesThreshold is set to 18 ADC counts (for ECAL it is equivalent to

≈ 0.05 GeV of transverse energy)Nentries(full) is the same as the number of events

Typical occupancy map for ECAL(~300K of noBias events, μ = 1.592)

Typical ADC spectrum (~300K of noBias events, one hour of data taking).

Cell O 04/08(one of Outer most

peripheral, i. e. worst statistical case)

ADC countsthreshold

ECAL occupancies: method


• Idea:– Fix occupancy map for certain run as the reference (e.g. the run where the fine

calibration is available) and then correct detector response drift due to rad. damage, PMT, etc. on the level of individual cells, using ratio of occupancies

• Benefits:– raw ADC readings, which means that no reconstruction, no information from other sub-

detectors, no alignment, etc is required– noBias data: at fixed beam energies the only normalization required is the one on μ (see

below). The following slides: occupancies are always normalized on μ.– processing is very fast– statistics collected during one [typical] fill will be enough (see below)– correction is possible for each individual cell

• Limitations: – will not provide or improve absolute calibration, only allowing relative adjustment to

keep trigger rates and detector response more or less stable– precision: particle flux stability; ECAL resolution;– does not take into account changes in PRS/SPD response (though as concerns rad.

damage, it should be correlated with the ECAL damage)

Theoretically, absolute calibration is possible if one takes MC occupancy map as the reference, but it requires very good MC description…

ECAL occupancies: check #1 (1)


• Data Samples:– 28 Aug: run 126660, Fill 3011, μ = 1.724– 29 Aug: ECAL HV change– 31 Aug: run 126831, Fill 3016, μ = 1.592

• Conditions:– Raw Data files– NoBias stream

• Parameters:– Parameter #1 (P1) – normalized occupancy ratio

[OCC(126831) / μ(126831)] / [OCC(126660) / μ(126660)]– Parameter #2 (P2) – required gain change (input

parameter for HV adjustment)



P1 (normalized OCC ratio)

P2(req. gain change)

Occ Change Vs Gain Change



P1 /P2 P1 /P2

P1 /P2 P1 /P2

All Cells Inner

Middle Outer

ECAL occupancies: check #2dependence on μ (1)

• Data Samples:– 31 Aug: run 126831, Fill 3016, μ = 1.592– 02 Sep: run 126972, Fill 3020, μ = 1.700ratio: μ(126972)/μ(126831) = 1.0678


ALL Inner Middle Outer<Occ(126972) / Occ(126831)> 1.065 1.061 1.065 1.068

Good agreement taking into account 2 days of data taking in between + couple of days without beam before fill 3016

ECAL occupancies: dependence on μ (2)


All Cells Inner

Middle Outer

Occ(126972) / Occ(126831

Occ(126972) / Occ(126831

Occ(126972) / Occ(126831

Occ(126972) / Occ(126831

ECAL occupancies: dependence on μ (3)P1 (normalized OCC ratio)


• Data Samples (1 hour of data taking each):– 15 May: run 115556 – taken as the reference– 17 Jun: run 118828Both runs: reco 13a (all CaloCalib coefficients were set to 1)


P1 (normalized OCC ratio)

ECAL occupancies: check #3Verification with π⁰’s (2)

Calo data for run 118828 (bhadron stream) were re-reconstructed using coefficients obtained from normalized occupancy ratios

Input: photons from Phys/StdLoosePhotons/ParticlesSelection cuts: Et(γ) > 200 MeV, Et(γγ) > 1 GeV; NoSpd3x3


Inner Middle Outer

Run 115556 (reco 13a) M = 128.2±0.6σ = 11.86±0.7

M = 134.7±0.4σ = 11.51±0.4

M = 135.4±0.3σ = 12.9±0.3

Run 118828 (reco 13a) M = 123.5±0.5σ = 12.7±0.6

M = 130.4±0.3σ = 11.8±0.3

M = 133.5±0.2σ = 13.12±0.2

Run 118828 (re-rec) M = 129.3±0.6σ = 13.0±0.5

M = 134.5±0.4σ = 12.1±0.4

M = 136.0±0.3σ = 13.0±0.3

ECAL occupancies: check #3Verification with π⁰’s (2)

ECAL occupancies: statistical error


Relative Error for normalized occupancies ratio

Run #1: 126660, 1 hour of data taking, μ = 1.724Run #2: 126661, 1 hour of data taking, μ = 1.736

Fill 3011 (28 Aug):– Runs 126660 … 126673 (~9 hours), μ ≈ 1.7Parameter: R(run) = <OCC(run)/OCC(126660)>, OCC – occupancy,

normalized on average μ for current run


R(126660) R(126661) R(126663) R(126672) R(126673)

Run start: 03:01 am 04:01 05:46 08:16 09:16

ALL cells 1. 0.995r.m.s. 0.029

0.997r.m.s. 0.028

0.998r.m.s. 0.028

0.999r.m.s. 0.028

Inner 1. 0.994r.m.s. 0.027

0.993r.m.s. 0.027

0.996r.m.s. 0.027

0.994r.m.s. 0.027

Middle 1. 0.995r.m.s. 0.028

0.998r.m.s. 0.027

0.998r.m.s. 0.028

1.000r.m.s. 0.027

Outer 1. 0.997r.m.s. 0.030

0.998r.m.s. 0.029

0.999r.m.s. 0.030

1.001r.m.s. 0.030

ECAL occupancies: check #4stability during the fill

UNEXPECTED(for me, at least)



There were two periods when data were taken / initially reconstructed with calibration constants 1. (after HV tuning):

I. Fill 2596 (7 May, run 114752) – Fill 2737 (17Jun, run 118828), CONDDB 20120420

II. Fill 3016 (31 Aug, run 126831) – Fill 3071(16 Sep, run 128480), CONDDB 20120829

OCC(118828) / OCC(114752) OCC(128480) / OCC(126831)

Period I


OCC(115454) / OCC(114752) OCC(115556) / OCC(115454)

OCC(118828) / OCC(11556)

MAGNET POLARITY CHANGE:DOWN → UP

Period II


OCC(128418) / OCC(128100)


OCC(128100) / OCC(128631)

HCAL occupancies


OCC(128100) / OCC(128631) OCC(128418) / OCC(128100)


Attempt to increase the threshold


PmPin(128418) / PmPin(128100)PmPin(115556) / PmPin(115454)

OCC(128480) / OCC(126831), threshold 18 OCC(128480) / OCC(126831), threshold 50

Check with LEDs

Check with π⁰Input: photons from Phys/StdLoosePhotons/ParticlesSelection cuts: Et(γ) > 200 MeV, Et(γγ) > 1 GeV; NoSpd3x3


Run 115454 Run 115556C-side A-side C-side A-side

InnerN = 606.±61.

M = 128.2±0.8σ = 10.1±0.7

N =1011.±46. M = 127.3±0.7σ = 12.3±0.6

N=532. ±34M = 128.5±0.8

σ = 9.8±0.7

N=884. ±42.M = 128.2±0.8σ = 13.5±0.6

MiddleN = 2633. ±84.M = 134.6±0.5σ = 12.8±0.5

N = 2646. ±82.M = 132.9±0.5σ = 12.1±0.4

N = 1817.±69.M = 135.5±0.6σ = 11.4±0.5

N=1805. ±70.M = 133.8±0.6σ = 11.4±0.5

OuterN = 7342. ±158.M = 137.5±0.4σ = 14.1±0.3

N = 7055. ±153.M = 134.9±0.4σ = 13.4±0.3

N = 4950. ±133.M = 137.1±0.5σ = 12.7±0.4

N = 5324. ±131.M = 133.8±0.4σ = 12.9±0.3

No obvious changes in energy scaleNumber of π⁰ in the Outer: (?) reflects change in charged tracks distribution (?)(prefer to check more data / other streams before making any statements)

Conclusions


• Fast tuning / monitoring of ECAL response, based on occupancy values is possible on the level of individual cells. Let’s try?

• Asymmetrical change of occupancy map with magnet polarity change (up to 20% in the Outer)– ECAL energy scale seems to be unaffected– as concerns occupancy tuning / monitoring, the effect

can be easily compensated by comparing occupancies for two fills before and after polarity change and then producing the new reference map, but…

– the reason? How it affects charge particles’ distribution? Can it be seen in MC?

ecal status & studies

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