in situ hadronic e/p calibration of the atlas barrel calorimeters using minimum bias events...

IIn situ Hadronic E/p Calibrationn situ Hadronic E/p Calibration of the ATLASof the ATLASbarrel calorimetersbarrel calorimeters using Minimum Bias Eventsusing Minimum Bias Events

N.Huseynov1,2, Y.Kulchitsky1,3, P.Tereshko1,3,V.Vinogradov1

1.JINR, Dubna, Russia1.JINR, Dubna, Russia2.IP ANAS, Baki, Azerbaijan 2.IP ANAS, Baki, Azerbaijan 3.IP NAS, Minsk, Belarus3.IP NAS, Minsk, Belarus

18.04.23 14:59 N.Huseynov The Xth International School-Seminar, Gomel

The ATLAS experiment at the LHC will have the huge physics discoverypotential, in particular in the detection of a heavy Higgs boson. Calorimeters will play a crucial role in it. The key question of calorimetry is the absolute energy calibration.

The precise measurement of the momentum of hadrons in the tracking

detectors ( ), compared to the energy E measured

in the calorimeters ( ) can provide a calibration of the response of the calorimeter to pions at the percent level. The tracking system can be used to verify the hadronic calorimeter calibration in the energies rage between 400 MeV to about 200 GeV. The E/p ratio allows to check the absolute energy scale calibration over the pseudo-rapidity range of the tracking detectors which covers the barrel part of LAr and Tile Calorimeter ( |η| <1). The single hadron E/p performances are studied in two data samples: the minimum bias sample (within energy range from 400 MeV to 12 GeV, may be more) and in tau single prong decay, with tau from W and Z decays (which covers the energy range between 10 to 150 GeV).

It was used MonteCarlo data: mc08.105001.pythia_minbias.recon.ESD.e357_s462_r541 - (dataset name)containing 250K events, ( ≈ 6 mil. tracks).

MMotivationotivation

)(0.00034)( 441 TPTP=TP

TP

EEE % 2295% 2.09.3% 267

25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel

ATLAS DETECTORATLAS DETECTORR


Analysis of Minimum Bias EventsAnalysis of Minimum Bias Events

Event Selection:•Rejection of events with energy deposition ELAr0 > 3σ

noise_cell (150 MeV)

•Selection of events with energy depositions (E > 2σnoise_cell

) in the LAr2

and LAr3 layers•Shower isolation:

η -P track selection: |ηtrack | < 0.6 1< Ptrack< 8 GeV/c by step of 1 GeV/c.Quality of tracks:At least one hit in the B layer of the pixel detectorNo more than one hole in the other pixel and SCT layersχ2/ndof < 2. The ID tracking performance group doesn't recommend to use cut on the χ2. We will not use this cut in our future analysis.

Energy reconstruction by the Local Hadronic Calibration method for cells with Ecell > 2σnoise (σnoise are different for each sampling).

Tracks isolation: no other tracks within ∆Rdistance< 0.4 (η,φ coordinates)

1.0P/,E1.1,1.1EK iiiiisol


Results: E/P distributions for P=1 - 5 GeV/cResults: E/P distributions for P=1 - 5 GeV/cwith LAr cuts: ELAr0<3σ

noise_cell; ELAr2 and ELAr3>2σ

noise_cell

<E/P>=0.99±0.02σ=0.51±0.02

2-3 GeV1 - 2 GeV

<E/P>=0.966±0.025

σ=0.525±0.025

1-2 GeV

<E/P>=0.96±0.03σ=0.50±0.03

4-5 GeV

<E/P>=1.05±0.02σ=0.40±0.03σ=0.46±0.01

<E/P>=1.03±0.01

3-4 GeV


Results: E/P distributions for P=5 - 8 GeV/cResults: E/P distributions for P=5 - 8 GeV/cwith LAr cuts: ELAr0<3σ

noise_cell, ELAr2 and ELAr3>2σ

noise_cell

5 - 6 GeV

<E/P>=1.11±0.02σ=0.36±0.02

7 - 8 GeV

<E/P>=1.10±0.05

σ=0.39±0.05

6 - 7 GeV

<E/P>=1.10±0.03

σ=0.36±0.03


Results of the analysis: linearity Results of the analysis: linearity

There is linearity for E>3 GeV : the points are within ±1% within the errors.

Nonlinearity is observed. This is an effect of the noise cuts: selection of cells with E cell> 2σnoise that leads to energy losses especially at low energies (E<3 GeV).


General agreement between the obtained minbias events resolution and the extrapolation of the CTB04 resolution is observed. (ATL-TILECAL-PUB-2008-009)

E.Abat et al. "Study of the response of the ATLAS central calorimeter to pions of energies from 3 to 9 GeV"; ATL-COM-GEN-2009-009

Our energy resolution (hadronic scale ) about 1.1-1.5 times better than resultfrom this work (EM scale)

Comparison with CTB-2004 resultsComparison with CTB-2004 results

E1

ATL-TILECAL-PUB-2008-009

ATL-COM

-GEN-2

009-

009

given

study


Conclusions Conclusions We have investigated the possibility in situ E/p Calibration of the

ATLAS barrel calorimeters on the basis of Minimum Bias Events (250K events,

6 million tracks, ATHENA release 14.2.20) and the Local Hadronic Calibration Method for particles

with |η| < 0.6 and P > 1 GeV/c with 1 GeV/c step.

It is shown that such calibration is possible.However, nonlinearity is observed especially at low energies

(E<3 GeV/c) due to effect of the noise cuts: selection of cells with E cell> 2σnoise that leads to energy losses. There is linearity for P>3 GeV: the points are within ±1% within the errors. Agreement between the minimum bias energy calorimeter resolution and the CTB04 testbeam one (Y.Kulchitsky et al. ATL-TILECAL-PUB-2008-009) is observed.The used simulated data in this work, 250K minbias events, will be registered by ATLAS during about 5 days at the integrated luminosity of 5 pb-1 (ATL-COM-PHYS-2008-074, ATL-COM-PHYS-2009-081).


We should reject background from egamma and neutral hadrons (K0 and π0 ).

We should reject fake traks.

We are going to use low energy hadrons without showering in

Lar calorimeter from minbias events for calibration of TILE

calorimeter.

We should use more statistic of the Minimum bias events to

E/P study in the energy range between 8 to 12 GeV, may be

more.

PLANSPLANS


Why should we measure minimum bias at ATLAS?– dNch/dη at η = 0: compare to NSD data from SppS and Tevatron.– Pile-up studies: calorimeter & physics analyses.– Overlap with underlying event studies: jets studies, VBF, …– Expected to improve modeling of soft hadronic interactions– Inter-calibration of detector elements: uniform events.– Baseline for heavy-ion studies.

pp collisions at the LHC

•Essentially all physics at LHC are connected to the interactions of quarks and gluons (small & large transferred momentum).•Hard processes (high-pT): well described byperturbative QCD•Soft interactions (low-pT): require nonperturbative phenomenological models

•Minimum-bias and the underlying event aredominated by “soft” partonic interactions.

14

Measuring the minimum bias events at ATLAS

First, you need to select minimum bias events…

difndifddifselastot ...

σNSD ~ 65 - 73mbσtot ~ 102 - 118 mb

(PYTHIA) (PHOJET) (PYTHIA) (PHOJET)

Minimum bias Minimum bias trigger trigger

scintillators scintillators (MBTS)(MBTS)

15

• Experimental definition: depends on the experiment’s trigger!

• “Minimum bias” is usually associated to non-single-diffractive events (NSD), e.g. ISR, UA5, E735, CDF,…

σNSD ~ 65 - 73mbσtot ~ 102 - 118 mb

(PYTHIA) (PHOJET) (PYTHIA) (PHOJET)

• At the LHC, studies on minimum bias should be done early on, both for collisions at √s=900 GeV and √s=14 TeV at low luminosity to remove the effect of overlapping proton-proton collisions!

• A minimum-bias event is what one would see with a totally inclusive trigger.

• On average, it has low transverse energy, low multiplicity. Many can be diffractive (single and double).

UA5UA5

CDFCDF

Minimum bias eventsMinimum bias events

difndifddifselastot σ+σ+σ+σ=σ ...


In this method the reconstructed energy in a calorimeter is

Tile)DM(LArE+TileE+LArE=recE

LAr3E+LAr2E+LAr1E=LArE

Tile2E+Tile1E+Tile0E=TileE

Longitudinal samplings – LAr1, LAr2, LAr3, Tile0, Tile1, Tile2

cellhadE=samplingE

cellem

cellhad Ew=E

cellMCem,

EcellMCtrue,

E=w

ρ,sampling,

particleEw=f

cellcellem volumeE=ρ /

─ weights, Monte Carlo simulation

─ Energy density in cell

)(EE cellhad

cellem ─ cell energy deposition in

electromagnetic (hadronic) scale

Local Hadronic Calibration Method Local Hadronic Calibration Method


We have used our own created weights.Weights were packed to TProfile2D(E,ρ,w), containing for 6 samplings of 43 logarithmically equidistant incident particle energies in the range 0.8 – 500 GeV and 20 bins of logarithm of cell energy density.

Before we have used similar weights for the analysis of the Combined Test Beam 2004 data.

Good results have been obtained!

(Y. Kulchitsky et al. ATL-TILECAL-PUB-2008-009)

Local Hadronic Calibration Method Local Hadronic Calibration Method

log(ρ) , log(GeV/L)

log(

E)

w


Oxford-Stockholm group: Local Hadronic Calibration (w≥0.6 (ATL-LARG-PUB_2009-001), η =0.45)

Our energy resolution about 1.5 times better than the O-S group results

Comparison with the results ofComparison with the results of

ATL-CAL-PUB-2007-001

Energy linearity with our weights are mostly within ±1%

Linearity of the O-S group results is within ±8%


Momentum distribution

<P>=3.5 GeVWithout η selection

Results of the analysisResults of the analysis

||ηη|< 0.6|< 0.6

Momentum distribution

<P>=3.5 GeV after η cut

about 2K tracks with P>10GeV

<Ntrack>=27 tracks / event

Number track distribution

Without η selection

Mean momentum in barell part of Calorimeter <P>=3.5GeV.

We have 2K particles with energy greater than 10 GeV which go to BarrelLAr and Tile Calorimeter.



Most particles go to Most particles go to Extended Extended Barrel Tile Calorimeter andBarrel Tile Calorimeter andLLAAr Hadronic End-r Hadronic End-CCap Calorimeterap Calorimeter

About 15% of particles go to About 15% of particles go to barell part of calorimeter (|η|<0.6)barell part of calorimeter (|η|<0.6)

η-distribution after η - P selection

|η|<0.6

891128

η-distribution before η - P selection

5915378


Tracks quality cutsTracks quality cuts At least one hit in the B layer of the pixel detector No more than one hole in the other pixel and SCT layers χ2 / ndof < 2

Track isolation: no other tracks within ΔR < 0.4ΔR is the distance between impact point in the beginning of the calorimeter for given track and ones of other tracks

Rejected tracks

The ID tracking performance The ID tracking performance group doesn't recommend to group doesn't recommend to use cut on the use cut on the χχ22. We will not . We will not use this cut in our future use this cut in our future analysis. analysis.

Rejected ≈10% tracks


For selection of “shower cells” related with extrapolated track all cells of the calorimeter are considered and the cells satisfying to the following criteria are taken :

|φext,i- φi,k | < ∆φi

|ηext,i- η i,k | < ∆ ηi

E i,k > 2σnoise ,i ,

where

φi,k , ηi,k are coordinates of the centre of the i,k cell,

φext,i , ηext,i are coordinates of track extrapolation in i-layer, i=0,…,6.

The values of ∆φi and ∆ηi have been determined from the lateral profiles in each

longitudinal layer obtained in given work.

Analysis of Minimum Bias EventsAnalysis of Minimum Bias Events


LAr showers ∆LAr showers ∆ηη Lateral profiles for 4-5 GeV Lateral profiles for 4-5 GeV

Energy depositions of showers in the LAr cells as a function of ∆η=ηcell -ηtrack,extr

Ecell/∆η Ecell/∆η

Ecel l /∆η Ecell/∆η


Tile showers ∆Tile showers ∆ηηLateral profiles for 4-5 GeVLateral profiles for 4-5 GeV

Energy depositions of showers in the Tile cells as a function of ∆η=ηcell-ηtrack,extr

Ecell/∆η Ecell/∆η

Ecell/∆η


LAr showers ∆φ Lateral profiles for 4-5 GeVLAr showers ∆φ Lateral profiles for 4-5 GeV

Energy depositions of showers in the LAr cells as a function of ∆φ= φcell- φextr.track

Ecell/ ∆φ

∆ φ

Ecell/ ∆φ

∆ φ

Ecell/ ∆φ

∆ φ

Ecell/ ∆φ

∆ φ


Tile showers ∆φ Lateral profiles for 4-5 GeVTile showers ∆φ Lateral profiles for 4-5 GeV

Energy depositions of showers to the Tile cells as a function of ∆φ= φcell_centre- φextr.track

Ecell/ ∆φ

∆ φ

Ecell/ ∆φ

∆ φ

Ecell/ ∆φ

∆ φ


Lateral η-region of showersLateral η-region of showers

0.4

0.2

2.3 m0

LAr

TileCal

0

∆η =ηcell center - ηtrack extr coordinate difference

1longitudinal coordinate along the shower axis

-0.2

-0.4

0 1 20 1

2 3

INN

ER

DE

TE

CT

OR

INN

ER

DE

TE

CT

OR

Track

extrapolation


Lateral φ-region of showersLateral φ-region of showers

0.4

0.2

2.3 m0

LAr

TileCal

0

∆φ=φcell,centre

] φtrack,extr

coordinate difference

1

longitudinal coordinate along the shower axis

-0.2

-0.4

INN

ER

DE

TE

CT

OR

INN

ER

DE

TE

CT

OR

Track extrapolation

10 20 1 2 3


Cuts in the LAr0 energy deposition and shower isolation Cuts in the LAr0 energy deposition and shower isolation

Rejection of events with energy deposition ELAr0 > 3σ

noise_cell

(150 MeV) for elimination of eventswith considerable energy loss before the calorimeter. In other words we have rejected most of hadrons created showers before calorimeter.

The Kisol

is a shower

isolation coefficient.

Energy deposition in LAr0

1-2 1-2 GeVGeV

Shower isolation

Distribution of Kisol

1-2 1-2 GeVGeV 1.0P/,E1.1,1.1EK iiiiisol


Effect of the LAr cuts on E/p distributions Effect of the LAr cuts on E/p distributions

Events selection with energy depositions in LAr2 and LAr3 layers:ELAr2 and ELAr3>2σnoise_cell .These cuts are empirically founded ones.Due to these cuts the E/P distributions closer to 1 and smaller widths have been obtained.

1-2 GeV

1-2 GeV

without the LAr2 and LAr3 selection

with the LAr2 and LAr3 selection


0.39

0.49

0.59

0.69

0.79

0.89

0.99

1.09

1 3 5 7 9P [GeV/c]

<E/P>

Comparison with CTB04 Data

E/P ratio measured (open points) and predicted by Monte Carlo

simulation (full points) as a function of Ebeam for ηbeam

=0.35.

test-beam data, em scale

minimum-bias, had scale

E.Abat et al."Stmudy of the response of the ATLAS central calorimeter to pions of energies from 3 to 9 GeV" ATL-COM-GEN-2009-009

ATL-TILECAL-PUB-2008-009

ATL-COM-GEN-2009-009



0.36±0.021.11±0.023605 - 6

0.40±0.03 1.05±0.021K4 - 5

0.36±0.031.10±0.031806 - 7

0.45±0.011.03±0.012K3 – 4

7 - 8

2 – 3

1 - 2

Energy range,GeV/c

0.39±0.051.10±0.05106

0.51±0.020.99±0.0210K

0.52±0.030.97±0.0370K

σ(E/P)<E/P>tracksN


Charged Hadron Track IsolationCharged Hadron Track IsolationATL-COM-PHYS-2008-074

ΔR between cone center and closest neutral particle from Monte-Carlo truth.

ΔR between cone center and closestreconstructed non-candidate track

In minimum bias events, extra particleswithin the ΔR cone of the track considerablybias the measured pion energies.

The main source of background was foundto be photons from π0 decay closely spacedin ΔR to the track.Almost all pions in the range 1-10 GeVin minimum bias events are accompaniedby another particle within ΔR < 1.

ΔR=sqrt((Δφ)2 +(Δη)2)


Cut-away view of the ATLAS Inner DetectorCut-away view of the ATLAS Inner Detector

TPTP=TPTP44

10.00034

CERN-OPEN-2008-020

Momentum resolution

[PT ]=GeV/c0.25<|η|<0.5 σ(PT )/PT= 2% for 1-2 GeV/cσ(PT )/PT= 4% for 100 GeV/c


Calorimeters in ATLASCalorimeters in ATLAS

EM LAr |η| < 3 : Pb/LAr 24-26 X0

3 longitudinal sections; 1.2 λ;

Δη×Δφ=0.025×0.025

Central Hadronic |η|<1.7:

Fe(82%)/scintillator (18%)

3 longitudinal sections; 7.2 λ;

Δη×Δφ=0.1×0.1

End Cap Hadronic 1.7 <|η|<3.2:

Cu/LAr – 4 longitudinal sections; Δη×Δφ<0.2×0.2

Forward calorimeter 3<|η|<4.9 :

EM Cu/LAr – HAD W/Lar;

3 longitudinal sections

E

%2295%2.09.3

E

%267E

(ATL-TILECAL-PUB-2008-009)

Linearity within ±1% (10-350 GeV)

LAr + TileCal resolution

(obtained at 2004 Combined TestBeam)

Tile Calorimeter EM barrel and EndCap

Hadronic EndCap Forward Calorimeter


Table 1. ∆φTable 1. ∆φii and ∆ and ∆ηηii values used for cell shower selection values used for cell shower selection

0.1×0.2

0.1×0.1

0.1×0.1

0.025×0.05

0.025×0.025

0.1×0.003

0.1×0.025

cell size ∆φ×∆η

0.480.36Tile2

0.320.29Tile1

0.230.21Tile0

0.150.12LAr3

0.0770.082LAr2

0.0290.086LAr1

0.0740.112LAr0

∆ ηi∆φilayer


Comparison with recent E/p studiesComparison with recent E/p studies

Talk «Pion E/p Studies» given by N.Davidson, ATLAS TILECAL meeting 20th April 2009

|η|<1.5p

T=1- 3 GeV

<E/p> =0.572±0.003

|η|<0.6|η|<0.6E=2- 3 GeV/cE=2- 3 GeV/c<E/P>=0.99±0.02<E/P>=0.99±0.02

Our result of the E/P study Our result of the E/P study

The result of <E/P>=0.99±0.02 obtained in our work (hadronic scale) is considerably better the result of<E/p> =0.572±0.003 obtained in N.Davidson talk (EM scale).


0.5

0.7

0.9

1.1

1 3 5 7

P (GeV/c)

<E/P>

given work

Talk «Pion E/p Studies» given by N.Davidson, ATLAS TILECAL meeting 20th April 2009

Comparison of linearity with recent E/p studiesComparison of linearity with recent E/p studies


Weights for 0.8-500 GeVWeights for 0.8-500 GeV

in situ hadronic e/p calibration of the atlas barrel calorimeters using minimum bias events...

Documents

noise noise

energy e

gev slide

e cell

absolute energy calibration

noise cuts

e3 gev

energy depositions e