in situ hadronic e/p calibration of the atlas barrel calorimeters using minimum bias events...
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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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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).
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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).
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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 ...
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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%
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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.
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
Results of the analysisResults of the analysis
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
Results of the analysisResults of the analysis
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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)
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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).
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
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
25.07.2009 N.Huseynov The Xth International School-Seminar, Gomel
Weights for 0.8-500 GeVWeights for 0.8-500 GeV
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