Transcript Modification of the Local Hadronic Calibration Method for

Local Hadronic Calibration for
ATLAS Barrel Calorimeter
on CTB04 and MC data
Y.Kulchitsky, P.Tereshko
JINR, Dubna, Russia
IP National Academy of Sciences, Minsk, Belarus
V.Vinogradov
JINR, Dubna, Russia
ATLAS Physics and Computing workshop
JINR, Dubna, Russia
21 January 2008
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Calorimeters in ATLAS
Tile Calorimeter
EM barrel and EndCap EM LAr || < 3 : Pb/LAr 24-26 X0
3 longitudinal sections; 1.2 ; =0.0250.025
Central Hadronic ||<1.7: Fe(82%)/scintillator (18%)
3 longitudinal sections; 7.2 ; =0.10.1
End Cap Hadronic 1.7 <||<3.2:
Cu/LAr – 4 longitudinal sections;  < 0.2  0.2
Forward calorimeter 3<||<4.9 :
EM Cu/LAr – HAD W/Lar; 3 longitudinal sections
Hadronic
EndCap
Forward
Calorimeter
EM LAr + TileCal resolution (obtained
at 1998 Combined TestBeam)

 41 . 9 %
 1 .8

 1 .8 %  
E 
E
E

Linearity within ±2% (10-300 GeV)
Amount of Material (absorption lengths) in
the ATLAS calorimetry as a function of η
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CTB 2004 setup
Beams: e, π, μ
•
•
•
•
Data-taking May-October 2004
Pixel, SCT, TRT, LAr, TileCal, MDT, RPC integrated (not all at once)
Integrated triggers, e.g. full calo trigger chain used for first time
Mostly beam with no RF structure, except a few runs with a 25 ns
bunched beam
• Electron and pion beams contaminated with muons
• Mostly 10-350 GeV, some Very Low Energy runs at 1-9 GeV
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Local Hadronic Calibration Method Description
Our work is devoted to Pion Energy Reconstruction on CTB04 data by the
Local Hadronic Calibration Method
In this method the reconstructed energy is
E
E
rec
LAr
 C LAr * E LAr 

E
LAr 0

E
E
LAr 1

Tile

E
E
LAr 2
DM ( LAr  Tile )

E

E
DM ( bef  LAr 0 )
and
LAr 3
E
Tile

E
DM ( LAr 0  LAr 1 )

E
Tile 0

E

Tile 1
E

leak
E
Tile 2
Longitudinal samplings – LAr0, LAr1, LAr2, LAr3, Tile0, Tile1, Tile2
cell
cell

E rec , em - reconstructed energy deposition in
E sampling  E cor
cell in electromagnetic scale
E
cell
cor
cell
 w * E rec , em
w 
w  f ( E beam , sampling ,  )
E
 
cell
E
rec , em
cell
E
/ Volume
truth , MC
cell
/
rec , em , MC
cell
- weights, MC – Monte Carlo simulation
- Energy density in cell
Data
• The CTB04 data for E=10-350 GeV at η=0.25
• ATHENA release 12.0.31
• 4/2/0 CaloTopoCluster
• 10000 events at each Energy
Selection criteria
• Muons removal from beam, MuTag < 500
• Electrons removal E_tile/E_beam > 0.03
• Beam space restriction
• Noise suppression |E cellreco|<2 σ (noise)
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Cut to Weights
Crucial ingredient in this method are weights. For improving of
energy resolution by the enlargement of relative difference
between weights for the low and high energy densities in cells and
taking into account that our calorimeters are non-compensated
(e/h LAr =1.74 and e/h Tile =1.36) e/π>1 and on cells level
we have introduced the weight cuts.
E
truth

E
rec , em
and w  1
We have analysed data with several weights:
• weights without cut,
• weights with different cuts wi >w-cut= 1, 1.025, 1.05, in which
the high energy density region (where the electromagnetic
energy deposition >90%) is without cut, i.e. we did not weight
the electromagnetic clusters.
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There is a significant difference (28% in
“a” parameter) in energy resolution
between the real and MC data in
electromagnetic scale. This gives
evidence that energy fluctuations in cells
in real events are bigger than in MC
events.
σ/E (%)
Electromagnetic energy scale
Energy reconstruction vs
w-cut for 180 GeV
σ/E (%)
The energy resolution is decreasing
with the increasing of w cut
The mean energy is increasing
with the increasing of w cut
25%
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~10% worse
then MC Y.Kulchitsky, ATLAS Physics & Computing
1/√E (1/√GeV)
7%
6
Electromagnetic fraction
For each beam energy and sampling
the min values of cell energy density
at which the electromagnetic fraction
>90% have been determined. Some
values of are shown in these figures.
E
em
/ E tot
Lar 22, 180 GeV
LAr
180
GeV
Comparison of cut functions with
Truth Weights
w
truth

E
truth
/(
E
em

E
non  em
)
Log(ρ GeV/L)
 f ( )
truth
The cut functions do not cut the mean
E
em
/ E tot
truth weights.
Lar 2, 180 GeV
Log(ρ GeV/L)
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Dead Material corrections
1. Before LAr0 (Presampler):
E bef
 LAr 0
 p1 E LAr 0
2. Between LAr0 and LAr1:
E LAr 0  LAr 1  p 0  p1
3. Between LAr and Tile
E LAr  Tile  1 . 52 
4. Leakage
E LAr 0  E LAr 1
E LAr 3  E Tile 0
E leak  p1 E beam
100%
10%
1%
The relative contributions of the various dead
material corrections. The largest contribution
(~90%) comes from Edm (LAr-Tile).
The comparison E(truth) and E(rec) experimental for LAr-Tile dead material
region at η=0.35. We recalculate this constant equal to 1.56 at η=0.35 for
our case to 1.52 at η=0.25. We will show later that the 1, 2, 4 dead
material correction improve the resolution only on about 3% in “a”.
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DM corrections (dm-5)
E bef
 1 . 614  0 . 000675
 LAr 0
 E beam
  E LAr 0
E LAr 0  LAr 1  0 . 260  0 . 331  0 . 000104  E beam  

E LAr 0  E LAr 1
E leak  0 . 00103  0 . 00522  ln E beam  0 . 00792  ln E beam
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2   E beam
9
MC & CTB04 longitudinal profiles comparison
Difference between MC and
CTB04 profiles at 100 GeV
(%)
Longitudinal profiles at 100 GeV
normalized on Ebeam
This is reason why for improving CTB04 hadron resolution we use for LAr
additional parameter in energy reconstruction formula:E=1.05 ELAr+ETile+Edm
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Weights with w≥1.05 for 100 GeV
w 
E
cell
truth
/
70%
E
cell
rec , em
 f ( )
370%
Tile0
Tile0
370%
LAr2
log(ρ) , log(GeV/L)
log(ρ) , log(GeV/L)
The differences between the weights at low and high densities are enlarged
(60->70%, 350->370%) compared to the weights with w≥1.0
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Energy resolution
w-cut
a,% b,% c,%
0
90±3
4.8±0.4
70±60
1.0
72±2
3.6±0.2
58±34
1.025
67±2
3.9±0.2
115±30
1.05
66±2
3.8±0.2
110±20
MC
59±1
4.1±0.1
90±11
Energy resolution improves
with increasing of w-cut.
The best energy resolution among
the investigated cuts is for the
w-cut=1.05 for which a=66±2%.
We have corrected the miscalibration of the Tile1 (on 2%) and Tile2 (on 4%)
samplings. The mean value of energy linearity has been increased by ~1%
and becomes equal to 1.002±0.002.The energy resolution did not change.
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Comparison with the results of
Oxford-Stockholm group: Local Hadronic
Calibration (w≥0.6, η =0.45)
ATL-COM-CAL-2007-002
Pisa group: H1-method (η =0.35)
ATL-PHYS-PUB-2005-019
a=(97±13)%
a=(66±2)%
Our energy resolution about1.5 times better
than the O-S group results
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Our energy resolution slightly better
than the H1 method results
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Energy linearity
w-cut=1.0
w-cut=0.6
w-cut=1.05
Our energy linearity are mostly within ±1%
cut
±8%
mean
1.0
1.057±0.001
1.025
1.083±0.002
1.05
1.093±0.003
Linearity of the O-S group results is within ±8%
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Energy linearity with the general normalization
constant of 0.91
We have determined the general normalization constant of 0.91 for which the mean
value of linearity for w-cut=1.05 is about 1. At this we do not touch the cells with the
electromagnetic energy more 90%. In other words, we apply this normalization
constant only to cells with non-electromagnetic energy.
Points with statistical errors
Uncertainties in the nominal beam energies
are quadraticaly added
The obtained energy linearity is within ±1%
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Energy resolution with correction
Comparison of TileCal corrected (squares) and
non-corrected (circles) energy resolutions. The
energy resolutions coincide within the errors
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Hadron energy resolution with Neural Networks for
Lar/Tile DM energy lost correction
(In co-authorship with V.SHIGAEV)
Energy resolutions with the Neural Networks LAr-Tile
DM at 250 and 350 GeV are shown by squares. The
dashed line is the projected resolution in the ATLAS
Technical Proposal.
In this case we have reached the
projected resolution
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Conclusions
We have constructed new weights, performed pion energy reconstruction and
compared with previous results.
The best energy resolution among the investigated weight cuts is for the w-cut=1.05

67

% 
E
95  22
 2
 3 . 9  0 . 2  
E
E

We have obtained 8% improvement of energy resolution compared with our previous
results for w-cut =1.
The obtained energy resolution slightly better than the H1 method results for CTB04
obtained by the Pisa group.
We have obtained energy resolution about 1.5 times better than the Oxford-Stockholm
group.
There is the difference in energy resolution between CTB04 and MC. This one is
(7±2)% for parameter “a”.
The obtained energy linearity is mostly within ±1%. The mean value is equal to
1.093±0.003.
We have determined the general normalization constant of 0.91 for which the mean
value of linearity for w-cut=1.05 is about 1. At this we do not touch the cells with the
electromagnetic energy more 90%. At applying of the general normalization constant
the energy resolution has not worsen.
We have corrected the miscalibration of the Tile1 (on 2%) and Tile2 (on 4%)
samplings. The mean value of energy linearity has been increased by ~1% and
becomes equal to 1.002±0.002.The energy resolution did not change.
We have reached the projected energy resolution for ATLAS Barrel calorimeter in 250
– 300 GeV region using Neural Networks for Lar-Tile DM energy lost correction.
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