comparison of available measurements of the absolute air
TRANSCRIPT
Comparison of available measurements of the
absolute air-fluorescence yield*
J. Rosado, F. Blanco and F. Arqueros
Universidad Complutense de Madrid
*J. Rosado et al., Astropart. Phys. 34 (2010) 164
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Outline
1. Introduction
2. Normalization procedure
3. Monte Carlo analysis of experiments
4. Comparison of results
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1. Introduction
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1. Introduction: Motivation
Comparison of absolute FY cannot be done directly in many occasions because:
a) Single bands vs wide spectral range
b) Conversion from ph/m to ph/MeVdepends on geometry: (dE/dx)dep
c) Discrepancies in the P’ parameters
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1. Introduction: Motivation
Summary of FY results used in the comparison
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1. Introduction: Objectives
Comparison of results in ph/MeV normalized
to the 2P(0-0) band at 800 hPa and 293 K
MC analysis of experiments including
geometrical features for comparison with calculations of the authors and to propose
corrections to the FY values
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2. Normalization procedure
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2. Normalization procedure: wavelength reduction
Measurements performed for a wide
spectral range ∆λ are normalize to 337 nm
Experimental relative intensities of AIRFLY*
within 290 – 430 nm
∑∆
∆
∆
∆ ==λ
λλ
λ
λ III
I,FYFY 337
337
*M. Ave et al., Astropart. Phys., 28 (2007) 41
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2. Normalization procedure: wavelength reduction
Relative intensities of AIRFLY follow (for bands belonging to the same system) *:
Fluorescence spectrum can be extended
beyond the 290 – 430 nm spectral range
0000
0
00000 /1
/1
P'
P'
Aq
Aq
P'P
P'P
Aq
Aq
I
I v
X
vv'vX
vX
vv'vXvv'
→
→
→
→ ≈+
+=
P >>P’
*F. Arqueros et al., NJP 11 (2009) 065011
independent of P
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0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Predicted relative intensities
Experim
enta
l re
lative inte
nsitie
s
2P(0,v')
2P(1,v')
2P(2,v')
2P(3,v')
2P(4,v')
AIRFLY data
2. Normalization procedure: wavelength reduction
000000
'
P'
P'
Aq
Aq
I
I v
X
vv'vXvv
→
→≈
Comparison between experimental and
predicted relative intensities
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2. Normalization procedure: wavelength reduction
Two weak bands beyond the range of AIRFLY
2P(0-4) with I ~ 2% I337
2P(4-9) with I ~ 0.2% I337
Results of the wavelength reduction
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2. Normalization procedure: units and geometry
Conversion of ε (ph/m) to Y (ph/MeV)
where (dE/dx)dep should be calculated for the
observation volume of the experiment
Some authors assume (dE/dx)dep = (dE/dx)loss
( )depd/d xEY
ε=
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2. Normalization procedure: units and geometry
A MC simulation including the microscopic
molecular processes was carried out for
each experiment:
a)a) Energy depositionEnergy deposition
b)b) Geometrical factorsGeometrical factors
Comparison with results reported by the authors
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2. Normalization procedure: scaling
Normalization to common P and T
a)a) Pressure dependence:Pressure dependence:
a)a) Temperature dependence:Temperature dependence:
P
P'Y
P'P
YY
00
/1≈
+=
2/1~ TP'
P >>P’
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2. Normalization procedure: scaling
Scaling law nearly independent of P’:
Except for AirLight:
( ) ( )T
PTP,YY
293
800K293hPa,800 ≈
( ))K293(/8001
K293hPa,8000
P'
YY
+=
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3. Monte Carlo analysis of
experiments
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3. MC analysis: basics
e- sourceelectrons
––––––––––––––––––––––––––––––
step
geometry end
ioniz.excit.brem.elast.
loop
e-
<x>=(Nσ)-1
Predictions of Edep
and F. emission
Layout of the simulation algorithm
Cutoff energy of 11 eV !
X-rays also included
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3. MC analysis: basics
Simulation results:
a)a) Energy depositionEnergy deposition
b)b) Geometrical acceptance (if possible)Geometrical acceptance (if possible)
∫∫
=
track
voldep
depd
d
x
E
x
E
∫ Ω=Ωvol
lightφ
Primary electrons lose energy in collisions
and have fluctuating trajectories
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3. MC analysis: Nagano’s experiment
Nagano et al.* made three assumptions:
a)a) ∆∆xx = = ∆∆xxgapgap
b)b) <Ω><Ω> == <Ω><Ω>beambeam
c)c) ((ddEE/d/dxx))depdep = (= (ddEE/d/dxx))lossloss
*M. Nagano et al., Astropart. Phys. 20 (2003) 293;
M. Nagano et al., Astropart. Phys. 22 (2004) 235
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3. MC analysis: Nagano’s experiment
Three corrections have been applied:
FY of Nagano should be increased by 7%
( )
dep
lossbeamNag
d/d
d/d
xE
xE
x
xYY
gap
∆
∆
Ω
Ω=
~1% increase
~1% decrease
7% increase
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3. MC analysis: AirLight experiment
AirLight* performed a GEANT4 simulation to
obtain:
a)a) Energy depositionEnergy deposition
b)b) Acceptance Acceptance <Ω><Ω>
*T. Waldenmaier et al., Astropart. Phys. 29 (2008) 205
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10
12
14
16
18
20
22
24
200 400 600 800 1000 1200 1400 1600 1800 2000
Detected energy (keV)
En
erg
y d
ep
ositio
n o
r lo
ss (
ke
V) Deposited energy (AirLight)
Deposited energy (this work)
Integrated Edep vs E at atmospheric pressure
Deviations decrease with P resulting in an
effective correction of about -7% in the FY
3. MC analysis: AirLight experiment
~10% difference
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10
12
14
16
18
20
22
24
200 400 600 800 1000 1200 1400 1600 1800 2000
Detected energy (keV)
En
erg
y d
ep
ositio
n o
r lo
ss (
ke
V)
Energy loss (AirLight)
Energy loss (this work)
Integrated Eloss vs E at atmospheric pressure
Discrepancy in Eloss could be due to AirLight
assuming straight trajectories of electrons
3. MC analysis: AirLight experiment
Discrepancy
at low energy
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3. MC analysis: FLASH experiment
FLASH* performed an EGS4 simulation to
obtain:
a)a) Energy depositionEnergy deposition
b)b) Acceptance Acceptance <Ω><Ω>
*R. Abbasi et al., Astropart. Phys. 29 (2007) 77
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Comparison of (dE/dX)dep vs P at 28.5 GeV
Also a small correction in <Ω>, resulting in a total correction of about -2% in the FY
1.90
1.95
2.00
2.05
2.10
2.15
0 100 200 300 400 500 600 700 800 900 1000
P (hPa)
dE
dep/d
X (
Me
V g
-1 c
m2)
FLASH
This work
This work(dens. corr. at 1 atm)
3. MC analysis: FLASH experiment
~1% Discrepancy could be due to a
different treatment of the
density correction
Similar behavior if applying a fixed
dens. corr.
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3. MC analysis: MACFLY experiment
MACFLY* performed a GEANT4 simulation to
obtain:
a)a) Energy depositionEnergy deposition
b)b) Acceptance Acceptance <Ω><Ω>
*P. Colin et al., Astropart. Phys. 27 (2007) 317
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E dependence of (dE/dX)dep at atmospheric P
Proposed corrections of the FY are +2% at
1.5 MeV and -6% at 20 GeV and 50 GeV
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
E (eV)
dE
de
p/d
X (
Me
V g
-1 c
m2) MACFLY
This work
105
109
108
107
106
1011
1010
3. MC analysis: MACFLY experiment
~ 6%Unexpected behavior of the Edep curve of
MACFLY at low
energies
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3. MC analysis: Kakimoto’s experiment
Kakimoto et al.* made similar assumptions than
Nagano’s, in particular:
*F. Kakimoto et al., Nucl. Instr. Meth. A 372 (1996) 527
lossdep d
d
d
d
=
x
E
x
E
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*F. Blanco et al., Phys. Lett. A 345 (2005) 355
F. Arqueros et al., New J. Phys. 11 (2009) 065011
Simulation results for a simple geometry*
Geometrical details are not relevant
Obs. volume R ~ 10 cm
3. MC analysis: Kakimoto’s experiment
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3. MC analysis: Kakimoto’s experiment
Corrections are larger than 25% at high electron energy!
Correction to FYEnergy (MeV)
+29%1000
+28%650
+25%300
+6%1.4
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Lefeuvre et al.* performed a GEANT
simulation to obtain:
Electron scattering by the lead walls of the chamber has an important role
3. MC analysis: Lefeuvre’s experiment
a)a) Contribution of highContribution of high--
energy secondariesenergy secondaries
b)b) Acceptance Acceptance <Ω><Ω>
*G. Lefeuvre et al., Nucl. Instr. Meth. A 578 (2007) 78
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3. MC analysis: Lefeuvre’s experiment
Simulation results for a simple geometry assuming R = 4 cm
The effect of scattering by the chamber
walls was estimated using CASINO2.42
Correction to FYEnergy (MeV)
+8%1.5
+7%1.1
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4. Comparison of results
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4. Comparison of results: table
Absolute FY values normalized to 337 nm,
800 hPa and 293 K
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4. Comparison of results: table
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4. Comparison of results: concluding remarks
Most measurements lead to Y337 ~ 6.5
ph/MeV, except for those of MACFLY and
the preliminary result of AIRFLY*
Discrepancies larger than uncertainties: error in Edep should be considered
Proposed corrections are non-negligible, in particular when authors assume: (dE/dx)dep = (dE/dx)loss
*M. Ave et al., Nucl. Instr. Meth. A 597 (2008) 55
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Normalized FY using calculations of authors
4. Comparison of absolute FY values
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
0.1 1 10 100 1000 10000 100000
E (MeV)
Y3
37 (
ph/M
eV
)
Kakimoto Nagano
Lefeuvre MACFLY
FLASH AirLight
6.5 ph/MeV
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Normalized FY after applying corrections
4. Comparison of absolute FY values
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
0.1 1 10 100 1000 10000 100000
E (MeV)
Y3
37 (
ph/M
eV
)
Kakimoto Nagano
Lefeuvre MACFLY
FLASH AirLight
6.5 ph/MeV
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Normalized FY using calculations of authors
4. Comparison of absolute FY values
4.0 5.0 6.0 7.0 8.0 9.0
Y 337 (ph/MeV)
Kakimoto
Nagano
Lefeuvre
MACFLY
FLASH
AirLight<Y 337> = 6.42 ph/MeV
Χ2/ndg = 1.69
Theoretical value (7.5 ph/MeV)
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Normalized FY after applying corrections
4. Comparison of absolute FY values
4.0 5.0 6.0 7.0 8.0 9.0
Y 337 (ph/MeV)
Kakimoto
Nagano
Lefeuvre
MACFLY
FLASH
AirLight<Y 337> = 6.74 ph/MeV
Χ2/ndg = 1.27
Theoretical value (7.5 ph/MeV)
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Thanks!