Comparison of available measurements of the absolute air

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

J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 of 41of 4122

Outline

1. Introduction

2. Normalization procedure

3. Monte Carlo analysis of experiments

4. Comparison of results


1. Introduction


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


1. Introduction: Motivation

Summary of FY results used in the comparison


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


2. Normalization procedure


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



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


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


000000

'

P'

P'

Aq

Aq

I

I v

X

vv'vXvv

→

→≈

Comparison between experimental and

predicted relative intensities



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


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=


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


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’


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

+=


3. Monte Carlo analysis of

experiments


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


3. MC analysis: basics

Simulation results:


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


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


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


3. MC analysis: AirLight experiment

AirLight* performed a GEANT4 simulation to

obtain:


b)b) Acceptance Acceptance <Ω><Ω>

*T. Waldenmaier et al., Astropart. Phys. 29 (2008) 205


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


~10% difference


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


Discrepancy

at low energy


3. MC analysis: FLASH experiment

FLASH* performed an EGS4 simulation to

obtain:



*R. Abbasi et al., Astropart. Phys. 29 (2007) 77


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.


3. MC analysis: MACFLY experiment

MACFLY* performed a GEANT4 simulation to

obtain:



*P. Colin et al., Astropart. Phys. 27 (2007) 317


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


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


*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




Corrections are larger than 25% at high electron energy!

Correction to FYEnergy (MeV)

+29%1000

+28%650

+25%300

+6%1.4


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


*G. Lefeuvre et al., Nucl. Instr. Meth. A 578 (2007) 78


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


4. Comparison of results


4. Comparison of results: table

Absolute FY values normalized to 337 nm,

800 hPa and 293 K


4. Comparison of results: table


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


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


Normalized FY after applying corrections


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


Normalized FY using calculations of authors


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)


Normalized FY after applying corrections


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)


Thanks!

Documents

Comparison of available measurements of the absolute air