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
Outline 1. Introduction 2. Normalization procedure 3. Monte Carlo analysis of experiments 4. Comparison of results J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 2
1. Introduction J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 3
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/mev depends on geometry: (de/dx) dep c) Discrepancies in the P parameters J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 4
1. Introduction: Motivation Summary of FY results used in the comparison J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 5
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 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 6
2. Normalization procedure J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 7
2. Normalization procedure: wavelength reduction Measurements performed for a wide spectral range λ are normalize to 337 nm FY = FY 337, I = 337 λ λ I λ I λ I λ Experimental relative intensities of AIRFLY * within 290 430 nm * M. Ave et al., Astropart. Phys., 28 (2007) 41 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 8
2. Normalization procedure: wavelength reduction Relative intensities of AIRFLY follow (for bands belonging to the same system) * : I vv' = q X v A vv' 1+ P / P' 0 q X v A vv' P' v I q A 1+ P / 00 X 0 00 P' v q X 0 A 00 P' 0 P >>P independent of P Fluorescence spectrum can be extended beyond the 290 430 nm spectral range * F. Arqueros et al., NJP 11 (2009) 065011 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 9
2. Normalization procedure: wavelength reduction Comparison between experimental and predicted relative intensities Experimental relative intensities 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 I I vv' 00 q q X v X 0 A A vv' 00 P' P' v 0 AIRFLY data 2P(0,v') 2P(1,v') 2P(2,v') 2P(3,v') 2P(4,v') 0.0 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 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 10
2. Normalization procedure: wavelength reduction Results of the wavelength reduction Two weak bands beyond the range of AIRFLY 2P(0-4) with I ~ 2% I 337 2P(4-9) with I ~ 0.2% I 337 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 11
2. Normalization procedure: units and geometry Conversion of ε (ph/m) to Y (ph/mev) Y = ε ( de / dx) dep where (de/dx) dep should be calculated for the observation volume of the experiment Some authors assume (de/dx) dep = (de/dx) loss J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 12
2. Normalization procedure: units and geometry A MC simulation including the microscopic molecular processes was carried out for each experiment: a) Energy deposition b) Geometrical factors Comparison with results reported by the authors J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 13
2. Normalization procedure: scaling Normalization to common P and T a) Pressure dependence: Y = Y 0 Y 0 P' 1+ P / P' P P >>P a) Temperature dependence: P' ~ T 1/ 2 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 14
2. Normalization procedure: scaling Scaling law nearly independent of P : Y ( 800 hpa, 293 K) Y ( P,T ) P 800 293 T Except for AirLight: Y ( 800 hpa, 293 K) = 1+ Y 0 800 / P' (293 K) J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 15
3. Monte Carlo analysis of experiments J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 16
3. MC analysis: basics Layout of the simulation algorithm e - source loop electrons step <x>=(nσ) -1 Cutoff energy of 11 ev! geometry end e - Predictions of E dep and F. emission elast. brem. excit. ioniz. X-rays also included J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 17
3. MC analysis: basics Simulation results: a) Energy deposition de dx dep = vol E track dep x Primary electrons lose energy in collisions and have fluctuating trajectories b) Geometrical acceptance (if possible) Ω = Ω φ light vol J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 18
3. MC analysis: Nagano s experiment Nagano et al. * made three assumptions: a) x = x gap b) <Ω> = <Ω> <Ω> beam c) (de/dx) dep = (de/d( /dx) loss * M. Nagano et al., Astropart. Phys. 20 (2003) 293; M. Nagano et al., Astropart. Phys. 22 (2004) 235 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 19
3. MC analysis: Nagano s experiment Three corrections have been applied: Y = Y Nag Ω Ω beam x gap x ( de / dx) de / dx loss dep ~1% increase 7% increase ~1% decrease FY of Nagano should be increased by 7% J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 20
3. MC analysis: AirLight experiment AirLight * performed a GEANT4 simulation to obtain: a) Energy deposition b) Acceptance <Ω> * T. Waldenmaier et al., Astropart. Phys. 29 (2008) 205 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 21
3. MC analysis: AirLight experiment Integrated E dep vs E at atmospheric pressure 24 Energy deposition or loss (kev) 22 20 18 16 14 12 Deposited energy (AirLight) Deposited energy (this work) ~10% difference 10 200 400 600 800 1000 1200 1400 1600 1800 2000 Detected energy (kev) Deviations decrease with P resulting in an effective correction of about -7% in the FY J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 22
3. MC analysis: AirLight experiment Integrated E loss vs E at atmospheric pressure Energy deposition or loss (kev) 24 22 20 18 16 14 12 Discrepancy at low energy Energy loss (AirLight) Energy loss (this work) 10 200 400 600 800 1000 1200 1400 1600 1800 2000 Detected energy (kev) Discrepancy in E loss could be due to AirLight assuming straight trajectories of electrons J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 23
3. MC analysis: FLASH experiment FLASH * performed an EGS4 simulation to obtain: a) Energy deposition b) Acceptance <Ω> * R. Abbasi et al., Astropart. Phys. 29 (2007) 77 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 24
3. MC analysis: FLASH experiment Comparison of (de/dx) dep vs P at 28.5 GeV de dep /dx (MeV g -1 cm 2 ) 2.15 2.10 2.05 2.00 1.95 1.90 FLASH This work 0 100 200 300 400 500 600 700 800 900 1000 P (hpa) ~1% Discrepancy could be due to a different treatment of the density correction This work (dens. corr. at 1 atm) Similar behavior if applying a fixed dens. corr. Also a small correction in <Ω>, resulting in a total correction of about -2% in the FY J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 25
3. MC analysis: MACFLY experiment MACFLY * performed a GEANT4 simulation to obtain: a) Energy deposition b) Acceptance <Ω> * P. Colin et al., Astropart. Phys. 27 (2007) 317 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 26
3. MC analysis: MACFLY experiment E dependence of (de/dx) dep at atmospheric P Unexpected behavior of the E dep curve of MACFLY at low energies de dep /dx (MeV g -1 cm 2 ) 2.8 2.6 2.4 2.2 2.0 1.8 MACFLY This work ~ 6% 1.6 1.4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 E (ev) Proposed corrections of the FY are +2% at 1.5 MeV and -6% at 20 GeV and 50 GeV J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 27
3. MC analysis: Kakimoto s experiment Kakimoto et al. * made similar assumptions than Nagano s, in particular: de dx dep = de dx loss * F. Kakimoto et al., Nucl. Instr. Meth. A 372 (1996) 527 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 28
3. MC analysis: Kakimoto s experiment Simulation results for a simple geometry * Geometrical details are not relevant *F. Blanco et al., Phys. Lett. A 345 (2005) 355 F. Arqueros et al., New J. Phys. 11 (2009) 065011 Obs. volume R ~ 10 cm J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 29
3. MC analysis: Kakimoto s experiment Corrections are larger than 25% at high electron energy! Energy (MeV) 1.4 300 650 1000 Correction to FY +6% +25% +28% +29% J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 30
3. MC analysis: Lefeuvre s experiment Lefeuvre et al. * performed a GEANT simulation to obtain: a) Contribution of high- energy secondaries b) Acceptance <Ω> Electron scattering by the lead walls of the chamber has an important role * G. Lefeuvre et al., Nucl. Instr. Meth. A 578 (2007) 78 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 31
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 Energy (MeV) 1.1 1.5 Correction to FY +7% +8% J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 32
4. Comparison of results J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 33
4. Comparison of results: table Absolute FY values normalized to 337 nm, 800 hpa and 293 K J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 34
4. Comparison of results: table J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 35
4. Comparison of results: concluding remarks Most measurements lead to Y 337 ~ 6.5 ph/mev, except for those of MACFLY and the preliminary result of AIRFLY * Discrepancies larger than uncertainties: error in E dep 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 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 36
4. Comparison of absolute FY values Normalized FY using calculations of authors 9.0 8.0 Y 337 (ph/mev) 7.0 6.0 5.0 4.0 3.0 2.0 1.0 Kakimoto Lefeuvre FLASH 6.5 ph/mev Nagano MACFLY AirLight 0.0 0.1 1 10 100 1000 10000 100000 E (MeV) J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 37
4. Comparison of absolute FY values Normalized FY after applying corrections 9.0 8.0 Y 337 (ph/mev) 7.0 6.0 5.0 4.0 3.0 2.0 1.0 Kakimoto Lefeuvre FLASH 6.5 ph/mev Nagano MACFLY AirLight 0.0 0.1 1 10 100 1000 10000 100000 E (MeV) J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 38
4. Comparison of absolute FY values Normalized FY using calculations of authors AirLight <Y 337 > = 6.42 ph/mev Χ 2 /ndg = 1.69 FLASH MACFLY Lefeuvre Nagano Theoretical value (7.5 ph/mev) Kakimoto 4.0 5.0 6.0 7.0 8.0 9.0 Y 337 (ph/mev) J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 39
4. Comparison of absolute FY values Normalized FY after applying corrections AirLight <Y 337 > = 6.74 ph/mev Χ 2 /ndg = 1.27 FLASH MACFLY Lefeuvre Nagano Theoretical value (7.5 ph/mev) Kakimoto 4.0 5.0 6.0 7.0 8.0 9.0 Y 337 (ph/mev) J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 40
Thanks! J. Rosado et al, 7th AFW, Coimbra, Portugal, September of 2010 41