Comparison of available measurements of the absolute air-fluorescence yield*

Transcription

1 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

2 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

3 1. Introduction J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

4 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

5 1. Introduction: Motivation Summary of FY results used in the comparison J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

6 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

7 2. Normalization procedure J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

8 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 nm * M. Ave et al., Astropart. Phys., 28 (2007) 41 J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

9 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 nm spectral range * F. Arqueros et al., NJP 11 (2009) J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

10 2. Normalization procedure: wavelength reduction Comparison between experimental and predicted relative intensities Experimental relative intensities 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') Predicted relative intensities J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

11 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

12 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

13 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

14 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

15 2. Normalization procedure: scaling Scaling law nearly independent of P : Y ( 800 hpa, 293 K) Y ( P,T ) P T Except for AirLight: Y ( 800 hpa, 293 K) = 1+ Y / P' (293 K) J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

16 3. Monte Carlo analysis of experiments J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

17 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

18 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

19 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

20 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

21 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

22 3. MC analysis: AirLight experiment Integrated E dep vs E at atmospheric pressure 24 Energy deposition or loss (kev) Deposited energy (AirLight) Deposited energy (this work) ~10% difference 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

23 3. MC analysis: AirLight experiment Integrated E loss vs E at atmospheric pressure Energy deposition or loss (kev) Discrepancy at low energy Energy loss (AirLight) Energy loss (this work) 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

24 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

25 3. MC analysis: FLASH experiment Comparison of (de/dx) dep vs P at 28.5 GeV de dep /dx (MeV g -1 cm 2 ) FLASH This work 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

26 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

27 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 ) MACFLY This work ~ 6% 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

28 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

29 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) Obs. volume R ~ 10 cm J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

30 3. MC analysis: Kakimoto s experiment Corrections are larger than 25% at high electron energy! Energy (MeV) Correction to FY +6% +25% +28% +29% J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

31 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

32 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) Correction to FY +7% +8% J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

33 4. Comparison of results J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

34 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

35 4. Comparison of results: table J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

36 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

37 4. Comparison of absolute FY values Normalized FY using calculations of authors Y 337 (ph/mev) Kakimoto Lefeuvre FLASH 6.5 ph/mev Nagano MACFLY AirLight E (MeV) J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

38 4. Comparison of absolute FY values Normalized FY after applying corrections Y 337 (ph/mev) Kakimoto Lefeuvre FLASH 6.5 ph/mev Nagano MACFLY AirLight E (MeV) J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

39 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 Y 337 (ph/mev) J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

40 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 Y 337 (ph/mev) J. Rosado et al, 7th AFW, Coimbra, Portugal, September of

41 Thanks! J. Rosado et al, 7th AFW, Coimbra, Portugal, September of