GRAND Simulations of Ultra high Energy Cosmic Ray showers - - PowerPoint PPT Presentation

GRAND

Simulations of
 Ultra high Energy Cosmic Ray showers Motivations: Estimate the performances for detection of UHECRs.

Nicolas Renault-Tinacci


On behalf of GRAND group at IAP TREND@Ulastai, 21CMA antennas

How did we proceed ?

Array :

_Flat array 17x18 lines _1km-step ⇒ 306 km2

~ GRANDproto300

_Array altitude = 1500 m _At Ulastai location

Antenna trigger condition:

_conservative ✴ Vpp>150µV (10σnoise) _aggressive ✴ Vpp>50µV (3σnoise)

Shower detection condition:

_5+ triggered antennas

• 120 combinations of (E, ϕ, θ):

_ E in [1017.5 - 1019.5] eV with

1/2-decade step (5 values)

_ ϕ in [0, 180[ deg with 45deg

step (4 values, the 4 others obtained by

symmetry)

_ θ in [95-120] deg (larger than in prelim

study) in GRAND convention (⬄ [60-85] deg in CR convention) with 5deg

step (6 values)

_ for each set 10 random core

positions. Simulations performed with ZHAireS

Core position random drawing

• Random uniform draw of (x,y) in a [-50km, +50km] box
• Computation of the number of antennas within the footprint

_ If Nantennas ≥5 ⇒ shower selected, otherwise new draw.

✴

Minimum number of antennas quite agressive (8 should be considered instead)

_ Ntries is stored for each set and each core position selected.

Northing [m] Easting [m] array footprint Easting [m] Northing [m] selected shower core Tried shower core

Performance calculations

• Aeff(θ, E) = Adraw cos(θ) Ntrig(θ, E) / Ntries(θ, E)

with Nxx = ∑ϕ Nxx(θ, E, ϕ) for xx = trig or tries

• Aperture(E) = ∫∫ Aeff(θ, E) sin(θ) dθ dϕ
• Exposure(E) = Aperture(E) Ỏt
• dN/dE/dt(E) = Exposure(E) Flux(E)
• Event rate(E) = ∫ dN/dE/dt(E) dE

draw area = 10000 km2 number of tries to obtain a core position with 5 antennas in the footprint Number of detected showers for a (θ, E) combination Summed of all the ϕ values

Effective area

• The differences between scenarios are more important at low θ i.e.

where the footprints are smaller.

• At high θ, a factor 2 or 3 max is lost from aggressive to conservative.
• Not many differences in terms of loss between high and low energies

Aperture and Exposure

1 year livetime

• Above 1019 eV, the aperture is ~470 000 km2.sr compared to 107 000

km2.sr obtained in the preliminary study.

• It corresponds to an exposure after 5 years of live time of 2.4e6 km2.sr.yr

(~8e13 km2.sr.s) compared to 535 000 km2.sr.yr in the preliminary study

• Results are a factor 4/5 above those of the preliminary study

=10.4 Preliminary study

Bias warning!


when rescaling from 306 km2 to GRAND200k. Only showers with core within array should be accounted for (edge effect).

Event rates for agressive (resp. conservative) case

• 348 (resp. 229) events expected daily for E in [10

17.5-10 19.5] eV for GRANDproto300

• 2.3x10

5 (resp. 1.5x10 5) day

• 1 for E in [10

17.5-10 19.5] eV for GRAND200k compared 


to 2x10

6 (resp. 4x10 5) day

• 1 in the preliminary study for [10

17-10 19] eV.

• 11 (resp. 8.5) events expected daily for E in [10

18-10 19] eV for GRANDproto300

• 448 (resp. 296) day
• 1 for E>10

19 eV for GRAND200k compared to ~100 day

• 1 in 


the preliminary study (4/5 times higher)

Bias warning!


when rescaling from 
 306 km

2

to GRAND200k. 
 Only showers with core 
 within array should be accounted for 
 (edge effect).

Event rates for agressive (resp. conservative) case

• 4071 (resp. 3115) events expected in 1 year for E in [1018 - 1019] eV for

GRANDproto300

• 29 061 (resp. 25 286) events expected in 1 year for E>1019.5 eV for GRAND200k

compared to the ~6400 UHECRs 
 predicted in the preliminary study (4/5 times higher)

Bias warning!


when rescaling from 306 km2 to GRAND200k. Only showers with core within array should be accounted for (edge effect).

Conclusion, remarks, perspectives

• High performances but increased by a factor of 4/5 w.r.t the preliminary study (which was an

underestimation of the perfs)

• Can be explained by:

_ preliminary study perfs underestimated ⇐ only showers with their core within the array which is not

the case in the current study.

_ GRAND200k perfs overestimated ⇐ showers with core not within the array are accounted for

making the extrapolation from GRANDproto300 tricky (edge effect).

_ low minimum number of antennas criterion (NminAnt = 5) used to determine a shower as detected. ✴ From a very quick look (only on perfs calculations), with NminAnt = 8, performances are decreased

by 10 to 50% depending on energy range.

✴ Re-run simulations with NminAnt = 8 (for core position random drawing) 


⇒ ↗ Ntries ⇒ ↘︎ performances.

• For the WP v2:

_ analysis redone with a more conservative minimum number of antenna criterion and 10k instead of

300 km

2

_ extrapolate the results from GRANDproto300 to GRAND by considering ONLY events with the core

within the array

_ compute the number of “fully included in the array” events

• Done within the next month or so.