A new approach to EAS investigations A new approach to EAS investigations in energy region 10in energy region 101515 - 10 - 101919 eV eV
R.P.Kokoulin for DECOR CollaborationR.P.Kokoulin for DECOR Collaboration
Moscow Engineering Physics Institute, RussiaMoscow Engineering Physics Institute, Russia
Istituto Nazionale di Astrofisica, Sezione di TorinoIstituto Nazionale di Astrofisica, Sezione di TorinoUniversita di Torino, ItalyUniversita di Torino, Italy
ContentsContents
RICAP'07, Roma, June 21, 2007
1. Introduction2. Local muon density phenomenology3. DECOR data VS simulation4. Conclusions
IntroductionIntroduction
• In EAS data interpretation, primary spectrum, composition, and interaction characteristics are unknown.
• To solve the problem involving several unknown functions, measurements of different
EAS observables are necessary.
• In this talk, phenomenology and recent data on a new EAS observable – local muon density distributions in a wide range of zenith angles – are considered.
Local muon density phenomenology - 1Local muon density phenomenology - 1
For inclined EAS, dimensions of muon LDF exceed hundreds meters. The detector with sizes of tens meters may be considered as a point-
like probe. In a muon bundle event, the local muon density D (in a random point of the shower) is estimated:
D = (number of muons) / (detector area); [D] = particles / m2.
Without considering fluctuations, spectrum of events in local density may be written as
where N (> E) - primary spectrum, E is defined by the equation:
F D N E ,D dS , r
ρ(E, r) = D.
Dimension: [F (> D) ] = events / (s sr).
For a nearly scaling LDF around some energy E0
0 0 0 9E, E E E , , . r r
and power type primary spectrum 0N E A E E ,
1) Power type spectrum of local density, a bit steeper than the
primary one ( = / ).
0F D AD E , dS r
2) Enhanced sensitivity to the central part of the shower ( 2).
Local muon density phenomenology - 2Local muon density phenomenology - 2
Contribution of different distances to total number Contribution of different distances to total number of muons in EAS and to local muon density spectrumof muons in EAS and to local muon density spectrum
1 10 100 1000 100000.0
0.5
1.0
1.5
Arb
itra
ry u
nits
Distance from shower axis, m (log scale !)
QG, 1017 eV, 60o (protons)
Contribution to local density
r2*(r), = 2.0
Contribution tonumber of muons
r2*(r)
Enhanced sensitivity to the central part of the shower (forward interaction region) !
Contribution of distances, different zenith anglesContribution of distances, different zenith angles
• Collection area increases with zenith angle.• The effect is enhanced by the EMF influence.
General view of NEVOD-DECOR complexGeneral view of NEVOD-DECOR complex
Side SM:
• 8.4 m2 each;• σx 1 cm;• σψ 1°.
A typical muon bundle event in Side DECORA typical muon bundle event in Side DECOR( 9 muons, 78 degrees)( 9 muons, 78 degrees)
3468:0 3319:1 3290:2 3094:3
0:3264
SM=0 1:3216 2:3072 3:3207
3621:0 3336:1 3270:2 3294:3
0:2987
SM=1 1:3147 2:3051 3:3146
3514:0 3384:1 3110:2 3158:3
0:3596
SM=2 1:3446 2:4148 3:3509
3649:0 3511:1 3353:2 3378:3
0:3476
SM=3 1:3205 2:3331 3:3000
7190:0 3453:1 3239:2 3388:3
0:3705
SM=4 1:3597 2:3600 3:3859
4073:0 3360:1 4413:2 3888:3
0:3405
SM=5 1:3394 2:3410 3:3626
3623:0 3554:1 3470:2 3444:3
0:3521
SM=6 1:3532 2:3429 3:3159
3564:0 3299:1 3058:2 3303:3
0:3871
SM=7 1:3568 2:3545 3:3697
01234567
01234567
Plate1:Step=25nsec
Plate2:Step=25nsec
Run 8 --- Event 219242 ----06-12-2004 23:25:26.27 Trigger(1-16):01110100 00000000 Weit_Time:109.072 msec
X-projection Y-projection
Muon bundle event (geometry reconstruction)Muon bundle event (geometry reconstruction) Nlam=40,N5=26,N6=23,NR1=0 ,NR2=0 ,Sum1=0 ,Sum2=0 ,Sob-00000001,00000000
N1=35,N3=14 nCup= 0 SumAmp=1.26e+03 01110100,00000000 NGroup2=8,n=8,n1=8,n2=9,n0=8,nx=9,ny=8,One=0N2=32,N4=13 nCdow n= 0 NPMT=143 ETel= 0.0% ERec= 60.8%
Date=06-12-04 23:25:26.027 Nevent=219242 Group: fm=53.15 tm=77.87 Recon: f i=54.41 t=80.70 F= 0.0
A “record” muon bundle event A “record” muon bundle event (~ 160 muons, θ = 80°)(~ 160 muons, θ = 80°)
4873:0 3644:1 3754:2 3814:3
0:3923
SM=0 1:3332 2:3387 3:3266
3859:0 4199:1 3877:2 5106:3
0:3054
SM=1 1:3101 2:3351 3:3591
3562:0 3149:1 3376:2 3672:3
0:3570
SM=2 1:3435 2:3511 3:3948
4000:0 4098:1 4109:2 4255:3
0:3619
SM=3 1:3601 2:3894 3:3760
3786:0 3732:1 3712:2 4030:3
0:3750
SM=4 1:3582 2:3655 3:3992
4000:0 3388:1 3477:2 4119:3
0:3641
SM=5 1:3639 2:3849 3:4104
4050:0 4120:1 4164:2 5038:3
0:3609
SM=6 1:3508 2:3684 3:3647
3961:0 3769:1 3844:2 4323:3
0:4245
SM=7 1:3814 2:4037 3:4338
3352:0 3438:1 3922:2 4134:3
0:4850
SM=8 1:4191 2:3898 3:5122
3181:0 3942:1 5269:2 5326:3
0:3347
SM=9 1:3879 2:3924 3:4615
3820:0 4458:1 4688:2 4870:3
0:475
SM=10 1:5515 2:5367 3:6392
3239:0 3452:1 4038:2 4575:3
0:3800
SM=11 1:5594 2:4104 3:4670
01234567
01234567
Plate1:Step=25nsec
Plate2:Step=25nsec
Run 242 --- Event 847205 ----05-05-2003 06:11:04.43 Trigger(1-16):01110101 00111100 Weit_Time:30.065 msec
X-projection Y-projection
DECOR data summary - 1. DECOR data summary - 1. Muon bundle statisticsMuon bundle statistics
Muon multiplicity
Zenith angle range (*)
Live time, (hours)
Number of events
3 30 – 40 524.7 4754
3 40 – 60 524.7 7945
3 60 1552 4114
5 60 6848 4531
10 60 16668 1651
10 75 16668 332
(*) For zenith angles < 75°, only events in limited intervals of azimuth angle (with DECOR shielded by the water tank) are selected.
DECOR data summary - 2. DECOR data summary - 2. Distribution in multiplicityDistribution in multiplicity
DECOR data summary - 3. DECOR data summary - 3. Distribution in zenith angleDistribution in zenith angle
Procedure of the analysisProcedure of the analysis
Calculation detailsCalculation details
Reference primary “all-particle” spectrum:Power type spectrum with the knee at 4 PeV. Below the knee, dN / dE = 5.0 (E, GeV) 2.7 cm-2 s-1 sr-1 GeV-1; steepening to ( 1) = 3.1 after the knee.
Close to MSU “all-particle” spectrum as given by PDG (T. Gaisser, T. Stanev); not much different from most of other data around the knee; close to Fly’s Eye “stereo” at 1018 eV.
CORSIKA simulation of 2D muon LDF:CORSIKA 6.502; two combinations of interaction models QGSJET01c + GHEISHA2002, SIBYLL2.1 + FLUKA2003.1.b.
Set of fixed zenith angles and of primary energies.Primary protons and Fe nuclei; with and without EMF.
Effective primary energy rangeEffective primary energy range
Lower limit ~ 1015 eV (limited by DECOR area).Upper limit ~ 1019 eV (limited by statistics).
Differential local muon density spectrum - 35°Differential local muon density spectrum - 35°
0.01 0.1 1 10
10-4
10-3
D
3 d
F/d
D, 1
/ (
s sr
m 4
)
D, m - 2
solid: QGSJET01dashed: SIBYLL
DifStar35 23.05.2007
1015 eV 1016 eV 1017 eV
Fe
p
35 o
Differential local muon density spectrum - 65°Differential local muon density spectrum - 65°
PCR intensity around 10PCR intensity around 101818 eV: two models eV: two models
HiRes Collaboration: astro-ph/0703099v1 (March 2007)
PCR intensity around 10PCR intensity around 101818 eV: two models eV: two models
ConclusionsConclusions - 1- 1
1. Local muon density spectra are sensitive to primary spectrum and composition, and have an enhanced sensitivity to forward region of hadronic interactions.
2. A new approach based on local muon density spectrum phenomenology provides possibility to study PCR in a very wide energy range (from 1015 to 1019 eV) by means of a single, relatively small-size detector.
3. Analysis of local muon density spectra together with data of experiments on other EAS observables will allow putting new constraints on combinations of spectrum, composition and interaction models.
ConclusionsConclusions - 2- 2
1. DECOR data at moderate zenith angles are in a reasonable agreement with simulations based on a usual picture of PCR spectrum and interaction around the knee.
2. Within the frame of the considered spectrum model (with γ 2.1 after the knee), DECOR data favor an increase of the effective primary mass up to energies 1017 eV.
3. There is an indication (at 2σ-level) for an increase of local muon density spectrum slope at effective primary energy around 1017 eV.
4. Within the considered interaction models, DECOR data at large zenith angles (E0 ~ 1018 eV) are not compatible in absolute intensity with spectrum model based on HiRes data, and are in agreement with AGASA-based intensity.
Thank you !Thank you !