21 st ecrs , košice, slovakia

21st ECRS, Košice, Slovakia

Investigation of primary cosmic Investigation of primary cosmic ray spectrum shape by means of ray spectrum shape by means of

EAS muon density techniqueEAS muon density technique

I.I.Yashin, I.I.Yashin, [email protected]@mephi.ruMoscow Engineering Physics Institute Moscow Engineering Physics Institute

A.G. Bogdanov, D.V.Chernov, D.M. Gromushkin, R.P. Kokoulin, A.G. Bogdanov, D.V.Chernov, D.M. Gromushkin, R.P. Kokoulin, G. Mannocchi, A.A. Petrukhin, O. Saavedra, V.V. Shutenko, G. Mannocchi, A.A. Petrukhin, O. Saavedra, V.V. Shutenko,

G. Trinchero, I.I. YashinG. Trinchero, I.I. Yashin

Moscow Engineering Physics Institute, RussiaMoscow Engineering Physics Institute, RussiaIstituto di Fisica dello Spazio Interplanetario, INAF, Istituto di Fisica dello Spazio Interplanetario, INAF, Torino, ItalyTorino, ItalyUniversita di Torino, ItalyUniversita di Torino, Italy


MotivationMotivation In EAS data interpretation, primary spectrum,

composition, interaction characteristics, and their energy dependence are unknown.

To solve the problem involving several unknown functions, measurements of different EAS observables are necessary.

In this talk, a new approach to study of the features of primary CR spectrum shape based of a new EAS

observable – local muon density distributions in a wide range of zenith angles – is considered.


Local muon density phenomenologyLocal muon density phenomenology If the size of the detector is small compared to typical distances of substantial changes of muon LDF, the detector 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.

Collection area rapidly increases with zenith angle (~ 1 km2 at 80)

New approachNew approach::Local density spectra of EAS muonsLocal density spectra of EAS muons

Preliminary analysis of method:


where N (> E) - primary spectrum, E is defined by the equation:

F D N E r ,D dS,

E,r D

[ events / (s sr)]

For a nearly scaling LDF around some energy E0

0 0 0 9E,r E E E ,r , .

and power type primary spectrum 0 N E A E E ,

0 2F D AD E ,r dS, /

/ ( / ) / ( , ) /dF dD dN dE dS d E r dE

New approachNew approach::Local density spectra of EAS muonsLocal density spectra of EAS muons

Spectra exhibits a power type behavior : β = γ/κ ~ 2; κ ~ 0.9 (steeper than that of primary particles).

Zenith angle distributions are amazingly well described by power function of zenith angle cosine :

Frequency of detected bundles is determined by muon density in central part of shower.

LMDS sensitive to primary CR composition and to the features of VHE hadron-nucleus interaction, especially in the forward kinematical region.

Preliminary analysis of method:

1 cos-( + )dF(D, )/dD = CD α ~ (4.5 - 4.8); β ~ (1.9 - 2.3)



General view of NEVOD-DECOR complexGeneral view of NEVOD-DECOR complex

Side SM: 8.4 m2 each• σx 1 cm; σψ 1°

Coordinate-tracking detector DECOR (~115 m2)

Cherenkov water detector NEVOD (2000

m3)

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


A typical muon bundle event in Side DECORA typical muon bundle event in Side DECOR

X-projectionX-projection Y-projectionY-projection


Muon bundle event (geometry reconstruction)Muon bundle event (geometry reconstruction)

m Live time, hr No. events

3 30 - 60 120 < 160; 200 < 240 758 18137 5 30 - 60 120 < 160; 200 < 240 1296 8864 10 30 - 60 120 < 160; 200 < 240 2680 3272 3 60 120 < 160; 200 < 240 1552 4109 5 60 120 < 160; 200 < 240 10102 6786 10 60 120 < 160; 200 < 240 19922 2013 10 75 0 < 360 19922 395


DECOR data summary DECOR data summary Muon bundle statistics 2002 - 2007Muon bundle statistics 2002 - 2007

(*) For zenith angles < 75°, only events in limited intervals of azimuth angle (with DECOR shielded by the water tank) are selected.


DECOR data summary DECOR data summary Distribution in multiplicityDistribution in multiplicity


DECOR data summaryDECOR data summaryDistribution in zenith angleDistribution in zenith angle


Calculation details

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 ; After the knee: steepening to ( 1) = 3.1.

CORSIKA simulation of 2D muon LDF:

CORSIKA 6.200 – 6.600

QGSJET 01c + GHEISHA 2002; SIBYLL 2.1 + FLUKA 2003.1bSet of fixed zenith angles, fixed primary energies Primary protons and Iron nuclei

EMF


Effective primary energy rangeEffective primary energy range

Lower limit ~ 1015 eV (limited by DECOR area).Upper limit ~ 1019 eV (limited by statistics).


Low angles: around the “knee”Low angles: around the “knee”

θθ = = 5050ºº : 10 : 101616 – 10 – 101717 eV eV21st ECRS, Košice, Slovakia

θθ = = 6565ºº : 10 : 101616 – 10 – 101818 eV eV21st ECRS, Košice, Slovakia

Combined estimator of primary energy

For every event with some set of (m, θ, φ) it is possible to attribute a certain effective primary energy

1.07 3.8EST 0 0 0( / )=( ) (sec / sec ) E E D/D

Densities: (0.05 - 2.0 m-2); zenith angles: (40º - 80º); E ~ (1016 - 1018 eV)



Distributions of experimental and expectedprimary energy estimates


Combined estimator of primary energy

Dependence of LMDS index Dependence of LMDS index ββ on primary energyon primary energy21st ECRS, Košice, Slovakia

ConclusionConclusion

gives a possibility to study features of spectrum and composition of primary CR and characteristics of hadron interaction in wide energy range (from 1015 up to 1019 eV) on the basis of a single technique and by means of a single experimental setup.

revealed some important features of the shape: steepening of LMDS related with the knee of primary CR spectrum at PeV energies.

1. In the frame of used assumptions about spectrum and hadron interaction model the analysis of DECOR data:

2. New method based on a combined estimator of effective primary energy also reveal the steepening of spectrum around 108 GeV.


Thank you for the attention!

Large angles: around 10Large angles: around 101818 eV eV

21 st ecrs , košice, slovakia

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