- Email: [email protected]
cm2
ELSEVIER
Nuclear Physics B (Proc. Suppl.) 52B (1997) 198-200
PROCEEDINGS SUPPLEMENTS
Experimental Check of the New Method of Selection of EAS with Constant Energies at Observation Level 700 g/cm 2 A.A. Chilingarian a, V.S. Eganov a, V.A. Ivanov a, A.P. Garyaka a, E.A. Mamidjanian b, R.M. Martirosov a, N.M. Nikolskayab, S.I. Nikolsky b, J. Procureur c, V.A Romakhin b, J.N. Stanlenov d, B.V. Subbotin b ayerevan Physics Institute, Yerevan, Armenia bLebedev Physical Institute, Moskow, Russia CCENBG, Bordeaux, France aINRNE, Sofia, Bulgaria The experimental data obtained in the new EAS experiment Gamma at Mt. Aragats (Armenia) allows to select showers generated by primaries with different masses but with the same primary energy. Such a selection gives the possibility to estimate the primary mass composition for given energies by much more simple and precise way. In this work, the recent experimental data obtained with the help of Gamma array are compared with the Tien Shan results. An excellent agreement is shown, which confirms our Monte Carlo calculations, carried out for EAS muon and electrons components.
1. I n t r o d u c t i o n Because the very strong decrease of the primary energy flux, cosmic particles phenomena are not investigated in direct experiments for energies larger than 105 GeV. The correspondent experimental information for this energy range is provided by the EAS arrays. However, the proper treatment of experimental fluctuations is important for obtaining the needed physical information about the mass composition and energy spectrum of the parmary cosmic flux. As we have shown in previous paper, the EAS selection parameter is of large importance for the selection of events generated by primaries with different masses but for given primary energy. In attempt to realize this selection, a new parameter easy to be measured and named by us [1] as was defined. A general view of our method could be found in [1]. The definition of the selection parameter a is slightly changing in respect to the observation level and the existing detector displacement of the analyzed EAS array. However, basically, mountain observation levels are preferable, because of the relative low level of fluctuations of the muon 0920-5632(97)/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII: S0920-5632(96)00882-1
and electron components of showers. The aim of this paper is to present the first preliminary results from the Gamma experiment at Aragats for showers selected using the new shower parameter a. In this experiment for the first time the detector displacement is specially designed in attempt to obtain good estimation for the new a parameter. For this purpose, a distant point (DP) consisting of electron flux detectors with an effective area of 20 m 2, at distance ~ 120m from the center of the Gamma array was put in operation. Details of the experiment could be found
in [2]. 2. M e t h o d
The ae(120m) parameter needed to select EAS generated by primaries with the same energy as been defined in detail in the work [3] such as : ae (120m) =
1202p" (120m)
fNKG(lO,Sfi--70)
where pc(r) is the electron lateral density and fNKG(IO, S6--70) is the Nishimura-KamataGreisen function at 10m from the shower axis. Ss-vo is the the local age [4] calculated from
A.A. Chilingarian et al./Nuclear Physics B (Proc. Suppl.) 52B (1997) 198-200
p~(6m) and pe(7Om). Figure 1 shows that a crossing point for r = 120m exists in the c~(r) - r dependence for a large primary energy range.
199
108 a T i c n S h a h (83) • Aragats (96)
o o ta =
]07 i(i 5
[
ill nOcl gig
IO7GeV I(I
4
/
~8
5 II)6GeV J
tR~ m~
/:/
105 ' l(i 6GeV
:// ,~
/
/
IO 3
/ "~/,
~8H~
]o 6
/
/
/
,N ~,,
i L IIJIHI 103
I(I4
105
10 5
107 (I
5 5111 GeV
/
Figure 2. data
from Tien Shan and Aragats
(Ne)-O~ e
:,,/
10 2 i/ //
10 6
!//
[] T i e n S h a n (83) ¢ Aragats (96)
p . . . . . . . Fe L I ~lLIht[
I01 I 0 II
10 I
U I JLIJlll
t 11)2
L nl~t~
I0 5
11)3
r (m) Figure 1. ~e (r) - r dependence for primary protons and iron nuclei for different energies 3. R e s u l t s
IJ
104
~ o
10 3
J
10 3
In Aragats experiment it were selected the showers with axes on the distances of 110-130 m from DP center, i.e. the pe(120) and respectively he(120) were found directly. It can be noticed that, as we precised in the introduction, no detector were placed at 120m from the shower axis in Tien Shan. Consequently, for this experiment, c~ has been defined using the electron lateral density pe (r) measured at only 70 m. Figure 1 shows that [~(70m)]proto,~and [~(70m)]~ron are not very different which makes this approximation available. In figures 2 and 3, we compare the (~ dependence of the average size (Ne) and the average muon number (N~) in showers selected with a = cons• in Tien Shan and in Agarats experiments. A very good agreement is obtained
,
, , ,,,,I 10 4
,
t
i
, ill,I
,
L
i illll
10 5
10 6 E(
Figure 3. (N~)-ae from Tien Shan and Aragats data between these two experiments. To obtain information for the primary mass composition, the most promising method [5-7] remains to analyze, for given primary energies, i.e. for given values of a(120m), the shape of the muon fluctuation distributions W(K~,), where K~ = N#/(N~,). For such an analysis, it is necessary to compare the dependences (Ne) and (N~) versus a(120m) with the new experimental data from Gamma in the Aragats array. Such comparisons are shown in figures 4 and 5.
200
A.A. Chilingarian et al./Nuclear Physics B (Proc. Suppl.) 52B (1997) 198-200
107
A VZm
i0 6
I
........
,
experiment. More, average EAS sizes and muon numbers obtained using simulation are in agreement with these new data which makes a future analysis of the muon number fluctuations possible for the determination of the primary mass composition at given energies. Also it seems promissing to use the new parameter along other for multidimensional EAS analisis [8]. Acknowledgments This work is supported by Russian Academy of Sciences, Armenian Ministry of Industry and the French CNRS.
105 103
10 4
10 5
1~(120m)
Figure 4. Simulation of (Are) for different values of (~e for primary protons and primary iron nuclei 10 5
v
T
10 4 .,".," F . . . . . "/" y'"
•Z / / /
I'~//
•
• Aragats (96) h
10 3 10 3
I
I
I
I i I If 10 4
I
I
I
I
J I
a l
10 5 ~(120m)
Figure 5. Simulation of (Nu) for different values of c~e for primary protons and primary iron nuclei 4. C o n c l u s i o n The Gamma experiment at Aragats gives the opportunity to select showers generated by primaries with different masses but with the same primary energy. In such a way, from the corresponding data, it will be possible to determine the mass composition for given energy without using the usual uncertain relation " E A S size ¢=~ primary energy". We verify that the experimental data from the new Gamma array are confirmed by previous ones obtained in the Tien Shan
REFERENCES 1. Procureur J., Stamenov J.N., 1995, Nucl. Phys. B , 39, 242 2. Arzumanian S.A. et al, 1995, Proc. 24 th ICRC, Roma, 3, 482 3. Martirosov R.M., Procureur J. and Stamenov J.N., 1995, Nuovo Cimento, 108, 299 4. Bourdeaux M.F., Capdevielle J.N., Procureur J., 1980, J. Phys. G, 6, 901 5. Linsley J., Scarci L., 1962, Phys. Rev. Lett., 9, 3, 193 6. Nikolsky S.I., Stamenov J.N., Ushev S.Z., 1984, Soy. Phys. JETP, 60, 1, 10 7. Nikolsky S.I. and Stamenov J.N., 1983, Proc. 18th ICRC, Bangalore, 2, 199 8. Chilingarian A., Zazyan H.,1991, Nuovo Cimento,14C.
Nuclear Physics B (Proc. Suppl.) 52B (1997) 198-200
PROCEEDINGS SUPPLEMENTS
Experimental Check of the New Method of Selection of EAS with Constant Energies at Observation Level 700 g/cm 2 A.A. Chilingarian a, V.S. Eganov a, V.A. Ivanov a, A.P. Garyaka a, E.A. Mamidjanian b, R.M. Martirosov a, N.M. Nikolskayab, S.I. Nikolsky b, J. Procureur c, V.A Romakhin b, J.N. Stanlenov d, B.V. Subbotin b ayerevan Physics Institute, Yerevan, Armenia bLebedev Physical Institute, Moskow, Russia CCENBG, Bordeaux, France aINRNE, Sofia, Bulgaria The experimental data obtained in the new EAS experiment Gamma at Mt. Aragats (Armenia) allows to select showers generated by primaries with different masses but with the same primary energy. Such a selection gives the possibility to estimate the primary mass composition for given energies by much more simple and precise way. In this work, the recent experimental data obtained with the help of Gamma array are compared with the Tien Shan results. An excellent agreement is shown, which confirms our Monte Carlo calculations, carried out for EAS muon and electrons components.
1. I n t r o d u c t i o n Because the very strong decrease of the primary energy flux, cosmic particles phenomena are not investigated in direct experiments for energies larger than 105 GeV. The correspondent experimental information for this energy range is provided by the EAS arrays. However, the proper treatment of experimental fluctuations is important for obtaining the needed physical information about the mass composition and energy spectrum of the parmary cosmic flux. As we have shown in previous paper, the EAS selection parameter is of large importance for the selection of events generated by primaries with different masses but for given primary energy. In attempt to realize this selection, a new parameter easy to be measured and named by us [1] as was defined. A general view of our method could be found in [1]. The definition of the selection parameter a is slightly changing in respect to the observation level and the existing detector displacement of the analyzed EAS array. However, basically, mountain observation levels are preferable, because of the relative low level of fluctuations of the muon 0920-5632(97)/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII: S0920-5632(96)00882-1
and electron components of showers. The aim of this paper is to present the first preliminary results from the Gamma experiment at Aragats for showers selected using the new shower parameter a. In this experiment for the first time the detector displacement is specially designed in attempt to obtain good estimation for the new a parameter. For this purpose, a distant point (DP) consisting of electron flux detectors with an effective area of 20 m 2, at distance ~ 120m from the center of the Gamma array was put in operation. Details of the experiment could be found
in [2]. 2. M e t h o d
The ae(120m) parameter needed to select EAS generated by primaries with the same energy as been defined in detail in the work [3] such as : ae (120m) =
1202p" (120m)
fNKG(lO,Sfi--70)
where pc(r) is the electron lateral density and fNKG(IO, S6--70) is the Nishimura-KamataGreisen function at 10m from the shower axis. Ss-vo is the the local age [4] calculated from
A.A. Chilingarian et al./Nuclear Physics B (Proc. Suppl.) 52B (1997) 198-200
p~(6m) and pe(7Om). Figure 1 shows that a crossing point for r = 120m exists in the c~(r) - r dependence for a large primary energy range.
199
108 a T i c n S h a h (83) • Aragats (96)
o o ta =
]07 i(i 5
[
ill nOcl gig
IO7GeV I(I
4
/
~8
5 II)6GeV J
tR~ m~
/:/
105 ' l(i 6GeV
:// ,~
/
/
IO 3
/ "~/,
~8H~
]o 6
/
/
/
,N ~,,
i L IIJIHI 103
I(I4
105
10 5
107 (I
5 5111 GeV
/
Figure 2. data
from Tien Shan and Aragats
(Ne)-O~ e
:,,/
10 2 i/ //
10 6
!//
[] T i e n S h a n (83) ¢ Aragats (96)
p . . . . . . . Fe L I ~lLIht[
I01 I 0 II
10 I
U I JLIJlll
t 11)2
L nl~t~
I0 5
11)3
r (m) Figure 1. ~e (r) - r dependence for primary protons and iron nuclei for different energies 3. R e s u l t s
IJ
104
~ o
10 3
J
10 3
In Aragats experiment it were selected the showers with axes on the distances of 110-130 m from DP center, i.e. the pe(120) and respectively he(120) were found directly. It can be noticed that, as we precised in the introduction, no detector were placed at 120m from the shower axis in Tien Shan. Consequently, for this experiment, c~ has been defined using the electron lateral density pe (r) measured at only 70 m. Figure 1 shows that [~(70m)]proto,~and [~(70m)]~ron are not very different which makes this approximation available. In figures 2 and 3, we compare the (~ dependence of the average size (Ne) and the average muon number (N~) in showers selected with a = cons• in Tien Shan and in Agarats experiments. A very good agreement is obtained
,
, , ,,,,I 10 4
,
t
i
, ill,I
,
L
i illll
10 5
10 6 E(
Figure 3. (N~)-ae from Tien Shan and Aragats data between these two experiments. To obtain information for the primary mass composition, the most promising method [5-7] remains to analyze, for given primary energies, i.e. for given values of a(120m), the shape of the muon fluctuation distributions W(K~,), where K~ = N#/(N~,). For such an analysis, it is necessary to compare the dependences (Ne) and (N~) versus a(120m) with the new experimental data from Gamma in the Aragats array. Such comparisons are shown in figures 4 and 5.
200
A.A. Chilingarian et al./Nuclear Physics B (Proc. Suppl.) 52B (1997) 198-200
107
A VZm
i0 6
I
........
,
experiment. More, average EAS sizes and muon numbers obtained using simulation are in agreement with these new data which makes a future analysis of the muon number fluctuations possible for the determination of the primary mass composition at given energies. Also it seems promissing to use the new parameter along other for multidimensional EAS analisis [8]. Acknowledgments This work is supported by Russian Academy of Sciences, Armenian Ministry of Industry and the French CNRS.
105 103
10 4
10 5
1~(120m)
Figure 4. Simulation of (Are) for different values of (~e for primary protons and primary iron nuclei 10 5
v
T
10 4 .,".," F . . . . . "/" y'"
•Z / / /
I'~//
•
• Aragats (96) h
10 3 10 3
I
I
I
I i I If 10 4
I
I
I
I
J I
a l
10 5 ~(120m)
Figure 5. Simulation of (Nu) for different values of c~e for primary protons and primary iron nuclei 4. C o n c l u s i o n The Gamma experiment at Aragats gives the opportunity to select showers generated by primaries with different masses but with the same primary energy. In such a way, from the corresponding data, it will be possible to determine the mass composition for given energy without using the usual uncertain relation " E A S size ¢=~ primary energy". We verify that the experimental data from the new Gamma array are confirmed by previous ones obtained in the Tien Shan
REFERENCES 1. Procureur J., Stamenov J.N., 1995, Nucl. Phys. B , 39, 242 2. Arzumanian S.A. et al, 1995, Proc. 24 th ICRC, Roma, 3, 482 3. Martirosov R.M., Procureur J. and Stamenov J.N., 1995, Nuovo Cimento, 108, 299 4. Bourdeaux M.F., Capdevielle J.N., Procureur J., 1980, J. Phys. G, 6, 901 5. Linsley J., Scarci L., 1962, Phys. Rev. Lett., 9, 3, 193 6. Nikolsky S.I., Stamenov J.N., Ushev S.Z., 1984, Soy. Phys. JETP, 60, 1, 10 7. Nikolsky S.I. and Stamenov J.N., 1983, Proc. 18th ICRC, Bangalore, 2, 199 8. Chilingarian A., Zazyan H.,1991, Nuovo Cimento,14C.