Gamma-families with total energy greater than 10 TeV, found in the EX chamber which was cooperated with the EAS array were combined with EAS triggered by big bursts. The absolute intensity of the size spectrum of these combined EAS was compared with that of general EAS obtained by AS trigger. The EAS with sizes greater than 2x1 million were always accompanied by gamma-families with sigma E sub gamma H  10 TeV, n sub gamma, H  2 and Emin=3 TeV, although the rate of EAS accompaning such gamma-families decreases rapidly as their sizes decrease

Dake, S.

Kawamoto, M.

Kusumose, M.

Mitsumune, T.

Nakatsuka, T.

Nishikawa, K.

Saito, T.

Sakata, M.

Shima, M.

Yamamoto, Y.

English

NASA Technical Reports Server

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COMPARISON OF ABSOLUTE INTENSITY BETWEEN EAS WITH GAMMA-FAMILIES
AND GENERAL EAS AT MT. NORIKURA
Mitsumune_ T., Nakatsuka, T., Nishikawa, K., Saito, To.,
Sakata, M., Shima, M. and Yamamoto, Y.
Konan University, Kobe, Japan.
Dake, S. and Kawamoto, M.
Kobe University, Kobe.
Kusunose, Mr, Ohmori, N. and Sasaki, H.
Kochi University, Kochi, Japan.
Hotta, N.
Ut sunomiya University, Ut sunomiya, Japan.
ABSTRACT
Gamma-families with total energy greater than i0 TeV, found
in the EX chamber which was cooperated with the EAS array at
Mt. Norikura, were combined with EAS triggered by big bursts.
The absolute intensity of the size spectrum of these combined
EAS was compared with that of general EAS obtained by AS
trigger. EAS with sizes greater than 2x106 were always
accompanied by gamma-families with 7E_ =>i0 TeV, n_ u>_2 andy, J._-- y zz
Emin=3 TeV, although the rate of EAS accompaning suck gamma-
familyies decreases rapidly as their sizes decrease.
i. Introduction
The results of the cooperative experiment of the 20 m 2 iron EX
(emulsion and/or X-ray film) chamber and the EAS array at Mt. Norikura
(738 gcm -2) were reported once at Bangalore (Nakatsuka et al., 1983).
Thereafter, the reanalysis of combination between gamma-families and EAS
was done and a few new combined events were obtained. And, some of the
old data were revised, especially the EAS size Ne and age parameter s were
renewed by taking account of the transition effect of the materials over
the scintillation counters and of the plastic scintillator itself for EAS
density measurement. The data of general EAS obtained by the AS trigger
in the same period of this experiment were analysed. In this report the
EAS combined with gamma-families of total energy greater than i0 TeV is
compared with the general EAS thus obtained with respect to the absolute
intensities of EAS size spectrum.
2. Experiment
The experimental apparatus was described before (Yamamoto et al.,
1981). The EAS data were taken by two kind of triggers. One was a burst
trigger under the 14 r.l. thick EX chamber when any one of 72 burst
scintillation counters responded to bursts greater than about 2000
particles per detector of 0.25 m 2 unit area. These EAS events with big
bursts were provided for the analysis of combination with gamma-families.
Another one was an AS trigger by four sets of four-fold coincidence of the
nearest four out of the central nine non-covered scintillation counters.
https://ntrs.nasa.gov/search.jsp?R=19850027616 2020-03-20T17:20:34+00:00Z
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o e
o
o. _ _o
. ! I _** %e _,* •
(a) (b)
Fig. 1 Map of EAS axis locations.
(a): the EAS combined with gamma-families of EEv __>i0 TeV. Two
small rectangles indicate the EX chambers (I0-_ "i each) and a big
one is the spark area (9x6 m2).
(b): the general EAS with Nea2xl06. Only the events hit the area
within r=5 m were used for the analysis.
The period of the experiment was 302.5 days and the live time of recording
system of EAS data was 292.2 days (95.7 %). The total number of EAS
recorded by the burst trigger in this period was about 12000 events and
the number of EAS obtained by the AS trigger was about 6000 events during
about 240 days. The arrival angles of EAS, which are necessary for
combining them with gamma-families and for deducing absolute intensity of
EAS size spectrum, were detected by four sets of spark chambers. The
live time of spark chamber system was a little higher than 80 %.
3. Selection of events
53 gamma-families with total energy ZEy,H>_IO TeV and nT, H>_2 for
Emin=3 TeV were found in our EX chamber and 44 events out of them were
combined with EAS triggered by big bursts. The rate of combination was
83 %. Nine gamma-families were not combined with EAS. This is mainly
due to the lack of arrival angle data of EAS because of dead time of the
spark chamber system. The data of these 44 combined events were used for
deducing the absolute intensity of EAS with big gamma-families assuming
that the residual nine unknown EAS have the same size distribution as the
combined events. The EAS size Ne and age parameter s were determined by
fitting the experimental shower particle density to the NKG lateral
function with the Moliere unit ii0 m, where the shower axis was put on the
location of the gamma-family whose map was given in Fig. 1 (a). On the
other hand, about 4200 EAS recorded during the last 170 days by the AS
trigger were served for the size spectrum of general EAS. The axis
locations of the general EAS whose axes hit the area within radius r=7 m
from the array center are shown in Fig. 1 (b) for Ne_2xl06. But, only the
EAS whose axes hit the area of r<_5 m were employed for the analysis here.
4. Results
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Using the experimental
result about the transition
effect of EAS shower particle 1.2
density by thin materials
(Saito et al., 1983) the w
corrections were made on the _O.8 __._ o--_ ._o_.___o oraw values of Ne and s for == o
the response excesses of 3 cm "< 0.4 o
thick plastic scintillator w
and also for the transition < ......
effect due to the roof and 0103 104 105 106 107 10s
ceiling materials for indoor EAS SIZE Ne
counters and due to the
counter box material for all Fig. 2 Ne-s correlation for
counters. As a result, the the combined EAS with gamma-
age parameter s was increased families with EE%H_I0 TeV
by the amount of 0.18 ~ 0.16 (scatter plot and crosses)
and the shower size Ne was and for the general EAS with
multiplied by a factor 0.65 ~ sizes Ne_2xl06 (open diamonds).
1.16 depending on the raw
values of s from 0.4 to 1.2.
The Ne-s scatter plot of the combined events after the correction is shown
in Fig. 2. In this figure are also shown the Ne-dependences of average
age parameters for combined events (crosses) and for the general EAS (open
d lamond s).
In order to get the vertical intensity of size spectrum of EAS it is
necessary to know the zenith angle distribution of them. In Fig. 3 (a)
are shown the distributions for the combined EAS with gamma-familles of
EEy u>10 TeV (closed circles) and for the general EAS with Ne__2xl06 (open
clr['_es). It is natural that the zenith angle distribution of the
combined EAS is steeper than the general EAS but almost same as the gamma-
families shown in Fig. 3 (b). Using the values of a factor xo/Aatt in the
102 102
I-- = °
-- Z Z
# '"
u. _
0 0
_ ul w
m
Z Z
0 024 0[8 1;2 0 0.4 0.8 1.2
ZENITH ANGLE (tane) ZENITH ANGLE(tane)
(a) (b)
Fig. 3 Zenith angle distributions.
(a): the general EAS with Ne>_2xlO 6 (open squares) and the combined
EAS with gamma-familles with EEy, HZlO TeV (closed circles).
(b): all gamma-families with EEy,H>_IO TeV, ny,H_>2 and Emin=3 TeV.
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HE-3.3-11
theoretical zenith angle distribu- 10_I0tion fitted to the experimental ........
data, we can easily get vertical _ ._
O OOoo
intensity of EAS size spectrum as _u -=_ .,_I.85
shown in Fig. 4. The spectrum of _,_10_11 , ; _
the general EAS, marked by open
squares in this figure, is consid- _ _
ered to be free from detection bias _> T '_[I
in the size region Ne>_2xlO 6 _ 10"1_ _'%1.Closed circles and open triangles
indicate the combined EAS with z
EE_,H_>I0 TeV and >20 TeV, respec- ,,
tively. It is concluded from this _"D
figure that the EAS with Ne>_bxl06 _ 10_1_
are always associated with gamma- rn
families with lEy H >I0 TeV at the <
altitude of Mt. _orikura (Xo=738 ' " 10 6 ' ' ' 10 7 10 8
gcm-2). This is consistent with
the fact seen in Fig. 2 that both SHOWER SIZE
the average values of s agree each Fig. 4 Integral size spectra for
other for Ne!5xl06 between the the general EAS (open squares)
general EAS and the combined EAS and the combined EAS with gamma-
with gamma-familles with 7.Ey,H_I0 families of lEv H.>10 TeV (closed
TeV. Also, the figure 4 suggests circles) and of' EE¥,H->20 TeV
that the EAS with Ne_>107 are always (open triangles).
accompanied by gamma-families with
EEv __>20 TeV at the same altitude.
The'se results are important to study the absolute intensity of energy
spectrum of the primary protons in the energy region Eo=I015~I017 eV.
5. Conclusions
EAS with sizes greater than about 5xl06 are always accompnied by
gamma-families with ZE.,H>I0 TeV, ny,H_,2 for Emin=3 TeV at the altitude of
Mr. Norikura. This size at Mr. Norikura is nearly equivalent to the
primary proton's energy 1016 eV. The size of EAS which are always
accompanied by gamma-families with ZEy,l_.>20 TeV seems to be greater than
about 107 . Then, if the gamma-families with higher cutoff energy are
observed together with EAS, the data will provide an available key to get
the absolute intensity of the primary proton's spectrum up to 1017 eV.
6. Acknowled$ ement s
The authors would like to express their thanks to the members of the
Norikura Air Shower Group for kind offer of the EAS array and assistance
and also to staffs of Norlkura Observatory of the Institute for Cosmic Ray
Research for kind offices and continuous support. This work is
supported financially by a Grant-in-aid for Scientific Research from the
Ministry of Education, Science and Culture.
7. References
Nakatsuka et el., 1983; Conference Papers of the 18th ICRC (Bangalore),
Vol. ii, 346.
Saito et el., 1983; ibid Vol. Ii, 217.
Yamamoto et el., 1981; Conference Papers of the 17th ICRC (Paris), Vol.
ii, 130.


Comparison of absolute intensity between EAS with gamma-families and general EAS at Mount Norikura

Comparison of absolute intensity between EAS with gamma-families and general EAS at Mount Norikura

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