The energy spectra of high energy gamma-rays and hadrons were obtained by the emulsion chamber with 40 c.u. thickness at Mt. Fuji (3750 m). These results are compared with the Monte Carlo calculation based on the same model which is used in a family analysis. Our data are compatible with the model of heavy-enriched primary and scaling in the fragmentation region

Amenomori, M.

Hotta, N.

Kasahara, K.

Kobayashi, T.

Konishi, E.

Mikumo, E.

Mizutani, K.

Nanjo, H.

Sato, K.

Yuda, T.

English

NASA Technical Reports Server

HE3.1-3
208
HIGH ENERGY GAMMA-RAYSAND HADRONS AT Mt.FUJI
Mt. Fuji Collaboration
Amenomori,M., Nanjo,H. and Konishi,E.
Hirosaki University, Hirosaki, Aomori
Hotta,N.
Utsunomiya University, Utsunomiya, Tochigi
Mizutani,K.
Saitama University, Urawa, Saitama
Kasahara,K., Kobayashi,T., Miktmlo,E., Sato,K. and Yuda,T.
ICR, University Of Toky0, Tanashi, TokyO
Mito,I.
Shibaura Institute of Technology, Shibaura, Tokyo
Shibata,M.
Yokohama National University, Yokohama, Kanagawa
Shirai,T., Taira,T., Tateyama,N. and Torii,S.
Kanagawa University, Yokohama, Kanagawa
Sugimoto,H. and Taira,K.
Sagami Institute of Technology, Fujisawa, Kanagawa
The energy spectra of high energy gamma-rays and hadrons were
obtained by the emulsion chamber with 40 c.u. thickness at Mt.Fuji
(3750m). These results are compared with the Monte Carlo calculation
based on the same model which is used in a family analysis. Our data
are compatible with the model of heavy-enrichedprimary and scaling in
the fragmentation regio_
i_ Introduction.
The energy spectra of both gamma-rays and hadrons at high energies
have been measured withthe large-scaleemulsion chambers at Mt. Fuji
(3750 m, 650g/cm2)l), 2). The present scale of Fuji experiment is
possible to cover the energy range of 2-'100 TeV both for gamma-rays
and hadrons with a sufficient statistics.
These spectra are known to be very sensitive to the proton compo-
nent in the primary and also well reflect the particle production
spectra in the fragmentation region, increasing cross sections.
This problem has been frequently discussed by many authors, mainly
based on the analytical calculation with some approximations.
In this report, we present new spectra of uncorrelated gan_a-rays
and hadrons observed with the emulsion chamber(FH) of 40 c.u. thick-
ness and compare this with the Monte Carlo simulation made with the
same model used in the family analysis.
2. Experiment
In the Mt.Fuji experiments, two types of emulsion chambers have
been exposed, i.e., one is of thin-type, With the total thickness less
than i0 c.u. and the other of thick-type. The total exposure amounts
to about i000 m2.y. Among this, the chamber FH, exposed for two years
https://ntrs.nasa.gov/search.jsp?R=19850027590 2020-03-20T17:20:49+00:00Z
209 HE 3.1-3
from 1982 to 1984, has high quality for detecting both gan_na-rays and
hadrons. The detection efficiency of hadrons is estimated to be 60 %.
The X-ray films were inserted at every 2 c.u. from 4 to 40 c.u.. In
the depth shallower than i0 c.u., two kinds of films with a different
sensitivity (Sakura-N and Fuji-#100) were used.
The energy of each shower is estimated by comparing the transition
of shower spots in the x-ray films extending over several layers with
the theoretical one (note that the energy of hadron is that released
as the electro-magnetic component in the chamber). The separation of
gamma-rays and hadrons is made statistically referring to the starting
point of showers observed in the chamber. That is, if the showers
start in the depth less than 6 c.u., except ones with successive
interactions, then they are regarded as gamma-rays (including elec-
trons and positrons) and others as hadrons.
As discussed already in the previous paper 2), the Landau-
Pomeranchuk effect becomes dominant at high energies over several 10
TeV. Showers become more penetrative at higher energies so that some
of gamma-rays are misidentified as hadrons in the usual statistical
method mentioned above. In our data processing, this problem is
adequately taken into account.
3. Monte Carlo simulation. _ • Grigorov etoL
,o-' • _ JACEE
The Monte Carlo simulation _ __
has been done to get some
conclusive results from our _ -.-,0,_.....VH_._."_"_.FE'_'_
experimental data. The mo- _ ............ .. ..
del adopted here is the same .. -. ._
one as used in the family ! ,o-,--__L "'%"'_"
analysis 3). That is, the sca- _z ---___.
ling in the fragmentation re- ""_'--.-._.
gion, increasing cross sec- l i .....I"-.. j
tion as Eou'u4 and the heavy ,o, ,o, ,o, ,o,
enriched primary are assumed _v_<_
in the calculation. In the Fig. i.
other papers, it has been
shown that the scaling is not
appreciably broken in the
fragmentation region and the P_/_,, FH =
heavy enriched primary can / \_. 10
well explain the family phe- '_ _,! zo
nomena which are the products _.j_;_-_-- -_-
- of nuclear interactions in l0z _ _ _i___ _
air by primary particles at "_ / I_
energies over 1015eV. It > !i ......'.' :... '. :" ' \t II I0examine whether the same model _ • : : \
can also reproduce the energy 10 [\J
', spectra of uncorrelatedandhadrons _i,,_:i:_,'_2::::_!i!_;.!_i_iii_:_::.il}:i...::/gamma-rays or .: . _:,_/ ..:.o.._.'_::
not, since these are concer- 0 Io 20 30
ned in the wide energy _t(c.u )
range of primaries from seve-
ral TeV to about 1016 eV. In Fig. 2.
Fig. 1 is shown the primary
21() HE 3.1-3
spectrum assumed in this calculation. A special feature of this
spectrum is that the proton component becomes steeper (change of
spectral index : 1.7->2.0) at around 1014 eV, lower than the knee (
3x10 ±b eV) appeared in the total spec_rt_n. This proton spectrum is
not inconsistent with the JACEE data =J, though statistics is still
insufficient.
4. Results.
In Fig. 2, we show the starting point (At) distribution of showers
with energy higher than 4 TeV, observed in the FH-chamber. The curves
are the expectation of attenuation of high energy showers in the
chamber calculated by the Monte Carlo method. In this calculation,
the collision mean free path of hadrons is assumed to be 28 c.u. in
lead. This data is used for obtaining the absolute vertical fluxes of
gan_na-rays and hadrons.
The energy spectrum of gamma-rays and hadrons, obtained with the
chamber FH, is shown in Fig. 3 and 4, with the one presented at
Bangalore Conference 2). As discussed in the previous paper 2), we
revised the energy of showers by using a new energy-determination
method. This change was made by a statistical way using a simple
relation of E_ew=l.3 x Eold, i.e., old energy is increased by 30 %.
On the other _and, the energy of each shower observed in the FH-
chamber is determined individually by use of a new transition curve.
A good agreement of both data means that the previous method is with
considerable justification.
The absolute fluxes at 5 TeV and spectral indices are listed in
Table 1 for gan_na-rays and hadrons.
\
-I0 .\ o EXPERIMENT
_0 _ o EXPERIMENT ','k ', FH
_'_,, * FH '_,"e
', -I0 _,_
_,' -_2.oo:_o.o5_ _I0 %
-11 _o_ ,ET t./) ",,, _(2.0+0.1 )
U
_-:ll
"_¢ u10 q\in
-12 _\ "'h-. _\
o- £
\
I
I , | i I _ _ .,, i I I I " _ | , ' -
10 10 2 10 10 2
E_ (TeV) Eh( TeV )
Fig. 3. Fig. 4.
2 1 1 HE 3.1-3
Table 1
Spectral index Flux value at 5 TeV
( cm-2sec-lsr -1 )
gamma-rays 2.00 + 0.05 ( 1.1 + 0.i ) x i0-10
hadrons 2.0 + 0.i ( 2.1 + 0.i ) x 10-10
5. Discussions.
We compare our data with the Monte Carlo result (dotted curve) in
Fig. 3 and 4. As noticed from these figures, a slight difference may
be found between the data and the calculation. But, this is not
serious problem if we consider the uncertainty involving in the assum-
ption of primary composition. Of course strong scaling break in the
fragmentation region is compatible with proton dominant primary at
least up to about 1015 eV. However, there is little hope for this
possibility, because the primary energy responsible for generating
these particles is not so high compared with the energy of CERN SPS
collider where the strong scaling break has not been observed.
Our conclusion is that the model of scaling and heavy enriched
primary can well explain both of uncorrelated particle spectra and
family phenomena which are originated by the primary particles ran-
ging from several TeV to about 1016 eV. The implication is that the
fraction of primary proton decreases with increasing energy and reaches
about 20 % at energies around 1015 eV. The proton spectrum should
become steeper at least at around 1014 eV. This is very interesting
result when we consider the problem of acceleration and confinement of
high energy cosaic rays in our galaxy.
6. Acknowledgements
The authors would like to express their sincere thanks to Sengen
Shrine, Kawaguchi-ko Office of the Ministry of enviro_nent Maintenance
for extending every facilities necessary for carting out the experi-
ment at Mt. Fuji to us.
References
i) Akashi, M. et al, Nuovo Cimento, 65A, 355 (1981).
2) Amenomori, M. et al, 18th ICRC(Bangalore), ii, 57 (1983).
3) Ding, L.K. et al, Proc. Int. Symp. of Cosmic Rays and Particle
Physics (ICR, Univ. of Tokyo), 142 (1984, Tokyo).
4) JACEE Collaboration, ibid, 468 (1984, Tokyo).


High energy gamma-rays and hadrons at Mount Fuji

High energy gamma-rays and hadrons at Mount Fuji

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