The energy spectra of atmospheric cosmic rays at Mt. Kanbala (520 g/sq cm.) are measured with emulsion chambers. The power indexes of the spectra are values of about 2.0 for both gamma-rays and hadrons. Those fluxes are consistent with the ones expected from the model of primary cosmic rays with heavy nuclei of high content in the energy around 10 to the 15th power eV

He, M.

Huo, A. X.

Kuang, H. H.

Lu, S. L.

Ren, J. R.

Su, S.

Wang, C. R.

Wang, Y. X.

Xue, Y. G.

Zhang, N. J.

English

General features of family events with Summary E sub gamma  200 TeV, observed by the emulsion chambers at Mt. Kanbala, are presented in comparison with the Monte Carlo simulation. The lateral and cluster structure, and the energy spectra of constituent gamma-rays and hadrons are shown to be consistent with the Monte Carlo results calculated under the assumption of heavy-enriched primary, scaling, QCD jets and increasing cross-section

NASA Technical Reports Server

HE 3.7-5
439
ON THE MEAN CHARACTERS OF FAMILY EVENTS
OBSERVED AT MT.KANBALA
China-Japan Emulsion Chamber Collaboration *
ABSTRACT
General features of family events
with _ E3,> 200 TeV, observed by the
emulsion chambers at Mt. Kanbala, are
presented in comparison with the Monte
Carlo simulation. The lateral and cluster
structure, and the energy spectra of
constituent gamma-rays and hadrons are
shown to be consistent with the Monte
Carlo results calculated under the
assumption of heavy-enriched primary,
scaling, QCD jets and increasing cross-
section.
i. Introduction.
Upto now, the total amount of exposure of emulsion
chambers(ECs) at Mt. Kanbala has reached about 420 m2year. We
already observed i0 big family events with energies _ Ey
> i000 TeV. The main purpose of our experiment is to clarify
what kinds of phenomena are new in the energy region beyond
1016 eV, though the problem of primary composition at these
energies is inevitably interwined with this subject.
In this paper we present the average behaviour of the
family events in comparison with the Monte Carlo simulation
made by an assumption on primary and interaction. First, we
discuss the flux of gamma-families at Mt.Kanbala, since this
is known to be very sensitive to the model of both
• interaction and primary composition. Then the average
features of family events are shown.
2. Experiment.
Two types of chambers are assembled on the Mt.Kanbala
station. One is the Pb-EC, usually used at the mountain
experiments, and the other the Fe-EC. The exposure list is
shown in ref. i).
In our data processing, hadrons are defined as showers
with its starting point deeper than 6 c.u. and/or with
accompanying successive interactions in the EC, and others
are identified as gamma-rays. The minimum energy of showers
accepted fn our analysis is set to be 4 TeV. The detection
efficiency of hadrons is estimated to be about 40 % for Pb-EC
and about 80 % for Fe-EC in an average.
Here, we use only the data taken from the Pb-chambers
https://ntrs.nasa.gov/search.jsp?R=19850027651 2020-03-20T17:19:49+00:00Z
440 HE 3.7-5
Kanbal.a y Kanbe_a
'_,X.xxe .ZEI'_*2OOTeV
"f"" Em=4TeV '
"','_ Era=4TeV%. .
_ xI "%, \ •
L2 "
I I%% \ \,o-, ,o,_,ooo, b " ""- ",_l
""""°'"°°°''o., t,"xt\ \'s°""°°'
k%k_ "MSQI(IO0) . 't _ I
\ MSQI ( 100)
10"= I i I i i I f I I r I
lOZ lOJ 10 1OO
ZET (Te V) ET,E_"(TeV)
Fig. i. Fig. 2.
because the amount of exposure of the Fe-chambers is still
insufficient to get quantitative results.
3. Monte Carlo simulation.
In order to make a standard picture on family phenomena
and also to learnthe size of its fluctuations, we have done
the Monte Carlo simulations based on the conventional model
of interaction and primary composition. Details of the
simulation calculation are found in ref. 2). The meaning of
the symbols appeared in this text is as follows ; M : Mixed
chemical composition with a significant amount of heavy
nuclei. The spectrum of Proton/He/L/M/H/VH/Fe becomes steeper
at a bending energy (Eb) from 1.7/1.7/1.7/1.6/1.6/1.6/1.5 to
2.0 (all). The bending energy of proton spectrum is denoted
in the bracket, and other nuclei steepen at energy of Z*Eb. •
P : Proton dominant primary (In both cases, the total flux
is normarized to the Grigorov's total spectrum at 1015 eV).
S : Scaling in the fragmentation region. F : Fire-ball
model normalized at 150 TeV. Q : QCD-jet. I : Increasing
cross-section as E0"06. T : Increasing average Pt as E0"04.
4. Resul ts
4.1. Intensity of gamma-families at Mt.Kanbala.
The absolute flux of gamma-families is compared with the
Monte Carlo calculations as shown in Fig. i. As learned from
HE3.7-5
441
Kanba(a •
4 _ Konbo_o
..,.. p..- £m=4 "re v
1 Io
J _ I , I -i I I I , a I
lOZ 103 104 I0' |0_ 10'
_£_ (TeV) Z£; (TeV)
Fig. 3(a). Fig. 3(b).
this figure, both cases of the model PSQI(1000) and
MSQI(3000) give too high intensity compared with our data.
In order to accord with the data, the proton spectrum must be
bent at around 1014 eV. In this case, the fraction of
protons and irons to the total is estimated to,be about 20 %
and 40 % at around 1015eV respectively. Even if we adopt
the fire-ball model, the fraction of protons doesn't exceed
5O %.
4.2 Energy spectra of gamma-rays, hadrons.
Figure 2 shows the energy spectrum o_ gamma-rays and
hadrons superposed in the energy interval of 7 E y> 200 TeV.
The solid and dotted line corresponds to the model MSQI(100)
and MFQI(IO0), respectively. No clear difference is found
between the data and the model MSQI (100) both oh the number
of showers and the slope of spectrum. However, the fire-ball
model (MFQI, heavy enriched primary and scaling break) gives
steeper spectrum compared with the experiment. That is,
strong scaling break is
incompatible with the heavy io
enriched primary and requires the h_. _o,0a_a
proton dominant" primary. -k_, ZE,20o~500T,V
" _6 "_ Em=4Tev
4.3 Lateral structure of gamma- _ z..4_r,v.=,
families. _;o
¢ _MSQIT(IO0)
The mean values of <R> and
• Vj .... MSQI(IO0)
<ER> of gamma-rays averaged in
the respective energy range are _3
shown with the Monte Carlo _ _
results in Fig. 3(a), (b). Our _o; bdata come between the model %%
MSQIT(100) and PSQI(1000), and ',_
remain close to the MSQI(100). %
At accelerator energy regions, , I , , ,J; lo
the mean Pt near central region
seems to increase with energy as ScRc (GeV.Km)
E0-04. But, it is also well Fig. 4.confirmed that the behaviour of
442 HE 3.7-5
gamma-families is sensitive to the fragmentation region. If
we take this into consideration, then we may say that the
average Pt in the fragmentation region remains almost
constant at least up to about 1015 eV (Here it should be
noted that the QCD-jet effect is taken into account.).
The ER distribution of clusters in the gamma-families
with _ Ey= 200-500 TeV is shown in Fig. 4, comparing with the
results of the model MSQIT(100) and MSQI (i00). This
comparison tells us that the increasing mean Pt (smooth
extrapolation from the accelerator energy region) gives
merely a minor effect on the cluster structures.
5. Conclusions.
Our discussions are summarized as follows,
i) Scaling in the fragmentation region, increasing cross-
section as E _ , 8=0.04-0.06, and the heavy enriched primary
spectrum can well explain our experimental data.
2) A fraction of protons and irons to the total flux takes a
value of about 20 % and 40-60 % at around 1015 eV,
i0_re_ectieV_ely" The proton spectrum should steepen at around
3) The energy dependence of average Pt is very weak in the
fragmentation region.
These conclusions are compatible with other data, i.e.,
uncorrelated g_mma-ray/hadron spectrum and the behaviour ofJ)
super-families . We also observed several family events
with a peculiar structure, and some of these events are
described in other paper 4).
This work is financially supported in part by IHEP,
Academia Sinica in China and ICR, University of Tokyo, and
Grant-in Aid from the Ministry of Education in Japan. Data
analysis was made by using the Computer FACOM M380R of INS,
University of Tokyo.
* For full list of authors, see HE 3.1-2.
i) Ren,J.R. et al, HE3.1-2, in this volume.
2) Ding,L.K. et al, Proc. Int. Symp. on Cosmic Rays and
Particle Phys.(ICR, Univ. of Tokyo, 1984), p142.
3) Ren,J.R. et al, HE3.4-9, in this volume.
4) Ren,J.R. et al, HE3, in this volume.


Intensities of high-energy cosmic rays at Mount Kanbala

204 HE 3.I-2
INTENSITIESOF HIGH=ENERGY COSMIC RAYS AT Ivrr.KANBALA
Chiha-Japan Emulsion Chamber ColIaboration
Ren.J.R., Kuang,H.H., Huo,A.X.. Lu,S.L.. Su,S., hlang,Y.X,and
Xue,Y.G. (Inst. of High Energy Physics, Academia Sinica,
Beijing. China). gang.C.R.. He,M., Zhang,N.J.. Cao,P.¥. and
Li,J.Y. (Shangdong Univ., Jinan, China), Wang,S.Z. (Zhengzhou
Univ.. Zhengzhou, China), Bai,G.Z., Liu. Z.H., Li,G.J. and
Gang,G.X.(Chongqing Inst. of Architecture and Engineering,
Chongqing, China), Zhou,tO.D.and He,R.D. (Yunnan Univ.,
Kunming, China),
Amenomori.M. and Nanjo.H. (Hirosaki Univ., Hirosaki. Japan).
Hotta,N.. Ohta,I. and Sakai,M. (UtsunomiyaUniv.. Utsunomiya.
Japan), Mizutani,K. (Saitama Univ., Urawa, Japan), Kasahara,K.
and Yuda,T. (Inst. for Cosmic Ray Research, Univ. of Tokyo,
Tokyo, Japan), Shibata,k_.(Yokohama National Univ., Yokohama,
Japan). Shiral.T., Tateyama.N. and Torii.S. (Kanagawa Univ..
Yokohama, Japan), Sugimoto,H. and Taira.K. (Sagami Inst. of
Technology. Fujisawa, Japan).
Abstract
The energy s_ectra of atmospheric cosmic rays at Mr.
Kanbala (520 g/cm-) are measured with emulsion chambers
The power-indeces of the spectra are values of about 2.0
for both gamma-rays and hadrons. Those fluxes are
consistent with the ones expected from the model of
primary cosmic rays,with heavy nuclei of high content in
the energy around I0_a eV.
I. Introduction
The China-Japan Cooperative Emulsion Chamber Experiment is
continued with a large-area exposure at r_It.Kanbala2 Tibet in China(5500 m above sea level, atmospheric depth 520 g/cm ), in order to
observe big families with energy over I000 TeV. Details of
character'istics of those famiIies are discussed in another pap_}(I),by concerning with primary cosmic rays in the energy around I0 eV
or more. Also, uncorrelated particles of atmospheric cosmic rays.
such as gamma-rays (hereafter. these mean high energy photons and
electrons) and hadrons, are observed in a lower energy region with
the same emulsion chambers. The intensities of those particles as
well as:_he members of families are presented in this paper'.
2. Experimental procedure
The emulsion chamber used in the Mr. Kanbala experiment
consists of photosensitive materials and metal plates, piled up
alternately. Several sorts of X-ray film withdifferent sensitivity
are generally used as the photosensitivematerials, such as type-N
(Sakura). type-Ill (Tianjin). type-lO0 (Fuji), Gongyuan (Shantou)
and tylYe-5F(Shanghai).
Two kinds of metal are used at Mr. Kanbala, as listed in
Table I. One is the lead emulsion chamber (Pb-EC), as genre'ally
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205
HE 3.1-2
used ill mountain Table I. Exposure list at Mt. Kanbala.
experiments. Another is ..........................................................
the irob one (Fe-EC) Series Date Exposure Materlal Thlckness(m y) (c,u.I
which is exposed to ..........................................................
observe efficiently KO Sep, 1980-Sep. 1981 a.7 Pb 14
11.0 Pb 30
hadron components. In KI Sep.1981-Sep.1982 1.0 Pb 14
this paper, the results 49.0 Pb 28
are presented given from K2 Oct.1982-May 1984 143.0 Pb 1439.1 Fe 29
the Fe-ECs as well as the g3 May1983-May1984 6.3 Pb 14
Pb-ECs whose preliminary 31.1 Fe 29
K4 May 1984-MaY 1985 85.0 Pb 14
data are shown in the 58.o Fe 29
previous paper(2}. -..............................................-..........
The showers Droduc:edby high enerqy particles are observed as
the series of shower spots on X-ray films over several layers and
tile energy of each shower is estimated by measuring optical density
of those spots. Details of the method for" the Pb-EC are found in
the previuos paper(2). For the analysis of the Fe-EC. the similar
manner is applied. For the purpose of enerqy determination of
_hower's in the Fe-EC. massive simulations have been made (m the
cascade showers developin9 in iron.
-h
..." ..3. Results -,,..y _
In order to cjet the lo .{_(.,
intensities of atmospheric ,4 \,_+
cosmic rays, a part of the _ __..., :...
emulsion chambers of thick a. _k ,,_ _-t-
o ,; ,\,, .......
type (28 - 30 c.u. thick) , /-xT_?[--aa_-/-.... __a_
has been analysed with _ ' / _ " _---I=-4----I--_--T-i/f--_.--_,.., I I I _-_
I /% _', "'._:_L_ _'1
careful sc'anninq 2 for the \ ;/\ --F\,
exposure of 7.0 in2 y in the l?,, \ -1-_,+,
Pb-EC and 6.0 m y in the
Fe-EC. \ I,
the observed showers i s
displayed in Fig. 1. The I\
distribution of a deep l x
region qives tlS the 0.z 7
|
attenuation lengt2h of
hadrons indi cat ins 42. t) c.u. , ,
in lead and 13.5 c.u. in o lo 2o
i ton. Those va l ties c.u.
corresPOlld to the coIlisio/l Flq. I. Startln_J point distribution of showers In the
length of 28.0 C,U. in lead emulsion chamber of thick type. Tim upper and lower
and 9.0 c,tl. in iron, both crosses represent the number of detected showers with
energy above 3 TeV for the Pb-EC and above 5 TeV for
of which are consistent with the Fe-EC. respectively. The dashed and solid curves
the values expected fl'olll the are expected from gamma-rays and hadrons, respectively.
respective interaction cross section. By takin9 the attenuation
into account, the detection probabilities of hadrons are determined
to be 39 % in the Pb-EC and 78 % ill the Fe-EC. A statistical
seParation of gamma-raYs and hadrons has been performed by us Jl}g
those detection probabil ities(2). (3).
Tile resulting vertical energy spectra at _t. Kanbala are shown
206
HE 3.1-2
in Fig. 2 and Fig. 3 for the showers initiated by gamma-rays and
hadrons, respectively. Both results given from tim Pb-ECs and the
Fe-ECs are consistent with eacll other. Those power indices and
fluxes are listed in Table 2.
Table 2. Spectra of atmospheric cosmic rays at Mr. Kanbala.
Spectral index Intensity a_ 5 TeV(in s st)
0-6
gamma-rays 2.00_+0.08 (2.8-0.2)X 10_6showers induced by hadrons 2.03+--0.08 (6.0+--0.6)X1
10 -5 10-5 _
0 tO
% '0% ,, \,_,.),o
lO- o; \i,
I I I
1_0 i00 10 i00
TeV TeV
Fig. 2. Integral energy spectrum of vertical Fig. 3. Illlegral energy spectrum of showers
gamma-raYs at Mr. Kanbala. The open and Induced by badrons at l_It. Kanbala. The open
solid circles represent the results given a|_d solid circles rep|'esent the results given
from the Pb-EC and tile Fe-EC, respectively, from the Pb-gC and the Fe-EC, re.'_pectlvely.
'rile dashed line is tile best flt. The solid The dashed line Is tile best flt. Tile solid
curve Is expected by the assumptions curve Is expected by tile assumptions
mentioned tn tile text. mentioned In the text.
4. Discussions
There is no serious difference between both spectra derived
from the Pb-EC and the Fe-EC. This indicates that on the
experimental method and procedure, such as shower detection and
energy determination, no systematic error is recognized for the Fe-
EC. This gives a fundamental supporting factor for the reliability
of the family data detected in the Fe-ECs(l).
According to tim results of families, as described in another
paper(l) and others(4),(5), the primary CO._IIIJcrays do not indicate
207
HE 3.1-2
16proton dominant in the energy around 10 eV. It seems that the
high energy interaction, the Feynman scaling is not appreciably
broken in the fragmentation region of particle production andEOt_..
collision cross section 2 of hadrons in air ginCreases asrresponding to tim In s depen ence. In Fi . 2 nd Fig. 3 are
displayed the results calculated with almost the same assumption as
the above mentioned. Those spectra of atmospheric cosmic rays are
genetically related to the primary co._mic-ray spectrum of a proton
equivalent in which tile primary cosmic-ray nuclei are broken up into
nucleons. Those spectra, therefore, do not much sensitive to the
composition of primary cosmic rays. It i._. however, interesting to
indicate in these figures that the atmospheric cosmic ray spectra
may be also interpreted by the same assumption in a sligt_tly lower
energy region.
On the atmospheric _0-5
cosmic rays, the spectral
measurements have been_ --1_$-.-
performed with emulsion
chambers of a similar _ 0-_
type at Mt2 Fuji (3750 m._E . _{_ _,.
650 g/cm )(3).(61 and _ {__other mountain altitudes z0-_(7).(8).(9). Tile Present
results are compared with Q K c ? F
, _ _ _, _ ,
_,those intensi ties in
'" 400 500 600 700
Fig. 4. Tile comparison g/cm 2
shows tile attenuation Fig. 4. Comparison of intensities of atmospheric
lengtil also to be cosmic rays at mountain altitudes. The open and solid
circles represent the fluxes of gamma-ray and showers
consistent with t.he induced by hadrons, respectively, with the energy above
assumption mentioned 5 TeV; the pre_ent results (1<) and the results at Mt.
above. FuJI 2 1650 g/cm_)(6) (FI, at the Pamir _lateau (594
g/cm )(7) (P), at I4t. Chacaltayao(540 g/cm')(8) (C) and
at the Qomolangma root (455 g/cm_)(9) (Q). The curves
Acknowledgements represent the expected attenuat Ion.
This work is supported by the grants from Academia Sinica in
China and Japanese _.linistry of Education illcluding the Grant in Aid
for Scientific Research. Data analysis was made with the computer
FACOM14380R of Institute for Nuclear Study. University of Tokyo.
References
.. 1. Ren,J.R. et al., the paper in this conference HE 3.7-5.
2. Ren,J.R. et al., 18th ICRC (Bangalore). 5, 285 (1983).
3. Akashi,bl. et a1., Nuovo Cimento, _65_8.355 (1981).
._ 4. Akashi,t4. et al., Phys. Rev. D, 2_4_,2353 (1981).
5. Amenomori,_4. et al., Phys. Rev. D, 2_5_,280? (1982).
6. Amenomori,_4. et al., 18th ICRC (Bangalore), 1_1_,57 (1983,1.
?. Pamir Collaboration. l?th ICRC (Paris), 5_,29? (1981).
8. Brasil-Japan Emulsion Ct_amber Collaboration. Suppl. Prog.
Theor. Phys., No. 47. 1 (1979).
9. Lu.S.L. et al.. 17th ICRC (Paris). 5, 254 (1981).


Intensities of high-energy cosmic rays at Mount Kanbala

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