The sigma epsilon gamma spectrum in 1 approx. 5 x 1000 TV observed at Mt. Fuji suggests that the flux of primary protons 10 to the 15 approx 10th eV is lower by a factor of 2 approx. 3 than a simple extrapolation from lower energies; the integral proton spectrum tends to be steeper than around to the power V and the spectral index tends to be steeper than Epsilon to the -17th power around 10 to the 14th power eV and the spectral index becomes approx. 2.0 around 10 to the 15th power eV. If the total flux of primary particles has no steepening up to approx 10 to the 15th power eV, than the fraction of primary protons to the total flux should be approx 20% in contrast to approx 45% at lower energies

Amenomori, M.

Hotta, N.

Kasahara, K.

Kobayashi, T.

Konishi, E.

Mikumo, E.

Mito, I.

Mizutani, K.

Sato, K.

Yuda, T.

English

NASA Technical Reports Server

OG 5.2-4
206
Composition of Primary Cosmic Rays at Energies I015_I016 eV
Inferred from Mt.Fuji Emulsion Chamber Experiment
l'lt.Fuji Emulsion Chamber Collaboration:
Amenomori,H., Nanjo,H. and Konishi,E. (Hirosc_i University, Hirosaki,
Aomori) Hotta,N. (Utsur_omi_a University, Utsunomiya, Tochig{)Mizutani,K.
(Shi tama Uni versi ty, Uram:l, Sai tama ) Kasahara ,K., Kobayashi ,T.,
Mikumo,E., Sato,K. and Yuda,T. (Institute Jot Cosmic-Ray Research,
University of Tokyo, Tanashi , Tokyo) Mito,I. (Shibaura Institute of
Technology, Shibaura, Tokyo) Shibata,M. (Yokohama National University,
Yokohama, Kanagam) Shirai,T., Taira,T., Tateyama,N. and Torii,S.
([<anaga_a Uni versi ty , Yokohama, Kanagawa ) Sugimoto,H. and Taira,K.
(Sagami Institute of Technology, Fujisawa, Kanagawa)
The F_Ey spectrum in 102% 5 x 103 TeV observed at Mt.Fuji (
3725 m a.s.1.) strongly suggests that the flux of primary protons
in 1015%1016 eV is lower by a factor of 2% 3 than a simple
extrapolation from lower energies; the integral proton spectrum
tends to be steeper thane -17 around lO14 eV and the spectral index
becomes % 2.0 around 1015 eV. If the total flux of primary
particles has no steepening up to %10 I5 eV, then the fraction of
primary protons to the total flux should be % 20 % in contrast to
45% at lower energies.
!, Introduction. As well known, the integral energy spectrum of all
primary particles steepens toe -2° over _5xlOISeV in contrast toe -16 at
lower energies. This "knee" of the spectrum may come from I) a change of
the acceleration mechanism resulting in a steeper source spectrum and/or
2) a breakdown of magnetic trapping in the galaxy. Study on the
composition around the "knee" is an important key to resolving the
problems of the origin and propagation of cosmic rays. However, the
definite result has not yet been obtained because of the too low primary
flux for the direct observation and too poor response of the air shower
observation to the primary mass.
The emulsion chambers ( RE ) at Mt.Fuji have been extended to the
scale of I000 max year, and a few hundred events produced by primaries
with energy I015_I016 eV have been accumulatedI). Meanwhile, accelerators
has clarified the feature of nuclear interactions up to 150 TeV (in lab.
energy). These circumstances enable us to investigate the primary
composition around the "knee" by analysing the EC events through
simulations based on a reliable model of nuclear interactions.
___T-ray Family. A group of high energy particles (mostlyy-rays with
energy > a few TeV) produced by successive collisions of a primary
particle with air nuclei is called a family. Particles which penetrate
deep in the atmosphere can produce families effectively,otherwise
00 .2-4 
06 
o position f rim r  os i  a s t er i s 1 15",1016 e  
red rom t. uji ulsi  be  e im t 
Mt.Fuji ulsion er llaboration: 
enomori,M., anjo,H. d onishi,E. irosaki iversity, irosaki, 
ori) otta,N. ( tsunomiya iversity, t unomiya, ochigi) Mizutani,K. 
( ai ta a i ersi tj), rawa, ai ta a) asahara, ., obayashi.T., 
ikumo,E., ato,K. d uda,T. Institute j'or ic-Raj) search, 
iversitj) j' kj)o, nashi, kyo) ito,I. ( hibaura I stitute j' 
chnologj), hibaura, kj)o) ibata,M. ( ha a ational iversity, 
okoha a, ](anagawa) hirai,T., aira,T., ateyama,N. and orii,S. 
(](anagaw  i ersi tj), k a, ]( agawa) gimoto,H. a  aira,K. 
( agami sti tute j' chn logy, jisawa, ]( gawa) 
he LEy spectrum in 1()2", 5 x leY Te  observed at t. uji ( 
", 5  .s.l.) strongly s gests t at t e flux f rimary rotons 
in 15", 16  is l er   ctor f ",  t an  i ple 
xtrapolation fr  l er e ergies; t e i tegral roton s ectrum 
tends t  e st eper t an g-1.7 around 1014 e  a d t e s ectral i dex 
co es '" .0 round 15 . f e otal l ux f r imary 
articles has no steepe ing up t  ",1015 e , then t e fraction f 
rimary rotons to the total flux ould  '"   i  ontrast t  
'"    r . 
1. trod tion. s ell , t  i t l r  trum  l  
primary particles steepens to c 2.0 over "'V5x 10T5 eV in contrast to g-1.6 at 
lo er r i s. his " ee" f t  s ectrum ay c e from 1) a c a e f 
t  l tion ec ism lting i   tee   trum /  
2) a breakdown of agnetic trapping in the galaxy. Study on the 
position roun  t  " e" i   i port t  t  r s lving t  
problems of the origin and propagation of cos ic rays. o ever, the 
definite result has not yet been obtained because of the too low primary 
lu  f r t  i t s r tion  t  r r spo e  t  i  r 
ser ation t  t e rimar  ass. 
 ulsion bers ( EC ) t t. uji   tend d t  t  
scale of 1000 2 x year, and a few hundred events produced by pri aries 
i t  energy 1015",1016 e  have been accu ulated1) • eanwhile, accelerators 
 l ified t  f t re f l r i teractions  t    (in l . 
energy). hese circumstances enable us to investigate the pri ary 
position roun  t  " e"  l sing t   ts through 
l ions    a e ode  f cl  a tions. 
~y-ray Fa ily.  group of high energy particles ( ostly "I-rays ith 
energy > a few Te ) produced by successive collisions of a pri ary 
particle with air nuclei is called a fa ily. Particles which penetrate 
deep in the at osphere can produce fa ilies effectively, other ise 
https://ntrs.nasa.gov/search.jsp?R=19850025748 2020-03-20T18:02:05+00:00Z
03 5.2-4.
207
produced particles are usually absorbed in the atmosphere. Therefore
protons are most efficient in producing families; the average energy of
protons responsible for 7-ray families with FET>IO0 TeV is _2× I015 eV
while that of irons is almost one order of magnitude higher.
It has been found that the fraction of proton-induced families in
all families in FE_>IO0 TeV is _ 70% even if protons constitute only
10% of all particles around 1015 eV. Therefore, if we convert the family
intensity into the primary flux assuming that all families are produced
by protons, we obtain an upper bound of the proton flux within an
accuracy of 30%.
3. Monte-Carlo Simulation, The Monte-Carlo method has been used to
simulate the family phenomena and to deduce the primary intensity by
comparing the obtained family flux with the experimental one. Important
factors in the simulation are the cross-sectionof nuclear interactions,
the leading particle spectrum and the secondary particles spectrum
(especially, the degree of scale breaking in the fragmentation region).
These are summarized in the following.
.Cross Secfion Using the
data of pp and pp interactions up
to 150 TeV, the mean free path of 1.8
the N-Air collision is expressed as
_.=?,0xE-_, where E is in TeV, 8 is
0.04 _ 0.06 and _0=82 g/cm2. 1.6 B
Elas t ici__tll Two cases of
the elasticity distribution are
assumed as shown in Fig.l. Case A z.2- / \ _ C_FA ]
disregards the difference between _, .i_ii.._ _
protons and neutrons and gives the dN
-_- _ 4.
average elasticity of 0.44. In case 0.s :.,-..
" B is considered the absence of the ": "-,
diffraction peak in charge exchange ".. "_-. ,'
processes, for which we refer to 0.4 "_ P-_p._ "_-.._!
. p-C and p-Be data3) at 100 - 400 ... (c_ _) ..... J
p-+n (CASEB) "".....GeV. The average elasticity in a
non-charge exchange process like 0 I I I I ...."..
p+Air-*p+X is 0.45 while that of o 0.z o.4 0.6 0.e
p+Air_n+X is 0.28. With a charge
exchange probability of 28 %, the ELASTICITY(x)
average elasticity in case B Fig.1 Elasticity distribution.
becomes O.40.
neE_crgy disfribufion of secondary particles The QCD-jet2)
automatically introduces a mild scale braking in the fragmentation as
shown in Fig.2a. The rapidity distribution shown in Fig.2b is compatible
with the CERN-SFS data. To see the effect of a strong violation of
scaling in the fragmentation region we employed a fireball model of which
the multiplicity grows as g I/4
In Table I, the models are characterized by the parameters discussed
00 -4 
7 
roduced rticles re s ally a sorbed in the atm sp ere. erefore 
protons are ost efficient in producing fa ilies; the average energy of 
protons responsible for y-ray fa ilies ith L y 100 eV is ~ x101~ eV 
ile th t f irons is lm st  r r f a itude ig r. 
t s n found th t the fraction f r ton-induced fa ilies in 
all fa ilies in LEy>100 TeV is ~ 70% even if protons constitute only ~ 
10% of all articles around 1015 e . herefore, if e convert the fa ily 
inte sity into the primary flux assuming that ll fa ilies are produced 
 r to s, e tain a  er und f the r ton flux it in a  
racy   
~~Carlo Ulat on.  onte- a o et od  n d  
simulate the fa ily phenomena and to deduce the primary intensity by 
aring th  t ined f ily flux ith the rim tal . I rtant 
f tors in th  i l tion r  t  r -section f l r interactions, 
t e leading artic.le s ectrum a  t e sec ary rticles s ectrum 
(especially, the degree of scale breaking in the frag entation region). 
  ari d  t  ollowing. 
ss ection ing e 
ata f    i teractions  
  , e  r e ath f 
e - ir ollision s xpressed  
A AOX~o  ere    , 0 s 
0.04 ~ 0.06 and Ao=82 g/cm2 . 
lasticity   f 
 l t ty i ribution  
assumed as shown in Fig.l. Case A 
disregards the difference between 
t   t o   i   
average elasticity of 0.44. In case 
  s ed t   f  
i ion  i    
proc sses, for which we refer to 
  8   3  t   
e . h   l ty   
non-charge exchange process like 
p+Air->p+X is 0.45 while that of 
i ->   .  it    
 r babili y f  ,  
average elasticit  in case  
 0. . 
dN 
ax 
1.8 
1.6 
1.2 
0.8 
0.4 
.. " '. , 
'. " 
-.. " 
. , 
.'. .... ..... 
.... ..... .......... 
"". " 
"., ............... 
", .. , p~p ...................... ' 
. •••• (CASE B) "--.. -_  
p-. n (CASE B) ••••••••• , 
-.... -.. _---- .. - ........ 
". o '----L--____ L--_--' __ --' __ .::.,.j •• 
 0.2 0.4 0.6 .8 
ELASTI CI'IY ( ?C ) 
i .l lasticit  istrib tion. 
Enfrrgy istribution J secondary particles he ~D j t2) 
automatically introduces a ild scale raking in the fragmentation s 
shown in Fig.2a. The rapidity distribution sho n in Fig.2b is compatible 
ith the - P  data. To see the ffect of a strong iolation f 
scaling in the fragmentation region we e ployed  fireball odel of hich 
t  ultipli   gr s s E /4 . 
I  abl  1, t  odels ar  charact ize  b  t  par eter  i  
0(3 5.2-4
208
above. The calculated flux of 7-ray families at _7=I00 TeV for each
model is listed by normalizing the flux to model QA6.
Ay
1017 eV
i0 i0 _,,
.... FI_B_L
/ 'x \\ 101'e o.1
(15o Te_ I
I I I I I I, ,tlitllllll
0.1 0.3 0.5 -7 -5 -3 -1 +1
x''E/go Y'Ybeam
Fig._ x-distribution of Fig.2b fl-distribution
secondary pions in p-Air corresponding to Fig.1. Black
collisions at 1012 eV and I0T6 dots show databy the CERN-SPS.
eV. A mild-violation of scaling _rrection due to Air-target
is seen in the model with _D effect is included.
jet.
Table 1. Interaction model and the relative flux of 7- ray family.
model x distribution elasticity m.f.p.(6) flux ratio
QA4 QCD case A 0.04 I._ "
QA6 QCD case A O.06 I
QB6 QCD case B O.06 O.72
FA4 Firebali case A 0.04 0.41
4, Proton Spectrum in 1015_1016__e_Y_,_ Under the assumption that all
7-ray families are produced by protons, an expected spectrum of protons
is deduced as shown in Fig.3. The upper bound is given by model QB6 and
the lower one by model QA4. As mentioned already, a maximum of 30 _
decrease might take place in the expected flux (due to the heavy primary
contribution). Even if we take the experimental errors (both statistical
and systematic) into account, we are forced to conclude that the proton
spectrum should steepen around 1014 eV, and the ratio of protons to all
particles in 1015_ 1016 eV should be lower by a factor of 2_ 3 than that
at lower energies.
I 
0 .2-4 
08 
ve. he al ulated fl  f y-rayf ilies t LEy=100 e  f r  
odel    r alizing t    odel A6. 
1 
0.1 
\ 
\ 
\ 
\ 
\ 
\ 
0.1 
\ 
\ 
,\ 
\ , 
-QeD 
---- FIREBALL 
(150 TeV) 
, 
\ 
'].'016 .. 
, ev 
" , 
.  
x • 'E I Eo 
.  
i .2a - istri ti n f 
secondary pions i  p- ir 
ll s t 12   1 16 
.  ild-violation f li  
    odel it  qeD 
j t. 
10 
1 
0.1 -QCD 
---- FIREBALL 
(150 TeV) 
-7 -5 -3 -1 +l 
Y - Ybeam 
i . b y-distributio  
corresponding t  ig.l. lack 
ts  at  by  RN-SPS. 
Correction  t  ir-target 
f ct  ed. 
able  t t  odel  t  t  l  f y  il . 
odel  i tri ti n l sti it  .f. . (0) l  ti  
4 qe    .  1.32 
6 qe  s   0.  1 
6 qeD case  0.  0.  
4 i all   .   
. r t  ect  i  15"",1016 ~ nder t  pti n t t l  
y-ra  fa ilies are produced by r t s, an expected spectru  f protons 
i  ce    i  i . .  r  i  i   odel   
t  l er   odel 4. s enti ed l ,  axi  f  % 
r ase ight t  l  i  t  ect d fl  (  t  t   ri ar  
ntri uti n).    t  t  eri ental rs ( t  t ti ti al 
a  s ste atic) i t  acc nt, e r  f rce  t  c cl e t t t e r t  
s ectru  s l  stee e  ar  14 e , a  t  r ti  f r t s t  ll 
arti l s i  15"", 16 e  s ul   lo r   f t r f "",  t  t t 
t lo er er ies. 
OG 5.2-4
209
_Grigorov et al.Total
-I
10 IZZE3AKENO( 1984)
E_I,7
i0 2
*'_/_ Suggested Proton Spectrum
10
i01 i0g 103 104
E/Nucleus ( TeV )
Fig.3 Expected primary proton spectrum.
5, Discussion, By an analysis of air shower data, some authors
reported a proton-dominantcomposition4) . In their estimation, a scaling
violation in the central region are included to be consistent with the
CERN-SPS data while the z-distribution in the fragmentation region is not
properly considered, which is most effective to the cosmic-ray
propagation in the atmosphere. Even if we assume a strong scaling
violation (FA4) which is unrealistic already at the accelerator energies
as shown in Fig.2b, the expected proton flux never exceeds the simple
extrapolation from low energies.
The general (i.e., all observed particles independent of family
correlation) hadron and 7 spectra observed at Mt.Fuji also supports the
" present picture5 . In Ref.6, we estimated the composition around the
"knee" by the use of the "rigidity cut-off model". The proton spectrum
there is consistent with the present estimation.
Acknowledgement.
Data analysis and simulation calculation were done using the
computer FACOM M380 of the Institute for Nuclear Study, the University of
Tokyo and the FACOM MI80II-AD of Kanagawa University.
References
1. Mt.Fuji group, M.Amenomori et al., Phys. Rev. D_ (1982) 2807.
2. L.Ding et al., Proc. of 18th ICRC (Bangalore),vol.5, p.483 (1983).
8. L.W.Jones, Proc. of 18th ICRC (Bangalore),vol.5, p.17 (1983).
" 4. See for example; J.Wdowczk and A.W.Wolfendale,Nature 306 (1983)347.
5. Mt.Fuji group, M.Amenomori et al., in this conference, HE3.1-3.
6. Mt.Fuji group, M.Amenomori et al., Proc. of Int. Sympo. on Cosmic
, Rays and Particle Physics, p.494 (1984).
'-' 
-1 
1U 
-2 
x lU 
B 
~ 
L, 
 
9 
____ Grigorov et al. 
=--t tal C:=J AKENO ( 984 ) 
Suggested Proton Spectrwn 
/ ucleus ( Te  ) 
i .  ted rim ry r ton s trum. 
00 -4 
. i on.   s   o  t  o   
re rted a r ton-dominant c position4) . I  t ir estimation, a s lin  
i l tion i  t  t l r ion  in luded t   si t t it  th  
-  t  hile t e x- istribution i  t e frag e tation re ion i  t 
r rly i red, hi h i  ost ff tive t  th  s i -ray 
propagation i  the atmosphere. ven if e assume a stron  scaling 
violation (FA4) hich is unrealistic already at the accelerator energies 
as shown i  i .2 , the expected proton flu  never exceeds t e si ple 
tr l tion from low r i . 
he general (i.e., ll observed articles independent of fa ily 
rr l tion) r   ~ tr  s r d t t. uji l  s rts t  
r t i t r s. I  ef. , e stim ted t  position r  t  
"knee" by the use f the "ri i ity c t- ff odel". he proton spectrum 
t   si te t it  t  r t tim tion. 
c l . 
ata a al sis and si ulatio  calc lation ere done si  t e 
put r F O  380 f t  I titute f r ucl r t , t  niversity f 
  t  O  180I -AD f a  niversit . 
ef  
. t. uji r , . en ori t l., hys. e . 25 ( ) . 
2. . ing et al., Proc. of 18th ICRC ( angalore), vol.5, p.483 (1983). 
3. . .Jones, roc. f 18th I  ( angalore), ol. , p.17 (1983). 
• 4. See for exa ple; J.Wdo czk and . . olfendale, ature 306 (1983) 347. 
. t. uji r , . en ori t l., i  t i  f r , E3.1- . 
6. t. uji group, . eno ori et l., roc. of I t. Sy po. on os ic 
a   arti l  hysi , .494 ( ). 


Composition of primary cosmic rays at energies 10(15) to approximately 10(16) eV

Composition of primary cosmic rays at energies 10(15) to approximately 10(16) eV

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