Arrival directions of air showers with primary energies in the range 10 to the 16.5 power eV to 10 to the 18th power eV show the first harmonic in right ascension (RA) with amplitude of 2.7 + or -  1.0% and phase of 13-16h. However, the second harmonic in RA slightly seen for showers in the range 10 to the 18th power eV to 10 to the 19th power eV disappeared by accumulation of observed showers. The distribution of arrival directions of low-mu air showers with primary energies around 10 to the 15th power eV observed at Chacaltaya from 1962 to 1967 is referred to, relating to the above-mentioned first harmonic. Also presented in this paper are arrival directions of old-age low-mu air showers observed at Chacaltaya from 1962 to 1967, for recent interest in gamma-ray air showers

Hagiwara, K.

Inoue, N.

Kakimoto, F.

Kaneko, T.

Martinic, N.

Miranda, P.

Obara, T.

Siles, L.

Suga, K.

Yoshii, H.

English

NASA Technical Reports Server

2 8 8 OG 5.3-2
Arrival Directions of Large Air Showers,
Low-Mu Air Showers and Old-Age Low-Mu Air Showers
Observed at Mt. Chacaltaya
Kaneko, T.
Department of Physics, Okayama University, Okayama 700, Japan
Hagiwara, K.
The Institute of Physical and Chemical Research, Wako, Saitama
351, Japan
Yoshii, H.
Faculty of General Education, Ehime University, Matsuyama 790,
Japan
Martinic, N., Siles, L. and Miranda, P.
Instituto de Investigaciones Fisicas, Universidad Mayor de
San Andres, LaPaz, Bolivia
Kakimoto , F., Obara, T., Inoue, N.* and Suga,K.**
Department of Physics, Tokyo Institute of Technology, Meguro,
Tokyo 152, Japan
ABSTRACT
Arrival directions of air showers with primary energies in the range
1016.5eV to 1018.0eV show the first harmonic in right ascension(RA) with
amplitude of 2.7±1.0% and phase of 13-16h. However, the second harmonic
in RA slightly seen for showers in the range lOl8.0eV to lOlg-0eV disap-
peared by accumulation of observed showers. The distribution of arrival
directions of low-mu air showers with primary energies around 1015eV ob-
served at Chacaltaya from 1962 to 1967 is referred to, relating to the
above-mentioned first harmonic.
Also presented in this paper are arrival directions of old-age low-
mu air showers observed at Chacaltaya from 1962 to 1967, for recent in-
terest in gamma-ray air showers.
i. Arrival directions of large air showers
Arrival directions of large air showers observed at Mt. Chacaltaya
(16°20'52"S in latitude and 68°7'57"W in longitude, 5200m a.s.l, or 550
gcm -2 atmospheric depth) until 1979 were reported at the Paris Conference
(i). In the present paper we report on arrival directions of large air
showers observed at Chacaltaya until 1984. The air-shower array and the
detectors after 1979 were same as those described in the previous paper *
(i). Procedures to determine the arrival directions(e,_) and the electron
sizes(Ne) as well as the uncertainties for showers observed after 1979 are
also same as those described in the previous report(l). The primary ener-
gies(Eo) of showers observed after 1979 were determined from a relation
between Eo and Ne at the maximum development(_max ) given as Eo(eV)=2.0x
109(eV).Nemax described also in the previous report(l). Nemaxwas esti-
mated from Ne and the effective atmospheric depth where the shower was
observed(550gcm-2xsece), following the longitudinal development of elec-
trons determined at Chacaltaya(2).
•Present addres: Graduate School of Science and Technology,Kobe University
, Nada, Kobe 657, Japan
•*Present addres: Department of Physics, Meisei University,Hodokubo 337,
Hino-shi, Tokyo 191, Japan
3  
rrival irections of Large ir Showers, 
- u ir owers  ld- ge - u ir owers 
bserved at t. hacaltaya 
aneko, . 
OG 5.3-2 
epartment of Physics, kayama niversity, kayama 700, Japan 
agiw ra, . 
The Institute of Physical and Chemical esearch, ako, Saita a 
1, J an 
oshii, . 
aculty of eneral ducation, hi e niversity, atsuyama 790, 
an 
artinic, ., iles, . d iranda, . 
I stituto de I vestigaciones isicas, niversidad ayor de 
an ndres, aPaz, olivia 
akimoto, ., bara, ., Inoue, .* and uga,K.** 
epartment of Physics, Tokyo Institute of Technology, eguro, 
Tokyo 152, Japan 
STRACT 
rrival directions of air showers ith pri ary energies in the range 
1016.5eV to 1018.0eV show the first har onic in right ascension(RA) ith 
plitude f . 1.  a d ase f l -l h. owever, t  s nd ar onic 
in RA slightly seen for showers in the range 1018.0 eV to 1019.0 eV disap-
eared  accumulation f served s wers. he istri ution f rri al 
directions of low-mu air showers ith pri ary energies around 1015eV ob-
served at hacaltaya fro  1962 to 1967 is referred to, relating to the 
ove-mentioned st r onic. 
Also presented in this paper are arrival directions of old-age low-
mu air showers observed at hacaltaya fro  1962 to 1967, for recent in-
t rest i  ga ma-ray ir s ers. 
1. rrival directions of large air showers 
.Arrival ir ctions f l r e ir s ers served t t. hacaltaya 
(16°20'52"Sinlatitude and 68°7'57"  in longitude, 5200  a.s.l. or 550 
gc -2 at ospheric depth) ntil 1979 ere re orted t t e aris onference 
(1). In the present paper we report on arrival directions of large air 
showers observed t hacaltaya ntil 1984. he air-s wer array and t e 
detectors after 1979 ere sa e as those described in the previous paper ~ 
(1). Procedures to determine the arrival directions(B,~) and the electron 
sizes(Ne ) as well as the uncertainties for showers observed after 1979 are 
also sa e as those described i  the previous re ort(l). he pri ary ener-
gies(Eo) of showers observed after 1979 were determined from a relation between Eo and Ne at the maximum development(~max) given as Eo (eV)=2.0x 
109 (eV) ·Ne max described also in the previous report (1). Ne max was esti-
mated from Ne and the effective atmospheric depth where the shower was 
observed(550gcm-2xsecB), follo ing the l ngitudinal development f elec-
tr s t r ined t hacaltaya(2). 
* resent a dres: raduate chool f cience and echnology,Kobe niversity 
, Nada, Kobe 657, Japan 
**Present addres: epartment of Physics, eisei niversity,Hodokubo 337, 
ino-shi, Tokyo 191, Japan 
https://ntrs.nasa.gov/search.jsp?R=19850025756 2020-03-20T18:00:43+00:00Z
2 3 9 OG 5.3-2
Table i and 2 show the results of harmonic analyses in right ascen-
sion of the arrival directions of showers with zenith angles smaller than
60 ° . In the tables,figures in upper row correspond to the first harmonic
and those in the lower row correspond to the second harmonic. As is seen
in tables 1 and 2, the first harmonic is predominant at primary energies
in the range lO16.SeV to 1018.0eV as was seen for showers observed until
1979(1). However, the second harmonic slightly seen for showers observed
until 1979 with primary energies in the range 1018.0eV to 1019.0eV dis-
appeared by including the showers observed until 1984.
Table i.
Energy Number of Amplitude Phase
(E O in eV) showers (r in %) (in hour) ko p(>r) period
2.7± i.l 13.1±1.5 3.11 0.05 19811016"5-1017.0 17477
1.2± i.i ii.2±2.8 0.61 0.55 -1984
2.6± i.i 15.5±1.7 2.21 0.ii 1977
1017"0-1017"5 12914
0.9± 1.2 0.2±3.6 0.28 0.76 -1984
4.9± 2.4 16.3±1'8 1.99 0.14 1977
1017"5'-1018.0 3372
1.9± 2.4 i0.0±3.5 0.30 0.74 -1984
1018"0-1018-5 593 6.6± 5.8 7.0±2.7 0.65 0.52 1977
4.4 ± 5.8 10.0±3.5 0.29 0.75 -1984
6.0±13.1 12.2±4.4 0.i0 0.90 1977
1018"5-1019-0 117
17.8±13.1 2.0±2.4 0.93 0.39 -1984
Table 2.
Energy Number ofiAmplitude Phase
(bin eV) showers (r in %) (in hour) k° p(>r) period
2.7± 1.0 15.0±1.3 3.94 0.02 19641017-0-1018.0 21534
0.6± 1.0 8.8±3.9 0.19 0.83 -1984
3.5± 4.2 2.7±3.3 0.35 0.71 1972
1018"0-1019-0 1118
6.2± 4.2 8.7±2.3 1.01 0.34 -1984
. 2. Arrival directions of
! | i | ;
low-mu showers
30 269 10w-mu showeFs Relating to first har-
monic at primary energies
° in the range 1016.5eV-
lOlS.0eV, arrival direc-
tions of low-mu showers
20 observed at Chacaltaya
__ If should be mentioned Figure
o 1 shows the distribution of
¢- uJ
low-mu showers with zenith
4- angles smaller than 60 °O
i0 along right ascension. The
| average size of the showers
_n
E I is about 3xlO 5 and the pro-
z portion of the low-mu show-
ers is about one thousandth
0 ! I ! ! ! of ll showers. This figure
was drawn in 1978 after the
0 60 120 180 2q0 300 360 Calgary Conference in 1967
. Rightascension (3) by including all show-
ers observed from 1962 to
Fig, i 1967. An excess of the
239 O  5  
Table 1 and 2 show the results of har onic analyses in right ascen-
sion of the arrival directions of showers with zenith angles smaller than 
°. I  th  t 1es,figures in er ro  c rr s ond to th  fi t r onic 
and t se in the lo er ro  c rres ond to the second har onic. s is see  
i  ta les 1 and 2, the first har onic is predo inant at pri ary energies 
i  th  e 10 16 • 5eV to 18 • OeV   se   sh ers rved til 
9(1). owever, t  s d r onic li tly s  f r s ers served 
til 1979 ith pri ary energies in the range 10 18 • OeV to 10 19 • OeV dis-
eared  in l ing th  s ers served til . 
ble 1  
nergy u ber f mplitude 
(Eo i  e ) sho ers (r ip..%) 
6.5_1017.0  . ±1 1  1 1 
1017.°_1017.5 14  1 1 + ".  
1017.50_1018.0   .  + .  
18.°_1018.5  6.6± 5.8 
.. . ± .  
1018.5_1019.0  . 13.1 . ±13.1 
able   
nergy umber f mplitude 
(Eb in eV) showers (r in %) 
17.°_1018.0 34 .  .  .   
18.°_1019.0 18 .  .  .  .  
30  lo - u er$ 
en 20 
l-
Q) 
3: 
0 
.c 
en 
4-
0 
l- 1  
Q) 
..a 
E 
:J 
Z 
 
0 60 120 180 240 300 
i ht cension 
ig, 1 
ase 
ko p(>r) period (in hour) 
. 1.5    
11. 2.8   -1  
. 1.7  11 1  
+3.6    
. 1.8     
1 . +3.5    
7.0±2.7 0.65 0.52 1977 
. 3.5    
. 4.4 .1    
. 2.4 .  .  - 4 
hase 
ko p(>r) period (in hour) 
. ±1.3 .  .   
3.9 .  .  4 
. 3.3 .  .   
. 2.3 .  .  4 
. rival i ctions f 
- u ers 
Relating to first har-
onic at pri ary energies 
i  t e range 10 16 • 5eV-
1018.0 eV, arrival direc-
s f - u wers 
observed at Chacaltaya 
should be mentioned. Figure 
 s  istribution f 
l - u wers ith nith 
angles s aller than 60° 
along right ascension. The 
average size of the showers 
is about 3x105 and the pro-
ortion f t e lo - u sho -
rs i  bout ne t usandth 
of all showers. This figure 
~ as r n i  78 fter t e 
560 algary onference in 1967 
(3) by including all show-
rs bserved  962 t  
967. n exce s f t e 
240
OG 5.3-2
showers is observed between 180°(12.0h) and 260°(17.3h) in right ascen-
sion. At that time,we assumed that these low-mu showers were candidates of
gamma-ray showers. However, these low-mu showers may be showers produced
by primary protons which encountered the first interactions in the deep
atmosphere or produced mainly neutral pions at the first interactions,
referring to the argument described in section 3. Then, it is very inter-
esting that the right ascension where the excess of low-mu showers are
observed coincides with the phase of the first harmonic described in sec-
tion i at primary energies in the range 1016.5eV to 1018.0eV, since that
fact may be related with the composition of primary cosmic rays.
3. _yrival directions of old-age low-mu showers
Relating to the low-mu showers, it is worth while mentioning the
arrival directions of old,age low-mu showers observed at Chacaltaya from
1962 to 1967. Arrival directions of these showers were plotted on the
celestial sphere in 1967 as shown in figure 2 but was not published(4).
2.,2.'.LO!._IMU" EVENTS
• oSIZE_ 4,XIO5
_Oili _ _L'ANE _F GAL'_N¥ ' /...
z,. o /\.oO .
o. , \ o _o.,_oo _ o oO-/_o0° o
O-- . _ o . o • o . i o - . --
z _ oo° ,:, • o_.. . o o_O.o o o / o o._
_ (_,,, o o^o_, o_ o o oo o ..-. o,,, / ,w ,o . o(._ v _ o vo " " _ o. o o " o
-_n , v _ , • o • / O° O°D " o o
oL'J _o _ , ,° , \ "R,^o 8, @ (p ._e ./ _ ' oO •
_ o'o- _ -." o \ o " o . • _p,:p_, _ v o..(o o_o
-30 • . ._ • .o '_ -o. o . . e._o /\o _.'o -
-.'.oOOoo • - _11o, o _oO 8;i,_./ \oo _,°o
"_" o • o ,r_ o. .". / o\_ . _ o
o . , oy%-\:.:., oo.
-60-- _ GA'LA(!TICENTER - ,.
I I ,z,," I , I.... I I I , I f I
O 60 120 180 ' ' 240 300 360 "
RIGHT ASCENSION
Flg. 2
The following criteria were imposed to select these showers:
(i) The zenith angle of shower is smaller than 37°(sec8<1.25).
(2) The number of muons observed in the 60m 2 shielded detector is smaller
than four.
(3) The expected number of electrons at the muon detector is larger than
2000/60m 2 .
(4) The shower initiation point is in the first 80gcm -2 of the atmosphere.
The point is estimated from the zenith angle (550gcm-2×sec8: depth of
observation), the electron size and the lateral distribution(s) by
comparing the value of s with those of s for gamma-ray initiated pure-
ly eleCtromagnetic showers. This is a criterion effective to select
old,age showers produced probably primary gamma rays.
40 
 . -2 
s ers i  bserved et een Q (12.0h) a  Q (17.3h) i  ri ht s en-
i n. t t t ti e, e ed t at t se l - u ers ere ndidates f 
ma-ray s wers. owever, t se l - u s ers ay  s wers r duced 
by pri ary rotons hich encountered t e first i teractions i  t e deep 
t osph re r r duced ainly eutral i s t t  i t i t ractions, 
r ferring t  t e argu ent escribed i  secti n . hen, it is ery i ter-
ti g t at t  ri ht s ension here t  cess f lo - u s ers r  
served incides ith t  ase f t  t ar onic escribed i  c-
ti  I at pri ary energies i  the range I016.5eV to I018.0 eV, since t at 
ct ay  lated ith t  position f ri ary s ic s. 
. A-rrival ir ctions f l -age lo - u sho ers 
elating t  t e lo - u s ers, it i  orth hile entioning t  
rri al irections f l -age l - u s ers served t hacaltaya fro  
1962 t  1967. rrival irections f t ese sho ers ere l tted on t e 
elestial s here i  1967 as sho n i  fi re 2 t as ot ublished(4). 
2' 
o 
30 
'I 
~ 0 'I 
'I 
Z IJ' Q. 'I q a en. 'I 
l·J <w> 
 • 'I 'I 
-30 'I 0 
• I. '1'1 00 
'I 
 
-60-
o 
'I 
• 
• ~ 'I 
.,. e. 
'I 
• 
32 .. "L W U"  
Z :> )(105 
-SIZE >4)(105 . 
-
PLANE OF GALAXY 
 
Q. 'I 0 
• 
'I 
'I 'I Q .• Q. • 'I 
'I Q. 
00'1 . Cl> '1'1 '1'1 'I 
• 0 • 'I 'I 
 . ~ 0 
• () 0'1 'I 
'I 'I 'I '1'1 8." .. 
o 0 .00 ~ . 
roo 
.q, '1'1 8> iQ cP • 
o • 
'I 
'I 
'I 'I 
.'1 
'I 0 
o 'I 
o· 00 •. 0. . 00 0 
o 
QO·~\:~ 'I Q\, 'I 
LACTIC  
! I 
  0 0  
 ION 
lg.  
e ll ing riteria ere i posed t  lect t se ers: 
(1) e nith gle f s er i  s aller t n Q (sec6<1.25). 
( ) he ber f uons served i  t  2 i l ed etector i  aller 
 r. 
( ) he pected ber f l trons t t  uon tector i  l r er t  
0/60m2 • 
( ) he s er i itiation oint i  i  t  i st c -2 f t  t osph re. 
he point is esti ated fro  the zenith angle (550gcm-2xsec6: depth of 
servation), t  l ctron i   t  l t ral istribution(s)  
co paring the value of s ith those f s f r ga ma-ray i iti ted pure-
ly electromagnetic showers. This isa criterion effective to select 
old~age sho ers produced probably pri ary ga a rays. 
2 4 1 OG 5.3-2
Areas in which the densities of arrival directions were several times
higher than average are found near (e:135°,6:-40°),(240°_255°,-20°_-40 °)
and at some locations adjoining the blank area seenaround(10°,-20°). The first
location corresponds exactly to that of Vera X-l(09h00m13.18s,-40°21'25.3").
The Adelaide group reported recently gamma-ray air showers from this
X-ray source synchronized with period of the eclipsing binary (5). There
are some X-ray sources in the second location and a strong X-ray eclipsing
binary X1700-377(3.4d period;17hO0m32.70s,-37°46'28.8 '') is neaby. Regard-
ing to the third location, a high peak is seen at galactic latitude of
-60 ° to -70 ° when the distribution of the arrival directions is examined
in galactic latitude. The expected number of showers for this region is
13.5: the number observed is 27. For showers with Ne smaller than 4x105,
the corresponding number are 10.4 and 25.
Stimulated by the interesting old BASJE results looked back upon the
past and mentioned in sections 2 and 3, the BASJE group has begun the pre-
paration for a new project to observe iow-mu and gamma-ray showers with
32 Im 2 unshielded scintillation detectors located around the 60m 2 muon
detectors, among which 12 detectors are moved from the locations in the
present large array, and to determine the arrival directions within an
uncertainty of I°. The observation will be begun in the middle of 1986.
References
(i) Anda, R. et al: Proc. 17th Inter. Cosmic Ray Conf., Paris,_(1981)164
(2) Kakimoto, F. et al: J. Phys. G:Nucl. Phys.,_(1983)339
(3) Kamata, K. et al: Canadian J. Phys.,46(1968)s72
(4) Drawn for internal discussion among members of the Bolivian Air Shower
Joint Experiment(BASJE). The members of BASJE at that time were
I. EscObar, V. Domingo, J. Gaebler, K. Kamata, M. LaPointe,
K. Murakami, O. Saavedra, S. Shibata, K. Suga and Y. Toyoda
(5) Protheroe, R. J. et al: Astrophys. J.(Letters) 280(1984)L47
241  .  
reas i  hich th  nsities  i al i ti ns ere s eral tim s 
higher than average are found near (a:135°,o:-400),(2400~255°,-200~-400) 
and t so e l cati ns a j ining the blank area seen around(lO° ,-20°). he first 
location corresponds exactly to thatof era -l(09hOOm13.l8s,-4002l'25.3"). 
he delaide group re orted recently ga ma-ray ir sho ers fro  t is 
-ray source synchronized ith period of the eclipsing binary (5). There 
are so e -ray s rces i  t e second locati n and a stro  -ray li sing 
binary 1700-377(3.4d period;17hOOm32.70s,-37°46'28~8") is neaby. Regard-
ing to the third location, a high peak is seen at galactic latitude of 
_   ° hen  i tri ution  th  i al ti ns  ined 
i  alactic latit e. he expected nu ber of sho ers f r t is region is 
13.5: the number observed is 27. For showers with Ne smaller than 4xl05, 
 rr sponding ber  .   . 
ti ulated by the i teresting old SJ  res lts looked back upon the 
past and entioned in sections 2 and 3, the BASJE group has begun the pre-
paration for a ne  project to observe io - u and ga ma-ray sho ers ith 
1 2 shielded inti lation tectors ted d  2 uon 
etectors, ong hich  etectors  oved fro  t  l ations  t  
resent l r e y,  t  t r ine t  ri al i ctions ithin  
ncertainty f 1°. he servation ill be begun i  t e iddle f 1986. 
eferences 
(1) Anda, R. et al: Proc. 17th Inter. Cosmic Ray Conf., Paris,2(198l)164 
(2) Kakimoto, F. et al: J. Phys. G:Nucl. Phys.,5(1983)339 
(3) Kamata, K. et al: Canadian J. Phys.,~(1968)s72 
( ) ra n f r i t rnal i u sion ong embers f t  olivian ir er 
int xperiment(BASJE). he embers f SJ  t t t ti e ere 
I. scobar, . omingo, . aebler, . amata, . aPointe, 
. urakami, . Saavedra, S. Shibata, . Suga and . Toyoda 
(5) Protheroe, R. J. et al-: Astrophys. J.(Letters) 280(1984)L47 


Arrival directions of large air showers, low-mu showers and old-age low-mu air showers observed at St. Chacaltaya

Arrival directions of large air showers, low-mu showers and old-age low-mu air showers observed at St. Chacaltaya

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