The progress is presented of the nuclear emulsion experiment to determine abundance of low energy antiprotons in cosmic rays. No antiprotons have been detected so far at upper limit of p/p less than or similar to 4 x .0001 in the energy range 50 MeV to 15 MeV

Apparao, K. M. V.

Biswas, S.

Durgaprasad, N.

Stephens, S. A.

English

NASA Technical Reports Server

ABUNDANCE OF LOW ENERGY (50-150 MeV) 
ANTIPROTONS IN COSMIC RAYS 
Apparao, K.M.V., Biswas, S., Durgaprasad, N. 
and Stephens, S.A. 
Tata Institute of Fundamental Research 
Homi Bhabha Road, Bombay 400005, India 
ABSTRACT 
We present the progress of our nuclear emulsion 
experiment to determine on abundance of low energy 
antiprotons in cosmic rays. We have not detected 
any so far and obtain an upper limit of ~ / ~ ~ 4 x 1 0 - ~  
in the energy range 50-150 MeV. 
During the last International Conference on Cosmic Rays 
at Bangalore, we1 reported preliminary results of an experi- 
ment to determine the abundance of low energy antiprotons in 
cosmic rays. We are using a nuclear emulsion stack of 200 
Ilford G5 emulsion pellicles exposed on July 3, 1972 at Fort 
Churchill, Canada for 13h 45m at a depth of 1.7 g.cm-2 of 
residual atmosphere. We scanned at a depth of mostly 2 cms 
from the top edge, for nuclear interactions containing one 
high energy track and then followed all tracks in the uGper 
hemisphere towards the edge of the entry. This will pick 
out interactions produced by a particle coming from outside 
the stack. The signature of a low energy anti-proton is a 
track corresponding to a slow particle (<200 MeV) of protonic 
mass and producing an interaction with a visible energy re- 
2 lease more than the kinetic energy of the incoming  roto on . 
In the previous ICRC we had reported five candidates. 
These were obtained by making grain density measurements 
along the track, which indicated the direction of motion of 
the particle producing the track, i.e. whether the particle 
326 
U   LOW ENERGY (50-150  
PROTONS IN C AYS 
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and ephens, S .
a In itute  e t l ch 
  ,  400005, India 
TRACT 
 e e  the o ess o  o   e l ion 
OG 6.1-1 
ex rim  to d termine on abundance 
a iprotons in cosm c ra   ve 
any so far and in an u  lim  
in the energy range 50-150  
 low en rgy 
 ected 
- -4 
o  p/p~4x10 
ng the last International ence on c  
a  l , I rep ted eliminary res ts  an e -
 to d termine the abundance o  low en rgy a iprotons in 
cosm c ray .  are u ing a  e l ion stack o  200 
Ilford G5 e l ion icles exp ed on July 3, 1972 a   
-2 rchil , da for 13h 45m  a d h  1 g.cm o  
residual atm .  scanned a  a d h o  st y 2 cms 
from the top edge, for n  interactions c aining one 
high energy track and then fol owed a l tracks in the up  
h i e tow ds the edge o  the e ry  s i  ck 
 interactions produced b  a icle com ng from o side 
the stack. e signature o  a low energy a i-proton is a 
track corresponding to a slow icle «20  V) o  p oto c 
 and prod ng an interaction i h a sible energy re-
lease e than the n ic en rgy o  the incom ng p ton2 . 
In the previous ICRC  ha  rep ted five ca . 
T se e o ained b  ng g ain d ty em s 
along the track, ch indicated the d rection o  t on o  
the icle prod ng the track, i. t  the o icle 
https://ntrs.nasa.gov/search.jsp?R=19850025779 2020-03-20T18:00:30+00:00Z
is coming into the interaction or produced in the interaction 
and going away from the interaction. None of the candidates 
stopped in the emulsion at the point of interaction. We have 
now scanned a total volume of 7.8 ~ r n - ~  of emulsion. A total 
of about 19,590 interactions were looked at and 10,169 tracks 
were followed towards the to9 of the stack. Out of these 288 
tracks left the stack at the top and grain density measure- 
ments were carried out on them. Those that showed that they 
are proceeding towards the interaction are called candidates 
for 6 and were subjected to blob-gap measurements in all 
pellicles through which they pass. We have made extensive 
grain density and blob-gap measurements on relativistic alpha 
tracks in various regions of the stack to determine variations 
of the sensitivity of the emulsion in a single pellicle as 
well as from pellicle to pellicle. We used stopping protons 
and electron pairs to obtain the calibration curves for ioni- 
zation versus range. 
With the above effort, we found that the previous candi- 
dates are not anti-protons. We also found another 15 candi- 
dates, which also did not turn out to be antiprotons. We 
have calculated the gathering power of our volume to be 
3 2 2.38~10 m .sr.s.MeV yielding as an upper limit to 6 flux of 
-2 -1 -1 
-4x10-~ m .s .sr .M~v-' in the energy range 50-150 MeV. 
This flux limit is to be compared to the flux of (1.7 f 0.5) 
-2 -1 -1 
x m . sr . s . M~v-' obtained by Buffington et a1. 3; 
however the flux obtained by Buffington et al. is in the 
energy range 130-320 MeV. The upper limit to the hip ratio 
in the energy range 50-150 MeV is obtained using the proton 
flux in this energy range of 0.96 f 0.07 m-2. s .  sr-I M~V' 
obtained* from IMP-6 satellite on this date, and is 
4.3 (10). 
* We are thankful to Dr. T. von Rosenvinge for this infor- 
mation. 
327 OG 6.1-1 
i  io ion
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t 59  ion er o 1  rac  
er low o  op  ut  
rac  ac si easur
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 p er j eas r ent l
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t er um
38xl0 3 2 sr.s.M v i n i i p lu
4xl0- 4 - 2 -1 -1 . eV-1   e . 
i lu i i par lux ± .
-4   -1 3 
 10  •    eV t uff l
e e lux t  uff o l  
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  e t n
-2 -1 -1 -1 lu   ± .   .  .  e  
t ned  rom -  t l te  
.  x 10-4 cr).
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ati .
In the last ICRC we reported an event which we interpre- 
ted as an anti-triton event on the basis of grain density 
measurements. Since then we have made blob gap measurements 
and multiple scattering measurements on the track in all the 
pellicles through which it passes. After taking into account 
the plate to plate variations, we found that the ionization 
measurements made the identification of the incoming track 
between t and I3e3 ambiguous; perhaps more consistent with He 3 
nucleus (Fig. 1). In Fig. 2 we show the plot of normalised 
ionization parameter obtained from blob-gap measurements, 
versus the multiple scattering parameter for 1 0 0 ~  cell length. 
(The parameter for 1 0 0 ~  is obtained from values obtained 
from higher cell lengths and the usual third difference method 
to remove distortion effects). The curves for H~ and ~e~ are 
shown. Here again we do not find convincing evidence that 
the incoming track is a triton, eventhough the measurements 
do not fit well with a 13e3 curve. Therefore, we do not 
believe the track to be due to an anti-triton. 
Acknowledgements: Our thanks are due to Dr. R. Silberberg 
and the authorities of the Naval Research Laboratory, USA for 
loaning the emulsion stack. We appreciate the patient scan- 
ning and measuring work of Ms. S. Savitri, Mrs. S.P. 
Prabhudesai, Mrs. R. Chandrasekhar, Mr. D.M. Pawar and 
Mr. D. Mane. 
References 
1. Apparao, K.M.V., Durgaprasad, N., Stephens, S.A. and 
Biswas, S., 1983, Proc. 18th ICRC, Vo1.2, gp.75 and 79. 
2. Apparao, K.M.V., 1967, Nature Phys. Sci., 2, 98. 
3. Buffington, A., et al. 1981, Ap.J. Lett., 247, L105. 
328 OG 6.1-1 
In the la  ICRC  rep ted n e  i h  interpre-
ted as an triton   the   n y 
e e t . nce then  e  ob p e s 
an  ult e tering e e s n the track in  the 
icles through i  it  f  taking into cco  
the e to e ations,  found th  the ion zation 
e e   the id fication  the incom ng track 
tw en t an  He 3 a i ; h   en  i h 3 
eus (Fig. In  2  show the   al sed 
io zation a t  ained from ob-gap ea ent , 
su  the ult e s tering a et  for 0 ~  len  
(The a et  for 0 ~ is ained from ues ained 
from g   lengths an  the  th rd fference t  
to rem e tortion  c rves for 3 an  H 3 re 
show   a n  do  find ing idence th  
the incom ng track is a riton, v nthough the e t  
o  t el  i h a He3 c  r ,  do  
iev  the track to  e to an t riton  
l ent   thanks re e to r   lberberg 
and the r ies  the  ch r ory, A for 
loaning the l on stack   te the e  sca
ng an  e ng   s   i , rs. . 
, rs  . r , r. . .  n  
r. . ane. 
ences 
  . .V., r , .  te~hens, . an  
sw , . 1 ,  h ICRC, ol. , p sJS an   
  . .V., 1 , t   i  ~,  
 f n on, .    19 , p.J. ett. , S  
Fig. 1. Normalised ionisation parameter 1/10 obtained from 
blob-gap measurements versus residual range. The curves for 
protons (P) and He4 are obtained from calibration tracks. 
The measurements of the candidate track are plotted once on 
the triton curve and once on He3 curve to examine the fits. 
Fig. 2. Normalised ionisation parameter 1/10 obtained from 
blob-gap measurements versus scattering parameter. The 
measured values for the candidate track are plotted; typical 
error is shown. 
2 0  
0 
n 
\ 
,+ 
5  
I ' I  " I  I I I 
-- - 
l o - - /  I 8 r / H 3  ‘ 
I , , , , (  I 1 i 
'* 0.5 1.0 2 . 0  5.0 
SECON3 DIFFERENCE 
328 OG 6.1-1 
15 
0 He3~ I-t 
'-
J--< 10 ,~. 
5 
T 
P 0 
  r ali ed io sation a et  1 ined from 
ob-gap e t   e id  an .  v s o  
o  (P)   e ined from ibration rac  
 ea e t   the e track e e e n 
the riton ve     ve to a e the ts. 
 
o g
eas
ro  is 
0 
0 
...... H3 
'-
H 10 3 De / HE 
~7 
 
·05 1-0 0 50 
COND I F ENCE 
r ali  o ion et  1 ined rom 
e t  su  tering et r   
u  o  he e rack e ted  y  
show  


Abundance of low energy (50-150 MeV) antiprotons in cosmic rays

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