Upper limit of antinuclei content in cosmic ray

Gagarin, Yu. F.

Ivanova, N. S.

Kulikov, V. N.

English

NASA Technical Reports Server

? 
b 
Pv- - ' t '  1 
National Aeronautics and Space Administrat ion 
Goddard Space F l ight  Center 
Contract No.NAS-5-12487 
I ,  
4+ 
ST -CR - N p  -10688 
ON THE UPPER LIMIT OF ANTINUCLEI CONTENT 
I N  COSMIC RAYS 
GPO PRICE $ 
CFSTI PRICE(S) $ 
I 
~ 
by 
N.  S. Ivanova 
Yu. F. Gagarin 
V. N. Kulikov 
Hard copy (HC) 
Microfiche (MF) ,& 
ff 653 July65 
(USSR) 
(THRU) I 8 
3 
Q 
E 
(WAGES) 
= 
3 (&KR $T:?& NUMBER) 
1 8  MARQI 1968 
https://ntrs.nasa.gov/search.jsp?R=19680009889 2020-03-12T09:28:30+00:00Z
ON "HE UPPER ~ _ _ _  LIMIT OF --. ANTINUCLEI. . -_ - - CONTENT 
IN COSMIC RAYS 
Kosmiche ki e Issledovaniya 
I zdatel ' s tvo "NAUKA" , 1968 
$3. \i,L.Tom 6, vyp.1, 83 - 87, 
by N. S. Ivanova 
Yu. F. Gagarin 
V. N. Kulikov 
The upper limit of the number of antinuclei in the content of cosmic 
rays is estimated on the basis of the study of nuclear emulsions exposed at 
300 km, and of the investigation of all multi-charge particles at rest in 
the emulsion and of all interactions induced by them. 
When determining the upper limit of the number of antinuclei, account was 
taken of the corrections of the difference in the interaction cross-sections 
of nuclei and antinuclei in the emulsion and for the secoGdary origin of a cer- 
tain part of stopping multi-charged particles. A value nA < 0.59% is obtained 
for the upper limit of the multi-charge component of primary cosmic rays. 
* 
* *  
One of the interesting questions of contemporary astrophysics is that of 
symmetry of the Universe relative to matter and antimatter content. The inves- 
tigation of primary cosmic rays may provide some information on antimatter con- 
tent in our solar system. 
Estimates of the upper limit of the number of antinuclei relative to stan- 
dard multi-charge nuclei in cosmic rays were made in some works [1-3] on the 
investigation of the heavy component of primary rays by the photoemulsion 
method. Following are the assumptions made during these estimates: 
a) the energy and charge spectra of primary multi-charge nuclei and anti- 
nuclei hitting the emulsion are identical; 
b) the fraction of antinuclei stopped in the emulsion relative to the 
total number of stopped standard multi-charge nuclei must be equal to the share 
of antinuclei in the total flux of multi-charge cosmic rays [ 3 ] .  
(*) 0 VERKHNEM PREDELE SODERZHANIYA ANTIYADER V KOSMIGISKIKH LUCHAKH 
2 
The first assumption rnay be admitted with a certain approximation. Qua- 
litative consideration shows that no great difference can be expected in the 
energy and charge spectra of nuclei and antinuclei at the atmosphere boundary 
under the condition of their identity at the outlet from the sources (provided 
the paths covered by nuclei and antinuclei are about identical). 
difference is possible in the region of low energies. 
A certain 
As to the second point, it will be valid only in the assumption that the 
interaction cross-sections of nuclei and antinuclei in the emulsion are iden- 
tical. 
of the annihilation process of antinuclei on nuclei of the emulsion. 
However, generally speaking these cross-sections must differ on account 
In connection with this it appeared to us to be of interest to examine in 
detail the interaction of antinuclei (8) with nuclei (A) in the emulsion, to 
bring to light the singularities of annihilation stars from at rest and in 
flight and to estimate to what extent the difference in the interaction cross- 
sections of A and A will be reflected in the determination of the upper limit 
of A in cosmic rays. 
Besides, we considered it appropriate to estimate the upper limit of A 
in cosmic rays on the basis of experimental data obtained by us during the stu- 
dy of emulsion irradiated at 300 km altitude in the course of 72 hours aboard 
"Kosmos-4", account being taken of all corrections stemming from our consi-' 
derations. 
1. ESTIMATE OF INTERACTION PATHS OF ANTINUCLEI ANI> NUCLEI 
I N  THE EMULSION 
First of all the question must be clarified whether o r  not there is 
any sense in searching for the antinucleus in the emulsion among stopped multi- 
charge particles. 
X 10 cm3) the percentage of nuclei and antinuclei having hit the chamber, stop-  
in the emulsion upon deceleration (on condition of identical initial energy 
an charge distributions). To that effect deceleration and interaction must 
be taken into account in the case of standard multi-charge nuclei, and decele- 
ration and interaction with annihilation (in flight) for antinuclei. 
Perhaps all antinuclei undergo annihilation in flight. 
With this in view we estimated for our own emulsion chamber (of 10 X 10 X 
The energy distributions ofincidentmulti-charge particles were borrowed 
Incidently, an identical distribution was from the experimental data of 141. 
taken also for antinuclei. 
nuclei L (Z = 3 - S), M (Z = 6 - 9) and H (Z 2, 1 0 ) .  
experimental charge distribution [S I  for these groups mean values of Z were 
computed for these groups; these values were precisely used during computations. 
Calculations were Londucted for the groups of 
Correspondingly with the 
Deceleration Path>. - The deceleration of antinuclei during their passage 
in the emulsion is conditioned by usual ionization losses and it must not differ 
from thedecelerationof standard nuclei (for the enerkv region with f3 >/ Z/137). 
Consequently, the deceleration paths for a and A may be considered identical. 
At the end of the path, at stop, the destiny of nuclei and antinuclei is dif- 
ferent. Antinuclei undergo annihilation. 
We computed for the groups L ,  M and H the deceleration paths in the emul- 
sion as a functi0.n of energy of falling particles, utilizing the standard for- 
mulas for the deceleration capability. 
Interaction Paths in the Emulsion for Simple Nuclei. - The paths were 
determined as hint = 1  / Cniai, where n 
in the emulsion and ai is the cross-section on that nucleus. hint may be com- 
puted knowing the composition of the emulsion and utilizing the semiempirical 
lormula for the cross section [6] u1 =. v(Rj + Ri- R) , where R, = lL,yll'/; and 
11, = Rb-t are the radii of the bombai ding nucleus ( j  ) and target-nucleus (i j , 
and R = 1.17 Ro ( R o  = 1.45. lo-'' cm). 
those measured experimentally within the limits of 10%. We utilized the f o l -  
lowing values of paths: group L) 15 cm of emulsion, group M) 13.5 cm and 
group fl) 
experimental data of [ 7 -101 . 
is the number of nuclei of the kind 
?he thus computed paths coincide with 
10 cm. These quantities agree well with the mean values obtained from 
Paths for the Annihilation of - When computing these paths we started 
from the data according to which the path 6 in nuclear matter is of the order 
(0.6 - 0.7) .10-13cm, i. e. it is very small by comparison with the dimensions 
of nuclei (s cm) and consequently, all fi must annihilate in the superfi- 
cial layer OS the nucleus [ll, 121. 
During the interaction -nucleus (Z z 4), the latter constitutes an 
"absolutely 1,lack'' (absorbing) sphere of radius Reff = RII, + 11, where 
R I ~  = 4.08 A'/ , .  10-13 cm is the radius of the nucleus corresponding to half-density 
p = (l/2)p0, and rl = 2 
surface of the nucleus, practically identical for all nuclei with A > 4. 
way of analogy, when computing the paths for the annihilations of A in the emul- 
sion (Xann =- 1 / Cniai) is the radius R i  in the cross-section ai = TRi2 was de- 
termined by is as the sum of two effective radii of the bombarding nucleus ( j j  
and the target-nucleus (i) (for nuclei with Z = 4 of group L the radius of the 
bombarding nucleus was defined as R = r0A43 , where ro = 1.35 
the target-nucleus as R,ff(i)) : 
cm is the effective thickness of the diffusive 
By 
cm, and 
where Reff (j, i) = Rl/>[j, i) -'i- r. Paths For annihilation in the emulsion (the composi- 
tion of the latter being known) were estimated for all the groups L, M and H. 
Utilizing the obtained values of paths for deceleration, interaction and 
annihilation we may estimate NX / NA is the ratio of the numbers of antinuclei 
and nuclei which, having decelerated, maystop in our emulsion chamber. 
was obtained the valae k = NJ / NA = 0 . 4 8 .  
charge spectra hitting the chamber, the number ofantinucleiatrestwill be two 
times less than the standard multi-charge nuclei. 
limit of A in cosmic rays, this coefficient must be taken into account. 
Thus 
Therefore, for identical energy and 
When derermining the upper 
4 
2. ANNIlIILATION OF h 
'he above cstimatcs show that in the prescnce of A in primary cosmic 
rays there cxists n probability of detecting them among the number of stopped 
n w  1 ci . 
'fie form of tracks of and A at rest in the emulsion is sharply different. 
The standard nuclei form at stops a characteristic strongly narrowing track 
(after thickness maximum), which is conditioned by a decreasing energy of 6-  
electrons (in proportion of energy loss by the nucleus), and over the ver). last 
portion of the path by the decrease of the effective charge of the nucleus 
(capture of atomic electrons of the medium). 
During deceleration in the emulsion and prior to attaining a velocity 
equal to the velocity of atomic electrons, antinuclei form a track analogous 
to that of the standard. nucleus. No electron capture can take over the last 
portion of the path. 
from the bound (a) state. At stop the antinucleus will necessarily annihilate 
Thus an annihilation star must be observed for a track of an antinucleus 
at rest after thickness maximum and further narrowing. 
Estimates carried out by A. Z. Dolginov and D.A. Varshalovich for A and 
with Z >, 4 have shown that during annihilation "antinucleus-nucleus" (A > A) 
at rest (or at small kinetic energy) only Y, 30 to 40 percent of antinucleons 
from the antinucleus will annihilate. The forming .rr-mesons (5n0+-mesons for 
each pair NN as an average) must undergo the usual interactions with nucelons 
and antinucleons of nuclei-residues, such as elastic and inelastic scattering 
and absorption (most probably on a pair of nucleons). 
As a result of these processes cascade (fast) N and fi will be observed, 
and the residues of nucleus and antinculeus, having remained excited, will 
vaporize the slow nucleons and antinucleons. 
According to the estimate T, 30% of all antinucleons will be slow (vapor- 
izable) and 30% will be fast. 
fission in annihilation stars during stops. 
The slow N may be revealed among products of 
3. ESTIMATES OF THE UPPER LIMIT OF A IN COSMIC RAYS 
Whwn looking over the area of the relativistic emulsion which was irradia- 
ted by cosmic rays at 300 km ("Kosmos-4"), all ending multi-charge particles 
(Z 2 3) and all interactions induced by multi-charge particles were registered. 
474 ends and 325 interactions were revealed in all. Each multi-charge particle 
forming fission or stopping in the emulsion was tracked to the entry of the 
emulsion chamber. Among the ending particles, multi-charge ones had a second- 
a r y  origin in 122 cases ( 2 5 . 8 % ) ,  i. e. they formed in stars under tee action 
of cosmic rays. Thus, 352 cases were revealed of primary multi-charge par- 
ticles having stopped in the emulsion. The tracks of such particles had the f 
shape of "carrots", very characteristic for the stops of standard multi-charge 
particles. 
Moreover, we investigated all the interactions induced by multi-charge 
particles. 
of the multi-charge particle from the emulsion camera inlet to the place of 
formation of interaction. Secondly, we investigated all tracks with the view 
of ascertaining in their composition the existence of slow antinucleons and 
annihilation n-mesons; this was done in fissions induced by multi-charge par- 
ticles of low energy ( < 200 Mev/nucleon) . 
Studied first was the ionization of the track during the transit 
Not a single case was revealed that would satisfy the enumerated singular- 
ities of annihilation "antinucleus-nucleus!'. 
Making use of these data we may evaluate the upper limit of antinucleus 
content in the composition of primary cosmic rays, taking into account all the 
noted corrections. The quantity 
where Nemch = 352 is the number of primary multicharge nuclei ending in the 
emulsion, and the coefficient k=0.48 takes into account the difference in 
the interaction cross-sections of A and A in the emulsion (see Section 1). 
IIence we obtain ni < 0.59% of the multi-charge component of primary 
cosmic rays. The estimates available in literature of the upper limit 
nA < 1% El], ni < 0.1% [ Z ]  and n i  < 0.23% [3] were apparently obtained with- 
out taking into account the corrections. 
of the works by N. L. Grigorov et a1 [3], where the case statistics are closer 
to our own (442 ends of multi-charge particles), and if we introduce the cor- 
rections a) for the secondary origin of a certain part of stopping multi- 
charge particles (25.8%) and b) for the difference in the cross-sections 
of interactions of A and A in the emulsion (k = 0.48) ,  we shall obtain 
If we borrow the experimental data 
which is close to our own value. 
The data obtained show that for the admitted assumptions about the charge 
and energy spectra of antinculei, their number in the composition of cosmic 
rays and near-ground space is in any case less than 0.6% of the number of 
standard multi-charge cosmic particles (the investigated energy region for 
nuclei stopping in our chamber is < 1.4 Bev/nucleon). 
However, we still cannot estimate on the basis of these data the upper 
limit of antinuclei in the Galaxy, and the more so in the Universe. 
ledge of the sources of cosmic rays, of acceleration mechanisms and propaga- 
tion of cosmic rays are still tooincomplete to allow any reliable conclusion 
in this direction. 
In conclusion the authors express their gratitude to academician B. P. 
Konstantinov for his interest in the present work and his particiaption in 
the discussion of results. 
Our know- 
- w . 6 
The authors also extend their thanks to A; Z. Dol inov, D. A. Varshalo- 
vich and M. M. Rredov for  their valuable discussions and to N. L. Grigorov, 
I. A,  Savenko and D. A. Zhuravlev for their cooperation in setting up the 
experiment. 
Manuscript rece ived 
on 24 April 1967 
REFERENCES 
[1[. D. M. KHASKIN, P. L ,  DZHEYN, E. LORMAN, M. SHAYN, M. TOYKHER. Trudy 
H. AIZU, Y. FUJIMOTO, S. HASEGAVA, M. KOSHIBA ET AL. 
N. L. GRIGOROV, D. A. ZHURAVLEV, M. A. KONDRAT'YEVA, I. D. RAF'OPORT, 
I. A. SAVENKO. 
H. AIZU, Y. FUJIMOTO, S. HASEGAVA, M. KOSHIBA ET AL. 
Koskovskoy mezhdurarodnoy konferentsii PO kosmi- 
Phys.Rev., 121, 
chekim lucham, T. 111, p.138, 1960. 
[2]. 
[3]. 
[4]. 
[ S I .  C. J. WADDINGTON. Progress Nuclear Phys., 8, 3, 1960. 
[b]. H. L.  BRAD", B. PETERS. Phys. Rev. 80, 943, 1950. 
[7]. M. F. KAPWN, J. H. NOON, G. W. RACE'ITE. 
[SI. C. J. WADDINGTON, V. Y. RAJOPADHYE. Phyl. Mag. 3, 25, 1958. 
[9]. 
[ l o ] .  
[ll]. A. G. EKSPONG, B. E. RONNE. Nuovo Cim. l3, 27, 1957. 
[12]. A. E. GLASGOLD. Phys, Rev. 110, 220, 1958. 
1206, 1961. 
Sb. "ISZ" (AES", vyp.10, AN SSSR, p.96, 1961. 
Progr.Theor.Phys. 
Suppl. No.16, p.54, 1960. 
Phys. Rev. 96, 1408, 1954. 
R. CESTER, A. DEBENEDE'ITI, C. M. GARELLI ET AL. Nuovo Cim. z, 371, 1958. 
P. i t .  FOWLER, R. R. HILBER, C .  J. WADDINGTON, Phyl.Mag. 2, 293, 1957. 
CONTRACT N0.W-5-12487 
1145 - 19th St.NW 
VOLT TECHNICAL CORPORATION 
WASHINGTON D. C. 20036. 
Telephone: 223-6700 (X-36) 
Translated by ANDRE L. BRICHANT 
on 16 - 17 March 1968 


On the upper limit of antinuclei content in cosmic rays

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server