IL NUOV0 CIMENT0 VOL. XI I I , N. 1 lo Luglio 1959

Possible Example of an Interaction in Emulsion

Producel by a Deateron of ~ 1 0 ~ e V .

P. K. A D I T Y A (*) (**)

Physics Ho~wurs School, Pan, jab U~iversiiy - Chandigarh

(ricevuLo il 4 Aprile 1959)

In high energy disintegrations ini- tiated, by singly charged particles of the cosmic radiation secondary interactions produced by neutral particles have been usually observed (~8). It is conventional to assume the neutral partic, les to be neutral mesons of long lifetime or neutral baryons created as nueleon- antinucleon or hyperon-antihyperon pairs. This is possible as long as the energy

(*1 Former ly known as P r e m Kuill&r. (**) At presen t ut the InstALute for Theo-

re t ical Physics, Un ive r s i ty of Copenhagen. (~) J . H. MULVEY: Proc. Foy . Soc., A 294,

367 (1.(t54). (e) |~]. LOHRMANN: Zeils . I. Naluryor. , 2 a,

561 (1956). (a) F. D. II;~.NNI, (~. LANG, M. TEUCHER,

H. ~,VINZELEI( and E. LOItI¢MANN : Y u o v o Cimento, @, 1473 (1956).

(') F. A. BRISBOUT, C. DAHANAYAKE, A. ENGLElt, Y. FUJ15IOTO and D. I t , I)EI~KINS: Phil . 3lag. , 1, 605 (1956).

(~) P. KV3IAR: Proc. 45lb. Ind . Sci . Cong., I I I - 3 , Abs. n. 9 (Jan , 1958).

(~) B. EDWARDS, J. LOSTY, D. H. PERKINS, ]( . P1NKAU and J . ItEYNOLDS: Phi l . Mag . , 3, 237 (1958).

(v) E. LOHRSIANN and M. W. TEIYCHEI¢: Phys . Ilec., 112, 587 (1958).

(s) 51. SCIIEIN and D. M. I[ASKIN: Supp l . Nuovo Cimcnlo, 8, 719 (1958).

of the secondary interaction is reasonably well of tile same order as that expected for the secondary particles created in the disintegration.

In a recent communication (3), we considered the possibility that some of the neutral interactions (events produced by neutral particles) observed as secon- dary events in high energy showers could be init iated also by the neutrons of the original projectile. I t was pointed out that, apart from a neutron being pro- dueed by charge exchange of the primary proton, in ease the singly charged partiele be tile nucleus of a heavy isotope of hydrogen, those neutrons of tile projectile which get stripped off in the first interaction might contribute to secondary neutral interactions. As an example of the process we shall first describe the characteristics of two inter- actions ('~) which we have interpreted as being due to the proton and neutron of a deuteron of ~ 10lacV. This is followed be an approximate estimate of the proportion of deuteron interactions at very high altitudes in the atmosphere.

(9) p . K. ADIT~'a: Nuovo Cimento, 11, 872 (1959).

2 2 0 P. 1~. ADITYA

The primary interaction of the type (30 + 26), was produced by a singly charged, particles of the cosmic radiation, observed in a stack of stripped emulsions exposed in the stratosphere above India, at 19 ° geomagnetic la t i tude0°) . The event was detected while following back the ensuing cascades of high energy, needed for another investiga- tion (n). The primary particle made an angle of I1 ° to the zenith, the core traversing 2.5 em per emulsion and left the stack after i0 cm axial length. The collimation of ten tracks within a cone of 1.5.10 2 rad, indicated the pri- mary energy to be very high. At 1 420 ~m from the primary event (called hereafter as A) another interaction (called as B) of the type (5 + 14)~ took place near the air surface of the emulsion, so tha t the angular distribution of its shower particles could be obtained only in the next emulsion. From target diagrams of the core made at 3 600 ~zm, 4 600 I~m, and 8400 ~m from the origin of A and the angular distribution of the tracks from A, it was possible to find the integral angular distribution of the particles emitted from B. Proper account was taken of the electron pairs materializing in the core since these tracks could be identified by their characteristic closeness in the begining and subsequent development of electron pairs on or around them. Unfortunately none of the two interactions could be safely considered as a nucleon-nucleon collision, especially A, because the col- lision oeeured with a heavy nucleus of the emulsion. Assuming the interactions to be elementary nucleon-nucleon colli- sions, the velocity fie of the e.m. system was deduced from the angular distri- butions, giving y~(A)=31 ±6 and y~(B)= = 5 6 i 1 5 , where y~= [ 1 - - /~]-~. As

(1~) R.. R . DANIEL, G. FBIEDI~IANN, D. LAI~, YAS~ PAL a n d B. ]PETERS: Proc. Ind . Acad. Sei . , 40 A, 151 (1954).

(11) p . K . ADITYA: Nuovo Cimento, 11, 546 (1959).

may be seen, the estimated energy dif- ference is appreciable especially since it is in contradiction to the expectations, event B having apparently an energy greater than that of A. This pointed out the fallaeiousness of the assumption about the collisions being elementary. For event A all the usual cheeks of symmetrical distribution of tracks in the e.m. system were made by using the conventional trasformation relations. The angular distribution in tile e.m. system was in accordance with a cos 2 0 type distribution and the symmetry allowed the removal of about six mesons on the basis of having been created by secondary processes occurring during the collision. The energy of high energy electron-positron pairs from A was obtained from shower development and other means (11). This evidence was also against the energy being ~ 2 0 0 0 GeV as obtained from the angular distribution of tile shower tracks. The removal of 6 mesons as mentioned before, allowed the energy of A to be raised to about (4 4- 1). 1012 eV, and we consider this to be a reliable estimate. The proximity of event B did not allow many measu- rements to be made on it. Apart from the angular distribution of its narrowly collimated shower tracks, two high energy pairs eIearly pointing to B con- firmed the very high energy involved in the event. I t was not possible from the experimental data, to increase the energy of A beyond tha t of B, or to decrease the energy of B below tha t of A, the two being at most and probably of the same order. This excluded the possibility of the event B being due to a particle emitted from A and made it difficult to assume tt~e neutral particle to be even a neutron created by the eh%rge exchange process. I t appeared that if the singly charged primary par- tiele were a deuteron or a tr i ton instead of the normally assumed proton, there would be no difficulty in interpreting the event. To support this idea, we eonsi-

P O S S I B L E E X A M P L E OF AN I N T E R A C T I O N I N E M U L S I O N E T C . 221

dered it desiderable to obtain an ap- proximate estimate of the ratio of deu- teron to proton interactions expected in a stack exposed in the stratosphere.

I t is not possible to distinguish by direct means between deuterons or :protons and neither between the inte- ractions produced by them. The enor- mous flux of protons coming in the p, imary cosmic ray beam, obscures the presence of heavy singly charged par- ticles. In stacks exposed at a particular a l t i tude in the stratosphere, there is however one observable quant i ty that may be used. to estimate the magnitude of secondary processes. This is tile ratio of interactions produced by neutrons and singly charged particles, all within same energy limits and preferably at such high energies tha t any possible contri- bution of those disintegrations that may be produced by neutrons and deuterons ejected from the target nuclei may be safely neglected. For ,n~ ~ 5 i.e., energy

15GeV, it is possible to identify unambi~ously the neutral stars. Since both neutrons and deuterons are assumed to arise almost entirely from identical secondary processes, i.e. fragmentations occuring near the top of the atmosphere, it is logical to employ the observations on neutral staxs to predict the proportion of deuteron interactions. The assump- tions and results of such an approximate • estimate are the following:

a) For all primary particles of Z > 1 having the same energy per nucleon, the relat 've numbers of protons (P), ~-par. ticles (~), medium nuclei (M, 6 < Z < 9 ) and heavy nuclei (H, Z ~ 10) are 6 000, 400, 30 and 6 respectively. The flux of light nuclei (3 < Z < 5) is assumed small and has been neglected.

b) There are no neutrons, deu- terons or tritons incident with the primary cosmic ray beam (12).

(~2) Neutrons and tritons because of being

unstablc cannot be expected in the high energy

primary radiation. There might however be

c) The interaction mean free path values for P, a, M and H in gc m -2 of atmosphere are 60, 35, 25 and 18 re- spectively.

(l) The proport.ion of secondary particles is negligible as compared to the primary flux i.e., no account is taken of the particles Z~>2 arising from fragmentation of heavy primary nuclei.

e) Among those protons which produce inelastic collisions in the atmos- phere, the inelasticity is small and half the number maintain identi ty after emerging out while the other half und ergo charge exchange.

/) Denoting by Fi___>~, the frag- mentat ion probability for the produc- tion of singly charged particles s, from a heavy primary nucleus i, and assuming that protons and deuterons are equally abundant among the fragmentation pro- ducts (13), we adopt for the atmosphere the following values for the fragmenta- tion probability :

1 7 = 0.77 (14) o r F~-~(po~o~) 0.38,

/~ -~s= 1.7 (16) o r FM~(Por2VorD): 0 . 8 5 ,

-FH_. ~ 4.0 (16) or FH_~(eo~,o~,~=2.0.

s o m c d c u t c r o n s , b u t t h e i r f lux i s u n p r e d i c t a b l e a n d m i g h t be v e r y s m a l l a s c o m p a r e d to t h e p r o t o n f lux . S o m e c a l c u l a t i o n s on t h i s v a b l o h a v e b e e n n l a d e b y SINGER [•. F . ~IN(~F~R: S u p p L Nuovo Cimer~to, 8, 549 (1958)] .

(x3) T(, bc p u b l i s h e d s e p a r a t e l y . (~4) T h i s v a l u e is b a s e d u p o n 136 s i n g l y

c h a r g e d p a r t i c l e s t h a t e m e r g e d w i t h o u t p a r - t i c i p a t i o u f r o m 176 co l l i s ions p r o d u c e d b y a - p a r t i c l e s i n e n l u l s i o n (15). T h e f r a g m e n t a t i o n p r o b a b i l i t y i u a i r m i g h t be a l i t t l e less t h a n t h i s v a l u e , b u t i t h a s n o t b e e n pos s ib l e fo r u s to take any account of this.

(,5) M. V. ~ . APPA I~AO, R . l:(. DANIEL a n d K . A . . NEELAK_kNTAN: Proc. Ind . -4cad. Sci. , 43, 181 (1956).

(IG) T h e s e v a l u e s a rc b a s e d u p o n t h e f r a g - m e n t a t i o n p r o b a b i l i t i e s o b s e r v e d fo r co l l i s ion of h e a v y p r i m a r y n u c l e i w i t h l i g h t n u c l e i of t h e em~fls ion a u d t h o s e d e r i v e d fo r a i r (~D.

(*7) j . H . NOON a n d M. F . KAPLON: Phys . Rev. , 97, 769 (1955).

222 P . K . ADITYA

g) In emulsion the int, e rac t ion mean free p a t h of neut rons and pro tons is 35cm(15) and t h a t of deuterons is 15 cm (13).

The calcula ted percen tage of inter- ac t ions t h a t would be produced by neu t rons and. deuterons in ra t io to those by protons , (all observed in a s tack

TABLE I. - Experimentally observed ratios o/the interactions produced by neutral par- ticles to those produced by singly charged particles, observed at various depths in the atmosphere. The n u m b e r of i n t e r ac t i ons m a r k e d wi th (*) are der ived f rom t h e results , assuming the quoted errors to be s ta t i s t ica l . A comba t ion of (b), (c) and (d) yields a va lue of 14.6=[=3.1 a t 1 5 g c m -~, whi le (]) and (g) give a va lue of 2 6 ± 5

a t 40 g cm 2.

S u b - reference Selection

cr i ter ia in (is)

(a) (b) (c) (d) (e) (/) (g) (h) (i)

E > 1012 e V

E ~ 10 H e V

n ~ > 5 i n~>~5 !

E , (101°--10 la) eV ~ n ~ 5

i n ~ 5 n ~ 5 n,, ~ 5 n ~ 6

D e p t h in thel Secondary in terac t ions a tmos . . . . . . .

phere ( * * ) neu t ra l charged (g cm 2)

8 - - 1 0 2 I4 12

[ 16 6 ( ' ) 16 4( ' ) ~2 20 9 31 40 23 96 40 7 20 50 89 294

8 8 52

Ra t io neu t ra l

to charged

27 79 15 60 (*) 10

(*) 32 29 24 35 3O 15

7 . 4 ~ 5.3 ~ 4 . 3 ~ 4 ~ t 5 ± 9 ± 5 ± 1 3 ± 3 ± 5 . 5

( " ) I n these vahles, no account tins been t aken of ~he a m o u n t of packing mate r ia l of the sta('k.

(is) (a) E. LOHRMANN: p r i va t e colnmuni- ca t ion (Feb. lq59).

(b) H. ~VINZELER: p r iva t e c o m m u n i c a t i o n (March 1959). The d a t a were collected by E. LOHRMANN, M. TEUCHER a nd H. WINZELER.

(C) A. ENGLER, Y. HABER-SCHAIM and W. WINKLER: N•OVO Cimento, 12, 930 (1954).

(d) t t . YAGODA: Canad. Journ . Phys . , 34, 122 (1956).

(e) I . G-UREVI¢, A. P. MI~AKOVA, B. A. NIKOLSKIJ and L. V. SUR];OVA: Supp l . Nuovo Cimento, 8, 786 (1958).

(]) M. ~V. TEUCHER: Zeits . ]. Natur]or . , 8 a , 127 (1953).

(g) G. BERTOLINO a nd D. PESCETTI: NUOVO Cimento, 12, 630 (1954).

(h) U. CAMERIN1, J . t t . DAVIES, I ). I=I. 1~ 0"W:LEY% C. FRANZINETTI, I t . MUll~HEAD, W. O. LOCK, D. H. PERKINS a nd G. YEKUTELI: Phi l . 3Tag., 42, 1241 (1951).

(i) J . GIERULA and M. Mn~sowIcz: pri- v a t e c o m m u n i c a t i o n (March 1959). D a t a collec- ted in a col laborat ion expe r imen t a t K r a k o w , P r a h a and Vearsaw, a nd publ ished by C~OK el aL: Nuovo Cimento, 10, 741 (1958).

exposed a t a pa r t i cu la r al t i tude), ha s been p lo t ted in Fig. 1. F o r compar ison some of t he exper imenta l points (is) h a v e also been included. (see Table I). These are based upon in te rac t ions of n ~ 5 (energy ~ 15 GeV) produced by singly charged and neut ra l part icles. One migh t expec t t h a t some of the singly charged par t ic le in te rac t ions are due t o mesons c rea ted in high energy disinte- grat ions, so t h a t the N/P ra t io is essen- t ia l ly N/(P ± M), M for mesons. Th is effect will however gain impor t ance a t depths ~ in te rac t ion mean free pa th , i.e. 60 g cm -2. I t m a y be men t ioned t h a t on account of t he simplified assumptions, t he absolute values of N/P or DIP migh t no t be correct , bu t t he ra t io N/D would no t be very sensi t ive to the ap- p rox imat ions , because b o t h N and D'

P O S S I B L E : E X A M P L E OF AN I N T E R A C T I O N IN E M U L S I O N E T C . 223:

are secondary particles. We find that for a stack exposed under about 15 g c m -2 out of 100 interactions of the salne energy those produced by protons, neutrons and deuterons would be 84, 12 and 4 respectively.

100

qo

k

2 Cm ) 1

~0 100

F i g . 1. - V a r i a t i o n of t h e p e r c e n t a g e of i n t e r a c - t i o n s p r o d u c e d ir~ a n e n u f l s i o n s t a c k b y n e u t r o n s a n d d e u t e r o n s as e o n l p a r c d to t h o s e p r o d u c e d b y p r o t o n s , p l o t t e d a g a i n s t t h e a m o u n t oi r e s i d u a l a t m o s p h e r e in g e m - L T h e l ine s h o w s t h e r e s u l t of a n a p p r o x i m a t e c a l c u l a t i o n (sea t e x t ) . T h e e x p e r i m e n t a l p o i n t s a r e t h o s e m e n t i ( m c d in

T a b l e I a n d r e f e I ' enee (~) .

The percentage of deuteron interac- tions being so small, their presence is not directely detectable. There would be no appreciable influence of their presence on the composition of shower particles, as thought earlier(9). Their presence may however be felt througll other characteristics of deuteron inter- actions. For instance, in a case an example of which has been described above, one might observe two interac- tions one being apparently a secondary from the other and the characteristics of the two events being similar within experimental errors. The latter event can be neutral or charged depcnding upon whether the first interaction is produced by the proton or neutron of the deuterons, respectively. SCHEIN and IIASKIS(s) have observed a neutral interaction of 2.1012 eV in the core of

an interaction produced by a singly charged particle of 5.1012 eV. Though in this case the measured energies allow the possibility of the neutral particle bein~ a neutron produced by charge exchan,~e of the l)roion, if one expects seine ener~'y uncertainity, two collisions nlight have had similar characteristics.

While in Ihose eases in which both tile nucleons (if lhe deuteron (or three in the case of a triton) partieil)ate in tim collision, the meson multiplicity would be much different fronl that expe(.ted f)r the collision of a single nucleiin of energy equal to that obtained. from the angular distribution of the shower. Such an interaction is expected to l(tok mu(.h different from another in which the increased meson nmltiplicity results from multiple collisions within the target mn.leus (*).

* * *

This investigation is part of a pro- gramme of work on high energy pheno- mena, started earlier. Thanks are due Professor B. M. ANAND for encourage- ment. I am thankful to Professor B. t':ETFI¢S for laborat(iry facilities al the Tara. Insti tute of Fmldamental Research, Bombay and for the loan of tile plates. [ th~mk Drs. I~OIIRMANN, MII~SOWICZ an(]. W I N Z E L : E R for priw~te communications.

(*) .Vote ~utded in prooJs. - .'4into t h e e o m - n n l n i e a t i o n ()f t h i s p a p e r , t h e r e h a s a l ) l )eared a n al'ti(.lc b y |{RISBOUT el al. (Nuoco (!imelt,to. 11, 4Sl (1959)) in w h i c h a l a rgo ( e s t a t e r a y jet~ (SI).OVCUI' }'.S {If BRINBOI'T ~1 a t : Phil..][¢t{l., ~, 605 (1,956)) h a s b e e n d e s c r i b e d . T h e y h a v e fonI ld t h a t for a s t r a i g h t f o r w a r d e x p l a m t t i o n , t h e c h a r a c t e r i s t i c s ef l ira e v e n t reqllil ' , , t h e l ) r i m a r y to be a d e u t e r o n . T h i s is in a e e o r d a n ( e w i t h ollr Sl lgge~t ion.

F u r t h e r , wh i l e g i v i n g a r g u m e n t s as Cxl)la-

n a t i o n of t h e o b s c r w ~ t i e n o£ t w o , g r o u p ~ ,' of j e t s i n v o l v i n g a b o u t t h e s a m e e n e r g y but, diff( , i 'ent m u l t i p l i c i t y , ])ILV;OrCTll ('~ aL (Nuuro ('imc~dc*, !0 , 1261 (1953)) (lid n o t c o n s i d e r t h e p r o b a b i l i t y Of s e ine Of t h e i r int(!ra(~tions hfl,vitlg bOClt p ro- (i l lccd by d e u t e r o n s , wh ich pos s ib i l i t y c a n e x p l a i n t h e p h ( m o n l e n a o b s e r v e d by t h e m . i t w o u h [ bc usehzl to COilfirlu t h i s w i t h i n c r e a s e d s t a t i s t i c s

aI ld a t h i g h e r cncvgics .