The picture of the hadron nucleus collision process is presented as it emerges on the basis of newly obtained experimental data. The picture is applicable to models of cascade propagation in Earth atmosphere

Strugalski, Z.

English

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EXPERIMENTAL BASIS FOR THE MODELS OP CASCADE PROPAGATION IN
ATMO SPHERE
Strugalski Z.
Institute of Physics of the Warsaw Technical University
ul. Kcszykowa 75
00-662 Warsaw, Poland
and
Joint Institute for Nuclear Research, High Energy7 Labor
Dubna, USSR
ABSTRACT
The picture of the hadron-nucleus collision pro-
cess is presented as emerged on the basis of new
ly obtained experimental data. The picture is ap
plicable for models of cascade propagation in
Earth atmosphere.
1. Introduction
Results from studies of cascades ond of their propaga-
tion in the Earth atmosphere form a basis for our knowledge
about ultra-high energy cosmic ray particles; these results
are fundamental for the cosmic ray astrophysics as well.
But, the knowledge about the cascade propagation in a medi-
um rests on the information about the hadron-nucleon, had -
ron-nucleus, and nucleus-nucleus collision processes first
of all.
Now, various models of the hadron-nucleon and hadron -
nucleus collision processes, and of the particle-producing
reactions in them, are in use, based on different almost ar
bitrarily introduced physical processes assumed. The assump
tions do not correspond in many cases to the reality -
they are inadequate. The question: "Is an assumption adequ-
ate or not ?" should find its answer primarily in experimen
ts.
We have _tudied experimentally the hadron-nucleus col-
lisions at the conditions when the reaction outcome was al-
most totally identified, Strugalski Z. et al. (1981 a, b;
1982 a - c; 1983 a -e); experimental data have been obtai -
ned as well on the hadron-nucleon collision processes in
their initial stages - before decays of produced resonances,
using massive target nuclei as detectors, Strugalski Z.
(1981 a,b; 1982; 1984 a-d; 1985). The results are crucial
for any model of the hadron-nucleon, hadron-nucleus, and
nucleus-nucleus collisions and, therefore, for a more adequ
ate model of the cascade propagation in media - in the Ear-
th atmosphere in particular.
https://ntrs.nasa.gov/search.jsp?R=19850027641 2020-03-20T17:19:23+00:00Z
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2. Experimental procedure
In experiments, the 26 and 180 litre xenon bubble cham
bers, Kanarek T. et al. (1959), Kuznetsov E. V. et al.
(1970), were used. The smaller chamber was exposed to beams
of pions with 2.34, 5, and 9 GeV/c momentum from the synch-
rophasotron of the Joint Institute for Nuclear Research in
Dubna; the bigger chamber was exposed to pion beam at 3.5
GeV/c momentum from the accelerator of the Institute of Ex-
perimental and Theoretical Physics in Moscow.
General experimental information about the pion-xenon
nucleus collisions is contained in series of Communications
of the JINR: Strugalski Z. et al. (1981, 1982, 1983, 1984,
1985). Additional appropriate information has been found in
various emulsion works: Andersson B. etal. (1978), Babecki
J. and Nowak G. (1978), Bannik B.P. et al. (1980), Gurtu A.
et al. (1979), Meyer H. et el. (1963), Otterlund I. et al.
(1978), Tsai-Ch_ et al. (1977), Winzeler H. (1965); the ac-
celerator data there are at energies up to about 400 GeV in
the lab, the cosmic ray data are up to a few thousands GeV.
_. Results
Pour main phenomena are usually observed, when hadrons
collide with atomic nuclei: a) The emission of nucleons wi-
th energies from about 20 up to about 400 MeV; b) The produ
ction of particles; c) The evaporation of target fragments;
d) The fission of residual target nucleus.
_.I. Nucleo _ Emission. Any hadron with kinetic energy
higher than the pion production threshold may pass through
some layer of nuclear matter before to come into particle -
producing reaction in it; there are events in which incide-
nt hadrons with energies of a few GeV traverse nuclei or a-
re stopped in them without causing particle production. In
any case, are the particles produced or not, any hadron cau
ses emission of nucleons in passing through atomic nucleus.
The number n_Tof the emitted nucleons equals2the number of
nucleons contained within the volume v = X DoA centered
" on the hadron path k in nuclear matter, where Do is the di
ameter of the nucleon. The particle production process does
not effect an influence on the nucleon emission.
. Any hadron loses its kinetic energy monotonically alo-
ng its path in nuclear matter, by nucleon emission. Energy
spectra and angular distributions of emitted nucleons are
practically the same in pion-xenon nucleus collisions with
and without particle production; they do not depend neither
on the multiplicity of emitted protons nor on the multipli
city of produced pions. The spectra and distributions are
the same for pion-xenon collisions at 3.5 GeV/c momentum
and for the proton-nucleus collisions in emulsions at 400
GeV/c.
3.2. Particle Production. Particles are produced via
intermediate Objects, we have called them "generons", crea
ted firstly in 2 ---*2 type endoergic reactions and decay-
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406
ing after the lifetimes 35 _10 -22 s into particles and re-
sonances. Generons behave themselves in passage through nuc
lear matter as usual hadrons do it - in particular, they
can produce new generons in colliding with the downstream
nucleons. A quasilinear cascade of generons may develop in
nuclear matter, therefore. This way, the outcomes in hadron
-nucleus collisions at an energy E are the compositions
of m outcomes in hadron-nucleon collisions at energies
in average E/m, where m is the number of particle-produ-
cing collisions of the incident hadron.
The nucleon emission process does not depend on the
particle production process. The region of the particle pro
duction process in the target nucleus is not larger than
the region of the nucleon emission, therefore; it is rather
almost linear and situated collinearly with the incident
hadron course in predominant number of collisions.
3.3. Evaporation of Target Fragments. Relation between
the multiplicity of the emitted protons and the mean multi-
plicity of the charged fragments in collisions with a given
proton multiplicity allows to determine the size and locali
zation of the fragment evaporation region, Strugalski Z.
(1984). Nuclear fragments are evaporated from the surface
of the damaged part of the target nucleus; the damage is
due to the nucleon emission process accompanying the passa
ge of any hadron through nuclear matter.
3.4. Fission of the Residual Target Nucleus. In any had
ron-nucleus col]ision the target nucleus is"damaged, and re
latively large part of it is removed, as it may be conclu -
ded from experimental results on the nucleon emission and
target fragment evaporation. Obviously, such damaged nucle-
us is instable and it must decay into stable smaller nuclei
in the final state.
more information about the experimental picture of the
hadron-nucleus and hadron-nucleon collision processes can
be found in series of works: Strugalski Z. (1982, 1984,1985_
References
Andersson B. et al., 1978, Phys. Lett., 73B,343.
Babecki J. et al., 1978, Acta Phys. Polon., B142, 445.
Bannik B.P., 1980, Comm. JENR, Dubna, 91-13055.
Gurtu A. et al., Pramana, _, 311.
meyer H. et al., 1963, Nuovo Cim., 2__8,1399. "
0tterlund I. et al., 1978, Nucl. Phys., BI_, 445.
Strugalski Z. et al., Comm. JINR, Dubna: 1982, a)E1-82-
718, b) E1-82-719, c) EI-82-841! 1983, a) RI-83-68,
b) 91-83-237, c) RI-8_-564, d) 91-83-568, e) 91-83
-234.
Strugalski Z.Communications JINR, Dubna: 1981 a) EI-81-
576, b) E1-81-577; 1982, a) EI-82-718, b) E1-82-
719,c_I-82-841; 1983, a)EI-83-155, b) EI-83-850;
1984, a) E1-84-195, b) E1-84-268, c) E1-84-853,
d) EI-84-854; 1985, EI-85-231.
Tsai-Ch_ et al., 1977, Nuovo Cim. Lett., 20, 257.
Winzeler H., 1965, Nuclear Phys., 69, 661_'-


Experimental basis for the models of cascade propagation in atmosphere

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