The spectra of leading particles of different nature in pp-collisions at E sub 0 = 33 GeV are obtained. The multiplicities and the spectra of secondaries, mesons, gamma-quanta, lambda and lambda-hyperons and protons for different leading particle energy ranges are determined

Kruglov, N. A.

Proskuryakov, A. S.

Sarycheva, L. I.

Smirnova, L. N.

English

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270
HE 3.2-11
THE MULTIPLICITY AND T_ SP'ECT}_ OF SECONDARIES
CORRELATED WITIi T}_ LEADING PARTICLE E_ERGY
N .A.Kruglov, A .S.Proskuryakov,
L.I.Sarycheva and L.N.Smirnova
Institute of Nuclear Physics, _oscow State University,
Moscow Ii9899, USSR
Abstract. The spectra of leading particles of different na-
ture in pp-collisions at E o - 33 GeV are obtained. The mul-
tiplicities and _he spectra of secondaries_ _', g 4-me-
sons, y-quanta, A and _ -hyperons and protons for different
leading particle energy ranges are determined.
The interactions in which the leading particle conser-
ves a great fraction of the initial energy are essential
for the development of nuclear cascades in the atmosphere.
The leading particles form a deeply propagating part of the
cosmic rays. The accompaniment of these particles is deter-
mined by the peculiarities of the lo_inelasticity interac-
tions. Besides, the events with a leading particle are re-
liably identified in the cosmic-ray detectors.
The main information on the multiple production of par-
ticles obtained from accelerators, is averaged over all ty-
pes of events. This paper reports the multiplicities of
_-, _, R_, A and N -particles, the partial coefficients of
inelasticity and the spectra of particles in p_-interacti-
ons at Eo = 33 GeV in the lab.system that are correlated
with the origin and energy of the leading particle.
The experimental conditions
The experimental material consists of 200 thousands of
inelastic interactions of antiprotons with the momentum
32 GeV/c observed in the liquid hydrogen Mirabel_ bubble
chamber. The large dimensions of the chamber provided high
detection efficiency of photons, K#-mesons and A/_ _by_
perons. We use the events where all charged tracks are mea-
sured.
For the particles with the momentum Plab _ 1.2 GeV/c
the protons were discriminated from the _ -mesons by com-
paring track ionization. Neutrons and antineutrons are the
only unobservable species in the chamber. Their mean cha-
racteristics are restored proceeding from the condition of
energy balance /I/. In the present paper all inelastic in-
teractions are analyzed in the system of an incident anti-
proton which will be mark in following as lab-system. This
choice of system enabled us to establish the nature of a
leading particle with the fraction of initial energy
_lead = E/E o _ 0.@.
Classification of events
The particle carrying away the maximum, as compared
with other particles, fraction of energy in the lab.system
in a_ event is assumed to be the leading particle. When
https://ntrs.nasa.gov/search.jsp?R=19850027606 2020-03-20T17:20:23+00:00Z
2TI HE3.."-11
the total energy of unobservable neutral particles exceeds
the energy of the leading particle, a neutral system X ° is
regarded to be the leader. Table I presents the cross sec-
tions of the events with the leading particle of different
nature in different ranges of _lead"
Table I
The cross sections of the2icked out classes of interactions
_,_
1,eader ..... leading em_rgy ranges 24 lead .....
0.4 - 0.6 0.6 - 0.8 0.8 - 1.0
2
e8 3 + 0.03 3.55 + 0.I5+ 0.03 3.43
z.23¥ 0.02 0.23 ¥ o.ol 0.015_ 0.002
" 0.59 _ 0.0I 0.084 _ 0.005 0.007 _ 0.002
_o 7.46 0.04 6 78
- . . - 0.03 4._.9 , 0.9.3
50 3 +0'03 0.07 _ 0.02i+ 0.04 0.24
_f O.09 O.OI7 O.OI5 0.00# - O.00_
@
0.I5
o.o9 o.02 o.007-T.- ,..... .,0.0o5 ......
pF
¢C_(S2¢'_)= 45.6 +-0.3 mS._i. = 37.2 +-0.5m8. _o.,,.,,=
= 30.7 +-0.5 rn8/2/.
The events with the leader p ,Y[., _- and ZZle_d _ 0.4
make up I2 mb, i.e. (32 z 0,4)% of the inelastic pp-cr_oss
section. The events wit_ the leaders A , Y, K__ (= K° + K °)
at rile_ d _ 0.4 with the cross section 1.04 _-O.II mb are
observe_.
The total energy of the particles attending the charged
and neutral leader is presented in units of ze =E E_/E o in
fig.I. It is seen that the taking account of(Z41ead)in the
events with the charged leader permitted the complete re-
covery of the interaction energy. The measured fraction of
energy of the attending particles in the events with the
leader _.o is higher as compared with the events with the
P and2m-leader. In this case according to the selection
criteria a fraction of energy of the neutral leader X ° is
carried by photons and the mean value of this energy is me-
asured in the chamber for each group of evemts. The unobser-
vable energy is carried away by an outgoing neutron. The
. mean fraction of this energy is indicated in fig.I. Conse-
quently, the class of events with the leader _,ocontains
mainly the events with a leading neutron. The groups with
_lead (Z°) _ 0.6 correspond to the events with ZZ_ead(_)
" _ 0.#, since the mean value of _in these events _s _ 0.2.
The events with the leader A'°and _lead _ 0.6 are conside-
red in what follows as two groups of events with a leading
neutron: < z4 > - 0.78 ± O.O_ and 0.50 ± O.0_ , The
lead - _cross sectlons of the events with a leadino proton and neu-
tron with _ lead _ 0.4 are actually the same. This means
that the leader in (68.8 +-0.5)% of the nonannihilation
pp-interactions is a nucleon with _lead _O-_-
In fig.I there is no evidence for a fast neutron in the
events with the _m-leader and we therefore conclude that
these events are mainly due to the p_-annihilation. The
cross sections of the events are in accord with this con-
clusion.
272
HE 3.2-ii
Experimental Results
The spectrum of leading protons is uniform within _lead
= 0.5 -' 0.9 /2/. The spectra of leading _* and K_-mesons
with _ lead_0.5 decrease with increasing _lead and are
described by the function Aex p (-B _aa) wi_h the parame-
ters B_.= I2._ + 0.9 and B_-= I2.6 __ O.K. To the spectrum
of leading A with _lead _ 0.5 there corresponds the para-
meter B^ = 8.I ± 0.3.
The total Nultiplicity of the particles attending the
leading p, n, _., _-, _ is shown in fig.2a. The right sca-
le shows the ratio of the observed multiplicity to the es-
timated total multiplicity < _- L > for pp-interac-
tions at 32 GeV/c /3/. It is seen that at 7_lead close to
0.5 the multiplicity reaches the mean value.
• 2
. . ., o ' '8 ;sue,./0 !5 _G 'S_&_ 4. :_ . _ _.o
Fig.T. A fraction of Fig.2. Total multiplicity. (a) and mul-
,. tl_e measured energy tiplicity of the attending particles
in'the events with of species _ (b) for different lea-
different leaders ders
The multiplicity of _* and K_-mesons and photons at-
tending the leading nucleon is shown in fig.2b. The total
multiolioity of 2z -mesons is similar in the events with a
leading proton and "neutron". The vaSue of < _r_ proves
to be higher for a leading "neutron" which can be connected
with the identification procedure used.
The mean fraction of energy carried away by the attend-
ing _+ , _-, K _, Y is shown in fig.3. The mean fraction of
energy per _. and y is the same whether the leader is a
proton or a "neutron". The total fraction of energy carried
away by these particles is plotted in fig.4 versus _lead
of a proton and "neutron".
The spectra of the attending particles ame rather com-
plex and concentrated in the region of low z4 for high alead"
The parameters of the function describing these spectra are
listed in table 2.
In the events with a leading proton a great_ fraction of
the "invisible" energy carried away by the photons. In this
case _Ey_ =o-_E_-_EK_.mzand the spectrum of photons
can be obtained from the variable m4y = Ey/XEy used in the
cosmic rays. The spectra _@/_u_ are p_e_nted'in fig. 5
273
HE 3.2-11
for the events with a leading proton at _ead>0.8 and
Ztlead = 0.4 + 0.8.
Table 2
Parametrization of the spectra of the particles attending
the leading protons and "_eutrons" by the function _¢ =
_H exp (- _¢ _ - a2 7ga)
.... _ype o£ a ...........
leader Z/lead secondary N BI B2
,. .... _a_ticles ..............
o.4-o.6h _* -i.oo_o.oi-5.5?-0.322._o.6
0.027+-0.01# 34.3 -2.6 -9.0_13.6
p 0.6-0.8 3r. -1,31_0.06 -II.0_1,3 41 :; 2
_r- -I.85_0.0Z i-7.9I_0.08 32.5::0.4
O.027_Q.QI41 _4.I -2.5 -28 ::IO
@ • T O •0.8-I0 x, -0.2110,oi31 o; .9 -I5 6_:_,4
#r" -2.62z0.0I 10.8 -0.2 -6.71.4
-I.157-o.o5_2.5+1.8 58.Y6.3
o.6-o.8 _. -z.25_o.o2-I_.9_o,454.8_:o.7
X o m_:o.50 _- -1.20_0.05-2.3_I.1 59.8::2.5
*o.o_ _ -2._I+0.02 -20.2_I,3 i 8_._;8.4
(.._b"_ ._,m)=0.980"8-I'0 ....2T'0_* -1.98_0.0I-2"66_0"01.....-2 .IZ1.064 0 0.1287179 "_1"7.8"0"9
........ -*o.o.{ _ -2.3 _-0.I .17.2Z4.3 83.4_ "8._+
References:
±. vini=skii A.A. et al., Sov.Journ.Nucl.Phys., I98@, gO,_7@.
2. Hanume_ah B. et al. Nuovo Cim., I982, 68A, I6I; I7 ICR,
I98I, HE I-7, v.5, p.22.
3- Nikitaev D.N., Smirnova L.N. Sov.Journ.Nucl.Phys.,I985,
r'---, ] . , _. .[--1_,o._. P ,,_"_ I,_r._. i,._ • i _; • o ¢8.1.o, o _ _,- l,-.._.l o urn-' "II i i_"
i, v ..... _," /1_ '____.___".
",7i ill
_.... ;
Fig._._ean fraction Fig.4.Partial coef- Fig.5.Spectra of
of energy pe_ par- ficients of inelas-
Y in u_=_rlZg_.
ticle of species L ticity of pa=ticles for the events
for different lea- _ for different with a leading
ders leaders :_i=<ZLL> _/'Z,L)' proton


The multiplicity and the spectra of secondaries correlated with the leading particle energy

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