IL NUOVO CIMENTO VOL. 110 A, N. 7 Luglio 1997 NOTE BREVI
Pseudorapidity distribution of shower particle
in neutrino-emulsion collisions at high energy (*)
FU-HULIU(1) and JUN-FENSUN(2)
(1) Department of Physics, Shanxi Teachers University - Linfen, Shanxi 041004, PRC (2) Department of Physics, Hunan Education Institute - Changsha, Hunan 410012, PRC
(ricevuto il 2 Ottobre 1997; approvato il 3 Novembre 1997)
Summary. — We investigate the pseudorapidity distribution of shower particles
produced in collisions of neutrino with emulsion at high energies. The normalized pseudorapidity distribution, two-particle pseudorapidity distribution and the correlation between the mean maximum number density of shower particles and multiplicity are given.
PACS 13.85.Hd – Inelastic scattering: many-particle final states.
1. – Introduction
In high-energy collisions, an important experimental phenomenon is multiparticle production. The neutral leptons participate only in weak interactions and the cross-section is very small. So, the measurement in experiment is difficult. The investigation of multiparticle production in collisions of neutral lepton with nucleus is less than that in collisions of hadron with nucleus. What results will be presented in collisions of neutral lepton with nucleus? In this paper, we shall report experimentally the pseudorapidity distribution of shower particles (relativistic singly charged particles) produced in collisions of neutrino with emulsion at high energies.
2. – Experimental materials
Using the emulsion experimental sample of E531 Collaboration at Fermilab, we investigated the pseudorapidity distribution of shower particles in high-energy neutrino-emulsion collisions. Our previous analyses show that the incident neutrinos are in the energy range from 3 to 210 GeV. The most probable energy is 20 GeV and the mean energy is 43.5 GeV [1].
(*) The project supported by China National Education Committee Foundation of Scholarly Exchange, Shanxi Provincial Foundation of Scholarly Exchange and Shanxi Provincial Foundation of Leading Man in Science.
FU-HU LIUandJUN-FEN SUN
776
According to the grain densities of tracks in nuclear emulsion, we divide the secondary particles (tracks) into shower and heavy particles (tracks). Let I0denote the minimum track grain density of singly charged particle, the grain densities of shower particles are less than or equal to 1.4I0 and the grain densities of heavy particles are greater than 1.4I0. The numbers of shower and heavy particles in an event are called multiplicities of shower and heavy particles and are denoted by Ns (or n) and Nh, respectively.
According to the value of Nh, we divide the emulsion nuclei into two groups: the light nuclei ( H , C , N , O) and the heavy nuclei (Ag, Br). Events with NhE 7 are collisions between neutrinos and light nuclei, and events with NhD 6 are collisions between neutrinos and heavy nuclei. In the experimental sample, 325 events are measured completely. The event numbers corresponding to the light nuclei (HCNO) and heavy nuclei (AgBr) are 243 and 82, respectively.
3. – Experimental results
The definition of pseudorapidity is
h 42ln tg (uO2) ,
where u is the emission angle of shower particle.
The normalized pseudorapidity distribution
(
f (h))
of shower particles in neutrino-emulsion collisions in the energy range from 3 to 210 GeV is shown in fig. 1a). The value of maximum probability pseudorapidity is 2.3 and the distribution curve is symmetric. As a result of test, the pseudorapidity distribution is approximately of Gaussian type. Taking a mean value of 2.3 and a width of 1.1, the fitting curve is shown in fig. 1a). In the near energy range, if the contributions of leading particles areFig. 1. – a) Normalized pseudorapidity distribution in neutrino-emulsion collisions. The curve represents the Gaussian fitting. b) Normalized pseudorapidity distributions for light (solid histogram) and heavy (dotted histogram) nuclei in emulsion.
PSEUDORAPIDITY DISTRIBUTION OF SHOWER PARTICLE ETC. 777
Fig. 2. – a) Normalized two-particle pseudorapidity distribution in neutrino-emulsion collisions. Curve represents the Gaussian fitting. b) Normalized two-particle pseudorapidity distribution for light (solid histogram) and heavy (dotted histogram) nuclei in emulsion.
neglected, the experimental results shows that the pseudorapidity distributions of shower particles in pion-emulsion, proton-emulsion and nucleus-emulsion collisions are also approximately of Gaussian type [2-4].
In order to investigate the dependence of pseudorapidity distribution on target, fig. 1b) shows the experimental results for light (solid histogram) and heavy (dotted
Fig. 3. – Correlation between the mean maximum number density of shower particles and multiplicity in neutrino emulsion collisions. Solid, dotted and dashed curves correspond to the emulsion, light and heavy nuclei, respectively.
FU-HU LIUandJUN-FEN SUN
778
histogram) nuclei, respectively. One can see the dispersion between two kinds of nuclei. We can explain the extension of pseudorapidity distribution towards the low-h region for heavy target. In neutrino-emulsion collisions, the secondary collisions between shower particles and spectator nucleons, as well as shower particles and shower particles cause the emission angle to increase and the pseudorapidity to decrease. The effect of secondary collisions in heavy nuclei is greater than that in light nuclei. This effect displays the extension of pseudorapidity distribution towards the low-h region.
The normalized two-particle pseudorapidity (Dh 4h12 h2, h1D h2) distribution
(
f (h1, h2))
is shown in fig. 2a). In the two-particle pseudorapidity range from 0 to maximum, the distribution is approximately of Gaussian type with width 1.4. Figure 2b) shows the normalized two-particle pseudorapidity distribution for light (solid histogram) and heavy (dotted histogram) nuclei, respectively. The dispersion between two kinds of nuclei also reflects the secondary collisions in target nucleus.The correlations between the mean maximum number density of shower particles
(
a(DnODh)maxb)
and multiplicity (n) are plotted in fig. 3. The solid, dotted and dashed curves corresponds to the emulsion, light and heavy nuclei, respectively. The width of pseudorapidity window is Dh 40.1. It is seen that the mean maximum number density of shower particles grows with increasing multiplicity. This result is similar to that obtained from proton-proton collisions at 400 GeVOc [5].4. – Conclusions
The results obtained in the present study reveal that the pseudorapidity distribution of shower particle in neutrino-emulsion collisions is approximately of Gaussian type. The normalized pseudorapidity distribution and two-particle pseudorapidity distribution depend on the target size. These phenomena reflect the secondary collisions in target nucleus. The mean maximum number density of shower particles grows with increasing multiplicity.
* * *
The authors would like to thank Prof. J. HE´BERT for supplying the emulsion sample.
R E F E R E N C E S
[1] LIUF. H. and SUNJ. F., Trends Nucl. Phys. (Lanzhou, China), 13 (1966) 19. [2] HE´BERTJ. et al., Phys. Rev. D, 15 (1977) 1867, and references quoted therein.
[3] ADAMOVICH M. I. et al., in Proceedings of the X EMU01 Collaboration Meeting, Wuhan, China, September 19-21, 1991.
[4] STENLUND E., in Proceedings of Quark Matter ’95: Abstracts of Contributed Papers, Monterey, California, USA, January 9-13, 1995.
