Hadronic Component Research Articles

Mesons and quarks in nuclei

A short review of the topic of mesons in nuclei is exposed paying particular attention to the relationship between several mesonic processes. Special emphasis is put into the microscopic pictures that can ultimately relate all these processes with the elementary coupling of mesons to the nuclear hadronic components. The importance of the short range part of the nuclear interaction opens the doors to a more basic understanding in terms of the quark components of nucleons and isobars.

Current-current model for vector-meson photoproduction and related processes

We extend the Pomeron-photon analogy (i.e., the idea that the couplings of Pomerons and photons to hadronic matter are similar) to vector-meson photoproduction and related processes, such as $\ensuremath{\rho}$ electroproduction and Compton scattering. To avoid directly coupling the Pomeron to photons, which is awkward in this model, we follow conventional vector-meson-dominance ideas and approximate the photon's hadronic component by the $\ensuremath{\rho}$ meson. We then make a current-current ansatz for the $\ensuremath{\rho}$ elastic scattering amplitude. Spin is fully taken into account. We find that $s$-channel helicity conservation (SCHC) cannot be realized within this framework if the effective current is conserved; SCHC requires that either this current has a nonconserved component or the forward cross section vanishes. If an effective current with two components is introduced---one a conserved electromagnetic central component, and the other a nonconserved peripheral component---then all the main features of $\ensuremath{\rho}$ photoproduction can be accounted for. The same model gives a good qualitative description of $pp$, $\ensuremath{\pi}p$, and $\mathrm{Kp}$ elastic scattering, and of diffractive dissociation; in other words, it provides a unified description of all diffractive phenomena. Both components of the effective current have a simple explanation in terms of the quark-parton model.

Study of Shower Phenomena in the Atmosphere. I: Analytical Derivation of Lateral Structure Function of Hadronic Components

Study of Shower Phenomena in the Atmosphere. I: Analytical Derivation of Lateral Structure Function of Hadronic Components

The Biological Effects of High-Energy Radiation

The biological effects of high-energy radiation are reviewed, with emphasis on the effects of the hadronic component. Proton and helium ion effects are similar to those of the more conventional and sparsely ionizing x- and ?-radiation. Heavy-ions are known to be more biologically effective, but the long term hazard from accumulated damage has yet to be assessed. Some evidence of widely varying but dramatically increased effectiveness of very high-energy (~70 GeV) hadron beams is reviewed. Finally, the importance of the neutron component in many situations around high-energy accelerators is pointed out.

Hadrons in extensive air showers. I: Theoretical analysis

Calculations have been made of some features of extensive air showers (EAS) expected in the near vertical direction at different altitudes in the atmosphere for two models of the nucleon-air-nucleus interaction. Results are given for the electron and hadron components. It is shown that the lateral density distribution of hadrons in EAS is well described by the functionϱ H(r) dr=(N H(>E)/8!πr 0 2 ) exp $$\left[ { - \sqrt[4]{{{r \mathord{\left/ {\vphantom {r {r_0 }}} \right. \kern-\nulldelimiterspace} {r_0 }}}}} \right]$$ dr, wherer 0 is a parameter weakly dependent on the multiplicity law of secondary-particle production. The most useful energy for measurement of the total number of hadrons in showers with different numbers of particles is derived from the calculations.

Suppression ofψphotoproduction

We estimate the contribution to $\ensuremath{\psi}$ photoproduction from its conventional hadronic components by using an $\ensuremath{\epsilon}$-exchange model. The results, which are too small, are compared with the parallel ${\ensuremath{\rho}}^{\ensuremath{'}}$ case. A reduction factor is observed which also plays an important role in other models. We discuss, in particular, its occurrence in a peripheral model which assumes dominance of new states in the $\ensuremath{\psi}$ fragmentation vertex which interact strongly with conventional hadrons. The strong reduction factor follows from the mismatch between production thresholds and particle masses. Its role is discussed at length and compared with different points of view.

Cosmic‐ray‐produced electrons and gamma rays in the atmosphere

The propagation of the primary cosmic radiation through the earth's atmosphere is a phenomenon of considerable intrinsic complexity stemming from the large number and variety of parameters involved and their dependence on energy, latitude, and atmospheric depth. Although in the past the study of the hadronic component in the atmosphere has received appreciable attention, not much interest has been focused on the electron‐photon component until very recent years. As a consequence, the observational data now available on the latter are meager and fragmentary; such information as is available is reviewed here, and the existing gaps in our knowledge are highlighted. Because of the very complexity of the problem, it has been recognized that extensive and refined calculations are needed to understand the observations and to provide new motivation to experimenters. In the present article the limited theoretical calculations so far attempted are first reviewed; a summary of detailed calculations recently carried out by the present authors follows. Finally, the results from the calculations are compared with those available from experiments; wherever it is necessary, attempts are made to identify the areas in which further work is needed.

A new heavy particle?

A great deal of work on the hadronic component of cosmic rays has been done by Russian groups working at the high altitude (3340 m) laboratories at Tien Shan and employing very large 'ionization calorimeters' of area 40 m2 and depth of the order of 10 interaction lengths. The Leeds work was stimulated by some as yet unexplained phenomena, observed by the Russian groups to occur in the energy range 1013–1015 eV, which we thought ought to be observable in the energy spectrum of hadrons present in the atmosphere.

Evidence for change in the characteristics of strong interactions at ultra-high energies

An attempt has been made to understand the experimental results on the size dependence of several properties of high energy hadrons reported in a previous paper (see ibid., vol.6, no.7, 1050 of 1973) in terms of the characteristics of high energy collisions and primary composition using detailed Monte Carlo simulations. It is shown that the behaviour of the high energy hadron component, especially the size dependence, cannot be accounted for in terms of a change of primary composition alone in the energy range 1014-1016 eV which has been suggested by some of the earlier investigations to explain certain properties of air showers. The present analysis strongly suggests the need for invoking rather drastic changes in the characteristics of strong interactions at ultra-high energies.

Note on hadronic shadowing effects in high energy photon-nucleus interactions

A simple model is proposed to describe the hadronic shadowing effects observed in total photon-nucleus cross sections at high energies. The model combines the existence of hadronic components in the photon propagator with the Glauber theory of multiple scattering, without paying explicit reference to the ϱ - dominance picture. Some consequences of the present treatment are discussed and compared to previous work.

Time structure of the hadronic component of extensive air showers

A detailed study of the time structure of hadrons of energy > 5 GeV in extensive air showers has been carried out at Ootacamund (8·00 gm/cm2) using a total absorption spectrometer at the centre of the T.I.F.R. air shower array. A comparison of the experimental results with theoretical calculations shows that the experimentally observed spectra can be explained only on the basis of a rather large production (∼ 15%) of mucleon-antinucleon pairs among the secondaries of high energy interactions. Also it has been shown that an isobar-cum-pionisation type of model is preferred to a pure pionisation model in ultra high energy interactions. A small fraction of hadrons (∼0·5%) of energy > 20 GeV are found to arrive considerably delayed (> 25 ns) with respect to the shower front. While these are indicative of the presence of heavy mass particles (M ∼ 10 GeV/c2) among the hadrons in air showers it is concluded experiments of a more direct nature are essential for establishing the production of heavy mass particles.

Monte Carlo studies on the electromagnetic component of extensive air showers

On the basis of three-dimensional Monte-Carlo simultaneous of the hadronic component of extensive air showers the electromagnetic component of extensive air showers has been investigated theoretically using approximative electromagnetic cascade theory. Results include the relation between mean total electron number and primary energy as well as mean lateral distribution of electrons. Fluctuations of parameters of the structure function, central density and width of density distribution in sets of showers with given initial conditions are presented and found to be strong.

Monte Carlo studies on the hadronic component of extensive air showers

Three-dimensional Monte Carlo calculations have been performed on the development of the hadronic component of extensive air showers using a semi-empirical model of high-energy nuclear interactions. Results include integral energy spectra and lateral distribution of nuclear active particles as well as total hadronic energy flux. The probability of multi-core showers is discussed. The contribution of pionization tends to mask the dependence of this probability on primary atomic number. Fluctuations of total and central hadronic energy flux are investigated. Maps of hadronic energy flux in the core region of individual showers are presented.

Note on multiple-core structure of the hadronic component of extensive air showers

Monte Carlo calculations on high-energy hadrons in extensive air showers have been performed, using various models of hadronic interaction and fragmentation. Frequencies of showers the hadronic component of which shows multiple-core structure are discussed in terms of primary particle and hadronic interaction parameters. The existence of a correlation between the primary mass composition and the frequencies of specified types of showers is demonstrated.