Search

Experimental results are presented on high energy cosmic-ray hadron interactions recorded in homogeneous-type thick lead chambers (total thickness being 60 cm and 110 cm) exposed at the Pamirs (atmospheric depth 595 g/ cm 2 ). High energy cosmic-ray hadron flux is measured. The attenuation mean free path of the arriving cosmic-ray hadrons of E h γ ≥ 6 TeV measured in the chamber is obtained as 252 ± 30 g/cm 2 of lead. However, for the high energy hadrons ( E ( γ ) ≥ 10 TeV) constituting cosmic-ray families of the highest energy range, ΣE ( γ ) ≥ 700 TeV, which have been accumulated so far in the series exposures at the Pamirs and analysed by MSU group, the attenuation mean free path of hadrons in lead has turned out to be as short as 170 −26 +47 g/cm 2 with 95% CL by the maximum likelihood method. The present experimental result of such a short attenuation length of hadrons in cosmic-ray families is essentially consistent with that obtained for high energy hadrons ( E ( γ ) ≥ 10 TeV) constituting the “Chiron-type” families of ΣE ( γ )>100 TeV in the Chacaltaya two-storeyed chamber experiments. The anomalous transition characteristics of high energy hadrons in lead is found and examples are presented. The physical significance of the experimental results on extremely high energy hadron interactions is discussed.

A method for detecting strange-quark matter is discussed. In order to confirm the existence of strange-quark matter in the cosmic radiation, a new instrument under construction for a balloon experiment is presented.

Hayakawa Most of my discussion this morning will be based upon my book Cosmic Rays. This is a semi-popular book, whose aim was to present the nature of cosmic ray research to non-scientists. I) I feel, although I am not a historian, that the study of history of science is very important if we try to predict what developments may come in the near future. I am responsible for a branch of the Institute of Plasma Physics, which is involved in the planning of research. As an example of the kind of study which can be useful, here is a graph showing the number of papers per year on solitons as a function of time: 2l,3l The curve shows a knee around 1965, and can be analyzed into two parts. The first one corresponds to the interest in solitons in lattice dynamics and plasma physics; second part which shows a steep rise is related to their use in elementary particle physics. The study shows that one should enter a field when the slope is positive, and not when the excitement is all over. Unless you intend to be the person responsible for the beginning of the positive slope ! The vertical scale of the graph corresponds, by the way, to something like 200 papers per year in the last year. Now turning to cosmic rays, the subtitle of my book translates as something like: Progress in the Study of Nature. Nobody even knew of the existence of cosmic rays before the present century, although they must have existed even before the earth was born. Knowledge of their existence is closely related to the development of instru

A Comment on the article by Anchordoqui et al. 'Hunting long-lived gluinos at the Pierre Auger Observatory' [L. A. Anchordoqui, A. Delgado, C. A. Garcia Canal, and S. J. Sciutto, Phys. Rev. D 77, 023009 (2008)].

We argue that too much exotic scene setting is not necessary for the explanation of the Centauro events observed by the mountain based emulsion chambers. We show that a proper understanding of the detector helps to find a mundane solution to the 'decades old cosmic ray mystery'. We conclude that the exotic events observed so far are not inconsistent with the incorrect evaluation of the detector response and misinterpretation of the experimental signal.

We wish to put forward an explanation for a peculiar cosmic ray event with energy {sigma}E{sub {gamma}}{>=}2x10{sup 15} eV detected in 1975 by the balloon borne emulsion chamber experiment performed in the stratosphere, at the altitude {>=}30 km above sea level. For almost 30 years the event has been described as unusual, invoking new exotic mechanisms or models. In our opinion there is no need for an extraordinary explanation. Contrary to the widespread belief, the event gives us an example of 'unrecognized standard physics'. At the same time this event revealed a variety of features which are of considerable interest for cosmic rays, nuclear physics, and astrophysics. Here we show that the observed family is most likely to be a result of a heavy nucleus interaction with an air nucleus. In this case a primary particle would originally have been in the energy region above 'the knee' of the cosmic ray spectrum.

An unusual Centauro phenomenon in which cosmic rays enter the atmosphere producing tens of charged hadrons, but virtually no neutral pions, has been a mystery for more than 30 years. Since the discovery of Centauro I in 1972 by the Brazil-Japan Collaboration operating x-ray emulsion chambers at 5200 m on Mt. Chacaltaya in the Bolivian Andes, a variety of models have been proposed (including new types of interaction or the creation of new types of matter). Here we show that the solution to a long-standing scientific puzzle lies with the details of the Chacaltaya detector. The new analysis of the original Centauro I event reveals that there is a difference in the angle between the upper block and lower block events, so the two are not products of the same interaction. That leaves only the lower chamber data connected to the Centauro I event. It is shown that, with the revised understanding of the event, new physics is no longer required for the explanation.

A new analysis of mountain-top x-ray emulsion chamber data is presented. We utilize a refined experimental apparatus and a standardized analysis approach, including the simulated data. The results indicate that most of the phenomena reported previously can be explained as fluctuations within standard hadronic interaction physics. In the wide energy region we see no indication of a large change in the primary composition.

The inelasticity distribution of hadron-lead collisions in the energy region exceeding ${10}^{14}$ eV is estimated on the basis of 66 events, induced by cosmic ray hadrons and detected at high mountain altitudes at Pamir (4300 m, 595 ${\mathrm{g}/\mathrm{c}\mathrm{m}}^{2}).$ The distribution of the best fitting is approximated as $g(K)dK=[\ensuremath{\alpha}(1\ensuremath{-}{K)}^{{m}_{1}\ensuremath{-}1}+\ensuremath{\beta}{K}^{{m}_{2}\ensuremath{-}1}]dK,$ where ${m}_{1}=0.5,$ ${m}_{2}=1.125,$ $\ensuremath{\alpha}=0.26,$ $\ensuremath{\beta}=0.55,$ giving $〈K〉=0.60.$ The errors of the parameters are discussed in the text. The distribution is compared with those which are based on theoretical models.

The article describes a study of the multiple pion production through observation of gamma-rays produced by nuclear interactions at the target layer of the emulsion chambers exposed at Chacaltaya, Bolivia, 5200 m above sea level. The analysis was focused on 80 events with ΣEr>20 TeV, well above the detection threshold of the X-ray film spot scanning, ∼3 TeV. The distribution of gamma-rays is constructed on their energy, pt, and emission angle, and the comparison is made with the results from the simulation calculations based on FNAL hydrogen bubble chamber events and ISR minimum bias events. The cosmic-ray results are significantly out of the simple scaling extrapolation, showing higher rapidity density nr. and increasing pt. Recent p̄-p collider experiments gave the confirming results. From the plot of events in the diagram of nr. and 〈pt〉, the events are classified into two types; Mirim-jets (meaning small jets, nr= 2∼3, 〈pt〉∼140 MeV/c) and Açu-jets (large jets, nr = 6∼8, 〈pt〉∼220 MeV/c), with nearly equal frequency of production. Mirim-jets are those on the scaling extrapolation from the lower energy region of accelerators, while increasing rate of Açu-jets with energy is causing the scaling break. The analysis with the fire-ball model shows that the Mirim-jets are consistently interpreted as production and decay of a small fire-ball (a fire-ball quantum called H-quantum) with rest energy of 2∼3 GeV and decay temperature of about 130 MeV. While, the Açu-jets necessitate introduction of a heavy fire-ball (SH-quantum) with rest energy of 20∼30 GeV. The study of atmospheric interactions (A-jets) shows presence of events with still larger nr and higher pt, which are called Guaçu-jets. One C-jet is found to be a candidate of this type. The Guaçu-jets require presence of a huge fire-ball (UH-quantum) of rest energy 200∼300 GeV. Discussions are made on physical implication of the fire-ball model, particularly on those quanta of a fire-ball.

A simulation study is made on propagation and multiplication of the high energy cosmic-ray components in their passage through the atmosphere. The study is planned to simulate observation of high energy cosmic-ray phenomena by the emulsion chambers exposed at high altitude laboratories and to make clear how the observation of such kind will disclose unknown mechanism of the extremely high energy interactions-multiple production of mesons. In particular, the following two models of the multiple meson production are examined in the present simulation: 1) Two-fire-ball model,l> abbreviated as 2F; 2) H-quantum model,2> abbreviated as HQ. The outline of our simulation is as follows. A high energy primary cosmic-ray particle collides with an air nucleus of the upper atmosphere and causes the multiple meson production according to mechanism of the assumed models. The secondary nuclear-active particles, charged n-mesons and an outgoing nucleon, among the generated particles collide in their turn with air nuclei and they develop the so-called nuclear cascade processes while passing through the atmosphere. Gamma-rays, being the decay products of n°-mesons produced by the successive nuclear collisions, are the source of the atmospheric electromagnetic cascade showers. We make a record of particles with energies above a certain threshold energy both of the nuclear-active component and of the electro-magnetic component, which arrived at the observation level. The record consists of data of the arriving particles together with those on the primary particle. The present simulation calculation corresponds to observation of high energy cosmic-ray particles by the emulsion chamber exposed at the mountain altitudes. In particular, it provides us data of the artificial families: identity, energy and spatial distribution of member particles of the families. It is instructive to learn what kind of pattern the artificial families show at the observation plane under a certain assumption. This is indispensable for