Emulsion Chamber Data Research Articles

Emulsion chamber experiments; critical comments and future prospects

Emulsion chamber data give valuable information about particle production in the forward region of very high-energy nuclear interactions. Many characteristics of high-energy atmospheric families, observed by emulsion chambers, have not been fully described by simulations employing existing nuclear interaction models. Some of the events and the phenomena observed in emulsion chamber experiments have been considered to be unusual and new, never seen in lower energy accelerator experiments. We re-examine emulsion chamber data critically in order to get unbiased views of these unusual events and phenomena. It is shown that some of the previous interpretations need to be changed. We take up for the discussions scaling violation in C-jets, Centauro events, alignment of showers in high-energy families, hadrons of anomalous absorption in thick lead chambers. We will also discuss the results on the hybrid experiments of emulsion chamber and EAS-array.

Sensitivity of Pamir emulsion chamber data to test high-energy hadronic interaction models

Emulsion experiments placed at high mountain altitudes register hadrons and high energy γ-rays with an energy threshold in the TeV region. These secondary shower particles are produced in the forward direction of interactions of mainly primary protons and alpha particles in the Earth's atmosphere. Therefore the measurements are sensitive to the physics of high-energy hadronic interaction models, e.g. as implemented in the Monte-Carlo air shower simulation program CORSIKA. Including detailed simulations for the Pamir detector the measured observables are compared with predictions from various hadronic interaction models which leads to the exclusion of some of the current models. In this context, general problems of the measurement technique by emulsion chambers like the large intrinsic shower fluctuations are discussed.

ON THE DEFICIT OF CALCULATED MUON FLUX AT SEA LEVEL FOR ENERGIES > 100 GEV

In this paper we discuss the problem why the use of the direct data on primary nuclei spectra together with the modern hadronic interaction models leads to a significant deficit of computed vertical muon flux at sea level for energies above 100 GeV. We suggest that to find out the source of this inconsistency it is necessary to perform an analysis of sensitivity of emulsion chamber data to variations of hadron-nucleus interaction characteristics. Such analysis will give more ground for discussion of adequacy of the up-to-date interaction models and of mutual compatibility of primary nuclei spectra, obtained in direct and EAS experiments.

A halo event observed with an emulsion chamber and air shower array at Mt Chacaltaya

A hybrid experiment to operate simultaneously an air shower array, a hadron calorimeter and an emulsion chamber is under way at Mt Chacaltaya (5200 m, Bolivia). An event with a halo, a blackened area of ∼1 cm on x-ray film of the emulsion chamber, was observed with the experiment. Information about the halo (Ehalo = 850 TeV) and on high energy particles of electromagnetic and hadronic components outside the halo (∑Eγ = 632.5 TeV and ∑E(γ)h = 278.8 TeV with a detection threshold of 2 TeV) was obtained from emulsion chamber data. Details about low energy hadrons were determined from the hadron calorimeter data, and characteristics of the accompanying air shower (Ne = 7.0 × 107, s = 0.59) were determined by the air shower array. We reconstruct the event, based on the observed data. The event is compared with simulated events, which supports the conclusion that nuclear interactions change their characteristics in the high energy region so as to result in stronger energy subdivision.

Study of high energy cosmic ray interactions and primary composition at energies1015–1017eV using mountain based detectors

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.

New measurement of the electron flux from 10 GeV to 100 GeV with the bets instrument

Abstract The BETS (balloon-borne electron telescope with scintillating fibers) instrument has been developed for high-altitude balloon flights to observe the cosmic ray electrons with energies of 10 GeV to several 100 GeV. The detector is a Lead/SciFi sampling calorimeter consisting of 36 SciFi belts (each 280 mm wide) and 8 lead plates (each 5 mm thick). The electron identification is performed by triggering the electro-magnetic showers on board and by analyzing the three-dimensional shower images by an intensified CCD camera. It is demonstrated in the flight data in 1995 and 1997 that a reliable identification of the electron component against the proton background is achieved up to a few 100 GeV. The performance of detector was tested by the CERN-SPS electron beams in 1996 and with the proton beams in 1997. The obtained energy spectrum is consistent with the recent observation by HEAT, although our result still has a little room for improvement. The energy spectrum from 10 GeV to 1000 GeV which is obtained by combining these data and the emulsion chamber data (Nishimura 1997) suggests that the diffusion constant is about 1 × 10 28 ( E/GeV ) 0.3 cm 2 /sec in the energy range between 10 GeV and 1000 GeV. A hump in the energy spectrum is observed around several hundred GeV, which is expected from a nearby source.

Do the state-of-the-art simulation codes explain emulsion chamber data at mountain altitude?

Experimental data observed by emulsion chambers at Pamir and Chacaltaya are compared with simulation calculations using CORSIKA program employing VENUS and HDPM for high energy hadronic interactions. Although these models are considered to be based on modern theory and are widely-accepted as standard simulation codes, it is shown that no models can explain many characteristics observed in the experiments.

Semigroup theory and diffusion of hadrons in the atmosphere

We solve the one-dimensional diffusion equation of nucleons and mesons in the atmosphere using the semigroup theory. We show that the general solutions become simplified expressions when we assume a power-law dependence on energy for the p-air inelastic cross section, and for the primary energy spectrum, . Our solution is compared with the hadron fluxes of emulsion chamber data: we find a good consistency with an average inelasticity around 0.63, with the best fit of the coefficient a = 0.06.

Exact solution of the diffusion equation of cosmic-ray nucleons with rising cross section

The diffusion equation of cosmic-ray nucleons is exactly solved, taking into account the rising cross section of the form sigma 0(1+a ln(E/ epsilon )). Grigorov's well known approximate solution (1977) is compared with the authors' exact solution; it is found that the former overestimates the nucleon flux by, for example, 10-20% in the energy region 1-1000 TeV at mountain altitudes in case of a=0.06. Their solution is compared with the hadron fluxes of emulsion chamber data; they find a good consistency with a=0.06.

Simulation of Centauro events

Comparison between simulations and emulsion-chamber data on atmospheric interactions of 100--1000 TeV cosmic rays suggests that there could indeed exist an anomalous group of events with very little energy in secondary neutral pions. The group comprises two of the Centauro events from the Brazil-Japan experiment and three mini-Centauros, including one event from an independent experiment. Most events classified as mini-Centauros and three of five Centauros can be interpreted normally. Transverse momenta in the original Centauro event is likely to be about 1 GeV/c per secondary, rather than 1.7 GeV/c as originally claimed.

Energy spectra of secondary gamma rays at different atmospheric depths

The CERN Intersecting Storage Ring (ISR) data for p + p → π0 + X inclusive reaction have been used to derive the spectrum of secondary gamma rays at the top of the atmosphere. The measured primary nucleon spectrum of the Goddard Space Flight Group has been taken as a nucleon source spectrum. Using the cascade theory, the gamma ray spectra at the atmospheric depths 540, 650, and 735 g cm−2 have been calculated. The results are approximately in accord with the emulsion chamber data at Mt. Chacaltaya, Mt. Norikura, and Mt. Fuji in the spectral range 0.2–4 TeV.

Can We Understand High Energy Cosmic-Ray Spectra on the Basis of the Scaling Hypothesis?

Using the essential point of Feynman's hadronic scaling hypothesis, we have made a calculation of atmospheric cosmic-ray spectra, i.e., spectra of muons, hadrons and electro­ magnetic component. The results are compared with emulsion chamber data on the three components. In doing so, various factors related to the primary cosmic-ray spectrum are carefully examined. It is shown that the scaling feature of particle production in the entire energy region (up to several times lO"eV) is compatible with the data only when one assumes i) very large inelastic cross-sections (~380mb for p-air collisions) and ii) the steepening of the (proton equivalent) primary cosmic-rays above several times IO"eV, of which the intensity is much less than some air shower data. Another feasible way of understanding the phenomena is discussed by hypothesizing a break of the scaling feature in the fragmentation region at high energies (;(:10 14 e V).