Particles In Nuclear Emulsions Research Articles

Searching for high energy cosmic-ray protons using a new way of finding and tracking particles in stratospheric X-ray emulsion chambers (According to data from the Russian–Japanese RUNJOB experiment)

An continuing search for primary particles is performed using a new means of finding and tracking particles in nuclear emulsions. Particle interactions registered in stratospheric X-ray emulsion chambers (XECs) are attributed to nucleon–nuclei interactions recorded in the Russian–Japanese RUNJOB experiment. According to the data from processing the interactions between galactic particles and matter in XECs RUNJOB-3B, 6A, and RUNJOB-11A, 11B with energy thresholds ΣE γ ≥ 3 and ΣE γ ≥ 5 TeV, respectively, around 50% of all proton tracks went unidentified, which coincides with the initial results from the RUNJOB experiment.

The search for primary particle tracks in nucleon-nucleus interactions with gamma ray energy ΣEγ ≥ 3 TeV registered in stratospheric X-ray emulsion chambers using data of the RUNJOB experiment

We present here the result of a retreatment of data from the RUNJOB (RUssia-Nippon JOint Balloon) experiment of nucleon-nucleus interactions registered in stratospheric X-ray emulsion chambers (REC) using a new method for searching and tracing of galactic particles in nuclear emulsions. In about halfcof these interactions (∼ 50) recorded in REC RUNJOB‘96-3B, RUNJOB‘97-6A and RUNJOB‘99-11A,B with energy released in the electromagnetic component ΣE γ ≥ 3 TeV and ΣE γ ≥ 5 TeV respectively, single charged particle tracks are not found within the search area defined individually by the particle track location accuracy. The absence of primary proton tracks is consistent with the original treatment of the RUNJOB experimental data. There is a difference in the zenith angular distribution for two groups of events in which a single charged particle track is observed or absent. The average penetration depth of the primary particles in REC to the interaction vertex in the zenith angle range from 60∘ to 79∘ differs by a factor two for these groups.

Automatic track recognition for large-angle minimum ionizing particles in nuclear emulsions

We previously developed an automatic track scanning system which enables the detection of large-angle nuclear fragments in the nuclear emulsion films of the OPERA experiment. As a next step, we have investigated this system's track recognition capability for large-angle minimum ionizing particles (1.0 ⩽ |tan θ| ⩽ 3.5). This paper shows that, for such tracks, the system has a detection efficiency of 95% or higher and reports the achieved angular accuracy of the automatically recognized tracks. This technology is of general purpose and will likely contribute not only to various analyses in the OPERA experiment, but also to future experiments, e.g. on low-energy neutrino and hadron interactions, or to future research on cosmic rays using nuclear emulsions carried by balloons.

Experimental feature in the primary-proton flux at energies above 10 TeV according to the results of searches for primary particles in nuclear emulsions exposed in the stratosphere (RUNJOB Experiment)

In the RUNJOB experiment, a long-term exposure of x-ray emulsion chambers in the stratosphere from 1995 to 1999 with the aim of studying the composition and spectra of primary cosmic particles in the energy range 10–1000 TeV per nucleon revealed about 50% proton tracks. The remaining events of the proton group did not feature any candidate for a track of a singly charged particle within the search region determined from measurements of the coordinates of background nuclei going close to the sought track. Methodological factors that could explain this experimental observation are considered. A possible physical reason associated with the presence of a neutral component in the flux of primary protons in the energy region above 10 TeV is also analyzed.

Nonstatistical fluctuations of target fragments emitted in high-energy nucleus–nucleus collisions

Analysis of target-fragmented "black" particles in nuclear emulsion from high-energy relativistic interactions initiated by 28Si at 4.5 A GeV/c is investigated. The number of slowly emitted particles from the struck target nucleus is considered as a measure of the degree of excitation of the residual nucleus. This number shows a constant critical value, with the degree of the impact parameter or the degree of excitation. The target evaporation particles of nucleus–nucleus interaction reveal the existence of nonstatistical fluctuations in the azimuthal plane of the interaction. The asymmetry or nonstatistical fluctuations, while found to be independent of projectile mass or incident energy, are dependent on the excitation energy of the target nucleus. A multiparticle correlation is observed between created particles as well as target fragments. This assumes production of clusters. These clusters seem to be formed during the decoloring process. PACS No.: 25.70Mn

Measurement of Multiple Scattering of Charged Particles in Nuclear Emulsion and Determination of Errors in On-line Measurements with a KSM Microscope

Multiple scattering of singly charged particles was measured with an automated KSM microscope operating on-line with a PC. The experimental results were analyzed by the ρ- and the maximum-likelihood methods. A technique for on-line testing and error determination in these measurements was proposed.

A silicon tracker for track extrapolation into nuclear emulsions

This paper describes the construction of a silicon tracker built to investigate how well silicon detectors can predict the position of particles in nuclear emulsions over a large area. The tracker consists of 72 single-sided silicon microstrip detectors with a total surface of 0.13 m 2 distributed over four layers, providing two x and two y coordinate measurements. The set-up was installed in a CERN PS pion beam in September 1997.

Nonstatistical fluctuations in fragmentation of target nuclei in high energy nuclear interactions

Analysis of target fragmented 'black' particles in nuclear emulsion from high energy relativistic interactions initiated by 16O at 2.1 GeV/nucleon and 12C and 24Mg at 4.5 GeV/nucleon reveal the existence of nonstatistical fluctuations in the azimuthal plane of interaction. The asymmetry or the non-statistical fluctuations, while found to be independent of projectile mass or incident energy, are dependent on the excitation energy of the target nucleus.

Electronically controlled detection of charged particles in nuclear emulsions

The phenomenon of electric-field stimulated increases in the sensitivity of nuclear emulsion is described. In an emulsion with a low content of AgBr, a double field pulse with alternating sign drives the Ag + ions to the grain boundaries and creates an internal polarization field. The effect is used to construct a track detector with electronically controlled sensitivity.

The first observation of beauty particles in nuclear emulsion

A pair of beauty particles has been found in a stack of nuclear emulsion exposed at CERN in an hybrid experiment. Both particles are observed to decay into charm particles with proper times of the order of 10-13s.

Photoproduction of charmed particles in nuclear emulsion coupled to the Omega Prime spectrometer. Description of the experimental method

The hybridized system including the nuclear-emulsion target and the magnetic Omega Prime spectrometer is described. The set-up was used in a CERN experiment for the measurement of lifetimes of charmed particles produced by tagged photons from the bremsstrahlung beam. The emulsion served simultaneously as a target and as a high-spatial-resolution vertex detector in order to recognize decay vertices and measure decay distances of charmed particles. In order to avoid the blackening of the emulsion due to electromagnetic interactions the targets were delivered into the beam position one at a time and removed automatically after suitable dosage. The Omega Prime spectrometer allowed the determination of the parameters of the secondary particles and the reconstruction of the interaction points in the emulsion with a high precision. The method used was very successful in finding photohadronic events and in separating a practically background free subsample with the production of pairs of charmed particles decaying inside the emulsion.

An attempt to observe directly beauty particles in nuclear emulsions

An attempt at the direct observation of the cascade decay of beauty particles, produced by π − of 350 GeV/ c leading to 3 muons or 4 muons in the final state, has been made in an emulsion/counter hybrid experiment at CERN. Under the assumption that the lifetime of beauty particles is of the order of 10 −13s the non-observation of any candidates provides an upper limit for beauty production of ∼90 nb at the 90% confidence level.

Interaction of relativistic alpha particles in emulsion at 2.1 GeV/c/nucleon

An analysis for 2,000 events produced by 2.1 GeV/c/n alpha particles in nuclear emulsion has been carried out. Multiplicity and angular distributions of charged secondaries have been measured and correlation among them are discussed. The presented data are compared with relevant values from proton and14N interactions with nuclei. The multiplicity distribution of showers has been tested by a modified independent nucleon-nucleus multiple scattering model (INAM) of reference [8], and by the model of reference [12].

Track structure and identification of particles in nuclear emulsions

Although the nuclear emulsion technique no longer enjoys the position it had in the past, when many important discoveries were made using emulsion, however, high spatial resolution and the high discriminating power because of the ability to make direct high precision and reproducible microscopic measurements on track structure in emulsion as well as the relative ease of handling the emulsion are special advantages. Nuclear emulsion is still favoured for use in special studies in hypernuclear physics, cosmic rays, autoradiography and other applications. The study of the structure of tracks produced in nuclear emulsion provides information about the mass, charge and velocity of the particles producing the track. The axial as well as radial structures of the tracks have been studied extensively. Over the years these track structure studies have been greatly refined to yield accurate and reproducible values of the particle parameters. Classical methods of identification of particles in nuclear emulsion as well as recent work on track structures are briefly reviewed.

Detection of short-lived particles in nuclear emulsions

We present a method for detecting short-lived particles in nuclear emulsions. Production and decay vertices as close as 0.5 μm can be resolved. This corresponds to a lifetime of the order of 10 −15s. The principle is to fit straight lines to the tracks and make a chi-square test of the hypothesis of a single vertex. This technique may be useful for detecting decays of heavy quarks.

Dosimetry of cosmic particles in nuclear emulsions for the apollo 16, 17 and apollo-soyouz-test-project experiments (1972–1975)

Abstract In the Biostack I, II and III experiments flown on the Apollo 16 and 17 and ASTP missions, nuclear emulsion plates have been used for the first time for heavy-ion identification in connection with biological layers. After the calibration step using the heavy ions available at the Bevalac at Berkeley, the nuclear emulsion can give dosimetric results for the heavy ions hitting biological materials. These results have been sent for exploitation to the biological laboratories of Toulouse, Frankfurt and Marburg. We summarize all the dosimetric results in the field of heavy-ion tracks and nuclear stars induced by cosmic-ray particles. The last results from Biobloc (December, 1975) are presented.

Application of track formation theory to calibration of photometric measurements on cosmic ray tracks in nuclear emulsion

The δ-ray theory of Katz and co-workers is applied to charge calibration of cosmic ray particles in nuclear emulsion. Measurements were made with a photometric technique on nuclei in the charge interval magnesium to nickel. With two parameters of the theory determined by a fit to experimental data it is possible to obtain theoretical charge scales which agree with experimental ones. An attempt is made to expand the theory down to the carbon-oxygen region.

Simulation of particle tracks in emulsion

Abstract Micrographs of energetic particles in nuclear emulsion are simulated by computing the spatial distribution of developed grains with the δ-ray theory of track structure, and representing the developed grains by points of light on an IBM 2250 visual display unit. The simulated tracks display many of the features of actual track structure and serve as a visual comparison between experiment and theory.

Charge identification of stopping particles in nuclear emulsions

Track-width measurements have been made on 66 suitable tracks of known charges in L4 emulsions. It is found that for charge identification fine grain emulsions are better suited and in such emulsions a high level of confidence (≈90%) is obtained in charge resolution if the width of the solid core of the track is measured instead of the full width. An empirical relation between the width and the dip angle of tracks has been obtained. The track-width is found to vary linearly with charge.

Multiple coulomb scattering of high-energy particles in nuclear emulsions

Ilford G-5 emulsions were exposed to four primary proton beams of momentum 5, 8, 12 and 24 GeV/c at different angles in the same emulsion for the study of the scattering constant at higher cell sizes. The effect of higher-order differences has been considered along with the relative scattering method to remove spurious scattering. The results appear to indicate the necessity for a slight modification in the theory of multiple Coulomb scatterings at large cell lengths.