X-ray Emulsion Research Articles

First Results of Studying EAS Cores Using a High-Mountain Ionization Calorimeter

In high-altitude experiments to study the central cores of EAS at E0 ≳ 1016 eV (√s ≳ 5 TeV) using X-ray emulsion chambers and ionization calorimeters, phenomena such as the coplanarity of the arrival of the most energetic particles in super families of γ-rays and hadrons and a so-called Tien Shan effect (too slow absorption of cascades initiated by high-energy hadrons in the calorimeter) were observed. These effects could not be reproduced within the framework of theoretical models of the 80s and 90s. The coplanarity is explained via a process of coplanar generation of the most energetic secondary particles in interactions of super high-energy hadrons with nuclei of air atoms. Perhaps the Tien Shan effect could be explained using a high cross section for the generation of fragmentation-region charmed hadrons. To study these phenomena, a new set of detectors has been developed, including the world’s highest high-mountain ionization calorimeter, “Hadron-55”. This paper presents the initial experimental results.

The composition of cosmic rays according to the data on EAS cores

The main purpose of this work is to find the causes of the break of the cosmic ray spectrum at an energy of 3 PeV, which is called the knee. The solution of the problem is associated with the determination of the nuclear composition of cosmic rays in the knee area. The conclusions of this work are based on the analysis of the characteristics of the EAS cores obtained using X-ray emulsion chambers. According to these data, a number of anomalous effects are observed in the knee region, such as scaling violation in the spectra of secondary hadrons, an excess of muons in EAS with gamma families and others. At the same energies equivalent to 1-100 PeV the laboratory system colliders show scaling behavior. So analysis of the data on the EAS cores suggests that the knee in their spectrum is formed by a component of cosmic rays of a non-nuclear nature, possibly consisting of stable (quasi-stable) particles of hypothetical strange quark matter, which named strangelets. This is the only model of the knee compatible with the magnetic rigidity of the nuclear spectra break R=100 TV. In fact, stranglets are stable heavy quasi-nuclei with a positive electric charge of Z=30-1000, so the mechanism of their acceleration coincides with the nuclear one. The break of the cosmic ray spectrum can be associated with a significantly larger mass of strangelets compared to nuclei.

Strange Quark Matter and the Astrophysical Nature of Anomalous Effects in 1–100 PeV Cosmic Rays

The composition of cosmic rays is of decisive importance for the determination of reasons for change in the slope of the spectra of extensive air showers (knee) at energies of 1–100 PeV. The characteristics of the extensive air showers, where the highest energy secondary hadrons are concentrated, have been analyzed. Some anomalous effects such as an increase in the absorption length of hadron showers, scaling violation in the spectra of secondary hadrons, an excess of muons in extensive air showers with gamma-ray families, the appearance of the halos, and the alignment of energy centers along a straight line are observed in X-ray emulsion chambers in the knee region. At the same energies equivalent to 1–100 PeV in the laboratory system, LHC and RHIC data demonstrate a scaling behavior of the hadron spectrum, which means that new nuclear processes are absent. These data imply that anomalies observed in cosmic rays are due to astrophysical reasons, i.e., changes in the composition of cosmic rays. The analysis of the data on the EAS cores suggests that the knee in their spectrum is formed by a nonnuclear component of cosmic rays, possibly consisting of particles of strange quark matter.

Interactions of Neutral Particles with Energies >7 TeV in Stratospheric X-Ray Emulsion Chambers

Interactions of Neutral Particles with Energies >7 TeV in Stratospheric X-Ray Emulsion Chambers

The rise of muon content in extensive air showers after the 3 PeV knee of the primary cosmic ray spectrum according to data of the Tien Shan mountain installation

We put together the experimental results on muon component of extensive air showers (EAS) which were gained with various techniques at the detector complex of the Tien Shan mountain station. According to this comparison, the problem of the EAS muon content in the range of primary cosmic ray energies (1–100)PeV seems to be more complicated than it was usually supposed. Generally, from the models of nuclear interaction it follows that the EAS which have produced gamma-hadron families in the Tien Shan X-ray emulsion chamber did preferably originate from interaction of the light cosmic ray nuclei, such that their muon abundance must be ∼1.5 times below an average calculated over all showers. In contrary, the experimental muon counts in the EAS with families demonstrate a (1.5–2)-fold excess above the average, and this difference starts to be observable in the showers with the energy above the 3PeV knee of the primary cosmic ray spectrum. Later on, the rise of muon production in EAS after the knee was confirmed at Tien Shan by another experiment on detection of the neutrons stemmed from interaction of cosmic ray muons. Thus, the results obtained by the two completely different methods do mutually agree with each other but contradict to the common models of hadron interaction.

Is There a Relationship between the Collider “Ridge” Effect and Particle Coplanarity in Gamma Ray–Hadron Families?

Proton–proton interactions are modeled using the FANSY 2.0 model to show that the “long-range ridge effect” discovered by the CMS collaboration at the LHC can be explained within a single physical process, along with the coplanarity in gamma-ray–hadron families observed in extensive atmospheric shower cores during experiments with X-ray emulsion chambers.

Estimation of the $$\boldsymbol{p+\textrm{He}}$$ Fraction in the Mass Composition of Primary Cosmic Radiation the Energy Range of $$\boldsymbol{E_{0}=1}$$–100 PeV according to Gamma-Ray Families Featuring Halo

The present article reports on an analysis of the properties that gamma-ray families featuring a halo exhibit in the cores of extensive air showers (EAS). The events under analysis were obtained in the XREC (x-ray emulsion chambers) PAMIR experiment, and the properties of these events were studied at distances extending up to about 10 cm from the EAS axis with a resolution of approximately 30 $$\mu$$ m. The investigation of the parameters of events in EAS cores by the halo method permitted analyzing the mass composition of primary cosmic radiation (PCR) at $$E_{0}=10$$ PeV and assessing the fraction of light nuclei in PCR, which depend only slightly on the model of EAS propagation through the atmosphere. From an analysis of gamma-ray families featuring a halo and multicenter halos obtained in the PAMIR XREC, it was found that the fraction of the ( $$p+\textrm{He}$$ ) component of PCR was about 40 $${\%}$$ . The properties of proton-induced EAS events detected at the Tien-Shan high-mountain Scientific Station (TShSS) were studied along with the KASCADE-Grande experimental data. On the basis of studying the dependence of the EAS age and $$N_{\mu}$$ on $$N_{e}$$ in the TShSS EAS (EAS $$+$$ XREC TShSS) data, it is concluded that PCR mass composition becomes heavier in the range of $$E_{0}=1$$ –100 PeV.

Observation of a Significant Flow of Neutral Galactic Particles in the Stratosphere at Energies in the Range of 1013–1015 eV

A reanalysis of experimental data from the RUssia-Nippon JOint Balloon (RUNJOB) emulsion experiment on the basis of a new method aimed at searches for primary galactic particles in events identified as those of nucleon-nucleus interaction confirmed the original result that consisted in the absence of a large number (about 50%) of tracks of incident particles. A comparative analysis of such events where there is a detected primary track and where there is no primary track was performed in terms of the energy, angular distribution, and depth of penetration into x-ray emulsion chambers (XREC). The hypothesis that a neutral component is present in cosmic rays at the XREC exposure level is discussed.

On the Dominant Role of Charm Production in the Forward Kinematic Region According to Cosmic-Ray Experiments

A phenomenon of abnormally weak absorption of very-high-energy cosmic-ray hadrons in lead is discussed. This phenomenon was first observed in Tien-Shan high-altitude experiments in hadronic cores of extensive air showers and has encouraged to introduce the hypothesis of a so-called long-flying or penetrating cosmic-ray component. A similar effect was detected later with deep uniform lead X-ray emulsion chambers (XREC) at the Pamirs. Experiments, which are sensitive to the production of charmed hadrons in the forward kinematic region (xLab ≳ 0.1), have been carried out at the Tien-Shan and Pamirs with exposing two-storey XRECs with large air gaps to prove explanation of the experimental results with high charm production cross section $${\sigma _{pp \to c\bar c}} \sim 8$$ at xLab ≳ 0.1 at ⟨ELab⟩ ∼ 75 TeV. This $${\sigma _{pp \to c\bar c}}$$ value makes it possible to reproduce the experimental hadron-absorption curve observed with XRECs, including curve’s bending at a depth of ∼70 c.u.

Detection of the Rare Interaction of a Neutral Particle with Energy Higher than 15 TeV in the Stratospheric X-ray Emulsion Chamber (According to the RUNJOB Experiment Data)

A rare event observed in a nuclear emulsion is reported. The RUNJOB Russian-Japanese balloon experiment detected the interaction of a high-energy neutral particle in a nuclear emulsion plate of an X-ray emulsion chamber exposed in 1999.

Investigation of abnormal absorption of cosmic-ray hadrons in lead calorimeters

A phenomenon of abnormally weak absorption of very high energy cosmic ray hadrons in thick lead blocks is discussed. This phenomenon was first observed in a Tien Shan high altitude experiment to study hadronic cores of extensive air showers (EAS) with a deep ionization calorimeter and encouraged researchers to introduce the hypothesis of the so-called long-flying or penetrating cosmic ray component. A similar effect was detected later with deep uniform lead X-ray emulsion chambers (XREC) at the Pamirs, which we discuss in detail. To establish the nature of the phenomenon we are have carried out dedicated experiments at the Tien Shan and at the Pamirs by exposing two-storey XRECs with large air gaps. According to detailed simulation of the chamber response, these experiments are very sensitive to the production of charmed hadrons in the forward kinematic region and can prove a hypothesis that the phenomenon under study can be explained on the assumption of very high values of charm particle production cross section at 〈ELab〉 ~ 75 TeV in the forward kinematic region at xLab≳ 0.1 which are near the upper limit of recent results of collider experiments, i.e., σpp→c¯c~ 8 mb. The same factor makes it possible to fit all the features of the experimental hadron absorption curve observed by means of deep uniform lead XRECs, including its bending at a depth of ~ 70 c.u.

Exotic model of the cosmic ray spectrum

A detailed study of the cores of extensive air showers (EAS) at mountain level (Tien-Shan 690 g/cm2) was carried out in the hybrid experiment HADRON. An analysis of the fine structure of the EAS spectrum in the energy region1015- 1017(knee) showed that there are two breaks in the spectrum. Along with the previously known break at an energy of 3 · 1015eV, a change in the slope of the EAS spectrum is observed at an energy slightly below 1017eV. In addition the use of a large X-ray emulsion chamber (XREC) as a detector of EAS cores allowed us to obtain several new results. An abnormal scaling violation in hadron spectra for Ne~ 107(E0~ 1016eV) means the existence of a penetrating component of non-nuclear origin. The conclusion about the non-nuclear origin of the penetrating component in the primary radiation of CR is confirmed by the data about the excess of muons in the EAS containing hadrons of maximum energies. It is assumed that the mass composition of primary cosmic radiation varies sharply at energies of 1015- 1016eV, where quasi-nuclei (strangelets) appear instead of nuclei. A new model of the mass composition of cosmic rays in the region of ultrahigh energies is proposed on this basis .

Способ определения углов в рентгеновских эмульсионных камерах

An analysis of the measurement procedure for the zenith and azimuth angles υ and φ in the X-ray emulsion chambers (XREC) of ADRON and PAMIR experiments is presented. Earlier, asymmetry was observed in distributions of azimuth angles of gamma and hadron families. A detailed analysis of methodological errors in measuring θ, φ angles allowed us to establish the causes of the distortion of azimuth angles distributions. There are two reasons: systematic errors in the measurement of zenith angles by MBS-2 microscopes, used both in the PAMIR experiment, and in the ADRON experiment, and the inclination of XREC based on the subsidence. Calculations showed that the total systematic error Δυ≈4 ° completely explains the observed azimuthal asymmetry. Formulas for correcting θ and φ angles are given. The recalculation of the angles by the indicated formulas showed that this corrects the distribution of  the azimuthal angles φ. The REC plane should be set relative to the horizontal with an accuracy of no worse than 1 degree in order to avoid distortion of the angular distributions.

Neutron Monitoring at the Area of IRC “Pamir-Chakaltaya” for Radiation Safety Control

The results of neutron monitoring at the high-altitude area of the International Research Center “Pamir-Chakaltay” at an altitude of 4370 meters above sea level are presented. Measurements with the help of radiometers PDA-Pack Eye, МКS-RМ1401К and RSU-01R revealed an excess of 5–7 times the neutron flux density at the 2-tier X-ray emulsion chamber in the hangar and in the storage areas of lead and rubber plates. At the same time, instrument readings experienced significant (up to 30%) fluctuations in time.

Analysis of gamma-ray families with halos and estimation of mass composition of primary cosmic radiation at energies 1–100 PeV

Characteristics of γ-ray families with halos observed with X-ray emulsion chambers at the Pamirs and data of EAS experiments are analyzed to estimate the summary fraction of proton and helium nuclei (p + He) in the primary cosmic radiation (PCR) at E0 = 1–100 PeV. It is shown that the p + He fraction at E0 = 10 PeV is (39 ± 6) %. The mass composition, estimated by EAS age, remains mixed at E0 = 1–100 PeV with a tendency to become heavier with increasing energy.

Origin of Gamma-Ray Families Accompanied by Halos and Detected in Experiments with X-Ray Emulsion Chambers

The phenomenon of gamma-ray families featuring halos that is observed in an experiment with x-ray emulsion chambers (XREC) in the Pamir experiment and in other XREC experiments is explained. The experimental properties of halos are analyzed via a comparison with the results of their simulation. It is shown that gamma-ray families featuring halos are predominantly produced (more than 96% of them) by protons and heliumnuclei. This makes it possible to employ the experimental properties of halos to estimate the fraction of protons and helium nuclei in the mass composition of primary cosmic radiation.

Method for determining angles in X-ray emulsion chambers (XRECs) (ADRON experiment)

Paper presents an analysis of the measurement procedure of the zenith and azimuth angles υ and φ in theX-ray emulsion chambers (XREC) of ADRON and PAMIR experiments. Earlier, asymmetry wasobserved in distributions of azimuth angles of gamma and hadron families. A detailed analysis ofmethodological errors in measuring θ, φ angles allowed us to establish the causes of the distortion ofazimuth angles distributions. There are two reasons: systematic errors in the measurement of zenithangles by MBS-2 microscopes, used both in the PAMIR experiment, and in the ADRON experiment, andthe inclination of XREC based on the subsidence. Calculations showed that the total systematic errorΔυ≈4 ° completely explains the observed azimuthal asymmetry. Formulas for correcting θ and φ anglesare given. The recalculation of the angles by the indicated formulas showed that this corrects thedistribution of the azimuthal angles φ. The REC plane should be set relative to the horizontal with anaccuracy of no worse than 1 degree in order to avoid distortion of the angular distributions.

γ-families with halos observed by X-ray emulsion chamber in EAS and the estimate of the p+He fraction in primary cosmic rays at E0 = 1–100 PeV

The experimental γ-families in which events called “halos” were detected using X-ray emulsion chambers (XRECs) of the PAMIR experiment are described. The halo nature is explained within the standard model of nuclear interactions. Based on events with halo, the fraction of p+He in primary cosmic rays (PCR) was estimated. It is shown that the PCR mass composition remains mixed in the range E0 = 1–100 PeV.

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.

Study of the coordinate prediction accuracy for galactic particles with an energy of 10–1000 TeV/particle using a new method for searching and tracking particles in nuclear emulsion films. (Data of the Russia–Nippon Joint Balloon (RUNJOB) experiment)

Experimental and methodological errors in the coordinate prediction for primary cosmic ray nucleons and nuclei in nuclear emulsions using a new method for searching and tracing particle tracks in emulsion films of X-ray emulsion chambers (XRECs) exposed in the stratosphere in the Russia–Nippon Joint Balloon (RUNJOB) experiment are considered in detail. The dependence of errors on the relation between angular characteristics of the sought particle and auxiliary multiply charged nuclei is analyzed. Angular selection criteria for auxiliary nuclei, at which the methodological error of the particle track coordinate prediction decreases, are found.