Ultrahigh-energy Interactions Research Articles

On the Impact of Tsallis Statistics on Cosmic Ray Showers

We investigate the impact of the Tsallis nonextensive statistics introduced by intrinsic temperature fluctuations inp-Air ultrahigh energy interactions on observables of cosmic ray showers, such as the slant depth of the maximumXmaxand the muon number on the groundNμ. The results show that these observables are significantly affected by temperature fluctuations and agree qualitatively with the predictions of Heitler model.

Central production of lepton–antilepton pairs and heavy quark composite states in hadron diffractive collisions at ultrahigh energies

Central production of lepton–antilepton pairs (e+e- and μ+μ-) and heavy quark composite states (charmonia and bottomonia) in diffractive proton collisions (proton momenta transferred |q⊥| ~ m/ ln s) are studied at ultrahigh energies ( ln s ≫ 1), where σ tot (pp±) ~ ln N s with 1 ≲ N ≲ 2. The pp±-rescattering corrections, which are not small, are calculated in terms of the K-matrix approach modified for ultrahigh energies. Two versions of hadron interactions are considered in detail: the growth (i) σ tot (pp±) ~ ln 2 s, σ inel (pp±) ~ ln 2 s within the black disk mode and (ii) σ tot (pp±) ~ ln 2 s, σ inel (pp±) ~ ln s within the resonant disk mode. The energy behavior of the diffractive production processes differs strongly for these modes, thus giving a possibility to distinguish between the versions of the ultrahigh energy interactions.

Ring-Like and Jet-Like Events in Ultra High-Energy Interactions—an Analysis in Terms of Multifractal Parameters

Ring-like and jet-like events produced in 16O-AgBr interactions at 60 AGeV are analyzed in terms of multifractal G-moment method and factorial moment method in both η space and ϕ space for emitted pions. Further, the Levy indices and multifractal specific heat c have been calculated. The results clearly indicate that μ and c both are different in ring-like and jet-like events depicting different mechanism in the production process.

From eV to EeV: Neutrino cross sections across energy scales

Since its original postulation by Wolfgang Pauli in 1930, the neutrino has played a prominent role in our understanding of nuclear and particle physics. In the intervening 80 years, scientists have detected and measured neutrinos from a variety of sources, both man made and natural. Underlying all of these observations, and any inferences we may have made from them, is an understanding of how neutrinos interact with matter. Knowledge of neutrino interaction cross sections is an important and necessary ingredient in any neutrino measurement. With the advent of new precision experiments, the demands on our understanding of neutrino interactions is becoming even greater. The purpose of this article is to survey our current knowledge of neutrino cross sections across all known energy scales: from the very lowest energies to the highest that we hope to observe. The article covers a wide range of neutrino interactions including coherent scattering, neutrino capture, inverse beta decay, low-energy nuclear interactions, quasielastic scattering, resonant pion production, kaon production, deep inelastic scattering, and ultrahigh energy interactions. Strong emphasis is placed on experimental data whenever such measurements are available.

Ultra high-energy cosmic ray proton interactions

The recent Auger results suggest that the coincidences of arrival directions with ‘nearby’ AGN, and the HiRes discovery of the GZK cut-off, indicate protons to be at least the strongly dominant component of primary extra galactic cosmic ray flux. The measured longitudinal extensive air shower propagation characteristics, however, indicate at least a mixed composition, if the conventional interaction model is correct. For the present work we assume that the particles are indeed protons and examine the consequences for the high-energy interaction physics. We have found that such a supposition requires strong violation of the so-called Feynman scaling.

The Experimental Input to our Understanding of High-Energy Interactions

An overview is given of some of the experimental results reported during the Weihai meeting on ultra-high energy interactions. The work discussed has been chosen to reflect the current interest in the astrophysical interpretation of air-showers as progress in this area is hampered by uncertainties in the extrapolation of data on hadronic interactions from accelerators to high energies. It is anticipated that future accelerator work at CERN and FNAL will help to clarify some of these issues.

Evaluation of the fluence to dose conversion coefficients for high energy neutrons using a voxel phantom coupled with the GEANT4 code

Crews working on present-day jet aircraft are a large occupationally exposed group with a relatively high average effective dose from galactic cosmic radiation. Crews of future high-speed commercial flying at higher altitudes would be even more exposed. To help reduce the significant uncertainties in calculations of such exposures, the male adult voxels phantom MAX, developed in the Nuclear Energy Department of Pernambuco Federal University in Brazil, has been coupled with the Monte Carlo simulation code GEANT4. This toolkit, distributed and upgraded from the international scientific community of CERN/Switzerland, simulates thermal to ultrahigh energy neutrons transport and interactions in the matter. The high energy neutrons are pointed as the component that contribute about 70% of the neutron effective dose that represent the 35% to 60% total dose at aircraft altitude. In this research calculations of conversion coefficients from fluence to effective dose are performed for neutrons of energies from 100 MeV up to 1 GeV, irradiating MAX with mono-energetic beams in the mode Anterior-Posterior. An alternative methodology is developed too, using the atmospheric neutrons spectrum simulated with GEANT4 code at aircraft altitude instead of the traditional method that uses mono-energetic beams. To obtain the neutrons spectrum 1.5×105 extensive atmospheric showers are simulated by cosmic rays interactions with atmospherics atoms. The main characteristics of the spectrum are in agreement with literature confirming the validity of GEANT4. For 100 MeV energy the conversion coefficient calculated with spectrum shows a decrease of 8%, pointing out the importance of the environment influence.

STUDYING NEW PHYSICS USING ULTRAHIGH-ENERGY COSMIC-RAY γ-FAMILY DATA

This review discusses some recent developments in the study of ultrahigh-energy interactions using cosmic-ray γ-family data obtained with emulsion chambers at mountain altitudes. The apparent excess of the event rate at large transverse momenta with respect to the prediction based on perturbative QCD indicates new interaction mechanisms at E lab ≃104–105 TeV, an energy regime beyond the reach of existing colliders. To reconcile the data with a compositeness model of quarks, the characteristic energy scale would have to be as low as Λc≤0.1 TeV, in conflict with the lower limit of Λc>1.4 TeV or a possible value of Λc≃1.6 TeV obtained by the CDF experiment at Tevatron. Possible new physics beyond the standard model, together with future experiments at the LHC, are also discussed.

Properties of hadronic interactions at high energies and the nature of the cosmic-muon charge ratio.

We would like to highlight here the very recently emphasized properties of ultrahigh-energy interactions and to study their bearing on the analysis of the nature of the cosmic-muon charge ratio at ultrahigh energies. It is interesting to note that by combining the recently observed properties of all the relevant aspects of the problem and using the updated values of the necessary parameters, we can give a reasonably good description of the data even with the help of a phenomenological model for particle production of Rossi et al. and also with the induction of a hand-inserted value for moderate violation of Feynman scaling at ultrahigh energies. Our results on the muon charge ratio and some other observables will be compared with those of the quark-gluon string model of Erlykin, Krutikova, and Shabelskii, which is also a version of empirical theoretical model with scaling violation as a basic feature.

Measurement of cascade showers in lead with thermoluminescent sheets

A new type of detector, thermoluminescent (TL) sheets (BaSO 4:Eu), and a readout system for the TL sheets have been developed to study electromagnetic cascade showers in ultrahigh energy interactions. To perform a measurement of showers recorded in TL sheets, the longitudinal and radial development of an electromagnetic cascade shower in lead produced by accelerator electrons has been studied for comparison. Simulations of the longitudinal and radial development of cascade showers were also performed using the EGS code system. This study is useful for the design of a thermoluminescent calorimeter (TLC) for the measurement of electromagnetic cascade showers originating from ultrahigh energy (above 10 15 eV) interactions.

Thermoluminescent sheets for the detection of high energy hadronic and electromagnetic showers

A new detector, the thermoluminescent (TL) sheet, has been developed by using a new thermoluminescent powder. BaSO 4: Eu, for the study of hadronic and electromagnetic cascade showers in ultrahigh energy interactions. The TL sheet is an effective detector because of the following advantages: high sensitivity for the detection of cascade showers (around 1 TeV), high position resolution of about 50 μm, wide dynamic range over seven orders of magnitude and little thermal fading of the TL latent signal. Moreover, the TL sheet can be used repeatedly by annealing.

Study of highly ionizing particles at mountain altitude

The inspiration for this experiment was the widely acknowledged peculiar nature of the class of ultrahigh-energy interactions discovered at Mt. Chacaltaya about a decade ago by a Brazil-Japan collaboration. The rate of Centauro events is quite low, \ensuremath{\sim}0.02 ${\mathrm{m}}^{\ensuremath{-}2}$${\mathrm{yr}}^{\ensuremath{-}1}$. Among the proposed explanations is the possibility that they might be initiated by a highly charged primary particle. To look for such particles we deployed a series of CR-39 plastic track detectors with large collecting power at the summit of White Mountain, California (603 g/${\mathrm{cm}}^{2}$). Two experiments have been completed and analyzed: a single layer with a 10-${\mathrm{m}}^{2}$yr exposure, and three layers in coincidence with a 0.025-${\mathrm{m}}^{2}$yr exposure. In the first experiment, the single layer was adopted to maximize the collecting area at some sacrifice in velocity information. The results demonstrate the superiority of CR-39 as a detector of highly ionizing particles ($\frac{Z}{\ensuremath{\beta}}\ensuremath{\gtrsim}30$) and its particular suitability as a collector of very rare particles. The performance of the plastic was evaluated by examining the high density of tracks due to slow, light ions. The low-energy spectra of nuclei with $Z\ensuremath{\le}3$ have been measured and are found to be consistent with spectra calculated from a model where the source of ions is atmospheric collisions of energetic hadrons. This is the first time that energetic Li has been identified at mountain altitude and that enough He has been seen to permit measurements of its energy spectrum. A density \ensuremath{\sim} ${10\mathrm{m}}^{\ensuremath{-}2}$ of fast particles with $Z\ensuremath{\ge}4$ found in individual layers is consistent with the exposure received in a 10-hour commercial jet flight. A fast-scanning method was used to examine the entire single-layer array. In the interval $30\ensuremath{\lesssim}\frac{Z}{\ensuremath{\beta}}\ensuremath{\lesssim}100$, no events were found, from which we infer an upper limit of 0.4 ${\mathrm{m}}^{\ensuremath{-}2}$${\mathrm{yr}}^{\ensuremath{-}1}$ (95% C.L.) on the flux of electrically charged particles with $\frac{Z}{\ensuremath{\beta}}\ensuremath{\sim}30 \mathrm{to} \ensuremath{\sim}100$ and on the flux of superheavy magnetic monopoles with $\ensuremath{\beta}\ensuremath{\gtrsim}0.02$. Two objects were located which, if they are indeed tracks, would correspond to particles with $\frac{Z}{\ensuremath{\beta}}\ensuremath{\gtrsim}100$, with abundance \ensuremath{\sim}0.2 ${\mathrm{m}}^{\ensuremath{-}2}$${\mathrm{yr}}^{\ensuremath{-}1}$. Without sheets in coincidence, it is impossible to distinguish these objects from certain flaws in the plastic. A new detector, with three layers interleaved with absorbers and with an area of 20 ${\mathrm{m}}^{2}$, will correct this shortcoming and be able to measure the spectra of light elements to higher energies as well.

Investigations of azimuthal and rapidity effects at multiparticle production

Before the time of the operation of new accelerators at CERN in Geneva, Chicago m USA and Dubna iu USSR, most of the basic knowledge about the interaction of fundamental particles came from the studies of cosmic-ray physics. One of the interesting things studied was the angular distribution of the tracks of relativistic particles produced in the cosmic-ray primary jets. In those high-energy interactions it was noticed that in some of the individual interactions, secondary particles were not distributed in rotational symmetry around the direction of the incident nucleus but instead showed a tendency to cluster near a preferential plane and an azimuthal asymmetry was observed. But when wc consider the collective angular distribution of large number of primary events, the azimuthal asymmetry, observed in some individual events in a plane perpendicular to the collision axis, disappears due to the statistical fluctuations in the angular distribution. Among the different models used for the studies of the mechanism of high-energy particle production, the fireball model (1), proposed about 20 years ago, explained best the dynamics of ultra high-energy interactions. In fact the fireball idea was a very fruitful one. It provided the building blocks for many models of particle production. Indeed, almost any model o~ particle production was generated into a model of fireball production. Detection of the production of fireball is generally done through the angular distribution which is commonly plotted in terms of x variable where x ~ In tg 0~. and 0 L is the polar angle of the emitted particle with respect to the incident particle. This angular distribution helps one to understand whether the particles are produced from one fireball or two fireballs. The shape of the angular distribution determines the dispersion (a) which is a measure of the degree of auisotropy. For one center, we use a 0.90. In cosmic-ray studies (2) as well as in (~) P. CIOK, T. COGIIEN, 5. GIERULA, R. HOLYNSKI, A. 5UI~AK, ~r 1VIII~SOWICZ, T. SANIEWSKA an4 O. STXNISZ: NUOVO Cimento, 8, 166 (1958); 1O, 741 (1958); G. CocooN1: Phys. Rev., 111, 1699 (1958);

Multiplicity behaviour in ultrahigh-energy interactions

Multiplicity behaviour in ultrahigh-energy interactions

Test of Scaling and the Multiperipheral Model for Low Multiplicity Events at Cosmic Ray Energies

al authors3) have studied ultrahigh energy ( ~ 1012 e V) interactions to test scaling hypothesis, yet no study has been done to test scaling for low multiplicity events alone. The importance of low multiplicity (n,) events lies in their unique charac­ teristics; namely, their multiplicity, angular and momentum distributions are mark­ edly different from those of high multiplicity events. These features of low-ns events single them out as attractive cases to provide a sensitive test of scaling hypothesis. The 'universality' of a hypothesis can be verified only if it is true not only for the most frequent class of interactions (high-ns) but also for the less frequent class of interactions, namely the low-ns events. We discuss below the experimental characteristics of rapidity!) for low multi­ plicity events in nucleon-nucleon interactions at cosmic ray energies. Comparison of the results with the predictions of the multiperipheral model as well as Feyn­

Effects of inelastic p-air cross section, the Feynman scaling hypothesis and the primary composition on the maximum depth in EAS (1015-1017eV)

Simulations of extensive air showers (EAS) for several models of ultra-high energy interactions, involving isobar production and Psi production, are carried out with energy dependent cross sections. The sensitivity of the maximum depth to power or logarithmic multiplicity laws for secondaries and to scaling models is discussed together with the effect of the cross section and the chemical composition of the primary cosmic component. Agreement with experimental data on the maximum depth is obtained without requiring such an important multiple production as E12/.

An Elementary Interpretation of the Average Behavior of Multiple Production Processes at Very High Energies

It is shown that the model of ultra high energy interactions originally based on cosmic ray data can account for virtually all the CERN-ISR and FNAL data, including the angular distributions, the x-distributions, the (ymax-y) -distributions and the large transverse momentum distributions of single particles as well as the correlations of charged particles to the large transverse momentum γ-rays.

An indication of a simultaneous maximum of total cross section and average inelasticity near 30000 GeV from an interpretation of the Tian Shan extensive air shower experiment

Lateral electron distributions of cosmic extensive air showers (EAS) recorded at energies <or=105 GeV are not in agreement with constant inelasticity and constant cross section of ultra-high energy interactions. Theoretical analysis indicates that the p-p cross section and inelasticity are either decreasing together from a maximum larger than 56 mb and 0.55 when the energy is rising from 30000 GeV up to 105 GeV, or are decreasing separately from higher maximum values.

Search for massive interacting particles near the cores of extensive air showers of energies of about 2×1014-1016eV

An experiment carried out at mountain altitude to study the time structure of hadrons in extensive air showers has revealed the existence of a special class of delayed high energy interacting particles at distances less than 20 m from the axes of showers of energy greater than 2*1014 eV. These particles having energies more than 20 GeV and delays more than 20 ns relative to the air shower front, constitute about 0.5% of the hadrons of similar energy. Detailed calculations predict the frequency of events with such delay-energy characteristics to be less than 10-4 if they are due to known hadrons like nucleons and pions. The high energy large delay events however can be understood if there exist particles much heavier than nucleons (mass >10 GeV/c2) which are produced in ultrahigh energy interactions. Under certain circumstances the flux of such massive interacting particles has been deduced from the experimental data as approximately 10-9 cm-2 s-1 sr-1.

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.