Implications on cosmic ray injection and propagation parameters from Voyager/ACE/AMS-02 nucleus data

We study the propagation and injection models of cosmic rays using the latest measurements of the boron-to-carbon ratio and fluxes of protons, helium, carbon, and oxygen nuclei by the Alpha Magnetic Spectrometer and the Advanced Composition Explorer at top of the Earth, and the Voyager spacecraft outside the heliosphere. The Advanced Composition Explorer(ACE) data during the same time interval of the AMS-02 data are extracted to minimize the complexity of the solar modulation effect. We find that the cosmic ray nucleus data favor a modified version of the diffusion-reacceleration scenario of the propagation. The diffusion coefficient is, however, required to increase moderately with decreasing rigidity at low energies, which has interesting implications on the particle and plasma interaction in the Milky Way. We further find that the low rigidity( a few GV) injection spectra are different for different compositions. The injection spectra are softer for lighter nuclei. These results are expected to be helpful in understanding the acceleration process of cosmic rays.     

Self-affine multiplicity fluctuation of target residues in relativistic nuclear collisions at a few GeV to a few hundred GeV

Self-affine multiplicity scaling is investigated in the framework of two-dimensional factorial moment methodology using the concept of the Hurst exponent (H). Our investigation on experimental data of the target-evaporated slow particles emitted in ³²S-AgBr interactions at 200 AGeV and ²⁸Si-AgBr interactions at 14.5 AGeV reveals that a better power law behavior is exhibited in self-affine analysis than self-similar analysis. This work shows a clear evidence of self-affine target fragmentation. Received: 22 October 2001 / Accepted: 6 March 2002     

Spectral hardening of cosmic ray protons and helium nuclei in supernova remnant shocks

The observed hardening of the spectra of cosmic ray protons and helium nuclei is studied within the model of nonlinear diffusive shock acceleration of supernova remnants(SNRs). In this model, the injected particles with energies below the spectral "knee" are assumed to be described by two populations with different spectral indexes around 200 GeV. The high-energy population is dominated by the particles with energies above 200 GeV released upstream of the shock of SNR, and the low-energy population is attributed to the particles with energies below 200 GeV released downstream of the shock of SNR. In this scenario, the spectral hardening of cosmic ray protons and helium nuclei observed by PAMELA, AMS-02, and CREAM experiments can be reproduced.     

Calculation of LET-spectra of heavy cosmic ray nuclei at various absorber depths

The calculation is based on a factorization of fragmentation cross-sections into a projectile-depending and a target-depending part, which was found at Bavalac for high energy C and O ions. With this the known cross-sections for the fragmentation of heavy ions in collision with protons can be extrapolated to heavier targets. Considering the fragmentation and the energy loss of heavy nuclei the energy spectra of individual elements are calculated for different depths of absorber. This energy spectra can easily be converted to LET (linear energy transfer) spectra. The changes of the isotopic composition with absorber depth and its influence on the shape of the LET-spectra are discussed. The calculated results are compared with experimental data.     

Analysis of shower particle multiplicity in hadron-nucleus collisions in the few hundred GeV region

An analysis of relativistic charged secondaries produced in hadron-nucleus collisions in the few hundred GeV region is presented from the point of view of the structure of hadrons and to examine the possibility of discriminating different theoretical models. An attempt has been made to study the mean normalised multiplicity ratio in the central region and its dependence on the mean number of intranuclear collisionsv. The rate of increase in the production of particles exhibits good agreement with our proposed approach of the constituent supercluster model.     

Simulation of passage of gallactic cosmic ray nuclei in meteorite-pallasite substance

The results are presented of model calculation of the interaction and yield of galactic-cosmic-ray superheavy-element nuclear fragmentation products from the 50 < Z < 92 range of their charges as they pass through a certain meteorite-pallasite substance thickness.     

Feynman scaling violation on baryon spectra in pp collisions at LHC and cosmic ray energies

A significant asymmetry in baryon/antibaryon yields in the central region of high energy collisions is observed when the initial state has nonzero baryon charge. This asymmetry is connected with the possibility of baryon charge diffusion in rapidity space. Such a diffusion should decrease the baryon charge in the fragmentation region and translate into the corresponding decrease of the multiplicity of leading baryons. As a result, a new mechanism for Feynman scaling violation in the fragmentation region is obtained. Another numerically more significant reason for the Feynman scaling violation comes from the fact that the average number of cut Pomerons increases with initial energy. We present the quantitative predictions of the Quark-Gluon String Model for the Feynman scaling violation at LHC energies and at even higher energies that can be important for cosmic ray physics.     

Attenuation of cosmic ray heavy nuclei fluxes in the upper atmosphere by fragmentation

Two plastic stacks containing cellulose nitrate as detector material were flown several times with balloons at 40 g cm^?2 for a total time of 25 hours. From the tracks of 920 heavy nuclei the vertical intensities of the particles of four charge groups (6 ? Z ? 9, 10 ? Z ? 14, 15 ? Z ? 19, 20 ? Z ? 28) have been derived for atmospheric depths from 40 – 100 g cm^?2. Combining these intensities with other results obtained with emulsions and in counter measurements, the fragmentation probabilities in air have been determined by comparison with the primary spectra.     

The light nuclei energy spectrum of primary cosmic rays using EAS MSU array data

The change in the energy spectrum index Δγ in the knee region was determined by means of analysis of extensive air showers (EAS) spectra using the number of the particles measured by the EAS MSU array. The value was equal to 1.00 ± 0.12. A comparison of lightweight nuclei energy spectra collected with different installations was carried out.     

Photodisintegration of the deuteron in the few GeV region using asymptotic amplitudes

Exclusive photodisintegration of the deuteron in the 1–4 GeV range is described in terms of a simple covariant and gauge invariant approach using an effective counting rule as the hard part of the d–np vertex. At a scattering angle of θ_cm=90° a prescaling behavior of the differential cross section ∝s⁻⁽ⁿ⁻²⁾ with n≈12 is obtained; going away from 90° the value of n decreases slowly, in qualitative agreement with the recent data.     

Review of the results of measurements of the fluxes of the charged components of galactic cosmic rays in the experiments PAMELA and AMS-02

The paper provides a review of the results of precision measurements of the fluxes of different charged components of galactic cosmic rays (positrons and antiprotons, protons and helium nuclei) in modern experiments with magnetic spectrometers PAMELA and AMS-02, operating successfully for a few years (since 2006 and 2011, respectively) in Earth orbit. A priority of the PAMELA spectrometer scientific discoveries is noted. It is also noted that the measurements from the AMS-02 experiment are of high statistical accuracy and have reliably confirmed previous data, having been able to advance to a higher energy range.     

Energy spectra of abundant nuclei of primary cosmic rays from the data of ATIC-2 experiment: Final results

The final results of processing the data from the balloon-born experiment ATIC-2 (Antarctica, 2002–2003) for the energy spectra of protons and He, C, O, Ne, Mg, Si, and Fe nuclei, the spectrum of all particles, and the mean logarithm of atomic weight of primary cosmic rays as a function of energy are presented. The final results are based on improvement of the methods used earlier, in particular, considerably increased resolution of the charge spectrum. The preliminary conclusions on the significant difference in the spectra of protons and helium nuclei (the proton spectrum is steeper) and the non-power character of the spectra of protons and heavier nuclei (flattening of carbon spectrum at energies above 10 TeV) are confirmed. A complex structure of the energy dependence of the mean logarithm of atomic weight is found.     

Multifragmentation of Gold nuclei in the interactions with photoemulsion nuclei at 10.7 GeV/nucleon

Recent results from the EMU-01/12 collaboration are presented for 10.7 GeV/nucleon gold nuclei interactions in emulsion. The distributions of “bound” charge (Z _bound , Z _b3 ), multiplicity distributions, fragment correlations and fluctuations are discussed. The data are compared to similar results obtained on the ALADIN setup at 600 MeV/nucleon. It is shown that multifragmentation of gold nuclei at high and intermediate energies has common features. It is also obtained that the IMFs have reduced multiplicity at high energies. The data are analyzed within the scope of the statistical model of multifragmentation. This model requires the following predetermined model ingredients: mass, charge and excitation energy of nuclear residuals. The simple estimation method of these characteristics is proposed in the framework of the Glauber approach. It is shown that the multifragmentation model reproduces qualitatively the present data. A dramatic discrepancy between the predicted and experimental yield of two charged fragments is found. The evolution of transverse momentum of fragments as a function of Z _bound is presented. It is shown that the model greatly underpredicts the transverse momentum of fragments. It is interpreted as evidence of a strong radial flow of spectator fragments.     

Multiplicity fluctuation analysis of target residues in nucleusemulsion collisions at a few hundred MeV/nucleon

Multiplicity fluctuation of the target evaporated fragments emitted in 290 MeV/u12C-AgBr, 400 MeV/u12C-AgBr, 400 MeV/u20Ne-AgBr and 500 MeV/u56Fe-AgBr interactions is investigated using the scaled factorial moment method in two-dimensional normal phase space and cumulative variable space, respectively. It is found that in normal phase space the scaled factorial moment(ln Fq) increases linearly with the increase of the divided number of phase space(lnM) for lower q-value and increases linearly with the increase of lnM, and then becomes saturated or decreased for a higher q-value. In cumulative variable space ln Fq decreases linearly with increase of lnM. This indicates that no evidence of non-statistical multiplicity fluctuation is observed in our data sets. So, any fluctuation indicated in the results of normal variable space analysis is totally caused by the non-uniformity of the single-particle density distribution.     

Technique for determining the charge of cosmic ray nuclei by tracks in olivine crystals from meteorites

A technique for identifying the charge of cosmic ray nuclei, based on measurements of the length and average etch rate of tracks chemically etched in olivine crystals from the Marjalahti pallasite is described.     

Forward-backward multiplicity correlations of target fragments in nucleus-emulsion collisions at a few hundred MeV/u

The forward-backward multiplicity and correlations of a target evaporated fragment (black track particle) and target recoiled proton (grey track particle) emitted from 150 A MeV ⁴He, 290 A MeV ¹²C, 400 A MeV ¹²C, 400 A MeV ²⁰Ne and 500 A MeV ⁵⁶Fe induced different types of nuclear emulsion target interactions are investigated. It is found that the forward and backward averaged multiplicity of a grey, black and heavily ionized track particle increases with the increase of the target size. The averaged multiplicity of a forward black track particle, backward black track particle, and backward grey track particle do not depend on the projectile size and energy, but the averaged multiplicity of a forward grey track particle increases with an increase of projectile size and energy. The backward grey track particle multiplicity distribution follows an exponential decay law and the decay constant decreases with an increase of target size. The backward-forward multiplicity correlations follow linear law which is independent of the projectile size and energy, and the saturation effect is observed in some heavy target data sets.     

Multiplicity fluctuation analysis of target residues in nucleus-emulsion collisions at a few hundred MeV/nucleon

Multiplicity fluctuation of the target evaporated fragments emitted in 290 MeV/u ¹²C-AgBr, 400 MeV/u ¹²C-AgBr, 400 MeV/u ²⁰Ne-AgBr and 500 MeV/u ⁵⁶Fe-AgBr interactions is investigated using the scaled factorial moment method in two-dimensional normal phase space and cumulative variable space, respectively. It is found that in normal phase space the scaled factorial moment (ln<F_q>) increases linearly with the increase of the divided number of phase space (lnM) for lower q-value and increases linearly with the increase of lnM, and then becomes saturated or decreased for a higher q-value. In cumulative variable space ln<F_q> decreases linearly with increase of lnM. This indicates that no evidence of non-statistical multiplicity fluctuation is observed in our data sets. So, any fluctuation indicated in the results of normal variable space analysis is totally caused by the non-uniformity of the single-particle density distribution.     

Missing mass spectra in pp inelastic scattering at total energies of 23 GeV and 31 GeV

Results are reported of measurements of the momentum spectra of protons emitted at small angles in inelastic reactions at the CERN ISR. The data are for total energies $\text{s}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of 23 GeV and 31 GeV. The structure of the peak at low values of the missing mass M (of the system recoiling against the observed proton) is studied. The missing mass distributions have the form (M²)^?B(t) where t is the four-momentum transfer squared. B(t) drops from 0.98±0.06 at t=?0.15 GeV² to 0.20±0.15 at t=?1.65 GeV². The results are compared with a simple triple-Regge formula.     

Fragmentation of12C nuclei in emulsion at 50 GeV/c

A total of 852¹²C-emulsion nucleus interactions at 4.2 GeV/c per incident nucleon was investigated. At least one charged projectile fragment was observed in 733 events, in which the multiplicity and angular distributions ofZ=1,2, and ≧3 projectile fragments were studied. Five events were observed in which¹²C projectile nuclei were fragmented into twoZ=3 fragments. Thus the cross section of this process is about 6×10^?3 of the inelastic cross section. The angular distribution of projectile fragments becomes narrower as the fragment charge increases. At all values of fragment charges, a pronounced peak in the angular distribution can be observed at zero emission angle. In this paper, only the projectile-fragmentation events possessing no heavily ionizing particle (n _h =0 events) have been investigated. Our sample contains 84 of these events, i.e., about 10% of the total inelastic events. The number of events withZ _max, the charge of the emitted principal fragment, equal to 1, 2, 3, 4, and 5 are 11, 52, 13, 4, and 4, respectively. Of these 84 events, 36 interactions have a total charge of emitted projectile fragmentsZ ^* equal to 6, i.e., as much as the beam chargeZ _p . Of the 36 events, 17 produce no charged pions and of the 17 events, 10 only represent the dissociation of¹²C→3α, i.e., 1.2% of the total inelastic interactions. The number of events withZ ^*=5, 4, 3, 2, and 1 are 27, 14, 4, 2, and 1, respectively. The average number of produced charged pions per one interacting projectile nucleon was estimated to be 1.2±0.1. This value agrees with the corresponding one in elementary interaction at the same energy per nucleon, a result pertaining to the incoherent production model in collision of two nuclei. In this class of events,n _h =0, the number of stars in which H, He, Li, Be, and B isotopes were detected are 59, 58, 13, 4, and 4, respectively. The projected angular distributions ofZ=1 and 2 projectile fragments are Gaussian shaped, narrow, consistent with isotropy, and depend on the fragment. These distributions are consistent with quantum mechanical calculations using the sudden approximation and shell-model functions. From the angular measurements ofα-particle tracks in the dissociation¹²C→3α events, the distribution ofα-particle transverse momentum inside the carbon projectile nucleus was deduced. It seems that the dissociation of¹²C→3α happens via an intermediate⁸Be state.