The spectrum of cosmic-ray particles and their origin

An analysis of all the direct measurements of the spectrum for all cosmic-ray particles over the energy range 0.1–10 TeV reveals an anomaly in the spectrum in the form of a step if the spectrum is represented as E^βI₀(E). The pattern of the anomaly unequivocally implies a proton spectrum with a knee at energy close to 1 TeV. The qualitative difference between the spectra of protons and nuclei with Z≥2 (the latter have a purely power-law spectrum over a wide energy range) leads us to conclude that the acceleration conditions for protons and nuclei are different. We consider the process characteristic only of protons that may be responsible for the emergence of a knee in the proton spectrum.     

Tachyonic cascade spectra of supernova remnants and TeV blazars

The superluminal spectral densities of relativistic electrons in uniform motion are derived, semiclassically and in second quantization. The effect of electron spin on the tachyonic radiation field, a Proca field with negative mass-square, is studied. There is a longitudinally polarized spectral component due to the negative mass-square of the tachyonic quanta. The radiation densities are averaged with electron distributions, and high- and low-temperature expansions are obtained. Spectral fits to the γ-ray spectra of the Crab Nebula, the supernova remnant RX J1713.7–3946, and the BL Lacertae objects H1426+428, 1ES 1959+650, Mkn 501, and Mkn 421 are performed. In contrast to TeV photons, the extragalactic tachyon flux is not attenuated by interaction with the background light; there is no absorption of tachyonic γ-rays, as tachyons do not interact with infrared photons. The curvature of the TeV spectra in double-logarithmic plots is caused by the Boltzmann factor of the electron densities generating the tachyon flux. The extended spectral plateau in the GeV band, visible in the spectral maps of the two Galactic supernova remnants as well as in the flare spectra of the BL Lacertae objects, is reproduced by the tachyonic radiation densities. Estimates of the electron populations in the supernova remnants and active galactic nuclei are inferred from the spectral fits, such as power-law indices, electron temperatures, and source counts. Upper bounds on the Lorentz factors in the source populations are derived and compared to the breaks in the high-energy cosmic-ray spectrum. PACS  95.30.Gv; 11.10.Lm; 98.70.Sa; 03.50.Kk     

Cosmic-ray electron flux measured by the PAMELA experiment between 1 and 625 GeV

Precision measurements of the electron component in the cosmic radiation provide important information about the origin and propagation of cosmic rays in the Galaxy. Here we present new results regarding negatively charged electrons between 1 and 625 GeV performed by the satellite-borne experiment PAMELA. This is the first time that cosmic-ray e? have been identified above 50 GeV. The electron spectrum can be described with a single power-law energy dependence with spectral index -3.18 ± 0.05 above the energy region influenced by the solar wind (> 30 GeV). No significant spectral features are observed and the data can be interpreted in terms of conventional diffusive propagation models. However, the data are also consistent with models including new cosmic-ray sources that could explain the rise in the positron fraction.     

Superluminal cascade spectra of TeV γ-ray sources

Astrophysical radiation sources are scrutinized in search of superluminal γ-rays. The tachyonic spectral densities generated by ultra-relativistic electrons in uniform motion are fitted to the high-energy spectra of Galactic supernova remnants, such as RX J0852.0−4622 and the pulsar wind nebulae in G0.9+0.1 and MSH 15-52. The superluminal spectral maps of the unidentified TeV γ-ray sources HESS J1303−631, TeV J2032+4130 and HESS J1825−137 are inferred from EGRET, HEGRA and HESS data. Tachyonic cascade spectra are quite capable of generating the spectral curvature seen in double-logarithmic plots, as well as the extended spectral plateaus defined by EGRET flux points in the GeV band. The curvature of the TeV spectra is intrinsic, caused by the Boltzmann factor in the source densities. The spectral averaging with thermal and exponentially cut power-law electron densities can be done in closed form, and systematic high- and low-temperature expansions of the superluminal spectral densities are derived. Estimates on the electron/proton populations generating the tachyon flux are obtained from the spectral fits, such as power-law indices, temperature and source counts. The cutoff temperatures of the source densities suggest ultra-high-energy protons in MSH 15-52, HESS J1825−137 and TeV J2032+4130.     

What should be the spectrum of galactic cosmic rays?

Numerous experimental data on cosmic rays sensitive to the spectrum of primary cosmic rays were analyzed in the energy range E>1 TeV. They proved to be incompatible with the pure power-law spectrum of primary particles. The spectral index of the proton spectrum is derived from the data considered. It was found to be 0.4±0.1 greater than for the nuclei with Z≥2. Therefore, the flux of galactic cosmic rays consisting of protons and nuclei with Z≥2 cannot be described by a unified power law in the energy range 0.1–10³ TeV.     

Dark Matter Particle Explorer observations of high-energy cosmic ray electrons plus positrons and their physical implications

The DArk Matter Particle Explorer(DAMPE) is a satellite-borne, high-energy particle and γ-ray detector, which is dedicated to indirectly detecting particle dark matter and studying high-energy astrophysics. The first results about precise measurement of the cosmic ray electron plus positron spectrum between 25 Ge V and 4.6 Te V were published recently. The DAMPE spectrum reveals an interesting spectral softening arount 0.9 Te V and a tentative peak around 1.4 Te V. These results have inspired extensive discussion. The detector of DAMPE, the data analysis, and the first results are introduced. In particular, the physical interpretations of the DAMPE data are reviewed.     

New method for estimating the absolute flux and energy spectrum of solar cosmic rays based on neutron-monitor data

A new method is described for estimating the absolute flux of solar cosmic rays based on the data from a single neutron monitor. The method is capable of yielding the energy spectrum at the isotropic phase of a solar flare using the available data from the currently operable worldwide network of cosmic-ray stations. The method is based on the determination of the effective momentum or energy for which the particle flux derived from the neutron-monitor count rate is weakly sensitive to small variations in the exponent of the power-law spectrum. A comparison of the calculations with direct space-borne measurements and calculations by other authors based on the data from the neutron-monitor network shows their satisfactory agreement for the last ground-level enhancement of solar cosmic rays observed on December 13, 2006.     

Measurement of separate cosmic-ray electron and positron spectra with the fermi large area telescope

We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because the instrument does not have an onboard magnet, we distinguish the two species by exploiting Earth's shadow, which is offset in opposite directions for opposite charges due to Earth's magnetic field. We estimate and subtract the cosmic-ray proton background using two different methods that produce consistent results. We report the electron-only spectrum, the positron-only spectrum, and the positron fraction between 20 and 200?GeV. We confirm that the fraction rises with energy in the 20-100?GeV range. The three new spectral points between 100 and 200?GeV are consistent with a fraction that is continuing to rise with energy.     

Possible origin and spectrum of ultrahigh-energy cosmic rays

The complicated form of the cosmic-ray spectrum recorded in the energy range 10¹⁷–10²⁰ eV by giant detector arrays is analyzed. It is shown that the spectrum in the region 10¹⁸–10¹⁹ eV is apparently identical to the injection spectrum with power-law exponent approximately equal to 3.2–3.3. The flat component in the region (3.2–5)×10¹⁹ eV is due to the braking of extragalactic protons by relict photons. The spectrum apparently has no blackbody cutoff at energies above 3.2×10¹⁹ eV. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 10, 729–733 (25 May 1997)     

Precision measurement of cosmic-Ray antiproton spectrum

The energy spectrum of cosmic-ray antiprotons ( &pmacr;'s) has been measured in the range 0.18-3.56 GeV, based on 458 &pmacr;'s collected by BESS in a recent solar-minimum period. We have detected for the first time a characteristic peak at 2 GeV of &pmacr;'s originating from cosmic-ray interactions with the interstellar gas. The peak spectrum is reproduced by theoretical calculations, implying that the propagation models are basically correct and that different cosmic-ray species undergo a universal propagation. Future BESS data with still higher statistics will allow us to study the solar modulation and the propagation in detail and to search for primary &pmacr; components.     

The possibility of searching for new physics in cosmic rays

One possible explanation of cosmic-ray energy spectrum behavior around the knee (3–5 PeV) by means of production of new heavy particles or a new state of matter is considered. It is shown that, in this case, a large excess of muons and neutrinos with energies of >100 TeV must be generated. The existing VHE muon experimental data are analyzed. Possible experiments on VHE muon investigations are discussed.     

Ground-based gamma-ray astronomy

Summary This report covers developments in the field of gamma-ray astronomy, essentially in the energy range 300 GeV to 300 TeV, reported at the XXIV International Cosmic-Ray Conference in Rome in 1995. Highlights which receive the main attention are the failure of several experiments to detect TeV photons from several supernova remnants at the level predicted on current models of shock acceleration of cosmic-ray protons, and the detection of a rapidly variable flaring output of TeV photons from two BL Lac objects (Markarian 421 and Markarian 501). Although techniques are now maturing to the extent that different measurements of the flux and spectrum from the Crab Nebula are now converging, unresolved differences remain over the existence of TeV pulses from certain pulsars. However, one well-supported instance of very intense pulsation for an hour from AE Aquarii was presented. The Vela Pulsar was reported as a steady source. Rapporteur talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Cosmic-ray muon and atmospheric neutrino fluxes at very high energies

Estimates of cosmic-ray muon and atmospheric neutrino fluxes at TeV energies are obtained taking into account a “prompt” production of muons and neutrinos through charmed-particle decays and a “direct” lepton-pair production through the Drell-Yan mechanism and resonances. It is found that the contribution of charmed particles to the muon flux is equal to that from the conventional sources (pion and kaon decays) at 60 TeV, and the same equality can take place at 10 and 1 TeV for muon and electron neutrinos, respectively (for particles coming to sea level in the vertical direction). This “direct” production contribution to muon and neutrino fluxes is estimated very arbitrarily, but it cannot be excluded that this contribution is equal to that from the conventional source at energies of 0.5 and 0.05 PeV for muons and muon neutrinos, respectively. Currently, the estimates of the “prompt” and the “direct” contributions to cosmic-ray muons and atmospheric neutrinos are only qualitative. This is true especially for the “direct” contribution. Nevertheless, it seems reasonable to attract attention to these potentially important sources of atmospheric muons and neutrinos.     

R-violating decay of Wino dark matter and electron/positron excesses in the PAMELA/Fermi experiments

We show that R-parity violating decay of Wino dark matter of mass about 3 TeV can naturally account for the flux and spectral shape of the cosmic-ray electrons and positrons observed by the PAMELA and Fermi satellites. To provide a theoretical basis for the scenario, we present a model in which trilinear R-parity breaking appears with a coefficient suppressed by powers of the gravitino mass, which naturally leads to the Wino lifetime of O(10²⁶) seconds.     

Fine structure in the cosmic ray electron spectrum measured by the ATIC-2 and ATIC-4 experiments

A strong anomaly in form of a wide peak in the energy range 300–800 GeV was discovered in the first measurements of the electron spectrum in the energy range from 20 GeV to 3 TeV by the balloon-borne experiment ATIC [1]. The experimental data processing and analysis of the electron spectrum with different criteria for selection of electrons completely independent of the results reported in [1] is employed in the present paper. New independent analysis generally confirms the results of [1] but shows that the spectrum in the region of the anomaly is represented by a number of narrow peaks. Measured spectrum is compared to the spectrum of [1] and to the spectrum of the Fermi/LAT experiment.     

Tachyonic γ -ray wideband of an ultra-relativistic electron plasma: Spectral fitting with Fermi power-law densities

Fermionic power-law distributions are derived by the second quantization of classical power-law ensembles, and applied to ultra-relativistic electron populations in the Galactic center. The γ-ray flux from the direction of the compact central source Sagittarius A* is fitted with a superluminal cascade spectrum. In this way, estimates of the radiating electron plasma in the Galactic center region are obtained, such as the power-law index, temperature, particle number, and internal energy. The spectral averaging of the tachyonic radiation densities with Fermi power-laws is explained. Fugacity expansions of the thermodynamic variables (thermal equation of state, entropy, isochoric heat capacity, and isothermal compressibility) are obtained in the quasiclassical high-temperature/low-density regime, where the spectral fit is carried out. The leading quantum correction to these variables is calculated, and its dependence on the electronic power-law index and the thermal wavelength is discussed. Excess counts of cosmic rays from the Galactic center region are related to the plasma temperature inferred from the cascade fit.     

Thermodynamic variables of microquasars inferred from tachyonic spectral maps

Tachyonic spectral densities of ultra-relativistic electron populations are fitted to the γ-ray spectra of two microquasars, LS 5039 and LSI +61°303. The superluminal spectral maps are obtained from BATSE, COMPTEL, EGRET, HESS, and MAGIC data sets. The spectral averaging is done with exponentially cut power-law densities. Estimates of the electron distributions generating the tachyon flux are obtained from the spectral fits, such as power-law indices, electron temperature and source counts. The internal energy and heat capacities of the source populations are calculated. An extensive entropy functional is defined for Boltzmann power-law densities and its stability is checked. The high-temperature limit of the thermodynamic variables is determined by the power-law index of the electron plasma, which enters in the scaling exponents as well as the amplitudes.     

Fluxes of high- and ultrahigh-energy cosmic-ray muons

The positive excess of cosmic-ray muons at energies higher than 1 TeV is estimated taking into account the data obtained from accelerator experiments on the production of particle and antiparticles in proton-proton interactions at energies of ～20 TeV. The fluxes of cosmic-ray muons at energies up to ～10¹¹ GeV and the production functions of muon bremsstrahlung photons at different depths in the atmosphere are calculated with due regard for the contribution from the decay of J/ψ mesons. The analysis performed is based on the accelerator data and their extrapolation to higher energies.     

Superluminal spectral densities of ultra-relativistic electrons in intense electromagnetic wave fields

Superluminal radiation from electrons accelerated in electromagnetic waves is investigated. The radiation field is a Proca field with negative mass-square, minimally coupled to the electron current. The spectrum is continuous in the ultra-relativistic regime, where steepest-descent asymptotics can be used to evaluate the power coefficients. The time averaging of Lissajous orbits in polarized wave fields is discussed, and the tachyonic spectral densities of electrons orbiting in intense laser beams are derived. In the ultra-relativistic limit, realized by high injection energy or high field intensity, the spectral functions are evaluated in closed form in terms of Airy integrals. In contrast to electromagnetic radiation, there is a longitudinal polarization component, and oscillations emerge at high beam intensity in the longitudinal and transversal spectral slopes, generated by the negative mass-square of the tachyonic quanta. The thermal ultra-relativistic electron plasma of two active galactic nuclei is analyzed in this regard, based on TeV spectral maps obtained with imaging air Cherenkov detectors. Specifically, tachyonic cascade fits are performed to γ-ray flares of the TeV blazars RGB J0152+017 and 3C 66A, and the transversal and longitudinal radiation components are disentangled in the spectral maps. The curvature of the spectral slopes is shown to be intrinsic, caused by the Boltzmann factor of the electronic source plasma radiating the tachyonic cascades.     

Quark-gluon state of matter and positive excess of cosmic-ray muons at high energies

The problem of the relationship between the numbers of positively and negatively charged particles in the flux of cosmic-ray muons arriving at sea level with energies in excess of 0.1 TeV (up to 100 TeV) is discussed. It is shown that the formation of quark—gluon matter as the result of high-energy nuclear interactions leads to a reduction of the positive excess in cosmic-ray muons at the above energies. At the present time, the quark-gluon state of matter is studied in accelerator experiments at colliding-particle energies of up to √s = 200 GeV per nucleon. Estimates presented in this article for the positive excess of muons having energies of up to 3 or 4 TeV are based on available data from accelerator experiments; at higher muon energies, the respective estimates are based on extrapolating these data.