Cosmic rays in the heliosphere

Summary This is a rapporteur paper for the XXIV International Cosmic-Ray Conference covering topics of anomalous cosmic rays, shock acceleration, modulation and transport theory, cosmic-ray gradients, corotating interaction regions, coronal-mass ejections, and solar neutrinos. Among the highlights of the meeting are —conclusive proof that most anomalous cosmic rays are singly charged,—undisputed detection of anomalous cosmic-ray hydrogen,—discovery of unexpectedly large anisotropies of pickup ions,—observation of pronounced solar rotational modulation of cosmic-ray fluxes to the highest heliolatitudes (∼80°) probed by the Ulysses spacecraft, and—new measurements of modulation effects sensitive to particle charge sign. Rapporteur talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Ultra-high-energy cosmic rays and inflation relics

There are two processes of matter creation after inflation that may be relevant to the resolution of the puzzle of cosmic rays observed with energies beyond GZK cut-off: 1) gravitational creation of superheavy (quasi)stable particles, and 2) non-thermal phase transitions leading to the formation of topological defects. We review both possibilities.     

Cosmic rays and supernova SN 1987a

Summary We discuss the possibility of obtaining information on the contribution to the galactic cosmic-ray flux by young pulsars searching for high-energy gamma-rays from SN 1987a. A small extensive air shower array operating in Chacaltaya (Bolivia, 5200 m a.s.l.) could give significant information at primary energiesE ₀∼10¹⁴ eV.     

Cosmic rays at the highest energies

Cosmic rays at the highest energies are observed with the Pierre Auger Observatory. Recent results are discussed and the properties of high-energy cosmic rays are reviewed.     

Cosmic rays and high-energy interactions. Is there a necessity for a new phenomenon?

Summary A critical analysis of various secondary cosmic-ray phenomena has been performed. The difficulties in describing the longitudinal development by a unique assumption about the model of high-energy interactions and primary mass composition are pointed out. It is stated that the EAS development can be described better if direct production of γ and numerous production of barions are postulated. As a possible model for such a picture it is suggested the creation of a glob of condensed matter together with associated processes. This picture has the virtue that it also account for various strange cosmic-ray phenomena observed at various depths in the atmosphere.

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Riassunto Si effettua un'analisi critica di vari fenomeni secondari dei raggi cosmici. Si sottolineano le difficoltà nel descrivere lo sviluppo longitudinale mediante un unico assunto sul modello d'interazione ad alta energia e la composizione di massa della primaria. Si stabilisce che lo sviluppo degli EAS si può descrivere meglio se si ipotizza la produzione diretta di gamma e produzione copiosa di barioni. Come possibile modello di questa rappresentazione si suggerisce la creazione di un globulo di materia condensata con i processi associati. Questa rappresentazione ha il vantaggio di spiegare anche vari fenomeni strani dei raggi cosmici osservati a varie profondità nell'atmosfera.

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Резюме Проводится критический анализ различных вторичных эффектов космических лучей. Отмечаются трудности при описании долготного развития, с помощью единственного предположения о взаимодействии при высоких энергиях и первоначальном массовом составе. Утверждается, что EAS развитие можно описать лучще, если постулировать прямое рождение γ и множественное рождение барионов. Как возможная модель такой картины, предполагается образование шара конденсированного вещества вместе с ассоциированными процессами. Эта картина имеет достоинство, так как объясняет также различные странные явления космических лучей, наблюдаемые на различных глубинах в атмосфере.

     

PAMELA,FGST and sub-TeV dark matter

PAMELA's observation that the cosmic ray positron fraction increases rapidly with energy implies the presence of primary sources of energetic electron–positron pairs. Of particular interest is the possibility that dark matter annihilations in the halo of the Milky Way provide this anomalous flux of antimatter. The recent measurement of the cosmic ray electron spectrum by the Fermi Gamma Ray Space Telescope, however, can be used to constrain the nature of any such dark matter particle. In particular, it has been argued that in order to accommodate the observations of Fermi and provide the PAMELA positron excess, annihilating dark matter particles must be as massive as ∼1 TeV or heavier. In this Letter, we revisit Fermi's electron spectrum measurement within the context of annihilating dark matter, focusing on masses in the range of 100–1000 GeV, and considering effects such as variations in the astrophysical backgrounds from the presence of local cosmic ray accelerators, and the finite energy resolution of the Fermi Gamma Ray Space Telescope. When these factors are taken into account, we find that dark matter particles as light as ∼300 GeV can be capable of generating the positron fraction observed by PAMELA.     

Cosmic rays from the knee to the highest energies

This review summarizes recent developments in the understanding of high-energy cosmic rays. It focuses on galactic and presumably extragalactic particles in the energy range from the knee (10¹⁵ eV ) up to the highest energies observed (>10²⁰ eV). Emphasis is put on observational results, their interpretation, and the global picture of cosmic rays that has emerged during the last decade.     

Solar cosmic rays

Summary This report is a brief overview of the energetic-particle phenomena related to solar activity discussed at the XXIV International Cosmic-Ray Conference. In the rapporteur's opinion, the most significant results to be highlighted are: 1) the new higher-energy measurements of the solar energetic ion charge state which seem to be consistent with the older measurements at ∼1 MeV/nucleon, and 2) the many reports of extended gamma-ray production during solar flares with multiple episodes of emission implying multiple episodes of particle acceleration. Rapporteur talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Prompt-muon production in cosmic rays

Summary We discuss here the results obtained calculating the contribution of prompt muons in the vertical atmospheric muon flux, computed taking into account the up-to-date data from experiments at accelerators and the most recent theoretical achievements on charm generation in nucleon-air nucleus interactions. Our results are compared with the experimental data obtained with underground detectors.

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Riassunto Si discutono in questo lavoro i risultati ottenuti sul contributo di muoni pronti al flusso atmosferico verticale dei muoni, calcolato utilizzando i dati piú recenti di esperimenti degli acceleratori ed i risultati teorici sulla produzione di particelle charmate in interazioni nucleoni-nuclei atmosferici. I risultati ottenuti sono confrontati con i dati sperimentali forniti da esperimenti sotterranei.

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Резюме Мы обсуждаем результаты вычислений вклада мгновенных мюонов в вертикальный роток атмосферных мюонов. Вычисления учитывают данные из зкспериментов на ускорителях и недавние теоретические предсказания по рождению очарованных частиц при, взаимодействиях нуклонов с ядрами воздуха. Наши результаты сравниваются с зкспериментальными данными, полученными с помощью подземных детекторов.

     

On the biological effects of cosmic rays: Epidemiological studies

Summary Determining the biological effects of cosmic rays and other natural ionizing radiations, could possibly help us in shedding light on the more general problem of low-dose ionizing-radiation effects. In this work we provide a survey of the most recent studies available on epidemiological methods: we discuss the main difficulties in using these methods, as well as the discrepancies in their results. Work presented as a poster at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Cosmic radiation, production of antimatter and their implications

Summary The puzzles connected with the observation of a large ratio, the measured rising ratio of e⁺/e⁻ and some other unsolved, important problems led some theorists to conceive of the extra-galactic origin of cosmic rays and to postulate the existence of the antigalaxies. We have attempted here to understand the problems on the basis of the simple leaky box model (SLBM) with one particular phenomenological model for particle production, and some very recent observational features of high-energy collisions that call for theoretical attention. The conclusion is: the agreements are still not satisfactory if we accept and adhere to the correctness of the previous data. In recent times there has been a dramatic change in the situation with regard to this discrepancy. The latest data have just been taken note of but the conclusions are arrived at here more on the basis of the earlier data than on the recent ones as they necessitate further confirmation.     

The diffuse cosmic gamma rays

A careful and objective analysis is made of the available experimental observations which claim evidence for the existence of a shoulder in the spectrum of the diffuse cosmic gamma rays in the energy range of 1–40 MeV. In this, special cognisance is taken of the experimental data and theoretical calculations of the Bombay Group. These considerations cast serious doubts on the reliability of the high flux values obtained by many experimenters in this energy region emphasizing thereby the need for great caution in interpreting the shoulder as due to cosmological effects with far reaching implications.     

Spectral index of primary cosmic rays. A QCD-admissible derivation

Summary Considering p-p collisions in terms of Drell-Yan and other related processes, where the interaction at the quark level is represented by a dimensionaless interaction potential, we derive an analytical formula for predicting the spectral index of primary cosmic rays. Adjusting a single free parameter of this formula, we find excellent agreement with experimental data over a wide energy range.

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Riassunto Considerando le collisioni p-p in termini del processo di Drell-Yan e di altri processi ad esse collegati, in cui l'interazione al livello dei quark è rappresentata da un potenziale d'interazione senza dimensioni, si deduce una formula analitica per prevedere l'indice spettrale dei raggi cosmici primari. Adattando un parametro libero singolo di questa formula si trova un eccellente accordo con i dati sperimentali su un ampio intervallo d'energia.

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Резюме Рассматривая p-p соударения в терминах процессов Дрелла-Яна и других связанных процессов, где взаимодействие на кварковом уровне представляется с помощью потенциала безразмерного взаимодействия, мы выводим аналитическое выражение для определения спектрального показателя первичных космических лучей. Подгоняя единственный свободный параметр в этой формуле, мы получаем хорошее согласие с экспериментальными данными в широкой области енергий.

     

Relevance of multiple muons detected underground to the mass composition of primary cosmic rays

Summary Calculations have been made of the expected frequencies of multiple muons for the situation of the Soudan underground proton decay detector. Comparisons are made with the observations and it is concluded that with our model for high-energy collisions the flux of heavy nuclei (A>20, principally iron) in the range (10¹⁵÷10¹⁶ eV)/nucleus is at most 25% of the total particle flux in the same range.

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Riassunto Sono stati effettuati i calcoli delle frequenze attese di muoni multipli per situare il rivelatore di decadimento di protoni sotterraneo di Soudan. Si eseguono confronti con le osservazioni e si conclude che con il nostro modello per le collisioni ad alta energia il flusso di nuclei pesanti (A>20, specialmente ferro) nell'intervallo (10¹⁵÷10¹⁶) eV/nucleo è al massimo il 25% del flusso totale di particelle nello stesso intervallo.

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Резюме Вычисляются ожидаемые частоты появления множественных мюонов в суданском подземном детекторе распадов протонов. Проводится сравнение с результатами наблюдений. Делается вывод, что в рамках предложенной модели для соударений при высоких энергиях поток тяжелых ядер (A>20, в основном, ядра железа) в области энерий (10¹⁵÷10¹⁶) эВ составляет, в лучшем случае, 25% от полного потока частиц в этой области энергий.

     

Cosmic prompt-muon spectrum at super high energies estimated from the JACEE primary spectrum using recent charmed-particle production cross-sections

Summary The prompt-muon flux generated directly from the decay of short-lived particles like D-mesons and Λ_c-hyperons produced during primary cosmic proton-air collisions has been estimated. The inclusive production cross-sections of charmed particles based on the recombination of quark parton model developed by Bugaevet al. and the primary-nucleon spectrum based on the latest JACEE balloon flight data have been used in this investigation. The derived direct muon spectrum has been compared with the earlier results of Elbertet al., Inazawaet al. Bugaevet al. and Allkofer and Bhattacharyya.     

Cosmic rays from the knee to the ankle

The shape and composition of the primary spectrum as well as the large-scale anisotropy in the arrival direction of cosmic rays are key elements to understand the origin, acceleration and propagation of the Galactic radiation. Besides the well-known knee and ankle features, the measured energy spectrum exhibits also a less pronounced but still clear deviation from a single power law between the knee and the ankle, with a spectral hardening at $\sim 2\times {10}^{16}\text{eV}$ and a steepening at $\sim {10}^{17}\text{eV}$. The average mass composition gets heavier after the knee till $\sim {10}^{17}\text{eV}$, where a bending of the heavy component is observed. An indication of a hardening of the light component just above ${10}^{17}\text{eV}$ has been measured as well. First indications of anisotropy of the arrival direction in the southern hemisphere have been reported at $\sim {10}^{15}\text{eV}$.     

Primary cosmic-ray composition in the energy range of 1014 eV to 1016 eV and high-energy atmospheric cosmic rays observed with emulsion chambers at Mt. Kanbala

Summary We report on the results of the measurements of energy spectra of atmospheric cosmic rays in the energy around 10 TeV measured with emulsion chambers at Mt. Kanbala (5500 m above sea-level, atmospheric depth 520 g/cm²). The power indices of the integral spectra take the values of 2.00±0.08 for gamma-rays and 1.90±0.10 for hadrons, in the energy range from 5 TeV to 20 TeV. Their intensities are compatible with those expected from the primary cosmic rays containing fewer protons than in the lower energy region. The energy spectrum of family events is also discussed with reference to the composition of primary cosmic rays. It is concluded that the portion of protons in the primary cosmic rays gradually decreases in the energy range from 10¹³ eV to 10¹⁵ eV.

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Riassunto Si riportano i risultati delle misurazioni degli spetri di energia dei raggi cosmici atmosferici all'energia di circa 10 TeV misurata con camere d'emulsione a Mt. Kambala (5500 m sul livello del mare, profondità atmosferica 520 g/cm²). Gli indici di potenza degli spettri integrali assumono i valori di 2.00±0.08 per i raggi gamma e 1.90±0.10 per gli adroni, nell'intervallo di energia da 5 TeV a 20 TeV. Le loro intensità sono compatibili con quelle attese dai raggi cosmici primari che contengono meno protoni che nella regione d'energia inferiore. Lo spettro d'energia degli eventi della famiglia è discusso anche con riferimento alla composizione dei raggi cosmici primari. Si conclude che la porzione di protoni nei raggi cosmici primari diminuisce nell'intervallo d'energia da 10¹³ eV a 10¹⁵ eV.

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Резюме Мы приводим результаты измерений энергетических спектров атмосферных космических лучей при энергиях порядка 10 TeB, определенных с помощью змульсионных камер на г. Канбала (5500 м выше уровня моря, атмосферная глубина 520 r/cm²). Степенные показатели интегральных спектров имейт значения 2.00±0.08 для гамма-лучей и 1.90±0.10 для адронов, в области энергий от 5 ТэВ до 20 ТэВ. Полученные интенсивности оказывайтся совместимыми с ожидаемыми интенсивностями от первичных космических лучей, содержащих меньшее число протонов, чем в области меньших энергий. Также обсуждается энергетнческих спектр семейства событий относительно соства первичных космических лучей. Утверждается, что доля протонов в первичных космических лучах постепенно уменьшается в области энергий от 10¹³ зВ до 10¹⁵ эВ.