Low-energy muons in extensive air showers (EAS)

Summary A small air shower array of 21 detectors in conjunction with two shielded muon magnetic spectrographs has been operated for detection of muons of momentum in the range (2÷500) GeV/c at a geomagnetic latitude of 26^o 45′ N at North Bengal University Campus. The array is sensitive to air showers initiated by cosmic-ray primaries of energy in the range (10¹⁴÷10¹⁶) eV. The initial results on muons with a comparison of other recent measurements have been given to infer information on the characteristics of high-energy interaction. An evaluation on the Monte Carlo simulation and observational data on muons in air showers have also been given to indicate the present status of the study of muons in air showers.

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Riassunto Si utilizza un piccolo insieme di ventuno rivelatori di sciami cosmici congiunto a due spettrografi muonici magnetici schermati per rilevare muoni con momento nell'intervallo (2÷500) GeV/c ad una latitudine geomagnetica di 26^o 45′ N al North Bengal University Campus. L'insieme è sensibile a sciami cosmici iniziati da primarie con energia nell'intervallo (10¹⁴÷10¹⁶) eV. Si effettua un confronto dei risultati iniziali sui muoni con altre misure recenti per riferire informazioni sulle caratteristiche dell'interazione ad alta energia. Si dà una valutazione della simulazione di Monte Carlo e dei dati osservativi sui muoni negli sciami cosmici per indicare lo stato attuale dello studio dei muoni nei raggi cosmici.

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Реэюме НеболъшАя из 21 детектора атмосферных яяивней, соедненная с двумя мюонными магнитными спектрогафами, используется для детектектирования мюонов с импульсами в области (2÷500) ГзВ/с на геомагнитной широте 26° 45′ N в камрусе Северного ьенгалъского университета. Детектируюшая система чувстви-телъна к атмосферным ливням, образованным космическими частицами с знергиями в интервале (10¹⁴÷10¹⁶) зВ. Сравнение полученных резулътатов с данными других недавних измерений позволяет получитв информациу о характеристиках взаимо-действий при оченъ вюсоких знергиях. Проводится такзе сравнение моделирования по методу Монте Карло с данными наблюдений для мюонов в атмосферных ливнях.

     

Measurements of the characteristics of low-energy extensive air showers (EAS)

Summary New results on the characteristics of smaller air showers in the size range 10⁴÷10⁵ particles detected by a closely packed detector array are presented. The characteristics of showers such as local age parameter, average age parameter, electron lateral distribution and size spectrum have been determined and a critical comparison of the existing theoretical electron lateral distribution in air showers is given to indicate the present status in relation to the present experimental data on lowenergy EAS.

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Riassunto Si presentano nuovi risultati sulle caratteristiche degli sciami cosmici piú piccoli nell'intervallo di dimensione da 10⁴ a 10⁵ particelle rivelate da un insieme di rivelatori molto compatti. Si determinano le caratteristiche dello sciame come i parametri di età locale, età media, la distribuzione laterale di elettroni e lo spettro di dimensione e si fa un confronto critico con la distribuzione laterale teorica attuale degli elettroni negli sciami cosmici per indicare lo status attuale in relazione ai dati sperimentali attuali sugli EAS a bassa energia.

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Резюме Приводятся новые результаты о характеристиках небольших атмосферных ливней в области 10⁴÷10⁵ частиц, которые были зарегистированы с помощью плотноупакованной антенной решетки детыeкторов. Были определны такие характеристики ливней, как локальный возрастной параметр, поперечное распреденение электронов и спектр размеров. Продится критическое сравнение существующего теоретического поперечного распределения электронов в атмосферных ливнях с полученными экспериментальными данными для низкоэнергетических широких атмосферных ливней.

     

On the production mechanism of MF-HF radiopulses associated with large extensive air showers

Summary The existing theories on radio-emission from extensive air showers (EAS) are inadequate to explain the observed high fields associated with the emission of LF-MF-HF radiopulses. One of the attempts has been to explain the phenomenon in the light of the transition radiation (TR) mechanism from the excess negative charge of EAS on striking the ground. However, experimental data are very meagre. In order to concretise the theoretical basis of LF-MF-HF emission, experimental investigations on different aspects of radio-emission are essential. The present paper reports the experimental studies on radio-emission at some preselected frequencies (LF-HF) using a sophisticated data acquisition system. Results on i) variation of field strength with age parameter (S) for different primary energies (E _p) and different core distance (R), ii) lateral distribution of field strength for differentE _p andS and iii) frequency spectrum of radio-emission, are presented and analysed in the light of the TR mechanism.     

Time fluctuations of charged and neutral cosmic-ray component fluxes as measured in the region of the brazilian magnetic anomaly

Summary Measurements of charged particles, gamma emission and neutrons were fulfilled on balloon in the region of the Brazilian magnetic anomaly on 8 November 1991. The flight lasted approximately 18 hours, including 15 hours on the ceiling at the height of 32 km just during the beginning of the recovery phase of the moderate geomagnetic storm. The main conclusion from the analysis of the obtained experimental data is the following:a) the fluxes of charged and neutral particles were measured and are in agreement with the data of previous works for the close values of geomagnetic cut-off rigidity;b) no sporadic increases of charged- and neutral-particle fluxes were recorded;c) the pulsations of charged particles, gamma-rays and neutrons with characteristic time of ≈ 30 min were found. The sporadic pulsations of charged particles and gamma-rays with shorter periods were observed too. But later pulsations were absent in the neutron flux data. This points to the magnetospheric origin of the observed phenomenon.     

Galactic cosmic-ray anisotropy and its modulation in the heliomagnetosphere, inferred from air shower observation at Mt. Norikura

Summary Extensive air showers (EAS) with median primary energy (E _m) of (10¹³÷10¹⁵) eV have been observed since 1970 at Mt. Norikura (2770 m above sea level; geographic latitude 36.1°N, longitude 137.6°E) in order to study a cosmic-ray sidereal daily variation of galactic origin. We report here a summary of the observed results. EAS shows a significant sidereal diurnal variation with an amplitude (0.060±0.003)% and a phase (0.8±0.3) h sidereal local time forE _m≈1.5·10¹³eV. Sidereal semi- and tridiurnal variations also are statistically significant. These variations are proved to be of galactic origin by a method which uses the difference of two directional (eastward and westward) air shower observations. It is found that these variations are subject, as predicted by Nagashimaet al., to the annual variation due to the heliomagnetospheric modulation of the galactic anisotropy, which dominates in the rigidity region ≈10¹²V, and further that the annual variation changes its phase due to the polarity reversal of the polar magnetic field of the Sun, which occurs at the period of the maximum solar activity. This indicates that the anisotropy is produced by the charged cosmic rays, contrary to the expectation from the γ-ray origin hypothesis suggested by Alexeenko and Navara. With the increase ofE _m, the anisotropy seems to be reduced as we have not been able to detect any significant sidereal variation in EAS withE _m≈2·10¹⁴eV. This seems contradictory to the conventional conclusion that the energy spectrum of the anisotropy is flat or slightly increases with energy.

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Riassunto Sono stati osservati sciami cosmici estensivi (EAS) con energia primaria mediana (E _m) di (10¹³⋎10¹⁵) eV dal 1970 a Mt. Norikura (2770m, latitudine geografica 36.1° N, longitudine 137.6° E) per studiare una variazione gionarliera siderale dei raggi cosmici di origine galattica. Si riporta una sintesi dei risultati osservati. EAS mostra una significativa variazione siderale diurna con ampiezza (0.060±0.03)% e fase (0.8±0.3)h in tempo locale siderale perE _m∼1.5·10¹³eV. Le variazioni siderali semi e tri-diurne sono risultate anch'esse statisticamente significative. Si prova che queste variazioni sono d'origine galattica con un metodo che utilizza la differenza tra due osservazioni di sciami cosmici direzionali (est e ovest). Si trova che queste variazioni sono soggette, come previsto da Nagashimaet al., alla variazione annuale dovuta alla modulazione eliomagnetica dell'anisotropia galattica, che domina nella regione di rigidità ∼10¹²V e inoltre che la variazione annuale cambia fase a causa dell'inversione di polarità del campo magnetico polare del Sole, chesi verifica nel periodo di massima attività solare. Ciò indica che l'anisotropia è prodotta da raggi cosmici carichi, contrariamente a quanto previsto dall'ipotesi sull'origine da raggi gamma, suggerita da Alexeenko e Navara. Con l'aumento diE _m, l'anisotropia sembra ridursi in quanto non siamo riusciti a rilevare una variazione siderale significativa in EAS conE _m∼2·10¹⁴ eV. Questo risultato sembra in contraddizione con la conclusione convenzionale che lo spettro di energia dell'anisotropia è piatto o cresce appena con l'energia.

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Резюме Широкие атмосферные ливни со средней первичной энергией (E _m), равной (10¹³⋎10¹⁵) зВ, наблюдались с 1970 года на г. Нарикура (2770 м над уровнем моря; географическая широта 36.1°N, долгота 137.6°E), с целяю исследовать суточное изменение сидерических космических лучей галактической природы. Предлагается обзор полученных результатов. Широкие атмосферные ливни обнаруживают значительное сидерическое суточное изменение с амплитудой (0.060±0.003)% и фазой 0.8±0.3 часа сидерического времени дляE _m∼1.5·10¹³ эВ. Сидерические полу-и трех-суточные изменения являются также статистически заметными. Доказывается, что эти изменения имеют галактическое происхождение. Этот результат получен с помощью метода, который использует разности при наблюдениях атмосферных ливней в двух направлениях (в восточном и западном направлениях). Получено, что эти вариации подчиняются, как было предсказано Нагашима и др., годовому изменению, обусловленному гелиомагнитосферной модуляцией галактической анизотропии, которая доминирует в области жесткости ∼10¹² D, и кроме того, годовая вариация изменяет фазу, в связи с реверсированием полярности магнитного поля Солнца, котороепроисходит в период максимума солнечной активности. Этот реультат показывает, что возникает анизотропия, вызванная заряженными космическими лучами, в противоположность рредсказанию Алексеенко и Навара, связанному с гипотезой происхождения γ-лучей. При увеличенииE _m анизотропия, повидимому, уменьшается, так как мы не смогли зарегистрировать какого-либо существенного сидерического изменения в пироких атмосферных ливнях в случаеE _m∼2·10¹⁴эВ. Это противоречит общепринятому заключению, что энергетический спектр анизотропии является пологим или слегка увеличивается с энергией.

     

High-energy hadrons and cosmic-ray muons in the atmosphere

Summary The experimental data on fluxes of high-energy hadrons and muons in the atmosphere are compared with the predictions based on the latest information about the properties of high-energy interactions and the primary cosmic-ray composition. It is demonstrated that the expected fluxes are in good agreement with the observations if protons dominate at energies up to 10¹⁵ eV.

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Riassunto Si confrontano i dati sperimentali sui flussi degli adroni e muoni ad alta energia nell'atmosfera con de previsioni basate sulle informazioni piú recenti sulle proprietà delle interazioni ad alta energia e la composizione primaria dei raggi cosmici. Si dimostra che i flussi attesi sono in buon accordo con le osservazioni se i protoni dominano ad energie fino a 10¹⁵ eV.

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Резюме Экспериментальные данные для потоков высокоэнергетических адронов и мюонов сравниваются с предсказаниями, основанными на последней информации относительно свойств взаимодействий при высоких энергиях и составе первичных космических лучей. Показывается, что ожидаемые потоки хорошо согласуются с наблюдениями, если протоны доминируют при энергиях вплоть до 10¹⁵ эВ.

     

Short-period variation of cosmic-ray intensity observed in the stratosphere

Summary To investigate the variation of the cosmic-ray intensity in the Earth atmosphere, stratospheric balloon soundings are performed weekly at Campinas (Brazil). During the flight of May 20th, 1988 short-period variations were detected. Through Fourier analysis it was identified a period of ∼2.5 min, with a confidence level of 99.6% between 23 g/cm² and 173 g/cm². Apparently these oscillations are not correlated either with the earth magnetic field or solar activity, suggesting their atmospheric origin, nevertheless it is difficult to explain the production mechanisms of these disturbances.

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Riassunto Per studiare le variazioni dell'intensità dei raggi cosmici nell'atmosfera terrestre sono messi in funzione palloni sonda stratosferici settimanalmente a Campinas (Brasile). Durante il volo del 20 Maggio 1988 sono state registrate variazioni a breve periodo. Mediante l'analisi di Fourier è stato identificato un periodo di ≈2.5 min con un livello di confidenza di 99.6% tra 23 g/cm² e 173 g/cm². Apparentemente queste oscillazioni non sono correlate né con il campo magnetico terrestre né con l'attività solare, il che suggerisce la loro origine atmosferica, nonostante sia difficile spiegare i meccanismi di produzione di queste perturbazioni.

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Резюме для исследования изменения интенсивности комсических лучей в земной атмосфере еженелельно запускайтся стратосферные шарызонды в лаборатории Кампинас (Бразилия). Во время подыта 20 мая 1988 года, были зарегистрированы изменения с коротким периодом. С помощью фурье-анализа определен период 2.5 минуты, с уровнем достоверности 99.6%, в области между 23 г/см² и 173 г/см². По-видимому, эти осцилляции не связаны ни с магнитным полем Земли, ни с солнечной активностью. Предполагается их атмосферное происхождение, тем не менее трудно обБяснить механизм образования этих возмущений.

     

Response and yield functions of neutron monitor, galactic cosmic-ray spectrum and its solar modulation, derived from all the available world-wide surveys

Summary The differential response functionR(p, x, t) of cosmic-ray neutron monitors and its altitude and time dependence are obtained by a new method of analysis which uses all the available data obtained by oversea, overland and airborn surveys at different periods together with those of the space exploration. The simultaneous use of these data enables us to decomposeR(p, x, t) further into three terms; the unmodulated energy spectrumG(U) of galactic cosmic rays, the modulation functionM(p, t) of cosmic rays in solar system and the yield functionY(U, x) of neutrons in the atmosphere (x g/cm²). It is demonstrated that 1) the power exponent ofG(U) shows fairly a good agreement with those so far obtained, 2)Y(U, x) shows also fairly a good agreement with the theoretical expectation in the energy region ≥10 GeV and 3)M(p, t) gives the cosmic-ray mean free path showing a consistent rigidity spectrum with those obtained by the solar proton events. Using these terms, we can obtainR at any time and at any atmospheric depth. A brief historical review of the study of the response function is also made in the introduction.

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Riassunto La funzione di risposta differenzialeR(p,x,t) dei monitor a neutroni dei raggi cosmici e la sua dipendenza dall'altitudine e dal tempo sono ottenuti con un nuovo metodo di analisi che utilizza tutti i dati disponibili ottenuti con rilevamenti aerei, in mare e a terra effettuati in periodi diversi insieme ai dati delle esplorazioni spaziali. L'uso simultaneo di questi dati permette di scomporreR(p,x,t) ulteriormente in tre termini: lo spettro di energia non modulatoG(U) dei raggi cosmici galattici, la funzione di modulazioneM(p,t) dei raggi cosmici nel sistema solare e la funzione di produzioneY(U,x) di neutroni nell'atmosfera (x g/cm²). Si dimostra che 1) l'esponente della potenza diG(U) presenta un buon accordo con quelli ottenuti fino ad ora, 2)Y(U,x) presenta anche un buon accordo con i valori teorici attesi nella regione d'energia ≥10 GeV e 3)M(p,t) dà il percorso libero medio dei raggi cosmici che mostra un consistente spettro di rigidità ottenuto dagli eventi dei protoni solari. Usando questi termini, si può ottenereR in ogni momento e a tutte le profondità atmosferiche. Nell'introduzione c'è una breve rassegna storica dello studio della funzione di risposta.

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Резюме С помощью новочо метода анализа, который использует все имеющие данные мировых исследований в различные периоды вместе с данными космических исследований, получаются дифференциальная функция откликаR(p, x, t) для мониторов космических нейтронов и ее зависимость от высоты и времени. Одновременное испльзование этих данных позволяет нам представитьR(p, x, t) в виде трех членов: немодулированный энергетический спектрG(U) галактических космических лучей, функция модуляцииM(p, t) космических лучей в солнечной системе и функция выходаY(U, x) нейтронов в атмосфере (х·г/см²). Показывается, что 1) показатель экспонентыG(U) довольно хорошо согласуется с полученной величиной, 2)Y(U, x) также довольно хорошо согласуется с теоретическими предсказаниями в области энергий≽10 Гэв и 3)M(p, t) дает величину средней длины свободного пробега космических лучей, которая соответствует величине, полученной для солнечных протонов. Используя эти три члена, мы можем получитьR в любое время и на любой гдубине в атмосфере. Во введении предлагается краткий исторический обзор исследований функции отклика.

     

High-energy cosmic-ray physics with an EAS array on the top of the Gran Sasso Laboratory

Summary An air shower array on top of the underground Gran Sasso Laboratory (GSL) can give valuable information in the field of high-energy cosmic-ray physics. We discuss the performances of a specific apparatus (EAS-TOP) operating both in coincidence with the underground array (i.e. for measuring the total primary energy of multimuon events) and as an autonomous air shower detector (for studies of ultra-high-energy gamma-ray astronomy, cosmic-ray anisotropies and primary composition).

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Riassunto Un apparato per EAS posto in superficie nella zona sovrastante il laboratorio sotterraneo del Gran Sasso può fornire utili informazioni sulla radiazione cosmica primaria. Qui si presenta un apparato (EAS-TOP) the funzionerà sia in coincidenza con gli apparati posti nel tunnel per misure sull'energia primaria degli eventi multimuonici sia in modo autonomo come rivelatore EAS per ricerche di γ-astronomia ad energie molto elevate, di anisotropia dei raggi cosmici primari, e di composizione primaria.

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Резюме Установка для регистрации ШАЛ над подземной лабораторией Гран Сассо может дать полезную информацию для физики космических лучей высоких энергий. Мы обсуждаем возможности установки EAS-TOP, работающей как в совпадении с подземными детекторами (для измерения полной начальной энергии в многомюинных событиях), так и в автономном режиме—для исследований в области гамма-астрономии сверхвысоких энергий, измерений анизотропии космических лучей и химического состава первичного излучения.

     

Observations of high-energy electrons in the stratosphere

Summary To investigate the variation of the flux of cosmic radiation in the vicinity of the Earth, stratospheric balloon soundings are performed weekly at Campinas (Brazil). During some soundings, enhancements of the counting rates are detected. In this paper data from these excesses as well as their analysis are shown. It seems to indicate that possibly high-energy electrons are injected from the lower boundary of the radiation belt into the stratosphere.

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Riassunto Per ricercare la variazione del flusso delle radiazioni cosmiche in prossimità della Terra, sono fatti funzionare settimanalmente palloni sonda a Campinas (Brasile). In alcune sonde si registrano aumenti delle frequenze di conteggio. In questo lavoro si mostrano dati da questi eccessi nonché le loro analisi. Ciò sembra indicare che gli elettroni ad alta energia sono probabilmente immessi dallo strato inferiore della fascia di radiazioni nella stratosfera.

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Резюме для исследования изменения потока космического излучения в окрестности Земли еженедельно запускаются стратосферные шары-зонды в лаборатории Кампинас (Бразилия). Во время некоторых зондирований зарегистрированы увеличения интенсивности излучения. В этой статье приводятся данные измерений и их анализ. Проведенный анализ показывает, что эти случаи возможно связаны с электронами высоких энергий, инжектированными из нижней границы радиационного пояса в стратосферу.

     

Energy spectrum of cosmic-ray neutrinos in the atmosphere

Summary The energy spectrum of cosmic-ray neutrinos in the atmosphere has been calculated for the neutrino energy from 0.2 GeV to 10⁸ GeV by taking into account the results of p-p collision, p-nucleus collision, nucleus-nucleus collision, the energy spectrum of primary cosmic rays, momentum spectrum and charge ratio of cosmic-ray muons measured by MUTRON, and the production of prompt neutrinos in the decay of charmed particles. Our result on neutrino intensity is in good agreement with the result of Osborneet al. for the horizontal direction if their muon spectrum has been corrected, and also with the result of Volkova for the vertical direction except for the lower energies. For the horizontal direction the intensity of prompt muon-neutrinos exceeds that of muonneutrinos from the conventional processes at the neutrino energy of 10⁶ GeV and also the intensity of prompt electron-neutrinos exceeds that of electron-neutrinos from the conventional processes at the energy of 10⁵ GeV. The corresponding values for the vertical direction are 10⁵ GeV and 10⁴ GeV, respectively. In the energy region from 0.3 GeV to 3 GeV, the expected value for the ratio of intensity of electron-neutrino to that of muon-neutrino is obtained as 0.42±0.08 and this is excellent agreement with the experimental value 0.36±0.13 of NUSEX group.

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Riassunto è stato calcolato lo spettro d’energia dei neutrini dei raggi cosmici nell’atmosfera per un’energia neutrinica da 0.2 a 10⁸ GeV tenendo conto dei risultati delle collisioni p-p, p-nucleo, nucleo-nucleo, dello spettro d’energia dei raggi cosmici primari, dello spettro dell’impulso e del rapporto di carica dei muoni dei raggi cosmici misurato da MUTRON e dalla produzione di neutrini pronti nel decadimento di particelle con charm. Il nostro risultato sull’intensità dei neutrini è in buon accordo con il risultato di Osborneet al. per la direzione orizzontale se il loro spettro muonico viene corretto, ed anche con il risultato di Volkova per la direzione verticale tranne che per le energie piú basse. Per la direzione orizzontale l’intensità dei neutrini muonici pronti è maggiore di quella dei neutrini muonici che derivano dai processi convenzionali ad energia neutrinica di 10⁶ GeV ed anche l’intensità dei neutrini elettronici pronti è maggiore di quella dei neutrini elettronici che derivano dai processi convenzionali all’energia di 10⁵ GeV. I valori corrispondenti per la direzione verticale sono rispettivamente 10⁵ e 10⁴ GeV. Nella regione d’energia tra 0.3 e 3 GeV, il valore atteso ottenuto per il rapporto tra l’intensità dei neutrini elettronici e quella dei neutrini muonici è 0.42±0.08 e questo è in accordo eccellente con il valore sperimentale 0.36±0.13 del gruppo NUSEX.

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Ёнергетический спектр нейтрино космических лучей в атмосфере

Резюме Вычисляется Энергетический спектр нейтрино космических лучей в атмосфере для Энергий нейтрино от 0.2 ГЭВ до 10⁸ ГЭВ, учитывая р-р соударения, р-ядерные соударения, ядерно-ядерные соударения, Энергетический спектр первичных космических лучей, импульсный спектр и зарядовое отнощение мюонов космических лучей, измеренных с помошью МUTRON, и образование нейтрино в распадах очарованных частиц. Нащ результат для интенсивности нейтрино хорощо согласуется с результатом Осборна и др. для горизонтального направления, если их мюонный спектр является правильным, а также с результатом Волковой для вертикального направления, за исключением низких Энергий. Для горизонтального направления интенсивность мгновенных мюонных нейтрино превыщает интенсивность мюон-ных нейтрино из обычных процессов при Энергиях нейтрино 10⁶ ГЭВ. Йнтенсивность мгновенных Электронных нейтрино превыщает интенсивность Электронных нейтрино из обычных процессов при Энергии 10⁵ ГЭВ. Соответствуюшие величины для вертикального направления соответственно равны 10⁵ ГЭВ и ДО⁴ ГЭВ. В области Энергий от 0.3 ГЭВ до 3 ГЭВ ожидаемая величина отнощения интенсивностей Электронных нейтрино к интенсивности мюонных нейтрино составляет 0.42±0.08. Ёта величина прекрасно согласуется с Экспериментальным результатом 0.36±0.13, полученным группой

     

The ground-level cosmic-ray event of September 29, 1989 as recorded by the rome detectors

Summary An extraordinary increase in cosmic-ray intensity has been recorded on September 29, 1989 by the Rome detectors (rigidity threshold ∼6.2 GV). We show the time evolution of the event as recorded at Rome in the nucleonic component and in the total ionizing and muon components; as well as at Campo Imperatore (2300 m a.s.l. near Rome) in the nucleonic component by a special monitor designed for the detection of solar-neutron events. The one-minute time resolution of the Campo Imperatore data offers the possibility to follow in detail the development of the event for most of the time. The possible contribution of solar neutrons to the early phase of the Campo Imperatore event has been not clarified so far, further results may be obtained by the analysis of the multiplicity data registered in the event.     

The behaviour of the cosmic-ray equatorial anisotropy inside fast solar-wind streams ejected by coronal holes

Summary The cosmic-ray equatorial anisotropy inside broad high-speed solar-wind streams ejected by coronal holes,i.e. in quasi-stationary condition, is analysed over the years 1973–1974. From the beginning to the end of the stream the amplitudes of the first and second harmonics of the anisotropy are found to decrease remarkably by factors 2.5 and 2.0, respectively, while the phases do not show systematic variations. The development of the stream structure in the interplanetary space together with the Parker theory on the diurnal anisotropy in stationary condition give a plausible explaination for the large variation observed in the first harmonic of the anisotropy. The behaviour of the second harmonic is tentatively interpreted in the light of current theories. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

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.

     

Long-distance drifting of ionization electrons in liquid and solid argon

Summary A study of ionization electron drifting long distances in liquid and solid argon was carried out with a 10 cm gridded ionization chamber, operated with electric fields between 10 V/cm and 2 kV/cm. A detailed analysis of the ionization pulse shape was performed with a FADC readout, yielding information on both the degree of purity of the liquid and the electron drift velocity. Argon with an impurity concentration less than 0.2 p.p.b. oxygen equivalent was obtained with a very simple purification system. With this level of purity electrons remained free for periods of time in excess of one millisecond. The measured attenuation length extrapolates to 7.5 m for liquid argon and to 1 m for solid argon at a drift field of 1 kV/cm. This work was supported by the U.S. Department of Energy under contract number DE-AC02-76ER03064.     

Cosmic ray air showers in the knee energy region

The cosmic ray extensive air showers in the knee energy region have been studied by the North Bengal University array. The differential size spectra at different atmospheric depths show a systematic shift of the knee towards smaller shower size with the increase in atmospheric depth. The measured values of spectral indices at below and above the knee are −2.45 ±0.03 and −2.91 ±0.05 respectively. Measurements at different atmospheric depths correspond to the same values within the error limits both for below and above the knee. The present experimental results have been compared with similar such experiments     

Formulation of cosmic-ray solar daily variation and its seasonal variation, produced from generalized stationary anisotropy of solar origin

Summary In previous papers, we presented a formulation of the cosmic-ray solar daily variation and of its seasonal variation, produced from an axis-symmetric stationary anisotropy of solar origin. On the other hand, based on their theoretical study of cosmic-ray diffusionconvection in the solar system, Munakata and Nagashima have recently pointed out the existence of an axis-asymmetric anisotropy with respect to the IMF axis, which is not covered by the formulation. In order to include such a case, we extend, in this paper, the above formulation to a case of a generalized anisotropy, which is expressed by surface harmonics in the IMF polar-co-ordinate system.

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Riassunto In precedenti lavori abbiamo presentato una formulazione della variazione diurna solare dei raggi cosmici e della sua variazione stagionale, prodotta da un'anisotropia stazionaria assi-simmetrica di origine solare. D'altra parte, basandosi sui loro studi teorici della diffusione-convezione dei raggi cosmici nel sistema solare, Munakata e Nagashima hanno recentemente messo in evidenza l'esistenza di un'anisotropia assisimmetrica rispetto all'asse IMF che non è compresa nella formulazione. Per poter includere anche tale caso, abbiamo esteso, in questo lavoro, la suddetta formulazione al caso di un'anisotropia generalizzata che è espressa da armoniche di superficie nel sistema di coordinate polari IMF.

     

Charm hadroproduction cross-section up to 100 TeV from measurements of the cosmic-ray muon angular distribution. Results of the Mont Blanc experiment

Summary Accurate calculations of the angular distributions of underground conventional and prompt muons have been performed. The dependence of the angular enhancement functions on the primary spectrum, cross-sections, inclusive distributions, K/π ratio and survival probability have been studied and found to be negligible. The results have been used to interpret the data from the Mont Blanc experiment in the depth range (4200ρ5800) hg/cm². Since the measurements extend over a limited angular range (<60°) the ratio between the flux of prompt to conventional muons of higher energy (>1 TeV) is obtained with large associated statistical errors. In order to obtain the charm production cross-section in the energy region (50ρ100) TeV, accurate measurements over a very large angular range (>70°) at depths higher than 5000 hg/cm² are required.

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Riassunto Sono state calcolate le distribuzioni angolari di muoni convenzionali e pronti sottoterra ed è stata studiata la loro dipendenza, risultata trascurabile, dalla forma dello spettro primario, sezione d'urto, distribuzioni inclusive, rapporto di produzione K/π e probabilità di sopravvivenza. Questi risultati sono stati usati per interpretare i dati ottenuti nell'esperimento del Monte Bianco nell'intervallo di profondità (4200ρ5800) hg/cm². Poiché le misure si estendono solo sino a 60° il rapporto tra muoni pronti e convenzionali di alta energia (>1 TeV) è ottenuto con grande errore statistico. Se ne conclude che per derivare la sezione d'urto di produzione di charm nell'intervallo di energia (50ρ100) TeV sono necessarie misure accurate ad alta profondità (>5000 hg/cm²) ed estese sino ad oltre 70°.