P. V. Ramana Murthy

Cosmic-ray intensity measurements deep undergound at depths of (800÷8400) m w.e.

SummaryAn experiment has been carried out to investigate the variation of vertical cosmic-ray intensity with depth in the range (800÷8400) m w.e. Counter telescopes with plastic scintillator layers and Geiger counter trays, kept in the horizontal plane and in coincidence, were employed. The experiment was carried out in the Kolar Gold Fields (Mysore State, India). The results obtained at depths of 816, 1812, 3410, 4280, 6380 and 8400 m w.e. are given.RiassuntoSi è effettuato un esperimento per studiare la variazione dell’intensità verticale dei raggi cosmici nell’intervallo (800÷8400) m a.e. Si sono adoperati telescopi di contatori con strati di scintillatori plastici e vassoi di contatori di Geiger posti orizzontalmente e in coincidenza. L’esperimento fu eseguito nei Kolar Gold Fields (Stato di Mysore). Si riportano i risultati ottenuti alle profondità di 816, 1812, 3410, 4280, 6380 e 8400 m a.e.

A total absorption spectrometer for measuring the energies of nuclear interacting particles of the cosmic radiation in the energy range of a few GeV to a few hundred GeV

Abstract An instrument referred to as a “total absorption spectrometer” (of area 1.4 m 2 and solid angle = 0.25 steradians) has been constructed for measuring the energies of nuclear interacting particles of the cosmic radiation in the energy range of a new GeV to a few hundred GeV. The general features of the design, construction and the procedure used for calibration are discussed as also the factors which govern the accuracy (≈20%) of energy measurement.

The intensity and angular distribution of cosmic rays far underground

An apparatus incorporating scintillators, Geiger counters and neon flash-tubes has been operated at three locations underground in the Kolar Gold Fields, India, to measure the vertical intensity and angular distributions of penetrating cosmic-ray muons. The intensities at the three depths (816, 1812 and 4100 metres water equivalent of rock) are, respectively; (2.39 ± 0.15) × 10-6, (2.00 ± 0.12) × 10-7 and (4.63 ± 0.57) × 10-9 cm-2 sec-1 sterad-1. The angular distributions are well represented by expressions of the form I(θ) = I(0)cosnθ, where θ is the zenith angle, and the values of n at the successive depths are 1.93 ± 0.22, 3.03 ± 0.16 and 5.12 ± 0.82.

Energy spectrum of cosmic-ray muons at sea level

SummaryThe integral energy spectrum of cosmic-ray muons at sea level in the energy range (200÷7500) GeV is deduced from the results obtained by us (as reported in an earlier paper) on the variation of vertical cosmic-ray intensity with depth in the range (800÷8400) m w.e. In doing this, the effect of fluctuations in the energy losses of muons is taken into account. The deduced muon energy spectrum is compared with direct magnet spectrograph observations and with the muon energy spectrum deduced by the Bristol group from their observations on γ-ray cascades at high altitudes. The exponents of the integral production spectra of parents of muons are given and an upper limit to the energy losses of muons in nuclear collisions is set.RiassuntoDai risultati da noi ottenuti (e riferiti in un precedente articolo) sulla variazione della intensità verticale dei raggi cosmici con la profondita nell’intervallo (800÷8400) m a.e. si deduce lo spettro integrale dell’energia dei muoni dei raggi cosmici al livello del mare nell’intervallo di energia (200÷7500) GeV. Nel far ciò si tiene conto dell’effetto della fluttuazione nella perdita di energia dei muoni. Si confronta lo spettro d’energia dei muoni, cosi dedotto, con le osservazioni dirette allo spettrografo magnetico e con lo spettro d’energia dedotto dal gruppo di Bristol dalle loro osservazioni sulle cascate di raggi γ a grandi altezze. Si danno gli esponenti degli spettri integrali di produzione dei muoni generatori e si pone un limite superiore alle perdite di energia dei muoni nelle collisioni nucleari.

A design study of atmospheric Cerenkov radiation telescope for very high energy gamma-ray astronomy

Detection of cosmic sources of very high energy gamma rays based on the atmospheric Cerenkov technique is discussed. Very high energy gamma-rays initiate, on entering the terrestrial atmosphere, electron-photon cascade showers with in turn produce Cerenkov photons in the air. Parabolic reflectors are used to focus these photons onto fast photomultipliers. Two methods of deployment of parabolic reflectors are in vogue: one in which all the reflectors are located close to each other in a compact array and the other in which the reflectors are spread out farther apart forming a distributed array. In the latter mode, the arrival direction of individual showers can be determined accurately by using the measured relative arrival times between different detectors. Detailed studies with the distributed array helped us to understand the various parameters in the two designs and evaluate their relative merits in reaching the ultimate goals of lowering the energy threshold and improving the signal to background ratio for the detection of gamma-ray sources. It is found that the relative superiority among the two types of arrays is a function of the exponent assumed for the differential power law energy spectrum for the gamma ray source. It is also seen that with the type of reflectors commonly used in atmospheric Cerenkov work, lower energy thresholds can be achieved with use of larger aperture.

Test of scale invariance in pion production at high energies using cosmic ray primary nucleon and sea level Muon intensities

Abstract An analysis made using the ratio of intensities of the cosmic ray nucleons at the top of the atmosphere and muons at sea level indicates the validity of the hypothesis of Feynman regarding scale invariance in particle production in the energy region 50 GeV to 2 × 10 4 GeV.

Triggered spark counter arrays of large area (square meters) for experiments on very high energy cosmic ray particles

SummaryThe constructional and operational features of triggered spark counters of large area are described. These counters are being used, in conjunction with nuclear emulsions, in current experiments in this laboratory on high energy nuclear interacting particles which arrive simultaneously over large areas, sometimes associated and at other times unassociated with air showers. For these experiments the spark counters and emulsions are being used in arrays covering an area of a few square meters.RiassuntoSi descrivono le caratteristiche costruttive di contatori a scintillazione di grande superflcie. Questi contatori vengono usati, in unione con emulsioni nucleari, per esperimenti correnti in questo laboratorio su particelle ad alta energia da interazioni che arrivano simultaneamente su larghe aree, alcune volte in associazione con sciami dell’aria ed altre volte senza associazione con questi ultimi. Per questi esperimenti i contatori a scintillazione e le emulsioni sono usati in disposizioni che coprono un’area di alcuni metri quadrati.

Search for 12.6 Millisecond Periodicity in TeV Gamma Rays from Cygnus X-3

Cygnus X-3, an X-ray binary with an orbital period 4.8 hr was seen to be emitting γ-rays with the same period at TeV energies by several groups. In addition the Durham group (Chadwicket al. 1985) published their observations on the existence of a pulsar in the Cyg X-3 system, emitting TeV γ-rays with a periodicity of approximately 12.6 ms. We observed this object during 1986 October-November and did not detect any pulsed emission of TeV γ-rays in the range of periods from 12.5850 to 12.5967 ms.

Cosmic-ray intensity at great depths and neutrino experiments

SummaryA group from the Tata Institute of Fundamental Research, Bombay, has recently completed measurements on cosmic-ray intensities deep underground up to depths of 8400 m w.e. On the basis of these observations it is suggested that, for investigations on naturally occuring neutrinos, there are great advantages to be gained by performing the experiments at considerable depths — around 9000 ft. — below the earth‘s surface, essentially because of the very low background which is encountered at such depths. Some features relevant to neutrino physics which emerge from the measurements already made and the design of future experiments to detect cosmic ray produced and extra terrestrial neutrinos are discussed.RiassuntoUn gruppo del Tata Institute of Fundamental Research, Bombay, ha recentemente completato le misure delle intensità dei raggi cosmici sotterra sino a profondità di 8400 m a.e. Sulla base di queste osservazioni si suggerisce che si potrebbero ottenere grandi vantaggi eseguendo esperimenti a considerevoliprofondità — circa 9000 ft. — sotto la superficie, essenzialmente grazie al bassissimo fondo che si riscontra a queste profondità. Si discutono alcune caratteristiche, interessanti per la fisica del neutrino, che emergono dalle misure già fatte ed il progetto di nuovi esperimenti per rivelare i raggi cosmici prodotti ed i neutrini extra terrestri.

On the observations of muons in the direction of Cyg X-3

Abstract The binary X-ray source Cyg X-3, a known gamma ray emitter, was recently seen to be emmitting a new type of neutral radiation producing muons detected in deep underground experiments. Here an explanation is offered for the deviation of the observed muon directions from that of Cyg X-3. A new underground experiment is suggested to verify the explanation. The new observations enjoying reduced backgrounds will help establish the phenomenon with enormously improved statistical significance. The nature of the neutral radiation, however, remains obscure.