• M S Swami

      Articles written in Proceedings – Section A

    • Stars and single tracks in nuclear plates

      H J Taylor H J Bhabha R R Daniel J R Heeramaneck M S Swami G S Shrikantia

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      Photographic plates exposed at high altitudes show a population of stars and isolated single tracks. Statistics are given covering 288 stars and 655 isolated tracks found in an area of 17 sq. cm. Some tracks are closely associated with the stars, and these have a mean range of 4·1 cm. air. The remainder, which show no association with stars, have a mean range of 3·4cm. air. Some stars have more than one associated single track. Alternative explanations are discussed. The most probable hypothesis appears to be that the single tracks are due to the spontaneous disintegration of unstable neutral particles emitted from the stars.

    • Production and interaction of mesons at very high energies

      D Lal Yash Pal B Peters M S Swami

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      A shower containing ∼360 charged and neutral shower particles produced by a magnesium nucleus of 2×1014e.v. provides a source of mesons whose interactions have been studied over an aggregate track length of about 3 meters in emulsion. It is first shown that in very large showers not only the incident energy can be determined but also the energy of the shower particles. The angular distribution of the shower particles agrees closely and their multiplicity is consistent with Fermi’s theory.

      It is shown that the interaction cross-section of charged shower particles is geometric and that at an energy ∈ ∼ 1000µc2 they produce on the average 5 to 6 mesons. The mesons are preferentially emitted in the backward direction in the reference system in which the momentum of the incident meson balances that of a nucleon in the target. The excitation produced in the target nucleus is much lower than in nucleon-produced showers of comparable multiplicity.

      The charged mesons arenot emitted in pairs by a heavier meson of short lifetime.

      Charged shower particles as well as electrons produce electron-positron pairs with a cross-section of the order of that predicted by theory.

      The number of neutral mesons decaying intoγ-rays in a time ≤10−14 sec. is nearly equal to the number of charged shower particles.

      There exists evidence for the emission of neutral particles, different from neutrons, capable of producing meson showers.

      The energy balance of the event suggests that a few shower particles carry an appreciable fraction of the total energy.

    • Three examples ofΛBe7 hyperfragments

      K N Chaudhari S N Ganguli N K Rao M S Swami

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      In a systematic study of hyperfragments (HFs), three uniquely identified examples ofΛBe7 hyperfragments have been observed; one of them decayed byπ−1-mesic mode and the other two by non-mesic modes. The data from the presentπmesic decay ofΛBe7 when combined with that from the other two similar events reported in the literature, yielded a mean binding energy of 4·99±0·36 MeV for Λo relative to the lowest level of Be6.

    • Study of hyperfragments - Part III. Multinucleon interactions of Λ° in hyperfragments

      D P Burte K N Chaudhari S N Ganguli N K Rao M S Swami

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      1101 examples of non-mesic decay of hyperfragments, produced by high energy particles in nuclear emulsion stacks, have been used to obtain information on multinucleon interaction of Λ° hyperon in the decay of hyperfragments. From a study of events with two fast charged particles in decays of hyperfragments, the following two conclusions are drawn: (i) multinucleon interactions of Λ° in decay of hyperfragments is not significant; it occurs at the most in a few per cent of the cases, and (ii) there is strong evidence for the existence of final state interactions in decay of hyperfragments.

    • Study of hyperfragments - Part IV. Mechanism for production of hyperfragments

      D P Burte K N Chaudhari S N Ganguli N K Rao M S Swami

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      Hyperfragments (HFs) produced in interactions of high energy pions and protons with emulsion nuclei have been investigated to deduce information on their mechanism of production. From these studies it is concluded that (a) long-range HFs (R⩾20µm.) which are due to fragments with mass number ≲15, are produced in the evaporation stage of the disintegrations of Ag and Br nuclei of emulsion, (b) short-range HFs (R⩽10µm.) are mainly due to residues of the target nuclei and a small fraction (≈10%) of them in the range 5<RHF⩽15µm. are due to fission type of processes that occur in high energy interactions and (c) the relative probability of sticking of Λ° to fragments withZ=2 to that with 3⩽Z⩽6 is roughly in the ratio 1:10.

    • Determination of the flux of primary cosmic ray hydrogen and helium nuclei near the geomagnetic equator using nuclear emulsions - III. The flux of deuterons on March 12, 1960, at Hyderabad

      S N Ganguli N K Rao M S Swami

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      Nuclear emulsions exposed to the cosmic radiation over Hyderabad, India, at an altitude of 31·3 km. for six hours, have been used to derermine primary cosmic ray deuteron flux. The flux of deuterons of rigidity ⩾16·9 GV at the top of the atmosphere is found to be <10 m.−2 sec.−1 sterad−1; this may be compared with the proton fiux of 83±12 m.−2 sec.−1 sterad.−1 in the same rigidity region over Hyderabad.

    • Study of hyperfragments - Part V. Analysis of light hyperfragments

      K N Chaudhari S N Ganguli N K Rao M S Swami

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      464 non-mesic and 65 mesic decay of hyperfragments (HFs) produced by pions of momenta 3·5 GeV/c. and 17·2 GeV/c. and protons of momentum 23 GeV/c., have been used to obtain information on Q, the ratio of non-mesic toπ mesic events and S, the ratio of neutron to proton stimulated events as a function of charge of HFs. Q is found to increase rapidly with the increase in charge of HFs; the value of Q for HFs of Z⩾3 is 14·6±3·0 which is high compared to the theoretical value of about 4 to 5. The value of S is found to be >1 for all HFs of Z≥2.

    • Kinematical calculation ofΛ-nucleon stimulation reaction for hyperfragments of mass A=50

      S N Ganguli M S Swami

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      Energy spectra of fast protons (E⩾30 MeV) have been calculated for hyperfragments of mass A=50, from Λ-proton and Λ-neutron stimulation processes respectively. It has been concluded by comparing with experimental energy spectrum, that Λnp stimulation ratio is ∼5. It has been estimated, from this ratio, that the emission frequencies of two fast protons, from Λ-single nucleon stimulation, both with E⩾20 MeV and with E⩾30 MeV, are ≈3·3% and ≈1·7% respectively.

    • Binding energy andπ+ decay of light hyperfragments

      K N Chaudhari S N Ganguli N K Rao M S Swami A Gurtu J M Kohli M B Singh

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      Binding energy values of hyperfragments from a sample of 541 uniquely identified mesic decays with mass numbers A=3 to 14 are presented. There does not seem to be any detectable difference in the binding energy value of Λ inAH4 obtained from its two-body and three-body decay modes. Within statistical error, the binding energy values of Λ inAH4 andAH4 are also the same. From a sample of 2π+ decay events of hyperfragments the branching ratio ofAH4 decaying byπ+ toπ mode is found to be (1·5±1·0)%.

    • The ratio of non-mesic to π-mesic decay of light hyperfragments

      K N Chaudhari S N Ganguli N K Rao M S Swami A Gurtu M B Singh

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      A new method of obtaining the charge spectrum of light hyperfragments from their residual range distribution is described. This method has been used to determine the ratio (Q) of non-mesic to π-mesic decay of light hyperfragments. The values of Q for hyperfragments of different charges are found to be in good agreement with theoretical calculations of Dalitz.

    • On the hypernuclei resonant statesΛLi6,ΛHe5* andΛBe9*

      N K Rao M S Swami A Gurtu M B Singh

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      An attempt has been made to detect narrow resonant states ofΛHe5* (I = 2),ΛLi6 andΛBe9* (I = 1) from amongst a sample of 128 uniquely identifiedΛH4 and 195 uniquely identifiedΛHe5 hypernuclei produced by stopping Krmesons in a nuclear emulsion stack. From the experimental data presented, it is concluded that the production of any of these resonant states is not appreciable; upper limits of 20% and 15% are set for the proportion ofΛHe5 resulting from the decay ofΛLi6 andΛBe9* respectively.

    • The spin dependence of an weak interaction in the decay of hypernuclei

      N K Rao M S Swami A Gurtu M B Singh

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      From an analysis of 468 hypernuclei (HFs) with ranges > 120 μm, the non-mesic to π-mesic ratio (Q) forΛHe andΛHe5 HFs was found to be 1.37 ±0.17 and 1.58± 0.20 respectively. This data, together with results onΛHe4 and heavy hypernuclei, has been used to deduce spin dependences for Λn and ΛP weak interactions in decay of hypernuclei. It is found that the rates for triplet and singlet interactions between Λ and neutron are 22 ΓΛ and 11 ΓΛ and for Λ and proton are 8.2 ΓΛ and 5.5 ΓΛ respectively, where ΓΛ is the decay rate of Λ. The total decay rates for ΛHe4 andΛHe5 are 1.28 ΓΛ and 0.99 ΓΛ and the non-mesic decay rates are 0.17 ΓΛ and 0.51 ΓΛ respectively.

    • Final state interactions in the decay of light hypernuclei

      N K Rao M S Swami A Gurtu M B Singh

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      The excited states of Li4, Li5 and Be8 have been investigated by studying the final state interactions in the π-mesic decays ofΛHe4,ΛHe5 andΛLi8 respectively. The experimental results indicate the existence of final states like Li5* at 1·8 MeV and Be8* at 0 and 2·9 MeV to be dominant in the decay ofΛHe5* andΛLi8 respectively; the results on the decay ofΛHe4 suggest the presence of a Li4* state at about 4 MeV to dominate.

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