Ramachandran Gowravaram - Academia.edu (original) (raw)
Papers by Ramachandran Gowravaram
Journal of Physics G: Nuclear Physics, 1981
ABSTRACT
Journal of Physics G: Nuclear Physics, 1981
ABSTRACT
An ab initio method of taking Fermi motion effects in pion scattering into account combined with ... more An ab initio method of taking Fermi motion effects in pion scattering into account combined with proper antisymmetrization of the two nucleon final state in d(..pi../sup + -/,..pi../sup + -/p)n shows that the reaction amplitude consists of not only a contribution from pion scattering on a proton, but also pion scattering on a neutron, and that the two amplitudes differ considerably in their ..pi..-N c.m. energies. The neutron scattering contribution to the differential cross section exceeds 10% in as many as 51 out of 195 ..pi..â» events recorded in a recent kinematically complete experiment by Hoftiezer et al. in the ..delta..-resonance region. In several kinematical situations the neutron contribution exceeds 100% and could even be as high as approx.400%.
We show that it is possible to empirically partition the differential cross section for pp->pp... more We show that it is possible to empirically partition the differential cross section for pp->pp pi0 into initial singlet and triplet differential cross sections in a model independent way which can be implemented using the existing technological capabilities at the PINTEX facility to study the reaction employing polarized beam or polarized target or both simultaneously.
Journal of Physics G: Nuclear Physics, 1981
ABSTRACT
International Journal of Modern Physics E, 2013
The Primordial Deuterium Abundance is a key ingredient to sharpen the predictions of Big Bang Nuc... more The Primordial Deuterium Abundance is a key ingredient to sharpen the predictions of Big Bang Nucleosynthesis (BBN) as it varies sharply with baryon density. The formation of primordial deuterium is mainly through n-p fusion . Laboratory measurements play an important role in removing crucial ambiguities to sharpen the predictions in the astrophysical context. As such experimental measurements have been reported during the last 10 years on photodisintegration of deuteron using 100 % linearly polarized laser beams at lab photon energies, Eγ in the range 2.6 MeV < E γ < 6 MeV which corresponds to the center of mass neutron energy E n in the range 189 keV< E n < 1948 keV. It is worth mentioning here that while a large number of measurements exist for the n-p fusion cross section at thermal neutron energies which corresponds to E n ≈ 10 −6 keV, there are only two measurements at astrophysically relevant energies by Suzuki et al., at lab neutron energies E l n = 20, 40 and 60 keV and by Nagai et al., at E l n = 550 keV. As compared to the thermal neutron cross section of (334.2 ± 0.5) mb, the measured cross sections at the above four energies are (318 ± 2)10 −3 mb , (203 ± 19)10 −3 mb, (151 ± 7)10 −3 mb and (35.2 ± 2.4)10 −3 mb respectively. The reason for this sharp fall with increasing energy is attributed to the fact that the reaction d + γ n + p is governed by the dominant isovector M 1 v amplitude at thermal neutron energies which decreases sharply with increasing energy while the isovector E1 j v , j = 0, 1, 2 amplitudes are believed to be responsible for * Electronic address: shilpashreesp@gmail.com photodisintegration cross sections of order of mb at E γ of a few MeV. Thus all these amplitudes are expected to be comparable at astrophysical energies, where it is possible that the isoscalar amplitude M 1 s could also be of the same order of magnitude . Further there could also be another small amplitude like isoscalar E2 s which has been considered by some authors . The purpose of the present paper is to examine the observables associated with the photodisintegration of aligned deuterons using linearly polarized laser beams to detect the presence of these isoscalar amplitudes.
Journal of Physics G: Nuclear Physics, 1987
A maximal state of spin polarisation of a spin-1 system with all eight degrees of freedom (namely... more A maximal state of spin polarisation of a spin-1 system with all eight degrees of freedom (namely, three distinct axes and two non-zero scalars) is realised when a spin-1 nucleus with nonzero electric quadrupole moment is embedded in a suitable crystal lattice ...
Pramana, 2002
We discuss the notion of spin squeezing considering two mutually exclusive classes of spin-s stat... more We discuss the notion of spin squeezing considering two mutually exclusive classes of spin-s states, namely, oriented and non-oriented states. Our analysis shows that the oriented states are not squeezed while non-oriented states exhibit squeezing. We also present a new scheme for construction of spin-s states using 2s spinors oriented along different axes. Taking the case of s 1, we show that the 'non-oriented' nature and hence squeezing arise from the intrinsic quantum correlations that exist among the spinors in the coupled state.
Pramana, 1995
Following the recent work of Chandleret al on quasi probability distributions for spin-1/2 partic... more Following the recent work of Chandleret al on quasi probability distributions for spin-1/2 particles, we show that polarized light can be interpreted in terms of trivariate probability distributions in two different ways by choosing the variates to correspond to (i) the co-ordinates on the Poincare sphere, (ii) the components of the spin operator of the photon. In either case, it
Pramana, 1994
The Stokes parameters characterising the polarization of the photon in theγ-decay of12C*(1+) are ... more The Stokes parameters characterising the polarization of the photon in theγ-decay of12C*(1+) are examined in correlation with the scattered proton in12C(p,p′)12C*(1+). This opens up the possibility of efficiently determining empirically the six inelastic scattering amplitudes utilizing only 13 measurements. We identify several alternative sets of such measurements to encourage experimental efforts in this direction.
Physical Review C, 1983
ABSTRACT
Physical Review C, 2006
A model independent theoretical analysis of recent experimental data on deuteron photodisintegrat... more A model independent theoretical analysis of recent experimental data on deuteron photodisintegration with polarized laser beams is presented. We find that it is important to distinguish between the three isovector E1 amplitudes E1 j v in reaction channels with total angular momentum j = 0, 1, 2 and that the isoscalar M1 amplitude M 1 s is non-zero in the photon energy range 3.5M eV < E γ < 10M eV Experimental studies [1] have been carried out during the last decade at the Duke Free Electron Laser Laboratory on photodisintegration of deuterons using 100% linearly polarized laser beams from HIGS, in view of the importance of incisive knowledge on d + γ ⇋ n + p at the astrophysically relevant range of energies, to sharpen [2] the predictions of the big bang nucleosynthesis (BBN) and also of stellar evolution. The study of d + γ ⇋ n + p has a long history going back by seven decades to the earliest experimental[3] and theoretical[4] studies. Traditionally radiative thermal neutron capture has been identified with an isovector M1 v transition, while deuteron photodisintegration has been attributed to an isovector E1 v transition. The 10% discrepancy noted early in the total cross section between theory and experiment prompted Breit and Rustgi [5] to propose a polarized-target-beam test to detect a possible isoscalar M1 s transition, but Riska and Brown [6] explained this with surprising accuracy as due to meson exchange currents (MEC). Model calculations taking MEC, isobar current and pair current contributions revealed [7] that the dominant M1 v transition strength at thermal neutron energies decreases substantially with increasing neutron energy E n , while the E1 transition
Physical Review C, 2001
... Rev. C 61, 064002 (2000) [SPIN];[INSPEC];[SPIRES]. G. Ramachandran, PN Deepak, and MSVidya, P... more ... Rev. C 61, 064002 (2000) [SPIN];[INSPEC];[SPIRES]. G. Ramachandran, PN Deepak, and MSVidya, Phys. Rev. C 62, 011001(R) (2000) [SPIRES]. ... Rev. C 61, 064002 2000 . 38 G. Ramachandran, PN Deepak, and MS Vidya, Phys. Rev. C 62, 011001 R 2000 . ...
Physical Review C, 2002
The singlet and triplet differential cross sections for pp → ppπ • have been estimated for the fi... more The singlet and triplet differential cross sections for pp → ppπ • have been estimated for the first time at 325, 350, 375 and 400 MeV using the results of the recent experimental measurements [Phys. Rev. C 63, 064002 (2001)] of Meyer et al.
Physical Review C, 1994
In view of the current experimental interest in utilizing'C (p, p'y)'C... more In view of the current experimental interest in utilizing'C (p, p'y)'C spin observables to supplement the data on'C (p, p')'C*(1+), we study the inelastic scattering from the point of view of the Goldstein-Moravcsik theorem, and identify 32additional possible sets of (p, p'y) ...
Nuclear Physics A, 2001
A model-independent theoretical formalism is outlined to describe Nd fusion in terms of irreducib... more A model-independent theoretical formalism is outlined to describe Nd fusion in terms of irreducible tensor amplitudes labelled by the initial channel spins s = 1 2 , 3 2 . A comprehensive form for the initial spin density matrix ρ is given in the channel spin representation, when both the beam and target are polarized. It is then suggested that an incisive study of Nd fusion may be carried out employing a polarized beam on a polarized target, leading to the determination of the differential cross sections for the doublet and quartet states individually.
Modern Physics Letters A, 2004
A model-independent irreducible tensor approach to p( n, γ)d is presented and an explicit form fo... more A model-independent irreducible tensor approach to p( n, γ)d is presented and an explicit form for the spin-structure of the matrix M for the reaction is obtained in terms of the Pauli spin-matrices σ(n) and σ(p). Expressing the multipole amplitudes in terms of the triplet → triplet and singlet → triplet transitions, we point out how the initial singlet and triplet contributions to the differential cross section can be determined empirically.
Modern Physics Letters A, 1995
As a complement to Goldstein-Moravcsik theorem, we show that in parity conserving reactions with ... more As a complement to Goldstein-Moravcsik theorem, we show that in parity conserving reactions with spin structure 0+1/2-->1+1/2 the differential cross-section t00 ( {i, j} ; ) and the vector polarization tq1 ( {i, j} ; ) of spin-one particle are sufficient to determine the amplitudes unambiguously and there is no need to measure the tensor polarization tq2 ( {i, j}
Modern Physics Letters A, 1986
ABSTRACT We show that it is enough to measure the spherical tensor parameters with k=2j alone to ... more ABSTRACT We show that it is enough to measure the spherical tensor parameters with k=2j alone to determine the reaction amplitudes involving a spin j particle. The recent result of Goldstein and Moravcsik for spin-1 particles turns out to be a particular case of our general result.
Journal of Physics G: Nuclear Physics, 1981
ABSTRACT
Journal of Physics G: Nuclear Physics, 1981
ABSTRACT
An ab initio method of taking Fermi motion effects in pion scattering into account combined with ... more An ab initio method of taking Fermi motion effects in pion scattering into account combined with proper antisymmetrization of the two nucleon final state in d(..pi../sup + -/,..pi../sup + -/p)n shows that the reaction amplitude consists of not only a contribution from pion scattering on a proton, but also pion scattering on a neutron, and that the two amplitudes differ considerably in their ..pi..-N c.m. energies. The neutron scattering contribution to the differential cross section exceeds 10% in as many as 51 out of 195 ..pi..â» events recorded in a recent kinematically complete experiment by Hoftiezer et al. in the ..delta..-resonance region. In several kinematical situations the neutron contribution exceeds 100% and could even be as high as approx.400%.
We show that it is possible to empirically partition the differential cross section for pp->pp... more We show that it is possible to empirically partition the differential cross section for pp->pp pi0 into initial singlet and triplet differential cross sections in a model independent way which can be implemented using the existing technological capabilities at the PINTEX facility to study the reaction employing polarized beam or polarized target or both simultaneously.
Journal of Physics G: Nuclear Physics, 1981
ABSTRACT
International Journal of Modern Physics E, 2013
The Primordial Deuterium Abundance is a key ingredient to sharpen the predictions of Big Bang Nuc... more The Primordial Deuterium Abundance is a key ingredient to sharpen the predictions of Big Bang Nucleosynthesis (BBN) as it varies sharply with baryon density. The formation of primordial deuterium is mainly through n-p fusion . Laboratory measurements play an important role in removing crucial ambiguities to sharpen the predictions in the astrophysical context. As such experimental measurements have been reported during the last 10 years on photodisintegration of deuteron using 100 % linearly polarized laser beams at lab photon energies, Eγ in the range 2.6 MeV < E γ < 6 MeV which corresponds to the center of mass neutron energy E n in the range 189 keV< E n < 1948 keV. It is worth mentioning here that while a large number of measurements exist for the n-p fusion cross section at thermal neutron energies which corresponds to E n ≈ 10 −6 keV, there are only two measurements at astrophysically relevant energies by Suzuki et al., at lab neutron energies E l n = 20, 40 and 60 keV and by Nagai et al., at E l n = 550 keV. As compared to the thermal neutron cross section of (334.2 ± 0.5) mb, the measured cross sections at the above four energies are (318 ± 2)10 −3 mb , (203 ± 19)10 −3 mb, (151 ± 7)10 −3 mb and (35.2 ± 2.4)10 −3 mb respectively. The reason for this sharp fall with increasing energy is attributed to the fact that the reaction d + γ n + p is governed by the dominant isovector M 1 v amplitude at thermal neutron energies which decreases sharply with increasing energy while the isovector E1 j v , j = 0, 1, 2 amplitudes are believed to be responsible for * Electronic address: shilpashreesp@gmail.com photodisintegration cross sections of order of mb at E γ of a few MeV. Thus all these amplitudes are expected to be comparable at astrophysical energies, where it is possible that the isoscalar amplitude M 1 s could also be of the same order of magnitude . Further there could also be another small amplitude like isoscalar E2 s which has been considered by some authors . The purpose of the present paper is to examine the observables associated with the photodisintegration of aligned deuterons using linearly polarized laser beams to detect the presence of these isoscalar amplitudes.
Journal of Physics G: Nuclear Physics, 1987
A maximal state of spin polarisation of a spin-1 system with all eight degrees of freedom (namely... more A maximal state of spin polarisation of a spin-1 system with all eight degrees of freedom (namely, three distinct axes and two non-zero scalars) is realised when a spin-1 nucleus with nonzero electric quadrupole moment is embedded in a suitable crystal lattice ...
Pramana, 2002
We discuss the notion of spin squeezing considering two mutually exclusive classes of spin-s stat... more We discuss the notion of spin squeezing considering two mutually exclusive classes of spin-s states, namely, oriented and non-oriented states. Our analysis shows that the oriented states are not squeezed while non-oriented states exhibit squeezing. We also present a new scheme for construction of spin-s states using 2s spinors oriented along different axes. Taking the case of s 1, we show that the 'non-oriented' nature and hence squeezing arise from the intrinsic quantum correlations that exist among the spinors in the coupled state.
Pramana, 1995
Following the recent work of Chandleret al on quasi probability distributions for spin-1/2 partic... more Following the recent work of Chandleret al on quasi probability distributions for spin-1/2 particles, we show that polarized light can be interpreted in terms of trivariate probability distributions in two different ways by choosing the variates to correspond to (i) the co-ordinates on the Poincare sphere, (ii) the components of the spin operator of the photon. In either case, it
Pramana, 1994
The Stokes parameters characterising the polarization of the photon in theγ-decay of12C*(1+) are ... more The Stokes parameters characterising the polarization of the photon in theγ-decay of12C*(1+) are examined in correlation with the scattered proton in12C(p,p′)12C*(1+). This opens up the possibility of efficiently determining empirically the six inelastic scattering amplitudes utilizing only 13 measurements. We identify several alternative sets of such measurements to encourage experimental efforts in this direction.
Physical Review C, 1983
ABSTRACT
Physical Review C, 2006
A model independent theoretical analysis of recent experimental data on deuteron photodisintegrat... more A model independent theoretical analysis of recent experimental data on deuteron photodisintegration with polarized laser beams is presented. We find that it is important to distinguish between the three isovector E1 amplitudes E1 j v in reaction channels with total angular momentum j = 0, 1, 2 and that the isoscalar M1 amplitude M 1 s is non-zero in the photon energy range 3.5M eV < E γ < 10M eV Experimental studies [1] have been carried out during the last decade at the Duke Free Electron Laser Laboratory on photodisintegration of deuterons using 100% linearly polarized laser beams from HIGS, in view of the importance of incisive knowledge on d + γ ⇋ n + p at the astrophysically relevant range of energies, to sharpen [2] the predictions of the big bang nucleosynthesis (BBN) and also of stellar evolution. The study of d + γ ⇋ n + p has a long history going back by seven decades to the earliest experimental[3] and theoretical[4] studies. Traditionally radiative thermal neutron capture has been identified with an isovector M1 v transition, while deuteron photodisintegration has been attributed to an isovector E1 v transition. The 10% discrepancy noted early in the total cross section between theory and experiment prompted Breit and Rustgi [5] to propose a polarized-target-beam test to detect a possible isoscalar M1 s transition, but Riska and Brown [6] explained this with surprising accuracy as due to meson exchange currents (MEC). Model calculations taking MEC, isobar current and pair current contributions revealed [7] that the dominant M1 v transition strength at thermal neutron energies decreases substantially with increasing neutron energy E n , while the E1 transition
Physical Review C, 2001
... Rev. C 61, 064002 (2000) [SPIN];[INSPEC];[SPIRES]. G. Ramachandran, PN Deepak, and MSVidya, P... more ... Rev. C 61, 064002 (2000) [SPIN];[INSPEC];[SPIRES]. G. Ramachandran, PN Deepak, and MSVidya, Phys. Rev. C 62, 011001(R) (2000) [SPIRES]. ... Rev. C 61, 064002 2000 . 38 G. Ramachandran, PN Deepak, and MS Vidya, Phys. Rev. C 62, 011001 R 2000 . ...
Physical Review C, 2002
The singlet and triplet differential cross sections for pp → ppπ • have been estimated for the fi... more The singlet and triplet differential cross sections for pp → ppπ • have been estimated for the first time at 325, 350, 375 and 400 MeV using the results of the recent experimental measurements [Phys. Rev. C 63, 064002 (2001)] of Meyer et al.
Physical Review C, 1994
In view of the current experimental interest in utilizing'C (p, p'y)'C... more In view of the current experimental interest in utilizing'C (p, p'y)'C spin observables to supplement the data on'C (p, p')'C*(1+), we study the inelastic scattering from the point of view of the Goldstein-Moravcsik theorem, and identify 32additional possible sets of (p, p'y) ...
Nuclear Physics A, 2001
A model-independent theoretical formalism is outlined to describe Nd fusion in terms of irreducib... more A model-independent theoretical formalism is outlined to describe Nd fusion in terms of irreducible tensor amplitudes labelled by the initial channel spins s = 1 2 , 3 2 . A comprehensive form for the initial spin density matrix ρ is given in the channel spin representation, when both the beam and target are polarized. It is then suggested that an incisive study of Nd fusion may be carried out employing a polarized beam on a polarized target, leading to the determination of the differential cross sections for the doublet and quartet states individually.
Modern Physics Letters A, 2004
A model-independent irreducible tensor approach to p( n, γ)d is presented and an explicit form fo... more A model-independent irreducible tensor approach to p( n, γ)d is presented and an explicit form for the spin-structure of the matrix M for the reaction is obtained in terms of the Pauli spin-matrices σ(n) and σ(p). Expressing the multipole amplitudes in terms of the triplet → triplet and singlet → triplet transitions, we point out how the initial singlet and triplet contributions to the differential cross section can be determined empirically.
Modern Physics Letters A, 1995
As a complement to Goldstein-Moravcsik theorem, we show that in parity conserving reactions with ... more As a complement to Goldstein-Moravcsik theorem, we show that in parity conserving reactions with spin structure 0+1/2-->1+1/2 the differential cross-section t00 ( {i, j} ; ) and the vector polarization tq1 ( {i, j} ; ) of spin-one particle are sufficient to determine the amplitudes unambiguously and there is no need to measure the tensor polarization tq2 ( {i, j}
Modern Physics Letters A, 1986
ABSTRACT We show that it is enough to measure the spherical tensor parameters with k=2j alone to ... more ABSTRACT We show that it is enough to measure the spherical tensor parameters with k=2j alone to determine the reaction amplitudes involving a spin j particle. The recent result of Goldstein and Moravcsik for spin-1 particles turns out to be a particular case of our general result.