Papers by Nor Sofiah Ahmad
When neutrinos propagate through a medium and interact with the electrons, an effective potential... more When neutrinos propagate through a medium and interact with the electrons, an effective potential energy is produced due to the coherent forward scattering. This potential engenders significant changes in the neutrino masses and their mixing in the medium. Thus electron neutrinos would oscillate into a different mass eigenstate and this is dependent on the energy of the neutrinos. Some of the energy will be lost in the coherent scattering with the electrons by the charged current interaction. We have calculated the energy loss of the neutrinos by using a stopping power equation for both non-rotating and rotating 20M⊙ and 120M⊙ stellar models. The total energy loss of the neutrinos depends on the electron number density ne in the stars and on the survival probability of the electron neutrino Pne→ne . For higher ne and the survival probability, the energy loss will be significant. These models are generated by using the Geneva code and post-processed to include the oscillation effect....
Monthly Notices of the Royal Astronomical Society, 2021
We present a new overview of the life of very massive stars (VMS) in terms of neutrino emission f... more We present a new overview of the life of very massive stars (VMS) in terms of neutrino emission from thermal processes: pair annihilation, plasmon decay, photoneutrino process, bremsstrahlung, and recombination processes in burning stages of selected VMS models. We use the realistic conditions of temperature, density, electron fraction, and nuclear isotropic composition of the VMS. Results are presented for a set of progenitor stars with mass of 150, 200, and 300 M⊙Z = 0.002 and 500 M⊙Z = 0.006 rotating models which are expected to explode as a pair instability supernova at the end of their life except the 300 M⊙ would end up as a black hole. It is found that for VMS, thermal neutrino emission occurs as early as towards the end of hydrogen burning stage due to the high initial temperature and density of these VMS. We calculate the total neutrino emissivity, Qν and luminosity, Lν using the structure profile of each burning stages of the models and observed the contribution of photone...
AAPPS Bulletin
Nuclear astrophysics is an interdisciplinary research field of nuclear physics and astrophysics, ... more Nuclear astrophysics is an interdisciplinary research field of nuclear physics and astrophysics, seeking for the answer to a question, how to understand the evolution of the universe with the nuclear processes which we learn. We review the research activities of nuclear astrophysics in east and southeast Asia which includes astronomy, experimental and theoretical nuclear physics, and astrophysics. Several hot topics such as the Li problems, critical nuclear reactions and properties in stars, properties of dense matter, r-process nucleosynthesis, and ν-process nucleosynthesis are chosen and discussed in further details. Some future Asian facilities, together with physics perspectives, are introduced.
Issues, Jan 1, 2009
Neutrinos are produced copiously in the early universe. Neutrinos and antineutrinos ceased to be ... more Neutrinos are produced copiously in the early universe. Neutrinos and antineutrinos ceased to be in equilibrium with radiation when the weak interaction rate becomes slower than the rate expansion of the universe. The ratio of the temperature of the photon to the temperature of the neutrino at this stage is Tγ /Tν = (11/4) 1/3 . We investigate the neutrino energy loss due to the oscillation of the electron neutrino into a different flavor in the charged-current interaction of νe − e − based on the work of Sulaksono and Simanjuntak. The energy loss from the neutrinos ∆Eν during the decoupling of the neutrinos with the rest of the matter would be a gain in the energy of the electrons and can be obtained from the integration of stopping power equation ∆Eν = (dEν /dT −1 )dT −1 where Eν and T are the energy of the neutrinos and the temperature respectively. When the universe expands and matter-radiation decouples, an extra energy will be transferred to the photons via the annihilation of the electron-positron pairs, e + + e − → γ + γ. This consequently will increase the temperature of the photons. The net effect to the lowest order is an increase in the ratio of the photon temperature to the neutrino temperature. The magnitude of energy loss of the neutrino is ∼10 −4 − 10 −5 MeV for the probability of conversion of νe → ν i (i = µ, τ ) between 0 to 1.0.
Modern Physics Letters A
Neutrinos are produced copiously in the early universe. Neutrinos and antineutrinos ceased to be ... more Neutrinos are produced copiously in the early universe. Neutrinos and antineutrinos ceased to be in equilibrium with radiation when the weak interaction rate becomes slower than the rate expansion of the universe. The ratio of the temperature of the pho- ton to the temperature of the neutrino at this stage is T=T� = (11=4)1=3.We investigate the neutrino energy loss due to the oscillation of the electron neutrino into a dff�erent flavor in the charged-current interaction of �e e based on the work of Sulaksono and Simanjuntak. The energy loss from the neutrinos �E� during the decoupling of the neu- trinos with the rest of the matter would be a gain in the energy of the electrons and can be obtained from the integration of stopping power equation �E� = (dE�=dT1)dT1 where E� and T are the energy of the neutrinos and the temperature respectively. When the universe expands and matter-radiation decouples, an extra energy will be transferred to the photons via the annihilation of the el...
Current ideas on neutrino oscillation plus confirmation from neutrino experiments make possible t... more Current ideas on neutrino oscillation plus confirmation from neutrino experiments make possible the changing of neutrino flavor due to interactions with the electrons in medium. When neutrinos pass through a medium and interact with the electrons, an effective potential energy is ...
![Research paper thumbnail of Energy Loss of Neutrinos in 20 M[sub ☉] and 40 M[sub ☉] Massive Stars](https://attachments.academia-assets.com/43146157/thumbnails/1.jpg)
The progress from the theoretical and experimental aspects in neutrino physics shines light into ... more The progress from the theoretical and experimental aspects in neutrino physics shines light into neutrino physics as well as in astrophysics. It is known that when neutrinos pass through a medium, the neutrinos interact with electrons before emerging from the stars with an effective potential energy produced due to coherent forward scatterings that occurred in the medium. This potential engenders significant changes in the neutrino masses and their mixing in the medium. Thus electron neutrinos would oscillate into different mass eigenstate and this is dependent on the energy of the neutrinos. Some of the energy will be lost in the coherent scattering with the electrons by the charged current interaction. We have calculated the energy loss of the neutrinos by using a stopping power equation for both rotating and nonrotating 20M and 40M stars. The total energy loss of neutrinos depends on the electron density in the stars and on the survival probability of the electron neutrino. For high electron density profile and the survival probability, the energy loss will be significant.
Modern Physics Letters A, 2009
Neutrinos are produced copiously in the early universe. Neutrinos and antineutrinos ceased to be ... more Neutrinos are produced copiously in the early universe. Neutrinos and antineutrinos ceased to be in equilibrium with radiation when the weak interaction rate becomes slower than the rate expansion of the universe. The ratio of the temperature of the photon to the temperature of the neutrino at this stage is Tγ /Tν = (11/4) 1/3 . We investigate the neutrino energy loss due to the oscillation of the electron neutrino into a different flavor in the charged-current interaction of νe − e − based on the work of Sulaksono and Simanjuntak. The energy loss from the neutrinos ∆Eν during the decoupling of the neutrinos with the rest of the matter would be a gain in the energy of the electrons and can be obtained from the integration of stopping power equation ∆Eν = (dEν /dT −1 )dT −1 where Eν and T are the energy of the neutrinos and the temperature respectively. When the universe expands and matter-radiation decouples, an extra energy will be transferred to the photons via the annihilation of the electron-positron pairs, e + + e − → γ + γ. This consequently will increase the temperature of the photons. The net effect to the lowest order is an increase in the ratio of the photon temperature to the neutrino temperature. The magnitude of energy loss of the neutrino is ∼10 −4 − 10 −5 MeV for the probability of conversion of νe → ν i (i = µ, τ ) between 0 to 1.0.
AIP Conference Proceedings, 2011
The progress from the theoretical and experimental aspects in neutrino physics shines light into ... more The progress from the theoretical and experimental aspects in neutrino physics shines light into neutrino physics as well as in astrophysics. It is known that when neutrinos pass through a medium, the neutrinos interact with electrons before emerging from the stars with an ...
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Papers by Nor Sofiah Ahmad