Type 2 SN Neutrino Asymmetry

[trinitree88]

From Fun Papers. For 11 July 2012

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Neutrinos and supernova nucleosynthesis: http://arxiv.org/abs/1207.2527 Neutrino-driven wind simulations and nucleosynthesis of heavy elements
Arcones, F.-K. Thielemann

In core collapse supernovae, neutrinos are originally trapped within the neutron star. They eventually blow off the outer portion of the neutron star (I know, we’re used to thinking of neutrinos don’t interact with anything) and thus spewing out the heavier elements. This paper looks at how they also are responsible for the creation of the lighter heavy elements.

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Tensor. The Nucleosynthesis and Neutrino Wind simulations paper by Arcones &Thielemann neglects completely parity effects in core collapse supernovae. They successfully derive the evolution of the species in the process, but it is well known that core collapse Type 2's eject the new pulsars at velocities typically a few tens to several hundred km/sec.(sometimes as high as ~2000 km/sec) that requires an inherent asymmetry in the 3d hydrodynamic modeling. Wrote the paper in 1992 and gave the talk @ the AAPT @ Vassar, "Parity, Pulsars and Supernova Remnants. pete

[antoniseb]

I pulled this out of the Fun Papers in Today's arXiv thread since I'd like any spawned discussions to take place in separate threads, lest they get lost in the long resource thread.

[Tensor]

Tensor. The Nucleosynthesis and Neutrino Wind simulations paper by Arcones &Thielemann neglects completely parity effects in core collapse supernovae. They successfully derive the evolution of the species in the process, but it is well known that core collapse Type 2's eject the new pulsars at velocities typically a few tens to several hundred km/sec.(sometimes as high as ~2000 km/sec) that requires an inherent asymmetry in the 3d hydrodynamic modeling. Wrote the paper in 1992 and gave the talk @ the AAPT @ Vassar, "Parity, Pulsars and Supernova Remnants. pete

Cool, thanks Pete. Is it possible that when the neutrinos cause the outer portion of the neutron star to blow off, it blows off asymmetrically. And this is what gives the new pulsars their velocities?

[trinitree88]

Cool, thanks Pete. Is it possible that when the neutrinos cause the outer portion of the neutron star to blow off, it blows off asymmetrically. And this is what gives the new pulsars their velocities?

Tensor. It's not only possible, it's inherent. You have magnetic fields of 10¹¹ to 10¹³ Gauss in the nascent neutron star, and the highest neutrino fluxes since putative BB times. Weak interactions are universally asymmetric with regards to ambient magnetic fields. I calculated the asymmetry in the additional scattering claimed by Leinson, Oraevskii, due to spin waves (magnons) as ~ 40 % of the additional 30% needed to make a supernova "go", giving an overall kick of ~ 4 % of the neutrino induced kinetic energy in the ejecta. Gives approximately the seen velocities of pulsar surveys, and is coupled to the B field with a correlation coefficient of ~.7 (Lyne, Harrison, et al...A Survey of Southern Pulsars, MNRAS).

[Tensor]

Tensor. It's not only possible, it's inherent. You have magnetic fields of 10¹¹ to 10¹³ Gauss in the nascent neutron star, and the highest neutrino fluxes since putative BB times. Weak interactions are universally asymmetric with regards to ambient magnetic fields. I calculated the asymmetry in the additional scattering claimed by Leinson, Oraevskii, due to spin waves (magnons) as ~ 40 % of the additional 30% needed to make a supernova "go", giving an overall kick of ~ 4 % of the neutrino induced kinetic energy in the ejecta. Gives approximately the seen velocities of pulsar surveys, and is coupled to the B field with a correlation coefficient of ~.7 (Lyne, Harrison, et al...A Survey of Southern Pulsars, MNRAS).

It wasn't the magnetically driven process I was wondering about. When the neutrinos get trapped, within the forming neutron star, due to the opacity of the neutron star, the neutrino pressure builds. The action of the layers themselves blowing off asymmetrically, due to the neutrino pressure, was the action I was asking about.

Hmmmmm, didn't think about it before, but does that ejection process also contribute to some of the spin?

I think Arcones & Thielemann ignored parity effects purposely, as their paper seems to be the determination of how the formation of the different elements proceeds, more than the determination of the how the ejection of the neutron star proceeds.

Whenever I post a neutrino article, I always think of you. I usually either get more information, or a correction. Always worth it.

[trinitree88]

It wasn't the magnetically driven process I was wondering about. When the neutrinos get trapped, within the forming neutron star, due to the opacity of the neutron star, the neutrino pressure builds. The action of the layers themselves blowing off asymmetrically, due to the neutrino pressure, was the action I was asking about.

Hmmmmm, didn't think about it before, but does that ejection process also contribute to some of the spin?

I think Arcones & Thielemann ignored parity effects purposely, as their paper seems to be the determination of how the formation of the different elements proceeds, more than the determination of the how the ejection of the neutron star proceeds.

Whenever I post a neutrino article, I always think of you. I usually either get more information, or a correction. Always worth it.

Tensor. But the mental picture of the neutron star as a symmetrical three dimensional ball is incomplete, although used in many models. Conservation of angular momentum dictates increased spin as the core collapses, resulting in an axisymmetry, rather than spherical. This is further exacerbated by the nucleons acquiring "bean" shapes resulting in differential cross-sections for weak currents. In addition, neutrons, even if gravitationally bound, have drastically shorter half-lives in the growing fields near the poles of the new neutron star. Together, the effects allow a specific impulse to be delivered to the ejecta/pulsar combo.
When the data is checked, most Sne remnants are barrel-shaped...~85%, and empty....~495/500,....and many pulsars are not associated with their long gone remnants, but are free floating with high space velocities. pete

[Tensor]

Tensor. But the mental picture of the neutron star as a symmetrical three dimensional ball is incomplete, although used in many models. Conservation of angular momentum dictates increased spin as the core collapses, resulting in an axisymmetry, rather than spherical. This is further exacerbated by the nucleons acquiring "bean" shapes resulting in differential cross-sections for weak currents. In addition, neutrons, even if gravitationally bound, have drastically shorter half-lives in the growing fields near the poles of the new neutron star. Together, the effects allow a specific impulse to be delivered to the ejecta/pulsar combo.
When the data is checked, most Sne remnants are barrel-shaped...~85%, and empty....~495/500,....and many pulsars are not associated with their long gone remnants, but are free floating with high space velocities. pete

Ahhhhhhhhhh, that was the missing piece for me. And when I thought about it, it maked a lot of sense. Thanks for the explanations.

[trinitree88]

Ahhhhhhhhhh, that was the missing piece for me. And when I thought about it, it maked a lot of sense. Thanks for the explanations.

Tensor. you're welcome. pete

[Tensor]

Tensor. you're welcome. pete

Hey, another silly question. Are mu and tau neutrinos also produced? I would think so, but I haven't seen a specific reference to them.

[trinitree88]

Hey, another silly question. Are mu and tau neutrinos also produced? I would think so, but I haven't seen a specific reference to them.

Tensor. Yep. All the flavors are produced even at the lower temperatures of main sequence stars....that's what neutrino mixing is. Originally proposed by Bruno Pontecorvo and then, later by Lincoln Wolfenstein, and his cohorts, Mikheyev and Smirnov as MSW flavor mixing, it was long suspected by John Bahcall as being the solution to the apparent solar neutrino (electron-type).. deficit in the Homestake Mine experiment, and was later confirmed in the Sudbury Neutrino Observatory data.
The relative abundances depend upon the equation of state of the type-2 fireball which varies a bit from model to model. Basically, as I understand it, the eigenstates of the neutrinos become superimposed with the mass eigenstates in degenerate matter, and that allows them to flavor-switch from electron-type to muon or tau-type. The branching ratios are used to draw a triangle to form the mixing angle...analogous to the Cabibbo angle for quarks. They are just now finishing the work on theta 1,3..which was slowed by the Fukushima tsunami. It's ~ 0.1, and they were hoping for a non-zero result around there (MIT Phys. Colloq.).
In type 2's the temps are so high, lots of interesting stuff is going on. It will be interesting to see a nearby type 2's impact on SNO. (we should be so lucky this century)...pete



SEE:http://www.sno.phy.queensu.ca/

SEE:http://en.wikipedia.org/wiki/Neutrino_oscillation


SEE:http://en.wikipedia.org/wiki/Cabibbo...Maskawa_matrix