The Role of Neutrinos in Astrophysics

A.B. Balantekin University of Wisconsin

GDR Neutrino Laboratoire Astroparticule et Cosmologie

Joint analysis of the solar neutrino data including final SNO salt results along with the most recent KamLAND data

Balantekin, et al., PLB 613, 61 (2005)

Neutrinos from core-collapse supernovae

• Mprog ≥ 8 MSun

E ≈ 1053 ergs ≈ 1059 MeV• 99% of the energy is carried away by

neutrinos and antineutrinos with 10 ≤ E ≤ 30 MeV

• 1059 Neutrinos!

A recent SN remnant (Hubble Space Telescope)

X-ray remnant of the SN observed by Chinese in 185 A.D.

X-ray remnant of Kepler’s SN (1604)

Estimated intensity in the sky of the brightest historical SN (1066) - National Observatory of Turkey, Antalya

SN shock wave

Chandra

SN remnant

Neutron star

99% of the gravitational binding energy of the star

• Current theoretical prediction of solar neutrino flux and structure of main sequence stars. Solar neutrino measurements precisely confirm the Standard Solar Model. Temperature at the center of the Sun was correctly calculated ab initio to better than 2%. • Recognition of the importance of the neutrino-neutrino interactions on neutrino propagation in dense neutrino systems. Development of the theoretical tools to treat these effects in astrophysical sites. • New theoretical breakthroughs in nucleosynthesis in SN and GRB’s, and role of weak interactions in SN dynamics.• Tritium beta decay mass limit plus knowledge of the large mixing angles implying that all mass eigenstates are limited, meaning active neutrinos cannot be the dark matter.  This is independently confirmed by the cosmology limits.  Both results had important contributions from theory. • New limits on diffuse SN neutrino flux. Astrophysical uncertainties are now reduced to the point that these searches are primarily testing the neutrino emission per supernova, which is of fundamental interest to nuclear physics.  

Recent Accomplishments with neutrinos in astrophysics

• Current theoretical prediction of solar neutrino flux and structure of main sequence stars. Solar neutrino measurements precisely confirm the Standard Solar Model. Temperature at the center of the Sun was correctly calculated ab initio to better than 2%. • Recognition of the importance of the neutrino-neutrino interactions on neutrino propagation in dense neutrino systems. Development of the theoretical tools to treat these effects in astrophysical sites. • New theoretical breakthroughs in nucleosynthesis in SN and GRB’s, and role of weak interactions in SN dynamics.• Tritium beta decay mass limit plus knowledge of the large mixing angles implying that all mass eigenstates are limited, meaning active neutrinos cannot be the dark matter.  This is independently confirmed by the cosmology limits.  Both results had important contributions from theory. • New limits on diffuse SN neutrino flux. Astrophysical uncertainties are now reduced to the point that these searches are primarily testing the neutrino emission per supernova, which is of fundamental interest to nuclear physics.  

Recent Accomplishments with neutrinos in astrophysics

Neutrinos from SN1987A

Adopted from Raffelt

50

40

30

20

10

0

Energy (MeV)

14121086420Time of Event (sec)

Kamiokande II (PR D38 (1988) 448 IMB (PR D37 (1988) 3361 Baksan (PL B205 (1988) 209)

iron peak

Life stages of a core-collapse supernova

1. Collapse and bounce epoch. S/k ≈ 1

2. Shock-reheating epoch. S/k ≈ 40

3. Hot-bubble epoch. S/k ≈ 75 to 500?Possible site of r-

process nucleosynthesis

Neutrino-driven wind in post-core bounce supernova

-sphere

shock-wave

wind region

injection (heating) region

unshocked

matter

Mass outflow rate in the wind region is approximately constant

Observed r-process abundances

[Fe/H] ≈ -3.1

A > 100 abundance pattern fits the solar abundances well.

Yields of r-process nucleosynthesis are determined by neutron-to-proton ratio, n/p

Interactions of the neutrinos and antineutrinos streaming out of the core both with nucleons and seed nuclei determine the n/p ratio. Hence it is

crucial to understand neutrino-nucleon cross-sections.

Before these neutrinos reach the r-process region they undergo matter-enhanced neutrino oscillations as well as coherently scatter over

other neutrinos. Many-body behavior of this neutrino gas is not understood, but may have

significant impact on r-process nucleosynthesis.

How does neutrino mixing and neutrino-neutrino interactions effect the yield of r-

process nucleosynthesis?

Atmospheric ’s

Solar neutrinosReactor ’s, very little contribution

from solar ’s SuperK, K2K

SuperK, SNO,

KamLANDDaya Bay Double Chooz

MNS mixing matrix:

p = e + e- proton loss rate

n = e + e+ neutron loss

rate

Weak freeze-out radius: where neutron-to-proton conversion rate is less than the outflow

rate

dYe/dt = 0

Ye= (ne- - ne+) / nbaryons

Electron Fraction

X alpha fraction

dYe/dt = 0

If alpha particles are present

If alpha particles are absent

If Ye(0) < 1/2, non-zero X increases

Ye. If Ye(0) > 1/2, non-zero X

decreases Ye.

Non-zero X

pushes Ye to 1/2

Alpha effectFuller, McLauglin, Meyer

Can sterile neutrino fix the problem of alpha formation?

McLaughlin, Fetter, Balantekin, Fuller, Astropart. Phys., 18, 433 (2003)

Neutrino transport in Dense Matter - MSW

N : Allowed values of neutrino momenta N distinct commuting SU(2) algebras

Neutrino-Neutrino Interactions

Smirnov, Fuller and Qian, Pantaleone, McKellar,…

For systematic corrections to these equations see Balantekin & Pehlivan, JPG 34, 47 (2007)

Nonlinear supernova neutrino and antineutrino flavor transformation with coupled trajectories

One finds large-scale, collective flavor oscillations deep in the supernova envelope, even for the atmospheric neutrino mass-squared difference andfor allowed values of 13.

This is very different fromMSW; models for the r-process, explosion, and theneutrino signal could be affected.

Normal hierarchy Inverted hierarchy

Duan, Fuller, Carlson, Qian

References:• Balantekin & Yuksel, astro-ph/0411159, New J. Phys. 7, 51 (2005)

• Fuller, Qian, astro-ph/0505240, PRD 73, 023004 (2006)

• Duan, Fuller, astro-ph/0511275, PRD 74, in press.

• Duan, Fuller, Carlson, Qian, PRD 74, 105014 (2006); PRL 97, 241101 (2006).

• Balantekin & Pehlivan, J. Phys. G 34, 47 (2007).

Survival probabilities

Recall that nucleosynthesis in core-collapse supernovae occurs in conditions which are the isospin-mirror of the conditions for Big-bang

nucleosynthesis! Big-Bang: n/p << 1

Core-collapse SN: n/p >>1

In both cases species decouple when the expansion rate exceeds their interaction rate

Two possible hierarchies of neutrino energies:

• a) A pronounced hierarchy: E(x) > E(e) > E(e)

• b) A less-pronounced hierarchy: E(x) ~ E(e) ~ E(e)

10 MeV

13 MeV

15 MeV

15 MeV

24 MeV

16 MeVAverage energies

Maen-field approximation for the neutrino gas:

Evolution of neutrino fluxes

(1/r2 -dependence removed)

e e x x

L51: luminosity in units of 1051 ergs s-1

13~ π/10

13~ π/20

13 ~ π/20 with effect

L51 = 0.001, 0.1, 50

Equilibrium electron fraction

X= 0, 0.3, 0.5 (thin, medium, thick lines)

From Balantekin and Yuksel, New J. Phys. 7, 51 (2005).

13~ π/20 with effect

L51 = 0.002, 0.2, 200L51 = 0.001, 0.1, 50

13~ π/20

13~ π/10

X= 0, 0.3, 0.5 (thin, medium, thick lines)

Conclusions

•Neutrinos dominate a good part of the physics in a core-collapse supernova.

• Understanding the neutrino-nucleon and neutrino-nucleus cross-sections well is of crucial importance.

• Neutrinos set the value of the neutron-to-proton ratio in a core-collapse supernova. Hence matter-enhanced

neutrino flavor transformation can impact the physics of the explosion and the r-process nucleosynthesis.

• Neutrino-neutrino interactions could be the crucial component. At the moment calculation of the neutrino

propagation by taking the - interactions (the two-body term) into account is an open, unsolved, problem.