Why cross sections are important for astrophysics Gail McLaughlin North Carolina State University

1 Neutrinos in Astropysics A few environments where neutrinos play an important role • sun • Core Collapse Supernovae • Gamma Ray Bursts • Big Bang Nucleosynthesis • Neutron Stars • Massive Stars • + many more

2 About the scattering cross sections • ν + nucleon Complications occur when nuclear • ν + nucleus physics becomes important, • ν + e for example when • ν + ν • scattering on nuclei • production processes • scattering on nucleons in • reverse processes dense matter

3 Core Collapse Supernovae

• core unstable end of the life of a massive star Mcore ∼ 1.5Msun • Oxygen collapse to nuclear density C He Si H • core bounce • Fe core shock produced • shock stalls • neutrinos diffuse out of core, may energize shock

4 Supernova Neutrinos

All types of neutrinos emanate from the proto-neutron star core. They travel through the outer layers of the SN, then to earth.

long mean free path ν SN neutrinos are important core e ν for dynamics, e nucleosynthesis, and νµ νµ ν τ ν τ observation short mean free path

5 Model for Long Duration Gamma Ray Bursts: Collapsar/Hypernovae Model

• Failed Supernova jet punches out of star

• Too much rotation accretion disk for real collapse & bounce

black hole What provides the energy which drives the jet? The neutrinos! (at least in part)

Woosley 1993, MacFadyen and Woosley 1999

6 Short Gamma Ray Bursts: Compact Object Merger Models

• Neutron star and black hole spiral in • Create an accretion disk around a black hole

density data from M Ruffert

7 Explosions of Massive Stars: What’s happening at the center?

black hole, jet shock outflow

neutrinos

accretion disk

proto neutron star core

Standard core core collapse SN gamma ray burst

8 Explosions of Massive Stars: Where do the cross sections fit in?

neutrino nucleosynthesis oscillations black hole, jet shock nucleosynthesis outflow neutrino oscillations neutrinos

accretion disk neutrino neutrino nuclear physics scattering scattering of the disk nuclear physics proto neutron & emission star core & emission of core

Standard core core collapse SN gamma ray burst

9 What do these astrophysical neutrino spectra look like?

Figure from GM & Surman 2006, neutrino diffusion calculations: Breunn, Cardall, Pons, Prakash, Janka, and more

10 Spectra from stopped pions and low energy beta beams

700000 600000 ) ) -2

-2 600000 500000 cm cm -1

-1 500000 400000 Mev Mev 400000 -1 -1 300000 300000 200000 200000 100000 100000 Neutrino Flux (s Neutrino Flux (s Flux Neutrino 0 0 0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80 Energy (MeV) Energy (MeV) Beta beam spectrum at boost fac- Pion decay at rest νe spectrum tors of γ = 7 and γ = 14. proposed applications to astrophysics: nuSNS collaboration Low energy beta beam concept and applications: Volpe, Bal-

antekin, Jachowicz, Amanik, de Jesus, GM, etc..

11 Understanding the neutrino-nucleus cross sections

10

9 S 3n 1st forbidden 8 sum )

-1 7 1st forb S 2n

Mev 6

-1 allowed 5 S 2n Gamov−Teller−res 4 GT res S 1n IAS 3 0−,1−,2− Events (day Events S 1n 2 1

0 208 208 0 10 20 30 40 50 Pb Bi Energy (MeV) Schematic of resonances in lead for Multipole contributions to ∼ 40 MeV neutrinos νe-lead scattering GM 2004

12 The neutrino cross section - nucleosynthesis connection A few types of nucleosynthesis affected by an intense neutrino flux: • r-process, e.g. Uranium • p-process, e.g. Molybdenum • ν-process, e.g. Boron-11 Neutrinos can excite nuclei and spall neutrons and protons creating new nuclei. Or, they can subtly change the “path” of nuclear flow by converting neutrons to protons (in nuclei or alone).

13 Supernova Neutrino Nucleosynthesis Some rare nuclei will be produced from neutrino induced spallation in the outer layers of the star Woosley et al 1990 e.g. Where does the 10B in the universe come from? The Neutrino Process in Supernovae or Cosmic Ray Spallation?

Neutrinos diffuse out the proto-neutron star core on a timescale of ∼10 seconds ν +12 C →10 B + n + p + ν in the Carbon shell And many other nuclei too - 11B, 19Fl, 138La, 180Ta

Figure by J. Brockman

14 The r-process - neutrino cross section connection

Scaled solar data No oscillations ν ↔ ν oscillations e s −2 − νe + n → p + e

−4 and + Log Abundance Log ν¯e + p → n + e −6 determine the number of neutrons

50 100 150 200 250 Atomic Weight Figure from Beun et al 2006 neutrino capture (and spallation, fission) on nuclei is important for the details of the pattern see work by Fuller, Haxton, Qian, Langanke, GM

15 Neutrino captures: the p-process and other rare nuclei:

92Mo,94Mo Zinc-64,Titanium-49, p-process from GRBs, Pruet et al 2003, Surman et al 2005 Scandium-45 Ways to make the p-process (1) Fine tune n/p (2) νe captures on nuclei Fuller and Meyer 1995, (3) late time νe captures on nucleons Frohilch et al, Pruet et al

16 The neutrino cross section - hydrodynamic connection All phases of massive star collapse and explosion are affected by weak interaction processes • timescale: how quickly energy is transported out of the core

• cooling: energy loss due to νs

• heating: energy gained below shock due to νs

• deleptonization: loss of lepton number due to νs

17 Electron capture is important for SN explosions

0.5

0.4 (Electron Fraction) (Electron e Y 0.3 The influence of − e + A → A + νe 0 on shock dynamics

2 Hix et al 2003 km/s) 4

4

Velocity (10 Velocity 6

Bruenn prescription LMP+hybrid rates 8 0 0.2 0.4 0.6 0.8 1 1.2 Enclosed Mass

18 Neutrino-nucleon scattering is crucial for predicting the supernova neutrino signal

45

40 11.2 M GR 1D O. Figure 35 Stand opacities Stand + Brem opacities 30 from Stand + (! + N) opacities ! 25 Stand + Brem + ( + N) opacities S. 20 Bruenn 15

10

5

0 0 0.5 1 1.5 2 2.5

t (s) post bounce

19 Coherent scattering: learning about neutron star structure

ν 15.00 e-N Scattering Events at SNS NL3 14.50 S271 5000 Z271s r 14.00 Z271v 4500 r+10% 13.50 r-10% 4000 13.00 ) [km] sun 12.50 3500

12.00

R(1.4 M R(1.4 3000

11.50 2500 11.00 Events/(10 keV year tonne) 2000 10.50 0.12 0.15 0.18 0.21 0.24 0.27 0.30 5 10 15 20 25 30 35 R −R (fm) n p Nucleus Recoil Energy (keV) Dependence of neutron star Dependence of coherent neutrino- radii on neutron skin of nuclei nuclear scattering on form factor

Horowitz & Piekarewicz 2001 Amanik & GM 2007

20 Measuring the Supernova Neutrino Signal What happens when the neutrinos come?

+ • water detector: ν¯e + p → n + e • heavy water detector (SNO): deuteron break-up in all channels 16 15 • νx + O → N + p + νx 16 15 νx + O → O + n + νx ′ • lead detector (OMNIS): A(νe, e)A and neutral current channels Signal (γs) in a Water Detector, Kolbe et al 2003 bump: from e+s, peak: decays from 150, 15N We can only interpret the signal as well as we understand the cross section. But there’s no cross section data!

Galactic SN ν detectors: SuperKamiokande, KamLAND, MiniBoone and more 21 Conclusions • Neutrino cross sections are needed in astrophysics • Low energy cross sections are relevant for supernovae, gamma ray bursts, neutron stars and other environments • inelastic processes are important for dynamics • and for nucleosynthesis • coherent scattering could reveal hints about neutron star stucture

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