Theoretical study of supernova relic neutrinos Kenichiro Nakazato - - PowerPoint PPT Presentation

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Theoretical study of supernova relic neutrinos Kenichiro Nakazato - - PowerPoint PPT Presentation

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Theoretical study of supernova relic neutrinos Kenichiro Nakazato Kyushu University Revealing the history of the universe with underground particle and nuclear research 2016, May 13, 2016 Outline 1. Introduction 2. What does SRN

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SLIDE 1

Theoretical study of supernova relic neutrinos

Ken’ichiro Nakazato

（Kyushu University）

Revealing the history of the universe with underground particle and nuclear research 2016, May 13, 2016

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SLIDE 2

Outline

  • 1. Introduction
  • 2. What does SRN spectrum

depend on?

involving metallicity evolution of galaxies （K. Nakazato et al. 2015, ApJ 804, 75）

  • 3. Comparison with noise BG
  • 4. Summary
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SLIDE 3

Outline

  • 1. Introduction
  • 2. What does SRN spectrum

depend on?

involving metallicity evolution of galaxies （K. Nakazato et al. 2015, ApJ 804, 75）

  • 3. Comparison with noise BG
  • 4. Summary
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SLIDE 4

History of Universe

  • The Universe is

expanding!

  • Cosmological redshift

z denotes ``time’’.

Big Bang

Many generations of stars have exploded!

Now

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SLIDE 5

Supernova neutrinos

  • Clue for puzzle in supernova physics.

SN1987A @ Kamiokande

Burrows （1988）

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SLIDE 6

Light curves and spectra

  • Neutrino emission continues for 10 seconds.

Fischer+ （2012） Nakazato+ （2013）

e e x （diffusion time scale）

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SLIDE 7

Supernova relic neutrinos

  • The flux of neutrinos

and antineutrinos emitted by all core- collapse supernovae in the causally- reachable universe.

  • Is it possible to study

something from supernova relic neutrinos?

time z = 0 z = 1 z = 2

We are here!

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SLIDE 8

Detection status

  • The upper limit is near theoretical predictions.
  • E. Mochida, master thesis
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SLIDE 9

Outline

  • 1. Introduction
  • 2. What does SRN spectrum

depend on?

involving metallicity evolution of galaxies （K. Nakazato et al. 2015, ApJ 804, 75）

  • 3. Comparison with noise BG
  • 4. Summary
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SLIDE 10

What determines BG luminosity?

  • luminosity of a source
  • the source number
  • distance to sources

– cosmological redshift for the expanding universe

  • Also neutrino oscillation parameters

star formation history

supernova relic neutrinos

→ supernova physics

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SLIDE 11

Formulation

  • Supernova neutrino spectrum:
  • Cosmological parameters
  • Initial mass function:

（Salpeter）

z dE E d    1

 

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SLIDE 12

Formulation

z dE E d    1

 

  • Core collapse rate:

cosmic star formation rate related to stellar mass distribution of galaxies SFR of galaxy stellar mass function

（Drory & Alvarez, 2008）

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SLIDE 13

Cosmic star formation rate

  • It has a peak at redshift

z ~ 1-2, but uncertainty is large. → conversion from UV luminosity to star formation rate of galaxy → dust obscuration correction

Note: Contribution from stars in z > 2 is small.

Observation of galaxies Hopkins & Beacom （2006） Drory & Alvarez （2008） Theoretical model Kobayashi et al. （2013）

Cosmic star formation rate [M☉ yr-1 Mpc-3]

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SLIDE 14

Formulation

z dE E d    1

 

  • Metallicity distribution function of progenitors

mass metallicity relation （Maiolino+, 2008） SFR of galaxy stellar mass function （Drory & Alvarez, 2008）

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SLIDE 15

Cosmic chemical evolution

  • Old stars are low metallicity.
  • Low metallicity stars have massive cores.

→ Failed supernova progenitors are included.

Big Bang H, He only galaxy formation, evolution supernovae metal increase Now 

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SLIDE 16

Fraction of failed supernovae

  • It increases with redshift because metal poor

stars are abundant in high redshift universe.

M Z 0.02 0.004 13M☉ SN SN 20M☉ SN SN 30M☉ SN BH 50M☉ SN SN

Nakazato+ （2015） Fraction of failed supernovae

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SLIDE 17

Spectra of SN relic neutrinos

  • Uncertainty is large in low energy region.
  • Reflecting large uncertainty of cosmic star

formation rate in high redshift universe

Flux [cm-2 s-1 MeV-1]

0.001

10 1 0.1

0.01

10 20 30 40 50

Neutrino Energy [MeV] Event [MeV-1(22.5kt yr) -1]

0.16 0.12 0.08 0.04

10 20 30 40 50

Positron Energy [MeV]

difference of SFR high low difference of SFR

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SLIDE 18

Spectra of SN relic neutrinos

  • Uncertainty is large in high energy region.
  • If the shock revival is late, proto-neutron star

is heated and neutrino spectrum gets hard.

0.001

10 1 0.1

0.01 0.12 0.08 0.04

10 20 30 40 50 10 20 30 40 50 300 ms 100 ms

late early difference of trevive

200 ms

difference of trevive

Flux [cm-2 s-1 MeV-1] Neutrino Energy [MeV] Event [MeV-1(22.5kt yr) -1] Positron Energy [MeV]

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SLIDE 19

Spectra of SN relic neutrinos

  • Uncertainty is large in high energy region.
  • If the EOS is hard, the black hole formation is

delayed and neutrino spectrum gets hard.

0.001

10 1 0.1

0.01 0.12 0.08 0.04

10 20 30 40 50 10 20 30 40 50

LS

（220 MeV）

soft difference of EOS Shen difference of EOS

Flux [cm-2 s-1 MeV-1] Neutrino Energy [MeV] Event [MeV-1(22.5kt yr) -1] Positron Energy [MeV]

hard

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SLIDE 20

Flux [cm-2 s-1 MeV-1]

0.001

10 1 0.1

0.01

10 20 30 40 50

Neutrino Energy [MeV]

  • Uncertainty on SRN spectrum in low energies

is mainly from cosmic star formation rate.

  • To investigate star formation history, low

energy is better and SK-Gd is promising.

10 20 30 40 50

Neutrino Energy [MeV]

0.001

10 1 0.1

0.01

cosmic SFR

Uncertainties on SRN spectrum

IMF & Mmin fixed. uncertainties

  • f others

from SFR high low max. min.

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SLIDE 21

Outline

  • 1. Introduction
  • 2. What does SRN spectrum

depend on?

involving metallicity evolution of galaxies （K. Nakazato et al. 2015, ApJ 804, 75）

  • 3. Comparison with noise BG
  • 4. Summary
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SLIDE 22

Formulation

  • Min. mass of SN progenitors: Mmin=8 or 10M☉
  • Initial mass function

z dE E d    1

 

Mmin 10M☉ 8M☉ Chabrier (2003); Baldry, & Glazebrook (2003, SalpeterA); Salpeter (1955)

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SLIDE 23
  • These uncertainties are energy-independent.
  • Uncertainty of IMF is largest at high energies,

and as large as that of SFR at low energies.

Uncertainties of Mminand IMF

difference of Mmin difference of IMF

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SLIDE 24

Comparison with noise BG

  • Detectability highly depends on uncertainties.
  • Reduction of atmospheric NC is important.
  • E. Mochida, master thesis

@ SK-Gd

atmospheric NC Ueno (2012) invisible  & atmospherice Abe et al. (2011)

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SLIDE 25

Outline

  • 1. Introduction
  • 2. What does SRN spectrum

depend on?

involving metallicity evolution of galaxies （K. Nakazato et al. 2015, ApJ 804, 75）

  • 3. Comparison with noise BG
  • 4. Summary
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SLIDE 26
  • Uncertainties
  • To investigate the star formation history, low

energy is better and SK-Gd is promising, but reduction of atmospheric NC is important.

Summary

low energy high energy SFR large middle trevive small middle EOS（BH） small middle IMF large large Mmin middle middle