What low energy beta beams can tell about supernova physics
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What low-energy beta-beams can tell about supernova physics. N. Jachowicz, G.C. McLaughlin and C. Volpe Ghent University, Department of Subatomic and Radiation Physics, Proeftuinstraat 86, 9000 Gent, Belgium [email protected]

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What low energy beta beams can tell about supernova physics

What low-energy beta-beams can tell about supernova physics

N. Jachowicz, G.C. McLaughlin and C. Volpe

Ghent University, Department of Subatomic and Radiation Physics, Proeftuinstraat 86, 9000 Gent, Belgium

[email protected]


What low energy beta beams can tell about supernova physics1

In a type II supernova, a massive star at the end of its life

-undergoes gravitational collapse

- a shockwave develops

- travels outward, and the shock wave blows away the outer layers of the star

…. ?

Introduction

What low-energy beta beams can tell about supernova physics

Natalie JachowiczECT*, Trento, June 28 2007


weak interactions are important life

neutrinos are produced in the neutronization processes characterizing the gravitational collapse

neutrinos are responsible for the cooling of the proto-neutron star

neutrinos might reheat the stalled shock wave and cause a delayed explosion

What low-energy beta beams can tell about supernova physics

In the supernova process :

Observing the neutrinos from a future (Galactic) supernova explosion might learn a lot about the processes going on in the center of the star and the dynamics of the supernova im&explosion

H.-T. Janka astro-ph/0008432

Natalie JachowiczECT*, Trento, June 28 2007


Terrestrial detection of supernova neutrinos

What low-energy beta beams can tell about supernova physics life

Terrestrial detection of supernova neutrinos :

  • neutrinos are escaping from the center of the star

  • carrying away the largest part of the energy

  • Superkamiokande, SNO, OMNIS, LAND, LENA

  • Target material : e-, 16O, D, 56Fe, 208Pb, 12C

Neutrino-nucleus reactions provide an interesting detection mechanism :

SuperKamiokande

SNO

  • relatively large cross sections

  • thresholds in supernova-neutrino energy-region

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

Refs: N. Jachowicz, K. Vantournhout, J. Ryckebusch, K. Heyde, PRL 93, 082501 (2004) ; N. Jachowicz, K. Vantournhout, J. Ryckebusch, K. Heyde, PRC71, 034604 (2005).

From the signal in the detector, one can learn about :

  • arrival times

  • neutrino flavor

  • neutrinos vs antineutrinos

  • energy information

  • black hole formation

  • neutrino masses

  • charge-exchange vs neutral-current reactions

  • charge of the outgoing lepton in charged-current reactions

  • spin of the outgoing nucleon in neutral-current

  • nucleon-knockout reactions

  • threshold differences between different nuclei

  • 1 nucleon vs 2 nucleon knockout

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

208Pb

N.J. et al, PRC66, 065501 (2002) ;

E. Kolbe et al, PRC63, 025802 (2001) ;

J. Engel et al, PRD67, 013005 (2001)

The interpretation of the supernova signal can only be as good as the understanding of the

neutrino-nucleus reaction that occurs in the detector

  • little experimental data is available

    • very small cross sections

    • no monochromatic neutrino beams

Uncertainties :

  • one has to rely on theoretical predictions,

  • uncertainties induced by model dependence

Natalie JachowiczECT*, Trento, June 28 2007


Supernova neutrino spectra

What low-energy beta beams can tell about supernova physics life

Supernova neutrino spectra :

Experimentally :

Michel spectra :

Natalie JachowiczECT*, Trento, June 28 2007


Beta beam neutrino spectra

What low-energy beta beams can tell about supernova physics life

Beta-beam neutrino spectra :

18Ne

  • β-decay of a primary boosted nuclear beam generates intense neutrino beams,

  • with average energy and precise shape of the spectrum determined by the boost factor γ of the primary beam

  • First proposed to produce high energy neutrinos in oscillation experiments

  • (P.Zuchelli, Phys.Lett.B 532, 166 (2002).

  • At lower gamma factor, the neutrino energy becomes very suitable for neutrino-nucleus

  • scattering investigations

  • (C. Volpe, J.Phys. G30, 1 (2004).

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

Cross section as a function of the boost

factor γ of the beam

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

Procedure :

  • linear combinations of normalized beta-beam spectra :

  • fitting the constructed energy distribution to the supernova-neutrino spectrum by minimizing the expression,

  • varying the expansion parameters ai and the boost factors γi

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

Total folded cross sections :

  • 16O : CRPA calculation

  • deuteron : S. Nakamura, T. Sato, S. Ando et al.,

  • Nucl. Phys. A 707 (2002)

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

Differential folded cross section :

determines signal in the detector : energy transfer and excitation energy of the target nucleus indicate the decay products that will be observed in the detector

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

16O

… differential folded cross sections

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

2D

… differential folded cross sections

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

208Pb

… differential folded cross sections

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

16O

… differential folded cross sections –multipole contributions

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

This very satisfying agreement suggests that it is possible to reconstruct supernova-neutrino signal using the results of the beta-beam measurement without going through the intermediate step of using a nuclear structure calculation

  • For each set of beta-beam data at a given g, there will be a measured response in the detector

  • Taking appropriate linear combinations of the measured response provides a very accurate picture of the response of the detector to an incoming supernova-neutrino spectrum

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

Energy ‘resolution’

Width ‘resolution’

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

Reconstructing the supernova neutrino spectrum ?

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

Inversion of the method : reconstructing the supernova neutrino energy spectrum

Supernova neutrino signal in a terrestrial detector

Fit with linear combination of beta beam responses :

aγi, γi

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

?

Inversion of the method - test

Starting from a power-law supernova neutrino spectrum , we determine the best fit to this spectrum :

Adding noise to the expansion parameters mimicks the effect of various sources of uncertainties :

{

0.05

0.10

Noise : ai→ (1+ ) ai

We than check wich power law spectrum yields the best fit to

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

Inversion of the method – reconstruction in terms of average energy and width of the spectrum

curves : 90% confidence levels for spectra with

5 and 10 % uncertainty on the expansion parameters

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

… Neutrinos are oscillating !

Very schematically, the emitted supernova neutrino spectrum can be written as a combination of a ‘low’ energy and a ‘high’ energy component :

In a terrestrial detector, neutral current reactions are accessible for both components, the neutral current signal looks like :

In a terrestrial detector, only supernova electron neutrinos can produce a massive lepton, the charged current signal looks like :

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

In a first step the 2 combinations of beta-beam data that produce the best fit to the neutral current signal are determined :

are selected to minimize the difference between

and

In a second step these synthetic spectra are used to determine the oscillation parameters Rfit and Ifit that yield the best agreement with the charged current signal :

Rfit and Ifit are selected to minimize the difference between

and

Natalie JachowiczECT*, Trento, June 28 2007


What low-energy beta beams can tell about supernova physics life

… Neutrinos are oscillating : determining Rfit and Ifit

Natalie JachowiczECT*, Trento, June 28 2007


We take linear combinations of low-energy beta-beam spectra,

and fit those to supernova-neutrino energy-spectra , thus building ‘synthetic’ supernova spectra

the corresponding differential cross sections are in very good agreement

This technique can be inverted to reconstruct the parameters of the supernova neutrino spectrum

and learn about the oscillation characteristics of supernova neutrinos

The agreement is so good, we propose low-energy beta-beams as a ‘direct’ way to measure the nuclear response to a supernova neutrino signal and obtain information about the supernova neutrino spectrum and supernova neutrino oscillations

Conclusions

What low-energy beta beams can tell about supernova physics

Natalie JachowiczECT*, Trento, June 28 2007


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