TY - JOUR

T1 - Neutrinos from SN1987A

T2 - Flavor conversion and interpretation of results

AU - Lunardini, Cecilia

AU - Smirnov, Alexei Yu

N1 - Funding Information:
C.L. acknowledges support from the Keck fellowship at IAS and the NSF grant PHY-0070928. She would like to thank C. Pena-Garay and L. Sorbo for useful discussions.

PY - 2004/9

Y1 - 2004/9

N2 - After recent results from solar neutrino experiments and KamLAND we can definitely say that neutrinos from SN1987A underwent flavor conversion, and the conversion effects must be taken into account in the analysis of the data. Assuming the normal mass hierarchy of neutrinos we calculate the permutation factors p for the Kamiokande-2, IMB and Baksan detectors. The conversion inside the star leads to p=0.28-0.32; the oscillations in the matter of the Earth give partial (and different for different detectors) regeneration of the original ν̄e signal, reducing this factor down to 0.15-0.20 (at E=40 MeV). We study in details the influence of conversion on the observed signal depending on the parameters of the original neutrino spectra. For a given set of these parameters, the conversion could lead to an increase of the average energy of the observed events up to 50% and of the number of events by a factor of 2 at Kamiokande-2 and by a factor of 3-5 at IMB. Inversely, we find that neglecting the conversion effects can lead up to 50% error in the determination of the average energy of the original ν̄e spectrum and about 50% error in the original luminosity. Comparing our calculations with experimental data we conclude that the Kamiokande-2 data alone do not favor strong conversion effect, which testifies for small difference of the original ν̄e and ν̄μ spectra. In contrast, the combined analysis of the Kamiokande and IMB results slightly favors strong conversion effects (that is, large difference of the original spectra). In comparison with the no-oscillation case, the latter requires lower average energy and higher luminosity of the original ν̄e flux.

AB - After recent results from solar neutrino experiments and KamLAND we can definitely say that neutrinos from SN1987A underwent flavor conversion, and the conversion effects must be taken into account in the analysis of the data. Assuming the normal mass hierarchy of neutrinos we calculate the permutation factors p for the Kamiokande-2, IMB and Baksan detectors. The conversion inside the star leads to p=0.28-0.32; the oscillations in the matter of the Earth give partial (and different for different detectors) regeneration of the original ν̄e signal, reducing this factor down to 0.15-0.20 (at E=40 MeV). We study in details the influence of conversion on the observed signal depending on the parameters of the original neutrino spectra. For a given set of these parameters, the conversion could lead to an increase of the average energy of the observed events up to 50% and of the number of events by a factor of 2 at Kamiokande-2 and by a factor of 3-5 at IMB. Inversely, we find that neglecting the conversion effects can lead up to 50% error in the determination of the average energy of the original ν̄e spectrum and about 50% error in the original luminosity. Comparing our calculations with experimental data we conclude that the Kamiokande-2 data alone do not favor strong conversion effect, which testifies for small difference of the original ν̄e and ν̄μ spectra. In contrast, the combined analysis of the Kamiokande and IMB results slightly favors strong conversion effects (that is, large difference of the original spectra). In comparison with the no-oscillation case, the latter requires lower average energy and higher luminosity of the original ν̄e flux.

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U2 - 10.1016/j.astropartphys.2004.05.005

DO - 10.1016/j.astropartphys.2004.05.005

M3 - Article

AN - SCOPUS:4544332139

VL - 21

SP - 703

EP - 720

JO - Astroparticle Physics

JF - Astroparticle Physics

SN - 0927-6505

IS - 6

ER -