KamLAND bounds on solar antineutrinos and neutrino transition magnetic moments

Abstract

We investigate the possibility of detecting solar electron antineutrinos with the KamLAND experiment. These electron antineutrinos are predicted by spin-flavor oscillations at a significant rate even if this mechanism is not the leading solution to the SNP.KamLAND is sensitive to antineutrinos originated from solar 8 B neutrinos. From KamLAND negative results after 145 days of data taking, we obtain model independent limits on the total flux of solar electron antineutrinos Φ( 8 B) < 1.1 − 3.5 × 10 4 cm −2 s −1 , more than one order of magnitude smaller than existing limits, and on their appearance probability P < 0.15% (95% CL).Assuming a concrete model for antineutrino production by spin-flavor precession, this upper bound implies an upper limit on the product of the intrinsic neutrino magnetic moment and the value of the solar magnetic field µB < 2.3 × 10 −21 MeV 95% CL (for LMA (∆m 2 , tan 2 θ) values).Limits on neutrino transition moments are also obtained. For realistic values of other astrophysical solar parameters these upper limits would imply that the neutrino magnetic moment is constrained to be, in the most conservative case, µ≤3.9 × 10 −12 µ B (95% CL) for a relatively small field B = 50 kG. For higher values of the magnetic field we obtain: µ≤9.0 × 10 −13 µ B for field B = 200 kG and µ≤2.0 × 10 −13 µ B for field B = 1000 kG at the same statistical significance.

A comprehensive study of neutrino spin-flavour conversion in supernovae and the neutrino mass hierarchy

“…However, the recent KamLAND experiment [10] has shown that the large mixing angle (LMA) MSW solution is the most favourable one; the RSF mechanism is suppressed at the subdominant level. From the KamLAND negative results for the solar antineutrino search, an upper bound on the neutrino magnetic moment is obtained, µ ν 1 × 10 −12 µ B , where µ B is the Bohr magneton [11]. This upper bound is comparable to the most stringent limit from the stellar cooling argument, µ ν (1-4)×10 −12 µ B [12].…”

Enhanced solar antineutrino flux in random magnetic fields

“…We show that, under reasonable assumptions, such bound is comparable to the best astrophysical limit that follows from stellar cooling arguments [18]. An alternative analysis of the KamLAND data [1] using the ''delta-correlated'' model for the solar random magnetic field was done in [19].…”

Supernova Neutrino Oscillations and the Neutrino Magnetic Moment

“…However, the recent KamLAND experiment [9] has shown that the large mixing angle (LMA) MSW solution is the most favourable one; the RSF mechanism is suppressed at the subdominant level. From the KamLAND negative results for the solar antineutrino search, an upper bound on the neutrino magnetic moment is obtained, µ ν 1 × 10 −12 µ B , where µ B is the Bohr magneton [10]. This upper bound is comparable to the most stringent limit from the stellar cooling argument, µ ν (1-4)×10 −12 µ B [11].…”