Enhanced Sensitivities for the Searches of Neutrino Magnetic Moments through Atomic Ionization

Abstract

A new detection channel on atomic ionization for possible neutrino electromagnetic interactions is identified and studied. Significant sensitivity enhancement is demonstrated when the energy transfer to the target is of the atomic-transition scale. The interaction cross section induced by neutrino magnetic moments () is evaluated with the equivalent photon method. A new limit of ð " e Þ < 1:3 Â 10 À11 B at 90% confidence level is derived by using current reactor neutrino data. Potential reaches for future experiments are explored. Experiments with sub-keV sensitivities can probe to 10 À13 B. Positive observations of in this range would imply that neutrinos are Majorana particles.

Experiment GEMMA: Search for the Neutrino Magnetic Moment

“…3) and comparing the ON spectrum channel by channel with the obtained background curve, we extract their normalized difference X ≡ ON−OFF−Weak Electromagnetic which actually repre-GEMMA V. Egorov sents the NMM value squared (in terms of 10 −11 µ B ). Averaging over the total ROI and adding the data of the Phase-I, we get at the 90%CL the following upper limit: µ ν ≤ 3.2 × 10 −11 µ B , which could be an order of magnitude lower if the Atomic Ionization Enhancement [7] really exists (in this case our analysis gives the limit as low as µ ν ≤ 0.5 × 10 −11 µ B ). …”

Theory of Neutrino-Atom Collisions: The History, Present Status, and BSM Physics

“…3, one might expect the atomic-binding effects to play a subsidiary role when E ν ≫ ε b . The authors of [44], however, came to the contrary conclusion that the single-differential cross section dramatically enhances due to atomic ionization when T ∼ ε b . The enhancement mechanism proposed in [44] is based on an analogy with the photoionization process.…”

Constraining neutrino electromagnetic properties by germanium detectors

“…EPA: It was first claimed in Ref. [3] that atomic structure can greatly enhance the sensitivity to κ (eff) ν by orders of magnitude than the FEA prediction in the T < 1 keV region for germanium. However, later works inspired by this, using various approaches, all came to the opposite conclusion [17,[22][23][24].…”

“…The germanium detectors, with their excellent energy resolution and sub-keV threshold, are ideal as means of studying these effects. The experimental features as peaks or edges at the definite K-and L-X-rays energies as well as with predictable intensity ratios provide potential smoking-gun signatures of these effects [3,4].…”

“…The purpose of this article is twofold: On the theory part, we present our approach in full details, elaborate in particular the benchmark calculations that serve as a concrete basis on which the method and uncertainty estimate can be justified, and consider all observables that can be probed by atomic ionization. Comparisons with previous works [3,[18][19][20][21][22][23][24] are given so that differences in various approaches and the applicability of various approximation schemes at the sub-keV regime can be clearly examined.…”