A search for a cosmologically-relevant boson in muon decay

Abstract

Experiments looking for a lepton flavor-violating decay µ + → e + X 0 are reviewed in light of presentday germanium detector technology, with an eye on scenarios where a long-lived, slow-moving massive boson X 0 might have a cosmological impact. A broad swath of interesting, unexplored parameter space very close to the kinematic limit of the decay is found to be within the reach of a new proposed search. A number of possible roles for X 0 in past and present epochs can be investigated.

Germanium response to sub-keV nuclear recoils: a multipronged experimental characterization

“…8 inset). No measurable energy drift was observed over the two days of data-taking: all twelve calibration points are used for the linear fit in the figure . During data analysis, events in coincidence and in anticoincidence with the neutron capture signal from the backing detector were inspected using an edge-finding algorithm, illustrated using this same LEGe detector in [19]. It is able to identify the rising edge characteristic of radiation-induced pulses in preamplifier traces, while rejecting low-energy noise nuisances.…”

“…Low-noise p-type point contact (PPC) detectors [9] can register the ionization from sub-keV energy depositions in large (>1 kg) germanium crystals. As a result of this and other virtues, PPCs are presently used in searches for neutrinoless double-beta decay [10][11][12], WIMPs [13,14], CEνNS [15][16][17][18], and exotic modes of particle decay [19]. This work concentrates on the characterization of the QF * collar@uchicago.edu for ionization-sensitive germanium detectors in the sub-keV nr NR energy region.…”