We propose new searches for axionlike particles (ALPs) produced in flavor-changing neutral current (FCNC) processes. This proposal exploits the often-overlooked coupling of ALPs to W^{±} bosons, leading to FCNC production of ALPs even in the absence of a direct coupling to fermions. Our proposed searches for resonant ALP production in decays such as B→K^{(*)}a, a→γγ, and K→πa, a→γγ could greatly improve upon the current sensitivity to ALP couplings to standard model particles. We also determine analogous constraints and discovery prospects for invisibly decaying ALPs.
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http://dx.doi.org/10.1103/PhysRevLett.118.111802 | DOI Listing |
Phys Rev Lett
December 2024
Northwestern University, Department of Physics and Astronomy, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
Heavy neutral leptons (HNLs) are often among the hypothetical ingredients behind nonzero neutrino masses. If sufficiently light, they can be produced and detected in fixed-target-like experiments. We show that if the HNLs belong to a richer-but rather generic-dark sector, their production mechanism can deviate dramatically from expectations associated with the standard-model weak interactions.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Departement de Physique Theorique, Universite de Geneve, 24 quai Ernest Ansermet, 1211 Geneve 4, Switzerland.
Phys Rev Lett
December 2024
Department of Physics, Kyungpook National University, Daegu 41566, Republic of Korea.
We give for the first time theoretical estimates of unknown rare electron-capture (EC) decay branchings of ^{44}Ti, ^{57}Co, and ^{139}Ce, relevant for searches of (exotic) dark-matter particles. The nuclear-structure calculations have been done exploiting the nuclear shell model with well-established Hamiltonians and an advanced theory of β decay. In the absence of experimental measurements of these rare branches, these estimates are of utmost importance for terrestrial searches of dark-matter particles, such as axionic dark matter in the form of axionlike particles, anapole dark matter, and dark photons in nuclear transitions.
View Article and Find Full Text PDFEur Phys J C Part Fields
November 2024
ETH Zürich, Institute for Particle Physics and Astrophysics, 8093 Zurich, Switzerland.
Phys Rev Lett
October 2024
CERN, Geneva, Switzerland.
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