Improved constraints on monopole–dipole interaction mediated by pseudo-scalar bosons

• DOI: 10.1016/j.physletb.2017.09.019
• Publication Date: 2017-09-12T15:16:58Z
• Authors: N. Crescini; C. Braggio; G. Carugno; P. Falferi; A. Ortolan; G. Ruoso
• Keywords: Axions; Physics; QC1-999; FOS: Physical sciences; 01 natural sciences; High Energy Physics - Experiment; Long-range interactions; High Energy Physics - Phenomenology; High Energy Physics - Experiment (hep-ex); CP violation; High Energy Physics - Phenomenology (hep-ph); 0103 physical sciences; Spin-dependent interactions; Axion-like particles

13 pages, 6 figures, Physics Letters B, 2017<br/>We present a more stringent upper limit on long-range axion-mediated forces obtained by the QUAX-g$_p$g$_s$ experiment, located at the INFN - Laboratori Nazionali di Legnaro. We investigate the possible coupling between the electron spins of a paramagnetic GSO crystal and unpolarized nucleons of lead disks by measuring variations of GSO magnetization with a dc-SQUID magnetometer. Such an induced magnetization can be interpreted as the effect of a long-range spin dependent interaction mediated by axions or Axion Like Particles (ALPs). The corresponding coupling strength is proportional to the CP violating term $g_p^eg_s^N$, i.e. the product of the pseudoscalar and scalar coupling constants of electron and nucleon, respectively. Previous upper limits are improved by one order of magnitude, namely $g_p^eg_s^N/(\hbar c) \le 4.3\times10^{-30}$ at 95% confidence level, in the interaction range $10^{-3}$ m $<br/>