Search for axion-like particles using a variable baseline photon regeneration technique

TL;DR

GammeV tackles the search for axion-like particles with two-photon couplings in the milli-eV mass range using a photon-regeneration (light-shining-through-a-wall) approach. By employing a variable-baseline magnetic region and fast pulsed 532 nm laser with coincidence detection, it probes milli-eV ALP masses and covers the PVLAS region. No signal is observed, yielding stringent 3σ upper bounds: $g<3.1\times10^{-7}$ GeV$^{-1}$ for scalars and $g<3.5\times10^{-7}$ GeV$^{-1}$ for pseudoscalars in the $m_φ\to 0$ limit. These results exclude the PVLAS interpretation at more than 5σ and extend beyond previous BFRT limits in portions of parameter space, demonstrating the efficacy of a variable-baseline LSW setup.

Abstract

We report the first results of the GammeV experiment, a search for milli-eV mass particles with axion-like couplings to two photons. The search is performed using a "light shining through a wall" technique where incident photons oscillate into new weakly interacting particles that are able to pass through the wall and subsequently regenerate back into detectable photons. The oscillation baseline of the apparatus is variable, thus allowing probes of different values of particle mass. We find no excess of events above background and are able to constrain the two-photon couplings of possible new scalar (pseudoscalar) particles to be less than 3.1x10^{-7} GeV^{-1} (3.5x10^{-7} GeV^{-1}) in the limit of massless particles.

Figures (4)

• Figure 1: Diagram (not to scale) of the experimental apparatus. The initial vacuum chamber consists of a 10 m insulating warm bore which is offset by 1.6 m from the end of the 6 m magnetic field region, and is sealed to the sliding plunger via a double o-ring assembly. The sliding plunger has a range of motion of 1.9 m, and contains an independent vacuum chamber. The vacuum window at the far end slides within a stationary, long dark box.
• Figure 2: PMT trigger times for the four run configurations, shown relative to the expected time distribution of photons as calibrated from the leaky mirror data.
• Figure 3: 3$\sigma$ limit contours for scalar particles. The solid black line is the combined limit using data taken at both the central (red dot-dashed) and the edge (blue dashed) plunger positions. The PVLAS rotation signal (pink/dark grey) and the BFRT regeneration limit (tan/light grey) are also shown.
• Figure 4: 3$\sigma$ limit contours for pseudoscalar particles.