No “Light Shining through a Wall”: Results from a Photoregeneration Experiment

Recently, axionlike particle search has received renewed interest. In particular, several groups have started “light shining through a wall” experiments based on magnetic field and laser both continuous, which is very demanding in terms of detector background. We present here the $2\sigma$ limits obtained so far with our novel setup consisting of a pulsed magnetic field and a pulsed laser. In particular, we have found that the axionlike particle two photons inverse coupling constant $M$ is $>8\times {10}^5\mathrm{GeV}$ provided that the particle mass $m_a\sim 1\mathrm{meV}$. Our results definitively invalidate the axion interpretation of the original PVLAS optical measurements with a confidence level greater than 99.9%.

Figure 1

Scheme of our experimental setup.

Figure 2

Magnetic field $B_0$ at the center of the magnet as a function of time. The maximum is reached within 1.75 ms and can be considered as constant ($\pm 0.3\%$) during ${\tau }_B=150\mu \mathrm{s}$. The 5 ns laser pulse is applied during this interval. Inset: temporal profile of the laser pulse.

Figure 3

Coincidence rate between the arrival of photons on the detector and its 5 ns detection gate as a function of an arbitrary delay time. The arrow indicates our working point, chosen in order to maximize the coincidence rate.

Figure 4

95% confidence level limits on the axionlike particle two photons inverse coupling constant $M$ as a function of the axionlike particle mass $m_a$ obtained thanks to our null result (dotted line). The area below our curve is excluded. Our limits are compared to the 95% confidence level exclusion region obtained by the BFRT photon regeneration experiment [10].