Matter from light-light scattering via Breit-Wheeler events produced by two interacting Compton sources

We present the dimensioning of a photon-photon collider based on Compton gamma sources for the observation of Breit-Wheeler pair production and QED $\gamma \gamma$ events. Two symmetric electron beams, generated by photocathodes and accelerated in linacs, produce two gamma ray beams through Compton back scattering with two J-class lasers. Tuning the system energy above the Breit-Wheeler cross section threshold, a flux of electron-positron pairs is generated out of light-light interaction. The process is analyzed by start-to-end simulations. Realistic numbers of the secondary particle yield, referring to existing state-of-the-art set-ups and a discussion of the feasibility of the experiment taking into account the background signal are presented.

Figure 1

Scheme of the BW interaction.

Figure 2

Differential cross section $d{\sigma }_{\mathrm{BW}}/d(\cos {\theta }_{3,4}^{\mathrm{CM}})$ averaged on the angle ${\varphi }_{3,4}^{\mathrm{CM}}$ for Breit-Wheeler scattering in the plane $(\sqrt{s},{\theta }_{3,4}^{\mathrm{CM}})$.

Figure 3

Total cross section in b for gamma gamma (${\sigma }_{\gamma \gamma }$, red line), Breit-Wheeler (${\sigma }_{\mathrm{BW}}$, blue line), TPP (${\sigma }_{\mathrm{TPP}}$, green line), Møller (${\sigma }_M$, orange line) and Compton (violet line) scatterings versus the energy in the center of mass $\sqrt{s}$ (in MeV) of each process. In blue, green, and orange the center of mass energy regions involved in the various processes for electron energy of about 260 MeV. The arrows mark the values of the cross-sections. The Møller cross-section has been evaluated with a cut at $|\cos \theta |<0.999$.

Figure 4

Spectrum of the radiation (a) and angular distribution (b). Similar colors code similar groups of photons.

Figure 5

Energy-angle BW pair distribution in the laboratory frame.

Figure 6

Energy (a) and angular (b) BW pair distribution.

Figure 7

Total number of BW (blue curve) and TPP events (red curve).