Pair-Production in the Non-Perturbative Regime at CALA

One of the fundamental processes yet to be experimentally verified in modern physics involves the creation of electron-positron pairs through the interaction of a strong field with the quantum vacuum. Generating such pairs from the vacuum necessitates fields with intensities over the Schwinger critical field value of 1.3 × 10$^{18}$ V/m [1].
An experimental setup at the Centre of Advanced Laser Applications (CALA) has been proposed to investigate pair creation through the nonlinear Breit-Wheeler process [2]. In this experiment, bremsstrahlung γ-photons are generated by a monoenergetic 2.5 GeV plasmaaccelerated electron beam with a charge of 10 pC interacting with a 50 μm thick tungsten target.
These γ-photons collide with a high-intensity laser beam with an intensity of approximately 9.5 × 10$^{21}$ W/cm² (a$_{0}$ = 66), resulting in the production of around 80 pairs/hour at the design point of the experiment. To detect the few pairs generated, a single-particle detection system comprising tracking layers composed of LYSO:Ce scintillating screens and a Cherenkov
calorimeter has been designed [3].
In this talk, we provide an overview of the experimental planning and its current status. Additionally, we will present a preliminary report on our initial background noise measurements, along with the first detection of Bethe-Heitler pairs used for calibrating the Cherenkov calorimeter.

[1] V. I. Ritus, J. Sov. Laser Res. 6, 5 (1985)
[2] F. C . Salgado et al, New J. Phys. 23, 105002 (2021).
[3] F. C. Salgado et al, New J. Phys. 24, 015002 (2022).