4th dimensional tracking: the GigaTracker of NA62 experiment.

The GigaTracker is a lightweight hybrid silicon pixel detector built for the NA62 experiment at CERN, which aims at measuring the branching fraction of the ultra-rare kaon decay $K^+\rightarrow \pi^+\nu\bar{\nu}$ at the CERN SPS. The detector tracks charged particles in a 75 GeV/$c$ hadron beam with a flux reaching 1.3 MHz/mm$^2$. It consists of three stations, 61$\times$27 mm$^2$ each, which provide single-hit timing with 130 ps resolution. Each station is composed of a 200 $\mu$m thick planar silicon sensor, segmented in 300$\times$300 $\mu$m$^2$ pixels, bump-bonded to 2$\times$5 custom 100 $\mu$m thick ASIC, called TDCPix. Each TDCPix contains 40$\times$45 asynchronous pixels, and is instrumented with 360 pairs of time-to-digital converter channels with 100 ps bin. The three stations are installed in vacuum (about 10$^{-6}$ mbar) and cooled with liquid $\mathrm{C_6F_{14}}$ circulating through micro-channels etched inside silicon plates a few hundred microns thick. The total material budget is less than 0.5% $X_0$ per station. Detector description, operational experience and performance from the NA62 experimental run in 2016, at about 30% the nominal beam intensity, will be presented.