3D silicon pixel detectors for the CT-PPS tracking system

The measurement of central exclusive production will allow extending the LHC physics program in both the electroweak sector and in QCD, with unique sensitivity to physics beyond the Standard Model. To this purpose, the CMS-TOTEM Precision Proton Spectrometer (CT-PPS), with capability to operate in regular LHC high-luminosity conditions, has been recently installed. It consists of tracking and timing detectors located at $\simeq210$ m from the CMS interaction point on both sides, within movable structures called Roman pots that can go very close to the beam. Scattered protons emerging intact from the interaction with only a small fraction of their momentum lost are bent by the LHC magnets out of the beam envelope and measured by means of planes of silicon pixel detectors. The primary vertex determination, obtained using the timing information of the two protons on both arms, allows to strongly reduce the expected background due to the large number of pile-up events. Because of the high irradiation fluence ($\sim 3\times 10^{15}$ n$_{\text{eq}}/$cm$^2$) that the detectors will have to stand, 3D pixel sensors have been chosen for the CT-PPS tracker. Devices from the main 3D sensor producers (CNM, FBK e SINTEF) were measured in laboratory and on beam, before and after irradiation, in order to evaluate their characteristics and performances. CNM sensors, bump-bonded to the readout chips developed for the Phase I upgrade of the CMS pixel tracker, are used in the final detector. Two stations of six planes each have been assembled, tested and installed at the end of the 2016/2017 LHC winter shutdown. The commissioning of the detector is presently ongoing, making use of the DAQ software developed from that of the CMS central pixel tracker. The detector has been calibrated and is able to run within the CMS DAQ chain. Data of the first alignment run have been successfully collected and their analysis is in progress.