Davide Zuolo

Results of an extensive R&D program aiming at radiation hard, small pitch, 3D pixel sensors are reported. The CMS experiment is supporting this R&D in the scope of the Inner Tracker upgrade for the High Luminosity phase of the CERN Large Hadron Collider (HL-LHC). In the HL-LHC the Inner Tracker will have to withstand an integrated fluence up to 2.3×1016neq/cm2. A small number of 3D sensors were interconnected with the RD53A readout chip, which is the first prototype of 65 nm CMOS pixel readout chip designed for the HL-LHC pixel trackers. In this paper results obtained in beam tests before and after irradiation are reported. The irradiation of a single chip module was performed up to a maximum equivalent fluence of about 1×1016neq/cm2. The analysis of the collected data shows excellent performance: the spatial resolution in not irradiated sensors can reach about 3 to 5 μm, for inclined tracks, depending on the pixel pitch. The measured hit detection efficiencies are close to 99% measured both before and after the above mentioned irradiation fluence.

Test beam results obtained with 3D pixel sensors bump-bonded to the RD53A prototype readout ASIC are reported. Sensors from FBK Italy and IMB-CNM (Spain) have been tested before and after proton-irradiation to an equivalent fluence of about 1 × 1016 ≠cm-2 (1 MeV equivalent neutrons). This is the first time that one single collecting electrode fine pitch 3D sensors are irradiated up to such fluence bump-bonded to a fine pitch ASIC. The preliminary analysis of the collected data shows no degradation on the hit detection efficiencies of the tested sensors after high energy proton irradiation, demonstrating the excellent radiation tolerance of the 3D pixel sensors. Thus, they will be excellent candidates for the extreme radiation environment at the innermost layers of the HL-LHC experiments.

Results obtained with 3D columnar pixel sensors bump-bonded to the RD53A prototype readout chip are reported. The interconnected modules have been tested in a hadron beam before and after irradiation to a fluence of about 1×1016 neq cm−2 (1 MeV equivalent neutrons). All presented results are part of the CMS R&D activities in view of the pixel detector upgrade for the High Luminosity phase of the LHC at CERN (HL-LHC) . A preliminary analysis of the collected data shows hit detection efficiencies around 97% measured after proton irradiation.

Due to the large expected instantaneous luminosity, the future HL-LHC upgrade sets strong requirements on the radiation hardness of the CMS detector Inner Tracker. Sensors based on 3D pixel technology, with its superior radiation tolerance, comply with these extreme conditions. A full study and characterization of pixelated 3D sensors fabricated by FBK is presented here. The sensors were bump-bonded to RD53A readout chips and measured at several CERN SPS test beams. Results on charge collection and efficiency, for both non-irradiated and irradiated up to 1016 neq/cm2 samples, are presented. Two main studies are described: in the first the behaviour of the sensor is qualified as a function of irradiation, while kept under identical conditions; in the second the response is measured under typical operating conditions.

The High Luminosity upgrade of the CERN Large Hadron Collider (HL-LHC) calls for new high radiation-tolerant solid-state pixel sensors, capable of surviving irradiation fluences up to a few 1016 neq/cm2 at ∼3 cm from the interaction point. The INFN ATLAS-CMS joint research activity, in collaboration with Fondazione Bruno Kessler, is aiming at the development of thin n+ on p type pixel sensors to be operated at the HL-LHC. The R&D covers both planar and 3D pixel devices made on substrates obtained by the Direct Wafer Bonding technique. The active thickness of the planar sensors studied in this paper is 100μm or 130μm, that of 3D sensors 130μm. First prototypes of hybrid modules, bump-bonded to the present CMS readout chips (PSI46 digital), have been characterized in beam tests. First results on their performance before and after irradiation up to a maximum fluence of ∼5×1015 neq/cm2 are reported in this article.

The High Luminosity upgrade of the CERN Large Hadron Collider (HL–LHC) calls for an upgrade of the CMS tracker detector to cope with the increased radiation levels while maintaining the excellent performance of the existing detector. Specifically, new high-radiation tolerant solid-state pixel sensors, capable of surviving irradiation fluences up to 1.9×1016neq/cm2 at 3 cm from the interaction point, need to be developed. For this purpose an R&D program involving different vendors have been pursued, aiming at the development of thin n-in-p type pixel sensors. The R&D covers both planar (manufactured by Fondazione Bruno Kessler, FBK; Hamamatsu Photonics, HPK and LFoundry) and single-sided 3D columnar (manufactured by FBK and Centro Nacional de Microelectronica, CNM) pixel devices. The target active thickness is 150μm while two different pixel cell dimensions are currently investigated (25 × 100 and 50×50μm2). Sensors presented in this article have been bump-bonded to the RD53A readout chip (ROC), the first prototype towards the development of a ROC to be employed during HL–LHC operation. Test beam studies, both of thin planar and 3D devices, have been performed by the CMS collaboration at the CERN, DESY and Fermilab test beam facilities. Results of modules performance before and after irradiation (up to 2.4×1016neq/cm2) are presented in this article.

This paper reports on the INFN (Istituto Nazionale di Fisica Nucleare, Italy) research activity in collaboration with FBK foundry, which is aiming at the development of new pixel detectors for the LHC Phase-2 upgrades. The R&D covers both planar pixel devices and 3D detectors built using columnar technology. All sensors are low thickness n-in-p type, as this is the general direction envisaged for the High Luminosity LHC pixel detector upgrades. Hybrid modules with 100 $$\upmu $$ m and 130 $$\upmu $$ m active thickness, connected to the PSI46dig readout chip, have been tested on beam test experiments. Selected preliminary results from test beams are described for both planar and 3D devices. The results on the 3D pixel sensors before irradiation are very satisfactory and support the conclusion that columnar devices are very good candidates for the inner layers of the upgrade pixel detectors.

This paper describes the development of new 3D and planar silicon pixel sensors designed for the Compact Muon Solenoid (CMS) Phase-2 Upgrade at High Luminosity LHC (HL-LHC).The project is funded by INFN and sensors are produced in collaboration with the FBK foundry.The HL-LHC will operate at an instantaneous luminosity approximately 5 times larger than the original LHC design, significantly increasing the number of concurrent collisions per bunch crossing, the integrated luminosity delivered to the experiments and, as a consequence, the radiation dose that the detectors will have to sustain.In order to cope with these future conditions, upgrades to the detectors are required.This is necessary for the pixel tracker that is the closest to the interaction point and will be replaced.In this paper, the results, from beam tests performed at Fermilab Test Beam Facility, of thin (100 µm and 130 µm thick) n-in-p type sensors, assembled into hybrid single chip modules bump bonded to the PSI46dig readout chip, will be presented.A comparison of the performances obtained with planar sensors before and after proton irradiation up to 3 × 10 15 n eq /cm 2 will be also discussed.The paper will also report the results obtained with the first 3D pixel sensors 130 µm thick with columnar electrodes for different pixel cell prototypes.The novelty of the 3D prototypes is their small pixel cell size, ranging form the standard 100 µm × 150 µm, down to 50 µm × 50 µm and 25 µm × 100 µm, which are the preferred dimensions in the high pile-up environment of the HL-LHC.

The High Luminosity upgrade of the CERN Large Hadron Collider (HL-LHC) calls for new highly radiation tolerant silicon pixel sensors, capable of withstanding fluences up to 2.3 × 1016 neq/cm2 (1 MeV equivalent neutrons). In this paper results obtained in beam test experiments with 3D and planar pixel sensors interconnected with the RD53A readout chip are reported. RD53A is the first prototype in 65 nm technology issued by the RD53 collaboration for the future readout chip to be used in the upgraded pixel detectors. The interconnected modules have been tested in an electron beam at DESY, before and after irradiation, which was performed at the CERN IRRAD facility for the 3D sensors or at the KIT Irradiation Center for the planar sensors, up to an equivalent fluence of 1 × 1016 neq/cm2. The sensors were made by FBK foundry in Trento, Italy, and their development was done in collaboration with INFN (Istituto Nazionale di Fisica Nucleare, Italy). The analysis of the collected data shows hit detection efficiencies around 99% measured after irradiation. All results are obtained in the framework of the CMS R&D activities.

The High Luminosity upgrade of the CERN-LHC (HL-LHC) demands for a new high-radiation tolerant solid- state pixel sensor capable of surviving fluencies up to a few 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> particles cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at ∼3 cm from the interaction point. To this extent the INFN ATLAS-CMS joint research activity, in collaboration with Fondazione Bruno Kessler, is aiming at the development of thin n-in-p type pixel sensors for the HL-LHC. The R & D covers both planar and single-sided 3D columnar pixel devices made with the Si-Si Direct Wafer Bonding technique, which allows for the production of sensors with 100µm and 130µm active thickness for planar sensors, and 130µm for 3D sensors, the thinnest ones ever produced so far. First prototypes of hybrid modules bump-bonded to the present CMS readout chips have been tested in beam tests. Preliminary results on their performance before and after irradiation are presented.

A search for the non-resonant production of Higgs boson pairs (HH) via the gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two tau leptons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13~\mathrm{TeV}$ recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of $138~\mathrm{fb}^{-1}$. Events in which at least one tau lepton decays hadronically are considered and multiple machine learning techniques are used to identify and extract the signal. The data are found to be consistent, within uncertainties, with the standard model (SM) background predictions. Upper limits on the HH production cross section and constraints on anomalous Higgs boson couplings are set. The observed (expected) upper limit at 95% confidence level corresponds to 3.3 (5.2) times the SM prediction for the inclusive HH cross section and to 124 (154) times the SM prediction for the vector boson fusion HH cross section. At a 95% confidence level, the Higgs field self-coupling is constrained to be within -1.8 and 8.8 times the standard model expectation, and the coupling of two Higgs bosons to two vector bosons is constrained to be within -0.4 and 2.6.

The High Luminosity upgrade of the CERN LHC collider (HL-LHC) demands for a new, highradiation tolerant solid-state pixel sensor capable of surviving fluencies up to a few 10 16 n eq /cm 2 at ∼ 3 cm from the interaction point.To this extent the INFN ATLAS-CMS joint research activity, in collaboration with Fondazione Bruno Kessler (FBK), is aiming at the development of thin n-in-p type pixel sensors for the HL-LHC.The R&D covers both planar and single-sided 3D columnar pixel devices made with the Si-Si Direct Wafer Bonding technique, which allows for the production of sensors with 100 µm and 130 µm active thickness for planar sensors, and 130 µm for 3D sensors, the thinnest ones ever produced so far.Prototypes of hybrid modules, bumpbonded to the RD53A readout chip, have been tested on beam.First results on their performance before and after irradiation are presented.