The GigaTracKer (GTK) is the beam spectrometer of the CERN NA62 experiment. The detector features challenging design specifications, in particular a peak particle flux reaching up to 2.0 MHz/mm2, a single hit time resolution smaller than 200 ps and, a material budget of 0.5% X0 per tracking plane. To fulfil these specifications, novel technologies were especially employed in the domain of silicon hybrid time-stamping pixel technology and micro-channel cooling. This article describes the detector design and reports on the achieved performance.

$K^{+}\rightarrow\pi^{+}\nu\overline{\nu}$ is one of the theoretically cleanest meson decay where to look for indirect effects of new physics complementary to LHC searches. The NA62 experiment at CERN SPS is designed to measure the branching ratio of this decay with 10\% precision. NA62 took data in pilot runs in 2014 and 2015 reaching the final designed beam intensity. The quality of 2015 data acquired, in view of the final measurement, will be presented.

$K^{+}\rightarrow\pi^{+}\nu\overline{\nu}$ is one of the theoretically cleanest meson decay where to look for indirect effects of new physics complementary to LHC searches. The NA62 experiment at CERN SPS is designed to measure the branching ratio of this decay with 10\% precision. NA62 took data in pilot runs in 2014 and 2015 reaching the final designed beam intensity. The quality of 2015 data acquired, in view of the final measurement, will be presented.

K+ → π+v⊽ is one of the theoretically cleanest meson decay where to look for indirect effects of new physics complementary to LHC searches. The NA62 experiment at the CERN SPS is designed to measure the branching ratio of this decay with 10% precision. NA62 took data in pilot runs in 2014 and 2015 reaching the final designed beam intensity. The quality of data acquired in view of the final measurement will be presented.

In 2007 the NA62 experiment at CERN collected a large sample of charged kaon decays with a highly efficient trigger selecting events with electrons in the final state. The kaon beam represents a rich source of tagged neutral pion decays in vacuum. The electromagnetic transition form factor slope of the π0 in the time-like region has been measured from about 106 fully reconstructed π0 Dalitz decays collected in 2007. The preliminary result a = (3.68 ± 0.51stat ± 0.25syst) × 10-2 is the most precise to date. This value is compatible with theoretical expectations and consistent with the previous measurements.

The K+ -> pi(+)nu(nu) over bar branching ratio is one of the key observables to test the Standard Model. The NA62 experiment has been designed to measure this branching ratio with a 10% precision. Most of the experiment systems have been commissioned during 2014 and 2015 runs and physics data have been recorded. The analysis of this data shows performances close to the nominal ones.

Recent results and prospects for precision tests of the Standard Model in kaon decay-in-flight experiments at CERN are presented. A measurement of the ratio of leptonic decay rates of the charged kaon at the level of 0.4% precision constrains the parameter space of new physics models with extended Higgs sector, a fourth generation of quarks and leptons or sterile neutrinos. Searches for heavy neutrino mass states and the dark photon in the ∼ 100 MeV/c2 mass range based on samples collected in 2003-2007 are in progress and prospects will be discussed. The NA62 experiment, starting in 2014, will search for a range of lepton number and lepton flavour violating decays of the charged kaon and the neutral pion at improved sensitivities down to ∼ 10-12, which will probe new physics scenarios involving heavy Majorana neutrinos or R-parity violating SUSY.

The rare decays K+ -> pi(+)nu(nu) over bar are excellent processes to probe the Standard Model and indirectly search for new physics complementary to the direct LHC searches. The NA62 experiment at CERN SPS aims to collect and analyse O (10(13)) kaon decays before the CERN long-shutdown 2 (in 2018). This will allow to measure the K+ -> pi(+)nu(nu) over bar branching ratio to a level of 10% accuracy. The experimental apparatus has been commissioned during a first run in autumn 2014.

In the last years the Detector Technology group (PH-DT) [1] of the CERN Physics Department in Geneva, Switzerland, has started the study of novel micro-fluidic cooling systems obtained through standard micro-fabrication processes that outperform traditional cooling approaches for the thermal management of silicon particle detectors. The fabrication of the cooling devices starts with the etching of the microchannels in a silicon wafer; the channels are then closed with another silicon wafer through a direct bonding process. The devices are then interfaced to the front-end electronics of the detector via a thin adhesive layer. Silicon cooling devices with thickness of the order of few hundred microns guarantee the desired minimization of material in front of the tracking sensors and eliminate mechanical stresses due to the mismatch of Coefficient of Thermal Expansion (CTE) between the sensor and its related electronics. Combining the versatility of standard micro-fabrication processes with the high thermal efficiency typical of micro-fluidics, it is possible to produce effective thermal management devices that are well adapted to very different detector configurations.

The Gigatracker (GTK) is a hybrid silicon pixel detector developed for NA62, the experiment aimed at studying ultra-rare kaon decays at the CERN SPS. Three GTK stations will provide precise momentum and angular measurements on every track of the high intensity NA62 hadron beam with a time-tagging resolution of 150 ps. Multiple scattering and hadronic interactions of beam particles in the GTK have to be minimized to keep background events at acceptable levels, hence the total material budget is fixed to 0.5% X0 per station. In addition the calculated fluence for 100 days of running is 2×1014 1 MeV neq/cm2, comparable to the one expected for the inner trackers of LHC detectors in 10 years of operation. These requirements pose challenges for the development of an efficient and low-mass cooling system, to be operated in vacuum, and on the thinning of read-out chips to 100μm or less. The most challenging requirement is represented by the time resolution, which can be achieved by carefully compensating for the discriminator time-walk. For this purpose, two complementary read-out architectures have been designed and produced as small-scale prototypes: the first is based on the use of a Time-over-Threshold circuit followed by a TDC shared by a group of pixels, while the other uses a constant-fraction discriminator followed by an on-pixel TDC. The readout pixel ASICs are produced in 130nm IBM CMOS technology and bump-bonded to 200μm thick silicon sensors. The Gigatracker detector system is described with particular emphasis on recent experimental results obtained from laboratory and beam tests of prototype bump-bonded assemblies, which show a time resolution of less than 200 ps for single hits.

Micro-channel cooling is gaining considerable attention as an alternative technique for cooling of high energy physics detectors. This is of particular interest for future trackers, where large surfaces are involved and the amount of material must be drastically reduced. Combining the flexibility of standard micro-fabrication processes with the high thermal efficiency typical of micro-fluidics, it is possible to produce effective thermal management devices well adapted to different specific applications. The first case presented is the NA62 GTK silicon pixel detector, where low temperature liquid fluid will be circulated in a micro-fabricated silicon plate locally thinned to 130 mu m in the detector sensitive area. Other applications are presently being developed for evaporative cooling in the context of the ALICE and LHCb detector upgrades at LHC. In the former case the devices are being optimized for low pressure/room temperature evaporation; in the latter for high pressure and temperature below 0 degrees C.

The Gigatracker (GTK) is a hybrid silicon pixel detector developed for NA62, an experiment studying ultra-rare kaon decays at the CERN SPS. The main characteristics are a time-tagging resoluion of 150ps, with low material budget per station (0.5% X-0) and a fluence comparable to the one expected for the inner trackers of LHC detectors in 10 years of operation. To compensate the time-walk, two read-out architectures have been designed and produced. The first architecture is based on a Constant Fraction Discriminator (CFD) followed by an on-pixel Time-to- Digital-Converter (TDC). The second architecture is based on a on-pixel group shared TDC. The GTK system developments are described: the integration steps (assembly and cooling) and the results obtained from the prototypes fabricated for the two read-out architectures.

Micro-channel cooling is gaining considerable attention as an alternative technique for cooling of high energy physics detectors and front-end electronics. This technology is being evaluated for future tracking devices, where material budget limitations are a major concern. It is currently under investigation as an option for the cooling of the NA62 Gigatracker silicon pixel detector, where a micro-fabricated silicon cooling plate would stand directly in the beam. Other possible applications are also being studied in the context of LHC detectors upgrades. In this paper, the current status of this R&D at CERN is presented.

The Gigatracker (GTK) is a hybrid silicon pixel detector designed for the NA62 experiment at CERN. The beam spectrometer, made of three GTK stations, has to sustain high and non-uniform particle rate (∼1GHz in total) and measure momentum and angles of each beam track with a combined time resolution of 150ps. In order to reduce multiple scattering and hadronic interactions of beam particles, the material budget of a single GTK station has been fixed to 0.5% X0. The expected fluence for 100 days of running is 2×1014 1MeVneq/cm2, comparable to the one foreseen in the inner trackers of LHC detectors during 10 years of operation. To comply with these requirements, an efficient and very low-mass (<0.15%X0) cooling system is being constructed, using a novel microchannel cooling silicon plate. Two complementary read-out architectures have been produced as small-scale prototypes: one is based on a Time-over-Threshold circuit followed by a TDC shared by a group of pixels, while the other makes use of a constant-fraction discriminator followed by an on-pixel TDC. The read-out ASICs are produced in 130nm IBM CMOS technology and will be thinned down to 100μm or less. An overview of the Gigatracker detector system will be presented. Experimental results from laboratory and beam tests of prototype bump-bonded assemblies will be described as well. These results show a time resolution of about 170ps for single hits from minimum ionizing particles, using 200μm thick silicon sensors.

Novel cooling systems with very low material budget are being fabricated and studied. They consist of silicon wafers in which microchannels are etched and closed by bonding another wafer. This cooling option is being considered for future HEP detectors of the sLHC and linear colliders. It is currently under investigation as an option for the cooling of the NA62 Gigatracker silicon pixel detector and its front-end electronics where the rnicrofabricated cooling plate would stand directly in the beam. In this particular case, microchannel cooling meets both the very aggressive X(0) (0.15%) specifications and the anticipated 2 W/cm(2) power dissipation by the active electronics.

Novel cooling systems with very low material budget are being fabricated and studied. They consist of silicon wafers in which microchannels are etched and closed by bonding another wafer. This cooling option is being considered for future HEP detectors of the sLHC and linear colliders. It is currently under investigation as an option for the cooling of the NA62 Gigatracker silicon pixel detector and its front-end electronics where the microfabricated cooling plate would stand directly in the beam. In this particular case, microchannel cooling meets both the very aggressive X0 (0.15%) specifications and the anticipated 2 W/cm2 power dissipation by the active electronics.

The NA62 GigaTracker is a low mass time tagging hybrid pixel detector operating in a beam with a particle rate of 750 MHz. It consists of three stations with a sensor size of 60 × 27mm2 containing 18000 pixels, each 300 × 300μm2. The active area is connected to a matrix of 2 × 5 pixel ASICs, which time tag the arrival of the particles with a binning of 100 ps. The detector operates in vacuum at -20 to 0°C and the material budget per station must be below 0.5% X0. Due to the high radiation environment of 2 × 1014 1 MeV neutron equivalent cm−2/yr−1 it is planned to exchange the detector modules regularly. The low material budget, cooling requirements and the request for easy module access has driven the electro-mechanical integration of the GigaTracker, which is presented in this paper.