Measurements of Higgs boson production and decay rates and their interpretation with the ATLAS experiment

The event rates and kinematics of Higgs boson production and decay processes at the LHC are sensitive probes of possible new phenomena beyond the Standard Model (BSM). This talk presents precise measurements of Higgs boson production and decay rates, obtained using the full Run 2 and partial Run 3 pp collision dataset collected by the ATLAS experiment at 13 TeV and 13.6 TeV. These include total and fiducial cross-sections for the main Higgs boson processes as well as branching ratios into final states with bosons and fermions. Differential cross-sections in a variety of observables are also reported, as well as a fine-grained description of the Higgs boson production kinematics within the Simplified Template Cross-section (STXS) framework. Combinations of such measurements are also presented, as well as their interpretation in terms of Higgs boson couplings and in the context of Effective Field Theory (EFT) frameworks and specific BSM models

Studies on readout channel thresholds of resistive Micromegas for ATLAS Muon Spectrometer

ATLAS New Small Wheels upgrade project plans to replace the inner parts of the end-caps of ATLAS Muon Spectrometer with new detector structures equipped by a combination of small Thin Gap Chambers (sTGC) and resistive Micromegas (MM) detectors. During the integration of detectors, the sTGC and MM are separately tested before they are assembled together. On MM detectors, tests on the noise are performed together with measurements of tracking efficiency, exploiting the cosmic rays as incoming particles. The MM readout channels are floating copper strips with different lengths, from 284.0 mm to 1990.0 mm (capacitively coupled with carbon strips at few hundreds V). Due to the wide strip length range, the strip capacitance affects the noise with different magnitude, leading a larger spread in the baseline along a tracking plane, respect to a configuration with same size strips. It also impacts the thresholds that are proportional to baseline rms, with a settable factor. Especially if the variation in thresholds is large among close strips on a tracking layer, it compromises the time measurements for the μTPC procedure. To uniform the thresholds on the plane, a single-channel level correction can be applied, by an implemented trimmer in the electronic boards (based on VMM ASIC). Therefore, studies on the baseline and threshold were performed as function of the strip length. After them, studies on the efficiency and cluster parameters were carried on as function of the thresholds. Their results will be presented

Studies on readout channel thresholds of resistive MicroMegas for ATLAS Muon Spectrometer

ATLAS New Small Wheels upgrade project plans to replace the inner parts of the end-caps of the ATLAS Muon Spectrometer with new detector structures equipped by a combination of small-strip Thin Gap Chambers (sTGC) and resistive MicroMegas (MM) detectors. During the integration of detectors, the sTGC and MM are separately tested before being assembled. On MM detectors, tests on the noise are performed together with measurements of tracking efficiency, exploiting the cosmic rays as incoming particles. The MM readout channels are floating copper strips with different lengths, from 284.0 mm to 1990.0 mm, capacitively coupled with carbon strips at few hundreds V. Due to the wide strip length range, the strip capacitance affects the noise with different magnitude, leading a larger spread in the baseline along a tracking plane, respect to a configuration with same size strips. It also impacts the thresholds that are proportional to the baseline rms, with a settable factor. Especially if the variation in thresholds is large among close strips on a tracking layer, it compromises the time measurements for the μTPC procedure. To uniform the thresholds on the plane, a single-channel level correction can be applied, by an implemented trimmer in the electronic boards (based on VMM ASIC). Therefore, studies on the baseline and threshold were performed as a function of the strip length. After them, studies on the tracking efficiency were carried on as a function of the thresholds.On MicroMegas detectors for ATLAS Muon Spectrometer upgrade, tests on the noise are performed together with measurements of tracking efficiency, exploiting the cosmic rays as incoming particles. The MicroMegas readout channels are oating copper strips with different lengths, from 284.0 mm to 1 990.0 mm, capacitively coupled with carbon strips at a few hundred volts. Due to the wide strip length range, the strip capacitance affects the noise with different magnitude, leading to a larger spread in the baseline along a tracking plane, with respect to a configuration with the same size strips. It also impacts the thresholds that are proportional to the baseline rms, with a settable factor. Especially if the variation in thresholds is large among close strips on a tracking layer, it compromises the time measurements for the μTPC procedure. To uniform the thresholds on the plane, a single-channel level correction can be applied, by an implemented trimmer in the electronic boards (based on VMM ASIC). Therefore, studies on the baseline and threshold were performed as a function of the strip length. After them, studies on the tracking efficiency were carried on as a function of the thresholds

Measurements of Higgs boson production and decay rates and their interpretation with the ATLAS experiment

The event rates and kinematics of Higgs boson production and decay processes at the LHC are sensitive probes of possible new phenomena beyond the Standard Model (BSM). Precise measurements of Higgs boson production and decay rates were obtained using the full Run 2 and partial Run 3 pp collision dataset collected by the ATLAS experiment at 13 TeV and 13.6 TeV. These include total and fiducial cross-sections for the main Higgs boson processes as well as branching ratios into final states with bosons and fermions. Differential cross-sections in a variety of observables are also reported, as well as a fine-grained description of the Higgs boson production kinematics within the Simplified Template Cross-section framework. Combinations of such measurements are presented, as well as their interpretation in terms of Higgs boson couplings and in the context of Effective Field Theory frameworks and specific BSM models

Pixelated resistive bulk micromegas for tracking systems in high rate environment

One of the main objectives within the community of the Micro-Pattern-Gaseous-Detectors (MPGD) is the design of new detectors for operation with a very high particle flow. This research path is driven mainly by future upgrades of existing experiments at high-luminosity LHC or next generation accelerators where gaseous detectors will be operated at rates up to few MHz/cm2, three orders of magnitude higher than nowadays. The goal of our R&D project, started few years ago, is to develop a new generation of single amplification stage resistive MPGD based on Micromegas technology with the following characteristics: Stable and efficient operation up to particle fluxes of 10 MHz/cm2; high granularity readout, with pixels of order mm2 and fully integrated electronics; reliable and cost-effective production process. We present here the development status of our small-pads resistive Micromegas prototypes, focusing on the optimization of the spark protection resistive layer. Characterization and performance studies of the prototypes have been carried out by means of radioactive sources, X-Rays and test beams. A comparison of the performance obtained with the different resistive layout realized until now is presented, studying in particular the response under high rate irradiation. © 2020 IOP Publishing Ltd and Sissa Medialab

Rate capability and stability studies on small-Pad resistive Micromegas

Micromegas are among the most promising micro pattern gaseous detector (MPGD) technologies for applications in high energy physics (HEP). Micromegas are very versatile. They can be used for precision tracking and trigger, in particle flow sampling calorimetry, as anode planes for RICH detectors or for time projection chambers. Driven mainly by future upgrades of existing experiments at high-luminosity LHC (HL-LHC) and for applications at future accelerators, we started an R&D; project to push further this technology for operations under very high particle flow up to rates of tens MHz/cm$^{2}$, three orders of magnitude higher than current applications. The miniaturization of the readout elements and the optimization of the spark protection system, as well as the stability and robustness under operation, are the primary challenges of the project

Radiation studies on resistive bulk-micromegas chambers at the CERN Gamma Irradiation Facility

With the growing diffusion of resistive Micromegas detectors in HEP experiments the study of long-term aging behaviour is becoming more and more relevant. Two resistive bulk-Micromegas detectors were installed in May 2015 at the CERN Gamma Irradiation Facility and exposed to an intense gamma irradiation with the aim to study the detector behavior under high irradiation and the long-term aging. The detectors have an active area of 10 × 10 cm 2 , readout strip pitch of 400 μ m , amplification gap of 128 μ m and drift gap of 5 mm. The desired accumulated charge of more than 0.2 C/cm 2 has been reached for both chambers, equivalent to 10 years of HL-LHC operation. The efficiency, amplification, and resolution of the Micromegas after this long-term irradiation period is compared with the performance of a non irradiated detector. In addition, the latest results of the measured particle rate as a function of the amplification voltage is presented and compared with those obtained in 2015.With the growing diffusion of resistive Micromegas detectors in HEP experiments the study of long-term aging behaviour is becoming more and more relevant. Two resistive bulk-Micromegas detectors were installed in May 2015 at the CERN Gamma Irradiation Facility exposed to an intense gamma irradiation with the aim to study the detector behavior under high irradiation and the long-term aging. The detectors have an active area of 10$\times$10 cm$^2$, readout strip pitch of 400 $\mu m$, amplification gap of 128 $\mu m$ and drift gap of 5 mm. The desired accumulated charge of more than 0.2 C/cm$^2$ has been reached for both chambers, equivalent to 10 years of HL-LHC operation. The efficiency, amplification, and resolution of the Micromegas after this long-term irradiation period is compared with the performance of a non irradiated detector. In addition, the latest results of the measured particle rate as a function of the amplification voltage is presented and compared with those obtained in 2015

Small-pad Resistive Micromegas: Comparison of patterned embedded resistors and DLC based spark protection systems

We present the development of resistive Micromegas aiming at operation under high rates, up to tens MHz/cm2, focusing on the optimisation of the spark protection resistive layer and the miniaturisation of the readout elements. Several Micromegas detectors have been built with an anode plane matrix of 48x16 rectangular readout pads, each pad 0.8x2.8 mm2. The detectors differ for the spark protection resistive schemes being realised with the following techniques: A pad-patterned embedded resistor by screen printing, and uniform DLC (Diamond Like Carbon structure) layers. Characterisation and performance studies of the detectors have been carried out by means of radioactive sources, X-Rays, and test beam. A comparison of the performance obtained with the different resistive layouts is presented, in particular focusing on the response under high irradiation and high rate exposure. © 2020 Published under licence by IOP Publishing Ltd

Small-pads resistive Micromegas prototype

Detectors at future accelerators will require operation at rates up to three orders of magnitude higher than 15 kHz/cm2 the hit rates expected in the current upgrades forward muon detectors of LHC experiments. A resistive Micromegas detectors with modified readout system can achieve rate capability up to few MHz/cm2 low occupancy. We present the development of small-pad Micromegas detectors with a pad resistive readout of few mm2 in size, built with the spark protection resistive layer realized with different techniques. © 2019 Elsevier B.V

Small-Pad Resistive Micromegas: Rate capability for different spark protection resistive schemes

Started few years ago, the goal of this R&D project is to develop a new generation of single amplification stage resistive MPGD based on Micromegas technology with the following characteristics: stable and efficient operation up to 10 MHz/cm2 particle flows; high granularity readout with small pads of the order of mm2; reliable and cost-effective production process. The miniaturization of the readout elements and the optimization of the spark protection system, as well as the stability and robustness under operation, are the primary challenges of the project. Several Micromegas detectors have been built with similar anode planes, segmented with a matrix of 48 × 16 readout pads with a rectangular shape (0.8 × 2.8 mm2) and with a pitch of 1 and 3 mm in the two coordinates. The active surface is 4.8 × 4.8 cm2 with a total number of 768 channels, routed off-detector for readout. With this anode/readout layout, the spark protection resistive layer has been realized with two different techniques: a pad-patterned embedded resistor with screen printing, and a uniform DLC (Diamond Like Carbon structure) layer by sputtering. For each technique different configurations and resistivity values have been adopted. For the DLC series, the most recently built prototype exploits the availability of copper clad DLC foils to improve the construction. Characterization and performance studies of the detectors have been carried out by means of radioactive sources, X-Rays, and test beam. A comparison of the performance obtained with the different resistive layout and different configurations are presented, in particular focusing on the response under high irradiation and high rate exposure. © 2020 IOP Publishing Ltd and Sissa Medialab