50 research outputs found
A search for third-generation leptoquarks in the non-resonant production with the ATLAS experiment and development of the Level-0 muon trigger for the High Luminosity LHC
No full textRecent observations performed by several high-energy physics experiments have shown anomalies in b-hadron decays, which could be explained by assuming the existence of a particle, the leptoquark, coupled both to leptons and quarks. Such measurements also suggest a preferential coupling to third-generation fermions. In this thesis, a search for third-generation leptoquarks is presented, considering the non-resonant leptoquark production. The non-resonant production is expected to yield high sensitivity from the large interference term between the Standard Model Drell-Yan process and the leptoquark t-channel exchange. The leptoquark search uses the 140 fb−1 of pp collision data collected by the ATLAS detector during the LHC Run 2 and considers di-lepton final state events, with at least one hadronically decaying tau-lepton. Deviations from the Standard Model predictions are looked for in the visible invariant mass spectrum of the di-lepton system, binned in b-jet multiplicity. In the absence of a significant deviation, exclusion limits are determined on the leptoquark coupling for different leptoquark mass values.
This thesis also presents a contribution to the upgrade of the ATLAS Muon Spectrometer in preparation for the High-Luminosity LHC. In order to cope with the much harsher conditions of the high-luminosity phase of the LHC, the entire trigger and readout electronics of the Resistive Plate Chamber detectors in the barrel region of the Muon Spectrometer will be replaced and novel FPGA-based boards will be installed. On-detector Data Collector and Transmitter boards will collect the front-end data and transmit them to off-detector Sector Logic boards, which will execute the Level-0 Muon trigger algorithm and the readout logic. In this thesis, the development of the firmwares that will be implemented in the FPGAs of the Data Collector and Transmitter boards and of the barrel Sector Logic boards is presented
Status of the Level-0 ATLAS Barrel Muon Trigger for High-Luminosity LHC
No full textThe ATLAS level-0 barrel muon trigger for High-Luminosity LHC will use data from RPC and MDT muon detectors and from the Tile Calorimeter. RPC hit data will be collected by on-detector Data Transmitter and Collector (DCT) boards and will be sent off-detector to the Sector Logic (SL) boards. Within a latency of 390 ns the SL boards should provide muon pre-candidates to the MDT trigger processor for an improved momentum measurement. This contribution presents the design of the system and results of recent tests of DCT and SL prototypes and firmware
Status of the Level-0 ATLAS barrel muon trigger for High-Luminosity LHC
No full textThe Muon Spectrometer of the ATLAS detector will be substantially modified during the Phase-II Upgrade to cope with the higher particle rates and radiation levels of the High-Luminosity LHC. The entire trigger and readout electronics of the Resistive Plates Chambers will be replaced. The Resistive Plate Chambers hit data will be collected by on-detector Data Transmitter and Collector boards and will be sent off-detector to the Sector Logic boards, which will perform the Level-0 barrel muon trigger algorithm and the readout logic. This contribution presents the design of the Phase-II barrel muon trigger and data acquisition system and the developement of the barrel Sector Logic board firmware and its challenges
Estimation of backgrounds from jets misidentified as tau leptons using the Universal Fake Factor method with the ATLAS detector
No full textPhysical processes with one or more τ-lepton in the final state play an important role in several analyses of the ATLAS experiment physics program. The usage of hadronic channels, in which τ-leptons decay into one or more pions, enables to exploit the large statistics associated with hadronic τ-lepton decays, but also requires a precise estimate of a sizable background of hadronic jets mis-reconstructed as fake τ-leptons. This poster will present a new technique developed by the ATLAS Collaboration to estimate the fake τ-lepton background from data - the Universal Fake Factor method. This technique improves on previous methodologies as it enables a more solid validation of the estimated background. Details on how to implement this methodology will be given as well as on its validation with single and di-τ final states. Information on ATLAS physics analyses that successfully exploited this technique will also be given
A search for third-generation leptoquarks in the non-resonant production with the ATLAS experiment and development of the Level-0 muon trigger for the High Luminosity LHC
No full textRecent observations performed by several high-energy physics experiments have shown anomalies in -hadron decays, which could be explained by assuming the existence of a particle, the leptoquark, coupled both to leptons and quarks. Such measurements also suggest a preferential coupling to third-generation fermions. In this thesis, a search for third-generation leptoquarks is presented, considering the non-resonant leptoquark production. The non-resonant production is expected to yield high sensitivity from the large interference term between the Standard Model Drell-Yan process and the leptoquark t-channel exchange. The leptoquark search uses the 140 fb of collision data collected by the ATLAS detector during the LHC Run 2 and considers di-lepton final state events, with at least one hadronically decaying tau-lepton. Deviations from the Standard Model predictions are looked for in the visible invariant mass spectrum of the di-lepton system, binned in b-jet multiplicity. In the absence of a significant deviation, exclusion limits are determined on the leptoquark coupling for different leptoquark mass values. This thesis also presents a contribution to the upgrade of the ATLAS Muon Spectrometer in preparation for the High-Luminosity LHC. In order to cope with the much harsher conditions of the high-luminosity phase of the LHC, the entire trigger and readout electronics of the Resistive Plate Chamber detectors in the barrel region of the Muon Spectrometer will be replaced and novel FPGA-based boards will be installed. On-detector Data Collector and Transmitter boards will collect the front-end data and transmit them to off-detector Sector Logic boards, which will execute the Level-0 Muon trigger algorithm and the readout logic. In this thesis, the development of the firmwares that will be implemented in the FPGAs of the Data Collector and Transmitter boards and of the barrel Sector Logic boards is presented
The ATLAS Muon Trigger System for the High Luminosity LHC
No full textTo preserve the acceptance of critical signatures for physics in the increased particle rates, integrated radiation, and pile-up conditions of the High Luminosity the HL-LHC runs, the Trigger and Readout System of the ATLAS Muon Spectrometer must maintain low-momentum trigger thresholds in an acceptable trigger rate. This leads to an increase of the trigger rate and latency to 1MHz and 10μs, respectively, so that more complex trigger algorithms than in the present system can be implemented. That trigger scheme imposes the replacement of the current readout and trigger electronics, which accommodate a maximum rate of 100 kHz with a maximum latency of up to 3 μs. This paper presents the new muon hardware trigger architecture that exploits the Muon Spectrometer’s upgraded trigger and readout electronics, focusing on the new data collection and transmission electronics (DCT) of the Resistive Plate Chambers (RPC) trigger detector technology. The DCT boards implement the LPGBT optical link to handle data bandwidth up to 10.24 Gb/s. Due to the importance of the DCT system, the complexity of the signals it handles, and the large number of boards required (1570 DCTs), an automated test station will be developed to evaluate the performance of all its functionalities. Presented are the architecture and measurement results of a test bench developed to evaluate the DCT's optical link LpGBT by implementing its backend counterpart (lpGBTFPGA core). Since the DCT prototype is under irradiation tests, for the assessment of the lpGBT-FPGA a methodology has been implemented by using development boards and modifying the alternative of the LPGBT ASIC (lpGBT-Emulator). The successful operation of the above testing setup renders feasible indispensable implementations towards the complete validation of the functionalities of the DCT (or of any board that implements the LPGBT)
Constraining the leptoquark pair-production cross-section using tau leptons with the ATLAS detector
No full textThis contribution presents the results of an analysis performed with the full Run 2 proton-proton collision dataset collected by the ATLAS detector searching for pair-produced third-generation leptoquarks. Events in which at least one tau lepton decays hadronically are considered and multivariate discriminants are used to extract the signals. No significant deviations from the Standard Model expectation are observed and 95% confidence-level upper limits on the production cross-section are derived
Upgraded data readout and transmission electronics for the Resistive Plate Chambers of the ATLAS Muon Trigger System for the High Luminosity LHC
No full textThe Muon Spectrometer of the ATLAS detector will be significantly modified during the Phase-II upgrade in order to mantain low-momentum trigger thresholds at an acceptable trigger rate also in the increased particle rates, integrated radiation and pile-up of the High Luminosity LHC runs. The new requirements for trigger rate and latency impose the replacement of the current trigger and readout electronics of the Resistive Plate Chambers (RPCs). New Data Collector and Transmitter (DCT) boards will be installed to collect and digitize the RPC data. This paper presents the new trigger and readout scheme of the RPCs and the results of a test bench developed to evaluate the data transmission between the DCT and its back-end counterpart. The communication test bench has been performed using evaluation boards implementing an emulator of the lpGBT ASIC
Search for long-lived, massive particles in events with displaced vertices and multiple jets in pp collisions at s√ = 13 TeV with the ATLAS detector
No full textA search for long-lived particles decaying into hadrons is presented. The analysis uses 139 fb−1 of pp collision data collected at √s = 13 TeV by the ATLAS detector at the LHC using events that contain multiple energetic jets and a displaced vertex. The search employs dedicated reconstruction techniques that significantly increase the sensitivity to long- lived particles decaying in the ATLAS inner detector. Background estimates for Standard Model processes and instrumental effects are extracted from data. The observed event yields are compatible with those expected from background processes. The results are used to set limits at 95% confidence level on model-independent cross sections for processes beyond the Standard Model, and on scenarios with pair-production of supersymmetric particles with long-lived electroweakinos that decay via a small R-parity-violating coupling. The pair-production of electroweakinos with masses below 1.5 TeV is excluded for mean proper lifetimes in the range from 0.03 ns to 1 ns. When produced in the decay of m(g ̃) = 2.4 TeV gluinos, electroweakinos with m(χ ̃01) = 1.5 TeV are excluded with lifetimes in the range of 0.02 ns to 4 ns
Search for third-generation vector-like leptons in pp collisions at √s = 13 TeV with the ATLAS detector
No full textA search for vector-like leptons in multilepton (two, three, or four-or-more electrons plus muons) final states with zero or more hadronic τ-lepton decays is presented. The search is performed using a dataset corresponding to an integrated luminosity of 139 fb−1 of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the LHC. To maximize the separation of signal and background, a machine-learning classifier is used. No excess of events is observed beyond the Standard Model expectation. Using a doublet vector-like lepton model, vector-like leptons coupling to third-generation Standard Model leptons are excluded in the mass range from 130 GeV to 900 GeV at the 95% confidence level, while the highest excluded mass is expected to be 970 GeV. [Figure not available: see fulltext.]
