The Back-End Electronics for the ATLAS Hadronic Tile Calorimeter at the Large Hadron Collider

El Gran Colisionador de Hadrónes (LHC acrónimo en inglés de Large Hadron Collider) se encuentra en el laboratorio europeo para física de partículas (CERN) en la frontera Franco-Suiza cerca de Ginebra. En él se estudian las colisiones de protones e iones pesados en cuatro experimentos situados a lo largo del colisionador. Uno de estos experimentos, ATLAS (A Toroidal LHC Apparatus), es un detector de propósito general diseñado para aprovechar todo el potencial de descubrimiento de nueva física del LHC. Mide aproximadamente 45 metros de largo y algo más de 25 metros de alto y tiene un peso cercano a las 7000 toneladas. El detector interno, construido alrededor del tubo por el que circula el haz, ha sido diseñado para reconstruir los vértices y trazas de las partículas generadas en las colisiones. Los calorímetros electromagnético y hadrónico deben medir la energía de las distintas partículas. La última capa está formada por el espectrómetro de muones, que mide las trayectorias de las partículas cargadas que atraviesan completamente los calorímetros, y los toroides magnéticos que curvan la trayectoria de las partículas mediante un campo magnético de 0.5 Tesla. El calorímetro hadrónico de ATLAS ha sido diseñado principalmente para identificar “jets” y medir su energía y dirección así como para medir la deficiencia de energía total transversa. El calorímetro hadrónico de tejas (TileCal) es un detector de muestreo que utiliza acero como material absorbente y centelleador como medio activo y fotomultipliacdores para la adquisición de señal. Los eventos son analizados y tras una selección procesados y enviados a la electrónica lejana del detector. En esta tesis doctoral se describe el sistema electrónico de lectura lejano del detector. El sistema de adquisición de datos lejano es el encargado de procesar y reconstruir las señales digitales del detector y proporcionar los resultados al siguiente nivel en la cadena de adquisición. En primer lugar se muestran los resultados de producción y validación de los módulos “ReadOut Drivers” (RODs) que representa el núcleo de dicha electrónica. Posteriormente se describe la instalación, puesta a punto y resultados de operación de este sistema durante los tres primeros años de toma de datos del experimento ATLAS. Se muestran resultados de rendimiento desde el punto de vista de la eficiencia de adquisición de datos en comparación con el resto de subdetectores de ATLAS. Los algoritmos de reconstrucción empleados en los módulos ROD se encargan de estimar la energía depositada por las partículas en el detector así como su tiempo de paso. En la segunda parte de esta tesis se describen el algoritmo “Optimal Filtering” utilizado en los módulos ROD de TileCal. Se describe en detalle la metodología utilizada para la implementación de este algoritmo en los procesadores digitales de señal empleados para tal efecto. Se muestran los resultados de reconstrucción de señal a nivel de celda tanto para datos de laboratorio, de calibración así como para datos reales producidos en interacciones de partículas en el detector. Finalmente, se presentan resultados de reconstrucción de objetos físicos más complejos como “clusters” y “jets” en el calorímetro hadrónico TileCal de ATLAS

ATLAS search for a heavy gauge boson decaying to a charged lepton and a neutrino in pp collisions at root s=7 TeV

The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (W'), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.7 fb(-1). No excess beyond Standard Model expectations is observed. A W' with Sequential Standard Model couplings is excluded at the 95 % credibility level for masses up to 2.55 TeV. Excited chiral bosons (W*) with equivalent coupling strength are excluded for masses up to 2.42 TeV

Dynamics of isolated-photon plus jet production in pp collisions at root s=7 TeV with the ATLAS detector

The dynamics of isolated-photon plus jet production in pp collisions at a centre-of-mass energy of 7 TeV has been studied with the ATLAS detector at the LHC using an integrated luminosity of 37 pb(-1). Measurements of isolated-photon plus jet bin-averaged cross sections are presented as functions of photon transverse energy, jet transverse momentum and jet rapidity. In addition, the bin-averaged cross sections as functions of the difference between the azimuthal angles of the photon and the jet, the photon jet invariant mass and the scattering angle in the photon jet centre-of-mass frame have been measured. Next-to-leading-order QCD calculations are compared to the measurements and provide a good description of the data, except for the case of the azimuthal opening angle

Measurement of the cross-section for W boson production in association with b-jets in pp collisions at root s=7 TeV with the ATLAS detector

This paper reports a measurement of the W+b-jets (W+b+X and W+b (b) over bar +X) production cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. These results are based on data corresponding to an integrated luminosity of 4.6 fb(-1), collected with the ATLAS detector. Cross-sections are presented as a function of jet multiplicity and of the transverse momentum of the leading b-jet for both the muon and electron decay modes of the W boson. The W+b-jets cross-section, corrected for all known detector effects, is quoted in a limited kinematic range. Combining the muon and electron channels, the fiducial cross-section for W+b-jets is measured to be 7.1 +/- 0.5 (stat) +/- 1.4 (syst) pb, consistent with the next-to-leading order QCD prediction, corrected for non-perturbative and double-parton interactions (DPI) contributions, of 4.70 +/- 0.09 (stat) (+0.60)(-0.49) (scale) +/- 0.06 (PDF) +/- 0.16 (non-pert) (+0.52)(-0.38) (DPI) pb

Triggers for displaced decays of long-lived neutral particles in the ATLAS detector

A set of three dedicated triggers designed to detect long-lived neutral particles decaying throughout the ATLAS detector to a pair of hadronic jets is described. The efficiencies of the triggers for selecting displaced decays as a function of the decay position are presented for simulated events. The effect of pile-up interactions on the trigger efficiencies and the dependence of the trigger rate on instantaneous luminosity during the 2012 data-taking period at the LHC are discussed

Measurement of the flavour composition of dijet events in pp collisions at √s =7 TeV with the ATLAS detector

This paper describes a measurement of the flavour composition of dijet events produced in pp collisions at root s = 7 TeV using the ATLAS detector. The measurement uses the full 2010 data sample, corresponding to an integrated luminosity of 39 pb(-1). Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. Kinematic variables, based on the properties of displaced decay vertices and optimised for jet flavour identification, are used in a multidimensional template fit to measure the fractions of these dijet flavour states as functions of the leading jet transverse momentum in the range 40 GeV to 500 GeV and jet rapidity vertical bar y vertical bar < 2.1. The fit results agree with the predictions of leading-and next-to-leading-order calculations, with the exception of the dijet fraction composed of bottom and light flavour jets, which is underestimated by all models at large transverse jet momenta. The ability to identify jets containing two b-hadrons, originating from e. g. gluon splitting, is demonstrated. The difference between bottom jet production rates in leading and subleading jets is consistent with the next-to-leading-order predictions

Search for dark matter candidates and large extra dimensions in events with a jet and missing transverse momentum with the ATLAS detector

A search for new phenomena in events with a high-energy jet and large missing transverse momentum is performed using data from proton-proton collisions at root s = 7 TeV with the ATLAS experiment at the Large flatiron Collider. Four kinematic regions are explored using a dataset corresponding to an integrated luminosity of 4.7 fb(-1). No excess of events beyond expectations from Standard Model processes is observed, and limits are set on large extra dimensions and the pair production of dark matter particles

ATLAS search for new phenomena in dijet mass and angular distributions using pp collisions at root s=7 TeV

Mass and angular distributions of dijets produced in LHC proton-proton collisions at a centre-of-mass energy root s = 7TeV have been studied with the ATLAS detector using the full 2011 data set with an integrated luminosity of 4.8 fb(-1). Dijet masses up to similar to 4.0TeV have been probed. No resonance-like features have been observed in the dijet mass spectrum, and all angular distributions are consistent with the predictions of QCD. Exclusion limits on six hypotheses of new phenomena have been set at 95% CL in terms of mass or energy scale, as appropriate. These hypotheses include excited quarks below 2.83 TeV, colour octet scalars below 1.86TeV, heavy W bosons below 1.68 TeV, string resonances below 3.61 TeV, quantum black holes with six extra space-time dimensions for quantum gravity scales below 4.11 TeV, and quark contact interactions below a compositeness scale of 7.6 TeV in a destructive interference scenario

Development of the PreProcessor Modules for the Upgrade of the ATLAS Tile Calorimeter Towards the HL-LHC

The Tile Calorimeter (TileCal) is the central hadronic calorimeter of the ATLAS experiment at the Large Hadron Collider (LHC). The LHC will undergo a series of upgrades towards a High Luminosity LHC (HL-LHC) in 2025-2028. The ATLAS TileCal Phase-II Upgrade is planned in order to accommodate the detector and data acquisition system to the HL-LHC requirements. In the upgraded readout architecture, the on-detector readout electronics will transmit detector data to the PreProcessors (PPr) in the counting rooms for every bunch crossing (~25 ns). The new readout system will require a total data bandwidth of 40 Tbps. The PPr boards will transmit calibrated energy and time per cell to the first level of the ATLAS trigger system through the Trigger and Data Acquisition interface system, and trigger selected event data to the Front End LInk eXchange (FELIXs) system. In addition, the PPr boards will be responsible for the distribution of the LHC clock towards the on-detector electronics for the sampling of the PMT signals. A total of 32 PPr boards will be required to read out the entire calorimeter during the HL-LHC, where each PPr board will be composed of four Compact Processing Module and an ATCA carrier. The design of hardware, firmware and software components of the final PreProcessor modules for the ATLAS Tile Calorimeter will be presented. The results and experiences obtained from the first integration tests are discussed, as well as the plans for the production, validation and installation of the PreProcessor modules during the ATLAS Phase-II Upgrade

Development of the PreProcessor Modules for the Upgrade of the ATLAS Tile Calorimeter Towards the High-Luminosity LHC

The Tile Calorimeter (TileCal) is the central hadronic calorimeter of the ATLAS experiment at the Large Hadron Collider (LHC). During the Long Shutdown 3 (LS3) in 2026-2029, the LHC will undergo a series of upgrades towards a High Luminosity LHC (HL-LHC) to deliver an instantaneous luminosity 5 to 7 times the current nominal LHC luminosity. The ATLAS TileCal Phase-II Upgrade will take place during the LS3 in order to accommodate the detector and data acquisition system to the HL-LHC requirements. The on- and off-detector electronics of TileCal will be completely replaced using a new readout strategy with new interfaces to the full-digital ATLAS trigger system to process more complex physics events while maintaining the trigger efficiency. In the upgraded readout architecture, the on-detector readout electronics will transmit detector data to the PreProcessors (PPr) in the counting rooms for every bunch crossing (~25 ns). The new readout system will require a total data bandwidth of 40 Tbps for the complete read out of the calorimeter. The PPr boards will transmit calibrated energy and time per cell to the first level of the ATLAS trigger system through the Trigger and DAQ interface system (TDAQi) and trigger selected event data to the Front-End LInk eXchange (FELIX) system. In addition, the PPr boards will be responsible for the distribution of the LHC clock towards the on-detector electronics for the sampling of the PMT signals. A total of 32 PPr boards will be required to read out the entire calorimeter during the HL-LHC, where each PPr board will be composed of four Compact Processing Module (CPM) and an ATCA carrier. This contribution presents the design of the final PreProcessor modules for the ATLAS Tile Calorimeter at the HL-LHC, as well as the plans for the production, validation and installation of the PreProcessor modules during the ATLAS Phase-II Upgrade