Cosmological Constraints from a Combination of Galaxy Clustering and Lensing -- I. Theoretical Framework

We present a new method that simultaneously solves for cosmology and galaxy bias on non-linear scales. The method uses the halo model to analytically describe the (non-linear) matter distribution, and the conditional luminosity function (CLF) to specify the halo occupation statistics. For a given choice of cosmological parameters, this model can be used to predict the galaxy luminosity function, as well as the two-point correlation functions of galaxies, and the galaxy-galaxy lensing signal, both as function of scale and luminosity. In this paper, the first in a series, we present the detailed, analytical model, which we test against mock galaxy redshift surveys constructed from high-resolution numerical $N$-body simulations. We demonstrate that our model, which includes scale-dependence of the halo bias and a proper treatment of halo exclusion, reproduces the 3-dimensional galaxy-galaxy correlation and the galaxy-matter cross-correlation (which can be projected to predict the observables) with an accuracy better than 10 (in most cases 5) percent. Ignoring either of these effects, as is often done, results in systematic errors that easily exceed 40 percent on scales of \sim 1 h^{-1}\Mpc, where the data is typically most accurate. Finally, since the projected correlation functions of galaxies are never obtained by integrating the redshift space correlation function along the line-of-sight out to infinity, simply because the data only cover a finite volume, they are still affected by residual redshift space distortions (RRSDs). Ignoring these, as done in numerous studies in the past, results in systematic errors that easily exceed 20 perent on large scales (r_\rmp \gta 10 h^{-1}\Mpc). We show that it is fairly straightforward to correct for these RRSDs, to an accuracy better than $\sim 2$ percent, using a mildly modified version of the linear Kaiser formalism

Properties of galaxies reproduced by a hydrodynamic simulation.

Previous simulations of the growth of cosmic structures have broadly reproduced the 'cosmic web' of galaxies that we see in the Universe, but failed to create a mixed population of elliptical and spiral galaxies, because of numerical inaccuracies and incomplete physical models. Moreover, they were unable to track the small-scale evolution of gas and stars to the present epoch within a representative portion of the Universe. Here we report a simulation that starts 12 million years after the Big Bang, and traces 13 billion years of cosmic evolution with 12 billion resolution elements in a cube of 106.5 megaparsecs a side. It yields a reasonable population of ellipticals and spirals, reproduces the observed distribution of galaxies in clusters and characteristics of hydrogen on large scales, and at the same time matches the 'metal' and hydrogen content of galaxies on small scales

Searches for heavy top partners with the ATLAS detector and irradiation studies of the Tile hadronic calorimeter

Aquesta tesi presenta dues recerques de parelles pesades de tipus vectorial dels quarks top del Model Estàndard en dades de col·lisions protó-protó, amb una energia de centre de massa de 13 TeV, recollits pel detector ATLAS al Large Hadron Collider de CERN. La primera recerca es centra en la producció de parells de quarks de tipus vectorial (T), utilitzant el conjunt de dades de 2015-2016, corresponent a 36.1 fb-1 de lluminositat integrada. La recerca es centra principalment en les desintegracions de T a Ht i de T a Zt, analitzant esdeveniments en l'estat final leptó + jets, caracteritzat per un únic electró o muó aïllat, un gran moment transversal mancant i múltiples jets, així com en el estat final jets + ETmiss, que conté zero leptons, una gran multiplicitat de jets i un gran moment transversal mancant. Hi explota l'alta multiplicitat de b-jets i de quarks top amb decaïment hadrònic i bosons de Higgs, que són característics dels esdeveniments de senyal. La segona recerca se centra en la producció d'un sol quark T, utilitzant el conjunt de dades del Run 2 presos durant 2015-2018, corresponents a 139 fb-1 de lluminositat integrada. Hi analitza esdeveniments en estats finals amb un sol leptó amb múltiples jets i b-jets, també apuntant a decaïments de T a Ht i T a Zt, i utilitzant algoritmes d'etiquetatge per identificar objectes massius amb decaïment hadrónic i leptònic. La presència d'un jet a baix angle, característic de la senyal seleccionada, juntament amb la multiplicitat de jets, b-jets, i objectes massius hadrónics s'utilitza per categoritzar els esdeveniments analitzats. No s'observa cap excés significatiu per sobre de l'expectativa de l'Model Estàndard en cap dels dos anàlisis, i els resultats s'utilitzen per establir límits superiors del 95% de CL en la producció de quarks T. La primera recerca exclou masses de quarks T que van des de 0.99 TeV per a qualsevol configuració de paràmetres de decaïment, fins 1.43 TeV per decaïments de Ht. La segona recerca estableix límits en la manera de producció d'un sol quark T, dependent dell model, excloent un rang de masses en diferents escenaris de referència, entre 1.27 TeV per paràmetres de model desfavorables, fins a la massa més alta considerada de 2.1 TeV en el cas de valors d'acoblament més forts. A més, es presenten estudis sobre l'efecte de la irradiació acumulada durant la presa de dades en el calorímetre hadrònic Tile del detector ATLAS. Aquests estudis utilitzen esdeveniments amb requeriments cinemàtics mínims en combinació amb mesures d'altres sistemes de calibratge per monitoritzar i diagnosticar el comportament de diferents components de la cadena de lectura de l'calorímetre, així com per analitzar l'evolució a llarg termini de l'rendiment de les rajoles de centelleig per extrapolar el seu rendiment durant els propers períodes de presa de dades.Esta tesis presenta dos búsquedas de parejas pesadas de tipo vectorial de los quarks top del Modelo Estándar en datos de colisiones protón-protón, con una energía de centro de masa de 13 TeV, acumulados por el detector ATLAS en el Large Hadron Collider del CERN. La primera búsqueda se centra en la producción de pares de quarks de tipo vectorial (T), utilizando el conjunto de datos de 2015-2016, correspondiente a 36.1 fb-1 de luminosidad integrada. La búsqueda se centra principalmente en las desintegraciones de T a Ht y de T a Zt, analizando eventos en el estado final leptón+jets, caracterizado por un único electrón o muón aislado, un gran momento transversal faltante y múltiples jets, así como en el estado final jets+ETmiss, que contiene cero leptones, una gran multiplicidad de jets y un gran momento transversal faltante. La búsqueda explota la alta multiplicidad de b-jets y de quarks top con decaimiento hadrónico y bosones de Higgs, que son característicos de los eventos de señal. La segunda búsqueda se centra en la producción de un sólo quark T, utilizando el conjunto de datos del Run 2 tomados durante 2015-2018, correspondientes a 139 fb-1 de luminosidad integrada. La búsqueda analiza eventos en estados finales con un solo leptón con múltiples jets y b-jets, también apuntando a decaimientos de T a Ht y T a Zt, y utilizando algoritmos de etiquetado para identificar objetos masivos con decaimiento hadrónico y leptónico. La presencia de un jet a bajo ángulo, característico de la señal seleccionada, junto con la multiplicidad de jets, b-jets, y objetos masivos hadrónicos se utiliza para categorizar los eventos analizados. No se observa ningún exceso significativo por encima de la expectativa del Modelo Estándar en ninguno de los dos análisis, y los resultados se utilizan para establecer límites superiores del 95 % de CL en la producción de quarks T. La primera búsqueda excluye masas de quarks T que van desde 0.99 TeV para cualquier configuración de parámetros de decaimiento, hasta 1.43 TeV para decaimientos de Ht. La segunda búsqueda establece límites en el modo de producción de un sólo quark T dependiente del modelo, excluyendo un rango de masas en diferentes escenarios de referencia, entre 1.27 TeV para parámetros de modelo desfavorables, hasta la masa más alta considerada de 2.1 TeV en el caso de valores de acoplamiento más fuertes. Además, se presentan estudios sobre el efecto de la irradiación acumulada durante la toma de datos en el calorímetro hadrónico Tile del detector ATLAS. Estos estudios utilizan eventos con requerimientos cinemáticos mínimos en combinación con medidas de otros sistemas de calibración para monitorizar y diagnosticar el comportamiento de diferentes componentes de la cadena de lectura del calorímetro, así como para analizar la evolución a largo plazo del rendimiento de las baldosas de centelleo para extrapolar su rendimiento durante los próximos periodos de toma de datos.This dissertation presents two searches for heavy, vector-like partners of Standard Model top quarks in proton-proton collision data, with a center-of-mass energy of 13 TeV, collected by the ATLAS detector at the CERN Large Hadron Collider. The first search targets pair production of vector-like quarks (T), using the 2015--2016 dataset, corresponding to 36.1 fb-1 of integrated luminosity. The search primarily targets T to Ht and T to Zt decays, by analyzing events in the lepton+jets final state, characterized by a single isolated electron or muon, large missing transverse momentum, and multiple jets, as well as in the jets+ETmiss final state, containing zero leptons, a high multiplicity of jets, and large missing transverse momentum. The search exploits the high multiplicity of b-jets and hadronically decaying boosted top quarks and Higgs bosons, that are characteristic of signal events. The second search targets single T production, using the full Run 2 dataset taken during 2015--2018, corresponding to 139 fb-1 of integrated luminosity. The search analyzes events in final states with a single lepton with multiple jets and b-jets, also targeting T to Ht and T to Zt decays, and using tagging algorithms to identify both hadronically and leptonically decaying boosted objects. The presence of a forward jet, characteristic of the targeted signal, along with the multiplicity of jets, b-jets, and reconstructed boosted objects is used to categorize the analyzed events. No significant excess above the Standard Model expectation is observed in either analysis, and the results are used to set 95 % CL upper limits on the production of T quarks. The first search excludes T-quark masses ranging from 0.99 TeV for any configuration of decay parameters, up to 1.43 TeV for Ht decays. The second search sets limits on the model-dependent single T production mode, excluding a range of masses in different benchmark scenarios, between 1.27 TeV for unfavorable model parameters, up to the highest considered mass of 2.1 TeV in the case of stronger coupling values Additionally, studies are presented on the effect of accumulated irradiation during data taking on the Tile hadronic calorimeter in the ATLAS detector. These studies use events with minimal kinematic requirements in combination with measurements from other calibration systems to monitor and diagnose the behavior of different components of the calorimeter readout chain, as well as to analyze the long-term evolution of the performance of the scintillating tiles to extrapolate their performance during upcoming data taking periods.Universitat Autònoma de Barcelona. Programa de Doctorat en Físic

Beam-beam interactions with COMBI

During the summer of 2015 I spent eight weeks at CERN for the Summer Student Programme. This report summarizes the project on beam-beam interactions with a crossing angle that took place at the Beams Department. Beam-beam interactions with a crossing angle were studied from the simulation framework COMBI (COherent Multibunch Beam-beam Interaction). These studies were largely performed by analyzing the tune Fourier spectra to assess the tune shifts. Hints of new insights have been obtained on the crossing angle behaviour of the Yokoya factor, which relates the tune shift to the beam-beam parameter. Furthermore, the implementation of a crossing angle into the COMBI code is outlined, as well as the insertion of the longitudinal part of the beam-beam eects to model a 6D interaction

Performance of the ATLAS Hadronic Tile Calorimeter

The Tile Calorimeter (TileCal) of the ATLAS experiment at the LHC is the central hadronic calorimeter designed for the reconstruction of hadrons, jets, hadronically decaying tau leptons and missing transverse momentum. TileCal is a scintillator-steel sampling calorimeter and it covers the region of pseudorapidity $|\eta|< 1.7$. The scintillation light produced in the scintillator tiles is transmitted by wavelength shifting fibers to photomultiplier tubes (PMTs). The analog signals from the PMTs are amplified, shaped and digitized every 25 ns by sampling the signal. Each step of the signal reconstruction from scintillation light to the digital pulse reconstruction is monitored and calibrated. The performance of the calorimeter has been studied in-situ employing cosmic ray muons and a large sample of proton-proton collisions acquired during the operations of the LHC. Muons of high momentum from electroweak bosons decays are employed to study the energy response of the calorimeter at the electromagnetic scale. The calorimeter response to hadronic particles is evaluated with a sample of isolated hadrons and the modelling of the response by the Monte Carlo simulation is discussed. The calorimeter timing calibration and resolutions are studied with jets. Results on the calorimeter performance on absolute energy scale, timing, noise and associated stabilities are presented. These results show that the TileCal performance is within the design requirements and has given essential contributions to reconstructed objects and physics results

Searches for heavy top partners with the ATLAS detector and irradiation studies of the Tile hadronic calorimeter

This dissertation presents two searches for heavy, vector-like partners of Standard Model top quarks in proton-proton collision data, with a center-of-mass energy of $\sqrt{s}=13$ TeV, collected by the ATLAS detector at the CERN Large Hadron Collider. The first analysis searches for pair production of vector-like quarks ($T$), using the 2015-2016 dataset, corresponding to 36.1 fb$^{-1}$ of integrated luminosity. The search primarily targets $T\to Ht$ and $T\to Zt$ decays, by analyzing events in the lepton+jets final state, characterized by a single isolated electron or muon, large missing transverse momentum, and multiple jets, as well as in the jets+$E_{\text{T}}^{\text{miss}}$ final state, containing zero leptons, a high multiplicity of jets, and large missing transverse momentum. The search exploits the high multiplicity of $b$-jets and hadronically decaying boosted top quarks and Higgs bosons, which are characteristic of signal events. The second search targets single $T$ production, using the full Run 2 dataset taken during 2015-2018, corresponding to 139 fb$^{-1}$ of integrated luminosity. The search analyzes events in final states with a single lepton with multiple jets and $b$-jets, also targeting $T\to Ht$ and $T\to Zt$ decays, and using tagging algorithms to identify both hadronically and leptonically decaying boosted objects. The presence of a forward jet, characteristic of the targeted signal, along with the multiplicity of jets, $b$-jets, and reconstructed boosted objects, is used to categorize the analyzed events. No significant excess above the Standard Model expectation is observed in either analysis, and the results are used to set 95% CL upper limits on the production of $T$ quarks. The first search excludes $T$-quark masses ranging from 0.99 TeV for any configuration of decay parameters, and up to 1.43 TeV for $Ht$ decays. The second search sets limits on the model-dependent single $T$ production mode, excluding a range of masses in different benchmark scenarios, between 1.27 TeV for unfavorable model parameters, up to the highest mass considered in the analysis of 2.1 TeV in the case of stronger coupling values. Additionally, studies are presented on the effect of accumulated irradiation during data taking on the Tile hadronic calorimeter in the ATLAS detector. These studies use events with minimal kinematic requirements in combination with measurements from other calibration systems to monitor and diagnose the behavior of different components of the calorimeter readout chain, as well as to analyze the long-term evolution of the performance of the scintillating tiles for extrapolation to upcoming data taking periods

A census of stellar mass in ten massive haloes at z

Aims. We study the stellar mass content of massive haloes in the redshift range 0.86 < z < 1.34, by measuring (1) the stellar mass in the central galaxy versus total dynamical halo mass; (2) the total stellar mass (including satellites) versus total halo mass; and (3) the radial stellar mass and number density profiles for the ensemble halo. Methods. We use a Ks-band selected catalogue for the 10 clusters in the Gemini Cluster Astrophysics Spectroscopic Survey (GCLASS), with photometric redshifts and stellar masses measured from 11-band SED fitting. Combining the photometric catalogues with the deep spectroscopic component of GCLASS, we correct the cluster galaxy sample for interlopers. We also perform a dynamical analysis of the cluster galaxies to estimate the halo mass M200 for each cluster based on a measurement of its velocity dispersion. Results. (1) We find that the central galaxy stellar mass fraction decreases with total halo mass and that this is in reasonable, quantitative agreement with measurements from abundance matching studies at z ~ 1. (2) The total stellar mass fractions of these systems decrease with halo mass, indicating that lower mass systems are more efficient at transforming baryons into stars. We find the total stellar mass to be a good proxy for total halo mass, with a small intrinsic scatter. When we compare these results from GCLASS with literature measurements, we find that the stellar mass fraction at fixed halo mass shows no significant evolution in the range 0 < z < 1. (3) We measure a relatively high NFW concentration parameter cg ~ 7 for the stellar mass distribution in these clusters, and debate a possible scenario for explaining the evolution of the stellar mass distribution from the GCLASS sample to their likely descendants at lower redshift. Conclusions. The stellar mass measurements in the z ~ 1 haloes provided by GCLASS puts constraints on the stellar mass assembly history of clusters observed in the local Universe. A simple model shows that the stellar mass content of GCLASS can evolve in typical distributions observed at lower redshifts if the clusters primarily accrete stellar mass onto the outskirts

Second Analysis Ecosystem Workshop Report

International audienceThe second workshop on the HEP Analysis Ecosystem took place 23-25 May 2022 at IJCLab in Orsay, to look at progress and continuing challenges in scaling up HEP analysis to meet the needs of HL-LHC and DUNE, as well as the very pressing needs of LHC Run 3 analysis. The workshop was themed around six particular topics, which were felt to capture key questions, opportunities and challenges. Each topic arranged a plenary session introduction, often with speakers summarising the state-of-the art and the next steps for analysis. This was then followed by parallel sessions, which were much more discussion focused, and where attendees could grapple with the challenges and propose solutions that could be tried. Where there was significant overlap between topics, a joint discussion between them was arranged. In the weeks following the workshop the session conveners wrote this document, which is a summary of the main discussions, the key points raised and the conclusions and outcomes. The document was circulated amongst the participants for comments before being finalised here