A Monte Carlo study of a generic search for new resonances beyond the Standard Model (SM) in the CMS experiment is presented. The resonances are axigluon, coloron, E6 diquark, excited quark, W', Z', and the Randall-Sundrum graviton which decay to dijets. The dijet resonance cross section that the CMS can expect to discover at a 5[sigma] significance or to exclude at 95% confidence level for integrated luminosities of 100 pb-1, 1 fb-1, and 10 fb-1 is evaluated. It is shown that a 5[sigma] discovery of a multi-TeV dijet resonance is possible for an axigluon, excited quark, and E6 diquark. However, a 5[sigma] discovery can not be projected with confidence for a W', Z' and the Randall-Sundrum graviton. On the other hand, 95% CL exclusion mass regions can be measured for all resonances at high luminosities. In the second part of this dissertation, the analyses of the 2006 test beam data from the combined electromagnetic and hadronic barrel calorimeters are presented. The CMS barrel calorimeters response to a variety of beam particles in a wide momenta range (1 to 350 GeV/c) is measured. Furthermore, using these beam data, the expected performance of the barrel calorimeters to jets is predicted.
This document investigates experimental and theoretical issues relating to the detection of physics beyond the Standard Model using the Compact Muon Solenoid (CMS). First, the structure of the CMS detector is reviewed. Particular attention is paid to the hardware and software components of the pixel tracking system. A description is presented of the algorithms that are used to reconstruct physics objects such as electrons and jets. Next, theoretical motivations are given for seeking new physics processes in the energy regime that is accessible by CMS. Two different theories, the Minimal Supersymmetric Standard Model and the Littlest Higgs model with T-parity, are introduced as extensions of the Standard Model. Their experimental signatures are considered, and a technique for discriminating between them using CMS observations is studied with Monte Carlo computer simulations. The remainder of the document focuses on a search for evidence of a new physics signature using CMS events that contain two electrons, two jets, and large missing transverse energy. A data-driven technique for estimating the QCD background due to fake electrons is developed, tested, and applied to this channel. The other background estimates are obtained from Monte Carlo simulations, and several sources of systematic uncertainty are surveyed. A correction factor to the Monte Carlo backgrounds is calculated from the electron recon- struction efficiencies in data and in simulation, which are measured using a tag and probe procedure. A statistical model is developed for propagating all of the background uncertainties to the calculation of the signal. Both Bayesian and semi-frequentist measures of significance are considered. The expected value of the signal is s = 0.238 ± 0.996 (stat) ± 0.304 (sys) events, and its 95% confidence interval is [0, 4.4].
This book presents proceedings from the XXIV DAE-BRNS High Energy Physics (HEP) Symposium 2020, held at the National Institute of Science Education and Research, Jatni, Odisha, India. The contributions cover a variety of topics in particle physics, astroparticle physics, cosmology and related areas from both experimental and theoretical perspectives, namely (1) Standard Model Physics, (2) Beyond Standard Model Physics, (3) Relativistic Heavy-Ion Physics & QCD, (4) Neutrino Physics, (5) Particle Astrophysics & Cosmology, (6) Detector Development Future Facilities and Experiments, (7) Formal Theory, (8) Societal Applications: Medical Physics, Imaging, etc.
This is a “how to guide” for a calculus-based introductory course in electricity and magnetism. Students taking the subject at an intermediate or advanced level may also find it to be a useful reference. The calculations are performed in Mathematica, and stress graphical visualization, units, and numerical answers. The techniques show the student how to learn the physics without being hung up on the math. There is a continuing movement to introduce more advanced computational methods into lower-level physics courses. Mathematica is a unique tool in that code is written as "human readable" much like one writes a traditional equation on the board. Key Features: Concise summary of the physics concepts. Over 300 worked examples in Mathematica. Tutorial to allow a beginner to produce fast results. The companion code for this book can be found here: https://physics.bu.edu/~rohlf/code.html
This second open access volume of the handbook series deals with detectors, large experimental facilities and data handling, both for accelerator and non-accelerator based experiments. It also covers applications in medicine and life sciences. A joint CERN-Springer initiative, the "Particle Physics Reference Library" provides revised and updated contributions based on previously published material in the well-known Landolt-Boernstein series on particle physics, accelerators and detectors (volumes 21A, B1,B2,C), which took stock of the field approximately one decade ago. Central to this new initiative is publication under full open access
In the fit part, the Compact Muon Solenoid (CMS) forward calorimeter design studies are presented. The forward calorimeter consists of quartz fibers embedded in a steel absorber. Radiation damage studies of the quartz fiber and the absorber as well as the results of the first pre-production prototype PPP-I are presented. In the second part, the {Omega}{sub c}{sup 0}search studies at the SELEX (E781) experiment at FermiLab are presented. 107 {+-} 22 {Omega}{sub c}{sup 0} events are observed in three decay modes. The relative branching ratio ({Omega}{sub c}{sup 0} {yields} {Omega}{sup -}{pi}{sup -}{pi}{sup +}{pi}{sup +})/{Beta}({Omega}{sub c}{sup 0} {yields} {Omega}{sup -}{pi}{sup +}) is measured as 2.00 {+-} 0.45(stat) {+-} 0.32(sys).
In order to cope with the increased radiation level and the challenging pile-up conditions at High Luminosity-LHC, the CMS collaboration will replace its current calorimeter endcaps with the High Granularity Calorimeter (HGCAL) in the mid 2020s. This dissertation addresses two important topics related to the preparation of the HGCAL upgrade: experimental validation of its silicon- based design and fast simulation of its data. Beam tests at the DESY (Hamburg) and the CERN SPS beam test facilities in 2018 have been the basis for the design validation. The associated experimental infrastructure, the algorithms deployed in the reconstruction of the recorded data, as well as the respective analyses are reported in this thesis: First, core components of the silicon-based prototype modules are characterised and it is demonstrated that the assembled modules are functional. In particular, their efficiency to detect minimum ionising particles (MIPs) traversing the silicon sensors is found to be more than 98% for most of the modules. No indication of charge sharing between the silicon pads is observed. Subsequently, the energy response is calibrated in situ using the beam test data. Equalisation of the different responses among the readout channels is achieved with MIPs hereby deploying the HGCAL prototype as a MIP-tracking device. The relative variation of the inferred calibration constants amounts to 3% for channels on the same readout chip. The calibration of the time-of-arrival information is performed with an external time reference detector. With it, timing resolutions of single cells including the full prototype readout chain around 60ps in the asymptotic high energy limit are obtained. The calorimetric performance of the HGCAL prototype is validated with particle showers induced by incident positrons and charged pions. For electromagnetic showers, the constant term in the relative energy resolution is measured to be (0.52± 0.08) %, whereas the stochastic term amounts to (22.2 ± 0.3)% √GeV. This result is in good agreement with the calorimeter simulation with GEANT4. The prototype’s positioning resolution of the shower axis, after subtracting the contribution from the delay wire chambers in the beam line used as reference, is found to be below 0.4 mm at 300 GeV. At the same energy, the angular resolution in the reconstruction of the electromagnetic shower axis in this prototype is measured to be less than 5mrad. The analysis of the hadronic showers in this thesis makes use state-of-the- art machine-learning methods that exploit the calorimeter’s granularity. It is indicated that the energy resolution may be improved using software compensation and also that the separation of electromagnetic and charged pion-induced showers in the calorimeter may benefit from such methods. The measurements of the hadronic showers are adequately reproduced by GEANT4 simulation. Altogether, the obtained results from the analysis of the beam test data in this thesis are in agreement with the full functionality of the silicon-based HGCAL design. The final part of this thesis provides a proof of principle that generative modelling based on deep neural networks in conjunction with the Wasserstein distance is a suitable approach for the fast simulation of HGCAL data: Instead of sequential simulation, a deep neural network-based generative model generates all calorimeter energy depositions simultaneously. This genera t or network is optimised throu gh an adversarial training process using a critic network guided by the Wasserstein distance. The developed framework in this thesis is applied to both GEANT4- simulated electromagnetic showers and to positron data from the beam tests. Ultimately, this fast simulation approach is up to four orders of magnitude faster than sequential simulation with GEANT4. It is able to produce realistic calorimeter energy depositions from electromagnetic showers, incorporating their fluctuations and correlations when converted into typical calorimeter observables.
The BU CMS group led by PI Tulika Bose has made several significant contributions to the CMS trigger and to the analysis of the data collected by the CMS experiment. Group members have played a leading role in the optimization of trigger algorithms, the development of trigger menus, and the online operation of the CMS High-Level Trigger. The group's data analysis projects have concentrated on a broad spectrum of topics that take full advantage of their strengths in jets and calorimetry, trigger, lepton identification as well as their considerable experience in hadron collider physics. Their publications cover several searches for new heavy gauge bosons, vector-like quarks as well as diboson resonances.
The theoretical foundations of the Standard Model of elementary particles relies on the existence of the Higgs boson, a particle which has been revealed for the first time by the experiments run at the Large Hadron Collider (LHC) in 2012. As the Higgs boson is an unstable particle, its search strategies were based on its decay products. In this thesis, Francesco Pandolfi conducted a search for the Higgs boson in the H → ZZ → l + l - qq Decay Channel with 4.6 fb -1 of 7 TeV proton-proton collision data collected by the Compact Muon Solenoid (CMS) experiment. The presence of jets in the final state poses a series of challenges to the experimenter: both from a technical point of view, as jets are complex objects and necessitate of ad-hoc reconstruction techniques, and from an analytical one, as backgrounds with jets are copious at hadron colliders, therefore analyses must obtain high degrees of background rejection in order to achieve competitive sensitivity. This is accomplished by following two directives: the use of an angular likelihood discriminant, capable of discriminating events likely to originate from the decay of a scalar boson from non-resonant backgrounds, and by using jet parton flavor tagging, selecting jets compatible with quark hadronization and discarding jets more likely to be initiated by gluons. The events passing the selection requirements in 4.6 fb -1 of data collected by the CMS detector are examined, in the search of a possible signal compatible with the decay of a heavy Higgs boson. The thesis describes the statistical tools and the results of this analysis. This work is a paradigm for studies of the Higgs boson with final states with jets. The non-expert physicists will enjoy a complete and eminently readable description of a proton-proton collider analysis. At the same time, the expert reader will learn the details of the searches done with jets at CMS.
Oliver Pooth describes the silicon strip tracker of the CMS detector and discusses methods of quality control that are new to the field of particle detector physics. These methods were established to guarantee a uniform behaviour of all detector modules which were built and tested in various places worldwide.
