Search For Exotic Higgs Boson Decays With Cms And Fast Machine Learning Solutions For The Lhc
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Search For Exotic Higgs Boson Decays With Cms And Fast Machine Learning Solutions For The Lhc
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Author : Ho Fung Tsoi
language : en
Publisher:
Release Date : 2024
Search For Exotic Higgs Boson Decays With Cms And Fast Machine Learning Solutions For The Lhc written by Ho Fung Tsoi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2024 with categories.
There exists potential for discoveries beyond the Standard Model in scalar sector, which could manifest as Higgs boson exotic decays into new light pseudoscalars. This search targets such decays, focusing on pseudoscalar masses ranging from 12 to 60 GeV, in final states where one pseudoscalar decays into two b quarks and the other into two [tau] leptons or two muons. The analysis is based on a dataset of proton-proton collisions at √s=13 TeV, collected by the CMS detector during LHC Run 2, with an integrated luminosity of 138 fb−1 Dedicated neural networks are used to distinguish between signal and background, significantly enhancing sensitivity. The results are presented as exclusion limits at 95\% confidence level on the model-independent branching ratio and are interpreted within two-Higgs doublet models augmented by a singlet. The second part of this thesis presents machine learning methods to enhance overall sensitivity in the low-latency domain for the LHC experiments. A novel machine learning-based trigger algorithm is developed, using anomaly detection to search for new physics in a model-agnostic manner as close to the raw collision data as possible. This anomaly detection trigger is sensitive to a wide range of both conventional and unconventional physics signatures and has an inference latency of $\mathcal{O}$(100) ns on an FPGA. It is deployed during Run 3 in the CMS Level-1 trigger system, which processes the first round of real-time event selection from collision data at a rate of 40 MHz. Additionally, a novel model compression method using symbolic regression is developed to accelerate machine learning inference to nanosecond speeds on FPGAs. This method demonstrates potential to significantly reduce the computational costs of machine learning algorithms while maintaining performance comparable to that of neural networks. These advancements are crucial for meeting the sensitivity and computational demands of resource-constrained environments such as the LHC experiments.
Search For Exotic Higgs Boson Decays To Merged Diphotons
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Author : Michael Andrews
language : en
Publisher: Springer Nature
Release Date : 2023-03-02
Search For Exotic Higgs Boson Decays To Merged Diphotons written by Michael Andrews and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-03-02 with Science categories.
This book describes the first application at CMS of deep learning algorithms trained directly on low-level, “raw” detector data, or so-called end-to-end physics reconstruction. Growing interest in searches for exotic new physics in the CMS collaboration at the Large Hadron Collider at CERN has highlighted the need for a new generation of particle reconstruction algorithms. For many exotic physics searches, sensitivity is constrained not by the ability to extract information from particle-level data but by inefficiencies in the reconstruction of the particle-level quantities themselves. The technique achieves a breakthrough in the reconstruction of highly merged photon pairs that are completely unresolved in the CMS detector. This newfound ability is used to perform the first direct search for exotic Higgs boson decays to a pair of hypothetical light scalar particles H→aa, each subsequently decaying to a pair of highly merged photons a→yy, an analysis once thought impossible to perform. The book concludes with an outlook on potential new exotic searches made accessible by this new reconstruction paradigm.
Search For The Higgs Boson Produced In Association With Top Quarks With The Cms Detector At The Lhc
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Author : Cristina Martin Perez
language : en
Publisher: Springer Nature
Release Date : 2022-02-09
Search For The Higgs Boson Produced In Association With Top Quarks With The Cms Detector At The Lhc written by Cristina Martin Perez and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-02-09 with Science categories.
In this work, the interaction between the Higgs boson and the top quark is studied with the proton-proton collisions at 13 TeV provided by the LHC at the CMS detector at CERN (Geneva). At the LHC, these particles are produced simultaneously via the associate production of the Higgs boson with one top quark (tH process) or two top quarks (ttH process). Compared to many other possible outcomes of the proton-proton interactions, these processes are very rare, as the top quark and the Higgs boson are the heaviest elementary particles known. Hence, identifying them constitutes a significant experimental challenge. A high particle selection efficiency in the CMS detector is therefore crucial. At the core of this selection stands the Level-1 (L1) trigger system, a system that filters collision events to retain only those with potential interest for physics analysis. The selection of hadronically decaying τ leptons, expected from the Higgs boson decays, is especially demanding due to the large background arising from the QCD interactions. The first part of this thesis presents the optimization of the L1 τ algorithm in Run 2 (2016-2018) and Run 3 (2022-2024) of the LHC. It includes the development of a novel trigger concept for the High-Luminosity LHC, foreseen to start in 2027 and to deliver 5 times the current instantaneous luminosity. To this end, sophisticated algorithms based on machine learning approaches are used, facilitated by the increasingly modern technology and powerful computation of the trigger system. The second part of the work presents the search of the tH and ttH processes with the subsequent decays of the Higgs boson to pairs of τ lepton, W bosons or Z bosons, making use of the data recorded during Run 2. The presence of multiple particles in the final state, along with the low cross section of the processes, makes the search an ideal use case for multivariant discriminants that enhance the selectivity of the signals and reject the overwhelming background contributions. The discriminants presented are built using state-of-the-art machine learning techniques, able to capture the correlations amongst the processes involved, as well as the so-called Matrix Element Method (MEM), which combines the theoretical description of the processes with the detector resolution effects. The level of sophistication of the methods used, along with the unprecedented amount of collision data analyzed, result in the most stringent measurements of the tH and ttH cross sections up to date.
Higgs Boson Decays Into A Pair Of Bottom Quarks
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Author : Cecilia Tosciri
language : en
Publisher: Springer Nature
Release Date : 2021-10-22
Higgs Boson Decays Into A Pair Of Bottom Quarks written by Cecilia Tosciri and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-10-22 with Science categories.
The discovery in 2012 of the Higgs boson at the Large Hadron Collider (LHC) represents a milestone for the Standard Model (SM) of particle physics. Most of the SM Higgs production and decay rates have been measured at the LHC with increased precision. However, despite its experimental success, the SM is known to be only an effective manifestation of a more fundamental description of nature. The scientific research at the LHC is strongly focused on extending the SM by searching, directly or indirectly, for indications of New Physics. The extensive physics program requires increasingly advanced computational and algorithmic techniques. In the last decades, Machine Learning (ML) methods have made a prominent appearance in the field of particle physics, and promise to address many challenges faced by the LHC. This thesis presents the analysis that led to the observation of the SM Higgs boson decay into pairs of bottom quarks. The analysis exploits the production of a Higgs boson associated with a vector boson whose signatures enable efficient triggering and powerful background reduction. The main strategy to maximise the signal sensitivity is based on a multivariate approach. The analysis is performed on a dataset corresponding to a luminosity of 79.8/fb collected by the ATLAS experiment during Run-2 at a centre-of-mass energy of 13 TeV. An excess of events over the expected background is found with an observed (expected) significance of 4.9 (4.3) standard deviation. A combination with results from other \Hbb searches provides an observed (expected) significance of 5.4 (5.5). The corresponding ratio between the signal yield and the SM expectation is 1.01 +- 0.12 (stat.)+ 0.16-0.15(syst.). The 'observation' analysis was further extended to provide a finer interpretation of the V H(H → bb) signal measurement. The cross sections for the VH production times the H → bb branching ratio have been measured in exclusive regions of phase space. These measurements are used to search for possible deviations from the SM with an effective field theory approach, based on anomalous couplings of the Higgs boson. The results of the cross-section measurements, as well as the constraining of the operators that affect the couplings of the Higgs boson to the vector boson and the bottom quarks, have been documented and discussed in this thesis. This thesis also describes a novel technique for the fast simulation of the forward calorimeter response, based on similarity search methods. Such techniques constitute a branch of ML and include clustering and indexing methods that enable quick and efficient searches for vectors similar to each other. The new simulation approach provides optimal results in terms of detector resolution response and reduces the computational requirements of a standard particles simulation.
Search For Invisible Decays Of The Higgs Boson Produced Via Vector Boson Fusion At The Lhc With Cms Run 2 Data
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Author : Alp Akpinar
language : en
Publisher: Springer Nature
Release Date : 2024-12-23
Search For Invisible Decays Of The Higgs Boson Produced Via Vector Boson Fusion At The Lhc With Cms Run 2 Data written by Alp Akpinar and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2024-12-23 with Science categories.
This thesis reports the latest measurements on one of the leading dark matter searches conducted by the Compact Muon Solenoid (CMS) experiment at CERN, leading to some of the most stringent constraints on hypothesized interactions between the Higgs boson and dark matter. The thesis also includes further research about the future outlook of the experiment, including exploratory research on the adaptation of deep learning models in future dark matter analyses to improve analysis sensitivity, and the design of a new type of data processing hardware to be used in the next phase of the CMS experiment.
A Search For Exotic Higgs Decays
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Author : Jackson Burzynski
language : en
Publisher: Springer Nature
Release Date : 2023-05-23
A Search For Exotic Higgs Decays written by Jackson Burzynski and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-05-23 with Science categories.
The absence of new physics at the TeV scale observed thus far at the Large Hadron Collider (LHC) motivates an increasing focus on searches for weakly-coupled new particles and exotic signatures. In particular, particles with macroscopic mean proper lifetimes, known as long-lived particles (LLPs), are of significant interest due to their ability to elude the majority of searches which rely on the assumption that Beyond Standard Model particles decay close to the primary interaction point. Many models which aim to solve various issues with the Standard Model (SM) introduce new particles with lifetimes that are either unconstrained, or even shown to prefer the macroscopic regime. These theories often point to the Higgs boson as a possible portal to new physics, with exotic Higgs decays being the primary phenomenological consequence and means of discovery. It is well motivated both from theory and experimental constraints to consider the scenario in which the particles produced in these exotic decays have macroscopic proper lifetimes and give rise to unique detector signatures. This work describes a search for exotic decays of the Higgs boson to two long-lived, neutral, spin-0 particles which subsequently decay to pairs of b quarks, giving the striking signature of displaced hadronic jets in the ATLAS inner detector. Several other ATLAS searches have probed this decay topology previously, excluding branching ratios of the Higgs boson to LLPs of more than 10% for proper lifetimes greater than 100mm. These searches relied on dedicated triggers designed to select events with LLPs decaying in the ATLAS calorimeter or muon spectrometer. The lack of an equivalent trigger for LLP decays in the ATLAS inner detector has been a limiting factor in probing LLP lifetimes less than 100mm. To circumvent the difficulty of triggering on LLP decays, the search presented in this thesis exploits the ZH associated production mode, relying on leptonic trigger signatures to select interesting events. This is the first search for Higgs boson decays into LLPs to exploit this analysis methodology and additionally makes use of several novel methods for both background rejection and background estimation. No excess over Standard Model predictions is observed, and upper limits are set on the branching ratio of the Higgs boson to LLPs . Depending on the mass of the LLP, branching ratios greater than 10% are excluded for lifetimes as small as 4mm and as large as 100mm, probing an important gap in the ATLAS exotic Higgs decay programme. In comparison to the previous searches for Higgs decays to LLPs, these are among the most stringent limits placed on this scenario, and for LLPs with masses below 40 GeV these results represent the strongest existing constraints on the branching ratio of the Higgs boson to LLPs in this lifetime regime.
Search For Tt H Production In The H Bb Decay Channel
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Author : Marcel Rieger
language : en
Publisher: Springer Nature
Release Date : 2021-02-25
Search For Tt H Production In The H Bb Decay Channel written by Marcel Rieger and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-02-25 with Science categories.
In 1964, a mechanism explaining the origin of particle masses was proposed by Robert Brout, François Englert, and Peter W. Higgs. 48 years later, in 2012, the so-called Higgs boson was discovered in proton-proton collisions recorded by experiments at the LHC. Since then, its ability to interact with quarks remained experimentally unconfirmed. This book presents a search for Higgs bosons produced in association with top quarks tt̄H in data recorded with the CMS detector in 2016. It focuses on Higgs boson decays into bottom quarks H → bb̅ and top quark pair decays involving at least one lepton. In this analysis, a multiclass classification approach using deep learning techniques was applied for the first time. In light of the dominant background contribution from tt̄ production, the developed method proved to achieve superior sensitivity with respect to existing techniques. In combination with searches in different decay channels, the presented work contributed to the first observations of tt̄H production and H → bb̅ decays.
Search For Higgs Boson Pair Production In The Bb Decay Channel
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Author : Luca Cadamuro
language : en
Publisher: Springer
Release Date : 2018-12-06
Search For Higgs Boson Pair Production In The Bb Decay Channel written by Luca Cadamuro and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-12-06 with Science categories.
This thesis presents innovative contributions to the CMS experiment in the new trigger system for the restart of the LHC collisions in Run II, as well as original analysis methods and important results that led to official publications of the Collaboration. The author's novel reconstruction algorithms, deployed on the Field-Programmable Gate Arrays of the new CMS trigger architecture, have brought a gain of over a factor 2 in efficiency for the identification of tau leptons, with a very significant impact on important H boson measurements, such as its decays to tau lepton pairs and the search for H boson pair production. He also describes a novel analysis of HH → bb tautau, a high priority physics topic in a difficult channel. The original strategy, optimisation of event categories, and the control of the background have made the result one of the most sensitive concerning the self-coupling of the Higgs boson among all possible channels at the LHC.
The Standard Model Higgs Boson Discovery Potential In The Decay Channel H Zz Superscript 4 Mu With The Cms Detector
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Author : Alexey Alexandrovich Drozdetskiy
language : en
Publisher:
Release Date : 2007
The Standard Model Higgs Boson Discovery Potential In The Decay Channel H Zz Superscript 4 Mu With The Cms Detector written by Alexey Alexandrovich Drozdetskiy and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
ABSTRACT: The Compact Muon Solenoid (CMS) is a general purpose detector at the Large Hadron Collider (LHC) currently under construction at CERN with start-up date in 2008. The putative Higgs boson is the most plausible solution for the mystery of mass in the Standard Model of elementary particles and its discovery is one of the prime goals for the LHC. Higgs boson search. Our research presents an optimized strategy for a Higgs boson search in its four-muon decay channel, H--> ZZ[superscript*]--> 4[mu], also known as a golden decay channel. The method automatically ensures an optimal signal-to-background ratio for any mass, at which the Higgs boson might appear. The most important theoretical and instrumental systematic errors are taken into account and our search was conducted in a broad range of possible Higgs boson masses. Muon reconstruction. We developed an algorithm for a fast and efficient muon track segment reconstruction in Cathode Strip Chambers. Designed to be CPU-efficient, the algorithm is specifically targeted for High Level Trigger purposes. The segment-finding efficiency and the spatial resolution attainable with the proposed algorithm and the required CPU time were validated using the cosmic ray data taken by the CMS in 2006. The results of validation showed the efficiency and spatial resolution attainable with the algorithm are well within the High Level Trigger requirements and the algorithm's timing performance is by far superior to all algorithms previously used in CMS.
Search For Exotic Decays Of A Higgs Boson Into Undetectable Particles And One Or More Photons
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Author :
language : en
Publisher:
Release Date : 2015
Search For Exotic Decays Of A Higgs Boson Into Undetectable Particles And One Or More Photons written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
A search is presented for exotic decays of a Higgs boson into undetectable particles and one or two isolated photons in pp collisions at a center-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of up to 19.4 inverse femtobarns collected with the CMS detector at the LHC. Higgs bosons produced in gluon-gluon fusion and in association with a Z boson are investigated, using models in which the Higgs boson decays into a gravitino and a neutralino or a pair of neutralinos, followed by the decay of the neutralino to a gravitino and a photon. The selected events are consistent with the background-only hypothesis, and limits are placed on the product of cross sections and branching fractions. Assuming a standard model Higgs boson production cross section, a 95% confidence level upper limit is set on the branching fraction of a 125 GeV Higgs boson decaying into undetectable particles and one or two isolated photons as a function of the neutralino mass. For this class of models and neutralino masses from 1 to 120 GeV an upper limit in the range of 7 to 13% is obtained. Further results are given as a function of the neutralino lifetime, and also for a range of Higgs boson masses.