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Andre Sopczak

Publications and source records attributed to Andre Sopczak.

At least 19 recordsLinked to original sources
arXiv2026

High-mass new scalars at the LHC, with H in the final state

The search for new particles, conducted at the LHC by the ATLAS and CMS collaborations, covers several production and decay modes, leading to a large variety of final states that could be observed in both detectors. This review focuses on the production of new heavy scalars that have a Higgs boson in the final state. Three cases are covered: resonant production of a heavy scalar $X$ decaying into a Higgs boson and a lighter scalar $S$, heavy neutral Higgs boson decaying into another neutral Higgs boson and a $Z$ boson, and a heavy charged Higgs boson production with subsequent decay into another neutral Higgs boson and a $W$ boson. The reviewed searches are based on the complete LHC Run-2 dataset and partial Run-3 dataset.

hep-ex↗
arXiv2026

Hypothesis Tests for Observing Quantum Entanglement in HWW at the LHC

We present a novel experimental strategy for testing quantum entanglement in Higgs boson decays to $W$ boson pairs at the Large Hadron Collider. Unlike theoretical approaches that rely on expectation values of Bell operators, which are highly sensitive to outliers and detector effects, we introduce a continuous formulation of the CGLMP inequality that enables standard hypothesis testing between entangled and separable states. To overcome the fundamental challenge of reconstructing invisible neutrino momenta in the $H \rightarrow WW^* \rightarrow \ellν\ellν$ channel, we employ conditional denoising diffusion probabilistic models (cDDPM), which provide unbiased, multidimensional unfolding applicable to the full measured dataset, including backgrounds. We evaluate the diffusion-based reconstruction against analytical methods through profile likelihood hypothesis tests implemented in RooFit, with systematic uncertainties from background normalisation and unfolding shape fully propagated. Our results demonstrate that the diffusion-based approach enables robust hypothesis testing of quantum entanglement in a realistic collider environment, with 3$σ$ evidence of quantum entanglement projected at approximately 555~fb$^{-1}$ and exceeding 5$σ$ at 1600~fb$^{-1}$ to be well within the expected limits of the HL-LHC luminosity targets.

hep-ex↗
arXiv2025

Prospects for Higgs Boson Research at the LHC

The search for Higgs bosons in the Standard Model (SM) of particle physics and Beyond the Standard Model (BSM) started intensively at the Large Electron-Positron (LEP) collider, which operated from 1989 to 2000, and later at the Tevatron from 2001 to 2011. In 2012, with the discovery of a Higgs boson at the Large Hadron Collider (LHC) at CERN, a new era began. This allowed for precision measurements of the Higgs boson properties which, so far, are all consistent with the SM expectations. Many searches for predicted BSM Higgs bosons advanced the field of experimental Higgs boson physics. The LHC already operated in three running periods: Run-1 from 2010 to 2012, Run-2 from 2015 to 2018, and currently Run-3 from 2022 to 2026. The High-Luminosity LHC (HL-LHC) operation is foreseen from 2030. The prospects of experimental Higgs boson research for the next decade are reviewed.

hep-ex↗
arXiv2025

The Czech Particle Physics Project

We present the status of the Czech Particle Physics Project (CPPP). The CPPP is a learning tool in masterclasses aimed at high school students (aged 15 to 18). The project is structured in modules. The first module is dedicated to the detection of an Axion-Like-Particle (ALP) using the ATLAS Forward Proton (AFP) detector. The second module focuses on the reconstruction of the Higgs boson mass using the Higgs boson golden channel with four leptons in the final state. The third and fourth modules are educational aids and sources for expert information. These web portals are dedicated to Higgs boson research and searches for Supersymmetry. Two databases are created with more than 1000 relevant articles each, using the CERN Document Server API and web scraping methods. The databases are automatically updated when new results on Higgs bosons or searches for Supersymmetric particles become available. Using artificial intelligence and natural language processing, the articles are categorized according to properties of the results. The modules are accessible at https://cern.ch/cppp.

hep-ph↗
arXiv2025

Overview of the latest ATLAS and ATLAS-AFP photoproduction results

A key focus of the physics program at the LHC is the study of head-on proton-proton collisions. However, an important class of physics can be studied for cases where the protons narrowly miss one another and remain intact. In such cases, the electromagnetic fields surrounding the protons can interact producing high-energy photon-photon collisions. Alternatively, interactions mediated by the strong force can also result in intact forward scattered protons, providing probes of quantum chromodynamics (QCD). In order to aid identification and provide unique information about these rare interactions, instrumentation to detect and measure protons scattered through very small angles is installed in the beam pipe far downstream of the interaction point. We review photoproduction results from data collected with the ATLAS Forward Proton (AFP) and Absolute Luminosity For ATLAS (ALFA) detectors in proton-proton and heavy ion collisions.

hep-ex↗
arXiv2022

Outreach Modules for New Particle Searches Using the ATLAS Forward Proton Detector and for Higgs Boson Physics

We present two modules as part of the Czech Particle Physics Project (CPPP). These modules are intended as learning tools in masterclasses aimed at high-school students (aged 15 to 18). The first module is dedicated to the detection of an Axion-Like-Particle (ALP) using the ATLAS Forward Proton (AFP) detector. The second module focuses on the reconstruction of the Higgs boson mass using the Higgs boson golden channel with four leptons in the final state. The modules are accessible at http://cern.ch/cppp.

hep-ex↗
arXiv2022

A Portal Dedicated to Higgs Bosons for Experts and the General Public

As an educational aid and source for expert information, a web portal dedicated to Higgs boson research is presented. A database is created with more than 1000 relevant articles using CERN Document Server API and web scraping methods. The database is automatically updated when new results on the Higgs boson become available. Using artificial intelligence and natural language processing, the articles are categorized according to properties of the Higgs boson and other criteria. The process of designing and implementing the Higgs Boson Portal (HBP) is described. The components of the HBP are deployed to CERN Web Services using the OpenShift cloud platform. The HBP is accessible within the Czech Particle Physics Project (CPPP) at http://cern.ch/cppp and directly at http://cern.ch/higgs.

hep-ph↗
arXiv2021

Searches for Leptoquarks with the ATLAS Detector

Leptoquarks (LQ) are predicted by many new physics theories to describe the similarities between the lepton and quark sectors of the Standard Model and offer an attractive potential explanation for the lepton flavour anomalies observed at LHCb and flavour factories. The ATLAS experiment has a broad program of direct searches for Leptoquarks, coupling to the first-, second- or third-generation particles. The most recent 13 TeV results on the searches for Leptoquarks and contact interactions with the ATLAS detector are reviewed, covering flavour-diagonal and cross-generational final states.

hep-ex↗
arXiv2020

Precision Measurements in the Higgs Sector at ATLAS and CMS

A concise review of precision measurements in the Higgs sector of the Standard Model (SM) of particle physics is given using ATLAS and CMS data. The results are based on LHC Run-2 data, taken between 2015 and 2018. Impressive progress has been made since the discovery of the Higgs boson in 2012 for measuring all major production and decay modes. Good agreement with the SM predictions was observed in all measurements.

hep-ex↗
arXiv2017

SUSY (ATLAS)

During the LHC Run-II data-taking period, several searches for supersymmetric particles were performed by the ATLAS collaboration. The results from these searches are concisely reviewed. Model-independent and model-dependent limits on new particle production are set, and interpretations in supersymmetric models are given.

hep-ph↗
arXiv2017

Precision Luminosity of LHC Proton-Proton Collisions at 13 TeV Using Hit-Counting with TPX Pixel Devices

A network of Timepix (TPX) devices installed in the ATLAS cavern measures the LHC luminosity as a function of time as a stand-alone system. The data were recorded from 13 TeV proton-proton collisions in 2015. Using two TPX devices, the number of hits created by particles passing the pixel matrices was counted. A van der Meer scan of the LHC beams was analysed using bunch-integrated luminosity averages over the different bunch profiles for an approximate absolute luminosity normalization. It is demonstrated that the TPX network has the capability to measure the reduction of LHC luminosity with precision. Comparative studies were performed among four sensors (two sensors in each TPX device) and the relative short-term precision of the luminosity measurement was determined to be 0.1% for 10 s time intervals. The internal long-term time stability of the measurements was below 0.5% for the data-taking period.

physics.ins-det↗
arXiv2016

Searches for ttH (Multilepton+Diphoton) Production in ATLAS

After the discovery of a Higgs boson, the measurements of its properties are at the forefront of research. The determination of the associated production of a Higgs boson and a pair of top quarks is of particular importance as the ttH Yukawa coupling is large and thus an excellent probe for physics beyond the Standard Model (SM). For the complete LHC Run-1 dataset, the combined ATLAS and CMS signal strength (defined as the ratio of measured cross-section to the SM prediction) was $μ=2.3^{+0.7}_{-0.6}$, which indicated a mild excess with respect to the SM expectation. The results of the ttH search with multilepton and diphoton signatures are presented for the first LHC Run-2 data (13 fb$^{-1}$ at 13 TeV) recorded by the ATLAS experiment: $μ=2.5^{+1.3}_{-1.1}$ for the multilepton analyses and $μ=-0.3^{+1.2}_{-1.0}$ for the diphoton analyses. Both measurements are in agreement with the SM expectation.

hep-ph↗
arXiv2015

MPX Detectors as LHC Luminosity Monitor

A network of 16 Medipix-2 (MPX) silicon pixel devices was installed in the ATLAS detector cavern at CERN. It was designed to measure the composition and spectral characteristics of the radiation field in the ATLAS experiment and its surroundings. This study demonstrates that the MPX network can also be used as a self-sufficient luminosity monitoring system. The MPX detectors collect data independently of the ATLAS data-recording chain, and thus they provide independent measurements of the bunch-integrated ATLAS/LHC luminosity. In particular, the MPX detectors located close enough to the primary interaction point are used to perform van der Meer calibration scans with high precision. Results from the luminosity monitoring are presented for 2012 data taken at sqrt(s) = 8 TeV proton-proton collisions. The characteristics of the LHC luminosity reduction rate are studied and the effects of beam-beam (burn-off) and beam-gas (single bunch) interactions are evaluated. The systematic variations observed in the MPX luminosity measurements are below 0.3% for one minute intervals.

physics.ins-det↗
arXiv2013

Luminosity Monitoring in ATLAS with MPX Detectors

The ATLAS-MPX detectors are based on the Medipix2 silicon devices designed by CERN for the detection of multiple types of radiation. Sixteen such detectors were successfully operated in the ATLAS detector at the LHC and collected data independently of the ATLAS data-recording chain from 2008 to 2013. Each ATLAS-MPX detector provides separate measurements of the bunch-integrated LHC luminosity. An internal consistency for luminosity monitoring of about 2% was demonstrated. In addition, the MPX devices close to the beam are sensitive enough to provide relative-luminosity measurements during van der Meer calibration scans, in a low-luminosity regime that lies below the sensitivity of the ATLAS calorimeter-based bunch-integrating luminometers. Preliminary results from these luminosity studies are presented for 2012 data taken at sqrt(s)=8 TeV proton-proton collisions.

physics.ins-det↗
arXiv2010

Highlights of Current Higgs Boson Searches

Over the last years the Tevatron Run-II has extended several limits on Higgs boson masses and coupling which were pioneered during the LEP accelerator operation between 1989 and 2000. Higgs boson searches will also be at the forefront of research at the LHC. This review concisely discusses the experimental constraints set by the CDF and D0 collaborations in summer 2010 at the beginning of the LHC era. Model-independent and model-dependent limits on Higgs boson masses and couplings have been set and interpretations are discussed both in the Standard Model and in extended models. Recently, the Tevatron has extended the excluded SM Higgs boson mass range (158-175 GeV) beyond the LEP limit at 95% CL. The experimental sensitivities are estimated for the completion of the Tevatron programme.

hep-ph↗
arXiv2009

Comparison of Measurements of Charge Transfer Inefficiencies in a CCD with High-Speed Column Parallel Readout

Charge Coupled Devices (CCDs) have been successfully used in several high energy physics experiments over the past two decades. Their high spatial resolution and thin sensitive layers make them an excellent tool for studying short-lived particles. The Linear Collider Flavour Identification (LCFI) Collaboration has been developing Column-Parallel CCDs for the vertex detector of a future Linear Collider which can be read out many times faster than standard CCDs. The most recent studies are of devices designed to reduce both the CCD's intergate capacitance and the clock voltages necessary to drive it. A comparative study of measured Charge Transfer Inefficiency values between our previous and new results for a range of operating temperatures is presented.

physics.ins-det↗
arXiv2009

The LCFIVertex package: vertexing, flavour tagging and vertex charge reconstruction with an ILC vertex detector

The precision measurements envisaged at the International Linear Collider (ILC) depend on excellent instrumentation and reconstruction software. The correct identification of heavy flavour jets, placing unprecedented requirements on the quality of the vertex detector, will be central for the ILC programme. This paper describes the LCFIVertex software, which provides tools for vertex finding and for identification of the flavour and charge of the leading hadron in heavy flavour jets. These tools are essential for the ongoing optimisation of the vertex detector design for linear colliders such as the ILC. The paper describes the algorithms implemented in the LCFIVertex package, as well as the scope of the code and its performance for a typical vertex detector design.

physics.ins-det↗