Ulaşcan Sarıca

We present an extension of the JHUGen and MELA framework, which includes an event generator and library for the matrix element analysis. It enables simulation, optimal discrimination, reweighting techniques, and analysis of a bosonic resonance and the triple and quartic gauge boson interactions with the most general anomalous couplings. The new features, which become especially relevant at the current stage of LHC data taking, are the simulation of gluon fusion and vector boson fusion in the off-shell region, associated $ZH$ production at NLO QCD including the $gg$ initial state, and the simulation of a second spin-zero resonance. We also quote translations of the anomalous coupling measurements into constraints on dimension-six operators of an effective field theory. Some of the new features are illustrated with projections for experimental measurements with the full LHC and HL-LHC datasets.

We investigate the "low-$ν$" method (developed by the CCFR/NUTEV collaborations) to determine the neutrino flux in a wide band neutrino beam at very low energies, a region of interest to neutrino oscillations experiments. Events with low hadronic final state energy $ν

We describe the application of the `low-$\nu$' method to the extraction of the neutrino flux at MiniBooNE energies. As an example, we extract the relative energy dependence of the flux from published MiniBooNE quasielastic scattering cross sections with $\nu < 0.2$ GeV and $\nu < 0.1$ GeV (here $\nu$ is the energy transfer to the target). We find that the flux extracted from the `low-$\nu$' cross sections is consistent with the nominal flux used by MiniBooNE. We fit the MiniBooNE cross sections over the entire kinematic range to various parametrizations of the axial form factor. We find that if the overall normalization of the fit is allowed to float within the normalization errors, the extracted values of the axial vector mass are independent of the flux. Within the Fermi gas model, the $Q^2$ distribution of the MiniBooNE data is described by a standard dipole form factor with $M_A=1.41\pm0.04$ GeV. If nuclear transverse enhancement in the vector form factors is accounted for, the data are best fit with a modified dipole form factor with $M_A=1.10\pm 0.03$ GeV.

We investigate the low-$\nu$ method (developed by the CCFR/NUTEV collaborations) to determine the neutrino flux in a wide band neutrino beam at very low energies, a region of interest to neutrino oscillations experiments. Events with low hadronic final state energy $\nu<\nu_{cut}$ (of 1, 2 and 5 GeV) were used by the MINOS collaboration to determine the neutrino flux in their measurements of neutrino ($\nu_\mu$) and antineutrino ($\nub_\mu$) total cross sections. The lowest $\nu_\mu$ energy for which the method was used in MINOS is 3.5 GeV, and the lowest $\nub_\mu$ energy is 6 GeV. At these energies, the cross sections are dominated by inelastic processes. We investigate the application of the method to determine the neutrino flux for $\nu_\mu$, $\nub_\mu$ energies as low as 0.7 GeV where the cross sections are dominated by quasielastic scattering and $\Delta$(1232) resonance production. We find that the method can be extended to low energies by using $\nu_{cut}$ values of 0.25 and 0.50 GeV, which is feasible in fully active neutrino detectors such as MINERvA.

Recent studies in quantum computing have shown that quantum error correction with large numbers of physical qubits are limited by ionizing radiation from high-energy particles. Depending on the physical setup of the quantum processor, the contribution of muons from cosmic sources can constitute a significant fraction of these interactions. As most of these muons are difficult to stop, we perform a conceptual study of a two-layer silicon pixel detector to tag their hits on a solid-state quantum processor instead. With a typical dilution refrigerator geometry model, we find that efficiencies greater than 50% are most likely to be achieved if at least one of the layers is operated at the deep-cryogenic (<1 K) flanges of the refrigerator. Following this finding, we further propose a novel research program that could allow the development of silicon pixel detectors that are fast enough to provide input to quantum error correction algorithms, can operate at deep-cryogenic temperatures, and have very low power consumption.

Abstract Recent studies in quantum computing have shown that quantum error correction with large numbers of physical qubits are limited by ionizing radiation from high-energy particles. Depending on the physical setup of the quantum processor, the contribution of muons from cosmic sources can constitute a significant fraction of these interactions. As most of these muons are difficult to stop, we perform a conceptual study of a two-layer silicon pixel detector to tag their hits on a solid-state quantum processor instead. With a typical dilution refrigerator geometry model, we find that efficiencies greater than 50% are most likely to be achieved if at least one of the layers is operated at the deep-cryogenic (&lt;1 K) flanges of the refrigerator. Following this finding, we further propose a novel research program that could allow the development of silicon pixel detectors that are fast enough to provide input to quantum error correction algorithms, can operate at deep-cryogenic temperatures, and have very low power consumption.

This thesis documents the measurement of lifetime, width, mass, and couplings to two electroweak bosons of the Higgs boson using data from the CMS experiment at the Large Hadron Collider, along with development of the Monte Carlo and matrix element techniques for analysis of LHC data.

We investigate the low-ν method (developed by the CCFR/NUTEV collaborations) to determine the neu- trino flux in a wide band neutrino beam at very low en- ergies, a region of interest to neutrino oscillations experi- ments. Events with low hadronic final state energy ν< ν cut (of 1, 2 and 5 GeV) were used by the MINOS collabora- tion to determine the neutrino flux in their measurements of neutrino (νμ) and antineutrino (¯ νμ) total cross sections. The lowest νμ energy for which the method was used in MINOS is 3.5 GeV, and the lowest ¯ νμ energy is 6 GeV. At these energies, the cross sections are dominated by inelastic pro- cesses. We investigate the application of the method to deter- mine the neutrino flux for νμ, ¯ νμ energies as low as 0.7 GeV where the cross sections are dominated by quasielastic scat- tering and Δ(1232) resonance production. We find that the method can be extended to low energies by using νcut val- ues of 0.25 and 0.50 GeV, which are feasible in fully active neutrino detectors such as MINERvA.

This report presents the results of the Models and Effective Field Theories Subgroup of the Off-Shell Interpretations Task Force in the LHC Higgs Working Group. The main goal of the subgroup was to discuss and advance the potential impact of off-shell Higgs measurements on searches for BSM physics carried out in the EFT framework or as benchmark model studies. In the first contribution, the off-shell potential to resolve flat directions in parameter space for on-shell measurements is studied. Furthermore, the sensitivity of off-shell measurements to SMEFT dimension-6 operators for the gg $\to$ ZZ process is discussed, and studies of explicit models that are testable in off-shell production are reviewed. In the second contribution, the SMEFT effects in the off-shell gluon fusion and electroweak processes are discussed. Subsequently, the computation of integrated and differential effects using SMEFT@NLO and MG5_aMC@NLO, or JHUGen and MCFM, is demonstrated. On that basis, a study of the prospects of obtaining additional SMEFT constraints - beyond those from existing global fits - by utilising the off-shell process is presented. For clarification, a revised introduction, definition and discussion of the Higgs basis parametrisation of the SMEFT is given in the third contribution. In short notes on the SMEFT, the Higgs basis with an additional constraint is discussed and relations between the Higgs and Warsaw bases are presented. Lastly, an overview of EFT calculations and tools is given.

The conventional method for studying the interactions between fundamental particles at a desired energy has been to use a particle accelerator to accelerate a chosen particle to this energy, and then to either aim it at a fixed solid, liquid, or gaseous target or collide it with another accelerated particle. In fixed-target experiments, the energy available in the collision grows with the square-root of the incident beam energy, whereas in colliders, the collision energy grows linearly with the energy of the incident beam. The accelerated particles in both cases are typically protons or electrons, which are stable and easy to produce in abundance. In the case of electrons, the energy of the beam can be tuned precisely to make observations at a very narrow energy range. The proton is composed of valence and sea quarks and gluons, so even though the energy of the proton beam can still be tuned equally well, the energy of interaction between two constituent partons covers a wider range. The CERN Large Hadron Collider (LHC) is constructed as a circular proton–proton collider for this purpose, to be able to measure the properties of SM particles and search for physics beyond the SM (BSM physics) at a wide, high energy spectrum.

Constraints on anomalous HVV couplings are placed using events from the Run 1 or Run 2 data taking periods. The general formalism of these couplings was already mentioned in detail in Sect. 3.1 . In the Run 1 analysis, the tested contributions are a 2, a 3, Λ1 for the HZZ vertex, a2Zγ, a3Zγ, and Λ1Zγ for the HZγ vertex, and a2γγ and a3γγ for the Hγγ vertex. HZZ and HWW couplings are assumed to be the same, but test of separating them on the decay side are also performed via comparison to events from H →WW → 2ℓ2ν events. In Run 2, only the anomalous HZZ contributions, or the Λ1Zγ contribution, are tested from the 4ℓ decay with the assumption that HZZ and HWW couplings are the same.

Particle physics is the branch of physics that studies the different fundamental particles in nature and how one type interacts with another. There are two classes of these particles based on their spin: fermions and bosons. Fermions have an odd-integer multiple of $$\frac {1}{2}$$ spin and obey Fermi–Dirac statistics, and by the Fermi exclusion principle, two different fermions cannot occupy the same quantum state. Almost all of the ordinary objects with which humans interact are composed of fermions. Ignoring finer distinctions for the moment, only 12 elementary fermions are known, 6 leptons and 6 quarks, each of which can be subdivided into three generations with similar properties. Bosons, on the other hand, have an even-integer spin and obey Bose–Einstein statistics. Elementary bosons act as mediators between fermions and are the main carries of force in interaction, which could be either strong, weak, electromagnetic, or gravitational.

The observation of an H boson with the mass around 125 GeV by the ATLAS and CMS Collaborations is consistent with the expectations of the SM. There have been several experimental and theoretical observations made to this date about this recently discovered boson.

We present an extension of the JHUGen and MELA framework, which includes an event generator and library for the matrix element analysis. It enables simulation, optimal discrimination, reweighting techniques, and analysis of a bosonic resonance and the triple and quartic gauge boson interactions with the most general anomalous couplings. The new features, which become especially relevant at the current stage of LHC data taking, are the simulation of gluon fusion and vector boson fusion in the off-shell region, associated $ZH$ production at NLO QCD including the $gg$ initial state, and the simulation of a second spin-zero resonance. We also quote translations of the anomalous coupling measurements into constraints on dimension-six operators of an effective field theory. Some of the new features are illustrated with projections for experimental measurements with the full LHC and HL-LHC datasets.

Studies of the production and decay of the spin-0 H boson are described. In particular, anomalous HVV couplings are studied in Sect. 4.1 from on-shell H boson production in 4ℓ and WW → ℓνℓν decay using the Run 1 data collected by the CMS detector. These constraints and techniques are improved in the Run 2 on-shell analysis of the 4ℓ decay channel. Events from Run 1 are also analyzed in Sect. 4.2 for the 4ℓ vertex information to make a direct and model-independent measurement of the H boson lifetime, constraining it from above and thereby the H boson total width, ΓH, from below. The value of ΓH is constrained further in Sect. 4.3 by employing the off-shell technique in the 4ℓ decay channel. These constraints are placed using events from both Run 1 and Run 2 data sets.