Since the discovery of the Higgs boson with a mass near 125 GeV, much effort has been dedicated to studying its properties. This talk presents one such study, which investigates the CP structure of the Higgs boson by exploiting the gluon fusion production process in association with two jets. Analysis of the azimuthal angle correlations of the jets provides an insight into the CP nature of the...
We review the recent measurement of the inclusive ttZ cross-section with 36 fb-1 of data at 13 TeV at the ATLAS experiment, using EFT considerations and background modelling for generic SUSY/DM searches as motivation for continuing to improve the precision of this result. We then present plans for a differential ttZ measurement in the 3 and 4 lepton channels with the full 140 fb-1 Run 2...
Long-lived particles feature in many extensions to the Standard Model that have been proposed to address some of its open questions. Decays of long-lived particles created in collider experiments would produce unique signatures that may have been overlooked by previous searches for promptly decaying particles.
A search for pairs of neutral long-lived particles (LLPs) decaying in the volume...
A measurement of the top-antitop charge asymmetry is underway at the ATLAS experiment at the LHC. This is being being performed at 13 TeV with 80 fb-1 of proton-proton collision data, with the eventual aim to use the full 140 fb-1 Run 2 dataset. The method of Fully Bayesian Unfolding (FBU) is employed to determine the parton-level charge asymmetry. This technique generates a posterior...
At low energies, the world around us can be accurately described using the Standard Model. However, this is at best only an ''effective'' description: valid at low energies but destined to break down as experiments probe increasingly higher energies, ultimately requiring a new (UV complete) theory to take over.
In this talk, I will demonstrate that certain constraints must be placed on such...
The coupling strength of the higgs boson to fermions is predicted to be proportional to the fermions mass, making the higgs top coupling the strongest in the SM.
This coupling strength can be directly measured in the production of a higgs boson in combination with two top quarks, which was observed in 2018. In the SM, the higgs top coupling is predicted to be a CP-even coupling but measuring a...
Higgs decay to a muon pair is the most promising way to probe Yukawa couplings to the second generation fermions at the LHC. Experimentally the analysis is challenging due to a small branching ratio (2.2*10^-4) and proceeds as a search for an excess at the Higgs mass in the dimuon invariant mass spectrum dominated by the irreducible Drell-Yan background. This talk presents the search with 79.8...
I will be presenting an overview of the ATLAS analysis of the single dissociative diffraction cross-section in p-p collisions at 13 TeV. I am the main analyser for this measurement and it will be the topic of my PhD thesis.
Single dissociative diffraction (pp->pX) occurs when there is a t-channel exchange with the quantum numbers of the vacuum with one proton remaining intact and the other...
The discovery of the Higgs boson in 2012 by the ALTAS and CMS experiments at CERN was only the beginning, the properties of this particle still need to be measured and compared with theoretical predictions. The ttH production channel allows a direct measurement of the Higgs coupling to top quarks, the heaviest particle in the Standard Model, while the H→γγ decay channel gives a narrow peak in...
Since the discovery of the Higgs boson in 2012, the observed production and decay modes have all been related to its coupling to gauge bosons and to third generation fermions. The focus is now shifting towards the Higgs boson couplings to the second generation fermions, in particular to muons, but the first generation is much less explored. This talk will present the ongoing efforts within the...
The author/presenter will outline the status of the search for Supersymmetry (SUSY) in the 3rd generation sector, particularly the SUSY partner of the top quark, using the 140.5 ifb dataset collected from the ATLAS detector from LHC Run 2 (2015-2018).
This analysis is searching in the all-hadronic channel for a reconstructed final state of top-antitop pairs and Missing Energy, looking to...
The LHCb experiment provides unique detector coverage, 2 < η < 5, of high energy proton-proton interactions produced at the Large Hadron Collider. Designed to study b- & c-hadron physics, LHCb is fully instrumented in the forward region with excellent tracking and vertex resolution.
The top quark is the heaviest fundamental particle and is expected to play a special role in new physics...
T2K is a long baseline neutrino oscillation experiment designed to make precise measurements of the parameters governing neutrino oscillations. A muon (anti-)neutrino beam is produced at the Japan Proton Accelerator Research Complex (J-PARC) on the east coast of Japan, and is aimed towards the Super-Kamiokande (SK) detector 295km away near the west coast. In this analysis, Markov Chain Monte...
Measurements of CP violation in B decays are entering a high precision era, and with the increasing precision comes a need for an equally precise understanding of limiting uncertainties. I will present a recent, world-leading precision measurement of the CP-violating CKM phase gamma, using data from the LHCb experiment. The measurement used B -> DK decays, where the D meson decays to a neutral...
The IceCube Neutrino Observatory detects astrophysical neutrinos with energies above TeV scales which provides the first solid evidence for astrophysical neutrinos from cosmological accelerators. Here we describe The High Energy Starting Event (HESE) selection and why it is useful for probing the high energy astrophysical landscape. With higher statistics taken over 7.5 years, we have been...
The compact linear collider - or CLIC - is a proposed electron-positron collider and is currently the only mature option for a multi-TeV linear collider. The CLIC accelerator is based on a novel two-beam acceleration technique at an acceleration gradient of 100 MV/m. It would be built in stages, with three centre-of-mass energies of 380 GeV, 1.5 GeV and 3 TeV. CLIC will make precise...
SBND, a 112 ton liquid argon time projection chamber, is the near detector of the short-baseline neutrino program at Fermilab. Once data taking begins in 2020, it will provide flux constraints for sterile neutrino searches and produce world leading neutrino-argon cross-sections with seven million neutrino events in 3 years. This talk will demonstrate the capability of SBND's time projection...
Understanding neutrino-nucleus interaction cross-sections at the 1-2 percent level will be crucial for the next generation of long baseline neutrino experiments. Due to its low hadron momentum detection threshold, a High Pressure gas Time Projection Chamber (HPTPC) is a strong candidate for achieving a significant reduction in uncertainties on these cross-sections . An HPTPC is part of the...
The Short Baseline Neutrino (SBN) programme at Fermilab consists of three Liquid Argon Time Projection Chambers (LArTPCs) on the Booster Neutrino Beam. The key goal of the SBN programme is to perform the most sensitive search to date for sterile neutrinos in the eV-mass scale through appearance and disappearance oscillation channels. In order to achieve the sensitivities capable to the SBN...
LUX-ZEPLIN (LZ) is a dark matter direct detection experiment under construction at the Sanford Underground Research Facility in Lead, South Dakota. The dual-phase TPC at its core will contain seven tonnes of active liquid xenon to search for Weakly Interacting Massive Particles (WIMPs). Fabrication and assembly operations are on track to start a 1000-day science run in 2020 with a fiducial...
The measurement of the Unitarity Triangle angle γ is a cornerstone of our understanding of the CKM mechanism of quark interactions.
Due to the tiny theoretical uncertainty in self-tagging B decays to D^()K^() final states, these modes will provide a standard candle in CP-violation physics as we drive towards the ultimate precision in flavour physics.
Results in the simplest final states...
Numerous recent anomalies in the b→sll flavour sector give indication of potential lepton flavour universality (LFU) violation in (axial-)vector couplings.
To probe these anomalies and further assumptions about LFU in other couplings, now more than ever, precise measurements of the SM properties are needed.
This talk presents one arm of these investigations using B+ → K+ee decays, with...
Currently there is a lot of activity in R&D for future colliders. Multiple detector prototypes are being tested, each with different requirements for data acquisition and monitoring, which has generated different ad hoc software solutions. We present DQM4hep, a generic C++11 framework for online monitoring for particle physics experiments, and results obtained at several testbeams with...
Various theories beyond the Standard Model propose baryon number violating processes in order to explain the matter-antimatter asymmetry in the universe, many of which result in some form of nucleon decay. Some modes of nucleon decay are invisible, in the sense that the final state particles remain undetected. Following the disappearance of one or two nucleons in such a nucleus, the subsequent...
LUX-ZEPLIN (LZ) is a next-generation two-phase xenon TPC detector operating at 4850 feet below ground with an active mass of 7 tonnes. The primary goal of LZ is to search for low-energy interactions from the dark matter halo in our galaxy — hypothesised to be in the form of Weakly Interacting Massive Particles (WIMPs). Operating for 1000 days and using a 5.6-tonne fiducial mass, LZ is...
Flavour Changing Neutral Current processes are heavily suppressed in the Standard Model of particle physics and are potentially sensitive to contributions from as yet undiscovered particles. Recent measurements of b→s transitions by the LHCb collaboration show interesting tensions with Standard Model predictions.
The large LHC data set enables measurements of decays involving b→d transitions...
As the LHC gathers ever more data and makes measurements with increasingly high precision, it is essential for theorists to match this precision when making predictions for cross-sections. In QCD and other gauge theories, this high precision is achieved by including multi-loop Feynman diagrams when calculating scattering amplitudes. Integration-by-parts identities (IBPs) are widely used when...
Dark matter experiments searching for weakly interacting massive particles (WIMPs) probe a variety of rare processes leading to O(keV) energy transfers to ordinary matter. Two-phase xenon detectors record two different signals per interaction: a prompt scintillation response (S1) and a delayed signal from ionisation (S2), with the energy threshold of standard analyses (S1+S2) largely...
This project aims to explore the effects that changes in a matter density profile could have on neutrino oscillations, and whether these could potentially be seen by the future Hyper-Kamiokande experiment (T2HK). The analysis is extended to include the possibility of having a second detector in Korea (T2HKK).
DEAP-3600 is single-phase liquid argon (LAr) direct-detection dark matter experiment, operating 2 km underground at SNOLAB, Sudbury, Canada. The detector consists of 3279 kg of LAr contained in a spherical acrylic vessel.
In this talk, a summary of the second dark matter search analysis of a 758 tonne-day exposure will be presented with emphasis given to modelling the detector backgrounds.
TORCH (Time Of Internally Reflected CHerenkov light) is a novel concept of a Ring Imaging Cherenkov time-of-flight detector, which is being developed with a possible application in an upgrade of the LHCb experiment in 2030. Currently it is still in the Research and Development (R&D) phase. It utilises Cherenkov radiation to identify particles at low momenta. It would be located at 10m from the...
The Large Underground Xenon (LUX) experiment is a retired dual phase Liquid Xenon Time Projection Chamber (LXe TPC), designed for the direct detection of dark matter. In 2016, LUX published its final limit on the spin independent nuclear cross-section for the scattering of WIMPs with nucleons. Subsequently the collaboration’s focus has shifted to exploring new physics beyond this energy range....
TORCH is a time-of-flight detector designed to provide particle identification over the 2-10 GeV/c momentum range. Consisting of 18 large quartz plates, TORCH measures the time of arrival of charged particles through prompt Cherenkov light which is trapped by total-internal reflection. At the top of the plate the light is focused onto a row of micro-channel plate (MCP) detectors which measure...
The large amount of data collected at the Large Hadron Collider in its second phase of running, colliding protons at an unprecedented center of mass energy of 13 TeV, gives us the tremendous opportunity to conduct measurements of vector boson plus jets (V+jets) processes in regions of phase space that were previously limited.
This kind of processes play a key role in precision tests of the...
In the ATLAS HH -> bb̅bb̅ analysis, jets are paired to form Higgs boson candidates by minimizing the perpendicular distance between the pair and the line joining the point (120 GeV, 110 GeV) to the origin in the plane of leading Higgs boson candidate mass -- subleading Higgs boson candidate mass. This strategy is shown to reconstruct background events such that they peak around the point (120...
The decay of B mesons into a pair of oppositely charged muons is extremely rare in the Standard Model, due to the suppression of Flavour-Changing-Neutral-Current (FCNC). Their Standard Model prediction is accurate and the experimental signature is very clean, therefore these decays are considered one of the golden channels to test the Standard Model and to look for deviations from its...
The direct production of chargino-neutralino, pp→χ̃±1χ̃02, followed by their decays via intermediate WH states (χ̃±1χ̃02→W±Hχ̃01χ̃01), where H is the 125-GeV Standard Model Higgs boson, is a very important channel for the search for electroweak supersymmetry at the Large Hadron Collider. Amongst others, the search can be performed in the channel where both the W and the H decay fully...
If dark matter interacts weakly with standard model particles it could be produced at the LHC and therefore could be observed with the ATLAS detector. WIMP dark matter would not interact with the detector and therefore would leave a signature involving large amounts of missing transverse momentum. There are a number of models assume a mediator which couples to both dark matter and the...
This talk presents a search for pairs of light Higgs bosons produced in NMSSM decay cascades using the CMS detector. The analysis uses data sets corresponding to the 2016 and 2017 proton-proton collisions at a centre-of-mass energy of 13 TeV. The final state targeted is that where both Higgs bosons decay into bbbar pairs.
The signal model is of interest because, under certain mass...
After the discovery of a Standard Model like Higgs boson, new searches can now change focus towards using it as a tool to probe the Standard Model and new physics. With the largest branching fraction, the bb̅bb̅ final state is one of the leading candidates to observe this process, but the overwhelming backgrounds and the highly boosted topology reached by this process, present a challenge....
The aim of this analysis is to study the process pp-> J/psi + photon + X, in order to understand the production mechanisms of this final state, and possibly to assess some information on the spin structure of the gluon distribution inside the proton. Analysing the subprocess g+g->J/psi + photon there is the prospect of seeing azimuthal modulations in the Collins-Soper frame, induced by the...
The ATLAS experiment has never before measured the ratio of e+mu- to e-mu+ events in its data. Such a ratio is not expected to exceed one in the Standard Model in the LHC’s proton-proton collisions. However, it could exceed one for some Beyond the Standard Model (BSM) scenarios like R-Parity violating supersymmetry or scalar leptoquarks. This talk presents a general search for new physics...
Recent observations of B decays hint at discrepancies with predictions of the otherwise overwhelmingly successful Standard Model of Particle Physics. These observations are extremely intriguing, as they can be interpreted in a coherent way in a number of new physics models by introducing a new vector particle such as a Z' or a leptoquark.
This talk will concentrate on one of these...
When a muon passes through a matter it can liberate neutrons and produce radioactively unstable isotopes. These neutrons and cosmogenic radioisotopes form a background to deep underground low-background experiments.
With a 2 km overburden, SNO+ sees approximately 3 muons per hour passing through the detector. The water phase of the experiment has just completed, and the detector is currently...
In this talk a search for a Higgs boson cascade in the context of the two-Higgs-Doublet Model is presented. In this cascade, a heavy Higgs boson A decays to ZH, where H is another heavy Higgs boson with mass > 125 GeV. Subsequently, the Z boson decay leptonically and the H boson into a bb pair. The search is motivated by the mechanism which generates the matter-antimatter asymmetry in the...
We examine scenarios in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) whereby two Standard Model-like Higgs bosons are produced via squark and gluino decay cascades along with two light, low-momentum neutrino Lightest Supersymmetric Particles (LSPs), resulting in very little Missing Transverse Energy (MET). Firstly, by recasting a general-purpose Jets+MET αT-based analysis we...
The angular observables of the B0 -> K*0μμ decay are showing intriguing discrepancies with Standard Model (SM) predictions [1]. The discrepancies indicate a shift of the vector coupling (C9) with a significance of about 3.4 standard deviations. This could be explained by the existence of new heavy vector particles not described by the SM. However, the discrepancies may also be explained by...
The DEAP-3600 detector, based 2km underground at SNOLAB (Sudbury, Canada) is a dark matter direct detection experiment. The detector is a single phase liquid argon (LAr) target, of 3279 kg mass. In this talk, the results of a dark matter search analysis of 758 tonne-days will be presented. No candidate signal events were observed in the WIMP region of interest, resulting in the leading limit...
The CP-violating angle γ is the only angle of the unitarity triangle which can be measured via tree-level processes. γ can also be measured indirectly using loop-level processes, which are susceptible to the effects of new physics. An observed discrepancy between the direct and indirect measurements of γ would be evidence for new physics. Reducing the experimental uncertainty on the direct γ...
CP violation in the charm sector is predicted to be very small by the Standard Model and so precise measurements represent a low background environment for new physics searches. A sensitive probe is the parameter AΓ which measures time-dependent CP violation and has previously been measured with the LHCb detector in two-body D0 meson decays. D0 neutral mesons are the only ones where...
Supersymmetry (SUSY) is one of numerous, and one of the most famous, theoretical extensions to the Standard Model aiming to answer open questions in particle physics, such as the nature of dark matter and the origin of the electroweak symmetry breaking. SUSY extends the particle spectrum of the SM such that each SM particle has at least one supersymmetric partner. Mixtures of the SUSY partners...
With an abundance of cosmological evidence motivating the existence of dark matter, one of the topmost priorities of the High Energy Physics community is understanding its nature and integrating it into our extremely successful (yet incomplete) theory of the Standard Model. Presented here is a collider search for invisible new-physics phenomena using cross-section ratios for pp collisions at a...
The LHCb experiment focuses on CP violation, a process that explains the abundance of matter in the Universe. The Standard Model theory prediction of CP violation is much smaller than the observed asymmetry. The 'golden decay mode' B0s→J/ψφ could easily be influenced by New Physics particles, and shift the experimentally observed amount of CP violation from the theory prediction. I will...
We present a method for non-parametric, Bayesian neutrino event reconstruction for the Super-Kamiokande detector. Particle properties are determined in a way where the number of Cherenkov rings to be reconstructed, and therefore the number of parameters, is one of the unknowns. We discuss Bayesian model selection with Markov Chain Monte Carlo, future scalability and the issues surrounding...
CP violation has been established in kaon and B-meson systems, but has yet to be observed in baryonic decays. However, sizeable CP asymmetries of up to 20% are expected in certain beauty baryon decays in the Standard Model. A family of 4-body charmless baryonic decays offer a good theoretical motivation for the observation of CP violation. In this analysis a single decay channel of Lb->p3pi is...
The DarkSide-50 experiment at the LNGS underground laboratory is using a dual-phase liquid argon TPC to search for particle dark matter. A recent analysis, based on the use of only the ionization signal from very low energy events, shows the potential of liquid argon to detect low-mass WIMPs (<10 GeV/c^2). The null result of this search is currently the world-leading exclusion limit on...
ARIADNE is a 1-ton two-phase liquid argon (LAr) time projection chamber (TPC) featuring a novel optical readout method. The detector uses a Thick Gas Electron Multiplier (THGEM) in the extraction region to generate secondary scintillation light which is imaged using 4 Electron-Multiplying (EM)CCD cameras to produce high resolution images of particle interactions within the detector.
This...
Motivated by possible theoretical extensions to the standard model, hidden photons (HP) are a suitable candidate for cold dark matter. Their possible masses cover a broad region, from 10-12 to 106 eV [1]. Large scale direct detection experiments such as LUX-ZEPLIN (LZ), built primarily to detect WIMPs, could also be sensitive to HP dark matter via the so called hidden photoelectric effect in...
The DarkSide program for direct dark matter detection is a global collaboration of all the current argon-based dark matter experiments. The Darkside-20k detector will be located in the Laboratori Nazionali del Gran Sasso. It is designed to be experimental-background free and is optimized for sensitivity to high-mass WIMPs. Darkside-20k consists of an inner dual phase liquid argon (LAr) TPC...
The Moedal Experiment uses Passive Nuclear Track Detectors (NTDs) to look for magnetic monopoles, and other heavily ionising exotic particles at the LHC. Through a process of chemical etching, the latent ionisation tracks of particles can be converted into microscopically visible known as etch-pits.
This study looks at CNN image recognition for identifying particle etch pits in an NTD foil...
The leading upper limit on the Higgs boson to invisible state branching ratio (BR) is 24%, while the Standard Model prediction sits far below at 0.1%. The observed value was measured using pp collision data collected by the CMS experiment between 2011 and 2015. Our analysis targets a better limit by using 13 TeV data from 2016-2018 -- an integrated luminosity of over 130 fb-1 -- in addition to...
Neutrinoless double beta decay (NDBD) is a hypothesised nuclear decay process that, if observed, shows that neutrinos are Majorana particles, signals the existence of lepton number violation and places constraints on the neutrino mass hierarchy. However, with T1/2 > 10^25 years, searching for NDBD requires low backgrounds from intrinsic radiation and excellent energy resolution. In this talk,...
NEWS-G is an innovative experiment aiming to shine a light on the dark matter conundrum with a novel gaseous detector, the spherical proportional counter. It uses light gases, such as hydrogen, helium, and neon, as targets, to expand dark matter searches to the sub-GeV/c2 mass region. NEWS-G produced its first results with a detector -60 cm in diameter- installed at LSM (France), excluding...
The observation of a new resonance would be powerful evidence for new physics beyond the Standard Model. Searching for such new resonances at the LHC via their decay to pairs of quarks is a natural and broad search for new physics. In order to reduce QCD background and enhance our sensitivity to particles which preferentially couple to mass we search for particles which decay to pairs of...
Progress on the development of an analytic signal model for measuring the mass of the Higgs Boson employing the H→ZZ→4l (l=e,mu) channel is presented. The model consists of a double-sided Crystal ball function, which is a function with a Gaussian core and power-law tails. The model is fitted to the four-lepton invariant mass distribution of H→ZZ→4l signal Monte Carlo samples. Results from...
To demonstrate whether the particle discovered in 2012 is the Standard Model (SM) Higgs boson, all of its couplings to other SM particles have to be measured. In the SM, the coupling of the Higgs boson to fermions has a strength proportional to the mass of the fermion. Since the b-quark is the heaviest particle that the Higgs can kinematically decay into, it has the largest branching ratio....
A search is conducted for single-production of a vector-like B quark decaying into a Higgs boson and a b quark. Vector-like quarks are theorised to be highly massive colour triplet spin-1/2 fermions arising in models, such as the Little Higgs and Composite Higgs models, which tackle the hierarchy problem resulting from the measured value of the Standard Model Higgs boson mass. Vector-like...
H ->bb decays allow to probe the Yukawa coupling of the Higgs boson to down type quarks. Observing these processes at the LHC is extremely challenging due to the large multi-jet background; however, this can be greatly suppressed by triggering on Missing Energy Transfer and leptons coming from the decay of a weak vector boson produced together with the Higgs.
In this talk, the latest search...
A search is conducted for non-resonant high-mass phenomena in dielectron and dimuon final states. The search uses the full Run-2 proton-proton collision data collected between 2015 and 2018 at sqrt{s} = 13 TeV by the ATLAS experiment at the LHC corresponding to an integrated luminosity of 140 fb-1. A novel approach involving a functional form is fitted to the dilepton invariant mass...
A search is presented for decays of the Higgs boson to a Z boson and a hadronically decaying light resonance, h->ZX->ll+hadrons, using the Run 2 dataset of the ATLAS detector at the LHC. Due to its low mass and high boost, the resonance is reconstructed as a single jet of hadrons. A boosted decision tree is used to suppress the large multijet background. Beyond its potential for new physics,...
Progress on the search for invisibly decaying Higgs bosons at the LHC will be presented. The analysis is being performed using the CMS Run 2 data, taken in 2016-2018. Several key aspects of the analysis will be reviewed including a description of the novel analysis framework, background estimates including NLO QCD and electroweak corrections, and trigger studies. The search results will be...
