Multi-messenger astronomy combines astronomical measurements of photons, neutrinos, and gravitational waves. I will introduce this field and will review its main breakthroughs. I will then discuss future prospects and highlight important planned future observatories, which promise exciting science.
Highly relativistic nuclei, known as cosmic rays, bombard the Earth every second. These particles reach energies that go well beyond the ones that can be produced here at Earth, i.e. reaching up to 10^20~eV in the lab. In this talk, the state of the art of what we can learn from the interaction of these highest-energy particles will be reviewed. The first part of the talk will focus on what...
The ALICE detector is specifically designed for allowing a precise characterization of the quark-gluon plasma (QGP), a deconfined phase of nuclear matter which can be formed in heavy-ion collisions. Heavy quarks, i.e. charm and beauty, are created in the hard partonic scatterings at the early stage of the collision, prior to QGP formation, and could thus experience energy loss, transport,...
The study of the initial conditions of relativistic heavy-ion collisions and the subsequent development of hot and dense nuclear matter at the LHC is fundamental for the understanding of the strong nuclear force. The traditional approach of comparing observables with hydrodynamical models based on different initial conditions typically fails to isolate the effects of the initial conditions due...
Multi-particle correlations have been compelling tools to probe the properties of the Quark-Gluon Plasma (QGP) created in the ultra-relativistic heavy-ion collisions. In this seminar, I will present a generic recursive algorithm for multi-particle cumulants, which enables the calculation of arbitrary order multi-particle cumulants. Among them, I will emphasize a particular series of mixed...
The extreme temperatures and energy densities generated in the ultrarelativistic nuclear collisions produce a state of partonic matter, the quark-gluon plasma (QGP), which behaves almost like an ideal fluid. The created system may possess large orbital angular momentum leading to the global polarization of particles perpendicular to the reaction plane. Also, local asymmetries in the velocity...
The high quality experimental data on hard probes in heavy-ion collisions call for a more precise theoretical description of jet evolution in a quark-gluon plasma. To accomplish that we study jet fragmetation via 1 → 2 final-state parton splittings in the medium. In earlier works [1, 2] the authors have usually calculated these processes by invoking one or two approximations: the large-Nc and...
The evolution of the strongly interacting medium is modelled with hydrodynamic models, which are driven by a large number of parameters quantifying the properties of the medium. The need to find model parameters which give the best description of the experimental data imposes a multidimensional optimization problem. The Bayesian analysis has shown to be very effective in constraining the...
One of the primary goals of heavy-ion physics is to understand the transport properties of the quark-gluon plasma (QGP), which is composed of the smallest constituents of matter, the quarks and gluons, and which filled up our universe a few microseconds after the Big Bang.
The present most challenging question in this research field is to pin down the critical point of the QGP, where the...
The interplay of the chiral anomaly and the strong magnetic field ($\sim$ 10$^{15}$ T) created in heavy-ion collisions could give rise to a collective excitation in the quark--gluon plasma called the Chiral Magnetic Wave (CMW). This effect can be experimentally sought by the charge asymmetry ($A_{\rm ch}$) dependence of elliptic flow $v_{2}$. However, non-CMW mechanisms such as local charge...
Neutrino masses and mixing are a direct evidence that the standard model of elementary particles is incomplete. Furthermore, neutrinos are different from other fermions since, first, their masses are many orders of magnitude smaller in comparison, and second, their mixing angles are significantly larger in comparison to the mixing of the quarks. This brings significant challenge in creating...
The precision era of neutrino physics has started in 2012 with the first measurement of the size of theta_13. Since then, we have witnessed major advances nearly every year. In this talk, I will review the most impressive achievements gathered in the last two years through a wealth of high-precision experiments. These experiments are based on artificial (accelerator and reactor neutrinos) and...
One of the most remarkable possibilities of General Relativity concerns gravitational collapse to black holes, leaving behind a geometry with light rings, ergoregions and horizons. These peculiarities are responsible for uniqueness properties and energy extraction mechanisms that turn black holes into ideal laboratories of strong gravity, of particle physics (yes!) and of possible...
As datasets in particle physics get progressively larger, algorithms to swiftly and accurately process this data have become increasingly complex. Machine Learning (ML) has emerged as a solution to tackle several of the challenges experiments face: to efficiently select and reconstruct interesting observational data, to enhance sensitivity to increasingly rare processes and to efficiently...
In gamma-ray astronomy typically only the direct photon component is considered as signal when searching for annihilating WIMPS. This means that only photons that are produced during the WIMP annihilation and the consecutive hadronisation are taken into account. There is however also a non-negligible contribution to the gamma-ray signal that arises from the electrons that are produced in the...
We revisit the possibility that Dark Matter is composed of stable scalar glueballs of a confining dark ${\rm SU}(3)$ gauge theory coupled only to gravity. The relic abundance of dark glueballs is studied for the first time in a thermal effective theory accounting for strong-coupling dynamics. An important ingredient of our analysis is the use of an effective potential for glueballs that is...
Høgskulen på Vestlandet (HVL) has over the last couple of years built up a strong group working on machine learning (ML) for data analysis in collider experiments.
With the project “Use Artificial Intelligence to pinpoint Dark Matter at the LHC”, financed by the Research Council of Norway, we focus on dark matter searches in the tau lepton sector of the LHC phase space in ATLAS data...
Modern machine learning (ML) methods are widely used in LHC analyses, but considerably more time is invested in training ML models, than in understanding them. We present a small review of interpretation and explanation techniques relevant to ML classifiers used in collider experiments, and motivate why they should be consulted. Further, we present ongoing work on the related topic that is...
The application of machine learning has become popular in high energy physics within recent years. In addition to standard cut-based analyses, more and more effort is put to develop new strategies. One of a highly effective and widely recognised machine learning ensemble method are gradient boosted decision trees. This talk presents the current implementation of an optimized gradient boosting...
New physics has proven quite elusive, hence more data and increasingly sophisticated techniques are required to probe it. With Run 3 of the LHC started and major developments in modern machine learning techniques, we face a very interesting new era of experimental physics. We aim to quantify the gain in sensitivity by using the highly effective XGBoost framework in searches for supersymmetry...
The ATLAS detector is, in its most abstract form, a cylindrical camera. It captures the energy deposits left in the detector material from particles produced in high-energy particle collision events. Traditional methods of analysing this data rely on the reconstruction of the particle collision. This process transforms the high-dimensional, low-level data from the detector into...
Several beyond Standard Model theories predict the existence of heavy scalars which could decay into the Standard Model (SM) Higgs boson. This analysis focuses on the search for resonant heavy scalar $X$ decaying to a lighter scalar $S$ and the SM Higgs boson $H$ in a final state with two photons and 2 $b$-jets. A neural network (NN), parametrised on the resonant $X$ and $S$ masses, is used to...
In many extensions of the Standard Model, the electroweak transition is first order - in some cases, strongly so. The ensuing phase transition would result in collisions of bubbles of the new Higgs phase. These collisions, and the associated interactions of sound waves in the plasma, are substantial sources of gravitational waves. For a phase transition at or around the electroweak scale,...
The 2012 discovery of the Higgs boson by the ATLAS and CMS experiments at CERN's Large Hadron Collider (LHC) marked the completion of the Standard Model (SM). Since then the experiments have collected more than ten times the amount of data, which are being used to carefully map the properties of the Higgs boson and to search for additional scalars. Looking ahead, one of the main goals of the...
A general and conceptual introduction to effective field theories (EFT) is given and applied to EFT extensions of the Standard Model. The focus of the talk is on on the Higgs sector and examples of recent LHC experimental constraints from single and di-Higgs production are discussed. To be exploited to its full power EFTs requires complex analysis techniques involving multiple measurements,...
Ultralight bosons behave like coherent waves when the occupation number is large enough. If they are coupled to the Standard Model sector of the particle physics, such an oscillating background can induce a tiny signal. Near a fast rotating black hole, ultralight bosons within one order of the mass window can accumulate through superradiance with a large density expected. If linearly polarized...
Measuring Higgs pair production will give us information about the Higgs self coupling, which is key to determine the shape of the Higgs potential at higher order O(3).
The leading production mode is gluon gluon fusion, with a cross section of 31.05 fb at a centre of mass energy of 13 TeV. Given the small cross section, Higgs pair production has not yet been observed. However, despite...
SMARTHEP is an Innovative Training Network, bringing together researchers from all major four LHC collaborations and partners from industry, all working on real-time analysis. In this contribution, I will present work on intertwining the online and offline calibration of jets at CMS. We investigate the transverse momentum response between high level trigger (HLT) and several types of offline...
This paper presents a statistical combination of searches targeting final states with two top quarks and invisible particles, characterised by the presence
of zero, one or two leptons, at least one jet originating from a b-quark and missing transverse momentum.
The analyses are searches for phenomena beyond the Standard Model consistent with the direct production of dark matter in pp...
Our analysis is a direct top quark mass measurement where the mass is extracted from the reconstruction of the top quark decay products.The analysis operates on a lepton and jets final state in top quark pair event topology. Our analysis is based on a binned profile likelihood method which has been introduced to the top quark mass measurements at CMS during the LHC Run II data taking...
The observation of neutrons converting to antineutrons and/or sterile neutrons would demonstrate Baryon Number Violation (BNV) for the first time. BNV is an essential condition needed to produce the matter/anti-matter asymmetry in the universe and appears in a number of theories beyond the Standard Model. The existence of sterile neutrons would address the issue of a possible dark sector of...
A selection of "theoretical frameworks'' that are currently used in the analysis of dark matter (DM) search experiments is presented. These frameworks are divided into two classes: those extending the Standard Model (SM) by a DM candidate only, and those extending the SM by a new particle mediator in addition to a DM candidate (``dark sectors''). For each framework, examples are provided for...
Dark matter makes up 80% of the total matter content in the universe, but has so far only been observed through its gravitational pull on ordinary matter. Direct detection experiments aim to discover dark matter interacting with their detector, and these detectors have provided rapidly improving sensitivity to the popular WIMP dark matter model. This talk gives an overview of the concepts and...
In 2020, after a wide consultation of the community, the update of the European Strategy outlined an ambitious and visionary scientific program for HEP. It considers, over decades, a global experimental endeavour to discover and study phenomena beyond the predictions of the Standard Model; in direct or indirect searches, at accelerators, nuclear reactors or cosmic ray facilities. In this...
I will present the Oslo group's involvement in towards a future collider at the Energy Frontier, with focus on advanced accelerator technology, including plasma wakefield accelerators and plasma lenses. I will also elude to how the technological advances may be used for medical applicaitons.
The HIBEAM-NNBAR program is a proposed two-stage experiment at the European Spallation Source (ESS) designed to search for neutrons converting, or oscillating, into antineutrons and/or sterile neutrons. Such an observation would indicate baryon number violation, a fundamental Sakharov condition for baryogenesis, or act as a sign of a potential dark sector. The experiment would increase the...
The IceCube Neutrino Observatory at the South Pole has instrumented one cubic kilometer of ice by deploying digital optical modules (DOMs) in 86 drill holes, each containing a string of DOMs So far IceCube has used the GPS-determined location of the drill tower for the positions of DOMs in the transverse directions ($x$ and $y$) while the depth ($z$) is calibrated in situ. The large...
The High Luminosity LHC (HL-LHC) upgrade requires the planned Inner Tracker (ITk) of the ATLAS detector to tolerate extremely high radiation doses. Specifically, the innermost parts of the pixel system will have to withstand radiation fluences above $1\times10^{16}$ $n_{eq}cm^{-2}$. Novel 3D silicon pixel sensors offer a superior radiation tolerance compared to conventional planar pixel...
In high-energy physics it is a recurring challenge to efficiently and precisely (enough) calculate the global significance of, e.g., a potential new resonance. We propose a new method that models the significance in the search region as a Gaussian Process (GP). The kernel of the GP is approximated with a covariance matrix and is calculated with a carefully designed set of background-only data...
In the hunt for new physics phenomena, such as dark matter, it is
crucial to compare experimental data to theoretical models. During this
step, the most likely values of the model’s parameters — such as particle
masses and cross sections — are inferred. However, a rigorous statistical
treatment of such an inference is oftentimes not practically feasible with-
out making significant...
I will present the latest physics results from the GAMBIT Collaboration, focusing on a recent study of how the current combined set of LHC SUSY searches and LHC measurements of SM signatures constrain SUSY scenarios with multiple light neutralinos and charginos, and a near-massless gravitino. Through a large-scale global fit, with full Monte Carlo simulations of LHC searches and measurements...
