Experimental Particle Physics Consolidated Grant 2022-2025
Lead Research Organisation:
University of Liverpool
Department Name: Physics
Abstract
Fundamental physics strives to answer the big questions: what is our Universe made of; how did it evolve; what forces govern it and how do they shape the phenomena we observe? In particle physics we build experiments to examine the very smallest constituents of the Universe, fundamental particles, so that we can address these questions with our findings.
Our knowledge of how fundamental particles behave is encapsulated in a theory called the Standard Model. It has enormous predictive power and provides a simple framework to understand the nature of the Universe. However, we also know the theory is incomplete. Experiments at the highest energies let us test predictions and determine the limits of the validity of our theory. Dedicated high-precision experiments let us probe predictions to incredible levels of accuracy. The faintest trace of any disagreement between theory and experimental data could provide the first hint of new laws of physics operating, which would be a step forward in understanding the nature of the Universe.
One of the most pressing questions we have concerns why matter dominates so much over anti-matter. Matter and anti-matter should have been created in equal quantities in the early Universe, but very little anti-matter can be observed now. This defining feature of our Universe must ultimately be due to a difference in behaviour between matter and anti-matter, but this difference is a mystery. Neutrinos, the most elusive of particles, may hold the key to understanding why this happened. They have no charge, barely interact with matter, have a very small mass and to detect them we have had to build enormous but very sensitive detectors. An important part of our research is to make detailed measurements of neutrinos, to understand their masses and whether they are responsible for our matter-dominated universe.
Another mystery we seek to resolve concerns dark matter. We know that there are not enough stars visible in galaxies to explain the speed at which stars rotate around them. We explain this by hypothesising that galaxies also contain invisible (dark) matter. Dark matter supplies the extra gravitational force necessary to keep stars in their orbits, but its nature is unknown. Many explanations have been proposed, ranging from it being formed of extremely low mass particles to massive black holes. Some explanations have been excluded, but many are extremely challenging to either confirm or reject experimentally. To address this we develop more powerful experiments using a wide range of approaches and technologies, to perform the broadest search for the unknown particles that may form this elusive dark matter.
Our knowledge of how fundamental particles behave is encapsulated in a theory called the Standard Model. It has enormous predictive power and provides a simple framework to understand the nature of the Universe. However, we also know the theory is incomplete. Experiments at the highest energies let us test predictions and determine the limits of the validity of our theory. Dedicated high-precision experiments let us probe predictions to incredible levels of accuracy. The faintest trace of any disagreement between theory and experimental data could provide the first hint of new laws of physics operating, which would be a step forward in understanding the nature of the Universe.
One of the most pressing questions we have concerns why matter dominates so much over anti-matter. Matter and anti-matter should have been created in equal quantities in the early Universe, but very little anti-matter can be observed now. This defining feature of our Universe must ultimately be due to a difference in behaviour between matter and anti-matter, but this difference is a mystery. Neutrinos, the most elusive of particles, may hold the key to understanding why this happened. They have no charge, barely interact with matter, have a very small mass and to detect them we have had to build enormous but very sensitive detectors. An important part of our research is to make detailed measurements of neutrinos, to understand their masses and whether they are responsible for our matter-dominated universe.
Another mystery we seek to resolve concerns dark matter. We know that there are not enough stars visible in galaxies to explain the speed at which stars rotate around them. We explain this by hypothesising that galaxies also contain invisible (dark) matter. Dark matter supplies the extra gravitational force necessary to keep stars in their orbits, but its nature is unknown. Many explanations have been proposed, ranging from it being formed of extremely low mass particles to massive black holes. Some explanations have been excluded, but many are extremely challenging to either confirm or reject experimentally. To address this we develop more powerful experiments using a wide range of approaches and technologies, to perform the broadest search for the unknown particles that may form this elusive dark matter.
Organisations
Publications
Aad G
(2023)
ATLAS flavour-tagging algorithms for the LHC Run 2 pp collision dataset
in The European Physical Journal C
Aad G
(2023)
Search for pair production of third-generation leptoquarks decaying into a bottom quark and a $$\tau $$-lepton with the ATLAS detector
in The European Physical Journal C
Aad G
(2023)
Measurements of observables sensitive to colour reconnection in $$t{\bar{t}}$$ events with the ATLAS detector at $$\sqrt{s} =$$ 13 TeV
in The European Physical Journal C
Aad G
(2023)
Luminosity determination in pp collisions at $$\sqrt{s}=13$$ TeV using the ATLAS detector at the LHC
in The European Physical Journal C
Aad G
(2023)
Measurement of the nuclear modification factor of b-jets in 5.02 TeV Pb+Pb collisions with the ATLAS detector
in The European Physical Journal C
Aad G
(2023)
Performance of the reconstruction of large impact parameter tracks in the inner detector of ATLAS
in The European Physical Journal C
Aad G
(2023)
Search for Majorana neutrinos in same-sign WW scattering events from pp collisions at $$\sqrt{s}=13$$ TeV
in The European Physical Journal C
Aad G
(2023)
Search for doubly charged Higgs boson production in multi-lepton final states using 139 fb$$^{-1}$$ of proton-proton collisions at $$\sqrt{s}$$ = 13 TeV with the ATLAS detector
in The European Physical Journal C
Aad G
(2023)
Search for pair-produced vector-like top and bottom partners in events with large missing transverse momentum in pp collisions with the ATLAS detector
in The European Physical Journal C
Aad G
(2023)
Measurement of the CP properties of Higgs boson interactions with $$\tau $$-leptons with the ATLAS detector
in The European Physical Journal C
Aad G
(2023)
Search for dark matter produced in association with a single top quark and an energetic W boson in $$\sqrt{s}=$$ 13 TeV $$pp$$ collisions with the ATLAS detector
in The European Physical Journal C
Aaron E
(2023)
Measurement of isotopic separation of argon with the prototype of the cryogenic distillation plant Aria for dark matter searches
in The European Physical Journal C
Aad G
(2023)
New techniques for jet calibration with the ATLAS detector
in The European Physical Journal C
Aad G
(2023)
Search for Higgs boson pair production in association with a vector boson in pp collisions at $$\sqrt{s}=13\,\text {TeV}$$ with the ATLAS detector
in The European Physical Journal C
Aad G
(2023)
Observation of four-top-quark production in the multilepton final state with the ATLAS detector
in The European Physical Journal C
Aad G
(2023)
Measurements of $$W^{+}W^{-}$$ production in decay topologies inspired by searches for electroweak supersymmetry
in The European Physical Journal C
Aad G
(2023)
Measurement of the total cross section and $$\rho $$-parameter from elastic scattering in pp collisions at $$\sqrt{s}=13$$ TeV with the ATLAS detector
in The European Physical Journal C
André K
(2022)
An experiment for electron-hadron scattering at the LHC
in The European Physical Journal C
Buytaert J
(2022)
The HEV Ventilator: at the interface between particle physics and biomedical engineering
in Royal Society Open Science
Aad G
(2023)
Search for flavour-changing neutral-current couplings between the top quark and the photon with the ATLAS detector at s = 13 TeV
in Physics Letters B
Aad G
(2024)
Observation of W?? triboson production in proton-proton collisions at s = 13 TeV with the ATLAS detector
in Physics Letters B
Aad G
(2023)
Comparison of inclusive and photon-tagged jet suppression in 5.02 TeV Pb+Pb collisions with ATLAS
in Physics Letters B
Aad G
(2023)
Measurement of the Higgs boson mass with H ? ?? decays in 140 fb-1 of s = 13 TeV pp collisions with the ATLAS detector
in Physics Letters B
Aad G
(2024)
Search for the Z? decay mode of new high-mass resonances in pp collisions at s = 13 TeV with the ATLAS detector
in Physics Letters B
Aad G
(2023)
Measurement of the polarisation of W bosons produced in top-quark decays using dilepton events at s = 13 TeV with the ATLAS experiment
in Physics Letters B
Aad G
(2023)
Search for pairs of muons with small displacements in pp collisions at s = 13 TeV with the ATLAS detector
in Physics Letters B
Aad G
(2023)
Search for exclusive Higgs and Z boson decays to ?? and Higgs boson decays to K?? with the ATLAS detector
in Physics Letters B
Abreu H
(2024)
Search for dark photons with the FASER detector at the LHC
in Physics Letters B
Aad G
(2023)
Search for heavy long-lived multi-charged particles in the full LHC Run 2 pp collision data at s = 13 TeV using the ATLAS detector
in Physics Letters B
Aad G
(2023)
Evidence of off-shell Higgs boson production from ZZ leptonic decay channels and constraints on its total width with the ATLAS detector
in Physics Letters B
Aad G
(2024)
Search for non-resonant production of semi-visible jets using Run 2 data in ATLAS
in Physics Letters B
Aad G
(2024)
Search for the decay of the Higgs boson to a Z boson and a light pseudoscalar particle decaying to two photons
in Physics Letters B
Lees JP
(2022)
Search for an Axionlike Particle in B Meson Decays.
in Physical review letters
Aad G
(2023)
Test of CP Invariance in Higgs Boson Vector-Boson-Fusion Production Using the H??? Channel with the ATLAS Detector.
in Physical review letters
Lees J
(2022)
Search for Lepton Flavor Violation in ? ( 3 S ) ? e ± µ ±
in Physical Review Letters
Aad G
(2023)
Observation of the ? ? ? t t Process in Pb + Pb Collisions and Constraints on the t -Lepton Anomalous Magnetic Moment with the ATLAS Detector
in Physical Review Letters
Aad G
(2024)
Measurement of the Centrality Dependence of the Dijet Yield in p + Pb Collisions at s NN = 8.16 TeV with the ATLAS Detector
in Physical Review Letters
Aad G
(2023)
Measurement of Suppression of Large-Radius Jets and Its Dependence on Substructure in Pb + Pb Collisions at s N N = 5.02 TeV with the ATLAS Detector
in Physical Review Letters
Aad G
(2023)
Search for Dark Photons in Rare Z Boson Decays with the ATLAS Detector
in Physical Review Letters
Aalbers J
(2023)
First Dark Matter Search Results from the LUX-ZEPLIN (LZ) Experiment.
in Physical review letters
Aaij R
(2022)
Observation of Two New Excited ?_{b}^{0} States Decaying to ?_{b}^{0}K^{-}p^{+}.
in Physical review letters
Abreu H
(2023)
First Direct Observation of Collider Neutrinos with FASER at the LHC
in Physical Review Letters
Aad G
(2024)
Evidence for the Higgs Boson Decay to a Z Boson and a Photon at the LHC.
in Physical review letters