A5106627149- Dark Matter and Cosmic Phenomena
- Particle physics theoretical and experimental studies
- Cosmology and Gravitation Theories
- Atomic and Subatomic Physics Research
- Particle Detector Development and Performance
- Neutrino Physics Research
- Quantum, superfluid, helium dynamics
- Black Holes and Theoretical Physics
- Superconducting Materials and Applications
- Particle Accelerators and Free-Electron Lasers
- Galaxies: Formation, Evolution, Phenomena
- Advanced Thermodynamics and Statistical Mechanics
- Computational Physics and Python Applications
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Advanced MEMS and NEMS Technologies
- High-Energy Particle Collisions Research
- Spacecraft and Cryogenic Technologies
- Radiomics and Machine Learning in Medical Imaging
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Force Microscopy Techniques and Applications
- Distributed and Parallel Computing Systems
- Radioactive Decay and Measurement Techniques
- Mechanical and Optical Resonators
Royal Holloway University of London
2010-2024
University of Oxford
2004-2020
Universidad de Londres
2012-2015
Rutherford Appleton Laboratory
2009-2014
We propose an alternate, calculable mechanism of dark matter genesis, "thermal freeze-in," involving a Feebly Interacting Massive Particle (FIMP) interacting so feebly with the thermal bath that it never attains equilibrium. As conventional freeze-out" production mechanism, relic abundance reflects combination initial distributions together particle masses and couplings can be measured in laboratory or astrophysically. The freeze-in yield is IR dominated by low temperatures near FIMP mass...
We show that intermediate mass black holes conjectured to be the early precursors of supermassive and surrounded by relic cold dark matter density spikes can act as particle accelerators with collisions, in principle, at arbitrarily high centre energies case Kerr holes. While ejecta from such interactions will highly redshifted, we may anticipate possibility a unique probe Planck-scale physics.
This document a outlines set of simplified models for dark matter and its interactions with Standard Model particles. It is intended to summarize the main characteristics that these have when applied searches at LHC, provide number useful expressions reference. The list includes both s-channel t-channel scenarios. For s-channel, spin-0 spin-1 mediations are discussed, also realizations where Higgs particle provides portal between visible sectors. guiding principles underpinning proposed...
We examine the theoretical motivations for long-lived particle (LLP) signals at LHC in a comprehensive survey of Standard Model (SM) extensions. LLPs are common prediction wide range theories that address unsolved fundamental mysteries such as naturalness, dark matter, baryogenesis and neutrino masses, represent natural generic possibility physics beyond SM (BSM). In most cases LLP lifetime can be treated free parameter from $\mu$m scale up to Big Bang Nucleosynthesis limit $\sim 10^7$m....
The inferred values of the cosmological baryon and dark matter densities are strikingly similar, but in most theories early universe there is no true explanation this fact; particular, asymmetry thus density depends upon unknown, {\it a priori} unknown possibly small, CP-violating phases which independent all parameters determining density. We consider models possessing particle-antiparticle where determines both strongly effects density, naturally linking $\Omega_{\rm{b}}$...
We argue that WIMP dark matter can annihilate via long-lived "WIMPonium" bound states in reasonable particle physics models of (DM). WIMPonium occur at or near threshold leading to substantial enhancements the DM annihilation rate, closely related Sommerfeld effect. Large "boost factor" amplifications rate thus without large density enhancements, possibly preferring colder less dense objects such as dwarf galaxies locations for indirect searches. The radiative capture and transitions among...
Abstract Any new vector boson with non-zero mass (a 'dark photon' or 'Proca boson') that is present during inflation automatically produced at this time from vacuum fluctuations and can comprise all a substantial fraction of the observed dark matter density, as shown by Graham, Mardon, Rajendran. We demonstrate, utilising both analytic numerical studies, such scenario implies an extremely rich substructure arising purely interplay gravitational interactions quantum effects. Due to remarkable...
Abstract The focus of dark matter searches to date has been on Weakly Interacting Massive Particles (WIMPs) in the GeV/ $$c^2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>c</mml:mi> <mml:mn>2</mml:mn> </mml:msup> </mml:math> -TeV/ mass range. direct, indirect and collider this range have extensive but ultimately unsuccessful, providing a strong motivation for widening search outside Here we describe new concept experiment, employing superfluid $$^3$$...
The escape fraction at infinity is evaluated for massless particles produced in collisions of weakly interacting accreted into a density spike near the particle horizon an extremal Kerr black hole, case equatorial orbits. We compare with Schwarzschild case, and argue that holes, redshifted signatures can be could potentially explore physics center mass energies extend beyond those any feasible terrestrial accelerator.
We investigate the physics of dark matter models featuring composite bound states carrying a large conserved "nucleon" number. The properties sufficiently nuclei may obey simple scaling laws, and we find that this can determine number distribution resulting from Big Bang Dark Nucleosynthesis. For plausible asymmetric matter, nucleon number, e.g. > 10^8, be synthesised, with taking one two characteristic forms. If small-nucleon-number fusions are fast, takes on logarithmically-peaked,...
We investigate the interactions of large composite dark matter (DM) states with Standard Model (SM) sector. Elastic scattering SM nuclei can be coherently enhanced by factors as A^2, where A is number constituents in state (there exist models which DM very > 10^8 may realised). This enhancement, for a given direct detection event rate, weakens expected signals at colliders up to 1/A. Moreover, spatially extended nature leads an additional, characteristic, form factor modifying momentum...
We report the results of radioactivity assays and heat leak calculations for a range common cryogenic materials, considered use in QUEST-DMC superfluid 3He dark matter detector. The bolometer, instrumented with nanomechanical resonators, will be sensitive to energy deposits from interactions. Events radioactive decays cosmic rays constitute significant background must precisely modelled, using combination material screening Monte Carlo simulations. However, presented here are wider interest...
We calculate solar models including dark matter (DM) weakly-interacting massive particles (WIMPs) of mass 5-50 GeV and test these against helioseismic constraints on sound speed, convection zone depth, helium abundance, small separations low-degree p-modes. Our main conclusion is that both direct detection experiments particle accelerators may be complemented by using the Sun as a probe for WIMP DM in range. The most sensitive to this has suppressed annihilations large spin-dependent elastic...
We propose a unified theory of dark matter (DM) genesis and baryogenesis. It explains the observed link between DM density baryon density, is fully testable by combination collider experiments precision tests. Our utilises "thermal freeze-in" mechanism production, generating particle anti-particle asymmetries in decays from visible to hidden sectors. Calculable, linked, number are produced feeble interaction mediating two sectors, while out-of-equilibrium condition necessary for baryogenesis...
Direct detection experiments aimed at uncovering the elusive nature of dark matter (DM) have made significant progress in probing ever lower cross-sections for DM-nucleon interactions. At same time, an upper limit cross-section sensitivity region is present due to DM scattering Earth and atmosphere as a result never reaching detector. We investigate impact this effect both spin-dependent spin-independent In contrast previous studies that assume straight line path we employ semi-analytic...
Abstract Direct detection experiments aimed at uncovering the elusive nature of dark matter (DM) have made significant progress in probing ever lower cross-sections for DM-nucleon interactions. At same time, an upper limit cross-section sensitivity region is present due to DM scattering Earth and atmosphere as a result never reaching detector. We investigate impact this effect both spin-dependent spin-independent In contrast previous studies that assume straight line path we employ...
We analyze a class of supersymmetric models first introduced by Arkani-Hamed et al. and Borzumati in which the light neutrino masses result from higher-dimensional supersymmetry-breaking terms MSSM super-potentials Kahler potentials. The mechanism is closely related to Giudice–Masiero for μ parameter, leads TeV-scale right-handed sneutrino states, that are principle accessible direct experimental study. dominant contribution (Majorana) mass matrix one-loop term induced lepton-number...
There are several ways to explain the dark matter relic density other than by ordinary freeze-out scenario. For example, freeze-in mechanism may constitute an alternative for generating correct candidates whose predicted abundance is too low due a large total annihilation cross section. Here we show that although such could why candidate has density, some still be ruled out because they would lead gamma-ray flux in dwarf spheroidal galaxies or elastic scattering rate direct detection...
We present a mechanism for dark matter (DM) production involving self-interacting sector that at early times is ultrarelativistic but far underpopulated relative to thermal equilibrium (such initial conditions often arise, e.g., from inflaton decay). Although elastic scatterings can establish kinetic we show broad variety of self-interactions full never established despite the DM yield significantly evolving due $2\ensuremath{\rightarrow}k$ ($k>2$) processes (the carries no conserved quantum...
We argue that supersymmetric flat direction vacuum expectation values can decay nonperturbatively via preheating. Considering a toy $U(1)$ gauge theory, we explicitly calculate the scalar potential, in unitary gauge, for excitations around several directions. show mass matrix has nondiagonal entries which vary with phase of value. Furthermore, this zero eigenvalues whose eigenstates change time. these light degrees freedom are produced copiously nonperturbative
We study dark matter production by decaying topological defects, in particular cosmic strings.In defect or "top-down" (TD) scenarios, the injection rate varies as a power law with time exponent p -4.We find formula closed form for yield all < 3/2, which accurately reproduces solution of Boltzmann equation.We investigate two scenarios (p = 1, 7/6) motivated strings decay into TeV-scale states high branching fraction particles.For models annihilating either s-wave p-wave, we regions parameter...
Abstract We report the results of radioactivity assays and heat leak calculations for a range common cryogenic materials, considered use in QUEST-DMC superfluid $$^3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mn>3</mml:mn> </mml:msup> </mml:math> He dark matter detector. The bolometer, instrumented with nanomechanical resonators, will be sensitive to energy deposits from interactions. Events radioactive decays cosmic rays constitute significant...