Particle theory

Abstract:

We calculate the spectrum of light glueballs and the string tension in a number of SO(N) lattice gauge theories in 2+1 dimensions, with N in the range 3 ≤ N ≤ 16. After extrapolating to the continuum limit and then to N = ∞ we compare to the spectrum and string tension of the SU(N → ∞) gauge theory and find that the most reliably and precisely calculated physical quantities are consistent in that limit. We also compare the glueball spectra of those pairs of SO(N) and SU(N′) theories that possess the same Lie algebra, i.e. SO(3) and SU(2), SO(4) and SU(2)×SU(2), SO(6) and SU(4), and find that for the very lightest glueballs the spectra are consistent within each such pair, as are the string tensions and the couplings. Where there are apparent discrepancies they are typically for heavier glueballs, where the systematic errors are much harder to control. We calculate the SO(N) string tensions with a particular focus on the confining properties of SO(2N + 1) theories which, unlike SO(2N) theories, possess a trivial centre. We find that for both the light glueballs and for the string tension SO(2N) and SO(2N + 1) gauge theories appear to form a single smooth sequence.

Abstract:

Axion-like particles (ALPs) can induce localized oscillatory modulations in the spectra of photon sources passing through astrophysical magnetic fields. Ultra-deep Chandra observations of the Perseus cluster contain over 5× {10}5 counts from the active galactic nucleus (AGN) of the central cluster galaxy NGC1275 and represent a data set of extraordinary quality for ALP searches. We use this data set to search for X-ray spectral irregularities from the AGN. The absence of irregularities at the { O }(30 % ) level allows us to place leading constraints on the ALP-photon mixing parameter {g}aγ γ ≲ 1.4{--}4.0× {10}-12 {{GeV}}-1 for {m}a≲ {10}-12 {eV}, depending on assumptions on the magnetic field realization along the line of sight.

Abstract:

© Published under licence by IOP Publishing Ltd. The IceCube neutrino observatory at the South Pole is the largest operating neutrino detector in the world and spans a wide range of science topics, from astronomy at the PeV-scale to particle physics at the GeV-scale. We present results from the search for a light, O(1) eV 2 , sterile neutrino using the large IceCube array and, separately, using the lower energy extension DeepCore sub-array. Additionally, we review the atmospheric neutrino results and expected sensitivities related to oscillation physics (ν μ disappearance and ν τ appearance) as well as new limits on non-standard interactions. Continuing the success of the IceCube-DeepCore physics program, a proposed next generation in-fill detector with increased sensitivity to neutrinos of O(1) GeV will be covered.

Abstract:

We present a search for a neutrino signal from dark matter self-annihilations in the Milky Way using the IceCube Neutrino Observatory (IceCube). In 1005 days of data we found no significant excess of neutrinos over the background of neutrinos produced in atmospheric air showers from cosmic ray interactions. We derive upper limits on the velocity averaged product of the dark matter self-annihilation cross section and the relative velocity of the dark matter particles $\langle\sigma_{\text{A}}v\rangle$. Upper limits are set for dark matter particle candidate masses ranging from 10 GeV up to 1 TeV while considering annihilation through multiple channels. This work sets the most stringent limit on a neutrino signal from dark matter with mass between 10 GeV and 100 GeV, with a limit of $1.18\cdot10^{-23}\text{cm}^3\text{s}^{-1}$ for 100 GeV dark matter particles self-annihilating via $\tau^+\tau^-$ to neutrinos (assuming the Navarro-Frenk-White dark matter halo profile).