80 research outputs found
Preparing for Dark Matter: Maximising our discrimination power in the event of detection
Numerous experimental observations place Dark Matter (DM) as a central character in our cosmological history. Many extensions to the Standard Model of particles physics provide candidates for DM, often predicting interactions additional to gravity. This gives us the opportunity to experimentally probe these extensions and determine the nature of DM. In this thesis, we explore how direct DM detection could be used most effectively to achieve this goal. With this in mind, we have developed a tool for performing multidimensional parameter scans. This tool allows us to evaluate the capabilities of current and future detectors for detecting and understanding DM interactions. We show that by extending the energy region analysed, detection sensitivities and parameter reconstruction can be improved substantially. These insights play an important role in more global analyses, where hints of DM could come from other experiments, but verification depends on direct detection
Does the Orientation of an Euler Diagram Affect User Comprehension?
Euler diagrams, which form the basis of numerous visual languages, can be an effective representation of information when they are both well-matched and well-formed. However, being well-matched and well-formed alone does not imply effectiveness. Other diagrammatical properties need to be considered. Information visualization theorists have known for some time that orientation has the potential to affect our interpretation of diagrams. This paper begins by explaining why well-matched and well-formed drawing principles are insufficient and discusses why we should study the orientation of Euler diagrams. To this end an empirical study is presented, designed to observe the effect of orientation upon the comprehension of Euler diagrams. The paper concludes that the orientation of Euler diagrams does not significantly affect comprehension
Extending preferred axion models via heavy-quark induced early matter domination
We examine the cosmological consequences of the heavy quarks in KSVZ-type
axion models. We find that their presence often causes an early matter
domination phase, altering the evolution of the Universe. This extends the
axion mass into the region where standard cosmology leads to overproduction,
and allows for a greater number of axion models with non-renormalizable terms
to be viable. Quantitatively, we find that decays proceeding through effective
terms of up to dimension 9 () remain consistent with cosmological
constraints, in contrast with the result previously found in the
literature. As a consequence, the heavy quarks can be much heavier and the
axion mass window with the correct relic density for dark matter is extended by
orders of magnitude, down to . This is
achieved without resorting to fine-tuning of the initial misalignment angle,
bolstering the motivation for many future axion haloscope experiments.
Additionally, we explore how these models can be probed through measurements of
the number of relativistic degrees of freedom at recombination.Comment: 24 pages, 6 figure
Light and Darkness: consistently coupling dark matter to photons via effective operators
We revise the treatment of fermionic dark matter interacting with photons via
dimension-5 and -6 effective operators. We show how the application of the
effective operators beyond their validity introduces unphysical, gauge
violating effects that are relevant for current experimental searches.
Restoring gauge invariance by coupling dark matter to the hypercharge gauge
field has implications for the parameter space above and below the electroweak
scale. We review the phenomenology of these hypercharge form factors at the LHC
as well as for direct and indirect detection experiments. We highlight where
the electromagnetic and hypercharge descriptions lead to wildly different
conclusions about the viable parameter space and the relative sensitivity of
various probes. These include a drastic weakening of vector bosons fusion
versus mono-jet searches at the LHC, and the incorrect impression that indirect
searches could lead to better constraints than direct detection for larger dark
matter masses. We find that the dimension-5 operators are strongly constrained
by direct detection bounds, while for dimension-6 operators LHC mono-jet
searches are competitive or performing better than the other probes we
consider.Comment: 24 pages, 14 figures, 2 tables. Matches published version, additional
information in figure
Isospin-violating dark matter at liquid noble detectors: new constraints, future projections, and an exploration of target complementarity
There is no known reason that dark matter interactions with the Standard
Model should couple to neutrons and protons in the same way. This isospin
violation can have large consequences, modifying the sensitivity of existing
and future direct detection experimental constraints by orders of magnitude.
Previous works in the literature have focused on the zero-momentum limit which
has its limitations when extending the analysis to the Non-Relativistic
Effective Field Theory basis (NREFT). In this paper, we study isospin violation
in a detailed manner, paying specific attention to the experimental setups of
liquid noble detectors. We analyse two effective Standard Model gauge invariant
models as interesting case studies as well as the more model-independent NREFT
operators. This work demonstrates the high degree of complementarity between
the target nuclei xenon and argon. Most notably, we show that the Standard
Model gauge-invariant formulation of the standard spin-dependent interaction
often generates a sizeable response from argon, a target nuclei with zero spin.
This work is meant as an update and a useful reference to model builders and
experimentalists.Comment: 22 pages in total, 13 figures, 1 table, 3 appendices. Data from the
main results of this paper is available at
https://doi.org/10.1140/epjc/s10052-023-11826-
Dark matter production through a non-thermal flavon portal
The Froggatt-Nielsen (FN) mechanism provides an attractive way of generating
the determined fermion mass hierarchy and quark mixing matrix elements in the
Standard Model (SM). Here we extend it by coupling the FN field, the flavon, to
a dark sector containing one or more dark matter particles which are produced
non-thermally sequentially through flavon production. Non-thermal flavon
production occurs efficiently via freeze-in and through field oscillations. We
explore this in the regime of high-scale breaking of the global
group and at the reheating temperature
where the flavon remains out of equilibrium at all times. We identify
phenomenologically acceptable regions of and the flavon mass where the
relic abundance of dark matter and other cosmological constraints are
satisfied. In the case of one-component dark matter we find an effective upper
limit on the FN charges at high , i.e. . In
the multi-component dark sector scenario the dark particle can be the heaviest
dark particle that can be effectively stable at cosmological timescales,
alternatively it can be produced sequentially by decays of the heavier ones.
For scenarios where dark decays occur at intermediate timescales, i.e. , we find that existing searches can effectively probe
interesting regions of parameter space. These searches include indirect probes
on decays such as -ray and neutrino telescopes as well as analyses of
the Cosmic Microwave Background, as well as constraints on small scale
structure formation from the Lyman- forest. We comment on the future
prospects of such probes and place projected sensitivities.Comment: 21 pages, 4 figure
Concert recording 2016-09-16
[Tracks 1-3]. Passione amorosa / Giovanni Bottesini -- [Tracks 4-5]. Gran duo concertante for violin, double bass, and piano / Bottesini -- [Track 6]. Quintet for piano and strings in A major, op. 114, D. 667, Trout quintet / Franz Schubert
Evaporation of Primordial Black Holes in the Early Universe: Mass and Spin Distributions
Many cosmological phenomena lead to the production of primordial black holes
in the early Universe. These phenomena often create a population of black holes
with extended mass and spin distributions. As these black holes evaporate via
Hawking radiation, they can modify various cosmological observables, lead to
the production of dark matter, modify the number of effective relativistic
degrees of freedom, , source a stochastic gravitational wave
background and alter the dynamics of baryogenesis. We consider the Hawking
evaporation of primordial black holes that feature non-trivial mass and spin
distributions in the early Universe. We demonstrate that the shape of such a
distribution can strongly affect most of the aforementioned cosmological
observables. We outline the numerical machinery we use to undertake this task.
We also release a new version of FRISBHEE that handles the evaporation of
primordial black holes with an arbitrary mass and spin distribution throughout
cosmic history.Comment: 16 pages, 6 figures. Numerical codes released in
https://github.com/yfperezg/frisbhe
The problem with Kappa
It is becoming clear that traditional
evaluation measures used in
Computational Linguistics (including
Error Rates, Accuracy, Recall, Precision
and F-measure) are of limited value for
unbiased evaluation of systems, and are
not meaningful for comparison of
algorithms unless both the dataset and
algorithm parameters are strictly
controlled for skew (Prevalence and
Bias). The use of techniques originally
designed for other purposes, in particular
Receiver Operating Characteristics Area
Under Curve, plus variants of Kappa,
have been proposed to fill the void.
This paper aims to clear up some of the
confusion relating to evaluation, by
demonstrating that the usefulness of each
evaluation method is highly dependent on
the assumptions made about the
distributions of the dataset and the
underlying populations. The behaviour of
a number of evaluation measures is
compared under common assumptions.
Deploying a system in a context which
has the opposite skew from its validation
set can be expected to approximately
negate Fleiss Kappa and halve Cohen
Kappa but leave Powers Kappa
unchanged. For most performance
evaluation purposes, the latter is thus
most appropriate, whilst for comparison
of behaviour, Matthews Correlation is
recommended
- …