438 research outputs found
Directly detecting sub-GeV dark matter with electrons from nuclear scattering
Dark matter (DM) particles with mass in the sub-GeV range are an attractive
alternative to heavier weakly-interacting massive particles, but direct
detection of such light particles is challenging. If however DM-nucleus
scattering leads to ionisation of the recoiling atom, the resulting electron
may be detected even if the nuclear recoil is unobservable. We demonstrate that
including this effect significantly enhances direct detection sensitivity to
sub-GeV DM. Existing experiments set world-leading limits, and future
experiments may probe the cross sections relevant for thermal freeze-out.Comment: 8 pages revtex4, 5 figures; v2: analysis updated to include
constraints from XENON1T; accepted for publication in PR
A weighty interpretation of the Galactic Centre excess
Previous attempts at explaining the gamma-ray excess near the Galactic Centre
have focussed on dark matter annihilation directly into Standard Model
particles. This results in a preferred dark matter mass of 30-40 GeV (if the
annihilation is into b quarks) or 10 GeV (if it is into leptons). Here we show
that the gamma-ray excess is also consistent with heavier dark matter
particles; in models of secluded dark matter, dark matter with mass up to 76
GeV provides a good fit to the data. This occurs if the dark matter first
annihilates to an on-shell particle that subsequently decays to Standard Model
particles through a portal interaction. This is a generic process that works in
models with annihilation, semi-annihilation or both. We explicitly demonstrate
this in a model of hidden vector dark matter with an SU(2) gauge group in the
hidden sector.Comment: 5 pages, 4 figures. v2: Matches PRD version. Note: title of PRD
version is "Interpretation of the Galactic Center excess of gamma rays with
heavier dark matter particles
Transplanckian Censorship and Global Cosmic Strings
Large field excursions are required in a number of axion models of inflation.
These models also possess global cosmic strings, around which the axion follows
a path mirroring the inflationary trajectory. Cosmic strings are thus an
interesting theoretical laboratory for the study of transplanckian field
excursions. We describe connections between various effective field theory
models of axion monodromy and study the classical spacetimes around their
supercritical cosmic strings. For small decay constants and large
winding numbers , the EFT is under control and the string cores
undergo topological inflation, which may be either of exponential or power-law
type. We show that the exterior spacetime is nonsingular and equivalent to a
decompactifying cigar geometry, with the radion rolling in a potential
generated by axion flux. Signals are able to circumnavigate infinite straight
strings in finite but exponentially long time, . For
finite loops of supercritical string in asymptotically flat space, we argue
that if topological inflation occurs, then topological censorship implies
transplanckian censorship, or that external observers are forbidden from
threading the loop and observing the full excursion of the axion.Comment: v2: refs added, fig 6 extended. published in JHEP. 28 pages, 7
figure
Hadron Collider Sensitivity to Fat Flavourful s for
We further investigate the case where new physics in the form of a massive
particle explains apparent measurements of lepton flavour
non-universality in decays. Hadron collider
sensitivities for direct production of such s have been previously
studied in the narrow width limit for a final state. Here, we
extend the analysis to sizeable decay widths and improve the sensitivity
estimate for the narrow width case. We estimate the sensitivities of the high
luminosity 14 TeV Large Hadron Collider (HL-LHC), a high energy 27 TeV LHC
(HE-LHC), as well as a potential 100 TeV future circular collider (FCC). The
HL-LHC has sensitivity to narrow resonances consistent with the
anomalies. In one of our simplified models the FCC could probe 23 TeV
particles with widths of up to 0.35 of their mass at 95\% confidence
level (CL). In another model, the HL-LHC and HE-LHC cover sizeable portions of
parameter space, but the whole of perturbative parameter space can be covered
by the FCC.Comment: 24 pages, 11 figures; v2 Reference
F-theory GUTs with U(1) Symmetries: Generalities and Survey
We study the structure of SU(5) F-theory GUT models that engineer additional
U(1) symmetries. These are highly constrained by a set of relations observed by
Dudas and Palti (DP) that originate from the physics of 4D anomaly
cancellation. Using the DP relations, we find a general tension between
unification and the suppression of dimension 5 proton decay when one or more
U(1)'s are PQ symmetries and hypercharge flux is used to break the SU(5) GUT
group. We then specialize to spectral cover models, whose global completions in
F- theory we know how to construct. In that setting, we provide a technical
derivation of the DP relations, construct spectral covers that yield all
possible solutions to them, and provide a complete survey of spectral cover
models for SU(5) GUTs that exhibit two U(1) symmetries.Comment: 27 pages plus 5 appendices (70 pages total) ; v2 references adde
production at the LHC
The search for di-Higgs production at the LHC in order to set limits on Higgs
trilinear coupling and constraints on new physics is one of the main
motivations for the LHC high luminosity phase. Recent experimental analyses
suggest that such analyses will only be successful if information from a range
of channels is included. We therefore investigate di-Higgs production in
association with two hadronic jets and give a detailed discussion of both the
gluon- and weak boson fusion contributions, with a particular emphasis on the
phenomenology with modified Higgs trilinear and quartic gauge couplings. We
perform a detailed investigation of the full hadronic final state and find that
production should add sensitivity to a di-Higgs search combination at
the HL-LHC with 3 ab. Since the WBF and GF contributions are sensitive
to different sources of physics beyond the Standard Model, we devise search
strategies to disentangle and isolate these production modes. While gluon
fusion remains non-negligible in WBF-type selections, sizeable new physics
contributions to the latter can still be constrained. As an example of the
latter point we investigate the sensitivity that can be obtained for a
measurement of the quartic Higgs-gauge boson couplings.Comment: 11 pages, 9 figure
TopicFlow: Disentangling quark and gluon jets with normalizing flows
The isolation of pure samples of quark and gluon jets is of key interest at
hadron colliders. Recent work has employed topic modeling to disentangle the
underlying distributions in mixed samples obtained from experiments. However,
current implementations do not scale to high-dimensional observables as they
rely on binning the data. In this work we introduce TopicFlow, a method based
on normalizing flows to learn quark and gluon jet topic distributions from
mixed datasets. These networks are as performant as the histogram-based
approach, but since they are unbinned, they are efficient even in high
dimension. The models can also be oversampled to alleviate the statistical
limitations of histograms. As an example use case, we demonstrate how our
models can improve the calibration accuracy of a classifier. Finally, we
discuss how the flow likelihoods can be used to perform outlier-robust
quark/gluon classification.Comment: 10 pages, 5 figures. v2: Added footnote in Section III B. Added
baseline and related discussion to Section III C. v3: Match published versio
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