6,547 research outputs found
Impact of a XENONnT Signal on LHC Dijet Searches
It is well-known that dark matter (DM) direct detection experiments and the
LHC are complementary, since they probe physical processes occurring at
different energy scales. And yet, there are aspects of this complementarity
which are still not fully understood, or exploited. For example, what is the
impact that the discovery of DM at XENONnT would have on present and future
searches for DM in LHC final states involving a pair of hadronic jets? In this
work we investigate the impact of a XENONnT signal on the interpretation of
current dijet searches at the LHC, and on the prospects for dijet signal
discovery at the High-Luminosity (HL) LHC in the framework of simplified
models. Specifically, we focus on a general class of simplified models where DM
can have spin 0, 1/2 or 1, and interacts with quarks through the exchange of a
scalar, pseudo-scalar, vector, or pseudo-vector mediator. We find that
exclusion limits on the mediator's mass and its coupling to quarks from dijet
searches at the LHC are significantly affected by a signal at XENONnT, and that
signal events at XENONnT would drastically narrow the region
in the parameter space of simplified models where a dijet signal can be
discovered at C.L. at the HL-LHC.Comment: 23 pages, 3 figures, 3 tables, version accepted by JHE
Killing the Straw Man: Does BICEP Prove Inflation at the GUT Scale?
The surprisingly large value of , the ratio of power in tensor to scalar
density perturbations in the CMB reported by the BICEP2 Collaboration, if
confirmed, provides strong evidence for Inflation at the GUT scale. While the
Inflationary signal remains the best motivated source, a large value of
alone would still allow for the possibility that a comparable gravitational
wave background might result from a self ordering scalar field (SOSF)
transition that takes place later at somewhat lower energy. We find that even
without detailed considerations of the predicted BICEP signature of such a
transition, simple existing limits on the isocurvature contribution to CMB
anisotropies would definitively rule out a contribution of more than to
,. We also present a general relation for the allowed fractional
SOSF contribution to as a function of the ultimate measured value of .
These results point strongly not only to an inflationary origin of the BICEP2
signal, if confirmed, but also to the fact that if the GUT scale is of order
then either the GUT transition happens before Inflation or the
Inflationary transition and the GUT transition must be one and the same.Comment: 3 pages 2 figures, accepted for publication in Physics Letters B .
Accepted version revised slightly in response to referee's comment
Minimal Asymmetric Dark Matter
In the early Universe, any particle carrying a conserved quantum number and
in chemical equilibrium with the thermal bath will unavoidably inherit a
particle-antiparticle asymmetry. A new particle of this type, if stable, would
represent a candidate for asymmetric dark matter (DM) with an asymmetry
directly related to the baryon asymmetry. We study this possibility for a
minimal DM sector constituted by just one (generic) multiplet
carrying hypercharge, assuming that at temperatures above the electroweak phase
transition an effective operator enforces chemical equilibrium between
and the Higgs boson. We argue that limits from DM direct detection searches
severely constrain this scenario, leaving as the only possibilities scalar or
fermion multiplets with hypercharge , preferentially quintuplets or
larger representations, and with a mass in the few TeV range.Comment: 9 pages, 2 figures, included t-channel scattering, added details on
charged-neutral mass splitting and indirect detection, accepted in PL
Higher Dimensional Effective Operators for Direct Dark Matter Detection
We discuss higher dimensional effective operators describing interactions
between fermionic dark matter and Standard Model particles. They are typically
suppressed compared to the leading order effective operators, which can explain
why no conclusive direct dark matter detection has been made so far. The
ultraviolet completions of the effective operators, which we systematically
study, require new particles. These particles can potentially have masses at
the TeV scale and can therefore be phenomenologically interesting for LHC
physics. We demonstrate that the lowest order options require Higgs-portal
interactions generated by dimension six operators. We list all possible
tree-level completions with extra fermions and scalars, and we discuss the LHC
phenomenology of a specific example with extra heavy fermion doublets.Comment: 27 pages, 11 figures, 3 table
The 'anti-economics' of the European common market
I would like to preface my comments by extending a personal but public note of appreciation to the administrators, faculty and students of the Royal University for inviting me to visit and address this distinguished audience of scholars, business men and government officers, this evening on the theme of the 'Anti-Economics' of the European Common Market and its relation to the tax harmonization program of the Community. Perhaps the title of my talk warrants clarification? What is precisely meant by the 'anti-economics' of the European Economic Community for one; and what is meant by 'tax harmonization' for the other? And even more important, why should this distinguished gathering be interested in either one of them?peer-reviewe
Determining Dark Matter properties with a XENONnT/LZ signal and LHC-Run3 mono-jet searches
We develop a method to forecast the outcome of the LHC Run 3 based on the
hypothetical detection of signal events at XENONnT. Our
method relies on a systematic classification of renormalisable single-mediator
models for dark matter-quark interactions, and is valid for dark matter
candidates of spin less than or equal to one. Applying our method to simulated
data, we find that at the end of the LHC Run 3 only two mutually exclusive
scenarios would be compatible with the detection of signal
events at XENONnT. In a first scenario, the energy distribution of the signal
events is featureless, as for canonical spin-independent interactions. In this
case, if a mono-jet signal is detected at the LHC, dark matter must have spin
1/2 and interact with nucleons through a unique velocity-dependent operator. If
a mono-jet signal is not detected, dark matter interacts with nucleons through
canonical spin-independent interactions. In a second scenario, the spectral
distribution of the signal events exhibits a bump at non zero recoil energies.
In this second case, a mono-jet signal can be detected at the LHC Run 3, dark
matter must have spin 1/2 and interact with nucleons through a unique
momentum-dependent operator. We therefore conclude that the observation of
signal events at XENONnT combined with the detection, or the
lack of detection, of a mono-jet signal at the LHC Run 3 would significantly
narrow the range of possible dark matter-nucleon interactions. As we argued
above, it can also provide key information on the dark matter particle spin.Comment: 17 pages, 8 figures, updated operator coefficients and figures,
version accepted by PR
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