arXiv subjects

Sara Rydbeck

Publications and source records attributed to Sara Rydbeck.

5 recordsLinked to original sources

arXiv2014

Majorana Dark Matter with a Coloured Mediator: Collider vs Direct and Indirect Searches

We investigate the signatures at the Large Hadron Collider of a minimal model where the dark matter particle is a Majorana fermion that couples to the Standard Model via one or several coloured mediators. We emphasize the importance of the production channel of coloured scalars through the exchange of a dark matter particle in the t-channel, and perform a dedicated analysis of searches for jets and missing energy for this model. We find that the collider constraints are highly competitive compared to direct detection, and can even be considerably stronger over a wide range of parameters. We also discuss the complementarity with searches for spectral features at gamma-ray telescopes and comment on the possibility of several coloured mediators, which is further constrained by flavour observables.

hep-ph↗

arXiv2013

Status of the Inert Doublet Model and the Role of multileptons at the LHC

A possible feature of the inert doublet model (IDM) is to provide a dark matter candidate together with an alteration of both direct and indirect collider constraints that allow for a heavy Higgs boson. We study the IDM in light of recent results from Higgs searches at the Large Hadron Collider (LHC) in combination with dark matter direct detection limits from the XENON experiment. We ask under what conditions the IDM can still accommodate a heavy Higgs boson. We find that IDM scenarios with a Higgs boson in the mass range 160-600 GeV are ruled out only when all experimental constraints are combined. For models explaining only a fraction of the dark matter the limits are weakened, and IDMs with a heavy Higgs are allowed. We discuss the prospects for future detection of such IDM scenarios in the four-lepton plus missing energy channel at the LHC. This signal can show up in the first year of running at \sqrt{s} = 14 TeV, and we present detector-level studies for a few benchmark models.

hep-ph↗

arXiv2010

Early search for supersymmetric dark matter models at the LHC without missing energy

We investigate early discovery signals for supersymmetry at the Large Hadron Collider without using information about missing transverse energy. Instead we use cuts on the number of jets and isolated leptons (electrons and/or muons). We work with minimal supersymmetric extensions of the standard model, and focus on phenomenological models that give a relic density of dark matter compatible with the WMAP measurements. An important model property for early discovery is the presence of light sleptons, and we find that for an integrated luminosity of only 200--300 pb$^{-1}$ at a center-of-mass energy of 10 TeV models with gluino masses up to $\sim 700$ GeV can be tested.

hep-ph↗

arXiv2007

Expansion history and f(R) modified gravity

We attempt to fit cosmological data using $f(R)$ modified Lagrangians containing inverse powers of the Ricci scalar varied with respect to the metric. While we can fit the supernova data well, we confirm the $a\propto t^{1/2}$ behaviour at medium to high redshifts reported elsewhere and argue that the easiest way to show that this class of models are inconsistent with the data is by considering the thickness of the last scattering surface. For the best fit parameters to the supernova data, the simplest 1/R model gives rise to a last scattering surface of thickness $Δz\sim 530$, inconsistent with observations.

astro-ph↗

arXiv2007

Testing the DGP model with ESSENCE

We use the recent supernova data set from the ESSENCE collaboration combined with data from the Supernova Legacy Survey and nearby supernovae to test the DGP brane world model and its generalisations. Combination of this data with a flatness prior and the position of the peak of the CMB disfavours the DGP model slightly. Inclusion of the baryon acoustic peak from the Sloan Digital Sky Survey increase the tension of the DGP model with the data, although it is not clear how self consistent this procedure would be without a re-analysis of the survey data in the framework of the DGP cosmology. Generalisations of the DGP model are tested and constraints on relevant parameters obtained.

astro-ph↗