Susanne Westhoff

A Dark Matter Relic From Muon Anomalies

We show that the recently reported anomalies in

Physics at a 100 TeV pp collider: Standard Model processes

b\to s\mu^+\mu^-

Charged-Higgs effects in a new B ---> D tau nu differential decay distribution

transitions, as well as the long-standing

Integrating in the Higgs Portal to Fermion Dark Matter

g_\mu-2

Testing the muon g-2 anomaly at the LHC

discrepancy, can be addressed simultaneously by a new massive abelian gauge boson with loop-induced coupling to muons. Such a scenario typically leads to a stable dark matter candidate with a thermal relic density close to the observed value. Dark matter in our model couples dominantly to leptons, hence signals in direct detection experiments lie well below the current sensitivity. The LHC, in combination with indirect detection searches, can test this scenario through distinctive signatures with muon pairs and missing energy.

Top-Quark Initiated Processes at High-Energy Hadron Colliders

This chapter documents the production rates and typical distributions for a number of benchmark Standard Model processes, and discusses new dynamical phenomena arising at the highest energies available at this collider. We discuss the intrinsic physics interest in the measurement of these Standard Model processes, as well as their role as backgrounds for New Physics searches.This chapter documents the production rates and typical distributions for a number of benchmark Standard Model processes, and discusses new dynamical phenomena arising at the highest energies available at this collider. We discuss the intrinsic physics interest in the measurement of these Standard Model processes, as well as their role as backgrounds for New Physics searches.This chapter documents the production rates and typical distributions for a number of benchmark Standard Model processes, and discusses new dynamical phenomena arising at the highest energies available at this collider. We discuss the intrinsic physics interest in the measurement of these Standard Model processes, as well as their role as backgrounds for New Physics searches.

Leptophilic Dark Matter in Lepton Interactions at LEP and ILC

We show that the decay mode B -> D tau nu is competitive with and complementary to B -> tau nu in the search for charged-Higgs effects. Updating the relevant form factors, we find that the differential distribution in the decay chain B -> D nu tau[-> pi nu] excellently discriminates between Standard-Model and charged-Higgs contributions. By measuring the D and pi energies and the angle between the D and pi three-momenta one can determine the effective charged-Higgs coupling including a possible CP-violating phase.

Top-quark charge asymmetry goes forward: two new observables for hadron colliders

A bstractFermion dark matter (DM) interacting with the standard model through a Higgs portal requires non-renormalizable operators, signaling the presence of new mediator states at the electroweak scale. Collider signatures that involve the mediators are a powerful tool to experimentally probe the Higgs portal interactions, providing complementary information to strong constraints set by direct DM detection searches. Indirect detection experiments are less sensitive to this scenario. We investigate the collider reach for the mediators using three minimal renormalizable models as examples, and requiring the fermion DM to be a thermal relic. The Large Hadron Collider in its high-energy, high-luminosity phase can probe most scenarios if DM is lighter than about 200 GeV. Beyond this scale, future high-energy experiments such as an electron-positron collider or a 100-TeV proton-proton collider, combined with future direct detection experiments, are indispensable to conclusively test these models.

Top-Quark Charge Asymmetry with a Jet Handle

A bstractThe long-standing difference between the experimental measurement and the standard-model prediction for the muon’s anomalous magnetic moment, aμ = (gμ − 2)/2, may be explained by the presence of new weakly interacting particles with masses of a few 100 GeV. Particles of this kind can generally be directly produced at the LHC, and thus they may already be constrained by existing data. In this work, we investigate this connection between aμ and the LHC in a model-independent approach, by introducing one or two new fields beyond the standard model with spin and weak isospin up to one. For each case, we identify the preferred parameter space for explaining the discrepancy of aμ and derive bounds using data from LEP and the 8 TeV LHC run. Furthermore, we estimate how these limits could be improved with the 14 TeV LHC. We find that the 8 TeV results already rule out a subset of our simplified models, while almost all viable scenarios can be tested conclusively with 14 TeV data.

Dark Matter from Electroweak Single Top Production

A bstractIn hadronic collisions at high energies, the top-quark may be treated as a parton inside a hadron. Top-quark initiated processes become increasingly important since the top-quark luminosity can reach a few percent of the bottom-quark luminosity. In the production of a heavy particle H with mass mH> mt, treating the top-quark as a parton allows us to resum large logarithms log(mH2/mt2) arising from collinear splitting in the initial state. We quantify the effect of collinear resummation at the 14-TeV LHC and a future 100-TeV hadron collider, focusing on the top-quark open-flavor process gg→tt¯H