Particle theory

Abstract:

We present methods to achieve NLL+NLO accurate parton showering for processes with two coloured legs: neutral- and charged-current Drell-Yan, and Higgs production in pp collisions, as well as DIS and e+e− to jets. The methods include adaptations of existing approaches, as well as a new NLO matching scheme, ESME, that is positive-definite by construction. Our implementations of the methods within the PanScales framework yield highly competitive NLO event generation speeds. We validate the fixed-order and combined resummation accuracy with tests in the limit of small QCD coupling and briefly touch on phenomenological comparisons to standard NLO results and to Drell-Yan data. The progress reported here is an essential step towards showers with logarithmic accuracy beyond NLL for processes with incoming hadrons.

Abstract:

We present the projected sensitivity to non-relativistic Effective Field Theory (EFT) operators for dark matter (DM) direct detection using the QUEST-DMC experiment. QUEST-DMC employs superfluid Helium-3 as a target medium and measures energy deposition via nanomechanical resonators with SQUID-based readout to probe DM interactions. The experiment aims to explore new parameter space in the sub-GeV mass range, probing light DM and a broad range of interaction models. We analyse the sensitivity to a complete set of fourteen independent non-relativistic EFT operators, each parameterised by a Wilson coefficient that quantifies the strength of DM interactions with Standard Model particles. For each interaction channel, we determine the corresponding sensitivity ceiling due to attenuation of the DM flux incident on the detector, caused by DM scattering in the Earth and atmosphere. As a key component of this analysis, we provide the mapping between the non-relativistic EFT operators and the relativistic bilinear DM-nucleon interactions, and assess the interaction sensitivity to sub-GeV DM in the QUEST-DMC detector. Our findings demonstrate that QUEST-DMC provides a unique probe of DM interactions, particularly in previously unexplored parameter space for momentum- and velocity-dependent interactions, thereby expanding the search for viable DM candidates beyond traditional weakly interacting massive particles.