Particle theory

Abstract:

The detection of gravitational waves (GWs) from a binary neutron star (BNS) merger by Advanced LIGO and Advanced Virgo (GW170817), together with its electromagnetic counterpart, the short gamma-ray burst GRB 170817A, heralded the birth of multimessenger astronomy. The detection of TeV emission from GRBs motivates follow-up observations with the Cherenkov Telescope Array Observatory (CTAO), which is ideal for detecting such signals due to its unprecedented sensitivity, rapid response, and wide-field survey capabilities. The aim of this work is to evaluate GeV–TeV GW follow-up strategies for CTAO using a multistep simulation pipeline and to estimate the expected rate of joint GW–GRB detections during observing run O5. Using a simulated sample of BNS systems with corresponding GW detections, gamma-ray emission is simulated through phenomenological prescriptions based on the observed population of short GRBs, including off-axis jet scenarios. CTAO observations are simulated to account for instrument response, sky tiling strategies, integration times, and varying observing conditions. Strategies with variable and constant integration times are investigated. We find that, via an optimized follow-up strategy, about 5% of simulated GW-associated short GRBs produce GeV–TeV radiation detectable by CTAO. Detectability is strongly influenced by the jet opening angle and viewing angle, suggesting that even rough estimates of the viewing angle in GW alerts could enhance targeting. This framework motivates future follow-ups of GW-detectable events, including neutron star–black hole mergers, and further supports the development of advanced strategies incorporating galaxy distributions and synergies with future detectors such as the Einstein Telescope.

Abstract:

We introduce a class of collider observables, named Lund-Tree Shapes (LTS), defined from declustering trees originating from the Lund jet plane representation of the QCD radiation pattern in multi-jet scattering processes. At the differential level, they are continuous, global variables akin classical event shapes and n → n + 1 jet-resolution parameters, which probe the geometry and hierarchical structure of the radiation in an event. At the integrated, cumulative level, they naturally define n jet rates, providing a jet-multiplicity-based characterisation of multi-jet final states. In addition, the versatile definition of the LTS can be exploited to scan systematically the QCD radiation pattern in scattering events and jets. From a theoretical viewpoint, such observables feature a simple all-order structure and are free of non-global logarithmic corrections. Their definition applies to scattering processes with any number of resolved jets in the final state, as well as to groomed jets. They are thus usable as resolution variables in the context of higher-order calculations via phase-space slicing, matching fixed-order calculations to parton showers, and testing the logarithmic accuracy of shower algorithms. As an initial application, we derive next-to-next-to-leading-logarithmic accurate predictions for processes with two QCD legs at ee, pp and ep colliders, and matched predictions to next-to-next-to-leading order for the LHC, discussing aspects of collider phenomenology.

Abstract:

Nonperturbative corrections to hadronic observables represent a critical obstacle to increasing accuracy at colliders. Long taken to scale simply as $1/Q$ , where $Q$ is the center-of-mass scattering energy, recent work has opened the path toward calculating the anomalous dimension that modifies that scaling. , the problem is complex, requiring a resummation involving arbitrary numbers of large-angle and low-energy gluons. Within a specific framework for kinematic recoil, we show that it reduces to a simple exponential for key observables like the thrust, $C$ -parameter and energy correlators. This simplicity holds for a specific hadron-mass scheme, and also even beyond the two-jet limit.

Abstract:

We study the production of heavy, μ≳1 TeV, bosonic spin s=0, 1 dark matter (DM) via the simultaneous processes of Hawking evaporation and superradiance (SR) from an initial population of small, ≲106 kg, primordial black holes (PBHs). Even for small initial PBH spins, the SR process can produce extremely dense gravitationally bound DM Bose or Proca soliton “stars” of radius ≲pm and mass ∼10few kg that can survive to today, well after PBH decay. These solitons can constitute a significant fraction of the DM density, rising to ≳50% in the vector DM case.