Particle theory

Abstract:

The accurate identification of heavy-flavour jets — those which originate from bottom or charm quarks — is crucial for precision studies of the Standard Model and searches for new physics. However, assigning flavour to jets presents significant challenges, primarily due to issues with infrared and collinear (IRC) safety. This paper aims to address these challenges by evaluating recently-proposed jet algorithms designed to be IRC-safe and applicable in high-precision measurements. We compare these algorithms across benchmark heavy-flavour production processes and kinematic regimes that are relevant for LHC phenomenology. Exploiting both fixed-order calculations in QCD as well as parton shower simulations, we analyse the infrared sensitivity of these new algorithms at different stages of the event evolution and compare to flavour labelling strategies currently adopted by LHC collaborations. The results highlight that, while all algorithms lead to more robust flavour assignments compared to current techniques, they vary in performance depending on the observable and energy regime. The study lays groundwork for robust, flavour-aware jet analyses in current and future collider experiments to maximise the physics potential of experimental data by reducing discrepancies between theoretical and experimental methods.

Abstract:

We study the minimal requirements to obtain axion strings for axions with exponentially good quality. These ingredients appear in theories where an axion coming from a higher-form gauge field mixes with the phase of a complex scalar field. The resulting axion is perturbatively massless and inherits a high-quality shift symmetry from the global higher-form symmetry while being compatible with a post-inflationary axion scenario. Axions produced in this manner share features of both extra-dimensional and ordinary axions but are ultimately distinct from either. We refer to such axions as higher axions, as the mechanism responsible for the mixing is that of higher-groups. We present a simple toy model on a 5-dimensional manifold with boundary. The boundary hosts the complex scalar that provides axion strings through standard mechanisms. In addition, we study how these scenarios may arise in heterotic and type II string theory compactifications.

Abstract:

Abstract We extend the recently presented, fully exclusive, next-to-leading-order accurate event generator for the simulation of massless neutral- and charged-current deep inelastic scattering (DIS) to the case of incoming neutrinos. The generator can be used to study neutrino-nucleon interactions at (ultra) high energies, and is relevant for a range of fixed-target collider experiments and large-volume neutrino detectors, investigating atmospheric and astrophysical neutrinos. The matching with multi-purpose event generators such as is performed with the method, and accounts for parton showering and non-perturbative effects such as hadronization. This makes it possible to investigate higher-order perturbative corrections to realistic observables, such as the distribution of charged particles. To illustrate the capabilities of the code we provide predictions for several differential distributions in fixed-target collisions for neutrino energies up to $$1~\textrm{PeV} $$ 1 PeV .