Pressure isotropy, i.e., equality between radial and tangential pressure, is often assumed when studying neutron stars. However, mechanisms such as pion/kaon condensation, magnetic fields, and dark matter clustering can lead to pressure anisotropy. This work presents a comprehensive measurement of pressure anisotropy in neutron stars. Our analysis incorporates an extensive set of nuclear experimental constraints and multi-messenger astrophysical observations. We find that the Bayes factor for anisotropy against isotropy greater than or similar to 3:1, when the anisotropy is allowed to vary between individual stars. The posterior indicates a population-wide preference for negative anisotropy, primarily driven by PSR J0740 & thorn; 6620. Due to the lack of radius measurements for 2M circle dot neutron stars, we cannot rule out density-scale-dependent anisotropy. Therefore, both phase transitions and density-scale-independent mechanisms, such as magnetic fields, dark matter clustering, or deviations from general relativity are viable explanations. While the evidence for anisotropy remains inconclusive, these results demonstrate that pressure anisotropy can be utilized as a tool for identifying missing physics in neutron star modeling or revealing novel physics in the era of multimessenger astronomy.
The origin of the universal asymmetry between matter and antimatter remains a mystery. Electroweak baryogenesis is a well-motivated mechanism for generating the asymmetry dynamically, using interesting features of the Standard Model. In addition, it relies on beyond-the-Standard Model physics active around the electroweak scale: new physics coupling to the Higgs to make the electroweak phase transition first order, and a new mechanism of CP violation. The relatively low energy scale at which electroweak baryogenesis occurs makes certain aspects of the mechanism testable through collider experiments, electric dipole moment measurements, and gravitational wave observations. However, scenarios of electroweak baryogenesis are increasingly challenged by results from contemporary experiments. The developing experimental programs will play a crucial role in either falsifying or detecting the new physics responsible for electroweak baryogenesis. To achieve this, it is essential to make precise predictions for the baryon asymmetry and the corresponding experimental signatures within specific scenarios. This review aims to provide a comprehensive overview of the rich physics involved in these predictions. Our goal is to offer a practical computational guide, with a focus on recent developments in the field.
The discovery of the lepton number violation would be a smoking gun signal for physics beyond the Standard Model, and its most sensitive probe is the search for neutrinoless double beta decay (0v/3/3). Working in the framework of the Standard Model effective field theory (SMEFT), we show that one-loop effects can remarkably improve the tree-level bounds on the new physics scales for several dimension-7 operators. Using ultraviolet model examples, we then showcase the competition among 0v/3/3 contributions induced by dimension-7 and loop-level dimension-5 SMEFT operators.
A Time Projection Chamber (TPC) module with 32 GridPixes was constructed and the performance was measured using data taken in a test beam at DESY in 2021. The data analysed were taken at electron beam momenta of 5 and 6 GeV/c and at magnetic fields of 0 and 1 Tesla(T). Part I of the paper has described the construction, setup and tracking results. The dE/dx or dN/dx resolution for electrons in the 1 T data per metre of track length with 60% coverage was measured to be 3.6% for the dE/dx truncation method and 2.9% for the template fit method using the successive distances between the hits. The single-electron efficiency at high hit rates was studied. For hit rates up to 5.7 kHz per GridPix a reduction of at most 0.6% in the relative efficiency was measured. Large localised hit bursts from low energetic curling electrons were characterised. The single-electron resolution in the xy precision plane as a function of the local track angle cent was measured in the B = 1 T data using reconstructed circular tracks. The resolution is-as expected-independent of the local track angle within an uncertainty of 16 mu m. The projected particle identification (PID) performance for a GridPix Pixel TPC in the proposed ILD experiment at a future ILC e+e-collider is presented using the B = 1 T test beam results for the measured electron PID resolution. The expected pion-kaon PID separation for momenta in the range of 2.5-45 GeV/c at cos 0 = 0 is more than 5.5(4.5)a for the template fit (dE/dx truncation) method.
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.
