Gamma-Ray Bursts at TeV Energies: Observational Status

Gamma-ray bursts (GRBs) are some of the most energetic events in the Universe and are potential sites of cosmic ray acceleration up to the highest energies. GRBs have therefore been a target of interest for very high energy gamma-ray observatories for many years, leading to the recent discovery of a number of bursts with photons reaching energies above 100 GeV. We summarize the GRB observational campaigns of the current generation of very high energy gamma-ray observatories as well as describing the observations and properties of the GRBs discovered so far. We compare the properties of the very high energy bursts to the total GRB distribution and make predictions for the next generation of very high energy gamma-ray observations.

Ultra-high-energy Gamma-Ray Radiation from the Crab Pulsar Wind Nebula

It has been long debated whether the high-energy gamma-ray radiation from the Crab Nebula stems from leptonic or hadronic processes. In this work, we investigate the multiband nonthermal radiation from the Crab pulsar wind nebula with the leptonic and leptonic–hadronic hybrid models, respectively. Then we use the Markov Chain Monte Carlo sampling technology and method of sampling trace to study the stability and reasonability of the model parameters according to the recently observed results and obtain the best-fitting values of parameters. Finally, we calculate different radiative components generated by the electrons and protons in the Crab Nebula. The modeling results indicate that the pure leptonic origin model with the one-zone only can partly agree with some segments of the data from various experiments (including the PeV gamma-ray emission reported by the LHAASO and the other radiation ranging from the radio to very-high-energy gamma-ray wave band), and the contribution of hadronic interaction is hardly constrained. However, we find that the hadronic process may also contribute, especially in the energy range exceeding the PeV. In addition, it can be inferred that the higher energy signals from the Crab Nebula could be observed in the future.

$e^+e^-\gamma$ production at photon-photon colliders at complete electroweak NLO accuracy

We present the full NLO electroweak radiative corrections to $e^+e^-\gamma$ production in $\gamma\gamma$ collision, which is an ideal channel for calibrating the beam luminosity of Photon Linear Collider. We analyse the dependence of the total cross section on the beam colliding energy, and investigate the kinematic distributions of final particles at various initial photon beam polarizations at EW NLO accuracy. The numerical results show that the EW relative corrections to the total cross section are non-negligible and become more and more significant as the increase of the beam colliding energy, even can exceed $-10\%$ in $\text{J} = 2$ $\gamma\gamma$ collision at $\sqrt{\hat{s}}=1~ \text{TeV}$. Such EW corrections are very important and should be taken into consideration in precision theoretical and experimental studies at high-energy $\gamma\gamma$ colliders.