Higgs production in association with a dark-Z at future electron positron colliders

In recent years there have been many proposals for new electron-positron colliders, such as the Circular Electron-Positron Collider, the International Linear Collider, and the Future Circular Collider in electron-positron mode. Much of the motivation for these colliders is precision measurements of the Higgs boson and searches for new electroweak states. Hence, many of these studies are focused on energies above the h Z threshold. However, there are proposals to run these colliders at the lower WW threshold and Z-pole energies. In this paper, we study a new search for Higgs physics accessible at lower energies: e+e− → h Zd, where Zdis a new light gauge boson such as a dark photon or dark-Z. Such searches can be conducted at the WW threshold, i.e. energies below the h Z threshold where exotic Higgs decays can be searched for in earnest. Additionally, due to very good angular and energy resolution at future electron-positron colliders, these searches will be sensitive to Zd masses below 1 GeV, which is lower than the current direct LHC searches. We will show that at √s = 160 GeV with 10 ab−1, a search for e+e− → h Zd is sensitive to h −Z −Zd couplings of δ ∼ 9 × 10−3and cross sections of ∼ 2 − 3 ab for Zd masses below 1 GeV. The results are similar at √s = 240 GeV with 5 ab−1.

Particle identification at FCC-ee

Equipping an experiment at FCC-ee with particle identification (PID) capabilities, in particular the ability to distinguish between hadron species, would bring great benefits to the physics programme. Good PID is essential for precise studies in quark flavour physics and is also a great asset for many measurements in tau, top, and Higgs physics. The requirements placed by flavour physics and these other applications are surveyed, with an emphasis on the momentum range over which PID is necessary. Possible solutions are discussed, including classical RICH counters, time-of-flight systems, and dE/dx and cluster counting. Attention is paid to the impact on the global detector design that including PID capabilities would imply.

Explaining muon $${g}-2$$ data in the $$\mu \nu $$SSM

We analyze the anomalous magnetic moment of the muon $$g-2$$ g - 2 in the $$\mu \nu $$ μ ν SSM. This R-parity violating model solves the $$\mu $$ μ problem reproducing simultaneously neutrino data, only with the addition of right-handed neutrinos. In the framework of the $$\mu \nu $$ μ ν SSM, light left muon-sneutrino and wino masses can be naturally obtained driven by neutrino physics. This produces an increase of the dominant chargino-sneutrino loop contribution to muon $$g-2$$ g - 2 , solving the gap between the theoretical computation and the experimental data. To analyze the parameter space, we sample the $$\mu \nu $$ μ ν SSM using a likelihood data-driven method, paying special attention to reproduce the current experimental data on neutrino and Higgs physics, as well as flavor observables such as B and $$\mu $$ μ decays. We then apply the constraints from LHC searches for events with multi-leptons + MET on the viable regions found. They can probe these regions through chargino–chargino, chargino–neutralino and neutralino–neutralino pair production. We conclude that significant regions of the parameter space of the $$\mu \nu \mathrm{SSM}$$ μ ν SSM can explain muon $$g-2$$ g - 2 data.