Searching for Light New Physics with Fixed Target and Collider Experiments
In this seminar, I will discuss the sensitivity of high-luminosity
colliders and fixed target facilities to low-mass new physics in
so-called dark sectors that are coupled to the Standard Model of
particle physics. These new physics scenarios are motivated by the need
to explain empirical puzzles, including the nature of the dark matter in
the universe and the origin of neutrino mass. Avoiding over-production
and reproducing the observed relic abundance of thermal dark matter
candidates requires that low mass (sub-GeV) dark sector degrees of
freedom are coupled to the Standard Model via new light force mediators.
In this context, I will revisit the minimal case of a sub-GeV scalar
singlet S coupled to the Standard Model through the Higgs portal. New
constraints will be imposed by interpreting the dataset from the LSND
experiment. I will present the result of a study revisiting the
production of dark vectors and scalars via proton bremsstrahlung across
a range of beam energies. Proton bremsstrahlung, involving mixing with
meson resonances, serves as a primary production mode in the forward
direction near the resonance region. Furthermore, the newly proposed LHC
Forward Physics Facility (FPF) emerged as a highly promising site for
searching for long-lived particles, millicharged particles, and
especially for studying high-energy colliding neutrinos. Within this
framework, the FORMOSA experiment, located in the LHC forward region,
aims to offer exceptional sensitivity in the search for millicharged
particles by exploiting their scintillation signature. Additionally, I
discuss the potential of the FPF to probe various electromagnetic
properties of neutrinos, including neutrino millicharge, magnetic
moment, and charge radius, as well as the weak mixing angle. This will
be achieved using an intense beam of highly energetic neutrinos of all
three flavors.