61 research outputs found
Diphoton Resonances at the LHC
We review the current status of searches for new physics beyond the Standard
Model in the diphoton channel at the LHC and estimate the reach with future
collected data. We perform a model independent analysis based on an effective
field theory approach and different production mechanisms. As an illustrative
example, we apply our results to a scenario of minimal composite dynamics.Comment: 13 pages, 3 figures; invited review for MPLA; journal versio
Potential for probing three-body decays of Long-Lived Particles with MATHUSLA
Several extensions of the Standard Model predict the existence of Long-Lived
Neutral Particles (LLNPs) with masses in the multi-GeV range and decay lengths
of O(100 m) or longer. These particles could be copiously produced at the LHC,
but the decay products cannot be detected with the ATLAS or CMS detectors.
MATHUSLA is a proposed large-volume surface detector installed near ATLAS or
CMS aimed to probe scenarios with LLNPs which offers good prospects for
disentangling the physics underlying two-body decays into visible particles. In
this work we focus on LLNP decays into three particles with one of them being
invisible, which are relevant for scenarios with low scale supersymmetry
breaking, feebly interacting dark matter or sterile neutrinos, among others. We
analyze the MATHUSLA prospects to discriminate between two- and three-body LLNP
decays, as well as the prospects for reconstructing the underlying model
parameters.Comment: 11 pages, 4 figures, matches journal versio
CP Violation in the Lepton Sector, Thermal Leptogenesis and Lepton Flavour Violating Processes
It is a well established experimental fact that the Universe is strongly asymmetric in its matter and antimatter content. Indeed, there is no direct/indirect evidence up to now about the formation of primordial stars or galaxies made entirely of antiparticles. The only clear observation of antimatter in the Universe, besides the one created in particle accelerators, resides on the measurement of the cosmic ray flux through the Earth....
Collider Tests of (Composite) Diphoton Resonances
We analyze the Large Hadron Collider sensitivity to new pseudoscalar
resonances decaying into diphoton with masses up to scales of few TeVs. We
focus on minimal scenarios where the production mechanisms involve either
photon or top-mediated gluon fusion, partially motivated by the tantalizing
excess around 750 GeV reported by ATLAS and CMS. The two scenarios lead
respectively to a narrow and a wide resonance. We first provide a
model-independent analysis via effective operators and then introduce minimal
models of composite dynamics where the diphoton channel is characterized by
their topological sector. The relevant state here is the pseudoscalar
associated with the axial anomaly of the new composite dynamics. If the
Standard Model top mass is generated via four-fermion operators the coupling of
this state to the top remarkably explains the wide-width resonance reported by
ATLAS. Beyond the excess, our analysis paves the way to test dynamical
electroweak symmetry breaking via topological sectors.Comment: 17 pages, 5 figure
Minimal Composite Dynamics versus Axion Origin of the Diphoton excess
ATLAS and CMS observe deviations from the expected background in the diphoton
invariant mass searches of new resonances around 750 GeV. We show that a simple
realization in terms of a new pseudoscalar state can accommodate the
observations. The model leads to further footprints that can be soon observed.
The new state can be interpreted both as an axion or as a {highly natural}
composite state arising from minimal models of dynamical electroweak symmetry
breaking. We further show how to disentangle the two scenarios. Beyond the
possible explanation of the diphoton excess the results show that it is
possible to directly test and constrain composite dynamics via processes
stemming from its distinctive topological sector.Comment: 6 pages, Latex. Improved version with new figures and further detail
- …