A new light at LHC tunnels?
Last week, the CMS https://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO/index.html and ATLAS https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2015-081/ collaborations have released a summary of the first results from the data collected at the LHC at 13 TeV. Among them, there was a search for diphoton final states reconstructing a large invariant mass. Surprisingly, a slight excess of events over the standard model background is found around 750 GeV invariant mass, in both experiments. Although the statistics is still insufficient to make any claim about physics beyond the standard model, the community has already started to scrutinise it enthusiastically. The new data poses many interesting questions. As coincidences do happen (and they occurred many times in the past), one always wonders: Is this really new physics or just an irrelevant statistical fluctuation? Given that diphoton decays are usually loop suppressed, why nothing has been noticed in final states with other gauge bosons or fermions? Is it a spin-0 or a spin-2 resonance (since decays into two photons are forbidden for spin 1 particles)? Is it broad or narrow? How is this resonance produced at the LHC? The answers to these queries only future, next year data, can tell.