The existence and the production at colliders of dark photons, long range gauge field mediators belonging to the ¿dark sector¿ physics, have been predicted by many beyond the standard model (BSM) models. "Dark sector" particles and their messengers are good candidate for dark matter. The decay of the Higgs boson into one massless dark photon and one SM photon, by means of the triangular loop diagram mediated by the massive messenger particles, is a simple and clear signature for dark photon searches. H->gamma+darkphoton decay is driven by just one coupling constant (alpha), giving rise to kinematics identical to the SM H->gammagamma. Depending on the alpha values, it is possible to reach a branching ratio of 5%, more than one order of magnitude larger than the SM H->gammagamma branching ratio (0.23%). This signature is characterized by the presence of a single isolated photon and missing transverse energy ( MET ), arising from the undetected dark photon. In the context of the CMS experiment, this kind of analysis has never been performed, neither on data collected with 8 TeV nor 13 TeV centre-of-mass energies. The Higgs boson production required for this search allows to apply an additional constraint on the transverse mass, which peaks at mH . In addition, the Higgs boson different production modes with their own unique topologies can be exploited: the presence of two additional forward jets for the vector-boson-fusion (VBF) production. Generator level studies have been performed at 8 TeV and 14 TeV centre-of-mass energies, considering the main backgrounds (gammaj, jj, gammaZ->nunu, jZ->jnunu, W->enu, gammaW->gamma e nu) where the jets or leptons are misidentified as photons, or completely missed in the reconstruction. These results show that with a collected luminosity of 100 fb-1 it is possible to reach a 5sigma significance for branching ratios greater than 0.16%.
Tale ricerca non è mai stata effettuata usando dati raccolti e simulazioni prodotte dalla collaborazione di CMS. Le particelle "dark" e le particelle messaggere massive, create per poter accoppiare lo SM con il "dark sector", possono essere ottimi candidati di materia oscura. A causa di ciò, la scoperta di un fotone "dark" non massivo sarebbe un chiaro segnale dell'esistenza di un altro settore della fisica delle particelle elementari inesplorato, contente particelle che potrebbero essere ottimi candidati di materia oscura, o particelle che più precisamente darebbero ragione dei diversi valori degli accoppiamenti di Yukawa dello SM, mediante un solo coupling effettivo.