Ricerca di particelle pesanti che decadono in psi(2S)pi+pi- prodotte in collisioni e+e- con radiazione nello stato iniziale.

In this dissertation, we outline the appropriate theoretical framework for describing the recent experimental results about charmonium spectroscopy. We analyze a data sample of 520.87 inverse femtobarn collected by the BaBar detector during the years 1999-2008. We select Initial State Radiation (ISR) events e+e-->pi+pi-psi(2S), where the psi(2S)->pi+pi-J/psi with the J/psi->l+l- and psi(2S)->l+l-. We study the invariant mass spectrum of the pi+pi-psi(2S) system, to search for 1^{--} vector-like states such as the Y(4360) observed for the first time by the BaBar experiment and the Y(4660) observed by the BELLE experiment. In the psi(2S)->pi+pi-J\psi channel, we observe two distinct resonant structures, one at 4335+/-23 MeV/c2 with a width of 103+/-43 MeV, consistent with the structures previously discovered by BaBar, another at 4671+/-21 MeV/c2 with a width of 97+/-59 MeV, consistent with the structure observed by BELLE, which is thus confirmed for the first time. In the psi(2S)->mu+mu- channel, we observe a broad structure at around 4.36 GeV/c2, while the poor statistics inhibits speculations about the events in the region nearby 4.66 GeV/c2; the psi(2S)->e+e- decay mode is excluded from the final discussion due to the high level of background found in the signal region and the limited statistics. We finally measure the energy-dependent cross-section for the exclusive process e+e-->pi+pi-psi(2S), from threshold to 6 GeV center of mass energy.