(1995 - 1999) SELEX EXPERIMENT

Participation in the experiment SELEX (SEgmented LargE-X baryon spectrometer) at the Fermi National Laboratory (FERMILAB) in Chicago (USA) as a member of the Trieste I.N.F.N. group.
The study of charm baryon physics is the main goal of the experiment, in the mainframe of the Fermilab fixed target program of understanding the charm hadron production and decays.
SELEX run in a mixed 600 GeV/c hyperon/meson beam, using the S⁻ beam to produce the charm particles, hoping to enhance the number of strange-charmed states.
The full spectrometer, excellent for particle identification information coming from downstream, includes a two stage magnetic spectrometer and deploys a number of existing chambers and neutral particle detectors as well as the new silicon strip and pixel devices and the Ring Imaging Cerenkov Counter. This is especially important for identifying charm baryon decays in the large X_F region.
The initial charmed baryon paper was concerning the first observation of a Cabibbo suppressed decay mode X_c⁺ ® pK⁻ π⁺ with a total of 260 events in 3 modes.
In 2002 SELEX data anaylis showed the presence of three new massive particles: one of them is the X_cc⁺, which has never been observed before.
These results are reported in:
M. Mattson et al.: First Observation of the Doubly Charmed Baryon X_cc⁺, Phys. Rev. Letters 89 (2002) 112001.