Speaker
Dr
Alessandro Feliciello
(INFN - Sezione di Torino)
Description
The SuperB factory, whose construction was recently approved by the Italian government, is an asymmetric heavy flavour factory where e+, e- beams will collide with a peak luminosity in excess of 10^36 cm-2 s-1 at the Y(4S) resonance c.m. energy. The Y(4S) then decays in BBbar meson pair with a B.R. > 96%, thus allowing, among other topics, a systematic study of B-meson decays.
While for B-mesons a large set of experimental results exists, few data are available for B-baryons. The reason for this lack of information is essentially experimental: B-baryons cannot be abundantly produced with a mechanism similar to the one exploited for B-mesons, neither at electron, proton or ion colliders, nor in fixed target experiments.
However, thanks to its high luminosity, SuperB would offer a unique opportunity to indirectly produce huge quantities of B-baryons via a "beauty exchange" mechanism. Indeed, if for instance a B- meson is let to impinge on a nuclear target, the following reaction can occur:
B- + N(bound) --> Lambda0_b + pi (1)
where N(bound) indicates a nucleon inside a nucleus. With a similar "beauty exchange" mechanism Sigma_b and Sigma_star_b are accessible as well through reactions similar to (1). Production of Xi0_b and X0_b baryons, via the B- + N(bound) --> Xi_b + K, is at
the limit of the available phase space for a free nucleon, while
Omega_b is out of reach.
Moreover the SuperB features allow to reach a production yield for the above reactions very close to 100%, provided that the low beta-gamma B- mesons will brought to rest in very thin targets before decaying.
The study of B-baryons decay modes can be performed with the same SuperB companion apparatus. The only additional stuff is just a thin target installed inside the beam pipe and as close as possible to the interaction point without, of course, interfering with the circulating beams. The really reduced transverse dimensions of the beams at the I.P. (few microns) allows for such an arrangement.
The target, made of any suitable solid material, can have a rectangular prism or a cylindrical (both sector and full) shape. By keeping in mind that for B c_tau is ~ 0.5 mm, the target inner surface could be placed at a distance of ~ 0.2 mm from
the beam axis and its thickness could be of the order of 0.3 mm. As far as the longitudinal dimension is concerned, a 10-15 mm total length should full the needs of the described measurement. Such a device should be cooled and should be remotely operated in order to be moved away from the beam axis by exploiting, for instance, the technique routinely used for the DAFNE collider scrapers.
Primary authors
Dr
Alessandro Feliciello
(INFN - Sezione di Torino)
Prof.
Tullio Bressani
(INFN - Sezione di Torino)
Dr
Vincenzo Lucherini
(INFN - Laboratori Nazionali di Frascati)
