Microcanonical pentaquark production ine+e−annihilations

Abstract

The existence of pentaquarks, namely baryonic states made up of four quarks and one antiquark, became questionable, because the candidates, i.e. the Θ + peak, are seen in certain reactions, i.e. p+p collisions, but not in others, i.e. e + e − annihilations. In this paper, we estimate the production of Θ + (1540) and Ξ −− (1860) in e + e − annihilations at different energies using Fermi statistical model as originally proposed in its microcanonical form. The results is compared with that from pp collisions at SPS and RHIC energies. We find that, if pentaquark states exist, the production is highly possible in e + e − annihilations. For example, at LEP energy √ s=91.2 GeV, both Θ + (1540) and Ξ −− (1860) yield more than in pp collisions at SPS and RHIC energy.

Generalised Tsallis statistics in electron–positron collisions

“…Moreover, the TS distribution, being a generalisation of the canonical BG, has a non-compact support, and thus cannot be valid close to x ≈ 1, where it should have a cut due to the finiteness of the collision energy. Therefore, in order to achieve good agreement with data for large x, microcanonical effects, due to the finite available phase space, have to be taken into account, as it has also been proposed in [24]- [29]. In this paper, a possible microcanonical generalisation of the TS distribution is proposed, which gives a good fit to data on fragmentation functions measured in e + e − collisions for 0.01 x 1.…”

Dynamics of the Weyl scale invariant non-BPS p = 3 brane

“…On the other hand, in particle physics it has been well known that the scale symmetry plays an important role [7][8][9][10][11], and it has been applied to a wide range of physics sectors, which include string theory, branes [12][13][14][15][16][17][18][19], as well as recent unparticle physics theory [20]. Among them, there has been much attention on the theory of Weyl scale invariant p-branes, and considerable effort has been dedicated to their canonical formulations as well as their geometrical background [13,14,17,18].…”