Coalescence model for Θ_c pentaquark formation

Abstract

We present a model for the formation of the charmed pentaquark Θ c in hard scattering processes such as deep inelastic scattering, e + e − annihilation, and high-energy pp collisions. The model assumes that the cross section for Θ c formation is proportional to the rate of production of pD * − (orpD * + ) pairs in close proximity both in momentum space and in coordinate space. The constant of proportionality is determined from the Θ c cross section in deep inelastic scattering as reported by the H1 experiment. The HERWIG Monte Carlo is used to generate simulated DIS events and also to model the space-time structure of the final state. Requiring the proton and the D * be within a 100 MeV mass window and separated by a spacelike distance of no more than 2 fm, we find that a large "coalescence enhancement factor" F co ∼ 10 is required to account for the H1 signal. The same approach is then applied in order to estimate the number and characteristics of Θ c events produced at LEP and the Tevatron.

On the history of dibaryons and their final observation

“…This suggests that the attraction between quark clusters is largest, if each of the two clusters contain a heavy quark (or anti-quark). This has been worked out recently also for the dibaryon scenario by Karliner et al [425,426,427,428] predicting, e.g., a doubly heavy Σ + b Σ − b dibaryon. Pion assisted dibaryon candidates with charm have been discussed recently by Gal et al [9,429] within the chiral constituent quark model [430].…”

X(3872),Xb, and theKarliner1, Rosner2 2015Phys. Rev. DSelf Cite311260View full textAdd to dashboardCite

“…An independent estimate of M(X b ), to be mentioned in more detail below, was based on the expected binding energy of a B andB * , yielding 10585 MeV/c 2 [23]. This is 23 MeV above Tornqvist's value, but still fairly close to the expected mass of χ b1 (3P ).…”

“…The estimate of Ref. [23] predicts its mass to be about 10585 MeV/c 2 , about 23 MeV/c 2 above that of Tornqvist [11,12].…”

“…In Ref. [23] the X b binding energy was estimated with the help of the existing data: Z b (10610), Z c (3900) in the I = 1 channel and X(3872) in the I = 0 channel. Since the kinetic energy is inversely proportional to mass, the heavier the heavy quark, the deeper the binding.…”

Baryons with two heavy quarks: Masses, production, decays, and detection

“…On the † marek@proton.tau.ac.il ‡ rosner@hep.uchicago.edu optimistic side, one should notice that a large number of B c mesons has been seen both by the Tevatron experiments [11,12] and by LHCb [13][14][15][16][17][18][19]. From this one can infer [20] a substantial cross section for simultaneous production of two pairs of heavy quarks and their subsequent coalescence into a doubly-heavy hadron.…”