Related papers: New contributions to heavy-quarkonium production
By questioning the applicability of the static approximation of the Colour-Singlet Model, we have seen that the production amplitude receives contributions from two different cuts. The first one in its static limit gives the colour-singlet…
We have shown that if one relaxes the constraint that the quarks in a heavy quarkonium are at rest and on-shell, new contributions to the discontinuity of the production amplitude appear. These can be seen as a s-cut in the amplitude and…
This thesis can be divided into several parts. The first one consists in a detailed historical review of quarkonium physics, centered on the different production models successively introduced. Then comes a review of the currently available…
We study contributions from color-octet quarkonium formation mechanisms to $p_\perp$-integrated $\psi'$ production cross sections in pion-nucleon reactions. The observed polarization of the $\psi'$ is not reproduced by the lowest-order…
The precise mechanism for production of quarkonium at hadron colliders is still an open question. Within non-relativistic quantum chromodynamics, quarkonium production cross sections can be factorized into short-distance, perturbative…
We discuss the various mechanisms potentially at work in hadroproduction of heavy quarkonia in the light of computations of higher-order QCD corrections both in the Colour-Singlet (CS) and Colour-Octet (CO) channels and the inclusion of the…
The conventional color-singlet model was challenged by the recent data on quarkonium production. Discrepancies in production rates were observed at the Tevatron, at LEP, and in fixed-target experiments. The newly advocated color-octet…
We study contributions from color-octet quarkonium formation mechanisms to $J/\psi$ hadroproduction at low $p_\perp$. We include transitions of color-octet $c\bar{c}$ states into ``direct'' $J/\psi$ and into $\chi_{1,2}$ which decay…
The direct production rate of $J/\psi$ via the color-octet mechanism is calculated at the $Z$ resonance. The color-octet production process $Z\to J/\psi q \bar q$ is shown to have a substantial branching ratio as well as a distinctive…
We investigate the SM Higgs decays into heavy quarkonia J/\psi and \Upsilon in both color-singlet and color-octet mechanisms. It is found that in J/\psi production the contribution through color-octet processes overwhelm that in…
We consider the energy and the polar angle distributions of J/\psi's produced via the color-singlet and the color-octet (^3S_1^{(8)}) mechanisms in Z^0 \to J/\psi +X at LEP. Since both distributions of the J/\psi produced via color-octet…
The importance of including colour octet contributions in describing decay and production of quarkonium states is briefly discussed for two cases : the radiative decays of the $\Upsilon$ and the production of $J/\psi$ in the inclusive $B$…
We calculate the direct production rate of $J/\psi$ in top quark decays. The color-octet $J/\psi$ production via $t\rightarrow W^+ b J/\psi$ is shown to have a large branching ratio of order $1.5\times 10^{-4}$, which is over an order of…
The necessicity of the color-octet mechanism in describing heavy quarkonium production is a longstanding puzzle. Compared to the yields of heavy quarkonium, its polarizations should be a sensitive observable to pin down the color-octet…
Theoretical analyses of the results on quarkonium production at large transverse momentum ($p_T$) in $p\bar p$ collisions, at the Tevatron have revealed two novel features of the physics of quarkonium production : 1) the contribution of…
Bound-state corrections to $J/\psi$ production from almost real photons are calculated in the colour-singlet model. A systematic, gauge-invariant, theory of hard quarkonium processes is used upto $O(v^2)$, where $v$ is the relative velocity…
A new mechanism for heavy quarkonium production in high-energy collisions called the "s-channel cut" was proposed in 2005 by Lansberg, Cudell, and Kalinovsky. We identify this mechanism physically as the production of a heavy quark and…
The question how well nonrelativistic QCD (NRQCD) factorization can describe quarkonium production has been subject to debate since its invention. We review our recent reanalysis of a classic next-to-leading order color octet (CO) long…
We propose an improved version of the color evaporation model to describe heavy quarkonium production. In contrast to the traditional color evaporation model, we impose the constraint that the invariant mass of the intermediate heavy…
I describe the NRQCD factorization approach to the inclusive production of heavy quarkonium, contrasting it with the color-singlet and color evaporation models. These approaches differ dramatically in their assumptions about the roles…