Related papers: Color-octet mechanism and J/psi polarization at LE…
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 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 calculated the polarization of \psi' due to gg \to Q\bar{Q}[^3P_J^(8)]g \to \psi^\lambda color-octet quarkonia production. We find that at low transverse momenta the \psi' is unpolarized due to the contributions proportional to the L=S=0…
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…
Polarizations of the prompt $J/\psi$'s produced in the $e^+e^-$ annihilation at CLEO energy ($\sqrt{s} = 10.58$ GeV) are considered in the framework of NRQCD factorization formalism. We find that the $J/\psi$ polarization has strong…
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…
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…
At present the color-octet mechanism is still an important and debatable part in the non-relativistic QCD(NRQCD). We find in this work that the polarized double charmonium production at the LHC may pose a stringent test on the charmonium…
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…
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…
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…
To test the color-octet model of heavy quarkonium productions, we propose $\psi '$-productions at small-$p_T$ regions in polarized $pp$ collisions for the forthcoming RHIC polarized experiments, whose experimental test at $\sqrt s=50$ GeV…
We report that, unlike most inclusive quarkonium-production processes, the production rate for p p -> J/psi+Upsilon+X dominantly depends on two not well-known long-distance nonrelativistic QCD matrix elements, <O_8^{J/psi}(^3S_1)> and…
The direct production rates of $D$-wave charmonia in the decays of $Z^0$ is evaluated. The color-octet production processes $Z^0\rightarrow ^3D_J(c\bar c) q\bar q$ are shown to have distinctively large branching ratios, the same order of…
We review the current status of heavy quarkonium production phenomenology based on nonrelativistic effective field theories, focusing on spin-triplet $S$-wave states such as $J/\psi$, $\psi(2S)$, and $\Upsilon$. We present some…
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…
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…
We explore polarized heavy quarkonium production using the color evaporation model at leading order. We present the polarized to total yield ratio as a function of center of mass energy and rapidity in $p+p$ collisions. At energies far…
I compute the leading color-octet contributions to the process $\gamma + p \to J/\psi + \gamma (+ X)$ within the non-relativistic QCD (NRQCD) factorization formalism. In the color-singlet model, $J/\psi + \gamma$ can only be produced when…
We propose the measurement of $\chi_{cJ}$ polarizations at high energy hadron colliders to study heavy quarkonium production mechanism. We find that the color-singlet model in the $k_t$ factorization approach predicts very different…