Inclusive double-quarkonium production at the Large Hadron Collider

Based on the nonrelativistic QCD (NRQCD) factorization formalism, we investigate inclusive productions of two spin-triplet S-wave quarkonia pp->2J/psi+X, 2Upsilon+X, and J/psi+Upsilon+X at the CERN Large Hadron Collider. The total production rates integrated over the rapidity (y) and transverse-momentum (p_T) ranges |y|<2.4 and p_T<50 GGeV are predicted to be sigma[pp->2J/psi+X] = 22 (35) nb, sigma[pp->2Upsilon+X] = 24 (49) pb, and sigma[pp->J/psi+Upsilon+X] = 7 (13) pb at the center-of-momentum energy sqrt{s} = 7 (14) TeV. In order to provide predictions that can be useful in both small- and large-p_T regions, we do not employ the fragmentation approximation and we include the spin-triplet S-wave color-singlet and color-octet channels for each quarkonium final state at leading order in the strong coupling. The p_T distributions of pp->2J/psi+X and 2Upsilon+X in the low-p_T region are dominated by the color-singlet contributions. At leading order in the strong coupling, the color-singlet channel is absent for pp->J/psi+Upsilon+X. Therefore, the process pp->J/psi+Upsilon+X may provide a useful probe to the color-octet mechanism of NRQCD.Comment: 26 pages, 7 figures, 3 tables, version published in JHE

Color-Octet Fragmentation and the psi' Surplus at the Tevatron

The production rate of prompt $\psi'$'s at large transverse momentum at the Tevatron is larger than theoretical expectations by about a factor of 30. As a solution to this puzzle, we suggest that the dominant $\psi'$ production mechanism is the fragmentation of a gluon into a $c \bar c$ pair in a pointlike color-octet S-wave state, which subsequently evolves nonperturbatively into a $\psi'$ plus light hadrons. The contribution to the fragmentation function from this process is enhanced by a short-distance factor of $1/\alpha_s^2$ relative to the conventional color-singlet contribution. This may compensate for the suppression by $v^4$, where $v$ is the relative momentum of the charm quark in the $\psi'$. If this is indeed the dominant production mechanism at large $p_T$, then the prompt $\psi'$'s that are observed at the Tevatron should almost always be associated with a jet of light hadrons.Comment: 9 pages, LaTe

Fragmentation Function in Non-Equilibrium QCD Using Closed-Time Path Integral Formalism

In this paper we implement Schwinger-Keldysh closed-time path integral formalism in non-equilibrium QCD to the definition of Collins-Soper fragmentation function. We consider a high p_T parton in QCD medium at initial time t_0 with arbitrary non-equilibrium (non-isotropic) distribution function f(\vec{p}) fragmenting to hadron. We formulate parton to hadron fragmentation function in non-equilibrium QCD in the light-cone quantization formalism. It may be possible to include final state interactions with the medium via modification of the Wilson lines in this definition of the non-equilibrium fragmentation function. This may be relevant to study hadron production from quark-gluon plasma at RHIC and LHC.Comment: 15 pages latex, Accepted for Publication in European Physical Journal

Color Octet Contribution to High p_T J/\Psi Production in pp Collisions at \sqrt s = 500 and 200 GeV at RHIC

We compute \frac{d\sigma}{dp_T} of the J/\psi production in pp collisions at RHIC at \sqrt s = 500 and 200 GeV by using both the color octet and singlet models in the framework of non-relativistic QCD. The J/\psi we compute here includes the direct J/\psi from the partonic fusion processes and the J/\psi coming from the radiative decays of \chi_J's both in the color octet and singlet channel. The high p_T J/\psi production cross section is computed within the PHENIX detector acceptance ranges: -0.35 < \eta < 0.35 and 1.2 < \|\eta| < 2.4, the central electron and forward muon arms. It is found that the color octet contribution to J/\psi production is dominant at RHIC energy in comparison to the color singlet contributions. We compare our results with the recent preliminary data obtained by PHENIX detector for the high p_T J/\psi measurements. While the color singlet model fails to explain the data completely the color octet model is in agreement with the single data point above 2 GeV transverse momentum. A measurement of J/\psi production at RHIC in the next run with better statistics will allow us to determine the validity of the color octet model of J/\psi production at RHIC energies. This is very important because it is necessary to know the exact mechanism for J/\psi production in pp collisions at RHIC if one is to make predictions of J/\psi suppression as a signature of quark-gluon plasma. These mechanisms also play an important role in determining the polarized spin structure function of the proton at RHIC.Comment: 16 pages latex, 6 figure

Testing Quarkonium Production with Photoproduced J/ψ+γJ/\psi + \gamma

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 the photon interacts through its structure function, while the color-octet mechanism allows for production of $J/\psi + \gamma$ via direct photon-gluon fusion. Resolved photon processes can be easily be distinguished from direct photon processes by examining the fraction of the incident photon energy carried away by the $J/\psi$ in the event. Therefore, this process provides a conclusive test of the color-octet mechanism. $J/\psi + \gamma$ production is particularly sensitive to the NRQCD matrix element which figures prominently in the fragmentation production of $J/\psi$ at large $p_{\perp}$ in hadron colliders. I also examine the predictions of the color evaporation model (CEM) of quarkonium production and find that this process can easily discriminate between the NRQCD factorization formalism and the CEM.Comment: uses Revtex, 12 pages, 4 EPS figures embedded using epsf.sty. Some references have been added. Version accepted for publication in Phys. Rev.

Inclusive J/psi and psi(2S) Production from B Decay in p p-bar Collisions

Using information on B-meson fragmentation functions from CERN LEP 1 and adopting the nonrelativistic QCD factorization formalism proposed by Bodwin, Braaten, and Lepage, we predict the transverse-momentum distribution of J/psi mesons originating from the inclusive decays of b hadrons produced in p p-bar collisions at the Fermilab Tevatron. We determine the relevant colour-octet charmonium matrix elements from fits to CDF data on prompt charmonium hadroproduction and to CLEO data on charmonium production from B-meson decay. Our predictions are found to agree well with recent CDF and D0 data.Comment: 27 pages (Latex), 9 figures (Postscript

Inclusive S−S-wave charmonium productions in BB decays

The inclusive $S-$wave charmonium production rates in $B$ decays are considered using the Bodwin-Braaten-Lepage (BBL) approach, including the relativistic corrections and the color-octet mechanism suggested as a possible solution to the $\psi^{'}$ puzzle at the Tevatron. We first consider relativistic and radiative corrections to $J/\psi \rightarrow e^{+} e^{-}$ and $J/\psi \rightarrow$ Light Hadrons (LH), in order to determine two nonperturbative parameters, $\langle J/\psi | O_{1} (^{3}S_{1}) | J/\psi \rangle$, $\langle J/\psi | P_{1} (^{3}S_{1}) | J/\psi \rangle$, in the factorization formulae for these decays. Using these two matrix elements and including the color-octet $c\bar{c}(^{3}S_{1})$ state contribution, we get a moderate increase in the decay rates for $B$ decays into $J/\psi ~({\rm or}~\psi^{'}) ~+ X$. Our results, $B(B \rightarrow J/\psi~({\rm or}~\psi^{'}) + X) = 0.58~(0.23) \%$ for $M_{b} = 5.3$ GeV, get closer to the recent CLEO data. As a byproduct, we prefer a larger decay rate for $\eta_{c} \rightarrow$ LH compared to the present data.Comment: 12 page

Bloch-Nordsieck violating electroweak corrections to inclusive TeV scale hard processes

We point out that, since the colliders initial states (e+ e-,p p, p pbar, ... ) carry a definite nonabelian flavor, electroweak radiative corrections to inclusive hard cross sections at the TeV scale are affected by peculiar Bloch-Nordsieck violating double logs. We recall the setup of soft cancellation theorems, and we analyze the magnitude of the noncancelling terms in the example of electron - positron annihilation into hadrons.Comment: Minor typos corrected, references added. Final version to appear on Phys. Rev. Let

J/\psi production through resolved photon processes at e+ e- colliders

We consider J/psi photoproduction in e+ e- as well as linear photon colliders. We find that the process is dominated by the resolved photon channel. Both the once-resolved and twice-resolved cross-sections are sensitive to (different combinations of) the colour octet matrix elements. Hence, this may be a good testing ground for colour octet contributions in NRQCD. On the other hand, the once-resolved J/psi production cross-section, particularly in a linear photon collider, is sensitive to the gluon content of the photon. Hence these cross-sections can be used to determine the parton distribution functions, especially the gluon distribution, in a photon, if the colour octet matrix elements are known.Comment: Added a figure on parametrisation dependence of photonic parton densities and some reference

Charm-sea Contribution to High-p_T \psi Production at the Fermilab Tevatron

The direct production of $J/\psi(\psi')$ at large transverse momentum, $p_T \gg M_{J/\psi}$, at the Fermilab Tevatron is revisited. It is found that the sea-quark initiated processes dominate in the high-$p_T$ region within the framework of color-singlet model, which is not widely realized. We think this finding is enlightening for further investigation on the charmonium production mechanism.Comment: Conclusions not changed, to appear in J. of Phys.