Hee Sok Chung

Improved determination of color-singlet nonrelativistic QCD matrix elements for S -wave charmonium

We present a new computation of S-wave color-singlet nonrelativistic QCD matrix elements for the J/{psi} and the {eta}{sub c}. We compute the matrix elements of leading order in the heavy-quark velocity v and the matrix elements of relative order v{sup 2}. Our computation is based on the electromagnetic decay rates of the J/{psi} and the {eta}{sub c} and on a potential model that employs the Cornell potential. We include relativistic corrections to the electromagnetic decay rates, resumming a class of corrections to all orders in v, and find that they significantly increase the values of the matrix elements of leading order in v. This increase could have important implications for theoretical predictions for a number of quarkonium decay and production processes. The values that we find for the matrix elements of relative order v{sup 2} are somewhat smaller than the values that one obtains from estimates that are based on the velocity-scaling rules of nonrelativistic QCD.

Fragmentation Contributions to J/ Production at the Tevatron and the LHC

We compute leading-power fragmentation corrections to J/ψ production at the Tevatron and the LHC. We find that, when these corrections are combined with perturbative corrections through next-to-leading order in the strong coupling constant α(s), we obtain a good fit to high-p(T) cross section data from the CDF and CMS Collaborations. The fitted long-distance matrix elements lead to predictions of near-zero J/ψ polarization in the helicity frame at large p(T).

Exclusive heavy quarkonium + γ production from e+e-annihilation into a virtual photon

We compute the cross section for exclusive production of a photon associated with a heavy quarkonium H of charge-conjugation parity C=+1 from e{sup +}e{sup -} annihilation into a virtual photon at the center-of-momentum energy {radical}(s)=10.58 GeV. The nonrelativistic QCD factorization formulas for the differential and total cross sections are obtained at leading order in the strong coupling and in the relative velocity of the heavy quark in the quarkonium rest frame. The predicted cross sections for the S-wave spin-singlet cases are about 80 fb and 50 fb for H={eta}{sub c} and {eta}{sub c}(2S), respectively. Among P-wave spin-triplet charmonia, {chi}{sub c1} has a particularly large cross section of about 14 fb. The cross sections for bottomonium states {eta}{sub b} and {chi}{sub bJ} are about 3 fb. A rough estimate of the background reveals that the signal significances for charmonium processes are sufficiently large enough to be detected with ease with the integrated luminosities available at the present B factories.

Order-αs corrections to the quarkonium electromagnetic current at all orders in the heavy-quark velocity

We compute in order {alpha}{sub s} the nonrelativistic QCD (NRQCD) short-distance coefficients that match quark-antiquark operators of all orders in the heavy-quark velocity v to the electromagnetic current. We employ a new method to compute the one-loop NRQCD contribution to the matching condition. The new method uses full-QCD expressions as a starting point to obtain the NRQCD contribution, thus greatly streamlining the calculation. Our results show that, under a mild constraint on the NRQCD operator matrix elements, the NRQCD velocity expansion for the quark-antiquark-operator contributions to the electromagnetic current converges. The velocity expansion converges rapidly for approximate J/{psi} operator matrix elements.

Cornell Potential Parameters for S-wave Heavy Quarkonia

We compute derived quantities for various values of the model parameter of the Cornell potential model for the S-wave heavy quarkonia with radial quantum numbers n=1, 2, and 3. Our results can be used to determine leading and relative-order-v^2 nonrelativistic quantum chromodynamics matrix elements for S-wave charmonia and bottomonia such as psi(2S), eta_c(2S), and Upsilon(nS) for n=1, 2, and 3. These matrix elements will be essential ingredients for resumming relativistic corrections to processes involving those S-wave heavy quarkonium states.

NRQCD matrix elements for S-wave bottomonia and Γ[ηb(nS)→γγ] with relativistic corrections

We determine the leading-order nonrelativistic quantum chromodynamics (NRQCD) matrix element 〈O1〉ϒ and the ratio 〈q2〉ϒ , for ϒ=ϒ(nS) with n=1 , 2, and 3 by comparing the measured values for Γ[ϒ→e+e−] with the NRQCD factorization formula in which relativistic corrections are resummed to all orders in the heavy-quark velocity v . The values for 〈q2〉ϒ , which is the ratio of order- v2 matrix element to 〈O1〉ϒ , are new. They can be used for NRQCD predictions involving ϒ(nS) and ηb(nS) with relativistic corrections. As an application, we predict the two-photon decay rates for the spin-singlet states: Γ[ηb(1S)→γγ]=0.512−0.094+0.096 keV , Γ[ηb(2S)→γγ]=0.235−0.043+0.043 keV , and Γ[ηb(3S)→γγ]=0.170−0.031+0.031 keV .

Polarization of prompt J/ψ in proton-proton collisions at RHIC

Within the framework of the nonrelativistic QCD (NRQCD) factorization approach, we compute the polarization of prompt J/{psi} produced at the Brookhavens Relativistic Heavy-Ion Collider from proton-proton collisions at the center-of-momentum energy {radical}(s)=200 GeV. The perturbative contributions are computed at leading order in the strong coupling constant. The prediction reveals that the color-singlet contribution severely underestimates the PHENIX preliminary data for the differential cross section integrated over the rapidity range |y|<0.35 and its contribution is strongly transversely polarized, which disagrees with the PHENIX preliminary data. After including the color-octet contributions, we find that the NRQCD predictions for both the cross section and polarization over the transverse-momentum range 1.5 GeV<p{sub T}<5 GeV (1.5 GeV<p{sub T}<2 GeV) integrated over the rapidity range |y|<0.35 (1.2<|y|<2.2) agree with the data within errors.

Double logarithms in e + e !J/ +c

Double logarithms of

Polarization of prompt J/ψ in pp→J/ψ+X at √s=200GeV

Q^2/m_c^2

Invariant-mass distribution of cc̄ in Υ(1S)→cc̄+X

that appear in the cross section for