arXiv subjects

Jungil Lee

Publications and source records attributed to Jungil Lee.

At least 109 records · Page 6Linked to original sources

arXiv2000

Polarized J/psi from chi_{cJ} and psi' Decays at the Tevatron

We calculate the partonic cross sections for the hadroproduction of polarized chi_{cJ} mesons using the factorization formalism of nonrelativistic QCD. We also describe how the polarization is passed on to the J/psi mesons in the radiative feed-down chi_{cJ} -> J/psi + gamma and in the double-cascade decays of psi' mesons via chi_{cJ} intermediate states. These represent the missing ingredients needed to predict the polarization of prompt J/psi mesons at the Fermilab Tevatron.

hep-ph↗

arXiv2000

Current Issues In Quarkonium Production

As a stringent test of the nonrelativistic QCD factorization approach for inclusive heavy-quarkonium production in high-energy hadron collision, the polarized heavy-quarkonium production at the Tevatron is discussed. The polarization of prompt J/psi at the Tevatron is predicted within the nonrelativistic QCD factorization framework. The contribution from radiative decays of P-wave charmonium states decreases, but does not eliminate, the transverse polarization at large transverse momentum. The prediction agrees with measurements from the CDF collaboration at intermediate values of p_T, but disagrees at the large values of p_T measured. Recent preliminary data of heavy quarkonia from CDF and theoretical/experimental prospects related to the Run II heavy quarkonium physics are also discussed.

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arXiv2000

Prompt J/psi Polarization at the Tevatron

The polarization of prompt J/psi at the Tevatron is calculated within the nonrelativistic QCD (NRQCD) factorization framework. The contribution from radiative decays of P-wave charmonium states decreases, but does not eliminate, the transverse polarization at large transverse momentum. The prediction agrees with measurements from the CDF collaboration at intermediate values of p_T, but disagrees at the large values of p_T measured.

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arXiv2000

Next-to-leading Order Calculation of the Color-Octet 3S1 Gluon Fragmentation Function for Heavy Quarkonium

The short-distance coefficients for the color-octet 3S1 term in the fragmentation function for a gluon to split into heavy quarkonium states is calculated to order alpha_s^2. The gauge-invariant definition of the fragmentation function by Collins and Soper is employed. Ultraviolet divergences are removed using the MS-bar renormalization procedure. The longitudinal term in the fragmentation function agrees with a previous calculation by Beneke and Rothstein. The next-to-leading order correction to the transverse term disagrees with a previous calculation.

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arXiv2000

Phenomenology of the radion in Randall-Sundrum scenario at colliders

Phenomenology of a radion ($ϕ$) that stabilizes the modulus in the Randall-Sundrum scenario is considered. The radion couples to the trace of energy momentum tensor of the standard model (SM) with a strength suppressed only by a new scale ($Λ_ϕ$) of an order of the electroweak scale. In particular, the effective coupling of a radion to two gluons are enhanced due to the trace anomaly of QCD. Therefore, its production cross section at hadron colliders could be enhanced, and the dominant decay mode of a relatively light radion is $ϕ$ -> g g, unlike the SM Higgs boson case. We also present constraints on the mass $m_ϕ$ and the new scale $Λ_ϕ$ from the Higgs search limit at LEP and perturbative unitarity bound.

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arXiv1999

Color-octet mechanism in $γ+ p \to J/ψ+ X$

Photoproduction of $J/ψ$ is considered including the color-octet contributions from the various partial wave states, $^{2S+1}L_J$ = $^1S_0$, $^3S_1$ and $^3P_J$. The production cross section depends on three new nonperturbative parameters defined in NRQCD, called the color-octet matrix elements. Using the color-octet matrix elements determined by fitting the $J/ψ$ production at the Tevatron, we find that the color-octet($c\bar{c}) _{8}({^1S_0}~{\rm and~}~{^3P_J})$ contributions to the $J/ψ$ photoproductions at the fixed target experiments and HERA are too large compared to the data on $σ(γ+ p \to J/ψ+X)$ in the forward direction, the $z$ distribution of $J/ψ$. The $P_T^2$ distribution of $J/ψ$ and the total inelastic $J/ψ$ production rate as a function of $\sqrt{s_ {γp}}$ are predicted including color-octet contributions. We also briefly digress on the $B \to J/ψ+ X$ and observe the similar situation. This may be an indication that the color-octet matrix elements determined from the $J/ψ$ production at the Tevatron, especially $<0 | {\cal O}_{8}^ψ ({^1S_0}) | 0>$ and $<0 | {\cal O}_{8}^ψ ({^3P_J}) | 0>$, might have been overestimated by an order of magnitude.

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arXiv1999

Associated Production of Upsilon and Weak Gauge Bosons at the Tevatron

We calculate the rate of production of W+Upsilon and Z+Upsilon at the Tevatron. We find the cross sections at a center-of-mass energy of 1.8 TeV to be roughly 450 pb for W+Upsilon and 150 pb for Z+Upsilon. The dominant production mechanism involves the binding of a color-octet b-bbar pair into a P-wave bottomonium state which subsequently decays into Upsilon. The purely leptonic decay modes of Upsilon, W, and Z provide signatures with small backgrounds. In Run I of the Tevatron, the number of events in the purely leptonic decay channels before allowing for detector acceptances and efficiencies should be about 500 for W+Upsilon and about 60 for Z+Upsilon. We conclude that W+Upsilon events may be observable in the Run I data.

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arXiv1998

Polarized J/psi production at CLEO

Polarizations of the prompt $J/ψ$'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 $J/ψ$ polarization has strong dependence on the production mechanism. At CLEO energy, the most dominant $J/ψ$ production mechanism in the most phase space is the color-singlet mechanism, $e^+e^- \to J/ψ+gg$, for which $J/ψ$'s are highly longitudinally polarized. On the other hand, the dominant $J/ψ$ production mechanism at the upper end point of $J/ψ$ energy distribution is the color-octet process, $e^+e^- \to (c\bar{c})^{(8)} +g$, for which $J/ψ$'s are almost unpolarized. Thus, the measurement of the polarization of the end point $J/ψ$'s can give another test of color-octet mechanism, and constraint on the NRQCD matrix elements.

hep-ph↗

arXiv1998

Four-quark Operators Relevant to B Meson Lifetimes from QCD Sum Rules

At the order of 1/m_b^3, the B meson lifetimes are controlled by the hadronic matrix elements of some four-quark operators. The nonfactorizable magnitudes of these four-quark operator matrix elements are analyzed by QCD sum rules in the framework of heavy quark effective theory. The vacuum saturation for color-singlet four-quark operators is justified at hadronic scale, and the nonfactorizable effect is at a few percent level. However for color-octet four-quark operators, the vacuum saturation is violated sizably that the nonfactorizable effect cannot be neglected for the B meson lifetimes. The implication to the extraction of some of the parameters from B decays is discussed. The B meson lifetime ratio is predicted as τ(B^-)/τ(B^0)=1.09\pm 0.02. However, the experimental result of the lifetime ratio τ(Λ_b)/τ(B^0) still cannot be explained.

hep-ph↗

arXiv1997

Color-octet mechanism and J/psi polarization at LEP

Polarized heavy quarkonium productions in $Z^0$ decays are considered. We find that polarizations of the produced quarkonia are independent of that of the parent Z^0 provided that one considers the energy distribution or the total production rate. Produced J/psi's via the color-octet and the color- singlet mechanisms are expected to be 19% and 29% longitudinally polarized, respectively. The energy dependence of eta_{1,8}(x)=\frac{dGamma_{1,8}^L}{dx} /\frac{dGamma_{1,8}}{d x} is very sensitive to the production mechanism, and therefore the measurement of η(x)_exp will be an independent probe of the color-octet mechanism.

hep-ph↗

arXiv1997

Color-octet mechanism in the inclusive D-wave charmonium productions in B decays

The inclusive D-wave charmonium production rates in B decays are considered in the Bodwin-Braaten-Lepage (BBL) approach. We find that the color-octet subprocesses B->cc_(^3S_1^(8) or ^3P_J^(8))+s,d, followed by the transition cc_(^3S_1^(8) or ^3P_J^(8)) -> ^3D_J, strongly dominate over any other subprocess, due to the large Wilson coefficient for the ΔB = 1 effective lagrangian. Assuming that the numerical values of the matrix elements <0|O^{^3D_J}(^3S_1^(8))|0> and <0|O^{^3D_J}(^3P_J^(8))|0> are the same order of magnitudes with the <0| O^{ψ^'}(^3S_1^(8))|0>, we find that the ^{1,3}D_{2} can be observed at future B-factories.

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arXiv1996

Color-Octet Contributions in the Associate J/psi+gamma Hadroproduction

Color-octet contributions to the associate J/psi+gamma hadroproduction are studied in detail, and found to be negligible, compared to the ordinary color-singlet contribution. Within the color-singlet model the J/psi+gamma production in the leading order is possible only through gluon-gluon fusion process. Therefore, the associate J/psi+gamma hadroproduction remains to be useful as a clean channel to probe the gluon distribution inside proton, to study heavy quarkonia production mechanism, and to find proton's spin structure.

hep-ph↗

arXiv1996

Color-octet heavy quarkonium productions in Z0 decays at LEP

We consider the energy and the polar angle distributions of J/ψ's produced via the color-singlet and the color-octet (^3S_1^{(8)}) mechanisms in Z^0 \to J/ψ+X at LEP. Since both distributions of the J/ψproduced via color-octet mechanism are significantly different from those via color-singlet mechanism, these observables can be used as tests of color-octet production mechanism for heavy quarkonia. We also discuss Z^0 \rightarrow Υ+ X and W \to J/ψ( or Υ) + X in brief.

hep-ph↗

arXiv1995

Chiral perturbation theory vs. vector meson dominance in the decays $ϕ\to ργγ$ and $ϕ\to ωγγ$

It is pointed out that the radiative decays of a $ϕ$ meson, $\phirho$ and $\phiom$, receive dominant contributions from the pseudoscalar ($P = η, η^{'}$) exchanges. Using the vector meson dominance model, we find that $B (\phirho) \approx 1.3 \times 10^{-4}$ and $B (\phiom) \approx 1.5 \times 10^{-5}$, which are mainly from the $η^{'}$ pole. Thus, these decays are well within the reach of the $ϕ$ factory. Our estimates are a few orders of magnitude larger than the chiral loop contributions in the heavy vector meson chiral lagrangian, which is about ( a few ) $\times 10^{-9}$.

hep-ph↗

arXiv1995

Inclusive $S-$wave charmonium productions in $B$ 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 $ψ^{'}$ puzzle at the Tevatron. We first consider relativistic and radiative corrections to $J/ψ\rightarrow e^{+} e^{-}$ and $J/ψ\rightarrow$ Light Hadrons (LH), in order to determine two nonperturbative parameters, $\langle J/ψ| O_{1} (^{3}S_{1}) | J/ψ\rangle$, $\langle J/ψ| P_{1} (^{3}S_{1}) | J/ψ\rangle$, 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 $J/ψ~({\rm or}~ψ^{'}) ~+ X$. Our results, $B(B \rightarrow J/ψ~({\rm or}~ψ^{'}) + X) = 0.58~(0.23) \%$ for $M_{b} = 5.3$ GeV, get closer to the recent CLEO data. As a byproduct, we prefer a larger decay rate for $η_{c} \rightarrow$ LH compared to the present data.

hep-ph↗

arXiv1995

INVESTIGATION OF $WWγ$ COUPLINGS

We investigated how measurements of weak boson production at high energy $ep$ and $eγ$ collisions can provide important information on anomalous $WWγ$ couplings. We also considerd the sinlge muon production through the virtual $W$-decay at the Pohang Light Source (PLS) facility, and found this process is not adequate to be detected at the PLS until a large luminosity ($\sim 10^{33}$/sec/cm$^2$) Free Electron Laser is installed.

hep-ph↗

arXiv1994

The simplest form of the $κ$ and $κ^2$ order graviton self-interaction Lagrangian density in the weak field approximation

We derive the simplest form of the $κ(κ^2)$ order graviton self-interaction Lagrangian density $\lag{1}(\lag{2})$ in the weak field approximation. With the divergenceless condition, de Donder gauge and some combinatoric techniques, we derive the mathematically independent basis expressions for $\lag{1}(\lag{2})$ composed of 8(24) terms. By using the basis expressions $\lag{1}(\lag{2})$ is reduced to 6(18) terms.

hep-ph↗

arXiv1993

Probing $WWγ$ Couplings from $σ_{tot}(W)/σ_{tot}(Z)$ in High Energy ep Collisions

We investigate the sensitivity of total cross sections of $e+p \rightarrow W,Z$ to CP-conserving non-standard $WWγ$ couplings. We include all the important production mechanisms and study the dependence of the total $W$ cross sections on the anomalous $WWγ$ couplings, $κ$ and $λ$. We argue that the ratio of $W$ and $Z$ production cross sections is particularly well suited, being relatively insensitive to uncertainties in the theoretical and experimental parameters.

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