55 research outputs found
Hadronic production calculated in the NRQCD factorization formalism
The NRQCD factorization formalism of Bodwin, Braaten, and Lepage prescribes
how to write quarkonium production rates as a sum of products of short-distance
coefficients times non-perturbative long-distance NRQCD matrix elements. We
present, in the true spirit of the factorization formalism, a detailed
calculation of the inclusive cross section for hadronic production. We
find that in addition to the well known {\it color-singlet} production
mechanisms, there are equally important mechanisms in which the pair
that forms the is initially produced in a {\it color-octet} state, in
either a , , or angular-momentum
configuration. In our presentation, we emphasize the ``matching'' procedure,
which %is the method that allows us to determine the short-distance
coefficients appearing in the factorization formula. We also point out how one
may systematically include relativistic corrections in these calculations.Comment: 25 pages, 3 postscript figures, use Revtex and epsfig.sty We fixed
some typos, added some text regarding a reference, and changed some
equations. The file will be available at http://phenom.physics.wisc.edu
Inclusive wave charmonium productions in decays
The inclusive wave charmonium production rates in 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 puzzle at the Tevatron. We first consider
relativistic and radiative corrections to and
Light Hadrons (LH), in order to determine two
nonperturbative parameters, , , in the
factorization formulae for these decays. Using these two matrix elements and
including the color-octet state contribution, we get a
moderate increase in the decay rates for decays into . Our results, for GeV, get closer to the recent CLEO data.
As a byproduct, we prefer a larger decay rate for LH
compared to the present data.Comment: 12 page
Power counting and effective field theory for charmonium
We hypothesize that the correct power counting for charmonia is in the
parameter Lambda_QCD/m_c, but is not based purely on dimensional analysis (as
is HQET). This power counting leads to predictions which differ from those
resulting from the usual velocity power counting rules of NRQCD. In particular,
we show that while Lambda_QCD/m_c power counting preserves the empirically
verified predictions of spin symmetry in decays, it also leads to new
predictions which include: A hierarchy between spin singlet and triplet octet
matrix elements in the J/psi system. A quenching of the net polarization in
production at large transverse momentum. No end point enhancement in radiative
decays. We discuss explicit tests which can differentiate between the
traditional and new theories of NRQCD.Comment: 18 pages, 1 figure Replaced plot of the psi polarization parameter
alpha as a function of transverse momentum. Alpha is now closer to zero for
large transverse moment
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
Photoproduction in Scattering
We investigate the + c + photoproduction in
collision at the LEP II energy. The physical motivations for this study are: 1)
such next-to-leading order(NLO) process was not considered in previous
investigations of photoproduction in interaction, and it is
worthwhile to do so in order to make sound predictions for experimental
comparison; 2) from recent Belle experiment results, the process with same
final states at the factory has a theoretically yet unexplainable large
fraction; hence it is interesting to see what may happen at other colliders; 3)
the existing LEP data are marginal in observing such process, and at the planed
Linear Colliders(LCs) this process can be measured with high accuracy; 4) it is
necessary to take this process into consideration in the aim of elucidating the
quarkonium production mechanism, especially in testing the universality of
NRQCD nonperturbative matrix elements via photoproduction in
electron-position collisions.Comment: 15 pages, 3 figure
Inelastic production in polarized photon-hadron collisions
Presented here is a calculation of inelastic production in polarized
photon-hadron collisions under the framework of NRQCD factorization formalism.
We consider the photoproduction of \jpsi in the energy range relevant to
HERA. The Weizs\"acker-Williams approximation is adopted in the evaluation of
the cross sections for collisions. We found that this process can give
another independent test for the color-octet mechanism, and the different
features for the two color-octet processes may provide further informations on
the mechanism for inelastic \jpsi photoproduction. And the discrepancy on the
production asymmetry between various sets of polarized gluon distribution
functions is also found to be distinctive.Comment: 14pages, 6 PS figure
Determination of color-octet matrix elements from e^+e- process at low energies
We present an analysis of the preliminary experimental data of direct j/psi
production in e^e- process at low energies. We find that the color-octet
contributions are crucially important to the cross section at this energy
region, and their inclusion produces a good description of the data. By fitting
to the data, we extract the individual values of two color-octet matrix
elements: \approx 1.1\times 10^{-2} GeV^3, <{\cal
O}_8^{\psi}(^3P_0)> m_c^2\approx 7.4\times 10^{-3}GeV^3. We discuss the allowed
range of the two matrix elements constrained by the theoretical uncertainties.
We find that is poorly determined because it is
sensitive to the variation of the choice of m_c, \alpha_s and <{\cal
O}_1^{\psi}(^3S_1)>. However m_c^2 is quite stable
(about (6-9)\times 10^{-3}GeV^3) when the parameters vary in reasonable ranges.
The uncertainties due to large experimental errors are also discussed.Comment: 13 page, RevTex, 2 figures in postscript. To appear in Phys. Rev.
Color-Octet Production in the Decay
The direct production rate of in the decay is shown to be
dominated by the process followed by via
the color-octet mechanism proposed recently to explain the anomalous prompt
charmonium production at the Tevatron. We show that this plausibly dominant
process has a branching ratio compatible with the experimental data. Further
experimental study in this channel is important to test the significance of the
color-octet component of pair inside the system.Comment: 20 pages, Standard LaTeX, 2 figures; a couple of new processes added,
but conclusion unchange
Production of singlet P-wave and states
No spin-singlet quarkonium state has yet been observed. In this
paper we discuss the production of the singlet P-wave and
states and . We consider two possibilities. In the first the
states are produced via the electromagnetic cascades \ups(3S) \to
\eta_b(2S) + \gamma \to h_b + \gamma \gamma \to \eta_b +\gamma\gamma\gamma
and . A more promising process consists of single pion
transition to the state followed by the radiative transition to the
state: \ups(3S)\to h_b + \pi^0 \to \eta_b + \pi^0 +\gamma and . For a million \ups(3S) or
's produced we expect these processes to produce several hundred events.Comment: 13 pages, LaTeX, 1 figure, to be published Phys. Rev. D. Some
equation numbers and one table number correcte
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