1,424 research outputs found
Search for charmonium and bottomonium states in at B factories
We study the production of charmonium states in at B factories with (n=1,2,3), (m=1,2), and
. In the S and P wave case, contributions of tree-QED with one-loop
QCD corrections are calculated within the framework of nonrelativistic
QCD(NRQCD) and in the D-wave case only the tree-QED contribution are
considered. We find that in most cases the QCD corrections are negative and
moderate, in contrast to the case of double charmonium production , where QCD corrections are positive and large in most cases. We
also find that the production cross sections of some of these states in
are larger than that in by an
order of magnitude even after the negative QCD corrections are included. So we
argue that search for the X(3872), X(3940), Y(3940), and X(4160) in at B factories may be helpful to clarify the nature of these
states. For completeness, the production of bottomonium states in
annihilation is also discussed.Comment: 13pages, 4 figure
Higher Charmonia and X,Y,Z states with Screened Potential
We incorporate the color-screening effect due to light quark pair creation
into the heavy quark-antiquark potential, and investigate the effects of
screened potential on the spectrum of higher charmonium. We calculate the
masses, electromagnetic decays, and E1 transitions of charmonium states in the
screened potential model, and propose possible assignments for the newly
discovered charmonium or charmonium-like states. We find the masses
of higher charmonia with screened potential are considerably lower than those
with unscreened potential. The mass agrees well with that of
the Z(3930), and the mass of is compatible with rather
than . In particular, the discovered four states in the ISR
process, i.e., may be assigned as the
states respectively. The X(3940) and
X(4160) found in the double charmonium production in annihilation may
be assigned as the and states. Based on the
calculated E1 transition widths for and
and other results, we argue that the X(3872)
may be a dominated charmonium state with some admixture of the
component. Possible problems encountered in these assignments
and comparisons with other interpretations for these states are
discussed in detail. We emphasize that more theoretical and experimental
investigations are urgently needed to clarify these assignments and other
interpretations.Comment: Total width of X(3872) reestimated, references added; 12 pages, 1
figure; published version in PR
The Color-Octet intrinsic charm in and decays
Color-octet mechanism for the decay B\to \eta^\prime X is proposed to explain
the large branching ratio of Br(B\to \eta^\prime X)\sim 1\times 10^{-3}
recently announced by CLEO. We argue that the inclusive \eta^\prime production
in B decays may dominantly come from the Cabbibo favored b\to (\bar c c)_8s
process where \bar c c pair is in a color-octet configuration, and followed by
the nonperturbative transition (\bar c c)_8\to \eta^\prime X. The color-octet
intrinsic charm component in the higher Fock states of \eta^\prime is crucial
and is induced by the strong coupling of \eta^\prime to gluons via QCD axial
anomaly.Comment: 9 pages, RevTex, 1 PS figur
Cancellation of Infrared Divergences in Hadronic Annihilation Decays of Heavy Quarkonia
In the framework of a newly developed factorization formalism which is based
on NRQCD, explicit cancellations are shown for the infrared divergences that
appeared in the previously calculated hadronic annihilation decay rates of
P-wave and D-wave heavy quarkonia. We extend them to a more general case that
to leading order in and next-to-leading order in , the infrared
divergences in the annihilation amplitudes of color-singlet
pair can be removed by including the contributions of
color-octet operators ,
, ... in NRQCD. We also give the decay widths of
at leading order in .Comment: 8 pages, LaTex(3 figures included), to be publishe
High- production as signals for Double Parton scattering at hadron colliders
We present an analysis of the \psi\psi production from double parton (DP)
sacttering and single parton (SP) scattering in the large p_T region via
color-octet gluon fragmentation. We find that at the Tevatron the DP \psi\psi
production is at the edge of the detectability at present, and at the LHC the
DP cross section will dominate over the SP cross section in the lower p_T(min)
region (i.e., p_T(min)<7GeV). We also conclude that the color-octet mechanism
is of crucial importance to the double j/psi production at high energy hadron
colliders.Comment: Revtex, 12 pages, 3 Postscript figure
A Crucial Test for Color-Octet Production Mechanism in Z^0 Decays
The direct production rates of -wave charmonia in the decays of is
evaluated. The color-octet production processes are shown to have distinctively large branching ratios, the same order
of magnitude as that of prodution, as compared with other -wave
charmonium production mechanisms. This may suggest a crucial channel to test
the color-octet mechanism as well as to observe the -wave charmonium states
in decays. In addition, a signal for the charmonium as strong as
or with large transverse momentum at the Tevatron should
also be observed.Comment: 14 pages in LaTex (3 figures in PS-file
Pseuduscalar Heavy Quarkonium Decays With Both Relativistic and QCD Radiative Corrections
We estimate the decay rates of ,
, and ,
, by taking into account both relativistic and
QCD radiative corrections. The decay amplitudes are derived in the
Bethe-Salpeter formalism. The Bethe-Salpeter equation with a QCD-inspired
interquark potential are used to calculate the wave functions and decay widths
for these states. We find that the relativistic correction to the
ratio is negative and tends to compensate the positive contribution from
the QCD radiative correction. Our estimate gives and ,
which are smaller than their nonrelativistic values. The hadronic widths
and are then indicated accordingly to the first order
QCD radiative correction, if . The decay widths for
states are also estimated. We show that when making the assmption
that the quarks are on their mass shells our expressions for the decay widths
will become identical with that in the NRQCD theory to the next to leading
order of and .Comment: 14 pages LaTex (2 figures included
Gluonic and leptonic decays of heavy quarkonia and the determination of and
QCD running coupling constant and are
determined from heavy quarkonia and decays. The
decay rates of and for and
are estimated by taking into account both relativistic and QCD
radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter
formalism, and the decay rates are estimated by using the meson wavefunctions
which are obtained with a QCD-inspired inter-quark potential. For the
decay we find the relativistic correction to be very large
and to severely suppress the decay rate. Using the experimental values of ratio
R_g\equiv \frac {\Gamma (V\longrightarrow 3g)}% {\Gamma (V\longrightarrow
e^{+}e^{-})}\approx 10,~32 for respectively, and the
calculated widths , we find and
. These values for the QCD running coupling
constant are substantially enhanced, as compared with the ones obtained without
relativistic corrections, and are consistent with the QCD scale parameter
. We also find that these
results are mainly due to kinematic corrections and not sensitive to the
dynamical models.Comment: 15 pages in Late
Gluon fragmentation to ^3D_J quarkonia
We present a calculation of the leading order QCD fragmentation functions for
gluons to split into spin-triplet D-wave quarkonia. We apply them to evaluate
the gluon fragmentation contributions to inclusive ^3D_J quarkonium production
at large transverse momentum processes like the Tevatron and find that the
D-wave quarkonia, especially the charmonium 2^{--} state, could be observed
through color-octet mechanism with present luminosity. Since there are
distinctively large gaps between the contributions of two different (i.e,
color-singlet and color-octet) quarkonium production mechanisms, our results
may stand as a unique test to NRQCD color-octet quarkonium production
mechanism.Comment: 15 pages in LaTex (2 figures in PS-file
D-wave heavy quarkonium production in fixed target experiments
We calculate the -wave heavy quarkonium production at fixed target
experiments under the NRQCD factorization formalism. We find that the color
octet contributions are two orders of magnitude larger than color-singlet
contributions if color-octet matrix elements are taken according to the NRQCD
velocity scaling rules. Within the theoretical uncertainties, the prediction
for the production rate of -wave charmonium state agrees with the
preliminary result of E705 and other experiments. Searching for the
-wave state is further suggested.Comment: 13pages, 4 PS figures, final vertion to appear in PR
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