8,283 research outputs found
Charmonium-Nucleon Dissociation Cross Sections in the Quark Model
Charmonium dissociation cross sections due to flavor-exchange
charmonium-baryon scattering are computed in the constituent quark model. We
present results for inelastic and scattering amplitudes
and cross sections into 46 final channels, including final states composed of
various combinations of , , , and . These results
are relevant to experimental searches for the deconfined phase of quark matter,
and may be useful in identifying the contribution of initial
production to the open-charm final states observed at RHIC through the
characteristic flavor ratios of certain channels. These results are also of
interest to possible charmonium-nucleon bound states.Comment: 10 pages, 5 eps figures, revte
Charmonium - Pion Cross Section from QCD Sum Rules
The , and cross sections as a function of are evaluated in a QCD sum rule
calculation. We study the Borel sum rule for the four point function involving
pseudoscalar and vector meson currents, up to dimension four in the operator
product expansion. We find that our results are smaller than the cross sections obtained with models based on meson exchange,
but are close to those obtained with quark exchange models.Comment: revised version accepted for publication in Phys. Lett.
Dissociation cross sections of ground-state and excited charmonia with light mesons in the quark model
We present numerical results for the dissociation cross sections of
ground-state, orbitally- and radially-excited charmonia in collisions with
light mesons. Our results are derived using the nonrelativistic quark model, so
all parameters are determined by fits to the experimental meson spectrum.
Examples of dissociation into both exclusive and inclusive final states are
considered. The dissociation cross sections of several C=(+) charmonia may be
of considerable importance for the study of heavy ion collisions, since these
states are expected to be produced more copiously than the J/psi. The relative
importance of the productions of ground-state and orbitally-excited charmed
mesons in a pion-charmonium collision is demonstrated through the -dependent charmonium dissociation cross sections.Comment: 9 pages, 8 figure
The Hidden Charm Decay of and Final State Interaction Effects
We investigate whether the final state interaction (FSI) effect plays a
significant role in the large hidden charm decay width of X(3872) and Y(3940)
using a model. Our numerical result suggests (1) the FSI contribution to
is tiny; (2) from FSI is around several keV, far
less than Belle's experimental value 7 MeV.Comment: 5 pages, 3 figures, 1 table. Version to appear in Physics Letters
WMAP Polarization Results
The Wilkinson Microwave Anisotropy Probe (WMAP) has mapped the full sky in
Stokes I, Q, and U parameters at frequencies 23, 33, 41, 61, and 94 GHz. We
detect correlations between the temperature and polarization maps significant
at more than 10 standard deviations. The correlations are inconsistent with
instrument noise and are significantly larger than the upper limits established
for potential systematic errors. Correlations on small angualr scales are
consistent with the the signal expected from adiabatic initial conditions. We
detect excess power on large angular scales consistent with an early epoch of
reionization. A model-independent fit to reionization optical depth yields
results consistent with the best-fit LCDM model, with best fit value tau = 0.17
+/- 0.04 at 68% confidence, including systematic and foreground uncertainties.Comment: To be published in the proceedings of "The Cosmic Microwave
Background and its Polarization", New Astronomy Reviews, (eds. S. Hanany and
K.A. Olive
J/Psi mass shift in nuclear matter
The mass shift in cold nuclear matter is computed using an effective
Lagrangian approach. The mass shift is computed by evaluating and
meson loop contributions to the self-energy employing medium-modified
meson masses. The modification of the and masses in nuclear matter is
obtained using the quark-meson coupling model. The loop integrals are
regularized with dipole form factors and the sensitivity of the results to the
values of form-factor cutoff masses is investigated. The mass shift
arising from the modification of the and loops at normal nuclear
matter density is found to range from -16 MeV to -24 MeV under a wide variation
of values of the cutoff masses. Experimental perspectives for the formation of
a bound state of to a nucleus are investigated.Comment: 9 pages, latex file, 6 figures. Version published in Phys. Lett.
Empirical validation of statistical parametric mapping for group imaging of fast neural activity using electrical impedance tomography
Electrical impedance tomography (EIT) allows for the reconstruction of internal conductivity from surface measurements. A change in conductivity occurs as ion channels open during neural activity, making EIT a potential tool for functional brain imaging. EIT images can have >10 000 voxels, which means statistical analysis of such images presents a substantial multiple testing problem. One way to optimally correct for these issues and still maintain the flexibility of complicated experimental designs is to use random field theory. This parametric method estimates the distribution of peaks one would expect by chance in a smooth random field of a given size. Random field theory has been used in several other neuroimaging techniques but never validated for EIT images of fast neural activity, such validation can be achieved using non-parametric techniques. Both parametric and non-parametric techniques were used to analyze a set of 22 images collected from 8 rats. Significant group activations were detected using both techniques (corrected p < 0.05). Both parametric and non-parametric analyses yielded similar results, although the latter was less conservative. These results demonstrate the first statistical analysis of such an image set and indicate that such an analysis is an approach for EIT images of neural activity
Temperature-dependent cross sections for meson-meson nonresonant reactions in hadronic matter
We present a potential of which the short-distance part is given by one gluon
exchange plus perturbative one- and two-loop corrections and of which the
large-distance part exhibits a temperature-dependent constant value. The
Schrodinger equation with this temperature-dependent potential yields a
temperature dependence of the mesonic quark-antiquark relative-motion wave
function and of meson masses. The temperature dependence of the potential, the
wave function and the meson masses brings about temperature dependence of cross
sections for the nonresonant reactions pi pi -> rho rho for I=2, KK -> K* K*
for I=1, KK* -> K* K* for I=1, pi K -> rho K* for I=3/2, pi K* -> rho K* for
I=3/2, rho K -> rho K* for I=3/2 and pi K* -> rho K for I=3/2. As the
temperature increases, the rise or fall of peak cross sections is determined by
the increased radii of initial mesons, the loosened bound states of final
mesons, and the total-mass difference of the initial and final mesons. The
temperature-dependent cross sections and meson masses are parametrized.Comment: 42 pages with 10 figure
Two charged strangeonium-like structures observable in the process
Via the Initial Single Pion Emission (ISPE) mechanism, we study the
invariant mass spectrum distribution of . Our calculation indicates there exist a sharp peak
structure () close to the threshold and a broad
structure () near the threshold. In addition, we
also investigate the process due to
the ISPE mechanism, where a sharp peak around the threshold
appears in the invariant mass spectrum distribution. We
suggest to carry out the search for these charged strangeonium-like structures
in future experiment, especially Belle II, Super-B and BESIII.Comment: 7 pages, 5 figures. Accepted by Eur. Phys. J.
D mesons in matter and the in-medium properties of charmonium
We study the changes in the partial decay widths of excited charmonium states
into , when the D meson mass decreases in nuclear matter, taking the
internal structure of the hadrons into account. Calculations within the 3P0
model for and imply that naive estimates of the
in-medium widths based only on phase space are grossly exaggerated. Due to
nodes in the wave functions, these states may even become narrow at high
densities, if the D meson mass is decreased by about 200 MeV. For the
states, we generally expect stronger modifications of the widths. The relevance
of the widths for suppression in heavy ion collision is
discussed. These phenomena could be explored in experiments at the future
accelerator facility at GSI.Comment: 12 pages, 3 figures; allowed for two independent oscillator
parameters for the charmonium states and D mesons, results are not
significantly modified and conclusions remains unaltere
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