243 research outputs found
Exotic mesons with hidden charm and bottom near thresholds
We study heavy hadron spectroscopy near heavy meson thresholds. We employ
heavy pseudoscalar meson P and heavy vector meson P* as effective degrees of
freedom and consider meson exchange potentials between them. All possible
composite states which can be constructed from the P and P* mesons are studied
up to the total angular momentum J <= 2. We consider, as exotic states,
isosinglet states with exotic J^{PC} quantum numbers and isotriplet states. We
solve numerically the Schr\"odinger equation with channel-couplings for each
state. We found B(*)barB(*) molecule states for I^G(J^{PC}) = 1^+(1^{+-})
correspond to the masses of twin resonances Zb(10610) and Zb(10650). We predict
several possible B(*)barB(*) bound and/or resonant states in other channels. On
the other hand, there are no B(*)barB(*) bound and/or resonant states whose
quantum numbers are exotic.Comment: 10 pages, 1 figure, to appear in the proceedings of The 5th
International Workshop on Charm Physics (Charm 2012
Proposal for exotic-hadron search by fragmentation functions
It is proposed that fragmentation functions should be used to identify exotic
hadrons. As an example, fragmentation functions of the scalar meson f_0(980)
are investigated. It is pointed out that the second moments and functional
forms of the u- and s-quark fragmentation functions can distinguish the
tetraquark structure from . By the global analysis of f_0 (980)
production data in electron-positron annihilation, its fragmentation functions
and their uncertainties are determined. It is found that the current available
data are not sufficient to determine its internal structure, while precise data
in future should be able to identify exotic quark configurations.Comment: 4 pages, 4 figures, revtex, To be published in PR
Pervaporation of Acetic Acid-Water Mixture Using Silica Membrane Prepared by Sol-Gel Method
Silica membranes were developed and tested for the separation of acetic acid and water by pervaporation. Thin microporous silica membranes were prepared on a porous alumina tube by sol-gel method using tetraethyl orthosilicate (TEOS) as the silica precursor. Colloidal and polymeric silica sols were prepared by hydrolysis of TEOS. The pervaporation experiment results revealed that the silica membranes showed water selectivity towards acetic acid. The permeate flux and the separation factor were strongly influenced by the composition of the silica sols. For a feed concentration of 90 wt% acetic acid, the permeate flux varied between 0.016 to 0.91 kg/m2 h, with the separation factor varying between 3.7 and 324
Atomic-scale perspective on the origin of attractive step interactions on Si(113)
Recent experiments have shown that steps on Si(113) surfaces self-organize
into bunches due to a competition between long-range repulsive and short-range
attractive interactions. Using empirical and tight-binding interatomic
potentials, we investigate the physical origin of the short-range attraction,
and report the formation and interaction energies of steps. We find that the
short-range attraction between steps is due to the annihilation of force
monopoles at their edges as they combine to form bunches. Our results for the
strengths of the attractive interactions are consistent with the values
determined from experimental studies on kinetics of faceting.Comment: 4 pages, 3 figures, to appear in Phys. Rev B, Rapid Communication
Exotic mesons with double charm and bottom flavor
We study exotic mesons with double charm and bottom flavor, whose quark
configuration is \bar{Q}\bar{Q}qq. This quark configuration has no annihilation
process of quark and antiquark, and hence is a genuinely exotic states. We take
a hadronic picture by considering the molecular states composed of a pair of
heavy mesons, such as DD, DD* and D*D* for charm flavor, and BB, BB* and B*B*
for bottom flavor. The interactions between heavy mesons are derived from the
heavy quark effective theory. All molecular states are classified by I(J^P)
quantum numbers, and are systematically studied up to the total angular
momentum J \leq 2. By solving the coupled channel Schrodinger equations, due to
the strong tensor force of one pion exchanging, we find bound and/or resonant
states of various quantum numbers.Comment: 24 pages, 3 figure
First-principles study on field evaporation for silicon atom on Si(001) surface
The simulations of field-evaporation processes for silicon atoms on various
Si(001) surfaces are implemented using the first-principles calculations based
on the real-space finite-difference method. We find that the atoms which locate
on atomically flat Si(001) surfaces and at step edges are easily removed by
applying external electric field, and the threshold value of the external
electric field for evaporation of atoms on atomically flat Si(001) surfaces,
which is predicted between 3.0 and 3.5 V/\AA, is in agreement with the
experimental data of 3.8 V/\AA. In this situation, the local field around an
evaporating atom does not play a crucial role. This result is instead
interpreted in terms of the bond strength between an evaporating atom and
surface.Comment: 5 pages and 4 figure
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