3,795 research outputs found
The use of the chatter mode in self-adaptive systems
Chatter mode is used advantageously if the ideal model dynamics is described by a switching function, the chatter mode is reached quickly and then sustained, the chatter frequency is reduced, and any zero in the plant transfer function is cancelled
Studying Diquark Structure of Heavy Baryons in Relativistic Heavy Ion Collisions
We propose the enhancement of yield in heavy ion collisions at
RHIC and LHC as a novel signal for the existence of diquarks in the strongly
coupled quark-gluon plasma produced in these collisions as well as in the
. Assuming that stable bound diquarks can exist in the quark-gluon
plasma, we argue that the yield of would be increased by two-body
collisions between diquarks and quarks, in addition to normal
three-body collisions among , and quarks. A quantitative study of
this effect based on the coalescence model shows that including the
contribution of diquarks to production indeed leads to a
substantial enhancement of the ratio in heavy ion collisions.Comment: Prepared for Chiral Symmetry in Hadron and Nuclear Physics
(Chiral07), Nov. 13-16, 2007, Osaka, Japa
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
Effects of quark matter and color superconductivity in compact stars
The equation of state for quark matter is derived for a nonlocal, chiral
quark model within the mean field approximation. We investigate the effects of
a variation of the form factors of the interaction on the phase diagram of
quark matter under the condition of beta-equilibrium and charge neutrality.
Special emphasis is on the occurrence of a diquark condensate which signals a
phase transition to color superconductivity and its effects on the equation of
state. We calculate the quark star configurations by solving the Tolman-
Oppenheimer- Volkoff equations and obtain for the transition from a hot, normal
quark matter core of a protoneutron star to a cool diquark condensed one a
release of binding energy of the order of Delta M c^2 ~ 10^{53} erg. We study
the consequences of antineutrino trapping in hot quark matter for quark star
configurations with possible diquark condensation and discuss the claim that
this energy could serve as an engine for explosive phenomena. A "phase diagram"
for rotating compact stars (angular velocity-baryon mass plane) is suggested as
a heuristic tool for obtaining constraints on the equation of state of QCD at
high densities. It has a critical line dividing hadronic from quark core stars
which is correlated with a local maximum of the moment of inertia and can thus
be subject to experimental verification by observation of the rotational
behavior of accreting compact stars.Comment: 14 pages, 12 figures, Talk given at 2nd International Workshop on
Hadron Physics: Effective Theories of Low-Energy QCD, Coimbra, Portugal,
25-29 Sep 200
Exotic baryons from a heavy meson and a nucleon
We evaluate a hadronic molecule formed by a heavy meson and a nucleon
respecting heavy quark symmetry. The tensor force of pion exchange potential
plays a dominate role to produce an strong attraction in this system. Solving
coupled channel Schr\"odinger equations for PN and P* N, we find many bound and
resonant states with isospin I=0 while there are few resonances in I=1 state.
The rich structures with I=0 indicate that the spectrum of heavy baryons near
the threshold is influenced by the contributions from such hadron composite
structures.Comment: To appear in the proceedings of The 5th International Workshop on
Charm Physics (Charm 2012
Chiral symmetry breaking and vacuum polarization in a bag
We study the effects of a finite quark mass in the hedgehog configuration in
the two phase chiral bag model. We discuss the chiral properties, such as the
fractional baryon number and the chiral Casimir energy, by using the Debye
expansion for the analytical calculation and the Strutinsky's smearing method
for the numerical computation. It is shown that the fractional baryon number
carried by massive quarks in the vacuum is canceled by that in the meson
sector. A finite term of the chiral Casimir energy is obtained with subtraction
of the logarithmic divergence term
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