351 research outputs found

### Low-lying Dirac eigenmodes and monopoles in 3+1D compact QED

We study the properties of low-lying Dirac modes in quenched compact QED at
$\beta =1.01$, employing $12^3\times N_t$ ($N_t =4,6,8,10,12$) lattices and the
overlap formalism for the fermion action. We pay attention to the spatial
distributions of low-lying Dirac modes below and above the ``phase transition
temperature'' $T_c$. Near-zero modes are found to have universal
anti-correlations with monopole currents, and are found to lose their temporal
structures above $T_c$ exhibiting stronger spatial localization properties. We
also study the nearest-neighbor level spacing distribution of Dirac eigenvalues
and find a Wigner-Poisson transition.Comment: 10 pages, 10 figures, 1 tabl

### Role of Large Gluonic Excitation Energy for Narrow Width of Penta-Quark Baryons in QCD String Theory

We study the narrow decay width of low-lying penta-quark baryons in the QCD
string theoryin terms of gluonic excitations. In the QCD string theory, the
penta-quark baryon decays via a gluonic-excited state of a baryon and meson
system, where a pair of Y-shaped junction and anti-junction is created. Since
lattice QCD shows that the lowest gluonic-excitation energy takes a large value
of about 1 GeV, the decay of the penta-quark baryon near the threshold is
considered as a quantum tunneling process via a highly-excited state (a
gluonic-excited state) in the QCD string theory. This mechanism strongly
suppresses the decay and leads to an extremely narrow decay width of the
penta-quark system.Comment: Talk given at International Conference on the Structure of Baryons
(Baryons 04) October 25 - 29, 2004, Ecole Polytechnique, Palaiseau, Franc

### Behind the success of the quark model

The ground-state three-quark (3Q) potential $V_{\rm 3Q}^{\rm g.s.}$ and the
excited-state 3Q potential $V_{\rm 3Q}^{\rm e.s.}$ are studied using SU(3)
lattice QCD at the quenched level. For more than 300 patterns of the 3Q
systems, the ground-state potential $V_{\rm 3Q}^{\rm g.s.}$ is investigated in
detail in lattice QCD with $12^3\times 24$ at $\beta=5.7$ and with $16^3\times
32$ at $\beta=5.8, 6.0$. As a result, the ground-state potential $V_{\rm
3Q}^{\rm g.s.}$ is found to be well described with Y-ansatz within the 1%-level
deviation. From the comparison with the Q-$\rm\bar Q$ potential, we find the
universality of the string tension as $\sigma_{\rm 3Q}\simeq\sigma_{\rm Q\bar
Q}$ and the one-gluon-exchange result as $A_{\rm 3Q}\simeq\frac12 A_{\rm Q\bar
Q}$. The excited-state potential $V_{\rm 3Q}^{\rm e.s.}$ is also studied in
lattice QCD with $16^3\times 32$ at $\beta=5.8$ for 24 patterns of the 3Q
systems.The energy gap between $V_{\rm 3Q}^{\rm g.s.}$ and $V_{\rm 3Q}^{\rm
e.s.}$, which physically means the gluonic excitation energy, is found to be
about 1GeV in the typical hadronic scale, which is relatively large compared
with the excitation energy of the quark origin. This large gluonic excitation
energy justifies the great success of the simple quark model.Comment: Talk given at 16th International Conference on Particles and Nuclei
(PANIC 02), Osaka, Japan, 30 Sep - 4 Oct 200

### Lattice QCD Study for the Interquark Force in Three-Quark and Multi-Quark Systems

We study the three-quark and multi-quark potentials in SU(3) lattice QCD.
From the accurate calculation for more than 300 different patterns of 3Q
systems, the static ground-state 3Q potential $V_{\rm 3Q}^{\rm g.s.}$ is found
to be well described by the Coulomb plus Y-type linear potential (Y-Ansatz)
within 1%-level deviation. As a clear evidence for Y-Ansatz, Y-type flux-tube
formation is actually observed on the lattice in maximally-Abelian projected
QCD. For about 100 patterns of 3Q systems, we perform the accurate calculation
for the 1st excited-state 3Q potential $V_{\rm 3Q}^{\rm e.s.}$ by diagonalizing
the QCD Hamiltonian in the presence of three quarks, and find a large
gluonic-excitation energy $\Delta E_{\rm 3Q} \equiv V_{\rm 3Q}^{\rm
e.s.}-V_{\rm 3Q}^{\rm g.s.}$ of about 1 GeV, which gives a physical reason of
the success of the quark model. $\Delta E_{\rm 3Q}$ is found to be reproduced
by the ``inverse Mercedes Ansatz'', which indicates a complicated bulk
excitation for the gluonic-excitation mode. We study also the tetra-quark and
the penta-quark potentials in lattice QCD, and find that they are well
described by the OGE Coulomb plus multi-Y type linear potential, which supports
the flux-tube picture even for the multi-quarks. Finally, the narrow decay
width of penta-quark baryons is discussed in terms of the QCD string theory.Comment: Invited talk at Int. Conference on Quark Confinement and the Hadron
Spectrum 6, Sardinia, Italy, 21-25 Sep 200

### On the center-vortex baryonic area law

We correct an unfortunate error in an earlier work of the author, and show
that in center-vortex QCD (gauge group SU(3)) the baryonic area law is the
so-called $Y$ law, described by a minimal area with three surfaces spanning the
three quark world lines and meeting at a central Steiner line joining the two
common meeting points of the world lines. (The earlier claim was that this area
law was a so-called $\Delta$ law, involving three extremal areas spanning the
three pairs of quark world lines.) We give a preliminary discussion of the
extension of these results to $SU(N), N>3$. These results are based on the
(correct) baryonic Stokes' theorem given in the earlier work claiming a
$\Delta$ law. The $Y$-form area law for SU(3) is in agreement with the most
recent lattice calculations.Comment: 5 pages, RevTeX4, 5 .eps figure

### Runaway Dynamics and Supersymmetry Breaking

Supersymmetric SU(N_C) gauge theories possess runaway-type superpotentials
for N_F < N_C, where N_F is the flavor number of massless quarks. We show that
the runaway behavior can be stabilized for N_F nearly equal to N_C by
introducing singlets with the aid of perturbative corrections to the Kahler
potential, generating (local) minima of supersymmetry breaking.Comment: 6 page

### Effective field theories for baryons with two- and three-heavy quarks

Baryons made of two or three heavy quarks can be described in the modern
language of non-relativistic effective field theories. These, besides allowing
a rigorous treatment of the systems, provide new insight in the nature of the
three-body interaction in QCD.Comment: 7 pages, 1 figure; published versio

### Low-lying spectrum of the Y-string three-quark potential using hyper-spherical coordinates

We calculate the energies of three-quark states with definite permutation
symmetry (i.e. of SU(6) multiplets) in the N=0,1,2 shells, confined by the
Y-string three-quark potential. The exact Y-string potential consists of one,
so-called three-string term, and three angle-dependent two-string terms. Due to
this technical complication we treat the problem at three increasingly accurate
levels of approximation: 1) the (approximate) three-string potential expanded
to first order in trigonometric functions of hyper-spherical angles; 2) the
(approximate) three-string potential to all orders in the power expansion in
hyper-spherical harmonics, but without taking into account the transition(s) to
two-string potentials; 3) the exact minimal-length string potential to all
orders in power expansion in hyper-spherical harmonics, and taking into account
the transition(s) to two-string potentials. We show the general trend of
improvement %convergence of these approximations: The exact non-perturbative
corrections to the total energy are of the order of one per cent, as compared
with approximation 2), yet the exact energy differences between the
$[20,1^{+}], [70,2^{+}], [56,2^{+}], [70,0^{+}]$-plets are shifted to 2:2:0.9,
from the Bowler and Tynemouth separation rule 2:2:1, which is obeyed by
approximation 2) at the one per cent level. The precise value of the energy
separation of the first radial excitation ("Roper") $[56^{\prime},0^{+}]$-plet
from the $[70,1^{-}]$-plet depends on the approximation, but does not become
negative, i.e. the "Roper" remains heavier than the odd-parity
$[70,1^{-}]$-plet in all of our approximations.Comment: 19 pages, 6 figure

### Gamma rays and positrons from a decaying hidden gauge boson

We study a scenario that a hidden gauge boson constitutes the dominant
component of dark matter and decays into the standard model particles through a
gauge kinetic mixing. Interestingly, gamma rays and positrons produced from the
decay of hidden gauge boson can explain both the EGRET excess of diffuse gamma
rays and the HEAT anomaly in the positron fraction. The spectra of the gamma
rays and the positrons have distinctive features; the absence of line emission
of the gamma ray and a sharp peak in the positron fraction. Such features may
be observed by the GLAST and PAMELA satellites.Comment: 16 pages, 4 figures, adding PAMELA data, the version accepted by PL

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