51 research outputs found
Properties of the Strange Axial Mesons in the Relativized Quark Model
We studied properties of the strange axial mesons in the relativized quark
model. We calculated the decay constant in the quark model and showed how
it can be used to extract the mixing angle
() from the weak decay . The ratio is the most sensitive
measurement and also the most reliable since the largest of the theoretical
uncertainties factor out. However the current bounds extracted from the
TPC/Two-Gamma collaboration measurements are rather weak: we typically obtain
at 68\% C.L. We also calculated the
strong OZI-allowed decays in the pseudoscalar emission model and the flux-tube
breaking model and extracted a mixing angle of . Our analysis also indicates that the heavy quark limit does not give a
good description of the strange mesons.Comment: Revised version to be published in Phys. Rev. D. Minor changes. Latex
file uses revtex version 3 and epsfig, 4 postcript figures are attached. The
full postcript version with embedded figures is available at
ftp://ftp.physics.carleton.ca/pub/theory/godfrey/ocipc9512.ps.
Excited B mesons from the lattice
We determine the energies of the excited states of a heavy-light meson
, with a static heavy quark and light quark with mass approximately
that of the strange quark from both quenched lattices and with dynamical
fermions. We are able to explore the energies of orbital excitations up to L=3,
the spin-orbit splitting up to L=2 and the first radial excitation. These mesons will be very narrow if their mass is less than 5775 MeV -- the
threshold. We investigate this in detail and present evidence that the
scalar meson (L=1) will be very narrow and that as many as 6
excited states will have energies close to the threshold and should also
be relatively narrow.Comment: 17 pages, 6 ps figure
QCD strings with spinning quarks
We construct a consistent action for a massive spinning quark on the end of a
QCD string that leads to pure Thomas precession of the quark's spin. The string
action is modified by the addition of Grassmann degrees of freedom to the
string such that the equations of motion for the quark spin follow from
boundary conditions, just as do those for the quark's position.Comment: REVTeX4, 10 pages, no figure
Indices for Superconformal Field Theories in 3,5 and 6 Dimensions
We present a trace formula for a Witten type Index for superconformal field
theories in d=3,5 and 6 dimensions, generalizing a similar recent construction
in d=4. We perform a detailed study of the decomposition of long
representations into sums of short representations at the unitarity bound to
demonstrate that our trace formula yields the most general index (i.e. quantity
that is guaranteed to be protected by superconformal symmetry alone) for the
corresponding superalgebras. Using the dual gravitational description, we
compute our index for the theory on the world volume of N M2 and M5 branes in
the large N limit. We also compute our index for recently constructed Chern
Simons theories in three dimensions in the large N limit, and find that, in
certain cases, this index undergoes a large N phase transition as a function of
chemical potentials.Comment: a small typo corrected, 46 page
Hagedorn divergences and tachyon potential
We consider the critical behavior for a string theory near the Hagedorn
temperature. We use the factorization of the worldsheet to isolate the Hagedorn
divergences at all genera. We show that the Hagedorn divergences can be
resummed by introducing double scaling limits, which smooth the divergences.
The double scaling limits also allow one to extract the effective potential for
the thermal scalar. For a string theory in an asymptotic anti-de Sitter (AdS)
spacetime, the AdS/CFT correspondence implies that the critical Hagedorn
behavior and the relation with the effective potential should also arise from
the boundary Yang-Mills theory. We show that this is indeed the case. In
particular we find that the free energy of a Yang-Mills theory contains
``vortex'' contributions at finite temperature. Yang-Mills Feynman diagrams
with vortices can be identified with contributions from boundaries of moduli
space on the string theory side.Comment: 36 pages, 13 figures, uses harvma
Generating AdS String Solutions
We use a Pohlmeyer type reduction to generate classical string solutions in
AdS spacetime. In this framework we describe a correspondence between spikes in
AdS_3 and soliton profiles of the sinh-Gordon equation. The null cusp string
solution and its closed spinning string counterpart are related to the
sinh-Gordon vacuum. We construct classical string solutions corresponding to
sinh-Gordon solitons, antisolitons and breathers by the inverse scattering
technique. The breather solutions can also be reproduced by the sigma model
dressing method.Comment: 21 pages, 3 figures, references adde
Induced Gravity on Intersecting Branes
We establish Einstein-Hilbert gravity couplings in the effective action for
Intersecting Brane Worlds. The four-dimensional induced Planck mass is
determined by calculating graviton scattering amplitudes at one-loop in the
string perturbation expansion. We derive a general formula linking the induced
Planck mass for N=1 supersymmetric backgrounds directly to the string partition
function. We carry out the computation explicitly for simple examples,
obtaining analytic expressions.Comment: references added, minor changes to discussion of path integral
normalization on page
Nonperturbative QCD Vacuum Effects in Nonlocal Quark Dynamics
A straightforward calculation reveals the essentially nonlocal character of
the leading heavy interaction arising from nonperturbative gluon
field correlations in the model of a fluctuating QCD vacuum. In light of this
quarkonium spin splitting ratio predictions which have supported the scalar
confinement ansatz are reconsidered as a specific example of possible
consequences for spectroscopy.Comment: Latex, 9 page
Phases of Thermal N=2 Quiver Gauge Theories
We consider large N U(N)^M thermal N=2 quiver gauge theories on S^1 x S^3. We
obtain a phase diagram of the theory with R-symmetry chemical potentials,
separating a low-temperature/high-chemical potential region from a
high-temperature/low-chemical potential region. In close analogy with the N=4
SYM case, the free energy is of order O(1) in the low-temperature region and of
order O(N^2 M) in the high-temperature phase. We conclude that the N=2 theory
undergoes a first order Hagedorn phase transition at the curve in the phase
diagram separating these two regions. We observe that in the region of zero
temperature and critical chemical potential the Hilbert space of gauge
invariant operators truncates to smaller subsectors. We compute a l-loop
effective potential with non-zero VEV's for the scalar fields in a sector where
the VEV's are homogeneous and mutually commuting. At low temperatures the
eigenvalues of these VEV's are distributed uniformly over an S^5/Z_M which we
interpret as the emergence of the S^5/Z_M factor of the holographically dual
geometry AdS_5 x S^5/Z_M. Above the Hagedorn transition the eigenvalue
distribution of the Polyakov loop opens a gap, resulting in the collapse of the
joint eigenvalue distribution from S^5/Z_M x S^1 into S^6/Z_M.Comment: 40 pages text + 15 pages appendix, 3 figures, latex; v2: one minor
typo corrected and typeset in JHEP format; v3: computation of saddle points
in Sec. 4.2 improved, discussion of stability of saddle points added in Sec.
6.2, minor changes, ref. adde
Weak decays of the B_c meson to charmonium and D mesons in the relativistic quark model
Semileptonic and nonleptonic decays of the B_c meson to charmonium and D
mesons are studied in the framework of the relativistic quark model. The decay
form factors are explicitly expressed through the overlap integrals of the
meson wave functions in the whole accessible kinematical range. The
relativistic meson wave functions are used for the calculation of the decay
rates. The obtained results are compared with the predictions of other
approaches.Comment: 27 pages, 17 figures, 1 figure and 1 reference added, version to
appear in Phys. Rev.
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