1,357 research outputs found
Aspects Of Heavy Quark Theory
Recent achievements in the heavy quark theory are critically reviewed. The
emphasis is put on those aspects which either did not attract enough attention
or cause heated debates in the current literature. Among other topics we
discuss (i) basic parameters of the heavy quark theory; (ii) a class of exact
QCD inequalities; (iii) new heavy quark sum rules; (iv) virial theorem; (v)
applications (|V_cb| from the total semileptonic width and from the B->D*
transition at zero recoil). In some instances new derivations of the previously
known results are given, or new aspects addressed. In particular, we dwell on
the exact QCD inequalities. Furthermore, a toy model is considered that may
shed light on the controversy regarding the value of the kinetic energy of
heavy quarks obtained by different methods.Comment: 67 pages, 6 Figures; plain LaTeX. Changes: Some equations in Sect.4
related to spin-nonsinglet sum rules are corrected. The references are
updated
Calculation of 1/m^3 terms in the total semileptonic width of D mesons.
We calculate the 1/ corrections in the inclusive semileptonic widths
of mesons. We show that these are due to the novel penguin type operators
that appear at this level in the transition operator. Taking into account the
nonperturbative corrections leads to the predicted value of the semileptonic
width significantly lower than the experimental value. The worsen the
situation or at the very least, within uncertainty, give small contribution. We
indicate possible ways out. It seems most probable that violations of duality
are noticeable in the energy range characteristic to the inclusive decays in
the charm family. Theoretically these deviations are related to divergence of
the high-order terms in the power expansion in the inverse heavy quark mass.Comment: Final version accepted for publication in Physical Review D (19
pages, 5 figures appended as two PS files at the end of the LATEX file
Determining V(ub) from B+ --> D*+(s) e+ e- and B+ --> D*+ e+ e-
It was recently pointed out that the decays B^+ --> D^{*+}_s gamma and B^+
--> D^{*+} gamma can be used for an extraction of |V_{ub}|. The theory of these
decays is poorly understood. It was shown that in a world of almost degenerate
b and c-quarks the decay would be computable. The severe difficulties that are
encountered in the realistic calculation stem primarily from the very hard
photon produced in the two body decay. We point out that in the decays B^+ -->
D^{*+}_s e^+e^- and B^+ --> D^{*+} e^+e^- the photon vertex is soft when the
charmed meson is nearly at rest (in the B^+ rest frame). This allows us to
compute with some confidence the decay rate in a restricted but interesting
kinematic regime. Given enough data the extraction of V_{ub} with reasonably
small uncertainties could proceed through an analysis of these exclusive decays
much as is done in the determination of V_{cb}.Comment: 9 pages, latex (revtex), replaced with published versio
Multivalued Fields on the Complex Plane and Conformal Field Theories
In this paper a class of conformal field theories with nonabelian and
discrete group of symmetry is investigated. These theories are realized in
terms of free scalar fields starting from the simple systems and scalar
fields on algebraic curves. The Knizhnik-Zamolodchikov equations for the
conformal blocks can be explicitly solved. Besides of the fact that one obtains
in this way an entire class of theories in which the operators obey a
nonstandard statistics, these systems are interesting in exploring the
connection between statistics and curved space-times, at least in the two
dimensional case.Comment: (revised version), 30 pages + one figure (not included), (requires
harvmac.tex), LMU-TPW 92-1
Hierarchical wave function, Fock cyclic condition and spin-statistics relation in the spin-singlet fractional quantum Hall effect
We construct the hierarchical wave function of the spin-singlet fractional
quantum Hall effect, which turns out to satisfy Fock cyclic condition. The
spin-statistics relation of the quasi-particles in the spin-singlet fractional
quantum Hall effect is also discussed. Then we use particle-hole conjugation to
check the wave function.Comment: 23 pages, PHYZZ
Updated Analysis of a_1 and a_2 in Hadronic Two-body Decays of B Mesons
Using the recent experimental data of , , and various model calculations on form
factors, we re-analyze the effective coefficients a_1 and a_2 and their ratio.
QCD and electroweak penguin corrections to a_1 from and
a_2 from are estimated. In addition to the
model-dependent determination, the effective coefficient a_1 is also extracted
in a model-independent way as the decay modes are related by
factorization to the measured semileptonic distribution of at . Moreover, this enables us to extract model-independent
heavy-to-heavy form factors, for example,
and
. The determination of the magnitude of
a_2 from depends on the form factors ,
and at . By requiring that a_2 be
process insensitive (i.e., the value of a_2 extracted from and
states should be similar), as implied by the factorization
hypothesis, we find that form factors are severely constrained;
they respect the relation . Form factors and at
inferred from the measurements of the longitudinal
polarization fraction and the P-wave component in are
obtained. A stringent upper limit on a_2 is derived from the current bound on
\ov B^0\to D^0\pi^0 and it is sensitive to final-state interactions.Comment: 33 pages, 2 figures. Typos in Tables I and IX are corrected. To
appear in Phys. Rev.
Hadronic Spectral Moments in Semileptonic B Decays With a Lepton Energy Cut
We compute the first two moments of the final hadronic invariant mass in
inclusive semileptonic B decay, in the presence of a cut on the charged lepton
energy. These moments may be measured directly by experiments at the
Upsilon(4S) using the neutrino reconstruction technique, which requires such a
cut. Measurement of these moments will place constraints on the nonperturbative
parameters \bar\Lambda and \lambda_1, which are relevant for extracting the
quark masses m_b and m_c, as well as the CKM angle V_cb. We include terms of
order \alpha_s^2\beta_0 and 1/m_b^3 in the operator product expansion, and use
the latter to estimate the theoretical uncertainty in the extraction of
\bar\Lambda and \lambda_1.Comment: 13 pages, 5 figures, REVTe
The Baryonic Tully-Fisher Relation
We explore the Tully-Fisher relation over five decades in stellar mass in
galaxies with circular velocities ranging over 30 < Vc < 300 km/s. We find a
clear break in the optical Tully-Fisher relation: field galaxies with Vc < 90
km/s fall below the relation defined by brighter galaxies. These faint galaxies
are however very gas rich; adding in the gas mass and plotting baryonic disk
mass Md = M* + Mg in place of luminosity restores a single linear relation. The
Tully-Fisher relation thus appears fundamentally to be a relation between
rotation velocity and total baryonic mass of the form Md = A Vc^4.Comment: 10 pages including 1 color figure. Accepted for publication in ApJ
Letter
Stability of Chiral Luttinger Liquids and Abelian Quantum Hall States.
A criterion is given for topological stability of Abelian quantum Hall
states, and of Luttinger liquids at the boundaries between such states; this
suggests a selection rule on states in the quantum Hall hierarchy theory. The
linear response of Luttinger liquids to electromagnetic fields is described:
the Hall conductance is quantized, irrespective of whether edge modes propagate
in different directions.Comment: 12 pages, LaTeX (RevTeX 3.0
Annihilation, Rescattering, and CP Asymmetries in B Meson Decays
A number of meson decays may proceed only through participation of the
spectator quark, whether through amplitudes proportional to or via
rescattering from other less-suppressed amplitudes. An expected hierarchy of
amplitudes in the absence of rescattering will be violated by rescattering
corrections. Such violations could point the way toward channels in which
final-state interactions could be important. Cases in which final state phases
can lead to large CP asymmetries are pointed out.Comment: 9 page
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