2,143 research outputs found
Testing factorization in B -> D(*)X decays
In QCD the amplitude for B0 -> D(*)+pi- factorizes in the large Nc limit or
in the large energy limit Q >> Lambda_QCD where Q = {m_b, m_c, m_b-m_c}. Data
also suggests factorization in exclusive processes B-> D* pi+ pi- pi- pi0 and
B-> D* omega pi-, however by themselves neither large Nc nor large Q can
account for this. Noting that the condition for large energy release in B0-> D+
pi- is enforced by the SV limit, m_b, m_c >> m_b-m_c >> Lambda, we propose that
the combined large Nc and SV limits justify factorization in B -> D(*) X. This
combined limit is tested with the inclusive decay spectrum measured by CLEO. We
also give exact large Nc relations among isospin amplitudes for B -> D(*)X and
B -> D(*) D-bar(*)X, which can be used to test factorization through exclusive
or inclusive measurements. Predictions for the modes B-> D(*) pi pi, B-> D(*)K
K-bar and B-> D(*) D-bar(*) K are discussed using available data.Comment: 15 pages, 3 included .eps figures, minor change
Assessment of Deformations of Earth‘s Surface at Mine Construction on Sub-Soils
AbstractThe paper provides technical and technological solutions aimed at construction and support erection for up to 50 m deep underground facilities of a relatively moderate extend up to 100 m in unstable mantle rocks, which are carried out by small splitting according to the combined pattern without any specific methods. Thus, reduction of cost and construction period is achievable, which is of a significant importance for resource saving.The authors describe results of studies focused on development of methods to provide support of underground facilities with mass concrete under conditions of semi-stable rocks and application of the combined pattern. Reduction of the splitting value to 0.3 m results in decrease of plastic deformation area by 1.7 times and maximum displacements of adjacent strata contour with 10–15 kPa adhesion factor by 1.5 times.When an optimum volume of modifying agents are added to the composition, concrete strength is improved by 1.7 times after 12 hour curing and by a factor of 7 after 24 hour curing in comparison with that without any additives. The finite element theory was applied at simulating the stress-strain behavior of the non-supported bottom-hole area of rock solid mass and hardening concrete of the monolithic lining erected after wall advance. In such a manner, distribution of maximum strains in the support has been revealed with due regard to concrete hardening.The authors provide a regression model for calculation of an optimal value for splitting and selection of structure and support parameters. Areas of maximum displacements in the solid mass and their influence on the Earth surface deformation have been determined
Heavy meson semileptonic differential decay rate in two dimensions in the large Nc
We study QCD in 1+1 dimensions in the large limit using light-front
Hamiltonian perturbation theory in the expansion. We use this formalism
to exactly compute hadronic transition matrix elements for arbitrary currents
at leading order in . We compute the semileptonic differential decay
rate of a heavy meson, , and its moments, , using the hadronic
matrix elements obtained previously. We put some emphasis in trying to
understand parity invariance. We also study with special care the kinematic
region where the operator product expansion () or
non-local effective field theories () can
be applied. We then compare with the results obtained using an effective field
theory approach based on perturbative factorization, with the focus to better
understand quark-hadron duality. At the end of the day, using effective field
theories, we have been able to obtain expressions for the moments with relative
accuracy of in the kinematic region where the
operator product expansion can be applied, and with relative accuracy of
in the kinematic region where non-local effective field
theories can be applied. These expressions agree, within this precision, with
those obtained from the hadronic result using the layer-function approximation
plus Euler-McLaurin expansion. Very good numerical agreement for the moments is
obtained between the exact result and the result using effective field
theories.Comment: 52 pages, 30 figures, references added, small modifications, some
discussion of the four dimensional case changed, journal versio
Beam Energy Evolution of HBT Systematics at the AGS
We present preliminary results of the first pion interferometry (HBT)
excitation function at intermediate AGS energies. The beam energy evolution of
the correlations' dependence on mT, centrality, and emission angle with respect
to the reaction plane are discussed. Comparisons with predictions of the RQMD
cascade model are made.Comment: to appear in proceedings of Quark Matter '9
Note on Tests of the Factorization Hypothesis and the Determination of Meson Decay Constants
We discuss various tests of the factorization hypothesis making use of the
close relationship between semi-leptonic and factorized nonleptonic decay
amplitudes. It is pointed out that factorization leads to truely
model-independent predictions for the ratio of nonleptonic to semi-leptonic
decay rates, if in the nonleptonic decay a spin one meson of arbitrary mass or
a pion take the place of the lepton pair. Where the decay constants of those
mesons are known, these predictions represent ideal tests of the factorization
hypothesis. In other cases they may be used to extract the decay constants.
Currently available data on the decays are shown to be in excellent agreement with
the factorization results. A weighted average of the four independent values
for the QCD coefficient extracted from the data gives
suggesting that it may be equal to the Wilson coefficient evaluated
at the scale .Comment: (9 pages, ReVTeX, no figures), HD-THEP-92-3
Phase diagram for morphological transitions of wetting films on chemically structured substrates
Using an interface displacement model we calculate the shapes of thin
liquidlike films adsorbed on flat substrates containing a chemical stripe. We
determine the entire phase diagram of morphological phase transitions in these
films as function of temperature, undersaturation, and stripe widthComment: 15 pages, RevTeX, 7 Figure
Study of Bc --> J/psi pi, etac pi decays with perturbative QCD approach
The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD
approach. It is found that form factors and branching ratios are sensitive to
the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of
the charmonium wave functions for Coulomb potential and harmonic oscillator
potential, respectively, f_J/psi and f_etac are the decay constants of the
J/psi and etac mesons, respectively. The large branching ratios and the clear
signals of the final states make the Bc --> J/psi pi, etac pi decays to be the
prospective channels for measurements at the hadron collidersComment: 21 pages, revtex
Reducing theoretical uncertainties in mb and lambda1
We calculate general moments of the lepton energy spectrum in inclusive
semileptonic B -> X_c l \nu decay. Moments which allow the determination of
mb^{1S} and lambda1 with theoretical uncertainties Delta(mb^{1S}) ~ 0.04 GeV
and Delta(lambda1) ~ 0.05 GeV^2 are presented. The short distance 1S mass is
used to extract a mass parameter free of renormalon ambiguities. Moments which
are insensitive to mb and lambda1 and therefore test the size of the 1/mb^3
matrix elements and the validity of the OPE are also presented. Finally, we
give an expression for the total branching ratio with a lower cut on the lepton
energy, which allows one to eliminate a source of model dependence in current
determinations of |Vcb| from B -> X_c l \nu decay.Comment: 8 pages, one figur
Discrete Holomorphicity at Two-Dimensional Critical Points
After a brief review of the historical role of analyticity in the study of
critical phenomena, an account is given of recent discoveries of discretely
holomorphic observables in critical two-dimensional lattice models. These are
objects whose correlation functions satisfy a discrete version of the
Cauchy-Riemann relations. Their existence appears to have a deep relation with
the integrability of the model, and they are presumably the lattice versions of
the truly holomorphic observables appearing in the conformal field theory (CFT)
describing the continuum limit. This hypothesis sheds light on the connection
between CFT and integrability, and, if verified, can also be used to prove that
the scaling limit of certain discrete curves in these models is described by
Schramm-Loewner evolution (SLE).Comment: Invited talk at the 100th Statistical Mechanics Meeting, Rutgers,
December 200
Flavourful hadronic physics
We review theoretical approaches to form factors that arise in heavy-meson
decays and are hadronic expressions of non-perturbative QCD. After motivating
their origin in QCD factorisation, we retrace their evolution from quark-model
calculations to non-perturbative QCD techniques with an emphasis on
formulations of truncated heavy-light amplitudes based upon Dyson-Schwinger
equations. We compare model predictions exemplarily for the B\to\pi transition
form factor and discuss new results for the g_{D*D\pi} coupling in the hadronic
D* decay.Comment: Based on a talk given at Light Cone 2009: Relativistic Hadronic And
Particle Physics, 8-13 July 2009, Sao Jose dos Campos, Sao Paulo, Brazi
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