4,090 research outputs found
What is the Physics behind the 3He-4He Anomaly ?
We show that coalescence of nucleons emitted prior to thermalization in
highly excited nuclei can explain the anomaly of kinetic energies of helium
clusters. A new coalescence algorithm has been included into the statistical
approach to nuclear reactions formerly used to describe intermediate mass
fragment production.Comment: 5 pages, 4 figures, accepted at Eur. Phys.
A note on spectator effects and quark-hadron duality in inclusive beauty decays
In this paper, we evaluate the expectation values of four-quark operators for
the inclusive beauty decays from the differences in the inclusive total decay
rates, assuming that the heavy quark expansion converges at . The
obtained expectation values yeilds the ratio close to
the experimental onee. We further point out that the quark-hadron duality
violation would be rather small allowing predictions of inclusive quantities.Comment: 5 pages, typos corrected, version to be published in PL
Phenomenology of B -> pi pi, pi K Decays at O(alpha^2 beta_0) in QCD Factorization
We study O(alpha^2 beta_0) perturbative corrections to matrix elements
entering two-body exclusive decays of the form B -> pi pi, pi K in the QCD
factorization formalism, including chirally enhanced power corrections, and
discuss the effect of these corrections on direct CP asymmetries, which receive
their first contribution at O(alpha). We find that the O(alpha^2 beta_0)
corrections are often as large as the O(alpha) corrections. We find large
uncertainties due to renormalization scale dependence as well as poor knowledge
of the non-perturbative parameters. We assess the effect of the perturbative
corrections on the direct CP violation parameters of B -> pi^+ pi^-.Comment: 27 pages, 5 figures. Updated input parameters and added citations;
expanded discussio
Improved Currents for Heavy Quarks
We discuss lattice artifacts for matrix elements of hadrons containing one or
more heavy quark. In particular, we analyze interrelations between lattice
artifacts and the expansion. The implications for calculations of
heavy-light decay constants and of semi-leptonic form factors are discussed.Comment: 3 pages, no figures, uuencoded PostScript, proceedings of Lattice
'94. LaTeX at ftp://fnth06.fnal.gov/pub/Fermilab-Pub/95.00
Flavor Physics in the Randall-Sundrum Model: I. Theoretical Setup and Electroweak Precision Tests
A complete discussion of tree-level flavor-changing effects in the
Randall-Sundrum (RS) model with brane-localized Higgs sector and bulk gauge and
matter fields is presented. The bulk equations of motion for the gauge and
fermion fields, supplemented by boundary conditions taking into account the
couplings to the Higgs sector, are solved exactly. For gauge fields the
Kaluza-Klein (KK) decomposition is performed in a covariant R_xi gauge. For
fermions the mixing between different generations is included in a completely
general way. The hierarchies observed in the fermion spectrum and the quark
mixing matrix are explained naturally in terms of anarchic five-dimensional
Yukawa matrices and wave-function overlap integrals. Detailed studies of the
flavor-changing couplings of the Higgs boson and of gauge bosons and their KK
excitations are performed, including in particular the couplings of the
standard W and Z bosons. A careful analysis of electroweak precision
observables including the S and T parameters and the Zbb couplings shows that
the simplest RS model containing only Standard Model particles and their KK
excitations is consistent with all experimental bounds for a KK scale as low as
a few TeV, if one allows for a heavy Higgs boson and/or for an ultra-violet
cutoff below the Planck scale. The study of flavor-changing effects includes
analyses of the non-unitarity of the quark mixing matrix, anomalous
right-handed couplings of the W bosons, tree-level flavor-changing neutral
current couplings of the Z and Higgs bosons, the rare decays t-->c(u)+Z and
t-->c(u)+h, and the flavor mixing among KK fermions. The results obtained in
this work form the basis for general calculations of flavor-changing processes
in the RS model and its extensions.Comment: 70 pages, 12 figures. v2: Incorrect treatment of phases in zero-mode
approximation corrected, and discussion of electroweak precision tests
modified. v3: Additional minor modifications and typos corrected; version
published in JHE
Decays of bottom mesons emitting tensor meson in final state using ISGW II model
In this paper, we investigate phenomenologically two-body weak decays of the
bottom mesons emitting pseudoscalar/vector meson and a tensor meson. Form
factors are obtained using the improved ISGW II model. Consequently, branching
ratios for the CKM-favored and CKM-suppressed decays are calculated.Comment: 32 pages, to be published in Phys. Rev.
Identifying through its decay modes
We study how to assign the recently observed meson to an
appropriate level of the spectrum by the analysis of its decay modes
in final states comprising a light pseudoscalar meson. We use an effective
lagrangian approach with heavy quark and chiral symmetries, obtaining that the
measurement of the decay width would allow to distinguish between two
possible assignments.Comment: RevTex, 6 pages - references adde
Charmed decays of the B-meson in the quark model
Exclusive and inclusive, semileptonic and non-leptonic, charmed decays of the
B-meson are investigated in the context of a phenomenological quark model.
Bound-state effects are taken care of by adopting a single (model-dependent)
non-perturbative wave function, describing the motion of the light spectator
quark in the B-meson. A nice reproduction of both exclusive and inclusive
semileptonic data is obtained. Our predictions for the electron spectrum are
presented and compared with those of the Isgur-Scora-Grinstein-Wise quark
model. Finally, our approach is applied to the calculation of inclusive
non-leptonic widths, obtaining a remarkable agreement with experimental
findings.Comment: to appear in the Proc. of the 2^{nd} Int. Conf. on Hyperons, Charm
and Beauty Hadrons, Montreal, Canada, 27-30 August 199
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