1,102 research outputs found
Large Universality of The Baryon Isgur--Wise Form Factor: The Group Theoretical Approach
In a previous article, it has been proved under the framework of chiral
soliton model that the same Isgur--Wise form factor describes the semileptonic
and decays in the
large limit. It is shown here that this result is in fact independent of
the chiral soliton model and is solely the consequence of the spin-flavor SU(4)
symmetry which arises in the baryon sector in the large limit.Comment: 10 pages in REVTeX, no figure
Amplitude analysis of hadron decays
We provide succinct covariant amplitude decompositions of 2-body weak
hadronic decays, with which to compare data, including exclusive rates,
helicity amplitudes and polarizations. For weak decays, the systematic
dependence of these amplitudes on masses and quantum numbers of participating
particles are determined within a factor of about two by the CKM angles and the
Fermi constant so theoretical models need to be much more accurate if they are
to be convincing.Comment: 31 pages, RevTe
Exclusive semileptonic decays of D and Ds mesons in the covariant confining quark model
Recently, the BESIII collaboration has reported numerous measurements of various D(s) meson
semileptonic decays with significantly improved precision. Together with similar studies carried out at
BABAR, Belle, and CLEO, new windows to a better understanding of weak and strong interactions
in the charm sector have been opened. In light of new experimental data, we review the theoretical
description and predictions for the semileptonic decays of D(s) to a pseudoscalar or a vector meson.
This review is essentially an extended discussion of our recently published results obtained in the
framework of the covariant confining quark model
Nonleptonic Cabibbo Favoured -Decays and -Asymmetries for Charmed Final Hadron States in Isgur and Wise Theory
The Cabibbo allowed non-leptonic -decays in two hadrons are studied,
within the factorization hypothesis, in the framework of Isgur and Wise theory
for the matrix elements of the weak currents. The
symmetry relates to currents, which
have been measured in the semileptonic strange decays of charmed particles. By
assuming colour screening and allowing for invariant contributions from
the annihilation terms with charmed final states one is able to comply with the
present experimental knowledge.\\ The violating asymmetries in neutral
decays are given for charmed final states in terms of the angles. With
the central values found for the annihilation parameters there is a destructive
(constructive) interference between the direct and annihilation terms in the
Cabibbo allowed (doubly forbidden) amplitudes for the decays into
and so that they may be of the same order.
This would imply large asymmetries, for which however our present knowledge on
the amplitudes does not allow to predict even their sign.\\ We have better
confidence in our predictions for the charged final states than the neutral
ones and can draw the conclusion that the detection of the corresponding
asymmetries requires, at least, tagged neutral -particles.Comment: CERNTEX, 17 pages, DSF-92/23, INFN-NA-IV-92/2
Bounds on Heavy-to-Heavy Mesonic Form Factors
We provide upper and lower bounds on the form factors for B -> D, D^* by
utilizing inclusive heavy quark effective theory sum rules. These bounds are
calculated to leading order in Lambda_QCD/m_Q and alpha_s. The O(alpha_s^2
beta_0) corrections to the bounds at zero recoil are also presented. We compare
our bounds with some of the form factor models used in the literature. All the
models we investigated failed to fall within the bounds for the combination of
form factors (omega^2 - 1)/(4 omega)|omega h_{A2}+h_{A3}|^2.Comment: 27 pages, 10 figure
Heavy quark supermultiplet excitations
Lorentz covariant wave functions for meson and baryon supermultiplets are
simply derived by boosting representations corresponding to
multiquark systems at rest.Comment: 12 pages (Revtex), UTAS-PHYS-93-4
Biogeography of photoautotrophs in the high polar biome
The global latitudinal gradient in biodiversity weakens in the high polar biome and so an alternative explanation for distribution of Arctic and Antarctic photoautotrophs is required. Here we identify how temporal, microclimate and evolutionary drivers of biogeography are important, rather than the macroclimate features that drive plant diversity patterns elsewhere. High polar ecosystems are biologically unique, with a more central role for bryophytes, lichens and microbial photoautotrophs over that of vascular plants. Constraints on vascular plants arise mainly due to stature and ontogenetic barriers. Conversely non-vascular plant and microbial photoautotroph distribution is correlated with favourable microclimates and the capacity for poikilohydric dormancy. Contemporary distribution also depends on evolutionary history, with adaptive and dispersal traits as well as legacy influencing biogeography. We highlight the relevance of these findings to predicting future impacts on polar plant diversity and to the current status of plants in Arctic and Antarctic conservation policy frameworks
Importance of Tests for the Complete Lorentz Structure of the t --> W+ b vertex at Hadron Colliders
The most general Lorentz-invariant decay-density-matrix for , or for , is expressed in terms
of eight helicity parameters. The parameters are physically defined in terms of
partial-width-intensities for polarized-final-states in decay.
The parameters are the partial width, the quark's chirality parameter
, the polarimetry parameter , a "pre-SSB" test parameter
, and four - interference parameters , ,
, which test for violation. They can be
used to test for non-CKM-type CP violation, anomalous 's, top
weak magnetism, weak electricity, and second-class currents. By stage-two
spin-correlation techniques, percent level statistical uncertainites are
typical for measurements at the Tevatron, and several mill level uncertainites
are typical at the LHC.Comment: Minor clarifications. Expression for r_{+-} corrected. 19 pages LaTex
+ Tables + 1 Figur
Phenomenology of neutral heavy leptons
We continue our previous work on the flavour-conserving leptonic decays of
the Z boson with neutral heavy leptons (NHL's) in the loops by considering box,
vertex, and self-energy diagrams for the muon decay. By inclusion of these
loops (they contribute to the input parameter M_W) we can probe the full
parameter space spanned by the so-called flavour-conserving mixing parameters
ee_(mix), \mu\mu_(mix), \tau\tau_(mix) in a superstring-inspired model of
neutrino mass. We compare the results of our analysis with the existing work in
this field and conclude that flavour-conserving decays have certain advantages
over traditionally considered flavour-violating ones.Comment: submitted to Phys. Rev. D, 30 pages, 9 figures (ps), REVTE
CP--odd Correlation in the Decay of Neutral Higgs Boson into , , or
We investigate the possibility of detecting CP--odd angular correlations in
the various decay modes of the neutral Higgs boson including the modes of a
pair, a pair, or a heavy quark pair. It is a natural way to probe
the CP character of the Higgs boson once it is identified. Final state
interactions (i.e. the absorptive decay amplitude) is not required in such
correlations. As an illustrative example we take the fundamental source of the
CP nonconservation to be in the Yukawa couplings of the Higgs boson to the
heavy fermions. A similar correlation in the process is
also proposed. Our analysis of these correlations will be useful for
experiments in future colliders such as LEP II, SSC, LHC or NLC.Comment: 16 pages, plus 8 postscript graphs not posted befor
- …