1,525 research outputs found
GREENERGY - Energy optimisation in European greenhouses : D9: Delivery of the Energy Auditing Tool (EAT)
The exclusive rare decays B -> K l(bar) l and B_c -> D(D*) l(bar) l in a relativistic quark model
We study the exclusive rare decay B -> K l(bar) l. We calculate the relevant
form factors within a relativistic constituent quark model, for the first time
without employing the impulse approximation. The calculated form factors are
used to evaluate differential decay rates and polarization observables. We
present results on the q2-dependence of a set of observables with and without
long-distance contributions. A similar analysis is done for the exclusive rare
decays B_c -> D (D*) l(bar) l with special emphasis on the cascade decay B_c ->
D* (-> D pi) l(bar) l. We derive a four-fold angular decay distribution for
this process in terms of helicity amplitudes including lepton mass effects. The
four-fold angular decay distribution allows to define a number of physical
observables which are amenable to measurement. We compare our results with the
results of other studies.Comment: 28 pages, 12 figure
The semileptonic decay Lambda_b -> Lambda_c + tau(-) + antinu_tau in the covariant confined quark model
Recently there has been much interest in the tauonic semileptonic meson
decays B -> D + tau + nu_tau and B -> D* + tau + nu_tau where one has found
larger rates than what is predicted by the Standard Model. We analyze the
corresponding semileptonic baryon decays Lambda_b(0) -> Lambda_c(+) + tau(-) +
antinu_tau with particular emphasis on the lepton helicity flip and scalar
contributions which vanish for zero lepton masses. We calculate the total rate,
differential decay distributions, the longitudinal and transverse polarization
of the daughter baryon Lambda_c(+) and the tau-lepton, and the lepton-side
forward-backward asymmetries. The nonvanishing polarization of the daughter
baryon Lambda_c(+) leads to hadron-side asymmetries in e.g. the decay
Lambda_c(+) -> Lambda(0) + pi(+) and azimuthal correlations between the two
final state decay planes which we specify. We provide numerical results on
these observables using results of the covariant confined quark model. We find
large lepton mass effects in the q2-spectra and in the polarization
observables.Comment: 26 page
Four-quark structure of Zc(3900), Z(4430) and Xb(5568) states
We examine the four-quark structure of the recently discovered charged
, , and states. We calculate the widths of the
strong decays (, ,
), (), and
within a covariant quark model previously developed by us.
We find that the tetraquark-type current widely used in the literature for the
leads to a significant suppression of the and modes. Contrary to this a molecular-type current provides an
enhancement by a factor of 6-7 for the modes compared with the
, modes in agreement with recent
experimental data from the BESIII Collaboration. In case of the state
we test a sensitivity of the ratio of the
and decay rates to a choice of the size parameter
of the . Using upper constraint for the sum of
these two modes deduced from the LHCb Collaboration data we find that
varies from 4.64 to 4.08 when changes from 2.2 to 3.2 GeV.
Also we make the prediction for the decay rate.Comment: 14 page
- …