We provide results for the open-flavor strong decays of strange and nonstrange baryons into a baryon-vector/pseudoscalar meson pair. The decay amplitudes are computed in the P30 pair-creation model, ...where ss¯ pair-creation suppression is included for the first time in the baryon sector, in combination with the U(7) and hypercentral models. The effects of this ss¯ suppression mechanism cannot be reabsorbed in a redefinition of the model parameters or in a different choice of the P30 model vertex factor. Our results for the decay amplitudes are compared with the existing experimental data and previous P30 and elementary meson emission model calculations. In this respect, we show that distinct quark models differ in the number of missing resonances they predict and also in the quantum numbers of states. Therefore, future experimental results will be important in order to disentangle different models of baryon structure. Finally, in the appendixes, we provide some details of our calculations, including the derivation of all relevant flavor couplings with strangeness suppression. This derivation may be helpful to calculate the open-flavor decay amplitudes starting from other models of baryons.
The observation of five
Ω
c
= ssc states by LHCb Aaij et al. Phys. Rev. Lett.
118
, 182001 (
2017
) and the confirmation of four of them by Belle Yelton et al. Phys. Rev. D
97
, 051102 (
2018
), may ...represent an important milestone in our understanding of the quark organization inside hadrons. By providing results for the spectrum of
Ω
c
baryons and predictions for their
Ξ
c
+
K
-
and
Ξ
c
′
+
K
-
decay amplitudes within an harmonic oscillator based model, we suggest a possible solution to the
Ω
c
quantum number puzzle and we extend our mass and decay width predictions to the
Ω
b
states. Finally, we discuss why the set of
Ω
c
(
b
)
baryons is the most suitable environment to test the validity of three-quark and quark–diquark effective degrees of freedom.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
.
We present an unquenched quark model calculation of the mass shifts of ground-state octet and decuplet baryons due to the coupling to the meson-baryon continuum. All ground-state baryons and ...pseudoscalar mesons are included in our calculation as intermediate states. The
q
q
¯
pair creation effects are taken explicitly into account through a microscopic, QCD-inspired, quark-antiquark pair creation mechanism.
We discuss the latest applications of the Unquenched Quark Model (UQM) to the calculation of baryon observables. In particular, we focus on strangeness suppression effects in baryon-meson ...electro-production in the UQM formalism. We also briefly discuss our results of the mass shifts of ground-state octet and decuplet baryons due to the coupling to the meson-baryon continuum.
We describe the electroproduction ratios of baryon–meson states from nucleon, inferring from the sea quarks in the nucleon using an extension of the quark model that takes into account the sea. As a ...result we provide, with no adjustable parameters, the predictions of ratios of exclusive meson–baryon final states: ΛK+, Σ⁎K, ΣK, pπ0, and nπ+. These predictions are in agreement with the new JLab experimental data showing that sea quarks play an important role in the electroproduction. We also predicted further ratios of exclusive reactions that can be measured and tested in future experiments. In particular, we suggested new experiments on deuterium and tritium. Such measurements can provide crucial tests of different predictions concerning the structure of nucleon and its sea quarks helping to solve an outstanding problem. Finally, we compute the so called strangeness suppression factor, λs, that is the suppression of strange quark–antiquark pairs compared to nonstrange pairs, and we found that our finding with this simple extension of the quark model is in good agreement with the results of JLab and CERN experiments.
We review the status and prospects of heavy-ion double charge exchange (HI-DCE) reactions. Their important role for nuclear reaction, nuclear structure and double beta-decay investigations is ...outlined. From the experimental side the characteristically tiny cross sections for these processes and the high background generated by other more probable competing reactions is the main challenge, which has hindered HI-DCE spectroscopy until recent years. Modern magnetic spectrometers have proven to possess the right requisites to overcome past limitations, fostering the present and future development of the field. From the theory side, the description of the measured HI-DCE cross sections poses manifold challenges. Dealing with processes which involve composite nuclei, HI-DCE reactions can, in principle, proceed through several alternative paths. These, in turn, correspond to different reaction mechanisms probing competing aspects of nuclear structure, from mean field to various classes of nucleon–nucleon interactions and correlations. A powerful way to scrutinize the nuclear response to HI-DCE is to consistently link it to the information extracted from the competing direct reactions. Indeed, these complementary studies are mandatory in order to minimize the systematic errors in the data analyses and build a many-facets and parameter-free representation of the systems under study.
The formalism to describe heavy-ion double charge exchange (DCE) processes in the eikonal and small-momentum transfer approximations introduced in Phys. Rev. C 98, 061601(R) (2018) is briefly ...discussed. It is also shown that, under the previous approximations, the heavy-ion DCE cross-section can be factorized in terms of a reaction and a nuclear part. A double charge exchange effective potential is explicitly derived in the closure approximation and also for the first time the explicit form of the DCE nuclear matrix elements, that are of the form of double Gamow-Teller and double Fermi. The recent hypothesis of a linear correlation between double Gamow-Teller neutrinoless double beta decay and DCE nuclear matrix elements is confirmed thanks to the first explicit derivation of DCE nuclear matrix elements, and by means of microscopic IBM2 calculations.
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