arXiv subjects

Roelof Bijker

Publications and source records attributed to Roelof Bijker.

At least 19 recordsLinked to original sources

arXiv2026

Strong decay widths of S- and P-wave singly- and doubly-heavy charm and bottom baryons

We present a study of two-body decay widths of heavy baryons into another heavy baryon and a light pseudoscalar meson in the framework of the non-relativistic quark model in combination with the elementary emission model for the strong couplings. The present study includes the decays of 1S- and 1P-wave baryons with one or two heavy quarks, either charm (c) or bottom (b). The flavor, spin and orbital contributions are discussed explicitly as well as selection rules for forbidden decays. The relative partial widths are given by the appropriate flavor SU(3) isoscalar factors. The total widths are compared with the available experimental data as well as with other theoretical studies. The calculated widths of singly-heavy baryons are found to be in reasonable agreement with the observed widths. The decay widths of doubly-heavy baryons are suppressed with respect to those of the singly-heavy baryons by the ratios of the quark masses appearing in the orbital contributions.

hep-ph↗

arXiv2025

Algebraic treatment of alpha-cluster nuclei

In this contribution we review the algebraic cluster model (ACM) for $α$-cluster nuclei with $A=4k$ nucleons and its extension to the cluster shell model (CSM) for $A=4k+x$ nuclei. Particular attention is paid to the question to what extent the $α$-cluster structure survives under the addition of extra nucleons. As an example, we discuss the properties of $^{12}$C and $^{13}$C.

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arXiv2023

Spectroscopy of heavy baryons

We present a study of mass spectra and electromagnetic couplings of $S$- and $P$-wave heavy baryons in the framework of a non-relativistic harmonic oscillator quark model. Particular attention is paid to the properties of heavy cascade baryons, $Ξ_Q$ and $Ξ'_Q$.

hep-ph↗

arXiv2023

Structure of $^{13}$C in the Cluster Shell Model

We study the structure of $^{13}$C in the framework of the Cluster Shell Model. A comparison of the available experimental data with our model is made. Some predictions for level ordering and form factors are presented.

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arXiv2023

$^{10}$Be in the Cluster Shell Model

The Cluster Shell Model (CSM)describes light nuclei in terms of $k-α$ particles and $x$ extra nucleons, in which the extra nucleon move in the deformed field generated by the geometric configuration of $α$-particles. We present the first study for the case $x=2$ nucleons in application to $^{10}Be$ as a cluster of two $α$-particles and two neutrons.

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arXiv2023

Heavy $Ξ_{c/b}$ and $Ξ'_{c/b}$ baryons in the quark model

We present a study of the low-lying $Ξ_{c/b}$ and $Ξ'_{c/b}$ baryon states based on masses, strong and radiative decays. In a harmonic oscillator quark model analysis it is found that the majority of the detected states can be interpreted as $S$- and $P$-wave excitations.

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arXiv2023

Masses and radiative decay widths of S- and P-wave singly-, doubly- and triply-heavy charm and bottom baryons

We present a study of mass spectra and electromagnetic couplings of S- and P-wave baryons containing one, two or three heavy quarks, either charm (c) or bottom (b), in the framework of a non-relativistic harmonic oscillator quark model. A simultaneous fit to 41 known masses of heavy baryons (40 singly-heavy and 1 doubly-heavy) shows a r.m.s. deviation of 19 MeV. We present equal-spacing mass rules for excited baryons which may help to assign quantum numbers to experimentally observed heavy baryons. Explicit expressions are derived for electromagnetic couplings, both for spin-flavor matrix elements and radial integrals.

hep-ph↗

arXiv2021

Masses and decay widths of $Ξ_{c/b}$ and $Ξ^\prime_{c/b}$ baryons

In this article, we present a complete classification of the negative parity $Ξ'_{c/b}$ and $Ξ_{c/b}$ $P$-wave states: 7 belonging to the $SU(3)$ flavor sextet and 7 to the flavor anti-triplet, the calculation of the $Ξ'_{c/b}$ and $Ξ_{c/b}$ strong partial decay widths into $^2Σ_c \bar{K}$, $^2Ξ_c^{'} π$, $^2Σ_c \bar{K}$, $^4Ξ_c^{'} π$, $Λ_c^{'} \bar{K}$, $Ξ_c^{} π$ and $Ξ_c^{} η$ channels both within the Elementary Emission Model (EEM) and the $^3P_0$ model, and the calculation of the electromagnetic decay widths for $Ξ'_{c/b}$ and $Ξ_{c/b}$ radiative decays. By means of the equal-spacing mass rule and by the analysis of the strong partial decay widths, we suggest possible assignments for the new LHCb $Ξ_{c}(2923)$, $Ξ_{c}(2939)$, and $Ξ_{c}(2965)$ states, as well as for the $Ξ_{c}$'s previously reported by Belle and BaBar. Our results can be tested by future experiments, at LHCb and Belle, disentangling the remaining missing piece of information, {\it i.e.} the quantum numbers. Finally, a comparison is made between a three-quark and a quark-diquark description of $Ξ_c$ states. Very recently the LHCb collaboration reported the observation of two new $Ξ_b$ states, namely $Ξ_b(6327)^{0}$ and $Ξ_b(6333)$, in $Λ_b^0 K^{-} π^{+}$ channel with a statistical significance larger than nine standard deviations. The experimental masses and widths of these two states are consistent with our mass and width predictions for the doublet of D-wave excitations of the $Ξ_b$ system with $J^{P}_{Ξ_b(6327)^{0}}=\frac{3}{2}^{+}$ and $J^{P}_{Ξ_b(6333)^{0}}=\frac{5}{2}^{+}$.

hep-ph↗

arXiv2021

Transfer reactions between odd-odd and even-even nuclei by using IBFFM

Spectroscopic Amplitudes (SA) in the Interacting Boson Fermion Fermion Model (IBFFM) are necessary for the computation of $0νββ$ decays but also for cross sections of heavy-ion reactions, in particular, Double Charge Exchange reactions for the NUMEN collaboration, if one does not want to use the closure limit. We present for the first time: i) the formalism and operators to compute in a general case the spectroscopic amplitudes in the scheme IBFFM from an even-even to odd-odd nuclei, in a way suited to be used in reaction code, i.e., extracting the contribution of each orbital; 2) the odd-odd nuclei as described by the old IBFFM are obtained for the first time with the new implementation of Machine Learning (ML) techniques for fitting the parameters, getting a more realistic description. The one body transition densities for $^{116}$Cd $\rightarrow$ $^{116}$In and $^{116}$In $\rightarrow$ $^{116}$Sn are part of the experimental program of the NUMEN experiment, which aims to find constraints on Neutrinoless double beta decay matrix elements.

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arXiv2019

Hidden charm pentaquarks: mass spectrum, magnetic moments, and photocouplings

We develop an extension of the usual three flavor quark model to four flavors (u, d, s and c), and discuss the classification of pentaquark states with hidden charm. We fit our model to the known baryon spectrum and we predict the double and triple charm baryons, finding good agreement with the most recent lattice QCD calculations. We compute the the ground state of hidden charm pentaquarks and their associated magnetic moments and electromagnetic couplings, of interest to pentaquark photoproduction experiments.

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arXiv2019

Symmetries and order in cluster nuclei

It is shown that the rotational band structure of the cluster states in 12C and 16O can be understood in terms of the underlying discrete symmetry that characterizes the geometrical configuration of the alpha-particles, i.e. an equilateral triangle for 12C, and a regular tetrahedron for 16O. The structure of rotational bands provides a fingerprint of the underlying geometrical configuration of alpha-particles. Finally, some first results are presented for odd-cluster nuclei.

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arXiv2018

Electromagnetic and weak decays of baryons in the unquenched quark model

In this contribution, we discuss the electromagnetic and weak decays of baryons in the unquenched quark model and show that the observed discrepancies between the experimental data and the predictions of the constituent quark model can be accounted for in large part by the effects of sea quarks. Finally, the obtained results are discussed in terms of flavor-symmetry breaking.

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arXiv2017

Baryon spectroscopy in the unquenched quark model

We discuss some applications of the unquenched quark model which is an extension of the CQM that includes the effects of sea quarks via a 3P0 quark-antiquark pair-creation mechanism. Particular attention is paid to the electromagnetic couplings and beta decays of baryons. It is shown that the observed discrepancies between the experimental data and the predictions of the CQM can be accounted for in large part by the effects of sea quarks in the unquenched quark model.

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arXiv2017

Pentaquark states with hidden charm

I develop an extension of the usual three-flavor quark model to four flavors (u, d, s and c), and discuss the classification of pentaquark states with hidden charm. This work is motivated by the recent observation of such states by the LHCb Collatoration at CERN.

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arXiv2016

Geometric symmetries in light nuclei

The algebraic cluster model is is applied to study cluster states in the nuclei 12C and 16O. The observed level sequences can be understood in terms of the underlying discrete symmetry that characterizes the geometrical configuration of the alpha-particles, i.e. an equilateral triangle for 12C, and a regular tetrahedron for 16O. The structure of rotational bands provides a fingerprint of the underlying geometrical configuration of alpha-particles.

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arXiv2016

Strangeness suppression in the unquenched quark model

In this contribution, we discuss the strangeness suppression in the proton in the framework of the unquenched quark model. The theoretical results are in good agreement with the values extracted from CERN and JLab experiments.

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arXiv2016

Geometrical symmetries of nuclear systems: D(3h) and T(d) symmetries in light nuclei

The role of discrete (or point-group) symmetries in alpha-cluster nuclei is discussed in the framework of the algebraic cluster model which describes the relative motion of the alpha-particles. Particular attention is paid to the discrete symmetry of the geometric arrangement of the alpha-particles, and the consequences for the structure of the corresponding rotational bands. The method is applied to study cluster states in the nuclei 12C and 16O. The observed level sequences can be understood in a simple way as a consequence of the underlying discrete symmetry that characterizes the geometrical configuration of the alpha-particles, i.e. an equilateral triangle with D(3h) symmetry for 12C, and a tetrahedron with T(d) symmetry for 16O. The structure of rotational bands provides a fingerprint of the underlying geometrical configuration of alpha-particles.

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arXiv2015

The unquenched quark model

In this contribution, we briefly analyze the formalism of the unquenched quark model (UQM) and its application to the description of several observables of hadrons. In the UQM, the effects of $q \bar q$ sea pairs are introduced explicitly into the quark model through a QCD-inspired $^{3}P_0$ pair-creation mechanism. We present our description of flavour asymmetry and strangeness in the proton when baryon-meson components are included. In the meson sector, the charmonium and bottomonium spectra with self-energy corrections due to the coupling to the meson-meson components .

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