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H. García-Tecocoatzi

Publications and source records attributed to H. García-Tecocoatzi.

15 recordsLinked to original sources

Radiative decays of the 1$P$, 1$D$, 2$S$, and 2$P$ $Λ_c$ and 1$D$, 2$S$, and 2$P$ $Ξ_c$ charmed baryons

We analyze the radiative decays of the the 1$P$, 1$D$, 2$S$, and 2$P$ $Λ_c$ and 1$D$, 2$S$, and 2$P$ $Ξ_c$ charmed baryons, which belong to the flavor anti-triplet ($\bf {\bar 3}_{\rm F}$), using the constituent quark model. We compute electromagnetic transitions from ground and $P$-wave states to ground states, as well as from second-shell states to both ground and $P$-wave final states. Electromagnetic decay widths are especially valuable for identifying resonances when multiple states share the same mass and total decay width. We give branching ratios which can confirm the assignment of the $Ξ_c(3055)$ reported by LHCb. We also give branching ratios that can support the assignment of the $Ξ_c(3080)$, and discuss the possibilities for the $Ξ_c(3080)$ to be the 1$D$ state with $J^P=5/2^{+}$ or the 2$S$ with $J^P=1/2^{+}$. For the first time, this work provides calculations of electromagnetic decays for $D_ρ$-wave states, $ρ-λ$ mixed configurations, and $ρ$-mode radially excited states in singly charmed baryons of the flavor anti-triplet. Both experimental and model-dependent uncertainties are taken into account throughout our analysis.

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Radiative decays of the $Σ_c$, $Ξ'_c$ and $Ω_c$ charmed baryons

In this work, we study the radiative decays of the $Σ_c$, $Ξ'_c$ and $Ω_c$ charmed baryons, which belong to the flavor sextet ($\bf {6}_{\rm F}$), within the constituent quark model formalism. The electromagnetic transitions are calculated from the ground and $P$-wave states to ground states, as well as from the second shell states to both the ground and $P$-wave final states. These decays play a crucial role in confirming the existence of certain resonances when strong decays are not allowed. Moreover, electromagnetic decay widths are particularly useful for identifying resonances when states have the same mass and total decay width. A relevant case is the $Ω_c (3327)$ state, whose branching ratios between the strong decay channels are comparable; thus, the radiative decay widths may help assign this state. We also make the assignment of the recently discovered $Ξ'_c(2923)^{+}$ baryon, which is consistent with being the isospin partner of the $Ξ'_c(2923)^{0}$. This study presents, for the first time, the calculation of electromagnetic decays for $D_ρ$-wave states, $ρ-λ$ mixed states, and $ρ$-mode radially excited states in the charm sector. Throughout our calculations, we account for uncertainties arising from both experimental and model-dependent errors.

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Strong decays of the $DK^\ast$ and $\bar{D}K^{\ast}$ molecular states

Inspired by the abundant structure near the threshold of the $D^{(*)}K^{(*)}/\bar{D}^{(*)}K^{(*)}$, we estimate the strong decay properties of the $T_{c\bar{s}1}^{f/a}$ and $T_{\bar{c}\bar{s}1}^{f/a}$ with $I(J^{P})=0/1(1^{+})$ in $DK^{*}$ and $\bar{D}K^{*}$ molecular scenarios in the present paper. By employing the effective Lagrangian approach, the widths of the processes $T_{c\bar{s}1}^{f}\to D^{*}K, D_{s}^{*}η, DKπ$, $T_{c\bar{s}1}^{a}\to D^{*}K, D_{s}^{*}π, DKπ$, and $T_{\bar{c}\bar{s}1}^{f/a}\to\bar{D}^{*}K, \bar{D}Kπ$ are estimated. Considering the present estimations, we propose to search for $T_{c\bar{s}1}^{f/a}$ states in $D^{*}K$ and $D_{s}^{*}π/D_{s}^{*}η$ mass invariant spectra. Their ratios may serve as an important test of the molecular scenario.

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Radiative decays of the second shell $Λ_b$ and $Ξ_b$ bottom baryons

In this work, we investigate the radiative decays of the $Λ_b$ and $Ξ_b$ bottom baryons, which belong to the flavor anti-triplet ($\mathbf{\bar{3}}_{\rm F}$), within the constituent quark model formalism. The electromagnetic transitions are calculated from the second-shell states to both the ground and $P$-wave final states. These decays play a crucial role in confirming the existence of certain resonances. When strong decays are not allowed, the reconstruction of states relies on their electromagnetic decay channels. Moreover, electromagnetic decay widths are particularly useful for the identification of resonances when states have the same mass and total decay width. This study presents, for the first time, the calculation of electromagnetic decays for $D_ρ$-wave states, $ρ-λ$ mixed states, and $ρ$-mode radially excited states. Throughout our calculations, we account for uncertainties arising from both experimental and model-dependent errors.

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$Ξ_c(2790)^{+/0}$ and $Ξ_c(2815)^{+/0}$ radiative decays

In this work, we study the $Ξ_c$ baryon electromagnetic decay widths within the constituent quark model formalism through an analysis of the transitions from $P-$wave states to ground states. We use the non-relativistic limit of the Hamiltonian of the electromagnetic interaction on keeping all the terms up to the order $m_j^{-1}$. We calculate the electromagnetic decay widths analytically, for the first time, without any further approximation. Specifically, our theoretical results for the $Ξ_c(2790)^{+/0}$ and $Ξ_c(2815)^{+/0}$ radiative decay widths, without the introduction of any additional parameters, display a significant agreement with the recent experimental values obtained by the Belle experiment. The agreement is due to the fact that we have not introduced further approximation to simplify the calculation of the difficult convective term, unlike what was done in previous studies. Our predictions may be useful for future experiments at the Belle, BABAR, and LHC experiments.

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Decay widths and mass spectra of single bottom baryons

We develop a Hamiltonian model that incorporates the spin, spin-orbit, and isospin interactions to determine the masses of the ground states of single-bottom baryons and their excitations up to the $D$-wave. Furthermore, we calculate the strong decay widths of single-bottom baryons using the $^3P_0$ model. Our calculations consider final states comprising bottom baryon-(vector/pseudoscalar) meson pairs and (octet/decuplet) baryon-(pseudoscalar/vector) bottom meson pairs within a constituent quark model. In that respect, this is the most complete investigation which has ever been performed in the single bottom baryon sector so far. Additionally, we compute the electromagnetic decay widths from $P$-wave states to ground states. The electromagnetic decays become dominant in cases where the strong decays are suppressed. The experimental uncertainties are propagated to the model parameters using a Monte Carlo bootstrap method. Our quantum number assignments, as well as our mass and strong decay width predictions, are in reasonable agreement with the available data. We also provide the partial decay widths for each open flavor channel. Our predictions of mass spectra and decay widths provide valuable information for the experiments seeking to identify new bottom baryons and knowledge of possible decay channels can aid in their identification in the data. Therefore, our results will be able to guide future searches for the undiscovered single bottom baryons at LHCb, ATLAS, and CMS.

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The $Ω_{c}$-puzzle solved by means of spectrum and strong decay amplitude predictions

The observation of new $Ω_{c}=ssc$ states by LHCb \cite{Aaij:2017nav} and the confirmation of four of them by Belle \cite{Yelton:2017qxg} may represent an important milestone in our understanding of the quark organization inside hadrons. By providing results for the spectrum of $Ω_{c(b)}$ baryons and predictions for their $Ξ_{c(b)}^{+}K^{-}$ decay channels, we suggest a possible solution to the $Ω_{c}$ quantum number puzzle. We also discuss why the set of $Ω_{c(b)}$ baryons are the most suitable environment to test the validity of three-quark and quark-diquark effective degrees of freedom. Finally, we calculate the masses and the partial decay widths of the $Ξ_b(6227)$ and $Σ_b(6097)$ states, just observed by LHCb \cite{Aaij:2018yqz,Aaij:2018tnn}. Our results are in good agreement with LHCb experimental data.

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Heavy-ion double-charge-exchange and its relation to neutrinoless double-beta decay

We introduce the formalism to describe heavy-ion Double-Charge-Exchange (DCE) processes in the eikonal approximation. We focus on the low-momentum-transfer limit -- corresponding to the differential cross section at $θ=0^\circ$ -- and, for the first time, we show that it is possible to factorize the DCE cross-section in terms of reaction and nuclear parts. Whereas in the $θ\neq0^\circ$ case the nuclear part is a convolution of the beam and target nuclear matrix elements (NMEs), for $θ=0^\circ$ we demonstrate - for the first time- that the transition matrix elements can be written as the sum of Double-Gamow-Teller (DGT) and Double Fermi (DF) type parts, and that they can both be further factorized in terms of target and projectile NMEs. By making use of the Interacting Boson Model (IBM) formalism, we also show that the DGT and total parts of the neutrinoless double-beta decay NMEs are in linear correlation with DCE-DGT NMEs. This confirms the hypothesis of a linear correlation between them, as introduced in [Phys.\ Rev.\ Lett.\ {\bf 120}, 142502 (2018)]. The possibility of a Two-Step Factorization (TSF) of the very forward differential DCE-cross-section and the emergence of DGT and DF types for the DCE nuclear matrix elements, combined with a linear correlation between DCE-DGT and 0$νββ$ NMEs, opens the possibility of placing an upper limit on neutrinoless double-beta decay NMEs in terms of the DCE experimental data at $θ=0^\circ$.

nucl-th↗

Strong decays of baryons and missing resonances

We provide results for the open-flavor strong decays of strange and non-strange baryons into a baryon-vector/pseudoscalar meson pair. The decay amplitudes are computed in the $^3P_0$ pair-creation model, where $s\bar{s}$ 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 $s\bar{s}$ suppression mechanism cannot be re-absorbed in a redefinition of the model parameters or in a different choice of the $^3P_0$ model vertex factor. Our results for the decay amplitudes are compared with the existing experimental data and previous $^3P_0$ 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 appendices, 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.

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Open flavor strong decays

In this contribution, we discuss the results of a QM calculation of the open-flavor strong decays of **** light nucleon resonances. These are the results of a recent calculation, where we used a modified $^3P_0$ model for the amplitudes and the U(7) algebraic model and the Hypercentral Quark Model to predict the baryon spectrum. The decay amplitudes are compared with the existing experimental data.

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Electroproduction ratios of Baryon-Meson states and Strangeness Suppression

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:$ΛK^+$, $Σ^{*}K$, $ΣK$, $pπ^0$, 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 test of different predictions concerning the structure of nucleon and its sea quarks helping to solve an outstanding problem. Finally, we computed the so called strangeness suppression factor, $λ_s$, that is the suppression of strange quark-antiquarks 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.

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Hadron Spectroscopy in the Unquenched Quark Model

We present the last applications of the unquenched quark model (UQM) to the description of flavour asymmetry and strangeness in the proton when baryon-meson components are included. In the meson sector, the UQM is used to calculate the charmonium and bottomonium spectra with self-energy corrections due to the coupling to the meson-meson continuum.

nucl-th↗

Higher charmonia and bottomonia. Nature of the X(3872)

In this contribution, we will discuss our unquenched quark model re- sults for the spectra of cc and bb states. The spectra are calculated in the unquenched quark model formalism, where the physical mass of a meson is the sum of a bare mass contribution plus a self-energy correc- tion, due to the coupling to the meson-meson continuum. We will also discuss the quark structure of the X(3872). Its open-flavor and radiative decays are calculated in the quark model formalism. In our interpreta- tion, the wave function of the X(3872) is the sum of two contributions, a cc core plus higher Fock components, due to meson-meson continuum components. Our results for the spectra, open-flavor and radiative decays are compared to the existing experimental data.

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The unquenched QM

In this contribution, we briefly analyze the formalism of the unquenched quark model (UQM) and its application to the calculation of hadron spectra with self-energy corrections, due to the coupling to the meson-meson continuum. 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. The UQM formalism can be extended to include also the effects of hybrid mesons, i.e. hybrid loops. The main applications to spectroscopy and decays are analyzed.

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