arXiv subjects

Emmanuel Ortiz-Pacheco

Publications and source records attributed to Emmanuel Ortiz-Pacheco.

12 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

Generalized Parton Distributions from Symbolic Regression

AI/ML informed Symbolic Regression is the next stage of scientific modeling. We utilize a highly customizable symbolic regression package ``PySR" to model the $x$ and $t$ dependence of the flavor isovector combination $H_{u-d}(x,t,ξ)$ at $ξ=0$. These PySR models were trained on GPD results provided by both Lattice QCD and phenomenological sources GGL, GK, and VGG. We demonstrate, for the first time, the consistency and systematic convergence of Symbolic Regression by quantifying the disparate models through their Taylor expansion coefficients. In addition to PySR penalizing models with higher complexity and mean-squared error, we implement schemes that test specific physics hypotheses, including force-factorized $x$ and $t$ dependence and Regge behavior in PySR GPDs. We show that PySR can identify factorizing GPD sources based on their response to the Force-Factorized model. Knowing the precise behavior of the GPDs, and their uncertainties in a wide range in $x$ and $t$, crucially impacts our ability to concretely and quantitatively predict hadronic spatial distributions and their derived quantities.

hep-ph↗

arXiv2025

Doubly charm tetraquark channel with isospin $1$ from lattice QCD

Experimentally, the doubly charm tetraquark channel $cc\bar q\bar q$ with $q\!=\!u,d$ features an exotic hadron, $T_{cc}$, with isospin $I\!=\!0$ near the $DD^*$ threshold, while no peak was observed for $I\!=\!1$. We present a lattice QCD study of this channel with $I\!=\!1$, $J^P\!=\!1^+$ and $m_π\simeq 280~$MeV. Finite-volume energies calculated across five charm quark masses consistently feature a positive energy shift with respect to non-interacting energies, indicating repulsive interaction at energies near threshold. These energies are used to compute the $DD^*$ scattering amplitude using both the standard Lüscher method and the recently proposed effective-field-theory-based approach in the plane-wave basis, which incorporates the long-range interactions and the left-hand cut. Both analyses render a small negative scattering length and the scattering amplitude that does not feature any poles in the energy region near the $DD^*$ threshold, in line with LHCb results. We identify that the Wick contraction resembling $t$-channel isovector-vector meson exchanges between $D$ and $D^*$ plays a key role in distinguishing between the $I=0$ and $I=1$ channels, leading to repulsion in the $I=1$ and attraction in the $I=0$ channel.

hep-lat↗

arXiv2024

$T_{cc}^+$ via the plane wave approach and including diquark-antidiquark operators

The determination of the $DD^{*}$ scattering amplitude from lattice QCD is complicated by long-range interactions. In particular, the Lüscher method is no longer applicable in the kinematical region close to the left-hand cut. We tackle this problem by adopting plane-wave and effective-field-theoretic methods, which also address partial wave mixing. In addition, we incorporate a diquark-antidiquark interpolator in the operator basis (along with the relevant scattering operators) in order to achieve a better resolution of the energy spectrum. Results show that inclusion of it already has some impact at physical charm quark mass, although it is more significant for larger heavy quark masses, in line with expectations.

hep-lat↗

arXiv2023

Doubly charmed tetraquark: isospin channels and diquark-antidiquark interpolators

We perform a lattice simulation to investigate the doubly charmed tetraquark $T^+_{cc}$ observed by the LHCb collaboration, slightly below the $D^{*+}D^0$ threshold, with flavor content $cc\bar{u}\bar{d}$ and isospin-$0$. Two-meson interpolators are implemented to explore the isospin quantum numbers $I=0$ and $I=1$. We observe attraction near the $DD^*$ threshold for $I=0$ and repulsion for $I=1$. Moreover, we also include diquark-antidiquark interpolators to study their effect on the energy spectrum. There is no significant shift in the ground state energy when adding diquark-antidiquark interpolators to the interpolator basis when the heavy quark mass is close to the physical charm quark mass. However, we observe a non-negligible shift in the second energy level. This effect has to be taken into account to extract the scattering amplitude of the $T^+_{cc}$. Finally, with a higher mass (close to the bottom quark), the ground state is shifted down significantly. The simulation is performed on $N_f=2+1$ CLS ensembles with $m_π\simeq 280$ MeV.

hep-lat↗

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

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.

hep-ph↗

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↗

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.

nucl-th↗

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.

nucl-th↗

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.

nucl-th↗