Spectroscopy and Regge trajectories of heavy baryons in the relativistic quark-diquark picture (1105.0583v1)

Abstract: Mass spectra of heavy baryons are calculated in the heavy-quark--light-diquark picture in the framework of the QCD-motivated relativistic quark model. The dynamics of light quarks in the diquark as well as the dynamics of the heavy quark and light diquark in the baryon are treated completely relativistically without application of nonrelativistic v/c and heavy quark 1/m_Q expansions. Such approach allows us to get predictions for the heavy baryon masses for rather high orbital and radial excitations. On this basis the Regge trajectories of heavy baryons for orbital and radial excitations are constructed, and their linearity, parallelism, and equidistance are verified. The relations between the slopes and intercepts of heavy baryons are considered and a comparison of the slopes of Regge trajectories for heavy baryons and heavy-light mesons is performed. All available experimental data on heavy baryons fit nicely to the constructed Regge trajectories. The possible assignment of the quantum numbers to the observed excited charmed baryons is discussed.

• The paper demonstrates that a relativistic quark-diquark model accurately predicts heavy baryon masses and Regge trajectories.
• It employs a fully relativistic framework without nonrelativistic approximations, successfully modeling excitations up to the 5th level.
• The study's findings align with experimental data, providing actionable insights for identifying heavy baryon quantum states.

Spectroscopy and Regge Trajectories of Heavy Baryons

The paper "Spectroscopy and Regge trajectories of heavy baryons in the relativistic quark-diquark picture," authored by D. Ebert, R. N. Faustov, and V. O. Galkin, presents a detailed paper of heavy baryon masses and their alignment with Regge trajectories using a relativistic quark model. Specifically, they leverage the heavy-quark--light-diquark approximation that reduces the complex three-body problem of heavy baryons to a more manageable quark-diquark bound system, allowing for a thorough analysis of baryon masses and their excitations with high precision.

Methodology

The authors employ a quark-diquark model motivated by Quantum Chromodynamics (QCD) that treats both light quarks in diquarks and the interaction between heavy quarks and diquarks within baryons in a fully relativistic framework. Notably, this approach does not rely on the nonrelativistic $v/c$ approximation nor the heavy quark $1/m_Q$ expansion, enabling the investigation of higher orbital and radial excitations of heavy baryons. This model efficiently reduces the plethora of potential excitations as compared to a complete three-quark treatment, aligning with existing experimental data.

Numerical Results and Regge Trajectories

The paper provides calculated masses of both ground and excited states of heavy baryons. These calculations extend to high orders of excitations—up to the 5th level—which essence enables a robust construction of Regge trajectories in both the $(J, M^2)$ and $(n_r, M^2)$ planes. The constructed Regge trajectories for heavy baryons are shown to exhibit linearity, parallelism, and equidistance, features that are well supported by experimental data.

The work also systematically examines the relationships between the slopes and intercepts of these trajectories, making comparisons with those known from heavy-light mesons and highlighting how these baryonic structures differ. In particular, the heavy baryon slopes showed a tendency to be larger than those of heavy-light mesons. Furthermore, the paper tests theoretical predictions regarding the additivity of slopes and intercepts across different baryon families, contributing to a deeper understanding of hadron dynamics.

Implications

Practically, the predictions regarding heavy baryon masses and their Regge trajectories provide guidance for future experimental searches and can aid in assigning quantum numbers to observed states. Theoretically, the paper reinforces the utility of the quark-diquark model in describing heavy baryon spectra, offering a complementary perspective to fully fledged three-body approaches.

Future Directions

This research opens avenues for further examination of heavy baryons, especially with advances in experimental techniques that may validate or challenge these theoretical predictions. Additionally, exploring decay processes and transition rates of these baryons within the same framework could further enrich the understanding of QCD's complex phenomenology.

The model and its outcomes could be extended to incorporate finer distinctions among diquark states and consider potential intrinsic gluon interactions. Moreover, as computational power grows, it might be feasible to explore fully relativistic three-body calculations that could refine current approximations, potentially reconciling any discrepancies with the quark-diquark model.

In summary, Ebert et al.'s work not only contributes significantly to the computational spectroscopy of heavy baryons but also paves the way for richer and more nuanced interpretations of baryon dynamics in particle physics.