Core Concepts

Using QCD sum rules, the study predicts the masses and decay widths of hypothetical bbcc tetraquarks, specifically the pseudoscalar (TPS) and vector (TV) states, suggesting their unstable nature with decays into various Bc meson pairs.

Abstract

**Bibliographic Information:**S. S. Agaev, K. Azizi, & H. Sundu. (2024). Pseudoscalar and vector tetraquarks bbcc.*arXiv preprint arXiv:2406.06759v2*.**Research Objective:**This paper investigates the properties of hypothetical pseudoscalar (TPS) and vector (TV) tetraquarks composed of bbcc quarks using the QCD sum rule method.**Methodology:**The authors employ the QCD sum rule method to calculate the masses and current couplings of the TPS and TV tetraquarks. They then determine the kinematically allowed decay channels for each tetraquark and calculate their respective partial widths using three-point sum rules to determine the strong couplings at the relevant vertices.**Key Findings:**The study predicts the mass of the TPS tetraquark to be (13.092 ± 0.095) GeV with a full width of (63.7 ± 13.0) MeV. The TV tetraquark is predicted to have a mass of (13.15 ± 0.10) GeV and a full width of (53.5 ± 10.3) MeV. The analysis reveals that both TPS and TV are unstable against strong decays, with TPS decaying into B−c B∗−c, B−c B−c (13P0), and B∗−c B−c (11P1) meson pairs, while TV decays into 2B−c, 2B∗−c, and B−c B−c (11P1) pairs.**Main Conclusions:**The study concludes that the predicted masses and decay widths of the TPS and TV tetraquarks suggest their unstable nature. These predictions can be valuable for future experimental searches and analyses of four-quark resonances.**Significance:**This research contributes to the understanding of exotic hadron spectroscopy, particularly in the realm of fully heavy tetraquarks. The predicted properties of bbcc tetraquarks provide valuable input for experimental investigations at facilities like LHCb.**Limitations and Future Research:**The study relies on theoretical calculations and assumptions inherent to the QCD sum rule method. Future research could explore alternative theoretical approaches and incorporate experimental data on Bc meson properties to refine the predictions.

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The mass of the pseudoscalar tetraquark (TPS) is predicted to be (13.092 ± 0.095) GeV.
The full width of the TPS tetraquark is calculated to be (63.7 ± 13.0) MeV.
The mass of the vector tetraquark (TV) is predicted to be (13.15 ± 0.10) GeV.
The full width of the TV tetraquark is calculated to be (53.5 ± 10.3) MeV.
The mass of the B−c meson used in the calculations is (6274.47 ± 0.27) MeV.
The predicted masses for B∗−c, B−c (13P0), and B−c (11P1) mesons are 6338 MeV, 6706 MeV, and 6750 MeV, respectively.

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by S. S. Agaev,... at **arxiv.org** 10-15-2024

Deeper Inquiries

Discovering additional tetraquark states, especially those with exotic quark configurations like bbcc, would significantly impact our understanding of the strong force and Quantum Chromodynamics (QCD). Here's how:
Testing QCD in the non-perturbative regime: QCD, the theory describing the strong force, is notoriously difficult to solve at low energies where quarks are strongly coupled. Tetraquarks, being multi-quark states, provide a unique testing ground for QCD predictions in this non-perturbative regime. Their properties, like masses and decay widths, offer valuable insights into the complex interactions governing quark confinement and hadron formation.
Refining quark model predictions: The traditional quark model, while successful in describing many hadrons, primarily focuses on mesons (quark-antiquark pairs) and baryons (three-quark states). The existence of tetraquarks necessitates a more nuanced understanding of quark interactions and could lead to refinements or extensions of the quark model. For example, diquark models, where two quarks form a tightly bound pair within the tetraquark, might gain further support.
Unveiling new forms of matter: The discovery of tetraquarks opens up the possibility of even more exotic forms of hadronic matter, such as pentaquarks and hexaquarks. These states could exhibit novel properties and further challenge our understanding of the strong force. Their study could reveal new symmetries and principles governing the organization of quarks within hadrons.
Impacting astrophysical models: Exotic hadrons like tetraquarks could play a role in extreme astrophysical environments, such as neutron stars and the early universe. Their presence could influence the equation of state of dense matter and affect processes like neutron star cooling and the evolution of the early universe. Understanding tetraquark properties is crucial for building accurate models of these extreme environments.
In summary, discovering more tetraquark states would provide crucial experimental data to test and refine our theoretical models of the strong force and QCD. It could lead to a deeper understanding of quark confinement, the emergence of hadronic matter, and potentially impact our understanding of the universe on both microscopic and macroscopic scales.

Yes, bbcc tetraquarks could theoretically exist as both bound states and unbound resonances. The distinction is crucial:
Bound state: A bbcc tetraquark bound state would have a mass lower than the combined mass of the lightest Bc meson pair it could decay into. This means it would be stable against strong decays and could only decay through weaker interactions like electromagnetic or weak processes, resulting in a longer lifetime.
Unbound resonance: An unbound resonance has a mass above the relevant Bc meson threshold, making it unstable against strong decays. These resonances would decay rapidly, typically exhibiting broad widths in their mass spectra.
Here are some experimental signatures to differentiate between the two:
For bound states:
Narrow width in the mass spectrum: Bound states, due to their longer lifetimes, would appear as narrow peaks in the invariant mass spectrum of their decay products. This narrow width is a direct consequence of the Heisenberg uncertainty principle, relating lifetime and energy (mass) uncertainty.
Production through different mechanisms: Bound states, being more tightly bound, might be produced directly in high-energy collisions, similar to conventional mesons. This is in contrast to resonances, which often arise from the interaction of their decay products.
Specific decay channels: Bound states would decay through specific channels allowed by the conservation laws and their quantum numbers. Observing these unique decay modes with the expected branching ratios would strongly support their identification as bound states.
For unbound resonances:
Broad width in the mass spectrum: Resonances, being short-lived, would manifest as broad peaks in the invariant mass spectrum, reflecting their rapid decay.
Production near the threshold: Unbound resonances are often produced more abundantly near the threshold of their decay products, indicating their formation from the interaction of these particles.
Interference patterns: The presence of unbound resonances can lead to interference patterns in the mass spectra of their decay products, arising from their quantum mechanical nature.
Experimental challenges:
Distinguishing between bound states and resonances experimentally can be challenging, especially for tetraquarks with heavy quarks like bbcc. The high mass of these states requires high-energy collisions for production, and their decay products can be difficult to detect and reconstruct accurately. Sophisticated analysis techniques are needed to extract their properties from the experimental data.

The study of bbcc tetraquark decays, with their intricate multi-particle final states and involvement of both strong and weak interactions, presents a unique opportunity to inspire the development of novel algorithms for simulating particle interactions in extreme environments. Here are some potential avenues:
Improved Monte Carlo event generators: Simulating the production and decay of tetraquarks requires sophisticated Monte Carlo event generators that accurately model the underlying QCD processes. This research can drive the development of new algorithms for these generators, incorporating:
Multi-particle final states: Efficiently handling the complex kinematics and correlations of multi-particle final states in tetraquark decays.
Interplay of strong and weak interactions: Accurately simulating the interplay of strong and weak interactions, crucial for describing both production and decay processes.
Relativistic effects: Incorporating relativistic effects, essential for accurately describing the high-energy particles involved.
Advanced data analysis techniques: Extracting information about tetraquark properties from experimental data requires advanced data analysis techniques. This research can inspire the development of new algorithms for:
Signal extraction: Efficiently separating the signal of tetraquark decays from background noise.
Mass spectrum fitting: Accurately fitting the mass spectra of tetraquark decay products, considering their widths and potential interference patterns.
Angular distribution analysis: Analyzing the angular distributions of decay products to determine the spin and parity of the tetraquark.
Applications to other extreme environments: The algorithms developed for simulating tetraquark decays can be adapted and applied to other extreme environments where similar particle interactions occur, such as:
Heavy-ion collisions: Simulating the formation and evolution of the quark-gluon plasma, a state of matter thought to have existed in the early universe.
Neutron star interiors: Modeling the properties of dense nuclear matter and the interactions of particles within neutron stars.
By pushing the boundaries of particle physics simulations, this research can lead to a deeper understanding of not only tetraquarks but also the fundamental forces and particles that govern the universe. The development of new algorithms will have far-reaching applications in various fields, from high-energy physics to astrophysics and cosmology.

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