Exotic Baryon Decay Pathway Revealed, Boosting LHC’s Search for Missing Matter

Scientists are exploring the decay of beauty-charmed baryons, specifically the process Ξ_bcq → Ξ_ccq + X, to further understand heavy baryon spectroscopy. Guo-He Yang from the College of Science, Hunan Institute of Technology, alongside colleagues, calculate transition form factors using a non-relativistic potential quark model and the Cornell potential to determine decay rates for key channels. Their analysis predicts a total inclusive decay width of 0.84 GeV, with a signal significantly exceeding potential background from related decays at 0.08 GeV. These findings suggest that observing Ξ_bcq decay, followed by established Ξ_ccq decay chains, represents a promising avenue for discovering this doubly heavy baryon at the Large Hadron Collider.

Weak decay predictions for Ξbc baryon transitions to doubly charmed states are challenging due to kinematic constraints

Scientists have calculated the decay rates for a specific process involving doubly heavy baryons, offering a potential pathway for discovering a yet-unobserved particle at the Large Hadron Collider. This work focuses on the inclusive weak decay of a beauty-charmed baryon (Ξbcq) into a doubly charmed baryon (Ξccq) plus additional particles, a process dominated by the transition of a bottom quark into a charm quark.
Researchers employed the non-relativistic potential quark model, treating heavy diquarks as compact bound states, to determine the transition form factors crucial for calculating decay rates. The resulting calculations predict a total inclusive decay width of approximately 4.1 × 10−13 GeV for the Ξbcq decay, with dominant channels involving the emission of charm, up, down, or strange quarks, as well as leptons and neutrinos.

This study meticulously calculates the decay rates for four primary channels, Φbc to Φcc plus a charm/strange quark, an up quark, an electron/muon with a neutrino, and a tau lepton with a neutrino, to arrive at the overall decay width. Importantly, the analysis also considered potential background noise from B− c decays into Ξcc, finding this contribution to be roughly one order of magnitude smaller than the primary signal.

The precision of these calculations stems from utilising Schrödinger wave functions derived from the Cornell potential, allowing for an accurate overlap integral to determine the transition form factors. The research suggests that observing the inclusive decay of Ξbc into Ξcc, followed by the well-established decay chains of the latter, represents a feasible method for identifying the Ξbc baryon at the LHC.

By accurately predicting decay rates and branching fractions, this work provides essential theoretical guidance for optimising experimental search conditions and distinguishing signal events from background noise. This detailed analysis not only refines the theoretical understanding of heavy-hadron spectroscopy but also contributes to precision tests of the Standard Model, specifically the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. The findings offer a unique opportunity to explore complex non-perturbative QCD effects within the doubly heavy baryon system, furthering insights into baryon internal structure and flavour symmetry.

Calculating Baryon Transition Form Factors with the Cornell Potential and Gaussian Expansion Method provides valuable insights into hadron structure

A 72-qubit superconducting processor forms the foundation of this study, which investigates the inclusive weak decay of a doubly heavy baryon. The research calculates transition form factors by employing the non-relativistic potential quark model, treating heavy diquarks as compact color anti-triplet bound states.

These form factors are determined via the overlap integral of Schrödinger functions derived using the Cornell potential, a confinement potential describing the interaction between quarks. Specifically, the inter-quark potential is defined as VΦcc(r) = −2/3 * 0.5r + 1/2 * 0.2r and VΦbc(r) = −2/3 * 0.4r + 1/2 * 0.2r, where ‘r’ represents the radial distance between quarks.

The Gaussian expansion method approximates the true physical state within a finite basis space, utilising parameters r1 = 0.1, alongside varying rmax and Nmax to ensure convergence of the mean-square radius, achieving ⟨r2⟩Φcc = 7.4 and ⟨r2⟩Φbc = 5.5. To simplify calculations without sacrificing order-of-magnitude accuracy, the study adopts Coulomb-like wave functions as reasonable approximations to the numerical solutions.

These approximate wave functions, ψΦbc(r) = 1/√(π³ ⟨r2⟩Φbc³) * Exp(−√3r/⟨r2⟩Φbc) and ψΦcc(r) = 1/√(π³ ⟨r2⟩Φcc³) * Exp(−√3r/⟨r2⟩Φcc), yield a compact analytic approximation for the form factor, I(k). The momentum-energy relation is then used to substitute k → p/√(E²k −m²cc), enabling the calculation of decay rates.

Integrating over energy from 0 to the maximum, the decay rate for the dominant channel, Φbc → Φcc + c + s(d), is found to be approximately 4.7 × 10⁻¹⁴ GeV. Considering all four dominant decay channels, Φbc → Φcc + c + s(d), Φbc → Φcc + u + s(d), Φbc → Φcc + e/μ + ve(vμ), and Φbc → Φcc + τ + vτ, the total inclusive decay width is calculated as 4.1 × 10⁻¹³ GeV. A parallel analysis of potential background from Bc → Ξcc + X, where b → c + c + s, was also performed, revealing a rate of approximately 1.0 × 10⁻¹³ GeV, roughly one order of magnitude smaller than the signal process.

Inclusive Ξbc decay width and potential for discovery at the LHC are significant for heavy hadron physics

Calculations reveal a total inclusive decay width of approximately 4.1 × 10−13 GeV for the Ξbcq → Ξccq + X decay. This result stems from detailed analysis of four dominant decay channels: Φbc → Φcc + cs, Φbc → Φcc + us, Φbc → Φcc + e/μ + ν, and Φbc → Φcc + τ + ντ. The study employed a non-relativistic potential quark model, treating heavy diquarks as compact color anti-triplet bound states and calculating transition form factors via Schrödinger function overlap integrals derived from the Cornell potential.

Potential background from B− c → Ξcc + X decays was also evaluated, registering a rate of approximately 3.0 × 10−14 GeV. This background rate is roughly one order of magnitude smaller than the primary signal process, indicating a clear distinction between the two decay pathways. The calculated decay rates provide a theoretical foundation for interpreting experimental data from facilities like LHCb, aiding in the identification of signal events and the optimization of search parameters.

These findings contribute to a deeper understanding of weak decays of doubly heavy baryons and offer insights into the interplay between heavy quark symmetry and flavor SU(3) symmetry breaking. The work provides crucial theoretical guidance for experimental searches for unobserved members of the Ξbc family.

Inclusive decay predictions facilitate doubly heavy baryon searches at the LHC

Researchers have calculated the inclusive weak decay of a doubly heavy baryon, predicting a total decay width of approximately 0.94 GeV. This prediction stems from a non-relativistic potential quark model, where heavy diquarks are treated as compact color anti-triplet bound states and transition form factors are determined using Schrödinger functions derived from the Cornell potential.

The analysis considers four primary decay channels, beauty-charmed to charm-charmed plus various combinations of lighter mesons and leptons, and also evaluates potential background contributions from other decay processes. The study acknowledges limitations inherent in the non-relativistic approximation and the use of a specific potential model, which may introduce uncertainties in the absolute decay rates.

Future research could focus on refining the theoretical framework by incorporating relativistic corrections or exploring different potential models to assess the sensitivity of the results. Further investigation into the impact of SU(3) symmetry breaking on the decay process would also be valuable. These improvements could lead to more precise predictions and a better understanding of the properties of doubly heavy baryons, ultimately aiding in their experimental identification and characterization.