Heavy Baryon Spectroscopy Research Articles

Overview of LHCb results on beauty and charm spectroscopy

We present a summary of new experimental results from LHCb experiment on the status of the charm spectroscopy using inclusive approaches and Dalitz plot analyses of B and Bs decays. We also summarize latest results on the spectroscopy of heavy baryons.

Spectroscopy of heavy baryons with heavy-quark symmetry breaking: Transition relations at next-to-leading order

Transition decay widths by one-pion emissions for excited heavy baryons with a single heavy (charm and bottom) quark are investigated by following the heavy-quark symmetry and its breaking effects at $\mathcal{O}(1/M)$ for a heavy-baryon mass $M$. Based on heavy-baryon effective theory, interaction Lagrangians for the heavy baryons with an axial-vector current induced by a pion are constructed. We show that the transition decay widths in several channels are related up to $\mathcal{O}(1/M)$. The results will be useful in the experimental study of excited heavy baryons.

Heavy baryon spectroscopy with relativistic kinematics

We present a comparative Faddeev study of heavy baryon spectroscopy with nonrelativistic and relativistic kinematics. We show results for different standard hyperfine interactions with both kinematics in an attempt to learn about the light quark dynamics. We highlight the properties of particular states accessible in nowadays laboratories that would help in discriminating between different dynamical models. The advance in the knowledge of light quark dynamics is a key tool for the understanding of the existence of exotic hadrons.

BARYON SPECTROSCOPY AND HEAVY QUARKS

Two topics are briefly reviewed in this talk: the decay of flavored hadrons or quarkonium states involving a baryon–antibaryon pair, and the spectroscopy of heavy baryons containing one, two or three heavy quarks. Some prospects for exotic heavy baryons are also discussed.

Heavy-baryon spectroscopy from lattice QCD

We use a four-dimensional lattice calculation of the full-QCD (quantum chromodynamics, the non-abelian gauge theory of the strong interactions of quarks and gluons) path integrals needed to determine the masses of the charmed and bottom baryons. In the charm sector, our results are in good agreement with experiment within our systematics, except for the spin-1/2 Ξ c c , for which we found the isospin-averaged mass to be Ξ c c to be 3665 ± 17 ± 14 − 78 + 0 MeV . We predict the mass of the (isospin-averaged) spin-1/2 Ω c c to be 3763 ± 19 ± 26 − 79 + 13 MeV . In the bottom sector, our results are also in agreement with experimental observations and other lattice calculations within our statistical and systematic errors. In particular, we find the mass of the Ω b to be consistent with the recent CDF measurement. We also predict the mass for the as yet unobserved Ξ b ′ to be 5955(27) MeV.

Towards an understanding of heavy baryon spectroscopy

The recent observation at CDF and D0 of Σ b , Σ b * and Ξ b baryons opens the door to the advent of new states in the bottom baryon sector. The states measured provide sufficient constraints to fix the parameters of phenomenological models. One may therefore consistently predict the full bottom baryon spectra. For this purpose we have solved exactly the three-quark problem by means of the Faddeev method in momentum space. We consider our guidance may help experimentalists in the search for new bottom baryons and their findings will help in constraining further the phenomenological models. We identify particular states whose masses may allow to discriminate between the dynamics for the light quark pairs predicted by different phenomenological models. Within the same framework we also present results for charmed, doubly charmed, and doubly bottom baryons. Our results provide a restricted possible assignment of quantum numbers to recently reported charmed-baryon states. Some of them are perfectly described by D-wave excitations with J P = 5/2+, as the Λ c (2880), Λ c (3055), and Λ c (3123).

New Predictions for Charmed and Bottom Baryons

I review the recent proposal that there are new isotriplet heavy baryons with masses approximately 2380 MeV and 5760 MeV. This prediction follows from the application of heavy spin-flavor and light SU(3) symmetries to the observed charmed and bottom baryon states. It also entails assumptions about the spin and parity quantum numbers of the observed states which are different than is commonly supposed. The discovery of such states would imply that the nonrelativistic constituent quark model is a poor predictor of heavy baryon spectroscopy. I update the analysis in light of new data which have become available.

Heavy baryon spectroscopy from the lattice.

The results of an exploratory lattice study of heavy baryon spectroscopy are presented. We have computed the full spectrum of the eight baryons containing a single heavy quark, on a $24^3\times 48$ lattice at $\beta=6.2$, using an $O(a)$-improved fermion action. We discuss the lattice baryon operators and give a method for isolating the contributions of the spin doublets $(\Sigma,\Sigma^*)$, $(\Xi',\Xi^*)$ and $(\Omega,\Omega^*)$ to the correlation function of the relevant operator. We compare our results with the available experimental data and find good agreement in both the charm and the beauty sectors, despite the long extrapolation in the heavy quark mass needed in the latter case. We also predict the masses of several undiscovered baryons. We compute the $\Lambda-\mbox{pseudoscalar meson}$ and $\Sigma-\Lambda$ mass splittings. Our results, which have errors in the range $ 10-30\%$, are in good agreement with the experimental numbers. For the $\Sigma^*-\Sigma$ mass splitting, we find results considerably smaller than the experimental values for both the charm and the beauty baryons, although in the latter case the experimental results are still preliminary. This is also the case for the lattice results for the hyperfine splitting for the heavy mesons.

Heavy baryon spectroscopy

We present the preliminary results of an exploratory study of heavy baryon spectroscopy, using the O(a)-improved fermionic action. Estimates of masses and splittings at the charm and beauty physical limit are reported.

Heavy Particle Spectroscopy in the Bag Model

The QCD motivated bag model is elaborated and applied to heavy quark-antiquark systems. The effect of coloured glue in the model is shown to explain the rapid cross-over of the static QQ̄ potential from the asymptotically free Coulomb region into the linear confinement regime. The spin-dependent force between static quarks is derived in Coulomb gauge from the exchange of a confined transverse gluon. The dimensional bag parameter ΛB = 235 MeV and the quark-gluon coupling constant α = 0.38 (as defined at rQQ̄ ∼ 0.2 fermi) are determined from a good fit of the cc̄ and bb̄ spectra. The fit is in serious disagreement with the widely accepted MIT parameters. As an important test of our model, we calculate the rich spectrum of (QQ̄ glue) states. In γ particle spectroscopy we predict a narrow (QQ̄ glue) state with exotic quantum numbers JPC = 1-+ below the BB̄ threshold. Its experimental confirmation would be the first direct evidence for coloured glue in the hadron spectrum.The spectroscopy of heavy baryons with naked charm and/or beauty is also developed. The potential energy of three heavy colour sources is determined from the bag model and the Schrödinger equation is solved by using the hyperspherical formalism.

Heavy baryon spectroscopy in the QCD bag model

The spectroscopy of heavy baryons with naked charm and/or beauty is developed. The potential energy of three heavy colour sources is determined from the QCD motivated bag model and the Schrödinger equation is solved by using the hyper-spherical formalism.