Heavy Baryon Masses Research Articles

Spectroscopy and Regge trajectories of heavy baryons in the relativistic quark-diquark picture

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.

Doubly heavy Baryons from QCD Spectral Sum Rules

We consider the ratios of doubly heavy baryon masses using Double Ratios of Sum Rules (DRSR), which are more accurate than the usual simple ratios used for getting hadron masses. Our results are comparable with the ones from potential models. The Xi^*_{QQ}-Xi_{QQ} splittings seem to behave like 1/M_Q and can only allow the electromagnetic decay Xi^*_{QQ} to Xi_{QQ}+gamma but not to Xi_{QQ}+ pi. Our results also show that the SU(3) mass-splittings are (almost) independent of the spin of the baryons and behave approximately like 1/M_Q, which could be understood from the QCD expressions of the corresponding two-point correlator. Our results can improved by including radiative corrections to the SU(3) breaking terms and can be tested, in the near future, at Tevatron and LHCb.

Mass-splittings of doubly heavy baryons in QCD

We consider (for the first time) the ratios of doubly heavy baryon masses (spin 3/2 over spin 1/2 and SU(3) mass-splittings) using double ratios of sum rules (DRSR), which are more accurate than the usual simple ratios often used in the literature for getting the hadron masses. In general, our results agree and compete in precision with potential model predictions. In our approach, the αs corrections induced by the anomalous dimensions of the correlators are the main sources of the ΞQQ∗–ΞQQ mass-splittings, which seem to indicate a 1/MQ behaviour and can only allow the electromagnetic decay ΞQQ∗→ΞQQ+γ but not to ΞQQ+π. Our results also show that the SU(3) mass-splittings are (almost) independent of the spin of the baryons and behave approximately like 1/MQ, which could be understood from the QCD expressions of the corresponding two-point correlator. Our results can improved by including radiative corrections to the SU(3) breaking terms and can be tested, in the near future, at Tevatron and LHCb.

Formula omitted] mass-splittings of heavy-baryons in QCD

We extract directly (for the first time) the charmed (C=1) and bottom (B=−1) heavy-baryons (spin 1/2 and 3/2) mass-splittings due to SU(3) breaking using double ratios of QCD spectral sum rules (QSSR) in full QCD, which are less sensitive to the exact value and definition of the heavy quark mass, to the perturbative radiative corrections and to the QCD continuum contributions than the simple ratios commonly used for determining the heavy baryon masses. Noticing that most of the mass-splittings are mainly controlled by the ratio κ≡〈s¯s〉/〈d¯d〉 of the condensate, we extract this ratio, by allowing 1σ deviation from the observed masses of the Ξc,b and of the Ωc. We obtain: κ=0.74(3), which improves the existing estimates: κ=0.70(10) from light hadrons. Using this value, we deduce MΩb=6078.5(27.4) MeV which agrees with the recent CDF data but disagrees by 2.4σ with the one from D0. Predictions of the ΞQ′ and of the spectra of spin 3/2 baryons containing one or two strange quark are given in Table 2. Predictions of the hyperfine splittings ΩQ∗−ΩQ and ΞQ∗−ΞQ are also given in Table 3. Starting for a general choice of the interpolating currents for the spin 1/2 baryons, our analysis favours the optimal value of the mixing angle b≃(−1/5–0) found from light and non-strange heavy baryons.

Masses and magnetic moments of triple heavy flavour baryons in hypercentral model

Triple heavy flavour baryons are studied using the hypercentral description of the three-body system. The confinement potential is assumed as hypercentral Coulomb plus power potential with power index p. The ground state (J P = ½+ and 3/2+) masses of heavy flavour baryons are computed for different power index, p starting from 0.5 to 2.0. The predicted masses are found to attain a saturated value with respect to variation in p beyond the power index p > 1.0. Using the spin-flavour structure of the constituting quarks and by defining effective mass of the confined quarks within the baryons, the magnetic moments are computed with no additional free parameters.

Single heavy flavour baryons using Coulomb plus a power law interquark potential

Properties of single heavy flavor baryons in a non-relativistic potential model with colour Coulomb plus a power law confinement potential have been studied using a simple variational method. The ground-state masses of single heavy baryons and the mass difference between the J P = $ {\frac{{3}}{{2}}}$ + and J P = $ {\frac{{1}}{{2}}}$ + states are computed using a spin-dependent two-body potential. Using the spin-flavour structure of the constituting quarks and by defining an effective confined mass of the constituent quarks within the baryons, the magnetic moments are computed. The masses and magnetic moments of the single heavy baryons are found to be in accordance with the existing experimental values and with other theoretical predictions. It is found that an additional attractive interaction of the order of -200 MeV is required for the antisymmetric states of $ \Lambda_{{Q}}^{}$ (Q $ \in$ c, b) . It is also found that the spin-hyperfine interaction parameters play a decisive role in hadron spectroscopy.

Heavy baryon spectroscopy in QCD

We perform a systematic study of the masses of charmed and bottom baryons in the framework of the QCD sum rule approach. Contributions of the operators up to dimension six are included in operator product expansion. The resulting heavy baryon masses from the calculations are well consistent with the experimental values, and predictions to the spectroscopy of the unobserved bottom baryons are also presented.

Mass and magnetic moments of the heavy flavored baryons with [formula omitted] in light cone QCD sum rules

Inspired by the results of recent experimental discoveries for charm and bottom baryons, the masses and magnetic moments of the heavy baryons with J P = 3 / 2 + containing a single heavy quark are studied within light cone QCD sum rules method. Our results on the masses of heavy baryons are in good agreement with predictions of other approaches, as well as with the existing experimental values. Our predictions on the masses of the states, which are not yet discovered in the experiments, can be tested in the future experiments. A comparison of our results on the magnetic moments of these baryons and the hyper central model predictions is presented.

Masses and magnetic moments of heavy flavour baryons in the hyper central model

Heavy flavour baryons containing one or two charm (beauty) quarks with light flavour combinations are studied using the hyper central description of the three-body system. The confinement potential is assumed as hyper central Coulomb plus power potential with a power index p. The ground state ( and ) masses of heavy flavour baryons are computed for different power indices, p starting from 0.5 to 2.0. The predicted masses are found to attain a saturated value with respect to the variation in p beyond the power index p > 1.0. Using the spin-flavour structure of the constituting quarks and by defining the effective mass of the confined quarks within the baryons, the magnetic moments are computed with no additional free parameters. The masses and magnetic moments of the single heavy and double heavy flavour baryons are found to be in accordance with other model predictions.

Masses of excited heavy baryons in the relativistic quark–diquark picture

The mass spectra of the excited heavy baryons consisting of two light (u,d,s) and one heavy (c,b) quarks are calculated in the heavy-quark–light-diquark approximation within the constituent quark model. The light quarks, forming the diquark, and the light diquark in the baryon are treated completely relativistically. The expansion in v/c up to the second order is used only for the heavy (b and c) quarks. The internal structure of the diquark is taken into account by inserting the diquark–gluon interaction form factor. An overall good agreement of the obtained predictions with available experimental data is found.

Chiral Lagrangian with heavy quark-diquark symmetry

We construct a chiral Lagrangian for doubly heavy baryons and heavy mesons that is invariant under heavy quark-diquark symmetry at leading order and includes the leading O(1/m_Q) symmetry violating operators. The theory is used to predict the electromagnetic decay width of the J=3/2 member of the ground state doubly heavy baryon doublet. Numerical estimates are provided for doubly charm baryons. We also calculate chiral corrections to doubly heavy baryon masses and strong decay widths of low lying excited doubly heavy baryons.

Masses of heavy baryons in the relativistic quark model

The masses of the ground state heavy baryons consisting of two light (u,d,s) and one heavy (c,b) quarks are calculated in the heavy-quark--light-diquark approximation within the constituent quark model. The light quarks, forming the diquark, and the light diquark in the baryon are treated completely relativistically. The expansion in v/c up to the second order is used only for the heavy (b and c) quarks. The diquark-gluon interaction is taken modified by the form factor describing the light diquark structure in terms of the diquark wave functions. An overall reasonable agreement of the obtained predictions with available experimental data and previous theoretical results is found.

Chiral extrapolation of lattice data for heavy baryons

The masses of heavy baryons containing a b quark have been calculated numerically in lattice QCD with pion masses which are much larger than its physical value. In the present work we extrapolate these lattice data to the physical mass of the pion by applying the effective chiral Lagrangian for heavy baryons, which is invariant under chiral symmetry when the light quark masses go to zero and heavy quark symmetry when the heavy quark masses go to infinity. A phenomenological functional form with three parameters, which has the correct behavior in the chiral limit and appropriate behavior when the pion mass is large, is proposed to extrapolate the lattice data. It is found that the extrapolation deviates noticably from the naive linear extrapolation when the pion mass is smaller than about 500MeV. The mass differences between Sigma_b and Sigma_b^* and between Sigma_b^{(*)} and Lambda_b are also presented. Uncertainties arising from both lattice data and our model parameters are discussed in detail. We also give a comparision of the results in our model with those obtained in the naive linear extrapolations.

Charm and botom baryon masses in the 1/N expansion

The masses of heavy quark baryons are studied in an expansion in 1/ N c , SU(3) flavor symmetry breaking, and heavy-quark symmetry breaking. Very accurate model-independent mass relations are obtained for charm and bottom baryons.

Baryon masses in the 1/ Nc expansion

The masses of baryons and heavy quark baryons are studied analytically in an expansion in 1/ N c , SU(3) flavor symmetry breaking, and heavy-quark symmetry breaking. The measured baryon masses are in striking agreement with the 1/ N c hierarchy.

Excited heavy baryon masses in HQET QCD sum rules

We construct the interpolating currents for the fourteen p-wave excited heavy baryons in the framework of heavy-quark effective theory (HQET). At the leading order in the 1/ m Q expansion these interpolating currents do not mix different states with the same J P with each other. We use QCD sum rule to calculate the masses of the p-wave excited J=1/2 spin doublet heavy baryons in the m Q →∞ limit. We discuss some implications of our results.

Excited heavy baryon spectrum in largeNcheavy quark effective theory

L=1 excited heavy baryon masses are analyzed by heavy quark and large N_c expansions. In heavy quark limit, mass is parameterized by \Lambda-bar and it is expanded further by spin-flavor breaking operators to the zeroth order of 1/N_c. Expanding coefficients will be fixed by more data on the excited baryons in the near future.

Quenched chiral perturbation theory for heavy baryons

Heavy baryon chiral perturbation theory is extended to include the effects of quenching. In this framework the leading nonanalytic dependence of the heavy baryon masses on the light quark masses is studied. The size of quenching effects is estimated by comparing the results of quenched and ordinary chiral perturbation theories. It is found that in general they can be large. This estimate is relevant to lattice simulations of the heavy baryon masses.

How strange a non-strange heavy baryon?

We give some general arguments in favor of the large magnitude of matrix elements of an operator associated with nonvalence quarks in heavy hadrons. We estimate matrix element 1 2 m Λ b 〈 Λ b | s ¯ s | Λ b 〉 ≃ 1 − 2 for Λ b baryon whose valence content is b, u, d quarks. This magnitude corresponds to a noticeable contribution of the strange quark into the heavy baryon mass 1 2 m Λ b 〈 Λ b | m s s ¯ s | Λ b 〉 ≃ 200 − 300 MeV. The arguments are based on the QCD sum rules and low energy theorems. The physical picture behind of the phenomenon is somewhat similar to the one associated with the large strange content of the nucleon where matrix element 〈 p | s ¯ s | p 〉 ≃ 1 by no means is small. We discuss some possible applications of the result.

QCD sum rules for heavy baryons at next-to-leading order in αS

We derive QCD sum rules for heavy baryons at leading order in $1/m_Q$ and at next-to-leading order in $\alpha_s$. The calculation involves the evaluation of four different perturbative three-loop diagrams which determine the $\alpha_s$-corrections to the Wilson coefficients of the leading term in the Operator Product Expansion (OPE). From the sum rules we obtain estimates for the masses and the residues of the heavy baryons $\Lambda_Q$ and $\Sigma_Q$. The perturbative $O(\alpha_s)$ corrections to the leading order spectral function amount to about $100%$, and they shift the calculated values for the baryon masses slightly upward. The residues are shifted upward by about $20-50%$. For the bound state energy $\bar\Lambda$ given by the difference of the heavy baryon mass and the pole mass of the heavy quark $m_Q$ we obtain $m_{\Lambda_Q}-m_Q=780 MeV$ and $m_{\Sigma_Q}-m_Q=950 MeV$. For the residues we find $|F_\Lambda|=0.028 GeV^3$ and $|F_\Sigma|=0.039 GeV^3$.