Heavy Baryons Research Articles

Search for the doubly heavy baryon decaying to * *The project support from CERN and from the national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); MOST and NSFC (China); CNRS/IN2P3 (France); BMBF, DFG and MPG (Germany); INFN (Italy); NWO (Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MICINN (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); DOE NP and

A first search for the decay is performed by the LHCb experiment with a data sample of proton-proton collisions, corresponding to an integrated luminosity of 9 fb−1 recorded at centre-of-mass energies of 7, 8, and 13 TeV. Two peaking structures are seen with a local (global) significance of and standard deviations at masses of 6571 and 6694 MeV/, respectively. Upper limits are set on the baryon production cross-section times the branching fraction relative to that of the decay at centre-of-mass energies of 8 and 13 TeV, in the and in the rapidity and transverse-momentum ranges from 2.0 to 4.5 and 0 to , respectively. Upper limits are presented as a function of the mass and lifetime.

One-loop analysis of the interactions between doubly charmed baryons and Nambu-Goldstone bosons

The interactions between the spin-1/2 doubly charmed baryons and Nambu-Goldstone bosons are analyzed within a manifestly relativistic baryon chiral perturbation theory up to next-to-next-to leading order, by using the so-called extended-on-mass-shell scheme. We utilize heavy diquark-antiquark symmetry to estimate the low-energy constants in the chiral effective Lagrangians. The S- and P-wave scattering lengths are predicted. We find that those diagrams, vanishing exactly in the heavy-quark limit, do contribute slightly to the S-wave scattering lengths in reality. The influence of the spin-3/2 doubly charmed baryons, as heavy-quark spin partners of the spin-1/2 ones, on the scattering lengths is discussed as well. Finally, S-wave phase shifts for elastic scattering processes are presented in the energy region near threshold. Our results in this work will not only be very useful for performing chiral extrapolations of future lattice QCD data, but also provide us chiral inputs for the investigation of the spectroscopy of doubly heavy baryons.

Study of singly heavy baryon lifetimes

We study the inclusive decay widths of singly heavy baryons with the improved bag model in which the unwanted center-of-mass motion is removed. Additional insight is gained by comparing the charmed and bottom baryons. We discuss the running of the baryon matrix elements and compare the results with the non-relativistic quark model (NRQM). While the calculated two-quark operator elements are compatible with the literature, those of the four-quark ones deviate largely. In particular, the heavy quark limit holds reasonably well in the bag model for four-quark operator matrix elements but is badly broken in the NRQM. We predict 1 − τ (Ωb)/τ( {Lambda}_b^0 ) = (8.34 ± 2.22)% in accordance with the current experimental value of left({11.5}_{-11.6}^{+12.2}right)% and compatible with (13.2 ± 4.7)% obtained in the NRQM. We find an excellent agreement between theory and experiment for the lifetimes of bottom baryons. We confirm that {Omega}_c^0 could live longer than {Lambda}_c^{+} after the dimension-7 four-quark operators are taken into account. We recommend to measure some semileptonic inclusive branching fractions in the forthcoming experiments to discern different approaches. For example, we obtain mathcal{BF}left({Xi}_c^{+}to X{e}^{+}{nu}_eright) = (8.57±0.49)% and mathcal{BF}left({Omega}_c^0to X{e}^{+}{nu}_eright) = (1.88 ± 1.69)% in sharp contrast to mathcal{BF}left({Xi}_c^{+}to X{e}^{+}{nu}_eright) = left({12.74}_{-2.45}^{+2.54}right)% and mathcal{BF}left({Omega}_c^0to X{e}^{+}{nu}_eright) = left({7.59}_{-2.24}^{+2.49}right)% found in the NRQM.

Baryonic models of ultra-low-mass compact stars for the central compact object in HESS J1731-347

The recent attempt on mass and radius inference of the central compact object within the supernova remnant HESS J1731-347 suggests for this object an unusually low mass of M=0.77−0.17+0.20M⊙ and a small radius of R=10.4−0.78+0.86km. We explore the ways such a result can be accommodated within models of dense matter with heavy baryonic degrees of freedom which are constrained by the multi-messenger observations. We find that to do so using only purely nucleonic models, one needs to assume a rather small value of the slope of symmetry energy Lsym. Once heavy baryons are included higher values of the slope Lsym become acceptable at the cost of a slightly reduced maximum mass of static configuration. These two scenarios are distinguished by the particle composition and will undergo different cooling scenarios. In addition, we show that the universalities of the I-Love-Q relations for static configurations can be extended to very low masses without loss in their accuracy.

Strong decay properties of single heavy baryons ΛQ, ΣQ and ΩQ

Motivated by recent progresses in experiments in searching for the [Formula: see text] baryons, we systematically analyze the strong decay behaviors of single heavy baryons [Formula: see text], [Formula: see text] and [Formula: see text]. The two-body strong decay properties of [Formula: see text]-wave, [Formula: see text]-wave and some [Formula: see text]-wave states are studied with the [Formula: see text] model. The results support assigning the recently observed [Formula: see text] and [Formula: see text] as the 2S([Formula: see text]) and 1D([Formula: see text]) states, respectively. In addition, the quantum numbers of many other experimentally observed baryons are also suggested according to their strong decays. Finally, some baryons which have good potentials to be observed in experiments are predicted and the possible decay channels for searching for these predicted states are also suggested.

Mass spectroscopy and decay properties of Ξcb, Ξbb baryons

Using the Hypercentral Constituent Quark Model (hCQM), the mass spectra of doubly heavy baryons [Formula: see text] and [Formula: see text] are determined. The model describes an interaction inside the baryonic system. Screened potential has been considered as confining potential with color-Coulomb potential to enumerate the masses of baryonic states. Regge trajectories have been plotted in [Formula: see text] plane. The properties like magnetic moment and radiative decay width have been determined using the obtained results.

Study on the weak decay between two heavy baryons {mathcal {B}}_i(frac{1}{2}^+)rightarrow {mathcal {B}}_f(frac{3}{2}^+) in the light-front quark model

In this work, we study the weak decay between two heavy baryons {mathcal {B}}_i(frac{1}{2}^+)rightarrow {mathcal {B}}_f(frac{3}{2}^+) in the light-front quark model where three-quark picture is employed for baryon. We derive general form of transition amplitude of {mathcal {B}}_i(frac{1}{2}^+)rightarrow {mathcal {B}}_f(frac{3}{2}^+), and analyze two specific cases of transitions: the weak decays of single heavy baryon Sigma _{b} rightarrow Sigma _{c}^* and the decays of double-charmed baryon Xi _{cc}rightarrow Sigma _{c}^*(Xi _{c}^*). We compute the hadronic form factors for the transitions and apply them to study the decay widths of the semi-leptonic {mathcal {B}}_i(frac{1}{2}^+)rightarrow {mathcal {B}}_f(frac{3}{2}^+) lbar{nu }_l and non-leptonic {mathcal {B}}_i(frac{1}{2}^+)rightarrow {mathcal {B}}_f(frac{3}{2}^+)M. Previously we studied the transition Sigma _{b} rightarrow Sigma _{c}^* with the quark–diquark picture of baryon in the light-front quark model. Here we revisit this transition with three-quark picture of baryon. At the quark level, the transition Sigma _{b} rightarrow Sigma _{c}^* is induced by the brightarrow c transition.The subsystem of the two unchanged light quarks which possesses definite and same spin in initial and final state can be viewed as a spectator, so the spectator approximation can be applied directly. For the weak decay of doubly charmed baryon Xi _{cc}, a c quark decays to a light quark q_1, so both the initial state cc and final state q_1q_2 (q_1 and the original q_2 in initial state may be the same flavor quarks) which possess definite spin are no longer spectators. A rearrangement of quarks for initial and final states is adopted to isolate the unchanged subsystem cq_2 which can be viewed as the spectator approximately. Future measurements on these channels will constrain the nonperturbative parameter in the wavefunctions and test the model predictions.

Systematic analysis of strange single heavy baryons and * *Supported by the National Natural Science Foundation of China (11675265, 12175068), the Continuous Basic Scientific Research Project (WDJC-2019-13), the Leading Innovation Project (LC 192209000701) and the Central Government Guidance Funds for Local Scientific and Technological Development of China (Guike ZY22096024)

Motivated by the experimental progress in the study of heavy baryons, we investigate the mass spectra of strange single heavy baryons in the λ-mode, using the relativistic quark model and the infinitesimally shifted Gaussian basis function method. We show that experimental results are well captured using the predicted masses. The root mean square radii and radial probability density distributions of the wave functions are analyzed in detail. Meanwhile, the mass spectra allow us to successfully construct the Regge trajectories in the plane. We also preliminarily assign quantum numbers to the recently observed baryons, including , , , , , , , , , , , and . Finally, the spectral structure of strange single heavy baryons is discussed. Accordingly, we predict several new baryons that may be observed in forthcoming experiments.

Baryons and antibaryons in compressed nuclear matter

In this work we discuss the in-medium properties of baryons and antibaryons in nuclear matter at densities beyond saturation. We focus the attention on the in-medium optical potentials of heavy baryons with strangeness content. That is, the hyperons Λ, Σ with strangeness S=-1 and the cascade particle Ξ with S=-2 . The particular treatment of the hyperons inside compressed matter is crucial in order to understand the in-medium modifications of baryons in matter conditions that may occur in the interior of neutron stars. We dicsuss further the properties of their antiparticles, since there are experimental data for the nucleonic sector (S=0) while for the strangeness sector (S=-1,-2) experimental information will be available in the close future at the new facilities, for instance, at FAIR and J-PARC.

Mass spectra of doubly heavy tetraquarks in diquark−antidiquark picture* *Supported by the National Natural Science Foundation of China under the No. 12165017.

Inspired by the recent observation of the first doubly charmed tetraquark T cc , we apply the linear Regge relation and mass scaling to study low-lying mass spectra of the doubly heavy tetraquark in a heavy-diquark−light-antidiquark picture. The measured data and other compatible estimates of ground-state masses of doubly heavy baryons are employed to evaluate masses of heavy diquark M QQ (Q = c, b) and the D/D s meson masses are used in mass scaling to determine the hyperfine mass splitting. Our mass computation indicates that all low-lying states of doubly heavy tetraquarks are unstable against strong decays to two heavy-light mesons, except for the ground states of nonstrange bb tetraquarks.

Strong decays of singly heavy baryons from a chiral effective theory of diquarks

A chiral effective theory of scalar and vector diquarks is formulated, which is based on $SU(3)_R\times SU(3)_L$ chiral symmetry and includes interactions between scalar and vector diquarks with one or two mesons. We find that the diquark interaction term with two mesons breaks the $U(1)_A$ and flavor $SU(3)$ symmetries. To determine the coupling constants of the interaction Lagrangians, we investigate one-pion emission decays of singly heavy baryons $Qqq$ ($Q=c, b$ and $q=u,d,s$), where baryons are regarded as diquark--heavy-quark two-body systems. Using this model, we present predictions of the unobserved decay widths of singly heavy baryons. We also study the change of masses and strong decay widths of singly heavy baryons under partial restoration of chiral symmetry.

Doubly heavy tetraquark multiplets as heavy antiquark-diquark symmetry partners of heavy baryons

Symmetries play important roles in the understanding of hadron structures and spectroscopy. Motivated by the discovery of the doubly charmed tetraquark ${T}_{cc}^{+}(3875)$, we study the ground states of the doubly heavy tetraquarks with the QCD inspired heavy antiquark-diquark symmetry in the constituent quark model. Six ground states of ${T}_{QQ}(Q=c,b)$ are predicted and the lightest ${T}_{cc}$ state has a mass of $3875.8\ifmmode\pm\else\textpm\fi{}7.6\text{ }\text{ }\mathrm{MeV}$ and spin-parity ${1}^{+}$, which are consistent with those of the observed ${T}_{cc}^{+}(3875)$. In addition, the magnetic moments of the predicted tetraquarks ${T}_{cc}^{+}(3876)$ and ${T}_{bb}^{\ensuremath{-}}(10396)$ are also estimated in the same model, which provide further information to distinguish the structures of the ${T}_{QQ}$ states.

Systematic analysis of single heavy baryons ΛQ, ΣQ and ΩQ

Motivated by great progresses in experiments in searching for the heavy baryons, we systematically analyze the mass spectra and root mean square radius of single heavy baryons ΛQ, ΣQ and ΩQ. The calculations of the mass spectra are carried out in the frame work of relativized quark model, where the baryon is regarded as a three-body system of quarks. Our results show that the mass of single heavy baryon with λ-mode is lower than those of the ρ-mode and λ-ρ mixing mode, which indicates that the lowest state is dominated by the λ-mode. Basing on this research, we systematically calculate the mass spectra and the root mean square radius of the baryons with λ excited mode. With these predicated mass spectra, the Regge trajectories in the (J, M2) plane are constructed, and the slopes, intercepts of the Regge trajectories are obtained by linear fitting. It is found that all available experimental data are well reproduced by model predictions and fit nicely to the constructed Regge trajectories.

Supernova axion emissivity with Δ(1232) resonance in heavy baryon chiral perturbation theory

In this paper, we evaluate the energy loss rate of supernovae induced by the axion emission process $\pi^- + p \to n + a$ with the $\Delta(1232)$ resonance in the heavy baryon chiral perturbation theory for the first time. Given the axion-nucleon-$\Delta$ interactions, we include the previously ignored $\Delta$-mediated graphs to the $\pi^- + p \to n + a$ process. In particular, the $\Delta^0$-mediated diagram can give a resonance contribution to the supernova axion emission rate when the center-of-mass energy of the pion and proton approaches the $\Delta(1232)$ mass. With these new contributions, we find that for the typical supernova temperatures, compared with the earlier work with the axion-nucleon (and axion-pion-nucleon contact) interactions, the supernova axion emissivity can be enhanced by a factor of $\sim$4(2) in the Kim-Shifman-Vainshtein-Zakharov model and up to a factor of $\sim$5(2) in the Dine-Fischler-Srednicki-Zhitnitsky model with small $\tan\beta$ values. Remarkably, we notice that the $\Delta(1232)$ resonance gives a destructive contribution to the supernova axion emission rate at high supernova temperatures, which is a nontrivial result in this study.

Mass spectra of double-bottom baryons

Based on the relativistic quark model and the infinitesimally shifted Gaussian basis function method, we investigate the mass spectra of double-bottom baryons systematically. In the [Formula: see text]-mode which appears lower in energy than the other excited modes, we obtain the allowed quantum states and perform a systematic study of the mass spectra of the [Formula: see text] and [Formula: see text] families. We analyze the root mean square radii and quark radial probability density distributions to deeply understand the structure of the heavy baryons. Meanwhile, the mass spectra allow us to successfully construct the Regge trajectories in the [Formula: see text] plane. We also predict the masses of the ground states of double-bottom baryons and discuss the differences between the structures of our spectra and those from other theoretical methods. At last, the shell structure of the double-bottom baryon spectra is shown from which one could get a bird’s-eye view of the mass spectra. In this paper, we also make a hypothesis that the heavy baryon excitation may be dominated by the excitation of heavy quarks in the heavy quark limit. It could help to deepen the understanding of heavy baryons structure.

Twist-2 light-quark distribution functions in a singly heavy baryon in the largeNclimit

AbstractA singly heavy baryon can be considered as a state consisting of the Nc − 1 light valence quarks that create the pion mean field in the large Nc limit. In the limit of the infinitely heavy quark mass, a heavy quark inside a singly heavy baryon is regarded as a mere static color source. It is required only to make the singly heavy baryon a color singlet. Thus, the Nc − 1 valence quarks govern quark dynamics inside the singly heavy baryon. Within this pion mean field framework, we investigate the twist-2 unpolarized and longitudinally polarized light-quark distribution functions inside charmed and bottom baryons at a low renormalization point. We observe that the light quarks inside a heavy baryon carry less momentum than those inside a nucleon. This feature is more prominent as the heavy quark mass increases. We discuss the baryon sum rule, momentum sum rule, and the Bjorken spin sum rule for singly heavy baryons. We also discuss the inequality conditions for the quark distribution functions. In addition, we present the results for the light-quark quasi-distribution functions.

Hadronic structure on the light front. IV. Heavy and light baryons

This work is a continuation in our series of papers, that addresses quark models of hadronic structure on the light front. The chief focus of this paper is the quantum-mechanical solution of the three-quark model Hamiltonian, describing baryons. In Jacobi coordinates, we use a harmonic oscillator basis for the transverse directions. For the longitudinal momentum fractions $x_i$, the pertinent basis follows from quantum mechanics in a "triangular cup" potential, which we solve exactly. We calculate the masses and light front wave functions for the flavor symmetric $\frac 32^+$ baryons $bbb,ccc,sss,uuu$.

Chromopolarizabilities of fully heavy baryons

We compute the chromopolarizabilities of the fully heavy baryons ${\mathrm{\ensuremath{\Omega}}}_{QQ{Q}^{\ensuremath{'}}}$ ($Q,{Q}^{\ensuremath{'}}=b$, $c$) in the framework of potential nonrelativistic quantum chromodynamics. At leading order, the fully heavy hadrons are considered as ground chromo-Coulombic bound states. We find that the chromopolarizability ${\ensuremath{\beta}}_{\mathrm{\ensuremath{\Omega}}}$ of a fully heavy baryon $QQQ$ is 2.6 times the chromopolarizability ${\ensuremath{\beta}}_{\ensuremath{\psi}}$ of the quarkonium $\overline{Q}Q$ with the same heavy quark flavor $Q$. This result is accurate up to the correction of the order 0.3 for $Q=b$ and provides an order-of-magnitude estimate for $Q=c$. We discuss the dependence of the ratio ${\ensuremath{\beta}}_{\mathrm{\ensuremath{\Omega}}}/{\ensuremath{\beta}}_{\ensuremath{\psi}}$ on the heavy quark mass ${m}_{Q}$ and the strong coupling constant ${\ensuremath{\alpha}}_{s}$ as well as on the ratio of the masses ${m}_{{Q}^{\ensuremath{'}}}/{m}_{Q}$, in the case not all quarks in the baryon are identical. Since the chromopolarizability of heavy hadrons defines the strength of their interaction at low energies mediated by soft gluons, which at long range hadronize into pairs of pions and kaons, our findings argue in favor of the existence of near-threshold states composed of pairs of fully heavy baryons.

Invisible charm exotica

One possible interpretation of two narrow $\Omega^0_c$ states reported by the LHCb Collaboration at CERN in 2017 is that they are pentaquarks belonging to a $\overline{\boldsymbol{15}}$ exotic SU(3) representation, as predicted by the Chiral Quark--Soliton Model. If so, there must exist a number of other exotic states since the model predicts three different $\overline{\boldsymbol{15}}$ multiplets of heavy baryons. We show, that depending on the soliton spin $J$, these states are either very narrow or very broad. This explains why they might have escaped experimental observation. Furthermore, we show that the lightest members of these multiplets are stable against two body strong decays.

Light quark decays of doubly heavy baryons in light front approach

We explore the semileptonic and nonleptonic decays of doubly heavy baryons (Omega _{cc}^{(*)+},Omega _{bb}^{(*)0},Omega _{bc}^{(*)-},Omega _{bc}^{prime 0}) induced by the srightarrow u transition. Hadronic form factors are parametrized by transition matrix elements and are calculated in the light front quark model. With the form factors, we make use of helicity amplitudes and analyze semileptonic and nonleptonic decay modes of doubly heavy baryons. Benchmark results for partial decay widths, branching fractions, forward–backward asymmetries and other phenomenological observables are derived. We find that typical branching fractions for semileptonic decays into ell bar{nu } are at the order 10^{-7}-10^{-8} and the ones for nonleptonic decays are at the order 10^{-5}, which are likely detectable such as in LHCb experiment. With the potential data accumulated in future, our results may help to shape our understanding of the decay mechanism in the presence of two heavy quarks.