Jambul Gegelia, Ulf-G. Meißner, Dmitrij Siemens, De-Liang Yao
We calculate the width of the delta resonance at leading two-loop order in baryon chiral perturbation theory. This gives a correlation between the leading pion-nucleon-delta and pion-delta couplings, which is relevant for the analysis of pion-nucleon scattering and other processes.
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The Chiral String-Soliton Model is a joining of the two notions about the light chiral baryons: the chiral soliton models (like the Skyrme model) and the Quark-Gluon String models. The ChSS model is based on the Effective Chiral Lagrangian which was proposed in [arXiv:hep-ph/0306216]. We have studied the physical properties of the light chiral baryon within the framework of this ChSS model.
The chiral Lagrangian for baryons is formulated in an expansion in 1/N_c. The chiral Lagrangian implements the contracted spin-flavor symmetry of large-N_c baryons as well as nonet symmetry of the leading planar diagrams. Large-N_c consistency conditions ensure that chiral loop corrections are suppressed in 1/N_c through exact cancellation of chiral loop graphs to fixed orders in 1/N_c. Application of 1/N_c baryon chiral perturbation theory to the flavor-27 baryon mass splittings and the baryon axial vector currents are considered as examples.
We review applications of the Chiral Quark Soliton Model to heavy baryons and to doubly heavy tetraquarks.
This paper studies the leading chiral corrections to heavy quark-diquark symmetry predictions for doubly heavy baryon semileptonic decay form factors. We derive the coupling between heavy diquarks and weak current in the limit of heavy quark-diquark symmetry, and construct the chiral Lagrangian for doubly heavy baryons coupled to weak current. We evaluate chiral corrections to doubly heavy baryon zero-recoil semileptonic decay for both unquenched and partially quenched QCD. This theory is used to derive chiral extrapolation expressions for measurements of form factors of doubly heavy baryon ze…
The importance of exchange currents, and of conserving isotopic spin at both the quark and baryon levels in application of the chiral quark model to any calculation of baryon magnetic moments is emphasized.
A $1/\N$ expansion of the chiral Lagrangian for baryons is formulated and used to study the low-energy dynamics of baryons interacting with the pion nonet $π$, $K$, $η$ and $η^\prime$ in a combined expansion in chiral symmetry breaking and $1/\N$. Strong $CP$-violation is included. The chiral Lagrangian correctly implements nonet symmetry and contracted spin-flavor symmetry for baryons in the large $\N$ limit. The implications of nonet symmetry for low-energy baryon-pion interactions are described in detail. The procedure for calculating non-analytic pion-loop corrections to baryon amplitudes …
We establish exact relations between relativistic form factors and amplitudes for single-baryon processes and the corresponding quantities calculated in the framework of heavy baryon chiral perturbation theory. A crucial ingredient for the proper matching is the first complete treatment of baryon wave function renormalization in heavy baryon chiral perturbation theory.
After contrasting the low energy effective theory for the baryon sector with one for the Goldstone sector, I use the example of pion nucleon scattering to discuss some of the progress and open issues in baryon chiral perturbation theory.
An approach to baryons in the framework of the microscopic Generalized Nambu-Jona-Lasinio chiral potential quark model is considered and quite general arguments are given in favor of effective restoration of chiral symmetry in excited baryons.
We show that the recently constructed complete and ``minimal'' third order meson-baryon effective chiral Lagrangian can be further reduced from 84 to 78 independent operators.
We compute nonanalytical pion-loop corrections to baryon masses in a combined expansion in chiral symmetry breaking and 1/N_c, where N_c is the number of colors. Specifically, we compute flavor-27 baryon mass splittings at leading order in chiral perturbation theory. Our results, at the physical value N_c=3, are compared with the expressions obtained in heavy baryon chiral perturbation theory with no 1/N_c expansion.
To see whether heavy baryon and anti-baryon can form a bound state, the heavy baryonium, we study the interaction potential between them in terms of heavy baryon perturbation theory. The obtained potential is applied to calculate the heavy baryonium masses by solving Schrödinger equation. We find it is true that the heavy baryonium may exist in a reasonable choice of input parameters. The uncertainties remaining in the potential and their influences on the heavy baryonium mass spectrum are discussed.
The chiral SU(3) Lagrangian with the baryon octet and decuplet fields is considered. The Q^2 counterterms involving the decuplet fields are constructed. We derive the correlation of the chiral parameters implied by the 1/N_c expansion at leading order in QCD.
The chiral expansion of the one-loop corrections to baryon masses is examined in a generic meson-cloud model with meson-baryon form factors. For pion loops, the expansion is rapidly convergent and at fourth order in $m_π$ accurately reproduces the full integral. In contrast, the expansion is found to converge very slowly for kaon loops, raising questions about the usefulness of chiral expansions for kaon-baryon physics. Despite the importance of high-order terms, relations like that of Gell-Mann and Okubo are well satisfied by the baryon masses calculated with the full integral. The pion cloud…
We construct the general pion-nucleon SU(2) Lagrangian including both virtual photons and leptons for relativistic baryon chiral perturbation theory up to fourth order. We include the light leptons as explicit dynamical degrees of freedom by introducing new building blocks which represent these leptons.
I review the consequences of the chiral symmetry of QCD for the structure and dynamics of the low-lying baryons, with particular emphasis on the nucleon.
We investigate chiral properties of local (non-derivative) fields of baryons consisting of three quarks with flavor SU(3) symmetry. We construct explicitly independent local three-quark fields belonging to definite Lorentz and flavor representations. Chiral symmetry is spontaneously broken and therefore the baryon fields can have different chiral representations. It turns out that the allowed chiral representations are strongly correlated with the Lorentz group representations due to the color and spatial structure of the local three-quark fields. We discuss some implications of the allowed ch…
Baryon chiral perturbation theory as conventionally applied using dimensional regularization has a well-known problem with the convergence of the SU(3) chiral expansion. One can reformulate the theory equally rigorously using a momentum-space cutoff and we show that the convergence is thereby greatly improved for reasonable values of the cutoff. In effect, this is accomplished because the cutoff formalism removes the spurious physics of propagation at distance scales much smaller than the baryon size.
We study the masses of the doubly bottom baryons and the charmed bottom baryons up to $\mathcal{O}\left(p^{3}\right)$ in heavy baryon chiral perturbation theory. For the low-energy constants, $g_{A}$ was determined in the quark model, and we fit to the lattice QCD data to determine $m_{0}$, $c_{1}$, and $c_{7}$. We show the numerical results up to $\mathcal{O}\left(p^{3}\right)$, and our results are compared with other theoretical results.
We calculate chiral corrections to the semileptonic vector and axial quark coupling constants using a manifestly Lorentz covariant chiral quark approach up to order O(p4) in the two- and tree-flavor picture. These couplings are then used in the evaluation of the corresponding couplings which govern the semileptonic transitions between octet baryon states. In the calculation of baryon matrix elements we use a general ansatz for the spatial form of the quark wave function, without referring to a specific realization of hadronization and confinement of quarks in baryons. Matching the physical amp…
We study chiral symmetry aspects of the positive and negative parity baryons by identifying them with linear representations of the chiral group $SU(N_{f}) \otimes SU(N_{f})$. It is shown that there are two distinctive schemes: naive and mirror assignments. We construct linear sigma models for baryons in the two assignments and examine their physical implications. Then we investigate properties of the naive and mirror nucleons microscopically by using QCD interpolating fields. Finally, we propose experiments to distinguish the two chiral assignments for the nucleon.
We discuss the baryon-number susceptibility $χ_B$ and related topics which include the density fluctuations around the critical point of the chiral transition at finite temperature $T$ and baryon density $ρ_B$. Phenomenological implications of the density fluctuations near the first-order chiral transition at finite density are also discussed.
We calculate magnetic moments of light baryons and N -> Delta gamma transition characteristics using a manifestly Lorentz covariant chiral quark approach for the study of baryons as bound states of constituent quarks dressed by a cloud of pseudoscalar mesons.
We compute the spin asymmetry and polarization of the final-state baryon in its rest frame in two-body meson--baryon low-energy scattering with unpolarized initial state, to lowest non-trivial order in BChPT. The required absorptive amplitudes are obtained analytically at one-loop level. We discuss the polarization results numerically for several meson--baryon processes. Even at low energies above threshold, where BChPT can reasonably be expected to be applicable, sizable values of polarization are found for some processes.
The baryon magnetic and transition magnetic moments are computed in heavy baryon chiral perturbation theory in the large-N_c limit, where N_c is the number of colors. One-loop nonanalytic corrections of orders m_q^{1/2} and m_q ln m_q are incorporated into the analysis, where contributions of both intermediate octet and decuplet baryon states are explicitly included. Expressions are obtained in the limit of vanishing baryon mass differences and compared with the current experimental data. Furthermore, a comparison with conventional heavy baryon chiral perturbation theory is carried out for thr…
We present calculations of the decuplet baryon magnetic moments in the chiral quark model. As input we use parameters obtained in qualitatively accurate fits to the octet baryon magnetic moments studied previously. The values found for the magnetic moments of $Δ^{++}$ and $Ω^{-}$ are in good agreement with experiments. We finally calculate the total quark spin polarizations of the decuplet baryons and find that they are considerably smaller than what is expected from the non-relativistic quark model.
We construct the three-flavor Lorentz-invariant meson-baryon chiral Lagrangians at the order $p^4$, with which a full one-loop investigation may be performed. One obtains 540 independent terms. The processes with the minimal number of mesons and photons that this order Lagrangians may contribute to are also presented.
I show that in the large-N limit the ground state baryons with helicity h fall into an ((N-2h)/4,(N+2h)/4) irreducible representation of SU(2)XSU(2). This representation determines the absolute normalization of the ground state baryon axial vector couplings at large-N. Results map precisely to (spin-flavor) SU(4) results. For instance, I find g_A =(N+2)/3. As a consequence of this multiplet structure, chiral symmetry forbids pion transitions between the ground state baryons and other baryon towers in the large-N limit.
Finite-energy topological spherically symmetrical solutions of Chiral Born-Infeld Theory are studied. Properties of these solution are obtained, and a possible physical interpretation is also given. We compute static properties of baryons (mass,main radius, magnetic main radius, axial coupling constant) whose solutions can be interpreted as the baryons of QCD.
Within an extended chiral constituent quark formalism, we investigate contributions from all possible five-quark components in the octet baryons to the pion-baryon ($σ_{πB}$) and strangeness-baryon ($σ_{s B}$) sigma terms; $B \equiv N,~Λ,~Σ,~Ξ$. The probabilities of the quark-antiquark components in the ground-state baryon octet wave functions are calculated by taking the baryons to be admixtures of three- and five-quark components, with the relevant transitions handled {\it via} the $^{3}$P$_{0}$ mechanism. Predictions for $σ_{πB}$ and $σ_{s B}$ obtained by using input parameters taken from t…
In the framework chiral SU(3) quark model, the baryon spectra within the band of $N\leq 2$ are studied, and the effect of the confining potential in different configurations, namely the $Δ$-mode and Y-mode are compared. In the same way, the baryon spectra in the extended chiral SU(3) quark model, in which additional vector meson exchanges are introduced, are also calculated. It is shown that a reasonable baryon spectrum in the chiral SU(3) quark model can be achieved no matter whether the $Δ$-mode or the Y-mode confining potential is employed. In the extended chiral SU(3) quark model, several …
We perform the complete regularization of all Green functions with a single incoming and outgoing baryon to order q^3 in the low energy expansion for the SU(3) meson-baryon system in chiral perturbation theory. The divergences can be extracted in a chiral invariant manner by making use of the heat kernel representation of the propagators in d-dimensional Euclidean space.
We construct an effective hadronic model including single heavy baryons (SHBs) belonging to the $(\mathbf{3},\mathbf{3})$ representation under $\mbox{SU}(3)_L \times \mbox{SU}(3)_R$ symmetry, respecting the chiral symmetry and heavy-qaurk spin-flavor symmetry. When the chiral symmetry is spontaneously broken, the SHBs are divided into the baryons with negative parity of $\bar{\mathbf 3}$ representation under $\mbox{SU}(3)$ flavor symmetry which is the chiral partners to the ones with positive parity of ${\mathbf 6}$ representation. We determine the model parameters from the available experimen…
Mesonic fluctuations around the chiral solitons are investigated in the SU(3) chiral quark soliton model. Since the soliton takes the non-hedgehog shape for the hyperons and the hedgehog one for the non-hedgehog baryons in our approach, the fluctuations also change according to the baryonic state. The quantum corrections to the masses (the Casimir energies) are estimated for the octet and decuplet baryons. The lack of the confinement in this model demands the cutoff on the energy of the fluctuations. Under the assumption that the value of the cutoff energy is $2\times$(the lightest constituent…
We present in this talk recent results of the magnetic moments of the baryon antidecuplet within the framework of the chiral quark-soliton model in the chiral limit. The dynamic parameters of the model are fixed by using the experimental data for those of the baryon octet. Sum rules for the magnetic moments are derived. We found that the magnetic moments of the baryon antidecuplet have opposite signs to their charges. The magnetic moments of the neutral baryon antidecuplet turn out to be compatible with zero.
The chiral effective meson-baryon Lagrangian for the description of interactions between the doubly charmed baryons and Goldstone bosons is constructed up to the order of $q^{4}$. The numbers of linearly independent invariant monomials of $\mathcal{O}(q^2)$, $\mathcal{O}(q^3)$ and $\mathcal{O}(q^4)$ are 8, 32 and 218, in order. The obtained Lagrangian can be used to study the chiral dynamics and relevant phenomenology of the doubly charmed baryons at complete one-loop level in future. For completeness, the non-relativistic reduction of the Lagrangian is also discussed.
Motivated by the precision measurements of heavy flavor baryon masses, we analyze the modification of quark charge by employing the screening effect inside the baryon. In addition, we calculate the isospin mass splitting up to charmed baryons employing isospin symmetry breaking. Consequently, we obtain the masses, magnetic moments, and transition moments of $J^P=\frac{1}{2}^+$ and $\frac{3}{2}^+$ baryons to predict radiative decay widths for $\frac{1}{2}^{\prime +} \to \frac{1}{2}^+$ and $\frac{3}{2}^+\to \frac{1}{2}^{(\prime)+}$ transitions. Finally, we include the effects of state mixing in …
The approach of path integral hadronization, applied to a quark-diquark toy model, is used to derive an effective chiral meson-baryon Lagrangian. In this approach the Goldberger-Treiman relation, found at the quark-meson level, is re-established at the composite hadron level. For illu- strations, electromagnetic low energy characteristics of composite nucleons are estimated.
We study the 't Hooft coupling $g_{t}$ and the mass splitting of the ground-state baryons in a chiral quark model inspired by the large $N_{c}$ QCD. Depending on $g_{t}$ the Hartree wavefunction of light quark in baryons is used to map the mass hyperfine splittings for the octet and decuplet baryons. The 't Hooft coupling $g_{t}$ that reproduces the data of baryon masses is determined to be around $1.57$, which is small in the sense that $g_{t}^{2}/(4πN_{c})\ll $$1$.
A qualitative analysis of the chiral phase transition in QCD with two massless quarks and non--zero baryon density is performed. It is assumed that at zero baryonic density, $ρ=0$, the temperature phase transition is of the second order. Due to a specific power dependence of baryon masses on the chiral condensate the phase transition becomes of the first order at the temperature $T=T_{\mathrm{ph}}(ρ)$ for $ρ>0$. At temperatures $T_{\mathrm{cont}}(ρ) > T > T_{\mathrm{ph}}(ρ)$ there is a mixed phase consisting of the quark phase (stable) and the hadron phase (unstable). At the temperature $T = T…
Baryon chiral perturbation theory with explicit $Δ(1232)$ degrees of freedom is considered. Using the extended on-mass-shell renormalization scheme, a manifestly Lorentz-invariant effective field theory with a systematic power counting is obtained. As applications we discuss the mass of the nucleon, the pion-nucleon sigma term, and the pole of the $Δ$ propagator.
The charge radii of octet-baryons obtained in quenched lattice-QCD calculations are extrapolated within heavy-baryon chiral perturbation theory. Finite-range regularization (FRR) is applied to improve the convergence of the chiral expansion and to provide estimates of quenching artifacts. Lattice values of quark distribution radii and baryon charge radii for $\mpi^2$ in the range (0.1, 0.7)$\gev^2$ are described very well with FRR. Upon estimating corrections for both finite-volume and quenching effects, the obtained charge radii of the proton, neutron and $Σ^-$ are in good agreement with expe…
The baryon axial vector current is computed at one-loop order in large-N_c baryon chiral perturbation theory, where N_c is the number of colors. Loop graphs with octet and decuplet intermediate states are systematically incorporated into the analysis and the effects of the decuplet-octet mass difference and SU(3) flavor symmetry breaking are accounted for. As expected, large-N_c cancellations between different one-loop graphs are observed as a consequence of the large-N_c spin-flavor symmetry of QCD baryons. Fitting our analytical formulas against experimental data on baryon semileptonic decay…
The s-wave decay amplitude in the nonleptonic decay of baryons is analyzed within heavy baryon chiral perturbation theory in the large-N_c limit at one-loop order, where N_c is the number of color charges. Loop graphs with octet and decuplet intermediate states are systematically incorporated into the analysis and the effects of the decuplet-octet mass difference are accounted for. There are large-N_c cancellations between different one-loop graphs as a consequence of the large-N_c spin-flavor symmetry of QCD baryons. The predictions of large-N_c baryon chiral perturbation theory are in very g…
We report on recent progress on the chiral unitary approach, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV and meson baryon interaction up to the first baryonic resonances. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented, concretely the K^- p\toΛ(1405)γreaction and the N^\ast (1535)N^\ast(1535)πand ηcouplings.
We calculate the masses and sigma terms of the doubly charmed baryons up to next-to-next-to-next-to-leading order (i.e., $\mathcal{O}(p^4)$) in a covariant baryon chiral perturbation theory by using the extended-on-mass-shell renormalization scheme. Their expressions both in infinite and finite volumes are provided for chiral extrapolation in lattice QCD. As a first application, our chiral results of the masses are confronted with the existing lattice QCD data in the presence of finite volume corrections. Up to $\mathcal{O}(p^3)$ all relevant low energy constants can be well determined. As a c…
We compute the chiral corrections to octet baryon axial currents through ${\cal O}(p^3)$ in heavy baryon chiral perturbation theory, including both octet and decuplet baryon intermediate states. We include the latter in a consistent way by using the small scale expansion. We find that, in contrast to the situation at ${\cal O}(p^2)$, there exist no cancellations between octet and decuplet contributions at ${\cal O}(p^3)$. Consequently, the ${\cal O}(p^3)$ corrections spoil the expected scaling behavior of the chiral expansion. We discuss this result in terms of the $1/N_c$ expansion. We also c…
In this paper the stability of the hedgehog shape of the chiral soliton is studied for the octet baryon with the SU(3) chiral quark soliton model. The strangeness degrees of freedom are treated by a simplified bound-state approach, which omits the locality of the kaon wave function. The mean field approximation for the flavor rotation is applied to the model. The classical soliton changes shape according to the strangeness. The baryon appears as a rotational band of the combined system of the deformed soliton and the kaon.
The $O(p^4)$ calculation on pion-nucleon elastic scattering amplitude in EOMS scheme within covariant baryon chiral perturbation theory is reviewed. Numerical fits to partial wave amplitudes up to $\sqrt{s}=1.13$ GeV and 1.20 GeV are performed and the results are compared with previous studies.
We present the first heavy baryon chiral perturbation theory calculation at ${\mathcal O}(p^4)$ for the spin-dependent amplitudes for virtual Compton scattering off the nucleon, and extract the ${\cal O}(p^4)$ order results for the generalized spin polarizabilities of the nucleon.
New results on baryon structure and spectrum developed in collaboration with Dan Riska [1-4] are reported. The main idea is that beyond the chiral symmetry spontaneous breaking scale light and strange baryons should be considered as systems of three constituent quarks with an effective confining interaction and a chiral interaction that is mediated by the octet of Goldstone bosons (pseudoscalar mesons) between the constituent quarks.
We demonstrate how heavy mass methods, previously applied to chiral perturbation theory calculations involving the interactions of nucleons and pions, can be generalized to include interactions with the $Δ(1232)$ in a systematic formalism which we call the "small scale expansion."
We construct an $SU(3)_L \times SU(3)_R$ symmetric chiral effective model which includes parity pair baryon fields. It is assumed that the positive and negative parity baryons in the parity pair have opposite chiral transformation properties each other. Using this model, strong decays of the negative parity baryons are studied up to the order of one-loop corrections. The results agree qualitatively with experiment in the $π$ and $K$ channels. We examine how the model parameters are determined from the decay widths and study their physical meanings. Possibilities to build other models and relat…
Density fluctuations of intranuclear matter suffering collisions with projectile particles are capable to turn into multiquark clusters with chiral symmetry restored. Theoretical analysis of these processes requires an additional taking account of finite size effects in the region of the chiral phase transition. From the experimental point of view, this method of observation of the chiral phase transition has its inherent advantages due to a relatively moderate number of secondary particles to be registered.
We present a procedure to calculate 1-loop graphs in the soliton sector of chiral Lagrangians and use it to calculate quantum corrections to certain baryon observables in Skyrme-type models. Results generally show an improvement over the values obtained in tree approximation except for the case of the axial coupling g_A.
We study the chiral transformation properties of all possible local (non-derivative) interpolating field operators for baryons consisting of three quarks with two flavors, assuming good isospin symmetry. We derive and use the relations/identities among the baryon operators with identical quantum numbers that follow from the combined colour, Dirac and isospin Fierz transformations. These relations reduce the number of independent baryon operators with any given spin and isospin. The Fierz identities also effectively restrict allowed baryon chiral multiplets. It turns out that the chiral multipl…
The baryon axial vector current is computed at one-loop order in heavy baryon chiral perturbation theory in the large-N_c limit, where N_c is the number of colors. Loop graphs with octet and decuplet intermediate states cancel to various orders in N_c as a consequence of the large-N_c spin-flavor symmetry of QCD baryons. These cancellations are explicitly shown for the general case of N_f flavors of light quarks. In particular, a new generic cancellation is identified in the renormalization of the baryon axial vector current at one-loop order. A comparison with conventional heavy baryon chiral…
A regularization for the baryon number consistent with the energy in the Nambu-Jona-Lasinio model is introduced. The soliton solution is constructed with the regularized baryon number constrained to unity. It is furthermore demonstrated that this constraint prevents the soliton from collapsing when scalar fields are allowed to be space dependent. In this scheme the scalar fields actually vanish at the origin reflecting a partial restoration of chiral symmetry. Also the influence of this constraint on some static properties of baryons is discussed.
We discuss the consequences of the chiral doubling scenario for baryons built of heavy and light quarks. In particular, we use the soliton description for baryons, demonstrating why each heavy-light baryon should be accompanied by the opposite parity partner. Our argumentation holds both for ordinary baryons and for exotic heavy pentaquarks which are required by the symmetries of QCD to appear in parity doublets, seperated by the mass shift of the chiral origin. Interpreting the recently observed by BaBaR, CLEO and Belle charmed mesons with assignment $(0^+,1^+)$ as the chiral partners of know…
The masses of the charmed baryons in the ${\bf 6}$ representation of $SU(3)$ obey an equal spacing rule at lowest order in $SU(3)$ breaking, ${\cal O}(m_s)$. We compute the corrections to this relation at order ${\cal O}(m_s^{3/2})$ arising from meson loops using chiral perturbation theory combined with heavy quark symmetry and find them to be small. We also examine the hyperfine interaction responsible for the splitting between the $J^π={3\over 2}^+$ and $J^π={1\over 2}^+$ baryons in the ß representation. The results also hold in the b-baryon sector.
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