The quadrupole moments of ground state baryons are discussed in the framework of the 1/N(c) expansion of QCD, where N(c) is the number of color charges. Theoretical expressions are first provided assuming an exact SU(3) flavor symmetry, and then the effects of symmetry breaking are accounted for to linear order. The rather scarce experimental information available does not allow a detailed comparison between theory and experiment, so the free parameters in the approach are not determined. Instead, some useful new relations among quadrupole moments, valid even in the presence of first-order symmetry breaking, are provided. The overall predictions of the 1/N(c) expansion are quite enlightening.
The electric quadrupole moments of the decuplet baryons are calculated in the bound state approach of the Skyrme model. In this approach, all the quadrupole moments of the decuplets are found to be proportional to the third component of the baryon isospin. Contrary to the SU(3) collective model, the kaonic contribution is as important as the pionic one. The transitional quadrupole moments of the hyperons are also predicted.
Experiments with $Ω^{\pm}$ baryons moving in a crystal at LHC in addition to EDM measurement open possibility to study electric quadrupole moment, to observe birefringence effect (spin oscillations and spin dichroism) for $Ω^{\pm}$ baryons and to get information about constants describing P-odd, T-odd effects at $Ω^{\pm}$ baryon interactions with electrons and nuclei
Spin rotation of $Ω^{\pm}$ baryons channeling in a bent crystal at the LHC in addition to EDM measurement open possibility to study $Ω^{\pm}$ baryons electric quadrupole moment. Equations for spin and tensor polarization rotation are presented along with the estimations study for values of the effects under discussion.
The electric quadrupole and magnetic octupole moments of the light decuplet baryons are calculated in the framework of the light cone QCD sum rules. The obtained non-vanishing values for the electric quadrupole and magnetic octupole moments of these baryons show nonspherical charge distribution. The sign of electric quadrupole moment is positive for $Ω^-$, $Ξ^{*-}$, $Σ^{*-}$ and negative for $Σ^{*+}$, which correspond to the prolate and oblate charge distributions, respectively. A comparison of the obtained results with the predictions of non-covariant quark model which shows a good consistenc…
In the SU3 Skyrme model the electric quadrupole moments of $\frac{3}{2}^+$ baryons show a strong sensitivity with respect to flavor distortions in baryon wavefunctions. SU3 symmetric wavefunctions lead to quadrupole moments proportional to the charge of the baryon whereas for strongly broken flavor symmetry a proportionality to baryonic isospin emerges. Since the flavor distortions in the wavefunctions also determine the strangeness content of the proton the Skyrme model provides a link between both quantities.
The magnetic and quadrupole moments of the light-vector and axial-vector mesons are calculated in the light cone QCD sum rules. Our results for the static properties of these mesons are compared with the predictions of lattice QCD as well as other approaches existing in the literature.
Due to the very short life time of the $Δ$ baryons, a direct measurement on the electromagnetic moments of these systems is almost impossible in the experiment and can only be done indirectly. Although only for the magnetic dipole moments of $Δ^{++}$ and $Δ^{+}$ systems there are some experimental data, the theoretical, phenomenological and lattice calculations could play crucial role. In present work, the magnetic dipole ($μ_Δ$) , electric quadrupole ($Q_Δ$) and magnetic octupole ($O_Δ$) moments of these baryons are computed within the light cone QCD sum rules. The results are compared with t…
Quadrupole moments of decuplet baryons and the octet-decuplet transition quadrupole moments are calculated using Morpurgo's general QCD parameterization method. Certain relations among the decuplet and the octet to decuplet transition quadrupole moments are derived. These can be used to predict the $Δ$ quadrupole moments which are difficult to measure.
The magnetic dipole G_M(Q^2), electric quadrupole G_E(Q^2), and Coulomb quadrupole G_C(Q^2) form factors, describing the spin-3/2 to spin-1/2 electromagnetic transitions, are investigated within the light cone QCD sum rules. The Q^2 dependence of these form factors, as well as ratios of electric quadrupole and Coulomb quadrupole form factors to the magnetic dipole form factors are studied. We also compare our results on the magnetic dipole form factor with the prediction of the covariant spectator quark model.
Baryon charge radii and quadrupole moments are calculated in a quark model generalized to an arbitrary number (N_c) of colors. Several relations among the charge radii and quadrupole moments are found. In particular, a previously derived relation between the neutron charge radius and the N-->Delta transition quadrupole moment is shown to hold for physical baryons as well in the large N_c limit.
The chiral constituent quark model (\chiCQM) with general parameterization (GP) method has been formulated to calculate the quadrupole moments of the spin 3/2^+ decuplet baryons and spin 3/2^+ \to 1/2^+ transitions. The implications of such a model have been investigated in detail for the effects of symmetry breaking and GP parameters pertaining to the two- and three-quark contributions. It is found that the \chiCQM is successful in giving a quantitative and qualitative description of the quadrupole moments.
We derive number of relations between quadrupole energy, elastic pressure, and shear force distributions in baryons using the large $N_c$ picture of baryons as chiral solitons. The obtained large $N_c$ relations are independent of particular dynamics and should hold in any picture in which the baryon is the chiral soliton. One of remarkable qualitative predictions of the soliton picture is the nullification of the tangential forces acting on the radial area element for any tensor polarisation of the baryon. The derived relations provide a powerful tool to check the hypothesis that the baryons …
We develop a straightforward method to compute charge radii and quadrupole moments for baryons both with and without strangeness, when the number of QCD color charges is N_c. The minimal assumption of the single-photon exchange ansatz implies that only two operators are required to describe these baryon observables. Our results are presented so that SU(3) flavor and isospin symmetry breaking can be introduced according to any desired specification, although we also present results obtained from two patterns suggested by the quark model with gluon exchange interactions. The method also permits …
In this talk, we give a short review of our recent works on studying the singly heavy baryon, doubly heavy baryon, and triply heavy baryon spectra from QCD sum rules.
According to the flow narrative commonly applied to high-energy nuclear collisions a 1D cylindrical-quadrupole component of 2D angular correlations conventionally denoted by quantity $v_2$ is interpreted to represent elliptic flow: azimuth modulation of transverse or radial flow in noncentral nucleus-nucleus (A-A) collisions. The nonjet (NJ) quadrupole component exhibits various properties inconsistent with a flow or hydro interpretation, including the observation that NJ-quadrupole centrality variation in $A$-$A$ collisions has no relation to strongly-varying jet modification ("jet quenching"…
We use the method of QCD Sum Rules to estimate the masses of the charm baryon, $Λ^+_c$, bottom baryon $Λ^0_b$, strange baryon $Λ^0_s$ and compare them to their experimental values.
This is an extension of the prediction of strange baryon decays to the decays of charmed baryons using QCD Sum Rules. Using QCD Sum Rules we estimate the decay $Λ^+_c (udc) \rightarrow Λ^o_s(uds)+ π^+$. Although some weak decays of the $Λ^+_c$ have been measured, since it is difficult to measure $Λ^+_c \rightarrow Λ^o_s+ π^+$ our estimates should be useful for future experiments
Baryon production is studied within the framework of quantized fragmentation of QCD string. Baryons appear in the model in a fairly intuitive way, with help of causally connected string breakups. A simple helical approximation of QCD flux tube with parameters constrained by mass spectrum of light mesons is sufficient to reproduce masses of light baryons.
Chiral Magnetic Wave (CMW) is a gapless collective excitation of quark-gluon plasma in the presence of external magnetic field that stems from the interplay of Chiral Magnetic (CME) and Chiral Separation Effects (CSE); it is composed by the waves of the electric and chiral charge densities coupled by the axial anomaly. We consider CMW at finite baryon density and find that it induces the electric quadrupole moment of the quark-gluon plasma produced in heavy ion collisions: the "poles" of the produced fireball (pointing outside of the reaction plane) acquire additional positive electric charge,…
We discuss the QCD constraints on e+e- --> baryon-anti-baryon close to threshold, in light of the puzzling experimental data which indicate that close to threshold sigma (e+e- --> n n-bar) > sigma (e+e- --> p p-bar). We focus on the process e+e- --> Delta Delta-bar, which is particularly simple from the theoretical point of view. In this case it is possible to make exact QCD predictions for the relative yields of the four members of the Delta multiplet, modulo one crucial dynamical assumption.
The electromagnetic form factors of octet baryons are estimated within light cone QCD sum rules method, using the most general form of the interpolating current for baryons. A comparison of our predictions on the magnetic dipole and electric form factors with the results of other approaches is performed.
We calculate the magnetic moments of Delta baryons within the framework of QCD sum rules. A comparison of our results on the magnetic moments of the Delta baryons with the predictions of different approaches is presented.
Using the QCD sum rules method, we estimate the mass and residues of the first radial excitations of octet baryons. The contributions coming from the ground state baryons are eliminated by constructing the linear combinations of the sum rules corresponding to different Lorentz structures. Our predictions of the masses of the first radial excitations of octet baryons are in good agreement with the data.
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.
We discuss an application of QCD sum rules to the heavy baryons $Λ_Q$ and $Σ_Q$. The predictions for the masses of heavy baryons, residues and Isgur-Wise function are presented. The new results on two loop anomalous dimensions of baryonic currents and QCD radiative corrections (two- and three- loop contributions) to the first two Wilson coefficients in OPE are explicitly presented.
We investigate the transport of baryon number across phase boundaries in a putative first order QCD-phase transition. Two independent phenomenological models are employed to estimate the baryon penetrability at the phase boundary: chromoelectric flux tube models; and an analogy to baryon-baryon coalescence in nuclear physics. Our analysis indicates that baryon transport across phase boundaries may be order of magnitude more efficient than other work has suggested. We discuss the substantial uncertainties involved in estimating baryon penetrability at phase boundaries.
The hyperfine mass splittings of baryons in large $N$ QCD are proved to be proportional to ${\bf J}^2$. Hyperfine mass splittings are first allowed at order $1/N$ in the $1/N$ expansion.
Masses of the p-wave excited heavy baryons have been calculated to the Lambda_{QCD}/m_Q order using QCD sum rule method within the framework of heavy quark effective theory. Numerical results for kinetic energy lambda_1 and chromo-magnetic interaction lambda_2 are presented. The splitting between spin 1/2 and 3/2 doublet derived from our calculation is given, for which the agreement with the current experiment is desirable.
The magnetic moments of heavy sextet $J^P = {1\over 2}^+$ baryons are calculated in framework of the light cone QCD sum rules method. Linearly independent relations among the magnetic moments of these baryons are obtained. The results for the magnetic moments of heavy baryons obtained in this work are compared with the predictions of the other approaches.
The magnetic moments of the low lying, negative parity, spin-3/2 baryons are calculated within the light cone QCD sum rules method. The contributions coming from the positive parity, spin-3/2 baryons, as well as from the positive and negative parity spin-1/2 baryons are eliminated by constructing combinations of various invariant amplitudes corresponding to the coefficients of the different Lorentz structures.
Octet baryon magnetic moments are calculated in framework of the light cone QCD sum rules. The analysis is carried for the general form of the interpolating currents for octet baryons. A comparison of our results on the magnetic moments of octet baryons with the predictions of other approaches and experimental data is presented.
In this article, we study the ${1\over 2}^+$ doubly heavy baryon states $Ω_{QQ}$ and $Ξ_{QQ}$ by subtracting the contributions from the corresponding ${1\over 2}^-$ doubly heavy baryon states with the QCD sum rules, and make reasonable predictions for their masses. Those doubly heavy baryon states maybe observed at the Tevatron, the LHCb and the PANDA.
In this article, we restudy the mass spectrum of the ground state triply-heavy baryon states with the QCD sum rules by carrying out the operator product expansion up to the vacuum condensates of dimension 6 in a consistent way and preforming a novel analysis. It is the first time to take into account the three-gluon condensates in the QCD sum rules for the triply-heavy baryon states.
We give an overview over recent calculations of baryonic correlator functions with finite mass quarks in view on their applicability for QCD sum rules. The QCD sum rule method is then demonstrated within the Heavy Quark Effective Theory.
The magnetic moments of the negative parity, spin-1/2 baryons containing single heavy quark are calculated. The pollution that occur from the transitions between positive and negative parity baryons are removed by constructing the sum rules from different Lorentz structures.
We review standard applications of perturbative QCD to baryon production, and argue by examining data that it is generally relevant at high but experimentally feasible momentum transfers. Then we consider some new initiatives, particularly meson photoproduction off baryons and the seeming quagmire of Delta(1232) electroproduction.
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 calculate the magnetic dipole and electric quadrupole moments associated with the radiative $Ω_{Q}^{*}\rightarrowΩ_{Q}γ$ and $Ξ_{Q}^{*}\rightarrowΞ^{\prime}_{Q}γ$ transitions with $Q=b$ or $c$ in the framework of light cone QCD sum rules. It is found that the corresponding quadrupole moments are negligibly small while the magnetic dipole moments are considerably large. A comparison of the results on the considered multipole moments as well as corresponding decay widths with the predictions of the vector dominance model is performed.
In this article, we study the ${1\over 2}^{\pm}$ and ${3\over 2}^{\pm}$ triply heavy baryon states in an systematic way by subtracting the contributions from the corresponding ${1\over 2}^{\mp}$ and ${3\over 2}^{\mp}$ triply heavy baryon states with the QCD sum rules, and make reasonable predictions for their masses.
We construct the heavy baryonic currents by using the Bethe-Salpeter wave functions in the heavy quark limit. We discuss the one-loop renormalization of these heavy baryonic currents as well as their two-point correlators up to the order $1/M_h$. For a special case, we do the QCD sum rule for masses of the doublet (3/2,5/2).
We propose a model for baryons at finite temperature using AdS/QCD correspondence. In this model, we modify the AdS spacetime into the AdS-Schwarzchild spacetime and consider a couple of bulk spinors in this background. Solving this model, we get an eigenvalue equation for the baryon masses. We then investigate the effects of temperature on the baryon masses numerically, and find an interesting temperature dependence. Our result is consistent with the results from lattice QCD and other phenomenological models.
The structure of the 1/Nc expansion for the baryon distribution amplitude in QCD is tested using quark models. Earlier conjectures about this structure based on the evolution equation and on the soft-pion theorem are confirmed by the model analysis. The problem of the calculation of the baryon wave function at large Nc is reduced to the analysis of equations of motion for an effective classical dynamical system.
We compute the diagonal isovector axial-vector as well as induced pseudoscalar form factors of nucleon, $Σ$ and $Ξ$ baryons by employing the light-cone QCD sum rules to leading order in QCD and including distribution amplitudes up to twist 6. Extrapolating our sum-rules results to low-momentum transfers, we make a comparison with experimental and lattice-QCD results where we can achieve a nice qualitative and quantitative agreement.
We calculate the magnetic moments of decuplet baryons containing strange quarks within the framework of light cone QCD sum rules taking into account the SU(3) flavor symmetry breaking effects. It is obtained that magnetic moments of the neutral $\sso$ and $\xis0$ baryons are mainly determined by the SU(3) breaking terms. A comparison of our results on the magnetic moments of the decuplet baryons with the predictions of other approaches is presented.
We study the 5D Rarita-Schwinger fields to describe spin 3/2 baryons in AdS/QCD. We calculate the spectrum of spin 3/2 baryons (Delta resonances) and their form factors, together with meson-baryon couplings from AdS/QCD. The transition form-factors between Delta and nucleon are evaluated. Both pion and rho meson couplings have the same origin in the bulk and hence unified. The numerical values for the meson-baryon transition couplings are consistent with the values obtained from other methods. We also predict the numerical values of some new couplings associated with Delta resonances.
The magnetic moments of heavy $Ξ_{Q}$ baryons containing a single charm or bottom quark are calculated in the framework of light cone QCD sum rules method. A comparison of our results with the predictions of the quark models is presented.
We study the electromagnetic form factors of the lowest-lying singly heavy baryons in a pion mean-field approach, which is also known as the SU(3) chiral quark-soliton model. In the limit of the heavy-quark mass, the dynamics inside a singly heavy baryon is governed by the $N_c-1$ valence quarks, while the heavy quark remains as a mere static color source. In this framework, a singly heavy baryon is described by combining the colored soliton with the singly heavy quark. In the infinitely heavy-quark mass limit, we can compute the electric quadrupole form factors of the baryon sextet with spin …
The 1/N_c expansion provides a theoretical method for analyzing the spin-flavor symmetry properties of baryons in QCD that is quantitative, systematic and predictive. An exact spin-flavor symmetry exists for large-N_c baryons, whereas for QCD baryons, the spin-flavor symmetry is approximate and is broken by corrections proportional to the symmetry-breaking parameter 1/N_c = 1/3. The 1/N_c expansion predicts a hierarchy of spin and flavor symmetry relations for QCD baryons that is observed in nature. It provides a quantitative understanding of why some SU(3) flavor symmetry relations in the bar…
Using the QCD string theory, we investigate the physical reason of the narrow width of penta-quark baryons in terms of the large gluonic-excitation energy. In the QCD string theory, the penta-quark baryon decays via a gluonic-excited state of a baryon and meson system, where a pair of Y-shaped junction and anti-junction is created. On the other hand, we find in lattice QCD that the lowest gluonic-excitation energy takes a large value of about 1 GeV. Therefore, in the QCD string theory, the decay of the penta-quark baryon near the threshold is considered as a quantum tunneling process via a hig…
The transition form factors responsible for the radiative $Σ_Q \to Λ_Q γ$ and $Ξ_Q^\prime \to Ξγ$ decays of the negative parity baryons are examined within light cone QCD sum rules. The decay widths of the radiative transitions are calculated using the obtained results of the form factors.
I review the discovery of the color degree of freedom in hadronic physics, and the developments which led from that discovery to the local gauge theory of color, quantum chromodynamics.
In this article, we re-study the heavy baryon states $Ω_b$, $Ω_c$, $Ξ'_b$, $Ξ'_c$, $Σ_b$ and $Σ_c$ with the QCD sum rules, after subtracting the contributions from the corresponding negative parity heavy baryon states, the predicted masses are in good agreement with the experimental data.
The heavy spin--3/2 baryon--heavy spin--1/2 baryon vertices with light vector mesons are studied within the light cone QCD sum rules method. These vertices are parametrized in terms of three coupling constants. These couplings are calculated for all possible transitions. It is shown that correlation functions for these transitions are described by only one invariant function for every Lorenz structure. The obtained relations between the correlation functions of the different transitions are structure independent while explicit expressions of invariant functions depend on the Lorenz structure.
We have analyzed the theory of the baryon magnetic moments in the approximate) QCD setting suggested by Brambilla et al. By modifying their derivation of the $qqq$ interaction and wave equation for baryons, we derived expressions for the baryon moments in terms of the underlying quark moments, including the first corrections associated with the binding of the quarks in baryons. The results, which hold in the ``quenched approximation'' in which the contributions of virtual quark pairs are neglected, fail to describe the measured moments, with typical errors on the order of 7%. We conclude from …
Using the most general form of the interpolating currents of heavy baryons, the magnetic moments of heavy baryons "Lambda_Q (Q=b,c)" are calculated in framework of the light cone QCD sum rules. A comparison of our results on magnetic moments with the existing theoretical results calculated in various other frameworks are presented.
The mass spectra of doubly heavy baryons are systematically calculated in the framework of QCD sum rules. With a tentative heavy-diquark--light-quark configuration, the interpolating currents representing the doubly heavy baryons are proposed. Contributions of the operators up to dimension six are included in operator product expansion. The numerical results are compatible with other theoretical predictions, which may support the $(QQ)-(q)$ structure of doubly heavy baryons.
Using the general form of the baryon currents, we calculate the meson-baryon coupling constants and the F/D ratio within the framework of light cone QCD sum rules in the SU(3) flavor symmetry limit. The dependence of the results on the Dirac structure and on the free parameter (b) appearing in the general baryon current is considered. Comparison of our results on F/D ratio with the existing results is presented.
The semileptonic decays of heavy spin--1/2, $Ξ_{b(c)}$ and $Ξ'_{b(c)}$ baryons to the light spin-- 1/2, $Ξ$ and $Σ$ baryons are investigated in the framework of the light cone QCD sum rules. In particular, using the most general form of the interpolating currents for the heavy baryons as well as the distribution amplitudes of the $Ξ$ and $Σ$ baryons, we calculate all form factors entering the matrix elements of the corresponding effective Hamiltonians in full QCD. Having calculated the responsible form factors, we evaluate the decay rates and branching fractions of the related transitions.
Magnetic moments of baryons composed of light and strange quarks are computed for the first time through the only parameter of the model -- string tension $σ$. Resulting theoretical values differ from the experimental ones typically by about 10%.
