Semirelativistic Quark Model Research Articles

Structure of Baryons in a Semi-Relativistic Quark Model

The spectroscopy of light and strange baryons and elastic electromagnetic form factors of nucleon have been studied through a simple semi-relativistic quark model. For SU(6)-invariant part of spectrum, we treated the baryons as a spin-independent three-body bound system and presented the exact analytical solution of three-body Klein–Gordon equation. Considering the SU(6)-invariant interaction as a combination of scalar linear and vector Coulombic-like potentials, we obtained analytical formulas for energy levels and the hyperradial wave functions which have been employed in the calculations of the mass spectrum of baryons, electromagnetic elastic form factors, and charge radii of nucleon. The evaluated observables have been compared with experimental data, and it has been shown that the present model leads to a fairly good description of the observed resonances.

Electric polarizability of pions in semirelativistic quark model

The generalized and static polarizabilities of charged pions, which are considered a relativistic system of two pointlike spinor quarks with a linear interaction potential, are calculated. The relationship between static electricity and generalized polarizabilities of pions is studied in the context of this approach.

UNQUENCHED QUARK MODEL DESCRIPTION OF CHARMONIUM

We show that the charmonium spectrum may be reproduced to a good precision by means of a semirelativistic quark model approach based on a universal static potential effectively incorporating effects from sea quark-antiquark pairs. Detailed predictions for upcoming data are derived.

Doubly heavy baryons in a Salpeter model with AdS/QCD inspired potential

The spectrum of baryons with two heavy quarks is predicted, assuming a configuration of a light quark and a heavy diquark. The masses are computed within a semirelativistic quark model, using a potential obtained in a gauge-gravity (anti-de Sitter/QCD) framework. All the parameters defining the model are determined fitting the meson spectrum. The obtained mass of ${\ensuremath{\Xi}}_{cc}$ is in agreement with the measurements.

Construction of Lorentz-Invariant Amplitudes from Rest-Frame Wave Functions in HQET: Application to the Isgur-Wise Function

Succeeding in predicting 0^+ and 1^+ states of D and D_s heavy mesons by our semi-relativistic quark potential model, we examine a method how to construct Lorentz-invariant scattering amplitudes and/or decay widths and develop a formulation to calculate Lorentz-boosted ones given the rest frame wave functions in our model. To show how effective this is, we apply the formulation to calculate the semileptonic weak form factors out of the rest frame wave functions of heavy mesons and numerically calculate the dynamical 1/m_Q corrections to those for the process B-bar -> D^{(*)}\ell\nu based on our model for heavy mesons. It is shown that nonvanishing expressions for \rho_1(\omega)=\rho_2(\omega) and \rho_3(\omega)=\rho_4(\omega)=0 are obtained in a special Lorentz frame, where \rho_i(\omega) are the parameters used in the Neubert-Rieckert decomposition of form factors. Various values of form factors are estimated, which are compatible with recent experimental data as well as other theoretical calculations.

ηbandηcradiative decays in the Salpeter model with the AdS/QCD inspired potential

The decay constants and the radiative decay widths of {eta}{sub b}(nS) and {eta}{sub c}(nS) are computed within a semirelativistic quark model, using a potential found through the AdS/QCD correspondence. For {eta}{sub c}, the results are in agreement with experimental data, while in the case of {eta}{sub c}{sup '} a discrepancy is found and the possible reasons are discussed.

Is the [formula omitted] a radially excited state of [formula omitted

We present the interpretation that the recently discovered Z+(4430) by the Belle Collaboration can be a radial excitation of the cs¯ state, being consistent with an observed value of the product of branching ratios, B(B0→K∓Z±(4430))×B(Z±(4430)→π±ψ′)∼10−5. We give an explicit cs¯ candidate for this state by calculating the mass value in our semirelativistic quark potential model and also give a natural understanding for the facts that the decay mode Z→J/ψπ+ has not yet been seen while Z→ψ′π can be seen.

Construction of Lorentz-Invariant Amplitudes from Rest-Frame Wave Functions in HQET: Application to the Isgur-Wise Function

Succeeding in predicting 0+ and 1+ states of D and Ds heavy mesons with our semi-relativistic quark potential model, we examine a method for constructing Lorentz-invariant scattering amplitudes and/or decay widths and develop a formulation to calculate Lorentz-boosted ones given the rest-frame wave functions in our model. To illustrate the effectiveness of our method, we apply the formulation to the problem of calculating the semileptonic weak form factors from the rest-frame wave functions of heavy mesons and numerically calculate the dynamical 1/mQ corrections to those for the process B → D(*)ℓ v based on our model of heavy mesons. It is shown that nonvanishing expressions for ρ1(ω) = ρ2(ω) and ρ3(ω) = ρ4(ω)= 0 are obtained in a special Lorentz frame, where ρi(ω) are the parameters used in the Neubert-Rieckert decomposition of form factors. Various values of form factors are estimated. These values are compatible with recent experimental data as well as other theoretical calculations.

New Heavy-Light Mesons Q

We succeed in reproducing the = 1 B mesons B1(5720), B ∗ 2 (5745), and B ∗ s2(5839) that were recently reported by D0 and CDF, using our semi-relativistic quark potential model, which also succeeds in predicting the mass spectra of the narrow DsJ , as well as broad D∗ 0(0 ) and D′ 1(1 ) particles observed a couple of years ago. The mass of higher excited states ( = 1, 2) of B and Bs mesons, which have not yet been observed, is also predicted to first order in p/mb with the internal quark momentum p and the b quark mass mb. We find that the corresponding BsJ are below the BK/B ∗K threshold and should have narrow decay widths, contrary to most other predictions. Also, already established states ( = 0 and = 1) of D, Ds, B, and Bs heavy mesons are simultaneously reproduced in good agreement with experimental data, within one percent accuracy. To calculate these D/Ds and B/Bs heavy mesons, we use different values of the strong coupling, αs and α b s, respectively.

Radial excitations of heavy-light mesons

The recent discovery of D s states suggests the existence of radial excitations. Our semirelativistic quark potential model succeeds in reproducing these states within one to two percent of accuracy compared with the experiments, D s0(2860) and D s * (2715), which are identified as 0+ and 1− radial excitations (n = 2). We also present calculations of radial excitations for B/B s heavy mesons. The relation between our formulation and the modified Goldberger-Treiman relation is also described.

S-wave kaon–nucleon phase shifts with instanton induced effects

The kaon–nucleon S-wave phase shifts have been calculated, for both isospin channels I=0 and I=1, in the framework of a semirelativistic quark potential model which includes an instanton induced force. The agreement with experimental phase shifts is poor essentially because of a dominant attraction coming from instantons. The low-energy behaviour of S-wave phase shifts, for I=0 and I=1 channels, obtained in the kaon–nucleon system is characteristic of a potential which can produce one loosely bound state.

Observed Λb and Σb > Ξb

Masses of the bottom baryons are calculated discussing quark distances in a semi-relativistic quark model. Our result of Λb mass is consistent with the recent UA1 result, Λb = (5640 ± 50 ± 30) MeV within the experimental error. The predicted mass difference Ξb′(b[su])-Σb(bdu) is negative, contrary to the expectation from the fact thatms> md. We show that the quark distances in a baryon are the same as those of perturbation theory up to the 2s state of the harmonic oscillator, if quarks in the baryon have the same flavour.

Bs and Bc meson masses

Discussing the quark distances, we compute the masses ofs-wave heavy mesons in a semi-relativistic quark model. We reproduce the masses of the heavy mesons within ±4 MeV except for D*s. The new data of ARGUS imply a very different value of the B−−B0 mass difference, even in sign compared with the old data. The new data fit well in our model. We predict Bs=5344 MeV and B*s=5393 MeV, which are not so far from the B and B* masses and detectable in the γ(5S) decays.

Where Is the b?

The masses of s-wave bottom baryons are discussed in a semirelativistic quark model, on the basis of a quark-distance relation. We stress that the Σ b is heavier than Ξ' b (b[su], b[sd]) containing the antisymmetric su(or sd) subsystem. We conclude that the two candidates for Λ b with very different masses are different states; Basile et al.'s result 5425 +175 −75 MeV is Λ b (b([du]), but Arenton et al.'s result ∼5750 MeV is Ξ' 0 b (b[su])

Spectrum generating algebra for string-like hadrons. Mass formula for mesons

We explore implications on meson properties of the spectrum generating algebra U(4)⊗SU s(2)⊗SU f( n)⊗SU c(3) with U(4) ⊃ SO(4) dynamic symmetry. We suggest a semi-empirical mass formula consistent with this algebra. We find that this mass formula describes the mass squared of 65 relatively well-established meson states with an average deviation of 5.2%, to be compared with the semi-relativistic quark model approach (QM) which has an average deviation of 6.6%.

Test of O(4) symmetry in hadrons: radiative decays of mesons

We present results of a calculation of radiative decays of mesons in the string-like U(4) ⊗SU f(3)⊗SU s(2)⊗SU c(3) model with U(4) ⊃ O(4) dynamic symmetry. Decay widths are obtained in explicit analytic form and describe data as accurately as the numerical results of the semi-relativistic quark model. We conclude that O(4) [a compactification of O(3, 1)] is an approximate symmetry of hadrons.

Xi c and baryon spectroscopy.

Baryon masses are computed in a semirelativistic quark model. We determine quark distances in baryons on the basis of solutions of three-body harmonic oscillators and modifying them by forces due to the Fermi-Breit terms. We reproduce all the well-known s-wave baryon masses within \ifmmode\pm\else\textpm\fi{}9-MeV accuracy. We conclude that the csu state of 2465.4\ifmmode\pm\else\textpm\fi{}4.0\ifmmode\pm\else\textpm\fi{}1.5 MeV is ${\ensuremath{\Xi}}_{c}^{\mathcal{'}+}$ with the antisymmetric su flavor state and the csd state of 2471\ifmmode\pm\else\textpm\fi{}3\ifmmode\pm\else\textpm\fi{}4 MeV is ${\ensuremath{\Xi}}_{c}^{\mathcal{'}0}$ with the antisymmetric sd flavor state. To confirm these, it is important to find another csu baryon ${\ensuremath{\Xi}}_{c}^{+}$ near 2580 MeV and another csd baryon ${\ensuremath{\Xi}}_{c}^{0}$ near 2579 MeV, which may decay to ${\ensuremath{\Xi}}_{c}^{\mathcal{'}+}$+\ensuremath{\gamma} and ${\ensuremath{\Xi}}_{c}^{\mathcal{'}0}$+\ensuremath{\gamma}, respectively. We also give other charmed baryon masses.

Strong coupling approximation of geometric QCD and the semi-relativistic quark model

Strong coupling approximation of geometric QCD and the semi-relativistic quark model

Angular distribution in neutrino-induced single pion production processes

A partial wave decomposition of\({v \mathord{\left/ {\vphantom {v {\bar v}}} \right. \kern-\nulldelimiterspace} {\bar v}}\) single pion production is used for studying resonant and nonresonant contributions. The dominant resonance excitation is dynamically described by a semirelativistic quark model. Nonresonant background is considered to arise from Born-terms diminuished by the lowest order partial waves (which are determined by resonances alone.) The method permits evaluation of interferences between resonance and background amplitudes as well as, more importantly, among resonances themselves. Predicted interference patterns are reflected by the pion angular distribution coefficients which compare well with recent data. Results obtained this way are also in agreement with momentum transfer measurements if higher resonance excitation form factors are chosen to resemble those tested in pion photoproduction, rendering simultaneously any nonresonant background small.

Strong decay of hadrons in a semirelativistic quark model.

Pion decay amplitudes of nonstrange baryon resonances are calculated assuming a pseudoscalar single-quark-emission-type model for the decay process. The resonances as well as the nucleon ground state are described by configuration mixings obtained previously in a semirelativistic QCD-inspired quark model. The decay widths are compared to the available experimental data and to other theoretical results.