0000000000291104
AUTHOR
Li Sheng Geng
Octet-baryon axial-vector charges and SU(3)-breaking effects in the semileptonic hyperon decays
The octet-baryon axial-vector charges and the g(1)/f(1) ratios measured in the semileptonic hyperon decays are studied up to O(p(3)) using the covariant baryon chiral perturbation theory with explicit decuplet contributions. We clarify the role of different low-energy constants and find a good convergence for the chiral expansion of the axial-vector charges of the baryon octet, g(1)(0), with O(p(3)) corrections typically around 20% of the leading ones. This is a consequence of strong cancellations between different next-to-leading- order terms. We show that considering only nonanalytic terms is not enough and that analytic terms appearing at the same chiral order play an important role in t…
SU(3)-breaking corrections to the hyperon vector coupling f(1)(0) in covariant baryon chiral perturbation theory
We calculate the SU(3)-breaking corrections to the hyperon vector coupling f(1)(0) up to O(p(4)) in covariant baryon chiral perturbation theory with dynamical octet and decuplet contributions. We find that the decuplet contributions are of similar or even larger size than the octet ones. Combining both, we predict positive SU(3)-breaking corrections to all the four independent f(1)(0)'s (assuming isospin symmetry), which are consistent, within uncertainties, with the latest results from large N-c fits, chiral quark models, and quenched lattice QCD calculations.
Study of the J/psi -> phi(omega) f(2)(1270), J/psi -> phi(omega) f '(2)(1525) and J/psi -> K*(0)(892) (K)over-bar(2)*(0)(1430) decays
We present an approach to Study the decay modes of the J/psi into a vector meson and a tensor meson, taking into account the nature of the f(2)(1270), f'(2)(1525). (K) over bar (2)*(0)(1430) resonances as dynamically generated states from the vector meson-vector meson interaction. We evaluate four ratios of partial decay widths in terms of a flavor dependent OZI breaking parameter and the results obtained compare favorably with experiment, although the experimental uncertainties are still large. Further refinements of the data Would provide a more stringent test on the theoretical approach. The fit to the data is possible due to the particular strength and sign of the couplings of the reson…
The role of the Lambda(1405) in the pp -> pK(+)Lambda(1405) reaction
We report a theoretical study of the pp -> pK(+)Λ(1405) reaction, which was recently investigated at COSY-Jülich by using a 3.65 GeV/c circulating proton beam incident on an internal hydrogen target. The reaction is driven by single-kaon exchange, single-pion exchange, and single-rho exchange terms which have very different shapes due to the two-pole structure of the Λ(1405) and the presence of background terms. The shape for the sum of the three contributions, as well as the total cross-section, are consistent with present data within experimental and theoretical uncertainties, using reasonable form factors for the meson-baryon vertices.
X(2175) as a resonant state of the phi K(K)overbar system
We perform a Faddeev calculation for the three mesons system, ϕKK¯, taking the interaction between two pseudoscalar mesons and between a vector and a pseudoscalar meson from the chiral unitary approach which generates dynamically the low lying scalar mesons in the first case and the low lying axial vector mesons in the second. We obtain a neat resonance peak around a total mass of 2150 MeV and an invariant mass for the KK¯ system around 970 MeV, very close to the f0(980) mass. The state appears in I=0 and qualifies as a ϕf0(980) resonance. No state is seen in I=1. This finding provides a natural explanation for the recent state found at BABAR and BES, the X(2175), which decays into ϕf0(980).
Two-photon and one photon-one vector meson decay widths of the $f_0(1370)$, $f_2(1270)$, $f_0(1710)$, $f'_2(1525)$, and $K^*_2(1430)$
We calculate the radiative decay widths, two-photon ($\gamma\gamma$) and one photon-one vector meson ($V\gamma$), of the dynamically generated resonances from vector meson-vector meson interaction in a unitary approach based on the hidden-gauge Lagrangians. In the present paper we consider the following dynamically generated resonances: $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f_2'(1525)$, $K^*_2(1430)$, two strangeness=0 and isospin=1 states, and two strangeness=1 and isospin=1/2 states. For the $f_0(1370)$ and $f_2(1270)$ we reproduce the previous results for the two-photon decay widths and further calculate their one photon-one vector decay widths. For the $f_0(1710)$ and $f_2'(1525)$ the…
Testing the nature of the Lambda(1520) in the J / psi ---> anti-Lambda K- p and J / psi ---> anti-Lambda pi+ pi- Lambda reactions
We study the reactions J/ψ→Λ¯K−p and J/ψ→Λ¯π+π−Λ with a unitary chiral approach. We predict the ratio of the invariant mass distributions of these two reactions at the Λ(1520) peak position, which is free of the unknown production mechanism and reflects only the properties of the Λ(1520). An experimental measurement of this ratio will provide the couplings of the Λ(1520) to its decay channels, allowing to test the predictions of the chiral unitary approach on this resonance, which appears as dynamically generated in that approach.
Clues for the existence of two K-1(1270) resonances
The axial-vector meson K1(1270) was studied within the chiral unitary approach, where it was shown that it has a two-pole structure. We reanalyze the high-statistics WA3 experiment K-p-->K-pi+pi-p at 63 GeV, which established the existence of both K1(1270) and K1(1400), and we show that it clearly favors our two-pole interpretation. We also reanalyze the traditional K-matrix interpretation of the WA3 data and find that the good fit of the data obtained there comes from large cancellations of terms of unclear physical interpretation.
Role of the N-*(1535) in the J/psi -> pp and J/psi -> p(+)Lambda reactions
We study the J/psi -> p eta p and J/psi -> pK(+)Lambda reactions with a unitary chiral approach. We find that the unitary chiral approach, which generates the N-*(1535) dynamically, can describe the data reasonably well, particularly the ratio of the integrated cross sections. This study provides further support for the unitary chiral description of the N-*(1535). We also discuss some subtle differences between the coupling constants determined from the unitary chiral approach and those determined from phenomenological studies
Test of h(1)(1830) made of K*K* with the eta(c) ->phi K*K* decay
We present a new reaction, complementary to from which an h (1) resonance with mass around 1830 MeV was reported from a BESIII experiment. The new reaction is , or . Using the information from the analysis of , we find that the invariant mass distribution for those two Iu decays exhibits a clear peak around 1830 MeV perfectly distinguishable from what one obtains with pure phase space. We suggest the implementation of these reactions to assert the existence of this elusive resonance which, by its nature as a vector-vector molecule with 0(-)(1(+-)) quantum numbers, only couples to the channel.