Strange charmed baryons in QCD

QCD sum rules are used to predict the mass differences between strange and nonstrange single charmed baryons inSU (3) sextets 1/2⁺, 1/2^?, 3/2⁺ and antitriplet 1/2⁺ as well as the mass of the lowest nonstrange stateΣ _c ^++′ in the 3/2⁺ sextet. The mass difference obtained for the antitriplet 1/2⁺ is in a good agreement with the available experimental data.     

QCD string in mesons and baryons

The distributions of fields generated by static $Q\bar Q$ and QQQ sources are calculated analytically within the bilocal approximation of the method of vacuum correlation functions. At large distances between the quarks, the fields assume a clear-cut stringlike shape. The main contribution to the string comes from the longitudinal component of the chromoelectric field. The contribution of the transverse chromoelectric field is below 3% of the contribution from the longitudinal component. A baryonic string has a Y-like shape with a deep well in the region of the string-junction position. Field distributions are considered for a quark-diquark configuration and in the case of three quarks occurring on a straight line. The interaction potential is calculated for three quarks residing at the vertices of an equilateral triangle.     

Inclusive photoproduction cross sections of charmed mesons and baryons

The various mechanisms which may be responsible for charm photoproduction are reviewed and compared to experimental data. The photongluon fusion process provides the dominant contribution to the total cross-section at present energies. Emphasis is given to the final state structure. Assuming that hadronization takes place through string fragmentation, we calculate rapidity distributions and correlations for charmed mesons and baryons.     

Electromagnetic mass differences of the old and the charmed mesons

We predict for M_?⁺?M_?⁰ the values -3.4 ± 0.8 MeV using the ?-ω mixing and the quark model, respectively. The extracted parameters indicate the necessity of a relativistic treatment of the old mesons. The problem of extrapolating these parameters to the charmed mesons is discussed. Under conservative assumptions, we predict 1.7 ? M_D⁰ ? 2.2 MeV and .     

Comment of PCAC and the electromagnetic mass splittings of charmed mesons

Strong PCAC and a generalization of Dashen's relation for the K⁺?K⁰ mass difference as well as non-relativistic considerations are used in order to obtain insight into the mechanism which causes the mass splitting among the charmed pseudoscalar mesons D⁺ and D⁰. We find a value of 7–8 MeV for M_D⁺?M_D⁰.     

Diffractive production of charmed strange mesons by neutrinos and antineutrinos

The diffractive production of charmed strangeD _s ^* and possiblyD _s mesons by neutrinos and antineutrinos on nucleons in hydrogen, deuterium and neon targets is observed. The slope parameter of thet distribution is 3.3±0.8 (GeV)^?2. The production rate per charged current neutrino interaction with an isoscalar target times the D _s ⁺ →φτ⁺ branching fraction is (1.03±0.27)×10^?4.     

Couplings between pion and charmed mesons

We compute the couplings , and using QCD sum rules. These couplings are important inputs in the meson-exchange model calculations used to estimate the amount of absorption due to pions and rho mesons in heavy-ion collisions. Our sum rules are constructed at the first order in the pion momentum , which give the couplings that are not trivially related to the soft-pion theorem. Our calculated couplings, which somewhat depend upon the values of the heavy meson decay constants, are , , and . Received: 10 October 2001 / Revised version: 25 October 2001 / Published online: 7 December 2001     

Semileptonic decays of charmed mesons in the effective action of QCD

Within the framework of phenomenological Lagrangians we construct the effective action of QCD relevant for the study of semileptonic decays of charmed mesons. Hence we evaluate the form factors of at leading order in the 1/N _C expansion and, by demanding their QCD-ruled asymptotic behavior, we constrain the couplings of the Lagrangian. The features of the model-independent parameterization of form factors are provided, and their relevance for the analysis of experimental data are pointed out. Received: 28 October 2002 / Published online: 24 January 2003     

Spectroscopy of charmed baryons

We have fitted the masses and elastic widths of the S=0 baryons in the context of the QCD-improved quark shell model. All states in theN=0, 1, 2 and 3 harmonic oscillator bands have been included. Three models for the decay of these states have been studied, and it is concluded that the usual spectator model for the decays must be modified. Many resonances in theN=2 and 3 bands were found to decouple from the πN channel, supporting a previous solution to the missing resonance puzzle. No evidence has been found for the tensor force, while conflicting data exist for the 3-body spin orbit term. We also have found evidence that the contact force varies with band. The (56,1^?) multiplet is lower than expected.     

Ds1(2536)+ decays and the structure of P-wave charmed strange mesons

We calculate the D s 1 (2536) + decays into D*K channels,including the decay D s 1 (2536) + → D + π-K + through a virtual D*0 in a constituent quark model.Widths and S/D amplitudes ratio are in agreement with the recent Belle and BABAR data,being the results sensitive to 1 P 1 and 3 P 1 mixture.     

Electromagnetic mass differences between baryons in potential models

We calculate explicitly the electromagnetic mass splittings induced within the ground state baryons by the mass difference between theu andd quarks. This is performed in the framework of the non-relativistic potential model with an accurate treatment of the three-body problem. We also discuss the charge radius of the neutron.     

Strong coupling constants of light pseudoscalar mesons with heavy baryons in QCD

We calculate the strong coupling constants of light pseudoscalar mesons with heavy baryons within the light cone QCD sum rules method. It is shown that sextet–sextet, sextet–antitriplet and antitriplet–antitriplet transitions are described by one universal invariant function for each class. A comparison of our results on the coupling constants with the predictions existing in literature is also presented.     

Semi-leptonic decays of charmed baryons

We present estimates of semi-leptonic decays of the charmed $\text{1+}\text{2}$ baryons, members of the SU(3) 3¹ and 6 multiplets, into ordinary $\text{1+}\text{2}\text{and}\text{3+}\text{2}$ baryons. We give general expressions for decay rates and the mass M(B⁺?) spectra. We relate the relevant form factors for the $\text{1+}\text{2}\text{→}\text{1+}\text{2}$ transitions to the electromagnetic ones by means of CVC and SU(4). The form factors for $\text{1+}\text{2}\text{→}\text{3+}\text{2}$ transitions are related through SU(4) to those measured in Δ production. We discuss the dependence of the results on the masses of charmed baryons. The $\text{1+}\text{2}\text{→}\text{1+}\text{2}$ and $\text{1+}\text{2}\text{→}\text{3+}\text{2}$ transitions turn out to be dominant for the decays of the multiplets 3¹ and 6, respectively. The partial lifetimes are O(10^?10 ? 10^?14) sec as the masses of the decaying baryons are varied from 2 to 2.9 GeV. Possible ways of getting an idea about the masses of the charmed baryons are given.