Hyperon-nucleon coupling from QCD sum rules

The NKY coupling constant for $Y = \Lambda$ and $\Sigma$ is evaluated in a QCD sum rule calculation. We discuss and extend the result of a previous analysis in the $\rlap{/}{q}i\gamma_5$ structure and compare it with the result obtained with the use of the $\gamma_5 \sigma_{\mu \nu}$ structure. We find a huge violation of the SU(3) symmetry in the $\gamma_5 \sigma_{\mu \nu}$ structure.Comment: 4 pages, 2 figures, espcrc2.sty included. Talk presented at QCD99, Montpellier, France (to appear in Nucl.Phys.B Proc.Suppl.

Bs∗BKB_s^* B K vertex from QCD sum rules

The form factors and the coupling constant of the $B_s^* B K$ vertex are calculated using the QCD sum rules method. Three point correlation functions are computed considering both $K$ and $B$ mesons off-shell and, after an extrapolation of the QCDSR results, we obtain the coupling constant of the vertex. We study the uncertainties in our result by calculating a third form factor obtained when the $B^*_s$ is the off-shell meson, considering other acceptable structures and computing the variations of the sum rules' parameters. The form factors obtained have different behaviors but their simultaneous extrapolations reach to the same value of the coupling constant $g_{B_s^* B K}=10.6 \pm 1.7$. We compare our result with other theoretical estimates.Comment: 11 pages, 11 figure

D∗DπD^*D\pi and B∗BπB^*B\pi form factors from QCD Sum Rules

The $H^*H\pi$ form factor for H = B and D mesons is evaluated in a QCD sum rule calculation. We study the Borel sum rule for the three point function of two pseudoscalar and one vector meson currents up to order four in the operator product expansion. The double Borel transform is performed with respect to the heavy meson momenta. We discuss the momentum dependence of the form factors and two different approaches to extract the $H^*H\pi$ coupling constant.Comment: 12 pages, RevTeX including 6 figures in ps files, revised version accepted for publication in Phys. Lett.

D∗DsKD^* D_s K and Ds∗DKD_s ^* D K vertices in a QCD Sum Rule approach

We calculate the strong form factors and coupling constants of $D^* D_s K$ and $D_s^* D K$ vertices using the QCD sum rules technique. In each case we have considered two different cases for the off-shell particle in the vertex: the ligthest meson and one of the heavy mesons. The method gives the same coupling constant for each vertex. When the results for different vertices are compared, they show that the SU(4) symmetry is broken by around 40%.Comment: 10 pages, 8 figures. Submitted to Phys. Lett.

J/psi D*D* vertex from QCD sum rules

We calculated the strong form factor and coupling constant for the $J/\psi D^* D^*$ vertex in a QCD sum rule calculation. We performed a double Borel sum rule for the three point correlation function of vertex considering both $J/\psi$ and $D^*$ mesons off--shell. The form factors obtained are very different, but they give the same coupling constant.Comment: 7 pages and 4 figures, replaced version accepted for publication in Phys. Lett.

\rho D^*D^* vertex from QCD sum rules

We calculate the form factors and the coupling constant in the $\rho D^* D^*$ vertex in the framework of QCD sum rules. We evaluate the three point correlation functions of the vertex considering both $\rho$ and $D^*$ mesons off--shell. The form factors obtained are very different but give the same coupling constant: $g_{\rho D^* D^*} = 6.6 \pm 0.31$. This number is 50% larger than what we would expect from SU(4) estimates.Comment: 9 pages, 6 eps figure

Diquark-Antidiquark with open charm in QCD sum rules

Using the QCD sum rule approach we investigate the possible four-quark structure of the recently observed charmed scalar mesons $D_0^{0}(2308)$ (BELLE) and $D_0^{0,+}(2405)$ (FOCUS) and also of the very narrow $D_{sJ}^{+}(2317)$, firstly observed by BABAR. We use diquak-antidiquark currents and work to the order of $m_s$ in full QCD, without relying on $1/m_c$ expansion. Our results indicate that a four-quark structure is acceptable for the resonances observed by BELLE and BABAR: $D_0^{0}(2308)$ and $D_{sJ}^{+}(2317)$ respectively, but not for the resonances observed by FOCUS: $D_0^{0,+}(2405)$.Comment: 6 pages, 5 eps figures; Contribution to the 'Workshop on Light-Cone QCD and Nonperturbative Hadron Physics 2005 (LC2005)', Cairns-Australi

Quark-meson coupling model with constituent quarks: Exchange and pionic effects

The binding energy of nuclear matter including exchange and pionic effects is calculated in a quark-meson coupling model with massive constituent quarks. As in the case with elementary nucleons in QHD, exchange effects are repulsive. However, the coupling of the mesons directly to the quarks in the nucleons introduces a new effect on the exchange energies that provides an extra repulsive contribution to the binding energy. Pionic effects are not small. Implications of such effects on observables are discussed.Comment: 12 pages, latex, 1 figure, to appear in Phys. Lett.

Nuclear Coherent versus Incoherent Effects in Peripheral RHI Collisions

We derive simple and physically transparent expressions for the contribution of the strong interaction to one nucleon removal processes in peripheral relativistic heavy ion collisions. The coherent contribution,i.e, the excitation of a giant dipole resonance via meson exchange is shown to be negligible as well as interference between coulomb and nuclear excitation. Incoherent nucleon knock out contribution is also derived suggesting the nature of the nuclear interaction in this class of processes. We also justify the simple formulae used to fit the data of the E814 Collaboration.Comment: LATEX, 20 pags, Submited to Nucl. Phys. C, NUCPHA 176

Progress in the determination of the J/ψ−πJ/\psi-\pi cross section

Improving previous calculations, we compute the $J/\psi \pi\to {charmed mesons}$ cross section using QCD sum rules. Our sum rules for the $J/\psi \pi\to \bar{D} D^*$, $D \bar{D}^*$, ${\bar D}^* D^*$ and ${\bar D} D$ hadronic matrix elements are constructed by using vaccum-pion correlation functions, and we work up to twist-4 in the soft-pion limit. Our results suggest that, using meson exchange models is perfectly acceptable, provided that they include form factors and that they respect chiral symmetry. After doing a thermal average we get $\sim 0.3$ mb at T=150\MeV.Comment: 22 pages, RevTeX4 including 7 figures in ps file