QCD sum rules study of the J(PC)=1(- -) charmonium Y mesons

We use QCD sum rules to test the nature of the recently observed mesons Y(4260), Y(4350) and Y(4660), assumed to be exotic four-quark (c (c) over barq (q) over bar) or (c (c) over bars (s) over bar) states with J(PC)= 1(--). We work at leading order in alpha(s), consider the contributions of higher dimension condensates and keep terms which are linear in the strange quark mass m(s). We find for the (c (c) over bars (s) over bar) state a mass in m(Y) = (4.65 +/- 0.10) GeV which is compatible with the experimental candidate Y (4660), while for the (c (c) over barq (q) over bar) state we find a mass in m(Y) = (4.49 +/- 0.11) GeV, which is still consistent with the mass of the experimental candidate Y(4350). With the tetraquark structure we are working we cannot explain the Y(4260) as a tetraquark state. We also consider molecular D(s0)(D) over bar (s)* and D(0)(D) over bar* states. For the D(s0)(D) over bar (s)* molecular state we get m(Ds0 (D) over bars*) = (4.42 +/- 0.10) GeV which is consistent, considering the errors, with the mass of the meson Y(4350) and for the D(0)(D) over bar* molecular state we get m(D0 (D) over bar*) = (4.27 +/- 0.10) GeV in excellent agreement with the mass of the meson Y(4260). (C) 2008 Elsevier B.V. All rights reserved.

Absence of gluonic components in axial and tensor mesons

A quarkonium-gluonium mixing scheme previously developed to describe the characteristic of the pseudoscalar mesons is applied to axial and tensor mesons. The parameters of the model are determined by fitting the eigenvalues of a mass matrix. The corresponding eigenvectors give the proportion of light quarks, strange quarks and glueball in each meson. However, the predictions of the model for the branching ratios and electromagnetic decays are incompatible with the experimental results. These results suggest the absence of gluonic components in the states of axial and tensor isosinglet mesons analyzed here.

Light-Front model of transition form-factors in heavy meson decay

Electroweak transition form factors of heavy meson decays are important ingredients in the extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements from experimental data. In this work, within a. light-front framework, we calculate electroweak transition form factor for the semileptonic decay of D mesons into a pion or a kaon. The model results underestimate in both cases the new data of CLEO for the larger momentum transfers accessible in the experiment. We discuss possible reasons for that in order to improve the model.

Light-front quark-meson coupling model

We formulate a quark-meson coupling model for nuclear matter using light front variables. We present results for saturation properties of nuclear matter and in-medium nucleon properties. We also calculate the distribution function of the plus momentum carried by nucleons in nuclear matter. Our model predicts that vector mesons carry only 7% of the fraction per nucleon of the total plus momentum of the system.

Nuclear photoproduction of pseudoscalar mesons at forward angles up to 6.0 GeV

The nuclear incoherent π 0 photoproduction cross section from 12C is evaluated at forward angles in the 4.0 to 6.0 GeV energy range using the multicollisional intranuclear cascade model MCMC. The model incorporates some improvements in comparison with previous versions associated with the momentum distribution (MD) for light nuclei - extracted from the available (e,e ′p) data - as well as the evaluation of the shadowing effects during the photo-nucleus interaction. The final results of the single and double differential cross sections at forward angles are very sensitive to the MD parameterizations due to the Pauli principle, which largely suppresses the cross sections for low momentum transfer. The attenuation of the nuclear cross section due to pion - nucleus final state interactions is approximately 40% (without nuclear shadowing), which is in nice agreement with the predictions from the Glauber model. The single and double π 0 differential cross sections are presented for possible applications for the interpretation of the inelastic background in the PrimEx experiment at the Jefferson Laboratory. © 2007 American Institute of Physics.

The interaction of D mesons and nucleons at finite density

We present results on the the influence of changes in the masses and sizes of D mesons and nucleons on elastic DN scattering cross sections and phase shifts in a hadronic medium composed of confined quarks in nucleons. We evaluate the changes of the hadronic masses due to changes of the light constituent quarks at finite baryon density using a chiral quark model based on Coulomb gauge QCD. The model contains a confining Coulomb potential and a transverse hyperfine interaction consistent with a finite gluon propagator in the infrared. We present results for the total cross section and the s-wave phase shift at low energies for isospin I=1-for I=0 and other partial waves the results are similar.

Forward-angle incoherent photoproduction of pseudoscalar mesons off nuclei

The mechanism of forward angle incoherent photoproduction of pseudoscalar mesons off nuclei is revisited via the time-dependent multicollisional Monte Carlo (MCMC) intranuclear cascade model. Our results-combined with recent developments to address coherent photoproduction-reproduce with good accuracy recent JLab data of pi(0) photoproduction from carbon and lead at an average photon energy k similar to 5.2 GeV. For the case of. photoproduction, our results for k = 9 GeV suggest that future measurements to extract the eta ->gamma gamma decay width via the Primakoff method should be focused on light nuclei, where the disentanglement between the Coulomb and strong amplitudes is more easily achieved. The prospects to use heavy nuclei data to access the unknown eta N cross section in cold nuclear matter are also presented.

Light vector meson production in pp collisions at root s=7 TeV ALICE Collaboration

The ALICE experiment has measured low-mass dimuon production in pp collisions at root s = 7 TeV in the dimuon rapidity region 2.5 < y < 4. The observed dimuon mass spectrum is described as a superposition of resonance decays (eta, rho, omega, eta', phi) into muons and semi-leptonic decays of charmed mesons. The measured production cross sections for omega and phi are sigma(omega)(1 < p(t) < 5 GeV/c. 2.5 < y < 4) = 5.28 +/- 0.54(stat) +/- 0.49(syst) mb and sigma(phi)(1 < p(t) < 5 GeV/c. 2.5 < y < 4) = 0.940 +/- 0.084(stat) +/- 0.076(syst) mb. The differential cross sections d(2)sigma/dy dp(t) are extracted as a function of p(t) for omega and phi. The ratio between the rho and omega cross section is obtained. Results for the phi are compared with other measurements at the same energy and with predictions by models. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.