Vacuum structure of a modified MIT Bag

An alternative to introducing and subsequently renormalizing classical parameters in the expression for the vacuum energy of the MIT bag for quarks is proposed in the massless case by appealing to the QCD trace anomaly and scale separation due to asymptotic freedom. The explicit inclusion of gluons implies an unrealistically low separation scale.Comment: 5 pages, 2 figure

Magnetic moments of S-shell pentaquarks in the constituent quark model

We discuss the magnetic moments of the recently discovered exotic baryons Theta(+) and Xi(--) and their multiplet partners in the framework of a naive additive quark model. These baryons are set up as pentaquark states where four quarks and a single antiquark are located in their ground state orbit. The pentaquark states are classified as members of the flavor SU(3) octet and antidecuplet with spin-parity J^P = (1/2)^- and (3/2)^-, where we determine the magnetic moments of these pentaquark states.Comment: 13 pages, 2 figures, elsart; publication version, 8 pages, 1 figure, ptptex; upload miss correcte

Electromagnetic structure of the nucleon and the Roper resonance in a light-front quark approach

A relativistic light-front quark model is used to describe both the elastic nucleon and nucleon-Roper transition form factors in a large Q2 range, up to 35 GeV2 for the elastic and up to 12 GeV2 for the resonance case. Relativistic three-quark configurations satisfying the Pauli exclusion principle on the light-front are used for the derivation of the current matrix elements. The Roper resonance is considered as a mixed state of a three-quark core configuration and a molecular N+sigma hadron component. Based on this ansatz we obtain a realistic description of both processes, elastic and inelastic, and show that existing experimental data are indicative of a composite structure of the Roper resonance.Comment: 19 page

Radiative proton-antiproton annihilation and isospin mixing in protonium

A detailed analysis of the radiative $p\bar p$ annihilation is made in the framework of a two-step formalism, the $p\bar p$ annihilates into meson channels containing a vector meson with a subsequent conversion into a photon via the vector dominance model (VDM). Both steps are derived from the underlying quark model. First, branching ratios for radiative protonium annihilation are calculated and compared with data. Then, details of the isospin interference are studied for different models of the initial protonium state and also for different kinematical form factors. The isospin interference is shown to be uniquely connected to the $p\bar p - n\bar n$ mixing in the protonium state. Values of the interference terms directly deduced from data are consistent with theoretical expectations, indicating a dominant $p\bar p$ component for the $^1S_0$ and a sizable $n\bar n$ component for the $^3S_1$ protonium state. The analysis is extended to the $p\bar p \to \gamma \Phi$ transition, where the large observed branching ratio remains unexplained in the VDM approach.Comment: 34 pages, RevTeX, 2 figures, to appear in Phys. Rev. C; typos correcte

Pion dominance in RPV SUSY induced neutrinoless double beta decay

At the quark level there are basically two types of contributions of R-parity violating SUSY (RPV SUSY) to neutrinoless double beta decay: the short-range contribution involving only heavy virtual superpartners and the long-range one with the virtual squark and neutrino. Hadronization of the effective operators, corresponding to these two types of contributions, may in general involve virtual pions in addition to the close on-mass-shell nucleons. It is known that the short-range contribution is dominated by the pion exchange. In the present paper we show that this is also true for the long-range RPV SUSY contribution and, therefore, the RPV SUSY contributes to the neutrinoless double beta decay dominantly via charged pion exchange between the decaying nucleons.Comment: 7 pages, 1 figure. Minor corrections, several comments and references adde

Charmed baryon Sigmac(2800) as a ND hadronic molecule

The isotriplet Sigmac(2800) baryon with possible quantum numbers J(P) = 1/2(+), 1/2(-) or 3/2(+), 3/2(-) is considered as a hadronic molecule composed of a nucleon and a D meson. We determine the strong two-body decay widths Sigmac to Lambdac + pi which are shown to be consistent with current data for the J(P) = 1/2(+) and J(P) = 3/2(-) assignments.Comment: 8 pages, 2 figure

Effect of the ηη\eta\eta channel and interference phenomena in the two-pion transitions of charmonia and bottomonia

The basic shape of di-pion mass spectra in the two-pion transitions of both charmonia and bottomonia states is explained by an unified mechanism based on contributions of the $\pi\pi$, $K\overline{K}$ and $\eta\eta$ coupled channels including their interference. The role of the individual $f_0$ resonances in shaping the di-pion mass distributions in the charmonia and bottomonia decays is considered.Comment: 8 pages, 4 figures, Talk at the XXIII International Baldin Seminar on High Energy Physics Problems "Relativistic Nuclear Physics \& Quantum Chromodynamics" (Dubna, Russia, 19--24 September 2016). arXiv admin note: text overlap with arXiv:1610.0789