Exclusive K+K^+ production in proton-nucleus collisions

The exclusive $K^+$ meson production in a proton-nucleus collision, leading to two body final states, is investigated in a fully covariant two-nucleon model based on the effective Lagrangian picture. The explicit kaon production vertex is described via creation, propagation and decay into relevant channel of $N^*$(1650), $N^*$(1710) and $N^*$(1720) intermediate baryonic states in the initial collision of the projectile nucleon with one of its target counterparts which is modeled by the one-pion exchange process. The calculated cross sections show strong sensitivity to the medium effects on pion propagator and to the final hypernuclear state excited in the reaction.Comment: Two new figures, version accepted for publication by Phys. Rev.

Functional renormalisation group for few-nucleon systems: SU(4) symmetry and its breaking

We apply the functional renormalisation group to few-nucleon systems. Our starting point is a local effective action that includes three- and four-nucleon interactions, expressed in terms of nucleon and two-nucleon boson fields. The evolution of the coupling constants in this action is described by a renormalisation group flow. We derive these flow equations both in the limit of exact Wigner SU(4) symmetry and in the realistic case of broken symmetry. In the symmetric limit we find that the renormalisation flow equations decouple, and can be combined into two sets, one of which matches the known results for bosons, and the other result matches the one for fermions with spin degrees only. The equations show universal features in the unitary limit, which is obtained when the two-body scattering length tends to infinity. We calculate the spin-quartet neutron-deuteron scattering length and the deuteron-deuteron scattering lengths in the spin-singlet and quintet channels

QCD sum rule analysis for light vector and axial-vector mesons in vacuum and nuclear matter

Extending previous work we study the constraints of QCD sum rules on mass and width of light vector and axial-vector mesons in vacuum and in a medium with finite nuclear density. For the latter case especially the effect of nuclear pions leading to vector-axial-vector mixing is included in the analysis.Comment: RevTeX, 32 pages, 10 eps figure

g_{K LAMBDA N} and g_{K SIGMA N} coupling constants in light cone QCD sum rules

The strong coupling constants g_{K LAMBDA N} and g_{K SIGMA N} for the structure (sigma_{mu,nu} gamma_5) are calculated within light cone QCD sum rules. A comparison of our results on these couplings with predictions from traditional QCD sum rules is presented.Comment: 11 pages, 2 figures, LaTeX formatte

Negative Kaons in Dense Baryonic Matter

Kaon polarization operator in dense baryonic matter of arbitrary isotopic composition is calculated including s- and p-wave kaon-baryon interactions. The regular part of the polarization operator is extracted from the realistic kaon-nucleon interaction based on the chiral and 1/N_c expansion. Contributions of the Lambda(1116), Sigma(1195), Sigma*(1385) resonances are taken explicitly into account in the pole and regular terms with inclusion of mean-field potentials. The baryon-baryon correlations are incorporated and fluctuation contributions are estimated. Results are applied for K- in neutron star matter. Within our model a second-order phase transition to the s-wave K- condensate state occurs at rho_c \gsim 4 \rho_0 once the baryon-baryon correlations are included. We show that the second-order phase transition to the p-wave $K^-$ condensate state may occur at densities $\rho_c \sim 3\div 5 \rho_0$ in dependence on the parameter choice. We demonstrate that a first-order phase transition to a proton-enriched (approximately isospin-symmetric) nucleon matter with a p-wave K- condensate can occur at smaller densities, \rho\lsim 2 \rho_0. The transition is accompanied by the suppression of hyperon concentrations.Comment: 41 pages, 24 figures, revtex4 styl

Determination of pion-baryon coupling constants from QCD sum rules

We evaluate the pi-N-N, pi-Sigma-Sigma and pi-Sigma-Lambda coupling constants using QCD sum rules based on pion-to-vacuum matrix elements of correlators of two interpolating baryon fields. The parts of the correlators with Dirac structure k-slash gamma_5 are used, keeping all terms up to dimension 5 in the OPE and including continuum contributions on the phenomenological side. The ratios of these sum rules to baryon mass sum rules yield stable results with values for the couplings of g_{pi NN}=12+/-5, g_{pi Sigma Sigma}=7+/-4 and g_{pi Sigma Lambda}=6+/-3. The sources of uncertainty are discussed.Comment: 20 pages (RevTeX), 1 figure (attached). Revised version with corrected form for Y2 piece of hyperon correlators; numerical results differ from previous versio

Efimov physics from the functional renormalization group

Few-body physics related to the Efimov effect is discussed using the functional renormalization group method. After a short review of renormalization in its modern formulation we apply this formalism to the description of scattering and bound states in few-body systems of identical bosons and distinguishable fermions with two and three components. The Efimov effect leads to a limit cycle in the renormalization group flow. Recently measured three-body loss rates in an ultracold Fermi gas $^6$Li atoms are explained within this framework. We also discuss briefly the relation to the many-body physics of the BCS-BEC crossover for two-component fermions and the formation of a trion phase for the case of three species.Comment: 28 pages, 13 figures, invited contribution to a special issue of "Few-Body Systems" devoted to Efimov physics, published versio