Quark-Resonance model

We construct an effective Lagrangian for low energy hadronic interactions through an infinite expansion in inverse powers of the low energy cutoff $\Lambda_\chi$ of all possible chiral invariant non-renormalizable interactions between quarks and mesons degrees of freedom. We restrict our analysis to the leading terms in the $1/N_c$ expansion. The effective expansion is in (\mu^2/\cutoff^2 )^P \ln (\cutoff^2/\mu^2 )^Q. Concerning the next-to-leading order, we show that, while the pure \mu^2/\cutoff^2 corrections cannot be traced back to a finite number of non renormalizable interactions, those of order (\mu^2/\cutoff^2 ) \ln (\cutoff^2/\mu^2 ) receive contributions from a finite set of 1/\cutoff^2 terms. Their presence modifies the behaviour of observable quantities in the intermediate $Q^2$ region. We explicitely discuss their relevance for the two point vector currents Green's function.Comment: 41 pages, 11 figures, preprint ROM2F 93/3

The BES f_0(1810): a new glueball candidate

We analyze the f_0(1810) state recently observed by the BES collaboration via radiative J/\psi decay to a resonant \phi\omega spectrum and confront it with DM2 data and glueball theory. The DM2 group only measured \omega\omega decays and reported a pseudoscalar but no scalar resonance in this mass region. A rescattering mechanism from the open flavored KKbar decay channel is considered to explain why the resonance is only seen in the flavor asymmetric \omega\phi branch along with a discussion of positive C parity charmonia decays to strengthen the case for preferred open flavor glueball decays. We also calculate the total glueball decay width to be roughly 100 MeV, in agreement with the narrow, newly found f_0, and smaller than the expected estimate of 200-400 MeV. We conclude that this discovered scalar hadron is a solid glueball candidate and deserves further experimental investigation, especially in the K-Kbar channel. Finally we comment on other, but less likely, possible assignments for this state.Comment: 11 pages, 4 figures. Major substantive additions, including an ab-initio, QCD-based computation of the glueball inclusive decay width, evaluation of final state effects, and enhanced discussion of several alternative possibilities. Our conclusions are unchanged: the BES f_0(1810) is a promising glueball candidat

Observation of Pseudoscalar and Axial Vector Resonances in pi- p -> K+ K- pi0 n at 18 GeV

A new measurement of the reaction pi- p -> K+ K- pi0 n has been made at a beam energy of 18 GeV. A partial wave analysis of the K+ K- pi0 system shows evidence for three pseudoscalar resonances, eta(1295), eta(1416), and eta(1485), as well as two axial vectors, f1(1285), and f1(1420). Their observed masses, widths and decay properties are reported. No signal was observed for C(1480), an IG J{PC} = 1+ 1{--} state previously reported in phi pi0 decay.Comment: 7 pages, 6 figs, to be submitted to Phys. Let

A new measurement of direct CP violation in two pion decays of the neutral kaon

The NA48 experiment at CERN has performed a new measurement of direct CP violation, based on data taken in 1997 by simultaneously collecting K_L and K_S decays into pi0pi0 and pi+pi-. The result for the CP violating parameter Re(epsilon'/epsilon) is (18.5 +/- 4.5(stat)} +/- 5.8 (syst))x10^{-4}.Comment: 18 pages, 6 figure

A precision measurement of direct CP violation in the decay of neutral kaons into two pions

The direct CP violation parameter Re(epsilon'/epsilon) has been measured from the decay rates of neutral kaons into two pions using the NA48 detector at the CERN SPS. The 2001 running period was devoted to collecting additional data under varied conditions compared to earlier years (1997-99). The new data yield the result: Re(epsilon'/epsilon) = (13.7 +/- 3.1) times 10^{-4}. Combining this result with that published from the 1997, 98 and 99 data, an overall value of Re(epsilon'/epsilon) = (14.7 +/- 2.2) times 10^{-4} is obtained from the NA48 experiment.Comment: 19 pages, 5 figures, to be published in Physics Letters

Measurement of the J/Psi Production Cross Section in 920 GeV/c Fixed-Target Proton-Nucleus Interactions

The mid-rapidity (dsigma_(pN)/dy at y=0) and total sigma_(pN) production cross sections of J/Psi mesons are measured in proton-nucleus interactions. Data collected by the HERA-B experiment in interactions of 920 GeV/c protons with carbon, titanium and tungsten targets are used for this analysis. The J/Psi mesons are reconstructed by their decay into lepton pairs. The total production cross section obtained is sigma_(pN)(J/Psi) = 663 +- 74 +- 46 nb/nucleon. In addition, our result is compared with previous measurements

Leptonic and Semileptonic Decays of Charm and Bottom Hadrons

We review the experimental measurements and theoretical descriptions of leptonic and semileptonic decays of particles containing a single heavy quark, either charm or bottom. Measurements of bottom semileptonic decays are used to determine the magnitudes of two fundamental parameters of the standard model, the Cabibbo-Kobayashi-Maskawa matrix elements $V_{cb}$ and $V_{ub}$. These parameters are connected with the physics of quark flavor and mass, and they have important implications for the breakdown of CP symmetry. To extract precise values of $|V_{cb}|$ and $|V_{ub}|$ from measurements, however, requires a good understanding of the decay dynamics. Measurements of both charm and bottom decay distributions provide information on the interactions governing these processes. The underlying weak transition in each case is relatively simple, but the strong interactions that bind the quarks into hadrons introduce complications. We also discuss new theoretical approaches, especially heavy-quark effective theory and lattice QCD, which are providing insights and predictions now being tested by experiment. An international effort at many laboratories will rapidly advance knowledge of this physics during the next decade.Comment: This review article will be published in Reviews of Modern Physics in the fall, 1995. This file contains only the abstract and the table of contents. The full 168-page document including 47 figures is available at http://charm.physics.ucsb.edu/papers/slrevtex.p

Study of Tau-pair Production in Photon-Photon Collisions at LEP and Limits on the Anomalous Electromagnetic Moments of the Tau Lepton

Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb^{-1}. The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.Comment: 20 pages, 9 figures, Accepted by Eur. Phys. J.