Search results for "ISOSCALAR"
showing 10 items of 91 documents
Doubly charmed exotic mesons: A gift of nature?
2011
Article history: We study doubly charmed exotic states by solving the scattering problem of two D mesons. Our results point to the existence of a stable isoscalar doubly charmed meson with quantum numbers (I) J P = (0)1 + . We perform a thorough comparison to the results obtained within the hyperspherical harmonic formalism. Such exotic states could be measured at LHC and RHIC. Their experimental observation would,
Two-body effects in coherent η-meson photoproduction on the deuteron in the region of theS11(1535)resonance
2001
Coherent \ensuremath{\eta}-meson photoproduction on the deuteron has been studied, where the emphasis is on the relative importance of two-body contributions from hadronic rescattering and electromagnetic meson exchange currents besides the impulse approximation. For the elementary photoproduction amplitude a coupled resonance model developed by Bennhold and Tanabe has been used that fits reasonably well with the experimental data. The rescattering effects are treated within a coupled channel approach considering the intermediate excitation of the ${P}_{11}(1440),$ ${D}_{13}(1520),$ and ${S}_{11}(1535)$ nucleon resonances. The hadronic interaction between nucleon and resonances is modeled b…
Resonances and the Weinberg-Tomozawa 56-baryon-35-meson interaction
2006
Vector meson degrees of freedom are incorporated into the Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian by using a scheme which relies on spin--flavor SU(6) symmetry. The corresponding Bethe-Salpeter approximation successfully reproduces previous SU(3)--flavor WT results for the lowest-lying s--wave negative parity baryon resonances, and it also provides some information on the dynamics of the heavier ones. Moreover, it also predicts the existence of an isoscalar spin-parity $\frac32^-$ $K^*N$ bound state (strangeness +1) with a mass around 1.7--1.8 GeV, unstable through $K^*$ decay. Neglecting d-wave KN decays, this state turns out to be quite narrow ($\Gamma \le 15$ MeV) and it mi…
sigma meson in a nuclear medium through two pion photoproduction
2003
We show theoretical results for $(\gamma, \pi^0 \pi^0)$ production on nucleons and nuclei in the kinematical region where the scalar isoscalar $\pi \pi$ amplitude is influenced by the $\sigma$ pole. The final state interaction of the pions modified by the nuclear medium produces a spectacular shift of strength of the two pion invariant mass distribution induced by the moving of the $\sigma$ pole to lower masses and widths as the nuclear density increases.
The ρ–ω splitting in constituent quark models
2009
Abstract In this Letter we present a solution to describe simultaneously the light isoscalar and isovector vector mesons in constituent quark models. In Ref. [J. Vijande, F. Fernandez, A. Valcarce, J. Phys. G 31 (2005) 481] the q q ¯ spectrum was studied in a generalized constituent quark model constrained by the NN phenomenology and the baryon spectrum. An overall good fit to the available experimental data was obtained. A major problem of this description was the relative position of the vector ω and ρ mesons. The present results improve the description of the isoscalar meson spectroscopy. They should serve as a step forward in distinguishing conventional quark model mesons from exotic st…
Effects of the axial isoscalar neutral current for solar neutrino detection
1992
Abstract An essential assumption in the analysis of all the large solar neutrino experiments sensitive to neutral currents has been that the axial transitions are purely isovector. The recent results on the spin structure of the proton suggest the presence of an axial isoscalar neutral-current interaction. This would modify the assumed transition strengths for the neutral-current detection of solar neutrinos. We demonstrate that in the long wavelength limit a deuterium target is insensitive to such a mechanism. Our results for the situation of the planned BOREX experiment show that the suggested isoscalar strength would increase the observed rate by 30–40%, depending on the transition.
Short range correlations in the pion s-wave self-energy of pionic atoms
1995
We evaluate the contribution of second order terms to the pion-nucleus s-wave optical potential of pionic atoms generated by short range nuclear correlation. The corrections are sizeable because they involve the isoscalar s-wave $\pi N$ amplitude for half off-shell situations where the amplitude is considerably larger than the on-shell one. In addition, the s-wave optical potential is reanalyzed by looking at all the different conventional contributions together lowest order, Pauli corrected rescattering term, second order absorptive effects, terms from the interaction of pions with the virtual pion cloud (chiral corrections) and correlation effects. Different off-shell extrapolations for t…
The σ meson in a nuclear medium through two pion photoproduction
2002
We present theoretical results for (gamma,pi0 pi0) and (gamma,pi+- pi0) production on nucleons and nuclei in the kinematical region where the scalar isoscalar pi pi amplitude is influenced by the sigma pole. The final state interaction of the pions modified by the nuclear medium produces a spectacular shift of strength of the pi0 pi0 invariant mass distribution induced by the moving of the sigma pole to lower masses and widths as the nuclear density increases.
Chiral nonperturvative approach to the isoscalar s-wave pion-pion interaction in a nuclear medium
1997
The s-wave isoscalar amplitude for pion-pion scattering in a nuclear medium is evaluated using a nonperturbative unitary coupled channels method and the standard chiral Lagrangians. The method has proved successful to describe the pion-pion properties in the scalar isoscalar channel up to 1.2 GeV giving rise to poles in the t matrix for the f0(980) and the sigma. The extension of the method to the nuclear medium implies not only the renormalization of the pions in the medium, but also the introduction of interaction terms related to contact terms in the pion-nucleon to pion-pion-nucleon interaction. Off shell effects are also shown to be important leading to cancellations which reduce the c…
A precise measurement of the muon neutrino nucleon inclusive charged current cross section off an isoscalar target in the energy range 2.5
2008
Abstract We present a measurement of the muon neutrino–nucleon inclusive charged current cross section, off an isoscalar target, in the neutrino energy range 2.5 ⩽ E ν ⩽ 40 GeV . The significance of this measurement is its precision, ±4% in 2.5 ⩽ E ν ⩽ 10 GeV , and ±2.6% in 10 ⩽ E ν ⩽ 40 GeV regions, where significant uncertainties in previous experiments still exist, and its importance to the current and proposed long baseline neutrino oscillation experiments.