Search results for "meson"
showing 10 items of 1548 documents
Non-leptonic decays of Charmed mesons into two Pseudoscalars
2015
We examine the role of resonant coupled channel final state interactions (FSI), as well as weak annihilation and exchange contributions in explaining all the two body hadronic $D\rightarrow PP$ decay modes data. In the un-unitarized amplitudes we include modified Wilson coefficients with non-factorizable corrections as parameters. For the hadronic form factors, the z-series expansion method is used to get the $q^2$ dependence. The FSI effects are incorporated via a phenomenological approach with widths of resonances to various channels taken from observations where available, and others as additional parameters to be determined from fits of all the theoretical rates to the measured ones. Ou…
Branching fraction measurement ofB¯0→D(*)+π−andB−→D(*)0π−and isospin analysis ofB¯→D(*)πdecays
2007
Using 65 X 10(6) Y (4S) -> BB events collected with the BABAR detector at the PEP-II e(+) e(-) storage ring at the Stanford Linear Accelerator Center, we measure the color-favored branching fractions B(B-0 -> D+ pi(-)) = (2.55 +/- 0.05 +/- 0.16) X 10(-3), B(B-0 -> D*(+) pi(-)) = (2.79 +/- 0.08 +/- 0.17) X 10(-3), B(B- -> D-0 pi(-)) = (4.90 +/- 0.07 +/- 0.22) X 10(-3) and B(B- -> D*(0)pi(-)) = (5.52 +/- 0.17 +/- 0.42) X 10(-3), where the first error is statistical and the second is systematic. With these results and the current world average for the branching fraction for the color-suppressed decay B-0 -> D-(*()0)pi(0), the cosines of the strong phase difference delta between the I =1/2 and …
Electromagnetic Calorimeter for HADES Experiment
2014
Electromagnetic calorimeter (ECAL) is being developed to complement dilep- ton spectrometer HADES. ECAL will enable the HADES@FAIR experiment to mea- sure data on neutral meson production in heavy ion collisions at the energy range of 2-10 AGeV on the beam of future accelerator SIS100@FAIR. We will report results of the last beam test with quasi-monoenergetic photons carried out in MAMI facility at Jo- hannes Gutenberg Universitat Mainz.
Photoproduction of mesons and Compton scattering on the proton: Selected results from the A2 Collaboration at MAMI
2020
The A2 Collaboration performs a manifold research program using real photons in the Crystal Ball/TAPS experiment at the MAMI accelerator facility in Mainz. The experiments take advantage of high- intensity unpolarized, linearly or circularly polarized photon beams, and unpolarized or polarized targets. The detector setup provides almost complete coverage in solid angle and is well suited for the detection of multi particle final states. In order to probe the internal structure of the nucleon, the spectrum of baryon resonances is studied via measurements of unpolarized cross sections and various polarization observables in single and double meson photoproduction. The program aiming to determ…
J/\psi depletion in a nuclear medium
2012
In this talk, we have taken into account the main decay channel of J/ψ when travelling inside a nucleus. In analogy to all vector mesons in SU(3), where the main decay channel is to two pseudoscalars, in the case of the J/ψ the meson meson channel to which it couples strongly is DD. Taking this into account we study the J/ψN → DΛc and J/ψN → DΣc mediated by D-exchange. To obtain the couplings we use an extension to SU(4) of the local hidden gauge Lagrangians as done in [1]. Analogously, we consider the mechanisms where the exchanged D collides with a nucleon and gives πΛc or πΣc. The sum of these channels produces a J/ψN inelastic cross section which is larger than the elastic one and is re…
In-medium modifications of the pi pi interaction in photon-induced reactions
2002
Differential cross sections of the reactions $(\gamma,\pi^\circ\pi^\circ)$ and $(\gamma,\pi^\circ\pi^++\pi^\circ\pi^-)$ have been measured for several nuclei ($^1$H,$^{12}$C, and $^{\rm nat}$Pb) at an incident-photon energy of $E_{\gamma}$=400-460 MeV at the tagged-photon facility at MAMI-B using the TAPS spectrometer. A significant nuclear-mass dependence of the $\pi\pi$ invariant-mass distribution is found in the $\pi^\circ\pi^\circ$ channel. This dependence is not observed in the $\pi^\circ\pi^{+/-}$ channel and is consistent with an in-medium modification of the $\pi\pi$ interaction in the $I$=$J$=0 channel. The data are compared to $\pi$-induced measurements and to calculations within …
Double polarisation observable E and helicity dependent cross section for single π0 photoproduction off proton and neutron
2020
Photon-induced reactions, like meson photoproduction, allow to excite the nucleon, to have access to many different polarisation observables and are an essential tool to disentangle the role of the different electromagnetic multipoles due to the change of sign of some contributions and the presence of interference terms between different multipole amplitudes. In addition, the use of polarised beams and/or targets allow to access additional observables which are fundamental in order to accurately determine the nucleon resonance properties. The A2@MAMI collaboration is carrying out a broad and systematic study on this topics, both on the proton and the neutron. The experiments are performed a…
Unveiling the K1(1270) double-pole structure in the B¯→J/ψρK¯ and B¯→J/ψK¯*π decays
2021
By looking at the pseudoscalar-vector meson spectra in the $\overline{B}\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\rho}\overline{K}$ and $\overline{B}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\overline{K}}^{*}\ensuremath{\pi}$ weak decays, we theoretically investigate the double-pole structure of the ${K}_{1}(1270)$ resonance by using the chiral unitary approach to account for the final-state interactions between the pseudoscalar ($P$) and vector ($V$) mesons. The ${K}_{1}(1270)$ resonance is dynamically generated through these interactions in coupled channels and influences the shape of the invariant mass distributions under consideration. We show how these shapes are affect…
Unitary chiral dynamics in decays and the role of scalar mesons
2004
We make a theoretical study of the J/psi decays into omegapipi, phipipi, omegaK (K) over bar and phiK (K) over bar using the techniques of the chiral unitary approach stressing the important role of the scalar resonances dynamically generated through the final state interaction of the two pseudoscalar mesons. We also discuss the importance of new mechanisms with intermediate exchange of vector and axial-vector mesons and the role played by the OZI rule in the J/ psi phipipi vertex, quantifying its effects. The results nicely reproduce the experimental data for the invariant mass distributions in all the channels considered. (C) 2004 Elsevier B.V. All rights reserved.
The low lying scalar resonances in the D0 decays into Ks0 and f0(500), f0(980), a0(980)
2015
Abstract The D 0 decay into K s 0 and a scalar resonance, f 0 ( 500 ) , f 0 ( 980 ) , a 0 ( 980 ) , are studied obtaining the scalar resonances from final state interaction of a pair of mesons produced in a first step in the D 0 decay into K s 0 and the pair of pseudoscalar mesons. This weak decay is very appropriate for this kind of study because it allows to produce the three resonances in the same decay in a process that is Cabibbo-allowed, hence the rates obtained are large compared to those of B ¯ 0 decays into J / ψ and a scalar meson that have at least one Cabibbo-suppressed vertex. Concretely the a 0 ( 980 ) production is Cabibbo-allowed here, while it cannot be seen in the B ¯ s 0 …