Search results for "SCALAR"
showing 10 items of 1002 documents
Data-driven dispersive analysis of the ππ and πK scattering
2021
We present a data-driven analysis of the resonant $S$-wave $\ensuremath{\pi}\ensuremath{\pi}\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}$ and $\ensuremath{\pi}K\ensuremath{\rightarrow}\ensuremath{\pi}K$ reactions using the partial-wave dispersion relation. The contributions from the left-hand cuts are accounted for using the Taylor expansion in a suitably constructed conformal variable. The fits are performed to experimental and lattice data as well as Roy analyses. For the $\ensuremath{\pi}\ensuremath{\pi}$ scattering we present both a single- and a coupled-channel analysis by including additionally the $K\overline{K}$ channel. For the latter the central result is the Omn\`es m…
Three-dimensional point spread function of multilayered flat lenses and its application to extreme subwavelength resolution
2011
The three-dimensional (3D) point spread function (PSF) of multilayered flat lenses was proposed in order to characterize the diffractive behavior of these subwavelength image formers. We computed the polarization-dependent scalar 3D PSF for a wide range of slab widths and for different dissipative metamaterials. In terms similar to the Rayleigh criterion we determined unambiguously the limit of resolution featuring this type of image-forming device. We investigated the significant reduction of the limit of resolution by increasing the number of layers, which may drop nearly 1 order of magnitude. However, this super-resolving effect is obtained in detriment of reducing the depth of field. Li…
Integrated photoabsorption strength and sum rules for a bound Dirac particle
1985
Relativistic effects in the integrated total photoabsorption cross section are discussed using a simple model of a Dirac particle bound in a central potential of scalar or vector type. The integrated strength is calculated explicitly and compared to a new relativistic extension of the TRK-sum rule using positive energy projection and to predictions from dispersion relations. M1 and E2 sum rules are also considered. In all cases the integrated strength exceeds the classical sum rule up to a few percent. The dispersion sum rule cannot be compared directly to the integrated strength since it contains a negative contribution from pair production in the potential field which is of the order of 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 …
Observation of pseudoscalar and tensor resonances in J /ψ →γφφ
2016
Based on a sample of (1310.6 +/- 10.5) x 10(6) J/psi events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay J/psi -> gamma phi phi is performed in order to study the intermediate states. Results of the partial wave analysis show that the structures are predominantly 0(-+) states. The existence of the eta(2225) is confirmed, and its resonance parameters are measured. Two additional pseudoscalar states, the eta(2100) with a mass of 2050(-24-26)(+30+75) MeV/c(2) and a width of 250(-30-164)(+36+181) MeV/c(2) and the X(2500) with a mass of 2470(-19-23)(+15+101) MeV/c(2) and a width of 230(-35-33)(+64+56) MeV/c(2), are observed. In add…
Perturbative QCD study of Bs decays to a pseudoscalar meson and a tensor meson
2014
We study two-body hadronic B-s -> PT decays, with P(T) being a light pseudoscalar (tensor) meson, in the perturbative QCD approach. The CP-averaged branching ratios and the direct CP asymmetries of the Delta S = 0 modes are predicted, where Delta S is the difference between the strange numbers of final and initial states. We also define and calculate experimental observables for the Delta S = 1 modes under the B-s(0)-(B) over bar (0)(s) mixing, including CP averaged branching ratios, time-integrated CP asymmetries, and the CP observables C-f, D-f and S-f. Results are compared to the B-s -> PV ones in the literature, and to the B -> PT ones, which indicate considerable U-spin symmetry breaki…
Pseudoscalar decays into lepton pairs from rational approximants
2016
The pseudoscalar decays into lepton pairs P! ‘‘ are analyzed with the machinery of Canterbury approximants, an extension of Pade approximants to bivariate functions. This framework provides an ideal model-independent approach to implement all our knowledge of the pseudoscalar transition form factors driving these decays, can be used for data analysis, and allows to include experimental data and theoretical constraints in an easy way, and determine a systematic error. We find that previous theoretical estimates for these branching ratios have underestimated their theoretical uncertainties. From our updated results, the existing experimental discrepancies for p 0 ! e + e and h! m + m channels…
The pseudoscalar mixing angle ΘPS from ν and ν′ production in annihiltion at rest
1992
Abstract We have determined ratios of branching ratios for p p annihilations at rest into π0η and π0η′, into ηη and ηη′, and into ωη and ωη′. All reactins are observed in two different all-neutral final states. The ratios permit a determination of the pseudoscalar mixing angle. We find ΘPS = −(17.3±1.8)°.