Publisher’s Note: Model-independent measurement ofS-waveK−π+systems usingD+→<

Abstract

A model-independent partial-wave analysis of the S-wave component of the Kπ system from decays of D + mesons to the three-body K − π + π + final state is described. Data come from the Fermilab E791 experiment. Amplitude measurements are made independently for ranges of K − π + invariant mass, and results are obtained below 825 MeV/c 2 , where previous measurements exist only in two mass bins. This method of parametrizing a three-body decay amplitude represents a new approach to analysing such decays. Though no model is required for the S-wave, a parametrization of the relatively well-known reference P -and D-waves, optimized to describe the data used, is required. In this paper, a Breit-Wigner model is adopted to describe the resonances in these waves. The observed phase variation for the S-, P -and D-waves do not match existing measurements of I = 1 2 K − π + scattering in the invariant mass range in which scattering is predominantly elastic. If the data are mostly I = 1 2 , this observation indicates that the Watson theorem, which requires these phases to have the same dependence on invariant mass, may not apply to these decays without allowing for some interaction with the other pion. The production rate of K − π + from these decays, if assumed to be predominantly I = 1 2 , is also found to have a significant dependence on invariant mass in the region above 1.25 GeV/c 2 . These measurements can provide a relatively model-free basis for future attempts to determine which strange scalar amplitudes contribute to the decays.

Consistent Dalitz plot analysis of Cabibbo-favored D+→K¯ππ+Niecknig1, Kubis2 2018Physics Letters B440280View full textAdd to dashboardCite

“…[32,33] for analyses of similar B-meson decays), using various approximations in the description of final-state interactions. This corresponds to the rather good data situation for that channel [34][35][36][37]. However, a consistent, combined investigation of both final states is highly desirable, as they are coupled to each other by simple charge-exchange rescattering, but only the partially neutral final state allows for the observation of resonances in the pion-pion system (essentially the ρ(770)), while the π + π + system is necessarily a nonresonant isospin I = 2 state.…”

“…[26] concerning the phase motion of the I = 1/2 πK S -wave, whose phase rises much more quickly than the elastic scattering phase shift [56]. This has been observed before [34,37], but does not contradict Watson's final-state theorem [57]: the phase is modified due to rescattering with the third particle in the final state.…”

First results from an extended freed-isobar analysis at COMPASS

“…To avoid the necessity for this model input in the freed-isobar approach, the dynamic amplitudes are replaced by sets of step-like functions, that approximate the dynamic amplitude by a set of constants α b within narrow bins b of m 2π [2]:…”

Meson spectroscopy at COMPASS

“…In order to study possible bias due to these parametrizations and to ensure that the observed a 1 (1420) signal is truly related to the narrow f 0 (980), a novel analysis method inspired by Ref. [19] was developed [4]. In this so-called freed-isobar analysis, the three fixed parametrizations for the 0 ++ isobar amplitudes are replaced by a set of piecewise constant complex-valued functions that fully cover the allowed two-pion mass range.…”