Measurement ofD+→KS0K+andDs+→K<

Abstract

PACS numbers: 13.25. Ft, 14.40.Lb, 11.30.Hv Decays of charmed mesons play an important role in understanding the sources of SU(3) flavor symmetry breaking [1]. Such a breaking can originate from strong final-state interactions or interference between amplitudes with the same final state. In particular,are Cabibbosuppressed (CS) decays that involve color-favored tree, annihilation, and penguin diagrams. For D + decays, the Precise measurements of branching ratios for CS and CF charmed meson decay modes can thus improve the understanding of the underlying dynamics of these decays. In this paper, we report improved measurements of theS π + branching ratios with respect to the corresponding CF modes,The results are based on a data sample of 605 fbrecorded at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider [7]. An additional data sample with about 10% of this integrated luminosity recorded 60 MeV below the Υ(4S) was used for the optimization of the selection criteria (offresonance sample). The Belle detector is a large-solidangle magnetic spectrometer that consists of a silicon vertex detector (SVD), a 50-layer central drift chamber (CDC), an array of aerogel threshold Cherenkov counters (ACC), a barrel-like arrangement of time-of-flight scintillation counters (TOF), and an electromagnetic calorimeter comprised of CsI(Tl) crystals located inside a superconducting solenoid coil that provides a 1.5 T magnetic field. An iron flux return located outside the coil is instrumented to detect K 0 L mesons and to identify muons. The detector is described in detail elsewhere [8].We require that the charged tracks originate from the vicinity of the interaction point (IP) with the impact parameters in the beam direction (z-axis) and perpendicular to it of less than 4 cm and 2 cm, respectively. All charged tracks except those originating from K 0 S decays are required to have at least two associated hits in the SVD, both in the z and radial directions, to assure good spatial resolution on the D mesons' decay vertices. Charged tracks are identified as pions or kaons by requiring the ratio of particle identification likelihoods, L K /(L K + L π ), constructed using information from the CDC, TOF, and ACC, be larger or smaller than 0.6, respectively. For both kaons and pions, the efficiencies and misidentification probabilities are 86% and 10%, respectively.Pairs of oppositely charged tracks that have an invariant mass within 30 MeV/c 2 of the nominal K 0 S mass are used to reconstruct K 0 S → π + π − decays. The distance of the closest approach of the candidate charged tracks to the IP in the plane perpendicular to the z axis is required to be larger than 0.02 cm for high-momentum (> 1.5 GeV/c) K 0 S candidates and 0.03 cm for those with momentum less than 1.5 GeV/c. The π + π − vertex is required to be displaced from the IP by a minimum transverse distance of 0.22 cm for high-momentum candidates and 0.08 cm for the remaining candidates. The mismatch in the z direction at the K 0 S vertex...

Search forCPViolation in the DecaysD(s)+→KS0Ko1, Won2, Aihara3 et al. 2010Phys. Rev. Lett.Self Cite410100View full textAdd to dashboardCite

“…The parametrizations of the random combinatorial background and the peaking background due to K= misidentification are described in detail in Ref. [8].…”