Amplitude analysis and branching fraction measurement of the decay D s + $$ {D}_s^{+} $$ → K+π+π−

Journal of High Energy Physics, Aug 2022

Using 6.32 fb−1 of e+e− collision data collected at the center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform an amplitude analysis of the decay $$ {D}_s^{+} $$ → K+π+π− and determine the amplitudes of the various intermediate states. The absolute branching fraction of $$ {D}_s^{+} $$ → K+π+π− is measured to be (6.11 ± 0.18stat. ± 0.11syst.) × 10−3. The branching fractions of the dominant intermediate processes $$ {D}_s^{+} $$ → K+ρ0, ρ0 → π+π− and $$ {D}_s^{+} $$ → K*(892)0π+, K*(892)0 → K+π− are determined to be (1.96 ± 0.19stat. ± 0.23syst.) × 10−3 and (1.85 ± 0.12stat. ± 0.13syst.) × 10−3, respectively. The intermediate resonances f0(500), f0(980), and f0(1370) are observed for the first time in this channel.

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Amplitude analysis and branching fraction measurement of the decay D s + $$ {D}_s^{+} $$ → K+π+π−

Published for SISSA by Springer Received: May 20, 2022 Revised: July 5, 2022 Accepted: July 22, 2022 Published: August 19, 2022 The BESIII collaboration E-mail: Abstract: Using 6.32 fb−1 of e+ e− collision data collected at the center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform an amplitude analysis of the decay Ds+ → K + π + π − and determine the amplitudes of the various intermediate states. The absolute branching fraction of Ds+ → K + π + π − is measured to be (6.11 ± 0.18stat. ± 0.11syst. ) × 10−3 . The branching fractions of the dominant intermediate processes Ds+ → K + ρ0 , ρ0 → π + π − and Ds+ → K ∗ (892)0 π + , K ∗ (892)0 → K + π − are determined to be (1.96 ± 0.19stat. ± 0.23syst. ) × 10−3 and (1.85 ± 0.12stat. ± 0.13syst. ) × 10−3 , respectively. The intermediate resonances f0 (500), f0 (980), and f0 (1370) are observed for the first time in this channel. Keywords: Branching fraction, Charm Physics, e+ -e− Experiments, Particle and Resonance Production ArXiv ePrint: 2205.08844 Open Access, c The Authors. Article funded by SCOAP3 . https://doi.org/10.1007/JHEP08(2022)196 JHEP08(2022)196 Amplitude analysis and branching fraction measurement of the decay Ds+ → K +π +π − Contents 1 2 Detector and data sets 2 3 Event selection 3 4 Amplitude analysis 4.1 Event selection 4.2 Fit method 4.2.1 Propagator 4.2.2 Spin factors 4.2.3 Blatt-Weisskopf barriers 4.3 Fit results 4.4 Systematic uncertainties for the amplitude analysis 5 5 5 8 10 10 11 12 5 BF measurement 15 6 Summary 19 The BESIII collaboration 24 1 Introduction One popular approach for studies of hadronic charm decays involves application of approximate flavor symmetries, such as flavor SU(3)F [1]. However, the SU(3)F flavor symmetry breaking effect has been observed in D0 → K + K − and D0 → π + π − for the first time, and later in the other singly Cabibbo-Suppressed (SCS) charm decays [2]. The SCS decay Ds+ → K + π + π − , with low contamination from other charm decays, is a promising channel to study the SU(3)F breaking effect. Furthermore, the measurements of the asymmetries of the branching fractions (BFs) of the charge conjugated decays of charmed mesons aid our understanding of charge-parity violation in the charm sector. To date, there have been a few measurements of charge-parity asymmetries, ACP , in the SCS Ds± decay modes [3–5]. Two-body charmed meson decays Ds± → V P , where V and P denote vector and pseudoscalar mesons, respectively, have been studied in various approaches. The theoretical predictions of the BFs of the Ds+ → K + ρ0 (ρ0 represents ρ(770)0 throughout this paper) and Ds+ → K ∗ (892)0 π + processes are listed in table 1. References [6, 7] studied these decay channels taking into account the SU(3)F flavor symmetry breaking effect, while ref. [8] uses a factorisation-assisted topological-amplitude approach with the ρ-ω mixing. Information about Ds+ → K 0 ρ+ , Ds+ → K ∗ (892)0 π + and Ds+ → K ∗ (892)+ π 0 has been –1– JHEP08(2022)196 1 Introduction Channel PDG [2] Cheng et. al [6] Wu et. al [7] Qin et. al [8] Ds+ → K + ρ0 2.5 ± 0.4 1.22 ± 0.06 1.2 2.5 Ds+ → K ∗ (892)0 π + 2.13 ± 0.36 2.06 ± 0.08 3.3 2.35 Table 1. The experimental measurements and theoretical predictions of the BFs of Ds+ → K + ρ0 and Ds+ → K ∗ (892)0 π + (×10−3 ). 2 Detector and data sets The BESIII detector is a magnetic spectrometer [10, 11] located at the Beijing Electron Positron Collider (BEPCII) [12]. A helium-based multilayer drift chamber (MDC), a plastic scintillator time-of-flight system (TOF), and a CsI(Tl) electromagnetic calorimeter (EMC) compose the cylindrical core of the BESIII detector, and they are all enclosed in a superconducting solenoidal magnet providing a 1.0 T magnetic field. The solenoid is supported by an octagonal flux-return yoke with resistive plate counter muon identifier modules interleaved with steel. The acceptance of charged particles and photons is 93% over a 4π solid angle. The charged-particle momenta resolution at 1.0 GeV/c is 0.5%, and the specific energy loss (dE/dx) resolution is 6% for the electrons from Bhabha scattering. The EMC measures photon energies with a resolution of 2.5%(5%) at 1 GeV in the barrel (end-cap) region. The time resolution of the TOF barrel part is 68 ps, while that of the end-cap part is 110 ps. The end-cap TOF was upgraded in 2015 with multi-gap resistive plate chamber technology, providing a time resolution of 60 ps [13–15]. About 83% of the data used in this paper benefits from this upgrade. Data samples corresponding to a total integrated luminosity of 6.32 fb−1 are used in this analysis. The integrated luminosities of the data samples taken at different energy points are listed in table 2 [16–18]. These samples are classified into three sample groups, 4.178, 4.189– 4.219, and 4.226 GeV according to the years of data taking and their running conditions. Since the Ds∗± decays to γDs± and π 0 Ds± with BFs of (93.5±0.7)% and (5.8±0.7)% [2], respectively, the signal events discussed in this paper are selected from the process e+ e− → Ds∗± Ds∓ → γDs+ Ds− . Simulated inclusive Monte Carlo (MC) samples, forty times larger than the data sets, are produced with a geant4-based [19] MC simulation package, which includes the –2– JHEP08(2022)196 extracted from the decay Ds+ → KS0 π + π 0 [5], but is inconclusive regarding these models. More measurements are needed to confront the theoretical predictions. The CLEO collaboration has reported the absolute BF of Ds+ → K + π + π − to be (0.654 ± 0.033stat. ± 0.025syst. )% [3], using 600 pb−1 of e+ e− collisions recorded at a center√ of-mass energy s = 4.17 GeV. An amplitude analysis of this channel has been performed by the FOCUS collaboration with 567 ± 31 signal events [9]. Using 6.32 fb−1 of e+ e− √ collision data collected with the BESIII detector at s = 4.178 − 4.226 GeV, we perform an amplitude analysis and BF measurement of the Ds+ → K + π + π − decay with the world’s best precision. Charge conjugation is implied throughout this paper except when discussing CP violation. √ s (GeV) Lint (pb−1 ) Mrec (GeV/c2 ) 4.178 3189.0±0.2±31.9 [2.050, 2.180] 4.189 526.7±0.1± 2.2 [2 048, 2.190] 4.199 526.0±0.1± 2.1 [2.046, 2.200] 4.209 517.1±0.1± 1.8 [2.044, 2.210] 4.219 514.6±0.1± 1.8 [2.042, 2.220] 4.226 1056.4±0.1± 7.0 [2.040, 2.220] geometric description of the BESIII detector and the detector response, and are used to determine detection efficiencies and to estimate backgrounds. The production of open charm processes, the initial-state radiation production of vector charmonium(-like) states and the continuum processes incorporated in kkmc [20, 21] are included into the samples. The known decay modes are modeled with evtgen [22, 23] using BFs taken from the Particle Data Group (PDG) [2], and the remaining unknown charmonium decays are modeled with lundcharm [24, 25]. Final state radiation from charged final state (...truncated)


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F., Wang, Y. H., Wang, Y. Q., Wang, Z., Wang, Z. Y., Wang, Ziyi. Amplitude analysis and branching fraction measurement of the decay D s + $$ {D}_s^{+} $$ → K+π+π−, Journal of High Energy Physics, 2022, pp. 1-28, Volume 2022, Issue 8, DOI: 10.1007/JHEP08(2022)196