Radiative decays of theΥ(1S)to a pair of charged hadrons

Abstract

Using data obtained with the CLEO III detector, running at the Cornell Electron Storage Ring (CESR), we report on a new study of exclusive radiative Υ(1S) decays into the final states γπ + π − , γK + K − , and γpp. We present branching ratio measurements for the decay modes Υ(1S) → γf 2 (1270), Υ(1S) → γf ′ 2 (1525), and Υ(1S) → γK + K − ; helicity production ratios for f 2 (1270) and f ′ 2 (1525); upper limits for the decay Υ(1S) → γf J (2200), with f J (2220) → π + π − , K + K − , pp; and an upper limit for the decay Υ(1S) → γX (1860), with X(1860) → γpp.

A new hadron spectroscopy

“…The BESIII measurements find a much larger width for the π + π − η peak than that found for the pp peak in the BE-SIII partial wave analysis: Γ π + π − η = 190 ± 38 MeV versus Γ pp < 76 MeV. Another puzzling feature is the lack of any evidence for the pp threshold enhancement in any other channels, such as J/ψ → ωpp [25], Υ(1S) → γpp [26] or in B decays [27]. BESIII is actively looking at various other radiative J/ψ decay channels for evidence for or against other signs of resonance behaviour near 1835 MeV [28].…”

Study of ϒ(1S) radiative decays to γπ+Lees1, Poireau2, Tisserand3 et al. 2018Phys. Rev. D8230View full textAdd to dashboardCite

“…The experimental observation of radiative ϒð1SÞ decays is challenging because their rate is suppressed by a factor of ≈0.025 compared to J=ψ radiative decays, which are of order 10 −3 [17]. Radiative ϒð1SÞ decays to a pair of hadrons have been studied by the CLEO Collaboration [17,18] with limited statistics and large backgrounds from e þ e − → γ ðvector mesonÞ.…”

Phenomenology of a light cold dark matter two-singlet model

“…þ þ À Þ < 6:3  10 À5 for 1 GeV < m 1 [24], and (iii) BrðÇ 1S ! þ K þ K À Þ < 1:14  10 À5 for 2 GeV < m 1 < 3 GeV [25]. Figure 1 displays the corresponding branching ratios of Ç 1S decays via S 1 as functions of m 1 , together with these upper bounds.…”