Measurement of the eta'-meson mass using J/psi-->gammaeta

Physical Review Letters, 2008

We measure the mass of the η ′ meson using ψ(2S)→π + π − J/ψ, J/ψ → γη ′ events acquired with the CLEO-c detector operating at the CESR e + e − collider. Using three decay modes, η ′ →ρ 0 γ, η ′ →π + π − η with η→γγ, and η ′ →π + π − η with η→π + π − π 0 , we find M η ′ =957.793±0.054±0.036 MeV, in which the uncertainties are statistical and systematic, respectively. This result is consistent with but substantially more precise than the current world average.

Physical Review Letters, 2007

We measure the mass of the η meson using ψ(2S)→ηJ/ψ events acquired with the CLEO-c detector operating at the CESR e + e − collider. Using the four decay modes η→γγ, 3π 0 , π + π − π 0 , and π + π − γ, we find M η =547.785±0.017±0.057 MeV, in which the first uncertainty is statistical and the second systematic. This result has an uncertainty comparable to the two most precise previous measurements and is consistent with that of NA48, but is inconsistent at the level of 6.5σ with the much smaller mass obtained by GEM.

Physical Review D, 2000

In a sample of 7.8 million $J/\psi$ decays collected in the Beijing Spectrometer, the process J/$\psi\to\gamma\eta_c$ is observed for five different $\eta_c$ decay channels: $K^+K^-\pi^+\pi^-$, $\pi^+\pi^-\pi^+\pi^-$, $K^\pm K^0_S \pi^\mp$ (with $K^0_S\to\pi^+\pi^-$), $\phi\phi$ (with $\phi\to K^+K^-$) and $K^+K^-\pi^0$. From these signals, we determine the mass of $\eta_c$ to be $2976.6\pm2.9\pm1.3$ MeV. Combining this result with a previously reported result from a similar study using $\psi(2S)\to\gamma\eta_c$ detected in the same spectrometer gives $m_{\eta_c} = 2976.3\pm2.3\pm1.2$ MeV. For the combined samples, we obtain $\Gamma_{\eta_c} = 11.0\pm 8.1\pm 4.1$ MeV.

Physical Review Letters, 2004

Physics Letters B, 2005

Several processes of meson production in proton-deuteron collisions have been measured simultaneously using a calibrated magnetic spectrograph. Among these processes, the η meson is seen clearly as a sharp missing-mass peak on a slowly varying background in the p + d → 3 He + X reaction. Knowing the kinematics of the other reactions with well determined masses, it is possible to deduce a precise mass for the η meson. The final result, m(η) = 547.311 ± 0.028(stat) ± 0.032(syst) MeV/c 2 ,

Physics Letters B, 2003

A new high precision measurement of the J/ψ-and ψ ′-meson masses has been performed at the VEPP-4M collider using the KEDR detector. The resonant depolarization method has been employed for the absolute calibration of the beam energy. The following mass values have been obtained: M J/ψ = 3096.917 ± 0.010 ± 0.007 MeV, M ψ ′ = 3686.111 ± 0.025 ± 0.009 MeV. The relative measurement accuracy has reached 4 • 10 −6 for J/ψ and 7 • 10 −6 for ψ ′ , approximately 3 times better than in the previous precise experiments.

Physical Review Letters, 2006

We report first evidence for a fully reconstructed decay mode of the B_c^{\pm} meson in the channel B_c^{\pm} \to J/psi \pi^{\pm}, with J/psi \to mu^+mu^-. The analysis is based on an integrated luminosity of 360 pb$^{-1} in p\bar{p} collisions at 1.96 TeV center of mass energy collected by the Collider Detector at Fermilab. We observe 14.6 \pm 4.6 signal events with a background of 7.1 \pm 0.9 events, and a fit to the J/psi pi^{\pm} mass spectrum yields a B_c^{\pm} mass of 6285.7 \pm 5.3(stat) \pm 1.2(syst) MeV/c^2. The probability of a peak of this magnitude occurring by random fluctuation in the search region is estimated as 0.012%.

Physical Review Letters, 2000

Using 13.4 fb −1 of data collected with the CLEO detector at the Cornell Electron Storage Ring, we have observed 300 events for the two-photon production of ground-state pseudo-scalar charmonium in the decay η c → K 0 S K ∓ π ±. We have measured the η c mass to be (2980.4 ± 2.3 (stat) ± 0.6 (sys)) MeV and its full width as (27.0 ± 5.8 (stat) ± 1.4 (sys)) MeV. We have determined the two-photon partial width of the η c meson to be (7.6 ± 0.8 (stat) ± 0.4 (sys) ± 2.3 (br)) keV, with the last uncertainty associated with the decay branching

2016

Several processes of meson production in proton-deuteron collisions have been measured simultaneously using a calibrated magnetic spectrograph. Among these processes, the η meson is seen clearly as a sharp missing-mass peak on a slowly varying background in the p + d → He + X reaction. Knowing the kinematics of the other reactions with well determined masses, it is possible to deduce a precise mass for the η meson. The final result, m(η) = 547.311 ± 0.028 (stat) ± 0.032 (syst) MeV/c, Preprint submitted to Elsevier Science 19 November 2013 is significantly lower than that found by the recent NA48 measurement, though it is consistent with values obtained in earlier counter experiments.

Physical review, 2023