Inclusive radiativeJ/ψdecays

Abstract

Using data taken with the CLEO-c detector at the Cornell Electron Storage Ring, we have investigated the direct photon momentum spectrum in the decay J/ψ(1S) → γgg, via the "tagged" process: e + e − → ψ(2S); ψ(2S)→ J/ψ π + π − ; J/ψ → γ+X. Including contributions from two-body radiative decay processes, we find the ratio of the inclusive direct photon branching fraction to that of the dominant three-gluon branching fraction (R γ = B(ggγ)/B(ggg)) to be R γ = 0.137 ± 0.001 ± 0.016 ± 0.004, where the errors shown are statistical, systematic, and the model-dependent uncertainty related to the extrapolation to zero photon energy. The shape of the scaled photon energy spectrum in J/ψ → ggγ is observed to be very similar to that of Υ → ggγ. The R γ value obtained is roughly consistent with that expected by a simple quark-charge scaling (R γ ∼ (q c /q b ) 2 ) of the value determined at the Υ(1S), but somewhat higher than the value expected from the running of the strong coupling constant.

Ab initioexplanation of disorder and off-stoichiometry in Fe-Mn-Al-Cκcarbides

“…In a subsequent work by the same group 25 , low Mn concentrations in κ carbides have been investigated which show absence of any kind of interaction between substitutional Mn atoms thereby indicating a random alloy system. A previous work further indicates the relevance of point defects such as C vacancies (treated in the dilute limit) for the thermodynamic stability of the relevant phases 22 . While these studies provided important insight into the structure and thermodynamics, none of them fully explained the above mentioned C reduction of κ carbides.…”

“…The main focus of previous theoretical studies has been on perfectly ordered κ carbides. In a previous investigation, DFT has been employed to compare the properties of Fe 3 Al-L1 2 and ordered Fe 3 AlC-E2 1 structures and to underline the role played by C 21,22 . These studies have shown that the addition of C atoms decreases the magnetic moment of the neighboring Fe atoms and yields a heat capacity and elastic constants of Fe 3 AlC-κ that are appreciably different from Fe 3 Al-L1 2 21 .…”

Design and initial performance of the Askaryan Radio Array prototype EeV neutrino detector at the South Pole

“…If the bottom reflection coefficient is known, the resulting attenuation length measurement can be stated with higher confidence, although it still represents an average over a large range of ice temperatures. For South Pole ice, experiments in this vein have yielded several results on the ice attenuation that indicate km-scale attenuation lengths in the upper km of ice [13][14][15][16].…”

“…1. Solar Radio burst of Feb. 13,2011 On February 13, 2011, the Green Bank Solar Radio Burst Spectrometer detected a series of strong type II solar radio bursts in a broadband measurement spanning 10 MHz up to 1 GHz [18], as seen Fig. 15 (Bottom panels).…”

Scouring meson decays for true muonium

“…There are two processes with BR > 10%: η → ργ and the electromagnetic η → γγ, the latter along side the percent level η → γγ we will discuss in more detail. The large number of J/ψ events being collected in the nearfuture also presents the possibility of subpercent channels like J/ψ → η γ, as well as the percent-level but more complicated inclusive J/ψ → X h γ [45]. Predictions of X h + (µ + µ − ) decays require knowledge of hadronic transition form factors, and are more limited in precision compared to processes like η/η → (µ + µ − )γ where the better studied electromagnetic form factors are available.…”