Engineering topics
Gradl, W.
Publications and source records attributed to Gradl, W..
Measurement of the D s + → ℓ + ν ℓ branching fractions and the decay constant f D s +
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Measurement of the leptonic decay width of J/ψ using initial state radiation
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Insight into the Narrow Structure in η Photoproduction on the Neutron from Helicity-Dependent Cross Sections
Here, the double polarization observable E and the helicity dependent cross sections σ 1/2 and σ 3/2 were measured for η photoproduction from quasifree protons and neutrons. The circularly polarized tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost 4π detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from η→2γ and η→3π 0 . The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ 1/2 and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that contribute to this partial wave in η production are only N1/2 – (S11) and N1/2 + (P 11 ). Furthermore, the extracted Legendre coefficients of the angular distributions for σ1/2 are in good agreement with recent reaction model predictions assuming a narrow resonance in the P 11 wave as the origin of this structure.
Determination of the number of J/ψ events with inclusive J/ψ decays
A measurement of the number of J/ψ events collected with the BESIII detector in 2009 and 2012 is performed using inclusive decays of the J/ψ. The number of J/ψ events taken in 2009 is recalculated to be (223.7 ± 1.4) × 10 6 , which is in good agreement with the previous measurement, but with significantly improved precision due to improvements in the BESIII software. The number of J/ψ events taken in 2012 is determined to be (1086.9 ± 6.0) × 10 6 . In total, the number of J/ψ events collected with the BESIII detector is measured to be (1310.6 ± 7.0) × 10 6 , where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.
Observation of e + e − → η ′ J / ψ at center-of-mass energies between 4.189 and 4.600 GeV
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Search for a muonic dark force at BaBar
Many models of physics beyond the standard model predict the existence of new Abelian forces with new gauge bosons mediating interactions between "dark sectors" and the standard model. We report a search for a dark boson Z' coupling only to the second and third generations of leptons in the reaction e+e-→μ+μ-Z',Z'→μ+μ- using 514 fb -1 of data collected by the BABAR experiment. No significant signal is observed for Z' masses in the range 0.212-10 GeV. Lastly, limits on the coupling parameter g' as low as 7×10 -4 are derived, leading to improvements in the bounds compared to those previously derived from neutrino experiments.
Tests of C P T symmetry in B 0 - B ¯ 0 mixing and in B 0 → c c ¯ K 0 decays
Here, using the eight time dependences e- Γt (1 + C i cos Δmt + S i sin Δmt) for the decays Y(4S)→B 0 $\bar{B}$ 0 →f j f k , with the decay into a flavor-specific state f j = ± X before or after the decay into a CP eigenstate f k =c$\bar{c}$ K S,L , as measured by the BABAR experiment, we determine the three CPT-sensitive parameters Re(z) and Im(z) in B 0 $\bar{B}$ 0 mixing and |$\bar{A}$/A| in B 0 →c$\bar{c}$ K 0 decays. We find Im(z) = 0.010 ± 0.030 ± 0.013, Re(z) = -0.065 ± 0.028 ± 0.014, and |$\bar{A}$/A|=0.999±0.023±0.01, in agreement with CPT symmetry.
Improved measurement of the absolute branching fraction of $D^{+}\rightarrow \bar{K}^0 \mu ^{+}\nu _{\mu }$
Here, by analyzing 2.93 fb -1 of data collected at √s = 3.773 GeV with the BESIII detector, we measure the absolute branching fraction B(D + → K¯ 0 μ + ν μ ) = (8.72 ± 0.07 stat. ± 0.18 sys. )%, which is consistent with previous measurements within uncertainties but with significantly improved precision. Combining the Particle Data Group values of B(D 0 → K - μ + ν μ ), B(D + → K¯ 0 e + ν e ), and the lifetimes of the D 0 and D + mesons with the value of B(D + → K¯ 0 μ + ν μ ) measured in this work, we determine the following ratios of partial widths: Γ(D 0 → K - μ + ν μ )/Γ(D + → K¯ 0 μ + ν μ ) = 0.963 ± 0.044 and Γ(D + → K¯ 0 μ + ν μ )/Γ(D + → K¯ 0 e + ν e ) = 0.988 ± 0.033.
Measurement of the neutral D meson mixing parameters in a time-dependent amplitude analysis of the D 0 → π + π - π 0 decay
Here we perform the first measurement on the D 0 -D 0 mixing parameters using a time-dependent amplitude analysis of the decay D 0 →π + π - π 0 . The data were recorded with the BABAR detector at center-of-mass energies at and near the $Y$(4S) resonance, and correspond to an integrated luminosity of approximately 468.1 fb -1 . The neutral D meson candidates are selected from D*(2010) + →D 0 π$+\atop{s}$ decays where the flavor at the production is identified by the charge of the low-momentum pion, π$+\atop{s}$. The measured mixing parameters are x=(1.5±1.2±0.6)% and y=(0.2±0.9±0.5)%, where the quoted uncertainties are statistical and systematic, respectively.
Measurements of the center-of-mass energies at BESIII via the di-muon process
From 2011 to 2014, the BESIII experiment collected about 5 fb -1 data at center-of-mass energies around 4 GeV for the studies of the charmonium-like and higher excited charmonium states. By analyzing the di-muon process e + e - → γ ISR/FSR μ + μ - , the center-of-mass energies of the data samples are measured with a precision of 0.8 MeV. The center-of-mass energy is found to be stable for most of the time during data taking.
Study of ψ decays to the Ξ − Ξ ¯ + and Σ ( 1385 ) ∓ Σ ¯ ( 1385 ) ± final states
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