By analyzing a data sample corresponding to an integrated luminosity of 2.93 fb−1 collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure for the first time the ...absolute branching fraction of the D+ → ημ+νμ decay to be BD+→ημ+νμ = ( 10.4 ± 1.0stat ± 0.5syst) × 10−4. Using the world averaged value of BD+ → ηe+νe, the ratio of the two branching fractions is determined to be BD+ → ημ+νμ/BD+ → ηe+νe = 0.91 ± 0.13(stat+syst), which agrees with the theoretical expectation of lepton flavor universality within uncertainty. By studying the differential decay rates in five four-momentum transfer intervals, we obtain the product of the hadronic form factor f+η(0) and the c → d Cabibbo-Kobayashi-Maskawa matrix element |Vcd| to be fη+(0) |Vcd| = 0.087 ± 0.008stat ± 0.002syst. Taking the input of |Vcd| from the global fit in the standard model, we determine fη+(0) = 0.39 ± 0.04stat ± 0.01syst. On the other hand, using the value of fη+(0) calculated in theory, we find |Vcd| = 0.242 ± 0.022stat ± 0.00 6 syst ± 0.033theory.
Using an e+e− collision data sample of 2.93 fb−1 collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of D0→a0(980)−e+νe and evidence for ...D+→a0(980)0e+νe with significances of 6.4σ and 2.9σ, respectively. The absolute branching fractions are determined to be B(D0→a0(980)−e+νe)×B(a0(980)−→ηπ−)=1.33−0.29+0.33(stat)±0.09(syst)×10−4 and B(D+→a0(980)0e+νe)×B(a0(980)0→ηπ0)=1.66−0.66+0.81(stat)±0.11(syst)×10−4. This is the first time the a0(980) meson has been measured in a D0 semileptonic decay, which would open one more interesting page in the investigation of the nature of the puzzling a0(980) states.
We report new measurements of the branching fraction B (Ds+ → ℓ+ν), where ℓ+ is either μ+ or τ+ ( → π+ ντ), based on 6.32 fb−1 of electron-positron annihilation data collected by the BESIII ...experiment at six center-of-mass energy points between 4.178 and 4.226 GeV. Simultaneously floating the Ds+ → μ+ νμ and Ds+ → τ+ ντ components yields B (Ds+ → τ+ ντ) = ( 5.21 ± 0.25 ± 0.17 ) × 10−2, B (Ds+ → μ+ νμ) = ( 5.35 ± 0.13 ± 0.16 ) × 10−3, and the ratio of decay widths ..., where the first uncertainties are statistical and the second systematic. No evidence of CP asymmetry is observed in the decay rates Ds± → μ± νμ and Ds± → τ± ντ : ACP (μ± ν) = (− 1.2 ± 2.5 ± 1.0) % and ACP (τ± ν) = ( + 2.9 ± 4.8 ± 1.0)%. Constraining our measurement to the Standard Model expectation of lepton universality (R = 9.75), we find the more precise results B (Ds+ → τ+ ντ) = ( 5.22 ± 0.10 ± 0.14 ) × 10−2 and ACP ( τ± ντ) = ( − 0.1 ± 1.9 ± 1.0 )%. Combining our results with inputs external to our analysis, we determine the c →s quark mixing matrix element, Ds+ decay constant, and ratio of the decay constants to be | Vcs | = 0.973 ± 0.009 ± 0.014 , fD+s = 249.9 ± 2.4 ± 3.5 MeV , and fD+s / fD+ = 1.232 ± 0.035, respectively.
We report the experimental results of the commissioning phase in the 10 PW laser beamline of the Shanghai Superintense Ultrafast Laser Facility (SULF). The peak power reaches 2.4 PW on target without ...the last amplifying during the experiment. The laser energy of 72 ± 9 J is directed to a focal spot of approximately 6 μm diameter (full width at half maximum) in 30 fs pulse duration, yielding a focused peak intensity around 2.0 × 1021 W/cm2. The first laser-proton acceleration experiment is performed using plain copper and plastic targets. High-energy proton beams with maximum cut-off energy up to 62.5 MeV are achieved using copper foils at the optimum target thickness of 4 μm via target normal sheath acceleration. For plastic targets of tens of nanometers thick, the proton cut-off energy is approximately 20 MeV, showing ring-like or filamented density distributions. These experimental results reflect the capabilities of the SULF-10 PW beamline, for example, both ultrahigh intensity and relatively good beam contrast. Further optimization for these key parameters is underway, where peak laser intensities of 1022–1023 W/cm2 are anticipated to support various experiments on extreme field physics.
In former studies, fires were always assumed to occur at the longitudinal centerline of tunnels. In fact, fires will occur at any locations in tunnels, with different distances to the sidewall. A set ...of model scale experiments were carried out, to investigate the influence of different transverse fire locations on maximum smoke temperature under the tunnel ceiling. Results show that the restriction effect of the sidewalls of tunnels cause the maximum smoke temperature rise under the ceiling to increase compared with the unconfined space, even fires occurs at the longitudinal centerline. The maximum smoke temperature rises above the fire keep almost unchanged with the fire moving closer to the sidewall at the beginning and then increase significantly after the distance between the fire and the sidewall decreases to a certain value. For small pools of wall fire, the “mirror” effect is reasonable, and for large pools, will bring a relatively large error without considering the influence of the equivalent diameter of a wall fire, resulting in underestimating the mass flow rate of fire plume and then overestimating the smoke temperature. Under all fires, the maximum smoke temperature rise under the ceiling decreases exponentially as the longitudinal distance from fire increases. Correlations for related parameters are proposed.
Using 1310.6×106 J/ψ and 447.9×106 ψ(3686) events collected with the BESIII detector at the BEPCII e+e− collider, the branching fractions and the angular distributions of J/ψ and ψ(3686) decays to ...ΛΛ¯ and Σ0Σ¯0 final states are measured. The branching fractions are determined, with much improved precision, to be 19.43±0.03±0.33, 11.64±0.04±0.23, 3.97±0.02±0.12 and 2.44±0.03±0.11 for J/ψ→ΛΛ¯, J/ψ→Σ0Σ¯0, ψ(3686)→ΛΛ¯ and ψ(3686)→Σ0Σ¯0, respectively. The polar angular distributions of ψ(3686) decays are measured for the first time, while those of J/ψ decays are measured with much improved precision. In addition, the ratios of branching fractions B(ψ(3686)→ΛΛ¯)B(J/ψ→ΛΛ¯) and B(ψ(3686)→Σ0Σ¯0)B(J/ψ→Σ0Σ¯0) are determined to test the “12% rule.”
From 1310.6 x 10(6) J/psi and 448.1 x 10(6) psi (3686) events collected with the BESIII experiment, we report the first observation of Sigma(+) and (Sigma) over bar (-) spin polarization in e(+)e(-) ...-> J/psipsi(3686) -> Sigma(+)(Sigma) over bar (-) decays. The relative phases of the form factors Delta Phi have been measured to be (-15.5 +/- 0.7 +/- 0.5)degrees and (21.7 +/- 4.0 +/- 0.8)degrees with J/psi and psi(3686) data, respectively. The nonzero value of Delta Phi allows for a direct and simultaneous measurement of the decay asymmetry parameters of Sigma(+)-> p pi(0) (alpha(0) = -0.998 +/- 0.037 +/- 0.009) and (Sigma) over bar (-)-> (p) over bar pi(0) ((alpha) over bar (0) = 0.990 +/- 0.037 +/- 0.011), the latter value being determined for the first time. The average decay asymmetry, (alpha(0 )- (alpha) over bar (0))/2, is calculated to be -0.994 +/- 0.004 +/- 0.002. The CP asymmetry A(CP,Sigma) = (alpha(0) + (alpha) over bar (0))/(alpha(0) - (alpha) over bar (0)) = -0.004 +/- 0.037 +/- 0.010 is extracted for the first time, and is found to be consistent with CP conservation.
We present the first amplitude analysis of the decay Ds+→π+π0η. We use an e+e− collision data sample corresponding to an integrated luminosity of 3.19 fb−1 collected with the BESIII detector at a ...center-of-mass energy of 4.178 GeV. We observe for the first time the W-annihilation dominant decays Ds+→a0(980)+π0 and Ds+→a0(980)0π+. We measure the absolute branching fraction B(Ds+→a0(980)+(0)π0(+),a0(980)+(0)→π+(0)η)=(1.46±0.15stat±0.23sys)%, which is larger than the branching fractions of other measured pure W-annihilation decays by at least one order of magnitude. In addition, we measure the branching fraction of Ds+→π+π0η with significantly improved precision.
Using an e+e− annihilation data sample corresponding to an integrated luminosity of 2.93 fb−1 collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we measure the absolute ...branching fractions of D+ → ηηπ+, D+ → ηπ+π0, and D0 → ηπ+π− to be (2.96 ± 0.24 ± 0.10) × 10−3, (2.23 ± 0.15 ± 0.10) × 10−3, and (1.20 ± 0.07 ± 0.04) × 10−3, respectively, where the first uncertainties are statistical and the second ones are systematic. The D+ → ηηπ+ decay is observed for the first time, and the branching fractions of D+(0) → ηπ+π0 (−) are measured with much improved precision. In addition we test for CP asymmetries in the separated charge-conjugate branching fractions; no evidence of CP violation is found.
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