The Luminometer: A Sensitive Instrument for Measuring Low Amounts of Oxygen and some Applications to Problems Involving the Measurement of Photosynthesis

A new method for the continuous measurement of low rates of oxygen production is described, which is useful for the study of photosynthetic systems. An inert carrier gas flows at a controlled rate through a cuvette, then over a solution of luminol and potassium t-butoxide in dimethylsulfoxide (DMSO). The light generated by the chemiluminescent reaction of luminol with oxygen is measured with a photomultiplier. A constant rate of oxygen production by photosynthesis in the cuvette is seen as a constant displacement from a steady baseline. The baseline is caused by the oxygen impurity in the carrier gas. Electrolysis of water is a convenient method for the calibration of the luminometer. The response of the luminometer is linear with oxygen concentration over at least six orders of magnitude, and changes of 0.01 ppm or 5 x 10-14 moles/sec. in rate of generation of oxygen are detectable when the carrier gas contains 1 ppm oxygen impurity. The system has a response time of about 3 minutes, and a precision of better than 5%. Various mutants of Chlorella having a variety of abnormal pigments were screened for their photosynthetic activity. Some mutants could make oxygen photosynthetically though they were discolored by abnormal quantities of chlorophyll precursors and had only about 1% of the normal chlorophyllJconcentrations. Mutant 610, a carotenoid-containing mutant which, unlike normal Chlorella, cannot synthesize chlorophyll in the dark, was found to green in the lighto During greening, the synthesis of chlorophyll and the development of the ability to produce oxygen were shown to be independent of cell division. On the other hand, during degreening in the dark, the loss of chlorophyll and photosynthetic ability was shown to be dependent on cell division. The luminometer was found to be capable of measuring the light-saturation curve of Chlorella at light intensities down to at least three orders of magnitude below the half saturation intensity. Other possible ways of using the luminol detection method are discussed, and some advantages of mutant 610 for the study of greening are pro

Measurement of fs/fuf_s / f_u Variation with Proton-Proton Collision Energy and BB-Meson Kinematics

International audienceThe ratio of the Bs0 and B+ fragmentation fractions fs and fu is studied with Bs0→J/ψϕ and B+→J/ψK+ decays using data collected by the LHCb experiment in proton-proton collisions at 7, 8, and 13 TeV center-of-mass energies. The analysis is performed in bins of B-meson momentum, longitudinal momentum, transverse momentum, pseudorapidity, and rapidity. The fragmentation-fraction ratio fs/fu is observed to depend on the B-meson transverse momentum with a significance of 6.0σ. This dependency is driven by the 13 TeV sample (8.7σ), while the results for the other collision energies are not significant when considered separately. Furthermore, the results show a 4.8σ evidence for an increase of fs/fu as a function of collision energy

Updated measurement of time-dependent CP-violating observables in Bs0→J/ψK+K−B^{0}_{s}\to J/\psi K^+ K^- decays

International audienceThe decay-time-dependent $CP$ asymmetry in ${{B} ^0_{s}} \rightarrow J/\psi {{K} ^+} {{K} ^-}$ decays is measured using proton–proton collision data, corresponding to an integrated luminosity of $1.9\,\mathrm{fb}^{-1}$ , collected with the LHCb detector at a centre-of-mass energy of $13\,\mathrm {TeV}$ in 2015 and 2016. Using a sample of approximately 117 000 signal decays with an invariant ${{K} ^+} {{K} ^-}$ mass in the vicinity of the $\phi (1020)$ resonance, the $CP$ -violating phase $\phi _s$ is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the ${{B} ^0_{s}}$ - ${{\overline{B}{}} {}^0_{s}}$ system, $\Delta \Gamma _s$ . The difference of the average ${{B} ^0_{s}}$ and ${{B} ^0}$ meson decay widths, $\Gamma _s-\Gamma _d$ , is determined using in addition a sample of ${{B} ^0} \rightarrow J/\psi {{K} ^+} {{\pi } ^-}$ decays. The values obtained are $\phi _s = -0.083\pm 0.041\pm 0.006\mathrm { \,rad}$ , $\Delta \Gamma _s = 0.077 \pm 0.008 \pm 0.003 {\mathrm { \,ps^{-1}}}$ and $\Gamma _s-\Gamma _d = -0.0041 \pm 0.0024 \pm 0.0015{\mathrm { \,ps^{-1}}}$ , where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of these quantities to date and are consistent with expectations based on the Standard Model and with a previous LHCb analysis of this decay using data recorded at centre-of-mass energies 7 and 8 TeV. Finally, the results are combined with recent results from ${{B} ^0_{s}} \rightarrow J/\psi {{\pi } ^+} {{\pi } ^-}$ decays obtained using the same dataset as this analysis, and with previous independent LHCb results