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Register a new userA study of event mixing for two-pion Bose-Einstein correlations in the {gamma}p -> {pi}^0 {pi}^0 p reaction
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We develop an event mixing technique with a missing mass consistency (MMC) cut and a pion energy (PE) cut for the measurement of two-pion Bose-Einstein correlations (BEC) in reactions with only two identical pions produced in the final state. A multi mixing mode that allows one event to be mixed with multiple other events is proposed for the purpose of improving the statistics of mixed samples, and compared with the single mixing mode which requires one original event can be mixed only once. Numerical tests using the {gamma}p -> {pi}^0 {pi}^0 p events are used to testify its ability to measure two-pion correlations. To improve the mixing speed, the optimal MMC cut window is also explored via simulations.
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A measurement of the double-polarization observable $E$ for the reaction $gamma pto pi^0 p$ is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (C$_4$H$_9$OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from $E_gamma =600$~MeV to $E_gamma =2310$~MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.
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An amplitude analysis of the decay $Lambda_b^0to D^0 p pi^-$ is performed in the part of the phase space containing resonances in the $D^0 p$ channel. The study is based on a data sample corresponding to an integrated luminosity of 3.0 fb$^{-1}$ of $pp$ collisions recorded by the LHCb experiment. The spectrum of excited $Lambda_c^+$ states that decay into $D^0 p$ is studied. The masses, widths and quantum numbers of the $Lambda_c(2880)^+$ and $Lambda_c(2940)^+$ resonances are measured. The constraints on the spin and parity for the $Lambda_c(2940)^+$ state are obtained for the first time. A near-threshold enhancement in the $D^0 p$ amplitude is investigated and found to be consistent with a new resonance, denoted the $Lambda_c(2860)^+$, of spin $3/2$ and positive parity.
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