Abstract
An amplitude analysis of the decay Λb0 → D0pπ− is performed in the part of the phase space containing resonances in the D0p 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 Λc+ states that decay into D0p is studied. The masses, widths and quantum numbers of the Λc(2880)+ and Λc(2940)+ resonances are measured. The constraints on the spin and parity for the Λc(2940)+ state are obtained for the first time. A near-threshold enhancement in the D0p amplitude is investigated and found to be consistent with a new resonance, denoted the Λc(2860)+, of spin 3/2 and positive parity.
Highlights
Background distributionBackground in the vicinity of the Λ0b → D0pπ− invariant mass peak is dominated by random combinations of D0 mesons, proton, and pion tracks
The online event selection is performed by a trigger [33], which consists of a hardware stage, based on information from the calorimeter and muon systems, followed by a software stage, which applies a full event reconstruction
Where Jp = 1/2, JD = 0 and JR are the spins of the proton, D0 meson and resonance R, respectively, and ηp = +1, ηD = −1 and ηR are their parities. This relation reduces the number of free parameters in the helicity amplitudes: |bλp| is absorbed by aλR, and each coefficient aλR enters the amplitude multiplied by a factor ηλp = ±1
Summary
The selection of Λ0b → D0pπ− candidates is described, followed by the measurement of signal and background yields (section 5), evaluation of the efficiency (section 6), determination of the shape of the background distribution (section 7), and discussion of the effects of momentum resolution (section 8).
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