Abstract
A search for CP violation in the Cabibbo-suppressed D0 → K+K−π+π− decay mode is performed using an amplitude analysis. The measurement uses a sample of pp collisions recorded by the LHCb experiment during 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb−1. The D0 mesons are reconstructed from semileptonic b-hadron decays into D0μ−X final states. The selected sample contains more than 160 000 signal decays, allowing the most precise amplitude modelling of this D0 decay to date. The obtained amplitude model is used to perform the search for CP violation. The result is compatible with CP symmetry, with a sensitivity ranging from 1% to 15% depending on the amplitude considered.
Highlights
Background descriptionThe sidebands of the D0-mass distribution are used to describe the background, assuming that the sum of the lower (m(K+K−π+π−) ∈ [1.81, 1.835] GeV/c2) and upper (m(K+K−π+π−) ∈ [1.895, 1.92] GeV/c2) sidebands gives a good description of the background in the signal region (SR)
This paper presents a search for CP violation in the individual amplitudes of the decay1 D0 → K+K−π+π−, produced in semileptonic decays of b hadrons into D0μ−X, where X represents any combination of undetected particles
This misreconstruction generates a structure in the upper end of the K+K−π− invariant mass spectrum, which is removed with the requirement m(K+K−π+π−) − m(K+K−π−) > 0.18 GeV/c2
Summary
The LHCb detector [16, 17] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. The detector includes a high-precision tracking system consisting of a silicon-strip vertex detector surrounding the pp interaction region, a large-area silicon-strip detector. The tracking system provides a measurement of momentum of charged particles with a relative uncertainty that varies from 0.5% at low momentum to 1.0% at 200 GeV/c. The configuration with the magnetic field vertically upwards (downwards) bends positively (negatively) charged particles in the horizontal plane towards the centre of the LHC. Different types of charged hadrons are distinguished using information from two ring-imaging Cherenkov detectors. Decays of hadronic particles are described by EvtGen [21], in which final-state radiation is generated using Photos [22]. The interaction of the generated particles with the detector, and its response, are implemented using the Geant toolkit [23, 24] as described in ref. The interaction of the generated particles with the detector, and its response, are implemented using the Geant toolkit [23, 24] as described in ref. [25]
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