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Measurement of the CP Asymmetry in B+ -> K+ mu(+) mu(-) Decays

Abstract

A measurement of the CP asymmetry in B+ -> K+ mu(+)mu(-) decays is presented using pp collision data, corresponding to an integrated luminosity of 1.0 fb(-1), recorded by the LHCb experiment during 2011 at a center-of-mass energy of 7 TeV. The measurement is performed in seven bins of mu(+)mu(-) invariant mass squared in the range 0.05 < q(2) < 22.00 GeV2/c(4), excluding the J/psi and psi(2S) resonance regions. Production and detection asymmetries are corrected for using the B+ -> J/psi K+ decay as a control mode. Averaged over all the bins, the CP asymmetry is found to be A(CP) = 0.000 +/- 0.033 (stat) +/- 0.005 (syst) +/- 0.007 (J/psi K), where the third uncertainty is due to the CP asymmetry of the control mode. This is consistent with the standard model prediction.

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Abstract

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Related concepts (26)

LHCb experiment

The LHCb (Large Hadron Collider beauty) experiment is a particle physics detector experiment collecting data at the Large Hadron Collider at CERN. LHCb is a specialized b-physics experiment, designed primarily to measure the parameters of CP violation in the interactions of b-hadrons (heavy particles containing a bottom quark). Such studies can help to explain the matter-antimatter asymmetry of the Universe. The detector is also able to perform measurements of production cross sections, exotic hadron spectroscopy, charm physics and electroweak physics in the forward region.

Invariant mass

The invariant mass, rest mass, intrinsic mass, proper mass, or in the case of bound systems simply mass, is the portion of the total mass of an object or system of objects that is independent of the overall motion of the system. More precisely, it is a characteristic of the system's total energy and momentum that is the same in all frames of reference related by Lorentz transformations. If a center-of-momentum frame exists for the system, then the invariant mass of a system is equal to its total mass in that "rest frame".

CP violation

In particle physics, CP violation is a violation of CP-symmetry (or charge conjugation parity symmetry): the combination of C-symmetry (charge symmetry) and P-symmetry (parity symmetry). CP-symmetry states that the laws of physics should be the same if a particle is interchanged with its antiparticle (C-symmetry) while its spatial coordinates are inverted ("mirror" or P-symmetry). The discovery of CP violation in 1964 in the decays of neutral kaons resulted in the Nobel Prize in Physics in 1980 for its discoverers James Cronin and Val Fitch.

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