840 research outputs found

    Determination of the T- and CPT-violation parameters in the neutral-kaon system using the Bell-Steinberger relation and data from CPLEAR

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    Data from the CPLEAR experiment, together with the most recent world averages for some of the neutral-kaon parameters, were constrained with the Bell--Steinberger (or unitarity) relation, allowing the T-violation parameter \ree and the CPT-violation parameter \imd of the neutral-kaon mixing matrix to be determined with an increased accuracy: \ree = (164.9 \pm 2.5)\times 10^{-5}, \imd = ( 2.4 \pm 5.0)\times 10^{-5}. Moreover, the constraint allows the CPT-violation parameter for the neutral-kaon semileptonic decays, \rey, to be determined for the first time. The ΔS≠ΔQ\Delta S \neq \Delta Q parameters \rexm and \imxp are given with an increased accuracy. The quantity Re(y + x−)\mathrm{Re}(y~+~x_-), which enters the T-violation CPLEAR asymmetry previously published, is determined to be (0.2±0.3)×10−3(0.2 \pm 0.3)\times 10^{-3}. The value obtained for \red is in agreement with the one resulting from a previous unconstrained fit and has a slightly smaller error

    The neutral kaon decays to π+π−π0\pi^+ \pi^- \pi^0: a detailed analysis of the CPLEAR data

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    A detailed analysis of neutral kaons decaying to \Pgpp \Pgpm \Pgpz\ is presented based on the complete data set containing half a million events. Time-dependent decay rate asymmetries are measured between initially tagged \PKz\ and \PaKz\ and for different regions of the phase space. These asymmetries, resulting from the interference between the CP-conserving decay amplitude of \PKzL\ and the decay amplitude of \PKzS\ -- either CP-violating or CP-conserving -- allow the determinationof the \PKzS\ parameters \etapmz\ (CP-violating) and \lampmz\ (CP-conserving), and also of the main i sospin components of the \PKzS\ decay amplitude. The branching ratio of \PKzS\ →\rightarrow \Pgpp \Pgpm \Pgpz\ (CP-conserving) is deduced directly from \lampmz . In addition, we extract the slope parameters describing the energy dependence of the \PKzL \rightarrow \Pgpp \Pgpm \Pgpz Dalitz plot. The whole set of our results fits well within the current phenomenological picture of the neut ral-kaon system including CP violation and Chiral Perturbation Theory (ChPT)

    A determination of the CPT violation parameter Re(ÎŽ\delta) from the semileptonic decay of strangeness-tagged neutral kaons

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    We have improved by two orders of magnitude the limit currently available for the CPT violation parameter \red . To this purpose we have analyzed the full sample of neutral-kaon decays to \semi\ recorded in the CPLEAR experiment, where the strangeness of the neutral kaons was tagged at production and decay time. An appropriate function of the measured decay rates, including information from the analysis of \pip\pim\ decay channel, gives directly \red . The result =(3.0±3.3stat±0.6syst)×10−4\red = (3.0 \pm 3.3_\mathrm{{stat}} \pm 0.6_\mathrm{{syst}}) \times 10^{-4} is compatible with zero. Values for the parameters \imd, \rexm and \imxp were also obtained

    Contribution of CPLEAR to the physics of the neutral kaon system

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    We present the physics results of the CP-- and CPT--violation measurements performed by CPLEAR. CPLEAR has experimentally determined for the first time, the violation of T invariance and is able to disentangle all the CP-- and CPT--violating quantities from each other. This allows each of the CPT violating parameters to be determined with a precision of a few 10−410^{-4} and, in particular, the mass and width equality between the \kn and \knb to be tested down to the level of 10−1910^{-19} GeV. Moreover, the precision of the CPLEAR measurements allows us to probe for the first time physics on a scale approaching the Planck mass
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