arXiv subjects
Publications and source records attributed to Evgueni Goudzovski.
Searches for lepton flavour and lepton number violation in kaon decays by the NA48/2 and NA62 experiments at CERN are presented. A new measurement of the helicity suppressed ratio of charged kaon leptonic decay rates $RK=BR(Ke2)/BR(Kmu2) to sub-percent relative precision is discussed. An improved upper limit on the lepton number violating K+- --> pi-+mu+-mu+- decay rate is also presented.
A precision test of lepton universality by measurement of the ratio RK of K-->e nu to K-->mu nu decay rates was performed using a sample of 59963 K-->e nu candidates with 8.8% background contamination collected by the CERN NA62 experiment. The result RK = (2.486 +- 0.013)*10^{-5} is in agreement with the Standard Model expectation.
The NA62 experiment at CERN collected a large sample of K+ --> enu decays during a dedicated run in 2007, aiming at a precise test of lepton universality by measurement of the helicity suppressed ratio RK = BR(K+ --> enu)/BR(K+ --> munu). A preliminary result of the analysis of a partial data sample of 51089 K+ --> enu candidates is presented.
The NA62 experiment at CERN collected a large sample of $K^+\to e^+ν$ decays during a dedicated run in 2007, which allows a precise test of lepton universality by measurement of the helicity suppressed ratio $R_K = Γ(K^+\to e^+ν)/Γ(K^+\toμ^+ν)$. The preliminary result of the analysis of a partial data sample of 51089 $K^+\to e^+ν$ candidates is $R_K=(2.500\pm0.016)\times10^{-5}$, consistent with the Standard Model expectation.
A sample of 7253 $K^\pm\toπ^\pm e^+e^-$ decay candidates with 1.0% background contamination has been collected by the NA48/2 experiment at the CERN SPS, which allowed a precise measurement of the form factor, the branching ratio, and the CP violating asymmetry of $K^+$ and $K^-$ decay widths was investigated. The results of the $K^\pm\toπ^\pm e^+e^-$ analysis, as well as the status of the $K^\pm\toπ^\pmμ^+μ^-$ analysis based in the same data set, are reported.
Recent precise measurements of CP violation parameters in kaon decays at the NA48 experiment: indirect CPV parameter $|η_{+-}|$, and charge asymmetries in $K^\pm\to3π$ decays, are presented.
The ratio $R_K = Γ(K^{\pm}\to e^{\pm}ν(γ)) / Γ(K^{\pm}\toμ^{\pm}ν(γ))$ provides a powerful probe of the structure of weak interactions. It is calculated with very high precision within the Standard Model, but corrections due to the presence of New Physics could be in a few percent range. Development of NA48/NA62 method based on test data samples of 2003-04, and the status of analysis based on a dedicated 2007 run are discussed. In addition, a proposal to measure the ultra rare decay $K^+\toπ^+ν\barν$ at the CERN SPS is presented.
The NA48/2 experiment at the CERN SPS carried out data taking in 2003 and 2004. Analysis of the selected data samples of 7,146 $K^\pm\toπ^\pm e^+e^-$ decay candidates with 0.6% background, 1,164 $K^\pm\toπ^\pmγγ$ candidates with 3.3% background, and 120 $K^\pm\toπ^\pmγe^+e^-$ candidates with 6.1% background allowed precise measurements of branching fractions and other characteristics of these rare kaon decays.
Several recent results from the NA48 experiment are presented: a measurement $|η_{+-}|$, search for CP violating phenomena in $K^\pm\to3π$ decays, and a measurement of $|V_{us}|$.
The NA48/2 experiment at the CERN SPS has collected an unprecedented sample of $K^\pm\to3π$ decays. The high statistics and the good resolution of the detectors allow a unique investigation of the detailed phase space distributions of these decays. The effects of final state pion rescattering observed in the Dalitz plot distribution of the $K^\pm\toπ^\pmπ^0π^0$ decays turned out to be a powerful tool for extraction of the S-wave $ππ$ scattering lengths. The large statistics also allowed a precise measurement of the Dalitz plot slope parameters for the $K^\pm\to3π^\pm$ decays.
Preliminary results of study of $K^\pm\to3π^\pm$ decays by the NA48/2 experiment at CERN SPS are presented. They include a precise measurement of the direct CP violating charge asymmetry of Dalitz plot linear slope parameters $A_g=(g^+-g^-)/(g^++g^-)$, and a measurement of the Dalitz plot slope parameters $(g,h,k)$ themselves. Due to the design of the experiment, and a large data set collected, unprecedented precisions were achieved.