NA48/2 results contributing to ChPT testing are presented. A sample of 1663 events of the rare decay $ K^ \pm \to \mu ^ \pm ve^ + e^ - $ has been selected with a minimum
e
+
e
−
effective mass of 140 ...MeV. The measured model independent decay rate is in agreement with ChPT predictions. The branching ratio of the $ K^ \pm \to \mu ^ \pm ve^ + e^ - $ decay, never observed so far, has been obtained from a sample of about 5000 candidates with less than 6% background, also in agreement with ChPT predictions. In addition, a most precise measurement of the charged kaon semileptonic formfactors has been obtained from 4.4 million
K
e3
and 2.3 million
K
µ3
events collected in 2004.
Effects of new physics in flavor could be found both in Flavor Changing Neutral Current (FCNC) processes and in Lepton Flavor Violation (LFV) modes. The former offer the possibility to deeply test ...the standard model in a clean environment, while the latter are sensitive to contribution from several models beyond the standard model. In the Kaon sector both FCNC and LFV will be investigated in the NA62 experiment. In addition the kaons sector is an ideal place where to look for new particles and tiny effects, in the region of hundreds of MeV/c2. In this paper prospects for exotic searches in NA62 will be presented, together with recent results from NA48/2 and NA62-RK on LFV kaon decays modes.
The NA48/2 experiment at CERN collected two data samples with minimum bias trigger conditions in 2003 and 2004. A measurement of the rate and dynamic properties of the rare decay K±→π±γγ from these ...data sets based on 149 decay candidates with an estimated background of 15.5±0.7 events is reported. The model-independent branching ratio in the kinematic range z=(mγγ/mK)2>0.2 is measured to be BMI(z>0.2)=(0.877±0.089)×10−6, and the branching ratio in the full kinematic range assuming a particular Chiral Perturbation Theory description to be B(Kπγγ)=(0.910±0.075)×10−6.
SICAL — a high precision silicon-tungsten luminosity calorimeter for ALEPH Bédérède, D.; Beuville, E.; Bloch-Devaux, B. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/1995, Letnik:
365, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The design, construction and performance of a silicon-tungsten electromagnetic calorimeter built to achieve an experimental luminosity measurement precision at LEP≤0.1% is described. The detector ...uses homogeneous construction to give full azimuthal acceptance for Bhabha scattering over polar angles from 24 to 58 mrad. Detailed information concerning shower development is obtained from zero-suppressed readout of the 12288 pads of the detector. Trigger decisions are generated from a rapid flash-ADC system using programmable gate arrays.
We present a measurement of the ratio of the decay rates Γ(KL→π+π−)/Γ(KL→π±e∓ν), denoted as ΓK2π/ΓKe3. The analysis is based on data taken during a dedicated run in 1999 by the NA48 experiment at the ...CERN SPS. Using a sample of 47 000 K2π and five million Ke3 decays, we find ΓK2π/ΓKe3=(4.835±0.022stat.±0.016syst.)×10−3. From this we derive the branching ratio of the CP violating decay KL→π+π− and the CP violation parameter |η+−|. Excluding the CP conserving direct photon emission component KL→π+π−γ, we obtain the results BR(KL→π+π−)=(1.941±0.019)×10−3 and |η+−|=(2.223±0.012)×10−3.
From the 2002 data taking with a neutral kaon beam extracted from the CERN-SPS, the NA48/1 experiment observed 97 Ξ0→Σ+μ−ν¯μ candidates with a background contamination of 30.8±4.2 events. From this ...sample, the BR(Ξ0→Σ+μ−ν¯μ) is measured to be (2.17±0.32stat±0.17syst)×10−6.
Recent results and prospects for precision tests of the Standard Model in kaon decay-in-flight experiments at CERN are presented. A measurement of the ratio of leptonic decay rates of the charged ...kaon at the level of 0.4% precision constrains the parameter space of new physics models with extended Higgs sector, a fourth generation of quarks and leptons or sterile neutrinos. Searches for heavy neutrino mass states and the dark photon in the ∼ 100 MeV c2 mass range based on samples collected in 2003-2007 are in progress and prospects will be discussed. The NA62 experiment, starting in 2014, will search for a range of lepton number and lepton flavour violating decays of the charged kaon and the neutral pion at improved sensitivities down to ∼ 10-12, which will probe new physics scenarios involving heavy Majorana neutrinos or R-parity violating SUSY.
The direct CP violation parameter Re(epsilon'/epsilon) has been measured from the decay rates of neutral kaons into two pions using the NA48 detector at the CERN SPS. With 3.3 million KL->pi0pi0 ...events collected during the 1998 and 1999 running periods, a result of Re(epsilon'/epsilon) = (15.0 +- 2.7)x10-4 has been obtained. The result combined with the published 1997 sample is Re(epsilon'/epsilon) = (15.3 +- 2.6)x10-4.
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