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.
The New Cylindrical GEM Inner Tracker of BESIII Lavezzi, L; Alexeev, M; Amoroso, A ...
International Journal of Modern Physics: Conference Series,
2018, Letnik:
46
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The Cylindrical GEM-Inner Tracker (CGEM-IT) is the upgrade of the internal tracking system of the BESIII experiment. It consists of three layers of cylindrically-shaped triple GEMs, with important ...innovations with respect to the existing GEM detectors, in order to achieve the best performance with the lowest material budget. It will be the first cylindrical GEM running with analog readout inside a 1T magnetic field. The simultaneous measurement of both the deposited charge and the signal time will permit to use a combination of two algorithms to evaluate the spatial position of the charged tracks inside the CGEM-IT: the charge centroid and the micro time projection chamber modes. They are complementary and can cope with the asymmetry of the electron avalanche when running in magnetic field and with non-orthogonal incident tracks. To evaluate the behaviour under different working settings, both planar chambers and the first cylindrical prototype have been tested during various test beams at CERN with 150 GeV/
c
muons and pions. This paper reports the results obtained with the two reconstruction methods and a comparison between the planar and cylindrical chambers.
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.
Using the full data set of the NA48/2 experiment, the decay K±→π±e+e−γ is observed for the first time, selecting 120 candidates with 7.3±1.7 estimated background events. With K±→π±πD0 as ...normalisation channel, the branching ratio is determined in a model-independent way to be Br(K±→π±e+e−γ,meeγ>260 MeV/c2)=(1.19±0.12stat±0.04syst)×10−8. This measured value and the spectrum of the e+e−γ invariant mass allow a comparison with predictions of chiral perturbation theory.
We report a measurement of the direct CP violation asymmetry parameter Ag in charged kaon decays K±→π±π+π− by the NA48/2 experiment at the CERN SPS. The experiment has been designed not to be limited ...by systematics in the asymmetry measurement. Using 1.67×109 such decays collected during the 2003 run, the charge asymmetry in the Dalitz plot linear slope parameter g has been measured to be Ag=(1.7±2.9)×10−4. The precision of the result is limited by the statistics used.
A precision test of lepton flavour universality has been performed by measuring the ratio R sub(K of kaon leptonic decay rates Ksuper+-->esuper+nu and Ksuper+-->microsuper+nu in a sample of 59 813 ...reconstructed Ksuper+-->esuper+nu candidates with (8.71+/-0.24)% background contamination. The result R) sub(K)=(2.487+/-0.013)x10super-5 is in agreement with the Standard Model expectation.
The K sub(S--pisuper+pisuper-esuper+esuper- decay mode was investigated using the data collected in 2002 by the NA48/1 Collaboration. With about 23 k K) sub(S)--pisuper+pisuper-esuper+esuper- events ...and 59 k inline imageinline image normalization decays, the K sub(S--pisuper+pisuper-esuper+esuper- branching ratio relative to the inline imageinline image one was determined to be inline imageinline image. This result was used to set the upper limit)
Experiment E835 at Fermilab Garzoglio, G.; Gollwitzer, K.; Hahn, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2004, Letnik:
519, Številka:
3
Journal Article
Recenzirano
We provide a comprehensive description of experiment E835 at Fermilab, a high-precision experimental study of charmonium bound states. The
c
̄
c
states are formed in
p
̄
p
annihilations of cooled ...antiprotons stored in the Fermilab Antiproton Accumulator using a dense internal hydrogen gas-jet target. We describe the experimental strategies adopted for detecting the tiny
c
̄
c
resonant signals in the huge non-resonant hadronic background, and for measuring resonance parameters with high precision.
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