NA48

NA48 is an experiment from elementary particle physics , in which the physics of kaons is investigated. Particular attention is paid to CP violation . The experiment is located in the N orth A rea of CERN at the Super Proton Synchrotron . The experiments NA48-1, NA48-2 and NA48-3, also called NA62 , emerged from the setup .

history

In 1999 NA48, as well as KTeV , succeeded in confirming the evidence for a direct CP violation from experiment NA31 .

The first stage NA48-1 went in 2002 with minimally altered structure in operation, searching primarily for rare K _S - decays . But some hyperon and less rare K _s decays have also been investigated.

NA48-2, in turn, had set itself the goal of investigating the decay of charged kaons with the highest possible statistics . The data collection took place between 2003 and 2004.

The third extension NA48-3, which is now listed under NA62 , is said to have the rare decay

${\displaystyle K^{+}\rightarrow \pi ^{+}\nu {\bar {\nu }}}$

examine. The experiment is currently in the development phase and should start taking data in 2014.

How it works and results

The double ratio was measured for NA48 . ${\displaystyle R=\left\vert {\frac {L^{00}}{S^{00}}}{\frac {L^{+-}}{S^{+-}}}\right\vert =\left\vert {\frac {A(K_{L}\rightarrow \pi ^{0}\pi ^{0})}{A(K_{S}\rightarrow \pi ^{0}\pi ^{0})}}{\frac {A(K_{L}\rightarrow \pi ^{+}\pi ^{-})}{A(K_{S}\rightarrow \pi ^{+}\pi ^{-})}}\right\vert }$

The denotes the different decay amplitudes of the two states (long-lived) and (short-lived). ${\displaystyle A}$ ${\displaystyle K_{L}}$ ${\displaystyle K_{S}}$

This ratio can be used to measure direct CP violation via the relationship . ${\displaystyle \Re \left({\frac {\epsilon '}{\epsilon }}\right)=(1-R)/6}$

The K _L beam, like the K _S beam, was generated by means of 450 GeV protons which hit a target . The K _L target was 200 m in front of the detector , the K _S target 100 m. The distinction between the K _L and K _S decays was carried out by  measuring the flight time with an accuracy of 10 ⁻¹⁰ s and thereby determining the place of origin.

The charged pions were detected in the experiment in four drift chambers , which were set up in pairs behind and in front of a dipole magnet . The uncharged pions were detected by their decay into photons in a krypton tank which was divided into 13,212 cells measuring 2 × 2 cm ² .

The result of the experiment is ${\displaystyle {\frac {\epsilon '}{\epsilon }}=(1,47\pm 0,22)\times 10^{-3}.}$

Web links

• Some datasets of the NA48 experiment can be found in the Durham HepData Project : Datasets for NA48

Individual evidence

1. ↑ CERN / SPSC 2000-002 (file type: Postscript ; GZIP ; 258 kB)
2. ↑ Overview page of the NA48-2 experiment.
3. ^ Project page from NA62
4. ↑ Konrad Kleinknecht - Tracking the CP violation in Physik Journal 7 (2008) No. 8/9 page 37