THEME02-2-1043-2002/2008

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02-2-1043-2002/2008

Priority:

Status:

Approved for completion
in 2008

Lifetime Measurement of ⁺ ^- and ^± K Atoms
to Test Low-Energy QCD Predictions

Leader:	L.G. Afanasyev
Scientific leader:	L.L. Nemenov

Scientific Programme:
The experiment aims to measure simultaneously the lifetime of

⁺

^- atoms (A₂), to observe

K atoms (A_K) and to measure their lifetime using 24 GeV proton beam. The precise measurement of these quantities will enable us to determine the combination of s-wave pion-pion |a₀ - a₂| and pion-kaon |a_1/2-a_3/2| scattering lengths (with isospin 0, 2 and 1/2, 3/2, respectively) in a model-independent way. The precision of A₂ lifetime measurement will be better than 6% and the difference |a₀ - a₂| will be determined within 3% or better. The accuracy of A_K lifetime measurement will be at the level of 20% and the difference |a_1/2-a_3/2| will be determined at the level of 10%. Low energy QCD predicts these values with an accuracy about 2% for the pion-pion scattering lengths and about 10% for the

K-scattering lengths. The pion-pion and pion-kaon scattering lengths have never been verified with experimental data with the same level of precision. For this reason the proposed measurements will be a crucial check of the low energy QCD predictions and our understanding of the nature of the QCD vacuum.

Expected main results in 2008:

Tuning of the upgraded detectors and the whole setup at the beam.
Data taking for observation of the atoms consisting of ⁺K ^- and ^-K ⁺ mesons.
Data taking for improvement of the accuracy in the lifetime measurement of ⁺ ^- atoms.

List of projects:
	Project	Leader	Priority (period of realisation)
1.	DIRAC	L.L. Nemenov	1 (1995-2008)

List of Activities

Activity or Experiment

Leader

Status

DIRAC

L.G. Afanasyev

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Collaboration
Country or international organization	City	Institute or Laboratory
CERN	Geneva
Czech Republic	Prague	CTU
		IP ASCR
Greece	Ioannina	UI
Italy	Frascatti	INFN LNF
	Messina	Univ.
	Trieste	INFN
Japan	Kyoto	KSU
	Tsukuba	KEK
	Tokyo	TMU
Romania	Bucharest	IAP
Russia	Moscow	SINP MSU
	Protvino	IHEP
Spain	Santiago de Compostela	USC
Switzerland	Bern	Univ.
	Basel	Uni Basel
	Zurich	Univ.

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Lifetime Measurement of + - and ± K Atoms to Test Low-Energy QCD Predictions

Lifetime Measurement of ⁺ ^- and ^± K Atoms
to Test Low-Energy QCD Predictions