THEME02-2-1043-2002/2006

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02-2-1043-2002/2006

Priority:

Status:

Extended

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

Leader:	L.L. Nemenov
Deputy:	L.G. Afanasyev

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 2006:

Processing of all data collected in 2000-2003 for the lifetime measurement with statistical accuracy of about 10% on the Ni and Ti targets and evaluation of systematic errors in the lifetime.
Publication of the results on the ⁺ ^- atom lifetime measurement basing on the all data collected in 2000-2003.
Manufacturing of detectors for the particle identification system.
Installation and tuning of all modified detectors.
The first run with modified setup during 4 months for calibration and data taking for observation of the states.

List of projects:
	Project	Leader	Priority (period of realisation)
1.	DIRAC	L.L. Nemenov	1 (1995-2006)

List of Activities

Activity or Experiment

Leader

Status

DIRAC

L.L. Nemenov

Data analysis

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	SRC-IHEP
Spain	Santiago de Compostela	USC
Switzerland	Bern	Univ.
	Basel	Uni Basel
	Zurich	Univ.

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

List of projects:

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