THEME02-2-1043-2002/2005

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02-2-1043-2002/2005

Priority:

Status:

Extended

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

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

Scientific Programme:
The DIRAC experiment is aimed to measure the lifetime of

⁺

^- atoms in the ground state with a 10% precision using the 24 GeV/c proton beam of the CERN Proton Synchrotron. As the value of the above lifetime of the order of 10 ^-15s is dictated by a strong interaction at low energy, the precise measurement of this quantity enables one to determine a combination of S-wave pion scattering lengths to 5%. Pion scattering lengths have been calculated in the framework of the chiral perturbation theory with a high precision. Thus, the accurate measurement of these values would put the understanding of chiral symmetry breaking of QCD to a crucial test.

Expected main results in 2005:

Processing data collected in 2001-2003 for the lifetime measurement with statistical accuracy of 10%.
Publication of the results on the ⁺ ^- atom lifetime measurement.
Production of three new SFD detectors with new electronics. Total number of channels 1600.
Production of new readout electronics for Vertical and Horizontal Hodoscopes.
Development of the system for identification , K-mesons and protons.
Modification of the electron/positron identification system.
Modification of the Data Acquisition System and Slow Control System.

List of projects:
	Project	Leader	Priority (period of realisation)
1.	DIRAC	L.L. Nemenov	1 (1995-2005)

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	CU
		IP ASCR
France	Paris	Univ. VI
		Univ. VII
Greece	Ioannina	UI
Italy	Frascatti	INFN LNF
	Pisa	INFN
	Trieste	INFN
Japan	Kyoto	KSU
	Fukuoka	Kyushu Univ.
	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

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

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