THEME02-2-1043-2002/2004

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02-2-1043-2002/2004

Priority:

Status:

Approved for completion
in 2004

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

Leader:	L.L. Nemenov
Deputy:	.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 2004:

Processing of the lifetime data collected in 2000-2003 in measurements with Ni and Ti targets statistically accurate to about 10% and evaluation of systematic errors in the lifetime.
Publications of the results for the ⁺ ^- atom observation and the lifetime measurement.
Analysis of the experimental measurements of multiple scattering angles in the target, detectors and elements of the setup to reduce the systematic errors due to uncertainties in the multiple scattering description. Refinement of the theoretical description of the multiple scattering.
Analysis of the micro-drift chamber test to study systematic errors in the experimental data.
Design and production of the TDC-ADC electronic unit with a readout system for the scintillation fiber detector and their test at the PS CERN.
Development of the addendum to the DIRAC project on the measurement of the ⁺ ^- atom lifetime with an accuracy of 5%, observation of K atoms and long-lived states of ⁺ ^- atom.
Development of the proposal for the ⁺ ^- and K atom lifetime measurement of the accelerator J-PARC in Japan following the recommendation of the J-PARC directorate after approval of the Letter of Intent.

List of Activities

Activity or project

Spokespersons

Status

DIRAC

L.L. Nemenov

Data taking

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	TM CAE
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