THEME02-2-1080-2009/2011

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02-2-1080-2009/2011

Priority:

Status:

In-progress

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

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

Participating Countries, Institutes and International organizations:
CERN, Czech Republic, Greece, Italy, Japan, Romania, Russia, Spain, Switzerland.

Scientific Programme:
The experiment aims to measure the lifetime of

⁺

^- atoms (A₂), to observe

K atoms (A_K) and to measure their lifetime using the 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 2010:

Preparation of the addendum to the DIRAC project on the observation of the long-lived states of ⁺ ^- atoms.
Data taking run for observation of the long-lived states of ⁺ ^- atoms.
Completion of the analysis of the data on the ⁺ ^- atom lifetime measurement and publication of the results.
Processing of the 2008-2009 data on the K atoms observation and investigation of ⁺ ^- atoms.

List of Activities

Activity or experiment

Leader

Status

Laboratory

Responsible
person

Leading researchers
and number of participants

DIRAC

L.G. Afanasyev

Data analysis

DLNP

L.G. Afanasyev + 11 pers.

LIT

P.V. Zrelov + 2 pers.

Collaboration
Country or international organization	City	Institute or Laboratory
CERN	Geneva
Czech Republic	Prague	CTU
		IP ASCR
Greece	Ioannina	UI
Italy	Frascati	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	Uni Bern
	Zurich	UZH

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

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