THEME02-2-1080-2009/2015

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02-2-1080-2009/2015

Priority:

Status:

Extended

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, Italy, Japan, Romania, Russia, Spain, Switzerland.
Scientific Programme:
The experiment aims to measure the lifetime of

⁺

^- atoms (A₂), observe

K atoms (A_K), and 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 the 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 2014:

Completion of the processing of the 2008-2010 data for observation and lifetame measurement of ^±K atom. Publishing results.
Preparation of the letter of intend for investigation of ^±K and ⁺ ^- atoms at the SPS accelerator, CERN.
Publishing of the result on observation of the long-lived states of ⁺ ^- atom basing on 2012 data.
Processing of the data collected in 2011-2012 for measurement of the multiple scattering in thing foils with accuracy better than 1%.
Completion of the processing of the 2008-2010 data for lifetime measurement of ⁺ ^- atom. Preparation of publication.

List of Activities

Activity or Experiment

Leader

Status

Laboratory or other
Division of JINR
Responsible person

Main researchers

Experiment DIRAC

L.G. Afanasyev

Data taking
Data analysis

DLNP

M.V. Zhabitsky, A.V. Dudarev, V.V. Kruglov, V.V. Karpukhin, E. Kulish, A.V. Kulikov, L.L. Nemenov, M.V. Nikitin

LIT

P.V. Zrelov, O.V. Voskresenskaya, L.Yu. Kruglova

Collaboration
Country or International Organization	City	Institute or Laboratory
CERN	Geneva	CERN
Czech Republic	Prague	CTU
		IP ASCR
	Rez	NPI ASCR
Italy	Frascati	INFN LNF
	Messina	UniMe
	Trieste	INFN
Japan	Kyoto	KSU
	Tokyo	TMU
	Tsukuba	KEK
Romania	Bucharest	IFA
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