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Status: Extended

Lifetime Measurement of pi +pi - and pi ± K mp 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 |a1/2-a3/2| 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 |a1/2-a3/2| 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:
List of Activities
  Activity or Experiment Leader
  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

Country or International
City Institute or Laboratory
Czech Republic Prague CTU
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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