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DIRAC before & beyond 2011 The main task of the DIRAC experiment is to check precise predictions of low-energy QCD investigating properties of hadronic atoms consisting of pions and kaons. Lifetimes of ππandπK atoms and Lamb shifts are strictly related to ππ and πKs-wave scattering lengths, which are accurately calculated in the low-energy QCD. Thus measurement of the hadronic atom lifetime and Lamb shift provide the model independent way to get the values of the corresponding scattering lengths. Importance of K scattering length measurement The measurement of the s-wave πKscattering lengths would test our understanding of the chiralSU(3)L SU(3)Rsymmetry breaking of QCD(u, dands quarks),while the measurement of ππ scattering lengths checks onlythe SU(2)L SU(2)Rsymmetry breaking(u, d quarks).
DIRAC before & beyond 2011 Present low-energy QCD predictions forππand πKscattering lengths will be improved by Lattice calculations will be significantly improved by ChPT calculations Expected results of DIRAC ADDENDUM at PS CERN after 2008-2009 2010-2011 Observation of metastable π+π− atoms and estimation its Lamb shift Study of the possibility to observe K+K− and atoms using 2008-2009 data. DIRAC at SPS CERN beyond 2011 DIRAC at PS2 CERN beyond 2011 - under investigation
DIRAC before & beyond 2011 Low-energy QCD predictions for ππscattering lengths (s-wave): Status of Pion Scattering Lengths Experiments K →π+π e+ve(Ke4): *) 1977 Geneva-Saclay: (PR D15, 574) *) using Roy equations - quadraticaly sum of all errors for estimation only *) 2001 E865 / BNL: (PRL 87, 221801) *) 2008 NA48 / 2: (EPJ C54, 411) K →π0π0π+: 2006 NA48 / 2: (PL B633, 173) 2008 DIRAC: preliminary
DIRAC before & beyond 2011 Yields of atoms at PS and SPS