L. Nemenov, EXA05 Using  -  and  -K atoms for the experimental check of low-energy QCD L. Nemenov (CERN, Switzerland) Presented by L. Tauscher Basel University, Switzerland

L. Nemenov, EXA05 Why atoms ? Particles scatter off each other in well defined atomic quantum states Very low Q’s  atomic level scheme sensitive to scattering length Strong interaction leads to complex energy eigenvalues E nl - i  nl /2 = E nl QED +  nl - i  nl /2 Example:   1S  2a 0 + a 2  1S  |a 0 - a 2 | 2 “Model-independent” determination of scattering lengths

L. Nemenov, EXA05 Experimental status on  K +  +  - e + v e (K e4 )  phase difference    (s)-    (s) for 4m   <s<m K 2 a 0 = 0.26 ± 0.05[m   ]Roy eq. Rosselet et al. CERN 1977 a 0 = ± 0.033[m   ]Roy eq. Pislak et al. BNL / E865 a 2 = ± 0.023[m   ] 2001/2003 a 0 = ± stat ± syst ± th [m   ] Roy eq a 2 = from ChPT DIRAC (A  ) after analysis of ALL collected data so far  |a 0 -a 2 |  ± 5% stat (± 3% syst ± 2% th ) estimated  ± stat (± syst ± th ) estimated

L. Nemenov, EXA05 Theory  a 0 = ± [m   ] (2.3%) a 2 = ± [m   ] (2.3%) a 0 - a 2 = ± [m   ] (1.5%)

L. Nemenov, EXA05 Theory 

L. Nemenov, EXA05 Experimental status on  In the 60’s and 70’s set of experiments were performed to measure πK scattering amplitudes. Most of them were done studying the scattering of kaons on protons or neutrons, and later also on deuterons. The kaon beams used in these experiments had energies ranging from 2 to 13 GeV. The main idea of those experiments was to determine the contribution of the One Pion Exchange (OPE) mechanism. This allows to obtain the πK scattering amplitude. Analysis of experiments gave the phases of πK-scattering in the region of 0.7 ≤ m(πK) ≤ 2.5 GeV. The most reliable data on the phases belong to the region 1 ≤ m(πK) ≤ 2.5 GeV.

L. Nemenov, EXA05 Theoretical accuracy on atomic quantities

L. Nemenov, EXA05 Theoretical accuracy on atomic quantities

L. Nemenov, EXA05 Principle of lifetime measurement

L. Nemenov, EXA05 Pbr to lifetime conversion

L. Nemenov, EXA05 DIRAC II (Addendum)

L. Nemenov, EXA05 DIRAC II Set-up

L. Nemenov, EXA05 DIRAC II Set-up Decrease the systematic errors. 1.Single–multilayer targets 2.Identification of e ±,  ±, K ± and p Increasing of statistics and efficiency of the setup Shielding K ≈ 1.9  Formation of time structure of the spill with the trigger of setup  Microdrift chambers  New electronics for SFD  Increase in the aperture on VH hodoscope and PSH  Total K ≈ 4

L. Nemenov, EXA05 Metastables

L. Nemenov, EXA05 Metastables

L. Nemenov, EXA05 Metastables

L. Nemenov, EXA05 Metastables

L. Nemenov, EXA05 Metastables

L. Nemenov, EXA05 Metastables

L. Nemenov, EXA05 Metastables

L. Nemenov, EXA05 Metastables

L. Nemenov, EXA05 Metastables

L. Nemenov, EXA05 Prospects beyond DIRAC II Measure at machines with higher proton current Higher duty factor Higher energy

L. Nemenov, EXA05 Yields of atoms as a function of the proton beam momentum Yields of pion pairs and atoms for 24 GeV protons per pNi-interaction at  Θ lab =5.7° (DIRAC accept.) P, GeV/c +-+- A2A2 A2/+-A2/+- A  K +A K  (A  K +A K  )/  +  · · · · ·10 -8 Relative yields of pion pairs and atoms as a function of the proton beam momentum P, GeV/c +-+- A2A2 A2/+-A2/+- A  K +A K  (A  K +A K  )/  +  - Duty factor PS CERN (0.06) GSI (SIS100) J-PARC GSI (SIS200) GSI (SIS300) SPS CERN

L. Nemenov, EXA05 Estimation of error sources in  |a 0 -a 2 |/ |a 0 -a 2 | based on data taken with the upgraded DIRAC setup during 12 months (20h/day) Single-layer target nAnA statτ=f(a 0 -a 2 ) P br =f(  )*) Non- pointli ke produc tion PS CERN 24 GeV/c %0.6%1.2%  1% J-PARC 50 GeV/c 4.1* %0.6%1.2% GSI 90 GeV/c 1.2* % 1.2% SPS CERN 450 GeV/c 1.26* %0.6%1.2% *) Precision of P br =f(  ) can be increased to better then 0.6% private communication by D.Trautmann

L. Nemenov, EXA05 Estimation of error sources in Δ|a 1/2 -a 3/2 |/ |a 1/2 -a 3/2 | based on data taken with the upgraded DIRAC setup during 12 months (20h/day) Single-layer target nAnA statτ=f(a 1/2 -a 3/2 ) P br =f(  ) *) syst PS CERN 24 GeV/c %1.1%1.2% J-PARC 50 GeV/c 1.7*10 4 7%1.1%1.2% GSI 90 GeV/c 1.4* %1.1%1.2% SPS CERN 450 GeV/c 1.2* %1.1%1.2% *) Precision of P br =f(  ) can be increased to better then 0.6% private communication by D.Trautmann

L. Nemenov, EXA05 Conclusions