1. Status Report of DIRAC SPS and PS experiments Committee L. Nemenov 22 April 2008 DIRAC Addendum LIFETIME MEASUREMENT OF AND ATOMS TO TEST LOW-ENERGY QCD

2. DIRAC collaboration CERN Geneva, Switzerland Zurich University Zurich, Switzerland Kyoto Sangyou University Kyoto, Japan Bern University Bern, Switzerland KEK Tsukuba, Japan Basel University Basel, Switzerland Santiago de Compostela University Santiago de Compostela, Spain University of Messina Messina, Italy IHEP Protvino, Russia Trieste University and INFN-Trieste Trieste, Italy SINP of Moscow State University Moscow, Russia INFN-Laboratori Nazionali di Frascati Frascati, Italy JINR Dubna, Russia Nuclear Physics Institute ASCR Rez, Czech Republic IFIN-HH Bucharest, Romania Institute of Physics ASCR Prague, Czech Republic Tokyo Metropolitan University Tokyo, Japan Czech Technical University Prague, Czech Republic 75 Physicists from 19 Institutes SPS and PS experiments Committee L. Nemenov 22 April 2008

3. Outline I. RUN 2007. 1. Main tasks 2. Upgrade setup. 3. Characteristics of the new detectors. 4. Data taking. 5. Status of the data process. II. RUN 2008. 1. Main tasks. 2. Status of the new electronics and DAQ. 3. RUN schedule. III. A 2π lifetime measurement and expected physical results after RUN 2008 and RUN 2009. SPS and PS experiments Committee L. Nemenov 22 April 2008

4. Plan for the run 2007 Tuning of all detectors downstream the magnet Start of the data taking towards the first observation of A πK and A Kπ Tuning of the Scintillating Fiber Detector and the Ionization hodoscope with the new electronics in parallel with data taking. Tuning of the Micro Drift Chambers in parallel with data taking. SPS and PS experiments Committee L. Nemenov 22 April 2008

5. Method of A πK and A Kπ observation and lifetime measurement Main features of the DIRAC set-up Thin targets: ~ 7 ×10 –3 X 0, Nuclear efficiency: 3 ×10 −4 Magnetic spectrometer Proton beam ~ 10 11 proton/spill Resolution on Q: Q x ≈ Q y ≈ Q L ≈ 0.5 MeV/c “atomic pairs”  (A πK ) is too small to be measured directly e. m. interaction of A πK in the target A πK → π + K − A Kπ → K + π − Q < 3MeV/c,,Θ lab < 3 mrad Coulomb from short-lived sources non-Coulomb from long-lived sources “free pairs” Target Ni 98  m AπKAπK p 24 GeV/c p π+π+ K−K− SPS and PS experiments Committee L. Nemenov 22 April 2008 K−K− π+π+

6. Trajectories of π − and K + from the A πK break-up The numbers to the right of the tracks lines are the π  and K + momenta in GeV/c The A Kπ, π − and K + momenta are shown in the following table : P atom (GeV/c) P π (GeV/c) P K (GeV/c) 5.131.134.0 5.771.274.5 6.411.415.0 10.262.268.0 SPS and PS experiments Committee L. Nemenov 22 April 2008

7. Upgraded DIRAC experimental setup SPS and PS experiments Committee L. Nemenov 22 April 2008

8. Upgraded DIRAC experimental setup description SPS and PS experiments Committee L. Nemenov 22 April 2008

9. All Cherenkov detectors SPS and PS experiments Committee L. Nemenov 22 April 2008

10. Cherenkov detector C 4 F 10 I Responsibility: JINR (Dubna, Russia) with participation of INFN ( Frascati National Lab, Italy); IFIN-HH (Bucharest, Romania); Zurich University (Zurich, Switzerland); Adviser: O. Ullaland (CERN) SPS and PS experiments Committee L. Nemenov 22 April 2008

11. Cherenkov detector C 4 F 10 II Cherenkov detector quality factor N 0 = 125 cm -1 Efficiency to detect pions with momenta >4Gev is >99.5% SPS and PS experiments Committee L. Nemenov 22 April 2008

12. Aerogel Cherenkov detector I Responsibility: Zurich University (Zurich, Switzerland) SPS and PS experiments Committee L. Nemenov 22 April 2008

13. Aerogel Cherenkov detector II The n=1.008 counter Status: Aerogel detectors were installed on the setup Responsibility: Zurich University (Zurich, Switzerland) SPS and PS experiments Committee L. Nemenov 22 April 2008

14. Proton rejection efficiency for a cut in the ADC 20 channels above pedestal: 94.2 % for the heavy aerogel @p= 4.5-5 GeV/c 89.3 % for the light aerogel @p = 6-8 GeV/c Kaon detection efficiency for the same cut: 95.6 % for the heavy aerogel @p= 4.5-5 GeV/c 92.4 % for the light aerogel @p= 6-8 GeV/c n=1.015 module N pe =6.9N pe =3.9 n=1.008 module Pure proton signal from Λ decay and TOF separation Negative kaon spectrum for p=4.5 -5 GeV/c Negative kaon spectrum for p = 6-8 GeV/c Aerogel: Kaon and proton signal III SPS and PS experiments Committee L. Nemenov 22 April 2008 24 6 8100

15. Preshower detector I Responsibility: IFIN-HH (Bucharest, Romania) SPS and PS experiments Committee L. Nemenov 22 April 2008

16. Preshower detector II SPS and PS experiments Committee L. Nemenov 22 April 2008

17. Scintillation Fiber Detector I Sensitive area = 98.5 x 107 mm 2 SPS and PS experiments Committee L. Nemenov 22 April 2008

18. Scintillation Fiber Detector II Characteristics: Size of the plane 100×100 mm 2 Thickness of the material for one plane 3 mm (1% X 0 ) Mean light output: ≈ 11 p.e. Mean Detector Efficiency: ≈ 98 % Time Resolution without coordinate and amplitude corrections ≈ 0.46 ns Space resolution σ ≈ 60  m New electronics (ADC-TDC for each channel) 960 channels SPS and PS experiments Committee L. Nemenov 22 April 2008

19. Number of channels tested with F1 SFD-X : 464 channels (out of 480) IH : all 64 channels Number of channels tested with F1 SFD-X : 464 channels (out of 480) IH : all 64 channels Optimum threshold SFD-X : ~15–20 mV IH : ~20 mV Optimum threshold SFD-X : ~15–20 mV IH : ~20 mV TDC channelADC channel Events TDC spectrum SFD Trigger peak Background ADC spectrum IH Thr = 20 mV Pedestal tail ADC spectrum SFD Pedestal + Single p.e. (light crosstalk) Thr = 10 mV Good events ~2.4 ns (FWHM) SFD and IH with new TDC/ADC beam test 2007 SPS and PS experiments Committee L. Nemenov 22 April 2008

20. Main features: High spatial accuracy σ < 30 µm (2004 result); Distinguish two close tracks with distance < 200 µm; Efficiency > 98% at I = 2×10 11 protons/spill; total detector thickness <5×10 -3 X 0 ; time resolution < 1 ns; readout time < 3  s. Responsibility: JINR (Dubna, Russia), Basel University (Basel, Switzerland) Micro Drift Chambers I SPS and PS experiments Committee L. Nemenov 22 April 2008

21. Examples of event Status During 2007 run Micro Drift Chambers with the new electrodes and all electronics were finally implemented into the DIRAC setup and DAQ system. Data with different MDC working condition were collected. Online data 2007 Target: Pt (28µm) Intensity: 2x10 11 Micro Drift Chambers II SPS and PS experiments Committee L. Nemenov 22 April 2008

22. Drift time: τ ~ 23ns Beam profile, reconstructed by MDC Micro Drift Chambers III SPS and PS experiments Committee L. Nemenov 22 April 2008

23. Improvement of the proton beam time structure and the beam intensity distribution at spills. R.Steerenberg, A.Grudiev, L.Gatignon et al. Beam intensity about 1.9  10 11 proton/spill 1 st level triggers numbers 3200( π + π − )+2100( K + π − )+1000( π + K − )=6300 1/spill Number of recorded events 2000 1/spill is near to the hardware limit of DAQ Full number of π + π − and πK events recorded during 3 months of data taking is 1.4  10 9 Run 2007 SPS and PS experiments Committee L. Nemenov 22 April 2008

24. Estimation of A  K and A K  atom fluxes Assuming an additional factor of inefficiency for kaonic atoms of 2 and using expected value of the lifetime 3.7 fs we estimate the number of collected kaonic atoms: n AπK +n AKπ = 700 ± 200. This value coincides with the estimations made in Addendum and reported at SPSC last year. First estimation of A 2π observed in 2007 with Pt target: 10000±3000 (with suppression factor 2 in respect to πK atom trigger) From theory and FRITIOF6 simulation production of atoms relates as: SPS and PS experiments Committee L. Nemenov 22 April 2008 Before autumn 2008 we will prepare a paper titled: “Search for πK atoms” or “ Observation of πK atoms ”

25. RUN 2008 Main tasks. To tune DIRAC setup with the new front-end electronics, trigger logic, readout system and DAQ To perform data taking for the lifetime measurement of A 2π, A Kπ and A πK SPS and PS experiments Committee L. Nemenov 22 April 2008

26. Responsibility: JINR (Dubna, Russia) with participation of IFIN-HH (Bucharest, Romania); Zurich University (Zurich, Switzerland) Front-end electronics and Readout System 1 Logical output signals for trigger (flat cables) Experimental Area Barrack USB Host computer USB hubs Central storage (IT division ) Č VH HH … ADC-TDC (D412) 1 SFD Transmitter (1 st level) 2 2 ADC&TDC signals for readout (maximal distance ~10 m) ADC-TDC (D412) ADC-TDC (D412) ADC-TDC (D412) ADC-TDC (D412) 1 1 1 1 2 2 2 2 Transmitter (1 st level) Transmitter (1 st level) Transmitter (1 st level) Transmitter (1 st level) Transmitter (2 nd level) Transmitter (2 nd level) SPS and PS experiments Committee L. Nemenov 22 April 2008

27. Status of the new electronics All electronics is ready, tuned and will be installed before the rung beginning The setup tuning, in according to our plan, will be done during 6 weeks Data taking will continue 4 months SPS and PS experiments Committee L. Nemenov 22 April 2008

28. Pion scattering lengths Low-energy QCD predictions for ππ scattering lengths (s-wave) : 1) 1977 Geneva-Saclay: (PR D15, 574) Experiments K → π + π  e + v e (K e4 ): 2) 2001 E865 / BNL: (PRL 87, 221801) 3) 2008 NA48 / 2: (EPJ C54, 411) *) 2006 NA48 / 2: (PL B633, 173) K → π 0 π 0 π + : *) using Roy equations *) SPS and PS experiments Committee L. Nemenov 22 April 2008 *)

29. Experimental results 2001-2003 SPS and PS experiments Committee L. Nemenov 22 April 2008

30. > 2008 DIRAC:...after data collection in 2008 & 2009 3) > 2008 DIRAC:...after data collection in 2008 & 2009 Experimental results Low-energy QCD predictions for scattering lengths (s-wave) : 1) 2005 DIRAC: (PL B619, 50)...based on 2001 data (6530 observed atoms) Experiments A 2π lifetime: 2) 2008 DIRAC: preliminary...from major part 2001-03 data (13390 observed atoms) A πK lifetime: ππ: πK: SPS and PS experiments Committee L. Nemenov 22 April 2008

31. Run 2009 will increase the statistics of A 2π, A πK and A Kπ on factor 2.5 Run 2009 SPS and PS experiments Committee L. Nemenov 22 April 2008

32. The measurement of the s- wave πK scattering lengths would test our understanding of the chiral SU(3) L  SU(3) R symmetry breaking of QCD ( u, d and s quarks), while the measurement of ππ scattering lengths checks only the SU(2) L  SU(2) R symmetry breaking ( u, d quarks). What new will be known if  K scattering length will be measured?  K scattering This is the main difference between ππ and πK scattering! SPS and PS experiments Committee L. Nemenov 22 April 2008