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pp and p K atoms as a tool to check precise low energy QCD

pp and p K atoms as a tool to check precise low energy QCD. International Workshop “Exotic hadronic atoms, deeply bound kaonic nuclear states and antihydrogen: present results, future challenges” Trento, June 19 to 23, 2006. Outline. High-energy and low-energy QCD

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pp and p K atoms as a tool to check precise low energy QCD

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  1. pp and pK atoms as a tool to check precise low energy QCD International Workshop “Exotic hadronic atoms, deeply bound kaonic nuclear states and antihydrogen: present results, future challenges” Trento, June 19 to 23, 2006 Leonid Nemenov, CERN (presented by L. Tauscher)

  2. Outline • High-energy and low-energy QCD • Precise predictions of low-energy QCD • Experimental check of low-energy QCD predictions • First lifetime measurement of the π+π–-atom • The new experiment on the investigation of π+π–-atom and observation of πK-atoms at PS CERN • Potentials of the DIRAC setup at SPS CERN, GSI and J-PARC Leonid Nemenov, CERN (presented by L. Tauscher)

  3. Standard Model Q>> Q<< Theoretical motivation QCD LOW energy HIGH energy perturbative QCD Spontaneous chiral symmetry breaking (1967 – Weinberg) QCD Lagrangian in presence of quark masses: LQCD(q,g) = Lsym+ Lbreak-sym • high energy (small distance) • “weak” interaction (asymptotic freedom) • expansion in coupling • low energy (large distance) • strong interaction (confinement) • expansion in momentum & mass Leff( ,K,) = Lsym+ Lbreak-sym Lsym M, for large Q, depends only on: M, for small Q, depends on both: Lsymand Lbreak-sym and q-condensate At low energies, QCD is replaced by an effective quantum field theory (ChPT) formulated in terms of asymptotically observable fields like , K,  1979,Weinberg 1984,Gasser & Leutwyler Leonid Nemenov, CERN (presented by L. Tauscher)

  4. A and AK observation and lifetime measurement (AπK) too small to be measured directly e. m. interaction of AπK in the target AπK π+K- AKπ K+π- Q < 3MeV/c, , lab< 3 mrad • Coulombfrom short-lived sources • non-Coulombfrom long-lived sources Target Ni 98 m π p AπK “atomic pairs” 24 GeV/c K π p “free pairs” 24 GeV/c K Main features of the DIRAC set-up Thin targets: ~ 7 10–3 X0, Nuclear efficiency: 3 10−4 Magnetic spectrometer Proton beam ~ 1011proton/spill Resolution on Q: Qx≈ Qy≈ QL≈ 0.5 MeV/c Leonid Nemenov, CERN (presented by L. Tauscher)

  5. π+ π0 π0 π Theoretical limitations (A) 1. A2πlifetime H. Jalloul, H.Sazdjian 1998 M.A. Ivanov et al. 1998 A. Gashi et al. 2002 J. Gasser et al. 2001 Current accuracy from the A2π lifetime calculation 2. A2π interaction with matter (break-up) L.Afanasyev, G.Baur, T.Heim, K.Hencken, Z.Halabuka, A.Kotsinyan, S.Mrowczynski,C.Santamarina, M.Schumann, A.Tarasov, D.Trautmann, O.Voskresenskaya fromBasel, JINRandCERN Current accuracy from break-up probability Pbr To be reduced by factor 2 Leonid Nemenov, CERN (presented by L. Tauscher)

  6. K+ π0 K0 π Theoretical limitations (AK) J. Schweizer (2004) Current accuracy from the AKπ lifetime calculations Leonid Nemenov, CERN (presented by L. Tauscher)

  7. Energy splitting Lifetime: A2  00 Energy Splitting between np - nsstates in A2 atom For n = 2 eV from QED calculations s eV estimate from ChPT a0 = 0.220 ± 0.005, a2 =  0.0444 ± 0.0010 (2001)G. Colangelo, J. Gasser and H. Leutwyler  E2 ≈  0.56 eV (1979)A. Karimkhodzhaev and R. Faustov(1999) A. Gashi et al. (1983)G. Austen and J. de Swart(2000)D. Eiras and J. Soto (1986) G. Efimov et al. Measurement of  and E allows one to obtain a0 and a2 separately Leonid Nemenov, CERN (presented by L. Tauscher)

  8. +   External beam is a metastable atom small angle  * A2 Metastable atoms For pA = 5.6 GeV/c and  = 20 1s= 2.9  10 15 s, 1s= 1.7  10 3 cm 2s= 2.3  10 14 s, 2s= 1.4  10 2 cm 2p= 1.17  10 11 s, 2p= 7 cm 3p  23 cm 4p  54 cm p Probabilities of the A2π breakup (Br) and yields of the long-lived states for different targets provided the maximum yield of summed population of the long-lived states:(l ≥1) Leonid Nemenov, CERN (presented by L. Tauscher)

  9. Atomic pairs Leonid Nemenov, CERN (presented by L. Tauscher)

  10. DIRAC analysis • Improvements on systematics in PBr • CC background no improvement ± 0.007 • signal shape no improvement ± 0.002 • Multiple scattering measured to ±1% (DONE) + 0.002 /-0.002 • K+K/ppbar admixtures to be measured* + 0.000 /-0.023 • Finite size effects to be measured** + 0.000 /-0.017 • Total+ 0.008 /-0.030 • * To be measured in 2007/2008 with new PID • ** To be measured in 2006/2008 with new trigger for identical particles at low Q • Improvements on data quality by fine tuning • Adjustments of drift characteristics almost run-by-run • B-field adjustment and alignment tuning with -mass •  New pre-selection for all runs (DONE) • Comments on analysis strategies • Using only downstream detectors (Drift chambers) and investigating only QL causes less sensitivity to multiple scattering and to the signal shape. Studies are under way and very promising. Leonid Nemenov, CERN (presented by L. Tauscher)

  11. Finite-size effects characteristic scale |a| = 387 fm (Bohr radius of pp system) average value of r* ~ 10 fm range of  ~ 30 fm range of ' ~ 900 fm critical region of r* ~ |a| is formed by  and ' pairs UrQMD simulation pNi 24 GeV: • ~15%  pairs • < 1% ' pairs  shift in Pbr mainly due to  pairs  ' Leonid Nemenov, CERN (presented by L. Tauscher)

  12. Finite-size effects p-p-corr. Function (CF), arbitrary units Simulation vs fit of DIRAC p-p-CF simulation Nw(pp-) = 19.2% fit result Nw(pp-) = 21±7% Þ good description of  pairs by UrQMD In π+πsystem finite-size effect induces shift in Pbr • UrQMD simulation Nw(π+π) = 15% ÞdPbr ~ 2% Þdt ~ 5% • upper limit at 1 of p-p-fit Nw (π+π)= 20% ÞdPbr ~ 3% Þdt ~ 7.5% Þ Systematic shift in t measurement from finite-size effect < 10% i.e. less then present DIRAC statistical error in t. Expected shift with multi-layer target in future DIRAC five times less Leonid Nemenov, CERN (presented by L. Tauscher)

  13. Dual Target Method • Single/Multilayer target comparison: • Same amount of multiple scattering • Same background (CC, NC, ACC) • Same number of produced A2 , but lower number of dissociated pairs Leonid Nemenov, CERN (presented by L. Tauscher)

  14. ππ scattering lengths Presentlow energy QCD predictions: First result (L. Rosseletet al., Phys. Rev. D15(1977) 574): Results from E865/BNL (S.Pislaket al., Phys. Rev. Lett. 87 (2001) 221801): K π+πe+ve(Ke4) using Royeqs. using Royeqs.and ChPT constraints a2=fChPT(a0) Results from NA48/2 (J.R.Batley et al., Phys. Lett. B633 (2006) 173): K+ π0π0π+ DIRAC,2001data (Phys. Lett. B 619 (2005) 50) DIRACexpected results,2001–2003 data Upgraded DIRAC (DIRAC II) Leonid Nemenov, CERN (presented by L. Tauscher)

  15. Trajectories of π− and K+ from the AπK break-up AπK, π-and K+momenta π and K+ momenta in GeV/c Leonid Nemenov, CERN (presented by L. Tauscher)

  16. Upgraded DIRAC experimental set-up description Leonid Nemenov, CERN (presented by L. Tauscher)

  17. I. ChPT predicts s-wave scattering lengths: πK scattering V. Bernard, N. Kaiser, U. Meissner. – 1991 L (2), L (4) and 1-loop A. Rossel. – 1999 L (2), L (4), L (6) and 2-loop J. Bijnens, P. Talaver. – April 2004 II. Roy-Steiner equations: III. AK lifetime: J. Schweizer. – 2004 Leonid Nemenov, CERN (presented by L. Tauscher)

  18. What new will be known whenK scattering length will be measured? The measurement of s-wave πK scattering length would test our understanding of chiral SU(3)L SU(3)R symmetry breaking of QCD (u, dand s), while the measurement of ππ scattering length checks only SU(2)L SU(2)R symmetry breaking(u, d). This is the main difference between ππ and πK scattering! Leonid Nemenov, CERN (presented by L. Tauscher)

  19. Time scale for the A2π and AπK experiment 2006 Manufacture and installation of new detectors and electronics: 6 months Test of the Upgraded setup and calibration:3 months 2007 and 2008 Measurement of A2π lifetime: 12 months In this time 86000 ππ atomic pairs will be collected to measure A2π lifetime with precision of: At the same time we also should observeAπK and, if so, detect5000 πKatomic pairs to estimate AπK lifetime with precision of: This estimation of the beam time is based on the A2π statistics collected in 2001 and on the assumption of having 2.5 spills per supercycle during 20 hours per day. Leonid Nemenov, CERN (presented by L. Tauscher)

  20. Expected accuracy for ππ-scattering (*)Precision on Pbr = () can be increased and the error will be less than 0.6% private communication by D. Trautmann Leonid Nemenov, CERN (presented by L. Tauscher)

  21. Expected accuracy for πK-scattering (*)Precision on Pbr = () can be increased and the error will be less than 0.6% private communication by D. Trautmann Leonid Nemenov, CERN (presented by L. Tauscher)

  22. DIRAC collaboration75 Physicists from 18 Institutes CERN Geneva, Switzerland IFIN-HH Bucharest, Romania Czech Technical University Prague, Czech Republic Institute of Physics ASCR Prague, Czech Republic JINR Dubna, Russia INFN Laboratori Nazionali di Frascati Frascati, Italy Trieste University and INFN-Trieste Trieste,Italy University of Messina Messina, Italy SINP of Moscow State University Moscow, Russia IHEP Protvino, Russia Santiago de Compostela University Santiago de Compostela,Spain KEK Tsukuba, Japan Kyoto Sangyou University Kyoto, Japan Tokyo Metropolitan University Tokyo,Japan Basel University Basel,Switzerland Bern University Bern,Switzerland Zurich University Zurich,Switzerland Leonid Nemenov, CERN (presented by L. Tauscher)

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