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Overview of Meson Production Experiments at JLAB

Overview of Meson Production Experiments at JLAB. Cole Smith University of Virginia New Theoretical Tools for Nucleon Resonance Analysis Workshop Argonne National Lab, Aug 29, 2005. e’. γ v. e. N*,△. N’,△’. N. N* Program at JLAB. Physics Goals

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Overview of Meson Production Experiments at JLAB

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  1. Overview of Meson Production Experiments at JLAB Cole Smith University of Virginia New Theoretical Tools for Nucleon Resonance Analysis Workshop Argonne National Lab, Aug 29, 2005 Cole Smith - ANL Theory Workshop - Aug 29 2005

  2. e’ γv e N*,△ N’,△’ N N* Program at JLAB Physics Goals • Photocouplings A3/2 A1/2 S1/2 vs Q2 for known Δ,N* resonances • Understand confinement and excitation mechanisms from QCD • Search for missing resonances expected from SU(6)xO(3) • Details of quark wave functions (symmetric vs. di-quark) Theoretical Challenges • Partial wave, isospin and channel couplings ofhadronic decay • Interference between EM and strong interaction vertices • Appropriate kinematic/dynamical d.o.f.: relativity, gluons vs. mesons Cole Smith - ANL Theory Workshop - Aug 29 2005

  3. Kaon-Hyperon Electromagnetic Production • Open questions • Strangeness content of proton (G0, HAPPEX, SAMPLE, PVA4) • What mechanism produces ss pair (sea quarks, flux tube breaking, gluon radiation) ? • Which previously known resonances contribute to KΛ,KΣ final states? • How significant are Born terms? • Can missing resonances which couple to KΛ, KΣ channels be identified reliably? • Advantages of KΣ,KΛ final states • Easier to measure and analyze vs. ππN final states • Resonance couplings to KY channels different from πN • KΛ channel is an isospin filter (pure I=1/2) • Weak decay Λ→ pπ- self analyzing • : measurement of W(cos θ) yields Λ polarization. Cole Smith - ANL Theory Workshop - Aug 29 2005

  4. s-channel u-channel t-channel contact Structure in σtot near W=1.9 GeV 1998: SAPHIR / ELSA D13(1895) ? Kaon-Hyperon Electromagnetic Production: Hadrodynamic Models dσ vs. cosθ* More observables need to constrain models, especially polarization. SAPHIR, CLAS SPRING-8 DESY SAPHIR, CLAS CLAS CLAS Cole Smith - ANL Theory Workshop - Aug 29 2005

  5. Quark models: Insight into mechanism for creation of ss pair? a) Direct knockout of u quark. Flux tube breaks to create ss pair. b) VMD: reaction probes hadronic structure of photon c) Photon probes virtual ss pairs in proton Flux tube picture: Measurement of Λ polarization can be used to study spin alignment of ss pair Cole Smith - ANL Theory Workshop - Aug 29 2005

  6. Review of CLAS K+Λ0 photoproduction experiments CLAS/McNabb et al., PRC 69, 042201R (2004) Induced recoil polarization Py Sensitive to interference between resonances and background Structure at higher W moves with C.M. angle – interfering resonances? Bump at threshold from known S11(1650), P11(1710), P13(1720) Cole Smith - ANL Theory Workshop - Aug 29 2005

  7. K+Λ Summary of Recent Fits: Operator Product Expansion PWA A.V. Sarantsev et al., hep-ex/0506011 • Analysis finds new P11 state at 1840 MeV, and Γ = 140 MeV • Fit also requires D13(1870), D13(2170) • P11 state @ 1840 MeV consistent with SU(6) x O(3) symmetric quark model • Inconsistent with diquark-quark symmetry Combined fit to KY, pπ0,nπ+,pη CLAS, SAPHIR and LEPS data (dσ, Py, Σ). Authors note sharp peak at W~1700 GeV cannot be fitted using conventional resonance parameters K+Λ0 S11(1650) P13(1720) CLAS data Cole Smith - ANL Theory Workshop - Aug 29 2005

  8. K+Σ0 P11(1840) K* exchange Summary of Recent Fits: Operator Product Expansion PWA (cont’d) A.V. Sarantsev et al., hep-ex/0506011 K0Σ+ K+Σ0 CLAS / E89-004 Bryan Carnahan (CUA) Cole Smith - ANL Theory Workshop - Aug 29 2005

  9. K0Σ+ photoproduction - Different isospin channel CLAS / E89-004 Bryan Carnahan (CUA) Requires measurement of 3 final state particles Resonances contribute with different Clebsch-Gordon weights. Scarcity of previous measurements Cole Smith - ANL Theory Workshop - Aug 29 2005

  10. Channel-coupling suppressed ρ off - ηS11 Summary of Recent Fits: Coupled-Channel Analysis A. Usov and O. Scholten, nucl-th/0503013 • Rescattering contributions enhance cross section near threshold • Cancellation from γ+ p → π + N → S11 → K + Λ • Peak near W=1700 dominated by γ+ p → S11 → π + N → K + Λ • Σ0/Σ+ ratio sensitive to gauge prescription • Isospin symmetry imposes strong contraints on resonance contributions Cole Smith - ANL Theory Workshop - Aug 29 2005

  11. Summary of Recent Fits: Dynamical Coupled-Channel Analysis B. Julia-Diaz et al., nucl-th/0501005 • Coupled-channel effects from π0p and π+n intermediate states contribute strongly • Forward angle cross section suppressed by CC near threshold • Fit prefers third S11 state at W~1780 with Γ~100 MeV Cole Smith - ANL Theory Workshop - Aug 29 2005

  12. Giessen model: previously fitted non-strange parameters held fixed. Separate fits to CLAS and SAPHIR KΛ data only Summary of Recent Fits: Coupled-Channel Analysis V. Shklyar et al., PRC 72, 015210 (2005) • No effect from P11(1710) , D13(1890) or D13(1950) • CLAS fit requires more non-resonant strength in S11 channel • P13 channel saturated by P13(1720) and P13(1900) Cole Smith - ANL Theory Workshop - Aug 29 2005

  13. K+Λ photoproduction – New CLAS 2005 data set CLAS / E89-004 Robert K. Bradford (CMU) submitted to PRC CLAS data more backward peaked compared to SAPHIR (u-channel contributions?) Prominent bumps around W=1.9 GeV visible at backward C.M. angles Cole Smith - ANL Theory Workshop - Aug 29 2005

  14. K+Λphotoproduction – New CLAS 2005 data set CLAS / E89-004 Robert K. Bradford (CMU) Discrepancies between CLAS and SAPHIR KΛ data persist. Cole Smith - ANL Theory Workshop - Aug 29 2005

  15. K+Λ photoproduction – New CLAS 2005 data set CLAS / E89-004 Robert K. Bradford (CMU) K+Λ production exhibits Regge scaling up to –t~1.5 Some t-channel scaling evident for Σ0, but Δ isobars can contribute in s-channel Cole Smith - ANL Theory Workshop - Aug 29 2005

  16. K+Λ photoproduction – New CLAS 2005 data set CLAS / E89-004 Robert K. Bradford (CMU) Backward c.m. angles Forward c.m. angles CΛz = +1 : Λ maximally polarized along photon beam direction ! Cole Smith - ANL Theory Workshop - Aug 29 2005

  17. K+Σ0 photoproduction – New CLAS 2005 data set CLAS / E89-004 Robert K. Bradford (CMU) Possible bump near W=2 GeV Zero crossing in Cz Cole Smith - ANL Theory Workshop - Aug 29 2005

  18. CLAS Frozen Spin Target (FROST) Exp. E-02-112 Existing database Planned coverage CLAS-g1: dσ/dΩ, P, Cx, Cz CLAS-g8: Σ, Ox, Oz E-02-112: T, E, H, Tx, Tz, Lx, Lz Full set of observables will be measured for first time, permitting model independent PWA. First experiments scheduled in 2007-2008 Cole Smith - ANL Theory Workshop - Aug 29 2005

  19. CLAS K+Λ Electroproduction : Spin Polarization Transfer Raue and Carman, PRC 71, 065209 (2005) Carman et al., PRL 90, 131804 (2003) Systematically smaller R compared to Hall C Rosenbluth separation Λ polarized almost maximally along γ* Parallel kinematics Cole Smith - ANL Theory Workshop - Aug 29 2005

  20. K+Λ electroproduction – Structure functions vs cosθ* at Q2=0.65 CLAS / E00-112 Pavel Ambrozewicz (CMU) Strong forward peaking for σU, σTT and σLT Cole Smith - ANL Theory Workshop - Aug 29 2005

  21. K+Σ0 electroproduction – Structure functions vs cosθ* at Q2=0.65 CLAS / E00-112 Pavel Ambrozewicz (CMU) σLT structure function for Σ0production is consistent with zero. Cole Smith - ANL Theory Workshop - Aug 29 2005

  22. K+Λ electroproduction – Structure functions vs W at Q2=0.65 CLAS / E00-112 Pavel Ambrozewicz (CMU) Strong enhancement in σU at forward angles around W=1.7 not seen in models Cole Smith - ANL Theory Workshop - Aug 29 2005

  23. K+Σ0 electroproduction – Structure functions vs W at Q2=0.65 CLAS / E00-112 Pavel Ambrozewicz (CMU) Models clearly should be refitted to these new data Cole Smith - ANL Theory Workshop - Aug 29 2005

  24. K+Λ, K+Σ0 electroproduction – Q2 Dependence CLAS / E00-112 Pavel Ambrozewicz (CMU) More rapid falloff for K+Σ0 Cole Smith - ANL Theory Workshop - Aug 29 2005

  25. γ*p→Δ(1232) Magnetic Dipole Transition Form Factor Sato,Lee PRC 63, 055201 (2001) C. Alexandrou et al, PRL, 94, 021601 (2005) Pion Cloud Dynamical models: Strong contribution from pion cloud rescattering at low Q2. Quenched Lattice: Agrees with data near Q2=0, falls more slowly than data for Q2 > 0 Cole Smith - ANL Theory Workshop - Aug 29 2005

  26. e / e / e e What are we probing at low Q2? E0+,S0+,M1-,S1- E1+,S1+,M1+,… M1, E2, C2 • Short Range Physics? • Gluon exchange → D-state admixtures • Deformation of N / Δ • Long Range Physics? • Coupling to pion cloud • 2-body currents Cole Smith - ANL Theory Workshop - Aug 29 2005

  27. Quadrupole Transition – Lattice QCD vs. Pion Cloud Models C. Alexandrou et al, PRL, 94, 021601 (2005) γ*p→Δ(1232)→π0p E2/M1 (%) C2/M1 (%) Low Q2 behavior of C2/M1 strong test of calculations ! Cole Smith - ANL Theory Workshop - Aug 29 2005

  28. Preliminary CLAS Results for REM and RSM CLAS / E89-112 C. Smith (UVA) Preliminary Still unclear whether apparent dip in S1+/M1+ at low Q2 is real. Preliminary Reanalysis of ELSA low Q2 points in progress. (R. Gothe, private comm.) Cole Smith - ANL Theory Workshop - Aug 29 2005

  29. MAID2003 Sparveris Kunz Mertz DMT CLAS Preliminary E=1.046 Q2=0.16 Sato-Lee W=1.17 W=1.232 Response at Δ(1232) peak - Comparison to Bates at Q2=0.127 GeV2 Model variation negligible between Q2=0.127 and 0.16. Good agreement between Bates and CLAS for T+L and TT measurements. Preliminary Disagreement with Kunz point (■) for LT. Global fit (-----) favors Sato-Lee model at W=1.232. Cole Smith - ANL Theory Workshop - Aug 29 2005

  30. Sato-Lee MAID03 DMT MAMI experiment: LT-asymmetry at Q2=0.2 GeV2 D. Elsner nucl-ex/05? Raw asymmetry in agreement with CLAS data, however MAID03 fit yields larger RSM. Θπ* (deg) Cole Smith - ANL Theory Workshop - Aug 29 2005

  31. Model Dependence most easily visible in Legendre coefficients Preliminary Leading order M1+ multipole terms Large difference between dynamical models for A1 and D0. Large difference between MAID and dynamical models for D1, which is dominated by Re(S1+) Cole Smith - ANL Theory Workshop - Aug 29 2005

  32. Sato-Lee Model: Sensitivity to details E1+ Models agree well S1+ Strong disagreement away from Δ(1232) peak Cole Smith - ANL Theory Workshop - Aug 29 2005

  33. Recoil Polarization in p(e,e’p)π0 Hall A / E91-011 J.J. Kelly (U.Md.) • E0=4.53 GeV Q2=1.0 GeV2 1.17 < W < 1.35 GeV • Measured angular distributions for 16 response functions: 14 separated + 2 Rosenbluth combinations • Both real and imaginary type responses → phase information for amplitude analyses • EMR, SMR without sp truncation or M1+ dominance Cole Smith - ANL Theory Workshop - Aug 29 2005

  34. Recoil Polarization : Separated Response Functions Hall A / E91-011 J.J. Kelly (U.Md.) Some LT responses not well described by reaction models Cole Smith - ANL Theory Workshop - Aug 29 2005

  35. Recoil Polarization: Extracted Multipoles Hall A / E91-011 J.J. Kelly (U.Md.) Multipoles extracted starting with Born baseline fit First “model-independent” determination of multipole phases in electroproduction Cole Smith - ANL Theory Workshop - Aug 29 2005

  36. Recoil Polarization: Results Hall A / E91-011 J.J. Kelly (U.Md.) NΔ quadrupole ratios Roper Form Factors Cole Smith - ANL Theory Workshop - Aug 29 2005

  37. Observables used in global fit UIM DR Cole Smith - ANL Theory Workshop - Aug 29 2005

  38. Global Fit - Sensitivity to P11(1440) 0.5 υb1/2 shift in S1/2 0.5 υb1/2 shift in A1/2 σLT/ sensitive to imaginary part of P11(1440) through interference with real Born background. Forward peaking shows importance of pion pole. Cole Smith - ANL Theory Workshop - Aug 29 2005

  39. Li Cano RQM-Capstick RQM-Simula Global Fit to CLAS Data P11(1440) Photocoupling Amplitudes Strong longitudinal strength. Breathing mode or pion cloud? A1/2 zero crossing ~ Q2=0.5 GeV2 Hybrid (q3G) model excluded Cole Smith - ANL Theory Workshop - Aug 29 2005

  40. Exclusive π+ Electroproduction at High Q2 Hall B / E99-107 K. Park (USC, Kyungpook) σLT / vs. W at Q2=2.05 See I. Aznauryan’s talk for preliminary fit results Cole Smith - ANL Theory Workshop - Aug 29 2005

  41. Asymptotic behavior of p→Δ helicity amplitudes pQCD scaling: No pQCD scaling observed up to Q2=4 GeV2 Yang and Kamalov, Mod.Phys.Lett. A18(2003) 248 Helicity conserving A1/2 scales as expected, but strongly supressed relative to A3/2 DMT model fits to JLAB π0 electroproduction data Cole Smith - ANL Theory Workshop - Aug 29 2005

  42. Exclusive π0 Electroproduction at High Q2 Hall B / E99-107 M. Ungaro (RPI,UConn) See talk by I. Aznauryan for preliminary fit results Cole Smith - ANL Theory Workshop - Aug 29 2005

  43. Exclusive Meson Electroproduction at High Q2 Hall C / E01-002 A.N. Villano (RPI) , M. Dalton (U. Witwatersrand) Goal: Extend measurements of P33(1232) and S11(1535) transition form factors to Q2=7.5 GeV2 How reliable are reaction models at these Q2 (e.g. - π+ form factor)? Preliminary Background contributions may dominate Δ response. Cos θ* Cole Smith - ANL Theory Workshop - Aug 29 2005

  44. CPhysDB: CLAS Physics Database clasweb.jlab.org/physicsdb Developed by Moscow State University V. Mokeev, V. Sapunenko, M. Stepanov Cole Smith - ANL Theory Workshop - Aug 29 2005

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