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Recent Results from CLAS

Recent Results from CLAS. K. Hicks (Ohio University) Hadron 2013 (Nara, Japan) Thursday, November 7. General Comments. There are is so much data from CLAS that it is not possible to cover it all in 25 minutes. I must make some choices: New resonances from KY photoproduction

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Recent Results from CLAS

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  1. Recent Results from CLAS K. Hicks (Ohio University) Hadron 2013 (Nara, Japan) Thursday, November 7

  2. General Comments • There are is so much data from CLAS that it is not possible to cover it all in 25 minutes. • I must make some choices: • New resonances from KY photoproduction • Meson photoproduction: p, h, w, pp • New cross sections: K*Y and KY* photoproduction • Dark photon search from p0Dalitz decays • Apologies to Stan: I have only 50 slides.

  3. The CLAS Detector

  4. Polarization observables in pseudoscalar meson production 4Complex amplitudes: 16real polarization observables. Complete measurement from 8carefully chosen observables. πN has large cross section but in KY recoil is self-analysing ☻ πN KY recoil targγ γ targrecoil ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ ☻☻☻ I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975). Complete, and over-determined circ polarized photons longitudinally polarized target linearly polarized photons transversely polarized target

  5. Establishing the nucleon spectrum From elastic πN scattering to γN reactions. Essential new data on hyperon production γp→K+Λ→K+pπ- A.V. Anisovich et al (BnGa), EPJ A48, 15 (2012) M. Mc Cracken et al.(CLAS), Phys.RevC81,025201,2010

  6. Strangeness production γp→K+Λ→K+pπ- Λ Recoil polarization γ->Λ Polarization transfer M. Mc Cracken et al. (CLAS), Phys. Rev. C 81, 025201, 2010 D. Bradford et al. (CLAS), Phys.Rev. C75, 035205, 2007

  7. N/Δ spectrum in RPP 2012 Photoproduction data from JLAB, ELSA, GRAAL, LEPS V. Crede & W. Roberts, Rept. Prog. Phys. 76 (2013)

  8. N* spectrum in LQCD Do new candidate states fit in projected Lattice QCD spectrum? N(2060)5/2- N(2120)3/2- N(1875)3/2- N(1895)1/2- N(1860)5/2+ N(1900)3/2+ N(1880)1/2+ N(1675)5/2- N(1700)3/2- N(1520)3/2- N(1650)1/2- N(1535)1/2- mπ=396MeV Ignoring the mass scale, new candidate states fit in current LQCD projections

  9. Σ for γp →nπ+ DU12 CM12 MAID BbGa 60 60 0 0 120 120 M. Dugger et al.

  10. Σ for γ p → p π0 DU12 CM12 MAID BbGa M. Dugger et al.

  11. Changes in couplings

  12. T for γ p → n π+ (new) (new) (new)

  13. F for γ p → n π+ (new) (new) • Agreement with predictions get much worse at higher energies • SAID13 are predictions based on preliminary fits to CLAS pion Σ measurements (new)

  14. E for γ p → p π0 (new) • Early stage results • Predictions agree better at lower energies Cos(θπc.m.)

  15. Summary of meson photoproduction ✔ -published✔- acquired

  16. N* states in γp➝pω➝pπ+π-π0? W=1.7 – 2.4 GeV, ΔW=10 MeV bins • Very precise cross sections in W, cosθω. From ω decays => SDME ρ000, ρ01-1, ρ010, shown inblue - blue shades. • (ω data not yet included in coupled-channel amplitude analyses, in preparation by several groups.) • M. Williams, et al. (CLAS), Phys. Rev. C80:065209, 2009

  17. N* states in γp➝pω➝pπ+π-π0 • M. Williams, et al. (CLAS) , Phys.Rev. C80 (2009) 065208 • The data are used as input to a single channel event-based, energy independent partial wave analysis (the first ever for baryons). • ωphotoproduction is dominated by the well known F15(1680) and G17(2190), and the “missing” ** F15(2000). F15(2000)/G17(2190)

  18. Differential cross sectionsγppφ φ K0sK0l φ K+K- First precision measurement in 80 energy bins at W=10 MeV, and nearly full angle range (CLAS). • SDME from φdecay angular distributions.

  19. The L=1 QM assignments From Klempt and Richard, Rev. Mod. Phys. 82 (2010). Note: x = “missing” state (not seen in experiments)

  20. The L=2 QM assignments From Klempt and Richard, Rev. Mod. Phys. 82 (2010). Some of these are 2-star PDG Unknown! Note: x = “missing” state (not seen in experiments)

  21. The L=3 QM assignments From Klempt and Richard, Rev. Mod. Phys. 82 (2010). Note: x = “missing” state (not seen in experiments). Half of these are 2-star = evidence is only “fair”.

  22. K*Y Photoproduction • The following work is done primarily by the Ohio group at CLAS: • Wei Tang and KH.

  23. Moorhouse Selection Rule • The transition amplitudes for gp to all [70,48] are zero. • For gn, these transitions are allowed, e.g. the N5/2-(1675). N1/2+ N3/2- N5/2- Data from N. Bianchi et al., PRC 54 (1996).

  24. Lambda Selection Rule Reference: Q. Zhao and F.E. Close, Phys. Rev. D 74 (2006) 094014. • The [70,48] resonances decouple from the KL and K*L channels. • This assumes the spectator approximation, where the [ud] quarks are coupled to s=0 in the L. • In the [70,48] N*’s, the [ud] are coupled to s=1. • The selection rule applies to both p and n targets. • This doesn’t apply to KS and K*S final states. • A study of KL, K*L, KS and K*S final states will test this spectator (diquark) hypothesis.

  25. Theoretical models for the K*photoproduction 1. Isobar models: To describe the physics process completely, all possible Feynman diagrams that could lead to the final state are required to be taken into account in the calculation. evaluate tree-level Feynman diagrams that include resonant and non-resonant exchanges of baryons and mesons. Advantage: Identify the dominant contributions to the final states Disadvantage: Too many parameters, tuning and fixing of those parameters sometimes are tricky. Mandelstam variables: From: Wei Tang, Ph.D. Dissertation Defense, August, 2012

  26. 2. Regge-izedmodels: Rather than focus on selecting of all possible s, t and u channel reaction processes, the reggeized models emphasis the t-channel. The standard propagators in the Lagrangian are replaced by Regge propagators. Originally applied to high energy hadron reactions Might not be able to produce the results in detail, but at least it can tell us about how t-channel mesons exchanges affects the reaction Sho Ozaki, http://ific.uv.es/nucth/chirall10/talks/ozaki.pdf From: Wei Tang, Ph.D. Dissertation Defense, August, 2012

  27. K*+L Differential Cross Sections Curves are simple fits using 4th order Legendra polynomials.

  28. K*+S0 Differential Cross Sections

  29. Total Cross Sections Both data peak at about W=2.25 GeV. There are 3 well-known N*’s there: the N7/2-(2190), N9/2-(2250) and N9/2+(2250). Note: the N9/2- is part of the L-forbidden [70,48] multiplet.

  30. Comparison with theory Cyan: Oh and Kim (O-K) Isobar Model Blue: Kim, Nam, Oh, Kim (KNOK) Regge Model Dotted curves include additional s-channel N* with M<2.2 GeV and L<3. Clearly, the currently available theoretical models cannot reproduce the data. This suggests that higher-mass and higher-L resonances are needed.

  31. Ratio of K*0S/K*+L and k-meson Solid: mostly t-channel k-meson Dotted: very little k-meson There is scarce evidence for the strange scalar called the kappa (k), which is the octet partner of the a0(980) and f0(980) mesons. The CLAS data support an earlier claim by LEPS that also measured K*0S+photoproduction.

  32. KY* Photoproduction • The following work is done primarily by the Carnegie-Mellon University group at CLAS: • Kei Moriya and Reinhard Schumacher.

  33. Detect K+pp-(p0) orK+p+p-(n) L(1520) L(1405) S(1385) S(1385) has small branching ratio into the L(1405) state we want

  34. Events in K+S+p- Final State Note K* overlap: must be subtracted in some W bins

  35. Differential S0(1385) Cross Section • g + p K+ + S0 (1385) • Experiment: see t-channel-like forward peaking & u-channel backward rise • Agreement with LEPS • Theory by Oh et al.1: contact term dominant; included four high-mass N* and D resonances • Prediction was fitted to preliminary CLAS total cross section 1. Y. Oh, C. M. Ko, K. Nakayama, Phys. Rev. C 77, 045204 (2008)

  36. Differential L(1520) Cross Section 2.45<W<2.55 GeV 2.05<W<2.15 GeV Agreement between S+p- decay modes: tests acceptance consistency Agreement among S+p-,S0p0, S-p+ decay modes: tests acceptance consistency • g + p K+ + L(1520) • Good agreement among Spdecay modes • Corrected with 42% branching fraction to Sp

  37. Differential L(1520) Cross Section • g + p K+ + L(1520) • Experiment: see t-channel-like forward peaking & u-channel backward rise • Agreement with LEPS1,2 • Theories: • Nam & Kao3: contact term dominant; no K* or u-channel exchanges • He & Chen4: K*and N(2080)D13 JP=3/2-added 1. H. Kohri et al. (LEPS) Phys Rev Lett104, 172001 (2010) 2. N. Muramatsu et al. (LEPS) Phys Rev 103, 012001 (2009) 3. S.I. Nam & C.W. Kao, Phys. Rev. C 81, 055206 (2010) 4. J. He & X.R. Chen, Phys. Rev. C 86, 035204 (2012)

  38. Differential L(1405) Cross Section • g + p K+ + L(1405) • Experiment: each S p channel yields a different cross section (! Not expected1 !) • Indication of isospin interference in L(1405) mass region • Threshold < mSp< 1.50 GeV • 1. K. Moriya, R. A. Schumacher et al., Phys. Rev. C 87, 035206 (2013)

  39. Differential L(1405) Cross Section • g + p K+ + L(1405) • Experiment: first-ever measurements • See t-channel-like forward peaking & u-channel backward rise at high W • Same as other hyperons • See very different behavior at low W • Charge channels differ • Channels merge together at high W

  40. Differential L(1405) Cross Section • g + p K+ + L(1405) • Sum three Sp decay modes  “total” differ-ential cross section • Mixed agreement with LEPS data1 • Theories: • Nam et al.2: s-channel Born term dominant ; K* exchange for 3 values of g K*NL* • Williams, Ji, Cotanch3: crossing and duality contraints; no N*, estimated g KNL* Williams Nam 1. M. Niiyama et al. (LEPS) Phys Rev C78, 035202 (2008) 2. S.I. Nam et al., J. Kor. Phys. Soc. 59, 2676 (2011) 3. R. Williams et al., Phys. Rev. C43, 452 (1991)

  41. Direct Y* Cross Section Comparison L(1115) S0(1193) S0(1385) L(1405) L(1520) • g + p K+ + Y* • SumL(1405) channels • Apply branching fractions for L(1520), S(1385) • All three hyperons have • Strong forward peaking • Similar t-slopes • Back-angle rises • Similar-size cross sections

  42. Direct Y* Cross Section Comparison • g + p K+ + Y* • (showing spline fits) • All three have • Near- threshold peaking • Similar size cross sections • Sp-fraction (42%) of L(1520) has same cross section as L(1405)at high W! • L*’s have a hint of second peak/plateau +0.6 < cosQKc.m. < +0.9 L(1115) S0(1193) S0(1385) L(1405) L(1520) -0.2 < cosQKc.m. < +0.1 -0.7 < cosQKc.m. < -0.5

  43. Total Cross Section Comparison L(1115) S0(1193) S0(1385) L(1405) L(1520) • g + p K+ + Y(*) • All three Y*s have similar total cross sections • Ground states L and S0 are comparable to Y* in size1 1. R. Bradford et al. (CLAS) Phys. Rev. C 73, 035202 (2006)

  44. Dark Photon Search • The following work is done primarily by the ODU group at CLAS: • M. Kunkel and M. Amaryan

  45. Summary • Precise data from CLAS has contributed to identification of new baryon resonances. • Complete set of spin observables for PS mesons. • New data from K*Y and KY* will likely help to identify new high-mass baryon resonances. • PWA for these data are in progress. • Search for dark photons possible at CLAS using the high statistics data set. • Better limits on parameter space.

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