Highlights on hadron physics at CLAS K. Hicks (Ohio U.) Hadron - PowerPoint PPT Presentation

Highlights on hadron physics at CLAS K. Hicks (Ohio U.) Hadron 2011 Conference June 16, 2011

Outline • Meson-Baryon Cloud (MBC) Effects – New results on baryon photocouplings – Need for coupled-channels analysis • Spectroscopy of baryons and mesons – New and future analysis of K L – New data: 2 p , K*Y, KY*, etc. • Future upgrade to CLAS12 – Probe transition from MBC to quark core. 16 June 2011 Hadron 2011 Meeting 2

Hadron Structure with Electromagnetic Probes Quark mass extrapolated to the chiral limit, where q p,r,w … resolution is the momentum variable of the tree-level quark low propagator (curve=DSE, data=LQCD). N,N * , D,D * … meson dressed quark LQCD, DSE and … 3q-core+MB-cloud quark mass (GeV) confinement 3q-core current quark high pQCD 16 June 2011 Hadron 2011 Meeting 3

N Δ Transition Form Factor (G M ) from EBAC analysis The area of Q 2 <7.0 GeV 2 is far from pQCD domain  One third of G * M at low Q 2 is due to contributions from meson – baryon CLAS (MB) dressing: Hall A  Hall C Meson- MAMI Baryon Bates Cloud Effect bare quark core In the relativistic QM framework, the bare-core contribution is well Q 2 =5GeV 2 described by the three-quark component of the wavefunction. B.Julia-Diaz et al ., PRC 69, 035212 (2004) 16 June 2011 Hadron 2011 Meeting 4

Dynamical coupled-channels model of EBAC For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)  Partial wave (LSJ) amplitude of a  b reaction: coupled-channels effect  Reaction channels:  Transition potentials: Meson-exchange potentials (Derived from Lagrangians) bare N* states 16 June 2011 Hadron 2011 Meeting 5

Dynamical coupled-channels model of EBAC For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)  Partial wave (LSJ) amplitude of a  b reaction: Physical N*s will be a “mixture” of the two pictures: baryon meson cloud coupled-channels effect  Reaction channels: core meson  Transition potentials: exchange potentials of ground state bare N* states mesons and baryons 16 June 2011 Hadron 2011 Meeting 6

Jefferson Lab Today Hall B Large acceptance spectrometer electron/photon beams A B C 16 June 2011 Hadron 2011 Meeting 7

Radiative Decay of Strange Baryons 16 June 2011 Hadron 2011 Meeting 8

General Motivation • Electromagnetic interactions are the cleanest way to access information on wavefunctions. – For strange baryons, the EM coupling can only be studied by measuring the decay. • SU(6) wavefunctions provide a zeroth-order prediction for M1 transitions. – SU(6) symmetry provides a link between N* and Y* radiative decays: constrain SU(6) symmetries. 16 June 2011 Hadron 2011 Meeting 9

U-spin: connects D and S * decays • SU(3) has three equal symmetries: – I-spin: exchange of u and d quarks – U-spin: exchange of d and s quarks – V-spin: exchange of u and s quarks • With respect to known symmetries: – I-spin conserves chiral symmetry (mass) – U-spin conserves EM symmetry (charge) – V-spin conserves neither chiral nor EM symmetry 16 June 2011 Hadron 2011 Meeting 10

Group structure of U-spin: 16 June 2011 Hadron 2011 Meeting 11

How is this useful? 16 June 2011 Hadron 2011 Meeting 12

CLAS result ~10% uncert. PhD thesis, Dustin Keller 16 June 2011 Hadron 2011 Meeting 13

Predictions from other models Experiment: 660 +/- 60 479 +/- 73 16 June 2011 Hadron 2011 Meeting 14

Interpretation • Meson-Baryon Cloud effects are substantial for the Y* resonances also. – U-spin relation works better than QM, etc. • We can now make a prediction for S * + decay. – The Wigner-Eckart theorem requires that the branching ratios D +  p g and D 0  n g are equal. – U-spin predicts a ratio: 16 June 2011 Hadron 2011 Meeting 15

New CLAS result Preliminary! 16 June 2011 Hadron 2011 Meeting 16

The MBC in electroproduction 16 June 2011 Hadron 2011 Meeting 17

N* electrocouplings from analyses of exclusive channels Resonant amplitudes Non-resonant amplitudes p, h, pp ,.. p, h, pp,.. γ v * N*, △ + N ’ N N ’ A 3/2 , A 1/2 , S 1/2 N G M , G E , G C • Separation of resonant/non-resonant contributions • N* ‘s can couple to various exclusive channels with entirely different non- resonant amplitudes, while their electrocouplings should remain the same. • Consistent results from the analyses of N p and N pp electroproduction channels show that model uncertainties are under control. See the afternoon talk today by Victor Mokeev. 16 June 2011 Hadron 2011 Meeting 18

g v NN* electrocouplings from N p /N pp production N pp CLAS (New!) preliminary. S 1/2 A 1/2 N p CLAS I. Aznauryan,V. Burkert, et al., PRC 80,055203 (2009). P 11 (1440) P 11 (1440) N p world V. Burkert, et al., PRC A 3/2 67,035204 (2003). A 3/2 D 13 (1520) N p Q 2 =0, PDG. N p Q 2 =0, CLAS F 15 (1685) M. Dugger, et al., PRC 79,065206 (2009). Good agreement between the N p and N pp channels. N* electrocouplings are measurable and model independent. 16 June 2011 Hadron 2011 Meeting 19

High lying resonance electrocouplings from p + p - p Δ (1700)D 33 N pp CLAS A 3/2 S 1/2 A 1/2 preliminary. N p world V.D.Burkert, et al., PRC 67, 035204 (2003). N p Q 2 =0, PDG. N p Q 2 =0, CLAS Electrocouplings of S 31 (1620), S 11 (1650), F 35 (1685), M.Dugger, et al., D 33 (1700) ,and P 13 (1720) states were obtained for PRC 79,065206 the first time from p + p - p electroproduction data . (2009). 16 June 2011 Hadron 2011 Meeting 20

Mystery of P 11 (1440) structure is solved Quark models: I. Aznauryan LC S 1/2 S. Capstick LC Relativistic covariant approach by Ramalho & Gross A 1/2 EBAC-DCC MB dressing (absolute values). The electrocouplings are consistent with P 11 (1440) structure as combination: a) quark core as a first radial excitation of the nucleon, and b) meson-baryon dressing . MBC effects could explain the data at low Q 2 . 16 June 2011 Hadron 2011 Meeting 21

Coupled-channels effect in various reactions Pion photoproductions Full c.c. effect of pp N( pD , r N, s N) & Pion electroproductions h N off Full c.c. effect of pp N( pD , r N, s N) & h N off Double pion productions Full c.c effect off EBAC 16 June 2011 Hadron 2011 Meeting 22

Lineshape of the L (1405) 16 June 2011 Hadron 2011 Meeting 23

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K. Moriya & R. Schumacher (CMU/IU) (CMU) 16 June 2011 Hadron 2011 Meeting 26

Interpretation • For a baryon resonance with a single pole, isospin symmetry  S + p - = S - p + . • The data favor a dynamically-generated resonance (two-pole solution Sp and NK). – Evidence of MB coupled-channels effects? 16 June 2011 Hadron 2011 Meeting 27

Spectroscopy with KY, K*Y and KY* 16 June 2011 Hadron 2011 Meeting 28

Quark Model Classification of N* + q³g D 13 (1520) S 11 (1535) + q³qq + N-Meson New P 11 , P 13 , or D 13 states? + … D (1232) Roper P 11 (1440) 16 June 2011 Hadron 2011 Meeting 29

Amplitude Uncertainty in g p K + L A. Sandorfi et al., J. Phys. G 38 (2011) 053001 CLAS (g1c, g11a) and GRAAL Real parts of the PWA multipoles s , C x ’ , C z ’ , s , P and S , T, P, O x’ , O z’ BoGa (dot-dashed), MAID (dashed), SAID (dotted), JSLT (solid) 16 June 2011 Hadron 2011 Meeting 30

FROST/HD g N p N, h N, K L , K S , N pp Discussed Monday, talk by V. Cede γp→K + Λ  Process is described by 4 complex, parity conserving amplitudes  8 well-chosen measurements are needed to determine amplitude  For hyperon finals state 16 observables will be measured in CLAS ➠ large redundancy in determining the photo- production amplitudes ➠ allows many cross checks  8 observables measured in reactions weak decay has large analyzing power without recoil polarization 16 June 2011 Hadron 2011 Meeting 31

K* + Y Photoproduction g Y Motivation: N* 1. Search for higher-mass N* resonances p K* 2. Compare with KY and K* 0 Y a. K * Y coupling sensitive to K 0 (800). b. K 0 (800) is part of the scalar nonet. c. K 0 (800) has not been directly observed. Oh and Kim, Phys Rev C 74, 015208(2006). 16 June 2011 Hadron 2011 Meeting 32

Differential cross sections of K* + Λ : 1.5 --- 2.1 GeV 2.1 ---2.7 GeV Preliminary result 16 June 2011 Hadron 2011 Meeting 33

Differential cross sections of K* + Σ 0 : 2.3 --- 2.9 GeV 1.7 --- 2.3 GeV Preliminary result 16 June 2011 Hadron 2011 Meeting 34

Total Cross Sections g +  + + S g +  + + L * 0 * p K p K PhD thesis of Wei Tang 16 June 2011 Hadron 2011 Meeting 35

P. Mattione, Rice/CMU 16 June 2011 Hadron 2011 Meeting 36

Meson Spectroscopy 16 June 2011 Hadron 2011 Meeting 37

See Thursday afternoon talks by D. Weygand, C. Bookwalter 16 June 2011 Hadron 2011 Meeting 38

New: Scalar Mesons from g p  K s K s p CLAS g11 CLAS g12 max =3.8 E g max =5.7 E g 4- p Invariant mass (GeV) 16 June 2011 Hadron 2011 Meeting 39

The future: CLAS12 16 June 2011 Hadron 2011 Meeting 40