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

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

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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

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Highlights on hadron physics at CLAS

  • K. Hicks (Ohio U.)

Hadron 2011 Conference June 16, 2011

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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 KL – New data: 2p, K*Y, KY*, etc.

  • Future upgrade to CLAS12

– Probe transition from MBC to quark core.

16 June 2011 2 Hadron 2011 Meeting

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3

quark mass (GeV)

Quark mass extrapolated to the chiral limit, where q is the momentum variable of the tree-level quark propagator (curve=DSE, data=LQCD).

LQCD, DSE and …

meson dressed quark confinement current quark

p,r,w…

resolution low high

Hadron Structure with Electromagnetic Probes

N,N*,D,D*… 3q-core+MB-cloud 3q-core pQCD

16 June 2011 Hadron 2011 Meeting

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NΔ Transition Form Factor (GM) from EBAC analysis

In the relativistic QM framework, the bare-core contribution is well described by the three-quark component of the wavefunction.

  • One third of G*

M at low Q2 is due

to contributions from meson–baryon (MB) dressing: bare quark core

Q2=5GeV2

CLAS Hall A  Hall C MAMI Bates

Meson- Baryon Cloud Effect

The area of Q2<7.0 GeV2 is far from pQCD domain B.Julia-Diaz et al., PRC 69, 035212 (2004)

16 June 2011 4 Hadron 2011 Meeting

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 Partial wave (LSJ) amplitude of a  b reaction:  Reaction channels:  Transition potentials:

coupled-channels effect

Dynamical coupled-channels model of EBAC

Meson-exchange potentials (Derived from Lagrangians) bare N* states

For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)

16 June 2011 5 Hadron 2011 Meeting

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 Partial wave (LSJ) amplitude of a  b reaction:  Reaction channels:  Transition potentials:

coupled-channels effect

Dynamical coupled-channels model of EBAC

exchange potentials

  • f ground state

mesons and baryons bare N* states

For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007) core meson cloud meson baryon

Physical N*s will be a “mixture” of the two pictures:

16 June 2011 6 Hadron 2011 Meeting

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Jefferson Lab Today

Large acceptance spectrometer electron/photon beams Hall B

B A C

16 June 2011 7 Hadron 2011 Meeting

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Radiative Decay of Strange Baryons

16 June 2011 8 Hadron 2011 Meeting

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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

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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

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Group structure of U-spin:

16 June 2011 Hadron 2011 Meeting 11

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How is this useful?

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CLAS result

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~10% uncert.

PhD thesis, Dustin Keller

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Predictions from other models

16 June 2011 Hadron 2011 Meeting 14

Experiment: 660 +/- 60 479 +/- 73

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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+  pg and D0  ng are equal. – U-spin predicts a ratio:

16 June 2011 15 Hadron 2011 Meeting

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New CLAS result

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Preliminary!

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The MBC in electroproduction

16 June 2011 17 Hadron 2011 Meeting

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N* electrocouplings from analyses of exclusive channels

γv

N N’ N*,△

A3/2, A1/2, S1/2 GM, GE, GC

p, h, pp,..

N

p, h, pp,..

N’ + *

  • 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 Np and Npp electroproduction

channels show that model uncertainties are under control.

Resonant amplitudes Non-resonant amplitudes

See the afternoon talk today by Victor Mokeev.

16 June 2011 18 Hadron 2011 Meeting

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Npp CLAS (New!)

preliminary.

Np CLAS

Good agreement between the Np and Npp channels. N* electrocouplings are measurable and model independent.

  • I. Aznauryan,V. Burkert, et

al., PRC 80,055203 (2009).

A1/2 S1/2 A3/2

F15(1685)

A3/2

P11(1440) P11(1440) D13(1520) Np world

  • V. Burkert, et al., PRC

67,035204 (2003).

Np Q2=0, PDG. Np Q2=0, CLAS

  • M. Dugger, et al., PRC

79,065206 (2009).

gvNN* electrocouplings from Np/Npp production

16 June 2011 19 Hadron 2011 Meeting

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High lying resonance electrocouplings from p+p-p

Δ(1700)D33

A1/2 A3/2 S1/2 Electrocouplings of S31(1620), S11(1650), F35(1685), D33(1700) ,and P13(1720) states were obtained for the first time from p+p-p electroproduction data .

Npp CLAS

preliminary.

Np world

V.D.Burkert, et al., PRC 67, 035204 (2003).

Np Q2=0, PDG. Np Q2=0, CLAS

M.Dugger, et al., PRC 79,065206 (2009).

16 June 2011 20 Hadron 2011 Meeting

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Mystery of P11(1440) structure is solved

Quark models:

  • I. Aznauryan LC
  • S. Capstick LC

Relativistic covariant approach by Ramalho & Gross

The electrocouplings are consistent with P11(1440) structure as combination: a) quark core as a first radial excitation of the nucleon, and b) meson-baryon dressing.

EBAC-DCC MB dressing (absolute values).

A1/2 S1/2

MBC effects could explain the data at low Q2.

16 June 2011 21 Hadron 2011 Meeting

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Coupled-channels effect in various reactions

Full c.c. effect of ppN(pD,rN,sN) & hN off Full Full c.c effect off c.c. effect of ppN(pD,rN,sN) & hN off

Pion photoproductions Pion electroproductions Double pion productions

EBAC

16 June 2011 22 Hadron 2011 Meeting

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Lineshape of the L(1405)

16 June 2011 23 Hadron 2011 Meeting

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  • K. Moriya & R. Schumacher

(CMU/IU) (CMU)

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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

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Spectroscopy with KY, K*Y and KY*

16 June 2011 28 Hadron 2011 Meeting

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Quark Model Classification of N*

D(1232) D13(1520) S11(1535) Roper P11(1440) + q³g + q³qq + N-Meson + … New P11, P13, or D13 states?

16 June 2011 Hadron 2011 Meeting

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Amplitude Uncertainty in gp K+L

CLAS (g1c, g11a) and GRAAL s, Cx’, Cz’, s , P and S, T, P, Ox’, Oz’ Real parts of the PWA multipoles

BoGa (dot-dashed), MAID (dashed), SAID (dotted), JSLT (solid)

  • A. Sandorfi et al., J. Phys. G 38 (2011) 053001

16 June 2011 Hadron 2011 Meeting

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  • 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

without recoil polarization

weak decay has large analyzing power

γp→K+Λ

FROST/HD gN pN, hN, KL, KS, Npp

16 June 2011 Hadron 2011 Meeting

Discussed Monday, talk by V. Cede

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K*+Y Photoproduction

Motivation:

  • 1. Search for higher-mass N* resonances
  • 2. Compare with KY and K*0Y
  • a. K*Y coupling sensitive to K0(800).
  • b. K0(800) is part of the scalar nonet.
  • c. K0(800) has not been directly observed.

g

p N* Y K*

Oh and Kim, Phys Rev C 74, 015208(2006).

16 June 2011 32 Hadron 2011 Meeting

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Differential cross sections of K*+Λ:

Preliminary result

2.1 ---2.7 GeV 1.5 --- 2.1 GeV

16 June 2011 33 Hadron 2011 Meeting

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Differential cross sections of K*+ Σ0:

Preliminary result

1.7 --- 2.3 GeV 2.3 --- 2.9 GeV

16 June 2011 34 Hadron 2011 Meeting

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L +  +

+ *

K p g

Total Cross Sections

*

S +  +

+

K p g

16 June 2011 35 Hadron 2011 Meeting

PhD thesis of Wei Tang

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  • P. Mattione, Rice/CMU
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Meson Spectroscopy

16 June 2011 37 Hadron 2011 Meeting

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See Thursday afternoon talks by D. Weygand, C. Bookwalter

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New: Scalar Mesons from gp KsKsp

16 June 2011 Hadron 2011 Meeting 39

4-p Invariant mass (GeV) CLAS g11 Eg

max=3.8

CLAS g12 Eg

max=5.7

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The future: CLAS12

16 June 2011 40 Hadron 2011 Meeting

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41

CLAS12

  • Luminosity > 1035 cm-2s-1
  • Hermeticity
  • Polarization
  • Baryon Spectroscopy
  • Elastic Form Factors
  • N to N* Form Factors
  • GPDs and TMDs
  • DIS and SIDIS
  • Nucleon Spin Structure
  • Color Transpareny
  • …

Central Detector Forward Detector 1m

CLAS12

16 June 2011 Hadron 2011 Meeting

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  • M. Battaglieri

Forward Photon Tagger for Spectroscopy

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A new N* regime at Q2>3.5 GeV2?

Data appear to reach a plateau at Q2>3.5 GeV2, but conclusive tests require higher Q2

P11 D13 S11

Transition to photon interactions with dressed quarks?

16 June 2011 Hadron 2011 Meeting

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Resonance Transitions at 12 GeV

CLAS12 projected

Experiment E12-09-003 will extend access to transition FF for many prominent states in the range to Q2=12GeV2.

quark mass (GeV)

Electromagnetic form factors are sensitive to the effective quark mass.

At 12 GeV we probe the transition from “dressed quarks” to elementary quarks.

accessible at 6 GeV accessible at 12 GeV 16 June 2011 44 Hadron 2011 Meeting

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Summary

  • The Meson-Baryon Cloud has significant

effects on photon coupling observables

– We cannot ignore coupled-channel effects!

  • There are precise new data on KY, K*Y, KY*

– This will help the search for missing resonances – K* data will determine the role of the K0(800).

  • PWA for mesons: exotics & scalar mixing
  • Future: CLAS12: transition to current quarks.

16 June 2011 Hadron 2011 Meeting 45

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Backup Slides

16 June 2011 Hadron 2011 Meeting 46

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t-dependence of f(1500)

16 June 2011 Hadron 2011 Meeting 47