Kijun Park Colloquium γ*γ* Feb. 25, 2011

College of William and Mary 02/25/2011 K. Park Universe

College of William and Mary 02/25/2011 K. Park Earth

College of William and Mary 02/25/2011 K. Park Including Human Life

College of William and Mary 02/25/2011 K. Park Over 98% of the mass of visible mattersnucleonsnucleons

6 College of William and Mary 02/25/2011 K. Park

strongly interacting composite particles composite fermions contain three valence quarks or antiquarks. protons, neutrons , ,…  +,  --, ??? composite bosons Contain one valence quark and one antiquark. J/  … pions, kaons, , D, B, … consist of protons and neutrons. consists of a small, heavy nucleus surrounded by a relatively large, light cloud of electrons the smallest particles into which a non-elemental substance

College of William and Mary 02/25/2011 K. Park

Where/what/how can we measure ? College of William and Mary 02/25/2011 K. Park Experiments

A A B B C C CEBAF Large Acceptance Spectrometers College of William and Mary 02/25/2011 K. Park

A A B B C C CEBAF Large Acceptance Spectrometers College of William and Mary 02/25/2011 K. Park E max 6 GeV I max 200  A Duty Factor 100%  E /E Beam P ~ 85% E g (tagged) ~ GeV

The CLAS Collaboration Old Dominion University, Norfolk, VA Rensselaer Polytechnic Institute, Troy, NY Rice University, Houston, TX University of Richmond, Richmond, VA University of Rome Tor Vergata, Italy University of South Carolina, Columbia, SC Thomas Jefferson National Accelerator Facility, Newport News, VA Union College, Schenectady, NY Virginia Polytechnic Institute, Blacksburg, VA University of Virginia, Charlottesville, VA College of William and Mary, Williamsburg, VA Yerevan Institute of Physics, Yerevan, Armenia Brazil, Germany, Morocco and Ukraine,, have individuals or groups involved with CLAS, but with no formal collaboration at this stage. Arizona State University, Tempe, AZ University Bari, Bari, Italy University of California, Los Angeles, CA California State University, Dominguez Hills, CA Carnegie Mellon University, Pittsburgh, PA Catholic University of America CEA-Saclay, Gif-sur-Yvette, France Christopher Newport University, Newport News, VA University of Connecticut, Storrs, CT Edinburgh University, Edinburgh, UK University Ferrara, Ferrara, Italy Florida International University, Miami, FL Florida State University, Tallahassee, FL George Washington University, Washington, DC University of Glasgow, Glasgow, UK University of Grenoble, Grenoble, France Idaho State University, Pocatello, Idaho INFN, Laboratori Nazionali di Frascati, Frascati, Italy INFN, Sezione di Genova, Genova, Italy Institut de Physique Nucléaire, Orsay, France ITEP, Moscow, Russia James Madison University, Harrisonburg, VA Kyungpook University, Daegu, South Korea University of Massachusetts, Amherst, MA Moscow State University, Moscow, Russia University of New Hampshire, Durham, NH Norfolk State University, Norfolk, VA Ohio University, Athens, OH College of William and Mary 02/25/2011 K. Park

 Introduction  Transition Form resonances  Scaling DIS  Exclusive Hard Process in DIS  Summary  Introduction  Transition Form resonances  Scaling DIS  Exclusive Hard Process in DIS  Summary College of William and Mary 02/25/2011 K. Park

Why are you using e.m. probe for hadron structure study ? Why are you using e.m. probe for hadron structure study ? College of William and Mary 02/25/2011 K. Park Electromagnetic Probe

“reveal physics hidden from us in mesons” Gell-Mann & Zweig - Quark Model O. Greenberg - The   problem/color 1)Elastic Scattering 2) Deep Inelastic Scattering 3) Resonance Excitation : ground state nucleon : quark-gluon short dist. : internal structure of ground & excited state Foundation of Quark model  Investigation tool for Nucleon where  Nucleons/baryons are complex enough to College of William and Mary 02/25/2011 K. Park

Transition Form Factors How we can describe the electroproduction of an excited state ? How we can describe the electroproduction of an excited state ?

College of William and Mary 02/25/2011 K. Park Probe resolution (GeV) lowhigh N π,  Q 2 =6 GeV 2 B=N,N*,  *

College of William and Mary 02/25/2011 K. Park Probe resolution (GeV) lowhigh N π,  Q 2 =12 GeV 2 Q 2 =6 GeV 2 The study of nucleon resonance transitions provides a testing ground for our understanding of these effective D.o.F B=N,N*,  * Access to the essence of non- perturbative strong interactions generation of > 97% of nucleon mass enhance capability to map out QCD  function in constituent regime

Lowest Baryon Supermultiplets SU(6)xO(3) Symmetry Particle Data Group Lowest Baryon Supermultiplets SU(6)xO(3) Symmetry Particle Data Group College of William and Mary 02/25/2011 K. Park

Lowest Baryon Supermultiplets SU(6)xO(3) Symmetry Particle Data Group Lowest Baryon Supermultiplets SU(6)xO(3) Symmetry Particle Data Group College of William and Mary 02/25/2011 K. Park D 13 (1520) S 11 (1535) D 33 (1700) P 33 (1232) P 11 (1440)

Lowest Baryon Supermultiplets SU(6)xO(3) Symmetry Particle Data Group Lowest Baryon Supermultiplets SU(6)xO(3) Symmetry Particle Data Group Missing States? * There are questions about underlying degrees-of-freedom of some well known state like P11, S11, D13 * Study of transition from ground state allows make more definite statement about the nature College of William and Mary 02/25/2011 K. Park D 13 (1520) S 11 (1535) D 33 (1700) P 33 (1232) P 11 (1440)

“why the world is the way it is”  Nucleons represent the real world, they must be at the center of any discussion on The contribution of the current quark masses into total baryon mass is very small Most of the hadron mass comes from strong fields. The contribution of the current quark masses into total baryon mass is very small Most of the hadron mass comes from strong fields. College of William and Mary 02/25/2011 K. Park

 photocoupling amplitudes → A 1/2, A 3/2 and S 1/2 → A 1/2, A 3/2 and S 1/2  Pion electroproduction multipole amplitude → E l , M l  and S l . l : the orbital angular momentum in Nπ system. ± sign : spin of proton couples to the orbital momentum. p ** N  N* E l , M l ,S l  A 1/2, A 3/2,S 1/2 College of William and Mary 02/25/2011 K. Park

p ** N  N* E l , M l ,S l  A 1/2, A 3/2,S 1/2  Light quark baryon spectrum (mostly pion probes)  Many high mass states couple to possibly photon instead of pion  Diff. photon virtuality can probe how relevant D.o.F change as distance scale  Both photon, nucleon carry spin → probe the spin strucure in QCD College of William and Mary 02/25/2011 K. Park

CEBAF Large Acceptance Spectrometers e-e- π+π+ e-e- College of William and Mary 02/25/2011 K. Park

 Study of Resonance to understand Nucleon Structure  Most Studies for NΔ(1232) and NN*(1535) using pπ 0, pρ channels  States with I=1/2 couple more to the nπ + than pπ 0  Cross Section & Asymmetry gives us information on resonances in excited states  Diagrams contributing into nπ + electroproduction College of William and Mary 02/25/2011 K. Park

Single pion electroproduction Asymmetry Cross Section College of William and Mary 02/25/2011 K. Park

 Spin J=3/2, Isospin I=3/2.  From angular momentum and parity conservation γN  Δ transition can be induced by E2, M1 and C2 multipoles.  SU(6)xO(3) symmetric quark model describes γN  Δ transition as a single quark spin flip. e e / e  M1 P(938) J=1/2 Δ(1232) J=3/2 R EM, R SM College of William and Mary 02/25/2011 K. Park

R EM College of William and Mary 02/25/2011 K. Park R SM

P 11 (1440) Poorly understood in nrCQMs. 1) lower mass, 2) wrong sign of photo-coupling Other models: - Light front kinematics (relativity) - Hybrid baryon with gluonic excitation |q 3 G> - Quark core with large meson cloud |q 3 m> - Nucleon-sigma molecule |Nσ> - Dynamically generated Nπ resonance S 11 (1535) Hard form factor (slow fall off with Q 2 ) Not a quark resonance, but KΣ dynamical system? D 13 (1520) Change of helicity structure with increasing Q 2 from λ=3/2 dominance to λ=1/2 dominance, predicted in nrCQMs, pQCD. Measure Q 2 dependence of Transition F.F. College of William and Mary 02/25/2011 K. Park

  CQM : N=2 radially excited state( Close, Capstick, Simula ).   Hard Quark core and a Vector Meson cloud ( Cano-Gonzalez ).   q 3 G ( Li-Burkert). Close Capstick Simula Cano-Gonzalez Li-Burkert College of William and Mary 02/25/2011 K. Park

  CQM : N=2 radially excited state( Close, Capstick, Simula ).   Hard Quark core and a Vector Meson cloud ( Cano-Gonzalez ).   q 3 G ( Li-Burkert). College of William and Mary 02/25/2011 K. Park ????? ?????

Number of data points >50,000 Ee = 1.515, 1.645, 5.754GeV Observable Q2Q2Q2Q2 # of data points ,5303, ,3081,71633, , Low Q2 : Aznauryan et al., I.PRC 71, , (2005). II.PRC 72, , (2005). high Q2 for Roper : Aznauryan et al., and CLAS collaboration I.arXiv, 0804,0447 (2008). K.Park et al., (CLAS) Phys. Rev. C 77, , (2008). College of William and Mary 02/25/2011 K. Park

Quadrupole RatiosMagnetic Dipole Form Factor  No sign for onset of asymptotic behavior, R EM → +100%, R SM → const.  R EM remains negative and small, R SM increases in magnitude with Q 2.  Meson-baryon contributions needed to describe multipole amplitudes R EM R SM CLAS Hall A Hall C MAMI CLAS Hall A Hall C MAMI QM Pion cloud 0.2 Pascalutsa, Vanderhaeghen Sato, Lee 37 College of William and Mary 02/25/2011 K. Park

 Precise multipole ratios: δR EM, δR SM < %  R EM remains small and negative at -2% to -3.5% from 0 ≤ Q 2 ≤ 6 GeV 2. No trend towards asymptotic behavior. Helicity conservation - R EM →+100 (%).  R SM negative and increase in magnitude. Helicity conservation – R SM → constant  Dynamical models allow description of multipole ratios in large Q 2 range.  R EM < 0 favors oblate shape of Δ and prolate shape of the proton at large distances. NΔNΔ NΔNΔ R EM <0 R EM >0 College of William and Mary 02/25/2011 K. Park R EM R SM

DRDR DR w/o P11 UIMUIM DRDR UIMUIM College of William and Mary 02/25/2011 K. Park

 Non-relativistic CQ Models do not reproduce sign of A 1/2 at Q 2 =0, and show no zero-crossing.  Relativistic CQ Models (LC) give correct sign and show zero-crossing but miss strength at Q 2 =0. → go to higher Q 2 to reduce effects of meson contributions. 1.Weber, PR C41(1990) Capstick..PRD51(1995) Simula…PL B397 (1997)13 4.Riska..PRC69(2004) Aznauryan, PRC76(2007) Cano PL B431(1998)270 College of William and Mary 02/25/2011 K. Park I. G. Aznauryan, V. Burkert, K.Park et al., (CLAS) Phys. Rev. C 78, , (2008). K.Park et al., (CLAS) Phys. Rev. C 77, , (2008).

Analysis with 1)Unitary Isobar Model (UIM) 2)Fixed-t Dispersion Relations (DR) pπ0pπ0 nπ+nπ+ Nπ, pπ + π - nπ+nπ+ DR UIM Include > 35,000 data points in fits. previous data In a nonrelativistic approximation A 1/2 (Q 2 ) and S 1/2 (Q 2 ) behave like the γ*NΔ(1232) amplitudes. Suppression of S 1/2 has its origin in the form of vertex γq→qG. It is practically independent of relativistic effects Z.P. Li, V. Burkert, Zh. Li, PRD46 (1992) 70  G q3q3 College of William and Mary 02/25/2011 K. Park

D 0 L+T D 2 L+T D 0 LT’ pπ 0 nπ + 42 DR UIM Q 2 =0.4 GeV 2 Nπ Nππ Nπ, Nππ LCQM Q3GQ3G  Sign change observed at same Q 2  Magnitudes of A 1/2 and S 1/2 consistent in the two channels.  High Q 2 behavior consistent with dominant radial excitation of nucleon.  Rules out gluonic excitation  Sign change observed at same Q 2  Magnitudes of A 1/2 and S 1/2 consistent in the two channels.  High Q 2 behavior consistent with dominant radial excitation of nucleon.  Rules out gluonic excitation College of William and Mary 02/25/2011 K. Park I. G. Aznauryan, V. Burkert, K.Park et al., (CLAS) Phys. Rev. C 78, , (2008).

P 11 (1440) 43 b x (fm) b y (fm) b x (fm) b y (fm) Lightpositive Light (dark) regions: positive (negative) charge densities L. Tiator and M. Vanderhaeghen, Phys. Lett. B 672, 344 (2009)  proton(P T ) and P 11 are in LF helicity +½ state..  proton and P 11 polarized along x-axis with opposite spin projections.  In a quark picture, the proton → N(1440)P 11 transition is dominated by up quarks in a central region of radius ~0.4 fm, and by down quarks in an outer band up to 0.8 fm. ρ0ρ0 ρTρT Meson-Baryon Dressing absolute meson-baryon cloud amplitudes (EBAC) quark core contributions (constituent quark models) College of William and Mary 02/25/2011 K. Park

 Hard form Factor (slow fall off vs. Q 2 )  Not a quark resonance, but a dynamically generated resonance of coupled channel, e.g, πN, ηp, ΚΣ, ΚΛ  Change of helicity structure with increasing Q 2 from λ=3/2 dominance to λ=1/2 dominance as predicted in CQMs, pQCD S 11 (1535) D 13 (1520) nrCQM Prediction from the 1970’s !! * It will be submitted to Phys. Rev. D soon College of William and Mary 02/25/2011 K. Park

45 CLAS pη CLAS nπ+ HallC pη LC SR LCQM CLAS 2007 CLAS 2002 previous results Analysis of pη assumes S 1/2 =0 Branching ratios β Nπ = β Nη = 0.45  A 1/2 (Q 2 ) from Nπ and p η are consistent  First extraction of S 1/2 (Q 2 ) amplitude. College of William and Mary 02/25/2011 K. Park H. Denizli et al., (CLAS) Phys. Rev. C 76, , (2007). I. G. Aznauryan, V. Burkert, K.Park et al., (CLAS) Phys. Rev. C 80, , (2009).

46  First data set that allows determination of S 1/2 (Q 2 )  Clear evidence of helicity switch from λ =3/2 dominance at Q 2 =0 to λ =1/2 dominance at high Q 2 => This is a stringent prediction of the CQM. Nπ, pπ + π - nπ+nπ+ pπ0pπ0 PDG pπ0pπ0 CQMs and pQCD A hel → +1 at Q 2 → nrCQM College of William and Mary 02/25/2011 K. Park I. G. Aznauryan, V. Burkert, K.Park et al., (CLAS) Phys. Rev. C 80, , (2009).

47  First data set that allows determination of S 1/2 (Q 2 )  Clear evidence of helicity switch from λ =3/2 dominance at Q 2 =0 to λ =1/2 dominance at high Q 2 => This is a stringent prediction of the CQM. Nπ, pπ + π - nπ+nπ+ pπ0pπ0 PDG pπ0pπ0 CQMs and pQCD A hel → +1 at Q 2 → nrCQM College of William and Mary 02/25/2011 K. Park I. G. Aznauryan, V. Burkert, K.Park et al., (CLAS) Phys. Rev. C 80, , (2009).

 Proton and N(1520)D 13 are in LF helicity +½ state, transition is dominated by negative charge near center (details sensitive to large Q 2 extrapolation), and by positive charge in a region up to 1.3 fm.  Very strong quadrupole pattern extending to large radius. 48 b y (fm) b x (fm) ρ0ρ0 P b y (fm)  Proton and N(1520)D 13 polarized along x-axis with opposite spin projections  Nearly full charge separation perpendicular to polarization vector in transverse space. ρTρT College of William and Mary 02/25/2011 K. Park

49 Resonance transition amplitudes should scale asymptotically as: Q 3 A 1/2 → const. Data appear to reach a plateau, but conclusive tests of scaling require higher Q 2. P 11 D 13 S 11 η π College of William and Mary 02/25/2011 K. Park I. G. Aznauryan, V. Burkert, K.Park et al., (CLAS) Phys. Rev. C 80, , (2009).

ImIm Re(DR)Re(DR) Re(UIM)Re(UIM) At Q 2 = GeV 2, resonance behavior is seen in these amplitudes more clearly than Q 2 =0 DR and UIM give close results for real parts of multiple amplitudes Imaginary Real P 11 (1440) College of William and Mary 02/25/2011 K. Park

what we can learn from measurements … P 11 (1440) S 11 (1535) D 13 (1520)  Rapid switch of helicity structure from A 3/2 dominance to A 1/2 dominance at Q 2 > 0.6GeV 2  Amplitude measured in nπ + channel, for the first time  Hard A 1/2 form factor confirmed  First measurement of S 1/2, sign inconsistent with CQM  Amplitude determined up to 4.5GeV 2 using two different analysis approaches (DR, UIM)  Sign change of A 1/2  Gluonic excitation ruled out due to Q 2 dependence of both amplitudes  High Q 2 behavior consistent with radial excitation of the nucleon as in CQM College of William and Mary 02/25/2011 K. Park

Comparison of MAID 08 and JLab analysis S 1/2 Impact of Roper A 1/2, S 1/2 Impact of Roper A 1/2, S 1/2 data on Model L. Tiator MAID 07 And new Maid analysis with K. Park data MAID 08 A 1/2 S 1/2 College of William and Mary 02/25/2011 K. Park

Impact of D 13 (1520) A 3/2, A 1/2 Impact of D 13 (1520) A 3/2, A 1/2 data on Model Get more reliable estimation of systematics from the good agreement for A 3/2 and S 1/2 determination among various resonance extractions Resonance fit done over a narrow range in W but for all Q 2 College of William and Mary 02/25/2011 K. Park

Deep Inelastic Scattering Region Why DIS is interested ? Forward scattering Why DIS is interested ? Forward scattering College of William and Mary 02/25/2011 K. Park

Pert. hard part soft part Successful Q2  ∞, t << fixed College of William and Mary 02/25/2011 K. Park

t-channel scaling behavior at large angle Non-pertubative transition between pion and baryon in backward angle Generalized scaling law appears at above resonance region and large angle( θ=90 o ) Investigation of Transition Distribution Amplitude L.Y. Zhu, PRL 91, (2003) J.P. Lansberg, B. Pire, PRD75, (2007) Why is it interesting ? Photoproduction !! College of William and Mary 02/25/2011 K. Park

AnalysisAnalysis for 9 xbj bins CRS with low t ACC CRS with high t ACC Preliminary W>2GeV cut Only College of William and Mary 02/25/2011 K. Park

Deep Inelastic Scattering Region Why DIS is interested ? Backward scattering Why DIS is interested ? Backward scattering College of William and Mary 02/25/2011 K. Park

Pert. hard part soft part What about u <<, DVCS ? Non-pert. Part does not describe the Hadron  Hadron transition Need a Transition DA (TDAs) ??? College of William and Mary 02/25/2011 K. Park

Non-pertubative transition between pion and baryon in backward angle Investigation of Transition Distribution Amplitude B. Pire, L. Szymanowski PRD71, (2005) Pert. Amplitude = Correlation between meson →  transition Mesonic TDA pp     GSI e+e- B-factories       Large Q2 would provide hard scale with pert. expansion pp  J/  GSI pp     t GSI College of William and Mary 02/25/2011 K. Park

Non-pertubative transition between pion and baryon in backward angle Investigation of Transition Distribution Amplitude B. Pire, L. Szymanowski PRD71, (2005) Pert. Amplitude = Correlation between meson →  transition Mesonic TDA pp     GSI e+e- B-factories       Large Q2 would provide hard scale with pert. expansion pp  J/  GSI pp     t GSI College of William and Mary 02/25/2011 K. Park

Non-pertubative transition between pion and baryon in backward angle Investigation of Transition Distribution Amplitude J.P. Lansberg, B. Pire, PRD75, (2007) GPD can not describe Non-perturbative part Baryon → π transition Pert. Amplitude = Meson almost stay at rest in the target(baryon) rest frame Pert. Baryonic TDA e’   n u CLAS   at 180 Hall-C e’p  e’p  CLAS JLAB 12GeV  *p  pJ/ COMPASS College of William and Mary 02/25/2011 K. Park

Blue square : data with stat. err. only Red triangle : fit with cos2  Average Chi2 ~ 1.74 except last Q 2 bin College of William and Mary 02/25/2011 K. Park

σ T +εσ L J.P. Lansberg, B. Pire, PRD75, (2007) But  0 – calculation for  =0.8,  =180 o College of William and Mary 02/25/2011 K. Park

Overall Summary College of William and Mary 02/25/2011 K. Park Summary & Plans ?

 Polarization data to improve resonance separation  New data on Q 2 dependence of higher mass states  An extensive program is underway with polarized photon beams and polarized target to search for new baryon states (CLAS)  Large effort underway at EBAC to develop the coupled channel analysis of these and other data  Proposal for a transition form factor program at high Q 2 for the Jlab 12 GeV upgrade with CLAS12  We measured the differential cross section with extended – t region  Hard exclusive process of meson in the backward angle opens a new window in the understand of hadronic physics in the framework of the collinear-factorization approach of QCD.  Measurement of cross sections and asymmetries are crucial to develop a realistic model for the TDAs. College of William and Mary 02/25/2011 K. Park

CEBAF Large Acceptance Spectrometers Thomas Jefferson National Accelerator Facility 12GeV 12GeV Upgrade Enhanced Detectors C A B D College of William and Mary 02/25/2011 K. Park

New Capabilities in Halls A, B, & C, and a New Hall D 9 GeV tagged polarized photons and a 4  hermetic detector D Super High Momentum Spectrometer (SHMS) at high luminosity and forward angles C High Resolution Spectrometer (HRS) Pair, and specialized large installation experiments A CLAS12 with new detectors and higher luminosity (10 35 /cm 2 -s) B

High Resolution Spectrometer (HRS) Pair, and specialized large installation experiments A Super High Momentum Spectrometer (SHMS) at high luminosity and forward angles C 9 GeV tagged polarized photons and a 4  hermetic detector D CLAS12 with new detectors and higher luminosity (10 35 /cm 2 -s) B Thank you for your attention Thank you for your attention College of William and Mary 02/25/2011 K. Park