1 Single  0 Electroproduction in the Resonance Region with CLAS Kyungseon Joo University of Connecticut For the CLAS Collaboration N* 2009 Beijing, China April 19, 2009

2 Electromagnetic Excitation of N* resolution of probe low high N π - Allows to address the central question: What are the relevant degrees-of-freedom at varying distance scale? q

3

4 SU(6)xO(3) Classification of Low Lying N*

5 p(e,e’)X Exclusive Processes in N* Studies C LAS Hadronic mass

6 N* Transition Form Factors in the 2nd N* Transition Form Factors in the 2nd Resonance Region – Resonance Region – “Roper” P 11 (1440), S 11 (1535), D 13 (1520) Transition Form Factors of Low Lying N* States p  0 channel is important to study:

7

8

9

10 N* Transition Form Factors in the 2nd Resonance Region P 11 (1440) Poorly understood in nrCQMs. Other models: - Hybrid baryon with gluonic excitation |q 3 G> - Quark core with large meson cloud |q 3 m> - Nucleon-sigma molecule |Nσ> - Dynamically generated 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.

11 Roper P 11 (1440) Helicity amplitudes + +

12 Transverse amplitudes for   p->D 13 (1520) preliminary +

13 CLAS Single Pion Electro-production Data Data in the  region up to W = 1.4 GeV JLab/Hall CFrolov1999 p0p0 Q² = GeV² BatesMertz et al.2001 p0p0 Q² = GeV² MainzPospischil et al.2001 p0p0 Q² = GeV² JLab/CLASJoo et al.2002 p0p0 Q² = 0.4 – 1.8 GeV² BonnBantes, Gothe2002 p0p0 Q² = 0.6 GeV² JLab/CLASEgiyan et al.2006 n+n+ Q² = 0.3 – 0.6 GeV² MainzElsner et al. / Stave et al.2006 p0p0 Q² = GeV² Jlab/CLASUngaro et al.2006 p0p0 Q² = 3.0 – 6.0 GeV² JLab/Hall AKelly et al.2007 p0p0 Q² = 1.0 GeV² JLab/CLASPark et al.2008 n+n+ Q² = 3.0 – 6.0 GeV²

14 CLAS Single Pion Electro-production Data Data up to the 3rd resonance region up to W = 1.7 GeV JLab/CLASJoo et al. (A e only)2003 p0p0 Q² = 0.4 – 0.65 GeV² JLab/CLASJoo et al. (A e only)2004 n+n+ Q² = GeV² JLab/Hall ALaveissiere et al.2004 p0p0 Q² = 1.0 GeV² JLab/CLASEgiyan et al.2006 n+n+ Q² = 0.3 – 0.6 GeV² JLab/CLASPark et al.2008 n+n+ Q² = 1.7 – 4.5 GeV²

15 CLAS Single  0 Electro-production Data Analysis E1E: Beam Energy:1 GeV and 2 GeV Low Q 2 up to 1.5 GeV, and W up to 1.7 GeV E1-6: Beam Energy: 5.75 GeV Low Q 2, up to 4.5 GeV and W up to 2.0 GeV Beam polarization: ~ 70 – 80 % Target: Liquid Hydrogen

16 CEBAF at Jefferson Lab E max ~ 6 GeV I max ~ 200  A Duty Factor ~ 100%  E /E ~ Beam P ~ 80% E g (tagged) ~ GeV CLAS A CB

17 CEBAF Large Acceptance Spectrometer (CLAS) Six identical sectors 5 T toroidal B-field Δθ= degrees Δφ = 0-50 degrees Δp/p =

18  Electron PID

19  Electron PID

20  Proton PID Use TOF timing and DC momentum of positive tracks

21  0 selection e + p -> e’ + p + X on  resonance region from 5.7 GeV MX2MX2 M X 2 from e + p -> e’ + p + X on  resonance region from 2. 0 GeV MX2MX2

22  0 selection (E1-6) M X 2 from e + p -> e’ + p + X for 1.1 < W < 2.0 GeV M  2 MX2MX2 Currently working on bench-mark studies on  (1232) region with/without tagging  0

23 Typical ep→ e ’ pπ 0 cross sections vs cos θ* and φ* Q 2 = 0.2 GeV 2 W=1.22 GeV Very preliminary

24 π + electroproduction at Q 2 =0.20 GeV 2 using CLAS Very preliminary

< Q 2 < 0.7, 1.3 < W < 1.35 Differential Cross section from 2.0 GeV Very preliminary

< Q2 < 0.7 Legendre Moment Legendre Moment Very preliminary A0A0

27 E1+/M1+ and S1+/M1+ pπ 0 only nπ + only pπ 0 and nπ + CLAS e1e UIM Fit

28

29 Roper P 11 (1440) Helicity amplitudes + +

30 Transverse amplitudes for   p->D 13 (1520) preliminary +

31

32

33 Summary Single   electro-production analysis is under way for low and high Q 2 range up to 2.0 GeV in W. Able to perform combined analysis with n  + and two pion channels  p   channel is an important part of 12 GeV N* program with CLAS12. Current p   analysis measuring all final states will provide an important step for 12 GeV N* program.