1. Measurement of differential cross sections of p(e,e’p+)n for high-lying resonances at Q2 < 5GeV2
K. Park
What we can learn from this experiment ?
NSTAR 2013 Workshop
May, , 2013

2. Why e.m. probes for study of hadron structure ?
B=N,N*,D*
Allows to address central question:
“ What are the relevant degrees-of-freedom
at varying distance scale ?” N q q q
Why do we use electromagnetic probes to study hadron structure? I think the answer is that the e.m. probe allows us to efficiently address the central question of hadron physics: What are the relevant degrees of freedom at varying distance scales? To simply illustrate this I show here the quark propagator mass calculated in LQCD, Dyson Schwinger, and other approaches as a function of the momentum transfer. In the e.m. probe we can vary the resolution and momentum transfer. In doing so, we probe the effective degrees of freedom in the nucleon from meson-nucleon, to constituent quarks, to elementary partons. The study of nucleon resonance transitions provides a testing ground for our understanding of these effective degrees of freedom. e' e' e' g* g* g* e e e
NSTAR Workshop at Valencia SPAIN May , K. Park 2

3. Electroproduction Amplitudes
Sz= 1
Sz= 1/2
photocoupling amplitudes
→ A1/2, A3/2 and S1/2
Sz= 1
Sz= 1/2
Sz= 0
S1/2
Sz= 1/2 p g* N N*
Pion electroproduction multipole amplitude
→ El, Ml and Sl .
l : the orbital angular momentum in Nπ system.
± sign : spin of proton couples to the orbital momentum.
Electroproduction of hadronic final states via s-channel resonance decay.
A: transverse coupling
S : scalar coupling respect to the total helicity of the gammaN system.
The electroproduction of an excited state can be described in terms of 3 photocoupling amplitudes A1/2, A3/2 and S1/2 .
We still need to learn a lot more about the light quark baryon spectrum. It has been studied mostly with pion probes. However, there may be many states that do not coupleto pions, especially higher mass state, while possibly coupling to photons.
The spectrum can tell us about the underlying symmetry properties due to different quark-gluon configurations, or interaction mechanism
At different photon virtualities we probe how the relevant dof change as a function of the distance scale. The quantities of interest are the helicity amplitudes A1/2,... as a function of Q2.
Since both photon and nucleon carry spin, we probe the spin structure in the regime of strong QCD.
Our main tool in resonance studies is meson production. However, mesons are not only produced via resonance decays. In order to understand the full production mechanism in terms of resonant and non-resonant amplitudes we need to further develop, what one may call the Standard Model of meson production.
Finally, N* electroexcitation allows us to better understand the observed connections between the nucleon resonance region and the deeply inelastic regime.
A1/2, A3/2,S1/2
El, Ml ,Sl
NSTAR Workshop at Valencia SPAIN May , K. Park

4. from CLAS Q2 evolution in low-mass has been done so far… A1/2 S1/2 GM*
P11(1440)
D(1232)
from CLAS
Q2 < 5.0GeV2
GM*
A1/2
A1/2
PRC77, (2008)
PRC78, (2008)
PRC80, (2009)
PRC73, (2006)
PRL97, (2006)
PRC72, (2005)
PRC68, (2005)
PRL88, (2002)
* Publication includes analyses of Np channels …
S1/2
REM
S1/2
RSM
A3/2
NSTAR Workshop at Valencia SPAIN May , K. Park 4

5. Q2 evolution in high-mass … ?
I may skip this page …. By words, high mass is poorly known…..
(1996) 30 years ago….
Transverse photocoupling amplitudes for state belongs to the [70,1-] super-multiplets
0 =neutron
+ = proton
Data :
Breuker H. et al, Z. Phy. C 17 (1983) 121 (Bonn)
Foster F. and Hughes G : Rep. Prog. Phys. 46 (1983) 1445
Curves : SQTM.
Dashed-lins : different parametrization of th S11. D13
RPP (PDG) J. Phys. G 37 (2010)
I.G. Aznauryan, Phys. Rev. C 72 (2005)
MAID 2007 (global fit)
NSTAR Workshop at Valencia SPAIN May , K. Park

6. Single and double pion electroproduction
2PION CHANNEL HAS MORE STRONG SENSTIVITY ON THE HIGH-LYING RESONSNCES THAN SINGLE PION CHANNELS.
HOWEVER, SIGNLE PION AND DOUBLE PION HAS THEIR OWN SPIN-FAVOR DECOMPOSITION,
BRANCHING FRACTION…
S11(1650), F15(1685) = 60%-90% FOR SINGLE PION
HADRONIC DECAY PROMINENT N* FOR W<1.8GeV
W (GeV)
NSTAR Workshop at Valencia SPAIN May , K. Park

7. Single and double pion electroproduction
2PION CHANNEL HAS MORE STRONG SENSTIVITY ON THE HIGH-LYING RESONSNCES THAN SINGLE PION CHANNELS.
HOWEVER, SIGNLE PION AND DOUBLE PION HAS THEIR OWN SPIN-FAVOR DECOMPOSITION,
BRANCHING FRACTION…
S11(1650), F15(1685) = 60%-90% FOR SINGLE PION
HADRONIC DECAY PROMINENT N* FOR W<1.8GeV
W (GeV)
NSTAR Workshop at Valencia SPAIN May , K. Park

8. Kinematic binning ~ 29K cross-section data
Exclusive single positively charged pion electroproduction off the proton
Q2 < 5.0GeV2
This Work
W (GeV)
E0 =5.499 GeV
Kinematic binning ~ 29K cross-section data
Variable
Range
Number of bin (size) W
1.6 ~2.0 GeV
5(40MeV) , 3(60MeV) Q2
1.7 ~4.5 GeV2
5 (vary)
cos qp*
-1.0~+0.5,+0.5~+1.0
7 (0.2) , 10 (0.05)
fp*
0o ~ 360o
24 (15o) , 48(7.5o)
NSTAR Workshop at Valencia SPAIN May , K. Park

9. Differential cross sections
Single pion electroproduction
cross-section w/ one-photon exchange approx.
NSTAR Workshop at Valencia SPAIN May , K. Park

10. Preliminary Fit differential cross sections vs. f* Samples Exp. e1-f
NSTAR Workshop at Valencia SPAIN May , K. Park

11. Preliminary Fit differential cross sections vs. f* Samples
A + B cos f + C cos2 f
Samples
Exp. e1-f
NSTAR Workshop at Valencia SPAIN May , K. Park

12. Preliminary Differential cross sections vs. W MAID 2003 (Isobar model)
DMT2001 (Dynamic model)
MAID 2007 (Isobar model)
Exp. e1-f : this work
PRC 77, (2008)
NSTAR Workshop at Valencia SPAIN May , K. Park

13. Preliminary Differential cross sections vs. W W (GeV)
MAID 2003 (Isobar model)
DMT2001 (Dynamic model)
MAID 2007 (Isobar model)
Exp. e1-f : this work
PRC 77, (2008)
NSTAR Workshop at Valencia SPAIN May , K. Park

14. Preliminary Structure functions @ W=1.62GeV (sT + e sL) (sTT) (sLT)
Exp. e1-f
PRC 77, (2008)
(sLT)
** systematic uncertainty is NOT taken into account.
NSTAR Workshop at Valencia SPAIN May , K. Park

15. Preliminary Structure functions @ W=1.74GeV (sT + e sL) (sTT) (sLT)
Exp. e1-f
(sLT)
** systematic uncertainty is NOT taken into account.
NSTAR Workshop at Valencia SPAIN May , K. Park

16. Analysis ; (forward angle with finer binning)
(sTT)
NSTAR Workshop at Valencia SPAIN May , K. Park

17. Analysis ; (forward angle with finer binning)
(sTT)
+0.5
+0.9
+0.7
cosine bins
+1.0
0.575
0.625
0.525
0.675
0.725
0.775
0.825
0.875
0.925
0.975
fine cosine bins at forward angle
NSTAR Workshop at Valencia SPAIN May , K. Park

18. Preliminary Preliminary differential cross sections
fine-angle binning at forward region
Preliminary
Only Yields, acceptances, radiative corrections and normalization were taken into account to get cross sections.
No detail efficiencies and corrections are not yet applied.
Samples
NSTAR Workshop at Valencia SPAIN May , K. Park

19. Preliminary Preliminary differential cross sections
fine-angle binning at forward region
Preliminary
Only Yields, acceptances, radiative corrections and normalization were taken into account to get cross sections.
No detail efficiencies and corrections are not yet applied.
NSTAR Workshop at Valencia SPAIN May , K. Park

20. Preliminary Structure functions fine-angle binning at forward region
(sTT)
Exp. e1-f w/ fine-bin
Exp. e1-f
PRC 77, (2008)
NSTAR Workshop at Valencia SPAIN May , K. Park

21. Preliminary Structure functions W=1.89, 1.95, 2.01 GeV (sT + e sL)
Exp. e1-f
Exp. e1-f w/ fine-bin
NSTAR Workshop at Valencia SPAIN May , K. Park

22. Preliminary ? ? Structure functions W=1.89, 1.95, 2.01 GeV (sT + e sL)
Exp. e1-f
Exp. e1-f w/ fine-bin
NSTAR Workshop at Valencia SPAIN May , K. Park

23. Preliminary Zoom–in forward angle region (sT + e sL) W=1.89 GeV
Exp. e1-f coarse-bin
Exp. e1-f w/ fine-bin
Exp. e1-f w/ hyper-fine bin
NSTAR Workshop at Valencia SPAIN May , K. Park

24. Preliminary Legendre moments Exp. e1-f (dW= 20MeV)
PRC 77, (2008)
NSTAR Workshop at Valencia SPAIN May , K. Park

25. Preliminary Helicity Amplitude Extraction : N(1680)5/2+
RPP (PDG) J. Phys. G 37 (2010)
I.G. Aznauryan, Phys. Rev. C 72 (2005)
M. Dugger Phys. Rev. C 76 (2007)
Do not show 2pion data
SHOULD mention, no systematic uncertainty taken into account for either data and extraction of the helicity amplitude.
Q2=0GeV2 should be updated with M.Dugger data value.
Gianini (sound like : Janini) Quark model calculation curve ??
This analysis, I.G. Azauryan (UIM)
MAID global analysis
M.M. Gianini/E. Santopinto (hQCM)
WARNING : systematic uncertainty is NOT taken into account.
NSTAR Workshop at Valencia SPAIN May , K. Park

26. Preliminary Helicity Amplitude Extraction : N(1680)5/2+
RPP (PDG) J. Phys. G 37 (2010)
I.G. Aznauryan, Phys. Rev. C 72 (2005)
M. Dugger Phys. Rev. C 76 (2007)
This analysis, I.G. Azauryan (UIM)
MAID global analysis
M.M. Gianini/E. Santopinto (hQCM)
WARNING : systematic uncertainty is NOT taken into account.
NSTAR Workshop at Valencia SPAIN May , K. Park

27. Preliminary Helicity Amplitude Extraction : N(1680)5/2+
I.G. Aznauryan, Phys. Rev. C 72 (2005)
This analysis, I.G. Azauryan (UIM)
MAID global analysis
M.M. Gianini/E. Santopinto (hQCM)
WARNING : systematic uncertainty is NOT taken into account.
NSTAR Workshop at Valencia SPAIN May , K. Park

28. Preliminary Helicity Amplitude Extraction : N(1720)3/2+
RPP (PDG) J. Phys. G 37 (2010)
I.G. Aznauryan, Phys. Rev. C 72 (2005)
M. Dugger Phys. Rev. C 76 (2007)
This analysis, I.G. Azauryan (UIM)
MAID global analysis
M.M. Gianini/E. Santopinto (hQCM)
WARNING : systematic uncertainty is NOT taken into account.
NSTAR Workshop at Valencia SPAIN May , K. Park

29. Preliminary Helicity Amplitude Extraction : N(1720)3/2+
RPP (PDG) J. Phys. G 37 (2010)
I.G. Aznauryan, Phys. Rev. C 72 (2005)
M. Dugger Phys. Rev. C 76 (2007)
This analysis, I.G. Azauryan (UIM)
MAID global analysis
M.M. Gianini/E. Santopinto (hQCM)
WARNING : systematic uncertainty is NOT taken into account.
NSTAR Workshop at Valencia SPAIN May , K. Park

30. Summary and Plans
Using the exclusive single positively charged pion off the proton data, the differential cross sections have been measured for high-lying resonances.
(1.6 GeV< W< 2.0 GeV, GeV 2< Q2 < 4.5 GeV 2).
Preliminary results are consistent with the published data.
Angular distribution at high W likely indicate the pion pole contribution.
Preliminary helicity-amplitudes for F15(1680), P13(1720) resonances have been extracted using a unitary isobar model.
Systematic study for fine-bin data is on going.
Combined analysis of available and future data on all exclusive meson electroproduction channels at W >1.6 GeV and at Q2 >2.0 GeV 2 within the framework of coupled channel approaches will improve considerably our knowledge on high mass N*-state electro-couplings.
NSTAR Workshop at Valencia SPAIN May , K. Park

31. Thank you for your attention
Questions/comments ?

33. Preliminary Helicity Amplitude Extraction : N(1680)5/2+
Exp. e1-f ( this analysis )
MAID global analysis
I. Aznaryannna (Old)
NSTAR Workshop at Valencia SPAIN May , K. Park

34. Preliminary Helicity Amplitude Extraction : N(1720)3/2+
Exp. e1-f ( this analysis )
MAID global analysis
I. Aznaryannna (Old)
NSTAR Workshop at Valencia SPAIN May , K. Park

35. Helicity Amplitude Extraction: S11, S31, D13, D33
ad = 0.53
as = 0.46
S11: N(1650) 1/2-
S31: Delta(1620) 1/2-
D13: N(1700) 3/2-
D33 : Delta(1700) 3/2-
Preliminary
Exp. e1-f ( this analysis )
SQTM
SQTM
NSTAR Workshop at Valencia SPAIN May , K. Park

36. Exclusive single positively charged pion electroproduction
Exclusive single positively charged pion electroproduction off the proton
Q2 < 5.0GeV2
from CLAS
PRC85, (2012)
Eur. Phys. J. A 49, 16 (2013)
PRC77, (2008)
PRC78, (2008)
PRC80, (2009)
This Work
GM*
REM
RSM
A1/2
S1/2
P11(1440)
D(1232)
S11(1535)
D13(1520)
ds/dt vs. xB, Q2,
-t (<5GeV2)
G1 and GA form factors
W (GeV)
NSTAR Workshop at Valencia SPAIN May , K. Park

37. Preliminary Zoom–in forward angle region (sT + e sL) W=1.89 GeV (sTT)
(sLT)
Exp. e1-f
Exp. e1-f w/ fine-bin
Exp. e1-f w/ hyper-fine bin
NSTAR Workshop at Valencia SPAIN May , K. Park