# Presentation: 839291

- Outline:

- Analysis objectives.
- JLAB-MSU model and candidate  3/2+(1720) state.
- Model extension from analysis of recent CLAS  data.
-  Comprehensive test of 2005’ JLAB-MSU model in
-   combined fit of 1 and 2 data from CLAS.
- N* photocouplings and hadronic parameters extracted
-   from CLAS 2 data fit within the framework of 2005’
-   JLAB-MSU model.
- Conclusion and outlook.

- Victor Mokeev

**Nucleon resonance studies in phenomenological analysis of recent CLAS data on double charged pion photo- and electroproduction off proton.**** **

## JLAB-MSU model for 2-  photo- electro-production from 2003’ to 2005’-versions.

**3-body processes**

**Quasi-2-body mechanisms included**

**All well established N* with ********decays +P33(1600)&P11(1710)&P13(1720)&P33(1920) 3-star states**
**Minimal set of Reggetized gauge invariant Born terms**
**Effective treatment of couplings** **with other open channels**

**All well established N* with ********p decays**
**+P11(1710)&P13(1720) 3-star states.**
**Diffractive ansatz for non-resonant ********p**
**production**

- P33(1600)

- mechanisms added to
- 2005’ model version

## JLAB-MSU model  from 2003’ to 2005’ version.

**3-body processes**

**Quasi-2-body mechanisms included**

**Minimal set of Born terms similar to what was**
**used for ******** states, except an additional ********5**** matrix**
**to account for the opposite parities of ******** and **
**D13(1520)**

- Details of the 2003’-version of model may be found in:
- M.Ripani et. al., Nucl. Phys., A672, 220 (2000);
- V.Mokeev, et. al., Phys. of Atom. Nucl., 64, 1292 (2001);
- V.D.Burkert, et.al., Phys. of Atom Nucl.,66, 2199 (2003);
- V.D.Burkert, et. al., Phys. of Atom Nucl., 67, 1018 (2004);

- First step in data analysis needed to establish all relevant mechanisms of
- 2 production from their manifestations in measured cross-sections. Valuable
- input for further model development within the framework of rigorous coupled
- channel approach.

- F15(1685)

- mechanisms added to
- 2005’ model version

## Electroproduction data fit. A candidate 3/2+(1720) baryon state.

- CLAS data  fit

**M.Ripani et. al. **
**Phys. Rev. Lett.91, 022002 (2003)**

- Difference between curves due to signal from candidate 3/2+(1720) state

- Fit with candidate 3/2+(1720)
- state

- Contributions from conventional
- states only

**N*********photocouplings were varied within 30% ******** around values obtained from world meson photo and **
**electroproduction data analysis in SQTM approach: V.D.Burkert et. al., Phys. Rev. C67, 035204 (2003)**

## Manifestation of direct 2 production mechanisms.

- JLAB-MSU model:

- 2003’

- 2005’

- 2 direct production
- mechanisms

- W=1.49 GeV

- Q2=0. GeV2

- Q2=0.65
- GeV2

- Q2=0.95
- GeV2

## 2 direct production mechanisms and an additional term for  channels needed to fit data.

- 2 = 1.64 GeV2

## Description of total  photoproduction cross-section off   protons in 2005’ version of JLAB-MSU model.

-  Signal from candidate
-  3/2+(1720) state  present,
-  but masked by large
-  background

- Background

- Resonances

- full calculation

- no 3/2+

- Q2=0. GeV2

- W, GeV

****, mcbn

** **Initial values of N* photocouplings were taken from analysis of CLAS 2 data within the framework of 2003’ JLAB-MSU model: V.Burkert et.al., Nucl. Phys. A737, S231 (2004) and further adjusted to the data, using recent version of model.

##  Description of total +- electroproduction cross-sections  off protons in 2005’ JLAB-MSU model.

**W, GeV**

- b

**Q****2****=0.65 GeV****2**

**Q****2****=0.95 GeV****2**

**Q****2****=1.30 GeV****2**

** **All CLAS 2 photo and electro production data were described implementing meson-baryon mechanisms seen in observables without need for an additional mechanisms of unknown dynamics.

-  Quality of CLAS data allowed
- to establish all relevant mechanisms
- for 2 production in N* excitation
- region at Q2<1.5 GeV2

- Would adopted parameterization of
- background provide credible
- N*/background separation?

## Combined analysis of the CLAS data on 1 and 2 electroproduction at Q2=0.65 GeV2

- Successful fit of all 1/2 observables with common set of N* photocouplings would provide evidence for reliable background description and N*/background separation.

- Single pion data: d/ddifferential cross-sections:
-                             + at W between 1.1-1.41 GeV,
-                             0  at W between  1.1-1.68 GeV;
-                             beam asymmetries:
-                             + and 0 at W between 1.1-1.58 GeV
-                             9870 data points

- Double pion data: +-,  +p,  -p mass and
-                              CM - angular distributions at
-                              W between 1.41-1.89 GeV
-                              680 data points
- The data are available in CLAS Physics DB: http://clasdb3.jlab.org

- 1 analysis models: I.G. Aznauryan, Phys. Rev. C68, 065204 (2003);
-                                  I.G. Aznauryan, et. al., Phys. Rev. C71, 015201
-                                  (2005).

- CLAS 1 data
- K.Joo, L.C.Smith, et.al

- CLAS 2 data
- M.Ripani, V.D.Burkert,
- et.al.

**Notes:**
CLAS 1- data (K.Joo, L.C.Smith, et.al.)

## 1 data description with N* photocouplings from combined analysis of 1/2channels at Q2=0.65 GeV2.

- vp→0p

- W=1.52 GeV

- W=1.68 GeV

- Bunches of curves correspond to calculated 1/2 cross-sections with common sets of  N* photocouplings

## 2 data description with N* photocouplings from combined analysis of 1/2channels.

- W=1.54 GeV Q2=0.65 GeV2

- W=1.66 GeV Q2=0.65 GeV2

**accepted**  by PRC

## N* photocouplings and hadronic parameters from analysis of the CLAS 2 data within the framework of 2005’ JLAB-MSU model.

- Fitted data: , p, -p mass and CM - angular distributions at 20 W-bins between 1.41-1.89 GeV  and photon virtualities Q2:  0., 0.65, 0.95, 1.30 GeV2. The data may be found in CLAS Physics DB: http://clasdb3.jlab.org.
- Combined fit of 4 Q2 bins was carried out within a framework of 2005’ JLAB-MSU model. W-intervals between 1.41-1.51 GeV, 1.54-1.64 GeV, 1.66-1.76 GeV, 1.79-1.89 GeV were fitted independently.
- Photocouplings and poorly known masses,  and p couplings of N* were varied and fitted to the data together with parameters of  non-resonant  mechanisms implemented to the 2005’ JLAB-MSU model. Hadronic couplings were further constrained, exploiting their Q2-independence. The photocouplings at 4 mentioned above Q2’s were derived from data fit for the states: P11(1440), D13(1520), S31(1620), S11(1650), P33(1600)*), F15(1685), D13(1700), D33(1700), P13(1720), candidate 3/2+(1720), F35(1905), P33(1920), F37(1950).
- *)1.65 GeV mass from our analysis

**Notes:**
Yes

## Description of total +-p cross-sections with  N* photocouplings, hadronic and non-resonant mechanism parameters fitted to the data.

- _Parameter variations_
- N* photocouplings: within 30% **** around values obtained in previous fit (2003’ JLAB-MSU model)
****, ****p decays: wide range, which led to the total width variation between 40-600 MeV
- N* masses: inside PDG uncertainties

| W-interv., GeV | 2/d.p thresh. |
| --- | --- |
| 1.41-1.54 |    2.45 |
| 1.56-1.64 |    2.19 |
| 1.66-1.76 |    2.04 |
| 1.79-1.89 |    2.06 |

- Sub-sets of calculated cross-sections most close to the data were isolated, applying restriction 2<2 thresh, listed in the table

- Q2=0 GeV2

- Q2=0 95GeV2

- Q2=0 65GeV2

- Q2=1 30 GeV2

**Notes:**
Yes

## N* photocouplings from analysis of CLAS 2 data within the framework of 2005’ JLAB-MSU model.

- D13(1520)

- (A1/22+S1/22)1/2, GeV-1/2

- A3/2, GeV-1/2

- Q2 GeV2

- Q2 GeV2

- CLAS 2 data
- analysis

- PDG
- 1/2 combined
- CLAS data analysis

- World data
- before CLAS,
- obtained in
- analysis of 1
- electroproduction:

- V.D. Burkert, et. al.,
- Phys. Rev. C67,
- 035204 (2003)

## Cont’d

- D33(1700)

- D33(1700)

- P13(1720)

- P13(1720)

**D33(1700), P13(1720)**
**resonances mostly **
**decay with 2******** **
**emission. 1******** data**
**have not  enough**** **
**sensitivity to these **
**states.**

**First data on  **
**Q****2**** ****-evolution of **
**S31(1620), D13(1700),**
**D33(1700), P13(1720).**
**F35(1905),P33(1920),**
**F37(1950) **
**photocouplings were **
**obtained from analysis **
**of CLAS experiments on  **
**2******** photo- and electro-**
**production.**

**Notes:**
No?Yes

## Conclusions and outlook.

- Phenomenological approach was developed for description of 2 production by real and virtual photons in N* excitation region and at  Q2<1.5 GeV2. The approach provides most complete treatment of  contributed mechanisms and allows most reliable evaluation of N* photocouplings and, in part, hadronic parameters from the fit to all measured observables in ** ******************p final state.
- Quality of CLAS data allowed to establish all relevant 2 production mechanisms, implementing particular meson-baryon diagrams needed for data fit. Good description of all unpolarised CLAS/world data was achieved without any necessity for remaining mechanisms of unknown dynamics. Reliability of background description and N*/background separation was confirmed in combined analysis of CLAS 1 and 2 electroproduction data.
- The photocouplings in Q2-area between 0 and 1.5 GeV2 were extracted from CLAS 2 photo- and electroproduction data for most N*’s with masses less then 2.0 GeV. Q2-evolution of photocouplings for S31(1620), D13(1700), D33(1700), P13(1720), F35(1905), P33(1920), F37(1950) states were determined for the first time.
- First comprehensive data on Q2-evolution of photocouplings for many N*’s open up an opportunity to establish driving symmetry for quark binding potential in baryons and to access N* structure in terms of contributing 3q-configurations.