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Nucleon resonance studies in collaboration between SINP at MSU and Hall B at Jefferson Lab
Presented by V.I.Mokeev

Hall-B/SINP Collaboration:
G.V.Fedotov, B.S.Ishkhanov, E.N.Golovach, V.I.Mokeev, E.L.Isupov, K.Stopani, N.V.Shvedunov. V.D.Burkert, L.Elouadrhiri, V.I.Mokeev, D.Weygand. M.E.Stepanov, V.Chesnokov,

R.Gothe, K.Joo.

V.I.Mokeev SINP Seminar June 23 09'


Primary objectives in N* studies with CLAS
Our experimental program seeks to determine · N-N* transition helicity amplitudes (electrocouplings) at photon virtualities 0.2< Q2<5.0 GeV2 for almost all excited proton states from analyzing various meson electro- production channels · Studies of N* spectrum (masses,spin/parities,hadronic decays) in meson photo- and electro- production with primary objective of searching for so called "missing" baryon states OEPVAYa group is actively involved in both major directions of the N* Program with CLAS detector.

V.I.Mokeev SINP Seminar June 23 09'


SU(6)xO(3) Classification of Baryons
Lowest Baryon Supermultiplets SU(6)xO(3) Symmetry Particle Data Group **** ***

3

**

Capstick and Roberts

"Missing" P13(1870)

(56,3-) (70,3-)

(20,3-)

2

D13(1520) S11(1535)

(56,2+) (70,2+)
7/2 5/2 3/2 1/2

(70,2-)

L

3q

(70,1-)

(20,1+)

(56,1-) (70,1-)

1

5/2 3/2 1/2

(1232 )
(56,0+)

(70,1-) (20,1-)

Roper P11(1440)
(56,0+)(70,0+)
3/2 1/2

0

0 h

1 h

2 h

3 h

(1135 MeV)

(1545 MeV)

(1839 MeV)

(2130 MeV)

N (Mass)

V.I.Mokeev User Group Meeting June 18 2008


"Missing" Baryon States
Quark models with underlying SU(6)xO(3) symmetry predict many states, not observed in either hadronic experiments or in meson photo- and electro-production.

Possible solutions:
1.states don't exist, e.g. di-quark, DSE models predicts fewer states. Part of expected N*'s can not be created because of qq-correlation or final size of quarks 2 exist but have not been found.

.

|q2q>

Possible reason: they decouple from Nchannel. Model expectations: Hadronic couplings to N ( , N ) much larger, while photocouplings are more comparable to those for observed states. Other channels sensitive to "missing" states are: K, K, p
V.I.Mokeev User Group Meeting June 18 2008

|q3>


Dressed quark properties and transition from nonperturbative to perturbative regimes of strong interactions
· ~few MeV current quark mass is approached at asymptotically high momentum p running over quark · sharp mass evolution at p<2.0 GeV reflects transition between non-perturbative/perturbative regime of strong interaction ·directly related to long range behavior of the QCD -function ·>98% of nucleon mass comes from dynamical dressing of current quarks

The studies of the ground and excited nucleon state structure allow us to access properties and interactions of dressed quarks at various distance scales Key part in the studies of quark confinement in baryons!
V.I.Mokeev SINP Seminar June 23 09'


How N* electrocouplings can be accessed
· Isolate the resonant part of production amplitudes by fitting the measured observables within the framework of reaction models, which are rigorously tested against data. · N* electrocouplings can then be determined from resonant amplitudes under minimal model assumptions. e' e

, , ,..

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

, , ,..



v

v p=1/2

N*,

*
N'

+

N

N p=3/2 Non-resonant amplitudes.

N'

Consistent results on N* electrocouplings obtained in analyses of various meson channels (e.g. N, p, N) with entirely different non-resonant amplitudes will show that they are determined reliably
Advanced coupled-channel analysis methods are being developing at EBAC: B.Julia-Diaz, T-S.H.Lee et al., PRC76, 065201 (2007);B.Julia-Diaz, et al., arXiv:0904.1918[nucl-th]
V.I.Mokeev User Group Meeting June 18 2008

6


Jefferson Lab ­ CEBAF
Emax Imax Duty Factor E/E Beam P E(tagged) ~ 6 GeV ~ 200 A ~ 100% ~ 2.5 10-5 ~ 80% ~ 0.8- 5.5 GeV

CLAS
V.I.Mokeev User Group Meeting June 18 2008


CEBAF Large Acceptance Spectrometer
Torus magnet 6 superconducting coils Liquid D2 (H2)target + start counter; e minitorus Drift chambers argon/CO2 gas, 35,000 cells Large angle calorimeters Lead/scintillator, 512 PMTs

Gas Cherenkov counters e/ separation, 216 PMTs

Electromagnetic calorimeters Lead/scintillator, 1296 PMTs Time-of-flight counters plastic scintillators, 684 PMTs

V.I.Mokeev User Group Meeting June 18 2008


Why N/N electroproduction channels are important
· N/N channels are the two major contributors in N* excitation region; · these two channels combined are sensitive to almost all excited proton states; · they are strongly coupled by NN final state interaction; · may substantially affect exclusive channels having smaller cross sections, such as p,K, and K. Therefore knowledge on / electro production mechanisms is key for the entire N* Program
V.I.Mokeev SINP Seminar June 23 09'

CLAS data on meson electroproduction at Q2 < 4.0 GeV2


HallB/SINP results on the studies of epe'p + exclusive channel with CLAS

-

2 : 1.31 < W < 1.56 0.2 < Q2 < 0.6 2 Q2=0.05 120000 1.41 < W < 2.10 0.5 < Q2 < 1.5 2 Q2=0.3 150000 Number data points > 8200 1.3 Fedotov GeV ; G.V.Fedotov- G.< W < 2.1et al., PRC 0.25 79,015204 (2009)< Q2< 1.5 GeV2
M. Ripani et al., PRL,91, 022002 (2003); E.N.Golovach -M. Ripani et al., G. Fedotov et al., PRC 79, PRL 91,022002 (2003) 015204 (2009).

2

2

W=25 MeV W/W<2%
> 10000 epe'p +
V.I.Mokeev SINP Seminar June 23 09'

-

.


CLAS data and JM model
W=1.5125 GeV, Q =0.375 GeV
2 2

The measurements with an unpolarized e- beam onto a proton target offer nine independent differential cross sections in each (W,Q2) bin. Meson-baryon model JM was developed with a primary goal of extracting N* electrocouplings from the fit of all observables: V. Mokeev et al., arXiv:0809:4158[hep-ph], V. Mokeev, V .Burkert, J. Phys. 69, 012019 (2007)

d/dM bn/GeV

d/dM bn/GeV

200

200

d/dM bn/GeV 0.25 0.5 0.75 + mass, GeV d/d(-cos ) bn/rad

200

100

100

100

0

1

1.2 1.4 + p mass, GeV d/d(-cos ) bn/rad

0

0

1

1.2 1.4 p mass, GeV

d/d(-cos ) bn/rad

30 20 10 0

30 20 10 0 0 100

20 10 0

200 -, deg d/d bn/rad

0

100

200 +, deg d/d bn/rad

0

100

200 pf, deg

d/d bn/rad

8 6 4 2 0 0 200
(- p)(+ pf)

8 6 4 2 0 0 200
(+ p)(- pf)

8 6 4 2 0 0 200
(pf p)(- +)

, deg

, deg

, deg

V.I.Mokeev SINP Seminar June 23 09'

.


Resonant & non-resonant parts of N cross sections as determined from the CLAS data fit within the framework of JM model

full cross sections

resonant part

non-resonant part

V.I.Mokeev SINP Seminar June 23 09'


P11(1440) electrocouplings from the CLAS data on N/N electroproduction
N preliminary

N
Light front models: I. Aznauryan S. Capstick hybrid P11(1440) · Good agreement between the electrocouplings obtained from the N and N channels: Reliable measure of the electrocouplings. · The electrocouplings for Q2 > 2.0 GeV2 are consistent with P11(1440) structure as a 3-quark radial excitation of the nucleon. · Zero crossing for the A1/2 amplitude has been observed for the first time, indicating the importance of light-front dynamics.
V.I.Mokeev SINP Seminar June 23 09'


D13(1520) electrocouplings from the CLAS data on N/N electroproduction

· hypercentric Consituent Quark Model calculations reasonably describe electrocouplings at Q2>2.5 GeV2, suggesting that the 3-quark component with L=1 is the primary contribution to the structure of this state at high Q2. · Electrocouplings of P11(1440) and D13(1520) states can not be described at Q2<1.0 GeV2 accounting for quark degrees of freedom only. There are additional contributions, that are relevant at low photon virtualities
V.I.Mokeev SINP Seminar June 23 09'

error bars include systematic uncertainties
M.Giannini/ E.Santopinto hyper-centric CQM


- N*
EBAC: B.Julia-Diaz et al., PRC 76, 5201 (2007).

P11(1440)
. I.Aznauryan

D13(1520)
. M.Giannini / E.Santopinto

· Q2 < 1.5 2 N* (r < 0.8) - (r > 0.8)

V.I.Mokeev SINP Seminar June 23 09'


Meson-baryon & quark degrees of freedom for high lying N*'s at Q2<1.0 GeV2
Analysis of e1e CLAS data on N electroproduction by G.V.Fedotov

1.4 First information on the structure of a major part of N*'s at the distances corresponding to the sizable contributions from both meson-baryon and quark degrees of freedom

V.I.Mokeev SINP Seminar June 23 09'


W~1.7 CLAS E.Golovach, M.Ripani
30

p +

-

no 3/2
+

25

20

full calculation Background

15

10

Resonances
5

Interference
0 1.4 1.5 1.6 1.7

W(GeV)

1.8

1.9

2

2.1

W(GeV)

V.I.Mokeev User Group Meeting June 18 2008


W~1.7 : · P13(1720) ( ) · 3/2+(1720) , CLAS ( ).

M, MeV modified P13(1720) PDG P13(1720) new state 3/2+(1720) 1725±20

,MeV 114±19

/, % 60±12

P/, %

19±9
70-85 17±10

1650-1750 100-200 absent 1720±20 88±17 41±13

V.I.Mokeev User Group Meeting June 18 2008

18


V.I.Mokeev User Group Meeting June 18 2008

19


N photoproduction cross sections from the CLAS g11 data. E.N.Golovach.
p p + W=1.71 GeV. p p + W=1.71 GeV.

d/dM, b/GeV

establish an origin of the structure at W=1.7 GeV from combined studies of N photo- and electroproduction · peaks in M+- distributions require the contributions from P13(1720) with PDG and p couplings . ·in this scenario the electroproduction data can be described only employing 3/2+ (1720) candidate state.

150

d/dM, b/GeV
0.4 0.6
+ -

200

100

100 50

0

0.8

0

1.2

1.4
+

1.6

M( ) , GeV
p p + W=1.73 GeV. p p + -

M(p ) , GeV
W=1.73 GeV.

d/dM, b/GeV

150

d/dM, b/GeV
0.4 0.6
+ -

200 150 100

100

50 50 0 0

0.8

1.2

1.4
+

1.6

M( ) , GeV

M(p ) , GeV

V.I.Mokeev User Group Meeting June 18 2008

20


N photoproduction cross sections from the CLAS g11 data. E.N.Golovach.
W=2.61 GeV.
(p), rad
3
300 250

W=2.61 GeV.
( +) , rad
3
60 50

W=2.61 GeV.
( ) , rad
3
160 140 120

2

200 150

2

-

40 30

2
100 80

1

100 50

1

20 10

1

60 40 20

0

0.5

1

1.5

0

0

1.5

2

2.5

0

0

1.5

2

2.5

0

M( + -) , GeV

M(p -) , GeV

M(p +) , GeV

First results on correlated 2D (inv. mass & angle) cross sections offer new capabilities for the studies of reaction mechanisms Direct experimental evidences for t-channel amplitudes in - ++, + D13(1520), p isobar channels incorporated into the JM model
V.I.Mokeev User Group Meeting June 18 2008

21


High lying resonance electrocouplings from N CLAS data analysis

N CLAS preliminary

(1700)D

33

N world N(1720)P N CLAS Q2=0
13

V.I.Mokeev SINP Seminar June 23 09'


N electroproduction at high Q2. E.L.Isupov

First data on electrocouplings of almost all N*'s at 2.0
·Evidence for substantial resonance contributions. ·Srtructure at 1.7 GeV becomes more pronounced at high Q2.
V.I.Mokeev SINP Seminar June 23 09'

23


N electroproduction off deuterons from e1e data. N.V.Shvedunov
ep(n)->e'+n(n) informatrion on binding effects en(p)->e'-p(p) -p cross sections off free neutrons ep(n)->e'+X(n) Q2=0.4 GeV2

W=1.45 GeV

W=1.60 GeV

Mx,GeV data 1 events

Mx,GeV 2 events

The ultimate goal: evaluation of N-N* electrocouplings off neutrons
V.I.Mokeev SINP Seminar June 23 09'


CLAS12

Projections for N* Transitions

For the foreseeable future, CLAS12 will be the only facility worldwide, which will be able to access the N* electrocouplings in the Q2 regime of 5 GeV2 to 10 GeV2, where the quark degrees of freedom are expected to dominate.

CLAS published CLAS PRL subm. CLAS12projected

CLAS published CLAS preliminay CLAS12 projected

V.I.Mokeev SINP Seminar June 23 09'


Nucleon Resonance Studies with CLAS12
D. Arndt4, H. Avakian6, I. Aznauryan11, A. Biselli3, W.J. Briscoe4, V. Burkert6, V.V. Chesnokov7, P.L. Cole5, D.S. Dale5, C. Djalali10, L. Elouadrhiri6, G.V. Fedotov7, T.A. Forest5, E.N. Golovach7, R.W. Gothe*10, Y. Ilieva10, B.S. Ishkhanov7, E.L. Isupov7, K. Joo9, T.-S.H. Lee1,2, V. Mokeev*6, M. Paris4, K. Park10, N.V. Shvedunov7, G. Stancari5, M. Stancari5, S. Stepanyan6, P. Stoler8, I. Strakovsky4, S. Strauch10, D. Tedeschi10, M. Ungaro9, R. Workman4, and the CLAS Collaboration

http://www.physics.sc.edu/~gothe/research/pub/nstar12-12-08.pdf.
Argonne National Laboratory (IL,USA)1, Excited Baryon Analysis Center (VA,USA)2, Fairfield University (CT, USA)3, George Washington University (DC, USA)4, Idaho State University (ID, USA)5, Jefferson Lab (VA, USA)6, Moscow State University (Russia)7, Rensselaer Polytechnic Institute (NY, USA)8, University of Connecticut (CT, USA)9, University of South Carolina (SC, USA)10, and Yerevan Physics Institute (Armenia) 11 Spokesperson Contact Person*

JLab PAC 34, January 26-30, 2009 Approved for 60 days beamtime

V.I.Mokeev User Group Meeting June 18 2008

26


Physics objectives in the N* studies with CLAS12
· explore the interactions between the dressed quarks, which are responsible for the formation for both ground and excited nucleon states. · probe the mechanisms of light current quark dressing, which is responsible for >97% of nucleon mass. Approaches for theoretical analysis of N* electrocouplings: LQCD, DSE, relativistic quark models. See details in the White Paper of EmNN* JLAB Workshop, October 13-15, 2008: http://www.jlab.org/~mokeev/white_paper/
Parallel sessions #9,13 of GHP09 Workshop
V.I.Mokeev SINP Seminar June 23 09'

Q2=10GeV2

DSE: lines and LQCD: triangles Q2 = 10 GeV2 = (p times number of quarks)2= 10 GeV2 p = 1.05 GeV


Theory Support Group
V.M. Braun8, I. CloÊt9, R. Edwards5, M.M. Giannini4,7, B. Julia-Diaz2, H. Kamano2, T.-S.H. Lee1,2, A. Lenz8, H.W. Lin5, A. Matsuyama2, M.V. Polyakov6, C.D. Roberts1, E. Santopinto4,7, T. Sato2, G. Schierholz8, N. Suzuki2, Q. Zhao3, and B.-S. Zou3

JLab PAC 34, January 26-30, 2009
Argonne National Laboratory (IL,USA)1, Excited Baryon Analysis Center (VA,USA)2, Institute of High Energy Physics (China)3, Istituto Nazionale di Fisica Nucleare (Italy)4, Jefferson Lab (VA, USA)5, Ruhr University of Bochum (Germany)6, University of Genova (Italy)7, University of Regensburg (Germany)8, and University of Washington (WA, USA)9

Open invitation.
List is open to any and all18who wish to participate! V.I.Mokeev User Group Meeting June 2008
28


Outlook
A wide international collaboration is needed for · theoretical interpretation on the N* electrocouplings (see http://www.jlab.org/~mokeev/white_paper) · development of reaction models that will be capable to take into account the contributions from the quark/parton degrees of freedom at high Q2. · development of the methods for experimental data analysis Everybody willing to contribute please contact Ralf Gothe gothe@sc.edu or Victor Mokeev mokeev@jlab.org

V.I.Mokeev SINP Seminar June 23 09'


Back-up

V.I.Mokeev SINP Seminar June 23 09'


CLAS Resonance transition amplitudes should scale asymptotica lly as: Q3A1/2

Resonance scaling behavior?



S

11

P

11

D13

V.I.Mokeev SINP Seminar June 23 09'

31


Conclusions
· Phenomenological approaches have been developed with the goal of determining N* electrocouplings from combined fits of measured observables in N & N electroproduction data. A good description of the CLAS data on N electroproduction and differential cross sections in +-p channel has been achieved, affording us to access the resonant parts of amplitudes, which are directly related to N* electrocouplings. The P11(1440) and D13(1520) electrocouplings have been determined for the first time from both the N & N datasets. The consistent results extracted from these two channels strongly indicate a reliable electrocoupling measurement. Preliminary results on electrocouplings of high lying D33(1700) , P13(1720) resonances have been obtained from analysis of the N CLAS data. Comparison of the data on N* electrocouplings with quark model expectations in coordination with EBAC evaluations for MB cloud show that for Q2<1.0 GeV2 both the MB cloud and quark core play an important role in the N* structure. Contribution from the MB cloud decreases with Q2, but can be still sizable at Q2<5.0 GeV2, while at Q2>5.0 GeV2 quark degrees of freedom are expected to dominate.

·

· · · ·

·

V.I.Mokeev SINP Seminar June 23 09'


Input for N/N coupled channel analysis : partial waves of total spin J for non-resonant helicity amplitudes in -++ isobar channel

J
1/2 3/2 5/2 Born terms

f TJ p =
2J +1 2 f T p · J d(f )sinf df
Will be used for N* studies in coupled channel approach developing by EBAC.
V.I.Mokeev SINP Seminar June 23 09'

Extra contact terms


Ground state and P11(1440) electrocouplings & quark model expectations Ground p state
S.Capstick light cone (LC) model B.Metsch Bethe-Salpeter model I.Aznauryan LC model 3q core

P11(1440)

3q core +??

M.Giannini/ E.Santopinto hyper-centric CQM

P11(1440) electrocouplings at Q2>2.0 GeV2 are consistent with substantial contribution from 3-quarks in first radial excitation, while at Q2<0.6 GeV2 additional contributions become evident.
V.I.Mokeev SINP Seminar June 23 09'

34


New regime in N* excitation at high Q2
· the photons of high virtuality penetrate meson-baryon cloud and interact mostly to quark core ·data on N* electrocouplings at high Q2 allow us to access quark degrees of freedom, getting rid of meson-baryon cloud. ·can be obtained at 5
EBAC calculations for meson-baryon cloud of low lying N*'s.

B.Julia-Diaz, T-S.H.Lee, et.al, Phys. Rev. C77, 045205 (2008).

V.I.Mokeev SINP Seminar June 23 09'


JLAB-MSU meson-baryon model (JM) for N electroproduction.

3-body processes:

Isobar channels included: -
++

· All well established N*s with decays and 3/2+(1720) candidate, seen in CLAS 2 data. · Reggeized Born terms with effective FSI & ISI treatment . · Extra contact term.

p
·All well established N*s with p decays and 3/2+(1720) candidate. ·Diffractive ansatz for non-resonant part and -line shrinkage in N* region.
V.I.Mokeev User Group Meeting June 18 2008

36


continued
3-body processes:
(-)
(P++33(1640)) F015(1685)

Isobar channels included:
· +D013(1520), +F015(1685), -P++33(1640) isobar channels; observed for the first time in the CLAS data at W > 1.5 GeV.

(+)

Direct 2 production
( )( )
+ +



(

+

- )

p

/

+ ( ) p

/

p (p /)( )

/

-

Most relevant at W<1.65 GeV
p
/+ p ( ) -

p

-(+)( p')

V. Mokeev, V .Burkert, J. Phys. 69, 012019 (2007); V. Mokeev et al., arXiv:0809:4158[hep-ph]
V.I.Mokeev SINP Seminar June 23 09'


Description of the CLAS N differential cross sections within the framework of JM model

full JM calc. -++

+0 2 direct
V.I.Mokeev SINP Seminar June 23 09'

p +D
0 13

+F015(1685) (1520)