Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://nuclphys.sinp.msu.ru/conf/jlab/theory_meeting.pdf Äàòà èçìåíåíèÿ: Tue Sep 1 09:43:49 2009 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 00:36:13 2012 Êîäèðîâêà:

The models for evaluation of vNN* electrocouplings from the N, N electroproduction data and their extension for photon virtualities up to 12 GeV2.

presented by V.I.Mokeev

V.I.Mokeev September 10 Meeting


Major objective of the Meeting
Determine the prospects for extension of the model descriptions of nonresonant N,N electroproduction amplitudes at 1.1
V.I.Mokeev September 10 Meeting


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

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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, C.D. Roberts1, E. Santopinto4,7, T. Sato2, G. Schierholz8, N. Suzuki2, Q. Zhao3, and B.-S. Zou3 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, University of Genova (Italy)7, University of Regensburg (Germany)8, and University of Washington (WA, USA)9 Development of approaches that will be capable to relate phenomenological information on N* electrcocouplings at high photon virtualities to non perturbative strong interaction mechanisms, that are responsible for formation of ground and excited nucleon states from quark and gluons, and to study their emergence from QCD The current plans are outlined in the paper: "Theory Support for the Excited Baryon Program at the JLAB 12 GeV Upgrade", arXiv:0907.1901 [nucl-th],[nucl-ex],[lat-ph], JLAB-PHY-09-993.
V.I.Mokeev User Group Meeting June 18 2008 4


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

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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* studies at high photon virtualities with CLAS12 detector
V.I.Mokeev September 10 Meeting

CLAS data on meson electroproduction at Q2 < 4.0 GeV2


Energy-Dependence of + Multipoles for P11, S11
I. Aznauryan (UIM)
Q2 = 0 GeV
2

Q2 = 2.05 GeV

2

Resonance contributions become more pronounced at higher Q2.

real part
V.I.Mokeev September 10 Meeting

imaginary part
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Resonance signals in the CLAS data on N electroproduction at 2.0< Q2<5.0 GeV2

Resonance structures are clearly seen in an entire Q2 area covered by the CLAS data on N electroproduction

Resonances with masses above 1.65 GeV becomes more pronounced at high Q2.
V.I.Mokeev September 10 Meeting

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Resonance signals in N electroproduction at high Q2.
Fully integrated 2 cross section at Q2 from 4.5 to 5.2 GeV2

Resonant contributions in N and N exclusive channels remains substantial at high Q2. It makes possible to determine resonance electropcouplings at 3.0
D33(1700),P13(1720) 3/2+(1720),F15(1685)

D13(1520) S11(1535)

V.I.Mokeev September 10 Meeting

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CLAS12

Projections for N* Transitions

The projected electrocouplings were estimated based on expected counting rate and requirements for statistical data accuracy needed in order to obtain N* electrocouplings from the data on N and N electroproduction

Unexplored area of 5.
CLAS published CLAS PRL subm. CLAS12projected

CLAS published CLAS preliminay CLAS12 projected

V.I.Mokeev September 10 Meeting


Meson-baryon vs Quark contributions in N Transition Form Factor ­ GM. EBAC analysis.
One third of G*M at low Q is due to contributions from meson­baryon (MB) dressing:
2

Data from exclusive 0 production

bare quark core Within the framework of relativistic QM [B.Julia-Diaz et al., PRC 69, 035212 (2004)], the bare-core contribution is very well described by the threequark component of the wf.

GD =

1 (1+Q2/0.71)

Q2=5GeV2
2

V.I.Mokeev September 10 Meeting


Meson-baryon dressing / Quark core contributions in the A1/2 electrocouplings of the P11(1440) & D13(1520) states.

Estimates from EBAC for the MB dressing (absolute values): B.Julia-Diaz et al., PRC 76, 5201 (2007).

Light Front quark model by I.Aznauryan

hypercentric quark model by M.Giannini

P11(1440)

D13(1520)

V.I.Mokeev September 10 Meeting


N CLAS data at low & high Q2
Number of data points > 83,000, W < 1.7 GeV
Observable [GeV2] d/d(0) d/d(+) 0.35-1.6 0.25-0.65 1.7-4.3 0.40 0.65 0.40 0.65 1.7 - 4.3 0.375 0.750 31 018 13 264 33 000 956 805 918 812 3 300 172 412

Q

2

Number of Data points

Low Q2 results: I. Aznauryan et al., PRC 71, 015201 (2005); PRC 72, 045201 (2005); High Q2 results on Roper: I. Aznauryan et al., PRC 78, 045209 (2008). Prelim. high Q2 results on D13(1520), S11(1535): V.Burkert, AIP Conf.Proc. 1056, 248 (2008).

Ae(0)

Ae(+)

d/d()

full data set in: http://clasweb.jlab.org/physicsdb/

V.I.Mokeev September 10 Meeting


Unitary Isobar Model (UIM) for N electroproduction

Non-resonant contributions were described by gauge invariant Born terms: · pole/reggeized meson t-channel exchange; · s- and u-nucleon terms. Final-state N rescattering was taken into account through the K-matrix approximation

n
+


+

I. Aznauryan, Phys. Rev. C67, 015209 (2003)
V.I.Mokeev September 10 Meeting



+


Fixed-t Dispersion Relations for invariant Ball amplitudes (Devenish &Lyth) *pN
Dispersion relations for 6 invariant Ball amplitudes:
17 UnsubtractedDispersion Relations

(i=1,2,4,5,6) 1 Subtracted Dispersion Relation

V.I.Mokeev September 10 Meeting


Fits to N diff. cross sections & structure functions
Q2=2.05 GeV
2

DR DR w/o P11 UIM

Q2=2.44 GeV

2

DR UIM

V.I.Mokeev September 10 Meeting


Request for modeling of non-resonant amplitudes at high Q2
· Evaluate the prospects of describing non-resonant N amplitudes at 1.1 V.I.Mokeev September 10 Meeting


electroproduction data from CLAS
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. Number data points > 8200 1.3 < W < 2.1 GeV ; 0.25 < Q2< 1.5 GeV2
M. Ripani et al., PRL,91, 022002 (2003); G. Fedotov et al., PRC 79, 015204 (2009).

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 September 10 Meeting

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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

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Evidence for extra contact term in -

++

isobar channel.

full calculations extra contact term is taken off

2 2 Parametrization of M t = ( A(W , Q ) U U p P + B(W , Q ) U U p (2 P - P )) extra contributions 1

·

t - 2
20

V.I.Mokeev User Group Meeting June 18 2008


Evidence for extra contact term in +0 isobar channel.
full calculation:
extra contact term:
d/dM, mcbn/GeV
80 70 70

W=1.76 GeV Q2=0.95 GeV2

on off

60



+ 0

60

50 50 40 40 30 30

p+0 contributin:
extra contact term: on off

20

20

10

10

0

1

1.2

1.4

1.6

1.8

0

1

1.2

1.4

1.6

1.8

80

70

W=1.81 GeV Q2=0.95 GeV2
70 60 50 40

60

50

40 30 30

20

20

10

10

0

1

1.2

p mass, GeV
+

1.4

1.6

1.8

0

1

1.2

1.4

-p mass, GeV

1.6

1.8

V.I.Mokeev September 10 Meeting

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

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 mechanisms without formation of unstable hadrons in the intermediate states were established in the CLAS N data analysis for the first time and shown in the slides #25-29. They are most relevant at W<1.65 GeV, contributing <30 % to fully integrated N cross sections. All details of JM model may be found in: V. Mokeev, V .Burkert, J. Phys. 69, 012019 (2007); V. Mokeev et al., arXiv:0809:4158[hep-ph], submitted to PRC

V.I.Mokeev September 10 Meeting


Manifestation of +D013(1520) isobar channel in the CLAS N data

full calculation:
+D013(1520) channel on +D013(1520) channel off

100 75 50 25 0

W=1.79 GeV
80 60 40 20 0 80 60 40 20 0 60 40 20 1 1.2 1.4 1.6 1.8 0 1 1.2 1.4 1.6 1.8
23

1

1.2

1.4

1.6

1.8

1

1.2

1.4

1.6

1.8

+D013(1520) contribution

80 60 40 20 0

1

1.2

1.4

1.6

1.8

1

1.2

1.4

1.6

1.8

60 40 20 0

V.I.Mokeev September 10 Meeting


Manifestation of p-P33++(1640) and p+F15(1685) isobar channels.
d/dM mcbn/GeV

W=1.89 GeV Q2=0.95 GeV2

d/dM mcbn/GeV

50

50

full calculations
40

P33 (1640) and +F150 (1685) isobar channels off
++

p+F15(1685) p P 33(1640)
-
20 30

40

30

Contributions from isobar channels: -P33++(1640) +F15 0(1685)

20

10

10

0

1

1.2

1.4

1.6 1.8 + P Mass,GeV

0

1

1.2

1.4

1.6 1.8 - P mass, GeV

V.I.Mokeev User Group Meeting June 18 2008

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Evidence for exchange processes in direct 2 production from the CLAS N data
Fit of the CLAS data on angular distributions with direct 2 production mechanisms parameterized as : exchange processes, shown in the slide # 26 3-body phase space

W=1.49 GeV
Q2=0.65 GeV
2

Q2=0.95 GeV

2

contribution from direct 2 production, described by diagrams in slide # 26

V.I.Mokeev September 10 Meeting

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Direct 2 production mechanisms derived from the CLAS data on the final hadron invariant masses and - angular distributions
( )( )
2 2 + - +

(p )
+ /

P

p (p )(-) p (+)( p )
- /

/

/

P

( )

-

+

p

p ( )

/-

The amplitudes were parameterized as:

M

d

1 = A(W , Q ) U p / U p 4 e W
2



2 2 b ( P - P

min

)

( P P2 ) 1

V.I.Mokeev User Group Meeting June 18 2008

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Description of invariant mass and angular distributions with direct 2 production mechanisms shown in the slide #26
full 2 direct

The +p, -+ , -p mass and - angular distributions were described successfully

Failure in description of + and proton angular distributions, revealed necessity to modify direct 2 production mechanisms.

V.I.Mokeev User Group Meeting June 18 2008

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Direct 2 production mechanisms determined from analysis of all available CLAS data on N electroproduction

V.I.Mokeev User Group Meeting June 18 2008

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

full JM calc. -++

+0 2 direct

p +D
V.I.Mokeev September 10 Meeting

+F015(1685)
0 13

(1520)


Cross sections for contributing isobar channels derived from the N CLAS data fit, that can be used for reaction model development

band of differential cross sections calculated in JM model that are closest to experimental N data, being determined under requirement : 2/d.p.< 2/d.p._max

differential cross sections for contributing isobar channels:

- +

++ 0

V.I.Mokeev September 10 Meeting


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
V.I.Mokeev September 10 Meeting

non-resonant part


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 September 10 Meeting


High lying resonance electrocouplings from N CLAS data analysis

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

Pr eli mi

na ry

N CLAS preliminary

(1700)D

33

V.I.Mokeev September 10 Meeting


Extension of reaction models for N electroproduction into kinematic area of 3.0 · Analysis of the available CLAS N data clearly demonstrated our capabilities to establish all relevant mechanisms from their manifestation in various observables, offering reliable separation between resonant/ non-resonant processes, if the contribution of mechanisms described at the level of phenomenological parameterization to fully integrated cross sections is < 30 %. Substantial part of N cross sections should be described implementing relevant diagram explicitly. It makes problematic to utilize meson-baryon diagrams with typical cut-off parameters ~ 1.0 GeV for description of N electroproduction at Q2>5.0 GeV2. The models accounting for relevant quark degrees of freedom looks attractive for description of N electroproduction in N* excitation region at these distance scales.

·

V.I.Mokeev September 10 Meeting


Request for modeling of non-resonant amplitudes at high Q2
· Evaluate the prospects of describing non-resonant N amplitudes at 1.1-++ · Study possibilities to implement quark degrees of freedom in description of non-resonant amplitudes in isobar channels with smaller cross sections: vp->p vp->+D130(1520)
V.I.Mokeev September 10 Meeting


Back-up

V.I.Mokeev September 10 Meeting


Kinematic Coverage of CLAS12
L= 10 GeV2
35

cm-2 sec

-1

60 , W = days0.025

GeV, Q2 = 0.5

Genova-EG
Q2 GeV2

(e',p+-) detected

Number of events

90000 80000 70000 60000 50000 40000 30000 20000 10000 0 8 7.5 1.85 7 1.825 6.5 6 5.5 1.7 5 1.725 1.75 1.8 1.775 1.9 1.875

Q

2

(GeV
2

W

(GeV)

)

W GeV
37

V.I.Mokeev User Group Meeting June 18 2008


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 September 10 Meeting

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An additional contact terms in channels needed to fit data.
( )
-+

( ) ( ) p p
++ 0

+

-

M

t

= ( A(W ) U U P + B(W ) U U p (2 P - P ))
= 1.64 GeV
2 2





p









1 · t - 2

t = ( P - P )

2

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The amplitudes for p+F015(1685) and p-P++33(1600) channels.

(M 2 M = A(W , Q ) · U p U p ( PF 15 · P + ) · exp-

_

p

-

-M

F 15

2 F 15

)2





_

p
++

/

* p p P33(1600)
++ /

p

/



_

(M 1 2 exp- M = A(W , Q ) · U p U p · 2 t - m *
V.I.Mokeev User Group Meeting June 18 2008



+

-p

-M

P 33

2 P 33

)2 1 · Pp P

-


40


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 September 10 Meeting

Extra contact terms


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

Q2=10GeV2

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

V.I.Mokeev September 10 Meeting