v.i.mokeev nstar at high q2 workshop, may 16, 2011, jefferson lab, newport news, va victor i. mokeev...

V.I.Mokeev NSTAR at high Q2 Workshop , May 16, 2011, Jefferson Lab, Newport News, VA

Victor I. MokeevJefferson Lab

Workshop scope and N* parameters available/expected from the CLAS/CLAS12 detector data.

Victor I. MokeevJefferson Lab

V.I.Mokeev User Group Meeting June 18 2008V.I.Mokeev NSTAR at high Q2 Workshop , May 16, 2011, Jefferson Lab, Newport News, VA 2

Nucleon Resonance Studies with CLAS12 R. 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

Approved by PAC for 40 days beam timefor the first five years of running

http://www.jlab.org/exp_prog/proposals/09/PR12-09-003.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

SpokespersonContact Person*

V.I.Mokeev User Group Meeting June 18 2008V.I.Mokeev NSTAR at high Q2 Workshop , May 16, 2011, Jefferson Lab, Newport News, VA

3

Anticipated N* Electrocouplings from a Combined Analysis of Np & Npp

Open circles represent projections and all other markers the available results with the 6-GeV electron beam

Examples of published and projected results obtained within 60d for three prominent excited proton states from analyses of Np and Npp electroproduction channels. Similar results are expected for many other resonances at higher masses, e.g. S11(1650), F15(1685), D33(1700), P13(1720), …

Our experiment will – for the foreseeable future – be the only experiment that can provide data on gvNN* electrocouplings for almost all well established excited proton states at the highest photon virtualities ever achieved in N* studies up to Q2 of 12 GeV2

S11(1535)D13(1520)P11(1440)

CLAS CLAS

CLASHall C


4

gvNN* Electrocouplings at Q2>5.0 GeV2 as a probe of the Resonance Quark Structure

Meson-Baryon Dressing

absolute values of meson-baryon dressing amplitudes ( EBAC)

quark core contributions (constituent quark

models)

D13(1520)

Resonance structures can be described in terms of an internal quark core and a surrounding meson-baryon cloud whose relative contribution decreases with

increasing Q2.

Data on gvNN* electrocouplings from this experiment (Q2 > 5 GeV2) will afford for the first time direct access to the non-perturbative strong interaction among dressed

quarks, their emergence from QCD, and the subsequent N* formation.

P11(1440)

CLAS: Np and N /p Npp combined (Phys. Rev. C80, 055203, 2009)


gvNN* Electrocouplings at Q2>5.0 GeV2 as a probe of the Resonance Quark Structure

Topic for discussion:

Prospects to establish the area of Q2 with minor meson-baryon dressing for N* states of various quantum numbers within the framework of the EBAC-DCC approach

V.I.Mokeev User Group Meeting June 18 2008V.I.Mokeev NSTAR at high Q2 Workshop , May 16, 2011, Jefferson Lab, Newport News, VA 6

Theory Support Group I.Aznauryan9, V.M. Braun8, S.Capstick3, I.Cloët10, R. Edwards6, M.M. Giannini5,7, B. Julia-Diaz2, H. Kamano2, T.-S.H. Lee1,2, A. Lenz8, H.W. Lin6, A. Matsuyama2,C.D. Roberts1, E. Santopinto5,7, T. Sato2, G. Schierholz8, N. Suzuki2, Q. Zhao4,

and B.-S. Zou4

Argonne National Laboratory (IL,USA)1, Excited Baryon Analysis Center (VA,USA)2, Florida State University(FL,USA)3 Institute of High Energy Physics (China)4,

Istituto Nazionale di Fisica Nucleare (Italy)5, Jefferson Lab (VA, USA)6, University of Genova (Italy)7,University of Regensburg (Germany)8, Yerevan Physics

Institute (Armenia)9 and University of Washington (WA, USA)10

:

“Theory Suport for the Excited Baryon Program at the JLAB 12 GeV Upgrade” ,

arXiv:0907.1901[nucl-th].


Major directions in theoretical interpretation of gvNN* electrocouplings

• Interpretation of gvNN* electrocouplings in LQCD.

• QCD-based description of gvNN* electrocouplings

within the framework of DSE.

• Combined LQCD and Light Cone Sum Rule (LCSR) approach.

• Constituent Quark Models.


N* electrocouplings from LQCD

F1,2 form factors for P-P11(1440) transition (exploratory calculations)

Current calculations with mp~0.5 GeV , stable P11(1440) and limited operator basis

H.W.Lin et al, Phys.Rev. D78, 114508 (2008)

Topics for discussion:

• Which N* parameters can be evaluated in LQCD for unstable excited states?

• Prospects to determine gvNN* electrocouplings from the QCD Lagrangian at Q2 >5.0 GeV2, approaching physical pion mass and appropriate box size.


LQCD & Light Cone Sum Rule (LCSR) Approach

S11(1535)CLASHall C

V.Braun et al., Phys. Rev. Lett.,103,072001 (2009).

mp=380 MeV

mp=280 MeV

Topics for discussions:• The prospects for evaluation of S11(1535) electrocouplings at

Q2>2.0 GeV2 with pion masses closer to physical limit. • Can these evaluations be extended for others parity partners?• Prospect to relate results on gvNN* electrocouplings and quark

distribution amplitudes in N*’s.


Dyson-Schwinger Equation (DSE) Approachstrong confinement

quark anom. chromo- magn. moment

quark anom. electro magn. moment

L.Chang et al, PRL 106, 072001 (2011)

Topics for discussions:• The prospects to observe manifestation of running dynamical

quark masses and structure in Q2 evolution of N* electrocouplings

• Prospects to compare LQCD and DSE evaluation for quark/gluon propagators and quark-gluon vertices in infrared


• Only available tool to evaluate electrocouplings of most N* states

• Electrocouplings of most excited proton states are already available

at Q2<4.0 GeV2 from hQCM by M. Giannini/E. Santopinto

Constituent Quark Models

Topics for discussions:• Light front and other approaches for relativistic treatment

• High Fock components at high Q2

• Prospects of AdS/CFT in describing N* electrocouplings at high Q2

How constituent quark models can be related to QCD in the domain 2.0<Q2<10 GeV2, where quark mass running becomes most evident ??


N* parameters from analyses of exclusive electroproduction channels

γv

N N’

N*,△

A3/2, A1/2, S1/2

GM, GE, GC

, , p hpp,..

N

, , ,..p h pp

N’+*

Resonant amplitudes Non-resonant amplitudes

A1/2, A3/2, and S1/2 electrocouplings are proportional to the helicity amplitudes for transition between the initial photon-proton state of the initial particle helicities, and the final state with unstable N*, D* resonances. Electrocouplings are well defined, directly related to N* structure and are part of observable quantities, e.g. cross sections.


N* parameters from analyses of exclusive electroproduction channels

• Separation of resonant/non-resonant contributions represents most challenging part, and can be achieved within the framework of reaction models.

• N* ‘s can couple to various exclusive channels with entirely different non-resonant amplitudes, while their electrocouplings should remain the same.

• Consistent results from the analyses of major meson electroproduction channels show that model uncertainties in extracted N* electrocouplings are under control.

• Will similar strategy be feasible for LQCD evaluation of gvNN* electrocouplings?


gvNN* electrocouplings from the CLAS data on Np/Npp electroproduction

N pp CLAS preliminary.

N p CLAS

Good agreement between the electrocouplings obtained from the Np and Npp channels. N* electrocouplings are measurable and model independent quantities.

I. Aznauryan,V. Burkert, et al., PRC 80,055203 (2009).

A1/2S1/2

A3/2

F15(1685)

A3/2

P11(1440) P11(1440)

D13(1520)

N p world

V. Burkert, et al., PRC 67,035204 (2003).

N p Q2=0, PDG.

N p Q2=0, CLAS

M. Dugger, et al., PRC 79,065206 (2009).


The web-page with the data on gvNN* electrocouplings

http://www.jlab.org/~mokeev/resonance_electrocouplings/

Numerical results on gvNN* electrocouplings determined from analysesof meson electroproduction data may be found in:

Relations between gvNN* electrocouplings and N* electromagnetic decay widths are given under the link “Definition”

The web-page incorporates all CLAS results, and only available for us part of the gvNN* electrocouplings obtained

worldwideThe CLAS data on ND electromagnetic form factors are published in I.G. Aznauryan, et al., PRC 80, 055203 (2009)

All comments can be sent to V.Mokeev [email protected]. Submission of the results on gvNN* electrocouplings is encouraged!

mailto:[email protected]


Reaction models for extraction of gvNN* electrocouplings at Q2>5.0 GeV2

• Separation between resonant/non-resonant contributions in N* analyses carried out so far was achieved employing reaction models with meson-baryon (MB) degrees of freedom.

• At Q2>5.0 GeV2 MB degrees of freedom are mostly replaced by relevant quark degrees of freedom. Such a behavior is encoded in MB vertices cut-off parameters (L2~1.0 GeV2), and supported by preliminary analyses of the CLAS p+p-p data at Q2>2.0 GeV2.


Reaction models for extraction of gvNN* electrocouplings at Q2>5.0 GeV2

• Reaction models are needed for description of Np and N pp electroproduction at W<2.0 GeV and Q2>5.0 GeV2 that employ relevant quark degrees of freedom, and which are capable of describing non-resonant contributions to p+n, p0p, pD and rp reaction channels, at least.

• Combined approaches that incorporate superposition of explicit MB/quark mechanisms and phenomenological parametrization of remaining contributions represent a reasonable initial option.


Preliminary analysis of the CLAS π+π-p electroproduction data at Q2>2.0 GeV2

Data fit requires to increase effective coupling with -p Regge trajectory by a factor ~1.8 Indication of the transition to other degrees of freedom

0.65

0.95

1.30

2.30

2.70

3.30

3.90

4.60

Q2 (GeV2)

Resonance structures become more prominent with increasing Q2.

D33, P13 ,F15

3/2+(1720) D13

Extension of JM model toward high Q2

Very p

relim

inary

dat

a an

d an

alysis


Workshop Expectations

Tools for based on QCD theoretical interpretations of gvNN* electrocouplings

further development

Reaction models for Np and Npp electroproduction at W<2.0 GeV and Q2>5.0 GeV2

establishment of the framework, commitments…..

The White Paper

v.i.mokeev nstar at high q2 workshop, may 16, 2011, jefferson lab, newport news, va victor i. mokeev...

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