Study of n excitations in 2 pion production
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Study of N* excitations in 2-pion production. Analysis of p + p - p single differential cross-sections. Isobar Model JM05. V. Mokeev. g p  p - D ++. g p  p + D 0. g p  p + D 13 (1520). g p  r p. g p  p - P ++ 33 (1600). g p  p + F 0 15 (1685). direct 2 p production. JM06.

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Analysis of p p p single differential cross sections
Analysis of p+p-p single differential cross-sections.

Isobar Model JM05

V. Mokeev

gpp-D++

gpp+D0

gpp+D13(1520)

gprp

gpp-P++33(1600)

gpp+F015(1685)

direct2p production

JM06


Test of jm05 program on well known states
Test of JM05 program on well known states.

ep → epp+p-

A3/2,GeV-1/2

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

D13(1520)

Q2 GeV2

Q2 GeV2

→ JM05 works well for states with significant Npp couplings.


P 11 1440 and d 13 1520 electrocouplings from n p and p
P11(1440) and D13(1520) electrocouplings from Np and pπ+π-

P11(1440)

D13(1520)

from analysis of 1p CLAS data

from analysis of CLAS 2p data

within JM06

combined analysis of 1p/2p CLAS data

  • 2p data show clear evidence for sign flip of P11(1440) A1/2 electrocoupling.

  • Electrocouplings obtained in two independent analyses of 1p and 2p channels are in reasonable agreement.


First consistent amplitudes for a 1 2 q 2 a 3 2 q 2 of d 33 1700
First consistent amplitudes for A1/2(Q2), A3/2(Q2) of D33(1700)

Many of the higher mass states have significant coupling to Nππ.

State has dominant

coupling toNpp : PDG:80-90%

Np: (10-20)%

ep → epp+p-

D33(1700)


Study of n excitations in 2 pion production

Search for

New Baryon States


Study of n excitations in 2 pion production

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 model predicts

fewer states, with different underlying symmetry

group

|q2q>

2. States exist but have not been found.

|q3>

“Missing” Baryon States

Possible reason: they have small coupling to pN-channel.

  • Model expectations:Hadronic couplings toNpp(Dp, Nr) much larger, while photocouplings are more comparable to those for observed states. Other channels that may be sensitive to “missing” states are: KL, KS, pw


Study of n excitations in 2 pion production

Evidence for new baryon states? many states, not observed in either hadronic experiments or in meson photo- and electro-production.

- Is the P33(1600)*** is really there?

- One more 3/2+(1720) state ?

- New resonances in KY ?


Study of n excitations in 2 pion production

Search for Baryon States in many states, not observed in either hadronic experiments or in meson photo- and electro-production.gp pp+p -

  • Two methods:

  • Isobar models (similar approach as in single pion analysis):

    • energy-dependences of amplitudes are parameterized.

    • fits to several (or all) one-dimensional projections.

  • Event-by event analysis:

    • fit partial-wave content independently for every energy bin.

    • makes maximum use of all correlations in the multi-dimensional phase space.

    • ambiguities can give multiple solutions.


Su 6 xo 3 classification of baryons
SU(6)xO(3) Classification of Baryons many states, not observed in either hadronic experiments or in meson photo- and electro-production.

P33(1600)


Evidence for p 33 1600 state
Evidence for P many states, not observed in either hadronic experiments or in meson photo- and electro-production.33(1600) *** state

g p pp +p -

W=1.59 GeV

Sample data

Fit to high statistics

photoproduction data

requires inclusion of

P33(1600) state.

no P33(1600)

with P33(1600)


P 33 1600 state parameters
P many states, not observed in either hadronic experiments or in meson photo- and electro-production.33(1600) state parameters

world

this analysis


A new 3 2 1720 baryon state
A new 3/2 many states, not observed in either hadronic experiments or in meson photo- and electro-production.+(1720) baryon state?

  • epp +p -

ep

  • JM03 Isobar Model Analysis

Contributions from conventional

states only

Fit with new 3/2+(1720) state

M.Ripani et. al.

Phys. Rev. Lett.91, 022002 (2003)

Difference between curves due to

signal from possible 3/2+(1720) state


Study of n excitations in 2 pion production

Photo- and electroproduction comparsion many states, not observed in either hadronic experiments or in meson photo- and electro-production.

pp +p -

electroproduction

photoproduction

Q2=0

Q2=0

W(GeV)

W(GeV)


Total g p p p p cross section off protons
Total many states, not observed in either hadronic experiments or in meson photo- and electro-production.gppp +p -cross-section off protons.

no 3/2+

full calculation

Background

Resonances

Interference

  • Hadronic couplings and mass derived from the fit of virtual photon data, and 3/2+(1720) photocouplings fitted to the real photon data.

  • Signal from 3/2+(1720) state

    present, but masked by large

    background and destructive

    N*/background interference.


Parameters derived from combined analysis
Parameters derived from combined analysis many states, not observed in either hadronic experiments or in meson photo- and electro-production.

Mass and decays


Study of n excitations in 2 pion production

Search for CQM predicted states many states, not observed in either hadronic experiments or in meson photo- and electro-production..

CLAS

  • To reduce ambiguities, the search for new excited states aims at “complete” or nearly complete measurements in γp→πN, ηN, K+Y and γn→πN, K0Y and using combinations of beam, target, and recoil polarizations:

    • differential cross sections with unpolarized, circularly polarized, and linearly polarized photon beams,

    • recoil polarizations for hyperons,

    • longitudinally or transversely polarized proton and neutron (deuteron) targets.

  • Other reactions include γp → ρN, ωp, ππN with linearly polarized beams, and with polarized beam and polarized targets.


New results in p p 0
New Results in many states, not observed in either hadronic experiments or in meson photo- and electro-production.γp→pπ0

CLAS

FA06 solution

of SAID analysis

  • A1/2 from Nπ analysis for

  • S11(1535) now agrees with Nη results as was found earlier in electro-production.

  • Strong excitation of P13(1720) is consistent with earlier analysis of pπ+π- electro-couplings.


Photoproduction of k k 0
Photoproduction of K many states, not observed in either hadronic experiments or in meson photo- and electro-production.+Λ, K+Σ0

P11

K exchange

P13

CLAS

P13

Fit: Bonn-Gatchina group, Anisovich et al., 2007


Photoproduction of k 0
Photoproduction of K many states, not observed in either hadronic experiments or in meson photo- and electro-production.+Λ/Σ0

Fit with P13(1900)

Fit: Bonn-Gatchina group, Anisovich et al., 2007


P k polarization transfer
γ many states, not observed in either hadronic experiments or in meson photo- and electro-production.p—>K+Λ Polarization transfer

Quark-Diquark Model

(E. Santopinto, 2005)

Includes *** / **** states

CLAS

w/o P13(1900)

with P13(1900)

Coupled channel fit: Bonn-Gatchina group, Anisovich et al, 2007

Fit shows strong preference for second P13 state. Existence of this state would be evidence against the quark-diquark model.


Excited cascades
Excited Cascades many states, not observed in either hadronic experiments or in meson photo- and electro-production.Ξ*

CLAS

  • Advantage over search for N*’s and Y*’s is narrow widths of Ξ’s

  • Possible production mechanism through decay of excited hyperons – requires large acceptance and high luminosity experiments

Ξ(1320)

Possible production mechanism

Ξ(1530)

Missing mass MM(K+K+) works for narrow states, but higher energy and higher statistics are needed.


Search in p k k
Search in many states, not observed in either hadronic experiments or in meson photo- and electro-production.γp―>π-K+K+Ξ*

CLAS

Ξ(1530)

A Ξ state at 1.62GeV and 50 MeV width could be the 1* candidate in PDG. Such a state would be consistent with a dynamically generated Ξπstate. It would contradict quark models. Requires more statistics and PWA.

New high statististics run in 2008!


Study of n excitations in 2 pion production

CLAS many states, not observed in either hadronic experiments or in meson photo- and electro-production.

Experiment Status & Plans of Search for New N* States


D k 0 p p s

E many states, not observed in either hadronic experiments or in meson photo- and electro-production.γ=1.5 – 1.7

Ks

Λ

M(π+π-), GeV

M(pπ-), GeV

CLAS

γd→K0Λ, π-p, (ps)

Eγ=1.1-1.3 GeV

All polar angles

< 0.1%

of all data

Photons produced coherently from aligned diamond crystals are linearly polarized.

Online beam asymmetry for γn→π-p

Identify:

Ks→π+π-

Λ→pπ-

  • Plots show a 5 GeV run with the coherent edge at 1.9 GeV


Study of n excitations in 2 pion production
γ many states, not observed in either hadronic experiments or in meson photo- and electro-production.p →K+Λ

Projected Accuracy of Data (4 of over 100 bins)


Study of n excitations in 2 pion production

γ many states, not observed in either hadronic experiments or in meson photo- and electro-production.n →K0Λ

Projected Accuracy of Data (4 of over 100 bins)


Conclusions
Conclusions many states, not observed in either hadronic experiments or in meson photo- and electro-production.

  • The study of N* excitations in photo- and electroproduction of mesons from nucleons is key for the understanding of the strong force that confines the quarks into nucleons.

  • The experimental and theoretical analysis we are all engaged in will make gigantic contributions towards that goal.


Study of n excitations in 2 pion production

N*’s many states, not observed in either hadronic experiments or in meson photo- and electro-production.AREFUN !


Fit of clas 2 p data on 3 invariant masses and p angular distributions within the framework of jm05
Fit of CLAS 2 many states, not observed in either hadronic experiments or in meson photo- and electro-production.p data on 3 invariant masses and p- angular distributions within the framework of JM05.

s, mcbn

Q2=0.65 Gev2

Q2=0.95 Gev2

Q2=1.30 Gev2

W, GeV

Reasonable description of invariant mass and p- angular distributions was achieved in entire kinematics area covered by CLAS data.


Diquark quark model
Diquark-Quark Model many states, not observed in either hadronic experiments or in meson photo- and electro-production.

(E. Santopinto, 2005)

Spectrum predicted for masses below 2 GeV.

Includes all observed

*** & **** states