Transcript N*’s as determined from exclusive reactions Volker D. Burkert Outline:  Goals of the N* Program  Large Acceptance Detectors  N* related data from.

N*’s as determined from exclusive reactions
Volker D. Burkert
Outline:
 Goals of the N* Program
 Large Acceptance Detectors
 N* related data from JLab
 Status of the N* Analysis
 Upcoming experiments at Jlab @ 6 GeV
 Tools for more complex analyses
 Penta-Quarks and N*’s
 Conclusions
PAC25 - Mini Workshop on Nucleon Excited States, January 17, 2004, Kingsmill Resort
Goals of the N* Program
Two main motivations for the N* program:
• The study of the nucleon wave function though measurement
of e.m. transition form factors for known resonances,
e.g. D(1232), P11(1440), S11(1520), D13(1520), F15(1680), ...
=> analyze Np, Nh, (Npp) final states
• The study of the underlying symmetry properties through the search
for SU(6)xO(3) symmetry predicted, yet undiscovered resonances
(“missing resonance problem”), in measurements of Np, Npp, K+L,
K+S, pw, Nr, .. final states.
Large Acceptance Detectors for N* Physics.
CLAS: (photon and electron reactions)
 Measure many final states with mostly charged
particles simultaneously.
 Operate with high luminosity electron beams,
and with unpolarized and polarized energy-tagged
bremsstrahlung photon beams.
 Coverage for photons limited to lab angles < 45o
Crystal Barrel-ELSA: (photon reactions)
 CsI with excellent photon detection, e.g. Npopo , Npoh
SAPHIR-ELSA (photon reactions, detector dismantled)
 Charged particles in final state
GRAAL (photon reactions):
 BGO crystals, with excellent photon detection, limited
charged particle, polarized laser-backscattered tagged photon
Crystal Ball – MAMI (photon reactions)
neutral final states in limited W range
BES (Beijing) – N* in e+e- collisions.
LEPS – SPring-8 – (photon reactions)
 Charged particle detection in forward dipole spectrometer, and
TPC with large angle coverage.
Status of N*- exclusive meson production
Experiment
Reaction
E89-037
ep
ep
ep
eD
ep
ep
ep
ep
ep
ep
ep
ep
ep
ep
ep
ep
ep
ep
ep
E89-038
E89-039
E89-042
E01-102
E01-103
E91-002
E99-107
E91-024
E93-006
E99-108
E93-036
E93-030
E94-005
E91-023
eppo
enp+
enp+
eppeph
eppo
enp+
eppo
enp+
eppo
eppo
epw
epp+pepp+peppo
ep+n
eK+L
epp+peX
Physics
Data
Status
Analysis
Status
Publication
Status
REM, RSM
REM, RSM
gpN*
gnN*
gNS11
sLT’ ND
sLT’ ND
sLT’ NN*
sLT’ NN*
REM high Q2
REM high Q2
miss. N*
miss. Res.
miss. Res.
Aet, At
Aet
N*, miss N*
Axial ff
Aet
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
compl.
ongoing
ongoing
ongoing
--ongoing
ongoing
ongoing
ongoing
ongoing
ongoing
ongoing
ongoing
ongoing
started
ongoing
compl.
ongoing
ongoing
ongoing
PRL88, 122001 (2002)
in preparation
in preparation
--PRL86, 1702 (2001)
PRC68, 032201 (2003)
in CLAS review
----in preparation
----PRL91, 022002 (2003)
--PRC68, 035202 (2003)
PRL88, 82001 (2002)
PRL90, 131804 (2203)
--PRL91, 222002 (2003)
Status of N*- exclusive meson production
Experiment
Reaction
Physics
Data
Status
Analysis
Status
Publication
Status
E00-112
E91-011
E93-050
ep
ep
ep
eK+L
epp0
epg(p0)
miss. N*
REM,RSM
N*
compl.
compl.
compl.
ongoing
ongoing
compl.
PRL90, 131804
in preparation
nucl-ex/0308009
E94-014
ep
ep
epp0
eph
ND(1232)
S11(1535)
compl.
compl.
compl.
compl.
PRL82:45 (1999)
PRD60:052004 (1999)
Status of N*- exclusive meson production
Experiment
Reaction
Physics
Status
Data
Status
Analysis
Status
Publication
E89-004
E91-008
E93-033
E94-008
E94-103
E94-109
E99-013
E02-112
E03-105
gp
gp
gp
gD
gp
gp
gp
gp
gp
miss. N*
S11, P11
miss. N*
N*
N*
miss. N*
miss. N*
miss. N*
N*
compl.
compl.
compl.
compl.
compl.
ongoing
ongoing
tbd
tbd
ongoing
compl.
ongoing
ongoing
ongoing
ongoing
ongoing
-
nucl-ex/0305028
PRL89, 222002
in prep.
-
K+Y
ph
pp+phX
Np
pro
pw
K+Y
pN
Penta-Quark Baryons and N* Physics
E03E05-xxx
gd
K+K-p(n) 5-quark B5
sched.
ongoing PRL91, 252001(2003)
+
+
gp
K K p (n) 5-quark B5
sched.
ongoing PRL92, 01 (2004)
K0nK+
Status of N*- exclusive meson production
--E03-xxx
--E04-xxx
E04-xxx
E04-xxx
gd
K+K-p(n) 5-quark B5
gp
K+K-p+(n)
KonK+, ..
p-p-p-p
many
ed
ep
5-quark B5
Excited Q+
Search for X-Q+, X--
--sched
--sched.
tbd
tbd
ongoing
--ongoing
-------
PRL91, 252001(2003)
--PRL92, 01 (2004)
-------
Kinematics ep
epX, E=4GeV
2p thresh.
2
1.5
1
0.
0.5
1.0
1.5
ND(1232) Transition
 Data published after 1998
ND(1232) – current program
(data in hand, partially analyzed)
 pp0 with high statistics are currently being analyzed
covering Q2 = 0.1 – 6.0 GeV2
 ep
ep+n channel for Q2 = 0.1 – 6.0 GeV2
 Data on sLT’ for ppo, np+ in D(1232) region at Q2 < 4 GeV2
 Data on At , Aet for ppo, np+, pp- at Q2 < 4 GeV2
 Single and double polarization resp. functions – at Q2 = 1 GeV2
 Cross section for pp0 at backward p0 angles – at Q2 = 1 GeV2
 pp0 with high statistics taken at Q2 = 6.0 & 7.5 GeV2
Response Functions from p0 Electroproduction
in the D(1232) Region
ds/dW = sT + esL + esTTcos2f+ 2e(e+1)sLTcosf;
si(cosq*,W)
CLAS
Preliminary
N* program – ND(1232) transition
Q2=3GeV2
f
ND(1232) Transition
s T + es L = A0 + A1 P1 (cos q ) + A2 P2 (cos q )
+ A3 P3 (cosq ) + A4 P4 (cosq )
Polarization Observables
s = so[1 + P·sp + h(A + P’·sp)]
so = no(nLRL + nTRT - nLTRLTcos fpq + nTTRTTcos 2fpq)
Aso = no(-n’LTR’LT sin fpq)
Pnso = no(nLRnL + nTRnT - nLTRnLTcos fpq + nTTRnTTcos 2fpq)
Pl,tso = no(-nLTRl,tLTsin fpq + nTTRl,tTTsin 2fpq)
P’nso = no(-n’LTR’nLTsin fpq)
P’l,t so = no(-n’LTR’l,tLTcos fpq + n’TTR’l,tTT)
Response Functions – Hall A
PRELIMINARY
CLAS ND(1232) – Asymmetries
ND(1232) Transition
 Published + publicly presented
data.
ND(1232) Transition
HALL A
• With current data from CLAS,
Hall A & Hall C, JLab data on REM,
RSM, and GMD will cover the range
Q2 = 0.1 – 7.5 GeV2 with excellent
statistics and low systematics.
Results projected from
completed experiments.
Hall A data include recoil and
double polarization responses.
CLAS data include pp0, np+,
beam asymmetries Ae,
beam/target asymmetries
At, Aet
Analysis Tools for Meson Production above the D(1232)
 Unitary Isobar Model (JLab-Yerevan) for single p, h production
- Born terms + w, r exchange
- Resonances as relativistic Breit-Wigner
- Regge exchange at high W
 Fixed- t Dispersion Relations (JLab-Yerevan)
- Imaginary part of amplitude as sum of Resonances
- Real part by dispersion relations
- High energy behavior by Regge parametrization
 Isobar Model for two-pion analysis (JLab-Moscow-Genova)
- Non-resonant 3-body p.s., diffractive Nr, Dp, D13p,
Reggeon exchange at high W, s-channel Breit-Wigner
resonances
 Event-based Partial-Wave Analysis with Maximum-Likelihood
fits for Npp final state (RPI-JLab)
Second Nucleon Resonance Region
Resonances: P11(1440), S11(1535), D13(1520)
 Structure of the Roper P11 ?
• |Q3> quark state?
• |Q3G> state?
• |Ns> molecule?
• |Q4Q> penta-quark?
• quark core with meson cloud
 Structure of the S11(1535)
• hard transition form factor?
• a 3-quark resonance?
• a KS molecule?
 Q2 evolution of the D13 helicity structure, A3/2
dominance.
A1/2
Second Nucleon Resonance Region
 Single pion and eta production
1) ep
2) ed
3) ep
4) ep
5) ep
e(np+, ppo), Q2 = 0.1 – 5.0 GeV2
epp-(p)
Q2 = 0.1 – 3.5 GeV2
eph
Q2 = 0.1 – 5.0 GeV2
eppo
Q2 = 0.1 – 3.5 GeV2
ep+n
Q2 = 0.1 – 3.5 GeV2
E89-038,42 E1-6
E89-038/42
E89-039
E93-036
E93-036
 Global analysis using DR (JLab-Yerevan) and
UIM (JLab-Yerevan) fits performed for 1) - 3) at low Q2 .
 First analysis of a consistent set of p0, p+, h cross sections
and polarized beam structure functions.
The 2nd Resonance Region
CLAS
ep
enp+ Unitary Isobar fit
Fit to p, h Electroproduction
W = 1.23 GeV,
sT+esL, sTT, sLT
p+
W = 1.53 GeV
Q2=0.4 GeV2
UIM
DR
sLT’ (S)
Fit to p, h Electroproduction
po
p+
W = 1.18 – 1.58 GeV
UIM
W = 1.18 - 1.58 GeV
DR
Global Fit to h Photoproduction
h
h
W > 1.49 GeV
UIM
DR
sT, S
W > 1.49 GeV
Global Fit to h Photoproduction Target asymmetry
UIM
DR
Global Fit to h Photoproduction
UIM
stot
DR
First Results from JLab Global Analysis
Zero crossing?
Large longitudinal
coupling !
First Results from JLab Global Analysis
First Results from JLab Global Analysis – cont’d
10-3GeV-1/2
A1/2
S1/2
S11(1535)
S11(1535)
0
100
-20
80
60
0.5 Q2 (GeV2)
DR
UIM
h
DR
UIM
PDG
-40
0
p
0
0.5
Q2 (GeV2)
First Results from JLab Global Analysis – cont’d
D13(1520)
p
DR
UIM
h
DR
UIM
0
A1/2
200
A3/2
-50
100
-100
PDG
0
0.5
Q2 (GeV2)
S1/2
0
-50
-100
0
0.5
Q2 (GeV2)
0
0
0.5
Q2 (GeV2)
Third Nucleon Resonance Region
 Resonances: S31(1620), S11(1650), D13(1700), D15(1675),
F15(1680), P11(1710), P13(1720), D33(1700), …..
 Transition form factors in a large Q2 range
- test of the Single Quark Transition Model (SQTM)
for g + [56,0+]
[70,1-], and
g + [56,0+]
[56,2+] transitions
 Does the P11(1710) have a 5-quark component as required
by the chiral soliton model of Diakonov et al.? cSM
predicted the Q+(1540) as a 5-quark state.
 Main tools to study transitions in 3rd resonance region
- g*N
- g*N
Np
Npp, many states couple strongly to Npp
Test of the Single Quark Transition Model
Proton
Test of the Single Quark Transition Model
Neutron
Tools to search for “Missing” Resonances
 Search for new baryon states (N*, D) in Npp
- Developed Isobar Model for the analysis of pp+p- photoand electro-production data (Moscow-JLab-Genova).
- Developing IM including neutral channel, e.g. np+po, ppopo.
- Developed event-based PWA approach for the analysis of
pp+p- photo-production data.
 Search for new baryon states (N*, D) in KY.
- Appropriate tools for resonance analysis are currently
lacking. Coupled-channel analysis essential because of large
background.
 Search for new baryon states (N*) in pw.
- Dynamical Model developed by Y. Oh. We are adopting this
model to fit experimental data in single channel analysis. Need
to include other channels because of background.
Partial Wave Formalism for gp
pp+p-
 Transition matrix:
Tfi
=
<pp+p-;t
=
S<pp+p-;t
a
p+
f|T|gp;E>
pp
f|a><a|T|gp;E>
= Sya(tf)Va(E)
a
p
JP, M
D,N*
 Decay amplitude ya(tf) calculated using isobar
model:
e.g. JP, M = ½+, +½
[D++p-]l=1, lPf = +½
p
+
p
r, s
L
 Production amplitude Va(E) is fitted in unbinned
maximum likelihood procedure. Assume Va(E) is
independent of E in small energy range.
p
p
p
+
...
=
Waves in the current analysis
JP
M
Isobars
1/2+
1/2
Dp (={D++p-, Dop+})
1/2-
1/2
Dp, (pr)(s=1/2
3/2+
1/2, 3/2
(Dp)(l=1) ,(pr)(s=1/2) ,(pr)(s=3/2;l=1,3) ,N*(1440)p
3/2-
1/2, 3/2
(Dp) (l=0,2)
5/2+
1/2, 3/2
(Dp)(l=1), ps
5/2-
1/2, 3/2
(Dp)(l=2)
 Total of 35 waves (complex amplitudes)
 Diffractive production (“t-channel”) also included
Samples of event-based PWA for gp
F15(1680)?
P33(1600)?
A new P33?
pp+p-
Isobar Model for the g*N
 All established resonances
included as Breit-Wigners
 Non-resonant Born terms for
all D(1232)p isospin channels,
and for D13(1520)p channels.
 Non-resonant pro production
through diffractive ansatz.
 High mass behavior through
Reggeon exchange.
 Good fits to one-dimensional
cross sections at low pp+pmasses.
Npp channel
Isobar Model for the g*N
W=1.70 GeV Q2=0.
Npp channel
W=1.71 GeV Q2=0.65 GeV2
Isobar Model for the g*N
W=1.71GeV Q2=0.95 GeV2
Npp channel
W=1.71 GeV Q2=1.30 GeV2
Resonances in g*p
pp+p-
Total cross section
CLAS
Genova-Moscow
Isobar model fit
GNpp PDG
GNg AO/SQTM
(with amplitudes
adjusted)
missing resonance strength?
Isobar fit to D13(1700) and new PI3
Total cross section
CLAS
Isobar model fit
GNpp PDG
GNg AO/SQTM
PI3
D13(1700)
W(GeV)
Isobar fit - A new PI3 state?
W = 1.74GeV
CLAS
PI3
Mp+p
D13(1700)

Mp+p
M = 1.72 +/- 0.02 GeV 1650-1750
100-200
GT = 114 +/- 19 MeV
~0
Dp : 0. 63+/- 0.12
0.8 - 0.9
Nr : 0.19 +/- 0.09
-
qp- (deg)
Data described best by new PI3

consistent with “missing”
P13 state, but mass low
known P13
Strangeness Photoproduction
Dominant
resonances
S11(1650)
P11(1710)
P13(1720)
D13(1895) ?
Similar data sets
exist from SAPHIR.
Carnegie Mellon
Strangeness Photoproduction
 Sample of data covering the
full kinematic range in energy
and angles for K+L and K+S,
including recoil polarization
 Data indicate significant
resonance contributions,
interfering with each other
and with non-resonant
amplitudes.
 Extraction of resonance
parameters requires a large
effort in partial wave
analysis and reaction theory.
Strangeness in electroproduction
CLAS
ep
eK+Y response functions
Strangeness in electroproduction
CLAS
forward hemisphere
g*p
K+L
backward hemishere
known
N*
new N*?
CLAS - Resonances in gp
PRELIMINARY
Model: Y. Oh
OPE + Pomeron
N* Capstick model
Sum
w
g
p
p
g
w
p0
p
g
p
w
N*
p
p
pw?
w - electroproduction
above
resonance
region
g
s
w
p
p
g
p
-1
CLAS
w
N*
p
cosqpw
in
resonance
region
+1
Penta-Quark Baryons
• They are part of the baryon spectrum
• Some (most?) will mix with ordinary baryons, so they have to be
analyzed together with the other excited states.
• They may be produced via the decay of excited N*’s.
• They will help us to understand the symmetries underlying
the baryon spectrum
• They provide fundamentally new insight into how QCD works
in the complex regime where the interaction is strong
CLAS - Q Production on Protons
+
gp
Q+
p+K+K-
N*5 ?
(n)
7.8s
g
cut
p+
pN*
Combined analysis of all CLAS data
p
on protons with > 5 GeV beam
Q+
energy; minimal cuts - forward p+,
backward K+.
V. Kubarovsky, et al.; PRL submitted
KK+
n
NA49 Experiment – Q+
M(p,K0,K-), if 1.525 M(p,K0)<1.545 GeV
Conclusions
What is needed for a full success of the N*
program?
 More data on polarization observables
• linearly polarized photons
• transverse/longitudinally polarized
hydrogen and deuterium targets
 Full coupled channel analysis including all
final states, in all isospin channels
 Excited Baryon Analysis Center