The N* programme at CLAS Dan Watts University of Edinburgh For the - - PowerPoint PPT Presentation
The N* programme at CLAS Dan Watts University of Edinburgh For the CLAS collaboration at Jefferson Lab 1 Outline Outline Outline General motivations General motivations Observables in meson Observables in meson
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Dan Watts University of Edinburgh For the CLAS collaboration at Jefferson Lab
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Masses, widths, and coupling constants not well known for many constants not well known for many resonances resonances Many models: relativised quark model, Goldstone-boson exchange,
model, Goldstone-boson exchange, diquark and collective models, instanton-induced interactions, flux- tube models, holographic dual, lattice QCD… Big Puzzle: Most models Big Puzzle: Most models predict more resonance states predict more resonance states than observed than observed
Lattice QCD predictions Hadron spectrum collab. Arxiv:1104.5152 (2011)
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γ γ γ
Finding missing resonances and better establishing the properties of “known” resonances requires an extensive measurement programme Requires measurement of a complete or close to complete set of
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Such goals are finally coming within reach ! Such goals are finally coming within reach !
The CLAS facility will contribute a large fraction of the required high quality meson quality meson photoproduction photoproduction data data
Differing isospin overlaps of N* and ∆+ for the π0 p and π+ n final states The π0 p and π+ n final states can help distinguish between the ∆ and N*
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2 1 3 2 1 2 1 3 2 3 2 1 3 2 1 2 1 3 2 3
+
The ηp, K+Λ and pω systems have I=½ and act as isospin isospin filters filters to the resonance spectrum.
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σ σ Σ Σ T T P P E E F F G G H H T Tx
x
T Tz
z
L Lx
x
L Lz
z
O O
x x
O O
z z
C C
x x
C C
z z
Proton target Proton target p pπ π0
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
n nπ π+
+
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
p pη η
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
p pη η’ ’
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
p pω ω
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K K+
+Λ
Λ
✔ ✔ ✓ ✓ ✓ ✓ ✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✔ ✔ ✔ ✔
σ σ Σ Σ T T P P E E F F G G H H T Tx
x
T Tz
z
L Lx
x
L Lz
z
O O
x x
O O
z z
C C
x x
C C
z z
Proton target Proton target p pπ π0
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
n nπ π+
+
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
p pη η
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
p pη η’ ’
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
p pω ω
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K K+
+Λ
Λ
✔ ✔ ✓ ✓ ✓ ✓ ✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✔ ✔ ✔ ✔
✔ -
published, , ✔ -
acquired, , planned planned
K K Λ Λ K K+
+Σ
Σ0
✔ ✔ ✓ ✓ ✓ ✓ ✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✔ ✔ ✔ ✔
K K0*
0*Σ
Σ+
+
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓
Neutron target Neutron target p pπ π-
✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
p pρ ρ-
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K K-
Σ+
+
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K K0
0Λ
Λ
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K K0
0Σ
Σ0
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K K0*
0*Σ
Σ0
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K K Λ Λ K K+
+Σ
Σ0
✔ ✔ ✓ ✓ ✓ ✓ ✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✔ ✔ ✔ ✔
K K0*
0*Σ
Σ+
+
✔ ✔ ✓ ✓ ✓ ✓ ✓ ✓
Neutron target Neutron target p pπ π-
✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
p pρ ρ-
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K K-
Σ+
+
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K K0
0Λ
Λ
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K K0
0Σ
Σ0
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K K0*
0*Σ
Σ0
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K+Σ-
tracking, calorimetry, time of flight Near complete coverage in azimuthal angle and from 8°to 140°in polar angle.
accelerator with two LinAc sections. Operating at up to 6 GeV.
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Eγ = 20-95% of E0 - up to ~5.5 GeV Unpolarised, circularly polarised or linearly polarised photons
(→ timing)
Circular polarization from 100% polarized electron beam Circular polarization from 100% polarized electron beam
Circular photon beam from longitudinally polarized electrons Electron beam polarization > ~85%
Counts
14 Circular polarization Circular polarization
2 2
3 4 4 4 k k k k P P
e
+ − − ⋅ =
γ
k = Eγ/Ee
Coherent bremsstrahlung from 50 oriented diamond Two linear polarization states (vertical & horizontal)
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Analytical QED coherent bremsstrahlung calculation fit to actual spectrum
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Longitudinal nucleon polarisation (g9a) more recently with transverse (g9b)
Butanol composition: C composition: C4H9OH OH
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Carbon target used to measure bound nucleon measure bound nucleon contribution of contribution of butanol butanol
Frozen spin butanol (C4H9OH) Pz ≈ 80% Target depolarization: τ ≈100 days
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For g9a (longitudinal orientation) ~10% of time polarizing target For g9b (transverse orientation) ~ 5% of time polarizing target
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2 / 3 2 / 1 2 / 3 2 / 1
C zP
2 / 3 2 / 1 2 / 3 2 / 1
C Z
C z
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2 / 3 2 / 1
C Z
H bound H
γ p →p π+ π- X
Butanol
Butanol Bound nucleon events Bound nucleon events
m2
X(GeV2)
Counts
V/c) Scale factors = Butanol/Carbon Carbon z (cm) Counts Proton momentum (GeV Proton angle (deg)
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2 / 3 2 / 1 2 / 3 2 / 1
PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY
γ+ p → p + X p0= 1.00 ± 0.04 γ + p → p + X (n.c.) p0= 1.02 ± 0.04
PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY
γ + p → p + X (γ det.) p0= 0.99 ± 0.04 γ + p → p + X (γ det. n.c.) p0= 0.98 ± 0.04 *n.c. implies no charged particles other than the proton. cos(θc.m.)
within statistical uncertainties
PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY
E
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PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY
Preliminary data prefers SAID for W >1.75 GeV
cos(θc.m.)
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For W> 1.75 GeV none of the models represents the data well. For W< 1.75 GeV all of the models represent the data fairly well.
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W = 1.433 GeV W = 1.465 GeV W = 1.497 GeV W = 1.433 GeV W = 1.497 GeV W = 1.588 GeV W = 1.558 GeV W = 1.528 GeV
W = 1.617 GeV W = 1.646 GeV
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W = 1.674 GeV W = 1.702 GeV W = 1.730 GeV W = 1.809 GeV W = 1.783 GeV W = 1.756 GeV
W = 1.835 GeV W = 1.860 GeV W = 1.885 GeV W = 1.910 GeV W = 1.934 GeV W = 2.041 GeV W = 1.994 GeV W = 1.959 GeV
Agreement with models breaks down for W > 1850 > 1850 MeV MeV
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Models represent the data better than for K K+
+ Λ
Λ
z T T
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p3 = pTpzfG
Asymmetry +ve polarised target
PRELIMINARY! PRELIMINARY!
Asymmetry -ve polarised target
PRELIMINARY PRELIMINARY
W = 1475-1500 MeV W=1640 – 1680 MeV
SAID MAID2007 Bonn-Gatch
PRELIMINARY
Early stage results -
beam polarization values
PRELIMINARY
W = 2032 – 2088 MeV W = 1840 - 1880 MeV
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Beam: Circular polarization; Linear polarization; Un-polarized Data obtained for Σ, F, H, P and T T (for (for pseudoscalars pseudoscalars)
Data is in calibration phase right now
Beam Target Observable
σ σ d d
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) sin( ) cos( 1 ϕ β ϕ β σ σ − + − − Ω = Ω T P F P P d d d d
lab xy lab xy
) 2 sin( ) cos( ) 2 cos( 1 ϕ ϕ β ϕ σ σ − + Σ − Ω = Ω H P P P d d d d
T lab xy T
σ0 = unpolarized cross section, PT = transverse beam polarization P0= circular polarization, Pz= longitudinal target polarizaion CircularTransverse
) 2 cos( ) sin( ) sin( ϕ ϕ β ϕ β − − − + P P P T P
T lab xy lab xy
Linear Transverse
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Used only 2 uncalibrated runs Eγ from 0.65 to 1.2 GeV cos(θπ
c.m.) = 0.95
T = -0.34 ± 0.09
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Target offset (in φ) is within one standard deviation of the set value (-60 degrees) The measured value of T is within 1.14 standard deviations of SAID TSAID
SAID =
= -0.440 440
CLAS will provide a large fraction of the quality data needed to better constrain the reaction amplitudes in meson photoproduction → Improve determination of “known” resonance properties and a basis to search for predicted but unseen resonances Preliminary beam-target observables for pion, K+, η photoproduction differentiate between models and indicate various mass regions where no
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differentiate between models and indicate various mass regions where no models currently describe the data → implications for resonance properties to be assessed when data finalised! More to come from CLAS: lots lots of data for π+ π- p, pω, transverse target
An exciting time for nucleon spectroscopy !
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