Baryon spectroscopy at CLAS and CLAS12 Baryons’10, Dec 2010, Osaka, Japan Ken Livingston, University of Glasgow, Scotland For the CLAS collaboration • Hadron spectroscopy at CLAS • The N* programme • CLAS 12 • Summary • Hadron spectroscopy at CLAS • The N* programme • CLAS 12 • Summary • Study of nucleon resonances: • Measurement of the transition form factors • Search for missing states • Strangeness production • and production • Cascade spectroscopy • Search for “unconventional states” • high statistics search of pentaquark states • search for hybrid mesons
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Baryon spectroscopy at CLAS and CLAS12 Baryons’10, Dec 2010, Osaka, Japan Ken Livingston, University of Glasgow, Scotland For the CLAS collaboration Hadron.
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Baryon spectroscopy at CLAS and CLAS12
Baryons’10, Dec 2010, Osaka, Japan
Ken Livingston, University of Glasgow, ScotlandFor the CLAS collaboration
• Hadron spectroscopy at CLAS
• The N* programme
• CLAS 12
• Summary
• Hadron spectroscopy at CLAS
• The N* programme
• CLAS 12
• Summary
• Study of nucleon resonances:• Measurement of the transition form factors• Search for missing states
• Strangeness production• and production• Cascade spectroscopy
• Search for “unconventional states”• high statistics search of pentaquark states• search for hybrid mesons
> 100 analyses in progress
Missing baryon resonances
• Clear indication of resonances in γp cross section for many channels
• Constituent quark models predict many resonances, but several missing
• Mostly from πN scattering and single π photoproduction
• Eg. Cross sections show some hints of new D13.
• Better to look at angular distributions and polarization observables.
•Really missing or undetected since weak coupling to these channels
• Try other channels. Eg. K photoproduction
With D13
Without D13
Mart & Benhold, Phys. Rev. C 61 012201(R) (1999)
After Cx, Cy from CLAS, revised as most likely P13. Eur Phys J A34 (07) 243
Polarization observables in pseudoscalar meson production
4 Complex amplitudes: 16 real polarization observables.
Complete measurement from 8 carefully chosen observables.
πN has high statistics but in KY recoil is self-analysing
I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975).I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975).
• “Only” need to know Plin, the degree of linear polarization.
1st pol. observables in K photoproduction on p at CLAS.
P, Cx and Cz
2 2 2x zR P C C
→ fully polarised
R. Bradford et al., Phys. Rev. C 75, 035205 (2007).
g8b, July 2005Lin. polarized photon energy range: 1.3 – 2.1 GeV
preliminary results:p, Mike Dugger, ASU
CLAS data SAID
• Very high statistics. Good agreement with previous measurement. • We have P well determined – expect <5% systematic error in P.• ~10MeV Eg bins, and will extend up to 2.1GeV• Similar for np, ’p
Bea
m A
sym
met
ry Σ
g8b preliminary results - and
Craig Paterson, Glasgow
pppp
Single polarization observablesPhoton asymmetryP Recoil polarization (induced pol. along y)T Target asymmetry
Double polarization observablesOx Polarization transfer along xOz Polarization transfer along z
figure by R.Schumacher, CMU
g8b preliminary results -
• Results compared with previous results from LEPS
• 6, 100MeV Energy bins
• 1550 -> 2050MeV
• More bins for our data
Increase the angular coverage to backward angles
LEPS also recently have some consistent, new points at backward angles.Hicks et al., PRC 76, 042201(R) (2007).
PREL
IMIN
A
RY
g8b preliminary results -
Ox/O
z extracted from fit to 2d asymmetry
T Target asymmetry from 2d asymmetry (not shown)
P Recoil pol. from acceptance corrected proton dist.
g8bGRAALCLAS J.W.C. McNabb, et al. (CLAS) Phys. Rev. C 69, 042201(R) (2004).
P R
ecoi
l pol
.
G8 summary
Several analyses at advanced stage. Only a small sample presented here
Single (P,T,) and double (Ox,O
z) polarization observables
pnp, ’p, pp : polarization photon beam asymmetry,
…. several publications expected next year
Meson photoproduction with linearly and circularly polarized photons on polarized target
g9a running conditionsNovember 3, 2007– February 12, 2008Longitudianally polarized targetCircularly and linearly polarized photon beam 0.5-2.4 GeVTrigger: at least one charged particle in CLASTarget Pol > 80%, Relaxation time > 1600hrs – better that design goals
g9 FROST – FROzen Spin Target (butanol = C4H9OH)
g9b March – July 2010 Transversely polarized target
Racetrack coils for transverse polarization
butanol 12C CH2
g9 FROST sample analysis of gp+n
butanol 12C CH2
Steffen Strauch, University of South Carolina
PREL
IMIN
A
RY
• G10. Unpolarized photons on Deuterium• 1st measurement of σ for the γ n → K+ Σ-
Measurements on n (Deuterium) target
• Detect - n, K+
• Σ from - n inv. mass
• Circularly and linearly polarized photons on n (g13, Deuterium target)• γ n → K+ Σ- analysis for polarization observables underway. Edwin Munevar, GWU
Sergio Anefalos Pereira, INFN. Phys. Lett. B 688 (2010) 289-293
• CLAS Data ▲ LEPS _____ Gent RPR model
Edwin Munevar, GWU
PREL
IMIN
A
RY
Measurements on n (Deuterium) target
• G13 Linearly polarized photons on n (Deuterium)• Measurement of for γ n → - p Daria Sokhan, Edinburgh
PREL
IMIN
A
RY
PREL
IMIN
A
RY
G13 1st measurement of Beam Asymmetry n (p)s p
Neil Hassall, Glasgow
Single, and double polarization observables in progress
Measurements on n (Deuterium) target
Measurements on n (Deuterium) target
HDIce Solid Deuterium-Hydride (HD) – a new class of polarized target
• Spin can be moved between H and D with RF transitions
• All material can be polarized with almost no background
• Run in Spring 2011
• Spin density matrix elements in bins ΔW = 10 MeV, for W = 1.7–2.4 GeV in blue - blue shades. • Previous world data in red.
Search for baryon states in γp pω pπ➝ ➝ +π-(π0)
M. Williams, et al. (CLAS) , Phys.Rev.C80:065208,2009 M. Williams, et al. (CLAS) , Phys.Rev.C80:065209,2009
F15(2000)/G17(2190)
The CLAS data are used as input to a single channel event-based, energy independent partial wave analysis (the first ever for baryons).
ω production is dominated by the well known F15(1680), D13(1700) and G17(2190), and a predicted “missing” F15(2000).
Preliminary Σ for γ p →ω p
Oh, et al Patrick Collins, ASU
Paris
Sarantsev, et al
CHL-2CHL-2
Upgrade of the arc magnets
12 GeV CEBAF Construction of the new Hall D
Beam Power: 1MWBeam Current: 90 µAMax Pass energy: 2.2 GeVMax Enery Hall A-C: 10.9 GeVMax Energy Hall D: 12 GeV
Upgrade of the instrumentation of the existing Halls
< 6 GeV
Spectroscopy with CLAS12
The construction of Low Q Tagging Facility or Forward Tagger has been proposed to continue the spectroscopy program with CLAS12 using quasi-real photoproduction
• electron scattering at “0” degrees (LowQ, post-target tagging): low-Q2 virtual photon real photon
• photons tagged by detecting the scattered electron
• quasi-real photons are linearly polarized and the polarization can be determined event by event
• high luminosity on thin (gas)- targets
• can exploit CLAS12 PiD for final states with strangeness
• Complementary to GLUEX Coh. Brem. photon beam
• Parasitic running
A new physics programme•Meson spectroscopy
– Spectroscopy on H target and search for exotics– Spectroscopy on 4He and other gas targets
•Hadron spectroscopy– Heavy mass baryon resonances (Cascades and -)