1 Ralf W. Gothe Basic Tools: Experiment and Theory Goals: Unveil the dynamics of the strong interaction Connections: Not everything is difficult Ralf W. Gothe Users Group Workshop and Annual Meeting June 8-10, 2009 Jefferson Lab, Newport News, VA Roadmap to the CLAS12 Physics Program
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Basic Tools: Experiment and Theory Goals: Unveil the dynamics of the strong interaction
Roadmap to the CLAS12 Physics Program. Ralf W. Gothe. Basic Tools: Experiment and Theory Goals: Unveil the dynamics of the strong interaction Connections: Not everything is difficult that sounds difficult. Users Group Workshop and Annual Meeting June 8-10, 2009 - PowerPoint PPT Presentation
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1Ralf W. Gothe
Basic Tools: Experiment and Theory Goals: Unveil the dynamics of the strong interaction Connections: Not everything is difficult that sounds difficult
Ralf W. Gothe
Users Group Workshop and Annual MeetingJune 8-10, 2009
Jefferson Lab, Newport News, VA
Roadmap to the CLAS12 Physics Program
2Ralf W. Gothe
A B C
Jefferson Lab Today
Two high-resolution 4 GeV spectrometers
Large acceptance spectrometer electron/photon beams
7 GeV spectrometer 1.8 GeV spectrometer
Hall A Hall B
Hall C
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6 GeV CEBAF11
CHL-2CHL-2
12
Upgrade magnets Upgrade magnets and power and power suppliessupplies
Two 0.6 GeV linacs1.1
Enhanced capabilities in existing Halls
1.1
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Overview of Upgrade Technical Performance Requirements
Hall D Hall B Hall C Hall A4 hermetic detector
GlueExluminosity 1035
CLAS12High Momentum
Spectrometer SHRSHigh Resolution
Spectrometer HRS
polarized photons hermeticity precision space
E~ 8.5-9.0GeV 11 GeV beamline
108 photons/s target flexibility
good momentum/angle resolution excellent momentum resolution
high multiplicity reconstruction luminosity up to 1038
.
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CLAS12
Luminosity > 1035 cm-2s-1
Baryon Spectroscopy N and N* Form Factors GPDs and TMDs DIS and SIDIS Nucleon Spin Structure Color Transpareny …
Central Detector
Forward Detector
1m
CLAS12
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CLAS12 Approved ExperimentsProposal Contact Person Physics Energy
Quark mass extrapolated to the chiral limit, where q is the momentum variable of the tree-level quark propagator using the Asqtad action.
… resolution
low
high
q
e.m. probe
LQCD (Bowman et al.)
Physics Goals
N,N*,*…
3q-core+MB-cloud
3q-core
pQCD
LQCD, DSE and …
Study the structure of the nucleon spectrum in the domain where dressed quarks are the major active degree of freedom.
Explore the formation of excited nucleon states in interactions of dressed quarks and their emergence from QCD.
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Hadron Structure with Electromagnetic Probes
v N
p
p
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Hadron Structure with Electromagnetic Probes
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Cross Section Decomposition
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What do we really know?
Spectroscopy
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Quark Model Classification of N*
(1232)
D13(1520)S11(1535)
Roper P11(1440)
+ q³g
+ q³qq
+ N-Meson
+ …
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“Missing” Resonances?
fewer degrees-of-freedom open question: mechanism for q2 formation?
Problem: symmetric CQM predicts many more states than observed (in N scattering) Possible solutions: 1. di-quark model
2. not all states have been found
possible reason: decouple from N-channel model calculations: missing states couple to N, N, N, KY
3. coupled channel dynamicsall baryonic and mesonic excitations beyond the groundstate octets and decuplet are generated by coupled channel dynamics (not only (1405), (1520), S11(1535) or f0(980))
old but always young
new
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Process described by 4 complex, parity conserving amplitudes 7 well-chosen measurements are needed to determine amplitude. For hyperon finals state 16 observables will be measured in CLAS huge ➠redundancy in determining the photo-production amplitudes allows many ➠cross checks. 7 observables measured in reactions without recoil polarization.
weak decay has large analyzing power
γp→K+Λ
FROST/HD N N’, N, K, K, N
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Quasi-Real Electroproduction
Meson spectroscopy:exotic, high t, coherent, J/
Baryon spectroscopy:heavy mass N*, hyperons
Time-like Compton scattering: GPDs, …
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Quasi-Real Electroproduction
Meson spectroscopy:exotic, high t, coherent, J/
Baryon spectroscopy:heavy mass N*, hyperons
Time-like Compton scattering: GPDs, …
DDVCS?
pXeeep
Missing momentum analysis
of all final state particles
Double Deep Virtual Compton scattering
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Photoproduction of Lepton Pairs
’e+e-
Mee > 1.2 GeV for TCS analysis
CLAS/E1-6 CLAS/G7
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Color Transparency Color Transparency is a spectacular prediction of QCD: under the right
conditions, nuclear matter will allow the transmission of hadrons with reduced attenuation.
Unexpected in a hadronic picture of strongly interacting matter, but straightforward in quark gluon basis.
Small effects observed at lower energy. Expect significant effects at higher energy.
CLAS12 projected
A
e+
e-
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Dynamical Mass of Light Dressed Quarks
DSE and LQCD predict the dynamical generation of the momentum dependent dressed quark mass that comes from the gluon dressing of the current quark propagator.
These dynamical contributions account for more than 98% of the dressed light quark mass.
The data on N* electrocouplings at 0<Q2<12 GeV2 will allow us to chart the momentum evolution of dressed quark mass, and in particular, to explore the transition from dressed to almost bare current quarks as shown above.
Q2 = 12 GeV2 = (p times number of quarks)2 = 12 GeV2 p = 1.15 GeV
per dressed quark DSE: lines and LQCD: triangles
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S11 Q3A1/2
F15 Q5A3/2
P11 Q3A1/2
D13 Q5A3/2
F15 Q3A1/2
D13 Q3A1/2
Constituent Counting Rule
A1/2 1/Q3
A3/2 1/Q5
GM 1/Q4*
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N → Multipole Ratios REM , RSM
New trend towards pQCD behavior does not show up.
CLAS12 can measure REM and RSM up to Q²~12 GeV².
REM +1
M. Ungaro
GM 1/Q4*
GD = 1
(1+Q2/0.71)2
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Electrocouplings of N(1440)P11 from CLAS Data
N (UIM, DR)PDG estimation N, N combined analysis N (JM)
The good agreement on extracting the N* electrocouplings between the two exclusive channels (1/2) – having fundamentally different mechanisms for the nonresonant background – provides evidence for the reliable extraction of N* electrocouplings.
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Electrocouplings of N(1520)D13 from the CLAS 1/2 data
world data
10-3 G
eV-1
/2
N (UIM, DR)PDG estimation N, N combined analysis N (JM)
TMDs are complementary to GPDs in that they allow to construct TMDs are complementary to GPDs in that they allow to construct 3-D images of the nucleon in of the nucleon in momentum space space
TMDs can be studied in TMDs can be studied in SIDISSIDIS experiments measuring azimuthal experiments measuring azimuthal asymmetries or moments.asymmetries or moments.
Semi Inclusive Deep Inelastic Scattering
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TMDs in SIDIS Land
Many spin asymmetries
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TMDs in SIDIS Land
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The cos2 moment of the azimuthal asymmetry gives access to the Boer-Mulders function, which measures the momentum distribution of transversely polarized quarks in unpolarized nucleons..
4 <Q2< 5 GeV2
TMDs in SIDIS Land
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The sin2 moment gives access to the Kotzinian-Mulders function, which measures the momentum distribution of transversely polarized quarks in the longitudinally polarized nucleon.