basic tools: experiment and theory goals: unveil the dynamics of the strong interaction
DESCRIPTION
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 PresentationTRANSCRIPT
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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
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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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3Ralf W. Gothe
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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4Ralf W. Gothe
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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5Ralf W. Gothe
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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6Ralf W. Gothe
CLAS12 Approved ExperimentsProposal Contact Person Physics Energy
(GeV)PAC days Parallel
RunningRun Group days Comment
E12-09-103 Gothe, Mokeev N* at high Q2 11 60
80
20
20
120
E12-06-119(a) Sabatie DVCS pol. beam 11 80
E12-06-112 Avakian ep→eπ+/-/0 X 11 60
E12-06-108 Stoler DVMP in π0,η prod
L/T separation
11 80
8.8
6.6
20
20
E12-06-119(b) Sabatie DVCS pol. target 11 120 120
50
5
175
Assume polarized
experiments run 50% of
time w/ reversed field
E12-06- 109 Kuhn Long. Spin Str. 11 82
E12-07-107 Avakian TMD SSA 11 103
E12-09-007(b) Hafidi Partonic SIDIS 11 103
E12-09-009 Avakian Spin-Orbit Corr. 11 103
E12-06-106 Hafidi Color Trans. ρ0 11 40 40 40
E12-06-117 Brooks Quark Hadronizat. 11 60 60 60
E12-06-113 Bültman Neutron Str. Fn. 11 40 40 40 cond. appr.
E12-07-104 Gilfoyle Neutron mag. FF 11 56 56
26
82
007/008 need 26d reversed
fieldE12-09-007(a) Hafidi Partonic SIDIS 11 56
E12-09-008 Contalbrigo Boer-Mulders w/ Kaons 11 56
Total 1139 517
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7Ralf W. Gothe
quar
k m
ass
(GeV
)
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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8Ralf W. Gothe
Hadron Structure with Electromagnetic Probes
v N
p
p
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9Ralf W. Gothe
Hadron Structure with Electromagnetic Probes
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10Ralf W. Gothe
Cross Section Decomposition
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12Ralf W. Gothe
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13Ralf W. Gothe
What do we really know?
Spectroscopy
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14Ralf W. Gothe
Quark Model Classification of N*
(1232)
D13(1520)S11(1535)
Roper P11(1440)
+ q³g
+ q³qq
+ N-Meson
+ …
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16Ralf W. Gothe
“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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17Ralf W. Gothe
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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18Ralf W. Gothe
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19Ralf W. Gothe
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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20Ralf W. Gothe
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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21Ralf W. Gothe
Photoproduction of Lepton Pairs
’e+e-
Mee > 1.2 GeV for TCS analysis
CLAS/E1-6 CLAS/G7
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22Ralf W. Gothe
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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23Ralf W. Gothe
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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24Ralf W. Gothe
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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25Ralf W. Gothe
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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26Ralf W. Gothe
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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27Ralf W. Gothe
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)
Ahel = A1/2
2 – A3/22
A1/22 + A3/2
2
A1/2
A3/2
L. Tiator
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29Ralf W. Gothe
Kinematic Coverage of CLAS12
60 daysL= 1035 cm-2 sec-1, W = 0.025 GeV, Q2 = 0.5 GeV2
Genova-EG (e’,p) detected
W GeV
Q2 G
eV2 2 limit > 1 limit >
2 limit > 1 limit >
1 limit >
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30Ralf W. Gothe
Proton Electromagnetic Form Factors
green : Rosenbluth data (SLAC, JLab)
Pun05Gay02
JLab/HallA recoil polarization data
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31Ralf W. Gothe
Quark Transverse Charge Densities in Nucleons
longitudinally polarized nucleon
q+ = q0 + q3 = 0
photon only couples to forward moving quarks
quark charge density operator
p’p
z
Light-Front Formalism
Miller
(2007)
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32Ralf W. Gothe
transversely polarized nucleon
transverse spin
e.g. along x-axis :
dipole field pattern Carlson, Vanderhaegen (2007)
Quark Transverse Charge Densities in Nucleons
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33Ralf W. Gothe
data : Arrington, Melnitchouk, Tjon (2007)
densities : Miller (2007); Carlson, Vdh (2007)
induced EDM : dy = F2p (0) . e / (2 MN)
ρ0
ρT
Quark Transverse Charge Densities in the Proton
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34Ralf W. Gothe
p nn p -> + (1232) p -> N* (1440)
quadrupole pattern Tiator, Vdh (2008)Carlson, Vdh (2007)
Transverse Transition Densities
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35Ralf W. Gothe
p -> D13(1520)
Tiator, Vdh (2009)
ρ0
ρT
Transverse Transition Densities
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36Ralf W. Gothe
Elastic Scatteringtransverse quark distribution
in coordinate space
DISlongitudinal quark distribution
in momentum space
DES (GPDs)fully-correlated quark
distribution in both coordinate and momentum space
3-dim quark structure of nucleon3-dim quark structure of nucleonBurkardt (2000,2003)
Belitsky,Ji,Yuan (2004)
GGeneralizedeneralized P Partonarton D Distributionsistributions
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37Ralf W. Gothe
Fourier transform of GPDs gives simultaneous distributions of quarks w.r.t. longitudinal momentum x P and transverse position b
P + Δ/2
*Q2 >>
x + ξ
x - ξP - Δ/2
t = Δ2
ξ = 0
GGeneralizedeneralized P Partonarton D Distributionsistributions
H,H,E,E (x, ξ ,t)~ ~
GPDs
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38Ralf W. Gothe
DVCS Kinematics Coverage of the 12 GeV Upgrade
H1, ZEUS
JLab Upgra
de
11 GeV
H1, ZEUS
JLab @
12 G
eV11 GeV27
GeV
200 G
eV
W =
2 G
eV
Study of high xB domain requires high luminosity
HERMES
COMPASS
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39Ralf W. Gothe
Unpolarized beam, longitudinal target:
ULUL~~ sinsin {F {F11HH++ξξ(F(F11+F+F22)()(HH ++ξξ/(1+/(1+ξξ))EE) -) -
… … }d}d
~~
Kinematically suppressed
H(ξ,t)~
A =
=ξ ~ xB/(2-xB)
k = t/4M2
Unpolarized beam, transverse target:UTUT~ cos~ cossin(sin(ss--)){k(F{k(F22HH – – FF11EE) ) + …+ … }d}d
Kinematically suppressed
E(ξ,t)
How to Extract GPDs ?How to Extract GPDs ?
H(ξ,t)
Polarized beam, unpolarized target:
LULU~~ sinsin {F {F11HH++ξξ(F(F11+F+F22))HH ++kFkF2EE))}d}d ~~
Kinematically suppressed
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40Ralf W. Gothe
DVCS Polarized Beam Asymmetry
2/25/092/25/09 4040Volker Burkert, CLAS12 Workshop, GenoaVolker Burkert, CLAS12 Workshop, Genoa
e p ep
A =
=
LU~sin{F1H+…}d
Extract H(ξ,t)
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41Ralf W. Gothe
DVCS Longitudinal Target Asymmetry
e p ep
UL~sinIm{F1H+ξ(F1+F2)H...}d~
Extract H(ξ,t)~
2/25/092/25/09 4141Volker Burkert, CLAS12 Workshop, GenoaVolker Burkert, CLAS12 Workshop, Genoa
e p ep
A =
=
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42Ralf W. Gothe
Transverse Momentum Distributions
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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44Ralf W. Gothe
TMDs in SIDIS Land
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45Ralf W. Gothe
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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46Ralf W. Gothe
The sin2 moment gives access to the Kotzinian-Mulders function, which measures the momentum distribution of transversely polarized quarks in the longitudinally polarized nucleon.
TMDs in SIDIS Land
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47Ralf W. Gothe
per dressed quark
Summary and Outlook