Transcript Roadmap to the CLAS12 Physics Program Ralf W. Gothe Users Group Workshop and Annual Meeting June 8-10, 2009 Jefferson Lab, Newport News, VA  Basic Tools:

Roadmap to the CLAS12
Physics Program
Ralf W. Gothe
Users Group Workshop and Annual Meeting
June 8-10, 2009
Jefferson Lab, Newport News, VA
 Basic Tools: Experiment and Theory
 Goals: Unveil the dynamics of the strong interaction
 Connections: Not everything is difficult that sounds difficult
Ralf W. Gothe
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Jefferson Lab Today
Hall B
Hall A
Large acceptance spectrometer
electron/photon beams
Two high-resolution
4 GeV spectrometers
Hall C
A
7 GeV spectrometer
W. Gothe
1.8 GeVRalfspectrometer
B
C
2
6 GeV CEBAF
12
11
Upgrade magnets
and power
supplies
CHL-2
Two 1.1
0.6 GeV linacs
Enhanced capabilities
in existing Halls
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Overview of Upgrade Technical Performance Requirements
Hall D
Hall B
Hall C
4p hermetic detector
GlueEx
.
luminosity 1035
CLAS12
polarized photons hermeticity
Eg ~ 8.5-9.0 GeV
108 photons/s
good momentum/angle resolution
high multiplicity reconstruction
Hall A
High Momentum
High Resolution
Spectrometer SHRS Spectrometer HRS
precision
11 GeV beamline
space
target flexibility
excellent momentum resolution
luminosity up to 1038
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CLAS12
CLAS12
Forward
Detector
 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
1m
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CLAS12 Approved Experiments
Proposal
Contact Person
Physics
Energy
(GeV)
PAC days
E12-09-103
Gothe, Mokeev
N* at high Q2
11
60
E12-06-119(a)
Sabatie
DVCS pol. beam
11
80
E12-06-112
Avakian
ep→eπ+/-/0 X
11
60
Parallel
Running
Run Group days
Comment
80
120
E12-06-108
Stoler
DVMP in π0,η prod
L/T separation
11
80
8.8
6.6
20
20
20
20
E12-06-119(b)
Sabatie
DVCS pol. target
11
120
120
E12-06- 109
Kuhn
Long. Spin Str.
11
82
50
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
E12-09-007(a)
Hafidi
Partonic SIDIS
11
56
82
007/008 need
26d reversed
field
E12-09-008
Contalbrigo
Boer-Mulders w/ Kaons
11
56
Total
1139
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Assume
polarized
experiments
run 50% of
time w/
reversed field
5
26
517
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Physics Goals
p,r,w…
 Study
themass
structure
of the nucleon
spectrum
in the domain
Quark
extrapolated
to the
chiral limit,
where q
where dressed quarks are the major active degree of freedom.
is the momentum variable of the tree-level quark
 Explore the formation of excited nucleon states in interactions
using
Asqtad
action.
ofpropagator
dressed quarks
andthe
their
emergence
from QCD.
q
resolution
low
N,N*,D,D*…
LQCD
LQCD,(Bowman
DSE andet …
al.)
quark mass (GeV)
3q-core+MB-cloud
3q-core
e.m. probe
pQCD
high
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Hadron Structure with Electromagnetic Probes
lgp=1/2
gv
N
lgp=3/2
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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*
+ q³g
D13(1520)
S11(1535)
+ q³qq
+ N-Meson
+…
D(1232)
Roper P11(1440)
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“Missing” Resonances?
Problem: symmetric CQM predicts many more states than observed (in pN scattering)
Possible solutions:
1. di-quark model
old but always young
fewer degrees-of-freedom
open question: mechanism for q2 formation?
2. not all states have been found
possible reason: decouple from pN-channel
model calculations: missing states couple to
Npp (Dp, Nr), Nw, KY
3. coupled channel dynamics
new
all baryonic and mesonic excitations beyond the groundstate
octets and decuplet are generated by coupled channel
dynamics (not only L(1405), L(1520), S11(1535) or f0(980))
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FROST/HD gN pN’, hN, KL, KS, Npp
γp→K+Λ
L weak decay has
large analyzing power
Ralf 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 photoproduction amplitudes ➠ allows many
cross checks.
 7 observables measured in reactions
without recoil polarization.
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Quasi-Real Electroproduction
Meson spectroscopy:
exotic, high t, coherent, J/Y
Baryon spectroscopy:
heavy mass N*, hyperons
Time-like Compton
scattering: GPDs, …
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Quasi-Real Electroproduction
DDVCS?
Missing momentum analysis
of all final state particles
Meson spectroscopy:
exotic, high t, coherent, J/Y
ep  e e  pX
Baryon spectroscopy:
heavy mass N*, hyperons
Time-like Compton
scattering: GPDs, …
Double Deep Virtual
Compton scattering
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Photoproduction of Lepton Pairs
CLAS/E1-6
CLAS/G7
w
f
r
Mee > 1.2 GeV for
TCS analysis
ge+e-
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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.
A
e+
e-
CLAS12 projected
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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.
per dressed quark
Q2 = 12 GeV2 = (p times number of quarks)2 = 12 GeV2
DSE: lines and LQCD: triangles
p = 1.15 GeV
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.
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Constituent Counting Rule
S11 Q3A1/2
F15 Q5A3/2
P11 Q3A1/2
D13 Q5A3/2
A1/2 a 1/Q3
A3/2 a 1/Q5
F15 Q3A1/2
* a 1/Q4
GM
D13 Q3A1/2
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N → D Multipole Ratios REM , RSM
M. Ungaro
GD =
1
(1+Q2/0.71)2
 New trend towards pQCD behavior
does not show up.
 REM +1
 G*M
1/Q4
 CLAS12 can measure REM and RSM
up to Q²~12 GeV².
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Electrocouplings of N(1440)P11 from CLAS Data
PDG estimation
Np (UIM, DR)
Np, Npp combined analysis
Npp (JM)
The good agreement on extracting the N* electrocouplings between the two exclusive
channels (1p/2p) – having fundamentally different mechanisms for the nonresonant
background – provides evidence for the reliable extraction of N* electrocouplings.
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10-3 GeV-1/2
Electrocouplings of N(1520)D13 from the CLAS 1p/2p data
Ahel =
A1/22 – A3/22
A1/22 + A3/22
A1/2
L. Tiator
A3/2
world data
PDG estimation
Np (UIM, DR)
Np, Npp combined analysis
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Npp (JM)
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Kinematic Coverage of CLAS12
60 days
L= 1035 cm-2 sec-1, DW = 0.025 GeV, DQ2 = 0.5 GeV2
(e’,ppp) detected
Q2 GeV2
Genova-EG
2p limit > 1p limit >
2p limit > 1p limit >
1h limit >
W GeV
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Proton Electromagnetic Form Factors
green : Rosenbluth data (SLAC, JLab)
Pun05
Gay02
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JLab/HallA recoil
polarization data
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Quark Transverse Charge Densities in Nucleons
Light-Front Formalism
q+ = q0 + q3 = 0
z
p
p’
photon only couples to forward moving quarks
quark charge density operator
longitudinally polarized nucleon
Miller
(2007)
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Quark Transverse Charge Densities in Nucleons
transversely polarized nucleon
transverse spin
e.g. along x-axis :
dipole field pattern
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Carlson, Vanderhaegen (2007)
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Quark Transverse Charge Densities in the Proton
ρT
ρ0
induced EDM : dy = F2p (0) . e / (2 MN)
data : Arrington, Melnitchouk, Tjon (2007)
densities : Miller (2007); Carlson, Vdh (2007)
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Transverse Transition Densities
p
n
p -> D+ (1232)
p -> N* (1440)
Carlson, Vdh (2007)
quadrupole pattern
Tiator, Vdh (2008)
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Transverse Transition Densities
p -> D13(1520)
ρT
ρ0
Tiator, Vdh (2009)
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Generalized Parton Distributions
Burkardt (2000,2003)
3-dim quark structure of nucleon
Elastic Scattering
transverse quark distribution
in coordinate space
DIS
Belitsky,Ji,Yuan (2004)
DES (GPDs)
longitudinal quark distribution
fully-correlated quark
in momentum space
distribution in both coordinate
and momentum space
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Generalized Parton Distributions
Q2 >>
P - Δ/2
*
t = Δ2
x+
ξ
xξ
GPDs
~ ~
H,H,E,E (x, ξ ,t)
P + Δ/2
ξ=
0
Fourier transform of GPDs gives simultaneous distributions of quarks w.r.t.
longitudinal momentum x P and transverse position b
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DVCS Kinematics Coverage of the 12 GeV Upgrade
H1, ZEUS
H1, ZEUS
COMPASS
11 GeV
HERMES
Study of high xB domain
requires high luminosity
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How to Extract GPDs ?
 ~ xB/(2-xB)
D

=
A= 
2
 
k = t/4M2
Polarized beam, unpolarized target:
~
DLU ~ sinf {F1H+ξ(F1+F2)H +kF2E)}df
H(ξ,t)
Kinematically suppressed
Unpolarized beam, longitudinal target:
~
DUL ~ sinf {F1H+ξ(F1+F2)(H +ξ/(1+ξ)E) -… }df
~
H(ξ,t)
Kinematically suppressed
Unpolarized beam, transverse target:
DUT ~ cosfsin(fs-f){k(F2H – F1E) + … }df
E(ξ,t)
Kinematically suppressed
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DVCS Polarized Beam Asymmetry
D

=
A= 
2
 
ep
epg
DLU~sinf{F1H+…}df
Extract H(ξ,t)
2/25/09
Volker Burkert, CLAS12 Workshop, Genoa
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DVCS Longitudinal Target Asymmetry
D

=
A= 
2
 
ep
ep
epg
epg
~
DUL~sinfIm{F1H+x(F1+F2)H...}df
~
Extract H(ξ,t)
2/25/09
Volker Burkert, CLAS12 Workshop, Genoa
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Transverse Momentum Distributions
 TMDs are complementary to GPDs in that they allow to construct 3-D
images of the nucleon in momentum space
 TMDs can be studied in SIDIS experiments measuring azimuthal
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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TMDs in SIDIS Land
4 <Q2< 5 GeV2
The cos2F moment of the
azimuthal asymmetry gives
access to the Boer-Mulders
function, which measures the
momentum distribution of
transversely polarized quarks
in unpolarized nucleons..
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TMDs in SIDIS Land
The sin2F moment gives
access to the KotzinianMulders function, which
measures the momentum
distribution of transversely
polarized quarks in the
longitudinally polarized
nucleon.
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Summary and Outlook
per dressed quark
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