The 12 GeV Upgrade of

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Nov 16, 2013 (4 years and 1 month ago)

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The 12 GeV Upgrade of
Jefferson Lab

Volker Burkert

Jefferson Lab

Highlights of the 12 GeV Science Program



New and revolutionary access to the structure
of the proton and neutron (GPDs, TMDs)


Unlocking the secrets of QCD: confinement and
space
-
time dynamics


Exploring the quark structure of nuclei


Precision tests of the Standard Model

JLab Upgrade to 12 GeV

CHL
-
2

Enhance equipment
in existing halls

Add new
hall

New Capabilities in Halls A, B, & C, and a New Hall D

9

GeV tagged polarized photons
and a 4


hermetic detector

D

Super High Momentum Spectrometer (SHMS)
at high luminosity and forward angles

C

High Resolution Spectrometer (HRS) Pair,
and specialized large installation experiments

A

CLAS12 with new detectors and
higher luminosity (10
35
/cm
2
-
s)

B

New and revolutionary access to the
structure of the proton and neutron

CLAS12

2m

Forward

Detector

Central

Detector


Lum > 10
35
cm
-
2
s
-
1



GPDs & TMDs



Nucleon Spin Structure



N* Form Factors



Baryon Spectroscopy



Hadron Formation

Generalized Parton Distributions and 3D Quark Imaging

Proton form factors,
transverse
charge &
current densities

Last 50 years

Structure functions,

quark
longitudinal

momentum & spin

distributions

Last 40 years

?

Correlated
quark momentum

and helicity distributions in

transverse space
-

GPDs

Last 10 years

x


Deeply Virtual Compton Scattering (DVCS)

2x



longitudinal

momentum transfer

x


longitudinal quark


momentum fraction


t



Fourier conjugate

to transverse impact

parameter

Basic Process


Handbag Mechanism





x
B

2
-
x
B

x

=

GPDs depend on 3 variables, e.g
.
H(x,
x
Ⱐ琩,

They probe

the quark structure at the amplitude level.

What is the physical content of GPDs?

t

x+
x

x
-
x

hard vertices

g

Physical content of GPDs

M
2
(t)

:
Mass distribution inside the nucleon



J (t)

:
Angular momentum distribution


d
1
(t)

:
Forces and pressure distribution


Nucleon matrix element of the Energy
-
Momentum Tensor

contains three form factors:

GPDs are related to these form factors through moments

Kinematics of deeply virtual

exclusive processes

H1, ZEUS

H1, ZEUS

0.7

Study of high x
B

domain requires
high luminosity

The path towards the extraction of GPDs

Selected

Kinematics

Ds
LU
~
sin
f
{F
1
H
+.
.
}d
f

e p ep
g


Kinematically

suppressed

A =

Ds

2s

s
+

-

s
-

s
+

+ s
-

=

Extract H(
ξ
,t)

Projected
results

Spatial Image

Projected precision in extraction of
GPD
H

at x =
ξ


Exclusive
r
0

production on transverse target

2
D

⡉((
䅂A



A
UT

~
-



A ~

2H
u

+ H
d

B ~ 2E
u

+ E
d

r
0

Q
2
=5 GeV
2

Eu, Ed

measure the
contributions of the
quark orbital angular
momentum to the
nucleon spin.

r
0

B

Should be known

from DVCS

Separate with
ρ
+


d
X
(
x
,b )


T

E
d
(
x,t
)

M. Burkardt

Tomographic Images of the Proton


E
u
(
x,t
)


u
X
(
x
,b )

T

CAT scan slice

of human abdomen

flavor

polarization



d
2
t

(2

)
2

e
-
i

t

b

E(x,0,t)

T

q
(
x,
b ) =

T

Target polarization

The guts of the


proton?

Valence structure function flavor dependence

Hall B 11 GeV with CLAS12

Valence structure function spin dependence

Proton

Deuteron & He
-
3

W > 2; Q
2

> 1

Improvements in
Δ
u,
Δ
d,
Δ
G,
Δ
s

Important complement to RHIC Spin data

Proton electric form factor


Neutron Magnetic Form Factor


At 12 GeV extend knowledge of magnetic structure of neutron to
much shorter distances. Needed for constraints of GPDs at large t;
related to moments of GPDs:

F
1
(t)= ∫H(t,x,
ξ
)dx
,
F
2
(t)=
∫H(t,x,
ξ
)dx

Projections for N* Transition
Amplitudes @ 12 GeV

Probe the transition from effective degrees of
freedom, e.g. constituent quarks, to elementary
quarks, with characteristic Q
2

dependence.

CLAS published

CLAS preliminary

CLAS12

projected

Hybrid mesons

Flux Tube Model



Provides a framework to understand gluonic
excitations.



Conventional mesons

have the color flux
tube in the ground state. When the flux tube
is excited
hybrid mesons

emerge. For static
quarks the excitation level above the ground
state is ~1 GeV.



The excitation of the flux tube, when
combined with the quarks, can lead to spin
-
parity quantum numbers that cannot be
obtained in the quark model



(J
PC
-

exotics).




The decay of hybrid mesons leads to
complex final states.


1GeV

qqG

qq

J
PC
= 0
+
-
, 1
-
+
, 2
+
-

LQCD supports the idea of flux tubes.

Flux distribution between

static quarks.

Flux tubes lead to a linear confining

potential.

Exotic Hybrid Mesons Masses

With 3 light quarks the
conventional and hybrid
mesons form flavor
nonets for each J
PC
.

Photons may be more suited to excite exotics




In the flux tube model, using photon beams, the production rate of hybrid
mesons is not suppressed compared to conventional mesons.


N. Isgur, PRD (1999); A. Afanasev & A. Szczepaniak, PRD (2000); F. Close & J. Dudek (2004)

GlueX


Exotic meson program at 12GeV


To meet these goals GlueX will:

Quark Propagation and Hadron Formation:

QCD Confinement in Forming Systems


How long can a light quark remain deconfined?


The
production time t
p

measures this


Deconfined quarks emit gluons


Measure t
p

via medium
-
stimulated gluon emission



How long does it take to form the color field
of a hadron?


The
formation time t
f
h

measures this


Hadrons interact strongly with nuclear medium


Measure t
f
h

via hadron attenuation in nuclei

CLAS12

Expected data


Hadronic multiplicity ratio

Color transparency in
ρ

electroproduction


Color

Transparency

is a spectacular prediction
of QCD: under the right conditions, nuclear
matter will allow the transmission of hadrons
with reduced attenuation


Totally unexpected in an hadronic picture of
strongly interacting matter, but
straightforward in quark gluon basis


Why
ρ
?
Should be evident first in mesons


The signature of CT is the rising of the nuclear
transparency TA with increasing hardness of the
reaction (Q)


Measurement at
fixed coherence
length needed for
unambiguous
interpretation


)
(
2
2
2
Q
M
V
c
+




Predicted results
high
-
precision, will
permit systematic
studies

CLAS preliminary

56
Fe

Color transparency in
ρ

electroproduction

CLAS12
projected

Precision Tests of the Standard Model

Electron
-
Quark Phenomenology

C
1u

and C
1d

will be determined to high precision by APV and Qweak

C
2u

and C
2d

are small and poorly known: can be accessed in PV DIS

New physics such as

compositeness, new gauge bosons:

Deviations in C
2u

and C
2d

might be fractionally large

A

V

V

A

Proposed JLab upgrade experiment will improve
knowledge of 2C
2u
-
C
2d

by more than a factor of 20




C

1

i



2

g

A

e

g

V

i




C

2

i



2

g

V

e

g

A

i

Parity Violating Electron DIS

e
-

N

X

e
-

Z
*

g
*

Must measure A
PV
to fractional accuracy better than 1%




11 GeV at high luminosity makes very high precision feasible



JLab is uniquely capable of providing beam of extraordinary stability



Control of systematics being developed at 6 GeV


A
PV

G
F
Q
2
2


a
(
x
)
+
f
(
y
)
b
(
x
)



a
(
x
)

3
10
(
2
C
1
u
-
C
1
d
)



b
(
x
)

3
10
(
2
C
2
u
-
C
2
d
)
u
v
(
x
)
+
d
v
(
x
)
u
(
x
)
+
d
(
x
)






For an isoscalar target like
2
H, one can write
in good approximation:

provided Q
2

and W
2

are high enough and x ~ 0.3


2
H Experiment at 11 GeV

E’: 6.8 GeV
±

10%


lab

= 12.5
o

A
PV

= 290 ppm

I
beam

= 90 µA


800 hours


(A
PV
)=1.0 ppm

60
cm LD
2

target

1 MHz DIS rate, π/e ~ 1


HMS+SHMS

x
Bj

~ 0.45

Q
2

~ 3.5 GeV
2

W
2

~ 5.23 GeV
2


(2C
2u
-
C
2d
)=0.01

PDG:
-
0.08
±

0.24

Theory: +0.0986

Conclusions


The JLab Upgrade has well defined physics goals of fundamental
importance for the future of hadron physics, addressing in new and
revolutionary ways the quark and gluon structure of mesons, nucleons,
and nuclei by




accessing generalized parton distributions



exploring the valence quark structure of nucleons



understanding quark confinement and hadronization processes



extending nucleon elastic and transition form factors to short distances



mapping the spectrum of gluonic excitations of mesons



searching for physics beyond the standard model



Design of accelerator and equipment upgrades are underway



Construction scheduled to begin in 2009



Accelerator shutdown scheduled for 2012

2007 NSAC Long Range Plan (4 recommendations)

We recommend the completion of the 12 GeV Upgrade at
Jefferson Lab.


-

It will enable
three
-
dimensional imaging of the nucleon
,
revealing hidden aspects of its internal dynamics.


-
It will complete our understanding of the
transition between the
hadronic and quark/gluon descriptions

of nuclei.


-
It will test definitively the
existence of exotic hadrons
, long
-
predicted by QCD as arising from quark confinement.


-
It will provide
low
-
energy probes of physics beyond the Standard
Model

complementing anticipated measurements at the highest
accessible energy scales.

Recommendation 1


DOE Generic Project Timeline

We are here

DOE Reviews

A first search for exotic meson with photons

a
1

a
2

p
2

Gluonic Meson?


p
1
(1600)

0.8 1.2 1.6 2.0

10
2

Events/ 20 MeV

45



35




25



15



5



Clarify evidence for exotic meson states,
e.g. at 1600 MeV with high statistics.



Prepare for full study with GlueX.

Events from previous CLAS experiment.

Expect 1
-
2 million 3
-
pion events,

3 orders more than any previously

published meson photoproduction

results, allowing a partial wave analysis.

Experiment planned to

run in
2008.

Physical content of GPDs

M
2
(t)

Mass/energy density

J(t)

Angular momentum density

In the Chiral Quark Soliton Model

d
1
(t)

Pressure density

repulsion

attraction

CLAS12

-

DVCS/BH Target Asymmetry

e p ep
g


Longitudinally polarized

target

Ds
~
sin
f
Im{F
1
H
+
x
(F
1
+F
2
)
H
...
}d
f

~

E = 11 GeV

L = 2x10
35
cm
-
2
s
-
1

T = 1000 hrs

D

2

= 1GeV
2

D
x = 0.05

DVCS

DVMP

Separating GPDs in Flavor & Spin

hard vertices



DVCS depends on all 4 GPDs




Photons cannot separate u/d quark

contributions.

M =
r
0
/r
+

select
H, E
, for u/d


quarks

M =
, h

select
H, E

Isolate longitudinal photons by

decay angular distribution.

CAT scan slice of human abdomen

liver

right kidney

pancreas

stomach

gall bladder

Can we do similar imaging in the microscopic world?

Tools are being developed to add this new dimension to nuclear research
.

z




y

3
-
D Scotty

x


GPDs & PDFs

Deeply Virtual
Exclusive
Processes &
GPDs

2
-
D Scotty

z

x

1
-
D Scotty

x

Calcium

Water

Carbon

Deep Inelastic Scattering &
Parton Distribution Functions.

X. Ji and F. Yuan, 2003

3D image obtained by rotation around the z
-
axis

Charge density
distributions
for u
-
quarks


y

z

Tomographic Images of the Proton II

x=0.4

1.5

0

-
1.5

fm

-
1.5

1.5

0

fm

x=0.9

1

0

-
1

fm

-
1

fm

x=0.01

2

0

-
2

fm

-
2

2

0

fm

interference

pattern

1

0