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Backward Particle Detection for 12 GeV in Hall
C
Hall C Meeting, January 18-19, 2008 Jefferson
Lab, Newport News, VA USA
Eli Piasetzky
Tel Aviv University, ISRAEL
2
Large solid angle multi particle (charge and
neutral) detector
HMS
SHMS
e
p,p,
e
Coverage of a large fraction of the hemisphere
(backward 4p-forward) consistent operation
with the forward spectrometers.
Ability to detect multi charge particles with
good PID and moderate momentum resolution.
Ability to detect neutrons with high efficiency.
Ability to operate at 10-100 of the full
luminosity of Hall C (10-100 times the planned
luminosity for CLAS).
3
The physics driving a 4p-forward detector
Short Range Correlations (SRC)
EMC
Hadronization
Study of GPDs
Nuclear Matter in non - equilibrium condition
4
12C
Results summary
12C
185
2N SRC dominance
np-SRC dominance 18
5
2N
1N gtgt 2N - SRC gtgt 3N SRC.
0.60.2
194
3N
cure
XBgt2
PR 08-14 / PAC 33
or
6
Exclusive measurement
From (e,ep) N to (e,ep)2N
From triple coincidence (2N SRC) to 4 fold
coincidence (3N SRC)
star geometry
Need to detect two recoil nucleons
Colinear geometry
0.3-1 GeV/c p and n
7
For a 1 fm separation, the central density is
about 4 times nuclear central density

• Are the nucleons in the SRC pair different from
  free nucleons (e.g size,shape, mass, etc.) ? Are
  they nucleons ?

8
Looking for non-nucleonic degrees of freedom
? ? 5?o
2N-SRC
?1.f
1 fm
Breaking the pair will yield more backward ?, p ,
k
Nucleons
The signature of a non-nucleonic SRC intermediate
state is a large branching ratio to a
non-nucleonic final state.
9
Looking for non-nucleonic degrees of freedom
Expected ?s rates 5-10 of recoil N
Detected by spectrometer
4 fold coincidence
2 particles in the backward detector
3-5 fold coincidence
2-4 particles in the backward detector
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Title Search for cumulative Delta 0(1232) and Delta (1232) isobars in neutrino interactions with neon nuclei
Authors Ammosov, V. V. Asratyan, A. É. Burtovoi, V. S. Gapienko, V. A. Gapienko, G. S. Gorichev, P. A. Denisov, A. G. Zaets, V. G. Klyukhin, V. I. Koreshev, V. I. Kruchinin, S. P. Kubantsev, M. A. Makhlyueva, I. V. Pitukhin, P. V. Sirotenko, V. I. Slobodyuk, E. A. Usubov, Z. U. Fedotov, A. V. Shevchenko, V. G. Shekelyan, V. I.
Publication Journal of Experimental and Theoretical Physics Letters, Vol. 40, p.1041
Publication Date 09/1984
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Kinematics
p?640 MeV/c
With SHMS(e) and HMS(p) acceptances and G110 MeV
?
12
Even the triple coincidence SRC experiment could
be done better with a larger acceptance detector.
Measured ratio
Extrapolated ratio
The Limited acceptance allows determination of
only two components of the pair cm momentum.
Extrapolation factor 10
13

EMC
A large acceptance detector allows tagging
of the DIS event
High nuclear density tagging
A recoil high momentum nucleon to the backward
hemisphere is a signature of 2N-SRC i.e large
local nuclear density.
Due to the dominance of np-SRC pairs a recoil
neutron tags a proton structure function a
recoil proton tags a neutron structure function
Flavor tagging
Identifying a p or p - with a large z can point
to the flavor of the struck quark ( u or d).
Recoil and forward tagging allows the study of u,
d in p, n
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Hadronization
Measure the multiplicity and the type of emitted
particles in a large acceptance backward
direction in coincidence with the forward
(large z) leading p , p -, k , k - particle.
Difference in hadronization of different quarks
Difference between hardonization in a free space
and nuclear medium
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GPDs
Hall B
Hall C
With a large acceptance detector
With Deuteron one can measure imultaneously both
proton and neutron by detecting the recoil
neutron or proton respectively ?
low mass pN system- a test of chiral symmetry
16

Nuclear Matter in non - equilibrium condition
Using hard processes to remove a single or a few
nucleons from the nucleus creates a non-stable
state.
How does such a non-stable state decay to a
stable system?
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A (4p forward) DETECTOR
Multi particle detection
Particle ID
Large solid angle- 4p non-symmetric opening in
the forward hemisphere
Cover up to 1800 (the planed 12GeV CLAS cover
up to 1350 only)
Large (full) luminosity
Can operate in coincidence with small solid
angle, high resolution spectrometer /
spectrometers
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G0
BONUS TPC
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PID
d
p
p
beam
beam
200 counters
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PID
?E
d
p
n-detection efficiency 20 15(?)
p
TOF
Also E vs. ?E
5 cm
beam
20 cm
beam
LAC
LAC
200 counters
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Quo vadis ?
2008
2-3 physics proposals to the 12 GeV PAC
Conceptual detector design
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Acknowledgment
Discussions and ideas exchange with
Stepan Stepanyan
Sebastian Kuhn
Larry Weinstein
Steve Wood
Rolf Ent
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Large Angle Calorimeter (LAC)
2 mm lead foil
1.5 cm plastic Scintillator
33 layers
neutron momentum GeV/c
24
The CLAS as a 4p-forward detector
For the new 12 GeV clas The current magnet,
Drift chambers, and scintillator counters are not
to be used.
Need new power supplies, and electronics
Require a careful, non trivial dismount of the
current detector at Hall B and non trivial setup
at hall c.
Improve n-detection
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The CLAS as a 4p-forward detector
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CLAS 3-D View
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G0
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BONUS TPC
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SRC in nuclei Roadmap
What is the role played by short range
correlation of more than two nucleons ?
How to relate what we learned about SRC in nuclei
to the dynamics of neutron star formation and
structure ?
? ? 5?o
2N-SRC
SRC in nuclei
?1.f
1 fm
1.7 fm
1.7f
Nucleons
?o 0.16 GeV/fm3

• Are the nucleons in the SRC pair different from
  free nucleons (e.g size,shape, mass, etc.) ? Are
  they nucleons ?

NN interaction what is the role played by the
repulsive core ?
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12C

2N-SRC
np-SRC
204.5
184.5
pp-SRC
0.95 0.2
nn-SRC
A single particle in an average potential
0.95 0.2
804.5
32

Identifying Future Experiments
Looking for SRC with more than 2 nucleons
33

Identifying Future Experiments
Looking for SRC with more than 2 nucleons
The problems
The cross sections are small.
1N gtgt 2N - SRC gtgt 3N SRC.
Questions
What is the signature for 3N correlation ?
star geometry
What is the difference from two 2N correlations
?
What is the expected isospin structure of the 3N ?
34

Identifying Future Experiments
Looking for SRC with more than 2 nucleons
The problems
The cross sections are small.
1N gtgt 2N - SRC gtgt 3N SRC.
The cure for 1N background is large pmiss
and/or large XB
The cure for 2N-SRC XBgt2 or suppression
of the 2N-SRC at prel300-600 MeV/c for nn or pp
pairs.
35

Identifying Future Experiments
Looking for SRC with more than 2 nucleons
Colinear geometry
Initial configurations
A very strong isospin dependence is expected for
the 2N part. For the 3N?
The 2N-SRC interaction is suppressed, opening a
window of opportunity to identify 3N correlation.
The signal of today is tomorrows background
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Identifying Future Experiments
Looking for SRC with more than 2 nucleons
Colinear geometry
FSI are strong function of ?
SRC are not
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Identifying Future Experiments
Looking for non-nucleonic degrees of freedom
Breaking the pair will yield more backward ?, p ,
k
The signature of a non-nucleonic SRC intermediate
state is a large branching ratio to a non
nucleonic final state.
38
Looking for non-nucleonic degrees of freedom
In coincidence with (e, ep), as a function of
the missing momentum we want to detect p, n,
p-, p k - triple coincidence
39
Identifying Future Experiments
Looking for non-nucleonic degrees of freedom
np ? pn

• p?0 ?p p - p

pp ? pp

• p? ?p p n

4 fold coincidence
Expected rates 5-10 of recoil N
40
Kinematics
?
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The selected kinematics for E01-015
p
Pm 300,400,500 MeV/c
Ee 3.724 GeV
e
Ee 4.627 GeV
19.50
e
50.40
40.1, 35.8, 32.00
P 300-600 MeV/c
n or p
p 1.45,1.42,1.36 GeV/c
Q22 (GeV/c)2
p
qv1.65 GeV/c
99 50
Increasing, energy, ?,N?? ?
X1.245
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The selected kinematics
Increasing, energy and ?, N??
p
Ee 9.8 GeV
Pmiss 770 MeV/c
e
Ee 11 GeV
8.80
e
48.50
34 0
P? 770 MeV/c
Cannot produce backward going ?.
Cannot produce larger momentum difference
between the recoil ? and the struck nucleon.
p 1.32 GeV/c
?
Q22.5 (GeV/c)2
p
qv1.65 GeV/c
X1.12
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Ee 11.00000 Eout 9.790000 theta_e
8.800000 Q2 2.535372 x 1.116600
input angle of (qe) and (qp) planes
0.0000000E00 theta of q -48.49650 The
format of the following output is type of the
particle, momentum, angle vs q, angle vs e,
azimuthal angle in lab knock-out nucleon
1.328000 13.52419 34.97231
180.0000 missing 0.7737520
156.3361 107.8397 0.0000000E00
recoil 0.7737520 23.66388
72.16035 180.0000 tet between recoil
and scattred proton -37.18803 pmiss in the
q direction 0.7086919
Ee 11.00000 Eout 9.960000 theta_e
8.200000 Q2 2.240232 x 1.147892
input angle of (qe) and (qp) planes
0.0000000E00 theta of q -51.20859 The
format of the following output is type of the
particle, momentum, angle vs q, angle vs e,
azimuthal angle in lab knock-out nucleon
1.200000 5.490372 45.71821
180.0000 missing 0.6385024
169.6408 118.4322 0.0000000E00
recoil 0.6385024 10.35917
61.56776 180.0000 tet between recoil
and scattred proton -15.84955 pmiss in the
q direction 0.6280947
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The selected kinematics for the measurement
Pm 640 MeV/c
Ee 9 GeV
p
e
Ee 11 GeV
8.20
e
16.60
31.50
p
P? 640 MeV/c
p 2.3 GeV/c
Ee 11.00000 Eout 9.000000 theta_e
8.200000 Q2 2.024307 x 0.5393709
input angle of (qe) and (qp) planes
0.0000000E00 theta of q -31.53330 The
format of the following output is type of the
particle, momentum, angle vs q, angle vs e,
azimuthal angle in lab knock-out nucleon
2.300000 14.94191 16.59142
179.9802 missing 0.6368749
111.3839 79.85064 0.0000000E00
recoil 0.6368749 68.61605
100.1494 180.0000 tet between recoil
and scattred proton -83.55794 pmiss in the
q direction 0.2322146
?
Q22 (GeV/c)2
1000
qv2.5 GeV/c
X0.5
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With SHMS(e) and HMS(p) acceptances
p?640 MeV/c
With SHMS(e) and HMS(p) acceptances and G110 MeV
46
The LargeAcceptanceMINUSFORWARD detector
Multi particle detection
Particle ID
Large solid angle- 4p non symmetric gape at the
forward hemisphere
Large (full) luminosity
Can operate in coincidence with small solid angle
high resolution spectrometer / spectrometers
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CLAS12
Toroidal field ? lt 45o Solenoidal field 45 lt ? lt
135o
TOF
DC
CO2 Cer
Solenoid
Toroid
CF4 Cerenkov
Calorimeter
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SRC in nuclei Roadmap
What is the role played by short range
correlation of more than two nucleons ?
? ? 5?o
2N-SRC
SRC in nuclei
?1.f
1 fm
1.7 fm
1.7f
Nucleons
?o 0.16 GeV/fm3

• Are the nucleons in the SRC pair different from
  free nucleons (e.g size,shape, mass, etc.) ? Are
  they nucleons ?

50
12C

2N-SRC
np-SRC
204.5
184.5
pp-SRC
0.95 0.2
nn-SRC
A single particle in an average potential
0.95 0.2
804.5
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TOF scintillators
LAC