Analyzing CLAS Hall B Data to Extract New Results on QCD Nuclear Physics

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Analyzing CLAS / Hall B Data to Extract New
Results on QCD Nuclear Physics An Initiative to
Maximize the Return on Already Collected Data M.
Strikman, L. Weinstein, S. Kuhn, S. Stepanyan, E.
Piasetzky, K. Griffioen, M. Sargsian
Eli Piasetzky
Tel Aviv University, ISRAEL
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MEGIDDO THE FLAGSHIP OF TEL AVIV UNIVERSITY DIGS
A mound with 32 cities one on top of the other
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The physics driving the proposed analysis
Short Range Correlations (SRC)
Detailed study on few body systems (Deuteron, 3He)
Nuclear transparency
Hadronization
Nuclear Matter in non - equilibrium condition
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Nucleon Short Range Correlations (SRC)
1 fm
1.7 fm
A1057
What SRC in nuclei can tell us about
High Momentum Component of the Nuclear Wave
Function.
The Strong Short-Range Force Between Nucleons.
tensor force, repulsive core, 3N forces
Cold-Dense Nuclear Matter (from deuteron to
neutron-stars).
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What did we learn recently about SRC ?
CLAS / HALL B
The probability for a nucleon to have momentum
300 MeV / c in medium nuclei is 25
. PRL. 96, 082501 (2006)
More than 90 of all nucleons with momentum
300 MeV / c belong to 2N-SRC.
The probability for a nucleon with momentum
300-600 MeV / c to belong to np-SRC is 18 times
larger than to belong to pp-SRC.
The dominant NN force in the 2N-SRC is the tensor
force.
PRL 98,132501 (2007).
2N-SRC mostly built of 2N not 6 quarks or N?
??. All the non-nucleonic components can not
exceed 20 of the 2N-SRC.
EVA / BNL and Jlab / HALL A
Three nucleon SRC are present in nuclei.
PRL 162504(2006) Science 320, 1476 (2008).
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12C
2N-SRC Results (summary)
12C
185
2N SRC dominance
np-SRC dominance 18
Sensitivity required 1 of (e,ep) 5 of (e,
e p) with Pmissgt300 MeV/c
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Looking for non-nucleonic degrees of freedom
? ? 5?o
For the non nucleonic component
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.
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?s rates 5-10 of recoil N rates
Nucl-th 0901.2340
Search for cumulative Delta 0(1232) and Delta
(1232) isobars in neutrino interactions with neon
nuclei
Ammosov, et al.
Journal of Experimental and Theoretical Physics
Letters, Vol. 40, p.1041 (1984).
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a measurement of (e,e pback) by the Yerevan group
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How to search for pre-existing ?s in CLAS data?
(e, e ?back) and
(e, e N ?back)
Search for backward emitted ?, both
to separate initial state from background
multistep processes

• Look at xlt1 and xgt1
• Vary Q2 and ?

Search for forward emitted ? at xgt1
Look for ? at large x, corresponding to the
larger expected ? - momentum in the nucleus.
By studying the dependence on x and A we can
separate the charge exchange ? production (main
effect for a 1 increasing with A ) and
scattering off primordial ? ( larger x).
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3N-SRC
3N SRC arise from two mechanisms
pair interactions
3N force
Isospin ratios and selected kinematics may allow
to separate them

Colinear geometry
Needs to detect two recoil nucleons
0.3-1 GeV/c p and n
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1N gtgt 2N - SRC gtgt 3N SRC.
0.60.2
2N
0.6 / 19 3
3N
194
(large uncertainty on this ratio)
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How to search for these in the CLAS data?
Inclusive measurement of two backward recoil
nucleons
(e, 2Nback)
In coincidence with the scattered electron
(e, e 2Nback)
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a2(A/d)
1.7
3.33 (2)
4.27 (6)
5.10 (6)
208Pb(e,e) / 3He(e,e) Is there a reduction
of the a2 for neutron rich nuclei ?
a step toward neutron stars
A2(A / d)
Available data
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Even the triple coincidence SRC experiment could
be done better with a larger acceptance detector.
Measured ratio
Extrapolation factor 10
The limited acceptance allows determination of
only two components of the pair c.m. momentum
with very limited acceptance.
Extrapolated ratio
Can we look for a signature of the l2 pair in
the relative angular distribution of the pair ?
Can we learn more on the CM motion of the pair ?
R.B. Wiringa, R. Schiavilla, Steven C. Pieper, J.
Carlson . Jun 2008. arXiv0806.1718 nucl-th
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Detailed study of the Fermi sea level ( the SRC
onset).
The transition from single particle to SRC phases
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Available now 12C only
Available now Q22 only
very limited CM momentum range (in 2 direction)
only
Available now 12C only
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Detailed study on few body systems (Deuteron, 3He)
These are interesting by themselves but also are
important doorway to study complex nuclei. The
clearly determined kinematics offered by these
systems can be useful.
2N-SRC are dominant with T0 np pairs.
Fingerprints of the deuteron can be used to
study 2N-SRC in nuclei.
Effects related to EMC and CT can be tested on
few body systems
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Some examples
Search for ?? admixtures in the deutron
Important also for the study of non-nucleonic
componnets of SRC in nuclei.
Measurements of tagged structure functions
(electron scattering in coincidence with a fast
backward proton or neutron)
Important also for the study of EMC with the 12
GeV upgrade
Measurements of the spin structure of SRC in the
deuteron using polarized electron scattering off
polarized or unpolarized deuteron
Important also for the study of SRC in nuclei
Detailed study of FSI as a function of the final
state particles, momenta, and Q2
Important also for the study of CT, hadronization
and medium modification to the nucleon form
factors.
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Color Transparency
PLC
?
Q1 Is the strong interaction of small neutral
(colorless) objects suppressed ?
Q2 Can we produce small hadrons (PLC) ? Q3
Can we freeze the PLC long enough to observe the
suppression of its interaction ?
If the answers to all the questions above is
positive we can expect a phenomenon known as
Color Transparency.
Q4 Where is the onset of CT ?
(CT is a necessary condition for factorization of
exclusive hard processes)
Q5 What is the time / space structure of the
transition from the PLC to a normal hadron ?
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Data from Hall C indicate that maybe the onset of
CT is low enough to look for CT effects at the
current JLab energy range
(e, e p)
DATA Jlab / Hall C B. Clasie et al. PRL
242502 (2007).
Coherence length 0.2-0.5 fm
with CT
with CT
with CT
no CT
no CT
no CT
with CT
With CT
Dashed area from Pion nucleus scattering Carroll
et al., PLB 80, 319 (79)
no CT
no CT
dot-dash Glauber (Relativistic) dotted
Glauber CT (quantum diff.) SRC Cosyn et al.
PRC 74, 062201R (2006) Also PRC 77, 034602 (2008)
solid Glauber (semi-classical) dashed Glauber
CT (quantum diff.) Larson et al , PRC 74,
018201 (2006)
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If CT is relevant at JLab energies one can look
for suppression of the pion cloud and its
interaction with the nuclear medium close to the
point where a hadron is being produced in a hard
process.
e
e
Study A(e, e ?0) as a function of Q2 and A
d
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e
e
s11
A
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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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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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Data sets E gt 1 GeV, Agt1, electron or photon
beams
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Plan of action
White paper, seek for funding - Jan 2009
Exploration 2009
Narrow down the effort to the most promising
analysis projects
1full time experience postdoc at JLab.
Use existing data summary files
1st stage analysis developing analysis tools,
Re-cooking
2010-2011
3full time experienced researchers at JLab. and
up to 6 students
Create new data summary files
Full analysis effort at Jlab. and home institutes
2011-2015
3full time experimental and 1 theoretical
researcher at JLab. and up to 61 students
Use the new data summary files
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Organization
steering committee
Core of postdocs and students at Jlab
Groups of Postocs and students at the universities
Weekly conferences calls
Two annual meetings
Open for everyone interested , Please join the
initiative
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How to search for these in the CLAS data?
Inclusive measurement of two backward recoil
nucleons
(e, 2Nback)
In coincidence with the scattered electron
(e, e 2Nback)
Notice that FSI will not fill the gap
(e, e N) xgt2
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208Pb ? Is there a reduction of the a2 for
neutron reach nuclei ? a step toward
neutron stars
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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 the proton structure function a
recoil proton tags the 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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How to search for these in the CLAS data?
(e, e ?back)
or even
XBgt1 and XBlt1
(e, e n ?back)
(e, e p ?back)
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How to search for these in the CLAS data?
By studying the dependence on x and A we can
separate the charge exchange ? production (main
effect for a 1 increasing with A ) and
scattering off primordial ? ( larger x).