Download Data Mining Effort

CLAS12
European
Workshop
February 25-28, 2009- Genova, Italy
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
MEGIDDO: THE FLAGSHIP OF TEL AVIV UNIVERSITY DIGS
A mound with 32 cities one on top of the other
1903-1905 Schumacher
1920-1939 University of Chicago
1960s,1970s The Hebrew University
1994 -
Tel Aviv University
1903-1905 Schumacher
1920-1939 University of Chicago
1960s,1970s The Hebrew University
1994 -
Tel Aviv University
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
Nucleon Short Range Correlations (SRC)
2N-SRC
~1 fm
  5o
1.f
1.7f
o = 0.16 GeV/fm3
1.7 fm
Nucleons
A~1057
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).
What did we learn recently about SRC ?
1
The probability for a nucleon to have momentum
≥ 300 MeV / c in medium nuclei is ~25%
2
More than ~90% of all nucleons with momentum
≥ 300 MeV / c belong to 2N-SRC.
3
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.
4
The dominant NN force in the 2N-SRC
is the tensor force.
5
2N-SRC mostly built of 2N not 6 quarks or NΔ ΔΔ.
All the non-nucleonic components can not exceed
20% of the 2N-SRC.
Three nucleon SRC are present in nuclei.
6
. PRL. 96, 082501 (2006)
4
EVA / BNL and Jlab
/ HALL A
6
CLAS / HALL B
1
PRL 98,132501 (2007).
2
5
3
PRL 162504(2006); Science 320, 1476 (2008).
2N-SRC Results (summary)
12C
12C
18±5%
1±0.3%
2N –SRC dominance
np-SRC dominance ~18 %
The uncertainties allow a few percent of:
more than 2N correlations
Non - nucleonic degrees of freedom
Sensitivity required:
1% of (e,e’p)
5% of (e, e’ p) with Pmiss>300 MeV/c
Looking for non-nucleonic degrees of freedom
 SRC  a NN  b N  c   ...
For the non –nucleonic component:
a ,
b, c,... 
2N-SRC
  5o
1.f
~1 fm
Breaking the pair will yield more backward Δ, π , k
Nucleons
The signature of a non-nucleonic
SRC intermediate state is a large
branching ratio to a non-nucleonic
final state.
Δ’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).
a measurement of (e,e’ pback) by the
Yerevan group
src
How to search for pre-existing Δs in CLAS data?
Search for backward emitted Δ, both (e, e’ Δback) and (e, e’ N Δback)
to separate initial state from background multistep processes
a) Look at x<1 and x>1
b) Vary Q2 and ω
Search for forward emitted Δ++ at x>1
Look for Δ++ at large x, corresponding to the larger expected
Δ - momentum in the nucleus.
By studying the dependence on x and A we can separate the charge
exchange Δ++ production (main effect for α =1 increasing with A ) and
scattering off primordial Δ++ ( larger x).
3N-SRC
3N –SRC arise from two mechanisms:
pair interactions
3N force
p1 , p2, p3  pF
 

p1  p2  p3  0
Isospin ratios and selected kinematics may allow to separate them
~800 MeV/c
~800 MeV/c
Colinear geometry :
Needs to detect two recoil
nucleons
~400 MeV/c
~800 MeV/c
0.3-1 GeV/c p and n
1N >> 2N - SRC >> 3N – SRC.
0.6±0.2%
2N
19±4%
3N
0.6 / 19 ~ 3%
(large uncertainty on this ratio)
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)
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
System
3He
A
3
Z
2
N
1
4He,12C,40Ca
A2(A / d)
1.33
1
56Fe
56
26
30
0.93
48Ca
48
28
20
0.83
197Au
197
79
118
0.8
208Pb
208
82
126
0.79
0.05
0.95
0.1
0.1
0.9
0.2
n-star
Available data:
  1
nn  n p
A
Even the triple coincidence
SRC experiment could be
done better with a larger
acceptance detector.
12
C (e, e' pp)/ 12C (e, e' p)
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 l=2 pair in
the relative angular distribution of the pair ?
Can we learn more on the CM motion of the
R.B. Wiringa, R. Schiavilla, Steven C. Pieper, J. Carlson . Jun 2008.
pair ?
arXiv:0806.1718 [nucl-th]
Detailed study of the Fermi sea level ( the SRC onset).
The transition from single particle to SRC phases
Available now:
12C
only
Available now : Q2=2 only
Available now:
12C
only
very limited CM momentum
range (in 2 direction) only
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 T=0 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
Some examples:
Search for ΔΔ 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.
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 ?
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’ π)
DATA: Jlab / Hall C
B. Clasie et al. PRL 242502 (2007).
Coherence length: 0.2-0.5 fm
with CT
with CT
no CT
with CT
no CT
no CT
With CT
with CT
no CT
no CT
solid : Glauber (semi-classical)
dashed : Glauber +CT (quantum diff.)
Larson et al , PRC 74, 018201 (2006)
Dashed area: from Pion nucleus scattering
Carroll et al., PLB 80, 319 (’79)
  1 fm / c, M 2  0.7 GeV 2
dot-dash : Glauber (Relativistic)
dotted : Glauber +CT (quantum diff.) +SRC
Cosyn et al. PRC 74, 062201R (2006)
Also: PRC 77, 034602 (2008)
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
Study A(e, e’ Δ0) as a function of Q2 and A
d
e’
e
e’
s11
A
Hadronization
Measure the multiplicity and the type of emitted particles in a large
acceptance “backward direction ” in coincidence with the forward
(large z) leading π +, π -, k +, k - particle.
Difference in hadronization of different quarks
Difference between hardonization in a free space and nuclear medium
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?
Data sets: E > 1 GeV, A>1, electron or photon beams
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 6+1 students
Use the new data summary files
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
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)
(e, e’ N)
x>2
Notice that FSI will not fill the gap
q
EN MAX (A-1 recoil)
208Pb
? Is there a reduction of the a2 for neutron reach nuclei ?
a step toward neutron stars
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 π + or π - 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
How to search for these in the CLAS data?
(e, e’ Δback)
or even
XB>1 and XB<1
(e, e’ p Δback)
(e, e’ n Δback)
How to search for these in the CLAS data?
By studying the dependence on x and A we can separate the charge
exchange Δ++ production (main effect for α =1 increasing with A ) and
scattering off primordial Δ++ ( larger x).