CLAS12 European Workshop February 25-28, 2009- Genova, Italy Analyzing CLAS / Hall B Data to Extract...
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Transcript of CLAS12 European Workshop February 25-28, 2009- Genova, Italy Analyzing CLAS / Hall B Data to Extract...
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)
Hadronization
Nuclear Matter in non - equilibrium condition
Nuclear transparency
Detailed study on few body systems (Deuteron, 3He)
Nucleon Short Range Correlations (SRC)
1.f
Nucleons
2N-SRC
1.7f
o = 0.16 GeV/fm3
5o
~1 fm
1.7 fm
What SRC in nuclei can tell us about:
High – Momentum Component of the Nuclear Wave Function.
The Strong Short-Range Force Between Nucleons.
Cold-Dense Nuclear Matter (from deuteron to neutron-stars).
A~1057
tensor force, repulsive core, 3N forces
What did we learn recently about SRC ?
The probability for a nucleon to have momentum ≥ 300 MeV / c in medium nuclei is ~25%
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.
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.
. PRL. 96, 082501 (2006)
PRL 162504(2006); Science 320, 1476 (2008).
CLA
S /
HA
LL B
EV
A /
BN
L an
d Jl
ab /
HA
LL A
The dominant NN force in the 2N-SRC is the tensor force.
1
2
4
3
1
6
5 2
3
6
5
4
PRL 98,132501 (2007).
np-SRC dominance ~18 %
12C
2N-SRC Results (summary)
The uncertainties allow a few percent of:
more than 2N correlations
Non - nucleonic degrees of freedom
2N –SRC dominance
18±5%
1±0.3%
12C
Sensitivity required: 1% of (e,e’p) 5% of (e, e’ p) with Pmiss>300 MeV/c
Looking for non-nucleonic degrees of freedom
The signature of a non-nucleonic SRC intermediate state is a large branching ratio to a non-nucleonic final state.
... cba NNNSRC
c,...b, ,a
Breaking the pair will yield more backward Δ, π , k
1.f
Nucleons
2N-SRC 5o
~1 fm
For the non –nucleonic component:
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).
Δ’s rates 5-10% of recoil N rates
Nucl-th 0901.2340
a measurement of (e,e’ pback) by the Yerevan group
src
How to search for pre-existing Δs in CLAS data?
(e, e’ Δback) and (e, e’ N Δback) Search for backward emitted Δ, both
to separate initial state from background multistep processes
a) Look at x<1 and x>1b) Vary Q2 and ω
Search for forward emitted Δ++ at x>1
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).
Look for Δ++ at large x, corresponding to the larger expected Δ - momentum in the nucleus.
~800 MeV/c~800 MeV/c
~800 MeV/c~400 MeV/c
Colinear geometry :
3N-SRC
Needs to detect two recoil nucleons
0.3-1 GeV/c p and n
3N –SRC arise from two mechanisms:
pair interactions
3N force 0
,
321
3,21
ppp
pppp F
Isospin ratios and selected kinematics may allow to separate them
19±4%
0.6±0.2%2N
3N
1N >> 2N - SRC >> 3N – SRC.
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)
208Pb(e,e’) / 3He(e,e’) Is there a reduction of the a2 for neutron rich nuclei ? a step toward neutron stars
System A Z N
3He 3 2 1 1.33
4He,12C,40Ca 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
n-star 0.05 0.95 0.1
0.1 0.9 0.2
A
nn pn 1
A2(A / d)
Available data:
1.7
3.33 (±2%)
4.27 (±6%)
5.10 (±6%)
a2(A/d)
Extrapolation factor ~10
)',()/',( 1212 peeCppeeC
Measured ratio
Extrapolated ratio
The limited acceptance allows determination of only two components of the pair c.m. momentum with very limited acceptance.
Even the triple coincidence SRC experiment could be done better with a larger acceptance detector.
R.B. Wiringa, R. Schiavilla, Steven C. Pieper, J. Carlson . Jun 2008. arXiv:0806.1718 [nucl-th]
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 pair ?
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
very limited CM momentum range (in 2 direction) onlyAvailable now: 12C only
Detailed study on few body systems (Deuteron, 3He)
These are interesting by themselves but also are important doorwayto 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
Search for ΔΔ admixtures in the deutron
Important also for the study of non-nucleonic componnetsof 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
Some examples:
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.
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 ?
Color Transparency
PLC
(e, e’ π)DATA: Jlab / Hall C B. Clasie et al. PRL 242502 (2007).
solid : Glauber (semi-classical)dashed : Glauber +CT (quantum diff.) Larson et al , PRC 74, 018201 (2006)
dot-dash : Glauber (Relativistic)dotted : Glauber +CT (quantum diff.) +SRC Cosyn et al. PRC 74, 062201R (2006)Also: PRC 77, 034602 (2008)
no CT
no CT
with CT
With CT
with CT
no CTno CT
no CT
with CT
with CT
Dashed area: from Pion nucleus scatteringCarroll et al., PLB 80, 319 (’79)
Coherence length: 0.2-0.5 fm
22 GeV 7.0M ,/1 cfm
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
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’
dStudy A(e, e’ Δ0) as a function of Q2 and A
A
ee’
s11
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
3full time experienced researchers at JLab. and up to 6 students
Create new data summary files
2010-2011
Full analysis effort at Jlab. and home institutes
Use the new data summary files
2011-2015
3full time experimental and 1 theoretical researcher at JLab. and up to 6+1 students
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’ N) x>2
(e, e’ 2Nback)
qEN MAX (A-1 recoil)
Notice that FSI will not fill the gap
208Pb ? Is there a reduction of the a2 for neutron reach nuclei ? a step toward neutron stars
A large acceptance detector allows tagging of the DIS event
EMC
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
(e, e’ p Δback) (e, e’ n Δback)
XB>1 and XB<1
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).