1. E12-06-105 (“x>1”) PAC47 Jeopardy presentation John Arrington
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John Arrington
Donal day
Nadia Fomin
Argonne National Laboratory
Univ. Virginia
Univ. Tennessee
PAC47
July 30, 2019
Newport News, VA

2. High-momentum nucleons (Short-Range Correlations)
N-N interaction
Hard interaction at short range
Pairs of high-momentum nucleons (up to 1 GeV/c)
Nucleon momentum distribution in 12C
n(k) [fm-3]
Mean field
part
k [GeV/c]
N-N interaction as source of SRCs  SRCs should exhibit universal 2-body
behavior in nuclei

3. Experimental Goals Inclusive SRC ratios (moderate Q2, x>1)
A/D ratios for nuclear and isospin dependence of 2N SRCs
EMC/SRC correlation investigation
First observation of a 3N plateau
DIS at x>1 (high Q2)
Nuclear parton distributions
N. Fomin, et al., PRL 108, (2012)
Observation of universal behavior – inclusive ratios independent of x, Q2
Triple-coincidence data show strong dominance of np pairs

4. Experimental Goals Inclusive SRC ratios (moderate Q2, x>1)
N. Fomin, et al., PRL 108, (2012)
J. Seely, et al., PRL103, (2009)
Inclusive SRC ratios (moderate Q2, x>1)
A/D ratios for nuclear and isospin dependence of 2N SRCs
EMC/SRC correlation investigation
First observation of a 3N plateau
DIS at x>1 (high Q2)
Nuclear parton distributions
A dependence in light nuclei (impact of e.g. cluster structure)
Separating A dependence and isospin dependence: Varying N/Z for roughly fixed mass or density
Same nuclei for SRC and EMC proposal

5. Experimental Goals Inclusive SRC ratios (moderate Q2, x>1)
A/D ratios for nuclear and isospin dependence of 2N SRCs
EMC/SRC correlation investigation
First observation of a 3N plateau
DIS at x>1 (high Q2)
Nuclear parton distributions
More nuclei (greater N/Z range) to test
Simple pictures of EMC-SRC connection
EMC scales with number of high-p (np) pairs?
EMC scales with number of short-distance (NN) pairs?
Calculations predicting a2 for range of nuclei
JA, A. Dainel, D. Day, N. Fomin, D. Gaskell, P. Solvignon, PRC 86, (2012)
B. Schmookler, et al., Nature 566 (2019) 354
JA, N. Fomin, PRL 123 (2019)

6. Experimental Goals Inclusive SRC ratios (moderate Q2, x>1)
A/D ratios for nuclear and isospin dependence of 2N SRCs
EMC/SRC correlation investigation
First observation of a 3N plateau
DIS at x>1 (high Q2)
Nuclear parton distributions
Z. Ye, et al., PRC 97 (2018)

7. Search for a 3N SRC plateau
N. Fomin, et al., Ann. Rev. Nucl. Part. Sci. 67 (2017) 129 
Z. Ye, et al., PRC 97 (2018)
α3N_MIN=1.6
Where does 2N contribution become negligible?
αi represents the light-cone momentum fraction of 3N SRCs carried by the correlated nucleon i
αi –min = 1.6  scaling for Hall C data (blue diamonds) should set in at x~2.4
Data consistent with plateau, but limited statistics and single Q2 values do not allow for statement on 3N-SRCs
We will extract 4He/3He ratios for Q2 of approx. 2.5 and 3.5 GeV2
Examine both x and Q2 dependence with high statistics

8. qD(x) Experimental Goals two-nucleon only 5% 6 quark bag
Inclusive SRC ratios (moderate Q2, x>1)
A/D ratios for nuclear and isospin dependence of 2N SRCs
EMC/SRC correlation investigation
First observation of a 3N plateau
DIS at x>1 (high Q2)
Nuclear parton distributions
Difference only ~1% piece of EMC effect?
two-nucleon only
5% 6 quark bag
Simple model where overlapping nucleons yield EMC effect through direct quark exchange in overlapping protons (modeled as small 6q bag contribution)
Modification is at percent-level for x<1
Potentially % effect for x>1
Measure for deuteron (carbon); compare deuteron to simple p+n convolution

9. Run plan: Targets 1H 2H 3He 4He 6,7Li 9Be 10,11B 12C 27Al 40*,48Ca
Light nuclei: Reliable calculations of nuclear structure (e.g. clustering)
Run plan: Targets
x>1 uses wide range of nuclear targets to study impact of cluster structure, separate mass and isospin dependence on SRCs
Additional foil targets (dark blue) added to original proposal. No additional beam time required, no special target issues
All targets measured for SRCs at high-rate kinematics. Select targets run at higher Q2 to study Q2 dependence or extend kinematic reach 1H 2H
3He
4He
6,7Li
9Be
10,11B
12C
Targets selected to match 12 GeV EMC experiment
27Al
40*,48Ca
48Ti
54Fe
58,64Ni
64*Cu
108*Ag
119*Sn
197*Au
232Th
Heavier nuclei: Cover range of N/Z at ~fixed values of A

10. Physics impact: 2019
More
As important now as when approved and rated “High Impact”
All questions addressed in the original proposal are still relevant today
New data on 3N-SRCs, but no clear observation of scaling
Theory suggestions that ~3 GeV2 may be sufficient
Data in this region (~2.8 GeV2) from Hall C has limited statistics
We can provide good statistics for Q2 values (~2.5 and 3.5 GeV2)
Connection between SRCs and EMC effect
Several works looking at the potential connection
‘Overlap’ of nucleons in short-distance configurations
Off-shell effects of high-momentum nucleons in SRCs
Raises question of flavor dependence in EMC effect arising from isospin structure of SRCs
Existing data do now allow clean separation of A and N/Z dependence
Better theory support than when originally proposed
Complimentary to ‘tagged’ measurements
2N-SRCs still relevant

11. Experimental Goals Inclusive SRC ratios (moderate Q2, x>1)
A/D ratios for nuclear and isospin dependence of 2N SRCs
EMC/SRC correlation investigation
First observation of a 3N plateau
DIS at x>1 (high Q2)
Nuclear parton distributions
Combined kinematics for this experiment and EMC
DIS at x>1
3N SRC search
2N SRC scan
EMC effect

12. backups

13. Nuclear Targets
N/Z vs A
N/Z vs density
Light nuclei – sensitivity to some nuclear structure (clusters, halos, etc...)
Heavier nuclei – N/Z isospin lever

14. Experimental Goals Inclusive SRC ratios (moderate Q2, x>1)
A/D ratios for nuclear and isospin dependence of 2N SRCs
EMC/SRC correlation investigation
First observation of a 3N plateau
DIS at x>1 (high Q2)
Nuclear parton distributions
6 GeV data suggests that even for x (x) > 1, data consistent with QCD-inspired fit

15. Run plan: Kinematics overview
Both experiments cover range of angles (20-55º) to examine Q2 dependence of structure functions [angles shifted from proposal to increase compatibility]
Main PDF measurements at 20, 33º (EMC), or x≥1: modest pion backgrounds
High-x SRCs requires small angle
Need SHMS for E’ ≈ 11 GeV
Need ‘medium’ beam pipe
HMS: 20-55º, GeV/c
SHMS: 8-33º, GeV/c
All data taking at 11 GeV
Focus on target ratios
Light nuclei: cluster structure
Heavier nuclei: vary N/Z
EMC
x>1
EMC effect vs A, N/Z
Larger Q2 pushes to highest x
PDFs at x>1
x, Q2 dependence
A-dependence of SRCs

16. Run plan overview [x>1+EMC from ERR]
Basic Run plan: 23 PAC days EMC, 32 days x>1
Assume 2 days will be completed during Hall C commissioning
7 days for EMC effect at 20º [all targets, HMS and SHMS in parallel]
6 (3) days for selected targets at 35 (40) degrees
6 days overhead, calibrations, …
4 days for x>1 at 8º [SHMS]
4 days for selected targets at 10º
17 days for high Q2 x>1 (2H,C,Cu)
EMC
x>1
EMC effect vs A, N/Z
Larger Q2 pushes to highest x
PDFs at x>1
x, Q2 dependence
Notes:
Proposed 80uA; assuming 60uA
Single ladder with all solid targets
Start with 1,2H, taking data with all targets; 1 day target changeover before running 3,4He (+C, dummy)
Updated cross section models from 6 GeV x>1 suggests that cross section for 12 degrees is too small
Probably can’t wait until the VERY end to switch over to 3He/4He, but would normally make 55 degree data last, which DOES require hydrogen/deuterium. Hmmm…..
EMC really needs A-D together. 3He/4He ONLY for EMC He/2H (20/33 degrees) and very large x. Some advantage to doing 3He/4He first?
A-dependence of SRCs