Short-range NN interactions: Experimental Past and Future Nadia Fomin University of Tennessee April 12 th , 2017
The quick and the correlated : Progress towards understanding short-range NN interactions
The quick and the correlated : Progress towards understanding short-range NN interactions
Choosing an Appropriate Microscope Electron scattering is a great tool for studying subatomic structure: unlike a proton, it cannot be absorbed by the nucleus resolution varies with momentum transfer, allowing us to probe 1 the entire volume of the nucleus q
R. Hofstadter Nobel Prize 1961 "for his pioneering studies of electron scattering in atomic nuclei and for his thereby achieved discoveries concerning the structure of the nucleons"
Collisions – Measured Cross sections Number of scattering centers Target flux x F ( electrons trons of f energy gy E ) dN FN d θ ' E E d Ω scatt ttered ered 2 2 2 2 Q q q 2 2 2 electrons of energy E’ 2 W M M Q 2 Q dN x 2 M
Thomas Jefferson National D Lin inacs cs Accelerator Facility El Electr tron n now with an 11 GeV beam Source ce A B C Experi rimenta ental Hall lls
Shielded Detector Hut SOS HMS Hall C at Jefferson Lab Scattering Chamber Beam Line
Hall A at Jefferson Lab
High momentum nucleons - Short Range Correlations 3N SRC 2N SRC Nucleon momentum distribution in 12 C
High momentum tails in A( e,e’p ) • E89-004: Measure of 3 He( e,e’p )d Measured far into high momentum • tail: Cross section is ~5-10x expectation Difficulty culty • High momentum pair can come from SRC (initial state) OR • Final State Interactions (FSI) and Meson Exchange Contributions (MEC) “slow” nucleons “fast” nucleons p p p p
A( e,e’p ) 2 H( e,e’p ) Mainz PRC 78 054001 (2008) E =0.855 GeV θ = 45 o E’=0.657 GeV Q 2 =0.33 GeV 2 x=0.88 Unfortunately: FSI, MECs overwhelm the high momentum nucleons
Past A( e,e’p ) experiments in Hall A
High momentum nucleons - Short Range Correlations 3N SRC 2N SRC Nucleon momentum distribution in 12 C Try inclusive scattering! Select kinematics such that the initial nucleon momentum > k f
( x >1) x =1 ( x <1) QE Jlab E02-019 JLab, Hall C, 1998 Deuteriu m
High momentum nucleons - Short Range Correlations 3N SRC 2N SRC QE d ( , ) ( ) d k dE S k E Arg ei i ' d dE 2 2 * 2 2 Arg M M p M k A A 1 2 1 d q ( , ) F y q d d ( ) 2 2 Z N ( ) M y q p n Ok for for A=2 2 ( ) n k kdk | | y Deuterium Fomin et al, PRL 108 108 (2012)
High momentum nucleons - Short Range Correlations 3N SRC 2N SRC Nucleon momentum distribution in 12 C C. Ciofi degli Atti and S. Simula , Phys. Rev. C 53 (1996).
High momentum nucleons - Short Range Correlations 3N SRC 2N SRC Nucleon momentum distribution in 12 C Hig igh momentum entum fro rom SRCs Cs P>k ferm P> rmi Mean n C. Ciofi degli Atti and S. field fie ld Simula , Phys. Rev. C 53 (1996).
Short Range Correlations • To experimentally probe SRCs, must be in the high-momentum region (x>1) • To measure the relative probability of finding a correlation, ratios of heavy to light 1.4<x<2 => 2 nucleon correlation nuclei are taken 2.4<x<3 => 3 nucleon correlation • In the high momentum region, FSIs are thought to be confined to the SRCs and therefore, cancel in the cross section ratios • L. L. Frankfurt and M. I. Strikman, Phys. Rept. 76, 215(1981). • J. Arrington, D. Higinbotham, G. Rosner, and A 1 M. Sargsian (2011), arXiv:1104.1196 2 2 ( , ) ( ) ( , ) x Q A a A x Q • L. L. Frankfurt, M. I. Strikman, D. B. Day, and j j M. Sargsian, Phys. Rev. C 48, 2451 (1993). j 1 • L. L. Frankfurt and M. I. Strikman, Phys. j Rept. 160, 235 (1988). A • C. C. degli Atti and S. Simula, Phys. Lett. B 2 ( ) ( , ) a A x Q 325, 276 (1994). 2 2 2 • C. C. degli Atti and S. Simula, Phys. Rev. C 53, 1689 (1996). A 2 ( ) ( , ) .... a A x Q 2 A 3 3 3 ( ) a 2 A A D
Before my time 1.4<x<2 => 2 nucleon correlation 2.4<x<3 => 3 nucleon correlation A 1 2 2 ( , ) ( ) ( , ) x Q A a A x Q j j j 1 j A 2 ( ) ( , ) a A x Q 2 2 2 A 2 ( ) ( , ) .... a A x Q 3 3 3
Previous measurements 1.4<x<2 => 2 nucleon correlation 2.4<x<3 => 3 nucleon correlation Egiyan et al, Phys.Rev.C68, 2003 No observation of scaling for Q 2 <1.4 GeV 2
E02-019: 2N correlations in A/D ratios Fomin et al, PRL 108 (2012) <Q 2 >=2.7 GeV 2 Jlab E02-019
2 2 Test scaling in x and Q 2 2 4 q M W M 2 1 2 M W 3 He 3 He 12 C 12 C 𝒒 𝒋− α i represents the light cone nuclear momentum fraction carried by the 𝜷 𝒋 = 𝒒 𝑩− /𝑩 constituent nucleon
Look at nuclear dependence of NN SRCs N. Fomin et al, PRL 108 108 (2012) SRC 2 -1 a 2
J.Seely, et al., PRL 103 103, 202301 (2009) Enter 9 Be EM EMC N. Fomin et al, PRL 108 108 (2012) SRC J. Seely, , et al., PRL103, , 202301 (2009) N. Fomin, , et al., PRL 108, , 092052 (2012) 2 -1 JA, A. Daniel, , D. Day, N. Fomin, , D. a 2 Gaske kell, , P. Solvignon non, , PRC RC 86, , 065204 (2012) O. Hen, , et al, PRC RC 85, , 047301 (2012) L. Weinstein, n, et al., PRL 106, , 052301 (2011)
Discovery of the EMC effect • Goal was a measurement of the lepton-nucleon cross section at high Q 2 e - • To achieve statistical precision in a e - reasonable amount of time, an iron target was used, on the assumption that DIS / A A W 2 ≥( M n +M π ) 2 1 / 2 D M* A-1 meaning M A A p n ( ) ( ) ( ) F x ZF x NF x 2 2 2 1 2 ( ) [ ( ) ( )] F x e q x q x 1 i i i 2 1 ( ) ( ) F x F x 1 2 2 x
The EMC effect A p n ( ) ( ) ( ) F x ZF x NF x 2 2 2 Nuclear dependence of the structure functions discovered 30+ years ago by the European Muon Collaboration (EMC effect) Nucleon structure functions are modified by the nuclear medium Depletion of high-x quarks for Shado dowing wing A>2 nuclei is not expected or EMC region understood Anti-Shado Shadowi wing ng Fermi mi mot otion on effec fects ts (pion n exc xces ess) s)
Measurements before 2004 • NMC – extraction of F 2 n /F /F 2 p DMS -- 50 < Q 2 < 200 (GeV 2 ) • BCDM • HERMES – first measurement on 3 He • SLAC E139 – most precise large x data • Q 2 independent • Universal shape • Magnitude approximately scales with density
Models of the EMC effect Nucleo eon n structur ure e is modified ied in the nuclear medium • Dynamical rescaling • Nucleon ‘swelling’ • Multiquark clusters (6q, 9q ‘bags’) or or Nuclea ear r structur ure e is modified ified due to hadronic effects • More detailed binding calculations • Fermi motion + binding • N-N correlations • Nuclear pions
Nuclear Dependence of the EMC effect Quark distributions are modified in nuclei Modification scales with A 4 He ratio evaluated at x=0.6 4 He ratio evaluated at x=0.6
Jlab E03-103 2 H 3 He 4 He 9 Be 12 C 27 Al* 63 Cu 197 Au
Precision results on light nuclei from JLab E03-103 • C/D C/D and 4 He/D /D ratios – no isoscalar correction necessary • Consistent with SLAC results, but much higher precision at high x • Fit the slope of the ratios for 0.35<x<0.7: dR EMC dx • Compare across nuclei PhD theses: J. Seely, A. Daniel J.Seely, A. Daniel, et al., PRL103, 202301 (2009)
J.Seely, et al., PRL 103 103, 202301 (2009) Enter 9 Be EM EMC N. Fomin et al, PRL 108 108 (2012) SRC J. Seely, , et al., PRL103, , 202301 (2009) N. Fomin, , et al., PRL 108, , 092052 (2012) 2 -1 JA, A. Daniel, , D. Day, N. Fomin, , D. a 2 Gaske kell, , P. Solvignon non, , PRC RC 86, , 065204 (2012) O. Hen, , et al, PRC RC 85, , 047301 (2012) L. Weinstein, n, et al., PRL 106, , 052301 (2011)
2N knockout experiments establish NP dominance R. Sube R. bedi di et et al. l., Science e • Knockout high-initial- 320, , 1476 (2008) momentum proton, look for correlated nucleon partner. • For 300 < P miss < 600 MeV/c all nucleons are part of 2N-SRC pairs: 90% np, 5% pp (nn) R. Shneor et al., PRL 99, 072501 (2007)
2N knockout experiments establish NP dominance R. R. Sube bedi di et et al. l., Science e 320, , 1476 (2008) 96 ± 23 % 9.5 ± 2 % R. Shneor et al., PRL 99, 072501 (2007)
NP dominance R. Sube bedi di et et al. l., Science e 96 ± 23 320, , 1476 (2008) % R. Shneor et al., 9.5 ± 2 % PRL 99, 072501 (2007) also Ciofi and Alvioli PRL 100, 162503 (2008) Sargsian, Abrahamyan, Strikman, Frankfurt PR C71 044615 (2005)
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