SRC Studies using Triple Coincidence A(e,e'pp) & A(e,e'np) reactions

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1 SRC Studies using Triple Coincidence A(e,e'pp) & A(e,e'np) reactions A data-mining project using CLAS EG2 data Meytal Duer Tel-Aviv University July 12, 2018 NPWG meeting, JLab 1

2 SRC Pair Fraction [%] np-dominance in 2N-SRC 12 C(p,ppn) / 12C(p,pp) 12 C(e,e pn) / 12C(e,e p) BNL / EVA 12 C Hall-A [12C(e,e pp) / 12 [12C(e,e pp) / C(e,e pn)] / 2 12 n-p C(e,e p)] / 2 Missing Momentum [GeV/c] Subedi et al., Science 320 (2008) Piasetzky et al., PRL. 97 (2006)

3 SRC Pair Fraction [%] np-dominance in 2N-SRC Hall-A Missing Momentum [GeV/c] Korover et al. Phys. Rev. Let. 113, (2014). 3

4 SRC Pair Fraction [%] np-dominance in 2N-SRC Hall-B A O. Hen et al., Science 346, 614 (2014) protons 4

5 SRC Pair Fraction [%] np-dominance in 2N-SRC Hall-B A O. Hen et al., Science 346, 614 (2014) np fractions extracted from (e,e'p) & (e,e'pp) events protons No neutrons detection 5

6 Experimental Setup CLAS JLab Electron Incident electron Neutron Proton Duer et al., Nature, accepted for publication El Fassi, Phys. Lett B 712, (2012) Hen, Science 346, 614 (2014) Detecting neutrons in CLAS EC (M. Braverman TAU thesis, 2014) 6

7 Experimental Setup CLAS JLab Electron p p = p n 1.5 GeV / c Δ p/ p: Neutron n Duer et al., Nature, accepted for publication El Fassi, Phys. Lett B 712, (2012) Hen, Science 346, 614 (2014) Detecting neutrons in CLAS EC (M. Braverman TAU thesis, 2014) p 10% Proton <1% 7

8 Probing high-momentum protons and neutrons in asymmetric nuclei Using (e,e'p) & (e,e'n) reactions The selected cuts: x B >1.1, 0.62 P N / q 1.1, 0.4 P miss 1 GeV / c, Duer et al., Nature, accepted for publication o θ Nq 25, 2 M miss GeV / c 8

9 (e,e'n) & (e,e'p) Double coincidence Incident electron Scattered electron (e,e'np) & (e,e'pp) Triple coincidence Incident electron γ* Scattered electron γ* Not detected Recoil partner proton / neutron Knocked-out neutron / proton Recoil proton partner Knocked-out neutron / proton 9

10 (e,e'n) & (e,e'p) Double coincidence Incident electron Scattered electron (e,e'np) & (e,e'pp) Triple coincidence Incident electron γ* Scattered electron γ* Not detected Recoil partner proton / neutron Knocked-out neutron / proton Recoil proton partner Knocked-out neutron / proton (e,e'np) & (e,e'pp): all cuts used for (e,e'n) & (e,e'p) + P recoil > 0.35 GeV / c) high momentum recoil proton ( and energy deposit cut on it 10

11 Estimate C(e,e'pp)/C(e,e'np) ratio # pp # np 18 1/3 np-dominance 11

12 Estimate C(e,e'pp)/C(e,e'np) ratio # pp # np 18 1/3 np-dominance n-efficiency 12

13 Estimate C(e,e'pp)/C(e,e'np) ratio Leading p vs. leading n # pp # np 18 1/3 np-dominance n-efficiency 13

14 Estimate C(e,e'pp)/C(e,e'np) ratio Leading p vs. leading n p & n cross-sections ratio # pp # np 18 1/3 np-dominance n-efficiency 14

15 Estimate C(e,e'pp)/C(e,e'np) ratio Leading p vs. leading n p & n cross-sections ratio # pp # np 18 1/3 np-dominance #np=186 n-efficiency #pp=173 15

16 Estimate C(e,e'pp)/C(e,e'np) ratio Leading p vs. leading n p & n cross-sections ratio pp 1/(2 2.5) 1 # np 1/(18 1/3) What about # heavy asymmetric nuclei? np-dominance #np=186 n-efficiency #pp=173 16

17 Direct Observation of np-dominance σ A (e,e' np) /σ en σ A (e,e' pp)/ 2 σ ep [%] A(e,e'pp)/A(e,e'np) ratios A

18 Direct Observation of np-dominance σ A (e,e' np) /σ en σ A (e,e' pp)/ 2 σ ep A(e,e'pp)/A(e,e'np) ratios Stat uncertainties ES εn 6.31± ± ± ±1.26 Nuclei pp/np [%] C Al Fe Pb εp T A

19 Direct Observation of np-dominance σ A (e,e' np) /σ en σ A (e,e' pp)/ 2 σ ep A(e,e'pp)/A(e,e'np) ratios What about FSI? uncertainties A

20 Single Charge Exchange (SCX) np pp n p 20

21 Single Charge Exchange (SCX) np pp n p 21

22 Single Charge Exchange (SCX) np pp p p 22

23 Single Charge Exchange (SCX) np pp p p 23

24 Single Charge Exchange (SCX) pn pp n p 24

25 Single Charge Exchange (SCX) pn pp p p 25

26 Single Charge Exchange (SCX) np pp P [ p] p p p n p P n[n] n n n p P np n p n p P [n] p n p p p P p[n] p n p p pp p p p p P p 26

27 A(e,e'pp) & A(e,e'np) 'real' pp pp A(e, e ' pp)= # pp 2 σep P T pp 'real' np np A(e, e ' np)= # np σ en P T np 27

28 A(e,e'pp) & A(e,e'np) 'real' pp pp SCX [n ] p * p [n ] A(e, e ' pp)= # pp 2 σep P T pp + # np σ en P T + # pn σ ep P T * * 1 T = (T pp +T np )=T pp =T np 2 'real' np np A(e, e ' pp)= # np σen P T np 28

29 A(e,e'pp) & A(e,e'np) 'real' pp pp SCX [n ] p * p [n ] A(e, e ' pp)= # pp 2 σep P T pp + # np σ en P T + # pn σ ep P T * * 1 T = (T pp +T np )=T pp =T np 2 SCX 'real' np np [p]p * n [n ] A(e, e ' np)= # np σ en P T np + # pp 2 σ ep P T + # nn 2 σ en P T # pp < # nn < N (N 1) # pp Z (Z 1) (Combinatorial ratio) 29 *

30 Extracting pp/np ratios np [n]p p[n] σ ep σ p/n = σ en # pp 1 2 R P P P /σ p/n = pp # np 2 P 2 σ p/n R P[p] p 2 R η Pn[n] A (e, e ' pp)/2 σ ep R= A(e,e ' np)/σ en #nn η= # pp SCX probabilities, Ref. [1], change between ~ 3 7 % from C to Pb [1] C. Colle, W. Cosyn, and J. Ryckebusch, Phys. Rev. C93, (2016). 30

31 Extracting pp/np ratios 31

32 Direct Observation of np-dominance Preliminary σ A (e,e' np) /σ en σ A (e,e' pp)/ 2 σ ep [%] A(e,e'pp)/A(e,e'np) ratios A Subedi, Science 320 (2008) SCX correction: C. Colle, W. Cosyn, Phys. Rev. C 93, (2016). 32

33 Direct Observation of np-dominance Preliminary No A dependence in the ratios σ A (e,e' np) /σ en σ A (e,e' pp)/ 2 σ ep [%] A(e,e'pp)/A(e,e'np) ratios A Subedi, Science 320 (2008) SCX correction: C. Colle, W. Cosyn, Phys. Rev. C 93, (2016). 33

34 Direct Observation of np-dominance Preliminary No A dependence in the ratios σ A (e,e' np) /σ en σ A (e,e' pp)/ 2 σ ep [%] A(e,e'pp)/A(e,e'np) ratios Upper limit for pp/np ratios: < 6% A Subedi, Science 320 (2008) SCX correction: C. Colle, W. Cosyn, Phys. Rev. C 93, (2016). 34

35 Analysis Status Analysis review committee - Done Paper draft (to be submitted for PRL) Ad-hoc committee for the paper Pending 35

36 Thank you! Acknowledgment Analysis review committee Data-Mining collaboration CLAS collaboration 36

37 Backup Slides 37

38 Momentum sharing in asymmetric nuclei SRC (np-dominance) Pauli principle E kin n > E kin p E n(k) E kin p ( n) kin p? > E kin n neutrons protons N>Z k2 = n p ( n) d 3 k 2m nd (k) ~KF K Possible inversion of the momentum sharing 38

39 Momentum sharing in asymmetric nuclei SRC Pauli principle E kin n > E kin p E n(k) E kin p ( n) k2 = n p ( n) d 3 k 2m kin p? > E kin n neutrons protons vs N>Z nd (k) Who~Kwins? F K Possible inversion of the momentum sharing 39

40 Theoretical predictions (N>Z) Heavy nuclei (A>12) kin kin En / E p Light nuclei (A<12) Neutron Excess [N/Z] Z>N: 3 He N/Z =1/2 kin kin E n / E p =1.31 Wiringa, Phys. Rev. C89, (2014) Ryckebusch, J. Phys G42 (2015) 40

41 Simple np-dominance model η n n p(k ) = M.F. p k< k 0 ( k) A a 2 ( A / d ) nd ( k) 2Z Duer et al., Nature, accepted for publication Sargsian PRC 89 (2014) k> k 0 (for neutrons: Z N) Hen et al., Science 346 (2014) k 0 : 300 MeV/c, kf n 12 C 27 Al 56 Fe 208 Neutron Excess [N/Z] Pb M.F. ( k ): Wood-Saxon Serot- Walecka Ciofi & Simula n d ( k) : AV18 NN potential a 2 ( A/ d): Scaling factor η determined by: n p (n ) ( k) d 3 k =1 41

42 Calculation Measurement Simple estimate based on np-dominance 208 protons k>k Pb : Z =82 20 R P= =0.32 protons k<k Rn = F SRC fractions F C Al Fe SRC=20% N =126 neutronsk> k F neutronsk< k F ns o t o r p Neutron Excess [N/Z] = Pb 42

43 The goal: A(e,e' N) high/ low Extracting 12 C ( e,e ' N ) high/ low ratios ( N=n/ p) SRC fractions Prediction ns o t o pr neut ro ns Neutron Excess [N/Z] 43

44 Motivation Analysis II Selecting M.F. QE events M.F. SRC Emiss [GeV ] 0.5 p miss = p N q protons neutrons Emiss =ω T N T B Pmiss [GeV /c ] Problem: QE peak: Pmiss<0.25 GeV/c Emiss<0.08 GeV Poor resolution in the EC - Δ P 0.1GeV / c 44 Oneill et al., Phys. Lett. B 87 (1995), Abbott et al. Phys. Rev. Lett. 80 (1998), Garrow et al. Phys. Rev. C. 66 (2002)

45 Motivation Analysis II Selecting M.F. QE events M.F. SRC Emiss [GeV ] 0.5 p miss = p N q Emiss =ω T N T B protons Pmiss [GeV /c ] QE peak: Pmiss<0.25 GeV/c Emiss<0.08 GeV 45 Oneill et al., Phys. Lett. B 87 (1995), Abbott et al. Phys. Rev. Lett. 80 (1998), Garrow et al. Phys. Rev. C. 66 (2002)

46 Solution Analysis II Using smeared protons to: * Define and test the cuts * Study bin migration Emiss [GeV ] Emiss [GeV ] 0.5 smeared protons neutrons Pmiss [GeV /c ] With cuts: 0.05 < y < < ω<1.7gev Pmiss [GeV /c ] θ pq < 8 o 46

47 False Positive & Negative probabilities bad event good event (un-smeared p) 47

48 False Positive & Negative probabilities bad event smeared p good event (un-smeared p) 48

49 False Positive & Negative probabilities bad event smeared p False positive good event (un-smeared p) False negative 49

50 False Positive & Negative probabilities bad event smeared p False positive good event (un-smeared p) False negative Goal: Find cuts that minimize false positive & negative 50

51 Analysis II False Negative [%] False Positive [%] False Positive & Negative probabilities smeared p/n cuts: 'impurity' Emiss <[GeV ] 'inefficiency' P miss <0.3GeV /c, Emiss <0.19 GeV un-smeared p cuts: P miss <0.25GeV /c, Emiss <0.08 GeV False Positive False Negative 10 % Pmiss cut[gev /c] 51

52 Motivation Analysis II High-momentum QE events M.F. SRC (Same procedure as M.F.) The selected cuts: x B > < p / q <1.1 θ pq < 25o 0.4<P miss <1GeV / c M miss <1.175GeV / c 2 52

53 Analysis I Future plans Compare smeared & un-smeared protons un-smeared protons M.F. SRC A (e, e ' p) C (e,e ' p) smeared protons A Next step: Blind analysis for neutrons 53

54 σ A (e,,e' e' p)/ σ ep σ A (e,,e' e' n)/ σ en A(e,e'n)/A(e,e'p) ratios Neutron Excess [N/Z] Neutron Excess [N/Z] 54

55 σ A (e,,e' e' p)/ σ ep σ A (e,,e' e' n)/ σ en A(e,e'n)/A(e,e'p) ratios C Neutron Excess [N/Z] Neutron Excess [N/Z] 55

56 σ A (e,,e' e' p)/ σ ep σ A (e,,e' e' n)/ σ en A(e,e'n)/A(e,e'p) ratios C Al Fe Neutron Excess [N/Z] Neutron Excess [N/Z] Pb 56

57 σ A (e,,e' e' p)/ σ ep σ A (e,,e' e' n)/ σ en A(e,e'n)/A(e,e'p) ratios C Al Fe Neutron Excess [N/Z] Neutron Excess [N/Z] Duer et al., Nature, accepted for publication Pb p n Pb 57

58 SRC Pair Fraction [%] np-dominance in 2N-SRC A O. Hen et al., Science 346, 614 (2014) np fractions extracted from (e,e'p) & (e,e'pp) events protons No neutrons detection 58

59 Protons and neutrons super ratios A( e,e ' N )high / A(e,e' N)low 12 C ( e,e ' N )high / C (e,e' N )low High-Momentum Fraction 12 Neutron Excess [N/Z] More Neutrons => More Correlated Protons 59 Duer et al., Nature, accepted for publication

60 Building nuclei from C to Pb: Adding more neutrons increases the fraction of high momentum (correlated) protons. 60

61 Protons and neutrons super ratios A( e,e ' N )high / A(e,e' N)low 12 C ( e,e ' N )high / C (e,e' N )low High-Momentum Fraction 12 Neutron Excess [N/Z] Our simple model works Duer et al., Nature, accepted for publication 61

62 Kinetic Energy Sharing A (e, e ' N )high / A (e, e ' N )low High-Momentum Fraction 12 C (e, e ' N )high /12 C (e, e ' N )low C 27 Pb Fe Al Neutron Excess [N/Z] Duer et al., Nature, accepted for publication 62

63 Kinetic Energy Sharing A (e, e ' N )high / A (e, e ' N )low High-Momentum Fraction 12 C (e, e ' N )high /12 C (e, e ' N )low p move faster than n in N>Z nuclei > Neutron Excess [N/Z] Duer et al., Nature, accepted for publication 63

64 What happens in N>>Z? 1.6 n-star Pb Fe Al C? Neutron Excess [N/Z] 64

65 Detecting neutrons in CLAS o 8 θ 45 o * Hit inside the EC fiducial cut Y [cm] * No signals from Drift-Chambers & Time-Of-Flight Counters Neutral particle X [cm] * n/γ separation: β<0.95 (β<0.936) Neutron β 65

66 + Neutron resolution & detection efficiency σ ϵ P n [ GeV / c] P n [ GeV / c] d ( e, e ' p π+π-n) ϵ= d ( e, e ' p π+π)- n + - Using an exclusive reaction d (e, e ' p π π n) 66

67 Motivation Solution I Using electron & nucleon angular cuts Protons QE cuts:pmiss<0.25 GeV/c Emiss<0.08 GeV Before the QE cuts y θ pq [deg.] After the QE cuts 2 ω [GeV ] y [( M A 0.05< y< < ω<1.7gev W = ( M + ω ) q + ω) λ M W q λ ]/ W A A Q [GeV /c ] θ pq < 8o λ =( M A 1 M N + ω ) / 2 67

68 Motivation Solution II Using smeared protons to: * Define and test the cuts * Study bin migration σ P n [ GeV / c] P p P smeared = Gauss(P p,σ ) P p Psmeared [GeV /c] 68

69 Comparing the smeared protons and neutrons smeared protons neutrons P p/n [GeV /c] θ p/n [deg.] θ pq/nq [deg.] ϕ p/n ϕ e [deg.] 69

70 Applying corrections protons neutrons * Coulomb correction * Detection efficiency * Detection efficiency * Acceptance correction * Acceptance correction 70

71 Protons simulation * 10,000 electrons from the data. * Proton momentum & scattering angle uniformly distributed. * 100xphi angle uniformly distributed. * Running through CLAS MC simulation. * Dividing event by event by the ratio of reconstructed/generated. 71

72 Protons simulation - results Sector #1 Sector #2 Sector #3 Sector #4 Sector #5 Sector #6 72

73 Electron kinematics smeared protons neutrons Pe [GeV /c] θ e [deg.] Q2 [GeV 2 /c 2 ] xb 73 ω[gev ]

74 Recoil proton kinematics smeared protons neutrons Precoil [GeV /c] θ recoil [deg.] 74

75 Opening angle distribution smeared protons neutrons cos(θ P miss, Precoil ) 75