LNS. Tagging the EMC effect in d(e, e N) reactions using the BAND and LAD detectors at JLab12. Axel Schmidt MIT. July 5, 2017

Transcription

1 Tagging the EMC effect in d(e, e N) reactions using the BAND and LAD detectors at JLab12 Axel Schmidt MIT July 5, 2017 LNS Laboratory for Nuclear Science 1

2 The EMC effect still puzzles σ C 12σ d SLAC data (1994) x J. Gomez et al., PRD (1994) Miller + Smith, PRC (2001) 2

3 The EMC effect still puzzles σ C 12σ d SLAC data (1994) EMC slope: x J. Gomez et al., PRD (1994) Miller + Smith, PRC (2001) 3

4 The EMC effect still puzzles. 1.2 Fermi-motion 2σ C 12σ d SLAC data (1994) EMC slope: x J. Gomez et al., PRD (1994) Miller + Smith, PRC (2001) 4

5 Classifying EMC Models EMC Models Nucleon Motion Medium Modification Insufficient All nucleons modified slightly A few nucleons modified a lot 5

6 Theories identify virtuality as the key to producing EMC-like modification. Free Binding Rescaling Point-like Configuration Suppression Bound 6

7 Theories identify virtuality as the key to producing EMC-like modification. Binding Rescaling Point-like Configuration Suppression Free Free Bound Bound 7

8 Theories identify virtuality as the key to producing EMC-like modification. Binding Rescaling Point-like Configuration Suppression Free Free Free + ε Bound Bound Bound + ε A - 1 8

9 The EMC effect correlates with the density SRC pairs Fe EMC Slope ( dr/dxb) H 3 He 4 He 9 Be 12 C 197 Au SRC-pair density (a 2 ) 9

10 Two upcoming experiments will test the EMC-SRC connection. Deep inelastic scattering with a recoiling nucleon: LAD CLAS12 scattered electron 11 GeV e spectator proton GEMs SHMS scattered electron BAND 11 GeV e Spectator neutron Deuterium Deuterium HMS JLab Hall C jet from struck quark JLab Hall B jet from struck quark 10

11 The Correlations group MIT (Or Hen): Barak Schmookler Reynier Torres Efrain Segarra Afro Papadopoulou Axel Schmidt TAU (Eli Piasetzky): Erez Cohen Meytal Duer Igor Korover ODU (Larry Weinstein): Mariana Khachatryan George Laskaris Maria Patsyuk Adi Ashkenazy Florian Hauenstein UT Santa Maria (Chile) Iñaki Vega

12 I will cover: 1 Recoil-Tagged DIS Testing the SRC-EMC connection 2 The LAD Experiment Large Acceptance Detector 3 The BAND Experiment Backward Angle Neutron Detector 12

13 I will cover: 1 Recoil-Tagged DIS Testing the SRC-EMC connection 2 The LAD Experiment Large Acceptance Detector 3 The BAND Experiment Backward Angle Neutron Detector 13

14 Recoil-Tagging: using a high-momentum recoil to determine the virtuality of the struck nucleon. e e' 14

15 Recoil-Tagging: using a high-momentum recoil to determine the virtuality of the struck nucleon. e e' recoiling spectator 15

16 Short-range correlations are universal. Parallel cos Leading 5.9 GeV/c, GeV/c, GeV/c, GeV/c, GeV/c, 94 Recoil High-momentum tail 20% of nucleons correlated pairs high-relative momentum low CoM momentum Antiparallel p n (GeV/c) Recoil neutron momentum [GeV] J.L.S. Aclander et al., Phys. Lett. B 453, 211 (1999) A. Tang et al., Phys. Rev. Lett. 90, (2003) E. Piasetzky et al., PRL (2006) 16

17 There are some interpretation challenges. e e' recoiling spectator 1 relating the recoil momentum to the stuck nucleon momentum 2 rescattering in the nuclear medium 3 accounting for the nuclear remnant 17

18 There are some interpretation challenges. e e' recoiling spectator 1 relating the recoil momentum to the stuck nucleon momentum 2 rescattering in the nuclear medium 3 accounting for the nuclear remnant Use a deuterium target. Look at backward recoils. 18

19 Advantages of deuterium Struck nucleon had EXACTLY opposite momentum to recoil. No residual system Minimal final state interactions. e e' recoiling spectator 19

20 DEEPS showed little FSI at back angles. Anti-Parallel θ qs > 107 Transverse 73 < θ qs < counts PWIA data P s (G ev/c) P s (G ev/c) Klimenko et al., PRC (2006) 20

21 What we want to measure: F 2 (x, Q 2, α s ) bound F 2 (x, Q 2 σ DIS(x, Q 2, α s ) bound ) free σ DIS (low x, Q0 2, α σ DIS(low x, Q0 2) free s) bound σ DIS (x, Q 2 ) free R FSI 21

22 What we want to measure: F 2 (x, Q 2, α s ) bound F 2 (x, Q 2 σ DIS(x, Q 2, α s ) bound ) free σ DIS (low x, Q0 2, α σ DIS(low x, Q0 2) free s) bound σ DIS (x, Q 2 ) free R FSI. Tagged DIS measurement Input 1 22

23 What we want to measure: F 2 (x, Q 2, α s ) bound F 2 (x, Q 2 σ DIS(x, Q 2, α s ) bound ) free σ DIS (low x, Q0 2, α σ DIS(low x, Q0 2) free s) bound σ DIS (x, Q 2 ) free R FSI. Tagged DIS measurement Input 1 At low x, the EMC effect should be small: σ DIS (low x, Q 2 0, α s ) bound σ DIS (low x, Q 2 0) free 23

24 Different models predict different F 2 ratios. Bound F2 / Free F Binding Rescaling PLC suppression α s Melnitchouk, Sargsian, Strikman, Z. Phys A 359 p.99 (1997) 24

25 Experimental Requirements 1 DIS kinematics W > 2 GeV Q 2 > 2 GeV 2 10 GeV beam energy 2 Backward recoil detector Large acceptance for θ qs > < p r < 0.7 GeV Low x and High x coverage 25

26 I will cover: 1 Recoil-Tagged DIS Testing the SRC-EMC connection 2 The LAD Experiment Large Acceptance Detector 3 The BAND Experiment Backward Angle Neutron Detector 26

27

28 LAD will detect recoiling spectator protons. LAD spectator proton SHMS scattered electron 11 GeV e Deuterium HMS JLab Hall C jet from struck quark 28

29 LAD is three panels of scintillator bars, originally from the CLAS-6 ToFs. Large Single Panel #3 Large Double Panels #2 Large Double Panels #1 29

30

31 LAD Experiment Details Experiment Experiment E Approved for 820 hours Extended LD 2 target 11 GeV e beam cm 2 s 1 Low x and high x settings Large Acceptance Detector 5 panels of 11 bars 1.5 sr at back angles ±20 out-of-plane 31

32 The limit will be random coincidence background. Can be subracted using off-time events Statistical variation can drown signal δn S + B N = S Signal Reconstructued ToF Any reduction in background buys us statistics! 32

33 Energy deposition in LAD must match velocity. Figure 25: Energy loss versus TOF. To reduce the large singles rates we will set the detector threshold in the first layer of 33

34 Energy deposition in LAD must match velocity. Rate [arb. units] Randoms Signal Momentum (Edep) - Momentum (ToF) [MeV] 34

35 We plan to add GEMs to assist in vertexing. LAD spectator proton SHMS scattered electron 11 GeV e Deuterium HMS JLab Hall C jet from struck quark 35

36 We plan to add GEMs to assist in vertexing. LAD spectator proton GEMs SHMS scattered electron 11 GeV e Deuterium HMS JLab Hall C jet from struck quark 36

37 Multiple scattering in GEM material can reduce effectiveness σ = 1.3 cm σ = 1.7 cm Thin Regular Thick Randoms Counts σ = 2.5 cm z rec. z e [cm] 37

38 Expected Impact Bound F2 / Free F Binding Rescaling PLC suppression LAD α s 38

39 I will cover: 1 Recoil-Tagged DIS Testing the SRC-EMC connection 2 The LAD Experiment Large Acceptance Detector 3 The BAND Experiment Backward Angle Neutron Detector 39

40 JLab Hall B DC FTOF Solenoid CTOF Beamline SVT HTCC CLAS12 Torus PCal/ECal LTCC

41 BAND will detect recoiling spectator neutrons. BAND 11 GeV e CLAS12 Spectator neutron Deuterium scattered electron JLab Hall B jet from struck quark 41

42 BAND will surround the upstream beamline. 42

43 BAND will surround the upstream beamline. 43

44 BAND Experiment Details Experiment Experiment E A Approved for 90 days parallel with DVCS Run group I Extended LD 2 target 11 GeV e beam cm 2 s 1 Backward Angle Neutron Detector Currently being developed 5 rows of panels of 21 bars % azimuthal coverage 44

45 BAND must respect several constraints. Material in the n flight path Only is clear Narrow Keep-In Zone Must be thick to have high-efficiency (> 30%) Segmentation aids in path length resolution... at the cost of light yield Scintillator length 3 groups for long bars 1 group for short bars (500 mm) A B C D C BAND design June 7th, 2017 (evening update) Scintillator section: 74x74mm 2 18 rows & 5 layers (256 PMTs) 232 PMTs main detector 24 PMTs veto layer Lengths inside keep in zone ~28 mm from sides ~72 mm from beampipe Keep in zone 45

46 We are studying PMT performance at MIT. AND Trigger OR AND Reference Bar Test Bar 60 Co Source Efrain Segarra Adin Hrnjic help from Igor Korover 46

47 We are studying PMT performance at MIT. Time resolution [ps] m bar, 5 5 cm 2 cross section R R R13435 R Energy deposit [MeV] Each ps of resolution costs $

48 We have developed a detailed simulation of the experiment α s x 48

49 Analytic model for momentum resolution δp/p (pecσ t ) 2 /2 + E 4 w 2 /12/(m n z) Momentum resolution 2.5% 2% 1.5% 1% 500 ps PMTs 150 ps PMTs 300 ps PMTs 0.5% 7 cm bars 10 cm bars 0% Neutron momentum [MeV] 49

50 Analytic model for momentum resolution δp/p (pecσ t ) 2 /2 + E 4 w 2 /12/(m n z) 2.5% 500 ps Momentum resolution 2% 1.5% 1% 150 ps 300 ps 0.5% 7 cm bars 10 cm bars 0% Neutron momentum [MeV] 50

51 Background will be higher at large x Signal Q 2 > 2 GeV 2 W > 1.8 GeV Counts Random Bkg x 51

52 Even with background, we expect good statistical precision < x < % Counts % % % 4.2% α s 52

53 Even with background, we expect good statistical precision. x > % 2500 Counts % % 8.2% % α s 53

54 Expected Impact Bound F2 / Free F Binding Rescaling PLC suppression 0.5 BAND 0.4 LAD α s 54

55 As the mechanical design is getting fixed we are moving to a full Geant4 sim. Efrain Segarra Erez Cohen 55

56 The important points 1 Recoil tagging can test the EMC-SRC connection. 2 LAD will detect recoil protons in Hall C 3 BAND will detect recoil neutrons in Hall B e recoiling spectator e' 56

57 The important points 1 Recoil tagging can test the EMC-SRC connection. 2 LAD will detect recoil protons in Hall C 3 BAND will detect recoil neutrons in Hall B LAD 11 GeV e spectator proton Deuterium JLab Hall C GEMs SHMS scattered electron HMS jet from struck quark 57

58 The important points 1 Recoil tagging can test the EMC-SRC connection. 2 LAD will detect recoil protons in Hall C 3 BAND will detect recoil neutrons in Hall B BAND 11 GeV e Spectator neutron Deuterium JLab Hall B CLAS12 scattered electron jet from struck quark 58

59 The important points We will make a definitive statement about the role of virtuality in the EMC effect. Bound F2 / Free F Binding Rescaling PLC suppression BAND LAD α s 59

60 The EMC effect is still a puzzle. BAND and LAD will tell us if we are putting the pieces in the right spot. 56 Fe Be 12 C 197 Au 0.4 EMC Slope ( dr/ dxb ) He 3 He 2 H SRC-pair density (a2) 60