Momentum Distribution in A = 3 Asymmetric Nuclei Jefferson Lab - - PowerPoint PPT Presentation

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momentum distribution in a 3 asymmetric nuclei
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Momentum Distribution in A = 3 Asymmetric Nuclei Jefferson Lab - - PowerPoint PPT Presentation

Mar 04, 2024 40 likes •253 views

Momentum Distribution in A = 3 Asymmetric Nuclei Jefferson Lab Hall-A Experiment E12-14-011 Florian Hauenstein, Old Dominion University SRC/EMC Workshop, MIT, 03.12.16 Kinetic Energy Sharing Pauli-Principle: SRC np pairs <T>(Majority)

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SLIDE 1

Momentum Distribution in A = 3 Asymmetric Nuclei

Florian Hauenstein, Old Dominion University SRC/EMC Workshop, MIT, 03.12.16

Jefferson Lab Hall-A Experiment E12-14-011

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SLIDE 2

Kinetic Energy Sharing

Pauli-Principle: <T>(Majority) > <T> (Minority) SRC np pairs <T>(Majority) < <T> (Minority)

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SLIDE 3

VMC Prediction for <T>

  • R. Wiringa et al. (Phys. Rev. C 89, 024305 (2014))

<T>(Majority) < <T> (Minority)

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SLIDE 4

4

n p P

3He

SRC and Nucleon Counting

R=1

rRegion

R>2

Simple Nucleon Counting

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SLIDE 5

The A = 3 System

  • 3He and 3H are mirror nuclei
  • Neutron in 3He = Proton in 3H
  • Two-ways to study the proton-to-neutron momentum

distribution ratio in 3He:

  • Measure the 3He(e,e’p) / 3He(e,e’n) ratio

(Low accuracy due to the neutron measurement)

  • Measure the 3He(e,e’p) / 3H(e,e’p) ratio.

(Tritium Target necessary, available at JLab Hall-A (MARATHON))

5

n n P n p P

3He 3H

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SLIDE 6

6

σ PWIA = k ⋅σ ep ⋅Sp Emiss, pmiss

( )

Emiss = ω −Tp −TA−1 pmiss

→

= q

→

− p'

→

= − pinit

→

Complications:

  • Rescattering of the outgoing proton.
  • Off-shell proton cross-section.
  • Meson Exchange Currents (MEC).
  • Delta production (i.e. IC).

Extraction of Momentum Distribution from A(e,e‘)p

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SLIDE 7

Previous Hall-A 3He (e,e’p)X measurements

7

3He(e,e’p)d

PWIA PWIA Full

3He(e,e’p)np

pm [MeV/c]

Data: Rvachev et al., PRL94 192302 (2005); Benmokhtar et al., PRL94 082305 (2005) Theory: Ciofi degli Atti and Kaptari, PRL95 052502 (2005) ; Alvioli et al., PRC81 021001 (2010)

  • Dominated by FSI at

large momentum

  • Well described by

theory

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SLIDE 8

θnq= 45o θnq= 75o

Boeglin et al. (Hall-A Collaboration), PRL 107 (2011) 262501

Minimizing FSI Effects in d(e,e‘)p

θnq= 35o

  • FSI effects

decrease for smaller values

  • f θnq
  • Assume similar

suppression for A = 3 nuclei

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SLIDE 9
  • Rescattering minimized at small

angles (verified for deuterium).

  • Small angles => xB>1 => suppress

MEC and IC effects.

PWIA Calculation Full Calculation

3He 3H e,e' p

( )

R = σFull / σPWIA

200 MeV/c 400 MeV/c 500 MeV/c

3He e,e' p

( )

Access Momentum Distribution w/o FSI

Rescattering effects cancel in the

3He/3H ratio

Q2 = 2 GeV2 θnq = 30º

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SLIDE 10

10

<pm> (MeV/c) x Ee (GeV) θe pp θp Time 3H+3He (days) 100 1.15 3.47 20.9o 1.61 48.7o 1 300 1.41 3.64 20.4o 1.35 58.6o 10

JLab-Hall A Measurement E12-14-011

Kinematics:

  • Eb = 4.4 GeV
  • Ibeam = 20 μA
  • Q2 = 2 GeV2
  • x = Q2/2mω> 1 (quasi-elastic)
  • θnq < 40º

Setup:

  • MARATHON Target
  • HRS spectrometer in Hall-A at Jefferson

Lab

  • Low luminosity L (3H) = 8×1036 nucleons

cm-2 s-1

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SLIDE 11

| [MeV/c]

miss

|P

50 100 150 200 250 300 350 400 450 500

[degree]

rq

θ

20 40 60 80 100 120 140 1 10

2

10

Simulation Results for 3H

No cut on Q2

similar for 3He, no full acceptance cuts!

Q2 > 2 GeV2 Θrq < 40o

preliminary preliminary

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SLIDE 12

Expected Results

3He and 3H

reduced cross- sections; Compared to calculations. Kinetic Energy Sharing; Mapping of Inversion Proton/neutron momentum ratio

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SLIDE 13

Summary and Outlook

  • Measurement of momentum distribution in A = 3 mirror nuclei
  • Approved experiment scheduled for december 2017 at JLab Hall-A
  • Improved kinematic setting to reduce FSI, MEC and IC effects
  • Since Eb = 4.2 GeV next year kinematic setting will change slightly
  • Other theoretical calculation i.e 𝜓PT?
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SLIDE 14

Backup Slides

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SLIDE 15

Simulation 3H Results (2)

| [MeV/c]

miss

|P

100 200 300 400 500 600

]

2

/c

2

[GeV

2

Q

1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 1 10

2

10

[degree]

rq

θ

20 40 60 80 100 120 140

]

2

/c

2

[GeV

2

Q

1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 10 20 30 40 50 60 70 80 90

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SLIDE 16

Simulation 3H Results: Pmiss & Emiss

[MeV/c]

miss

E 20 40 60 80 100 120 140 160 180 200 | [MeV/c]

miss

|P 100 200 300 400 500 600 50 100 150 200 250 300 [MeV/c]

miss

E 20 40 60 80 100 120 140 160 180 200 | [MeV/c]

miss

|P 100 200 300 400 500 600 20 40 60 80 100

Cut Q2 > 2 GeV2 and θnq < 40º , no cross section scaling <pmiss> = 300 MeV/c <pmiss> = 100 MeV/c

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SLIDE 17

3He Spectral Function

2-body breakup channel 3-body breakup channel E2BB = mp + md –m3He E3BB = 2mp + mn –m3He

min

from Rey

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SLIDE 18

Previous 3H(e,e’p) measurements

18

  • A. Johansson, PR136, 1030B (1964)
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SLIDE 19

19 Reynier Cruz Torres

Hall A H

A

Experimental Setup – Hall A

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SLIDE 20

20

  • Open cell design allows a wide range of scattering angles
  • Wall thickness 0.018” Al (120 mg/cm2)
  • Entrance and exit windows: 0.010” Al (65 mg/cm2)
  • The proton HRS will not see the cell windows

Entrance window

Adopted From David Meekins

Marathon Target

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SLIDE 21

Pmiss distributions (slow kinematics configuration, scaled to 4 days)

ß before R-cut after R-cut à 3135 events 2681 events 1592 events 1407 events 4337 events 3708 events 2217 events 1961 events

3He 3He 3H 3H

from Rey