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Electrons for neutrinos Lawrence Weinstein Old Dominion University - - PowerPoint PPT Presentation

Mar 26, 2023 173 likes •560 views

Electrons for neutrinos Lawrence Weinstein Old Dominion University Neutrino Cross Section Strategy Workshop FermiLab, March 2018 Collaboration Old Dominion University Michigan State Larry Weinstein Kendall Mahn Florian

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SLIDE 1

Electrons for neutrinos

Lawrence Weinstein

Old Dominion University Neutrino Cross Section Strategy Workshop FermiLab, March 2018

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SLIDE 2

Collaboration

  • Old Dominion University

– Larry Weinstein – Florian Hauenstein (PD) – Mariana Khachatryan (grad)

  • MIT

– Or Hen – Adi Ashkenazi (PD) – Afroditi Papdolopou (grad)

  • Jefferson Lab

– Stepan Stepanyan

  • Tel Aviv U

– Eli Piasetky

  • L. Weinstein, Neutrino Cross Sections 2018

2

  • Michigan State

– Kendall Mahn – Luke Pickering

  • FermiLab

– Minerba Betancourt (PD)

  • Pitt

– Steve Dytman

slide-3
SLIDE 3

Outline

  • Why electrons?

– Nuclear Physics

  • The ``ideal” electron experiment
  • How to use electron data to reduce neutrino

uncertainties

  • Current results
  • Future plans
  • L. Weinstein, Neutrino Cross Sections 2018

3

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SLIDE 4

Why electrons?

  • Known incident energy
  • High intensity
  • Similar interaction with nuclei

– Single boson exchange – CC Weak current [vector plus axial]

  • !"

± = %

&

'()* + + (-" − -"-/)&

– EM current [vector]

  • !"

12 = %

& -"&

  • Similar nuclear physics
  • 3+ = ⃗

5+ − 6+

  • Energy transfer: 6 or 7
  • L. Weinstein, Neutrino Cross Sections 2018

4

W+

N N 78 9' p :' :'

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SLIDE 5

Nuclear Physics

dσ dω

  • L. Weinstein, Neutrino Cross Sections 2018

5

  • r ν

Dip Two body reaction mechanisms

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SLIDE 6

How Quasielastic is the (e,e’) QE peak?

RT ν

0.2

RL ν (GeV)

0.2 C(e,e’) |q|=0.4 GeV/c

Fermi gas model

y = minimum initial nucleon momentum = mν/q − q/2 (nonrelativistic only!) f = reduced response function y (GeV/c)

0.8 f(y)

L T

q=0.4 q=0.5

  • L scales
  • T scales
  • T≠L!!
  • P. Barreau et al, NPA 402, 515 (1983)

Finn et al, PRC 29, 2230 (1984)

L T

dσ dΩdν = σ M ′ E E Q4 ! q4 RL(Q2,ν)+ Q2 2! q2 + tan2 θ 2 ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ RT (Q2,ν) ⎡ ⎣ ⎢ ⎤ ⎦ ⎥

6

  • L. Weinstein, Neutrino Cross Sections 2018
slide-7
SLIDE 7

How to read an (e,e’p) spectrum

  • L. Weinstein, Neutrino Cross Sections 2018

7

Single nucleon knockout Undetected nucleon Missing energy (MeV) Undetected nucleon Undetected pion

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SLIDE 8

Extra Transverse even at the QE peak

RT RL ST-SL

12C(e,e’p)

q=0.4 GeV and x=1 extra transverse strength starting at the 2N KO threshold decreases with Q2

Ulmer et al, PRL 59, 2259 (1987); Dutta et al, PRC 61, 061602 (2000)

p3/2 s1/2

Emiss(MeV) T/L Q2 (GeV2) 1 2

8

  • L. Weinstein, Neutrino Cross Sections 2018
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SLIDE 9

QE 12C(e,e’p) q ~ 1 GeV/c

Non-QE reactions increase with ω

  • L. Weinstein, Neutrino Cross Sections 2018

9

  • S. Penn, unpublished
  • J. Morrison, PRC 59, 221, (1999)

Dip

! = #$ 2&'

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SLIDE 10

Fixed ω = 0.2 GeV, vary q

0.4 GeV/c dip 0.6 GeV/c x ~ 1 q =0.9 GeV/c x ~ 2

  • L. Weinstein, Neutrino Cross Sections 2018

10

  • R. Lourie, PRL 56, 2364 (1986)
  • L. Weinstein, PRL 64, 1646 (1990)
  • S. Penn, unpublished

Dip Missing energy [MeV]

From QE to dip: S-shell decreases Non-QE strength increases

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SLIDE 11

12C(e,e’p) Delta Region

q = 400 MeV/c ω = 275 MeV/c q = 473 MeV/c ω = 382 MeV/c ΔNèpN

  • r 2p2h

Δèπp

  • L. Weinstein, Neutrino Cross Sections 2018

11

Baghaei, PRC 39, 177 (1989) Missing Energy (MeV) Missing Energy (MeV)

Dip ΔNèpN Δèπp

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SLIDE 12

Average Two-Nucleon Properties in the Nuclear Ground State

Responsible for the high momentum part of of the Nuclear WF

Two-body currents are not Correlations (but everything adds coherently)

What are correlations?

!

!

in SRC

  • L. Weinstein, Neutrino Cross Sections 2018

12

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SLIDE 13

2N currents enhance correlations

Central correlations only Central + tensor corr Corr + MEC θpq

90

Em

30 360

σ

1250 12

σ σ

80

  • L. Weinstein, Neutrino Cross Sections 2018

13

MEC changes the magnitude

  • f the cross section,

not the distribution in Emiss vs Thetapq

O(e,e’p) Ryckebusch NP A672 (2000) 285

slide-14
SLIDE 14

Physics Summary

  • Electron scattering:

– Intense monochromatic beams – Can choose kinematics to minimize “uninteresting”(i.e., complicated) reaction mechanisms – Calculate cross sections after the fact

  • Neutrino interactions

– Continuous mixed beams – Must include all reaction mechanisms – Need good models in event generators

  • Correct initial state
  • MEC, IC
  • FSI (not discussed here)
  • L. Weinstein, Neutrino Cross Sections 2018

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SLIDE 15

The ideal electron experiment

  • Identify contributing reaction mechanisms
  • ver a wide kinematic range

– Full acceptance for all charged hadrons – High efficiency for neutrals

  • Neutrons
  • !"
  • Lots of targets

– Neutrino detector materials: C, O, Ar, Fe – More nuclei to constrain models

  • Enough beam energies to cover the full range
  • f interesting momentum transfers
  • L. Weinstein, Neutrino Cross Sections 2018

15

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SLIDE 16

Why momentum transfer and not beam energy?

  • The scattering cross section depends primarily on

energy and momentum transfer

  • For (e,e’p):

–

!"# !$%!$&!'&!( = *+,--[/010 + /313 + /03103456789 +

/33133 cos 2789] – Kinematic factors /? depend on {AB, D, EF} – Response functions 1? depend on {AB, D, E89} – Only beam energy dependence comes from EF

  • Need to account for boson propagator ∝

I JKL+K

– ∝

I +K for W exchange

– ∝

I JK for photon exchange (Mott Cross section)

  • L. Weinstein, Neutrino Cross Sections 2018

16

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SLIDE 17

How to use electron data for neutrino measurements

  • Tune vector models in generators to data,

especially the Q2 and A dependence

– Span a wide enough range in Q2 and A to constrain models well – Constrain final state interaction (outgoing particle rescattering) models

  • Tune remaining model elements to near

detector data

  • Guide event selection for “enhanced QE”

samples, “Res” samples, etc

  • L. Weinstein, Neutrino Cross Sections 2018

17

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SLIDE 18

A real electron experiment

CLAS6: 1996-2015

  • L. Weinstein, Neutrino Cross Sections 2018

18

TOF CER CAL DC1 DC2 DC3

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SLIDE 19

CLAS6 coverage

  • L. Weinstein, Neutrino Cross Sections 2018

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!"#$ ≈ 300 MeV/c !"#$ ≈ 150 MeV/c

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SLIDE 20

CLAS6 Data (million events)

  • L. Weinstein, Neutrino Cross Sections 2018

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1.1 GeV 2.2 GeV (e,e’) 2.2 GeV (e,e’p) 4.4 GeV (e,e’) 4.4 GeV (e,e’p) 3He Not done 29 12 4 1 4He Not done 46 17 8 3 12C Not done 19 11 5 2 56Fe Not done 1 1 0.4 0.1

E2a data only. E2b has more 4.6 GeV 3He and 56Fe Eg2 has 5 GeV d, C, Al, Fe, and Pb

Q2 (GeV2)

0.5 1 1.5 ! (GeV) 1 0.5 QE

2.2 GeV

3He

(stripes are detector artifacts)

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SLIDE 21
  • L. Weinstein, Neutrino Cross Sections 2018

21

4 GeV charged particle multiplicity

Protons: 3He Protons: 56Fe 1 2 1 2 3 Pions: 56Fe Pions: 3He 1 2 1 2

slide-22
SLIDE 22

Reconstructing the initial energy

  • Select an enhanced QE sample using

– Zero pion events – !"#$$

%

= !'

%+ !( % cuts for (e,e’p) and (e,e’X) events

  • Reconstruct the incident lepton energy:

– )*#+ =

,-./0,-.123"2

4

,(-.3120*267$82)

  • : single nucleon separation energy
  • ;< nucleon mass
  • {>(, )(, @(, A(} scattered lepton mass, energy,

momentum and angle

  • broadened by nucleon fermi motion

– )6C( = )D + F

' + : [for (e,e’p) ]

  • L. Weinstein, Neutrino Cross Sections 2018

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SLIDE 23
  • L. Weinstein, Neutrino Cross Sections 2018

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Reconstructed energy Ekin (GeV)

1 2 1 2 1 2 1 2

!"#$$

%

(GeV/c)

0.2 0.4 0.6 0.2 0.4 0.6

3He 3He 56Fe 56Fe

2.2 GeV (e,e’p) events

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SLIDE 24

Form “pure” 0!1# (e,e’p) spectrum: Subtract undetected pi and proton

  • For (e,e’p pi) events:

– Rotate pions around q – Determine pion acceptance for that event – Subtract undetected pions

  • Repeat for undetected two proton events
  • L. Weinstein, Neutrino Cross Sections 2018

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$%&' = $' + *

+

(all events weighted by 1/-./00to account for the different propagators)

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SLIDE 25

Compare Ekin and Ecal

  • L. Weinstein, Neutrino Cross Sections 2018

25

3He: low density, primarily 1-body 56Fe: typical density, more complicated

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SLIDE 26

Compare to generators

  • Genie for electrons

– QE and 2p2h mechanisms

  • Focus on peak of QE
  • Physics should be well described
  • ! =

#$ %&' = 1 ± 0.2

  • L. Weinstein, Neutrino Cross Sections 2018

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Genie Data

56Fe at 2.2 GeV

Energy Transfer [GeV] Energy Transfer [GeV] 0.5 1 0.5 1

slide-27
SLIDE 27
  • L. Weinstein, Neutrino Cross Sections 2018

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Electron energy [GeV] 1.2 1.6 2 data Genie Proton energy [GeV] 1 1.6 2 (MC-Data)/mc Genie data (MC-Data)/mc 0.25 0.5 0.75

56Fe 2.2 GeV

Genie Data

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SLIDE 28

Near term next steps

  • Add more reaction mechanisms to electron-

Genie

– Resonance production

  • Δ → #$
  • Δ# → ##

– Electron radiation

  • See effect on neutrino model parameters

– Tune models – Use beam energy reconstructions directly

  • Analyze the 1$ reaction channel %, %'($
  • Resubmit a proposal to take more data
  • L. Weinstein, Neutrino Cross Sections 2018

28

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SLIDE 29

Electrons for neutrinos proposal

CLAS12

  • 6-sector forward detector (8

– 40o)

– Toroidal magnetic field – !"

" ~ 0.5—1%

– 50% neutron detection efficiency for p > 1 GeV/c (Pb/scint cal) – 200 ps @ 5 m à

!" " ~10% at

1—1.5 GeV/c

  • Hermetic central detector

(40 – 135o)

– 5 T solenoidal field, 30 cm radius – 10—15% neutron detection efficiency (scintillator) – 60 ps @ 0.3 m

  • L. Weinstein, Neutrino Cross Sections 2018

29

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SLIDE 30

Electrons for neutrinos proposal

  • CLAS12

– 6-sector forward detector (8 – 40o)

  • Toroidal magnetic field
  • 50% neutron detection efficiency for p > 1 GeV/c (Pb/scint cal)
  • 200 ps @ 5 m à

!" " ~10 − 15% at 1—1.5 GeV/c

– Hermetic central detector (40 – 135o)

  • 5 T solenoidal field, 30 cm radius
  • 10—15% neutron detection efficiency (scintillator)
  • 60 ps @ 0.3 m
  • 37.5 beam days requested for

– 1.1, 2.2, 4.4, 6.6 and 8.8 GeV beam energies – H, He, C, O, Ar, and Pb

  • Conditionally approved by Jlab PAC45

– Need to return and optimize beam time request

  • L. Weinstein, Neutrino Cross Sections 2018

30

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SLIDE 31

Goals

  • We provide event yields and detector acceptance

maps

– Many beam energies – Many targets – Many event topologies

  • Let experts use these to tune generators
  • What do you want to see??

– Targets – Energies – Event topologies – Distributions

  • Proposal update due April 30 to CLAS!
  • L. Weinstein, Neutrino Cross Sections 2018

31

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SLIDE 32

Summary

  • Electron scattering can contribute dramatically

to neutrino experiments

  • We need guidance from the neutrino

community

  • We’ll provide data, you figure out what it

means

  • L. Weinstein, Neutrino Cross Sections 2018

32

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SLIDE 33

Backup slides

  • L. Weinstein, Neutrino Cross Sections 2018

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SLIDE 34

Mott weighting

  • L. Weinstein, Neutrino Cross Sections 2018

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SLIDE 35
  • L. Weinstein, Neutrino Cross Sections 2018

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SLIDE 36
  • L. Weinstein, Neutrino Cross Sections 2018

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SLIDE 37
  • L. Weinstein, Neutrino Cross Sections 2018

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Ekin Ecal

!"#$$

%

slices

3He 4He 12C 56Fe

!"#$$

%

< 0.2 0.2—0.4 !"#$$

%

> 0.4 MeV/c

> 0.4

0.2 – 0.4 !"#$$

%

< 0.2 0.2—0.4 !"#$$

%

> 0.4 MeV/c !"#$$

%

< 0.2 !"#$$

%

< 0.2 0.2—0.4 !"#$$

%

> 0.4 MeV/c !"#$$

%

< 0.2 0.2—0.4 !"#$$

%

> 0.4 MeV/c !"#$$

%

< 0.2 0.2—0.4 !"#$$

%

> 0.4 MeV/c