ProtoDUNE Pion Quasi-elastic scattering Aaron Higuera University - - PowerPoint PPT Presentation

Aaron Higuera

University of Houston

ProtoDUNE Pion Quasi-elastic scattering

Outline

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• 1. Physics motivation, why we want to this measure cross sections?

There are several pion analyses underway, this is just meant to show the physics deliverables for a pion quasi-elastic scattering analysis… I don't plan to step on someone's toes

Introduction

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Neutrino CC quasi-elastic scattering

• Early during this decade CC QE was used

as a standard candle for neutrino experiments to measure the flux

• Clean experimental signature
• Easily kinematics if you assume a nucleon

at rest, can reconstruct Ev and Q2 only using lepton kinematics

• It was assumed to be a very well

understood process

Introduction

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Neutrino CC QE scattering

• MiniBooNE puzzle PRD 81, 092005

(2010) Modern neutrino detectors are made

• f materials with heavy nuclei

Nucleons in the nucleus are no free How the nucleus changes the cross-section?

• Initial state nucleons have fermi momentum (RFG model take into account this)
• Other nuclear effects

Short range correlation, MEC, RPA, final state interaction, etc

Introduction

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Electron scattering

RevModPhys 80,189 (2008)

• Clean experimental signature

precise measurements of k(E,p) and k’(E’,p’) Clear signature of nuclear effects

PRD 72 053005 (2005)

Introduction

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Electron scattering

Electron-scattering experiments found that, approximately 20% of the time, electrons scattered from correlated pairs of nucleons instead of single nucleons

• R. Subedi et al. Science, 320(5882):1476–1478, 2008
• R. Subedi et al. Science, 320(5882):1476–1478, 2008

Introduction

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Electron quasi-elastic scattering

RevModPhys 80,189 (2008)

• Clean experimental signature

precise measurements of k(E,p) and k’(E’,p’) Quasi-elastic scattering

• The QE peak provides a direct measure
• f the average momentum of nucleons in

nuclei and the with of the peak reflects internal motion of nucleons in the nucleus

• However, the coupling of the electrons to

nucleons is almost entirely electromagnetic, and hadrons probes can be complementary to explore the full picture 


Introduction

Pion quasi-elastic scattering

Pion quasi-elastic scattering at 950 MeV/c with different nuclei 2H, 6Li, C, Ca, Zr and 208Pb PRC 64, 034608 (2001), thesis here

Introduction

There is great academic interest in quasi-elastic scattering and more measurements are always useful This new measurements can provide useful information for neutrino+40Ar interactions

Pion Quasi-elastic Scattering

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As neutrino interactions have to deal with FSI, we have too When the pion interacts with a nucleon within the nucleus (GEANT cross sections) the particles at the interaction vertex can go under different scattering process, this is modeled in GEANT by the Bertini cascade model

n π+ p

π+

So lets use the outgoing particles as the physics observables π++40Ar —> π+’ + X(Nucleons) where X can be any number of nucleons X>1

Pion Quasi-elastic Scattering

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Pion scattering: Elastic scattering Inelastic scattering ( QE, pion production, charged exchange, absorption, etc) For the scattering process where π++40Ar —> π+ + X(Nucleons) where X can be any number of nucleons X>1

1 2 3 4 5 6 7 8 9 10 Number of neutrons 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 1 2 3 4 5 6 7 8 9 10 number of protons 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 fraction

Number of nucleons What fraction are due to multi-nucleon correlations? What fraction are due to Bertini cascade?

Pion Quasi-elastic Scattering

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200 400 600 800 1000 Pion Kinetic Energy (MeV) 0.2 0.4 0.6 0.8 1 Fraction

Approximated a third of the inelastic scattering are QE events

q = k − k0

Q2 = −q2

q3 = p Q2 + q0 q0 = ω q3 = q

π++40Ar —> π+’ + X(Nucleons) where X can be any number of nucleons X>1

Pion Quasi-elastic Scattering

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100 200 300 400 500 600 700 800 900 1000 (MeV) ω Energy loss 100 200 300 400 500 600 q <350 MeV/c 100 200 300 400 500 600 700 800 900 1000 (MeV) ω Energy loss 50 100 150 200 250 350< q <450 MeV/c 100 200 300 400 500 600 700 800 900 1000 (MeV) ω Energy loss 100 200 300 400 500 600 700 650> q MeV/c 1 − 0.5 − 0.5 1 ) θ cos( 200 400 600 800 1000 1200 1400 1600 1800 2000 2200

Angle between the incoming pion and the outgoing pion is small (low Q2 ) π+40Ar —> π’ + X(Nucleons) where X can be any number of nucleons X>1 Kinematics distribution based on true information

Pion Quasi-elastic Scattering

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The QE peak provides a direct measure of the average momentum of nucleons in nuclei and the with of the peak reflects internal motion of nucleons in the nucleus

ΓF G = 1 √ 2 ⇣p M ∗2 + (q + kF )2 − p M ∗2 + (q − kF )2 ⌘

Fitting the width (FWHM) we can extract the Fermi momentum

200 300 400 500 600 700 800 900 1000 Momentum tranger (MeV/c) 50 100 150 200 250 300 350 400 450 500 FWHM (MeV)

kF = 235 ± 8.63 MeV/c

Pion Quasi-elastic Scattering

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How we measure the cross section? The thin slice method not applicable For given bin i

✓ d dqd! ◆

i

= 1 Ntgt beam · 1 (∆q)i · 1 (∆!)i · N data

i

− N bkgd

i

✏i

Need to define a fiducial volume and calculated the number of targets

Comments

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There is great academic interest in quasi-elastic scattering and more measurements are always useful dσ/dqdω, kF, quasi-elastic peak shift (relative to H), etc There are few challenges in terms of reconstruction How good we can measure the interaction vertex How good is our tracking reconstruction at small scattering angle? How good we can calculate pion energy? How good we can tag nucleons?

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The End