Tesis

S im u la tio n s a n d A n a ly s e s o f E x p e c te d N u c le o n T ra n s v e rs ity
M e a s u re m e n ts in th e M IN E R ν A N e u trin o E x p e rim e n t

A n H o n o rs T h e s is f o r th e D e p a rtm e n t o f P h y s ic s a n d A s tro n o m y
P a u li K e h a y ia s

T u f ts U n iv e rs ity , 2 0 0 9

Acknowledgements
I would like to thank my committee members BruceBoghosian, Hugh Gallagher, and Gary
Goldstein – Professor Gallagher in particular for his advice and patience throughout my time at
Tufts. I would also like to thank Dr. Costas Andreopoulos (Rutherford Appleton Laboratory) for
help with GENIE.

Table of Contents
Abstract

1

Introduction

1

Theory

3

1. Elementary Particles and the Standard Model

3

2. Elastic Scatteringand Deep Inelastic Scattering

7

3. Generalized Parton Distributions and Transversity

10

4. Coherent Charged Current Single Pion Production

11

Hardware, Software, and Methods

14

1. The MINERνA Experiment

14

2. Simulation Methods

17

3. Event Reconstruction and Detector Smearing

19

4. Pion φ Transversity Dependence

20

Results

21

1. Smearing andReconstruction Test Results

21

2. Testing Transversity-Dependent φ

29

Conclusions and Future Work

31

Bibliography

33

iii

Abstract
Coherent charged current single pion production events were simulated and analyzed for the
MINERνA neutrino experiment. The differential cross section of this reaction is transversitydependent in the pion azimuthal angle φ according to twomodels: the GPD model and the Regge
model. Our goal was to determine whether MINERνA will be able to differentiate between these
two models. We found that the GPD model predicts an event rate largely independent of φ while
the Regge model predicts a significant cos(2φ) contribution. MINERνA will have sufficient
resolution and statistics to distinguish between the two, though a more thoroughinvestigation is
needed.

Introduction
Neutrinos are neutral elementary particles that travel at nearly the speed of light. They are
much lighter than other elementary particles and interact less frequently with other matter.
Neutrinos were formulated by Pauli in 1930 to resolve why beta decay reactions appeared to
violate conservation of energy and were discovered in 1956 by Reines and Cowan ina nuclear
reactor experiment. Neutrino experiments have studied neutrinos from natural sources (the Sun,
supernovae, radioactive decay, and atmospheric cosmic ray interactions) and artificial sources
(nuclear reactors and proton accelerators). Neutrinos interact rarely with other matter, making
neutrino experiments difficult because of the low event rate. However, since neutrinos are a
uniqueprobe in particle physics, neutrino experiments are worth the difficulty.
MINERνA (Main Injector Experiments for ν-A) is a neutrino experiment at the Fermi
National Accelerator Laboratory (Fermilab). It is still under construction but recently started
taking data, and the detector and targets have a range of nuclear targets. MINERνA data will be

used to assess neutrino-nucleoncross-sections, nucleon substructure, and nuclear effects on
neutrino interactions. The cross section measurements will reduce the uncertainties in neutrino
experiments searching for other neutrino physics, such as flavor oscillation [1].
MINERνA data can be used for a novel nucleon substructure analysis. Nucleons consist of
pointlike particles called partons, which are quarks and gluons. Their behavioris described by
the quark parton model, a theory that makes predictions about the spatial and longitudinal
momentum probability distributions of the quarks within the nucleon. An extension to the quark
parton model that describes the transverse nucleon structure can be derived from more general
mathematical objects called generalized parton distributions (GPDs). Four of the eight quark
GPDs...