current status of a measurement of hadronic parity...

Current Status of a Measurement of HadronicParity Violation in the Capture of Cold Neutrons

on Helium-3

for the n3He Collaboration

Mark McCreaUniversity of Manitoba

2015 CAP Congress

June 18, 2015

Introduction

Motivation

Spallation Neutron Source

Experiment Setup

Ion Chamber Details

Ion Chamber Simulation

n3He Introduction

n3He probes the low energy strong interaction, using the weak

interaction by measuring the parity violating directional asymmetry

in the proton recoil from the reaction

~n +3He → p + T + 765keV

Beam n 3He p

θs,~k

T

The goal of the experiment is to measure the asymmetry to the2× 10−8 level.

Theoretical Motivation

q

q

q

q

g

Strong Interaction

q

q

q

q

Z 0,W±

Weak Interaction

u d d

u d d

udd

udd

?

Uncertain HWI

N

N

N

N

PC

Strong

PV

Weak

π, ρ, ω

DDH Parameterization

DDH Meson Exchange Parameters:

Opv = a1πh

1π + a0

ρh0ρ + a1

ρh1ρ + a2

ρh2ρ + a0

ωh0ω + a1

ωh1ω

A Brief Look at ParityUnder a parity transformation P polar vectors such as themomentum transform as

P(~kn)→ −~kn and P(~kp) = −~kpbut axial vectors, such as the neutron spin, remain unchanged

P(~sn)→ ~sn

Orignal State:

Beam n 3He p

θs,~k

T

Parity Transformed:

Beamn3Hep

θs,~k

T

Spin Flipped:

Beam n 3He p

θs,~k

T

Spallation Neutron Source

I Located at the Oak Ridge National Laboratory (ORNL) inTennessee

I 60 Hertz pulsed spallation sourceI approximately 1010 neutrons/secondI n3He is running at the FnPBI Three 20K liquid hydrogen moderator for cold neutron beam

lines

n3He Schematic Diagram

Biological Shielding

NeutronGuide

C1 C2

M1 SMP RFSF

Collimator

3He Target/Detector

HF Solendoid

n3He Target Chamber

Beam

HVSignal

17 HV Frames with 8 wires each16 signal Frames with 9 wires each

Assembled Frame Stack

I 17 HV frames

I 16 signal frames

I 9 signal wires per frame

I 144 signals to read out

Proton Asymmetry in Chamber

~n +3He → p + T + 765keV

Neutron Proton TritonElectron Collection

A proton and triton asymmetry occur in the chamber but thelonger range of the proton causes its asymmetry to dominate

Target Chamber on Stand

I 4 point adjustable stand

I roll, pitch, height were notindependent

I target electrically isolatedfrom stand

I angle block used for initialalignment

Components on Beamline

First Data from Ion Chamber

Ion Chamber Simulation - Garfield++

Garfield++ is a toolkit for the detailed simulation of particledetectors that use gas and semi-conductors as sensitive medium.

I Gas properties calculated using Magboltz

I Ion Mobility from Data from Atomic Data and Nuclear DataTables 17, 177-210 (1976)

I Signal calculated with Shockley-Ramo Theorem:

i(t) = −qv · Ew (r)

I Ew (r) is a calculated weighting field as though the electrodehad a potential of 1V and everything else is ignored

I Fields and Electrode locations from Gmsh and Elmer

I Looking at charge collection times and signals

Geometry - Gmsh

Fields - Elmer FEM

Initial Simulation Details

I 200 events at 6 locationsspaced evenly between HVand Signal wire

I ion and electronpropagated from each point

I collection time to becompared with measuredvalues

Collection Times

t(ns)0 500 1000 1500 2000 2500 3000 3500 40000

20

40

60

80

100

120

Electron Collection Times

I Six equally spaced starting positions gave 6 peaks.

I 200 electrons per positions

Integrated Signal - electron

hIntegratedSig-e-0

Entries 200Mean -22.85RMS 0.7114

-610×fC-25 -24 -23 -22 -21 -20

0

5

10

15

20

25 hIntegratedSig-e-0


hist Integrated Signal e -0hIntegratedSig-e-1


-610×fC-74 -72 -70 -68 -66

0

2

4

6

8

10

12

14

16

hIntegratedSig-e-1




-610×fC-114 -112 -110 -108 -106 -104 -102

0

2

4

6

8

10

12

14

16hIntegratedSig-e-2


hist Integrated Signal e -2

hIntegratedSig-e-3

Entries 200

Mean -126.5RMS 2.433

-610×fC-132 -130 -128 -126 -124 -122 -120

0

2

4

6

8

10

12


Entries 200

Mean -126.5RMS 2.433


Entries 200Mean -140.2

RMS 2.506

-610×fC-146 -144 -142 -140 -138 -136 -134

0

2

4

6

8

10


Entries 200Mean -140.2

RMS 2.506



-610×fC-150 -100 -50 0

0

20

40

60

80

100

hIntegratedSig-e-5


hist Integrated Signal e -5

Ion/Electron pair signals measure from 6 positions

Summary

I Target chamber assembled and tested November 2014

I Target chamber installed December 2014

I First Data from Chamber January 2015

I Data taking to continue until end of 2015

I Charge collection simulations are progressing

n3He Collaboration

Duke University, TriangleUniversities NuclearLaboratory

I Pil-Neo Seo

Istituto Nazionale diFisica Nucleare, Sezionedi Pisa

I Michele Viviani

Oak Ridge NationalLaboratory

I Seppo Penttila

I David Bowman

I Vince Cianciolo

I Jack Thomison

I Paul Mueller

University of Kentucky

I Chris Crawford

I Latiful Kabir

I Aaron Sprow

Western KentuckyUniversity

I Ivan Novikov

University of Manitoba

I Michael Gericke

I Mark McCrea

I Carlos Olguin

Universidad NacionalAutonoma de Mexico

I Libertad Baron

I Jose Favela

University of NewHampshire

I John Calarco

University of SouthCarolina

I Vladimir Gudkov

I Matthias Schindler

I Young-Ho Song

University of Tennessee

I Noah Birge

I Chris Coppola

I Nadia Fomin

I Connor Gautham

I Geoff Greene

I Irakli Garishvili

I Chris Hayes

I Serpil Kucuker

I Eric Plemons

I Mae Scott

University of Tennesseeat Chattanooga

I Josh Hamblen

I Jeremy Watts

University of Virginia

I S. Baessler

current status of a measurement of hadronic parity...

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