The Ghostly Neutrino

Steve Boyd, University of Warwick

“If we are to understand “why weare here” and the basic propertiesof the universe we live in, we mustunderstand the neutrino.”

American Physical Society Report - 2004

A little bit of history

What are they?

Where do they come from?

Why study them?

A recent surprise

The T2K Project

CRISIS

Energy(Ra) ≠ Energy(Ac)+Energy(e)

“At the present stage of atomictheory we have no argumentsfor upholding the concept ofenergy balance in the case ofb-ray disintegrations.”

Neils Bohr

Wolfgang Pauli

“Desperate remedy.....”“I do not dare publish this idea....”“I admit my way out may look improbable....”“Weigh it and pass sentence....”

“You tell them. I'm off to a party”

Energy(Ra) ≠ Energy(Ac)+Energy(e)

Energy(Ra) Energy(Ac)+Energy(e)+ Energy(Neutrino)

What are neutrinos?

Electron, e

Tiny mass ( 1 )

-

Electron Neutrino, ne

0

Very tiny mass(<0.0000001)

Electron, e

Tiny mass ( 1 )

-

x 500

Very tiny mass(<0.0000001)

e

ne

e

ne

Electron Neutrino, ne

0

Very tiny mass(<0.0000001)

Electron, e

Tiny mass ( 1 )

-

In experiments neutrinos are NEVER seen.

We can only detect them through the byproducts of their interactions with matter.

Type of the charged particle detected used to infer the type of incoming neutrino.

e e

Electron Neutrino, ne

Electron, e

mass ( 1 ) -Muon Neutrino, nm

Muon, m

mass ( 200 ) -TauNeutrino, nt

Tau, t

mass ( 3500 ) -3 Lepton Types

m

ne

t

ne

Electron Antineutrino, ne

Positron, e+

mass ( 1 ) +

3 Antiparticles

Muon Antineutrino, nm

Muon, m+

mass ( 200 ) +Tau Antineutrino, nm

Tau, t+

mass ( 3500 ) +

Where do they come from?

Everywhere

From the Big Bang

Artist's conception

From the Big Bang

Artist's conception

One cubic foot of space contains about 10,000,000 neutrinos leftover from the Big Bang.

From Astrophysical Objects

Supernovae created the heavy elements (us) and neutrinos appear to be important to the explosion dynamics.

From the Sun

≈ 70 million per cm2 per second at the Earth

From Cosmic Rays.

Geoneutrinos

From Us.

So why don't we notice?

n are almost ghosts. They interact extremely weakly with matter.

To a neutrino a planet is mostly empty space.

"The chances of a neutrino actually hitting something as it travels through all this howling emptiness are roughly comparable to that of dropping a ball bearing at random from a cruising 747 and hitting, say, an egg sandwich."

Douglas Adams

500,000,000,000,000 solar n just went through you

enpn

enpn

enpn

enpn

enpn

enpn

enpn

Why do we study them?

Probes of environments that we otherwise cannot see

Probes of objects too far away for anythingelse

Cosmological and astrophysical implications

Matter/Antimatter imbalance

Probes of environments that we otherwise cannot see

Probes of objects too far away for anythingelse

Cosmological and astrophysical implications

Matter/Antimatter imbalance

NEUTRINO

ASTROPHYSICS

Probes of environments that we otherwise cannot see

Probes of objects too far away for anythingelse

Cosmological and astrophysical implications

Matter/Antimatter imbalance

Universal Structure

m eV m eV

m eV m eV

Probes of environments that we otherwise cannot see

Probes of objects too far away for anythingelse

Cosmological and astrophysical implications

Matter/Antimatter imbalance

Why is there more matter than antimatter?

=

Why is there more matter than antimatter?

Sub-Atomic Talk Show Disasters

CP ViolationQ. Is there a difference betweenthe physics of matter and antimatter?

A.Yes there is.

We study this herewith an experimentcalled BaBar

“B0 / B0 mixing”

Q. Is there a difference betweenthe physics of matter and antimatter?

A.Yes there is.

We've never seen it in neutrinos, though.

Matter-Antimatter Asymmetry

n

n

nn

nn

n

n n

n

nn

“Leptogenesis”

How to study this?

Neutrino OscillationsTHE discovery in neutrinos of the last 20 years

l

nl

l

nl

A typical neutrino experiment

The Sun is Broken!!!

Ray Davis – Early 1970s

An atom a day

e Cl37 e- Ar37

1 Ar atom every two days

Only

Less than expected

Expected

Measured

Num

ber

n o

bse

rved

Neutrino OscillationsTHE discovery in neutrinos of the last 20 years

e

ne

m

nm

Neutrinos were changing flavour betweensun and detector!

Distance Travelled

Pro

b.

It is

ne

0

1

e

ne

m

nm

Eh?

Q. How can a ne spontaneously turn into a nm?

Eh?

Q. How can a ne spontaneously turn into a nm?A. The ne isn't a particle. It's three!

ne ≡ “that thing which was always produced/detected with an electron”

e

ne

Quantum Stuff

e

ne

en1

en2

en3

=or

or

60%

30%

10%

e

ne

m

nm

Original n1,n2,n3

mixture

Different n1,n2,n3

mixture

n1,n2,n3

travelsat differentspeeds

This can only happen if n1,n2,n3 have different massesOnly gives us differences in masses

Long journey

Why so important?The Standard Model of Particle Physicshas no explanation for a non-zero, but tiny, neutrino mass – so we are in “unknown physics” territory.

Neutrino masses link to GUT theories.

Has cosmological implications (mass balance,structure)

Posc e≠ Posc e

The T2K Experiment

University of Warwick

University of Sheffield

Imperial College, University of London

Oxford University

University of Liverpool

University of Lancaster

Queen Mary College, University of London

Rutherford-Appleton Laboratories

295 km

295 km

JPARC Facility

JPARC Facility

TARGET nm

295 km

Super-Kamiokande

nm

ne

Super-Kamiokande

Water Cerenkov

Electron-like : has a fuzzy ring

Muon-like : has a sharp edged ring andparticle stopped in detector.

Open Questions

How much do n1,n2 and n3 weigh?

Why are they so much lighter than all the other massive particles?

Are neutrinos the same as antineutrinos?

Are neutrinos the reason we are here at all?

‘‘...these kind of findings have implications that are not limited to the laboratory. They affect the whole of society — not only our economy, but our very view of life, our understanding of our relations with others, and our place in time.’’

Bill Clinton

P e=sin2 2sin21.27 m2 LE

L

sin2(2q)

Dm2 = m12-m2

2

Why do blue sky research?5% of jobs in UK are in physics-based sectorsGross added value from physics sectors was

estimated to be 70 billion pounds in 2005Synergy between PP projects and industry – industry

acquires added skills base for other applicationsTraining - 50% of PP PhDs go into other sectors

Radioisotope productionSensors for medical applicationsHigh level computing for biological modellingSpin off tools for other science (e.g. DIAMOND)Nuclear fusion researchMuon tomography in border securityAirport scannersRock ImagingCancer treatment using next gen cyclotrons