Neutrinos and the Case of the Missing Antimatter Steve Boyd, University of Warwick

A little bit of history What are neutrinos? Where do they come from? Why study them? A recent surprise

CRISIS

Energy(Ra) ≠ Energy(Ac)+Energy(e)

“At the present stage of atomic theory we have no arguments for upholding the concept of energy balance in the case of b-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(Neutrino)

What are neutrinos?

Electron, e Tiny mass ( 1 ) -

Electron Neutrino, n e 0 Very tiny mass (< ) Electron, e Tiny mass ( 1 ) -

mass of a neutrino =

mass of an electron =

mass of a nice cup of tea =

Very tiny mass (< ) e nene e nene Electron Neutrino, n e 0 Very tiny mass (< ) 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, n e Electron, e mass ( 1 ) - Muon Neutrino, n m Muon, m mass ( 200 ) - Tau Neutrino, n t Tau, t mass ( 3500 ) - 3 Lepton Types, or Flavours

m nene t nene

m nene t nene

Electron Antineutrino, n e Positron, e + mass ( 1 ) + 3 Antileptons Muon Antineutrino, n m Muon, m + mass ( 200 ) + Tau Antineutrino, n m Tau, t + mass ( 3500 ) +

Antimatter is not.... From Angels and Demons, Dan Brown, 2009

Negative electric charge Positive electric charge quark anti-quark MatterAnti-Matter Predicted by Dirac in 1928 Discovered by Anderson in 1932

Where do they come from?

Everywhere.... Sun Supernovae Atmosphere Reactors Accelerators

Geoneutrinos Here be dragons Earth's heat source is probably radioactive decay....which generates neutrinos

From the Big Bang One cubic foot of space contains about 10,000,000 neutrinos left over from the Big Bang (maybe).

They are present in vast numbers ≈ 5 billion per cm 2 per second at the Earth

5,000,000,000,000,000 solar n just went through you

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.

Probability 5 x = nene

"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

Probability 2 x

e n p enpnenpn enpnenpn enpnenpn enpnenpn enpnenpn enpnenpn

Why do we study them?

Probes of environments that we otherwise cannot study Cosmological and astrophysical probes IceCube Experiment

The Universe

but where is all the antimatter?

light matter antimatter Equal amounts created - but no antimatter now - so matter and antimatter must behave differently after creation Understanding this is a Big Physics Question TM

How are we studying this?

The Sun is Broken!!! Ray Davis in his solar neutrino detector – Early 1970s

Less than expected Expected Measured Number n observed The sun produces and Davis detected only e

Neutrino Oscillations THE discovery in neutrinos of the last 20 years e nene e nene A typical neutrino experiment

Neutrino Oscillations THE discovery in neutrinos of the last 20 years e nene m nmnm Neutrinos were changing flavour between sun and detector!

Distance Travelled Fraction of e 0 1 e nene m nmnm Fraction of e Fraction of 

Oh Come on, pull the other one! Q. How can a n e spontaneously turn into a n m ?

Oh Come on, pull the other one! Q. How can a n e spontaneously turn into a n m ? A. It's complicated...and can only be correctly described using the full mathematical machinery of quantum mechanics.

Oh Come on, pull the other one! Q. How can a n e spontaneously turn into a n m ? A. It's complicated...and can only be correctly described using the full mathematical machinery of quantum mechanics. where U  i is a unitary matrix

In English this time? Q. How can a n e spontaneously turn into a n m ?

In English this time? Q. How can a n e spontaneously turn into a n m ? A. The n e isn't a particle. It's three! n e ≡ “that thing which was always produced/detected with an electron but is never observed itself” e nene

Quantum Stuff e nene e n1n1 e n2n2 e n3n3 = or 50% 30% 20% Posit three other particles with definite mass : n 1, n 2 and n 3

e nene m nmnm Original n 1,n 2,n 3 mixture Different n 1,n 2,n 3 mixture n 1,n 2,n 3 travels at different speeds Long journey Fraction of e Fraction of 

Why? If the flavour change probability of neutrinos is different from that of anti-neutrinos, thenwe have a handle to study the matter/antimatter asymmetry on earth and hence find out how the universe worked at very early times

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

Summary The non-existence of antimatter in the universe is one of the outstanding problems in cosmology Understanding this problem brings us closer to a full Grand Unified Theory Neutrinos, the smallest and wierdest of the fundamental particles, could hold the key

Open Questions How much do n 1,n 2 and n 3 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?

“If we are to understand “why we are here” and the basic properties of the universe we live in, we must understand the neutrino.” American Physical Society Report

Thank you

Quantum Stuff    e    P(e    ) = (50%)  (25%) = 12%

Why do blue sky research? Curiosity about the world around us. 5-10% of jobs in UK are in physics-based sectors Gross added value from physics sectors was estimated to be 70 billion pounds in 2005 Synergy between PP projects and industry – industry acquires added skills base for other applications Training - 50% of PP PhDs go into other sectors Radioisotope production Sensors for medical applications High level computing for biological modelling Spin off tools for other science (e.g. DIAMOND) Nuclear fusion research Muon tomography in border security Security scanners Rock Imaging Cancer treatment using next gen cyclotrons

Funding UK Science Funding : 1.8% GDP (15 th in world) 18 billion to 2015 (BIS Press Release) Particle Physics Share : 1 billion to 2015 Total LHC Cost : 2.1 bn for accelerator 0.6 bn for experiments UK contribution : 500 million in development 95 million / year (STFC Press Release) Cost of the Shard : 1.2 bn Cost of one Vanguard submarine : 1.5 bn

Universal Structure m  eVm  eV m  eVm  eV

An atom a day 1 Ar atom every two days Only

From Cosmic Rays.

JPARC Facility

TARGET nmnm

295 km

Super-Kamiokande nmnm nene

Water Cerenkov

Electron-like : has a fuzzy ring Muon-like : has a sharp edged ring and particle stopped in detector.

From the Big Bang Artist's conception One cubic foot of space contains about 10,000,000 neutrinos left over from the Big Bang.

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