# Presentation: 247784

## neutrinos

- a brief introduction

**Paul Nienaber**
**Fermilab**

## particles, particles, particles...

- each of these has an uncharged, very light, elusive cousin
- these are the **NEUTRINOS** (“little neutrals”)
- three kinds:

- all matter in the universe is made up of **ATOMS**
- atoms are made up of tiny electrons whizzing around a dense, compact core: the nucleus
- electrons are fundamental, indivisible entities
- electrons have two heavier siblings, called the muon (μ) and the tau ().

- electrons

**NEUTRINOS**

- electron neutrino (e “noo – e”)
- muon neutrino (μ “noo – mew”)
- tau neutrino ( “noo – tau”)

## ’s (nu’s) in the news

- neutrinos abound in the universe – in every gallon of space, there are a million neutrinos
- they come from stars, from the Sun, and are leftover relics from the Big Bang
- they pass through matter essentially without a trace – they are very difficult to detect
- still, neutrinos matter! they are a crucial part of our understanding the workings of matter
- Two of the 2002 Physics Nobel Prize winners were neutrino physicists
- Ray Davis: neutrinos from the Sun
- Masatoshi Koshiba: supernova neutrinos

## vellcome to ze laborratory

- so... how do you do a neutrino experiment?
- three ingredients:
- BEAM
- TARGET
- DETECTOR
- since neutrinos interact so rarely, need LOTS of beam and LOTS AND LOTS of target/detector

## eye of neut, toe of frog?

- need a source or beam of neutrinos – recipe?
- neutrinos come from...
- reactions inside the atomic nucleus
- fusion (inside stars and the Sun)
- fission (nuclear power plants)
- decay of certain subatomic particles
- these “neutrino parent” particles are produced when fast-moving protons smack into matter
- in the upper atmosphere (atmospheric neutrinos)
- in a particle physics laboratory near you (accelerator neutrinos)

- ... requires making particles which decay into neutrinos ...

- Making neutrinos...

- ...which you accomplish by slamming protons into a chunk of matter, ...

- ...letting the “parents” decay ...

- (... and perhaps filtering out the leftovers).

## catch me if you can

- now you have a pitcher – need a catcher
- “catching” a particle only works if the particle is electrically charged
- “see” a neutrino ONLY if it hits something and knocks out or produces a charged particle
- one way a neutrino can interact: run into something and change into its own charged partner :
-  “tagger” reaction: partner ID’s neutrino species

******e **** +**

**X**

**+ X ́**

****

**e****-**

********** **** ****+**

**X**

**+ X ́**

****

******-**

********** **** ****+**

**X**

**+ X ́**

****

******-**

## neutrinos “oscillate” ?!

- if I make a beam entirely of (e.g.) muon neutrinos, and place my detector immediately downstream, I detect 100% muon neutrinos

- BUT if I move the detector a distance away, a small fraction of the muon neutrinos can change (“oscillate”) into electron neutrinos...

- ...and then back again!

**neutrin**
**-o-**
**taker**

**(100-x)% **********
**[?!!]**

**    ****x% ********e**

- change (“oscillate”)

## this astonishing behavior is actually not unusual in the weird and often counter-intuitive world of quantum physics

particles behave like: ________

wave frequency depends on energy (mass)

neutrino oscillation demonstrates that, contrary to what we once thought, neutrinos have mass

- particles behave like: ________
- wave frequency depends on energy (mass)
- neutrino oscillation demonstrates that, contrary to what we once thought, neutrinos have mass

**neutrinos “oscillate” ?!**

**WAVES**

**E = mc****2**** !**

## MiniBooNE experiment

**Booster: start with protons**

**protons strike beryllium**** **

**Magnetic focuser: “horn****”**

**Decay region**

**Absorber: filter out all but neutrinos**

**450 m earth: ************→********e****?**

**MiniBooNE detector**

**↞  ****decay pipe  ****↠**

## MiniBooNE detector

- 12 m diameter tank
- 800 tons ultra-pure mineral oil
- 1500 8” light sensors (photo-multiplier tubes)

**inside the MiniBooNE tank: looking up at the 1280 photomultiplier tubes...**

## MiniBooNE’s goal is to test a previous experiment performed at Los Alamos

if that result is confirmed, our picture of the “particle zoo” will have to change

MiniBooNE started running in August 2002, and will run for at least two years

we’ve collected more than 100,000 neutrino events so far

**if that result is confirmed, our picture of the “particle zoo” will have to change**
**MiniBooNE started running in August 2002, and will run for at least two years**
**we’ve collected more than 100,000 neutrino events so far**

**eye spy. . .**

**a typical MiniBooNE event**

**some new kind of nu?**

## we’ve made a lot of progress in understanding the fundamental structure of matter, and Fermilab has been a big part of that progress

neutrino physics, and particularly oscillations are one of the current exciting avenues of investigation

stay tuned!  the voyage of exploration continues...

**neutrino physics, and particularly oscillations are one of the current exciting avenues of investigation**
**stay tuned!  the voyage of exploration continues...**

**solving future puzzles...**

- . . . . . . thanks!

## Funding support for MiniBooNE comes from

- and

- United States Department of Energy
- Office of Science