The Elusive Neutrino - Caltech High Energy Physics

hep.caltech.edu

The Elusive Neutrino - Caltech High Energy Physics

The Elusive Neutrino

Ryan Patterson

74 th Annual Seminar Day

Caltech

May 14, 2011


Beta decay (pre­1930 picture)

nucleus A

nucleus B

electron


Beta decay (pre­1930 picture)

nucleus A

nucleus B

Beta decay (Pauli's picture)

nucleus A

electron

nucleus B

electron

something new?


If you can make this new particle... ...then you can (try to) detect it

A

B

electron

???

rate of production

(rate of beta decay)


???

B

rate of interaction

(anti)electron

A


If you can make this new particle... ...then you can (try to) detect it

A

B

electron

???

rate of production

(rate of beta decay)


???

rate of interaction

“I have done a terrible thing. I have postulated

a particle that cannot be detected.”

B

­ W. Pauli (1930)

(anti)electron

A


23 years later: detection

Reines (left) and Cowan


The sun

(Image of sun in neutrinos,

Super­Kamiokande collaboration)

The atmosphere

(Cosmic ray showers)

e +

+

e

+

p

0

Supernovae

(The Crab Nebula,

NASA / ESA)

Nuclear reactors

(Pickering Nuclear Generating Station)


source

e


source detector


e e

recoil

particles


source detector


e e





recoil

particles


source detector

e

e e





labels


recoil

particles


source detector

e

e e





labels


recoil

particles

Neutrinos come in three flavors


Fundamental

Forces

strong



elec./mag.

weak


Interaction of a muon neutrino


recoil

particles


muon following curved path

in a 1.3 T magnetic field

Detector for the

MINOS experiment

alternating layers of steel

and “plastic scintillator”


Interaction of a muon neutrino


recoil

particles


Super­Kamiokande

water surrounded by highly

sensitive light detectors


Electron neutrinos (e.g., from the sun)

Homestake Detector (c. 1970)

radiochemical approach using

dry cleaning fluid – C 2 Cl 4

(chlorine argon conversion)

e + 37 Cl 37 Ar + e –

can look for the

buildup of argon


Electron neutrinos (e.g., from the sun)

Homestake Detector (c. 1970)

radiochemical approach using

dry cleaning fluid – C 2 Cl 4

(chlorine argon conversion)

e + 37 Cl 37 Ar + e –

can look for the

buildup of argon

not not much much to look look at...

at...


source



short

distance

detect only


source





short

distance

medium

distance

detect only

detect mostly

e


source







short

distance

medium

distance

long

distance

detect only

detect mostly

e


e


source







short

distance

medium

distance

long

distance

detect only

Neutrinos can change flavor as they travel

detect mostly

e


e


Neutrinos are about 10,000,000,000 times lighter

than other fundamental particles


Neutrinos are about 10,000,000,000 times lighter

than other fundamental particles

smallness of neutrino mass


new physics at very high energy scales


The last 40 years at

the energy frontier

Accessible

energy scale

(in units of

proton masses)

10000

1000

100

ISR

Unification scale:

1,000,000,000,000,000

SPS

Tevatron,

Run I

1970 1980 1990 2000 2010

Year of collider turn­on

Tevatron,

Run II

LHC

(2013)

LHC

(today)


Fermilab

Batavia, Illinois

2 kilometers


Fermilab

Batavia, Illinois

2 kilometers


NOA far detector

810 km

Fermilab

NOA

NO

NOA near detector

Proton target


4 cm 6 cm

1600 cm

(not to scale)

to “avalanche

photodiode” array


proton proton

electron electron

muon muon

messy!

(simulated events)


proton proton

electron electron

muon muon

Real neutrino interaction in

the prototype NO NO A detector

messy!

(simulated events)


Far detector site, September 12, 2010


Far detector enclosure, October 7, 2010


Far detector enclosure, March 21, 2011


Prototype near detector, October 13, 2010


(Very) early universe

Today

Matter

+

Antimatter

Matter

+

Antimatter

Annihilation!


(Very) early universe

Today

Matter

+

Antimatter

Neutrinos might be the reason

there is anything in the universe.

Matter

+

Antimatter

Annihilation!


Mixed­up “flavors”

three

different

flavors

lightest

middle

Quarks

heaviest


Mixed­up “flavors”

three

different

flavors

lightest

middle

Quarks

heaviest

lightest

middle

Neutrinos

heaviest


Mixed­up “flavors”

three

different

flavors

lightest

middle

Quarks

heaviest

lightest

middle

Neutrinos

heaviest

Is this the same

for neutrinos

and

anti­neutrinos

?


Neutrinos

from

Supernovae

Remnant from

supernova 1987a

Several thousand interactions

for a supernova in our galaxy

(hours before any visible

light reaches Earth)


Just a taste...

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