The Fastest Way between Fermilab and Minnesota

Deborah Harris

Fermilab

Between Fermilab and Minnesota• By Plane:

– Flying there takes 3 hours plus airport security and traffic around O’Hare airport…

• By Car: – Driving there takes 10 hours plus 15-minute stop to

buy cheese in Wisconsin• By Phone:

– A Phone call must travel above the earth by satellite: few hundredths of a second

• By Neutrino: – Travels 450 miles straight through the earth at

99.999% the speed of light: 1/400 of a second

What is a Neutrino?• Breakfast Cereal• Japanese rhythm and

blues band• Penny-sized jumping

spider• Tiny neutral particles that

weigh almost nothing and almost never interact with anything else

Answer: most of the above

What do you mean they weigh almost nothing?

• Normal matter: made of elements• Elements: made of protons

and neutrons and electrons• How much do neutrinos weigh?

– Protons and neutrons: ~1GeV (a trillion trillion or per gram)

– Electrons: 2,000 per proton

– Neutrinos: >1,000,000 per electron

What do you mean they almost never interact?

• Good news and bad news:– We can send them long distances and they will go where we

send them– We have to send billions and billions of them through a huge

detector before one of them will interact there

…

- has a good chance of traveling thru 200 earths without interacting

- 100 billion neutrinos from the sun pass through your thumbnail every second and you don’t even know it

How can you see neutrinos?• Indirectly: by studying particles that

decay (radioactivity)

Y Y'

expect β’s emitted with a discrete energy E E energy

num

ber

of β

’s

Energy crisis

• Some famous physicists said…– Maybe energy is just not conserved, this quantum mechanics is

stranger than we thought• Wolfgang Pauli wrote (in famous “desperate remedy” letter)

– Maybe there’s a neutral particle that lives in the nucleus that can take away some of this energy during a decay, we just don’t see it because it’s neutral

Y Y'

“n”

Enter Enrico Fermi…

• Enrico Fermi introduced a new “weak” force to describe radioactive decay– proposed a smaller neutral particle: “neutrino” which

is created through this weak force– Paper rejected by Nature because it “contained

speculations too remote from reality to be of interest to the reader”

– Thirty years later…neutrino is discovered at a nuclear reactor

n p

“”

What makes the sun shine? • Since Newton, we have known roughly

how much the sun weighs: 2 million trillion trillion kilograms (2x1030kg)

• Since the development of fuel, we know how much energy you get from one gallon of fuel

• We know how much energy the sun produces in light, given how much we see…

• This calculation says that the sun is 100 million years old…

• We know the sun has been shining for at least 4 billion years…how can that be?

•Answer: neutrinos and the weak interaction

Neutrinos from the Sun

Why else should we care about neutrinos and the weak force?

• This is what allows nuclei to break up• This is what allows different nuclei to

come together– If no weak

force, then nothing more than hydrogen in the universe!

Beyond the periodic table…

• More to the universe than what’s in protons and neutrons

ud

cs

tb

ee

Protons and neutrons are made of these

Qua

rks

Lept

ons

Mass

Charge:

+2/3

-1/3

-1

0

Proton: uud Neutron: udd

Neutrinos are what let neutrons decay to protons: or a d quark turn into a u quark

• Neutrinos from the sun were first observed by the Homestake experiment over 30 years ago– Only found ~1/3 the number they expected

• A similar mystery was found with the atmospheric neutrinos – ~1/2 the number expected were observed

• Neutrino experiment at Los Alamos found five times as many electron-type neutrinos as expected…(which could mean that 0.3% of the muon neutrinos changed)

• These signals could be explained if neutrinos have mass, and if different neutrinos have different masses

The Case of the Missing Neutrinos

What are we doing with neutrinos at Fermilab?

• Now: Studying how neutrinos change from one flavor to another – MiniBooNE: looking for muon neutrinos

turning into electron neutrinos over short distances (Kane County)

– MINOS: looking for muon neutrinos turning into anything but muon neutrinos between here and Minnesota

Why Minnesota?• The state with the most saunas per

capita in the US• They have the best iron mines• Measurements of neutrinos from

atmosphere: – Neutrinos from above

don’t change flavors– Neutrinos from below change a lot – Neutrinos from the atmosphere have to

travel at least a few hundred miles to change at all

– So we have to send a beam of neutrinos far enough through the earth so that they will have had at least that much time to interact…

How can you make a beam of neutrinos?

• Like making a beam of light with a flashlight– Start with a putting

a current through a filament

– That makes light– Focus the light

through a lens

• One minor added complication: protons don’t make neutrinos, you have to make particles that decay to neutrinos

Booster

Main Injector

Beamline for MINOS

• MINOS: doing everything that other neutrino beams do, but from 450 miles away and at a 3.5o angle

• Miners excavated a mile of underground tunnels

• Filled decay pipe region back up with concrete: 1000 cement trucks’ worth of cement

• Two elevators, two large halls– Target hall: filled with target, horns shielding blocks– Near Detector Hall: 150ft long, filled with MINOS Near detector

• 3½ year construction: longer than MINOS has been taking data

350 ft150 ft

2000 ft

Photo of Chris Laughton With Tunnel Boring Machine

Image courtesy of Bartoszek

Engineering. MiniBooNE

These targets see 10’s’ of trillions of Particles:How can you keep something cool when you keep pumping energy into it?

MiniBooNE power: xxxx kWattsMINOS power: 200kWattsHair Dryer: 150Watts

• MiniBooNE Horn:– Has pulsed 100

million times– 5 times a second!

• MINOS Horns– 10 million pulses– Once every 2

seconds• Horn Currents:

~200,000 Amps• 200,000 toasters!

MiniBooNE

(sounds of horns)

Ode to those who put the protons right on target

• In order to make neutrinos, someone has to vigilantly watch over the protons as they are accelerated to high energies

• Direct them through the beamline• Hit the target• And never miss!• Like walking a mile with a glass full

of milk that you cannot spill…– Over and over and over again for years…

• And what thanks do they get?

How many detectors are there?

MINOS: trying to see how many muon neutrinos “DISAPPEAR” (really just change flavor)

MiniBooNE: trying to see how many electron neutrinos APPEAR

How can you see a neutrino?• These three neutrinos (’s)

are associated with three charged particles, who are as different in size as – Squirrel (e: electron)– Lion (: muon)

– Elephant (: tau)

p

e,,or

n

You can’t see the neutrino, but you can see their partners

How can you see Neutrinos Directly?

n p+

“”• If radioactivity occurs, then this also happens:

n p+“”

“”

• Even more rare, neutrinos can hit electrons too…

“”

Measuring Neutrino Flavors• You can’t see neutrinos,

but you can see what they produce when they hit protons and neutrons…

• Problem: you can’t see these products with a microscope, because you need lots of protons and neutrons and microscopes are expensive…

• How to tell the difference between flavors?

MINOS

MINOS Detector:5,400 tons of steel and plastic Not just any plastic: it gives off light when charged particles go through itCollect the light: more particles, more light

Telling the lions from the squirrels

• These particles all had the same energy, so “total light” is about the same

• but pattern in the detector is very different

Neutrino Patterns in MINOS

• This one has a muon in it: that’s the only thing with charge that can travel through a few feet of steel!

• This one does not has a muon in it: hard to tell in this detector between muons and anything else if many particles are produced

MiniBooNE Detector Technique

• Who here knows what a sonic boom is? – The noise that gets made when something goes faster than

sound• Who has heard one?

– Airplanes– Thunder

• When something goes faster than light, the same thing happens, only instead of a loud boom, you get a flash of light

MiniBooNE Detector

• tanks contains 250,000 gallons of mineral oil (neutrino target) - 44 tanker trucks worth! - 800 tons!• lined w/ 1520 PHOTOTUBES (electronic “eyes” of the detector)

Phototubes work like inverse light bulbs - produce an electrical signal whenever light strikes them

Neutrino Patterns in MiniBooNE

muon electron

How can neutrinos change flavors?• Quantum mechanics presents us with a lot of phenomena that seem weird & non-intuitive - neutrino oscillations is one of them

- ’s can shift their identity & transform into one another

- particles can sometimes behave like waves

• Quantum mechanical state can be the sum of several states

- let is suppose is sum of two different mass states (or “matter waves”) … - might seem odd, but is perfectly allowable - can generate the interference pattern we call neutrino oscillations

wave 1

wave 2

wave 1 + wave 2

νμ νμ

-ness begins to fade

sometimesthe waves are

in-phase

sometimes theyare out of phase

Neutrino Oscillations

- neutrinos “waves” can oscillate between types but only if they have different masses

- this interference causes first the disappearance & then reappearance of the original type

a neutrino can change its identity!

in much the same way as beats are formed through the interference of two

waves with different frequencies

How Do You Weigh a Neutrino?

flux

oscillates

neutrin-o-maker

100%

0% e

• so if we move the detector some distance away, a fraction of the muon neutrinos will become electron or tau neutrinos

MiniBooNE is looking for: e at “Los Alamos” frequencyMINOS is looking for at “Atmospheric” frequency

neutrin-o-

taker

100%

0% e

neutrin-o-

taker

100%

0% e

(100-x)%

x% e

neutrin-o-

taker

What’s Next?

• Just Around the Corner: two experiments to look at neutrino interactions with detectors that are closer to microscopes– SciBooNE: take detector from Japan, beamline from

Fermilab Booster – MINERvA: bring brand new detector in, as well as

nuclear physicists who want to see if neutrinos can tell what nucleus they are interacting in

– Both: will help still the next generation of oscillation experiments

What’s next for Oscillations?

• Just around two corners: NOvA– Best chance for seeing neutrino anti-neutrino

differences!– Will use the same neutrino beamline as

MINOS– Brand new detector in northern Minnesota:

better able to distinguish electrons (squirrels) from anything else

Why Neutrinos and Anti-Neutrinos?• Every fundamental particle has an anti-matter partner

• When they meet, they annihilate into pure energy. Alternatively, energy can become matter plus anti-matter

So you might ask…

• The early Universe had a lot of energy. Where is the anti-matter in the Universe?

• Good question… how do we know it isn’t around today?– look for annihilations.– As far away as we can tell, today there aren’t big

matter and anti-matter collisions

– Maybe it’s the neutrinos which are different from anti-neutrinos!

Conclusions

• Neutrinos are everywhere all the time• We wouldn’t be here without them• We are just beginning to understand what

they are • We have built the most powerful neutrino

beams and are getting to the best measurements of neutrinos changing flavors

• We’ve only just begun…

In Gratitude• Thank you for funding our research.  I find that when I talk to people

about the science that we do there is interest and pride that we, as a nation, are able and willing to pursue new and fundamental scientific knowledge.  Although many do not understand the details, the American people seem to understand that fundamental science is worth pursuing and is important to the future of our country.  We need to push back frontiers of our knowledge.  More practically, basic scientific research proves to be a wise investment for the future through creation and development of new technologies to which it invariably leads.  Thank you for the opportunity you have given us to pursue this remarkable science.

• Next, I would like to express deep respect and personal thanks to my colleagues both within and outside MINOS for your support, not only over the last couple of months but over the last decade of building this facility and experiment together.  Scientific results are of course the goal, but they come only at the end of a long and arduous process.  It is only possible to get there by working together with people of great skill and diligence.  The end result may be just a hard number, but the process is intrinsically human.  It is a pleasure to have so many fine colleagues with whom to share this work. 

• Finally, in my recent diagnosis and treatment I have frequently found myself marveling at the technology that is available for 21st century medical care.  It is very gratifying to me to know that many of the basic ideas and techniques for modern imaging equipment were either first developed IN our own field of high-energy physics or BY people TRAINED in our field.  I have gotten a first-hand view of the remarkable achievements in the engineering, technology, chemistry, and medicine which enable us to effectively treat diseases like the one that I have.  And just as in physics, the glue that brings it all together and makes it work are dedicated and skilled professionals.  Just as in our own field, the combination of technology and people can produce fantastic results.   

Doug Michael, March 30 2005