Unbelievable Particles

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Neutrinos

Unbelievable particles

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Neutrinos are unbelievable particles!

Who foresaw their existence?

Already in 1930 Wolfgang Pauli foresaw the existence of a new

particle, later getting the name neutrino (itl. for a little neutral one)The physicists had for a long time tried to find an explanation for

missing energy balance when beta particles (electrons) emanated by

some kinds of radioactivity.

There was something that would not agree; yes it was in conflict

with the principle of the law of conservation of energy.

Pauli suggested that a neutrino particle cut off with some of the

energy, but he added: I have done something awful; I havepredicted a particle which not can be detected. (2)

The neutrino is detected.

In 1955 a particle corresponding to what Pauli had predicted was found, and it was closely connected

to the electron. Later, one found out that there actually exist three variants of neutrino, where two of

them were some heavier muon- and tau-electrons. Those three has got their names as Ve (1955) Vm(1962) and Vt (1978). (1)

Common for these three types of electrons and their links to neutrinos is that they will not be affected

by the so called strong force, which keeps the atomic nucleus together. Such particles are calledleptons. Together with quarks, all attached to the atomic nucleus (protons and neutrons), these two

groups form the whole foundation of the universe (6).

There has been much disagreement whether a neutrino really has a mass. The existence of mass

would be of substantial interest to the comprehension of gravitation in the universe, and perhaps also

to the understanding of the assumeddark matter out in space. (1)

The sun stands for a considerable part of all neutrinos coming to our earth. Cosmic radiation going

into our athmosphere liberates neutrons of the muon type, and some kind of radioactivity contributes

for a certain amount of neutrinos. The so called high energy neutrinos are assumed to come from

super-nova explosions. By such occasions as much as 99 % of all energy is assumed released as

neutrinos. In 1987 there was observed a supernova in The Great Magellan Cloud. When this

happened, the density of neutrinos hitting the earth corresponded to 100 millions of neutrinos per

second on an area corresponding to a tumbfinger-nail!

Such neutrinos have a speed close up to light, and will unhindered pass the enormous electromagnetic

forces around galaxies. They go only straight forward, and could do so in eternity. Even if they meet a

barrier of lead, 50 light-years thick, they will unaffected pass. They also contain an unbelievable

quantity of energy. By collision with a proton, the energy liberated corresponds to the kinetic energy

in a baseball coming with an 80 km / h speed. (2)

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How to detect neutrinos?

This is possible because it happens (very, very seldom) that a neutrino particle collides with a proton.

When this happens, a muon type neutrino is formed. This muon particle should get a speed about 25

% higher than the speed of light, but here the nature takes over. For not exceeding the light speed(300 000 km/s) the muon must get rid of excessive energy, and gives away some light, the so called

Cherenkov Light, as a thin, bluish streak (4,5).

A neutrino-detector is therefore quite different

from an astronomic observatory. It has an

enormous tank filled up with pure water, and

rows of sensors, named photomultipliers.

When the surrounding medium is pure and clear

water, and it is complete darkness, the

photomultiplier will be able to detect the light

streaks in a range of some tenth meters. They

will also be able to indicate the direction with an

accuracy of 3.5 degrees, and therefore tell the

accurate point on the sky where the neutrino particle came from.

All we know today about the universe has come to us by observations of light, included all types of

photons as visible light, infrared and ultraviolet, and besides spectrum of electromagnetic radiation,

like radio waves and x-rays. All these kinds of radiation have on their way been influenced from

electromagnetic and gravimetric fields, causing uncertainty about their origin place.

This is not the case for the neutrinos. They have gone in a straight line from their origin, and this start

can be billions of light years away.

Different types of detectors

Detectors have been built on different places around the earth. To avoid

influence from cosmic radiation and neutrinos from our own sun, many

detectors are placed in great, blasted rooms in deep rock-ground, but also

in very deep and clear water.

The first project for detecting neutrino-induced muons in natural water

was the Russian installation in the deep Baikal.sea, with depths down to

1523 meters. (1)

Another type has been placed on the South Pole, on US Amundsen-Scott

Station, called Amanda. It was primarily aiming to detect high energetic

neutrinos from black holes, gamma outburst and supernovas in far galaxies.

The next detector, called Amanda II, followed this. After drilling 1900 meters down in the ice, they

installed 680 detectors (photomultipliers) in the size of basketballs, hanging down in 19 cables. The

detection system is surrounded by pure ice, and in complete darkness in a depth from 1500 to 1900

meters. Amanda did their first detection in summer 2001, and two years later the results was

published in Sidney. These have given astronomers very surprising and new visions about cosmos. (1)

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Japanese experiments

Japan has since 1985 got a lot more knowledge in neutrino researchafter starting up their Super-Kamiokadedetector in the Japanese

Alps. The heart in their detector is an enormous tank filled with

50 000 tons of super clean water. For detecting of Cherenkov-light

from collisions between neutrinos and protons, this tank is

surrounded by 13 000 high sensitive photomultipliers.

The detector made its great shots when the Great Magellan Cloud

showed up on 23.februar in 1987. It managed to detect 11 neutrino

hits from this unique event, and this was considered to be the

introduction of a new era in the exploration of the universe.

Many sources of error

It would be quite simpler if the detections only registered light flashes from high energetic neutrinos

from outer space, but this is not the fact. Cosmic radiation gives collisions with protons in our

atmosphere, and creates muons and the belonging muon-neutrinos. In addition, the surrounding rock

will have some radioactivity, which also can create Cherenkov-light. Such false flashing comes in

higher numbers than those from pure neutrinos.

Unexpected problems

Super Kamiokade detected thousands of electron-neutrinos from the sun, but only half of the numbers

they had expected. This problem strengthened when they studied muon-neutrinos from cosmic

radiation. In a shower of cosmic particles one should expect a double number of muon- neutrinos as

electron-neutrinos, but in the Super-Kamiokade and other experiments the numbers was about equal.

Seen in a connexion, it looked like some of the muon-neutrinos from cosmic radiation disappears, and

likewise the electron-neutrinos from the sun!

It was adjacent to think that something happened on the journey. The Japanese did an experiment, and

sent muon-neutrinos from their accelerator (KK in Tsjukuba) in the direction against the Super-

Kamiokade-detector, 250 km away. Although the detector totally registered a smaller number of

neutrinos, the amount of muon-neutrinos arrived as a minority.The conclusion of this was that if each of these three unlike types of neutrinos can oscillate over to

another type, it is not unlikely that only a third of electron-neutrinos reach the earth. The answer to

this was still to wait for in new detections.

The Antares detector

In the Mediterranean, 37 km out from Cote dAzur, not far from Toulon, there is an area with a depth

going down to 2400 meters, and the water is extraordinary clear and pure. This means that there is

sufficiant water up to the surface to protect against all muons that cosmic radiation can give. Besides,

it is not so far from land, making installation and maintenance simpler.

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The Frenchmen did a thorough preliminary work, as to study the problems with possible microbe

fouling for the detection with photomultipliers. After a whole year in the sea the light sensibility was

reduced with only 2 %.

Another problem was all the small organisms which produced some

kind of light flashes. This light was bluish, like the Cherenkov-light,

and could be rather strong. But because the Cherenkov light always

is coherent, just as laser-light, it was possible to filter out those

amorous flashes from Mediterranean creepy things, and only

detect the astronomic light.

Another problem with the Antares was the Cherenkov light from the

radioactive K40, which is present in sea water, but was considered to

be only a cosmetic problem, and could be subtracted. Antares was

expected to be operational in 2004, and could probably exceed the

American Amanda on the South Pole. (1)

One thing has Antares and Amanda in common. They plan toenlarge these detectors to about one cubic Kilometer! Someone

wrote the following about it: It will be possible to hear the scream

from far-off quasars and detect shock waves from the great gamma

flashes.

Canadian experiments

In Canada they have developed a new technique, making it possible to distinguish what type of

neutrinos they detect. The installation has got the name Sudbury Neutrino Observatory (SNO). It has

a tank containing 1000 tons of water, surrounded by 10 000 light sensors (photomultipliers).

A little trick has been used. For the most of time so called ultra clean water is used, but in a limited

time they use genuine heavy water (D2O) with a small addition of salt (NaCl) In the ultra pure water

they detect only electron-neutrinos, while in a smaller tank with D2O + NaCl all the three types will be

detected.

In this arrangement they are able to detect the total number of neutrinos. By subtracting the number of

electron- neutrinos from this, they can calculate the distribution between muon- and tau-neutrinos.

SNO will in an average only detect one neutrino per hour, and it took four years to gain meaningful

results. This has revealed the following relation:

Some of the electron-neutrinos from the sun changes to muon- or tau-neutrinos on their way to earth.

The total number of neutrinos being detected, and included all the three variants, agree with thenumber from the most advanced calculating models for the numbers from the sun. This has been

considered as an important result within experimental science (1), and was rewarded with the Nobel

Prize in physics for 2003, given to Ray Davis (University of Pennsylvania) and Mashatoshi Koshiba

(Tokyo University).

Neutrino generators

In 2004, intensions for producing a stream of muon-neutrinos from the Fermilab accelerator near

Chicago over to a detector in the Soudan- mine in Minnesota; a distance of 700 km. was established.

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In the meantime, plans for sending a neutrino stream from the LHC (Large Hadron Accelerator, Cern)

to Gran Sasso Laboratory in Italy came up. At the top of this, plans for building a neutrino- generator,

able to send a maelstrom of such particles to the other side of the earth, exist. (1)

New problemsThe discoveries in Canada created new problems. The fact that a neutrino can oscillate and transform

to one of the other variants means in fact that they must have different mass. Neutrinos could not be

massless, as earlier proposed.

Another problem also showed up. When neutrinos shall be described as spinning particles, they are

always left-handed. And this phenomenon also passes for their antiparticles, this being quite unique.

All other particles in nuclear physics exist in both forms, and this gives some imbalance in the system.

This fact gives the theoretic a little glimpse into a world far beyond our general comprehension of the

world, and our so called Standard Model for nuclear physics. In this other world, new dimensions

are brought in. Our normal four dimensions (room and time), could then be locked up in a multi-

dimensional system, with perhaps as many as eleven dimensions. In such a system the left- and righthanded rotations could freely operate. Quantum theory should allow such behaviour for the three

types of neutrinos in short sequences. (1)

The existence of so called super-heavy neutrinos gives new thoughts about the so called Dark

Matter in the universe. Neutrinos operate in incomprehensible numbers, and must have a fundamental

role in the universe.

Appendix

The article given here was published in the Norwegian periodical Astronomi October 2004.

Skien, 8. mars 2010

Kjell W. Tveten

References:

(1) Reluctant heroes, article from New Scientist, 7. Dec. 2002 p. 35-43

(2) Cosmic ghost hunt, article from Astronomy Now, Oct. 2003, 37-39

(3) Kamiokande, printing from Internet/Google, e pg.

(4) Imaging water Cherenkov detector, printing from Internet/Google, 3 pg.

(5) Measuring the velocity of light, printing from Internet/Google, 3 pg.

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What happened in neutrino

research after 2004 ?

The OPE RA project started in 2003, and has

been described like this :

The OPERA experiment has been designed to

perform the most straightforward test of the

phenomenon of neutrino oscillations. This

experiment exploits the CNGS (Cern Neutrino

beam to Gran Sasso) high intensity and high

energy beam of muon neutrinos produced at the

CERN SPS SPS in Geneva pointing towards the

LNGS underground laboratory at Gran Sasso, 730 km away in central Italy. OPERA is located in the

Hall C of LNGS and is aiming at detecting for the first time the appearance of tau-neutrinos from the

transmutation (oscillation) of muon-neutrinos during their 3 millisecond travel from Geneva to Gran

Sasso. In OPERA , tau- leptonsresulting from the interaction of tau-neutrinos will be observed in

bricksof photographic emulsion films interleaved with lead plates. The apparatus contains about

150 000 such bricks for a total mass of 1300 tons and is complemented by electronic detectors

(trackers and spectrometers) and ancillary infrastructure. Its construction has been completed in

spring 2008, and the experiment is currently in data taking.

http://opera.desy.de/project.html

In summer 2006, CERN gave the starting signal for the long-distance neutrino race to Italy. TheCNGS facility, embedded in the laboratorys accelerator complex, produced its first neutrino beam.

For the first time, billions of neutrinos were sent through the Earths crust to the Gran Sasso

laboratory, 732 km away in Italy, a journey at almost the speed of light which they completed in less

than 2.5 milli-seconds. The OPERA experiment at the Gran Sasso laboratory was then commissioned,

recording the first neutrino track.

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The CNGS project is expected to unravel some of the mysteries surrounding neutrinos. Neutrinos,

which are very light, neutral particles, interact very little with matter. They fill the Universe but are

virtually impossible to capture. 400 billions neutrinos pass through us every second, and yet only one

or two will ever interact with our bodies throughout our entire lives. The fact that they are extremely

hard to intercept goes some way to explaining the mystery that surrounds them.

We know there are three types or flavours of neutrino: the electron neutrino, the muon neutrino and

the tau neutrino. But physicists want to find out why the flux of neutrinos from the sun is much

smaller than theory predicts. This deficit may be due to the transformation (or oscillation) of neutrinos

from one flavour to another, a process which has been observed in recent experiments. This

phenomenon, known as oscillation, is directly linked to another fundamental question that torments

physicists: the neutrinos mass. Oscillations had shown that neutrinos have a mass, but it has yet to be

determined. The mass of neutrinos is crucial. Even if they are infinitesimally light, these particles

could contribute to the Universes mysterious dark matter, which is invisible to telescopes but whose

gravitational effect can be observed.

The CNGS project is to provide evidence of neutrino oscillations which is thought to occur over long

distances. To achieve this, OPERA, a first experiment nesting below 1440 meter of rock, has been

commissioned at the Gran Sasso laboratory. OPERAs huge detector, weighing 1800 tons, wouldidentify particles transformed from muon neutrinos into tau neutrinos during the journey, thus

demonstrating oscillation. OPERA is expected to intercept and detect around 25 muon neutrinos out

over the one hundred billion that will reach it every day. Around fifteen tau neutrinos produced by

oscillation are expected to be detected over five years.

The production of high-intensity neutrino beam at CERN requires a complex facility. A proton beam

produced and accelerated by the CERN accelerators is directed onto a graphite target to give birth to

other particles called pions and kaons. These particles are the fed into a system comprising two

magnetic horns which focus them into a parallel beam that is directed toward Gran Sasso. Next, in a

1000 metre long tunnel, the pions and kaons decay into muons and muon neutrinos. At the end of this

decay tunnel, an 18 metre thick block of graphite and metal absorbs the protons, pions and kaons that

did not decay. The muons are stopped by the rock. Impervious to all such obstacles, the muon

neutrinos will leave the CERN tunnels and streak through the rock on their 732 km journey to Italy.(September 2006). http://public.web.cern.ch/Public/en/Spotlight/SpotlightCNGS-en.html

The start-up for CERN accelerator was on the 10. September 2008. However, a very serious

incident happened on 19.September 2008, causing more than a year of delay to restart the

physics programs and a minimum of delay two years to reach full energy.

From Geneva, 23 November 2009 was reported:

Today the LHC circulated two beams simultaneously forthe first time, allowing the operators to test the

synchronization of the beams and giving theexperiments their first chance to look for theproton-proton collisions. With just one bunch of

particles circulating in each direction, the beams canbe made to cross in up to two places in the ring.

From early in the afternoon, the beams were made to crossat points 1 and 5, home to the ATLAS and CMS detectors, both of which were on the lookout for

collisions. Later, beams crossed at points 2 and 8,ALICE and LHCb .

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How far away experiments for the OPERA project lays now is hard to guess. Probably it will be a

question of priorities, and time will show.

Skien, 8. mars 2010

Kjell W. Tveten

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