On the 17th February we were once again very lucky to have a tour of CERN. We were also very lucky that as everything was turned off and we could visit underground.
Abbas, Alfie, Pameer and Aslam waiting for tram 18 to CERN. It was a bit cold but not as cold as the UK surprisingly.
Alfie, Abbas, Pameer, Aslam and Mrs Hare with ATLAS in the background
We first visited the Universe of Particles exhibition which is held in the Globe.
The above picture is an interactive map of CERN.
The above picture shows Pameer (left) and Aslam (right) listening to commentary about the Universe and various sub-atomic particles.
The picture above shows Abbas having a listen too
Below shows one of the interactive activities on the big bang.
The LHC is investigating the origin of the Big Bang and how the Universe formed.
It is also investigating dark matter and dark energy
Pameer looking at one of the exhibits
Alfie also looking at one of the exhibits
Pameer and Aslam
The exhibit is amazing. If you have a chance, then go.
Aslam and Pameer.
Abbas, Pameer, Alfie, Aslam and Mrs Hare (the one with the handbag) outside CERN reception
CERN has amazing grounds and it uses old equipment for decoration, mini-exhibition of detectors from CERN’s past (Gargamelle / BEBC bubble chambers and LEP RF cavity) as well as an LHC dipole magnet.
It’s brilliant being able to have lunch in the CERN restaurant. You never know whether you are sitting near the next Prof. Higgs. Pameer, Aslam and Abbas enjoying their food, perhaps one of them will be the next Peter Higgs?
Pameer, Alfie and Dr. Hare
After lunch Aslam, Abbas and Pameer looking at the old equipment.
In the afternoon we began our CERN tour with a brilliant talk by Mark Tyrell, a retired member of CERN who helped design the LHC. We shared the tour with the brilliant students from Hitchin Girls’ School.
Pameer, Alfie, Aslam and Abbas waiting for the talk to begin
An introduction to CERN
CERN was founded in 1954 by 12 European countries. Today there are 21 member states, 2415 staff members, 1300 fellows and 300 students.
There are over 10,500 users from all over the world and 200 external firm staff.
In total 16,000 people are involved. The annual budget is 1092 MCHF/909 Euros.
The above image shows the original signatures for the establishing of CERN.
The member states without Israel which joined at the end of 2013.
Mark Tyrell, our guide for the day. He is a retired member of CERN and was involved in the creation of the LHC.
Mark introduced the LHC by using the example of an old fashioned TV set.
The cathode-ray tube (CRT), the oldest version of the television, consists of a vacuum tube with a narrow end and a wide end. The narrow end contains an ion gun, which shoots out a series of negative charged electrons. Anodes accelerate the electrons and a series of electromagnet deflection coils guide the particles to specific points on the wide end of the tube, the screen that viewers look at.
The LHC contains very similar parts. Charged particles are accelerated by anodes (if the particles are negative) and cathodes (if the particles are positive). An accelerator comes either in the form of a ring (a circular accelerator), where a beam of particles travels repeatedly round a loop, or in a straight line (a linear accelerator), where the particle beam travels from one end to the other. At CERN a number of accelerators are joined together in sequence to reach successively higher energies.
They are guided around the accelerator ring by a strong magnetic field maintained by superconducting electromagnets.
There are, of course, differences. In a cathode ray tube electrons are boiled off metal and in the LHC the first part of the accelerator, an electric field strips hydrogen nuclei (consisting of one proton and one electron) of their electrons.
In a cathode ray tube the electric fields have the same polarity but in the LNC the electric fields along the accelerator switch from positive to negative at a given frequency, pulling charged particles forwards along the accelerator. CERN engineers control the frequency of the change to ensure the particles accelerate not in a continuous stream, but in closely spaced “bunches”.
In a cathode ray TV the electrons hit a screen to give an image and in the LHC the particles collide with each other.
The cathode ray tube does not require super-cooled magnets.
In a cathode ray TV electrons are accelerated to 20000 volts but in accelerators charged particles are accelerated to over 100000000000 volts.
Fundamental research in particle physics is interested in the elementary constituents of matter, the fundamental forces controlling them and the origin and structure of the Universe.
Particle physics and the standard model
All matter is made up of atoms. The conventional image is of a central nucleus with electrons whizzing around the outside.
The nucleus is made up of protons and neutrons. A proton or neutron are made up three quarks
A lot of the information given below has been obtained from the various wikipedia pages of the same titles.
Murray Gell-Mann (born September 15, 1929) is an American physicist who received the 1969 Nobel Prize in physics for his work on the theory of elementary particles.
In 1961 he introduced (with Kazuhiko Nishijima) a classification for hadrons (Baryons e.g. proton and mesons) which are elementary particles that participate in the strong nuclear force. In 1964 he went on to postulate the existence of quarks which are the particles that make up all hadrons. He coined the name from a reference in the novel Finnegans Wake by James Joyce (“Three quarks for Muster Mark!” book 2, episode 4).
Quarks, antiquarks, and gluons were soon established as the underlying elementary objects in the study of the structure of hadrons. He was awarded a Nobel Prize in physics in 1969 for his contributions and discoveries concerning the classification of elementary particles and their interactions.
Quarks and leptons are classed as fermions because they have spin (i.e. more than one type of angular momentum). Gauge bosons (g, g, W and Z) are force carriers. The Higgs boson is believed to give sub-atomic particles their mass and nobody knows yet where the graviton fits in to the model.
Up quark, down quark, electron and electron neutrino are classed as first generation matter as everyday matter like you and me are made up from them.
Charm quark strange quark, muon and muon neutrino are second generation matter and are heavier than the up, down, electron and electron neutrino.
Top quark, bottom quark, tau lepton and tau neutrino are third generation matter and even heavier (Bottom is the heaviest of all).
The up quark or u quark (symbol: u) is the lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the down quark, forms the neutrons (one up quark, two down quarks) and protons (two up quarks, one down quark) of atomic nuclei. It is part of the first generation of matter, has an electric charge of +2⁄3 e and a bare mass of 1.8–3.0 MeV/c^2. Like all quarks, the up quark is an elementary fermion with spin-1⁄2, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the up quark is the up antiquark (sometimes called antiup quark or simply antiup), which differs from it only in that some of its properties have equal magnitude but opposite sign.
The down quark or d quark (symbol: d) is the second-lightest of all quarks, a type of elementary particle, and a major constituent of matter. Together with the up quark, it forms the neutrons (one up quark, two down quarks) and protons (two up quarks, one down quark) of atomic nuclei. It is part of the first generation of matter, has an electric charge of −1⁄3 e and a bare mass of 4.8+0.5−0.3 MeV/c^2. Like all quarks, the down quark is an elementary fermion with spin-1⁄2, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the down quark is the down antiquark (sometimes called antidown quark or simply antidown), which differs from it only in that some of its properties have equal magnitude but opposite sign.
The electron (symbol: e−) is a subatomic particle with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron has a mass that is approximately 1/1836 that of the proton. Being fermions, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle. Electrons also have properties of both particles and waves, and so can collide with other particles and can be diffracted like light. Experiments with electrons best demonstrate this duality because electrons have a tiny mass.
The electron neutrino (ne) is a subatomic lepton elementary particle which has no net electric charge. Together with the electron it forms the first generation of leptons, hence its name electron neutrino. It was first hypothesized by Wolfgang Pauli in 1930, to account for missing momentum and missing energy in beta decay, and was discovered in 1956 by a team led by Clyde Cowan and Frederick Reines.
The charm quark or c quark (from its symbol, c) is the third most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks. It, along with the strange quark is part of the second generation of matter, and has an electric charge of +2⁄3 e and a bare mass of 1.29+0.05−0.11 GeV/c^2. Like all quarks, the charm quark is an elementary fermion with spin-1⁄2, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the charm quark is the charm antiquark (sometimes called anticharm quark or simply anticharm), which differs from it only in that some of its properties have equal magnitude but opposite sign.
The strange quark or s quark (from its symbol, s) is the third-lightest of all quarks, a type of elementary particle. Strange quarks are found in subatomic particles called hadrons. It, along with the charm quark is part of the second generation of matter, and has an electric charge of −1⁄3 e and a bare mass of 95+5−5 MeV/c^2. Like all quarks, the strange quark is an elementary fermion with spin-1⁄2, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the strange quark is the strange antiquark (sometimes called antistrange quark or simply antistrange), which differs from it only in that some of its properties have equal magnitude but opposite sign.
The muon (μ) is an elementary particle similar to the electron, with unitary negative electric charge of −1 and a spin of 1⁄2, but with a much greater mass (105.7 MeV/c^2). It is classified as a lepton, together with the electron (mass 0.511 MeV/c^2), the tau (mass 1777.8 MeV/c2), and the three neutrinos. As is the case with other leptons, the muon is not believed to have any sub-structure; namely, it is not thought to be composed of any simpler particles.
The muon is an unstable subatomic particle with a mean lifetime of 2.2 µs. Among all known subatomic particles, only the neutron and some atomic nuclei have a longer decay lifetime; others decay significantly faster. The decay of the muon (as well as of the neutron, the longest-lived unstable baryon), is mediated by the weak interaction exclusively. Muon decay always produces at least three particles, which must include an electron of the same charge as the muon and two neutrinos of different types.
Like all elementary particles, the muon has a corresponding antiparticle of opposite charge (+1) but equal mass and spin: the antimuon (also called a positive muon). Muons are denoted by μ− and antimuons by μ+. Muons were previously called mu mesons, but are not classified as mesons by modern particle physicists, and that name is no longer used by the physics community.
Muons have a mass of 105.7 MeV/c^2, which is about 200 times that of the electron. Due to their greater mass, muons are not as sharply accelerated when they encounter electromagnetic fields, and do not emit as much bremsstrahlung (deceleration radiation). This allows muons of a given energy to penetrate far more deeply into matter than electrons, since the deceleration of electrons and muons is primarily due to energy loss by the bremsstrahlung mechanism. As an example, so-called “secondary muons”, generated by cosmic rays hitting the atmosphere, can penetrate to the Earth’s surface, and even into deep mines.
The muon neutrino is a subatomic lepton elementary particle which has the symbol nμ and no net electric charge. Together with the muon it forms the second generation of leptons, hence its name muon neutrino. It was first hypothesized in the early 1940s by several people, and was discovered in 1962 by Leon Lederman, Melvin Schwartz and Jack Steinberger. The discovery was rewarded with the 1988 Nobel Prize in Physics.
The top quark, also known as the t quark (symbol: t) or truth quark, is an elementary particle and a fundamental constituent of matter. Like all quarks, the top quark is an elementary fermion with spin-1⁄2, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. It has an electric charge of +2⁄3 e, and is the most massive of all observed elementary particles. It has a mass of 173.34 ± 0.27 (stat) ± 0.71 GeV/c^2, which is about the same mass as an atom of tungsten. The antiparticle of the top quark is the top antiquark (symbol: t, sometimes called antitop quark or simply antitop), which differs from it only in that some of its properties have equal magnitude but opposite sign.
The top quark interacts primarily by the strong interaction but can only decay through the weak force. It decays almost exclusively to a W boson and a bottom quark, but it can decay also into a strange quark, and on the rarest of occasions, into a down quark. The Standard Model predicts its mean lifetime to be roughly 5×10−25 s. This is about 20 times shorter than the timescale for strong interactions, and therefore it does not form hadrons, giving physicists a unique opportunity to study a “bare” quark (all other quarks hadronize, meaning they combine with other quarks to form hadrons, and can only be observed as such). Because it is so massive, the properties of the top quark allow predictions to be made of the mass of the Higgs boson under certain extensions of the Standard Model (see Mass and coupling to the Higgs boson below). As such, it is extensively studied as a means to discriminate between competing theories.
Its existence (and that of the bottom quark) was postulated in 1973 by Makoto Kobayashi and Toshihide Maskawa.
The bottom quark or b quark (from its symbol, b), also known as the beauty quark, is a third-generation quark with a charge of −1⁄3 e. The bottom quark’s large bare mass (around 4.2 GeV/c^2, a bit more than four times the mass of a proton). The bottom quark is notable because it is a product in almost all top quark decays, and is a frequent decay product for the Higgs boson.
The bottom quark was theorized in 1973 by physicists Makoto. The name “bottom” was introduced in 1975 by Haim Harari. The bottom quark was discovered in 1977 by the Fermilab E288 experiment team led by Leon M. Lederman, when collisions produced bottomonium. On its discovery, there were efforts to name the bottom quark “beauty”, but “bottom” became the predominant usage.
The bottom quark can decay into either an up or charm quark via the weak interaction. Both these decays are suppressed, making lifetimes of most bottom particles (~10^−12 s) somewhat higher than those of charmed particles (~10^−13 s), but lower than those of strange particles (from ~10^−10 to ~10^−8 s).
The tau (τ), also called the tau lepton, tau particle or tauon, is an elementary particle similar to the electron, with negative electric charge and a spin of 1⁄2. Together with the electron, the muon, and the three neutrinos, it is classified as a lepton. Like all elementary particles, the tau has a corresponding antiparticle of opposite charge but equal mass and spin, which in the tau’s case is the antitau (also called the positive tau). Tau particles are denoted by τ− and the antitau by τ+.
Tau leptons have a lifetime of 2.9×10^−13 s and a mass of 1776.82 MeV/c^2 (compared to 105.7 MeV/c^2 for muons and 0.511 MeV/c^2 for electrons). Since their interactions are very similar to those of the electron, a tau can be thought of as a much heavier version of the electron. Because of their greater mass, tau particles do not emit as much bremsstrahlung radiation as electrons; consequently they are potentially highly penetrating, much more so than electrons. However, because of their short lifetime, the range of the tau is mainly set by their decay length, which is too small for bremsstrahlung to be noticeable: their penetrating power appears only at ultra-high energy (above PeV energies).
As with the case of the other charged leptons, the tau has an associated tau neutrino, denoted by t.
The tau neutrino or tauon neutrino is a subatomic elementary particle which has the symbol nτ ), also called the tau lepton, tau particle or tauon, is an elementary particle similar to the electron, with negative electric charge and a spin of 1⁄2. Together with the electron, the muon, and the three neutrinos, it is classified as a lepton. Like all elementary particles, the tau has a corresponding antiparticle of opposite charge but equaland no net electric charge. Together with the tau, it forms the third generation of leptons, hence its name tau neutrino. Its existence was immediately implied after the tau particle was detected in a series of experiments between 1974 and 1977 by Martin Lewis Perl with his colleagues at the SLAC–LBL group. The discovery of the tau neutrino was announced in July 2000 by the DONUT collaboration.
Gluons are elementary particles that act as the exchange particles (or gauge bosons) for the strong force between quarks, similar to the exchange of photons in the electromagnetic force between two charged particles.
A photon is an elementary particle, the quantum of light and all other forms of electromagnetic radiation, and the force carrier for the electromagnetic force, even when static via virtual photons. The effects of this force are easily observable at both the microscopic and macroscopic level, because the photon has zero rest mass; this allows long distance interactions. Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave–particle duality, exhibiting properties of both waves and particles. For example, a single photon may be refracted by a lens or exhibit wave interference with itself, but also act as a particle giving a definite result when its position is measured.
The W and Z bosons (together known as the weak bosons or, less specifically, the intermediate vector bosons) are the elementary particles that mediate the weak interaction; their symbols are W+, W− and Z. The W bosons have a positive and negative electric charge of 1 elementary charge respectively and are each other’s antiparticles. The Z boson is electrically neutral and is its own antiparticle. All three of these particles are very short-lived with a half-life of about 3×10^−25 s. Their discovery was a major success for what is now called the Standard Model of particle physics.
The W bosons are named after the weak force. The physicist Steven Weinberg named the additional particle the “Z particle”, later giving the explanation that it was the last additional particle needed by the model – the W bosons had already been named – and that it has zero electric charge.
The two W bosons are best known as mediators of neutrino absorption and emission, where their charge is associated with electron or positron emission or absorption, always causing nuclear transmutation. The Z boson is not involved in the absorption or emission of electrons and positrons.
The Z boson mediates the transfer of momentum, spin, and energy when neutrinos scatter elastically from matter, something that must happen without the production or absorption of new, charged particles. Such behaviour (which is almost as common as inelastic neutrino interactions) is seen in bubble chambers irradiated with neutrino beams. Whenever an electron simply “appears” in such a chamber as a new free particle suddenly moving with kinetic energy, and moves in the direction of the neutrinos as the apparent result of a new impulse, and this behaviour happens more often when the neutrino beam is present, it is inferred to be a result of a neutrino interacting directly with the electron. Here, the neutrino simply strikes the electron and scatters away from it, transferring some of the neutrino’s momentum to the electron. Since i) neither neutrinos nor electrons are affected by the strong force, ii) neutrinos are electrically neutral (therefore don’t interact electromagnetically), and iii) the incredibly small masses of these particles make any gravitational force between them negligible, such an interaction can only happen via the weak force. Since such an electron is not created from a nucleon, and is unchanged except for the new force impulse imparted by the neutrino, this weak force interaction between the neutrino and the electron must be mediated by a weak-force boson particle with no charge. Thus, this interaction requires a Z boson.
The Higgs boson or Higgs particle is an elementary particle initially theorised in 1964, whose discovery was announced at CERN on 4 July 2012. The discovery has been called “monumental” because it appears to confirm the existence of the Higgs field, which is pivotal to the Standard Model and other theories within particle physics. It would explain why some fundamental particles have mass when the symmetries controlling their interactions should require them to be massless and why the weak force has a much shorter range than the electromagnetic force. The discovery of a Higgs boson should allow physicists to finally validate the last untested area of the Standard Model’s approach to fundamental particles and forces, guide other theories and discoveries in particle physics, and potentially lead to developments in “new” physics.
This unanswered question in fundamental physics is of such importance that it led to a search of more than 40 years for the Higgs boson and finally the construction of one of the world’s most expensive and complex experimental facilities to date, the Large Hadron Collider, able to create Higgs bosons and other particles for observation and study. On 4 July 2012, it was announced that a previously unknown particle with a mass between 125 and 127 GeV/c^2 (134.2 and 136.3 amu) had been detected; physicists suspected at the time that it was the Higgs boson. By March 2013, the particle had been proven to behave, interact and decay in many of the ways predicted by the Standard Model, and was also tentatively confirmed to have positive parity and zero spin, two fundamental attributes of a Higgs boson. This appears to be the first elementary scalar particle discovered in nature. More data is needed to know if the discovered particle exactly matches the predictions of the Standard Model, or whether, as predicted by some theories, multiple Higgs bosons exist.
The Higgs boson is named after Peter Higgs, one of six physicists who, in 1964, proposed the mechanism that suggested the existence of such a particle. Although Higgs’s name has come to be associated with this theory, several researchers between about 1960 and 1972 each independently developed different parts of it. In mainstream media the Higgs boson has often been called the “God particle”, from a 1993 book on the topic; the nickname is strongly disliked by many physicists, including Higgs, who regard it as inappropriate sensationalism. In 2013 two of the original researchers, Peter Higgs and François Englert, were awarded the Nobel Prize in Physics for their work and prediction (Englert’s co-researcher Robert Brout had died in 2011).
In the Standard Model, the Higgs particle is a boson with no spin, electric charge, or colour charge. It is also very unstable, decaying into other particles almost immediately.
In physics, the graviton is a hypothetical elementary particle that mediates the force of gravitation in the framework of quantum field theory. If it exists, the graviton is expected to be massless.
The forces in nature
Strong nuclear force has a relative force intensity of 1. Its bonding particle is the gluon (mass) and occurs in the atomic nucleus.
The electromagnetic force (g) has a relative force intensity of 10^-3. Its bonding particle is the photon and it occurs in the atomic electron shell.
Weak nuclear force has a relative force intensity 10^-5. Its bonding particles are the Z0, W+, and W and it occurs in beta radioactive decay.
Gravitation force has a relative force intensity of 10^-38. Its bonding particle is believed to be a graviton and if it exists it will occur in stars.
The exchange of particles is responsible for forces
The Big Bang
Could superstring theory apply before 10^-43 seconds?
Were all the forces unified before 10^-35 seconds?
The open questions in particle physics
1) Does super-symmetry (SUSY) exist?
The Standard Model has worked beautifully to predict what experiments have shown so far about the basic building blocks of matter, but physicists recognize that it is incomplete. Super-symmetry is an extension of the Standard Model that aims to fill some of the gaps. It predicts a partner particle for each particle in the Standard Model. These new particles would solve a major problem with the Standard Model – fixing the mass of the Higgs boson. If the theory is correct, super-symmetric particles should appear in collisions at the LHC.
2) Origin of mass and the Higgs boson. Is the boson that was discovered in 2012 the Higgs boson consistent with the standard model?
3) Dark matter. The matter we know and that makes up all stars and galaxies only accounts for 4% of the content of the universe! But what is dark matter? One idea is that it could contain “super-symmetric particles” – hypothesized particles that are partners to those already known in the Standard Model. Experiments at the Large Hadron Collider (LHC) may provide more direct clues about dark matter.
4) Why is there more matter than antimatter? The big bang should have created equal amounts of matter and antimatter in the early universe. But today, everything we see from the smallest life forms on Earth to the largest stellar objects is made almost entirely of matter. Comparatively, there is not much antimatter to be found. Something must have happened to tip the balance. One of the greatest challenges in physics at the LHC is to figure out what happened to the antimatter, or why we see matter/antimatter asymmetry.
5) Quark –Gluon plasma. For a few millionths of a second, shortly after the big bang, the universe was filled with an astonishingly hot, dense soup made of all kinds of particles moving at near light speed. This mixture was dominated by quarks – fundamental bits of matter – and by gluons, carriers of the strong force that normally “glue” quarks together into familiar protons and neutrons and other species. In those first evanescent moments of extreme temperature, however, quarks and gluons were bound only weakly, free to move on their own in what’s called a quark-gluon plasma.
To recreate conditions similar to those of the very early universe, powerful accelerators at the LHC make head-on collisions between massive ions, such as gold or lead nuclei. In these heavy-ion collisions the hundreds of protons and neutrons in two such nuclei smash into one another at energies of upwards of a few trillion electronvolts each. This forms a miniscule fireball in which everything “melts” into a quark-gluon plasma.
Recently the ALICE, ATLAS and CMS experiments at CERN’s Large Hadron Collider (LHC) have confirmed the phenomenon of jet quenching in heavy-ion collisions. The much greater collision energies at the LHC push measurements to much higher jet energies than are accessible at RHIC, allowing new and more detailed characterization of the quark-gluon plasma.
ATLAS, CNS and Higgs
Data from the ATLAS and CMS Experiments at the Large Hadron Collider show the tracks of electrons (green) and their heavier cousins muons (red) during proton-proton collisions recorded on June 18, 2012. Physicists say the event could be evidence of the long-sought Higgs boson.
Image below is courtesy of ATLAS Experiment © 2012 CERN. –
The Higgs is identified because it is extremely unstable and is identified by the products it produced. It decays via a different number of processes and unfortunately some of the products are indistinguishable from the background noise
Higgs –> Z + Z
The blue section is associated with the Higgs. The backgrounds are the direct production of two Z bosons without any Higgs involved, or from rare decays of a single Z boson to four leptons, or other such backgrounds. The Higgs boson to two Z bosons followed by their decay to four leptons has to be seen on top of these backgrounds.
The images below show some of the decays of the Higgs
Higgs –> Z + Z –> 4U
Nobel Prize for physics in 2013
Francois Englert and Peter Higgs
For the theory of how particles acquire mass.
In 1964 they proposed the theory independently of each other.
In 2012 their ideas were confirmed by the discovery of a so called Higgs Particle at CERN.
François Baron Englert (born 6 November 1932) is a Belgian theoretical physicist. Peter Ware Higgs CH FRS FRSE (born 29 May 1929) is a British theoretical physicist, Emeritus professor at the University of Edinburgh.
Spin-offs of particle physics
1) Electronics that can work in harsh conditions.
2) NMR, PET, Hadron therapy and other medical treatments.
PET image of a patient with a breast cancer and a colon metastasis
3) More efficient solar panels.
4) Grid computing.
5) The World Wide Web
We left the main reception and travelled by mini-bus to our first stop, the CERN laboratory on the French side of the border (Prevessin), where we visited the AMS Control Room (http://ams.cern.ch/) and the CERN Control Centre (http://public.web.cern.ch/public/en/spotlight/SpotlightCCC-en.html). AMS (Alpha Magnetic Spectrometer) is a cosmic ray detector that is mounted on the International Space Station. The detector is used to study the matter/antimatter asymmetry and clues for the existence of dark matter. The collaboration is led by MIT professor, Samuel C. C. Ting.
The Alpha Magnetic Spectrometer, also designated AMS-02, is a particle physics experiment module that is mounted on the International Space Station. It is designed to measure antimatter in cosmic rays and search for evidence of dark matter. This information is needed to understand the formation of the Universe. The principal investigator is Nobel laureate particle physicist Samuel Ting. The launch of Space Shuttle Endeavour flight STS-134 carrying AMS-02 took place on 16 May 2011, and the spectrometer was installed on 19 May 2011. In July 2012, reported that AMS-02 had recorded over 18 billion cosmic ray events since its installation.
In March 2013, at a seminar at CERN, Professor Samuel Ting reported that AMS had observed over 400,000 positrons, with the positron to electron fraction increasing from 10 GeV to 250 GeV but showing a slower rate of increase at higher energies. There was “no significant variation over time, or any preferred incoming direction. These results are consistent with the positrons originating from the annihilation of dark matter particles in space, but not yet sufficiently conclusive to rule out other explanations.” The results are published in Physical Review Letters. Additional data are still being collected.
AMS-02 during integration and testing at CERN
AMS-02 installed on the ISS.
The above picture shows a real time image of the ISS.
The CERN Control Centre brings together the control rooms of the eight accelerators at CERN. The LHC beams (protons and lead ions) are constructed via an injector chain that includes the PS (Proton Synchrotron) and the SPS (Super Proton Synchrotron).
Moving on to CMS
We then continued our tour to CMS (http://cms.web.cern.ch/) located at the intersection point of the LHC directly opposite of the CERN main laboratory, about a 15 minute drive away.
In the picture below Mikhail is on the left. He is a Russian PhD student at CERN and he was our guide around CMS with Mark.
The tour began with an introduction to CMS.
The Compact Muon Solenoid (CMS) experiment is one of two large general-purpose particle physics detectors built on the Large Hadron Collider (LHC) at CERN in Switzerland and France. The goal of CMS experiment is to investigate a wide range of physics, including the search for the Higgs boson, extra dimensions, and particles that could make up dark matter.
CMS is 21.6 metres long, 15 metres in diameter, and weighs about 12,500 tonnes. Approximately 3,800 people, representing 182 scientific institutes and 42 countries, form the CMS collaboration who built and now operate the detector. It is located in an underground cavern at Cessy in France, just across the border from Geneva. In July 2012, along with ATLAS, CMS discovered a boson, which is very similar to the Standard Model Higgs Particle. Future research is required to decide if this boson is Higgs Particle or not.
Mikhail has his hand on 1 of 2 coils of the LHC dipole, 15 metres long, made of copper wires about 0.5mm diameter, containing 1000 strands of the superconducting material niobium tin which is cooled to 1.9 degrees Kelvin.
The superconducting (1.9 K) dipoles bend the beams around the 27 km circumference of the accelerator and represented a tremendous technological challenge.
The niobium-titanium coils create the magnetic fields to guide the two counter-rotating proton beams in separate magnetic channels, but within the same physical structure. The coils are surrounded by non-magnetic “collars” of austenitic steel, a material that combines the required properties of good thermal contraction and magnetic permeability. The collars hold the coils in place against the strong magnetic forces that arise when the coils are at full field – the force loading 1 m of dipole is about 400 tonnes!
The photograph below shows Mikhail explaining how CMS works with an interactive exhibit that the students could have a play with later.
The picture below shows a segment of the solenoid (from 1:1 – scale prototype), showing the superconducting cables within four layers of aluminium stabiliser, and the cooling tubes.
Before going underground we were given comprehensive safety instructions and told to wear the hard hats at all time. Lifts are the only way up and down as the depth is too great for stairs. The lifts are deliberately run on a separate power supply to the rest of CMS so that they can still run if the power has been cut.
Staff are actively encouraged to sound the alarm and leave the building and tunnel even if it is only a feeling that something is wrong although I don’t think this would work with Dr. Reavely and the school fire alarms.
The image below shows the security gate that staff and visitors have to pass through. The little black box on the right records the retina pattern of each person (not used when we were visiting) on site. This means in an emergency the authorities know exactly who is underground.
Below Mikhail is explaining the different stages involved in accelerating particles at the LHC. Whether the experiments are being completed by CMS, LHCb, ALICE or ATLAS they still rely on the same tunnels, magnets (for direction changes) and radiofrequency cavities (for acceleration).
Getting an overview of CMS
Please excuse all the pictures. I couldn’t think which ones to leave out.
1) The superconducting magnets – A cylindrical superconducting magnet about 12m long and 6m wide. Its mass is about 200 tonnes and it contains many of the CMS subsystems. The compact design led to the detector’s name. Scientists use the magnets to bend the paths of charged particles providing information on each particle’s charge, mass and speed.
2) The CMS tracker consists of 10 million silicon strips, 66 million pixels and specialised electronics that can determine the exact coordinates of a particle track to within the width of a human hair.
3) The electromagnetic calorimeter is a system of 80,000 lead tungsten crystals to identify the energy and direction of the electrons and photons produced in the collisions.
4) The Hadronic calorimeter consists of layers of dense material interspersd with plastic scintilator to primarily to measure the energy of hadrons-particles such as protons, neutrons, pions and kaons.
5) Muon chambers are a combination of drift tubes, cathode strip chambers and resistive chambers to identify and measure muons which are essentially heavier cousins of electrons.
6) The foundations of CMS are massive feet made of steel that can carry the weight of the entire detector of its sunsystems, a total of about 14000 tonnes.
Pameer looking a bit overawed by it all
We were very lucky to see the sections of the detector partly open.
Unfortunately we couldn’t go down to the tunnel but below is a picture of part of it.
Geneva at night
The end of a brilliant day with no fondue in sight
A lesser known Swiss delicacy – Chinese noodles
Going home via Geneva station
Rather tired on the flight home, but I think I know why
Too much computer games, texting etc.
We would like to thank all of the lovely people at CERN who arrange the tours.
We would like to thank Mrs Edwards and Ms Downey for doing all the hard work of sorting out the finances and paperwork for the trip.
We would like to thank Dr Anthony Hare for giving up his time to come on the trip with us.
We would like to thank Dr Hare and Pameer Saeed for some of the photographs.