Large Hadron Collider | SciByte 8

Disclaimer!

Some of today’s episode will talk a little about particle physics, what we will cover is going to be a more broad spectrum quick look. Just giving enough of a glance at it so that looking at the research going on at the LHC will mean a little bit more. Feel free to research these topics more on your own or request that we go into it a bit more on a future SciByte and as always we’ll tell you more about how to do that at the end of the episode.

What IS The Large Hadron Collider (LHC) in a nutshell?

• It is the world’s largest and highest-energy particle accelerator.
• It is expected to address some of the most fundamental questions of physics, advancing the understanding of the deepest laws of nature.

What does that mean and how does it do it?

• What kind of particles are the experiments at the LHC looking at?
• How does the LHC accelerate particles to produce the collisions that the experiments look at?
• What are the components, dangers and basics of the LHC?
• To get a better idea of what all of this actually means we’ll start by taking a quick look at the basic elements of the universe and what forces cause them and everything in the universe to interact.

We’ll start with The Standard Model Theory

Everything in the Universe is found to be made from basic building blocks called fundamental particles, governed by four fundamental forces.

What are those Four Fundamental Interactions of Nature ?

• From the strongest to the weakest … Strong, Electromagnetic, Weak, Gravity
• Strong Nuclear Force – Strong force carrier are gluons, they acts on quarks and act as the glue to hold them together to create neutrons and protons and the residual force holds nucleus together. About 100x stronger than the electromagnetic force, but the range is limited to about the size of a proton.
• Electromagnetism – Electromagnetic force carrier is a photon and acts on charged particles and is responsible for propagation of light, and gives a magnet the ability to pick up a paperclip
• Weak – Exchange particles of weak are the ‘w’ ‘z’ bozon and and explains the energy production of the sun and radioactive beta decay
• Gravity – Assumed that since the other three forces have force carriers gravity does to, called the graviton. Gravitational force is a natural phenomenon by which physical bodies attract with a force proportional to their mass. [ If the graviton does exists, it must be massless (because the gravitational force has unlimited range) ]

That poses an interesting thought …

• If electrons had a different mass, then electromagnetic field would be a different size, and therefore all matter would be a different size.

What are those ‘basic components’ of the Universe?

• Some of these were mentioned talking about the fundamental interactions
• Start off looking at the elements VIDEO
• All ~118 elements were made of Electrons, Protons and Neutrons VIDEO
• Beginning of the 20th century we found many other particles from cosmic rays, energetic charged subatomic particles, originating from outer space VIDEO
• They started to organize these particles by : spin, charge, mass, and lifetime (how long till they decay into simpler particles) VIDEO
• To simplify this picture, quarks were predicted VIDEO
• Six quarks were predicted, then discovered; bringing confidence to the model
• Boils down to basically Quarks, Bosons and Leptons [Electrons, Muons, Tau]

So what ARE Quarks ?

• They are elementary particle and a fundamental constituent of matter that you can’t see directly, they and they have some unusual properties,
• They make up and are permanently trapped inside other particles like neutrons and protons.
• Six types / flavors that come in pairs [Up/Down ; Charm/Strange ; Top/Bottom] : only UP/DOWN are stable and make up all ‘normal’ matter
• You can’t bring them out individually to study them, only be found within hadrons

Hadron … like in Large Hadron Collider? … what are they?

• Things made up of Quarks (including protons, neutrons) and are composite particle that scientist call Hadrons. There are many theorized types of Hadrons but most exist only very briefly.
• The best known Hadrons are protons and neutrons and excludes leptons and photons
• Made of Quarks and held together by the strong nuclear force (while atoms and molecules are held together by the electromagnetic force) and categorized into two families
  • Baryon [ made of 3 quarks ]
  • Mesons [ one quark and anti-quark ]

Do these exotic particles exist anywhere outside of physics experiments?

• They existed right after the Big Bang, and occur in cosmic-ray events when they strike atomic nuclei in the earth’s atmosphere, these rare particles can be produced.

The problem with the Standard model …

• It does not explain everything.
• Gravity is not fully explained in the Standard Model, instead it predicts (but we have not observed) the Higgs-Boson

So what is the Higgs-Boson Theory ?

• Predicted for ~40 years
• Permeates all of space acting like sticky bits that put a drag on other particles
• Interact with all particle except for photon, graviton, and gluons
  • gravitons – undiscovered/theoretical force carriers for gravity
• To detect a Higgs Boson in a lab; we must create a real one. We do this firing particles and anti-particle together, out of the collision can look for decay products that would indicate Higgs-Boson

Collisions? … that brings us to the Large Hadron Collider

Large Hadron Collider

• Looking beyond the Standard Model (dark matter, extra dimensions, … ) VIDEO
• What Hadron’s are used? : mostly lead ions (lead atoms stripped of electrons)
• Underground, below the border of Switzerland and France

The Large Hadron Collider – Basic Stats

• Circumference : ~ 17mi / 27 km
• Diameter : ~ 5mi / 8km
• Depth : roughly the height of a 42 story office building [ 175 m / 574 feet ]
• Magnets : 9300 throughout the facility
• Power : 120 MW [~roughly 5000 avg American homes] [ ~all the homes in Canton, Geneva]
• Cryogenics : ⅛ of the total system would qualify as the worlds largest refrigerator
• Operates at temperatures [1.9 K] even lower than outer space! [2.7 K]
• Temperatures Generated : more than 100,000 times hotter than the heart of the Sun [when two beams of protons collide, concentrated within a minuscule space]
• Pressure : 10 times less than the pressure on the surface of the Moon [internal pressure of the LHC is 10-13 atm]

Why Underground?

• Cheaper to excavate a tunnel than to acquire the land to build on the surface, impact on landscape is reduced to a minimum. It also had to be at least 5m below the top ‘molasse’ green sandstone stratum
• The moons tidal variations have to be taken into account then beams are injected into the collider
• Between new Moon and full Moon the Earths crust rises by slightly more than the width of notebook paper [9.8in/25cm] in Geneva, causes a variation of diameter of a pinhead [1mm] in the circumference of the LHC
• The Earth’s crust also provides good shielding for radiation.

LHC is not a perfect circle

• made of 8 arcs and 8 straight intersections
• Each arc contain 154 dipole ‘bending’ magnets
• Each Intersection consists of a long straight section

LHC Vacuum

• Insulation vacuum for the Cryomagnets
• Insulation vacuum for the Helium distribution line
• Beam Vacuum is kept at about 10x lower than on the Moon to avoid collisions with gas molecules

LHC Magnets

• Total of about 9600 magnets
• Contains about 10000 t of iron, that’s more iron than in the Eiffel Tower
• LHC Dipole magnets are superconducting electromagnets, use niobium-titanium cables
• dipole VIDEO : 1232; quadrupole VIDEO : 392; sextupole; octupoles; decapoles
• Magnet Coils are wound from cable made up of 36 twisted 0.6in/15mm strands, each strand is made up of 6000-9000 filaments. These filaments can have diameters 10 x thinner than a normal human hair [as small as 7 micrometers]
• Total strands for the LHC would circle the Earth 6x at the equator [270,000km]
• Total Filaments, if unravelled, would stretch to the Sun and back 6x, with leftover for about 150 trips to the moon

The Large Hadron Collider() ( L.H.C ) Acceleration Video

• Hydrogen atoms are fed into a linear accelerator at a precise rate.
• The Hydrogen electrons are stripped off leaving hydrogen nuclei, protons in a strong magnetic field which accelerates the protons to 1/3 the speed of light
  • low pressure hydrogen in a sealed container with a couple of electrodes in it, then apply a high enough voltage difference betweeen the electrodes the hydrogen becomes ionised. This means the electrons are stripped away from the hydrogen atoms leaving bare protons. This is what happens in fluorescent lights.
• Protons now enter a booster section, where it’s divided into 4 rings 0.6% of the LHC [515feet/157m] in circumference and accelerated with a pulsating electric field and kept bent with a magnetic field. The booster accelerates the protons to 91.6% the speed of light and squeezes them together
• The 4 packets are re-combined and passed into the Proton Synchrotron, which is [4x larger than the booster/2% of the LHC] in circumference [2060feet/628m] which they travel in 1.2 seconds [99.9% speed of light] Now additional energy can’t add velocity, it instead manifests as increased mass, which translates to 25 times the resting mass of the protons
• Now channeled into the Super Proton Synchrotron which is about [11x larger than the Proton Synchrotron/25% of the LHC] in circumference [7km/22965ft] and adds additional energy to the protons. Readying them to enter the Large Hadron Collider
• LHC ( 27km / 88582 feet in circumference). It houses two vacuum pipes for protons traveling in opposite directions The opposing beans cross in four detector caverns where they can collide
• The LHC adds extra energy from pulsed electric fields to the protons which now travel around the 27km/88582feet 11,000 times per second. The protons are now 7000 times heavier than they were at rest. Steering magnets bring them to collide

LHC Data

• 150 million sensors deliver data 40 mill times per second, filtered to about 100 collisions of interest per second
• Sampling Rate Capacity: sample / record the results of up to 600 million proton collisions per second
• Data from all four experiments : 700 MB/s, ~= 15,000,000 GB / year (15 PB)
• Data Recorded by each of the big experiments at the LHC will fill around 100 000 dual layer DVDs every year
• Data from all 4 experiments would will a stack of CD’s 12.4mi/20km tall

Before we get to the LHC Energies involved, what units are involved and what to they mean?

• TeV – teraelectronvolt : The amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt
• 1 TeV = 1.602×10^-7 J = 0.0000001602 J
• Watt is a J/sec [W = J/s] & conversely a Joule is a Watt*sec [ J = Ws ]

A TeV EXAMPLE : How long would a TeV light a a 60Watt bulb ?

• 1TeV = [ 1.602×10^-7 J ] = [ 60W ] * [sec]
• [ 1.602×10^-7 J ] / [ 60W ] = [sec]
• 2.67 nano seconds = 0.00000000268 seconds`

LHC Energies

• Each proton flying around the LHC has 7 TeV, which has the energy to light a 60W bulb for 18.69 nano seconds [0.00000001869 seconds]
• When you clap your hands, you probably do a ‘collision’ at an energy higher than that, but much less concentrated.
• 1 TeV is about the energy of a flying mosquito, the LHC is extraordinary for the ability to squeeze that energy into a space a million million times smaller
• Total energy in each beam at max speed [350 MJ] is about the same as a 400 ton train travelling at 93 mi/h [150 km/h]

Is the LHC Dangerous?

• Has the Large Hadron Collider Destroyed the World Yet.com
• Cosmic Rays have been bombarding the Earth, moon, Jupiter, Sun, … since our formation with no known affect, and in much larger numbers than the LHC will produce
• Mini Big-Bangs? : at the very small scale, the energy concentration does represent the energy density just moments after the Big Bang; the TOTAL energy is produced by these collisions is still very low
• LHC Black Hole? : Black holes are created by collapsing massive stars which contain enormous amounts of gravitational energy. Any microscopic black holes created by the LHC would be so microscopic that they could not interact with surrounding matter. In addition theories suggest that microscopic black holes would only exist for a few fleeting moments before they would evaporate and disappear.
• Radiation : Studies have shown that radioactivity released in the air contributes to an dose to the public such that 10 years of ‘exposure’ gives about the same as 1 round trip from Europe to Los Angeles produces and is 240 times less per year than an average year in Switzerland.

It’s a particle accelerator … but what does that mean?

• A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams.

LHC Beams

• Might circulate for 10 hours, travelling the distance to get to Neptune and back again
• Protons at full energy travel at 0.999999991 times the speed of light, and circles the 16.8mi / 27km ring 11,245 every second
• Only 2 nanograms of Hydrogen are accelerated / day … at that rate it would take ~ 1 million years to accelerate 1 gram of Hydrogen

Is it like smashing an apple and an orange together and getting bananas?

• Not really, it’s more like getting a whole bunch of apple and orange pieces, and also chips of banana and antibanana, grapes…

How does the LHC see particles?

• For each collision, scientists count, track particles
• If the detector is in magnetic field, the charge of a particle will be which way it bends, and the momentum ( mass x velocity ) can be determined based on the path of travel [high momentum particles travel in almost straight lines while low momentum particles make tight spirals]

– Main LHC Detectors –

ALICE – A Large Ion Collider Experiment

• Produces ~100Mb/s during proton-proton run; 1/25 GM/s during heavy-ion run of data
• Specializes in analysing lead-ion collisions
• Studies properties of quark-gluon plasma [when quarks and gluons are no longer confined in hadrons/Lead-ions] Quark-gluon plasma probably existed just after the Big Bang

ATLAS – AToroidal LHC ApparatuS

• Produces about 320 MB/s of data
• General-purpose detector designed to cover the widest range of physics possible
• The largest-volume collider-detector ever constructed
• Searches for everything from the Higgs boson to supersymmetry and extra dimensions
  Consists of 8 25-m long superconducting magnet coils

CMS – Compact Muon Solenoid

• Produces about 300 MB/s of data
• General-purpose detector like ATLAS, but with different tech and design
• Built around a huge superconducting solenoid
• Can generate a magnetic field about 100,000 times that of the Earth

LHCb – Large Hadron Collider beauty

• Produces about 50 MB/s of data
• Studies asymmetry between matter and anti-matter
• Uses a series of sub-detectors to detect mainly forward particles

– Additional LHC Detectors –

LHCf – Large Hadron Collider forward

• Small experiment to measure particles produced close to the direction of the beams in proton-proton collisions
• Testing models used to estimate energy of ultra high energy cosmic rays

TOTEM – TOTal Elastic and diffractive cross section Measurement

• Measure effective size / cross section of proton
• Detects particles produced close to the LHC beams

Additional Information

• LHC MACHINE OUTREACH
• CERN Public Outreach – Facts and Figures
• CERN – Large Hadron Collider
• WIKI – Large Hadron Collider
• CBS – World’s biggest particle collider smashes data record
• Discover Interview The Man Who Found Quarks and Made Sense of the Universe
• Large Hadron Rap
• The Quark Song
• YouTube : CERN
• YouTube : ALICE
• YouTube : ATLAS
• YouTube : CMS

Social Media

• YouTube – CERNTV
• Twitter – CERN
• Facebook – Large Hadron Collider