The Large Hadron Collider is the world's largest
and most powerful particle collider, built
by the European Organization for Nuclear Research
from 1998 to 2008. Its aim is to allow physicists
to test the predictions of different theories
of particle physics and high-energy physics,
and particularly prove or disprove the existence
of the theorized Higgs particle and of the
large family of new particles predicted by
supersymmetric theories. The Higgs particle
was confirmed by data from the LHC in 2013.
The LHC is expected to address some of the
unsolved questions of physics, advancing human
understanding of physical laws. It contains
seven detectors, each designed for certain
kinds of research.
The LHC was built in collaboration with over
10,000 scientists and engineers from over
100 countries, as well as hundreds of universities
and laboratories. It lies in a tunnel 27 kilometres
in circumference, as deep as 175 metres beneath
the Franco-Swiss border near Geneva, Switzerland.
As of 2014, the LHC remains one of the largest
and most complex experimental facilities ever
built. Its synchrotron is designed to initially
collide two opposing particle beams of either
protons at up to 7 teraelectronvolts per
nucleon, or lead nuclei at an energy of 574 TeV
per nucleus, with energies to be doubled to
around 14 TeV collision energy—more than
seven times any predecessor collider—by
around 2015. Collision data were also anticipated
to be produced at an unprecedented rate of
tens of petabytes per year, to be analysed
by a grid-based computer network infrastructure
connecting 140 computing centers in 35 countries.
The LHC went live on 10 September 2008, with
proton beams successfully circulated in the
main ring of the LHC for the first time, but
nine days later a faulty electrical connection
led to the rupture of a liquid helium enclosure,
causing both a magnet quench and several tons
of helium gas escaping with explosive force.
The incident resulted in damage to over 50
superconducting magnets and their mountings,
and contamination of the vacuum pipe, and
delayed further operations by 14 months. On
November 20, 2009 proton beams were successfully
circulated again, with the first recorded
proton–proton collisions occurring three
days later at the injection energy of 450 GeV
per beam. On March 30, 2010, the first collisions
took place between two 3.5 TeV beams, setting
a world record for the highest-energy man-made
particle collisions, and the LHC began its
planned research program.
By November 2012, the LHC had discovered two
previously unobserved particles) bottomonium
state and a massive 125 GeV boson, created
a quark–gluon plasma, and recorded the first
observations of the very rare decay of the
Bs meson into two muons.
The LHC operated at 3.5 TeV per beam in 2010
and 2011 and at 4 TeV in 2012. It operated
for two months in 2013 colliding protons with
lead nuclei, and went into shutdown for upgrades
to increase beam energy to 6.5 TeV per beam,
with reopening planned for early 2015.
Background
The term hadron refers to composite particles
composed of quarks held together by the strong
force. The best-known hadrons are protons
and neutrons; hadrons also include mesons
such as the pion and kaon, which were discovered
during cosmic ray experiments in the late
1940s and early 1950s.
A collider is a type of a particle accelerator
with directed beams of particles. In particle
physics colliders are used as a research tool:
they accelerate particles to very high kinetic
energies and let them impact other particles.
Analysis of the byproducts of these collisions
gives scientists good evidence of the structure
of the subatomic world and the laws of nature
governing it. Many of these byproducts are
produced only by high energy collisions, and
they decay after very short periods of time.
Thus many of them are hard or near impossible
to study in other ways.
Purpose
Physicists hope that the LHC will help answer
some of the fundamental open questions in
physics, concerning the basic laws governing
the interactions and forces among the elementary
objects, the deep structure of space and time,
and in particular the interrelation between
quantum mechanics and general relativity,
where current theories and knowledge are unclear
or break down altogether. Data are also needed
from high energy particle experiments to suggest
which versions of current scientific models
are more likely to be correct – in particular
to choose between the Standard Model and Higgsless
models and to validate their predictions and
allow further theoretical development. Many
theorists expect new physics beyond the Standard
Model to emerge at the TeV energy level, as
the Standard Model appears to be unsatisfactory.
Issues possibly to be explored by LHC collisions
include:
Are the masses of elementary particles actually
generated by the Higgs mechanism via electroweak
symmetry breaking? It is expected that the
collider will either demonstrate or rule out
the existence of the elusive Higgs boson,
thereby allowing physicists to consider whether
the Standard Model or its Higgsless alternatives
are more likely to be correct.
Is supersymmetry, an extension of the Standard
Model and Poincaré symmetry, realised in
nature, implying that all known particles
have supersymmetric partners?
Are there extra dimensions, as predicted by
various models based on string theory, and
can we detect them?
What is the nature of the dark matter that
appears to account for 27% of the mass-energy
of the universe?
Other open questions that may be explored
using high energy particle collisions:
It is already known that electromagnetism
and the weak nuclear force are different manifestations
of a single force called the electroweak force.
The LHC may clarify whether the electroweak
force and the strong nuclear force are similarly
just different manifestations of one universal
unified force, as predicted by various Grand
Unification Theories.
Why is the fourth fundamental force so many
orders of magnitude weaker than the other
three fundamental forces? See also Hierarchy
problem.
Are there additional sources of quark flavour
mixing, beyond those already predicted within
the Standard Model?
Why are there apparent violations of the symmetry
between matter and antimatter? See also CP
violation.
What are the nature and properties of quark–gluon
plasma, believed to have existed in the early
universe and in certain compact and strange
astronomical objects today? This will be investigated
by heavy ion collisions in ALICE.
Design
The LHC is the world's largest and highest-energy
particle accelerator. The collider is contained
in a circular tunnel, with a circumference
of 27 kilometres, at a depth ranging from
50 to 175 metres underground.
The 3.8-metre wide concrete-lined tunnel,
constructed between 1983 and 1988, was formerly
used to house the Large Electron–Positron
Collider. It crosses the border between Switzerland
and France at four points, with most of it
in France. Surface buildings hold ancillary
equipment such as compressors, ventilation
equipment, control electronics and refrigeration
plants.
The collider tunnel contains two adjacent
parallel beamlines that intersect at four
points, each containing a proton beam, which
travel in opposite directions around the ring.
Some 1,232 dipole magnets keep the beams on
their circular path, while an additional 392
quadrupole magnets are used to keep the beams
focused, in order to maximize the chances
of interaction between the particles in the
four intersection points, where the two beams
will cross. In total, over 1,600 superconducting
magnets are installed, with most weighing
over 27 tonnes. Approximately 96 tonnes of
superfluid helium 4 is needed to keep the
magnets, made of copper-clad niobium-titanium,
at their operating temperature of 1.9 K,
making the LHC the largest cryogenic facility
in the world at liquid helium temperature.
When running at full design power of 7 TeV
per beam, once or twice a day, as the protons
are accelerated from 450 GeV to 7 TeV, the
field of the superconducting dipole magnets
will be increased from 0.54 to 8.3 teslas.
The protons will each have an energy of 7 TeV,
giving a total collision energy of 14 TeV.
At this energy the protons have a Lorentz
factor of about 7,500 and move at about 0.999999991 c,
or about 3 metres per second slower than the
speed of light. It will take less than 90
microseconds for a proton to travel once around
the main ring – a speed of about 11,000
revolutions per second. Rather than continuous
beams, the protons will be bunched together,
into 2,808 bunches, 115 billion protons in
each bunch so that interactions between the
two beams will take place at discrete intervals
never shorter than 25 nanoseconds apart. However
it will be operated with fewer bunches when
it is first commissioned, giving it a bunch
crossing interval of 75 ns. The design luminosity
of the LHC is 1034 cm−2s−1, providing
a bunch collision rate of 40 MHz.
Prior to being injected into the main accelerator,
the particles are prepared by a series of
systems that successively increase their energy.
The first system is the linear particle accelerator
LINAC 2 generating 50-MeV protons, which feeds
the Proton Synchrotron Booster. There the
protons are accelerated to 1.4 GeV and injected
into the Proton Synchrotron, where they are
accelerated to 26 GeV. Finally the Super Proton
Synchrotron is used to further increase their
energy to 450 GeV before they are at last
injected into the main ring. Here the proton
bunches are accumulated, accelerated to their
peak 4-TeV energy, and finally circulated
for 10 to 24 hours while collisions occur
at the four intersection points.
The LHC physics program is mainly based on
proton–proton collisions. However, shorter
running periods, typically one month per year,
with heavy-ion collisions are included in
the program. While lighter ions are considered
as well, the baseline scheme deals with lead
ions. The lead ions will be first accelerated
by the linear accelerator LINAC 3, and the
Low-Energy Ion Ring will be used as an ion
storage and cooler unit. The ions will then
be further accelerated by the PS and SPS before
being injected into LHC ring, where they will
reach an energy of 2.76 TeV per nucleon, higher
than the energies reached by the Relativistic
Heavy Ion Collider. The aim of the heavy-ion
program is to investigate quark–gluon plasma,
which existed in the early universe.
Detectors
Seven detectors have been constructed at the
LHC, located underground in large caverns
excavated at the LHC's intersection points.
Two of them, the ATLAS experiment and the
Compact Muon Solenoid, are large, general
purpose particle detectors. A Large Ion Collider
Experiment and LHCb, have more specific roles
and the last three, TOTEM, MoEDAL and LHCf,
are very much smaller and are for very specialized
research. The BBC's summary of the main detectors
is:
Computing and analysis facilities
The LHC Computing Grid is an international
collaborative project that consists of a grid-based
computer network infrastructure connecting
140 computing centers in 35 countries. It
was designed by CERN to handle the significant
volume of data produced by LHC experiments.
By 2012 data from over 300 trillion LHC proton-proton
collisions had been analyzed, LHC collision
data was being produced at approximately 25
petabytes per year, and the LHC Computing
Grid had become the world's largest computing
grid, comprising over 170 computing facilities
in a worldwide network across 36 countries.
Operational history
Inaugural tests
The first beam was circulated through the
collider on the morning of 10 September 2008.
CERN successfully fired the protons around
the tunnel in stages, three kilometres at
a time. The particles were fired in a clockwise
direction into the accelerator and successfully
steered around it at 10:28 local time. The
LHC successfully completed its major test:
after a series of trial runs, two white dots
flashed on a computer screen showing the protons
travelled the full length of the collider.
It took less than one hour to guide the stream
of particles around its inaugural circuit.
CERN next successfully sent a beam of protons
in a counterclockwise direction, taking slightly
longer at one and a half hours due to a problem
with the cryogenics, with the full circuit
being completed at 14:59.
2008 quench incident
On 19 September 2008, a magnet quench occurred
in about 100 bending magnets in sectors 3
and 4, where an electrical fault led to a
loss of approximately six tonnes of liquid
helium, which was vented into the tunnel.
The escaping vapor expanded with explosive
force, damaging over 50 superconducting magnets
and their mountings, and contaminating the
vacuum pipe, which also lost vacuum conditions.
Shortly after the incident CERN reported that
the most likely cause of the problem was a
faulty electrical connection between two magnets,
and that – due to the time needed to warm
up the affected sectors and then cool them
back down to operating temperature – it
would take at least two months to fix. CERN
released an interim technical report and preliminary
analysis of the incident on 15 and 16 October
2008 respectively, and a more detailed report
on 5 December 2008. The analysis of the incident
by CERN confirmed that an electrical fault
had indeed been the cause. The faulty electrical
connection had led to a failsafe power abort
of the electrical systems powering the superconducting
magnets, but had also caused an electric arc
which damaged the integrity of the supercooled
helium's enclosure and vacuum insulation,
causing the coolant's temperature and pressure
to rapidly rise beyond the ability of the
safety systems to contain it, and leading
to a temperature rise of about 100 degrees
celsius in some of the affected magnets. Energy
stored in the superconducting magnets and
electrical noise induced in other quench detectors
also played a role in the rapid heating. Around
two tonnes of liquid helium escaped explosively
before detectors triggered an emergency stop,
and a further four tonnes leaked at lower
pressure in the aftermath. A total of 53 magnets
were damaged in the incident and were repaired
or replaced during the winter shutdown.
In the original timeline of the LHC commissioning,
the first "modest" high-energy collisions
at a center-of-mass energy of 900 GeV were
expected to take place before the end of September
2008, and the LHC was expected to be operating
at 10 TeV by the end of 2008. However, due
to the delay caused by the above-mentioned
incident, the collider was not operational
until November 2009. Despite the delay, LHC
was officially inaugurated on 21 October 2008,
in the presence of political leaders, science
ministers from CERN's 20 Member States, CERN
officials, and members of the worldwide scientific
community.
Most of 2009 was spent on repairs and reviews
from the damage caused by the quench incident,
along with two further vacuum leaks identified
in July 2009 which pushed the start of operations
to November of that year.
Full operation
On 20 November 2009, low-energy beams circulated
in the tunnel for the first time since the
incident, and shortly after, on 30 November,
the LHC achieved 1.18 TeV per beam to become
the world's highest-energy particle accelerator,
beating the Tevatron's previous record of
0.98 TeV per beam held for eight years.
The early part of 2010 saw the continued ramp-up
of beam in energies and early physics experiments
towards 3.5 TeV per beam and on 30 March 2010,
LHC set the present record for high-energy
collisions by colliding proton beams at a
combined energy level of 7 TeV. The attempt
was the third that day, after two unsuccessful
attempts in which the protons had to be "dumped"
from the collider and new beams had to be
injected. This also marked the start of its
main research program.
The first proton run ended on 4 November 2010.
A run with lead ions started on 8 November
2010, and ended on 6 December 2010, allowing
the ALICE experiment to study matter under
extreme conditions similar to those shortly
after the Big Bang.
CERN originally planned that the LHC would
run through to the end of 2012, with a short
break at the end of 2011 to allow for an increase
in beam energy from 3.5 to 4 TeV per beam.
At the end of 2012 the LHC would be shut down
until around 2015 to allow upgrade to a planned
beam energy of 7 TeV per beam. In late 2012,
in light of the July 2012 discovery of a new
particle, the shutdown was postponed for some
weeks into early 2013, to allow additional
data to be obtained prior to shutdown.
Timeline of operations
Findings
CERN scientists estimated that, if the Standard
Model is correct, a single Higgs boson would
be produced every few hours, and that over
a few years enough data to confirm or disprove
the Higgs boson unambiguously and to obtain
sufficient results concerning supersymmetric
particles would be gathered to draw meaningful
conclusions. Some extensions of the Standard
Model predict additional particles, such as
the heavy W' and Z' gauge bosons, which may
also lie within reach of the LHC to discover.
The first physics results from the LHC, involving
284 collisions which took place in the ALICE
detector, were reported on 15 December 2009.
The results of the first proton–proton collisions
at energies higher than Fermilab's Tevatron
proton–antiproton collisions were published
by the CMS collaboration in early February
2010, yielding greater-than-predicted charged-hadron
production.
After the first year of data collection, the
LHC experimental collaborations started to
release their preliminary results concerning
searches for new physics beyond the Standard
Model in proton-proton collisions. No evidence
of new particles was detected in the 2010
data. As a result, bounds were set on the
allowed parameter space of various extensions
of the Standard Model, such as models with
large extra dimensions, constrained versions
of the Minimal Supersymmetric Standard Model,
and others.
On 24 May 2011, it was reported that quark–gluon
plasma has been created in the LHC.
Between July and August 2011, results of searches
for the Higgs boson and for exotic particles,
based on the data collected during the first
half of the 2011 run, were presented in conferences
in Grenoble and Mumbai. In the latter conference
it was reported that, despite hints of a Higgs
signal in earlier data, ATLAS and CMS exclude
with 95% confidence level the existence of
a Higgs boson with the properties predicted
by the Standard Model over most of the mass
region between 145 and 466 GeV. The searches
for new particles did not yield signals either,
allowing to further constrain the parameter
space of various extensions of the Standard
Model, including its supersymmetric extensions.
On 13 December 2011, CERN reported that the
Standard Model Higgs boson, if it exists,
is most likely to have a mass constrained
to the range 115–130 GeV. Both the CMS and
ATLAS detectors have also shown intensity
peaks in the 124–125 GeV range, consistent
with either background noise or the observation
of the Higgs boson.
On 22 December 2011, it was reported that
a new particle had been observed, the χb
bottomonium state.
On 4 July 2012, both the CMS and ATLAS teams
announced the discovery of a boson in the
mass region around 125–126 GeV, with a statistical
significance at the level of 5 sigma. This
meets the formal level required to announce
a new particle which is consistent with the
Higgs boson, but scientists are cautious as
to whether it is formally identified as actually
being the Higgs boson, pending further analysis.
On 8 November 2012, the LHCb team reported
on an experiment seen as a "golden" test of
supersymmetry theories in physics, by measuring
the very rare decay of the Bs meson into two
muons. The results, which match those predicted
by the non-supersymmetrical Standard Model
rather than the predictions of many branches
of supersymmetry, show the decays are less
common than some forms of supersymmetry predict,
though could still match the predictions of
other versions of supersymmetry theory. The
results as initially drafted are stated to
be short of proof but at a relatively high
3.5 sigma level of significance.
In August 2013 the team revealed an anomaly
in the angular distribution of B meson decay
products which could not be predicted by the
Standard Model; this anomaly had a statistical
certainty of 4.5 sigma, just short of the
5 sigma needed to be officially recognized
as a discovery. It is unknown what the cause
of this anomaly would be, although the Z'
boson has been suggested as a possible candidate.
Proposed upgrade
After some years of running, any particle
physics experiment typically begins to suffer
from diminishing returns: as the key results
reachable by the device begin to be completed,
later years of operation discover proportionately
less than earlier years. A common outcome
is to upgrade the devices involved, typically
in energy, in luminosity, or in terms of improved
detectors. As well as the planned 2013–2015
increase to its intended 14 TeV collision
energy, a luminosity upgrade of the LHC, called
the High Luminosity LHC, has also been proposed,
to be made in 2018 after ten years of operation.
The optimal path for the LHC luminosity upgrade
includes an increase in the beam current and
the modification of the two high-luminosity
interaction regions, ATLAS and CMS. To achieve
these increases, the energy of the beams at
the point that they are injected into the
LHC should also be increased to 1 TeV. This
will require an upgrade of the full pre-injector
system, the needed changes in the Super Proton
Synchrotron being the most expensive. Currently
the collaborative research effort of LHC Accelerator
Research Program, LARP, is conducting research
into how to achieve these goals.
Cost
With a budget of 7.5 billion euros, the LHC
is one of the most expensive scientific instruments
ever built. The total cost of the project
is expected to be of the order of 4.6bn Swiss
francs for the accelerator and 1.16bn for
the CERN contribution to the experiments.
The construction of LHC was approved in 1995
with a budget of SFr 2.6bn, with another SFr
210M towards the experiments. However, cost
overruns, estimated in a major review in 2001
at around SFr 480M for the accelerator, and
SFr 50M for the experiments, along with a
reduction in CERN's budget, pushed the completion
date from 2005 to April 2007. The superconducting
magnets were responsible for SFr 180M of the
cost increase. There were also further costs
and delays due to engineering difficulties
encountered while building the underground
cavern for the Compact Muon Solenoid, and
also due to faulty parts provided by Fermilab.
Due to lower electricity costs during the
summer, it is expected that the LHC will normally
not operate over the winter months, although
an exception was made to make up for the 2008
start-up delays over the 2009/10 winter.
Computing resources
Data produced by LHC, as well as LHC-related
simulation, was estimated at approximately
15 petabytes per year.
The LHC Computing Grid was constructed to
handle the massive amounts of data produced.
It incorporated both private fiber optic cable
links and existing high-speed portions of
the public Internet, enabling data transfer
from CERN to academic institutions around
the world.
The Open Science Grid is used as the primary
infrastructure in the United States, and also
as part of an interoperable federation with
the LHC Computing Grid.
The distributed computing project LHC@home
was started to support the construction and
calibration of the LHC. The project uses the
BOINC platform, enabling anybody with an Internet
connection and a computer running Mac OSX,
Windows or Linux, to use their computer's
idle time to simulate how particles will travel
in the tunnel. With this information, the
scientists will be able to determine how the
magnets should be calibrated to gain the most
stable "orbit" of the beams in the ring. In
August 2011, a second application went live
which performs simulations against which to
compare actual test data, to determine confidence
levels of the results.
Safety of particle collisions
The experiments at the Large Hadron Collider
sparked fears among the public that the particle
collisions might produce doomsday phenomena,
involving the production of stable microscopic
black holes or the creation of hypothetical
particles called strangelets. Two CERN-commissioned
safety reviews examined these concerns and
concluded that the experiments at the LHC
present no danger and that there is no reason
for concern, a conclusion expressly endorsed
by the American Physical Society.
The reports also noted that the physical conditions
and collision events which exist in the LHC
and similar experiments occur naturally and
routinely in the universe without hazardous
consequences, including ultra-high-energy
cosmic rays observed to impact Earth with
energies far higher than those in any man-made
collider.
Operational challenges
The size of the LHC constitutes an exceptional
engineering challenge with unique operational
issues on account of the amount of energy
stored in the magnets and the beams. While
operating, the total energy stored in the
magnets is 10 GJ and the total energy carried
by the two beams reaches 724 MJ.
Loss of only one ten-millionth part of the
beam is sufficient to quench a superconducting
magnet, while the beam dump must absorb 362 MJ
for each of the two beams. These energies
are carried by very little matter: under nominal
operating conditions, the beam pipes contain
1.0×10−9 gram of hydrogen, which, in standard
conditions for temperature and pressure, would
fill the volume of one grain of fine sand.
Construction accidents and delays
On 25 October 2005, José Pereira Lages, a
technician, was killed in the LHC when a switchgear
that was being transported fell on him.
On 27 March 2007 a cryogenic magnet support
broke during a pressure test involving one
of the LHC's inner triplet magnet assemblies,
provided by Fermilab and KEK. No one was injured.
Fermilab director Pier Oddone stated "In this
case we are dumbfounded that we missed some
very simple balance of forces". This fault
had been present in the original design, and
remained during four engineering reviews over
the following years. Analysis revealed that
its design, made as thin as possible for better
insulation, was not strong enough to withstand
the forces generated during pressure testing.
Details are available in a statement from
Fermilab, with which CERN is in agreement.
Repairing the broken magnet and reinforcing
the eight identical assemblies used by LHC
delayed the startup date, then planned for
November 2007.
Problems occurred on 19 September 2008 during
powering tests of the main dipole circuit,
when an electrical fault in the bus between
magnets caused a rupture and a leak of six
tonnes of liquid helium. The operation was
delayed for several months. It is currently
believed that a faulty electrical connection
between two magnets caused an arc, which compromised
the liquid-helium containment. Once the cooling
layer was broken, the helium flooded the surrounding
vacuum layer with sufficient force to break
10-ton magnets from their mountings. The explosion
also contaminated the proton tubes with soot.
This accident was thoroughly discussed in
a 22 February 2010 Superconductor Science
and Technology article by CERN physicist Lucio
Rossi.
Two vacuum leaks were identified in July 2009,
and the start of operations was further postponed
to mid-November 2009.
Popular culture
The Large Hadron Collider gained a considerable
amount of attention from outside the scientific
community and its progress is followed by
most popular science media. The LHC has also
inspired works of fiction including novels,
TV series, and video games.
The novel Angels & Demons, by Dan Brown, involves
antimatter created at the LHC to be used in
a weapon against the Vatican. In response
CERN published a "Fact or Fiction?" page discussing
the accuracy of the book's portrayal of the
LHC, CERN, and particle physics in general.
The movie version of the book has footage
filmed on-site at one of the experiments at
the LHC; the director, Ron Howard, met with
CERN experts in an effort to make the science
in the story more accurate.
The novel FlashForward, by Robert J. Sawyer,
involves the search for the Higgs boson at
the LHC. CERN published a "Science and Fiction"
page interviewing Sawyer and physicists about
the book and the TV series based on it.
CERN employee Katherine McAlpine's "Large
Hadron Rap" surpassed 7 million YouTube views.
The band Les Horribles Cernettes was founded
by women from CERN. The name was chosen so
to have the same initials as the LHC.
National Geographic Channel's World's Toughest
Fixes, Season 2, Episode 6 "Atom Smasher"
features the replacement of the last superconducting
magnet section in the repair of the supercollider
after the 2008 quench incident. The episode
includes actual footage from the repair facility
to the inside of the supercollider, and explanations
of the function, engineering, and purpose
of the LHC.
The Large Hadron Collider was the focus of
the 2012 student film Decay, with the movie
being filmed on location in CERN's maintenance
tunnels.
Canadian rock musician, Nim Vind wrote and
recorded a song called "Hadron Collider".
See also
Bose–Einstein statistics
Compact Linear Collider
International Linear Collider
Very Large Hadron Collider
List of accelerators in particle physics
High Luminosity Large Hadron Collider
References
External links
Official website
Overview of the LHC at CERN's public webpage
CERN Courier magazine
CERN on Twitter
CMS Experiment at CERN on Twitter
Unofficial CERN on Twitter
LHC Portal Web portal
CERN, how it works on YouTube
Lyndon Evans and Philip Bryant. "LHC Machine".
Journal of Instrumentation 3: S08001. Bibcode:2008JInst...3S8001E.
doi:10.10883S08001.  Full documentation for
design and construction of the LHC and its
six detectors.
symmetry magazine LHC special issue August
2006, special issue December 2007
New Yorker: Crash Course. The world's largest
particle accelerator.
NYTimes: A Giant Takes On Physics' Biggest
Questions.
Why a Large Hadron Collider? Seed Magazine
interviews with physicists.
Thirty collected pictures during commissioning
and post- 19 September 2008 incident repair,
from Boston Globe.
Podcast Interview with CERN's Rolf Landua
about the LHC and the physics behind it
"Petabytes at the LHC". Sixty Symbols. Brady
Haran for the University of Nottingham. 
