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"26 July 2010"
LHCNews:
ICHEP 2010
conference highlights first results from the LHC
Geneva, 26 July 2010.
First results from the LHC at CERN are being revealed at ICHEP, the
world’s largest international conference on particle physics,
which has attracted more than 1000 participants to its venue in Paris.
The spokespersons of the four major experiments at the LHC –
ALICE, ATLAS, CMS and LHCb – are today presenting measurements
from the first three months of successful LHC operation at 3.5
TeV per beam, an energy three and a half times higher than
previously achieved at a particle accelerator.
With these first
measurements the experiments are rediscovering the particles
that lie at the heart of the Standard Model – the package that
contains current understanding of the particles of matter and
the forces that act between them. This is an essential step
before moving on to make discoveries. Among
the billions of collisions already recorded are some that
contain 'candidates' for the top quark, for the first time at a
European laboratory.
“Rediscovering our
‘old friends’ in the particle world shows that the LHC
experiments are well prepared to enter new territory” said
CERN’s Director-General Rolf Heuer. “It
seems that the Standard Model is working as expected. Now it is
down to nature to show us what is new.”
The quality of the
results presented at ICHEP bears witness both to the excellent
performance of the LHC and to the high quality of the data in
the experiments. The LHC, which is still in its early days, is
making steady progress towards its ultimate operating
conditions. The luminosity – a measure of the collision rate -
has already risen by a factor of more than a thousand since the
end of March. This rapid progress with commissioning the LHC
beam has been matched by the speed with which the data on
billions of collisions have been processed by the Worldwide LHC
Computing Grid, which allows data from the experiments to be
analysed at collaborating centres around the world.
“Within
days we were finding Ws, and later Zs – the two carriers of the
weak force discovered here at CERN nearly 30 years ago,” said
Fabiola Gianotti, spokesperson for the 3000-strong ATLAS
collaboration. “Thanks
to the efforts of the whole collaboration, in particular the
young scientists, everything from data-taking at the detector,
through calibration, data processing and distribution, to the
physics analysis, has worked fast and efficiently.”
“It is
amazing to see how quickly we have ‘re-discovered’ the known
particles: from the lightest resonances up to the massive top
quark. What we have shown here in Paris is just the first
outcome of an intense campaign of accurate measurements of their
properties.” said
Guido Tonelli, spokesperson for CMS. “This
patient and systematic work is needed to establish the known
background to any new signal.”
“The LHCb
experiment is tailor-made to study the family of b particles,
containing beauty quarks,” said
the experiment’s spokesperson Andrei Golutvin, “So it’s
extremely gratifying that we are already finding hundreds of
examples of these particles, clearly pin-pointed through the
analysis of many particle tracks.”
“The current
running with proton collisions has allowed us to connect with
results from other experiments at lower energies, test
and improve the extrapolations made for the LHC, and
prepare the ground for the heavy-ion runs,” said
Jurgen Schukraft, spokesperson for the ALICE collaboration. This
experiment is optimized to study collisions of lead ions, which
will occur in the LHC for the first time later this year.
Two further
experiments have also already benefited from the first months of
LHC operation at 3.5 TeV per beam. LHCf, which is studying the
production of neutral particles in proton-proton collisions to
help in understanding cosmic-ray interactions in the Earth’s
atmosphere, has already collected the data it needs at a beam
energy of 3.5 TeV. TOTEM, which has to move close to the beams
for its in-depth studies of the proton, is beginning to make its
first measurements.
CERN
will run the LHC for 18-24 months with the objective of
delivering enough data to the experiments to make significant
advances across a wide range of physics processes. With the
amount of data expected, referred to as one inverse femtobarn,
the experiments should be well placed to make inroads in to new
territory, with the possibility of significant discoveries.
23 July 2010
Europe reaches the top, err, the top reaches Europe
July 23, 2010
It might be a long way to the top, but the LHC experiments
are already half-way there. Today at the International
Conference on High Energy Physics in
Paris, the CMS and ATLAS experiments presented their first top
quark candidates. These candidates are collisions that have all
the hallmarks of having produced top quarks, but the experiments
don’t yet have enough data to be 100% sure that the events
created top quarks that decayed into other particles, rather
than another type of event.
“The signal is starting to rise from the background,” notes
Tim Christiansen from CMS.
The top quark, the heaviest particle in the Standard Model,
was discovered at
Fermilab’s Tevatron in 1995. The CDF and DZero experiments on
the Tevatron are still busy measuring its properties in detail
(one of this morning’s parallel sessions had
several talks on its width, mass and likely couplings to
particles of and beyond the Standard Model). Now the LHC
experiments are joining them on the way to explore the top: both
CMS and ATLAS showed selected candidate events of top quark
pairs.
Finding top quarks at the LHC is exciting because the top is
the last, and heaviest, particle that the LHC needed to add to
its list of ‘rediscoveries’. It is also an important partner in
the hunt for all sorts of new physics. The better the top and
its behavior are understood the easier it will be to distinguish
events that involve direct top quark production from events that
involve, for example, the Higgs or supersymmetric particles.
http://www.symmetrymagazine.org/breaking/2010/07/23/europe-reaches-the-top-err-the-top-reaches-europe/
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15 July 2010
Progress at the LHC
Geneva. 15 July, 2010
A month ago
we decided to focus fully on commissioning the LHC beam with the
goal of establishing the conditions for routine collisions
between bunches at design intensity at an energy of 3.5 TeV per
beam. This involved optimizing not only the LHC but also the
injection of protons from the SPS. The teams made very good
progress and the machine now runs smoothly for physics with
multiple bunches of 1011 protons
per bunch.
This is an excellent
achievement for a machine that is still in its infancy, having
produced its first collisions at 3.5 TeV only three and a half
months ago.
While there
remain issues to understand – as is hardly surprising with a new
machine operating in a new energy region – the effort on beam
commissioning has certainly paid off. The
peak luminosity, which depends on the number of protons per beam
and how tightly they are squeezed together, has risen by more
than a factor of 1000 to a value of 1.4 x 1030 cm-2 s-1.
Increased
luminosity means more collisions and more data for the
experiments. Today we are already above an integrated luminosity
of 200 nb-1. This puts the experiments in an
excellent position to present important results in a new energy
region at the major international conference, ICHEP 2010, which
starts later next week.
2 June 2010
The first two
months at 3.5 TeV per beam
Geneva 2 June
Two months is a very short time in
the life of a major particle physics project, but a lot can
happen in that time as the LHC has shown since 30 March.
Colliding beams at 3.5 TeV was an important milestone, a start
to the LHC physics programme, but it was just a single step on a
very long journey. Since then, we’ve lengthened our stride, and
are progressing well towards the key objectives for 2010.
The next major milestone came on 19 April with a ten-fold
increase in luminosity – in other words, the machine started
delivering ten times as many collisions to the experiments in a
given period of time than had previously been possible. This
came about thanks to two simultaneous developments: firstly the
number of particles in each bunch was doubled, and secondly the
beam size at the interaction point was squeezed down. The term
you’ll hear used to describe the beam size at the interaction
point is called beta-star, and the smaller the beta, the better.
Before squeeze, beta is 11 m at ATLAS and CMS. The ultimate goal
is to reduce it to 0.55 m. Today, we’re running with a beta of 2
m. That may not sound very small, and that’s because it’s not
the size of the beam: beta is the distance from the interaction
point that the beam is twice the size it is at the interaction
point. What’s important for physics is that the lower the beta,
the smaller the beam at the interaction point. With beta of 2 m,
the beam is just 45 microns across at the interaction point, a
quarter the width of a human hair, and its cross section is
about five times smaller than with a beta of 11 m.
Four weeks of running under these conditions led to significant
quantities of data being accumulated by the experiments, and
then came the next big step. Over the weekend of 22 May, we
started to run with 13 bunches in each beam.
The first
collisions on 30 March were done with one bunch per beam, and
the ultimate goal is to reach 2808, so there’s still some way to
go. Nevertheless, we set a new luminosity record that weekend of
2 ´ 1029.
To put that in context, we achieved 1027 on
30 March, the design figure for the LHC is 1034 and
the objective for 2010 is to reach 1032.
All this was
achieved during physics running, leading to incredible progress
being made by the experiments. They have been running with 90%
efficiency, a remarkable achievement for devices of such
complexity. Billions of collisions have been recorded and
successfully dispatched for analysis via the LHC Computing Grid.
The rediscovery of the Standard Model, which is necessary before
we can confidently say we’re ready for new physics, is well
underway. There are even some intriguing observations about the
properties of collisions at this new energy. As a measure of
their success to date, the experiments have already published or
submitted over a dozen papers to peer reviewed journals and
conferences based on LHC collision data.
Physics
running is interspersed with periods of machine development
essential for further progress to be made. As a foretaste of
what the experiments can expect over the next two months, the
LHC operations team has notched up some impressive results over
the last few machine development sessions. The first of these
was to inject bunches with more than the LHC’s design intensity
and collide them at 450 GeV. There’s nothing new about 450 GeV,
but it’s an important milestone nevertheless since the
difficulty of colliding bunches increases with intensity. By
comparison, adding extra bunches is a relatively easier task.
The icing on the cake of last week’s machine development came
when design intensity bunches were brought into collision at 3.5
TeV on 26 May.
Behind this
great progress is a guiding principle of caution. The masters of
ceremony are those responsible for the systems that protect the
LHC and the experiments from stray beam particles. Collimators
absorb particles that wander from their intended orbits before
they can impinge on LHC magnets or sensitive detector elements,
while the LHC beam dump system is there to extract the beams
safely in case of need. Any increase in intensity has to be
approved by the LHC machine protection teams, and progress is
incremental. Each increase in intensity, and therefore stored
energy in the machine, is a learning process for the machine
protection teams and only when they are ready do increases in
intensity happen.
With all eyes
on the amount of data being delivered to the experiments, it
would be easy to overlook some of the pioneering systems that
make the LHC possible. When I asked someone in the CERN Control
Centre last week about the cryogenics, they replied that it’s
working so well they’d almost forgotten it was there. For the
operators of the world’s largest cryogenic installation that’s
quite a compliment. And for anyone wondering whether large-scale
cryogenics may have broader applications, the LHC is proving to
be an interesting test case.
The same goes
for the vacuum systems. Beam lifetimes of 1000 hours have been
posted, which is truly exceptional for any particle accelerator.
Of course, we don’t keep beams for that long: there are many
reasons why beams are extracted long before they reach their
theoretical lifetimes. So far in the LHC, the longest fill for
physics has been 30 hours, which well exceeds my expectations
for the first months of running.
A lot can happen in two months, and we are well on course to
achieving our 2010 objectives for the LHC. The fact that the
LHC’s availability for operation is already over 60% is
testimony to the skills and professionalism of all those who
operate the machine and its supporting infrastructure, and it is
perhaps the one statistic that has made all the others possible.
As I write, we’ve recently completed a rather frustrating
weekend, with a short circuit in a cable terminal of an
electrical cabinet stopping us from running. By Monday morning,
however, we’d recovered and will resume LHC running tomorrow
after a scheduled technical stop. Glitches such as this are a
fact of life in a working lab, and do not detract from the fact
that we have much to be pleased with from these two months. As
the figures I’ve quoted above illustrate, however, we still have
a long way to travel. My congratulations go to all involved with
this great scientific adventure.
31 May 2010
CERN
Press Release - Particle Chameleon Caught in the act of Changing
Geneva, 31 May 2010. Researchers on the OPERA experiment at the
INFN [1]’s
Gran Sasso laboratory in Italy today announced the first direct
observation of a tau particle in a muon neutrino beam sent
through the Earth from CERN[2],
730km away. This is a significant result, providing the final
missing piece of a puzzle that has been challenging science
since the 1960s, and giving tantalizing hints of new physics to
come.
The neutrino
puzzle began with a pioneering and ultimately Nobel Prize
winning experiment conducted by US scientist Ray Davies
beginning in the 1960s. He observed far fewer neutrinos arriving
at the Earth from the Sun than solar models predicted: either
solar models were wrong, or something was happening to the
neutrinos on their way. A possible solution to the puzzle was
provided in 1969 by the theorists Bruno Pontecorvo and Vladimir
Gribov, who first suggested that chameleon-like
oscillatory changes between different types of neutrinos could
be responsible for the apparent neutrino deficit.
Several experiments since have observed the
disappearance of muon-neutrinos, confirming the oscillation
hypothesis, but until now no observations of the appearance of a
tau-neutrino in a pure muon-neutrino beam have been observed:
this is the first time that the neutrino chameleon has been
caught in the act of changing from muon-type to tau-type.
Antonio Ereditato, Spokesperson of the
OPERA collaboration described the development as: “an
important result which rewards the entire OPERA collaboration
for its years of commitment and which confirms that we have made
sound experimental choices. We are confident that this first
event will be followed by others that will fully demonstrate the
appearance of neutrino oscillation".
"The OPERA experiment has reached its
first goal: the detection of a tau neutrino obtained from the
transformation of a muon neutrino, which occurred during the
journey from Geneva to the Gran Sasso Laboratory,” added
Lucia Votano, Director Gran Sasso laboratories. “This
important result comes after a decade of intense work performed
by the Collaboration, with the support of the Laboratory, and it
again confirms that LNGS is a leading laboratory in
Astroparticle Physics”.
The OPERA result follows seven years of
preparation and over three years of beam provided by CERN.
During that time, billions of billions of muon-neutrinos have
been sent from CERN to Gran Sasso, taking just 2.4 milliseconds
to make the trip. The rarity of neutrino oscillation, coupled
with the fact that neutrinos interact very weakly with matter
makes this kind of experiment extremely subtle to conduct.
CERN’s neutrino beam was first switched on in 2006, and since
then researchers on the OPERA experiment have been carefully
sifting their data for evidence of the appearance of tau
particles, the telltale sign that a muon-neutrino has oscillated
into a tau-neutrino. Patience of this kind is a virtue in
particle physics research, as INFN President Roberto Petronzio
explained:
“This success is due to the tenacity and
inventiveness of the physicists of the international community,
who designed a particle beam especially for this experiment,” said
Petronzio. “In this way, the original design of Gran Sasso
has been crowned with success. In fact, when constructed, the
laboratories were oriented so that they could receive particle
beams from CERN”.
At CERN, neutrinos are generated from
collisions of an accelerated beam of protons with a target. When
protons hit the target, particles called pions and kaons are
produced. They quickly decay, giving rise to neutrinos. Unlike
charged particles, neutrinos are not sensitive to the
electromagnetic fields usually used by physicists to change the
trajectories of particle beams. Neutrinos can pass through
matter without interacting with it; they keep the same direction
of motion they have from their birth. Hence, as soon as they are
produced, they maintain a straight path, passing through the
Earth's crust. For this reason, it is extremely important that
from the very beginning the beam points exactly towards the
laboratories at Gran Sasso.
‘This is an important
step for neutrino physics,” said
CERN Director General Rolf Heuer. “My congratulations go to
the OPERA experiment and the Gran Sasso Laboratories, as
well as the accelerator departments at CERN. We’re all
looking forward to unveiling the new physics this result
presages.”
While closing a chapter on understanding
the nature of neutrinos, the observation of neutrino
oscillations is strong evidence for new physics. In the theories
that physicists use to explain the behaviour of fundamental
particles, which is known as the Standard Model, neutrinos have
no mass. For neutrinos to be able to oscillate, however, they
must have mass: something must be missing from the Standard
Model. Despite its success in describing the particles that make
up the visible Universe and their interactions, physicists have
long known that there is much the Standard Model does not
explain. One possibility is the existence of other, so-far
unobserved types of neutrinos that could shed light on Dark
Matter, which is believed to make up about a quarter of the
Universe’s mass.
[1] Italy's
national nuclear physics institute, INFN (Istituto
Nazionale di Fisica Nucleare), supports, coordinates and
carries out scientific research in subnuclear, nuclear and
astroparticle physics and is involved in developing related
technologies. The institute operates in conjunction with
universities and is involved in the wider international
debate as well as in cooperation programs. The Institute was
established by physicists in Milan, Padua, Rome and Turin on
8 August 1951with a view to pursuing and furthering the
research started by Enrico Fermi's team of researchers
during the 1930s. In over 50 years, INFN has gradually
extended and currently includes thirty detachments, four
national laboratories and a data processing centre.
Furthermore, the area outside Pisa is host to the
gravitational observatory EGO, jointly developed by INFN and
the French national research centre. As many as 5000
contribute to the institute's endeavours; 2000 of whom are
directly employed by it, 2000 university staff and more than
one thousand among students and scholarship holders.
[2] CERN, the
European Organization for Nuclear Research, is the world's
leading laboratory for particle physics. It has its
headquarters in Geneva. At present, its Member States are
Austria, Belgium, Bulgaria, the Czech Republic, Denmark,
Finland, France, Germany, Greece, Hungary, Italy,
Netherlands, Norway, Poland, Portugal, Slovakia, Spain,
Sweden, Switzerland and the United Kingdom. India, Israel,
Japan, the Russian Federation, the United States of America,
Turkey, the European Commission and UNESCO have Observer
status.
30
March
2010
CMS Statement for the 7 TeV collisions
Today the Large
Hadron Collider (LHC) at CERN has, for the first time, collided
two beams of 3.5 TeV protons – a new world record energy. The
CMS experiment successfully detected these collisions,
signifying the beginning of the “First Physics” at the LHC.
At 12:58:34 the LHC
Control Centre declared stable colliding beams: the collisions
were immediately detected in CMS. Moments later the full
processing power of the detector had analysed the data and
produced the first images of particles created in the 7 TeV
collisions traversing the CMS detector.
CMS was fully
operational and observed around 200000 collisions in the first
hour. The data were quickly stored and processed by a huge farm
of computers at CERN before being transported to collaborating
particle physicists all over the world for further detailed
analysis.
The first step for
CMS was to measure precisely the position of the collisions in
order to fine-tune the settings of both the collider and the
experiment. This calculation was performed in real-time and
showed that the collisions were occurring within 3 millimetres
of the exact centre of the 15m diameter CMS detector. This
measurement already demonstrates the impressive accuracy of the
27 km long LHC machine and the operational readiness of the CMS
detector. Indeed all parts of CMS are functioning excellently –
from the detector itself, through the trigger and data
acquisition systems that select and record the most interesting
collisions, to the software and computing Grids that process and
distribute the data.
“This
is the moment for which we have been waiting and preparing for
many years. We are standing at the threshold
of a new, unexplored territory that could contain the answer to
some of the major questions of modern physics” said CMS
Spokesperson Guido Tonelli. “Why does the Universe have any
substance at all? What, in fact, is 95% of our Universe actually
made of? Can the known forces be explained by a single
Grand-Unified force”. Answers may rely on the production and
detection in laboratory of particles that have so far eluded
physicists. “We’ll soon start a systematic search for the Higgs
boson, as well as particles predicted by new theories such as ‘Supersymmetry’,
that could explain the presence of abundant dark matter in our
universe. If they exist, and LHC will produce them, we are
confident that CMS will be able to detect them.” But prior to
these searches it is imperative to understand fully the complex
CMS detector. “We are already starting to study the known
particles of the Standard Model in great detail, to perform a
precise evaluation of our detector’s response and to measure
accurately all possible backgrounds to new physics. Exciting
times are definitely ahead”.
Images and
animations of some of the first collisions in CMS can be found
on the CMS public web site
http://cms.cern.ch
CMS is one of two
general-purpose experiments at the LHC that have been built to
search for new physics. It is designed to detect a wide range
of particles and phenomena produced in the LHC’s high-energy
proton-proton collisions and will help to answer questions such
as: What is the Universe really made of and what forces act
within it? And what gives everything substance? It will also
measure the properties of well known particles with
unprecedented precision and be on the lookout for completely
new, unpredicted phenomena. Such research not only increases
our understanding of the way the Universe works, but may
eventually spark new technologies that change the world in which
we live.
The current run of the
LHC is expected to last eighteen months. This should enable the
LHC experiments to accumulate enough data to explore new
territory in all areas where new physics can be expected.
The conceptual design
of the CMS experiment dates back to 1992. The construction of
the gigantic detector (15 m diameter by 21m long with a weight
of 12500 tonnes) took 16 years of effort from one of the largest
international scientific collaborations ever assembled: more
than 3600 scientists and engineers from 182 Institutions and
research laboratories distributed in 39 countries all over the
world.
13 March
2010
On the
threshold of new territory
Geneva March 9,
The LHC is already over a
week into its 2010 run, and the start of physics
at 7 TeV is just around the corner. Last week,
participants at the annual La Thuile workshop in
Italy had the chance to take stock of what lies
in store for the LHC’s first physics run. They
learned that there’s a great sense of
anticipation here at CERN and at particle
physics labs around the globe, and for good
reason – we’re about to open up the biggest
range of potential new discovery that particle
physics has seen in over a decade.
Our objective over the next
18 to 24 months is to deliver one inverse femtobarn of data to
the experiments. In other words, enough data to make significant
advances across a wide range of physics channels.
Take supersymmetry. ATLAS and
CMS will each have enough data to significantly extend today’s
sensitivity to new discoveries. Experiments today are sensitive
to some supersymmetric particles with masses up to about 400 GeV.
An inverse femtobarn at the LHC pushes that up to about 800 GeV.
This means that in the next two years, the experiments at the
LHC will explore as much territory in their quest for SUSY as
has been covered in the history of particle physics to date. In
other words, the LHC has a real chance over the next two years
of discovering supersymmetric particles, possibly elucidating
the nature of the dark matter that accounts for about a quarter
of the mass and energy of the Universe.
The Higgs particle is another
example. The last word that CERN had to say on the matter came
from LEP almost ten years ago. In the last year of LEP running
there were tantalising signs that the Higgs might have made an
appearance but all we could say for sure was that the Higgs must
have a mass above about 115 GeV. Since then, the Tevatron has
done great work towards ruling out some of the mass range that
the Higgs could inhabit. With an inverse femtobarn of data from
the LHC, the combined analyses of ATLAS and CMS will be able to
explore a wide mass range, and there’s even a chance of
discovery if the particle has a mass near 160 GeV.
At the more
exotic end of the potential discovery spectrum, LHC experiments
will be sensitive to new massive particles that could herald the
presence of extra dimensions. Discoveries up to masses of 2 TeV
will be possible, whereas today’s reach is around 1 TeV.
All this
makes now a very good time to be a particle physicist, and in
particular a student of particle physics. Some 2500 graduate
students are eagerly awaiting data from all the LHC experiments,
ALICE, ATLAS, CMS, LHCb, LHCf and TOTEM. They’re a privileged
group, set to produce the first PhD theses at the new
high-energy frontier.
Two years
of continuous running is a tall order both for the LHC operators
and the experiments, but it will be well worth the effort. By
abandoning CERN’s traditional annual operational cycle we’re
increasing the overall running time and discovery potential over
the next three years. This run will be followed by preparations
for 14 TeV collisions in a single shutdown and another major
advance into new territory as great as the one we are on the
threshold of achieving.
3 February
2010
LHC Run
in 2010
Geneva February 3,
Last week, the Chamonix workshop once again proved its worth as
a place where all the stakeholders in the LHC can come together,
take difficult decisions and reach a consensus on important
issues for the future of particle physics. The most important
decision we reached last week is to run the LHC for 18 to 24
months at a collision energy of 7 TeV (3.5 TeV per beam). After
that, we’ll go into a long shutdown in which
we’ll do all the necessary work to allow us to
reach the LHC’s design collision energy of 14 TeV
for the next run. This means that when beams go back into the
LHC later this month, we’ll be entering the
longest phase of accelerator operation in CERN’s
history, scheduled to take us into summer or autumn 2011.
What led us to
this conclusion? Firstly, the LHC is unlike any previous CERN
machine. Because it is a cryogenic facility, each run is
accompanied by lengthy cool-down and warm-up phases. For that
reason, CERN’s traditional ‘run
through summer and shutdown for ]winter’
operational model had already been brought into question.
Furthermore, we’ve known for some time that work
is needed to prepare the LHC for running at energies
significantly higher than the 7 TeV collision energy
we’ve chosen for the first physics run. The
latest data show that while we can run the LHC at 7 TeV without
risk to the machine, running it at higher energy would require
more work in the tunnel. These facts led us to a simple choice:
run for a few months now and programme successive short
shutdowns to step up in energy, or run for a long time now and
schedule a single long shutdown before allowing 14 TeV (7 TeV
per beam).
A long run now is
the right decision for the LHC and for the experiments. It gives
the machine people the time necessary to prepare carefully for
the work that’s needed before allowing 14 TeV.
And for the experiments, 18 to 24 months will bring enough data
across all the potential discovery areas to firmly establish the
LHC as the world’s foremost facility for
high-energy particle physics.
1 7
December 2009
LHC ends 2009 run on a high note
Yesterday evening at 18:03, the
LHC ended its first full period of operation in style.
Collisions at 2.36 TeV recorded since last weekend have set a
new world record and brought to a close a successful first run.
The LHC has now been put into standby mode, and will restart in
February 2010 following a short technical stop to prepare for
higher energy collisions and the start of the main research
programme.
A technical stop is needed to
prepare the LHC for higher energy running in 2010. Before the
2009 running period began, all the necessary preparations to run
up to a collision energy of 2.36 TeV had been carried out. To
run at higher energy requires higher electrical currents in the
LHC magnet circuits. This places more exacting demands on the
new machine protection systems, which need to be readied for the
task. Commissioning work for higher energies will be carried out
in January, along with necessary adaptations to the hardware and
software of the protection systems that have come to light
during the 2009 run.
The success of the 2009 run is
down to the skill and dedication of every one of you.
Congratulations and thanks to you all.
14
December 2009
First
Collisions in 2.36 TeV
After
only three weeks of running it almost felt like
routine operation in the CERN control centre and the
experiments' control rooms this weekend: long periods of stable
beams at 450 GeV, good beam lifetimes and beam intensities of up
to 7 x 10^10 protons per beam meant that all experiments took a
very good set of data. Over the weekend ATLAS, ALICE, CMS, LHCb,
TOTEM and LHCf recorded well over one million events. The
operators performed more tests at the higher energy of 1.18 TeV
per beam and the experiments saw about 50 000 collisions at 2.36
TeV. With only three days of operation to go before the
end-of-the-year technical stop, the experiments have many events
to look at in the new year, and the LHC operators have learnt a
lot about their machine, which is running more smoothly than
anyone could have expected.
30 November 2009
LHC sets new world record
Geneva, 30
November 2009. CERN’s Large Hadron Collider has
today
become the world’s highest energy particle
accelerator,having
accelerated its twin beams of protons to an
energy of 1.18 TeV in the
early hours of the morning. This exceeds the
previous world record of
0.98 TeV, which had been held by the US Fermi
National Accelerator
Laboratory’s Tevatron collider since 2001.
It
marks another important
milestone on the road to first physics at the
LHC in 2010.
“We are still coming to terms with just how
smoothly the LHC
commissioning is going,” said CERN Director
General Rolf Heuer.
"It is fantastic. However, we
are continuing to take it step by step, and
there is still a lot to do before we start
physics in 2010.
I’m keeping my champagne on ice until then.”
These developments come just 10 days after the
LHC restart,
demonstrating the excellent performance of the
machine. First beams
were injected into the LHC on Friday 20
November. Over the following
days, the machine’s operators circulated beams
around the ring
alternately in one direction and then the other
at the injection
energy of 450 GeV, gradually increasing the beam
lifetime to around 10
hours. On Monday 23 November, two beams
circulated together for the
first time, and the four big LHC detectors
recorded their first collision data.
Last night’s achievement brings further
confirmation that the
LHC is progressing smoothly towards the
objective of first physics early in
2010.The world record energy was first broken
yesterday evening, when
beam 1 was accelerated from 450 GeV, reaching
1050 GeV (1.05 TeV) at
21:28, Sunday 29 November. Three hours later
both LHC beams were
successfully accelerated to 1.18 TeV, at 00:44,
30 November.
"I was here 20 years ago when we switched on
CERN’s last major
particle accelerator, LEP,” said Research and
Technology Director
Steve Myers. “I thought that was a great machine
to operate,
but this is something else. What took us days or
weeks with LEP, we’re
doing in hours with the LHC. So far, it all
augurs well for a great research
programme.”
Next on the schedule is a concentrated
commissioning phase aimed at
increasing the beam intensity before delivering
good quantities of
collision data to the experiments before
Christmas. So far, all the
LHC commissioning work has been carried out with
a low intensity pilot
beam. Higher intensity is needed to provide
meaningful proton-proton
collision rates. The current commissioning phase
aims to make sure
that these higher intensities can be safely
handled and that stable
conditions can be guaranteed for the experiments
during collisions.
This phase is estimated to take around a week,
after which the LHC
will be colliding beams for calibration purposes
until the end of the
year.
First physics at the LHC is scheduled for the
first quarter of 2010,
at a collision energy of 7 TeV (3.5 TeV per
beam).
23 November 2009
First
collisions in the LHC!
Geneva, 23
November 2009.
Today the LHC circulated two beams simultaneously for the first
time, allowing the operators to test the synchronization of the
beams and giving the experiments their first chance to look for
proton-proton collisions. With just one bunch of particles
circulating in each direction, the beams can be made to cross in
up to two places in the ring. From early in the afternoon, the
beams were made to cross at 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.
“It’s a great
achievement to have come this far in so short a time,”
said CERN Director General Rolf Heuer. “But
we need to keep a sense of perspective–there’s still much to do
before we can start the LHC physics programme.”
Beams
were first tuned to produce collisions in the ATLAS detector,
which recorded its first candidate for collisions at 14:22 this
afternoon. Later, the beams were optimised for CMS. In the
evening, ALICE had the first optimisation, followed by LHCb. The
attached file shows the first collision candidate in CMS. It was
reported at 19:40.
“This
is great news, the start of a fantastic era of physics and
hopefully discoveries after 20 years' work by the international
community to build a machine and detectors of unprecedented
complexity and performance,"
said ATLAS spokesperson Fabiola Gianotti.
“The
events so far mark the start of the second half of this
incredible voyage of discovery of the secrets of nature,”
said CMS spokesperson Tejinder Virdee.
“It
was standing room only in the ALICE control room and cheers
erupted with the first collisions,”
said ALICE spokesperson Jurgen Schukraft. “This is simply
tremendous.”
“The
tracks we’re seeing are beautiful,”
said LHCb spokesperson Andrei Golutvin,
“we’re all ready for serious data taking in a few
days time.”
These developments come just
three days after the LHC restart, demonstrating the excellent
performance of the beam control system. Since the start-up, the
operators have been circulating beams around the ring
alternately in one direction and then the other at the injection
energy of 450 GeV. The beam lifetime has gradually been
increased to 10 hours, and today beams have been circulating
simultaneously in both directions, still at the injection
energy.
Next on the schedule is an
intense commissioning phase aimed at increasing the beam
intensity and accelerating the beams. All being well, by
Christmas, the LHC should reach 1.2 TeV per beam, and have
provided good quantities of collision data for the experiments’
calibrations.
20 November 2009
The
LHC is back !
http://cmsdoc.cern.ch/cms/performance/FirstBeam/cms-e-commentary09.htm
Geneva, 20 November 2009.
Particle beams are once again circulating in the world’s most
powerful particle accelerator, CERN*’s Large Hadron Collider (LHC).
This news comes after the machine was handed over for operation
on Wednesday morning. A clockwise circulating beam was
established at ten o'clock this evening. This is an important
milestone on the road towards first physics at the LHC, expected
in 2010.
“It’s great to see beam circulating in the LHC again,” said CERN
Director General Rolf Heuer. “We’ve still got some way to go
before physics can begin, but with this milestone we’re well on
the way.”
The LHC circulated its first beams on 10 September 2008, but
suffered a serious malfunction nine days later. A failure in an
electrical connection led to serious damage, and CERN has spent
over a year repairing and consolidating the machine to ensure
that such an incident cannot happen again.
“The LHC is a far better understood machine than it was a year
ago,” said CERN’s Director for Accelerators, Steve Myers.“We’ve
learned from our experience, and engineered the technology that
allows us to move on. That’s how progress is made.”
Recommissioning the LHC began in the summer, and successive
milestones have regularly been passed since then. The LHC
reached its operating temperature of 1.9 Kelvin, or about -271
Celsius, on 8 October. Particles were injected on 23 October,
but not circulated. A beam was steered through three octants of
the machine on 7 November, and circulating beams have now been
re-established. The next important milestone will be low-energy
collisions, expected in about a week from now. These will give
the experimental collaborations their first collision data,
enabling important calibration work to be carried out. This is
significant, since up to now, all the data they have recorded
comes from cosmic rays. Ramping the beams to high energy will
follow in preparation for collisions at 7 TeV (3.5 TeV per beam)
next year.
Particle physics is a global endeavour, and CERN has received
support from around the world in getting the LHC up and running
again.
“It’s been a herculean effort to get to where we are today,”
said Myers. “I’d like to thank all those who have taken part,
from CERN and from our partner institutions around the world.”
A press conference will be held at CERN, at the Globe of Science
and Innovation, at 2pm on Monday 23 November, and webcast at:
http://webcast.cern.ch/. Submit your questions to @CERN via
Twitter. We cannot guarantee that all questions will be
answered.
Follow LHC progress on twitter at
www.twitter.com/cern
For photos, video and latest information see:
http://press.web.cern.ch/press/lhc-first-physics/
Contact :
http://press.web.cern.ch/press/ContactUs.html
7 November 2009
http://cmsdoc.cern.ch/cms/performance/FirstBeam/cms-e-commentary09.htm
Can
LHC be a String Hunter?
Harvard physicist Cumrun
Vafa tells scientists at the Large Hadron Collider that the
discovery of a predicted,
long-lived particle during research there would be the first
experimental confirmation of string theory.
http://news.harvard.edu/gazette/story/2009/11/a-line-on-string-theory/?
 CMS sees the Beam Splash
The first CMS beam splashes was
detected on November 7th 2009.
Beam splashes are when a beam is threaded part-way through the
LHC
ring, then deliberately collided with a closed collimators, 150m
upstream of the CMS experiment. The secondary particles are
produced
by the interaction of the beam with the collimator, most of them
are
absorbed, with the exception of the muons and neutrinos. CMS can
detect muons, and what is seen is a huge splash of activity,
shown in
this event display.
The little red lines are reconstructed muon tracks, blue dots
are raw
hits, and the yellow/blue starburst in the center is the
calorimeter
energy.
It can be said that the beam is coming from the right-hand side
of the
detector ("LHC beam-1", the clockwise direction around the
ring).
more:
http://cmsdoc.cern.ch/cms/performance/FirstBeam/cms-e-commentary09.htm
Particles are back in the LHC!
News: 26 October 2009
Particles are back in the LHC!
During the last weekend
(23-25 October) particles have once again entered the LHC
after the one-year break that followed the incident of
September 2008.
Friday afternoon a first
beam of ions entered the LHC clockwise beam pipe through the
TI2 transfer line. The beam was successfully guided through
the ALICE detector until point 3 where it was dumped.
During the late evening on
Friday, the first beam of protons also entered the LHC
clockwise ring and travelled until point 3. In the afternoon
of Saturday, protons travelled from the SPS through the TI8
transfer line and the LHCb experiment, until point 7 where
they were dumped.
All settings and parameters
showed a perfect functioning of the machine, which is
preparing for its first circulating beam in the coming
weeks.
The first ion beam entering point 2 of the LHC, just
before the ALICE detector (23 October 2009)
LHC
NEWS:NATURE Article on LHC ؛LHC hopes for
collisions by Christmas
LHC NEWS: LHC
start up in 2009
The LHC will run for the first
part of the 2009-2010 run at 3.5 TeV per beam, with the energy
rising later in the run. That’s the conclusion
that we’ve just arrived at in a meeting involving
the experiments, the machine people and the CERN management.
We’ve selected 3.5 TeV because it allows the LHC
operators to gain experience of running the machine safely while
opening up a new discovery region for the experiments.
The developments that have
allowed us to get to this point are good progress in repairing
the damage in sector 3-4 and the related consolidation work, and
the conclusion of testing on the 10000 high-current electrical
connections last week. With that milestone, every one of the
connections has been tested and we now know exactly where we
stand.
The latest tests looked at the
resistance of the copper stabilizer that surrounds the
superconducting cable and carries current away in case of a
quench. Many copper splices showing anomalously high resistance
have been repaired already, and the tests on the final two
sectors revealed no more outliers. That means that no more
repairs are necessary for safe running this year and next.
The
procedure for the 2009 start-up will be to inject and capture
beams in each direction, take collision data for a few shifts at
the injection energy, and then commission the ramp to higher
energy. The first high-energy data should be collected a few
weeks after the first beam of 2009 is injected. The LHC will run
at 3.5 TeV per beam until a significant data sample has been
collected and the operations team has gained experience in
running the machine. Thereafter, with the benefit of that
experience, we’ll take the energy up towards 5 TeV per beam. At the end of 2010, we’ll run the LHC with lead-ions for the first time. After that, the LHC will
shut down and we’ll get to work on moving the
machine towards 7 TeV per beam
News on the LHC
- Information concernant le LHC
The foreseen shutdown work on
the LHC is proceeding well, including the powering tests with
the new quench protection system. However, during the past week
vacuum leaks have been found in two "cold" sectors of the LHC.
The leaks were found in sectors 8-1 and 2-3 while they were
being prepared for the electrical tests on the copper
stabilizers at around 80 K. In both cases the leak is at one end
of the sector, where the electrical feedbox, DFBA, joins Q7, the
final magnet in the sector.
Unfortunately, the repair
necessitates a partial warm-up of both sectors. This involves
the end sub-sector being warmed to room temperature, while the
adjacent sub-sector "floats” in temperature and
the remainder of the sector is kept at 80 K. As the leak is from
the helium circuit to the insulating vacuum, the repair work
will have no impact on the vacuum in the beam pipe. However the
intervention will have an impact on the schedule for the
restart. It is now foreseen that the LHC will be closed up and
ready for beam injection by mid-November.
Preparing for the LHC re-start
The end of
a Council week is a good opportunity to bring you up to
date with the status of the LHC, and I'm pleased to say
that we had a good deal of positive news to report to
the delegations today. The bottom line is that we remain
on course to restart the LHC safely this year, albeit
currently about 2-3 weeks later than we'd hoped at
Chamonix.
This
Council week has seen many important developments for
our future. I am particularly pleased that Council
approved the Medium Term Plan and budget for 2010 as
presented by the management. This is a strong vote of
confidence in all of you. The President of Council is
reporting on Council business in this issue of the
Bulletin, so I will focus on the status of the LHC.
A tremendous amount of work has been done to understand
fully the splices in the LHC's superconducting cable and
copper stabilizers. One of these splices was the root
cause of the incident last September that brought the
LHC to a standstill. We've learned a great deal since
then. It's mostly good news but there's also plenty of
food for thought. The good news is that all the
measurements done so far indicate that we will be ready
by September or October to run the LHC safely in the
range 4-5 TeV per beam. The food for thought is that the
same tests tell us that before we can run safely above 5
TeV, more work is needed. This will be carried out in
future shutdown periods.
Many
of you will have heard, or seen on the LHC web pages,
that we're warming up sector 4-5. This will give us
increased confidence that we fully understand the
splices. We're warming up this sector because we have
developed a new non-invasive technique for investigating
the splices. The sector has been measured at a
temperature of 80 K, indicating at least one suspect
splice. By warming the sector, the results of the test
can be checked at room temperature, allowing us to
confirm the reliability of the test at 80 K. If the 80 K
measurements are confirmed, any suspect splices in this
sector will be repaired. More importantly, validation of
the 80K measurements will allow the splice resistance in
the last three sectors to be measured at this
temperature, thereby avoiding the time needed for
re-warming. When these measurements are done, we'll have
to balance energy against time: 4 TeV should require no
further repairs, for example, whereas 5 TeV could call
for more work. The measurements in these last three
sectors will allow us to make that decision, determining
the initial operating energy of the LHC in the range 4-5
TeV, and the start date for the first run.
The Bulletin will continue to keep you up to date with
LHC progress, and if you are interested in a full
report, Steve Myers at CERN and Jim Strait at Fermilab
will be making detailed presentations on 2 July. Steve's
presentation will be webcast at
http://www.cern.ch/webcast.
Final LHC magnet goes underground
Geneva, 30 April 2009. The 53rd
and final replacement magnet for CERN's Large Hadron
Collider (LHC) was lowered into the accelerator's tunnel
today, marking the end of repair work above ground
following the incident in September last year that
brought LHC operations to a halt. Underground, the
magnets are being interconnected, and new systems
installed to prevent similar incidents happening again.
The LHC is scheduled to restart in the autumn, and to
run continuously until sufficient data have been
accumulated for the LHC experiments to announce their
first results.
"This is an important milestone in the repair process,"
said CERN's Director for Accelerators and Technology,
Steve Myers. "It gets us close to where we were before
the incident, and allows us to concentrate our efforts
on installing the systems that will ensure a similar
incident won't happen again."
The final magnet, a quadrupole designed to focus the
beam, was lowered this afternoon and has started its
journey to Sector 3-4, scene of the September incident.
With all the magnets now underground, work in the tunnel
will focus on connecting the magnets together and
installing new safety systems, while on the surface,
teams will shift their attention to replenishing the
LHC's supply of spare magnets.
In total 53 magnets were removed from Sector 3-4.
Sixteen that sustained minimal damage were refurbished
and put back into the tunnel. The remaining 37 were
replaced by spares and will themselves be refurbished to
provide spares for the future.
"Now we will split our team into two parts," explained
Lucio Rossi, Deputy head of CERN's Technology
Department. "The main group will carry out
interconnection work in the tunnel while a second will
rebuild our stock of spare magnets."
The LHC
repair process can be divided into three parts. Firstly,
the repair itself, which is nearing completion with the
installation of the last magnet today. Secondly, systems
are being installed to monitor the LHC closely and
ensure that similar incidents to that of last September
cannot happen again. This work will continue into the
summer. Finally, extra pressure relief valves are being
installed to
release helium in a safe and controlled manner should
there be leaks inside the LHC's cryostat at any time in
the machine's projected 15-20 year operational lifetime.
LHCNews:
LHC Luminosity Profile 2009/2010
A first estimate for the luminosity
performance for the 2009/2010 run has been posted at
http://lhc-commissioning.web.cern.ch/lhc-commissioning/luminosity/09-10-lumi-estimate.htm
LHCNews:
New Time Schedule for LHC
Message from the Director-General of CERN on the LHC
schedule
The CERN
Management today confirmed the restart schedule for the
Large Hadron Collider resulting from the recommendations
from the Chamonix workshop. The new schedule foresees
first beams in the LHC at the end of September this
year, with collisions following in late October. A
short technical stop has also been foreseen over the
Christmas period. The LHC will then run through to
autumn next year, ensuring that the experiments have
adequate data to carry out their first new physics
analyses and have results to announce in 2010. The new
schedule also permits the possible collisions of lead
ions in 2010.
This new
schedule represents a delay of 6 weeks with respect to
the previous schedule which foresaw LHC "cold at the
beginning of July". The cause of this delay is due to
several factors such as implementation of a new enhanced
protection system for the busbar and magnet splices,
installation of new pressure relief valves to reduce the
collateral damage in case of a repeat incident,
application of more stringent safety constraints, and
scheduling constraints associated with helium transfer
and storage.
In
Chamonix there was consensus among all the technical
specialists that the new schedule is tight but
realistic.
The
enhanced protection system measures the electrical
resistance in the cable joints (splices) and is much
more sensitive than the system existing on 19 September.
The new pressure relief system has been designed in two
phases. The first phase involves installation of relief
valves on existing vacuum ports in the whole ring.
Calculations have shown that in an incident similar to
that of 19 September, the collateral damage (to the
interconnects and super-insulation) would be minor with
this first phase.
The second
phase involves adding additional relief valves on all
the dipole magnets and would guarantee minor collateral
damage (to the interconnects and super-insulation) in
all worst cases over the life of the LHC. One of the
questions discussed in Chamonix was whether to warm up
the whole LHC machine in 2009 so as to complete the
installation of these new pressure relief valves or to
perform these modifications on sectors that were warmed
up for other reasons. The Management has decided for
2009 to install relief valves on the four sectors that
were already foreseen to be warmed up. The dipoles in
the remaining four sectors will be equipped in 2010.
LHC Performance Workshop, Chamonix 2009 - Message from
the Director-General
Many issues were tackled in Chamonix this
week, and important recommendations made. Under a
proposal submitted to CERN management, we will have
physics data in late 2009, and there is a strong
recommendation to run the LHC through the winter and on
to autumn 2010 until we have substantial quantities of
data for the experiments. With this change to the
schedule, our goal for the LHC's first running period is
an integrated luminosity of more than 200 pb-1 operating
at 5 TeV per beam, sufficient for the first new physics
measurements to be made. This, I believe, is the best
possible scenario for the LHC and for particle physics.
There were discussions in Chamonix between accelerator
and detector physicists on several important issues.
Agreements were reached whereby teams drawing from both
communities will work together on important subjects,
such as the detailed analysis of measurements made
during testing of magnets on the surface.
Since the incident, enormous progress has been made in
developing techniques to detect any small anomaly. These
will be used in order to get a complete picture of the
resistance in the splices of all magnets installed in
the machine. This will allow improved early warning of
any additional suspicious splices during operation. The
early warning systems will be in place and fully tested
before restarting the LHC.
Another important topic for the future was the radiation
hardness of electronics installed in the service areas
and the tunnel. For many years, particle detector
electronics have been designed to cope with events such
as loss of beam into the detectors. Until now, this has
not been necessary for the accelerators, but will become
so when the LHC moves to higher beam intensity and
luminosity. Again, with detector and accelerator
physicists working closely together, the experience
gained from the detectors can be applied to the LHC
itself.
As the Bulletin reported on 30 January, opening up a
magnet in which an anomalously high electrical
resistance was measured made the reason for the anomaly
immediately obvious - a splice had not been correctly
made. This is one of two such splices that were
identified in the five sectors tested, and as a result
the magnet containing the second will also be removed
from the tunnel for repair. Since resistance tests can
only be conducted in cold magnets, three sectors remain
to be tested: sector 3-4 where the original incident
occurred and the sectors on either side. Within sector
3-4, the 53 magnets that are being replaced in the
tunnel will all be tested before cool down, and the
sectors either side will be cooled down early enough to
intervene if necessary with no impact on the schedule.
This leaves around 100 dipole magnets that we'll not be
able to test until September and a correspondingly small
chance that we may find further bad splices that will
need to be repaired before operation starts.
The Chamonix workshop involved a lot of work by many
people. Much progress has been made, and the management
now has all it needs to make an informed decision next
Monday on LHC restart. I'd like to thank all those
involved, and I will be writing to you again early next
week to let you know our decision.
LHCNews:: LHC to restart in Summer 2009
http://press.web.cern.ch/press/PressReleases/Releases2008/PR17.08E.html
News on LHC Schedule for 2009
A
meeting, chaired by Jos Engelen, on the LHC schedule
took place on Tuesday afternoon. Participating were the
LHC Project Leader, Lyn Evans, the incoming Director of
Accelerators and Technology, Steve Myers, the LHC
coordinator, M. Ferro-Luzzi, and the Spokespersons and
Technical Coordinators of the LHC experiments.
Information was presented on the LHC schedule that
reflected present understanding. An official
presentation is being prepared for the CERN Council in
December. The schedule outlined below is therefore
still subject to changes.
Extracts from the summary of the meeting are given
below.
A lot of progress has been made in developing
diagnostic procedures (calorimetry) and tools to make
sure that no other bad splices are 'hidden' in the
machine
Moving out magnets affected by the incident has started.
It is foreseen to remove 39 dipoles, including 6 (3 at
each side) in a buffer zone. These magnets should not
be affected but will be re-tested just to confirm that
the limits of the affected region are understood.
All magnets to be brought to the surface should be out
before the Christmas shutdown. By then 20 dipoles should
already be back in the machine.
The plan is to install the first dipole (from the set of
spares) already this week.
The test bench (for cold testing) is a limiting factor.
Capacity to be ramped up after connection of 18 kW
plant (now 6 kW) in February 2009.
Last magnet should be back in end of March 2009; whole
machine cold again beginning of July. Meaning
optimistically first beam in the machine end of July.
Many activities are going on in parallel in the tunnel,
but are not (and should not come) on the critical path
(work on flanges, relief valves, cabling)
Point of concern of experiments: access conditions in
experimental caverns and service caverns. Is being
looked into by/ with Safety Commission.
Lyn Evans has been invited to give a talk on the status
of the machine on the Monday morning of the December CMS
Week.
TIME's Best Inventions of 2008
The Large Hadron Collider
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