 Large
Hadron Collider (LHC): the
next generation high energy collider being built at CERN,
European Center for Nuclear Research, near Geneva. 27 km in circumference,
the LHC will be housed in a tunnel about 100 m underground. The tunnel
will be filled with 1300 large (14-m long) powerful (8 T) magnets to keep
proton on circular trajectory. The huge ring you see in this aerial view
indicates where the tunnel goes (note Alps on the background). The collider
will become operational in 2006. The machine will accelerate protons and
make them collide head-on at two points. Amount of energy released in each
of such collisions is 14 TeV (14,000 times more than the proton's mass
converted into units of energy via E=mc2)
and will give rise to thousands of particles spraying away. Collisions
will happen every 25 ns (40,000,000 times per second!). LHC will have 7
times more energy and 100 times more intensity than Tevatron, the current
largest collider. Both the energy and intensity are critical for discovering
the new phenomena expected to show up at this new frontier. Two large experiments,
called ATLAS and CMS,
have been designed and now are being built around the collision points.
Two additional smaller ones, ALICE
and LHCb,
will soon follow. The physics goals are extremely ambitious. Among the
others, the most spectacular are:
-
explain the origin of masses (Higgs Boson? something else?)
-
search for bedeviled Super Symmetry
-
pin down the cause of the matter-antimatter tiny differences
-
will we see sub-structure of particles that we call today
"elementary"?
-
are there extra spatial dimensions?
-
any surprises? with such a leap in energy and intensity,
the chances are we will see something completely unexpected
|
 CMS:
Compact
Muon Solenoid, an apparatus comprised of various detectors, electronics,
online and off-line computing built to study the products of colliding
protons at LHC. The name "Compact" is somewhat misleading: this detector
will rise 15 m high and extend 22 m in length. It will weigh more than
12,500 tons. The heart of this experiment is a huge, largest in the world,
superconducting solenoid of 8 m in diameter, 16 m length, and 4 T field
(amount of energy stored in the magnetic field of this solenoid is going
to be 5x109 Joules---10,000
mid-size sedans at 55 miles per hour speed!). Number of electronic readout
channels is around 10,000,000. The CMS Collaboration consists of 1800 physicists
from 150 institutions representing 32 countries. |
 Detectors
for the CMS
Endcap Muon System.
LHC will
deliver the exiting physics---the question is how to detect it. E.g. we
expect about 100,000 Higgs bosons produced per year; however, for each
Higgs boson, there will be 100,000,000,000 of ordinary events. Luckily,
some of Higgs boson decays have particular signatures that would be very
rare for ordinary "no-Higgs" collisions. One of these decay modes is called
a golden mode: Higgs decaying into two Z-bosons with their consecutive
decay into two pairs of muons (muon is a cousin of an electron). Many other
new physics searches will rely on detecting high energy muons as well.
The CMS Endcap Muon System will be made of 400 individual detector units,
called chambers, to cover in total 1000 m2
of area and will detect muons with precision of 100 microns and a few nanosecond
time resolution. It will exceed the largest systems of similar purposes
built so far by a factor of 10 to 1000, depending on which design parameter
is in question. The cost of the detectors (not counting electronics) is
about $18M. The sub-collaboration involved in this project consists of
5 US universities (UF, UCLA, UC Riverside, Purdue, Wisconsin) and 3 national
labs (Fermilab in the US, Petersburg Nuclear Physics Institute in Russia,
and Institute of High Energy Physics in China). UF
Final Assembly and System Commissioning Site is one of the five construction
sites. |