LHC – New era ?Large Hadron Collider (protons + protons)

C.H. Wang/nuu

Outline• What is LHC?• CERN Accelerator • Recent News of LHC• History of Particle Physics• What Comes from LHC• Summary

Budget/Size/Man Power/Fact

• The largest machine in the world...• Circumference : 26659 m• Cost: 3 billion Euro (machine only)/6.0 billion (~15% de

tector)

• The fastest racetrack on the planet...• v = 99.9999991c 7 TeV per proton

• The emptiest space in the Solar System...• The internal pressure of the LHC is 10-13 atm, ten times l

ess than the pressure on the Moon!

• The hottest spots in the galaxy, but even colder than outer space...

• When two beams of protons collide, they will generate temperatures more than 100 000 times hotter than the heart of the Sun.

• The 'cryogenic distribution system', which circulates superfluid helium around the accelerator ring, keeps the LHC at a super cool temperature of -271.3°C (1.9 K) – even colder than outer space!

• The biggest and most sophisticated detectors ever built...

• Detector (scientists): CMS (2000), ATLAS(2000), ALICE(1000), LHCb(700)• 600 million collisions per second

• The most powerful supercomputer system in the world...

• The data recorded by each of the big experiments at the LHC will fill around 100 000 dual layer DVDs every year.

GRID

First Week of LHChttp://public.web.cern.ch/public/

• LHC started the beams on 10 September.

• On 18 September 2008, LHC successfully got beams around the ring in both directions on the first day with several hundred orbits being achieved.

• The next step in the commissioning process is to bring in the radio-frequency (RF) system that keeps the beams bunched, rather than spreading out around the ring, and will eventually accelerate them to 7 TeV.

• Next: To collide the beams !

Last Week of LHC

• Geneva, 23 September 2008. Investigations at CERN1 following a large helium leak into sector 3-4 of the Large Hadron Collider (LHC) tunnel have indicated that the most likely cause of the incident was a faulty electrical connection between two of the accelerator’s magnets.

• Before a full understanding of the incident can be established, however, the sector has to be brought to room temperature and the magnets involved opened up for inspection. This will take three to four weeks.

• Restart the accelerator complex to early spring 2009. LHC beams will then follow.

History of Particle Physics• What are the Elementary Constituents of Matter?• What are the forces that control their behaviour at the most basic level?

1930 - 1950• electron/proton/neutron/neutrino/photon…..• anti-matterProposed in 1928 and discovered in 1932: positrons (balloon flight) – Carl Anderson , PR43, 491 (1933)

• Neutron discovered by James Chadwick /1932• Fermi theory of beta decay n -> p+ + e- + νe /1933 (Weak Interaction)

• Yukawa’s meson hypothesis on nuclear force /1935

• (muon) lepton discovered by Carl Anderson /1937 (Yukawa?)

• Charged meson discovered + -> + + /1946

• Neutral meson discovered o -> /1950

By 1950• QED (Quantum Electrodynamics) -- quantum theory of

electrodynamics. Charged particles interact via exchange of photons.

Richard Feymann/ Julian Schwinger/ Tomonaga

• In 1947 kaons were discovered in the cosmic rays. At first, people thought kaons should have decayed to pions relatively rapidly. But this was not the case. And scientists did think this strange. And so the kaon was assigned a property called "strange."

• Discovery of anti-proton in 1955.

• In 1956, neutrino was detected directly.e p e+ + n

p

W h a t a j u n g l e !

From Fermi Lab:

http://www-donut.fnal.gov/web_pages/standardmodelpg/TheStandardModel.html

• -1956-57 Tsung-Dao Lee and Chen Ning Yang propose parity non-conservation in certain sub-atomic processes, which is confirmed by experimentalist Chien-Shiung Wu

• -1962 The first experimental observation of the muon neutrino

• -1964 Quarks are proposed by Murray Gell-Mann and George Zweig

• -1964 was discovered.• -1967 Steven Weinberg, Sheldon Glashow (collaboratio

n) and Abdus Salam (independent) create the electro-weak theory, unifying the electromagnetic and weak nuclear force (they win Nobel prizes in 1979)

• -1970-73 Standard model of particle physics is developed (QCD)

• -1974 The charmed quark is observed• -1975 Evidence of the tau lepton is found• -1977 Experimenters find proof of the bottom quark

/ KL detection 14/15 lyr. RPC+Fe

Central Drift Chamber small cell +He/C2H6

CsI(Tl) 16X0

Aerogel Cherenkov cnt. n=1.015~1.030

Si vtx. det. 3/4 lyr. DSSD

TOF conter

SC solenoid 1.5T

8 GeV e

3.5 GeV e

Belle Detector

sB sB

sD

KK

• -1983 Carlo Rubbia discovers the W and Z bosons, mediators of the weak-force

• -1994 Planning for LHC (Large Hadron Collider) at CERN begins

• -1995 Evidence for the top quark, the final undiscovered quark, is found at Fermilab

• -2000 The tau neutrino, the last piece to the standard model, (with the exceptopm of the higgs particle) is observed at Fermilab

Size: 46 m long, 25 m high and 25 m wide. The ATLAS detector is the largest volume particle detector ever constructed. Weight: 7000 tonnes

Size: 21 m long, 15 m wide and 15 m high. Weight: 12 500 tonnes

The Standard Model of Particle Physics (Electroweak + Strong)

• Fundamental Particles: quarks & leptons• In weak decays, quarks will change flavors. (quark mixing)• Source of the mass: Higgs Boson

Proton-Proton Collision (LHC)

• What is our plan? Search for Higgs! H -> Z0 Z0 / Z0 -> l+l-

• What is our dream? New Particles! Clues for new physics!

Summary

• LHC successfully ejects and maintain the beams inside the beam pipe.

• Maintenance is a challenge issue.• Plan to collide beams middle next year.• Hope for the unexpected results!