Title: The coming era of discoveries at the Large Hadron Collider
1The coming era of discoveries at the Large Hadron
Collider
2Colliders have been essential tools to understand
the worlds structure
3They started small
Discovery of Atomic Nucleus
no acceleration yet!
4They started small
The first cyclotron
5Then got a bit bigger
Lawrence next to the Berkeley cyclotron
discovery of pions (simultaneously with cosmic
rays)
6 and then even bigger
Most were just lets build it and see whats
there. Most discoveries in the field were indeed
surprises! SppS was built to see W/Z for masses
of which there were precise predictions LHC is
built to explore electroweak energy scale which
it completely covers
7 and bigger yet
Lac Leman
Jura Mountains
The Alps
Geneve
8Hadron Colliders
- Easiest way to achieve high center-of-mass energy
is colliding beams of protons or anti-protons - heavy, so no synchrotron radiation
- stable, so can take time accelerating
- But messy!
- quark/gluon colliders
constituents of proton that carry small
fraction of its energy
constituents of proton that carry large
fraction of its energy
9LHC
- 27km proton-proton ring at CERN
- Reuse the tunnel previously home for the LEP
collider - Dig new collision areas for new experiments
- ATLAS CMS
- hermetic, large, general purpose
- LHCb Alice
- Smaller in size and physics scope
10So colliders had gotten very big and relatively
expensiveWhat do we learn from them?
11Problems of Particle Physics
- Problem 1 while discovering building blocks of
matter we have found more pieces that we need
Problem 2 even with the extra pieces, we can
explain only 5 of what we see in the Universe
12The Standard Model
Why so many flavors? Why three
generations? For our world to function today
we just need the first generation! May be
three generations were needed to form the
Universe?
13Cosmological Connection
WMAP, astro-ph/0302207
- From studying microwave background
- W WM W? 1.020.02
- WM 0.29 0.07
- WB 0.047 0.006
- 70 of the universe is energy (some unknown
repulsive force?) - 5 is baryonic matter
- 25 is some non-baryonic cold dark matter
- Similar conclusions from galactic rotation
curves, type IA supernovae and gravitational
lensing
14Dont Be Fooled by Bright Lights
The Dark Side Rules The Universe
Dark Matter Binds It Together
Dark Energy Controls Its Destiny
stolen from M. Turner
15The Standard Model
Still, we have achieved a dramatic reduction
of complexity from gt100 atoms to just a few
quarks and leptons And achieved some
success in unification of forces
16Unification of Forces
Heavy Light
17The Standard Model
- Amazing Precision! But
-
- Gravity? What happens at energies Mplanck?
-
- Can forces be unified?
- Dark Matter candidate?
- What is origin of flavor? Why three
generations? - Why Mass?
18Mass
- Higgs Mechanism
- Separate piece of SM
- introduced by hand
- Mass ? Rest energy
- If we make particle interact with vacuum it will
acquire additional energy ? MASS - In the Standard Model the vacuum is skewed by
the Higgs field, and particles get mass from
interaction with the Higgs field
- If one just puts the masses into Lagrangian the
theory breaks looses gauge invariance and
becomes unrenormalizable - no viable theoretical alternatives
19Where Is the Higgs?
- Artificial add-on to the Standard Model (is it
even there?) - There is a mounting tension between direct and
indirect limits - SM fits prefer light Higgs, leading to vacuum
instability at high renormalization scales
160 GeV
115 GeV
20Higgs A Weak Link
- We want theory that can be unified with gravity
(energies MP) - Quantum correction to fundamental scalar mass
are order of MP 1019 GeV, and are obviously very
unlikely to cancel to give mh 102 GeV
All predict new particles, that can be looked for
directly or in loop effects
21Higgs Boson
- Electroweak symmetry breaking in the SM
- 1 complex Higgs scalar doublet (4 d.o.f.)
- W, W- and Z get mass (three Higgs d.o.f. become
longitudinal W/Z components) - photon remains massless - symmetry between
electromagnetism and weak force is broken! - Fermions get masses
- One remaining observable Higgs
boson - hasnt been observed yet
- can not hide much longer!
Precision measurements of SM parameters give
indirect limit Mh lt 144 GeV _at_95CL
Direct search (LEP) Mh gt 114.9 GeV
22Guaranteed Success
- Whatever the ultimate theory of everything is,
the electro-weak symmetry breaking
mechanism will be revealed at the
LHC - W boson scattering amplitude grows at large
masses - violates Unitarity at around 1000 GeV
- something has to appear and cancel the growth. In
the SM it is the Higgs but it does not have to
be
23SuperconductingSuper-Collider
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25Cryogenics
- Dipoles sit in a 1.9 K bath of superfluid helium
at atmospheric pressure - Bath cooled by low pressure liquid helium flowing
in heat exchanger tubes threaded along the string
of magnets - Each of 8 sectors is by itself the largest
operating cryogenic system
26LHC Progress
27 km of dipoles in liquid He!
Installation in progress
27Detectors
- Basic principles since Rutherford and Chadwick
- detect charge particles traversing the material
- use magnetic field to measure momentum
Calorimeter as dense as possible, particle
breaks up into many low energy particles, and
their combined ionization is proportional to the
initial particle energy
Type of particle is inferred from how far
it penetrated into material
Tracker as low as possible density, focus
on precise measurement of the path of the
particles
28Discovery of Z boson
C. Rubbia 1984 Nobel Prize
29A Typical Detector
- although charged pions and muons are unstable,
they live long enough to travel through the
detector - different types of particles interact with
detector material differently and are detected
through their (and their daughter particles)
ionization - curvature of particle tracks in magnetic field
determines momentum - for electrons, photons and hadrons measure
energy in the calorimeters
30Solenoid
4 Tesla
2.7 GJ stored
31Silicon Tracker
32PbWO4 Crystals for Calorimeter
33ECAL Crystal Matrix Production
Single Crystal
Sub - Module mounting
Assembled Sub - Modules
Free mounting bench
34CMS is coming together
35HCAL in the Solenoid in the Muon System
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37Heavy Lowering
1300 tons
38Tracker is Inserted
39Final Closure Sept.08
40First Events from CMS high energy cosmic rays!
41Cosmic Muons Spectra
42CMS Collaboration
1976 Physicists and Engineers 36 Countries
153 Institutions
43LHC Start-up
Carlo Rubbia, Nobel Laureate and LHC proponent
Lyn Evans, LHC Project Leader
44First Beam at CMS
45Meanwhile, at FNALs ROC
46No RF, debunching in 2510 turns, i.e.
roughly 25 mS
Courtesy E. Ciapala
47First attempt at capture, at exactly the wrong
injection phase
Courtesy E. Ciapala
48Capture with corrected injection phasing
Courtesy E. Ciapala
49Capture with optimum injection phasing, correct
reference
Courtesy E. Ciapala
50Black Friday(s)
- Friday night, 12-Sep.
- 1120pm Lose main 30ton 12 MVA transformer at
Point 8 (LHCb) - There are no spares, and it would take 6-9 months
to procure another. - Borrow from surplus capacity at CMS
- 13-18 Sep, Hardware commissioning consolidation
- Power, cryogenic, and vacuum problems lead to 6
days of downtime - Advance commissioning of magnet control system to
5 TeV beam operation for 2008 (avoid 10 day
shutdown) - CMS investigates issues with magnet
- Thu, 18-Sep
- Return to beam 1 operation
- CMS takes data overnight
- Friday noon, 19-Sep
- Massive helium loss in one arc of the tunnel
(1-2 tons), cryogenics lost - Broke insulation vacuum in sector
- Suspected failure of interconnection between
quadrupole and dipole magnet during 5 TeV
commissioning of last sector of LHC
51First Beam _at_ CMS
52First Beam _at_ CMS
53First Beam _at_ CMS
Muons associated with beam (but outside beam
pipe) arising from the decays of pions created
when off-axis protons scrape collimators or other
elements along beamline
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55QCD Confinement
- Quarks and gluons can not exist by themselves -
they only comes in pairs (mesons) or triplets
(baryons) - If an energetic quark or gluon is produced it
fragments
56- Very large background from gluon scattering
- jets are everywhere
- jets are least precise measured object,
especially bad at low energies - Many interesting things decay into jets too
- i.e. h?bb but signal to background ratio is
10-7 - 1. require multiple leptons or photons in the
final state then interesting events are very
rare, but very few spectacular events may
constitute a discovery - 2. look at high energy / high mass distributions
- 3. accumulate a lot of events and look for
deviations in distributions of energy, mass, etc
57Data Rates
- Event size 1Mbyte
- Event rate 40MHz collisions
- Total amount of data produced
40 Terabytes/sec - Equivalent to 100M simultaneous cell phone
conversations - How we handle this much data is a science in
itself!
58Trigger
- Store data in circular buffer
- Better decide by the end of the buffer length if
the data should be kept this is the trigger
decision - Implement trigger using custom built hardware
pipeline processor - Has to take less time than the smallest circular
buffer. For CMS this is 128 clocks - Output is either 1 (keep) or 0 (throw away)
- Accept rate is 1 in 400 crossings
- At the High Level trigger further reduces rate
to 100 Hz - O(1000) CPUs run simplified version of the
reconstruction program - Data Rate to tape
- 100 Hz x 1 MByte 1 Gbit/s
- Year of data taking 106 GB, 1PB
- And that is just RAW data
- it need to be calibrated, reconstructed,
distributed, skimmed - and we need to have even larger simulated sample!
- 1000 PB of data in the first decade of operations
59Tiered System for Data Mgmt
- T0 at CERN
- Record raw data and DST
- Distribute raw data and DST to T1s
FNAL Chicago
RAL Oxford
T1
T1
- T1 centers
- Pull data from T0 to T1 and store
- Make data available to T2
FZK Karlsruhe
T1
T0
T1
T1
CNAF Bologna
T1
IN2P3 Lyon
- T2 centers
- DST analysis.
- Local data distribution
PIC Barcelona
60LHC Grid
CMS Experiment
Online System
CERN Computer Center
200 - 1500 MB/s
Tier 0
10-40 Gb/s
Tier 1
gt10 Gb/s
OSG
Tier 2
2.5-10 Gb/s
Tier 3
Tier 4
Physics caches
PCs
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6310 11th Floors of the Wilson Hall
- Meeting Rooms/Video Conferencing/Internet
- terminals/printers/office supplies
- secretarial and computer support
- Coffee machines/Water cooler
Room for 200 visitors
64LHC Physics Center _at_ FNAL
65FNAL LPC
66Summary And Outlook
- The LHC is finally happening
- We might find out our world is even stranger then
we thought
- This very well may be a dawn of a new era in
physics STAY TUNED!