Transcript Document 7312018

It’s Big, it’s Large, it’s heavy and it’s clever.
How Glasgow physicists helped build the
machine that launches today..
Big Bang at the Large Hadron Collider
University of Glasgow
Open Day
September 10th 2008
Tony Doyle
Thank You!
For attending
today…
There are many
other things
you could be
doing on
Wednesday
September
10th at
11am…
Today! Worldwide News
Heritage - Past
• The first
electron
synchrotron
in Europe was
constructed
in this
building in
the 1950s
• E = 300 MeV
Heritage - Present
• The scale of
the Large
Hadron
Collider that
switches on
today is larger
• 27 km in
circumference
• E=7+7 TeV
Outline
• Ingredients
1. Motivation
2. Commissioning
A. Collider
B. Detectors
a) ATLAS
b) LHCb
C. Grid
3. Outlook
Universe – Particles – LHC?
Physics at the LHC corresponds
to conditions around here
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The Standard Model
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LHC Motivation:
Higgs Production in pp Collisions
q
q1
p
Z0
W
W
H
Z0
q
MH ≤ 1 TeV
EW ≥ 0.5 TeV
q2
p
Parton luminosities
Ecm=(4x1x2.EpEp)
E1 ≥ 1 TeV
E2 >≥ 1 TeV
 Proton Proton Collider with Ep ≥ 7 TeV
LHC Switches On
LHC Commissioning
Cool down status 7/9/08
• The LHC has cooled down..
• Today:
First particles injected, followed by
commissioning with beams
• Oct/Nov:
First detector collisions at 5+5=10 TeV
The ATLAS Detector
ATLAS = large international collaboration to find the Higgs
(and much more) in the range 0.1TeV < mH < 1TeV
The ATLAS experiment is
26m long, stands 20m high
and weighs 7000 tonnes
SCT alone has 6.2 million
read-out channels
A question of scale
Where Theory Meets Experiment:
1964 to 2005
The Higgs Mechanism
Higgs potential:
Theory: vacuum potential
Energy
V()= -2+ + (+)2
(>0)
The ultimate
green field site
=exp(ia(x) T’’a) | . (0 + H(x))
0
Ready to
interact
mH = 2 (a free parameter)
Where Theory Meets Experiment:
14th April 2008
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Dark Matter?
Astronomers say
that most of the
matter in the
Universe is
invisible
Dark Matter
‘Supersymmetric’ particles ?
We shall look for
them with the
LHC
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Dark Matter at the LHC?
•
Characteristic signature for Dark
Matter production at ATLAS:
Missing Transverse Energy (‘MET’)
•
Valid for any DM candidate
(not just SUSY)
•
Observation of MET signal necessary
but not sufficient to prove DM signal
(DM particle could decay outside
detector)
Combine LHC and
Astroparticle physics data in
order to prove that the
neutralino hopefully
observed at LHC would be
the DM particle…
~0
c
1
MET
~
c 01
Search for Extra Dimensions
Theories which try to explain
why gravity is so much weaker
than the other forces
Gravity may propagate in 4+n
dimensions, but we could see
strong effects only at very small
distances, reachable in pp LHC
collisions
Search for Extra Dimensions
If theories with Extra Dimensions are true,
microscopic black holes could be abundantly
produced and observed at the LHC
They decay immediately
through Hawking radiation
Simulation of a black hole
event with MBH ~ 8 TeV in
ATLAS
Progress on ATLAS
Today the cavern is filled (with the ATLAS detector)
and it is has become impossible to take a real picture…
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Progress on LHCb
LHC Experiment Commissioning
• Early 2008:
Cosmic rays measured
in ATLAS experiment
• Stop Press 09:19:
First beam-gas event in
the ATLAS experiment
Event number 40050
Event run 87765
June 15, 2008:
ALICE saw first hits
in silicon pixel detector
During clockwise beam
Synchronisation test
• Sunday 24th
August:
First tracks from
LHC beam in the
LHCb detector
The Grid
• The Grid
enables us to
analyse all
the data that
comes from
the LHC
• Petabytes
• 100,000 CPUs
• Distributed around
the world
• Now used in many
other areas
The Grid
Archeology
Astronomy
Astrophysics
Civil Protection
Comp. Chemistry
Earth Sciences
Finance
Fusion
Geophysics
High Energy Physics
Life Sciences
Multimedia
Material Sciences
…
>250 sites
48 countries
>50,000 CPUs
>20 PetaBytes
>10,000 users
>150 VOs
>150,000 jobs/day
Why (particularly) the LHC?
2. Complexity
10 orders of magnitude
1. Rare Phenomena
- Huge Background
All interactions
The HIGGS
“When you are face to face
with a difficulty you are up
against a discovery” Lord
Kelvin
The Challenges
I: Real-Time Event Selection
ON-line
OFF-line
10 orders of magnitude
LEVEL-1 Trigger
Hardwired processors (ASIC, FPGA)
Pipelined massive parallel
HIGH LEVEL Triggers
Farms of
processors
Reconstruction&ANALYSIS
TIER0/1/2
Centers
25ns
10
-9
3µs
10
-6
ms
sec
10
Real-Time
-3
10
Giga
-0
hour
103
Tera
In-Time
year
Petabit
Time
The Challenges
II: Real-Time Complexity
40 MHz
Detectors
COLLISION RATE
Charge
Time
Pattern
100 kHz
LEVEL -1 TRIGGER
Energy
Tracks
1 Terabit/s
(50000 DATA CHANNELS)
• Many events
– ~109 events/experiment/year
– >~1 MB/event raw data
1 MegaByte EVENT DATA
– several passes required
BUFFERS
200 GigaByte
500 Readout memories
 Worldwide Grid computing requirement
(2008):
16 Million channels
3 Gigacell buffers
EVENT BUILDER
500 Gigabit/s
Networks
~300 TeraIPS
(100,000 of today’s fastest processors connected
via a Grid)
20 TeraIPS
EVENT FILTER
Gigabit/s SERVICE LAN
Grid Computing
Service
PetaByte ARCHIVE
300 TeraIPS
Understand/interpret data via numerically intensive simulations:
• e.g. ATLAS Monte Carlo (gg
H
bb)
60 sec/3.5 MB event on 3 GHz linux CPU
Focus on LHC Physics
LHC Start-Up
Early Physics
Voyage of Discovery
L=1035
The decade to come will be exciting for
fundamental physics and
will shape our understanding of Nature
And finally
• We are privileged to stand on the shoulders
of giants and work in particle physics today
• The invention of the LHC will enable future
physicists, including perhaps some of you, to
rewrite the physics textbooks
• The first step is a degree in physics &
astronomy
• A degree will enable you to
1. understand how our
Universe works
2. find better places to
work within it
First year physics & astronomy
Physics includes lasers, quantum phenomena, dynamics and relativity
Astronomy includes stellar physics and cosmology
at work in the lab
Kelvin lecture theatre
A friendly place
to study
The University Observatory
The Departmental common room
Thanks to the many particle physicists who’ve helped to make this talk possible.
Esp. Peter Jenni for useful slides.
We get by with a little help from our friends…
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