Oliver Buchmueller, Imperial College London Buchmüller PHYSICS PROGRAMME
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A TRACK TRIGGER
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INtelligent Signal Processing for FrontIEr Research and Industry, held at the University Campus PARIS-DIDEROT, July 14-25.
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Outline of the Lecture
Buchmüller What is Particle Physics? The Large Hadron Collider (LHC) and its Experiments
The physics programme of the LHC: Example
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nd Higgs Discovery
2 Selection of interesting events: Triggering Track Trigger Expected Improvements from a Track Trigger Future Physics at the (HL-)LHC
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Outline of the Lecture
Buchmüller What is Particle Physics? The Large Hadron Collider (LHC) and its Experiments
The physics programme of the LHC: Example
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nd Higgs Discovery
2 Nice introduction Selection of interestingand technical events: details Triggering Track Trigger This morning by Stefano Mersi Expected Improvements from a Track Trigger Future Physics at the (HL-)LHC
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Particle Physics
Buchmüller Particle physics is a modern name for centuries old effort to understand the laws of nature E. Witten
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Aims to answer the two following questions:
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What are the forces that control their behaviour at the most basic level?
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Matter and Forces
Buchmüller
To remove a proton from a nucleus need ~10 MeV
~10 million ×
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2 To remove an electron from an atom need ~10 eV 10 ×
All known forces in the world can be attributed to these four interactions 5 5
The Standard Model of Particle Physics
Over the last 100 years: combination of Quantum Mechanics and Special Theory of relativity Buchmüller along with all new particles discovered has led to the Standard Model of Particle Physics (SM).
The new (final?) “Periodic Table” of fundamental elements
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Forceparticles
Matter Matter particles
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The Standard Model of Particle Physics
Over the last 100 years: combination of Quantum Mechanics and Special Theory of relativity Buchmüller along with all new particles discovered has led to the Standard Model of Particle Physics (SM). The new (final?) “Periodic Table” of fundamental elements
Yet, its most basic
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2 mechanism, that of
Forceparticles
granting mass to particles, was missing for many decades!
Matter Matter particles => The Higgs boson.
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Giving the Universe Substance – Generation of Mass
To Newton: F= ma, w = mg To Einstein: E = mc2 Buchmüller Mass curves space-time
All of this is correct. But how do objects become massive?
Simplest theory – all particles are massless !!
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2 A field pervades the universe Particles interacting with this field acquire mass – stronger the interaction the larger the mass
The field is a quantum field – its quantum is the Higgs boson. Finding the Higgs boson would establish the existence of this field!
Seminal papers published in 1964! 8 8
Groundbreaking Work in 1964 !
“Electroweak Symmetry Breaking Mechanism” 2010 Sakurai Prize of American Physical Society
R. Brout, F. Englert, Buchmüller P. Higgs, G. Guralnik, C. Hagen, T. Kibble
The References in CMS papers on the
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Groundbreaking Work in 1964 !
“Electroweak Symmetry Breaking Mechanism” 2010 Sakurai Prize of American Physical Society
R. Brout, F. Englert, Buchmüller P. Higgs, G. Guralnik, C. Hagen, T. Kibble
The References in CMS papers on the
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Three(!) seminal papers have paved the way to the Higgs Boson discovery in 2012!
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Physics Nobel Prize in 2013
François Englert Peter W. Higgs
Buchmüller Université Libre University of Edinburgh, de Bruxelles, Edinburgh, United Kingdom Brussels, Belgium
The Nobel Prize in Physics 2013 was awarded jointly to
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2 François Englert and Peter W. Higgs "for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN's Large Hadron Collider"
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Physics Nobel Prize in 2013
François Englert Peter W. Higgs
Buchmüller Université Libre University of Edinburgh, de Bruxelles, Edinburgh, United Kingdom Brussels, Belgium
The Nobel Prize in Physics 2013 was awarded jointly to
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2 François Englert and Peter W. Higgs "for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN's Large Hadron Collider" A triumph for particle physics! More the 100 years after the first elementary particle, the electron, was found, we now discovered the last particle missing in the SM! 12
Groundbreaking Work in 1964 !
“Electroweak Symmetry Breaking Mechanism” All six are equally deserving! Buchmüller R. Brout, F. Englert, P. Higgs,
G. Guralnik, C. Hagen, T. Kibble
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Physics Mission of the LHC
• The LHC project (the accelerator and experiments) was Buchmüller conceived & designed to tackle fundamental questions in science (some which go to the heart of our existence):
about the origin, evolution and composition of our
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In particular, what is the origin of mass? what constitutes dark matter? do we live in more than 3 space dimensions? why is the universe composed of matter, and not antimatter?
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This Study Requires…….
1. Accelerators : powerful machines that accelerate particles to extremely high
Buchmüller energies and bring them into collision with other particles
2. Detectors : gigantic instruments that record the resulting particles as they
“stream” out from the point of collision.
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2 3. Computing : to collect, store, distribute and analyse the vast amount of data produced by these detectors
4. Collaborative Science on a worldwide scale: thousands of scientists, engineers, technicians and support staff to design, build and operate these complex “machines”. 15 15
Timeline of the LHC Project
1984 Workshop on a Large Hadron Collider in the LEP tunnel, Lausanne 1987 Rubbia “Long-Range Planning Committee” recommends
Large Hadron Collider as the right choice for CERN’s future Buchmüller 1990 ECFA LHC Workshop, Aachen
1992 General Meeting on LHC Physics and Detectors, Evian les Bains 1993 Letters of Intent (ATLAS and CMS selected by LHCC)
1994 Technical Proposals Approved
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2 1996 Approval to move to Construction (materials cost of 475 MCHF) 1998 Memorandum of Understanding for Construction Signed 1998 Construction Begins (after approval of Technical Design Reports) 2000 ATLAS and CMS assembly begins above ground. LEP closes 2008 ATLAS & CMS ready for First LHC Beams 2009 First proton-proton collisions 2012 A new heavy boson discovered with mass ~125 × mass of proton
Almost 30 years! 16 16 CERN: The European Laboratory for Particle Physics
CERN is the European Organization for Nuclear Research, the world’s largest Particle Physics Centre, near Geneva, Switzerland It is now commonly referred to as European Laboratory for Particle Physics
Buchmüller It was founded in 1954 and has 20 member states + several observer states CERN employes >3000 people + hosts ~10000 visitors from >500 universities.
Annual budget ~ 1100 MCHF/year (2011)
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17 Breaking the Walls between
Cultures and Nations since 1954
Buchmüller
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The Large Hadron Collider at CERN
Buchmüller
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The LHC Accelerator
Protons are accelerated by powerful The dipole magnets operate at 8.3 Tesla electric fields to very (very) close to the (200’000 x Earth’s magnetic field) & 1.9K (- speed of light (superconducting r.f. 271°C) in superfluid helium. Buchmüller cavities) Protons travel in a tube which is under a And are guided around their circular better vacuum, and at a lower temperature, orbits by powerful superconducting than that found in
dipole magnets. inter-planetary space.
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120 tons of superfluid helium – a very interesting 20 engineering material!20
LHC Accelerator is Performing according to Design
Buchmüller X
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The LHC energy was increased in 2012 to 4 TeV/beam 2011: examined 350 trillion pp interactions 2012 (up to end-June) examined another 400 trillion pp interactions (500 million proton-proton interactions/s!)
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CERN’s Particle Accelerator Chain
Buchmüller
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23 The Large Hadron Collider at CERN
pp, B-Physics,
CP Violation Buchmüller LHC : 27 km long 100m underground
ATLAS
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General Purpose, pp, heavy ions
Heavy ions, pp
ALICE CMS 24 24 +TOTEM
Buchmüller
Electro-weak phase transition
(ATLAS, CMS…)
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QCD phase transition (ALICE…)
LHC studies the first 10-10 -10-5 second after
the big bang!! 25 25
Schematic of an HEP Detector
Physics requirements drive the design (e.g. search for the Higgs boson)
Analogy with a “cylindrical onion”: Buchmüller Technologically advanced detectors comprising many layers, each designed to perform a specific task. Together these layers allow us to identify and precisely measure the energies and
directions of all the particles produced in collisions.
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In 1980’s: “we think we know how to build a high energy, high luminosity hadron collider – we don’t have the technology to build a detector for it” 26 26 4T Superconducting Solenoid 3rd Layer: Hadron Calorimeter
4th Layer: Muon system
Buchmüller
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1st Layer: Silicon Tracker (pixels and microstrips) 2nd Layer: Lead tungstate electromagnetic calorimeter 27 Turing Festival TSV 27
ATLAS Cavern
Buchmüller
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Particles that are detected in an HEP Detector
Any new particles will manifest themselves through known particles Buchmüller
Photons, Electrons, Muons
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CMS Detector Closed
Buchmüller
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30 Turing Festival TSV 30
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Buchmüller
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Buchmüller
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Buchmüller
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Buchmüller
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Buchmüller
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“One picture” of a pp collusion at 8 TeV
Buchmüller
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Buchmüller Going to the
Science
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2 Example: Higgs Boson discovery
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Standard Model Higgs Boson
Buchmüller
Δχ2
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mh(GeV)
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Standard Model Higgs Boson
Buchmüller
Δχ2
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mh(GeV)
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Standard Model Higgs Boson
Pre-LHC: mh(SM)<161 GeV preferred @ 95% CL from Buchmüller EWK Fit Δχ2 mh(SM)< 114 GeV excluded @ 95% CL from direct searches at the LEP mh(SM) [156, 177] GeV
excluded @ 95% CL from INSPFRI INSPFRI O. Paris in school
direct searches at the Tevatron
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mh(GeV) The preferred mass region of a SM-like Higgs was below 200 GeV (and above 114 GeV).
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SM Higgs Boson Production
Gluon-gluon production (ttbar loop) dominates. -1
e.g. No. of “H125” produced = 25pb × 10fb = 250,000
Buchmüller
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SM Higgs Boson Decay
bb, tt
l Buchmüller
ZZ, WW
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2 gg
gg
gg is 2 per mille ~ 400 gg events ZZ → 4l is ~10-4 ~ 10 4l events 43 H gg
candidate
Buchmüller
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CMS - Search for the SM Higgs boson: H→gg
Observe a peak at 125.3 GeV
As particle seen in di-photon mode it must have spin 0 or 2
Buchmüller
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gg Mass Distribution 2 45 m γγ= 2 E1 E2 (1-cosα) 45
ATLAS - Search for the SM Higgs boson: H→gg
Observe a peak at 126.5 GeV
Buchmüller
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gg Mass Distribution
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ZZ(*) → 2m2e Channel
Buchmüller H ZZ4e
candidate
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47 Turing Festival TSV 47
CMS - Search for the SM Higgs boson: H→ZZ→4l
Buchmüller
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4l Mass Distribution 48 48
ATLAS - Search for the SM Higgs boson: H→ZZ→4l
Buchmüller
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4l Mass Distribution 49 49 Results from the Experiments
Higgs 2 photons!! Higgs 2 Z 4 leptons!!
A clear “excess” of events seen Buchmüller in both experiments around 125-126 GeV
It became very significant in 2012
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2 Sophisticated
CMS Preliminary s = 7 TeV, L = 5.05 fb-1 ; s = 8 TeV, L = 5.26 fb-1 Statistical Methods
V V e e 12 7 TeV 4e, 4m, 2e2m
Data 8 TeV 4e, 4m, 2e2m G
G have used to fully
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Z+X
/ /
10 s
s analyse this. t
t Zg*,ZZ
n n e
e 8 v
v mH=126 GeV
E E 6 And the result is…
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m4l [GeV]
80 100 120 140 160 180 50 m4l [GeV] Combining the Results from the Searches for the
Higgs boson
ATLAS and CMS have each independently discovered a new heavy
boson at approximately the same mass
Buchmüller
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ATLAS combined local significance CMS combined local significance Expected: 5.0σ Expected: 5.8σ Observed: 6.0σ Observed: 5.0σ At a mass of 126.5 ± 0.6 GeV At a mass of 125.3 ± 0.6 GeV 51 51
Is the Higgs Boson finally surfacing …?
Buchmüller
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Buchmüller A New
Heavy Boson
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2 Born on the 4th of July 2012!
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Buchmüller Where are
we Today?
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H->γγ: Example ATLAS (CMS similar)
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m γγ= 2 E1 E2 (1-cosα)
Buchmüller
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All available data are analyzed! 55
H->4l :Example ATLAS (CMS similar)
Buchmüller 4 isolated high pT leptons consistent with Z decays from same vertex
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The challenge of Buchmüller
Triggering at the
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2 LHC!
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The Challenge: physics production in pp collisions
1034 cm-2s-1 At the High Luminosity LHC (HL-LHC), assuming an instantaneous luminosity of ~1035 cm-2s-1, Buchmüller approximately 1010 proton proton collisions are produced per second! ~1010/s 1035 cm-2s-1 For comparison, at its peak performance in 2012 the LHC was producing a
few times 108 events per second. INSPFRI INSPFRI O. Paris in school
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2 However, the vast majority of these events are what we refer to a minimum-bias events - i.e. not the physics we are interested in!
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The Challenge: physics production in pp collisions
1034 cm-2s-1 At the High Luminosity LHC (HL-LHC), assuming an instantaneous luminosity of ~1035 cm-2s-1, Buchmüller approximately 1010 proton proton collisions are produced per second! ~1010/s 1035 cm-2s-1 For comparison, at its peak performance in 2012 the LHC was producing a
few times 108 events per second. INSPFRI INSPFRI O. Paris in school
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However,2 the vast majority of these events are what we refer to a minimum-bias events - i.e. not the physics we are interested in!
Production of New Physics processes like Supersymmetry or even the Higgs boson ~<10/s 1035 cm-2s-1 will exhibit rates of only 10 (or less) events per second!
Therefore, we need to achieve an event rate reduction of >109 to access the interesting physics! 59
The Trigger Challenge: Example Higgs Discovery
Buchmüller
Higgs Discovery ~ 2000 trillion ~600 trillion pp in total
pp collisions!
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The Trigger Challenge: Example Higgs Discovery
Buchmüller
~ 400 events Higgs Discovery ~ 2000 trillion ~600 trillion pp in total
pp collisions!
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~ 10 events
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The Trigger Challenge: Example Higgs Discovery
Buchmüller
~ 400 events Higgs Discovery ~ 2000 trillion ~600 trillion pp in total
pp collisions!
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Out ~600 trillion pp collisions we
~ 10 had to select ~400 gg and ~10 4l events events! In total only 250k of Higgs bosons were produced in 600 trillion pp
collisions 62
“One picture” of a pp collusion at 7 TeV
Buchmüller
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tau-mu dilepton candidate 63
A 3D Digital Camera
Trigger and Data flow: Analogy with a 3D 100Mio digital camera! CMS in 2012: Buchmüller 1. At the LHC 40 million pictures per second a produced! information content equals ~10.000 encyclopedias per second! We call these pictures “events”. (1PB/sec) 2. First selection of interesting pictures: 100.000/sec
Each picture has a size of about 1MB. The tool that performs INSPFRI INSPFRI O. Paris in school
this selections is called “L1 Trigger”. (100 GB/sec)
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2 3. The 100.000 events/sec are further analyzed in a big “online” computer farm (~20000 CPUs) called High Level Trigger (HLT) out of 100.000 events/sec the most interesting ~1000 events are permanently recorded. (up to 1GB/sec) 4. Recorded data are processed and distributed in the world for physics analysis: ~10 Mio GB/year (or ~3 Mio DVDs/year) 64
A 3D Digital Camera
Trigger and Data flow:
Analogy with a 3D 100Mio digital camera! CMS in 2012: Buchmüller 1. At the LHC 40 million pictures per second a produced!At this level (L1) a information content equals ~10.000 encyclopediasTrack per Trigger could second! We call these pictures “events”. (1PB/sec)be very useful! 2. First selection of interesting pictures: 100.000/sec
Each picture has a size of about 1MB. The tool that performs INSPFRI INSPFRI O. Paris in school
this selections is called “L1 Trigger”. (100 GB/sec)
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2 3. The 100.000 events/sec are further analyzed in a big “online” computer farm (~20000 CPUs) called High Level Trigger (HLT) out of 100.000 events/sec the most interesting ~1000 events are permanently recorded. (up to 1GB/sec) 4. Recorded data are processed and distributed in the world for physics analysis: ~10 Mio GB/year (or ~3 Mio DVDs/year) 65
HL-LHC Environment
2010 1032 cm-2 s-1 2011 1033
~107 collisions ~108 Buchmüller
close to 2012 conditions Expected for HL-LHC 1035 INSPFRI INSPFRI O. Paris in school
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2 (~7x10 ~10 ~109
At HL-LHC ATLAS and CMS face new challenges, for Factor 10 Tracking and Triggering, as well as Precision Calorimetry, to go … particularly in the End-Cap and Forward regions 66
Computing: Networks, farms and data flows
To regional centers
622 Mbit/s Buchmüller 10 TeraIPS 10 TeraIPS Remote control rooms
Controls: 1 Gbit/s Events:
5 TeraIPS 10 Gbit/s
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Controls: 1 Gbit/s
Raw Data: 1000 Gbit/s
67 67 World-wide coverage - over 200 sites Ultra high speed data transfers ~300,000 CPUs
>200 petabytes storage
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Basic Numbers: “Today vs HL-LHC”
2012-2013 run:
Lumi = 7 x 1033, PU = 30, E = 7 TeV, 50 nsec bunch spacing Buchmüller 2012 ATLAS, CMS operating: Detectors Detectors L1 Accept ≤ 100 kHz, Lvl-1 Front end pipelines Lvl-1 Front end pipelines
Latency ≤ 2.5 (AT), 4 μsec (CM) Lvl-2 Readout buffers Readout buffers HLT Accept ≤ 1 kHz Switching network Switching network
Lvl-3 Processor farms HLT Processor farms INSPFRI INSPFRI O. Paris in school
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ATLAS: 3 physical levels CMS: 2 physical levels Where ATLAS & CMS are expected to be: Lumi = ~ 1035 (increase × ~10)
Trigger & Data Acquisition & Computing Upgrade Plan
To maintain today’s physics performance of ATLAS and CMS
Buchmüller in the challenging environment of the high luminosity LHC, we need to improve the basic parameters such as the rate of events (“pictures”) selected and stored by an order of magnitude! [roughly speaking]
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2 Addition of tracking information and better calorimeter resolution/granularity at L1 to improve the selection efficiency for the interesting “pictures”. Increase the rate of “pictures” that can be selected to maximize the rate of interesting “pictures” that can be stored permanently.
[more details about the upgrade plans are in the backup] 70
Aiming for Flexibility
Muon EG Improvement Buchmüller Tau Factor L1 Hadronic
10
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1 Fractional 1 5 10 Bandwidth increase
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Aiming for Flexibility
Muon EG Improvement Buchmüller Tau Factor L1 Hadronic
No increase of L1 bandwidth 10
We need to improve all important physics
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nd objects by at least a factor of 10. The main tool
2 to our disposal would be the Track Trigger. 5 However, improvements for some objects are easier then for others.
1 Fractional 1 5 10 Bandwidth increase
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Aiming for Flexibility
Muon Significant increase of L1 bandwidth EG Improvement
Buchmüller Factor L1 Going significantly beyond 100 KHz would Tau per object provide flexibility to in playing L1 improvement Hadronic vs bandwidth increase.
10
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1 Fractional 1 5 10 Bandwidth increase per object
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Example CMS
Buchmüller
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Track Trig. Performance: muons
Buchmüller
↑
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Sharpens (!) turn-on curve, improves efficiency For a threshold of ~ 20 GeV, rate of single muon trigger can be reduced by a factor of O(10) 75
Example CMS
Buchmüller First studies indicate that a Track trigger at level 1 can reduce the required L1 bandwidth substantially. Yet, also an overall bandwidth increase is required!
So, we need BOTH!
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Buchmüller Again, going to the
Science:
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Future of LHC programme
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The Universe (as we know it today)
Buchmüller
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The Universe (as we know it today)
Normal Matter is only ~5% of our
Universe, and it is explained Buchmüller by the Standard Model.
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The Universe (as we know it today)
Normal Matter is only ~5% of our
Universe, and it is explained Buchmüller by the Standard Model.
Dark Matter accounts for about ~27% of our Universe.
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2 Supersymmetry provides a “natural” candidate for dark matter and, in certain regions of parameter space, can happily predict this amount! There are other possibilities but SUSY is a favorite.
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The Universe (as we know it today)
Normal Matter is only ~5% of our Universe, and it is explained Buchmüller by the Standard Model.
Dark Matter accounts for about ~27% of our Universe.
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2 Supersymmetry provides a “natural” candidate for dark matter and, in certain regions of parameter space, can happily predict this amount! There are other possibilities but SUSY is a favorite. Dark Energy is with ~68% believed to be the larges component of our Universe. The Higgs (scalar) field is thought to fill the entire universe. Could it give some handle of dark energy? A rather speculative thought! Yet, its first time we are dealing with a scalar particle … who know what we learn about scalar fields! 82
Higgs couplings: Today & Future
CMS Today ATLAS projected
(ATLAS similar) (CMS similar)
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Potential for huge improvements! 83 m LSP Direct squark Overview search limits Gluino mediated [GeV] Fall 2013 CMS-PAS-SUS-12-028
1000
CMS-PAS-SUS-12-028 ATLAS-CONF-2013-047
ATLAS-CONF-2013-053 CMS-PAS-SUS-12-024 Buchmüller ATLAS-CONF-2013-037 750 Direct stop in “gap” ATLAS-CONF-2013-061 ATLAS-CONF-2013-068 CMS-PAS-SUS -13-011
Direct slepton INSPFRI INSPFRI O. Paris in school 500
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Direct BR=100% ATLAS-CONF- 2013-049 all limits are observed nominal 95% CLs limits 250 RP conserved CMS-PAS-SUS-13-006
mSUSY [GeV] 0 0 250 500 750 1000 1250 1500 84 mLSP [GeV] LHC: 8 TeV 20 fb-1
1000 Direct squark
ATLAS-CONF-2013-037 Example of “difficult” Buchmüller Direct slepton SUSY channels! ATLAS-CONF-2013-049 Direct
CMS-PAS-SUS-13-006 INSPFRI INSPFRI O. Paris in school
500
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BR=100% all limits are observed nominal 95% CLs limits 250 RP conserved
mSUSY [GeV] 0 0 250 500 750 1000 1250 1500 85 mLSP [GeV] LHC: 8 TeV 20 fb-1 1000 Direct squark -1
LHC: 14 TeV 300 fb
ATLAS-CONF-2013-037
Buchmüller Direct slepton ATLAS-CONF-2013-049 Direct
CMS-PAS-SUS-13-006 INSPFRI INSPFRI O. Paris in school
500
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BR=100% all limits are observed nominal 95% CLs limits 250 RP conserved
mSUSY [GeV] 0 0 250 500 750 1000 1250 1500 86 mLSP [GeV] LHC: 8 TeV 20 fb-1 1000 Direct squark -1
LHC: 14 TeV 300 fb HL-LHC: 14 TeV 3000 fb-1 ATLAS-CONF-2013-037
Buchmüller Direct slepton ATLAS-CONF-2013-049 Direct
CMS-PAS-SUS-13-006 INSPFRI INSPFRI O. Paris in school
500
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BR=100% all limits are observed nominal 95% CLs limits 250 RP conserved
mSUSY [GeV] 0 0 250 500 750 1000 1250 1500 87 mLSP [GeV] LHC: 8 TeV 20 fb-1 1000 Direct squark -1
LHC: 14 TeV 300 fb HL-LHC: 14 TeV 3000 fb-1 ATLAS-CONF-2013-037
Buchmüller Direct slepton ATLAS-CONF-2013-049 Direct
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BR=100% all limits are observed nominal 95% CLs limits 250 RP conserved
mSUSY [GeV] 0 0 250 500 750 1000 1250 1500 88 mLSP [GeV] LHC: 8 TeV 20 fb-1 1000 Direct squark -1
LHC: 14 TeV 300 fb HL-LHC: 14 TeV 3000 fb-1 ATLAS-CONF-2013-037
Buchmüller Direct slepton ATLAS-CONF-2013-049 Direct
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mSUSY [GeV] 0 0 250 500 750 1000 1250 1500 89 mLSP [GeV] LHC: 8 TeV 20 fb-1 1000 Direct squark -1
LHC: 14 TeV 300 fb HL-LHC: 14 TeV 3000 fb-1 ATLAS-CONF-2013-037
Buchmüller Direct slepton ATLAS-CONF-2013-049 Direct Even for the difficult channels similar coverage (or better) can be
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Landscape of Dark Matter Searches
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Direct Searches
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Indirect Searches
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Dark Matter Limits from Direct Searches: LHC vs DD
Examples: CMS monojet search Based on OB, M.Dolan,C.McCabe: and recent LUX result: arXiv:1308.6799
Buchmüller interpretation in simplified models Evolution with time:
LHC: Today, 14 TeV 300fb-1, 14 TeV 3000fb-1
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Important complementarity of the two experimental approaches will allow good coverage of the relevant parameter space!
Big discovery potential! 92
Summary
The “order of magnitude” increase in collision rate represents a significant challenge for the Trigger, Data Acquisition, and Buchmüller computing strategy of ATLAS and CMS. The experiments have a well defined upgrade programme in place to tackle the challenge and to maintain (or even improve) their physics acceptance of today!
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The HL-LHC will give a substantial extra reach in some New
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BACKUP
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SMS: a few interesting features
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CMS-PAS-2012-028 See talk from
S. Sekmen
: LSP mass above : LSP
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TeV
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Why is Supersymmetry so attractive?
1. Quadratically divergent quantum corrections to the Higgs boson mass are avoided mSUSY ~ 1 TeV
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3. SUSY provides a candidate for dark matter,
The lightest SUSY particle (LSP)
4. A SUSY extension is a small perturbation, MHiggs (GeV) consistent with the electroweak precision data 96
Direct Detection Experiments: Projections
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Dark Matter Limits from Direct Searches: LHC vs DD
Different coupling assumptions!
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Energy vs Luminosity
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The Challenge: LHC@14 TeV (design)
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“One picture” of a pp collusion at 8 TeV
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TRIGGER UPGRADE
103 ATLAS & CMS Triggered vs. Triggerless
Architectures
1 MHz (Triggered): Network:
Buchmüller 1 MHz with ~5 MB: aggregate ~40 Tbps Links: Event Builder-cDAQ: ~ 500 links of 100 Gbps Switch: almost possible today, for 2022 no problem HLT computing: General purpose computing: 10(rate)x3(PU)x1.5(energy)x200kHS6 (CMS) Factor ~50 wrt today maybe for ~same costs Specialized computing (GPU or else): Possible
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Network:
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2 40 MHz with ~5 MB: aggregate ~2000 Tbps Event Builder Links: ~2,500 links of 400 Gbps Switch: has to grow by factor ~25 in 10 years, difficult Front End Electronics Readout Cables: Copper Tracker! – Show Stopper HLT computing: General purpose computing: 400(rate) x3(PU)x1.5(energy)x200kHS6 (CMS) Factor ~2000 wrt today, but too pessimistic since events easier to reject w/o L1 This factor looks impossible with realistic budget Specialized computing (GPU or …) Could possibly provide this …
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2012 ATLAS Trigger & DAQ Architecture
Calo MuTrCh Other detectors 40 MHz Trigger DAQ 1 PB/s
40 MHz
Buchmüller 2.5 2.5 specialized h/w D FE Pipelines ASICs LV ms E FPGA
L1 Lvl1 acc = 75 kHz T
ROD ROD ROD R/O Read-Out Drivers 75 kHz
RoI 120 GB/s RoI data = 1-2% 120 GB/s Read-Out Links
~ 10 ms RoI
LVL2 requests ROB ROB ROB Read-Out Buffers INSPFRI INSPFRI O. Paris in school RoI Builder
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2 L2 Supervisor D H ROS Read-Out Sub-systems L2 N/work A L2N L2 Proc Unit L2P T ~2+4 GB/s ~2 kHz L Lvl2 acc = ~2 kHz A Dataflow Manager DFM EBN F Event Building N/work ~ sec L T Event Filter SFI Sub-Farm Input O EFP EB ~4 ~4 GB/s Event Builder Event Filter W EFP Processors EFP EFN Event Filter N/work EFP EFacc = ~0.2 kHz
SFO Sub-Farm Output
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Bandwidth Increase: Aiming for Flexibility
Muon Electron Improvement Buchmüller Tau Factor L1 Photon Jets No increase of L1 bandwidth 10
We need to improve all important physics
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1 Fractional 1 5 10 Bandwidth increase (100 KHz) (500KHz) (1000 KHz)
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Aiming for Flexibility
Muon Significant increase of L1 bandwidth Electron Improvement Buchmüller Factor L1 Going significantly beyond 100 kHz would Tau per object provide flexibility to in playing L1 improvement Photon vs bandwidth increase. Jets
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HL-LHC Track Trigger Architectures:
“Push” path (CMS Tracker Approach): L1 tracking trigger data combined with calorimeter & muon trigger data regionally
Buchmüller with finer granularity than presently employed. After regional correlation stage, physics objects made from tracking, calorimeter & muon regional trigger data transmitted to Global Trigger. “Pull” path (ATLAS Tracker Approach): L1 calorimeter & muon triggers produce a “Level-0” or L0 “pre-trigger” after latency of present L1 trigger, with request for tracking info at ~0.5 MHz. Request only
goes to regions of tracker where candidate was found. Reduces data transmitted
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2 a tracker region to be found with candidates, which could be less than 10%, (e.g. 50 kHz, < speed of ATLAS FTK) Tracker sends out info. for these regions only & this data is combined in L1 correlation logic, resulting in L1A combining track, muon & cal. info.. “Afterburner” path (both ATLAS & CMS): L1 Track trigger info, along with rest of information provided to L1 is used at very first stage of HLT processing. Provides track information to HLT algorithms very quickly without having to unpack & process large volume of tracker information through CPU-intensive algorithms. Helps limit the need for significant additional processor power in HLT computer farm. 108
Example: Track Trigger at L1
ATLAS: Tau reconstruction CMS: Muon reconstruction
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For the same L1 rate (“pictures” passed For the physics acceptance of muons through the high-level selection) we can we reduce the rate of pictures we have select 300% more interesting events to take by an order of magnitude! including taus! 109
How to tackle the factor 10 challenge!
ATLAS (HL-LHC):Trigger Divide L1 Trigger into L0, L1 of latency 6, 20 μsec, Buchmüller rate ≥ 500, ≥ 200 kHz, HLT output rate of 5 - 10 kHz Calorimeter readout at 40 MHz w/backend waveform processing (140 Tbps) L0 uses Cal. & μ Triggers, which generate track trigger seeds L1 uses Track Trigger & more muon detectors & more fine-grained calorimeter trigger
information.
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2 CMS (HL-LHC):Trigger Considering L1 Trigger latency, rate: 10 – 20 μsec, 0.5 – 1 MHz L1 uses Track Trigger, finer granularity μ & calo. Triggers HLT output rate of 10 kHz In a nutshell Increase rate of “pictures” we can pass through the trigger by O(10) L1 rate: 100 kHz to 0.5 to 1 Mhz HLT rate: from ~1 kHz to 5 to 10 kHz Include track information at L1 (Track Trigger) 110
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Increase in Energy: 8 TeV vs 14 TeV
Use parton luminosities to illustrate the gain of 14 vs 8 TeV Buchmüller Higgs: Z’ pp H, HWW, ZZ and γγ ~5.0 TeV mainly gg: factor ~2 SUSY squarks/Gluino SUSY – 3rd Generation: ~1.5 TeV
Mass scale ~ 500 GeV
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2 SUSY 3rd Gen ~500 GeV SUSY – Squarks/Gluino: Higgs Mass scale ~ 1.5 TeV 125 GeV qq,gg,qg: factor ~40 to 80
Z’ : Mass scale ~ 5 TeV qq: factor ~1000 Increase in energy will help a lot! Not just for SUSY... 112
Interpretation in Simplified Models
CMSSM What the individual searches are sensitive to is much more
Buchmüller simple…
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Simplified model spectrum (SMS) with 3 particles, 2 decay modes
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