The CMS Experiment at the CERN Large Hadron Collider CMS

CMS

The CMS Experiment at the CERN Large Hadron Collider

Universal Laws and Particle Physics

Bari, Italy, 18 May, 2005

Introduction

Universal Laws of Physics

Introduction to Particle Physics

Matter, Forces and the Standard Model Back to Creation

Particle Physics Experiments

Large Hadron Collider at CERN

The CMS Experiment: Detector and Physics

Conclusions

December 1999

Can Physics Be Unified ?

Can Aging

Be Postponed ? What Secrets Do Genes Hold ?

How Was the Universe Born ?

How Does the Mind Work ? Can Robots Be Intelligent ? Is There Life In Outer Space?

How Much Do We Change the Climate?

Unfinished Business from Last Century

Path to Unification

10 ^-43 s Quantum gravity era

10 ^-35 s Grand unification era

10 ^-10 s Electro-weak era

10 ^-4 s Protons and neutrons form

100 s Nuclei are formed (e.g. He)

0.3 Myr Atoms formed, universe becomes transparent 1 Gyr Galaxy formation

Today Man wonders where it all came from !

Unveiling the Universe

Electroweak Transition Quantum

Gravity Metaphysics

T _sun

Back to Creation

1. Can we construct a unified theory of physics?

2. What is the origin of mass? Why are Z and W bosons massive whilst  is massless?

3. Are there additional space-time dimensions?

4. Are the particles fundamental or do they possess structure ? 5. What is the nature of dark matter?

6. Why is there overwhelmingly more matter than anti-matter in the Universe?

7. Are there new states of matter at exceedingly high density and temperature?

8. Are protons unstable ?

9. Why are there 3 generations of quarks and lepton?

Open Questions in Particle Physics

Various articles in Scientific American

The Elegant Universe – Brian Green, Jonathan Cape, 1999

Quarks Leptons and the Big Bang – Jonathan Allday, IOP Publishing, 1998 The First Three Minutes – Steven Weinberg, Flamingo, 1983

The Character of Physical Law, Richard Feynman, MIT Press, 1975

http://user.web.cern.ch/user/cern.html

References

Aim to answer the two following questions:

What are the elementary constituents of matter ?

What are the forces that control their behaviour at the most basic level

Experimentally

Aim to measure the energy, direction and identity of the products of hard interactions as precisely as possible

Particle Physics

Constituents of Matter

Ratio of electrical to gravitational force between two protons is ~ 10 ³⁸ !!

How are the composite objects held together ? by forces

Fundamental Forces

10 ^-34 10 ^-30 10 ^-26 10 ^-22 10 ^-18 10 ^-14 10 ^-10 10 ^-6 1m 10 ⁶ 10 ¹⁰ 10 ¹⁴ 10 ¹⁸

Earth radius Earth to Sun

Observables Instruments

Proton Nuclei Microscope

Telescope

Virus Cell Atom

SUSY particle?

Higgs?

Z/W (range of weak force) (range of nuclear force)

(Particle beams)

Electron Microscope

LHC, LEP

Accelerators

Size of Things

Power of a Microscope

Particle Interactions

Decay of a Z Boson

Where is Gravity?

M _e ~ 0.5 MeV M _ ~ 0

M _t ~ 175,000 MeV!

M _ = 0

M _Z ~ 100,000 MeV Why ?

The Standard Model of Particle Physics

The standard Model is one of the most precisely tested

theories in science

Why then do we need to probe further ?

Precision Measurements from LEP

Is the Standard Model Complete ?

Although the Standard Model has been very successful it is incomplete.

SM contains too many apparently arbitrary features

SM has an unproven element – not some minor detail but a central element – namely the mechanism to generate observed masses of known particles

A solution is to invoke the Higgs mechanism SM gives nonsense at high energies

At centre of mass energies > 1000 GeV the probability of W _L W _L scattering becomes greater than 1 !!

A solution is to introduce a Higgs exchange to cancel the bad high energy behaviour

SM is logically incomplete – does not incorporate gravity – needed to build a

Unified Theory

Origin of Mass and The Higgs Mechanism

Simplest theory – all particles are massless !!

A field pervades the universe

Particles interacting with this field acquire mass – stronger the interaction larger the mass

The field is a quantum field – the quantum is the Higgs boson

Finding the Higgs establishes the presence of the field

A Higgs Event

Supersymmetry

GRAVITY

Grand Unified Theory (GUTS)

STRONG

Quarks

Electroweak

SUSY (GUTS) SUPER QCD

MSSM Gluon

Graviton

Photons W's

Z's Higgs

Electrons Neutrinos

Gluino Gravitino

Photinos

Winos Zinos Higgsino Selectrons

Sneutrinos

SUPERGRAVITY

Unified Theory: Grand Unification

GUT : Perhaps strong and electroweak forces are related at ~ 10 ¹⁶ GeV

Quarks and leptons are put on the same footing they can make transitions amongst themselves Protons will be unstable e.g. p  e ⁺  ⁰

Charge is quantized: Q[d ₁ u ₁ u ₂ e ^-  ₁ ] = 0

Neutrinos have a small mass

Quantum Gravity ??

• Modern physics rests on two foundations:

• Einstein’s General Theory of Relativity (GR) – theoretical framework for understanding the universe on the largest scales – stars, galaxies etc.

• Quantum Mechanics (QM) - theoretical framework for understanding the universe on the smallest scales – molecules, atoms, electrons, quarks etc.

• Both experimentally confirmed to tremendous accuracy

• BUT as currently formulated GR and QM cannot both be right ??

• GR and QM simultaneously needed in extreme conditions – inside black holes,

first moments of Big Bang – ‘tiny yet incredibly massive’

Quantizing Gravity ?

QM + GR – examine microscopic properties of space

First three levels of magnification –flat space

QM changes this radically – everything is subject to quantum fluctuations !

HUP – E. t ~ h(p. x ~ h)

Classically – empty space  0 gravitational field QM – on average it is 0, but undulates up and down UP: undulations larger as focus on smaller regions Violent distortions of space - quantum foam

Smooth space (GR) destroyed by QM – calculations

give infinte answers – nature’s ‘rap on the wrist’

Are Particles Bits of Strings ?

Particles

Supersymmetry

Superpartner Particles

Particles are strings – all described as

just different vibrational patterns

One mode matches properties of the

graviton – gravity is part of string theory

Inclusion of Gravity

Traditional picture: gravity VERY weak

Coupling runs as E ² /M _pl ² ;

scale set by M _pl given by G ^-1/2 Weakness “explained” by large value of M _pl

Attempts to include gravity:

So far: modify Standard Model

Novel idea

Change gravity instead

Extra Dimensions

In 3-D: Gravity Law What is it in 2-D ?

Use lines of field – In 3-D no of lines of field crossed in a unit area of a sphere radius r is (unit area/area of sphere)  1/r ²

In 2-D it will be lines crossed (unit length/circumference)  1/r !!

Law of gravity depends on no. of space dimensions !

Space-time may have more dimensions than 4 !! EXTRA DIMENSIONS

We do not see them because they are

r 2

F = GMm

Extra Dimensions: Black Hole Production in CMS !

Semi-classical argument: two partons approaching with impact parameter <

Schwarzschild radius, R _S  black hole

Spectacular decays – democracy of SM particles – high multiplicity incl lots of charged

leptons and photons at high p _T

The Energy Frontier

New Energy Domain

Search for the unexpected

Cover domain ~ 1 TeV in which SM without the Higgs (or equivalent) gives nonsense

Exploratory machine required

 hadron-hadron collider with:

Largest possible primary energy

Largest possible luminosity

Proton- Proton Collider 7 TeV + 7 TeV

Luminosity = 10 ³⁴ cm ^-2 sec ^-1

Large Hadron Collider

CERN Site

Observables

Jets of particles

Electrons, Muons, Missing E _T

photons

Particle Detection

To detect particles energy must be transferred to the detecting medium Energy Loss if Charged Particles

Lose energy via interactions of virtual photons with atomic electrons

Can consider the medium as consisting of a gas of electrons The energy transferred to the electrons causes them to be ejected from the parent atom (ionization) or to be

excited to a higher energy state (excitation) Virtual photon Charged

particle

atom

Particle Detectors

25cm 2cm

Lead Tungstate Silicon Detector

300m

Charged particle

electron shower

Onion-like Structure of HEP Experiments

A ‘Typical’ HEP Detector

Central detector

• Tracking, p _T , MIP

• Em. shower position

• Topology

• Vertex

Electromagnetic and Hadron

calorimeters

• Particle identification (e, γ Jets, Missi E _T )

Eery esureet

•

µ µ  

  γ γ

Hevy terils

ν ν

Hevy terils

(Iro or Coer + Active teril)

e e

Mterils with hih uber of

rotos + Active teril

Liht terils Muo detector

µ idetifictio

•

Heretic clorietry

Missi Et esureets

•

A Typical Event in LEP-ALEPH

Particle Accelerators

Energy and Luminosity

Hadron colliders are broad-band exploratory machines May need to study W _L -W _L scattering at a cm energy of ~ 1 TeV

 E _W ~ 500 GeV

E _quark ~ 1 TeV -> E _proton ~ 6 TeV

 pp collisions at 7 + 7 TeV Event Rate = L.s.BR

e.g. H(1 TeV)  ZZ  2e+2 or 4e or 4

p p

q q q

q

Z ⁰

Z ⁰ H

W

W

Collisions at the LHC

Bunch Crossing 4 10 ⁷ Hz

7x10 ¹² eV Beam Energy 10 ³⁴ cm ^-2 s ^-1 Luminosity 2835 Bunches/Beam 10 ¹¹ Protons/Bunch

7 TeV Proton Proton colliding beams

Proton Collisions 10 ⁹ Hz Parton Collisions

New Particle Production 10 ^-5 Hz ^{p H p}

µ

µ

Z

p p

e- νe

q q

χ1-

~ q~

7.5  (25 s)

Experimental Challenge

High Interaction Rate

pp interaction rate 1 billion interactions/s

data can be recorded for only ~100 out of the 40 million crossings/sec Level-1 trigger decision will take ~2-3 ms

 electronics need to store data locally (pipelining)

Large Particle Multiplicity

~ <20> superposed events in each crossing

~ 1000 tracks stream into the detector every 25 ns

need highly granular detectors with good time resolution for low occupancy

 large number of channels

High Radiation Levels

 radiation hard (tolerant) detectors and electronics

Compact Muon Solenoid

The CMS Collaboration

1790 Physicists and Engineers

Slovak Republic

CERN

France

Italy

UK

Switzerland USA

Austria

Finland

Greece Hungary Belgium

Poland Portugal

Spain

Pakistan Georgia

Armenia Ukraine Uzbekistan

Cyprus Croatia

China, PR Turkey

Belarus

Estonia India

Germany

Korea Russia

Bulgaria

China (Taiwan) Iran

Serbia

New-Zealand

Brazil

Ireland

898 503 389 1790 Member States

Non-Member States

Total USA

Number of Scientists

57

40 157 Member States

Total USA

Non-Member States 60

Number of Laboratories

Associated Institutes Number of Scientists

Number of Laboratories

54 8

Mexico

Bari in CMS

Bari plays an important role in CMS

Muon System

Overall Management of both Barrel and Endcap System

Assembly, testing, installation and commissioning of chambers, Electronics Tracker

Module production for TIB, Co-ordination responsibility for Monitoring display

Software

Co-ordination responsibility for CMS software

Analysis

Compact Muon Solenoid

MUON BARREL

CALORIMETERS

Silicon Microstrips Pixels

ECAL Scintillating PbWO4 crystals

Drift Tube

SUPERCONDUCTING COIL

IRON YOKE

TRACKER

MUON ENDCAPS

Total weight : 12,500 t Overall diameter : 15 m Overall length : 21.6 m Magnetic field : 4 Tesla

HCAL

Plastic scintillator/brass

sandwich

CMS Buildings and Caverns

Delivered May 05

Delivered Jan 2000

Delivered Feb 05 Delivered May 05

SDX

SX5

UXC

SCX

Underground Experiment Cavern

QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture.

Installation of Infrastructure started

Platform for Forward shielding

HF “garage”

LHC tunnel

Trigger ducts

The CMS Magnet

http://cmsdoc.cern.ch/cms/outreach/html/

• 1 Mar 05: Completion of Cold-Mass

• All coil modules are electrically connected in series, hydraulic (welded) connections are completed and vacuum tight. Cold mass is ready to be covered by the outer radiation shield.

• Preparation of swiveling will start end of June, and be executed beginning of August.

• Q1-06: Finish Magnet Test on surface and

CMS Magnet: Cold Mass Completed

Magnet Operations

To be replaced by

the cold mass

USC5 20 kA bus bars pushed

through pillar wall

Heavy Lowering

15 heavy lifts of about 1 week duration each.

Heaviest piece (central wheel + solenoid) 2000 tonnes.

Complete – z end on the surface, in parallel with critical path work on the +z end underground.

Heavy lowering will start in Mar

2006, after magnet test

Inner Tracker

5.4 m

Outer Barrel –TOB-

Inner Barrel –TIB-

End cap –TEC-

Pixel

2 ,4 m

Inner Disks –TID-

A Silicon Charged Particle Detector

A Typical Electronics Chain

Module Integration into TIB Shells (Pisa)

L3: 43 strings out of 45 (2 tbd later)

Tracker Support Tube

ECAL

61200 barrel crystals 14648

endcap

crystals

Supermodule Assembly

Monitoring fibres

SM with Cooling System

ECAL: Energy Resolution

120 GeV electrons s/E = 0.52 % Area covered

• Corrections for “local containment” – not hitting the crystals in the middle – work as well as previous results and Monte-Carlo studies suggest

• Also corrections for losses close to 6 mm inter-module voids

all

Hadron Calorimeter

HCAL - HF

HF in Bat. 186: Start ‘burn-in’ of both HF in mid-2005

The two HF are the first elements to be lowered into UX

Muon System

Reduced RE system

|h| < 1.6

1.6

ME4/1 MB1

MB2 MB3 MB4

ME2 ME3

Barrel Muons: DT+RPC Assembly and Installation

Yoke Wheel YB+2, 34 chambers installed

Barrel RPCs

232 TOTAL CHAMBERS AT CERN:

0 100 200 300 400 500 600

Dec- 02

Feb- 03

Apr- 03

Jun- 03

Aug- 03

Oct- 03

Dec- 03

Feb- 04

Apr- 04

Jun- 04

Aug- 04

Oct- 04

Dec- 04

Feb- 05

Apr- 05

Jun- 05

Aug- 05

Oct- 05

Dec- 05

Feb- 06 all produced

all planning

production production

Item End production

Double gap December 05

CH-prod. January 06

CH-test April 06

Item End production

Double gap December 05

CH-prod. January 06

CH-test April 06

Endcap RPCs

97.4 97.6 97.8 98 98.2 98.4 98.6 98.8

1 2 3 4 5 6 7

C hambe r N o .

E ffic ie n c y

Endcap Muons: CSCs at SX5

CSCs installed: 60% (out of 396)

CSCs commissioned (cosmics): ~ 50%

CMS DAQ and Trigger System

Event size: 1MB from

~700 front-end electronics modules Level-1 decision time: ~3s

~1s actual processing

(the rest in transmission delays) DAQ bandwidth:

designed to accept Level-1 rate of 100kHz

HLT: designed to output O(10 ² )Hz.. Rejection of 1000 Modular DAQ:

8 x 12.5kHz units.

DAQ staging: start with 4

slices (50kHZ) for first physics

run at 2x10 ³³

How are Interesting Events Selected ?

Physics Selection

LEVEL-1 Trigger

Hardwired processors (ASIC, FPGA) Pipelined massive parallel

HIGH LEVEL Triggers Farms of processors

25ns 3µs ms hour year

Reconstruction&ANALYSIS TIER0/1/2 Centers

ON-line OFF-line

sec

Data Acquisition: Principle

16 Million ^channels

100 kHz

LEVEL-1 TRIGGER

1 Megabyte ^{EVENT DATA} 200 Gigabyte ^BUFFERS

500 Readout memories

3 Gigacell ^buffers

500 Gigabit/s

Energy Tracks

Networks 1 Terabit/s

(50000 DATA CHANNELS)

5 TeraIPS

EVENT BUILDER. A large switching network (512+512 ports) with a total throughput of approximately 500 Gbit/s forms the interconnection between the sources (Readout Dual Port Memory) and the destinations (switch to Farm Interface). The Event Manager collects the status and request of event filters and distributes event building commands (read/clear) to RDPMs

40 MHz

COLLISION RATE

Charge Time Pattern

Detectors

Data Flow to Computing Facilities

Raw Data:

1000 Gbit/s Raw Data:

1000 Gbit/s 5 TeraIPS

5 TeraIPS 10 Gbit/s Events: ^Events:

10 Gbit/s

10 TeraIPS 10 TeraIPS

Controls:

1 Gbit/s Controls:

1 Gbit/s

To regional centers 622 Mbit/s To regional centers 622 Mbit/s

CMS networks, farms and data flows

Remote control rooms Remote control rooms

Controls:

1 Gbit/s Controls:

1 Gbit/s

LCG and CMS Computing Model

Discovering a Higgs ?

In the favoured mass region, can observe Higgs via H:

decay is rare (B~10 ^-3 )

But with good energy resolution,

one gets a mass peak

Discovering SUSY ?

Simplest SUSY

Ample event rate for squark and gluino production

Gauginos produced in their decay;

example: q _L c ₂ ⁰ q _L

CMS Master Schedule

• Magnet test on surface start Nov 05

• Start Lowering CMS Feb 06 (HF..yoke mid Mar)

• ECAL barrel EB+ installation Mar 06

• ECAL: last EB- installation & cabling Oct 06

• Tracker installation + cabling start Nov 06

• Beampipe Installation 07 Mar 07 (CP from 1 Apr)

• CMS “ready to close” for beam 15 Jun 07

• CMS “ready for beam” 30 Jun 07

• Det/Trig/DAQ continue integ/commiss. Apr 07-Sep 07 (incl. single beams)

• Data Taking (first collisions) Sep 07

During first shutdown after pilot physics run:

• Pixel Tracker installation Dec 07 (rfi Jul 07)

Physics at Startup

3 months (80 fills)

@ L ₀ =10 ³³ cm ^-2 s ^-1 10fb ^-1 per expt.

Example SM Higgs Discovery Reach (5s): ATLAS +CMS

A T L A S + C M S

At L ₀ =10 ³³ cm ^-2 s ^-1 1 month ~ 0.7 fb ^-1 At L ₀ = 3.10 ³³ cm ^-2 s ^-1 1 month ~ 2 fb ^-1

Assumptions: 14hr run and 10hr to refill

i.e. 1 fill/day

t _L ~ 20 hr, Efficiency of 2/3

Physics at Startup

Squarks and Gluino mass reach

Conclusions

• We are poised to answer some of the biggest questions in physics.

• Many answers will come from LHC experiments.

• Our notion of space and time may be radically altered.

• The LHC at CERN opens the window on the crucial energy scale of 1 TeV

• The CMS experiment at the LHC is capable of discovering whatever nature has in store at the 1 TeV energy scale. It can also study a possibly new

state of matter, the quark-gluon plasma.

• The CMS experiment is under construction. Many sub-detectors are close

to completion. It will be ready to record first collisions in 2007. Exciting

physics is likely to start ‘tumbling out’ soon after startup.