Dean Karlen University of Victoria & TRIUMF APS NW Section Meeting 2005 Victoria, Canada.

Dean KarlenUniversity of Victoria & TRIUMF

APS NW Section Meeting 2005Victoria, Canada

May 13, 2005May 13, 2005 The International Linear Collider / Dean Karlen, UVic & TRIUMFThe International Linear Collider / Dean Karlen, UVic & TRIUMF 22

The International Linear ColliderThe International Linear Collider Next in the line of eNext in the line of e++ee-- colliders at the high colliders at the high

energy frontier of particle physicsenergy frontier of particle physics

SLAC/SLC

CERN/LEP


year

1980 1990 2000 2010 2020 2030

Cen

tre-

of-m

ass

ener

gy (

GeV

)

100

1000PETRAPEPTRISTANSLCLEP - ILEP - IIILCILC - II

eeee colliders at the frontier colliders at the frontier

Z0 threshold

W+W threshold

tt thresholdHZ0 threshold?

dark matter threshold?


Why Linear?Why Linear?

Centre-of-mass Energy (GeV)

0 100 200 300 400 500 600

Circ

umfe

renc

e /

Leng

th (

km)

0

10

20

30

40

50

60

$

circular colliders

linear colliders

2ER

EL

A circular 500 GeVmachine would be170 km around andconsume 45 GW


““High Energy” Particle PhysicsHigh Energy” Particle Physics

Increasing the collision energy allows for new Increasing the collision energy allows for new fundamental processes to be observed and fundamental processes to be observed and probes matter and space at smaller distance probes matter and space at smaller distance scalesscales

The two main HEP tools in the past 3 decades: The two main HEP tools in the past 3 decades: proton colliders and electron collidersproton colliders and electron colliders protons are more easily accelerated to high energies protons are more easily accelerated to high energies

because they radiate less synchrotron radiation in a because they radiate less synchrotron radiation in a circular acceleratorcircular accelerator

electron interactions are more easily studied because electron interactions are more easily studied because the initial state is simplerthe initial state is simpler

both tools have been essential to advance our both tools have been essential to advance our knowledge of fundamental physics:knowledge of fundamental physics:

discoveries of new phenomenadiscoveries of new phenomena testing models that account for these phenomenatesting models that account for these phenomena


Interplay of proton and electron Interplay of proton and electron colliderscolliders

proton collidersproton colliders electron colliderselectron colliders1980’s: SppS• discovery of the Z0, W, W

1990’s: LEP/SLC• detailed investigation of Z0, W, W production• indirect influence of top quark – definitive prediction of its mass• indirect influence of Higgs boson – mass estimated

2010’s: ILC• detailed study of the Higgs• detailed study of dark matter

2000’s: LHC• discovery of the Higgs boson?• discovery of the dark matter particle?

1990’s: Tevatron• discovery of the top quark


Linear Collider Physics: ILinear Collider Physics: I The electromagnetic and weak forces are now The electromagnetic and weak forces are now

known to arise from a unifying symmetry in natureknown to arise from a unifying symmetry in nature This was most precisely demonstrated by the LEP/SLC This was most precisely demonstrated by the LEP/SLC

experimentsexperiments

The symmetry between the electromagnetic and The symmetry between the electromagnetic and weak forces is broken (weak bosons are heavy)weak forces is broken (weak bosons are heavy) The Higgs model is an ad hoc component of the Standard The Higgs model is an ad hoc component of the Standard

Model that describes why the symmetry is brokenModel that describes why the symmetry is broken

it seems to work for low energy processes but falls it seems to work for low energy processes but falls apart at high energiesapart at high energies

the model predicts that a new particle exists (the the model predicts that a new particle exists (the Higgs boson) with definite propertiesHiggs boson) with definite properties

the ILC will be able to make a large variety of precision the ILC will be able to make a large variety of precision measurements that will provide critical data to measurements that will provide critical data to understand the real nature of electroweak symmetry understand the real nature of electroweak symmetry breakingbreaking


The golden processesThe golden processes At LEP, the golden processes for studying At LEP, the golden processes for studying

the electroweak sector were:the electroweak sector were:

At the ILC, the golden processes for At the ILC, the golden processes for studying the Higgs sector are:studying the Higgs sector are:

LEP beam energies were not sufficiently high LEP beam energies were not sufficiently high enough for these process to occurenough for these process to occur

0Zee WWee

HZee 0

Hee


Higgs production at a LCHiggs production at a LC


Linear Collider Physics: IILinear Collider Physics: II

From astrophysical observations, it appears From astrophysical observations, it appears that ~25% of the Universe is “Dark Matter”that ~25% of the Universe is “Dark Matter” neutral, stable, cold (massive), non-baryonicneutral, stable, cold (massive), non-baryonic new physics – a new (conserved) quantum number?new physics – a new (conserved) quantum number? production and detection of dark matter particles at production and detection of dark matter particles at

future colliders would be very exciting!future colliders would be very exciting!

One possible explanation arises in a model of One possible explanation arises in a model of particle physics known as “supersymmetry”particle physics known as “supersymmetry” in this model, all particles have supersymmetric in this model, all particles have supersymmetric

partners (sparticles) – the lightest would be stablepartners (sparticles) – the lightest would be stable


Dark Matter at the ILC?Dark Matter at the ILC?

There are strong hints that the dark matter There are strong hints that the dark matter could be produced at the ILCcould be produced at the ILC Supersymmetric models generally favour sparticle Supersymmetric models generally favour sparticle

masses below ~ 1 TeVmasses below ~ 1 TeV The dark matter density is consistent with a The dark matter density is consistent with a

neutral particle having “weak” strength couplingsneutral particle having “weak” strength couplings The LHC has the best chance to discover the The LHC has the best chance to discover the

supersymmetric particlessupersymmetric particles the signature: a large amount of energy is taken the signature: a large amount of energy is taken

away by invisible particlesaway by invisible particles challenging study at LHC: initial state is not well challenging study at LHC: initial state is not well

known, final state involves at least two DM known, final state involves at least two DM particlesparticles

The ILC offers the ability to study them in The ILC offers the ability to study them in detaildetail


Consensus in the HEP communityConsensus in the HEP community

Given the broad range of fundamental Given the broad range of fundamental physics questions that it addresses, the physics questions that it addresses, the HEP community sees the ILC to be the HEP community sees the ILC to be the next step that is needed to advance the next step that is needed to advance the fieldfield over 2700 particle physicists have signed a over 2700 particle physicists have signed a

document supporting the physics potential of document supporting the physics potential of the ILCthe ILC

the US DOE places the ILC as the top priority the US DOE places the ILC as the top priority for mid-term new facilities for mid-term new facilities

committees for future accelerators in Asia and committees for future accelerators in Asia and Europe also put the ILC as their first priorityEurope also put the ILC as their first priority


Building the ILCBuilding the ILC

Over the past decade, significant effort has Over the past decade, significant effort has gone into the necessary R&D to design a gone into the necessary R&D to design a linear collider to reach the required linear collider to reach the required specifications:specifications:

Energy: 500 GeV – 1000 GeVEnergy: 500 GeV – 1000 GeV requires RF cavities with a large accelerating requires RF cavities with a large accelerating

gradient (>30 MeV/m)gradient (>30 MeV/m)

Luminosity (density of collisions): > 10Luminosity (density of collisions): > 103434 cm cmss

requires large numbers of electrons (> 10requires large numbers of electrons (> 101010) ) packed into very small bunches (< 500 x 5 nmpacked into very small bunches (< 500 x 5 nm22) ) brought into collision at high rate (> 10brought into collision at high rate (> 1044 s s))


Building the ILCBuilding the ILC

Two complete designs were prepared that Two complete designs were prepared that met these requirementsmet these requirements the key feature distinguishing them was the the key feature distinguishing them was the

nature of the RF accelerating cavities:nature of the RF accelerating cavities: US + Japan – high frequency, room US + Japan – high frequency, room

temperaturetemperature Germany – lower frequency, superconductingGermany – lower frequency, superconducting

international technical review found both suitableinternational technical review found both suitable

In 2004, an international committee charged In 2004, an international committee charged with selecting one accelerating technology with selecting one accelerating technology chose the superconducting optionchose the superconducting option the world’s labs now work toward a single designthe world’s labs now work toward a single design


Superconducting accelerator cavitiesSuperconducting accelerator cavities


Possible Tunnel LayoutPossible Tunnel Layout

Need a 30 km tunnel to reach energy goalNeed a 30 km tunnel to reach energy goal


Damping ring R&DDamping ring R&D

ATF facility in Japan hasATF facility in Japan hasdemonstrated necessarydemonstrated necessaryreduction in emittancereduction in emittance


Linear collider detector conceptsLinear collider detector concepts

LDC

SiD

GLD


Linear collider detector challengesLinear collider detector challenges Compared to the LHC, the ILC environment is Compared to the LHC, the ILC environment is

much less severe, but the performance much less severe, but the performance requirements are much more demanding:requirements are much more demanding:

Vertexing: Vertexing: ipip ~ 5 ~ 5 m m 10 10 m/(p sinm/(p sin3/23/2 )) 1/5 r1/5 rbeampipebeampipe, 1/30 pixel area, 1/30 thickness c.f. LHC, 1/30 pixel area, 1/30 thickness c.f. LHC

Tracking: Tracking: (1/p(1/ptt) ~ 5 ) ~ 5 ×10×10-5-5 GeV GeV-1-1

1/10 of LHC. 1/6 material in tracking volume1/10 of LHC. 1/6 material in tracking volume

Calorimetry: Calorimetry: EE ~ 0.3 ~ 0.3 EE 1/200 granularity of calorimeter c.f. LHC1/200 granularity of calorimeter c.f. LHC


Vertex detectorVertex detector Precise Si pixel detectors near the collision Precise Si pixel detectors near the collision

point point to detect the displaced vertex of particles to detect the displaced vertex of particles

coming from the decay of a particle with a very coming from the decay of a particle with a very short lifetime (less than 10short lifetime (less than 10 s) s)

examples: charm, bottom quarks, tau examples: charm, bottom quarks, tau leptonsleptons


Tracking detectorTracking detector


Tracking challengeTracking challenge Example: Higgs recoil massExample: Higgs recoil mass

(1/pt) ~ 5 ×10-5 GeV-1

is necessary!


Tracking technologyTracking technology Two technologies considered: Si (few Two technologies considered: Si (few

precise measuring layers) or gas precise measuring layers) or gas (continuous) (continuous)

Gas tracker: Time projection chamberGas tracker: Time projection chamber to achieve resolution goal requires an advance to achieve resolution goal requires an advance

in TPC technologyin TPC technology see talk by Gabesee talk by Gabe

Rosenbaum thisRosenbaum thisafternoon (B2)afternoon (B2)


CalorimeterCalorimeter


Jet Energy Resolution RequirementsJet Energy Resolution Requirements

Goal: distinguish W and Z when they decay into Goal: distinguish W and Z when they decay into quarksquarks requires excellent jet energy resolution, requires excellent jet energy resolution, EE ~ ~

30% 30% E E , ZZeeWWee example:

E%30E%60


Calorimeter technologyCalorimeter technology

To reach resolution goal requires narrow To reach resolution goal requires narrow showers and fine segmentation: Si + W showers and fine segmentation: Si + W

Iron Tungsten


Bringing the ILC into realityBringing the ILC into reality

An international structure has been set up An international structure has been set up to complete the global design of the ILCto complete the global design of the ILC Leader of the Global Design Effort: Barry BarishLeader of the Global Design Effort: Barry Barish

ILCSC

GlobalDesignEffort

Asia Regional Team

N. American Regional Team

EuropeanRegional Team

Participating Labsand Universities




ILC timescaleILC timescale 2005:2005:

GDE put togetherGDE put together Detector concept groups in formationDetector concept groups in formation

2006:2006: GDE to prepare the ILC Conceptual DesignGDE to prepare the ILC Conceptual Design Detector concept groups to prepare outlinesDetector concept groups to prepare outlines

2007/8:2007/8: GDE to complete the ILC Technical DesignGDE to complete the ILC Technical Design Detector concepts complete Conceptual DesignsDetector concepts complete Conceptual Designs

2008/9:2008/9: Site selection, government approvals, begin constructionSite selection, government approvals, begin construction Detector collaborations formDetector collaborations form

2015?:2015?: earliest start of experimental programearliest start of experimental program


SummarySummary The physics case for a Linear Collider is The physics case for a Linear Collider is

very compellingvery compelling

The technologies for the machine and the The technologies for the machine and the experiments are in handexperiments are in hand

The international HEP community is solidly The international HEP community is solidly behind the project and is working together behind the project and is working together to bring it to reality!to bring it to reality!

For more information see:For more information see:www.linearcollider.org www.linearcollider.cawww.linearcollider.org www.linearcollider.ca

Dean Karlen University of Victoria & TRIUMF APS NW Section Meeting 2005 Victoria, Canada.

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