Barry Barish Czech Technical University 15-Nov-11

Future Lepton Collider 1

Barry BarishCzech Technical

University15-Nov-11

The Future of Accelerator Based Particle Physics

15-Nov-11 Czech Technical University

Path to higher energy

Collider History: Energy constantly increasing with timeo Hadron Collider at the

energy frontiero Lepton Collider for

precision physics

Consensus to build Linear Collider with Ecm > 500 GeV to complement LHC physics





Three Generations: Complementarity

DiscoveryOf

CharmParticles

and

3.1 GeV

Burt RichterNobel Prize

SPEAR at SLAC

First generation



Rich History of Discovery

DESY PETRA Collider

Second generation


Precision Measurements

CERN’s LEP Collider set the stage for

Terascale physics

0

2

4

6

10020 400

mH GeV

Excluded Preliminary

had =(5)

0.027610.00036

0.027470.00012

Without NuTeV

theory uncertainty

Winter 2003

• Reveal the origin of quark and lepton mass

• Produce dark matter in the laboratory

• Test exotic theories of space and time

Third generation




SPEAR

PETRA

LEP

EN

ER

GY

YEAR 2020+

1 Te

V ILC (or CLIC)

1970

1 Ge

V

Fourthgeneration?

Three Generations of Successful e+e- Colliders

The Energy Frontier



The next big accelerator: a lepton collider?

• Terascale science and how a lepton collider will complement the LHC?

• Electron-Positron: Why linear? What technology to employ?

• An option with muons?

• Designing the ILC -- a new paradigm in international collaboration.

• A thumbnail description of the ILC Reference Design and Cost?

• Present program and plans



Exploring the TerascaleThe Tools

• The LHC– It will lead the way and has large reach– Quark-quark, quark-gluon and gluon-gluon

collisions at 0.5 - 5 TeV– Broadband initial state

• The ILC– A second view with high precision– Electron-positron collisions with fixed energies,

adjustable between 0.1 and 1.0 TeV– Well defined initial state

• Together, these are our tools for the Terascale



Why e+e- Collisions?

• Elementary particles

• Well-defined

– energy

– angular momentum

• Uses full COM energy

• Produces particles democratically

• Can mostly fully reconstruct events



Comparison: ILC and LHC

ILC LHC

Beam Particle : Electron x Positron Proton x Proton

CMS Energy : 0.5 – 1 TeV 14 TeV

Luminosity Goal : 2 x 1034 /cm2/sec 1 x1034 /cm2/sec

Accelerator Type : Linear Circular Storage Rings

Technology : Supercond. RF Supercond. Magnet



LHC ILCe+ e– Z H Z e+ e–, H b …

Higgs event Simulation Comparison

b



Higgs Signal with LHC

Rare decay channel: BR~10-3

Projected signal and background after data cuts to optimize signal to background

Background large: S/B 1:20, but can estimate from non signal areas

CMS



Precision Higgs physics

Model-independent Studies

• mass

• absolute branching ratios

• total width

• spin

• top Yukawa coupling

• self coupling

Precision MeasurementsGarcia-Abia et al



Higgs Coupling-mass relation

ii vm

Remember - the Higgs is a Different!

• It is a zero spin particle that fills the vacuum

• It couples to mass; masses and decay rates are related



The linear collider will measure the spin of any Higgs it can produce by measuring the energy dependence from threshold

ILC: Is it really the Higgs ?

Measure the quantum numbers. The Higgs must have spin zero !



What can we learn from the Higgs?

Precision measurements of Higgs coupling

Higgs Coupling strength is proportional to Mass



e+e- : Studying the Higgsdetermine the

underlying model

SM 2HDM/MSSM

Yamashita et al Zivkovic et al



- Measure quantum numbers

- Is it MSSM, NMSSM, …?

- How is it broken?

ILC can answer these questions!

- tunable energy

- polarized beams

Supersymmetry at ILC

e+e- production crosssections



ILC Supersymmetry

Two methods to obtain absolute sparticle masses:

In the continuumKinematic Threshold:

Minimum and maximum determines masses of primary slepton and secondary neutralino/chargino

Determine SUSY parameters without model assumptions

Martyn

Freitas



• The abundance of the LSP as dark matter can be precisely calculated, if the mass and particle species are given.

• ILC can precisely measure the mass and the coupling of the LSP

• The Dark Matter density in the universe and in our Galaxy can be calculated.

The most attractive candidate for the dark matter is the lightest SUSY particle

Dark Matter CandidatesLSP



New space-time dimensions can be mapped by studying the emission of gravitons into the extra dimensions, together with a photon or jets emitted into the normal dimensions.

Linear collider

Direct production from extra dimensions ?



Possible TeV Scale Lepton Colliders

ILC < 1 TeVTechnically possible

~ 2020 +

QUADQUAD

POWER EXTRACTIONSTRUCTURE

BPM

ACCELERATINGSTRUCTURES

CLIC < 3 TeVFeasibility?

Longer timescaleMain beam – 1 A, 200 ns from 9 GeV to 1.5 TeV

Drive beam - 95 A, 300 nsfrom 2.4 GeV to 240 MeV

Muon Collider < 4 TeV

FEASIBILITY??Much longer timescale

Much R&D Needed• Neutrino Factory R&D +• bunch merging• much more cooling• etc

ILC

CLIC

Muon Collider



ILC Baseline DesignILC Baseline Design

250

250 Gev 250 Gev

e+ e- Linear ColliderEnergy 250 Gev x 250 GevLength 11 + 11 km# of RF units 560# of cryomodules 1680# of 9-cell cavities 145602 Detectors push-pull2e34 peak luminosity5 Hz rep rate, 1000 -> 6000 bunches per cycleIP spots sizes: x 350 – 620 nm; y 3.5 – 9.0 nm



RDR Design Parameters

Max. Center-of-mass energy 500 GeV

Peak Luminosity ~2x1034 1/cm2s

Beam Current 9.0 mA

Repetition rate 5 Hz

Average accelerating gradient 31.5 MV/m

Beam pulse length 0.95 ms

Total Site Length 31 km

Total AC Power Consumption ~230 MW


E ~ (E4 /m4 R)

Linear implies single passcost

Energy

CircularCollider Linear

ColliderR Synchrotron

Radiation

R

~ 200 GeV

< 5 nm vertical

• Low emittance (high brightness) machine optics• Contain emittance growth• Squeeze the beam as small as possible at collision point




ILC – Underlying Technology

• Room temperature copper structures

OR

• Superconducting RF cavities



SCRF Technology Recommendation

• The recommendation of ITRP was presented to ILCSC & ICFA on August 19, 2004 in a joint meeting

in Beijing. • This recommendation is made

with the understanding that we are recommending a technology, not a design. We expect the final design to be developed by a team drawn from the combined warm and cold linear collider communities, taking full advantage of the experience and expertise of both (from the Executive Summary). This led to the formation of the Global Design Effort (GDE)

ICFA unanimously endorsed the ITRP’s recommendation on August 20, 2004

Strong international interest in developing SCRF technology



main linacbunchcompressor

dampingring

source

pre-accelerator

collimation

final focus

IP

extraction& dump

KeV

few GeV

few GeVfew GeV

250-500 GeV

GDE -- Designing a Linear Collider

Superconducting RF Main Linac

Traveling wave structures• NC standing wave structures would have high Ohmic losses• => traveling wave structures

• RF ‘flows’ with group velocity vG along the structureinto a load at the structure exit

• Condition for acceleration: Δφ=d·ω/c (Δφ cell phase difference)• Shorter fill time Tfill= 1/vG dz - order <100 ns compared to ~ms for

SC RF

pulsed RFPowersource

d

RF load

particles “surf” the electromagnetic wave



CLIC (Compact Linear Collider)



QUAD

QUAD

POWER EXTRACTIONSTRUCTURE

BPM

ACCELERATINGSTRUCTURES

Drive beam - 95 A, 300 nsfrom 2.4 GeV to 240 MeV

Main beam – 1 A, 200 ns from 9 GeV to 1.5 TeV

Room Temperature RF

CLIC – in a nutshell

• CompactLinearCollider

• e+/e- colliderfor up to 3 TeV

• Luminosity 6·1034cm-2s-1 (3 TeV)

• Normal conducting RF accelerating structures

• Gradient 100 MV/m• RF frequency 12 GHz• Two beam acceleration principle for cost minimisation and efficiency• Many common points with ILC, similar elements, but different parameters



Test results

Accelerating structure developments

• Structures built from discs• Each cell damped by 4 radial

WGs• terminated by SiC RF loads• Higher order modes (HOM)

enter WG • Long-range wakefields

efficiently damped15-Nov-11 Czech Technical University


CLIC: Why 100 MV/m and 12 GHz ? • Optimisation - figure of merit:

– Luminosity per linac input power

• Structure limits: – RF breakdown – scaling

(Esurf<260MV/m , P/Cτ1/3 limited)– RF pulse heating (ΔT<56°K)

• Beam dynamics:– emittance preservation – wake

fields– Luminosity, bunch population,

bunch spacing– efficiency – total power

• take into account cost model

after > 60 * 106 structures:100 MV/m 12 GHz chosen,

previously 150 MV/m, 30 GHzA.Grudiev15-Nov-11

Czech Technical UniversityFuture Lepton Collider 33

Muon Collider A muon collider is an attractive multi-TeV lepton collider option, because muons do not radiate as readily as electrons (m / me ~ 207):- COMPACT Fits on laboratory site- MULTI-PASS ACCELERATION Cost Effective operation & construction- MULTIPASS COLLISIONS IN A RING (~1000 turns) Relaxed emittance requirements & hence relaxed tolerances- NARROW ENERGY SPREAD Precision scans, kinematic constraints- TWO DETECTORS (2 IPs)-Tbunch ~ 10 s … (e.g. 4 TeV collider) Lots of time for readout Backgrounds don’t pile up- (m/me)2 = ~40000 Enhanced s-channel rates for Higgs-like particles

A 4 TeV Muon Collider wouldfit on the Fermilab Site


Future Lepton Collider

Challenges

• Muons are produced as tertiary particles. To make enough of them requires a MW scale proton source & target facility.

• Muons decay everything must be done fast and we must deal with the decay electrons (& neutrinos for CM energies above ~3 TeV).

• Muons are born within a large phase-space. For a Muon Collider, it must be cooled by O(106) before they decay New cooling technique (ionization cooling) must be demonstrated, and it requires components with demanding performance

• After cooling, beams still have relatively large emittance.



MUON COLLIDER SCHEMATIC

Proton source: Example: upgraded PROJECT X (4 MW, 2±1 ns long bunches)

1021 muons per year that fit within the acceptance of an accelerator:N=6000 m//N=25 mm

√s = 3 TeV Circumference = 4.5kmL = 3×1034 cm-2s-1 /bunch = 2x1012

(p)/p = 0.1%N = 25 m, //N=70 mm* = 5mmRep Rate = 12Hz



Muon Collider cf. Neutrino Factory

NEUTRINOFACTORY

MUONCOLLIDER

In present MC baseline design, Front End is same as for NF(although the optimal initial coolers might ultimately be different)



Muon Collider: Ionization Cooling

TRANSVERSE COOLING: Muons lose energy by in material (dE/dx). Re-accelerate in longitudinal direction reduce transverse emittance. Coulomb scattering heats beam low Z absorber.

LONGITUDINAL COOLING: Mix transverse & longitudinal degrees of freedom during cooling. Can be done in helical solenoids.

FINAL COOLING: To get the smallest achievable transverse emittance, over-cool the longitudinal emittance, and then reduce transverse emittance letting the longitudinal phase space grow.

εt,

,N

(m

)

Liq. H2 Liq. H2 Liq. H2

RF RF

RF

liquid H

2solenoid

High Field (HTS) Solenoids

38

More detailabout optionsin R. Palmer’stalk



Muon Beam

Spectro-

meter

Cooling

section

Spectro-

meter

MICE – upstream beamline

- Tests short cooling section, in muon beam, measuring the muons before & after the cooling section. one at a time.

- Learn about cost, complexity, & engineeringissues associated with cooling channels.

-Vary RF, solenoid & absorber parameters & demonstrate ability to simulate response of muons

Muon Ionization Cooling Experiment (MICE)



Muon Collider Detectors

Unique to a Muon Collider are detector backgrounds from muon decay.

For TeV muon decays, the electron decay angles are O(10) mradians . Electrons typically stay inside beampipe for few meters. Hence decay electrons born within a few meters of the IP are benign.

Shielding strategy: sweep the electrons born further than ~6m from the IP into ~6m of shielding

40

Map of backgroundparticle densities in detector



International Linear Collider

ILC





ILC --- Deep Underground



LHC --- Superconducting Magnet



ILC - Superconducting RF Cryomodule


Future Lepton Collider 45Global Design Effort 45

Major R&D Goals for Technical Design

Accelerator Design and Integration (AD&I) • Studies of possible cost reduction designs and

strategies for consideration in a re-baseline in 2010

SCRF• High Gradient R&D - globally coordinated program to

demonstrate gradient by 2010 with 50%yield;

ATF-2 at KEK

• Demonstrate Fast Kicker performance and Final Focus Design

Electron Cloud Mitigation – (CesrTA)• Electron Cloud tests at Cornell to establish mitigation

and verify one damping ring is sufficient.



Proposed Design changes for TDR

RDR SB2009 • Single Tunnel for main linac

•Move positron source to end of linac ***

• Reduce number of bunches factor of two (lower power) **

• Reduce size of damping rings (3.2km)

• Integrate central region

•Single stage bunch compressor



The ILC SCRF Cavity

- Achieve high gradient (35MV/m); develop multiple vendors; make cost effective, etc

- Focus is on high gradient; production yields; cryogenic losses; radiation; system performance

Global Plan for ILC Gradient R&D

14-Nov-11 PAC - Prague

Global Design Effort 48

New baseline gradient:Vertical acceptance: 35 MV/m average, allowing ±20% spread (28-42 MV/m)Operational: 31.5 MV/m average, allowing ±20% spread (25-38 MV/m)

14-Nov-11 PAC - Prague

Global Design Effort 49

Cavity Gradient Milestone Achieved

2010Milestone

TDRGoal

• Toward TDR goal• Field emission;

mechanical polishing• Other progress





Test Facilities: FLASHSCRF accelerator tests



Example Experimental Results

• Flat gradient solution achieved– 4.5 mA beam

• Characterisation of solution by scanning beam current– model benchmarking

Beam Current (mA)1 2 3 4 5

Gra

dien

t cha

nge

over

400

us (%

)

0

-3

-5

+3

+5

Gradient Tilts vs Beam Current (ACC7)

Intended working

point

~2.5%



FLASH: Stability

• 15 consecutive studies shifts (120hrs), and with no downtime

• Time to restore 400us bunch-trains after beam-off studies: ~10mins

• Energy stability with beam loading over periods of hours: ~0.02%

• Individual cavity “tilts” equally stable

Energy stability over 3hrs with 4.5mA

~0.02% pk-pk

9 Feb 2011





Test Facilities: ATF-2large international collaboration

ATF2 Goals:

A. Achievement of 37nm beam size• A1) Demonstration of a new compact final focus system;

– proposed by P.Raimondi and A.Seryi in 2000,

• A2) Maintenance of the small beam size– (several hours at the FFTB/SLAC)

B. Control of the beam position• B1) Demonstration of beam orbit stabilization with nano-

meter precision at IP.– (The beam jitter at FFTB/SLAC was about 40nm.)

• B2) Establishment of beam jitter controlling technique• at nano-meter level with ILC-like beam





ATF2 – Beam size/stability and kicker tests

IP Shintake Monitor

Final Doublet



ATF / ATF2 After Earthquake?



See first reports in ILC Newsline 17-March-11Articles by Toshiaki Tauchi and Rika Takahashi



Test Facilities: Cesr-TA eCloudbroad accelerator applications



• Mitigating Electron Cloud

• Simulations – electrodes; coating and/or grooving vacuum pipe• Demonstration at CESR critical tests

eCloud R&D





CesrTA - Wiggler Observations

IWLC2010 - CERN, Geneva, Switzerland

0.002”radiusElectrode best performance



Field Region

Baseline Mitigation RecommendationAlternatives for

Further Investigation

Drift* TiN Coating Solenoid Windings NEG Coating

Dipole Grooves with TiN Coating

Antechambers for power loads and photoelectron control

R&D into the use of clearing electrodes.

Quadrupole*

TiN Coating R&D into the use of clearing electrodes or grooves with TiN coating

Wiggler Clearing Electrodes

Antechambers for power loads and photoelectron control

Grooves with TiN Coating

Proposed ILC Mitigation Scheme



Interaction Region

(old location)

Break point for push-pull disconnect

Provide reliable collisions of 5nm-small beams, with acceptable level of background, and be able to rapidly and efficiently exchange ~10kT detectors in a push-pull operation several times per year



Push – Pull Detector Concept

• Vibration stability will be one of the major criteria in eventual selection of a motion system design

Both detectors without platforms Both detectors with platforms



Detector Concepts Report



Detector Performance Goals







• ILC detector performance requirements and comparison to the LHC detectors:○ Inner vertex layer ~ 3-6 times closer to IP

○ Vertex pixel size ~ 30 times smaller

○ Vertex detector layer ~ 30 times thinner

Impact param resolution Δd = 5 [μm] + 10 [μm] / (p[GeV] sin 3/2θ)

○ Material in the tracker ~ 30 times less

○ Track momentum resolution ~ 10 times better

Momentum resolution Δp / p2 = 5 x 10-5 [GeV-1] central region

Δp / p2 = 3 x 10-5 [GeV-1] forward region

○ Granularity of EM calorimeter ~ 200 times better

Jet energy resolution ΔEjet / Ejet = 0.3 /√Ejet

Forward Hermeticity down to θ = 5-10 [mrad]


Final Reflections

• The energy frontier continues to be the primary tool to explore the central issues in particle physics

• The LHC at CERN will open the 1 TeV energy scale and we anticipate exciting new discoveries

• A companion lepton collider will be the logical next step, but such a machine has technical challenges and needs significant R&D and design now

• LHC results will inform the final design and even whether a higher energy options is needed, If so, this may also be possible, but on a longer time scale.


Documents

Barry Barish Czech Technical University 15-Nov-11