The Energy Frontier and a Lepton Collider Barry Barish Caltech Neutrino Oscillations in Venice 13-April-08

The Energy Frontier and a Lepton Collider

Barry BarishCaltech

Neutrino Oscillations in Venice13-April-08

11-Feb-08 Harvard Colloquium

The International Linear Collider 2

Answering the Questions

Three Complementary Probes + …

• Neutrinos as a Probe– Particle physics and astrophysics using a weakly

interacting probe

• High Energy Proton Proton Colliders– Opening up a new energy frontier ( ~ 1 TeV scale)

• High Energy Electron Positron Colliders– Precision Physics at the new energy frontier

• Increasing connections to Astrophysics/Cosmology



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



Three Generations of e+e- CollidersThe Energy Frontier

FourthGeneration?

SPEAR

PETRA

LEP

EN

ER

GY

YEAR 2020

1 Te

V

ILC

1970

1 Ge

V



Possible TeV Scale Lepton Colliders

ILC < 1 TeVTechnically possible

~ 2019

QUADQUAD

POWER EXTRACTIONSTRUCTURE

BPM

ACCELERATINGSTRUCTURES

CLIC < 3 TeVFeasibility?

ILC + 5-10 yrsMain 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??ILC + 15 yrs?

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

ILC

CLIC

Muon Collider



Why e+e- Collisions ?

• Elementary particles

• Well-defined

– energy,

– angular momentum

• Uses full COM energy

• Produces particles democratically

• Can mostly fully reconstruct events



LHC: Low mass Higgs: H MH < 150 GeV/c2

Rare decay channel: BR ~ 10-3

Requires excellent electromagnetic calorimeter performance

acceptance, energy and angle resolution,

g/jet and g/p0 separation Motivation for LAr/PbWO4

calorimeters for CMS

Resolution at 100 GeV: 1 GeV

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

CMS



ILC: Precision Higgs physics

Model-independent Studies

• mass

• absolute branching ratios

• total width

• spin

• top Yukawa coupling

• self coupling

Precision MeasurementsGarcia-Abia et al



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

How do you know you have discovered 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



Top Quark Measurements

Bounds on axial ttbarZ and left handed tbW for LHC and ILC compared to deviations in various models



- 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



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

?



– E ~ (E4 /m4 R)– Cost ~ a R + b E

~ a R + b (E4 /m4 R)– Optimization : R ~ E2 Cost ~ c E2

• Circular Machine

Why Linear?cost

Energy

CircularCollider Linear

Collider

– Cost (linear) ~ a L – where L ~ E

R

m,E

SynchrotronRadiation

R

~ 200 GeV



Parameters for the ILC

• Ecm adjustable from 200 – 500 GeV

• Luminosity ∫Ldt = 500 fb-1 in 4 years

• Ability to scan between 200 and 500 GeV

• Energy stability and precision below 0.1%

• Electron polarization of at least 80%

• The machine must be upgradeable to 1 TeV



ILC – Underlying Technology

• Room temperature copper structures

OR

• Superconducting RF cavities



Superconducting RF Technology

• Forward looking technology for the next generation of particle accelerators: particle physics; nuclear physics; materials; medicine

• The ILC R&D is leading the way Superconducting RF technology– high gradients; low noise; precision optics



main linacbunchcompressor

dampingring

source

pre-accelerator

collimation

final focus

IP

extraction& dump

KeV

few GeV

few GeVfew GeV

250-500 GeV

Designing a Linear Collider

Superconducting RF Main Linac



Luminosity & Beam Size

• frep * nb tends to be low in a linear collider

• Achieve luminosity with spot size and bunch charge

Dyx

repb HfNn

L

2

2

L frep [Hz] nb N [1010] x [mm] y [mm]

ILC 2x1034 5 3000 2 0.5 0.005

SLC 2x1030 120 1 4 1.5 0.5

LEP2 5x1031 10,000 8 30 240 4

PEP-II 1x1034 140,000 1700 6 155 4



• Low emittance machine optics• Contain emittance growth• Squeeze the beam as small as possible

Achieving High Luminosity

~ 5 nmInteraction Point (IP)

e- e+



– 11km SC linacs operating at 31.5 MV/m for 500 GeV– Centralized injector

• Circular damping rings for electrons and positrons

• Undulator-based positron source

– Single IR with 14 mrad crossing angle– Dual tunnel configuration for safety and availability

ILC Reference Design

Reference Design – Feb 2007

Documented in Reference Design Report



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



RDR Complete

• Reference Design Report (4 volumes)

ExecutiveSummary

Physicsat theILC

AcceleratorDetectors



US/UK Funding and Future Prospects

• UK ILC R&D Program– About 40 FTEs. Leadership roles in Damping Rings and

Positron Source, as well as in the Beam Delivery System and Beam Dumps.

– All of this program is generic accelerator R&D, some of which will be continued outside the specific ILC project.

• US Program– ILC R&D was basically terminated for FY08, but a reduced

level ($42M FY07 ~$35M) program proposed for FY09.

– Presently a broad based U.S. program. Future??

– Generic SCRF also terminated in FY08, but expected to be restored in FY09: broad applications (e.g. Project X at Fermilab; fulure particle accelerators). Primary focus is to build US SCRF capability ($25M proposed for FY09)



The Context

• THE SCIENCE !!!– Nothing has changed. A linear collider remains the consensus

choice as the highest priority long term investment for particle physics

• The Technology– Key technical, design & cost issues must be resolved before a

serious project could be proposed

• Increased Coordination with CERN CLIC R&D Program– A program to work together on areas of mutual interest was

initiated last fall, before the funding problems. – Major areas of cooperative work identified in February

• Conventional Facilities -- Civil, Cooling, Industry, etc• Non main linac technology – Particle sources, beam delivery• Detectors and simulations



Technical Design Phase 1 -- 2010

• Technical risk reduction:– Gradient

• Results based on re-processed cavities• Reduced number 540 390 (reduced US program)

– Electron Cloud (CesrTA)

• Cost risks (reductions) – Main Cost Drivers– Conventional Facilities (water, etc)– Main Linac Technology

• Technical progress (global design)– Cryomodule baseline design is a being developed (e.g.

plug compatible parts)



Technical Design Phase 2 - 2012

• RF unit test – 3 CM + beam (KEK)

• Complete the technical design and R&D needed for project proposal (exceptions*)– Documented design– Complete and reliable cost roll up

• Project plan developed by consensus– Cryomodule Global Manufacturing Scenario– Siting Plan or Process

ILC – Global Design Phase

2005 2006 2007 2008 2009 2010 2012 ?????

Global Design Effort

Baseline configuration

Reference Design

R&D Program

Technical Design

Siting Studies

International Mgmt

LHCPhysics

Omnibus

Omnibus

Project



ILC Reference Design and Plan

Producing Cavities

Cavity Shape

Obtaining Gradient



Cavity Gradient – Results

KEK single cell results:2005 – just learning2006 – standard recipe2007 – add final 3 μm fresh acid EPNote: multi-cells are harder than singles

2005

2007

2006



Superconducting RF Cryomodule



ILC Reference Design and Plan

Making Positrons6km Damping Ring

10MW Klystrons

Beam Delivery and Interaction Point



Electron cloud – Goal

• Ensure the e- cloud won’t blow up the e+ beam emittance.– Do simulations (cheap)– Test vacuum pipe coatings, grooved

chambers, and clearing electrodes effect on e- cloud buildup

– Do above in ILC style wigglers with low emittance beam to minimize the extrapolation to the ILC.



E Cloud – Results

SLAC



~30 km long tunnel

Particle Detector

Main Research Center

Two tunnels • accelerator units• other for services - RF power

Linear Collider Facility



Conventional Facilities

72.5 km tunnels ~ 100-150 meters underground

13 major shafts > 9 meter diameter

443 K cu. m. underground excavation: caverns, alcoves, halls

92 surface “buildings”, 52.7 K sq. meters = 567 K sq-ft



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]



detectorB

may be accessible during run

accessible during run Platform for electronic and

services (~10*8*8m). Shielded (~0.5m of concrete) from five sides. Moves with detector. Also provide vibration isolation.

Concept of IR hall with two detectors

The concept is evolving and details being worked out

detectorA



Conclusions

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

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

• A companion lepton collider appears to 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

The Energy Frontier and a Lepton Collider Barry Barish Caltech Neutrino Oscillations in Venice 13-April-08