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The Linear Collider: a UK perspective. Grahame A. Blair Edinburgh, 8 th February 2006. Introduction to the machine Detectors UIK activities Timescales Some key Physics (time ?) Summary. Superconducting Niobium Cavities. Y. Kokoya, GDE Frascati 2005.

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The linear collider a uk perspective
The Linear Collider: a UK perspective

Grahame A. Blair

Edinburgh, 8th February 2006

  • Introduction to the machine

  • Detectors

  • UIK activities

  • Timescales

  • Some key Physics (time ?)

  • Summary

Generic linear collider

Damping Rings

Beam Delivery System

Main Linac (RF)

Particle Sources

Generic Linear Collider

< ~20 km >

< ~4 km >

DR Circumf. Baseline: 6km

The linear collider a uk perspective

A Possible Layout

  • Approximately follow earth’s curvature

  • Upgrade path to ~1 TeV

Lc for physics purposes
LC for Physics Purposes:

  • e+e- collisions with √s tuneable 0.5 – O(1) TeV

  • e-e- mode.

  • Polarisation: e- 80% (L/R); e+ 60% (?).

  • Possibility to run at √s ~ 90 – 160 GeV (“GigaZ”)

  • Luminosity 3-6.1034 cm-2 s-1  specific

    analyses can assume up to about 1 ab-1

Also possible/important; Compton scattering to

produce  or e

Bunch interactions
Bunch Interactions




  • Increase in luminosity (×~2)

  • Beamstrahlung  Lumi. Spectrum

Luminosity spectrum
Luminosity Spectrum

  • sharp peak

  • approx same as ISR (tuned) – few % in tail

  • for 0.5-1 TeV machines


The linear collider a uk perspective

Precision Measurement of the Top Mass

Precision measurement of fundamental particle properties

The top quark is the heaviest: most sensitive to new physics

Cross section


Mtop=175 GeV

100 fb-1 per point



~0.05 GeV



Martinez et al.

Initial state







Initial State

  • W-production suppressed

  • s-wave production of charginos ~  sharp threshold

  • Specific polarisations for specific couplings (eg SUSY)

  • s-wave production of selectrons ~  sharp threshold

  • Direct production of higgs

Worldwide lc studies
Worldwide LC Studies

Worldwide studies 2
Worldwide studies (2)

The detectors
The Detectors lc/wwstudy/concepts/

The linear collider a uk perspective

Number of IPs

• 2 IPs + 2 detectors is the baseline.

• The cost of 2nd IP (beamline + exp.hall) corresponds to the energy 14-19% of 500GeV (change of tunnel cost not included).

Caveats: Total cost estimation from 3 regions agree well but the cost of individual components scatter in wide ranges.

• This means 405-430 GeV LC with 2IP is comparable in cost

with 500GeV LC with 1 IP

It is possible that 1 IP will become the baseline –

The physics community needs to make its case clear

Adapted from Y. Kokoya, GDE Frascati 2005

The linear collider a uk perspective


  • Design philosophy

  • Aim for SiW calorimeter

  • with best possible resolution

  • Keep radius small to make this affordable

  • Compensate by high B-

  • field (5 T) and very precise tracking (Si)

  • Fast timing of Silicon to suppress background

The linear collider a uk perspective


  • Design philosophy

  • Fine resolution calorimeter for particle

  • flow

  • Gaseous tracking for

  • High tracking efficiency

  • and redundancy

  • Large enough radius

  • and high enough B-field

  • (B=4 T) to get required

  • momentum resolution

The linear collider a uk perspective


  • Design philosophy

  • Large radius for particle-flow optimisation

  • Gaseous tracking for

  • High tracking efficiency

  • and redundancy

  • Fine grained scintillator-tungsten calorimeter

  • Moderate B-field (3 T)

The linear collider a uk perspective

Energy Flow in Jets

Some processes where WW and ZZ need to be separated without beam constraints.

Requires ΔE/E~30%/E

Particle machine physics
Particle/Machine Physics

  • The LC will be a very challenging machine

  • Particle physicists are taking part in machine studies

  • Beam diagnostics and control

  • Background estimates

  • Design studies

  • The particle physics programme now goes beyond “what comes out of the IP”.

Uk funding for accelerator science for particle physics 2004 2007
UK funding for accelerator science for particle physics 2004 - 2007

UK funding agency, PPARC, secured from Govt. £11M for ‘accelerator science’ for particle physics, spend period April 04 – March 07

Called for bids from universities and national labs; large consortia were explicitly encouraged

LC-Beam Delivery £9.1M + 1.5M CCLRC

UKNF £1.9M

2 university-based accelerator institutes:

John Adams: Oxford/RHUL

Cockroft: Liverpool, Manchester, Lancaster, NW dev. agency.

Funding period ends in 2007; new bid will be finalised in July 2006.

Lc abd collaboration
LC-ABD - 2007Collaboration

  • Bristol

  • Birmingham

  • Cambridge

  • Dundee

  • Durham

  • Lancaster

  • Liverpool

  • Manchester

  • Oxford

  • QMUL

  • RHUL

  • University College, London

  • Daresbury and

    Rutherford-Appleton Labs;

    41 post-doctoral physicists (faculty, staff, research associates)

    + technical staff + graduate students

Uk interests beam delivery system
UK Interests: - 2007Beam Delivery System

Beam delivery system

~3km - 2007

Beam Delivery System

  • Full simulations

  • Backgrounds

  • Optimisation

  • Precision Diagnostics

  • Energy

  • Polarisation

  • Luminosity

The linear collider a uk perspective

2 mrad Optics Design - 2007

  • Final Focus and extraction line optimized simultaneously

  • Quadrupoles and sextupoles in the FD optimized to

    • cancel FF chromaticity

    • focus the extracted beam

SLAC-BNL-UK-France Task Group

O.Napoly, 1997


pocket coil quad : C. Spencer

D. Angal-Kalinin

BDSIM - 2007

Beamlines are built

of modular



Full simulation

of em showers

All secondaries


Screenshot of an IR Design in BDSIM

Bds muon trajectories
BDS: Muon Trajectories - 2007

Concrete tunnel 2m radius


View from top

Multi seed luminosity studies with the ilc simulation model
Multi-Seed Luminosity Studies with the ILC Simulation Model - 2007

LUMI Feedback Optimisation (Position + Angle)

350 GeV CME

ANG + IP Fast Feedback

500 GeV CME

G. White

Font3 installation on atf beamline
FONT3 installation on ATF beamline - 2007

BPM processor board



Amplifier/FB board

ATF beamline installation

June 05

P. Burrows

Bunch bunch interaction simulations
Bunch-Bunch Interaction Simulations - 2007

TESLA parameters


low Q parameters


Before interaction

During interaction

After interaction

Laserwire petra
Laserwire - PETRA - 2007



System recently upgraded

Atf lw vacuum chamber
ATF-LW Vacuum Chamber - 2007

Built at


DO +





Superconducting helical undulator
Superconducting Helical Undulator - 2007


Superconducting bifilar helix

First (20 period) prototype constructed (RAL)

Cut-away showing winding geometry

The linear collider a uk perspective

Wakefields - 2007

Change in beamline aperture


  • Wake-fields from the head of the bunch can disturb the tail

  • Wake-fields from earlier bunches can disturb later ones

  • (such effects can also be useful – eg. Smith-Purcell radiation)

Wakefield box
Wakefield box - 2007


ESA sz ~ 300mm – ILC nominal

sy ~ 100mm (Frank/Deepa design)

Magnet mover, y range = 1.4mm, precision = 1mm

N. Watson

The linear collider a uk perspective

38 mm - 2007

h=38 mm

L=1000 mm


r=1/2 gap

As per last set in Sector 2, commissioning

Extend last set, smaller r, resistive WF in Cu


cf. same r, tapered

Overview of lc projects
Overview of LC Projects - 2007

Essentially independent of Linac-technology

The gde plan and schedule

2005 2006 2007 2008 2009 2010

Global Design Effort


Baseline configuration

Reference Design


The GDE Plan and Schedule

Technical Design

globally coordinated

regionial coord

ILC R&D Program

expression of interest



sample sites


International Mgmt


Machine summary
Machine Summary 2010

  • The ILC is now being defined.

  • The Baseline is under “Configuration Control”

  • Global Design Effort is in place, with a very active programme aiming at a Reference Design Report at end of 2006.

  • UK is involved in two detector projects and an exciting range of accelerator R&D.

  • The next round of accelerator-related bids are due for this summer.

     a great time to get involved.

Higgs production
Higgs Production 2010

For Mh~120 GeV,

500 fb-1, √s=350 GeV

80,000 Higgs


Higgs spin
Higgs Spin 2010

  • Threshold

  • excitation

  • curve

  • determine



20 fb-1 per point

Higgs mass
Higgs Mass 2010

mh=120 GeV


mh=150 GeV

500 fb-1 at √s=350 GeV

Higgs recoil mass



Higgs Recoil Mass



Etot= 2 Ebeam

Ptot = 0

500 fb-1, √s=350 GeV


Higgs mass precision
Higgs Mass Precision 2010

500 fb-1, √s=350 GeV

Higgs branching ratios
Higgs Branching Ratios 2010

For mh=120 GeV


Higgs potential
Higgs Potential 2010

λ/λ=0.22 (statistical) for mh=120 GeV

Requires 1000 fb-1

Muehleittner et al.

Supersymmetry 2010

To prove existence of SUSY:

  • Need to discover the SUSY partners

  • Every SM has a superpartner

  • Spins of SM/SUSY partner differ by ½

  • Identical gauge quantum numbers

  • Identical couplings

Needs accurate measurements of

Mass spectra, cross-sections, BRs,

Angular distributions, polarisation

Susy reference points

√s=1TeV 2010

√s=500 GeV

Higgs gauginos sleptons squarks

SUSY Reference Points

Work with Sugra SPS1a:

M1/2=250 GeV M0=100 GeV

A0=-100 GeV sign()=+ tan=10

Mass measurements

100 fb 2010-1

Mass Measurements

Threshold scans

chargino ~ 

slepton ~ 3

Martyn et al.

Endpoint measurements
Endpoint Measurements 2010

√s=400 GeV

L=200 fb-1

 Both

sparticle masses


E e running
e 2010-e- running

Including width effects

m~50 MeV for 4 fb-1

Freitas, Miller, Zerwas

Feng, Peskin

Luminosity budget
Luminosity Budget 2010

Grannis et al.

  • Several running modes required.

  • Input will already exist from LHC

Model independent extrapolation
Model-Independent Extrapolation 2010

Renormalisation Group Eqns

  • Measure complete spectrum

  • Extract soft SUSY parameters at EW scale

  • Input measured masses, couplings into RGEs

  • Extrapolate model independently to high scales

Extrapolation gaugino
Extrapolation: gaugino 2010



Porod, Zerwas, GB

Extrapolations mass terms

M 2010i2

Q (GeV)

Extrapolations mass terms




Fine structure?

GigaZ 2010

  • The LC can also provide high luminosity running at the Z-pole and at W-threshold

  • Approximately 100 fb-1 per year

  • Needs specific linac bypass design


Concrete example point b of updated benchmark points msugra w tan 10 sgn 1 m 0 57 m 1 2 250 a 0 0
Concrete example - point B’ of “updated benchmark” points:mSUGRA w/ tan = 10, sgn()=+1, m0=57, m1/2=250, A0=0






Trodden, Birkedal

LCWS04 (Adapted)

Physics summary
Physics Summary points:

  • The linear collider will provide high precision measurements at high energy: Masses, chiral couplings, branching ratios…

  • Together with LHC data, LC allows model-independent extrapolations to very high energy scales.

  • Exciting overlap with LHC analyses complementary searches, constraints in cascades… see G.W talk

  • Links to cosmology

  • Long term programme from O(1) TeV, GigaZ, , multi TeV.

  • An exciting time ahead!