Physics Opportunities and Experimental TechniquesPhysics Opportunities and Experimental Techniquesfor the Next Large Scale Facility in Accelerator Particle Physicsfor the Next Large Scale Facility in Accelerator Particle Physics

The International Linear ColliderThe International Linear Collider

Marco BattagliaUC Berkeley and LBNL

TASI, Boulder, June 2006

International e+e- Linear Collider

ILC highest priority for future major facility in HEPneeded to extend and complement LHC discoveries with accuracy which is crucial to understand nature of New Physics, test fundamental properties at high energy scale and establish their relation to Cosmology;

Technology decision promotes ILC towards next stage inaccelerator design definition, R&D and cost optimization:

Matching program of Physics studies and Detector R&D needed develop new accurate and cost effective detectortechniques from proof of concepts to a state of engineering readiness to be adopted in the ILC experiments.

Synergy of Hadron and Lepton Colliders

Synergy of Hadron and Lepton Colliders

Mass scale sensitivity vs. centre of mass energy

ILC Energy

Physics to define next thresholds beyond 100 GeV:

Top Quark pair production threshold:

Strong prejudice (supported bydata) on Higgs and New Physicsthresholds between EW scale and ~ 1 TeV:

ILC Energy in Perspective

Cosmotron (3.3 GeV), BNLBevatron (6.2 GeV), LBNL

Centre-of-Mass Energy vs. Year

as of 1992 as of 2000

?

we have fallen off the scaling predicted by Stanley Livingston’s curve.

Why Linear ?

?

Particles undergoing centripetal acceleration a=v2/R radiate at rate:

if R constant, energy loss is above rate x time spent in bending=2R/v

R

R

for e- (E in GeV, R in km)

for p(E in TeV, R in km)

Since energy transferred to beam per turn is constant: G x 2R x Fat each R there is a maximum energy Emax beyond which energyloss exceeds energy transferred, real limit set by dumped power;

Example: LEP ring (R=4.3 km) Ee=250 GeV W = 80 GeV/turn

Synchrotron Radiation

ILC Energy

Technology to define reachable energy:

Cold SC cavity technology chosen;Global Design Effort to produce costed Technical Proposal by end 2006CLIC technology being demonstratedby R&D CTF3 facility at CERN.

Major step towards construction of new HEP facility in August 2004:

Accelerator R&D reached maturity to assess technical feasibility and informed choice of most advantageous technology. ILC potential in future of scientific research praised by OECD. DOE Office of Science ranked ILC as top mid-term project.

ILC Baseline Design

9-cell 1.3GHz

TESLA Niobium Cavity

35 MV/m baseline gradient

2

0

$ lincryo

a Gb

G Q

ILC Baseline Design

Cavity Gradient Cavity Cost vs. Gradient

32 km44 km

51 km

Optimisation for 500 GeV ILCCost vs. Gradient

SC Cavity Gradient

TESLA Cavities 2005

LEP-2 Cavities 1999-2000

ILC Luminosity

Since cross section for s-channel processes scales as 1/s, luminosity must scale to preserve data statistics;

ILC Luminosity

Luminosity functional dependence on collider parameters:

Compared to circular colliders (LEP) frep and must be compensated by increasing the nb. of bunches (Nb) and reducing the transverse beam sizes (x, y);

Small beam size induces beam-beam interactions: self focusing and increase of beamstrahlung resulting in energy spread and degradedluminosity spectrum:

N = L x

ILC Luminosity Optimization

High Efficiency

High Beam Power

Parameter 0.5

TeV

1.0

TeV

Nb 2820 2820

y (nm) 5.7 3.5

BS 0.022 0.050

HD 1.7 1.5

PBS (W) 0.2 0.9

Large Beamstrahlung

Small vertical emittance and short bunch length

Parameter 0.5

TeV

1.0

TeV

G (MV/m) 30 30

L (1034 cm-2 s-1) 2.0 2.8

2.0 2.0

tb (ns) 307 307

ny 1.26 1.43

2005 2006 2007 2008 2009 2010

Global Design Effort Project

Baseline configuration

Reference Design

ILC R&D Program

Technical Design

Bids to Host; Site Selection;

International Mgmt

LHCPhysics

from B. Barish

ILC GDE : Plan and Schedule

CLICfeasibility

Three Main Physics Themes

• Solving the Mysteries of Matter at the TeraScale (= Higgs/SUSY/BSM);

• Determining what Dark Matter particles can be produced in the laboratories and

discovering their identities (=SUSY/ED);

• Connecting the Laws of the Large to the Laws of the Small (=EW/SUSY/ED)

ILC Physics Objectives

The Higgs Boson Profile at the ILC

Higgs Boson Production at ILC

MH (GeV)

(e+

e-

H)

(fb)

Model Independent Higgs Reconstruction

Associate H0Z0 production, with Z0 ll, allows to extract Higgs signal from recoil mass distribution, independent on H decay;

Analysis flavour blind and sensitiveto non-standard decay modes, suchas Hinvisible

Model Independent Higgs Reconstruction

H

Z

The Recoil Mass Technique

e+e- HZ

Ecm = EZ + EH

0 = pZ + pH

MH2 = EH

2 – pH2 =

= (Ecm-EZ)2 – pZ2 =

= Ecm2 + EZ

2 – EcmEZ – pZ = = Ecm

2 – 2EcmEZ + MZ2

Resolution on MH depends on knowledge of colliding beam energyand on lepton momentum resolution.

Yukawa couplings vs. fermion mass

Determining the Higgs Couplings

After discovery of a new boson at LHC, essential to verify that this new particle does indeed its job of providing gauge bosons andfermions with their masses;

ILC can perform fundamental test of scaling of Yukawa couplings with masses for Gauge bosons, quarks and leptons with accuracy matching theoretical predictions; Recent improvements in mb and mc determinations at B factoriesmake ILC measurements even more compelling.

Higgs Decay Branching Fractions vs. Higgs Mass

Determining the Higgs Couplings

Extract Higgs couplingsfrom decay branching fractions into fermions and gauge bosons and from production crosssections (controlled bygHZZ, and gHWW);

Strong dependence on(unknown) Higgs Boson mass.

Exc

lud

ed b

y L

EP

-2

Generation of Mass: the Gauge Sector

Ecm

TeV

MH

120

MH

140

MH

150

gHZZ/gHZZ 0.5 0.024 0.027 0.029

gHWW/gHWW 0.35 0.026 0.053 0.103

Determine HZZ coupling from Higgstrahlung cross section andHWW coupling from double-WW fusion and HWW branching ratio;

H also possible at colliderconsidered as ILC option;

The Jet Flavour Tagging Technique

Tag H hadronic decay products to separate b, c and g yields;

Jet flavour identification relies on distinctive topology and kinematics of heavy flavour decays;

H bb

The Jet Flavour Tagging Technique

Short lived particle with proper time has adecay distance l = c

B from H decay at 0.5 TeVmB = 5.2 GeV, c = 500 mEB = 0.7 x Ejet = 0.7 x 500/4 = 100 GeV<l> ~ 3.5 mm

b c g

<l> (mm) 3.5 1.3 ~ 0.

<Nsec> 5.1 2.7 ~ 0.

D from H decay at 0.5 TeVmD = 1.9 GeV, c ~ (123+311)/2 m<l> ~ 1.3 mm

Generation of Mass: the Quark Sector

Extract individual branching fractions from 3-parameter simultaneous fit:

gHbb/gHbb 0.006

gHcc/gHcc 0.060

gHgg/gHgg 0.041c-tag

b-tag

ccgg

bb

Coupling Accuracy forMH=120 GeV

Generation of Mass: the Lepton Sector

Ecm

TeV

MH

120 140 150

gH/gH0.5 0.027 0.050

gH/gH0.8 0.150

gH/gH3.0 0.035 0.060 0.11

Higgs decays intopairs identified by topology, multiplicity;

H as rare decay allows test of Yukawa coupling scaling with mass in leptonic sector;

Higgs Quantum Numbers

JPC numbers can be determined in model-independent way:

Threshold cross section rise and angular dependence of the Z boson production from longitudinal polarization at high energies allows to determine and to distinguish SM H0 boson from a CP-odd A0 boson and the ZZ backgroundas well as from a CP-violating mixture:

Observation of Hor H setsand ;

Determining the Higgs Potential

Fundamental test of Higgs potential shape through independent Determination of gHHH in double Higgs production

Opportunity unique to the ILC,LHC cannot access double HProduction and SLHC may haveonly marginal accuracy;

Determining the Higgs Potential

Experimental challenge: not only cross sections are tiny (< 1 fb), but need to discard HH production notsensitive to HHH vertex.

Double Higgstrahlung at 0.5 TeV Double WW Fusion at 1 TeV

HH Mass Decay Angle

pt/pt2 =

4 x 10-5

pt/pt2 =

8 x 10-5

pt/pt2 =

6 x 10-5

pt/pt2 =

2 x 10-5

Reconstructing the Higgs profilesets challenging requirements on vertexing, tracking and calorimetry:

E/E

BR(HWW)MH ee HHZ

E/EE/E

ee HZ X

Higgs Physics and Detector Response

The Higgs Profile and Physics beyond

In models with extended Higgs sector, such as SUSY, Higgs couplings get shifted w.r.t. SM predictions:

Precise BRs measurements determine the scale of extended sector:

The Higgs Profile and Physics beyond

Higgs/Radion mixing

In models with new particles mixing with the Higgs boson,branching fractions are modified,generally through the introduction of an additional (invisible) decaywidth;

Models of extra dimensions stabilised by the Radion are characterised by potentiallylarge changes to Higgs decayBranching fractions: