win'05, june 7 2005a. klier - muon collider physics1 physics at a future muon collider amit...

WIN'05, June 7 2005 A. Klier - Muon Collider Physics 1

Physics at a FutureMuon Collider

Amit Klier

University of California, Riverside

WIN’05 – Delphi, Greece – June 2005


OUTLINE

Why muon colliders?– Advantages– Problems

Some physics– Light Higgs Factory– Heavy Higgs

Toward a muon collider– Recent advances in 6-D Cooling R&D


Why Muons?

As fundamental as electrons…– Unlike p, p, all the collision energy is useful

…and 200 times as heavySync. radiation energy loss is 2 billion times less:

– Compact storage rings up to a few TeV– Very good energy resolution

Coupling to the Higgs boson is 40,000 times greater:

– Produce Higgs Bosons via the s-channel


Muon Colliders, Other Machines


The Problem with Muons

They DECAY: muon lifetime = 2.2 sEverything has to be fast, specifically:– Cooling (ionization)– Acceleration (RLA, FFAG)

Muon Collider detectors need shielding against ’s from decay electrons

Decay neutrinos can be harmful at E≳4 TeV(they can be useful for a Neutrino Factory, but that’s for another talk)


Some Physics


Light Higgs Boson

Precision EW data seem to favor light SM Higgs Boson

So does SUSY

(from theory)


SM (or SM-like) Higgs Factory

Higgs Boson width – few MeV for mhSM

<160 GeV Fine scan for E ≲hSM

Use spin precession for in situ energy determination to ~1 ppm

Luminosity is compromised by resolution, e.g. R=0.003% Lyear~ 0.1 fb-1

R=0.01% Lyear~ 0.22 fb-1

R=0.1% Lyear~ 1.0 fb-1

( R≡2E/E )


Precision Measurements

For a SM-like ~110-GeV Higgs Boson, a muon collider Higgs Factory can measure the mass to an uncertainty of ~10-6 with L=0.2 fb-1 (compared to ~10-4 at a 500 GeV, 500 fb-1 LC and ~10-3 at the LHC)

Only in the s-channel h can be measured directly (otherwise need accurate WW* rate measurement, difficult at mh<120 GeV)

Precise measurement of the cross section of +-h0bb – independent of mb


Heavy Higgs Bosons

SUSY H0 and A0 may be observed at the LHC Light h0 indicate high tan, which implies

greater H0-A0 mass degeneracy Muon g-2 results also favor high tan values

(≳8), with similar consequences An “intermediate energy” (few hundred GeV)

muon collider can be used to scan the the heavy Higgs mass range & separate the two


Separating the Heavy Higgses


Another Scenario

For some values of tan (~8-10) and mA (≳250 GeV) LHC/LC may not be able to observe H0 or A0

A muon collider may be needed to discover the heavy Higgs in this region


CP Violation in the Higgs Sector

Polarized muon beams can be used to measure CP violation in the Higgs sector


R&D Advances


Toward a Muon Collider

The physics part of this talk is mostly based on Snowmass 2001 (and earlier) results. That’s “old news”

Muon Collaboration attention has shifted to the (seemingly more feasible, and probably as important) neutrino factory

This shouldn’t have affected the Muon Collider R&D effort…

Indeed, impressive advances were made, especially in simulating 6-D cooling


How To Build a Muon Collider

p ± ±

targetproton driver(a few MW)

proton linac

pion decay

muon cooling

muon acceleration(up to 0.1 - 3 TeV) detectorstorage

ring

+

-


How Much Cooling is Needed

Beam reduction of about 100 needed in each transverse and in the longitudinal direction (~106 6-D cooling) compared with muons from pion decay

Light Higgs Factory


Ionization cooling:Fast, but cools only intransverse directions

(sufficient for factory) 6-D cooling via emittance exchange:

Repeated cooling/emittance exchangecools beam in all sixphase-space dimensions

6-D Coolingabsorber

RF RF

absorber

largeangularspread

smallangularspread


Ring Coolers

First suggested by V.Balbekov in 2001

6-D cooling – about 50

However: Problems trying to

introduce realistic magnetic fields

Injection/extraction very difficult and affects performance badly


The RFOFO Ring

Suggested by R.Palmer in 2002

6-D cooling ~ 300 Simulations work with

realistic magnetic field Injection/extraction still

a problem, but performance is less affected (still cools by about 200)


Gas-Filled Cooling Ring

The idea: use the dipole volume itself as a “wedge absorber” by filling it with high-pressure H2 gas

Small Dipole Ring – suggested by A.Garren, H.Kirk in 2004

Can be used to demonstrate 6D cooling experimentally: moderate performance, but low cost (no SC…)

1.6 m


Further Cooling – Lithium Lens

Recently simulated transverse cooling down to ~0.3 mm

But longitudinal emittance blows up

Latest development use bent Lithium Lenses (“ Li ring”)


Helical Cooling Channel

Suggested by Y.Derbenev/Muons Inc.

High-pressure-H2-filled helical dipole & RF cavities in a solenoid

Simulated cooling: 300 Advantage: no need for

injection/kicker Challenges: high dipole

fields, rather complicated


Parametric Resonance Cooling

Suggested by Y.Derbenev & Muons Inc.

Potential cooling 10 after the HCC/ Ring Cooler


Reversed Emittance Exchange

For TeV-scale muon colliders, longitudinal cooling is sufficient, but more transverse cooling is needed

Reverse the emittance exchange process


Conclusions

Muon colliders can contribute to Higgs physics in unique ways, complement LHC/LC

Being compact, muon colliders may eventually cost less than the “conventional” ones (LHC/LC), but are extremely challenging

A lot of progress in 6-D cooling simulations Greater effort is needed to put everything

together, demonstrate 6-D cooling in real life

win'05, june 7 2005a. klier - muon collider physics1 physics at a future muon collider amit...

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