MUON SUPERCOLLIDERS LECTURE

1
MUON SUPERCOLLIDERSLECTURE 3Advanced Study
Institute on Techniques and Concepts of High
Energy PhysicsSt. Croix, US Virgin Islands
June 13-24, 2002

• Gail G. Hanson
• University of California, Riverside

2
WHY MUON COLLIDERS?

• Muons are fundamental particles, so same
  advantage as ee- colliders
• ? Energy of interaction is full energy of
  particle, not of constituent quarks or gluons
  (factor 10)
• Synchrotron radiation by muons is less than for
  electrons by factor of (me/mm)4 6 ?10-10
• ? Energy lost by synchrotron radiation must be
  put back
• by rf power (cost of power for operation)
• ? Muon beam can have narrow energy spread
  (10-5)
• ? High energy collider can be much smaller!

3
COMPARISON OF HIGH ENERGY COLLIDERS
4
PHYSICS ISSUES

• Is there a light Higgs boson? Data suggests
  yes
• If only one light Higgs boson, crucial to measure
  properties - SM or SUSY?
• At muon collider, Higgs produced through
  s-channel
• Can measure CP properties of Higgs bosons through
  asymmetries with transversely polarized beams

5
LOW MASS HIGGS BOSON?
FITS TO PRECISION ELECTROWEAK DATA
6
LOW MASS HIGGS BOSON?
FITS TO PRECISION ELECTROWEAK DATA
7
SEARCH FOR STANDARD MODEL HIGGS BOSON
November 3, 2000, LEP Experiments Committee
(LEPC) presentation
2.9 s.d. incompatibility with background (1 -
CLb) 0.0042
8
EVENT WEIGHTS AT 115 GeV
9
SEARCH FOR STANDARD MODELHIGGS BOSON
Summer 2001 combination
Maximum likelihood ratio at mH 115.6 GeV.
Probability of background fluctuation 2.1 s.d.
10
SEARCH FOR STANDARD MODELHIGGS BOSON
Summer 2001 combination
1 - CLb 3.4
mH gt 114.1 GeV, 95 C.L. (115.4 GeV expected)
CLsb 44
11
SEARCH FOR STANDARD MODEL HIGGS BOSON
Now we will have to wait until 2007 to find out
from the LHC experiments, or possibly from the
Fermilab Tevatron, whether there really is a
Higgs boson at a mass of 115 GeV.
12
MUON ANOMALOUS MAGNETIC MOMENT
Recent results from BNL E821 gave a
measurement of (g-2)m ?to 1.3 ppm.
This result disagreed with the Standard Model
prediction by 2.6s.
However, a re-evaluation of the Standard Model
prediction exposed a sign error in the pion
pole contribution to the hadronic light-by-light
process, resulting in a disagreement by only
1.6s.
More data remain to be analyzed, and the
ultimate precision should be 0.4 ppm.
13
POSSIBLE IMPLICATIONS FOR SUPERSYMMETRY?

• Light Higgs boson (mh 120 GeV) indicates large
  value of tan b
• Disagreement (?) of muon anomalous magnetic
  moment (g-2)m with SM prediction also may
  indicate large tan b
• In decoupling limit, lighter Higgs boson h0 has
  couplings like SM Higgs, but heavier Higgses H0,
  A0 have non-SM couplings coupling to gauge
  bosons is suppressed
• For larger values of tan b there is a range of
  heavy Higgs boson masses (H0, A0) for which
  discovery at LHC or ee- linear collider is not
  possible
• Heavy Higgs bosons are largely degenerate in MSSM

14
LHC SENSITIVITY FOR DISCOVERY OF MSSM HIGGS
Muon collider?
15
DEGENERATE HEAVY HIGGS BOSONS
16
WHY MUON COLLIDERS? (Continued)

• The Higgs boson couples to mass, so cross
  section at s-channel Higgs pole is very large
  (Fig.)
• ? Small beam energy spread can allow measurement
  of mH to few hundred keV
• ? Direct measurement of Higgs width GH to 1
  MeV
• ? A Higgs Factory!

S-CHANNEL HIGGS PRODUCTION
(From T. Han, talk at FNAL, May 22, 1998)
17
A MUON COLLIDER AS A HIGGS FACTORY

• The CP properties of the Higgs bosons can be
  measured through asymmetries with transversely
  polarized m and m- beams.
• A Higgs factory muon collider is also a step
  towards a high energy (3-4 TeV) muon collider.

18
POSSIBLE HIGGS FACTORY SCHEMATIC

• Ring Cooler Higgs Factory
• One of the most crucial RD issues for a muon
  collider is cooling the muons - making the beam
  smaller in 6D phase space

19
CONVERTING A NEUTRINO FACTORY TO A HIGGS FACTORY
A muon collider requires the muon beams to be
cooled by several orders of magnitude compared
with a neutrino factory.
All the muons must be in one bunch.
20
HIGGS FACTORY PARAMETERS
21
HIGH ENERGY MUON COLLIDER PARAMETERS
22
COOLING
? 100 cooling needed in each transverse and in
longitudinal direction (106 in 6D emittance)
compared with ms from p decay.
23
EMITTANCE EXCHANGE
BUNCH STACKING
BENT SOLENOID
24
EMITTANCE EXCHANGE
BALBEKOV RING COOLER
25
EMITTANCE EXCHANGE
RFOFO RING COOLER (PALMER)
26
SUMMARY OF PROGRESS TOWARDS MUON COLLIDER COOLING

• Neutrino factory feasibility study simulations
  show cooling to eTN 2 pmm and eLN 30 pmm
  (bunched!)
• Ring Cooler cools ? 5 transverse, ? 2
  longitudinal
• Lithium lens (or other?) needed to cool ? 10
  to sub-mm in eTN

27
MUON COLLIDER DETECTORS
GEANT Simulation of a Higgs Factory Detector
Tungsten shielding from gs from showering es
from m decay
Background rates similar to LHC experiments
28
INTERNATIONAL MUON IONIZATION COOLING EXPERIMENT
(MICE)
Experimental demonstration of ionization cooling
- extend to emittance exchange
29
REFERENCES

• Charles M. Ankenbrandt et al. (Muon Collider
  Collaboration), Phys. Rev. ST Accel. Beams 2,
  081001 (1999).
• G. G. Hanson, Towards a Higgs Factory/Muon
  Collider, invited plenary talk at NuFACT01,
  Tsukuba, Japan, 2001.
• Higgs Factory Report, D. Cline and G. Hanson,
  eds., submitted to Snowmass 2001.
• The LEP Collaborations ALEPH, DELPHI, L3, OPAL,
  the LEP Electroweak Working Group, and the SLD
  Heavy Flavour Group, A Combination of Preliminary
  Electroweak Measurements and Constraints on the
  Standard Model, LEPEWWG/2002-01, May 2002.