Transcript International Muon Ionization Cooling Experiment Physics Motivation and Cooling Introduction Edward McKigney Imperial College RAL March 25, 2002

International Muon Ionization
Cooling Experiment
Physics Motivation and Cooling Introduction
Edward McKigney
Imperial College
RAL
March 25, 2002
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Physics Motivation
Neutrino Factory Layout
Feasibility Studies
Overview of Muon Cooling
Approaches to Cooling
Cooling Experiment Issues
Summary
Physics at a Neutrino Factory Complex I
Long baseline Neutrino oscillations: precision measurements of mixing parameters,
matter effects, CP violation!
Short baseline High brilliance neutrino beams, nuclear effects, polarized structure
functions, charm factory
High intensity proton source Unstable isotope beams and other synergies with nuclear physics
High brilliance muon beams Rare muon decays, muonic atoms, ...
R&DFirst step towards a muon collider: s-channel Higgs and Susy Higgs
production, high precision/resolution Ecm for new particle studies
Physics at a Neutrino Factory Complex II
Most fundamental particle physics discovery of the
decade: Neutrinos have mass and mix!
As in the quark sector, there
are three mixing angles
and a phase to measure,
but
the pattern of angles is very
different,
and
MNS Matrix (LMA)
(heavily mixed)
12  20-45°
23  35-45°
13 < 10°
CKM Matrix
(almost diagonal)
12  12.8°
23  2.2°
13  0.4°
2
 m32
 3  103 eV 2
the mass hierarchy needs to
be resolved.
m 221  O 10 4  eV 2
m22
m12
m32
Natural
m22
m12
Inverted
m32
Physics at a Neutrino Factory Complex III
2
P e     sin 2  23 sin 2 213 sin 2 (1.267m32
L/E )
2
P e    cos2  23 sin 2 213 sin 2 (1.267m32
L/E )
2
P     cos4 13 sin 2 2 23 sin 2 (1.267m32
L/E )
L=baseline (km)
E=energy (GeV)
A high energy e beam offers unique possibilities!
Gives best
sensitivity to
13 of any
technique:
A neutrino factory gives the best precision for measuring all of the neutrino mixing parameters!
Physics at a Neutrino Factory Complex IV
Comparing  e   , e   gives both sgn(m232) and CP phase:
A CP 
P e      P e    
P e      P e    


2
4 sin 212  sin   sin 2 m12
L/4E

sin 13
Physics at a Neutrino Factory Complex V
There is a rich program of non-oscillation physics at
a Neutrino Factory Complex
• High rate neutrino DIS with both polarized and unpolarized
targets
• Measurement of charm production and search for CP
violation in the D0 system (perhaps 1 million charm events
per year in a small near detector)
• Measurement of Ds branching ratios
and more ideas being developed…
Neutrino Factory Layout
There are several designs (CERN, US Study I and II, RAL) which all share
common features. This is the only way to produce high energy intense e beams.
Neutrino Factory Layout at RAL
You
Are
Here
Kamiokande
US Neutrino Factory Feasibility Studies
Two feasibility studies have been completed in the US, establishing:
that a neutrino factory is technically feasible
likely performance, cost, cost drivers and needed R&D
Both studies include cooling
Need for Muon Cooling
Need ~0.1 /p-on-target to reach Neutrino Factory flux goal
Must accept a large fraction of production phase space –
therefore must cool the muon beam
In current studies, cooling  X ~10 in accelerated muon flux
Only ionization cooling is fast enough to cool muons before most decay
The Neutrino Factory cooling program is the first step toward beams cold enough
to be used in a Muon Collider
Ionization cooling has never been observed experimentally and
studies show it is a delicate design and engineering problem
Need an Ionization Cooling Experimental demonstration!
Ionization Cooling: Background
RF dE/dx RF
dE/dx
RF dE/dx
Absorbers remove total momentum,
RF restores longitudinal momentum
d n
1 dE   n
1  0.014
 2
 3 
ds

ds E   2E  m  X 0
Approximation of the cooling relation
2
In principle ionization cooling should
work, but in practice it is subtle and complicated
Simplest Conceptual Scheme
But, there is an important subtlety: One must alternate the direction of
the focusing field in order to prevent a build-up of angular momentum
Tapered-SFOFO Cooling Lattice:
(R. Palmer – BNL)
CERN Cooling Channel Design
(A. Lombardi, CERN, Neutrino Factory Note NF-34)
Another Approach: Ring Cooler
Simulations show cooling in both the transverse and longitudinal planes
It is not known how to inject and extract the beam from this
configuration
A successful ring cooler design could give a Neutrino Factory higher
performance at lower cost.
Tapered-SFOFO Cooling Performance
Cooling Experiment
The aims of the muon ionization cooling experiment are:
• to show that it is possible to design, engineer and build a section of
cooling channel capable of giving the desired performance for a
Neutrino Factory
• to place it in a muon beam and measure its performance in a variety of
modes of operation and beam conditions
• to validate the cooling simulations
As stated in the 2001 review of Muon Collaboration activities
by the U.S. Muon Technical Advisory Committee:
• The “cooling demonstration” is the key systems test for the Neutrino
factory
• Much work over many years has established the components needed
for muon cooling: SC solenoids, absorbers, RF cavities
It is time to assemble a realistic cooling cell and
carry out the test
Single Particle Emittance Measurement
Multi-particle methods do not provide sufficient accuracy
Single Particle methods rely on HEP style instrumentation
• Trajectory in solenoid and TOF measurement of single
particles (x, y, z, x’, y’, z’, t) before and after cooling
channel
• A collection of single particle events is used to
reconstruct the beam phase space
• Emittance measurement comes from phase space
Must understand trajectories and B-Fields very well (fringe
fields!)
Emittance Measurement
(P. Janot)
Emittance Measurement
Quality of Measurements:
• Correctable bias from multiple scattering and measurement
precision smaller than 1%
• Statistical precision in / better than 1% for 1000 muons
• From these results we expect an ultimate precision on
out/in < 10-3
• Need particle ID for / separation ( TOF, upstream)
and /e separation (range or Cerenkov, downstream)
with purity better than 1%
Important Detector Issues
• Detectors must operate in strong solenoidal fields & with intense RF-cavity
backgrounds & contribute negligible emittance degradation
• Working out safe design and operating approaches is a crucial and challenging part
of the MUCOOL R&D effort underway at Fermilab
Summary
There is a strong case for doing Neutrino Physics
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Neutrino physics has been one of the most active areas of particle physics in the
last decade and ties together HEP, Solar Physics, Astrophysics and Cosmology
A Neutrino Factory offers unique opportunities for doing
Neutrino Physics
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A Neutrino Factory yields the highest flux neutrino beams achievable, and the
beam parameters are well controlled and understood
A Neutrino Factory is the only way to produce beams of electron type neutrinos
There is a diverse program of non-Neutrino physics to be done
at a Neutrino Factory Complex
A cooling experiment is the key milestone on the path
to a Neutrino Factory and there is a strong
international community determined to make it
happen!
Double-Flip Cooling Channel