General motivation S. Geer, K. Long

Charge: (July collaboration meeting)

• Neutrinos and our lives (PR motivation)

• Neutrino oscillation and the role of NuFact

• Other physics at Neutrino Factor complex and muon collider

• Neutrino factory description (the accelerator)

• Role of cooling in Neutrino Factory and muon collider, the need for MICE

Neutrinos and our lives:Recent observations imply neutrinos have mass and mix:

The Neutrino Factory; the ultimate tool:

• Neutrinos from decay of stored muons: intensity, beam composition, known and variable energy

• Step on the way to muon collider: perhaps the route of choice to multi-TeV lepton-lepton collisions

• The Standard Model is incomplete• Neutrino abundance and neutrino mass:

mass in neutrinos ~ that of visible stars

• CP violation in lepton sector: Lepto-genesis

astrophysical consequences!

cosmological consequences!

Birth of a new technique for particle physics

Neutrino oscillations: status

m212

m223

2323

2323

1313

1313

1212

1212

0

0

001

0

010

0

100

0

0

cs

sc

cse

sec

cs

sc

Ui

i

Solar Atmos.

CP-violation: 0

m223

m212

23232

23

232

eV 109.3eV 106.1

c.l.) (90% 92.02sin

cAtmospheri

m

Status (cont.):

24212

25

122

eV 102eV 104

LMA ... 2sin

solution preferred -Solar

m

Important for CP-violation search

Planned/proposed experiments:

* Designed for appearance

x: K2K, MINOS, CNGS (also *)J2K, NuMI off axis, CNGS off axis,

superbeam

e x: SNO, Kamland, GNO, Borexino, -beam

… comment on:

<0.013JHF-SK

<0.028<0.040? Low energy CNGS

<0.033<0.039<0.056CNGSx1.5*

<0.039<0.047<0.067CNGS*

<0.042<0.049<0.06<0.085MINOS

<0.14<0.14<0.14<0.14<0.14<0.14CHOOZ

200920082007200620052004

P. MigliozziIndication of time-line

Neutrino Factory cf. conventional sources:

NuFact cf. conventional sources (cont.):

Other physics at the Neutrino FactoryHigh precision -p and -n DIS

• PDFs: complete flavour

decomposition

• Nuclear shadowing

S from xF3 - S~0.003

• |Vcd| and |Vcs|, D0/ D0 mixing

• sin2W - sin2W ~ 0.0001

• Polarised structure functions

• Beyond the SM searchesCrucial: -N cross-sections for -oscillation measurements

Deep inelastic scattering

Other physics at the Neutrino Factory (cont.)

‘Other’ physics

Arising from high muon flux

• Rare (FL-violating) decays

• GSW parameters

• Search for CP, T and CPT

• Muonium (, m, )

• Muonic atoms (rN, weak

interaction)

-spin rotation (condensed

matter physics)

Arising from high proton flux

• Nuclear physics (heavy

nuclei, exotic nuclei)

• Nuclear astrophysics

• Atomic physics

• Medicine

• Materials

• CVC-hypothesis in beta

decay

Neutrino flux: The key to success at NuFct• Physics reach increases

with neutrino flux

• Maximise stored muon intensity

• Implies:

Require to capture and store as many of the ‘decay’ muons as possible Cool muon beam

Short muon lifetime requires novel technique:IONISATION COOLING

Ionisation coolingPrinciple Practice

Neutrino factory cooling channelCERN cooling channel • Ionisation cooling complicated

in principle and in practice

• Cooling effect comes from delicate balance between cooling (dE/dx) and heating (MCS)

• To achieve required cooling (at least a factor of 10) requires a LONG channel

• Require to demonstrate cooling works in principle (MuScat) and in practice - MICE

Muon ionisation cooling experiment

Mission statement:

Design, build, commission and operate a realistic section of cooling channel

Measure its performance in a variety of modes of operation and beam conditions

i.e. the results of MICE will allow design of Neutrino Factory complex to be optimised with confidence.

Status of draft:1 . I n t r o d u c t io n I n r e c e n t y e a r s t h e r e h a s b e e n m u c h in t e r e s t in t h e p o s s ib i l it y o f d e v e lo p in g a n e w t y p e o f v e r y in t e n s e m u o n s o u r c e c a p a b le o f p r o d u c in g a m i l lim o le o f m u o n s p e r y e a r . T h is in t e r e s t is w e l l m o t iv a t e d . A v e r y b r ig h t m u o n b e a m t h a t c a n b e r a p i d ly a c c e le r a t e d to h ig h e n e r g ie s w o u ld p r o v id e a n e w t o o l fo r p a r t ic le p h y s ic s . A t p r e s e n t t h e b e a m t o o lk it a v a i la b le fo r p h y s ic is t s in t e r e s t e d in p a r t ic le in t e r a c t io n s a t t h e h ig h e s t e n e r g ie s is l im it e d to b e a m s o f c h a r g e d s t a b le p a r t ic le s : e le c t ro n s , p o s it r o n s , p r o to n s , a n d a n t ip r o to n s . T h e d e v e lo p m e n t o f in t e n s e b r ig h t $ \m u ^ + $ a n d $ \ m u ^ - $ b e a m s w o u ld e x t e n d t h is t o o lk it in a s ig n i f ic a n t w a y , o p e n in g t h e d o o r fo r m u lt i - T e V m u o n c o ll id e r s i, lo w e r e n e r g y m u o n c o ll id e r s ( H ig g s fa c t o r ie s ) , a n d p e r h a p s m u o n - - p ro to n c o llid e r s . I n a d d it io n , a n in t e n s e c o ld m u o n s o u r c e w o u ld m a k e p o s s ib le a n e w g e n e r a t io n o f e x p e r im e n t s u s in g lo w e n e r g y o r s to p p e d m u o n s to s t u d y r a r e p r o c e s s e s . F in a l ly , s in c e a ll o f t h e m u o n s d e c a y t o p r o d u c e n e u t r in o s , a n in t e n s e s o u r c e o f c o ld m u o n s w o u ld e n a b le a n e u t r in o fa c t o r y to b e b u i lt in w h ic h t h e m u o n s a r e s t o r e d in a r in g w it h lo n g s t r a ig h t s e c t io n s . T h e in t e n s e b e a m s o f e le c t ro n - t y p e a n d m u o n - t y p e n e u t r in o s d o w n s t r e a m o f t h e s t r a ig h t s e c t io n s w o u ld p r o v id e a u n iq u e n e u t r in o fa c i l it y . I n t h e la s t f e w y e a r s , w it h t h e g ro w in g e v id e n c e fo r n e u t r in o o s c il la t io n s , n e u t r in o fa c t o r ie s h a v e e x c it e d t h e in t e r e s t o f t h e n e u t r in o o s c il la t io n c o m m u n it y a s t h e u lt im a t e to o ls t o s t u d y t h e n e u t r in o m ix in g m a t r ix . i i A f ir s t ro u n d o f fe a s ib i l it y s t u d ie s a r o u n d t h e w o r ld i i i , iv ,v , v i h a s s h o w n t h a t a N e u t r in o F a c t o r y c o u ld l ik e ly b e b u i lt w it h r e a l iz a b le t e c h n o lo g ie s , a n d w it h p e r fo r m a n c e m a t c h in g t h e r e q u ir e m e n t s fo r a n e x c it in g p h y s ic s p r o g r a m . N e u t r in o F a c t o r y d e s ig n is b e in g p u r s u e d in t h e U n it e d S t a t e s , iv a t C E R N , v a n d in J a p a n . v i I t b u ild s o n e a r lie r M u o n C o ll id e r s t u d ie s a n d it s v e r y s im i la r c o m p o n e n t s a r e b r ie f ly r e c a l le d h e r e ( F ig . 1 ) . A h ig h - f lu x p r o to n d r iv e r d e liv e r s o n t a r g e t t y p ic a l ly 4 M W o f p r o to n - b e a m p o w e r . U .S . d e s ig n s s p e c if y r a p id - c y c l in g 1 6 – 2 4 - G e V p r o to n

s y n c h r o t ro n s , w h ile a 2 .2 - G e V s u p e r c o n d u c t in g l in a c h a s b e e n s t u d ie d a t C E R N v a n d a 5 0 - G e V s y n c h r o t ro n in J a p a n ( n o w u n d e r c o n s t r u c t io n v i i) . T h e h ig h h e a t lo a d a n d t h e r m a l s h o c k im p o s e d o n t h e t a r g e t s u g g e s t a l iq u id - je t t a rg e t ; ro t a t in g h ig h - t e m p e r a t u r e s o lid s a n d a s s e m b l ie s o f g a s - c o o le d p e lle t s a r e a ls o b e in g c o n s id e r e d . P io n s p r o d u c e d a r e

F ig . 1 : S c h e m a t ic N e u t r in o F a c to r y la y o u t s in ( l e f t) U .S . S tu d y - I I a n d ( r ig h t ) a C E R N s c e n a r io

longitudinal momentum. The net effect is a reduction of transverse emittance, leading to transverse beam size of a few cm. A linac and one or two recirculating linacs (or Fixed-Field Alternating-Gradient synchrotronsError! Bookmark not defined.) provide fast acceleration of the muons to the desired final energy (20 to 50 GeV). Around 1021 muons per (107-s) year can then be stored in a ring, in which they circulate a few hundred times during their lifetime. The storage ring can be shaped as a racetrack, triangle, or bowtie, producing multiple beams of decay neutrinos that can be aimed at short- or long-baseline experiments.

As seen from this brief description, Neutrino Factory design involves extrapolations beyond the current state of the accelerator art. The first design studiesError! Bookmark not

defined.,Error! Bookmark not defined. imply that with present designs, such a machine could be built and would most likely reach the desired performance, but to reduce the cost and validate the key technological extrapolations will require serious work. Assuming adequate funding, about five years of R&D are believed to be required before a concrete and cost-evaluated machine can be proposed. As emphasized in the latest MUTACi,1 review,ii the experimental demonstration of a short cooling channel section is considered the key step in validating the technology required for a Neutrino Factory. This motivates the proposed muon cooling experiment. The aims of the proposed experimental demonstration are

to design, engineer, and build a section of cooling channel capable of giving the desired performance for a Neutrino Factory;

to place this apparatus in a muon beam and measure its performance in a variety of modes of operation and beam conditions.

The goal is not to demonstrate the principle of cooling, which is expected to result if all components work as specified, but to learn how to build and operate a device that performs as desired, and to prove this by measuring its performance in a beam. The experience gained from this experimental demonstration will provide input to the final design of the Neutrino Factory cooling channel.

This approach is an essential complement to, and benefits from, R&D on individual components already under way within the MUCOOLiii program and at CERN. An ionization-cooling channel combines low-Z absorbers, providing energy loss, with high-gradient RF cavities to re-accelerate the muons, all tightly packed within a magnetic focusing lattice. Practical, or perhaps fundamental, problems that would not necessarily show up in component R&D are bound to arise in such a combined system. Their discovery and solution could have a substantial impact on cooling-channel performance and design. The process of accumulating this irreplaceable experience will be long and should begin without delay.

An international collaboration has been organized to carry out this program. iv It consists of accelerator physicists and experimental particle physicists from Europe, Japan, and the U.S. Through a series of workshops,v it converged to a baseline scenario for a cooling experiment, presented in detail in the MICE Letter of Intentvi and summarized here. The main characteristics of the experiment are as follows:

1 The Muon Technical Advisory Committee (MUTAC), comprised of prominent accelerator and particle physics experts, is convened annually by the Muon Collaboration Oversight Group (MCOG) to review and evaluate the MC’s R&D progress (see Ref. i). MCOG is made up of representatives of the Directorates of three major U.S. national laboratories: the Brookhaven and Lawrence Berkeley National Laboratories and Fermilab.

More to do. Progress this week! Deadline 15Nov02

S. Geer