PRISM and Neutrino Factory

in Japan

Y. KunoKEK, IPNS

January 19th, 2000at CERN

PR

ISM

What is PRISM ?

PRISM (Phase Rotation Intense Slow Muon source)

= a dedicated secondary muon beam channel with high intensity and

narrow energy spread for stopped muon experiments.

PRISM Scheme

pulsed proton beam pion capture by high solenoid fiel

d pion decay section phase rotation section

PRISM Beam

Characteristics

intensity : 1011-1012±/sec muon kinetic energy : 20 MeV (=68 MeV/c)

– range = about 3 g kinetic energy spread : ±0.5-1.0

MeV– ±a few 100 mg range width

beam repetition : about 1 kHz

– in terms of muon lifetime, a 100kHz -1 MHz is ideal.

– increase in future, if technically possible.

Summary

PRISM would be a unique and novel facility in the world, born in Japan. It is attracting much attensions in the worldwide.

A search for muon LFV violation is one of main topics at PRISM, in particular -e conversion.

Applications like biology etc. might as well be incorporated.

Most of technology is in hand, but need some prototyping.

A design note by May, 2000 ? Cost estimation ?

We are hoping to construct PRISM by the time when the 50-GeV PS will be on.

maximum transverse momentum

– R : radius of magnet– ex: H=120kG(=12T), R=5cm

» PT < 90 MeV/c

capture yields

Pion Capture Yield

PT(MeV / c) =0.3×H(kG) ×R2⎛⎝

⎞⎠(cm)

low energy pions

for 50GeV protons

0.2 pions/proton

Guide Lines of SC Solenoid

Magnet

Configuration– A hybrid solenoid magnet of 10-12 T

at 4.2 K– Radiation shield with water cooling

Coil cooling– conductive cooling with high heat-tra

nsfer path– heat load < a few 10 W (goal)

Cryogenics– cryo-cooler in parallel operation or re

frigerator with remote heat exchanger.

– located at a few meter away from the coil.

Phase Rotation = decelerate particles with high energy and accelerate particle with low energy by high-field RF

A narrow pulse structure (<1 nsec) of proton beam is needed to ensure that high-energy particles come early and low-energy one come late.

Phase Rotation

energyenergy

time time

important

Phase Rotation Simulation

simulation with rf kicks

after phase rotation

before phase rotation

Why FFAG for Phase Rotation ?

a ring instead of linear systems– reduction of # of rf cavities– reduction of rf power comsumption– compact

(Fixed Field Alternating Synchrotron) synchrotron oscillation for phase rotatio

n– not cyclotron (isochronous)

large momentum acceptance– larger than synchrotron– ± several 10 % is aimed

large transverse acceptance– strong focusing– large horizontal emittance– reasonable vertical emittance at low energy

PRISM layout

not in scale

Phase Rotation Simulation at FFAG(1)

non-linear relation on energy vs. time at low energy

in case of sin-wave rf– after 5 turns

dp/p

(%)

phase (degree)

Phase Rotation Simulation at FFAG (2)

in case of saw-tooth wave rf

phase (degree)

dp/p

(%)

PRISM at the 50-GeV PS

why at the 50-GeV PS?– a narrow bunched proton beam

is needed. in the 50-GeV PS

experimental hall

Muon Yield Estimation at PRISM

muon yield – PT<90 MeV/c (12T 5cm radius) at p

ion capture– 3000 mm ・ mrad vertical accepta

nce of FFAG

in 20 MeV±(0.5-1.0)MeV range proton intensity at the 50-GeV PS

– 1014 proton/sec muon yield

– 1011-1012 ±/sec

0.005 - 0.01 ±/proton

OK!

How

, Mu

on L

FV

?

Status of Muon LFV

Experimental status

• 1) PSI experiment (2003)• 2) PSI experiment (running)• 3) BNL-E940 (MECO) experiment (2003)

Muon LFV at PRISM– the best for -e conversion

» a pulsed beam needed.– eeee

» continuous beam needed to reduce accidental background.

– muonium to anti-muonium conversion

» a pulsed beam is needed. 　

current limitsnear futurePRISM

μ+ → e+γ <1.2×10−11 <10−14 1) <10−15

μ+ → e+e+e− <1.0×10−12 none <10−15

μ−N → e−N <6.1×10−13 <10−14 2) <10−18

<10−16 3)

econversion in a Muonic Atom

muonic atom (1s state)

neutrinoless muon nuclear capture (=-e conversion)

muon decay in orbit

nucleus

−→ e−ν ν −+ (A, Z) → ν μ + (A,Z −1)

nuclear muon capture

−+ (A, Z) → e− + (A,Z )

lepton flavors changes by one unit.

B(−N→ e−N) =Γ(−N → e−N)Γ(−N → νN')

coherent process

econversion:Signal and Background

coherent conversion (Z5)

Event Signature– single mono-energetic electron of (m-B) M

eV Backgrounds

– no accidental background– muon decay in orbit (E)5)

» highest endpoint comes to the signal

– radiative muon capture with photon conversion

– pion capture with photon conversion» to remove pions in beam, a pulsed beam is usefu

l, where the measurement waits until pions decay.

– cosmic ray

−+ (A, Z) → e− + (A,Z )

MECO at BNL/AGS

E940 aim at B(AleAlat BNL AGS MECO

5x1011-/pulse, 1.1MHz pulse– 8GeV proton beam at AGS – high field capture solenoid of 4T

schedule : 2003 start ???

PRISM Beam Requirement

for -e conversion

higher muon intensity– 1012 -/sec

pulsed beam– background rejection

narrow energy spread– allow a thinner muon-stopping taret

» better e- resolution and acceptance» point source

– allow a beam blocker behind the target

» isolate the target and detector» tracking close to a beam axis

less beam contaminations– no pion contamination

» long flight path at FFAG (150 m)

– beam extinction between pulses» kicker magnet at FFAG

targ

et

bloc

ker

SC

sole

noid

magnet

trig

ger

counte

rtr

ack

ing c

ham

ber

106

MeV

ele

ctro

n

not

in s

cale

muo

n be

amfro

m P

RISM

a m

agneti

c field

is

gra

ded a

t th

e t

arg

et

regio

n.

(deta

ils a

re n

ot

dete

rmin

ed)

Improvement of Signal Sensitivity

PRISM MECOStopped

muons/sec1012/sec(x4 times protons in future)

1011/sec

Target

material

Ti Al

Target

arrangement

Single 0.005 cm plate

or

10 layers of 5 mplates

(17-25)layers of 0.05cm

plate

e-momentum

resolution

σRMS=100keV σRMS=150keV

e-detection

soli d angle

40% <20%(45<θ<62)

e- signal

acceptance

(response

function)

No tails

100 %

Tail due to energy loss

<50 %

Time window Full time window

100 %

Delayed window

50 %

B(μA→ eA)/ B(μ→ eγ)≈1/ 238 B(μA→ eA)/ B(μ→ eγ)≈1/389

100 cm

time time

energy energy

econversion:Muon Decay in Orbit

Muon decay in orbit ((Ee-Ee)5)– required e+ momentum resolution is determined

(100-200 keV) at 10-18 sensitivity

present limit

MECO goal

JHF goal

signal

Wh

at E

lse

from

PR

ISM

?

More Physics Lists with PRISM

muon (g-2)– muon momenum = 3 GeV/c– small beam may improve the sensiti

vity further.– muon polarization

muon EDM– muon momentum = 500 MeV/c– high intensity and small beam shoul

d improve the sensitivity.– muon polarization

muonium to anti-muonium conversion

muon lifetime muonium spectroscopy muonic atom spectroscopy

Application List with PRISM

Brain scan studies– muonic X-ray measurement.– - beam from PRISM with small stop

ping region. trace-element analysis

– living cells biology materials science nsec response spectroscopy with

muons.– phase rotation to make narrow time

width (instead of narrow energy spread).

time

Future studies on PRISM

muon polarization– with cost of muon intensity, can imp

rove muon polarization ? muon cooling

– can muon be cooled at PRISM ? – precooling by H2

– higher than 300 MeV/c– high rf gradient needed.

Additional acceleration– to an muon EDM ring ?

» 100-500 MeV/c– to a muon g-2 ring ?

» 3 GeV/c (magic momentum)– cooling or no-cooling ??

from

PR

ISM

to

neu

trin

o fa

ctor

y

Neutrino FactoryNeutrino Factory

Oscillation Signature at Neutrino Factory

Oscillation signature

charge identification needed.– +/ is easy.– e+/e is difficult.

μ− → e− ν e νμ

ν μ

μ−

μ+

oscillation

μ+ → e+ νe ν μ

νμ

μ+

μ−

oscillation

Advantages of Neutrino factory

…...compared with a neutrino source of pion decays,

large neutrino intensity at high energy– 2x1020 neutrinos/year (1020-1022) – about 100 times intensity at a few 1

0 GeV energy range extremely low backgrounds

– 10-5 to 10-6 level (charm background)

» a few % level at the pion sources. precise knowledge on neutrino int

ensity and emittance

Event Rates

CC event rate

Oscillation rate

higher energy, better…. a number of CC events/year

– 1021muons/year in the ring– for a 10 kton detector

LÅÅÇPÇOÇOÇOkm LÅÅÇPÇTÇOÇOkm

E=20 GeV 3 .2 10x 5 1 .4 10x 5

E=30 GeV 1 .1 10x 6 4 .8 10x 5

a la O.Yasuda

NCC(νe → e)∝θν2 ⋅σ ∝

Eμ2

L2 ⋅Eμ =Eμ

3

L2

Nosc(νe → μ)∝θν2 ⋅σ ⋅P(νe → νμ )

∝Eμ

3

L2 ⋅L2

Eμ2 =Eμ

Oscillation Probabilities

when

measurement of– appearance measurement, for insta

nce,– sensitivity is determined by backgou

nd level (10-5-10-6)» a la Juan Jose Gomez Cadenas

– enhancement of matter effect

Δm212 <<Δm32

2

P(νe → νμ) =sin2(2θ13)sin2(θ23)sin2 1.27Δm322 L

Eν

⎛

⎝ ⎜

⎞

⎠ ⎟

P(νe → ντ ) =sin2(2θ13)cos2(θ23)sin2 1.27Δm322 L

Eν

⎛

⎝ ⎜

⎞

⎠ ⎟

P(νμ → ντ ) =cos4(θ13)sin2(2θ23)sin2 1.27Δm322 L

Eν

⎛

⎝ ⎜

⎞

⎠ ⎟

θ13

P(νe → νμ)

Wrong Sign Muons: P(νeν1

Δm322 =2×10−3eV2

θ13 =1o

θ13 =9o

Wrong Sign Muons: P(νeν2

Δm322 =3.5×10−3eV2

θ13 =1o

θ13 =9o

Wrong Sign Muons: P(νeν3

Δm322 =6×10−3eV2

θ13 =1o

θ13 =9o

Opportunity of Neutrino Factory at 50-

GeV PS

A possible opportunity in Japan will be based on the case of the 50-GeV PS, as an existing proton driver.– 1st phase: 0.75 MW– 2nd phase: 4 MW??

If the 50-GeV PS is already available, construction of a neutrino factory is very cost-effective.

The PRISM (= a low-energy muon source) experience will be directly and effectively extended towards a

neutrino factory.

a factor of only 20!

Towards Neutrino Factory

at the 50-GeV PS

increase of muon yield– 1019 ±/year for PRISM– 2x1020 ±/year for a neutrino factory – possible improvements are

» higher capture magnetic field» pions capture of higher momentum » forward extraction at the target» precooling and after-cooling , etc.

increase of proton intensity at the 50-GeV PS– 1014 protons/sec for Phase-I– 5x1014 protons/sec for Phase-II

increase the detector size– cheeper than accelerator– an event yield is the product of bea

m intensity and detector size.

Long Baseline from 50-GeV PS

long baseline

Fuku

oka

(10

00

km)

Sh

an

gh

ai(

20

00

km)

Kam

ioka

(250

km)

Toka

i

Summary

PRISM would be a unique and novel facility in the world, born in Japan. It is attracting much attensions in the worldwide.

A search for muon LFV violation is one of main topics at PRISM, in particular -e conversion.

Applications like biology etc. might as well be incorporated.

Most of technology is in hand, but need some prototyping.

A design note by May, 2000 ? Cost estimation ?

We are hoping to construct PRISM by the time when the 50-GeV PS will be on.

Summary

PRISM experience is important towards a neutrino factory at the 50-GeV PS.

If the 50-GeV PS is given, a neutrino factory could be built cost-effectively in future.

A factor of about 20 is needed from PRISM intensity to achieve 2x1020/year.– a factor of 5 from the 50-GeV PS upgrade in

Phase-II– some modest efforts in improvement of mu

on yield– a larger detector (cheeper than acceleraor)

Quick start should be aimed with reasonable performance.– optimize just or a neutrino factory , and do

not aim too high for a muon collider.