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PRISM and Neutrino Factory
in Japan
Y. KunoKEK, IPNS
January 19th, 2000at CERN
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PR
ISM
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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.
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PRISM Scheme
pulsed proton beam pion capture by high solenoid fiel
d pion decay section phase rotation section
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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.
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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.
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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
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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.
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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
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Phase Rotation Simulation
simulation with rf kicks
after phase rotation
before phase rotation
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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
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PRISM layout
not in scale
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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)
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Phase Rotation Simulation at FFAG (2)
in case of saw-tooth wave rf
phase (degree)
dp/p
(%)
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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
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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!
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How
, Mu
on L
FV
?
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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)
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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
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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 )
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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 ???
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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
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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)
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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
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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
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Wh
at E
lse
from
PR
ISM
?
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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
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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
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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 ??
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from
PR
ISM
to
neu
trin
o fa
ctor
y
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Neutrino FactoryNeutrino Factory
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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
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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
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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
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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)
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Wrong Sign Muons: P(νeν1
Δm322 =2×10−3eV2
θ13 =1o
θ13 =9o
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Wrong Sign Muons: P(νeν2
Δm322 =3.5×10−3eV2
θ13 =1o
θ13 =9o
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Wrong Sign Muons: P(νeν3
Δm322 =6×10−3eV2
θ13 =1o
θ13 =9o
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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.
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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.
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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
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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.
![Page 43: PRISM and Neutrino Factory in Japan Y. Kuno KEK, IPNS January 19th, 2000 at CERN](https://reader035.vdocuments.us/reader035/viewer/2022062802/56649eb65503460f94bc0799/html5/thumbnails/43.jpg)
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.