Transcript BETA-BEAMS

Piero Zucchelli
On leave of absence from:
High Energy Physics
and
INFN - Sezione di Ferrara
M. Mezzetto
D. Casper
M. Lindroos
A. Blondel
U. Koester
S. Hancock
B. Autin
M. Benedikt
H. Haseroth
M. Grieser
A. Jansson
S. Russenschuck
F. Wenander
BETA-BEAMS
An idea
Physics Letters B 532 (3-4) (2002) pp. 166-172
GUIDELINES
A. Neutrino beams from a different perspective
B. The “Beta-Beam” Concept
C. Experimental Scenario
D. Beta-beams and neutrino physics
E. The Value question
Focussing Properties
n are produced by weak “decay” of a parent: m,p,K,nucleus.
We assume the decay to be isotropic at rest and call E0 the rest frame energy of the neutrino.
The focussing properties are given only by:
- the divergence of the parent “beam”
- the Lorentz transformations between different frames
PT= pT
PL=G ( p + p  cosq )
from which, on average (if spinless)
Q 1/G
EGE0
Q
(it depends ONLY on parent speed!)
E0 =daughter particle energy when parent is at rest
where. In the forward direction,
E2GE0 (I.e. same rest-frame spectrum shape multiplied by 2G)
LBL Scope
maximum neutrino flux for a given Dm2E/LGE0/L.
The neutrino flux onto a “far” detector goes like FG2/L2; Therefore
F(Dm2)2/E02.
At a given parent intensity, low energy decays in the CMS frame are the
most efficient in achieving the “LBL requirement”, and independently
of the G factor.
But we want to observe neutrino interactions:
N= F  s
If we assume to be in the regime where s  E (>300 MeV for nm)
N  (Dm2)2 G/E0
And acceleration enters into the game;
The “Quality Factor” of a “non-conventional”
neutrino beam is therefore
G/E0
The BETA-BEAM
1. Produce a Radioactive Ion with a short beta-decay lifetime
2. Accelerate the ion in a conventional way (PS) to “high” energy
3. Store the ion in a decay ring with straight sections.
4. It will decay. ne (ne) will be produced.
6He
Muons:
G~500
E0~34 MeV
QF~15
- SINGLE flavour
- Known spectrum
- Known intensity
- Focussed
- Low energy
- “Better” Beam of ne (ne)
Beta-:
G~150
E0~1.9 MeV
QF~79
18Ne
Beta+:
G~250
E0~1.86 MeV
QF~135
The “quality factor” QF=G/E0 is bigger than in a conventional neutrino
factory. In addition, ion production and collection is easier. Then, 500000X more
time to accelerate.
Possible b- emitters (ne)
Isotope
Z
A A/Z
T1/2
s
Qb (gs>gs) Qb eff. Eb av. En
MeV
av.
MeV MeV MeV
<E_LAB> ( MeV)
(@ 450 GeV/p)
6He
2
6
3.0 0.807
3.5
3.5
1.57 1.94
582
8He
2
8
4.0 0.119
10.7
9.1
4.35 4.80
1079
8Li
3
8
2.7 0.838
16.0
13.0 6.24 6.72
2268
9Li
3
9
3.0 0.178
13.6
11.9 5.73 6.20
1860
11Be
4 11 2.8 13.81
11.5
9.8
4.65 5.11
1671
15C
6 15 2.5 2.449
9.8
6.4
2.87 3.55
1279
16C
6 16 2.7 0.747
8.0
4.5
2.05 2.46
830
16N
7 16 2.3 7.13
10.4
5.9
4.59 1.33
525
17N
7 17 2.4 4.173
8.7
3.8
1.71 2.10
779
18N
7 18 2.6 0.624
13.9
8.0
5.33 2.67
933
23Ne
10 23 2.3 37.24
4.4
4.2
1.90 2.31
904
25Ne
10 25 2.5 0.602
7.3
6.9
3.18 3.73
1344
25Na
11 25 2.3 59.1
3.8
3.4
1.51 1.90
750
26Na
11 26 2.4 1.072
9.3
7.2
3.34 3.81
1450
Anti-Neutrino Source
Consider 6He++6Li+++ ne eE03.5078 MeV T/2  0.8067 s
1. The ion is spinless,
and therefore decays
at rest are isotropic.
2. It can be produced at
high rates, I.e.
5E13 6He/s
3. The neutrino spectrum
is known on the basis of
the electron spectrum.
B.M. Rustand and S.L. Ruby, Phys.Rev. 97 (1955) 991
B.W. Ridley Nucl.Phys. 25 (1961) 483
DATA and theory:
<Ekine>=1.578 MeV
<En>=1.937 MeV
RMS/<En>=37%
Bunched?
A
B
The interactions time structure
in the detector is identical to the
time structure of the parents in
the decay ring in a given position.
The beta decay position does not
matter, since the parents have
the same speed of the neutrinos
time
Interactions
Ion intensity
The far detector duty cycle is
bunch length / ring length
time
Next decades neutrino physics
A. Imagine that there will be a next generation neutrino detector.
An R&D, design and construction phase will lead us into next decade.
B. Imagine to explore non-accelerator physics first.
C. Imagine that this program is compatible with a superbeam shooting
muon neutrinos onto it. If this will expand the neutrino knowledge of the
period 2010-2020, you’re ready to do it (known technology).
D. Imagine that you have PREPARRED and STUDIED an
option to shoot electron neutrinos onto the same detector. If the
next decade neutrino physics will demand it, you’re ready to do it.
A Dream?
A. the ~600 Kton UNO detector.
B. Supernovae, Solar, Atmospheric, Proton Decay:
q12,m12,q23,m23.
C. Frejus site and SPL Super-Beam: possibly q13
D. Frejus site and SPS Beta-Beam: possibly q13 , possibly CP (2) and T
Is this physics program less visionary than a muon-based
neutrino factory program?
The objectives are wider, the discovery potential for some
specific assumptions is smaller. Speculations and fashions on
the d value will also last many years!
SuperBeam: a competition?
The proton requirements of the Beta-Beam are part of the
ISOLDE@SPL (100uA for 1s every 2-5 s).
The ISOLDE@SPL plans 100 uA protons overall.
The Superbeam uses 2mA from the SPL.
Therefore:
The BetaBeam affects the SuperBeam intensity by 3% at most.
Cherenkov? Opportunistic?
The detector has
to be massive,
and distinguish
electrons from
muons in the few
hundreds MeV region
Same as:
- SuperBeam
- Proton decay
- Atmospheric
neutrinos!
You don’t need
charge identification...
...and therefore a
magnetic detector!
The Far Detector Observables
The relative neutrino flux for a spinless* parents is ONLY
function of g and L, not even of the parent itself.
1  cos(r )
P
2
cos(l )  b
cos(r ) 
1  b  cos(l )
1
cos(l )  1 
2
2p L
m
(* as it is for 6He and 18Ne)
Distance (km)
1
12.5
50
100
130
Relative Flux (nu/m2)
7.1109E-03
4.5834E-05
2.8647E-06
7.1618E-07
4.2378E-07
The Far Detector Background
beam-related backgrounds
due to Lithium/Fluorine
interactions at the
end of the straight
sections
GEANT3 simulation,
3E6 proton
interactions
onto a Fe dump,
tracking down to 10 MeV
100 mrad
off-axis and
130 km distance.
DIF and DAR
(K+) contributions
<10-4 background @ g=150
The Signal maximization...
The signal coming from appearance nm interactions after oscillation @ 130 km
and 440 kt-year fiducial mass in the hypothesis (q13=p/2,m13=2.4E-3 eV2).
The machine duty-cycle is assumed to remain constant.
Oscillated and
Interacted/Year
20000
15000
10000
5000
table
0
95
115
135
Gamma
155
175
…and the interaction background...
NC interactions potentially produce D++ decays (almost at rest)
and the p+ is misidentified as a muon.
Asymmetries with Superbeams start to appear (the e/p0
separation becomes m/p)
Kinematical cuts are possible, still delicate and MC dependent.
Another strategy consists in having the pions below Cherenkov
threshold (M. Mezzetto).
Interaction
Background
...and the Atmospheric “background”
The atmospheric neutrino background has to be reduced mainly
by “timing” on the 6He bunches (protons for the SuperBeam).
The shortness of the ion bunches is therefore mandatory
(10 ns for a ~SPS ring length).
However, the directionality of the antineutrinos can be used
to further suppress this background by a factor ~4-6X
dependent on gamma.
Atmospheric
Background
Quantity
SPS Cycle time
Produced 6He
machine livetime
Anue Summary Figures
Produced 6He/year
Transfer efficiency
6He injected into storage ring per year
Straight section relative length
Gamma
potential 6He decays
Interaction rate/6He/kton
Ring length
number of bunches
Bunch intensity
Storage ring total intensity
Bunch spacing
Bunch length
storage ring occupation
Useful 6He decays
Betabeam anue Interactions
Betabeam anumu Interactions
Oscillation interactions (1.0,2.4E-3)
Signal emission time
Atmospheric Background
year
Detector fiducial mass
Atmospheric Background
Beam Background
Anue interactions
Oscillation signal
Noise/Oscillation Signal
Value
Unit
5 s
2.0E+13 per cycle
1.0E+07 s/year
Comments
4.0E+19
25%
1.0E+19
36%
150
3.6E+18
2.3E-17
6885
1
5.0E+12
7.8E+13
22950
10
4.4E-04
3.63E+18
85
84
31
4357
50
3.2E+07
440
0.8
1.4
37247
13756
1.55E-04
in one straight section
130 km, G=150
m
Single Bunch stacking
6He
6He
1/(1-exp(-8/120))
ns
ns
bunch length/ring length
cutoff in storage time
events/kton/year
events/kton/year
events/kton/year
s
event/kton/year
s
kton
events/year
kinematical/angular cuts (4X)
events/year
events/year
events/year
The Nue case
Neon production Intensity is lower, HOWEVER:
1. 18Ne has charge 10 and mass 18.
2. For the previous reason, SPS can accelerate the ion up to
G=250 (250 GeV/nucleon) WITH THE SAME MAGNETIC FIELD
used for 6He and G=150.
<En>=0.93 GeV !!!
3. For the same reasons explained for the antineutrino case, the
potential oscillation signal improves despite the fact
<E>/L=7E-3 GeV/km
Nue Summary Figures
Quantity
Value
Unit
SPS Cycle time
5.0 s
Produced 18Ne
8.0E+11 per cycle
machine livetime
1.0E+07 s/year
Produced 18Ne/year
1.6E+18
Transfer efficiency
38%
18Ne injected into storage ring per year 6.0E+17
Straight section relative length
36%
Gamma
250
potential Ne18 decays
2.2E+17
Interaction rate/18Ne/kton
2.0E-16
Ring length
6885 m
number of bunches
1
Bunch intensity
3.0E+11 18Ne
Storage ring total intensity
2.4E+13 18Ne
Bunch spacing
22950 ns
Bunch length
10 ns
storage ring occupation
4.4E-04 bunch length/ring length
Useful 18Ne decays
2.2E+17
Betabeam QE nue Interactions
43.09 events/kton/year
Betabeam QE numu Interactions
42.44 events/kton/year
Oscillation interactions (1.0,2.4E-3)
9.25 events/kton/year
Signal emission time
4357 s
Atmospheric Background
50 event/kton/year
year
3.2E+07 s
Detector fiducial mass
440 kton
Atmospheric Background
0.8 events/year
Beam Background
0.4 events/year
Nue interactions
18958 events/year
Oscillation signal
4071 events/year
Noise/Oscillation Signal
2.87E-04
Comments
in one straight section
130 km, G=75
Single Bunch stacking
1/(1-exp(-8/120))
cutoff in storage time
The Super-Beta
Beams (nufact02)
Beta-Beam nue: 18,950 QE/Year @ 930 MeV @ 130 km
Beta-Beam anue: 37,250 QE/Year @ 580 MeV @ 130 km
(Old) Super-Beam numu: 9,800 QE/Year @ 260 MeV @ 130 km
(Old) Super-Beam anumu: 2050 QE/Year @ 230 MeV @ 130 km
Obviously: the SuperBeam lower energy is “better”. Still,
the oscillation probability of the Beta-Beams are 37% (anue)
and 15% (nue) respectively.
The SuperBeam has more beam-related background,
but is much simpler to do.
Beta-beam detector backgrounds to be studied.
ONE DETECTOR, ONE DISTANCE, 2X2 (due) BEAMS!
A CP or a T search?
CP Asymmetry
J. Sato, hep-ph 0006127
T Asymmetry
In the T search, ambiguities are resolved!
The tunability of the beta-beam allows additional choice
of the phase cot (Dm213 L / 4E)
General Considerations
A. q13 is just the starting step for super&beta-beams.
B. CP violation at low energy is almost exempt from matter effect, therefore
already particularly attractive (nue beta-beam, anue beta-beam).
H. Minakata, H. Nunokawa hep-ph0009091.
C. Who else can do T violation without magnetic field and electron charge
identification? (nue beta-beam, numu super-beam).
D. CPT test by anue beta-beam, numu super-beam is the ultimate validation of
the 3-family mixing model and of the CP and T measurements.
E. If LSND is confirmed, 6 mixing angles and 3 CP violation phases are waiting
for us! The smallness of the LSND mixing parameter implies high purity beams,
the missing unitarity constraints will demand sources with different flavours.
CPT Asymmetry
One simple optimization (M.M.)
Background should
not generate a Cherenkov signal!
At the same time, it
maximizes the
overlap with the CP-odd
term (at CERN-Frejus
distance)
Quantity
SPS Cycle time
produced 18Ne
machine livetime
Value
Unit
2.0 s
8.0E+11 per cycle
1.0E+07 s/year
Comments
BetaBeam “downgrading”
Produced 18Ne/year
g=75, Flux Drop, Background Drop
Transfer efficiency
18Ne injected into storage ring per year
Straight section relative length
Gamma
potential Ne18 decays
Interaction rate/18Ne/kton
Ring length
number of bunches
Bunch intensity
Storage ring total intensity
Bunch spacing
Bunch length
storage ring occupation
Useful 18Ne decays
Betabeam QE nue Interactions
Betabeam QE numu Interactions
Oscillation interactions (1.0,2.4E-3)
Signal emission time
Atmospheric Background
year
Detector fiducial mass
Atmospheric Background
Beam Background
Nue interactions
Oscillation signal
Noise/Oscillation Signal
4.0E+18
38%
1.5E+18
36%
11X Flux Drop!!!
75
5.4E+17
8.3E-18
6885
1
3.0E+11
1.8E+13
22950
10
4.4E-04
5.45E+17
4.52
3.79
3.06
4357
50
3.2E+07
440
0.8
0.1
1989
1347
6.64E-04
in one straight section
130 km, G=75
m
Single Bunch stacking
18Ne
18Ne
1/(1-exp(-8/120))
ns
ns
bunch length/ring length
cutoff in storage time
events/kton/year
events/kton/year
events/kton/year
s
event/kton/year
s
kton
events/year
events/year
events/year
events/year
Poor man’s neutrino factory?
Redundant
measurements
of CP,T,CPT
(M.M. Nufact02)
Comment on BB cost estimates
(nufact02)
Educated guess on possible costs
UNO
SUPERBEAM LINE
SPL
PS UPGR.
SOURCE (EURISOL), STORAGE RING
SPS
DECAY RING CIVIL ENG.
DECAY RING OPTICS
TOTAL (MCHF)
TOTAL (MUSD)
INCREMENTAL COST (MCHF)
INCREMENTAL COST (MUSD)
USD/CHF
960
100
300
100
100
5
400
100
1,60
MCHF
MCHF
MCHF
MCHF
MCHF
MCHF
MCHF
MCHF
2065 MCHF
1291 MUSD
705 MCHF
441 MUSD
BB Value Proposition
Natural expansion of a program that starts with a
1. non-accelerator and scalable Water Cherenkov phase
2. SuperBeam phase.
3. Betabeam phase.
covering in an adaptive way
• supernovae detection
• proton decay
• atmospheric neutrinos
• solar neutrinos
• q13 search
• CP asymmetry
• T asymmetry
•CPT asymmetry.
(and our retirement)
Buy a BetaBeam?
• If somebody will prove it can be done
• If somebody will show it can deliver the neutrino
answers we will possibly need in 10-20 years from
now.
• If those questions will be within reach at all
• If the neutrino program will progress in the water
cherenkov direction
• If there will be no other - simpler, cheaper - solution
that will deliver the same or more
CONCLUSIONS
“Se son rose, fioriranno”.
“If they're roses, they will blossom”
“Si tiene barbas, San Antón, si no la Purísima Concepción”