BETA-BEAMSBETA-BEAMSBETA-BEAMSBETA-BEAMS

Piero ZucchelliOn leave of absence from:High Energy Physics andINFN - Sezione di Ferrara

M. MezzettoD. CasperM. LindroosA. BlondelU. KoesterS. HancockB. AutinM. BenediktH. HaserothM. GrieserA. JanssonS. RussenschuckF. Wenander

Physics Letters B 532 (3-4) (2002) pp. 166-172Physics Letters B 532 (3-4) (2002) pp. 166-172

An ideaAn idea

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

The focussing properties are given only by:- the divergence of the parent “beam” - the Lorentz transformations between different frames

PT= pT PL=( p + p cos)

from which, on average (if spinless)

1/ (it depends ONLY on parent speed!)EE0 E0 =daughter particle energy when parent is at rest

where. In the forward direction,E2E0 (I.e. same rest-frame spectrum shape multiplied by 2)

Focussing Properties

are produced by weak “decay” of a parent: ,K,nucleus. We assume the decay to be isotropic at rest and call E0 the rest frame energy of the neutrino.

LBL Scopemaximum neutrino flux for a given m2E/LE0/L.

The neutrino flux onto a “far” detector goes like 2/L2; Therefore (m2)2/E0

2.

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 factor.

But we want to observe neutrino interactions:N=

If we assume to be in the regime where E (>300 MeV for )N (m2)2 /E0

And acceleration enters into the game;

The “Quality Factor” of a “non-conventional” neutrino beam is therefore /E0

The BETA-BEAM1. 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. e (e) will be produced.

- SINGLE flavour - Known spectrum- Known intensity- Focussed- Low energy- “Better” Beam of e (e)

The “quality factor” QF=/E0 is bigger than in a conventional neutrino

factory. In addition, ion production and collection is easier. Then, 500000X more time to accelerate.

Muons:~500E0~34 MeVQF~15

6He Beta-:~150E0~1.9 MeVQF~7918Ne Beta+:~250E0~1.86 MeVQF~135

Possible - emitters (e)

Isotope Z A A/Z T1/2 Q (gs>gs) Q eff. E av. E av. <E_LAB> ( MeV)

s MeV MeV MeV 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 SourceConsider 6He++6Li+++ e e-

E03.5078 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.

DATA and theory:<Ekine>=1.578 MeV<E>=1.937 MeVRMS/<E>=37%

B.M. Rustand and S.L. Ruby, Phys.Rev. 97 (1955) 991B.W. Ridley Nucl.Phys. 25 (1961) 483

Bunched?

2500 m

R=300 m

The interactions time structurein the detector is identical to thetime 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

The far detector duty cycle is bunch length / ring length

A

B

Inte

ract

ions

time

Ion

inte

nsity

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 thenext 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:12,m12,23,m23.

C. Frejus site and SPL Super-Beam: possibly 13

D. Frejus site and SPS Beta-Beam: possibly 13 , 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 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 hasto 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 ObservablesThe relative neutrino flux for a spinless* parents is ONLYfunction of and L, not even of the parent itself.

Distance (km) Relative Flux (nu/m2)1 7.1109E-03

12.5 4.5834E-0550 2.8647E-06

100 7.1618E-07130 4.2378E-07

22

11)cos(

)cos(1

)cos()cos(

2

)cos(1

mL

l

l

lr

rP

(* as it is for 6He and 18Ne)

beam-related backgrounds due to Lithium/Fluorine interactions at the end of the straightsections

The Far Detector Background

GEANT3 simulation,

3E6 proton interactionsonto a Fe dump,

tracking down to 10 MeV

100 mradoff-axis and 130 km distance.DIF and DAR (K+) contributions

<10-4 background @ =150

The Signal maximization...

The signal coming from appearance interactions after oscillation @ 130 kmand 440 kt-year fiducial mass in the hypothesis (13=/2,m13=2.4E-3 eV2). The machine duty-cycle is assumed to remain constant.

table

0

5000

10000

15000

20000

95 115 135 155 175

Gamma

Osc

illat

ed

an

d

Inte

ract

ed

/Ye

ar

…and the interaction background...

NC interactions potentially produce ++ decays (almost at rest)and the + is misidentified as a muon.

Asymmetries with Superbeams start to appear (the e/0 separation becomes /)

Kinematical cuts are possible, still delicate and MC dependent.

Another strategy consists in having the pions below Cherenkov threshold (M. Mezzetto).

InteractionBackground

...and the Atmospheric “background”

The atmospheric neutrino background has to be reduced mainlyby “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 usedto further suppress this background by a factor ~4-6X dependent on gamma.

AtmosphericBackground

Anu

e S

umm

ary

Fig

ures

Quantity Value Unit CommentsSPS Cycle time 5 sProduced 6He 2.0E+13 per cyclemachine livetime 1.0E+07 s/year

Produced 6He/year 4.0E+19

Transfer efficiency 25%

6He injected into storage ring per year 1.0E+19

Straight section relative length 36%

Gamma 150potential 6He decays 3.6E+18 in one straight section

Interaction rate/6He/kton 2.3E-17 130 km, G=150Ring length 6885 mnumber of bunches 1 Single Bunch stackingBunch intensity 5.0E+12 6HeStorage ring total intensity 7.8E+13 6He 1/(1-exp(-8/120))Bunch spacing 22950 nsBunch length 10 nsstorage ring occupation 4.4E-04 bunch length/ring lengthUseful 6He decays 3.63E+18 cutoff in storage timeBetabeam anue Interactions 85 events/kton/yearBetabeam anumu Interactions 84 events/kton/yearOscillation interactions (1.0,2.4E-3) 31 events/kton/yearSignal emission time 4357 sAtmospheric Background 50 event/kton/yearyear 3.2E+07 s Detector fiducial mass 440 ktonAtmospheric Background 0.8 events/year kinematical/angular cuts (4X)Beam Background 1.4 events/yearAnue interactions 37247 events/yearOscillation signal 13756 events/yearNoise/Oscillation Signal 1.55E-04

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=250 (250 GeV/nucleon) WITH THE SAME MAGNETIC FIELDused for 6He and =150.

<E>=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

Sum

mar

y F

igur

esQuantity Value Unit CommentsSPS Cycle time 5.0 sProduced 18Ne 8.0E+11 per cyclemachine livetime 1.0E+07 s/yearProduced 18Ne/year 1.6E+18Transfer efficiency 38%18Ne injected into storage ring per year 6.0E+17Straight section relative length 36%Gamma 250potential Ne18 decays 2.2E+17 in one straight sectionInteraction rate/18Ne/kton 2.0E-16 130 km, G=75Ring length 6885 mnumber of bunches 1 Single Bunch stackingBunch intensity 3.0E+11 18NeStorage ring total intensity 2.4E+13 18Ne 1/(1-exp(-8/120))Bunch spacing 22950 nsBunch length 10 nsstorage ring occupation 4.4E-04 bunch length/ring lengthUseful 18Ne decays 2.2E+17 cutoff in storage timeBetabeam QE nue Interactions 43.09 events/kton/yearBetabeam QE numu Interactions 42.44 events/kton/yearOscillation interactions (1.0,2.4E-3) 9.25 events/kton/yearSignal emission time 4357 sAtmospheric Background 50 event/kton/yearyear 3.2E+07 s Detector fiducial mass 440 ktonAtmospheric Background 0.8 events/yearBeam Background 0.4 events/yearNue interactions 18958 events/yearOscillation signal 4071 events/yearNoise/Oscillation Signal 2.87E-04

The Super-BetaSuper-Beta Beams (nufact02)

(Old) Super-Beam numu: 9,800 QE/Year @ 260 MeV @ 130 km

Beta-Beam anue: 37,250 QE/Year @ 580 MeV @ 130 km

(Old) Super-Beam anumu: 2050 QE/Year @ 230 MeV @ 130 km

Beta-Beam nue: 18,950 QE/Year @ 930 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?

J. Sato, hep-ph 0006127

In the T search, ambiguities are resolved!The tunability of the beta-beam allows additional choiceof the phase cot (m2

13 L / 4E)

CP Asymmetry

T Asymmetry

General ConsiderationsA.13 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).

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.

H. Minakata, H. Nunokawa hep-ph0009091.

CPT Asymmetry

One simple optimization (M.M.)

At the same time, it maximizes the overlap with the CP-oddterm (at CERN-Frejusdistance)

Background should not generate a Cherenkov signal!

BetaBeam “downgrading”Quantity Value Unit CommentsSPS Cycle time 2.0 sproduced 18Ne 8.0E+11 per cyclemachine livetime 1.0E+07 s/year

Produced 18Ne/year 4.0E+18

Transfer efficiency 38%

18Ne injected into storage ring per year 1.5E+18

Straight section relative length 36%

Gamma 75potential Ne18 decays 5.4E+17 in one straight section

Interaction rate/18Ne/kton 8.3E-18 130 km, G=75Ring length 6885 mnumber of bunches 1 Single Bunch stackingBunch intensity 3.0E+11 18NeStorage ring total intensity 1.8E+13 18Ne 1/(1-exp(-8/120))Bunch spacing 22950 nsBunch length 10 nsstorage ring occupation 4.4E-04 bunch length/ring lengthUseful 18Ne decays 5.45E+17 cutoff in storage timeBetabeam QE nue Interactions 4.52 events/kton/yearBetabeam QE numu Interactions 3.79 events/kton/yearOscillation interactions (1.0,2.4E-3) 3.06 events/kton/yearSignal emission time 4357 sAtmospheric Background 50 event/kton/yearyear 3.2E+07 s Detector fiducial mass 440 ktonAtmospheric Background 0.8 events/yearBeam Background 0.1 events/yearNue interactions 1989 events/yearOscillation signal 1347 events/yearNoise/Oscillation Signal 6.64E-04

=75

, F

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d D

rop

11X Flux Drop!!!

Poor man’s neutrino factory?

Redundant measurementsof CP,T,CPT(M.M. Nufact02)

Comment on BB cost estimates(nufact02)

Educated guess on possible costs USD/CHF 1,60UNO 960 MCHFSUPERBEAM LINE 100 MCHFSPL 300 MCHFPS UPGR. 100 MCHFSOURCE (EURISOL), STORAGE RING 100 MCHFSPS 5 MCHFDECAY RING CIVIL ENG. 400 MCHFDECAY RING OPTICS 100 MCHF

TOTAL (MCHF) 2065 MCHFTOTAL (MUSD) 1291 MUSD

INCREMENTAL COST (MCHF) 705 MCHFINCREMENTAL COST (MUSD) 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• 13 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

“Se son rose, fioriranno”.

CONCLUSIONS

“If they're roses, they will blossom”

“Si tiene barbas, San Antón, si no la Purísima Concepción”

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