Potentiality of a (very) high- -Beam complex

Pasquale MigliozziINFN – Napoli

!!!WARNING!!!

The physics potential of the BB of any has been carefully evaluated by several groups

and discussed in this talk and in the previous ones

However, solid feasibility studies from the accelerator side are still missing, although some interesting ideas are on the market

The BB are “in principle” a great idea, but we need more studies (regardless of the option)

to endorse their “practical” realization

Future neutrino oscillation exps

Ep(GeV)

Power(MW)

Beam〈 E

〉(GeV)

L

(km)

Mdet

(kt)

CC

(/yr)

e

@peak

K2K 12 0.005 WB 1.3 250 22.5 ~50 ~1%

MINOS(LE) 120 0.4 WB 3.5 730 5.4 ~2,500 1.2%

CNGS 400 0.3 WB 18 732 ~2 ~5,000 0.8%

T2K-I 50 0.75 OA 0.7 295 22.5 ~3,000 0.2%

NOA 120 0.4 OA ~2 810? 50 ~4,600 0.3%

C2GT 400 0.3 OA 0.8 ~1200 1,000?

~5,000 0.2%

T2K-II 50 4 OA 0.7 295 ~500 ~360,000

0.2%

NOA+PD 120 2 OA ~2 810? 50? ~23,000 0.3%

BNL-Hs 28 1 WB/OA ~1 2540 ~500 ~13,000

SPL-Frejus 2.2 4 WB 0.32 130 ~500 ~18,000 0.4%

FeHo 8/120 “4” WB/OA 1~3 1290 ~500 ~50,000

Running, constructing or approved experiments

Possible scenarios after first results of the planned experiments and implications

13 is so small (< 3°, sin2213 ≤ 0.01) that all give null result We need a “cheap” experiment to probe sin2213

values down to O(0.001 - 0.0001) 13 is larger than 3° (sin2213 ≥ 0.01)

We need an experiment (or more than one) to ¤ Measure 13 more precisely¤ Discover (if not done yet) or precisely measure it¤ Measure the sign of m2

13¤ Measure 23 (is it ≠45°?)

NB Independently of the scenario the worsening of the experimental sensitivity due to the eightfold degeneracy has to be taken into account

Possible strategy(detector side)

We think that one should figure out the best setup depending on the results of phase I experiments

Null result for 13: are we ready to risk several billions $? NO, it is better to try a cheap, although not the

ultimate, approach to two important parameters like 13 and

Observation of a non vanishing 13: are we ready to invest several billions $? YES, since there is the possibility to fully measure the

PMNS mixing matrix

The -beam (BB) role

The BB was born in 2001 when P. Zucchelli put forward the idea to produce pure (anti-)e beam from the decay of radioactive ions

Originally the BB was thought as a low (~100) energy neutrino beam and its performance studied in combination with a Super-Beam (SB), by assuming a 130 km baseline and 1 Mton detector located at Frejus (M. Mezzetto et al.)

However, very recently (december 2003) the possibility of medium/(very) high energy BB was put forward (see hep-ph/0312068)

What is the impact of the BB (low (see S. Rigolin talk for details), medium, high, very-high ) in the future of neutrino oscillation experiments?

Comparison of low BB with some of the future projects

Low BB+SB

Why high BB?

statistics increases linearly with E (cross section) increase rates (very important for anti-neutrinos)

longer baseline enhance matter effects possibility to measure the sign of m2

13

increase the energy easier to measure the spectral information in the oscillation signal important to reduce the intrinsic degeneracies

Atmospheric background becomes negligible (this is a major background source in the low energy option) the bunching of the ions is not more a crucial issue

Which ’s?

Use a refurbished SPS with super-conducting magnets to accelerate ions Maximum ~600

Use the LHC to accelerate ions Up to ~2488 for 6He and 4158 for 18Ne

In the US (see talk of S.Geer and APS meeting @ Snowmass, 28-30 Jun 04):

How to exploit high BB?

Phase I exps give null result See hep-ph/0405081 for a cheap and

extremely sensitive to 13 experiment

Phase I discover 13

See Nucl.Phys.B695:217-240,2004 for possible setups to search for

New ideas

Signal: an excess of horizontal muons in coincidence with the beam spill (possible thanks to the BB flavour composition) Number of unoscillated events:

increase linearly with E

Range of muons: increase linearly with E as well. The effective volume of rock contributing to the statistics increase linearly with E

We gain a quadratic increase of the sensitivity if we increase and we reduce the detector cost by order of magnitudes!

We loose the possibility to fully reconstruct the events

F. Terranova, A. Marotta, M. Spinetti, P.M. hep-ph/0405081

The cost of the detector increase with the surface and not with the volume

A proposal for a cheap experiment

Schematic view of the detector

Rock

e

Instrumented surface: 15x15 m2 (one LNGS Hall)

Thickness: at least 8I (1.5 m) of iron for a good / separation

Iron detector interleaved with active trackers (about 3kton)

H

A possible scenario: BB from CERN to Gran Sasso

A cavern already exists at GS, but Too small to host 40 kton WC or LAr detectors On peak exp requires E ~ 1-2 GeV (= 350/580) too small to

efficiently exploit iron detectors What happens if we consider > 1000 (i.e. off-peak

experiment)? The oscillation probability decreases as -2

The flux increases as 2

The cross-section and the effective rock volume increase both as

Matter effects cancel out at leading order even if the baseline is large

We recover the quadratic increase of sensitivity but we test now CP-even terms and no matter effects

Beam assumptions1.1x1018 decays per year of 18Ne 2.9x1018 decays per year of 6He

Applied cuts2 GeV energy cut in a 20° cone

100 % oscillated events/year: 9.3x104 (e @ =2500)2.0x104 (anti e @ =1500)7.9x105 (e @ =4158)2.1x105 (anti e @ =2488)

Event rate

test sin2213 values down to 10-3-10-4!!!

Sensitivity of a “massless” detector located 730 km from a (very)high-

BB

Comparison of very-high BB with some of future projects

Low BB+SB

BB very high

In case of null result very difficult to build new facilities!

Two setups studied for the medium/high options

Medium (350) and high (1500) for medium (730 km) and far (3000 km) baselines

Water detector (UNO) like; 1 Mton mass. Includes full simulation of efficiencies and backgrounds (only statistical study for high gamma option)

Running time 10 years Full analysis (including the eightfold degeneracy,

all systematics on cross-sections, detector, beam, performance at small 13, etc.) still to be done

Results

J.Burguet-Castell et al., Nucl.Phys.B695:217-240,2004

Baseline option(Frejus)

40 Kton/y WC @ 730 km=350 (6He) / 580 (18Ne)

4 Mton/y WC detector @ 3000 km=1550 (6He) / 2500 (18Ne)

4 Mton/y WC @ 730 km=350 (6He) / 580 (18Ne)

L=732 km Uno like detector

L=3000 km Uno like detector

L=732 km SK like detector

L=130 km UNO like detector

99% CL

Comments The idea of medium/(very) high- BB is very appealing Whatever (medium, high, very-high) we consider its performance

is better than the low one The medium scenario has been put forward in Nucl.Phys.B695:217-

240,2004 to measure 13, and the sign of m213, but more studies

are needed to fully exploit its potential (i.e. the 23 ambiguity) However, we think this is not the optimal solution

It foresees the construction of a 1 Mton detector! There are no place in the world able to host it It is very expensive, so to risky to build if phase I exps give null results

The optimal solution is the very-high scenario In case of null result of phase I exps it allows a cheap investigation of

very small values of sin2213 (see hep-ph/0405081) In case of positive result of phase I exps it allows a complete study of

the PMNS matrix through different channels, see next slides for details On top of that it makes possible the usage of magnetized calorimeters

which are smaller (40 kton -> about 104 m3) than WC detectors (1 Mton -> about 106 m3) cheaper (easier) civil engineer costs

Preliminary studies/ideas on how to use the very-high BB

A. Donini, PM, S. Rigolin, …

High gamma; L = 732 km

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Energy (GeV)

Neutrinos

Anti-neutrinos

Very-high gamma; L = 732 km

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1000,00000

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1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33

Neutrinos

Anti-neutrinos

BB vs NuFact spectra

Ne

NeHe

He

NuFact

Expected rates (1ktonx1year)

NuFact BB

e anti- e anti-e

L=730 km 296x103 176x103 --- ---

L=730 km=2500/150

0--- --- 17x103 5.5x103

L=730 km=4158/248

8--- --- 77x103 25x103

L=3000 km 18x103 11x103 --- ---

L=3000 km=2500/150

0--- --- 1.0x103 0.3x103

L=3000 km=4158/248

8--- --- 4.6x103 1.5x103NB There is less than a factor 10 difference in the #evts

BB allows simultaneous run with and anti-, while NuFact does not

Potentiality of a very-high BB

Simultaneous search for e (golden) and e (silver) channels This combination is highly efficient in removing the

intrinsic and the sign degeneracy (see A.Donini, D.Meloni, P.Migliozzi Nucl.Phys.B646:321-349,2002)

Simultaneous search for and anti- channels (i.e. 1 year BB 2 years NuFact)

Detectors: 40kton magnetized iron detector (MID) at 3000km; ≥5kton ECC detector at 730km

The physics potential of this setup is currently under study as well as its comparison with a NuFact

Very preliminary results at a high- BB

with golden plus silver channels

Octan clone

68%, 90%, 99% CL

MID MID+ECC

Parameter extraction in presence of signal (II) with a low BB plus a SB

Continuous line: intrinsic degeneracy

Dashed line: sign ambiguity

Dot-dashed line: octant ambiguity

Dotted line: mixed ambiguity

Conclusion Whatever (medium, high, very-high) BB we consider its

performance is better than the low one The optimal solution is the very-high scenario

In case of null result of phase I exps it allows a cheap investigation of very small values of sin2213 (see hep-ph/0405081)

In case of positive result of phase I exps it allows a complete study of the PMNS matrix through different channels, see next slides for details

On top of that it makes possible the usage of magnetized calorimeters which are smaller (40 kton -> 104 m3) than WC detectors (1 Mton -> 106 m3) cheaper (easier) civil engineer costs

The potentiality of a very-high BB are under study including the eightfold degeneracy and both the golden and the silver channels. Some preliminary results look interesting

MORE STUDIES FROM THE ACCELERATOR SIDE ARE NEEDED INDEPENDENTLY OF THE OPTION

Is the proposed low energy setup (CERN to Frejus) the

optimal one? NO! Why?

In spite of the large detector mass, the performance is limited by small rates (due to small cross-sections) and by the eightfold degeneracy

By using the BB or the SB alone is not possible to solve any of the degeneracies, although for large enough 13 a first estimate of the two continuous parameters 13 and can be attempted

Neither the sign of m213 nor the absolute value of 23 can be

determined The combination of a BB and a SB (as proposed in the CERN

scenario) is not a real synergy (i.e. NO degeneracy is solved). Indeed, it only determines an increase of statistics for both and anti-

The sensitivity of a BB is comparable with the one of other proposed future projects

Can higher BB be more suitable?

Beam related background:

Pion punch-through deep hadron plugEarly /K decays in flight energy cut (charge id)Charm background only for the highest , energy cut

(charge id)

Beam unrelated background:

Atm. neutrinos energy cut (beam timing)Cosmics angular cut (huge slant depth near the horizon)

Beam unrelated background is so small that we can release by two order of magnitudes the request on the bunch length

of the BBAn enormous technical simplification

Can we handle background with such a rough detector?

Event rates vs (L = 732 km)

Parameter extraction in presence of signal (I)with a low BB plus a SB

SB

BB+SB

BB

Continuous line: intrinsic degeneracyDashed line: sign ambiguityDot-dashed line: octant ambiguityDotted line: mixed ambiguity

NB The black dots show the theoretical clone location computed following Ref. JHEP

0406:011,2004