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Potentiality of a (very) high- g b -Beam complex

Potentiality of a (very) high- g b -Beam complex. Pasquale Migliozzi INFN – Napoli. !!!WARNING!!!. The physics potential of the BB of any g has been carefully evaluated by several groups and discussed in this talk and in the previous ones

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Potentiality of a (very) high- g b -Beam complex

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  1. Potentiality of a (very) high-gb-Beam complex Pasquale Migliozzi INFN – Napoli

  2. !!!WARNING!!! The physics potential of the BB of any g 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 g option) to endorse their “practical” realization

  3. Future neutrino oscillation exps Running, constructing or approved experiments

  4. Possible scenarios after first results of the planned experiments and implications • q13 is so small (< 3°, sin22q13 ≤ 0.01) that all give null result • We need a “cheap” experiment to probe sin22q13 values down to O(0.001 - 0.0001) • q13 is larger than 3° (sin22q13 ≥ 0.01) • We need an experiment (or more than one) to • Measure q13 more precisely • Discover d (if not done yet) or precisely measure it • Measure the sign of Dm213 • Measure q23 (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

  5. 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 q13: 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 q13 and d • Observation of a non vanishing q13: are we ready to invest several billions $? • YES, since there is the possibility to fully measure the PMNS mixing matrix

  6. The b-beam (BB) role • The BB was born in 2001 when P. Zucchelli put forward the idea to produce pure (anti-)ne beam from the decay of radioactive ions • Originally the BB was thought as a low (g~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 g) in the future of neutrino oscillation experiments?

  7. Low g BB+SB Comparison of low g BB with some of the future projects

  8. Why high g 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 Dm213 • 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

  9. In the US (see talk of S.Geer and APS meeting @ Snowmass, 28-30 Jun 04): Which g’s? • Use a refurbished SPS with super-conducting magnets to accelerate ions • Maximum g~600 • Use the LHC to accelerate ions • Up to g~2488 for 6He and 4158 for 18Ne

  10. How to exploit high g BB? • Phase I exps give null result • See hep-ph/0405081 for a cheap and extremely sensitive to q13 experiment • Phase I discover q13 • See Nucl.Phys.B695:217-240,2004 for possible setups to search for d • New ideas

  11. A proposal for a cheap experiment 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 g and we reduce the detector cost by order of magnitudes! • The cost of the detector increase with the surface and not with the volume We loose the possibility to fully reconstruct the events F. Terranova, A. Marotta, M. Spinetti, P.M. hep-ph/0405081

  12. m H Schematic view of the detector Instrumented surface: 15x15 m2 (one LNGS Hall) Thickness: at least 8lI (1.5 m) of iron for a good p/m separation Iron detector interleaved with active trackers (about 3kton) Rock ne nm

  13. 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 En ~ 1-2 GeV (g= 350/580) too small to efficiently exploit iron detectors • What happens if we consider g > 1000 (i.e. off-peak experiment)? • The oscillation probability decreases as g-2 • The flux increases as g2 • The cross-section and the effective rock volume increase both as g • 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

  14. Event rate Beam assumptions 1.1x1018 decays per year of 18Ne 2.9x1018 decays per year of 6He Applied cuts 2 GeV energy cut in a 20° cone 100 % oscillated events/year: 9.3x104 (ne @ g=2500) 2.0x104 (anti ne @ g=1500) 7.9x105 (ne @ g=4158) 2.1x105 (anti ne @ g=2488)

  15. Sensitivity of a “massless” detector located 730 km from a (very)high-g BB test sin22q13 values down to 10-3-10-4!!!

  16. Low g BB+SB BB very high g Comparison of very-high g BB with some of future projects In case of null result very difficult to build new facilities!

  17. Two setups studied for the medium/high g options • Medium (350) and high (1500) g 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 q13, etc.) still to be done

  18. 4 Mton/y WC detector @ 3000 km g=1550 (6He) / 2500 (18Ne) L=732 km SK like detector 4 Mton/y WC @ 730 km g=350 (6He) / 580 (18Ne) 40 Kton/y WC @ 730 km g=350 (6He) / 580 (18Ne) Baseline option (Frejus) L=130 km UNO like detector L=3000 km Uno like detector L=732 km Uno like detector Results 99% CL J.Burguet-Castell et al., Nucl.Phys.B695:217-240,2004

  19. Comments • The idea of medium/(very) high-g BB is very appealing • Whatever g (medium, high, very-high) we consider its performance is better than the low one • The medium scenario has been put forward inNucl.Phys.B695:217-240,2004 to measure q13, d and the sign of Dm213, but more studies are needed to fully exploit its potential (i.e. the q23 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 g scenario • In case of null result of phase I exps it allows a cheap investigation of very small values of sin22q13 (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

  20. Preliminary studies/ideas on how to use the very-high g BB A. Donini, PM, S. Rigolin, …

  21. BB vs NuFact spectra NuFact Ne He Ne He

  22. Expected rates (1ktonx1year) NB There is less than a factor 10 difference in the #evts BB allows simultaneous run with n and anti-n, while NuFact does not

  23. Potentiality of a very-high g BB • Simultaneous search for nenm (golden) and nent (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 n and anti-n 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

  24. Very preliminary results at a high-g BBwith golden plus silver channels 68%,90%,99% CL MID+ECC MID Octan clone

  25. Continuous line: intrinsic degeneracy Dashed line: sign ambiguity Dot-dashed line: octant ambiguity Dotted line: mixed ambiguity Parameter extraction in presence of signal (II) with a low g BB plus a SB

  26. Conclusion • Whatever g (medium, high, very-high) BB we consider its performance is better than the low one • The optimal solution is the very-high g scenario • In case of null result of phase I exps it allows a cheap investigation of very small values of sin22q13 (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 g OPTION

  27. 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 q13 a first estimate of the two continuous parameters q13 and d can be attempted • Neither the sign of Dm213 nor the absolute value of q23 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 n and anti-n • The sensitivity of a BB is comparable with the one of other proposed future projects • Can higher g BB be more suitable?

  28. Can we handle background with such a rough detector? Beam related background: Pion punch-through deep hadron plug Early p/K decays in flight energy cut (charge id) Charm background only for the highest g, 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 BB An enormous technical simplification

  29. Event rates vs g(L = 732 km)

  30. BB SB Continuous line: intrinsic degeneracy Dashed line: sign ambiguity Dot-dashed line: octant ambiguity Dotted line: mixed ambiguity NB The black dots show the theoretical clone location computed following Ref. JHEP 0406:011,2004 BB+SB Parameter extraction in presence of signal (I)with a low g BB plus a SB

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