A neutrino program based on the machine upgrades of the LHC

1. A neutrino program based on the machine upgrades of the LHC Pasquale Migliozzi INFN – Napoli A. Donini, E. Fernandez Martinez, P.M., S. Rigolin, L. Scotto Lavina, T.Tabarelli de Fatis, F. Terranova

2. Motivations • Is there a window of opportunity for neutrino oscillation physics compatible with the machine upgrades of the LHC (>2015)? • Can we immagine an affordable facility that could fully exploit european infrastructures during the LHC era? • Is the sensitivity adequate for an experiment aiming at closure of the PMNS (precision measurement of the 1-3 sector)?

3. Neutrino oscillations(a glimpse beyond the Standard Model) The most promising way to verify if mn > 0 (Pontecorvo 1958; Maki, Nakagawa, Sakata 1962) Basic assumption: neutrino mixing e, , are not mass eigenstates but linear superpositions of mass eigenstates 1, 2, 3 with masses m1, m2, m3, respectively: • = e, ,  (“flavour” index) i = 1, 2, 3 (mass index) Uai: unitary mixing matrix (PMNS)

4. Mixing parameters:U = U (q12, q13, q23, d)as for CKM matrix Notation M2 = Dm212 , ± Dm223 Mass-gap parameters: The absolute neutrino mass scale should be set by direct mass measurements: · b-decay· 0n2b-decay· “W-MAP”

5. So what do we have to measure? • Three angles (q12, q13, q23) • Two mass differences (Dm212 (or dm2), Dm223 (or Dm2)) • The sign of the mass difference Dm2 (±Dm223) • One CP phase (d) • The source of atmospheric oscillations (detect t appearance) • The absolute masse scale • Are neutrino Dirac or Majorana particles (or both)? • Are there more - sterile - neutrinos? All the underlined items can be studied with LBL experiments

6. Atmospheric + LBL sector By G.L. Fogli, E. Lisi, A. Marrone, A. Palazzo (Bari U. & INFN, Bari) Submitted to Prog.Part.Nucl.Phys. e-Print Archive: hep-ph/0506083

7. Solar + reactors By G.L. Fogli, E. Lisi, A. Marrone, A. Palazzo (Bari U. & INFN, Bari) Submitted to Prog.Part.Nucl.Phys. e-Print Archive: hep-ph/0506083

8. Overall picture By G.L. Fogli, E. Lisi, A. Marrone, A. Palazzo (Bari U. & INFN, Bari) Submitted to Prog.Part.Nucl.Phys. e-Print Archive: hep-ph/0506083

9. Why q13 is important? small (~1/30) but non negligible If q13 is vanishing or too small the possibility to observe CP violation in the leptonic sector vanishes!!!

10. Sensitivity plot vs time for Phase I experiments Phase II 2022 2014 Beam upgrade and HK construction Data taking... 2022 2015 “Phase 2” lumi upgrade of the LHC LHC Energy upgrade? Phase I 2009 2012 T2K Nona q13 discovery ? 2007 2012 LHC and Double CHOOZ startup End of CNGS

11. How to approach Phase II in Europe? • Many ideas have been put on the market • Different accelerator technologies • Different baselines • Different detector technologies • We think that Phase II in Europe should be part of a common effort of the Elementary Particle community • Exploit as much as possible technologies common to other fields (e.g. LHC upgrades, EURISOL) • Exploit already existing infrastucture (e.g. LNGS halls) • Costs reduction!

12. Multi-MW SuperBeam • Technology similar to conventional n beams  • Neutrino beam has contamination from other flavours  • Main source of systematics • Proton driver to be built from scratch  • Useful for Neutrino Factory • Low energy neutrino beams  • Huge low density detectors mandatory (i.e. water Č) • Underground laboratory to be built from scratch (e.g. SPL-Frejus) • Gran Sasso halls are too small to host Mton detectors

13. Neutrino Factory • Excellent neutrino beam  • Flux composition very well known • Very challenging technology  • Start operations > 2020 • No relevant overlap with CERN accelerators  • Possible the study of the “silver channel” (νe→ν)  • If built at CERN, Gran Sasso Lab maybe too close 

14. Beta Beam • Excellent neutrino beam  • Flux composition very well known • Possibility to work in νμ appearance mode  • νμ CC are an easier channel than ne CC and allows for dense detector • No need to distinguish νμ from anti-νμ • No need for magnetic detectors! • Many energy configurations are envisaged: g~150 (current design), g~350 (S-SPS based design), g>1000 (LHC based design)

15. Comparison of the different designs • Current design (EURISOL DS) • Strong synergy with present CERN accelerator complex  • Low energy beam: needs huge and low density detectors  • Underground lab to be built from scratch (e.g. Frejus)  • Counting experiment  • Excellent θ13 and δ sensitivity  • No sensitivity to neutrino hierarchy  • S-SPS • Strong synergy with a LHC energy/luminosity upgrade  • Medium energy beam: small and high density detectors start to be effective  • Underground lab already exists (e.g. Gran Sasso)  • Spectrum analysis possible  • Very good θ13 and δ sensitivity (slightly smaller than current desing)  • Sensitivity to neutrino hierarchy  • NB both designs need an ion decay ring!

16. The Beta Beam complex + a decay ring Not needed for a Beta Beam Present design lenght: 6880m useful decays: 36% 5 T magnets S-SPS based design lenght: 6880m useful decays: 23% 8.3 T magnets (LHC)

17. ν anti-ν Why S-SPS is so interesting? • It is able to bring 6He up to g≤350 (18Ne up to g ≤580) • Neutrino energy above 1 GeV (spectrum analysis) • It is not in contrast with the LHC running • Iron detectors are already effective • Fermi motion is no more dominant (energy reconstruction) • Baseline fits the CERN-LNGS distance (730 km) and is large enough to study neutrino hierarchy

18. S-SPS technology (accidentally) ideal for high-energy BB • It provides a fast ramp (dB/dt=1.21.5 T/s) allowing for a reduction of the ion decays during the acceleration phase  • Super-SPS more performant than SPS (x2 intensity, faster cycle)  • Fluxes could be smaller than Frejus (higher g means higher lifetime)  • High field magnets (11-15 T) in the decay ring would increase the number of useful decays (higher flux) OPTIONAL! • We can allocate more ion bunches in the decay ring because we do not need a <10ns bunch length to get rid of the atmospheric background    • We can recover the losses due to the higher g (see next slide)

19. Frejus S-SPS ν anti-ν The duty cycle issue • In order to reduce the atmospheric backouground the timing of the parent ion is needed • Strong constraint on the number of circulating bunches and on the bunch length In the present design • bunch length 10 ns (very challenging) (10-3 suppression factor) • 8 circulating bunches With the S-SPS based scenario the atmospheric background is reduced by about a factor 10 and the bunch length can be correspondently increased

20. The detector at the Gran Sasso See e.g. T.Tabarelli @ LCWS05 40 kton iron (4 cm thickness) and glass RPC Digital readout (2x2 cm2 pads) Full simulation but event selection based on inclusive variables only (n. hits, layers etc.)  can be improved with pattern recognition

21. Event classification

22. Efficiency and background as a function of the neutrino enery

23. Discovery potential Assuming d=90° Assuming q13=3° d=-90o d=0o T2K d q13 d=90o g (18Ne)=350 , g (6He)=350, 10y with “nominal” flux (F0) Both plots have been obtained by assuming 5% systematic error and are computed at 99%C.L. Energy reconstruction not exploited yet!!!

24. Sensitivity to sign of Dm223 In progress. We expect sensitivity for q13>5° g (18Ne)=350 , g (6He)=350, 10y with “nominal” flux Exclusion plots @99%C.L. Both plots have been obtained by assuming 5% systematic error and are computed at 99% C.L. q13 Energy reconstruction not exploited yet!!! d Discovery plots @99%C.L. d F0x½ F0 F0x2 q13

25. Conclusion • The Super-SPS option for the luminosity/energy upgrade of the LHC strenghten enormously the physics case of a Beta Beam in Europe • No need of ultra-massive (1Mton) detectors • Possibility to leverage existing underground facilities (Gran Sasso laboratories) • Full reconstruction of the event in nm appearance mode • Baseline appropriate for exploitation of matter effects We strongly support a more detailed machine study. If technically affordable, this option is an opportunity we cannot miss!