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

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)?

Neutrino oscillations (a glimpse beyond the Standard Model) The most promising way to verify if m > 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 m 1, m 2, m 3, respectively:  = e, ,  (“flavour” index) i = 1, 2, 3 (mass index) U  i : unitary mixing matrix (PMNS)

Notation Mixing parameters: U = U (  12,  13,  23,  ) as for CKM matrix Mass-gap parameters: M 2 =  m 2 12, ±  m 2 23 The absolute neutrino mass scale should be set by direct mass measurements:  -decay  0 2  -decay  “ W-MAP ”

So what do we have to measure? Three angles (  12,  13,  23 ) Two mass differences (  m 2 12 (or  m 2 ),  m 2 23 (or  m 2 )) The sign of the mass difference  m 2 (±  m 2 23 ) One CP phase (  ) The source of atmospheric oscillations (detect  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

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/ G.L. FogliE. LisiA. MarroneA. PalazzoBari U.INFN, Bari

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/ G.L. FogliE. LisiA. MarroneA. PalazzoBari U.INFN, Bari

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/ G.L. FogliE. LisiA. MarroneA. PalazzoBari U.INFN, Bari

Why  13 is important? If  13 is vanishing or too small the possibility to observe CP violation in the leptonic sector vanishes!!! small (~1/30) but non negligible

T2K No a   discovery ? LHC and Double CHOOZ startup End of CNGS Phase I Sensitivity plot vs time for Phase I experiments Phase II Beam upgrade and HK construction Data taking “Phase 2” lumi upgrade of the LHC LHC Energy upgrade?

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!

Multi-MW SuperBeam Technology similar to conventional 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

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” ( ν e →ν  ) If built at CERN, Gran Sasso Lab maybe too close 

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

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 θ 13 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 θ 13 and δ sensitivity (slightly smaller than current desing)  Sensitivity to neutrino hierarchy NB both designs need an ion decay ring!

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

Why S-SPS is so interesting? It is able to bring 6 He up to  ≤350 ( 18 Ne up to  ≤580) Neutrino energy above 1 GeV (spectrum analysis) It is not in contrast with the LHC running ν anti- ν 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

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  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  (see next slide)

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 1.bunch length 10 ns (very challenging) (10 -3 suppression factor) 2.8 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 Frejus S-SPS ν anti-ν

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

Event classification

Efficiency and background as a function of the neutrino enery

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

 ( 18 Ne)=350,  ( 6 He)=350, 10y with “nominal” flux Both plots have been obtained by assuming 5% systematic error and are computed at 99% C.L.      F 0 x½ F 0 F 0 x2 Exclusion Discovery Sensitivity to sign of  m 2 23 In progress. We expect sensitivity for  13 >5° Energy reconstruction not exploited yet!!!

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  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!