A neutrino program based on the machine upgrades
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, Pasquale Migliozzi INFN T. Tabarelli Napoli de Fatis, F. Terranova
Motivations ü Is there a window of opportunity for neutrino oscillation physics compatible with the machine upgrades of the LHC (>2015)? ü Can we immagine an affordable facility that could fully exploit european infrastructures during the LHC era? ü 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: a = e, , (“flavour” index) i = 1, 2, 3 (mass index) Uai: unitary mixing matrix (PMNS)
Notation Mixing parameters: Mass-gap parameters: U = U (q 12, q 13, q 23, d) as for CKM matrix M 2 = Dm 212 , ± Dm 223 The absolute neutrino mass scale should be set by direct mass measurements: · b-decay · 0 n 2 b-decay · “W-MAP”
So what do we have to measure? n n n n Three angles (q 12, q 13, q 23) Two mass differences (Dm 212 (or dm 2), Dm 223 (or Dm 2)) The sign of the mass difference Dm 2 (±Dm 223) One CP phase (d) 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
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 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 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 Overall picture
Why q 13 is important? small (~1/30) but non negligible If q 13 is vanishing or too small the possibility to observe CP violation in the leptonic sector vanishes!!!
Sensitivity plot vs time for Phase I experiments I I e Phase I 2009 2007 T 2 K Nona LHC and Double CHOOZ startup 2012 2014 Beam upgrade and HK construction q 13 discovery ? 2012 End of CNGS s a h P 2015 “Phase 2” lumi upgrade of the LHC 2022 Data taking. . . 2022 LHC Energy upgrade?
How to approach Phase II in Europe? n Many ideas have been put on the market n n 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 F Exploit as much as possible technologies common to other fields (e. g. LHC upgrades, EURISOL) F Exploit already existing infrastucture (e. g. LNGS halls) ÄCosts reduction!
Multi-MW Super. Beam n n n Technology similar to conventional n beams Neutrino beam has contamination from other flavours n Main source of systematics n Useful for Neutrino Factory n Huge low density detectors mandatory (i. e. water Č) n Gran Sasso halls are too small to host Mton detectors Proton driver to be built from scratch Low energy neutrino beams Underground laboratory to be built from scratch (e. g. SPL-Frejus)
Neutrino Factory n n n Excellent neutrino beam n Flux composition very well known Very challenging technology n 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
Beta Beam n Excellent neutrino beam n n Possibility to work in νμ appearance mode n n νμ CC are an easier channel than ne CC and allows for dense detector No need to distinguish νμ from anti-νμ n n Flux composition very well known 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)
Comparison of the different designs n Current design (EURISOL DS) n n n n S-SPS n n n n 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 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!
Not needed for a Beta Beam The Beta Beam complex + a decay ring Present design lenght: 6880 m useful decays: 36% 5 T magnets S-SPS based design lenght: 6880 m useful decays: 23% 8. 3 T magnets (LHC)
Why S-SPS is so interesting? n It is able to bring 6 He up to g≤ 350 (18 Ne up to g ≤ 580) n n Neutrino energy above 1 Ge. V (spectrum analysis) It is not in contrast with the LHC running ν antiν • 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 n n n It provides a fast ramp (d. B/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 (x 2 intensity, faster cycle) Fluxes could be smaller than Frejus (higher g means higher lifetime) n n 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 <10 ns bunch length to get rid of the atmospheric background n We can recover the losses due to the higher g (see next slide)
The duty cycle issue Frejus In order to reduce the atmospheric backouground the timing of the parent ion is needed Ä 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 S-SPS ν anti-ν With the S-SPS based scenario the atmospheric background is reduced by about a factor 10 and the bunch length can be correspondently increased
See e. g. T. Tabarelli @ LCWS 05 The detector at the Gran Sasso 40 kton iron (4 cm thickness) and glass RPC Digital readout (2 x 2 cm 2 pads) Full simulation but event selection based on inclusive variables only hits, layers etc. ) can be improved with pattern recognition (n.
Event classification
Efficiency and background as a function of the neutrino enery
Discovery potential Assuming d=90° d=-90 o T 2 K d=0 o d=90 o d q 13 Assuming q 13=3° g (18 Ne)=350 , g (6 He)=350, 10 y with “nominal” flux (F 0) Both plots have been obtained by assuming 5% systematic error and are computed at 99%C. L. Energy reconstruction not exploited yet!!!
g (18 Ne)=350 , g (6 He)=350, 10 y with “nominal” flux Exclusion plots @99%C. L. q 13 Both plots have been obtained by assuming 5% systematic error and are computed at 99% C. L. Sensitivity to sign of Dm 223 In progress. We expect sensitivity for q 13>5° Energy reconstruction not exploited yet!!! d d Discovery plots @99%C. L. F 0 x½ F 0 x 2 q 13
Conclusion § The Super-SPS option for the luminosity/energy upgrade of the LHC strenghten enormously the physics case of a Beta Beam in Europe n n No need of ultra-massive (1 Mton) detectors Possibility to leverage existing underground facilities (Gran Sasso laboratories) Full reconstruction of the event in n 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!
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