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Scenarios for an entry-level Neutrino Factory

Scenarios for an entry-level Neutrino Factory. Mario Campanelli Geneva University. LSND and its results. The LSND experiment took data from 1993 to 1997 at LAMPF, searching for electron appearance in a   beam. L=30 m, 36 MeV<E ν <52.8 MeV     e

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Scenarios for an entry-level Neutrino Factory

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  1. Scenarios for an entry-level Neutrino Factory Mario Campanelli Geneva University

  2. LSND and its results The LSND experiment took data from 1993 to 1997 at LAMPF, searching for electron appearance in a  beam. L=30 m, 36 MeV<Eν<52.8 MeV •  e • using reaction e p->e+ n followed by n p-> d γ • Excess of 51.0+20.2-19.5 ±8.0 events (first run) • Total oscillation probability: (0.31 ± 0.12 ± 0.05)% • e • Electron from e C->e-X in range 60<Ee<200 MeV • Excess of 27.7 ±6.4 events • Osc. Probability: (0.26 ± 0.10 ± 0.05)%

  3. Karmen results Karmen (I and II), covering similar parameter space using a pulsed beam did not observe any oscillation. A corner of the parameter space is still permitted by the combination of the two experiments due to the slightly different L/E of the two experiments

  4. MiniBOONE Currently running at Fermilab, using neutrios from booster <Ep>= 8 GeV, <En>~1 GeV Main differences wrt LSND: • 30 times more energy • 20 times more distance • Cerenkov light 4 times larger than scintillation • Neutron capture not used • Neutrinos instead of (mainly) antineutrinos

  5. The MiniBOONE philosophy The experiment aims at large electron signals if LSND is correct • Background is also large: • 600 events from muons • 600 events from pions • 1800 events from νe in beam (controlled changing decay tunnel length) CC sample (1 nominal year): 6 105 events

  6. After 1021 POT (2 nominal years) Build another detector (BOONE) for precision measurements of oscillation parameters Run with anti-neutrinos to exclude non-oscillation effects So far, 10% taken, running at half the planned rate, but improving. Problems due to radiation issues in the booster tunnel.

  7. Interpretation of a positive result Great excitement! Need to add new pieces to the puzzle If signal only in antineutrino mode, lepton flavour and/or CPT violated If seen in both modes, we need sterile neutrino(s). Normally people tend to: (from NuFact’99 A.deRujula)

  8. Scenarios with 4 neutrinos • Sterile neutrinos are like cherries, if you have one you probably have more than one. • Depending on mass hierarchies, even the simplest case contains several scenarios: 2+2 (disfavored by atmos+ solar) 3+1 (disfavored by short-baseline) 3+1 scheme collapses into 3-family in the weak mixing limit, it can never be really ruled out, while 2+2 not justified if LSND disproved. 3+2 (hep-ph/0305255) not studied yet.

  9. Counting parameters Difference anyway irrelevant in oscillation experiments At least 2 masses for CPv One phase present, but only CP-even possible Rotations for neutrinos 123 irrelevant Ordering rotation matrices according to mass difference is convenient in case degeneracy is assumed: UMSN(2+2)= U14(θ14)U13(θ13)U24(θ24)U23(θ23,δ3)U34(θ34,δ2)U12(θ12,δ1) UMSN(3+1)= U14(θ14)U24(θ24)U34(θ34)U23(θ23,δ3)U13(θ13, δ2)U12(θ12,δ1)

  10. Bounds from data • Atmospherics and solars strongly disfavor pure oscillation into sterile • Limits to νe transitions (CHOOZ, CDHS etc.) set maximal size of gap crossing angles • In 2+2, c223sin2(2θ24)+c424sin2(2θ23)<0.2 • The LSND signal connects actives and steriles: • In 2+2, 10-3<c213c224sin2 (2θ23)<10-2 • In 3+1 schemes, only few zones of parameter space marginally allowed, with very small active-sterile mixing • (e.g. c434s214sin2(2θ24)  210-3) νs,νμ,νe, ντ

  11. Neutrino Factory and 4-ν scenarios Many simultaneous channels of the NF are a clear benefit to study these complicated scenarios. Interest is reciprocal: if LSND is true, larger probabilities mean an entry level NF with reduced fluxes, smaller detectors and shorter baselines • Several works done: • Donini, Gavela, Hernandez, Rigolin hep-ph/9910516 • Barger, Geer, Raja, Whisnant hep-ph/0007181 • Donini, Gavela, Hernandez, Rigolin hep-ph/0007283 • Donini, Meloni hep-ph/0105089 • Donini, Meloni hep-ph/0105163 • Donini, Lusognoli, Meloni hep-ph/0107231

  12. One mass-dominance approximation CP is conserved, and only the four angles θ13θ14θ23(2+2 only)θ24 are relevant. We can assume, from solar and atmospherics: • θ12= 45°; θ34= 45º; Δm212=10-4 Δm234=3.510-3 (2+2) • θ12= 22.5°; θ13= 13°; θ34= 45º (1+3) (Fogli Lisi Marrone Scioscia) Donini-Meloni studied sensitivity to gap-crossing angles in 2+2 and 3+1 schemes, for a NF of Eμ=20 GeV, 1021 useful muons, 1 ton (1 m3 water!) detector with εμ=0.5, ετ=0.35 placed at 1 km distance. For simplicity, only negative muon decays considered. Wrong-sign background assumed O(10-5).

  13. sin2θ23: μ+appearance 2+2 scheme sin2θ13: μ- disappearance sin2θ14,sin2θ14 : τ- appearance

  14. sin2θ14,sin2θ14 : μ+ appearance 3+1 scheme sin2θ34: τ appearance

  15. CP violation In 3 families, magnitude of effect depends on Δm212, while in 4 families on Δm223, so larger, can go closer and have small matter effects. Here we consider integrated asymmetry, ACP(δ)= (R- -R+) / (R- +R+) where R±=N(l±α)/N(l±β) as a function of δ, considering known the values of the mixing angles

  16. CPV sensitivity in 2+2 schemes e e  e

  17. e δ2=0,δ3=90° CP violation sensitivity in 3+1 schemes e e δ2=δ3=15°,45°, 90°

  18. Summary on physics Obviously, if LSND is confirmed, neutrino physics will receive a great boost, due to the relative ease to perform measurements. t identification becomes key issue due to complicated parameter space. Simple muon identification gives much worse understanding of oscillation picture. To a first approximation, sensitivity scales as N Due to the mass governing the effect, the study of CP violation requires detector size and baseline comparable to measuring parameters in a 3-family scenario. “simple” parameter measurement in 4 families requires modest effort- detector 2 order of magnitude closer and 4 lighter.

  19. Entry-level NF? We can consider a 100 ton detector, and lower machine power to 21018 μ/y (and 5 years run) Beware: due to beam width of ~1m, detector has to be cigar-shaped! Aiming to such a low intensity, we can assume: • No need for a new proton driver (JHF I or even FNAL booster could be sufficient) • No special radiation-hard targeting • No need for cooling • Energy: could be reduced, but not by large amounts (cannot gain like 1/L2 going closer since already embracing all beam with 1 m detector diameter)

  20. NF scheme Possible savings Detector at 10-20 km

  21. Pricing Overall, a total saving of about $600M could be envisaged (probably more due to lower cost of other components)

  22. What if MiniBOONE finds nothing? LSND could still be right, and have seen instead of oscillations LFV like +e+l or -e-el. It was shown (Bueno, MC, Laveder, Rico, Rubbia hep-ph/0010308) that a low-energy entry-level NF and a 10 ton LAr detector located 100 m from the machine improves limits on these decays, reaching sensitivities relevant to the LSND effect

  23. An even smaller machine A NF with ~1015 μ/y (muons trapped in the CERN AD or FNAL debuncher) has no interest for neutrino oscillations. However, such a machine could be used to measure neutrino cross section at low-energy with precision O(10%), much better than present data MC Navas-Concha Rubbia, hep-ph/0107221, 1015μ’s, Eμ =2 GeV, 100 ton detector 10 meters from machine

  24. A poor-(wo)man NF? It recently came out (B.Fleming) that neutrinos from muons trapped in FNAL debuncher can be seen in MiniBOONE: 8 GeV negatives captured ps and ps ps decay within 1st turn ms take ~200 ms to decay to nes, nms and es Debuncher captures 1 x 1011 antiprotons/hour 1:1 p:m captured 5.2 x 1014nes produced by debuncher/year (assumes 100 hr/wk) 13% produced off each straight section, the rest in a circle 6.24 x 1012 of these hit MiniBooNE Folding in the ne cross section at ~2 GeV 16 nes/year from Quasi-elastic and single p interactions Only useful to calibrate detector response to muon and electron neutrino and crosscheck flux calculations.

  25. Conclusions After many years of data analysis and checks, LSND effect is still alive and represents arguably the largest “mystery” of experimental neutrino physics In case of positive MiniBOONE result, sterile neutrinos will leave their limbo The neutrino factory coupled with a detector with τ identification is the best machine to explore them Due to larger mass difference scales, physics reach will come with far less effort than in 3 families LFV can be explored if no signal at MiniBOONE Very low-intensity NF in parasitic mode, cross-sections and calibration studies Hope nature prepared a surprise for us, otherwise this talk (and hundreds of papers) would mostly be “sterile”

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