Testing neutrino properties at the Neutrino Factory Astroparticle seminar INFN Torino December 3, 2009 Walter Winter Universitt Wrzburg TexPoint fonts used in EMF: AAAAA A A A 2 Contents The most prominent neutrino property: leptonic CP violation (CPV) CPV Phenomenology Neutrino factory experiment Near detectors at the Neutrino Factory New physics searches with near detectors Summary CPV: Motivation from theory 4 Where does CPV enter? Example: Type I seesaw (heavy SM singlets N c ) Charged lepton mass terms Eff. neutrino mass terms Block-diag. CC Primary source of CPV (depends BSM theory) Effective source of CPV (only sectorial origin relevant) Observable CPV (completely model-indep.) Could also be type-II, III seesaw, radiative generation of neutrino mass, etc. 5 From the measurement point of view: It makes sense to discuss only observable CPV (because anything else is model-dependent!) At high E (type I-seesaw): 9 (M R )+18 (M D )+18 (M l ) = 45 parameters At low E: 6 (masses) + 3 (mixing angles) + 3 (phases) = 12 parameters Connection to measurement There is no specific connection between low- and high-E CPV! But: thats not true for special (restrictive) assumptions! CPV in 0 decay LBL accessible CPV: If U PMNS real CP conserved Extremely difficult! (Pascoli, Petcov, Rodejohann, hep-ph/ ) Requires 13 > 0 6 Why is CPV interesting? Leptogenesis: CPV from N c decays If special assumptions (such as hier. M R, NH light neutrinos, ) it is possible that CP is the only source of CPV for leptogensis! If CPV discovery: It is possible to write down a model, in which the baryon asymmetry comes from CP only (N c ) i ~ M D (in basis where M l and M R diagonal) (Pascoli, Petcov, Riotto, hep-ph/ ) Different curves: different assumptions for 13, 7 How well do we need to measure? We need generic arguments Example: Parameter space scan for eff. 3x3 case (QLC-type assumptions, arbitrary phases, arbitrary M l ) The QLC-type assumptions lead to deviations O( C ) ~ 13 Can also be seen in sum rules for certain assumptions, such as ( : model parameter) This talk: Want Cabibbo-angle order precision for CP ! (Niehage, Winter, arXiv: ) (arXiv: ) CPV phenomenology 9 Terminology Any value of CP (except for 0 and ) violates CP Sensitivity to CPV: Exclude CP-conserving solutions 0 and for any choice of the other oscillation parameters in their allowed ranges 10 Measurement of CPV (Cervera et al. 2000; Freund, Huber, Lindner, 2000; Huber, Winter, 2003; Akhmedov et al, 2004) Antineutrinos: Magic baseline: Silver: Platinum, Superb.: 11 Degeneracies CP asymmetry (vacuum) suggests the use of neutrinos and antineutrinos Burguet-Castell et al, 2001) One discrete deg. remains in ( 13, )-plane (Burguet-Castell et al, 2001) Additional degeneracies: (Barger, Marfatia, Whisnant, 2001) Sign-degeneracy (Minakata, Nunokawa, 2001) Octant degeneracy (Fogli, Lisi, 1996) Best-fit Antineutrinos Iso-probability curves Neutrinos 12 Intrinsic vs. extrinsic CPV The dilemma: Strong matter effects (high E, long L), but Earth matter violates CP Intrinsic CPV ( CP ) has to be disentangled from extrinsic CPV (from matter effects) Example: -transit Fake sign-solution crosses CP conserving solution Typical ways out: T-inverted channel? (e.g. beta beam+superbeam, platinum channel at NF, NF+SB) Second (magic) baseline (Huber, Lindner, Winter, hep-ph/ ) NuFact, L=3000 km Fit True CP (violates CP maximally) Degeneracy above 2 (excluded) True Critical range 13 The magic baseline 14 CPV discovery reach in (true) sin 2 2 13 and CP Sensitive region as a function of true 13 and CP CP values now stacked for each 13 Read: If sin 2 2 13 =10 -3, we expect a discovery for 80% of all values of CP No CPV discovery if CP too close to 0 or No CPV discovery for all values of CP 33 ~ Cabibbo-angle precision at 2 BENCHMARK! Best performance close to max. CPV ( CP = /2 or 3 /2) 15 Next generation reach Includes Double Chooz, Daya Bay, T2K, NOvA (Huber, Lindner, Schwetz, Winter, a rXiv: ) 90% CL Beyond the next generation Example: Neutrino factory 17 Neutrino factory: International design study IDS-NF: Initiative from ~ to present a design report, schedule, cost estimate, risk assessment for a neutrino factory In Europe: Close connection to Euro us proposal within the FP 07 In the US: Muon collider task force ISS (Geer, 1997; de Rujula, Gavela, Hernandez, 1998; Cervera et al, 2000) Signal prop. sin 2 2 13 Contamination Muons decay in straight sections of a storage ring 18 IDS-NF baseline setup 1.0 Two decay rings E =25 GeV 5x10 20 useful muon decays per baseline (both polarities!) Two baselines: ~ km Two MIND, 50kt each Currently: MECC at shorter baseline (https://www.ids-nf.org/) 19 NF physics potential Excellent 13, MH, CPV discovery reaches (IDS-NF, 2007) Robust optimum for ~ km Optimization even robust under non-standard physics (dashed curves) (Kopp, Ota, Winter, arXiv: ; see also: Gandhi, Winter, 2007) 20 Steve Geers vision 21 Neutrino factory in stages? Phase I: Five years low-E NuFact, Phase II: 5 yr, energy upgrade 25 GeV, Phase III: 5 yr, second baseline km (Tang, Winter, arXiv: ) Example: 13 not found Near detectors at the Neutrino Factory 23 Near detectors for standard oscillation physics Need two near detectors, because + / - circulate in different directions For cross section measurements, no CID required, only excellent flavor-ID Possible locations: (Tang, Winter, arXiv: ) 24 Requirements for standard oscillation physics (summary) Muon neutrino+antineutrino inclusive CC event rates measured (other flavors not needed in far detectors for IDS-NF baseline) Charge identification to understand backgrounds (but no intrinsic beam contamination), no e, At least same characteristics/quality (energy resolution etc.) as far detectors (a silicon vertex detector or ECC or liquid argon may do much better ) Location and size not really relevant, because extremely large statistics (maybe size relevant for beam monitoring, background extrapolation) The specifications of the near detectors may actually be driven by new physics searches! 25 Beam+straight geometry Near detectors described in GLoBES by (E)=A eff /A det x on-axis flux and For (E) ~ 1: Far detector limit Example: OPERA- sized detector at d=1 km: L > ~1 km: GLoBES std. description valid (with L eff ) (Tang, Winter, arXiv: ) New physics searches with near detectors 27 Effective operator picture if mediators integrated out: Describes additions to the SM in a gauge-inv. way! Example: TeV-scale new physics d=6: ~ (100 GeV/1 TeV) 2 ~ compared to the SM d=8: ~ (100 GeV/1 TeV) 4 ~ compared to the SM Interesting dimension six operators Fermion-mediated Non-unitarity (NU) Scalar or vector mediated Non-standard int. (NSI) New physics from heavy mediators mass d=6, 8, 10,...: NSI, NU 28 Example 1: Non-standard interactions Typically described by effective four fermion interactions (here with leptons) May lead to matter NSI (for = =e) May also lead to source/detector NSI (e.g. NuFact: s for = =e, = ) These source/det.NSI are process-dep.! 29 Lepton flavor violation and the story of SU(2) gauge invariance Strong bounds ee e NSI (FCNC) ee e CLFV e 4 -NSI (FCNC) Ex.: e e Affects neutrino oscillations in matter (or neutrino production) Affects environments with high densities (supernovae) BUT: These phenomena are connected by SU(2) gauge invariance Difficult to construct large leptonic matter NSI with d=6 operators (Bergmann, Grossman, Pierce, hep-ph/ ; Antusch, Baumann, Fernandez-Martinez, arXiv: ; Gavela, Hernandez, Ota, Winter,arXiv: ) Need d=8 effective operators, ! Finding a model with large NSI is not trivial! 30 Systematic analysis for d=8 Decompose all d=8 leptonic operators systematically (tree level) The bounds on individual operators from non- unitarity, EWPD, lepton universality are very strong! (Antusch, Baumann, Fernandez-Martinez, arXiv: ) Need at least two mediator fields plus a number of cancellation conditions (Gavela, Hernandez, Ota, Winter, arXiv: ) Basis (Berezhiani, Rossi, 2001) Combine different basis elements C 1 LEH, C 3 LEH Cancel d=8 CLFV But these mediators cause d=6 effects Additional cancellation condition (Buchmller/Wyler basis) Avoid CLFV at d=8: C 1 LEH =C 3 LEH Feynman diagrams 31 On current NSI bounds (Source NSI for NuFact) The bounds for the d=6 (e.g. scalar-mediated) operators are strong (CLFV, Lept. univ., etc.) (Antusch, Baumann, Fernandez-Martinez, arXiv: ) The model-independent bounds are much weaker (Biggio, Blennow, Fernandez-Martinez, arXiv: ) However: note that here the NSI have to come from d=8 (or loop d=6?) operators ~ (v/ ) 4 ~ natural? NSI hierarchy problem? 32 Source NSI with at a NuFact Probably most interesting for near detectors: e s, s (no intrinsic beam BG) Near detectors measure zero-distance effect ~ | s | 2 Helps to resolve correlations (Tang, Winter, arXiv: ) ND5: OPERA-like ND at d=1 km, 90% CL This correlation is always present if: - NSI from d=6 operators - No CLFV (Gavela et al, arXiv: ; see also Schwetz, Ohlsson, Zhang, arXiv: for a particular model) 33 Other types of source NSI In particular models, also other source NSI (without detection) are interesting Example: (incoh.) e s from addl. Higgs triplet as seesaw (II) mediator 1 kt, 90% CL, perfect CID (Malinsky, Ohlsson, Zhang, arXiv: ) Requires CID! Geometric effects? Effects of std. oscillations Systematics (CID) limitation? CID important! 34 Example 2: Non-unitarity of mixing matrix Integrating out heavy fermion fields, one obtains neutrino mass and the d=6 operator (here: fermion singlets) Re-diagonalizing and re-normalizing the kinetic terms of the neutrinos, one has This can be described by an effective (non-unitary) mixing matrix with N=(1+ ) U Similar effect to NSI, but source, detector, and matter NSI are correlated in a particular, fundamental way (i.e., process- independent) also: MUV 35 Impact of near detector Example: (Antusch, Blennow, Fernandez-Martinez, Lopez-Pavon, arXiv: ) near detector important to detect zero-distance effect Magnetization not mandatory, size matters Curves: 10kt, 1 kt, 100 t, no ND 36 NSI versus NU For a neutrino factory, leptonic NSI and NU may have very similar correlations between source and matter effects, e.g. NU (generic, any exp.) NSI (d=6, no CLFV, NF) Difficult to disentangle with NuFact alone SB? (Meloni, Ohlsson, Winter, Zhang, to appear) NUNSI 37 Example 3: Search for sterile neutrinos 3+n schemes of neutrinos include (light) sterile states The mixing with the active states must be small The effects on different oscillation channels depend on the model test all possible two-flavor short baseline (SBL) cases, which are standard oscillation-free Example: e disappearance Some fits indicate an inconsistency between the neutrino and antineutrino data (see e.g. Giunti, Laveder, arXiv: ) NB: Averaging over decay straight not possible! The decays from different sections contribute differently! 38 SBL e disappearance Averaging over straight important (dashed versus solid curves) Location matters: Depends on m 31 2 Magnetic field if interesting as well (Giunti, Laveder, Winter, arXiv: ) 90% CL, 2 d.o.f., No systematics, m=200 kg Two baseline setup? d=50 m d~2 km (as long as possible) 39 SBL systematics Systematics similar to reactor experiments: Use two detectors to cancel X-Sec errors (Giunti, Laveder, Winter, arXiv: ) 10% shape error arXiv: Also possible with only two ND (if CPT-inv. assumed) 40 CPTV discovery reaches (3 ) (Giunti, Laveder, Winter, arXiv: ) Dashed curves: without averaging over straight Requires four NDs! 41 Summary of (new) physics requirements for near detectors Number of sites At least two (neutrinos and antineutrinos), for some applications four (systematics cancellation) Exact baselines Not relevant for source NSI, NU, important for oscillatory effects (sterile neutrinos etc.) Flavors All flavors should be measured Charge identification Is needed for some applications (such as particular source NSI); the sensitivity is limited by the CID capabilities Energy resolution Probably of secondary importance (as long as as good as FD); one reason: extension of straight leads already to averaging Detector size In principle, as large as possible. In practice, limitations by beam geometry or systematics. Detector geometry As long (and cylindrical) as possible (active volume) A eff < A det A eff ~ A det 42 What we need to understand How long can the baseline be for geometric reasons (maybe: use alternative locations)? What is the impact of systematics (such as X-Sec errors) on new physics parameters What other kind of potentially interesting physics with oscillatory SBL behavior is there? How complementary or competitive is a near detector to a superbeam version, see e.g.Workshop next week in Madrid! 43 Summary The Dirac phase CP is probably the only realistically observable CP phase in the lepton sector Maybe the only observable CPV evidence for leptogenesis This and 1, 2 : the only completely model-inpendent parameterization of CPV A neutrino factory could measure that even for extremely small 13 with Cabbibo-angle precision Near detectors at a neutrino factory are very important for new physics searches, such as Non-unitarity (heavy neutral fermions) Non-standard interactions (related to CLFV) (Light) sterile neutrinos Requirements most likely driven by new physics searches BACKUP 45 ~ current bound CPV from non-standard interactions Example: non-standard interactions (NSI) in matter from effective four-fermion interactions: Discovery potential for NSI-CPV in neutrino propagation at the NF Even if there is no CPV in standard oscillations, we may find CPV! But what are the requirements for a model to predict such large NSI? (arXiv: ) 33 IDS-NF baseline 1.0 46 CPV discovery for large NSI If both 13 and | e m | large, the change to discover any CPV will be even larger: For > 95% of arbitrary choices of the phases NB: NSI-CPV can also affect the production/ detection of neutrinos, e.g. in MUV (Gonzalez-Garcia et al, hep-ph/ ; Fernandez-Martinez et al, hep-ph/ ; Altarelli, Meloni, ; Antusch et al, ) (arXiv: ) IDS-NF baseline 1.0