Testing neutrino properties at the Neutrino Factory Astroparticle seminar INFN Torino December 3, 2009 Walter Winter Universität Würzburg 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: that‘s 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 33 ~ 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 (

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 Geer‘s 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 (Buchmüller/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: ) 33 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