1. Near detectors for new physics searches IDS-NF plenary meeting at TIFR, Mumbai October 12, 2009 Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAA A A A

2. 2 Contents  Near detectors for standard osc. physics  Three (new) physics examples:  Non-standard interactions  Non-unitarity of the mixing matrix  Sterile neutrinos  Requirements for new physics searches  What we need to understand … NB: For this talk, „near“ means L << 100 km (no std. osc. effect)

3. 3 Near detectors for standard oscillation physics  Need two near detectors, because  + /  - circulate in different directions  For the same reason: if only standard oscillations, no CID required, only excellent flavor-ID  Possible locations: (Tang, Winter, arXiv:0903.3039)

4. 4 Requirements for standard oscillation physics  Muon neutrino+antineutrino inclusive CC event rates measured (other flavors not needed in far detectors for IDS-NF baseline)  No charge identification, 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! See my talk tomorrow!

5. 5 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:0903.3039)

6. 6  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 ~ 10 -2 compared to the SM d=8: ~ (100 GeV/1 TeV) 4 ~ 10 -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

7. 7 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.!

8. 8 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/9909390; Antusch, Baumann, Fernandez-Martinez, arXiv:0807.1003; Gavela, Hernandez, Ota, Winter,arXiv:0809.3451)  Need d=8 effective operators, …!  Finding a model with large NSI is not trivial!

9. 9 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:0807.1003)  The model-independent bounds are much weaker (Biggio, Blennow, Fernandez-Martinez, arXiv:0907.0097)  However: note that here the NSI have to come from d=8 (or loop d=6?) operators   ~ (v/  ) 4 ~ 10 -4 natural?  „NSI hierarchy problem“?

10. 10 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:0903.3039) 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:0809.3451; see also Schwetz, Ohlsson, Zhang, arXiv:0909.0455 for a particular model)

11. 11 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:0811.3346) Requires CID! Geometric effects? Effects of std. oscillations Systematics (CID) limitation? CID important!

12. 12 Example 2: Non-unitarity of mixing matrix  Integrating out heavy fermion fields, one obtains neutrino mass and the d=6 operator (here: fermion singletts)  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“

13. 13 Impact of near detector  Example: (Antusch, Blennow, Fernandez-Martinez, Lopez-Pavon, arXiv:0903.3986)   near detector important to detect zero-distance effect  Magnetization not mandatory, size matters Curves: 10kt, 1 kt, 100 t, no ND

14. 14 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:0902.1992)  NB: Averaging over decay straight not possible! The decays from different sections contribute differently!

15. 15 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:0907.5487) 90% CL, 2 d.o.f., No systematics, m=200 kg Two baseline setup? d=50 m d~2 km (as long as possible)

16. 16 SBL systematics  Systematics similar to reactor experiments: Use two detectors to cancel X-Sec errors (Giunti, Laveder, Winter, arXiv:0907.5487) 10% shape error arXiv:0907.3145 Also possible with only two ND (if CPT-inv. assumed)

17. 17 CPTV discovery reaches (3  ) (Giunti, Laveder, Winter, arXiv:0907.5487) Dashed curves: without averaging over straight Requires four NDs!

18. 18 Summary of (new) physics requirements  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

19. 19 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. http://www-off-axis.fnal.gov/MINSIS/