1. Near detectors and systematics IDS-NF plenary meeting at TIFR, Mumbai October 13, 2009 Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAA A A A

2. 2 Contents  Initial IDS-NF questions  Beam and detector geometry  Systematics  Results for high energy NuFact  Results for low energy NuFact  Near detectors for new physics (examples)  Answers to initial questions  Systematics requirements (for simulation)  Summary of new physics requirements

3. 3 Introduction: Initial questions  What is the potential of near detectors to cancel systematical errors? (implies: need to address what kind of systematics …)  When do we need a near detector for standard oscillation physics?  What (minimal) characteristics do we require? (technology, number, sites, etc.)  What properties do near detectors need for new physics searches?

4. 4 Geometry of decay ring  Need two near detectors, because  + /  - circulate in different directions  For the same reason: if only std. oscillations, no CID required, only excellent flavor-ID; caveat: background extrapolation (Tang, Winter, arXiv:0903.3039)

5. 5 Geometry of the beam  Beam diameter ~ 2 x L x   We use two beam angles:  Beam opening angle:  Beam divergence: contains 90% of total flux (arXiv:0903.3039) Beam divergence Beam opening angle

6. 6 Geometry of the detectors? (ISS detector WG report) What are the physics requirements for the geometry of the detectors?

7. 7 Geometry: Extreme cases  Far detector limit: The spectrum is the same as the on-axis spectrum, i.e., the detector diameter D > s (size of source) not required for this limit. The extension of the source can be desribed by  Near detector limit: The detector catches almost the whole flux, i.e., the detector diameter D > 2 x L x , where  is the beam divergence, for any point of the decay straight

8. 8 Assumptions for NDs  Only muon neutrino+antineutrino inclusive CC event rates measured (other flavors not needed in far detectors for IDS-NF baseline)  No charge identification  At least same characteristics/quality (energy resolution etc.) as far detectors  No explicit BG extrapolation  Fiducial volume cylindrical  No systematical errors considered, which are potentially uncorrelated among ND and FD (they are present, but they cannot be improved on with the NDs)

9. 9 Different ND versions?  Near detectors described in GLoBES by  (E)=A eff /A det x on-axis flux and  Some ND versions: Near detector limit Far detector limit SciBar-sizeSilicon- vertex size? OPERA- size Hypothetical Nearest point Farthest point Averaged  =1: FD limit Dashed: ND limit (Tang, Winter, arXiv:0903.3039)

10. 10 Extreme cases: Spectra  Some spectra: ~ND limit~FD limit (Tang, Winter, arXiv:0903.3039)

11. 11 Systematics treatment  Cross section errors: Fully correlated among all channels, detectors etc. measuring the same cross section, fully uncorrelated among bins and neutrinos- antineutrinos (30% cons. estimate)  Flux errors: Fully correlated among all detectors in the same straight and all bins, but uncorrelated among polarities, storage rings (2.5% for no flux monitoring to 0.1%)  Background normalization errors: as IDS-NF baseline (20%)

12. 12 Systematics, qualitatively  Near detectors important for Leading atmospheric and CPV measurements  Flux monitoring (by NDs or other means) important for CPV measurement  Almost no impact for  13 and MH discovery (background limited) (arXiv:0903.3039)

13. 13 Relevance of statistics  Event rates (10 years) extremely large  Physics is limited by statistics in FD, not spectrum in ND  Near detector location and size not relevant (caveat: elastic scattering for flux monitoring)  However, for new physics searches, such as e ->    s,  e  s , size matters! (arXiv:0903.3039)

14. 14 Atmospheric parameters  Atmospheric parameters measured at L=4000km:  At L=4000km+7500km no impact of NDs! Unfilled: 30% XSec-errors, no ND Filled: Near detectors (Tang, Winter, arXiv:0903.3039) sin 2 2  13 = 0.08,  CP =0

15. 15 CP violation measurement (Tang, Winter, arXiv:0903.3039) IDS-NF systematics too conservative? 33

16. 16 Low-E NuFact  „High statistics“ setup from (Bross, Ellis, Geer, Mena, Pascoli, arXiv:0709.3889)  E  =4.12 GeV, L=1290 km  5 10 20 useful decays per polarity and year, 10 years, 20 kt mass x efficiency  Reference: 2% system.  Our ND3 with IDS-NF-like storage ring  PROBLEM: We need decay ring geometry for some applications! (Tang, Winter, arXiv:0903.3039)

17. 17 Low-E versus high-E NuFact (Tang, Winter, arXiv:0903.3039)  Low-E NuFact: Systematics estimate seems quite accurate Near detectors mandatory!  High-E NuFact: Qualitatively different, since two far detectors Need something like Double Chooz/Daya Bay systematics?

18. 18 NDs for new physics Example: SBL e disappearance  Two flavor short-baseline searches useful to constrain sterile neutrinos etc.  e disppearance:  Also some interest in CPT- invariance test (neutrino factory ideal!)  Averaging over straight important (dashed versus solid curves)  Pecularity: Baseline matters, depends on  m 31 2  Magnetic field if (Giunti, Laveder, Winter, arXiv:0907.5487) 90% CL, 2 d.o.f., No systematics, m=200 kg

19. 19 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

20. 20 Summary: Answers to initial questions  What is the potential of near detectors to cancel systematical errors?  Cancels X-section errors; possibly useful for flux monitoring etc.  When do we need a near detector to cancel cross section errors?  If we only operate one baseline for sure! Mainly needed for leading atmospheric and CP violation searches.  What (minimal) characteristics do we require? (technology, number, sites, etc.)  Two near detectors; at least as good as far detectors for  ; not necessarily magnetic field, site and size hardly important (statistics high)  What properties do near detectors need for new physics searches?  Also e,  detection; as large as possible (statistics matters!); magnetic field; site application-dependent; maybe more sites  Near detector characteristics driven by new physics requirements?

21. 21 Systematics requirements  For a more accurate simulation, PPEG needs to know systematics treatment  The simulation results depend not only on the numbers for some systematical errors, but also the implementation of systematics (cf., Double Chooz, Daya Bay!)  What systematical errors (and how large) are there correlated/uncorrelated among  Bins  Detectors  Storage rings  Channels at the same detector  Channels measuring the same X-secs  …  Possible alternative (discussed via mailing list some time ago): Show also curve with „no systematics“?

22. 22 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

23. 23 What we need to understand (for new physics)  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/