1. Optimization of a neutrino factory Discovery machine versus precision instrument NuFact 07 Okayama University, Japan August 6, 2007 Walter Winter Universität Würzburg

2. August 6, 2007NuFact 07 - Walter Winter2 Contents Introduction Introduction Optimization options Optimization options Optimization for Optimization for –  13 reach (statistics/systematics-limited regime) – Precision for small  13 (degeneracy regime) – Precision for large  13 (correlation regime) »High-E neutrino factory »Low-E neutrino factory Summary Summary

3. August 6, 2007NuFact 07 - Walter Winter3 Assume (for this talk): Decision for future program after T2K, NOvA, Double Chooz, etc. Assume (for this talk): Decision for future program after T2K, NOvA, Double Chooz, etc. Choose: sin 2 2  13 ~ 0.01 as „branching point“:  13 discovered or not If discovered:  Know ist value  Optimization clearly defined If not discovered:  What to optimize for? Choose: sin 2 2  13 ~ 0.01 as „branching point“:  13 discovered or not If discovered:  Know ist value  Optimization clearly defined If not discovered:  What to optimize for? Physics cases:  13 small,  13 large? (FNAL Proton Driver study)

4. August 6, 2007NuFact 07 - Walter Winter4 Discovery machine vs precision instrument  13 unknown  13 known Optimize for CP fraction (mainly CPV discovery) Choose specific true  13 3) Precision regime – large  13 Correlations dominate Optimize for CP fraction (mainly MH+CPV disc.) Choose specific true  13 2) Precision regime – small  13 Degeneracies dominate Optimize for  13 reach (  13 +MH+CPV disc.) Choose specific true  CP ‘s 1) Discovery regime – smallest  13 Statistics/syst. limited If  13 below branching point: We do not know if we are in case 1) or 2) !!!

5. August 6, 2007NuFact 07 - Walter Winter5 Describe improved detector Golden* here Optimization options Baseline(s), E  Baseline(s), E  Channels (next slide) Channels (next slide) Combine technologies: NF+superbeam etc. Combine technologies: NF+superbeam etc. Detector technology Detector technology Detector analysis (CID cuts etc.) Detector analysis (CID cuts etc.) Off-axis angle? Off-axis angle? Luminosity? Luminosity? … Better background model ~ E -2 Better energy resolution: MIND: ~ 0.15 x E, improve to: ~ 0.15 x sqrt(E)? Detector technology? Improved analysis for MIND: Old analysis/det. Golden* New analysis (diff. L  ) Golden* (Cervera@Golden 07)

6. August 6, 2007NuFact 07 - Walter Winter6 Optimization options: Channels (Cervera et al. 2000; Freund, Huber, Lindner, 2000; Huber, Winter, 2003; Akhmedov et al, 2004) Antineutrinos: Antineutrinos: Magic baseline: Magic baseline: Silver: Silver: Platinum: Platinum:

7. 1) Discovery regime – go for smallest  13

8. August 6, 2007NuFact 07 - Walter Winter8 Which baseline, which energy? CPV: L ~ 3000-5000 km CPV: L ~ 3000-5000 km MH, degeneracy resolution: L ~ 7500 km (Magic baseline) MH, degeneracy resolution: L ~ 7500 km (Magic baseline) Use two baselines: 4000 km+7500 km, E  > 40 GeV Use two baselines: 4000 km+7500 km, E  > 40 GeV MH CPV  13 sens. Figs. from Huber, Lindner, Rolinec, Winter, 2006; ISS study. See also: Barger, Geer, Whisnant, 1999; Cervera et al, 2000; Burguet-Castell et al, 2001; Freund, Huber, Lindner, 2001

9. August 6, 2007NuFact 07 - Walter Winter9 Magic baseline detector location? One baseline: Strong impact of matter density model One baseline: Strong impact of matter density model Two baselines: Exact detector location less important Two baselines: Exact detector location less important (Gandhi, Winter, 2006) Very long baseline detector window Magic baseline

10. August 6, 2007NuFact 07 - Walter Winter10 Further improvements Golden* helps Reduce E  : 50 GeV  20 GeV Golden* helps Reduce E  : 50 GeV  20 GeV MB helps MB helps (Huber, Lindner, Rolinec, Winter, 2006) CPV MH  13

11. 2) Precision for 10 -4 < sin 2 2  13 < 10 -2 Example: sin 2 2  13 ~ 0.001 (Degeneracy regime) (Degeneracy regime)

12. August 6, 2007NuFact 07 - Walter Winter12 Optimization options Golden* helps Golden* helps MB helps MB helps Silver* and Platinum* help in principle (with very optimistic implementations) Silver* and Platinum* help in principle (with very optimistic implementations) (Huber, Lindner, Rolinec, Winter, 2006) Bars: CPV MH  13

13. August 6, 2007NuFact 07 - Walter Winter13 Magic baseline for precision! (Gandhi, Winter, 2006)(Huber, Lindner, Winter, 2004)  CP precision  13 precision  CP dep. 33

14. 3) Precision for large  13 a) High-E NuFact: E  ~ 20 – 50 GeV b) Low-E NuFact: : E  << 20 GeV (Correlation regime)

15. August 6, 2007NuFact 07 - Walter Winter15 High-E NF challenges for large  13 Matter density uncertainties <= 5% relevant Matter density uncertainties <= 5% relevant Designed as discovery machine: first oscillation maximum below spectral peak! Designed as discovery machine: first oscillation maximum below spectral peak!  and energy threshold main impact factors for large  13  and energy threshold main impact factors for large  13 (from: Ohlsson, Winter, 2003) (from: Huber, Lindner, Winter, 2002) sin 2 2  13 =0.01,  CP =  /4

16. August 6, 2007NuFact 07 - Walter Winter16 Large-  13 -Competitors Wide band beam (WBB) Wide band beam (WBB) NOvA-like off-axis beam NOvA-like off-axis beam T2KK-like two detector setup T2KK-like two detector setup Beta beam (different configs) Beta beam (different configs) Neutrino factory? Neutrino factory? Possible optimization goals: 1. Physics potential optimal, effort ignored  High-E NuFact? 2. Effort x Physics potential optimal  Low-E NuFact? 3. Robustness (systematics,  m 31 2, exposure, …) 4. … See talks by Choubey (Thursday), Bishai (Friday), Dierckxens and Nakadaira (Friday, WG1)

17. August 6, 2007NuFact 07 - Walter Winter17 Competitors can also be optimized! Example: NuMI-like beam  100kt liquid argon  CP =-  /2  CP =+  /2 sin 2 2   CP violationMass hierarchy (Barger, Huber, Marfatia, Winter, 2007) Constraint from NuMI beam FNAL- DUSEL WBB Ash River OA

18. August 6, 2007NuFact 07 - Walter Winter18 Straightforward comparison … for sensitivity to CP violation Superbeam upgrades can easily outperform a „straightforward“ NF Superbeam upgrades can easily outperform a „straightforward“ NF How can one optimize a high-E neutrino factory for large  13 ? How can one optimize a high-E neutrino factory for large  13 ? (Barger, Huber, Marfatia, Winter, hep-ph/0703029)  =350 beta beam Burguet-Castell et al, 2005 Neutrino factory 3000 +7500 km 50 kt + 50 kt NuMI beam to 100kt LArTPC FNAL - DUSEL 100kt LArTPC 270kt+270kt WC detector

19. August 6, 2007NuFact 07 - Walter Winter19 Optimization options Magic baseline Magic baseline Better detector: Golden* Better detector: Golden* Platinum channel: Plat* Platinum channel: Plat* Better known matter density? Better known matter density? (from: Huber, Lindner, Rolinec, Winter, 2006) COMPETITIVE!   ~ 20 – 50 GeV Bars: CPV MH  13 Only CPV relevant!

20. August 6, 2007NuFact 07 - Walter Winter20 Platinum* for large  13 MINOS-like Electron detection properties (NuMI note NuMI-L-714) MINOS-like Electron detection properties (NuMI note NuMI-L-714) No upper threshold! Problem for large E (>7 GeV?): Electrons are showering (MIND). For small E  : May be no problem (low-E NuFact!?) No upper threshold! Problem for large E (>7 GeV?): Electrons are showering (MIND). For small E  : May be no problem (low-E NuFact!?) 40% efficiency 40% efficiency Energy resolution 0.15 x E Energy resolution 0.15 x E 1% BG from all NC events, 1% from CID 1% BG from all NC events, 1% from CID Limits the  13 for which this channel is useful! Golden+Platinum Golden

21. August 6, 2007NuFact 07 - Walter Winter21 High-E NuFact summary (E   20 - 50 GeV) (from: Huber, Lindner, Rolinec, Winter, 2006)

22. August 6, 2007NuFact 07 - Walter Winter22 Impact of matter density uncertainties? The more information added, the less important … The more information added, the less important … In fact: at L >> 6000 km, one can measure the matter density at the level of 0.5% (Winter, hep-ph/0502097; Minakata, Uchinami, hep-ph/0612002; Gandhi, Winter, hep-ph/0612158) In fact: at L >> 6000 km, one can measure the matter density at the level of 0.5% (Winter, hep-ph/0502097; Minakata, Uchinami, hep-ph/0612002; Gandhi, Winter, hep-ph/0612158) (from: Huber, Lindner, Rolinec, Winter, 2006) Dashed: 2% Solid: 5%

23. August 6, 2007NuFact 07 - Walter Winter23 Matter density: Geophysical use? Precision: Lower mantle density 0.4% (1  ) if upper mantle/crust density known to 5% (Gandhi, Winter, 2006) Precision: Lower mantle density 0.4% (1  ) if upper mantle/crust density known to 5% (Gandhi, Winter, 2006) Example: Plume hypothesis Example: Plume hypothesis A precision measurement << 1% could discriminate different geophysical models A precision measurement << 1% could discriminate different geophysical models  Side-product coming for free! (Courtillot et al., 2003; see talk from B. Romanowicz, Neutrino geophysics 2005)

24. August 6, 2007NuFact 07 - Walter Winter24 Effort matters! Low-E neutrino factory? Lower threshold (Golden*) allows for lower E  Lower threshold (Golden*) allows for lower E  For example: E  = 4.12 GeV, L=1280 km For example: E  = 4.12 GeV, L=1280 km (Geer, Mena, Pascoli, 2007) How does that compare to the other competitors? How does that compare to the other competitors? Possibly: somehow combination NF plus superbeam? Possibly: somehow combination NF plus superbeam? (Geer, Mena, Pascoli, 2007) (Burguet-Castell et al, 2002) see also: Ellis, Wednesday, WG 1

25. August 6, 2007NuFact 07 - Walter Winter25 Neutrino factory superbeam (NF-SB) Idea: Use on-axis superbeam from secondary pion/kaon beam in addition to NF beam (same accelerator facility!) p    e  SB appearance  e NF Platinum e  NF Golden p    e  SB appearance  e NF Platinum e  NF Golden  4 MW superbeam basically coming for free?  Same detector might be used at same baseline (if out-of-phase bunches from SB and NF)  Compared to platinum channel, no CID is required; higher efficiencies possible  Correlated matter effect between NF and superbeam if same L  Can be combined with low-E neutrino factory idea (arXiv:0706.2862 [hep-ph])

26. August 6, 2007NuFact 07 - Walter Winter26 NF-SB schematics Drawback: Target station challenging Conservative assumption: only half the muons go in NF channel (recycler?) Drawback: Target station challenging Conservative assumption: only half the muons go in NF channel (recycler?) Degrees of freedom: E p, E , L Degrees of freedom: E p, E , L (Huber, Winter, 2007) Target station/decay pipe(s): How can this be done?

27. August 6, 2007NuFact 07 - Walter Winter27 NF-SB requirements E , L varied E , L varied Assume: P target ~ 4 MW leading to 0.5 10 21 useful muon decays/year (50% of „standard-NF“) Assume: P target ~ 4 MW leading to 0.5 10 21 useful muon decays/year (50% of „standard-NF“) Detektor: 50 kt Golden* Detektor: 50 kt Golden* 5 yr running time in each polarity = 10 yr total 5 yr running time in each polarity = 10 yr total 80% electron detection efficiency (without CID!) 80% electron detection efficiency (without CID!) 5% systematics (except for normalization errors 2.5%) – as usual 5% systematics (except for normalization errors 2.5%) – as usual (high-Z target; Zisman @ IDS CERN, March 2007) E p : Tested MiniBOONE-like (E p =8 GeV) and AGS-like (E p =28 GeV) WBB for the superbeam E p : Tested MiniBOONE-like (E p =8 GeV) and AGS-like (E p =28 GeV) WBB for the superbeam  E p ~ 28 GeV better choice E p window

28. August 6, 2007NuFact 07 - Walter Winter28 Comparison of appearance rates NF Golden-SB appearance-NF Platinum E p chosen such that SB peaks at lower E E p chosen such that SB peaks at lower E Platinum peaks at higher E (spectrum!) Platinum peaks at higher E (spectrum!) (Huber, Winter, 2007) 2.5 10 21 useful muon decays Golden E  =5 GeV L=1250 km

29. August 6, 2007NuFact 07 - Walter Winter29 L-E  Optimization: CPV discovery Geer et al. choices are sufficiently close to optimum Geer et al. choices are sufficiently close to optimum NF-SB synergistic, better performance than NF alone NF-SB synergistic, better performance than NF alone Our choices : L = 900 km, E  = 5 GeV and L=1250 km, E  =5 GeV (given the low energy ~ minimum effort constraint) Our choices : L = 900 km, E  = 5 GeV and L=1250 km, E  =5 GeV (given the low energy ~ minimum effort constraint) CP fraction for discovery (3  ), sin 2 2  13 =0.1 (Huber, Winter, 2007) Double luminosity!

30. August 6, 2007NuFact 07 - Walter Winter30 Comparison to competitors NF-SB can outperform any of the discussed setups except from beta beam NF-SB can outperform any of the discussed setups except from beta beam But: Luminosity choice for beta beam arbitrary in this context! Parameters:  =350, L=712 km, 5 yr x 5.8 10 18 useful 6 He decays/yr, 5 yr x 2.2 10 18 useful 18 Ne decays/yr (Burguet-Castell et al, 2005) But: Luminosity choice for beta beam arbitrary in this context! Parameters:  =350, L=712 km, 5 yr x 5.8 10 18 useful 6 He decays/yr, 5 yr x 2.2 10 18 useful 18 Ne decays/yr (Burguet-Castell et al, 2005) (Huber, Winter, 2007) E p =28 GeV 500 kt WC

31. August 6, 2007NuFact 07 - Walter Winter31 Summary If sin 2 2  13 <0.01: Improved detector and magic baseline key components for high-E NuFact (for discovery and precision) If sin 2 2  13 <0.01: Improved detector and magic baseline key components for high-E NuFact (for discovery and precision) If sin 2 2  13 >0.01: Two options: Low-E versus high-E NuFact Different requirements for If sin 2 2  13 >0.01: Two options: Low-E versus high-E NuFact Different requirements for –Machine: Target station (NF-SB), baseline(s), muon acceleration, etc. –Detector: Optimization for high effs versus low backgrounds But: Better low-energy threshold useful for both! (though no prerequisite for high-E NuFact) –Low-E NuFact: Platinum* (CID) versus NF-SB (no CID)?  Optimize for two different NuFacts until T2K, Double Chooz, NOvA etc. are finished? Optimization for different goals?  23 non-maximal, systematics robustness, non-standard physics, geophysics, etc.? Optimization for different goals?  23 non-maximal, systematics robustness, non-standard physics, geophysics, etc.? Explore new options: off-axis neutrino factory, etc. Explore new options: off-axis neutrino factory, etc.