DAEδALUS. Janet Conrad LNS Seminar March 16, 2010

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1 DAEδALUS Janet Conrad LNS Seminar March 16, 2010

2 Decay At rest Experiment for δ cp studies At the Laboratory for Underground Science Use decay-at-rest neutrino beams, and the planned 300 kton H 2 O detector (Gd doped) at the Deep Underground Science & Engineering Laboratory to search for CP violation in the neutrino sector

3 Outline: Physics Motivation The Conventional Wisdom An uncoventional approach: DAEδALUS Plays well with others

4 Physics Motivation: Searching for CP violation in the Neutrino Sector

5 In the Standard Model, Neutrinos are part of the lepton weak doublets CC Leptons νe νµ ντ e µ τ νµ µ W + d u CC u c t d s b Quarks We identify the neutrino flavor via the CC interaction The quarks also form weak doublets

6 In the quark sector, we have mixing quark mass eigenstates quark weak eigenstates u c t d s b Small effect, but clearly seen in weak interactions... νµ µ W + d c... and kaon decays, D meson decays, etc.

7 The quark mixing matrix has to be unitary, but it doesn t have to be simple Any 3 3 unitary matrix has 3 associated free parameters (Euler angles) c ij =cosθ ij s ij =sinθ ij & can have a complex phase hidden in it! This CP violating phase can lead to a different decay rate for matter vs. antimatter

8 The effect shows up in weak decays when you have 2 paths to the same outcome You will get an interference term in the decay probability

9 Now consider the D 0 W + There are still 2 paths to the outcome. W + Compared to the D 0 the interference term changes sign! e.g. D 0 and D 0 decays can have different decay rates if δ is nonzero!

10 Does the lepton sector show similar phenomena? If not, Why Not? If so, how similar is it to the quark sector? and what are the implications?

11 Step 1: Observe mixing Consider the simple case of 2 flavor mixing

12 Observe mixing? YES! For example, in Kamland!

13 Observed at 2 different Δm 2 values in many experiments! Our Model mixing between neutrinos is parameterized by three mixing angles θ 12, θ 13, θ 23

14 What we know about mixing Quarks Leptons??? ( ) vs. ( ) Large entries on diagnonal small off diagonal Moderately large entries except for one, which might be zero!

15 Adding CP violation & rewriting as the product of 3 matrices c ij =cosθ ij s ij =sinθ ij The CP Violation Parameter From Atmospheric and Long Baseline Disappearance Measurements From Reactor Disappearance Measurements From Appearance Measurements From Solar Neutrino Measurements

16 This matrix is well-known Super K, K2K, MINOS, soon T2K From Atmospheric and Long Baseline Disappearance Measurements From Reactor Disappearance Measurements From Appearance Measurements From Solar Neutrino Measurements

17 & this matrix is well-known Super K, SNO, KamLAND From Atmospheric and Long Baseline Disappearance Measurements From Reactor Disappearance Measurements From Appearance Measurements From Solar Neutrino Measurements

18 But this one is not known at all! A major focus of MIT s Neutrino Group From Atmospheric and Long Baseline Disappearance Measurements From Reactor Disappearance Measurements From Appearance Measurements From Solar Neutrino Measurements

19 The Double Chooz Experiment searches for the last mixing angle θ 13 From Atmospheric and Long Baseline Disappearance Measurements From Reactor Disappearance Measurements From Appearance Measurements From Solar Neutrino Measurements

20 DAEdALUS will search for δ From Atmospheric and Long Baseline Disappearance Measurements From Reactor Disappearance Measurements From Appearance Measurements From Solar Neutrino Measurements

21 Leptonic CP violation could have big consequences, because if incorporated into a larger model where 1. Neutrinos are Majorana particles 2. With GUT scale partners 3. And there is CP violation Then CP violation in the neutrino sector may explain the matter-antimatter asymmetry in the universe

22 Before the electroweak phase transition Left handed l Right handed l + N 1 N 1 Gets mass from the Majorana term H + H H - N 1 N 2 l H + N 1 N 2 l + l + H + l - H The interference terms will have opposite sign!

23 It s a big question and it turns out to be very hard to answer! A first step would be observation of CP violation in the light neutrinos

24 Searching for CP violation in the neutrino sector is a priority of our field

25 Part II: The Conventional Wisdom on how to search for CP violation in the neutrino sector

26 The oscillation of muon-flavor to electron-flavor at the atmospheric Δm 2 may show CP-violation dependence! in a vacuum We want to see if δ is nonzero } terms depending on mixing angles } terms depending on mass splittings

27 The oscillation of muon-flavor to electron-flavor at the atmospheric Δm 2 may show CP-violation dependence! in a vacuum We want to see if δ is nonzero CP violation is all about interference. The δ-dependent terms arise from interference between the Δm 13 2 and Δm 12 2 oscillations

28 Most parameters are well known N/A N/A Except for that pesky θ 13! We will end up having to quote our sensitivity as allowed regions in both θ 13 and δ

29 So what do we know about δ vs θ 13??? The actual values could be anywhere in this region! This region ruled out by Chooz and Palo Verde

30 If we succeeded in observing a signal, what would this plot look like? Imagine the real values are: δ = 80 sin 2 2θ 13 = sigma error 2 sigma error

31 You get a jelly bean

32 Jelly bean plots identify hypothetical values of δ and θ 13 and show the expected contours at 1σ and 2σ

33 Our equation flips sign between ν µ ν e & ν µ ν e in a vacuum what we want to measure } terms depending on mixing angles } terms depending on mass splittings

34 The classic idea for how to see CP violation: P osc (ν µ ν e ) P osc (ν µ ν e ) P osc (ν µ ν e ) δ 0 π CP This is in a vacuum (or air). CP parameter P osc (ν µ ν e )

35 But the proposed experiments to search for CP violation shoot the neutrinos through a lot of matter Here s why The easiest way to make a high-flux beam which switches from ν to ν: p target magnetic field region for π and K decay dump ν or ν Conventional neutrino beam s of MeV to a few GeV

36 P is maximized when Δm 2 (L/E) ~ 1 The atmospheric Δm 2 ~0.001 ev 2 E from a convention beam is ~ 1 GeV So L = 1000 km!!!

37 E.g., LBNE -- starting in 2020 Beam from Fermilab Shoots to detectors in South Dakota 1300 km And there is lots and lots of matter along a 1300 km path! also true for MEMPHYS and HyperK designs

38 And the ground is made of matter (electrons) not antimatter (positrons) Forward scattering affects neutrinos differently than antineutrinos. P osc (ν α ν β ) δ 0 CP parameter π CP CP + matter, This slides the allowed ring off the diagonal This a type of CP violation, but not what we are looking for! P osc (ν α ν β )

39 Worse, we actually don t know which direction CP + matter, Δm 2 <0 P osc (ν α ν β ) δ 0 π CP CP + matter, Δm 2 >0 CP parameter P osc (ν α ν β )

40 Worse, we actually don t know which direction CP + matter, Δm 2 <0 P osc (ν α ν β ) δ 0 π CP All long-baseline experiments will need to introduce a model for matter effects, before they can study CP-violation!!! CP + matter, Δm 2 >0 CP parameter P osc (ν α ν β )

41 Other problems Long Baseline experiments are usually low in antineutrino statistics a combination of style of beam and cross section and the backgrounds are larger compared to signal

42 Expectation for inverted hierarchy:

43 If we know the mass hierarchy, then this is how well LBNE can do in 10 years of running (e.g. without Project X)

44 Decay At rest Experiment for δ cp studies At the Laboratory for Underground Science Part III An uncoventional approach to the problem

45 A π + decay at rest beam: p+c Shape driven by nature! Only the normalization varies from beam to beam use νe νe to normalize flux No intrinsic ν e Perfect for a ν µ ν e search

46 The plan: Use ν µ νe and use the L/E dependence to extract δ in a vacuum We want to see if δ is nonzero } terms depending on mixing angles } terms depending on mass splittings

47 For E=50 MeV L=1.5 km 8 km 20 km km - normal 1.5km - inverted km - normal 8km - inverted km - normal 20km - inverted Nuebar Events Nuebar Events Nuebar Events δ 0 CP δ CP δ CP Close to source Osc mid (π/4) Osc max (π/2) Find δ by comparing the number of events at multiple locations

48 For E=50 MeV L=1.5 km 8 km 20 km km - normal 1.5km - inverted km - normal 8km - inverted km - normal 20km - inverted Nuebar Events Nuebar Events Nuebar Events δ 0 CP δ CP δ CP There will be a degeneracy with hierarchy: We cannot tell the difference between δ=45 and normal hierarchy and δ=135 and inverted DAEδALUS cannot differentiate the hierarchy

49 How do you observe ~50 MeV ν e events? The signal: inverse beta decay, IBD ν e e + p n ν e +p e + + n You need a lot of free protons! Use the same ultra-large water Cerenkov detector system as LBNE at DUSEL! 300 kton fiducial volume

50 We want to observe a 2-fold signature in time The signal: inverse beta decay, IBD ν e e + p n 1st signal 2nd-- from capture We need to reject: ν e e - O F Lower xsec than IBD by 10 because of binding But even if the xsec is small there are a lot of ν e s in the beam!

51 To enhance the signal from n-capture, add gadolinium! thermal neutron capture xsec (barns) Gd Enormous xsec and produces Series1 ~8 MeV upon capture! Z of element Adding Gd is technically difficult But others need it too: Supernova Relic Neutrino Search Non-proliferation studies good progress is being made

52 Energy Dependence of IBD events The signal: inverse beta decay, IBD ν e e + p n ν e +p e + + n Event range is 20 < E ν < 55 MeV 20 MeV 55 MeV

53 Neutrino-electron scattering is also very important! ν e e - ν ν e - ν e e - e - Provides the normalization of the flux since the xsec is known to 1% Mostly from ν e s about 20% from muon flavor

54 We need 3 distances and we cannot have kton detectors! osc max (π/2) at 40 MeV off max (π/4) at 40 MeV Constrains flux 20km 8km 1.5km A multiple-baseline, single-detector experiment H2O w/ Gd An advantage: Nature assures decay-at-rest beams will be identifical in flavor and energy

55 1.5 km Accelerator Beam Off Beam Off 100µs 400µs 400µs 100µs 100µs 8 km Accelerators 100µs 400µs 400µs 100µs 100µs 20 km Accelerators 100µs 400µs 100µs 400µs 100µs 20% DF 20% DF 20% DF 20km 8km 1.5km We can know the distance for an event by the timing H2O w/ Gd

56 What proton energy is required? There is a Delta plateau where you can trade energy for current to get the same rate of ν/mw <600 MeV too little π + production Delta Plateau >1500 MeV energy goes into producing other particles besides π + at a significant level

57 Wanted: ~1 MW sources of protons, w/ energy > 600 MeV and <1500 MeV for a reasonable price What isn t needed: 1. A fancy beam structure -- CW is fine. (run 100 µs on and 400 µs off) 2. Ability to inject into another accelerator or need to make clean secondary beams. 3. Flexibility on beam energy.

58 Wanted: ~1 MW sources of protons, w/ energy > 600 MeV and <1500 MeV for a reasonable price Luckily there are others looking for this too! ADS -- accelerator driven systems for subcritical reactors. Also DTRA -- Defense Threat Reduction Agency We can gain a lot from what is learned in these efforts!

Approaches using cyclotrons: The compact

59 Approaches using cyclotrons: The compact cyclotron with self-extraction An H2+ accelerator for ADS applications Under dev. by INFN, Catania The stacked cyclotron: under development for DTRA at MIT 7 cyclotrons in one flux return Under dev. for ADS at TAMU

60 Strategy: Phase I -- find it In 5 years, a 3σ measurement -- δ =( 90 ± 2 2θ 13 =0.05 The canonical comparison point 3 MW 2 MW 1 MW 20km 8km 1.5km Likely more than one cyclotron at some locations H2O w/ Gd

61 Strategy: Phase II -- measure it In an additional 5 years: LBNE-level sensitivity δ= sin 2 2θ 13 = MW 2 MW 1 MW 20km 8km 1.5km H2O w/ Gd

62 Measurement strategy: Using near accelerator measure absolute flux normalization with ν-e events to ~1%, Also, measure the ν e O event rate. At far and mid accelerator, Compare predicted to measured ν e O event rates to get the relative flux normalizations between 3 accelerators In all three accelerators, given the known flux, fit for the ν µ ν e signal with free parameters: θ 13 and δ

63 Non-beam backgrounds Atmospheric ν µ Invisible muons : ν µ + p µ + + n where µ + is below Cherenkov threshold, stops and decays. ν µ µ + e+ p n Atmospheric ν e IBD events: ν e + p e + + n Measured in beam-off! Diffuse supernova neutrinos ν e e + p n

64 Beam-related Background Intrinsic ν e in beam From π µ events which failed to capture in the beam stop ~ ν e rate (low) Beam ν e in coincidence with random neutron capture signal Estimated to be very small from Super-K rates ν e -Oxygen CC scatters producing an electron+ n signal Subsequent n from nuclear de-excitation should be very small. All fall as 1/r 2 from the 3 accelerators, near accelerator provides a measurement

65 Total Events and background level, for sin 2 2θ 13 = km - normal 1.5km - inverted km - normal 8km - inverted km - normal 20km - inverted Nuebar Events Bkgnd Nuebar Events Bkgnd Nuebar Events Bkgnd δ 0 CP δ CP δ CP For the signal accelerators signal-to-background is excellent!

66 1.5km Daedalus Event Energy Distributions (Signal & Background) (sin 2 2θ 13 = 0.04) MeV beam off beam on 8km Blue: Intrinsic ν e bkgnd Red: Beam off bkgnd Black: δ CP = 0 0 Violet: δ CP = 45 0 Green: δ CP = km MeV MeV

67 Compare signal to-background 8km Blue: Intrinsic ν e bkgnd Red: Beam off bkgnd Black: δ CP = 0 0 Violet: δ CP = 45 0 Green: δ CP = km MeV MeV With LBNE LBNE ν 5yr LBNE ν 5yr

68 Systematic Uncertainties before fits By comparing measurements in the 3 accelerators, several of these systematics effectively cancel.

69 How well do we do? Daedalus Phase We can clearly observe CP violation!

70 How well do we do? By construction our capability is equal to LBNE, But our measurement has completely different issues! Daedalus Phase LBNE 5 yrs nu + 5 yrs nubar

71 Part IV: Plays well with LBNE

72 These are complementary experiments LBNE is mainly a ν experiment DAEdALUS is entirely ν LBNE is a high energy experiment (300 MeV - 10 GeV) DAEdALUS is a low energy experiment LBNE varies beam energy DAEdALUS varies beam distance What happens when the two are put together?

73 Consider 4 scenarios: 1) Standard DAEδALUS years, Phase I and II 2) Standard LBNE -- 5 years ν and 5 years ν 3) Short Combined --5 years total, with ν data from LBNE and and ν data from DAEδALUS I 4) Long Combined years total, with only ν data from LBNE and and ν data from DAEδALUS I+II

74 For sin 2 2θ 13 =0.05 if δ= 80 then the error on δ would be.. if δ=160 then the error on δ would be.. 4 Standard DAEδALUS ± Standard DAEδALUS ± Standard LBNE ± Standard LBNE ± Short Combined ± 23.7 Series1 2 Short Combined ± 15.0 Series1 1 Long Comb. ± Long Comb. ± Whatever the value of δ, the error from a combined analysis is smaller in 1/2 the time!

75 What the Combined Experiments can do! 5yr Combined Running Daedalus Phase 1 plus LBNE 5yr nu 10yr Combined Running Daedalus Phase 1&2 plus LBNE 10yr nu

76 Conclusion

77 We can potentially go from here:

78 To here, in a 10 year run Daedalus Phase With a novel 3-accelerator source, high statistics low background design

79 The design is complementary to LBNE, and offers even more exciting possibilities when combined

80 Lets discover that CP violation jelly bean! Thank you!

81 Backup

82 Some more examples for various sin 2 2θ 13 and δ Standard DAEδALUS (10 yrs) Short Combined Standard LBNE (10 yrs) Long Combined

83 Total of each type of event: Normalization Off Osc Max Osc Max sin 2 2θ 13 = 0.05 Phase 1 + Phase 2 Running

84 A tentative schedule for discussion First round prototyping is complete Propose a building for the near accelerator in MREFC? Begin data run for a cyclo in the near hall Revise designs of cyclos and far buildings based on near running Contract for the final cyclos and far site buildings Phase 0 : where we do near accelerator physics and learn about the cyclos 3 sites operational, in the Phase 1 arrangement Phase 1 run, near expts continue

DAEδALUS. A Novel Approach to CP violation in the ν sector. Janet Conrad, INT Workshop August 5,6 2010

DAEδALUS. A Novel Approach to CP violation in the ν sector. Janet Conrad, INT Workshop August 5,6 2010 DAEδALUS A Novel Approach to CP violation in the ν sector Janet Conrad, INT Workshop August 5,6 2010 Decay At rest Experiment for δ cp studies At the Laboratory for Underground Science Use decay-at-rest