1

Daedalus – LBNE Combinations

• Daedalus and LBNE Complementary– Each gives comparable measurements on their own for

oscillation parameters– Much improved measurements by combining Daedalus and

LBNE

• Daedalus provides a pure, well understood antineutrino oscillation search that can be combined with LBNE neutrino measurements.– Backgrounds are small and constrained by measurements– Very small wrong-sign (neutrino) background

2Comments on LBNE5 years of ν Running 5 years of⎯ν Running

• Experimental comments:– Large neutrino flux covering 1st and 2nd oscillation max points (0.8 and 2.4 GeV)– Fairly pure νμ flux with small νe contamination– Minimize flux with energy above 5 GeV that causes background

But– Still substantial neutral current π0 events that mimic νe events– Difficult to collect large antineutrino statistics– Antineutrino running has significant neutrino contamination

⇒ Difficult to make a precise measurement of CP violation

3Daedalus Experiment• Multiple beam sources using high-power cyclotrons

– Cyclotron beam impinges on dump where produced π+ and μ+ decay to neutrinos (Almost all π- capture before decay)⇒ Very few⎯νe produced so can do precise ⎯νμ →⎯νe search

– For study assume each cyclotron 1 MW at 0.6 to 1.4 GeV• Detector is assumed to be 300 kton water Cerenkov detector with gadolinium doping• Osc signal events are ⎯νe + p → e+ + n (Inverse-beta decay) which can be well

identified by a two part delayed coincidence.• Flux normalization can be determined by using ~15,000 νe + e- → νe + e- events.

5MW 2MW 1MW

(Described in Conrad and Shaevitz, PRL 104, 141802 (2010))

Each acceleratorset is run for 20%duty factor andevents tagged bytiming

40% time set asidefor beam off running to measure bkgnd

4Proton Economics for a Decay-at-Rest Cyclotron Neutrino Beam

• Assume 1 MW average proton power into beam dump / neutrino source– This is the rate for several existing dumps (i.e. JPARC Hadron Hall) and should be

achievable for reasonable cost.

• For the proton energy range from about to 0.6-1.3 GeV, the π+ production and neutrino flux is only dependent on the proton beam power.

• 1 MW proton beam power corresponds to:– 1 GeV @ 1ma continuous– 1 GeV @ 5ma with 20% duty factor (on time)– 0.8 GeV @ 6.25 ma with 20% duty factor

• Running with a reduced duty factor has the advantages– Can run different distances at different times– Non-beam background is reduced by the duty factor

• Since one cannot increase the average power into a dump, one can only increase the neutrino flux at a given distance by adding accelerators or adding dumps with multiple extraction lines

– Increasing the duty factor at a given distance does not increase the flux but only increases the beam off background.

5

Energy Spectrum for π Decay-at-Rest Beam(No uncertainty in energy spectrum)

⎯νe rate is verysmall since mostπ− capture beforedecay

6

Event Types in Water Detector

Used for relative normalization of different distances

then (IBD events)e e p e nμν ν ν +→ + → +

(Also νμe and⎯νμe)

NC

7Both ν−e elastic scattering (very forward) and νe – Oxygen (peaked

backwards) can be separately used for normalization samples

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

cos(theta)

nue-

Oxy

gen

Rat

e

0.8% havecos(theta)>0.95or theta<18 deg

This gives a <4% background to the ν-e ES sampleand negligible systematic uncertainty.

8Background Processes and Rates• Non-beam IBD backgrounds

(Evis > 20 MeV):– Atmospheric⎯νμ Invisible muons:⎯νμ + p → μ+ + n where μ+ is below Cherenkov threshold.

– Atmospheric⎯νe IBD events:⎯νe + p → e+ + n

– Diffuse supernova neutrinos

• Beam related IBD backgrounds– Intrinsic⎯νe in beam

• ~4 × 10-4 νe rate– Beam νe in coincidence with

random neutron capture • Estimated to be very small

from Super-K rates– νe-Oxygen CC scatters

producing an electron• Subsequent neutrons from

nuclear de-excitation are very small.Ee>20 MeV

9Expected Signal and Background Events

sin22θ13 = 0.0510yr Run

Normali

zatio

n

Off Osc

Max

OscMax

Abs Norm ⇒Relative Norm ⇒

10Measurement Strategy

• Daedalus oscillation measurement comes from a comparison of the absolute⎯νe rate compared to expectations from backgrounds and a possible oscillation signal parameterized by θ13 and δ.(Assuming that δ(sin22θ13) = 0.005 from reactor experiments.)

• Fits to observed⎯νe events from all three distances versus energy gives sensitivity to extracting θ13 and δ from expected oscillation formula

• For the neutrino flux, only uncertainty is the absolute normalization or how many π+ decays occur– Spectrum is known to high accuracy– ν-e elastic events from near accelerator sets absolute flux normalization

with a statistical error of ~1%– ν-Oxygen events at various distance constrain the relative normalization.

• Beam backgrounds (small intrinsic⎯νe rate) is measured from⎯νe IBD events from near accelerators (⎯νe + p → e+ + n) and then scaled by 1/L2

• Non-beam backgrounds are measured during the 40% beam-off running and scaled to

11

Systematic Uncertainties (before fit)

By comparing measurements for the three distances thesesystematic uncertainties are significantly reduced.

12Daedalus Insensitive to Systematic Uncertainties

due to Constraints from Three Distance Fits

Plot shows 1σ CP-δ measurement error as ν-e (ES) or IBD uncertaintyis increased from the nominal value of 1.1% and 0.5%

13Daedalus: Total Events vs δCP and Hierarchy

• Daedalus has excellent sensitivity for measuring δCP

– mainly from 20 km data where there is no hierarchy effects– 8 km data sensitive to cosδ oscillation term

0

200

400

600

800

1000

1200

1400

1600

1800

0 45 90 135 180 225 270 315 360

0CP

Nue

bar E

vent

s

1.5km - normal1.5km - inverted

0

200

400

600

800

1000

1200

1400

1600

1800

0 45 90 135 180 225 270 315 360

0CP

Nue

bar E

vent

s

8km - normal8km - inverted

0

200

400

600

800

1000

1200

1400

1600

1800

0 45 90 135 180 225 270 315 360

CP

Nue

bar E

vent

s

20km - normal20km - inverted

Bkgnd

Bkgnd Bkgnd

δCP δCP δCP

Due to short distance and low energy, there are no matter effects in Daedalus.

14Daedalus Event Energy Distributions (Signal & Background)(sin22θ13 = 0.04)

1.5km

8km

Blue: Intrinsic νe bkgndRed: Beam off bkgndBlack: δCP= 00

Violet: δCP= 450

Green: δCP=-450

20km

15

Estimates for Combining Daedalus and LBNE ν-Only Measurements

• Daedalus provides high-statistics antineutrino sample with low background and small systematics to be combined with LBNE ν-only data.– Use 10yrs Daedalus⎯ν data + 10yrs LBNE ν-only data

• LBNE sensitivity estimates use:– dusel120e250i002dr280dz1300km_flux.txt (neutrinos)– dusel120e250ni002dr280dz1300km_flux.txt (anti-neutrinos) – 300kt Water Cherenkov– Proton rate = 6 × 1020 pot/yr

16Estimates of Oscillation Parameter Sensitivity• Do fits to simulated data as a function of energy

– χ2 based fitting code developed that incorporates backgrounds and oscsignals

– Include event reconstruction efficiency and resolution smearing of oscillation probability

– Include systematic uncertainties through parameters constrained to be consistent with uncertainties.

• Use oscillation probability code with matter effects from S. Parke– Cross checked with “Globes” osc probability

• Simultaneous fits to various combinations of:– Daedalus:

• ⎯νe IBD events (signal+background at 1.5km, 8km, and 20 km) • ν-e elastic plus νe-O scattering samples for normalization.• Background uncertainties related to beam off running

– LBNE ν running or⎯ν running:• Efficiency, smearing, and backgrounds from LBNE Report archive:0705.4396• Assume that one uses near detector constraints for flux and backgrounds:

Syst error: 1% norm, 10% background, 5% earth density

17

Comparison of Osc Prob Parke vs Globes

Solid lines/boxes are GLoBES calculations; dashed lines/x’s are Parke program.

18Are Systematic Errors Larger for CombiningDaedalus+LBNE(ν-only) vs LBNE(ν plus⎯ν) ?

• To zeroth order, each of these measurements is a stand alone measurement of the osc probability

– LBNE uses the near detectors to determine flux, xsec, and bkgnd

– Daedalus uses the near accelerator to determine the flux and bkgnd (xsec uncertainty is very small)

– Absolute rate is providing important information especially if reactor sin22θ13 included

• Some systematic uncertainties (mainly detector efficiencies) for the LBNE ν and⎯ν measurements do partially cancel but they are masked by:

– the ν and⎯ν cross sections, flux, and background being so much different

– the large ν contamination for the⎯ν running

• This could be quantified by including detector uncertainties in the LBNE fit formalism and seeing how the sensitivity improves if ν /⎯ν correlations are included.

– These detector uncertainties have not, to my knowledge, been included in any of the LBNE studies so far but are probably much smaller than the assumed 10% background uncertainties.

5 years of ν Running

Blue: Intrinsic νe bkgndRed: Beam off bkgndBlack: δCP= 00

Violet: δCP= 450

Green: δCP=-450

20km

L/E: 2000 1000 400

L/E: 2000 1000 400

19sin22θ13 Measurement Regions where sin22θ13 ≠0 at 3σ

• Daedalus and LBNE(5yr+5yr) comparable but complementary in sensitivity

• Combination (Daedalus + LBNE ν-only) gives significantly better coverage by x2 to x3

-180

-120

-60

0

60

120

180

0.001 0.01 0.1

sin2(2θ13)

δ CP

Daedalus (10yrs)

LBNE (5yrs+5yrs)

Daedalus + LBNE nu-only (10 yrs)

0.0

0.2

0.4

0.6

0.8

1.0

0.001 0.01 0.1

sin2(2θ13)

Frac

tion

of δ

CP

Daedalus (10yrs)

LBNE (5yrs+5yrs)

Daedalus + LBNE nu-only (10 yrs)

20Mass Hierarchy Determination at 3σ

• Daedalus plus LBNE(ν-only) has good sensitivity for hierarchy determination comparable to LBNE(ν +⎯ν) around the 50% point.

• If hierarchy is not determining with Daedalus plus LBNE(ν-only), then run with LBNE antineutrinos⇒ Combination of Daedalus plus LBNE(ν +⎯ν) better by almost x2

3σ Determination(inverted hierarchy)

21Combined Daedalus and LBNE Sensitivity• Combining the high statistics Daedalus antineutrinos with the high

statistics LBNE neutrino data sets gives improved sensitivity for measuring CP violation (δCP)

• Plot below gives 1 σ error for measuring δCP as a function of δCP for sin22θ13 = 0.05

0

5

10

15

20

25

30

35

-180 -135 -90 -45 0 45 90 135 180

δCP (degrees)

1 σ u

ncer

tain

ty (d

egre

es)

LBNE (5ysr + 5yrsr

Daedalus (10yrs)

Daedalus 10yrs + LBNE nu-only 10yrs

sin22θ13 = 0.05

22Combined Daedalus and LBNE Running

Daedalus 5yr plus LBNE 5yr nu-only Daedalus 10yr plus LBNE 10yr nu-only

5yr Combined Running 10yr Combined Running

⇒ 5yr combined sensitivity as good as separate Daedalus 10yr or LBNE 10yr (ν plus⎯ν) running

⇒ 10yr combined much better than either

1 and 2 σ contours

23Exclusion of δCP= 00 or 1800 at 3σCombined running substantially better than either LBNE or Daedalus alone

(Even better than 10 yrs of Project X)

(Recent preprint has similar conclusions: Agarwalla,Huber,Link,Mohapatra - http://arxiv.org/abs/1005.4055 )

24Questions/Issues/Topics for INT Workshop

• What is the best optimization of cyclotron positions to combine with LBNE ν−only?

• Are there any issues with constraining the backgrounds using the near accelerator? Are there any other backgrounds that need to be added?

• Is an off-max, medium position (8km) necessary? How does it help make the CP violation measurement?

• Can one get by with only a far cyclotron site and a small monitoring detector? (Advantages/Disadvantages)

• Is there a different optimization of the LBNE beam for the Daedalus-LBNE ν−only CP measurement?

• How would a MiniBooNE/LSND signal effect the DUSEL CP violation measurements?

Overall Theme: How best can the DUSEL facility be exploited to measure CP Violation (and Mass Hierarchy?)

25Comparison of 1.5km+8km+20km vs 1.5km+20km

0

5

10

15

20

25

30

35

-180 -135 -90 -45 0 45 90 135 180

◊CP (degrees)

1 ◊ u

ncer

tain

ty (d

egre

es)

Daedalus Only: 1acc@1.5km, 2acc@8km,5acc@20kmDaedalus Only: 1acc@1.5km, 5acc@20kmLBNE Only(5yrs nu+ 5yrs nubar)1acc@1.5km, 2acc@8km,5acc@20km, LBNE nu-only for 10yrs1acc@1.5km, 5acc@20km, LBNE nu-only for 10yrs

sin22θ13=0.05

26

Near (1.5km) Site vs Local ν-Beam Detector

Use Near 1.5km Accelerator for beam and background monitoring.

Advantages:– Detector is the same so no

difference in efficiency, cross sections, or changes with time

– Provides calibration and other neutrino source for 300 ktondetector

– Large 300kton detector has large rate of ν−e ES to set the neutrino flux normalization.

• Disadvantages– Need extra accelerator site– Uncertainty for the integrated proton

intensity near compared to far ( this should be small)

Use Local small ν detector for beam and background monitoring.(No 1.5km accelerator)

• Advantages:– Only need one far accelerator site

(and no near accelerator site)

• Disadvantages:– Detector systematic differences

between small local detector and large 300 kton detector can be significant and hard to know

– Need to use water detector in order to cancel cross section uncertainties.

– Need to measure ν-e scattering with high statistic in order to know neutrino flux precisely. This demands a very close location and a fairly large detector

27Is there a different optimization of the LBNE beam for the Daedalus-LBNE ν−only CP measurement?

• LBNE wide-band beam has advantage of covering both the first and second maximum with the highest rate but ⇒– Second maximum region at low

energy has large backgrounds– Wide-band beam has large

high-energy tail that produces background from NC π0 events.

• Could an off-axis beam set to maximize the neutrino flux at oscillation maximum give better sensitivity when combined with the Daedalus⎯ν measurement?

5 years of ν Running

28

MiniBooNE/LSND High Mass Oscillation Signal Effects

• Assumptions:– High mass signal will be well

measured by Daedalus near accelerator (and possibly others) so osc params will be known

– No systematic uncertainty but these high-mass osc events increase the statistical uncertainty for CP violation search

• Size of sin22θ is approximately from about 0.002 to 0.032 which translate into an extra⎯νebackground of 0.1% to 1.6% of the⎯νμ rate.

29

Daedalus-Only LSND Osc Signal Effects

Exclusion of CP= 00 or 1800 at 3 (10yrs)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.001 0.01 0.1

sin2(2 13)

Frac

tion

of

CP

No LSND Osc EventsWith LSND anu Osc Events @ 1.5%

(Daedalus only-300kt Water Cherenkov)

Exclusion of CP= 00 or 1800 at 3 (10yrs)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.001 0.01 0.1

sin2(2 13)

Frac

tion

of

CP

No LSND Osc EventsWith LSND anu Osc Events @ 0.15%

(Daedalus only-300kt Water Cherenkov)

30

Effects for LBNE(ν plus⎯ν) and Daedalus plus LBNE

Exclusion of CP= 00 or 1800 at 3 ⎭(10yrs)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.001 0.01 0.1

sin2(2 13)

Frac

tion

of

CP

No LSND Osc EventsWith LSND anu Osc Events @ 1.5%

(Daedalus plus LBNE -only300kt Water Cherenkov)

Exclusion of CP= 00 or 1800 at 3 ⎭(10yrs)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.001 0.01 0.1

sin2(2 13)

Frac

tion

of

CP

With LSND anu Osc Events @ 1.5%No LSND Osc Events

(LBNE 5yr nu + 5yr anu300kt Water Cherenkov)

31Summary

• Use workshop to explore and brainstorm how best to exploit the DUSEL facility to measure CP Violation (and Mass Hierarchy?)– Combining measurements– Optimizing the experimental setups

• Tools available to look at these various setups and quantify sensitivities

• Generate ideas that can be studied further after the workshop.

32

Backup Slides

33Recent preprint has similar conclusions for 100kton Detector forDaeldalus plus LBNE nu-only

Agarwalla,Huber,Link,Mohapatra - http://arxiv.org/abs/1005.4055

34

35

36

Cross Check nue-e Scattering Rate(Daedalus Prediction vs LSND Measurement)

37

( )2: 0.35, 0.45 , 1 0.8 1e

e e

drate E E ydy

μ μ

ν

ν ν

σ

− −+ → +

⎛ ⎞= = + −⎜ ⎟

⎝ ⎠ ( )2

then (IBD events)

: 0.32, 0.42 , 1 1.2 1

e e

e

p e n

de e rate E E ydy

μ

μ μ ν

ν ν ν

σν ν

+

− −

→ + → +

⎛ ⎞+ → + = = + −⎜ ⎟

⎝ ⎠

( )

( )

2: 2.25, 0.49 , 1 0.1 1

Electron goes mainly backward for this process!

e e

e

e

e e

drate E E ydy

Oxygen e Fluorine

ν

ν ν

σ

ν

− −

−

+ → +

⎛ ⎞= = + −⎜ ⎟

⎝ ⎠+ → +

38Daedalus and LBNE Sensitivity for

200 kton and 300 kton Water Detectors

39Oscillation Formula (no matter effects, i.e. Daedalus)

Oscillation Formula (with matter effects, i.e. LBNE)