FLASY2011 Short Baseline Neutrino Anomalies and Future Probes - - PowerPoint PPT Presentation

FLASY2011

Short Baseline Neutrino Anomalies and Future Probes

Sanjib Kumar Agarwalla (Sanjib.Agarwalla@ific.uv.es) IFIC/CSIC, University of Valencia, Spain

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.1/32

Definition of Short Baseline

Short-baseline means : L/E ∼ 1 (m/MeV or km/GeV) It covers a wide range of experiments

Radioactive νe/¯

νe Source experiments

(L/E ∼ 1 m/1 MeV) Reactor ¯

νe experiments

(L/E ∼ 5 m/5 MeV) Accelerator produced ν experiments (L/E ∼ 1 km/1 GeV) Atmospheric Neutrinos in IceCube (L/E ∼ 1000 km/1 TeV)

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.2/32

Short Baseline Experiments

¯ νe disappearance search (reactor experiments)

Bugey-3 (at 15, 40 & 95 m), Bugey-4, ROVNO, Gösgen, Krasnoyarsk, ILL Also, Chooz and Palo Verde at L ≃ 1 km

νe disappearance search

KARMEN and LSND νe-carbon cross section estimates GALLEX & SAGE radioactive source experiments

Appearance searches (νµ → νe, ¯ νµ → ¯ νe)

LSND, MiniBooNE, KARMEN, NOMAD

νµ disappearance limits

CDHS, MiniBooNE, Atmospheric neutrinos Neutral Current measurement of MINOS

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.3/32

Short-baseline ν oscillation

Recent results from short-baseline neutrino experiments hint towards high ∆m2 ∼ 0.1–10 eV2 oscillation Are they pointing towards Sterile neutrinos or something else?

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.4/32

Positive Indications

LSND : L = 30 m, < Eν¯

µ > = 40 MeV

3.8 σ excess of ¯ νe events in a beam of ¯ νµ

PRL 75 (1995) 2650; PRC 54 (1996) 2685; PRL 77 (1996) 3082; PRD 64 (2001) 112007

MiniBooNE : L = 541 m, < Eνµ,ν¯

µ > = 700 MeV

A 2.8 σ excess of ¯

νe events in the anti-neutrino mode

above 475 MeV, consistent with LSND

PRL 103 (2009) 111801; PRL 105 (2010) 181801

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.5/32

Positive Indications

Recent Reactor Anomaly

Reanalysis of reactor fluxes in Mueller et al., (arXiv:1101.2663) shows 2.5% upward shift in flux Overall reduction in predicted flux compared to existing data can be interpreted as oscillations at baselines of

• rder 10–100 m (arXiv:1101.2755)

Gallium Anomaly

There is a deficit of νe measured in the radioactive source experiments of the GALLEX and SAGE detector Suggests possible νe disappearance at 2.7 σ (arXiv:1006.3244)

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.6/32

Negetive Indications : Tensions

In MiniBooNE, no oscillation in the ν-mode for energies above 475 MeV

PRL 98 (2007) 231801

An unexplained 3 σ excess of νe events in the ν-mode of MiniBooNE below 475 MeV

PRL 102 (2009) 101802

No hint of steriles in MiniBooNE νµ/¯

νµ disappearance

PRL 103 (2009) 061802

Strong limit on νµ disappearance from CDHS

PLB 134 (1984) 281

No trace of steriles in atmospheric and solar neutrino data in the required parameter range

PRD 76 (2007) 093005

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.7/32

3+1 SBL oscillations

Add one sterile ν with three active ones at the eV scale SBL approximation : ∆m2

21 ≈ ∆m2 31 ≈ 0 and xij ≡ ∆m2 ijL/4E

P(¯ νµ → ¯ νe) = 4|Ue4|2|Uµ4|2 sin2 x41 ≡ sin2 2θµe sin2 x41

Example Fit : ∆m2

41 = 0.57 eV2 and sin2 2θµe = 0.0097 using LSND, MB-¯

ν, KARMEN (Karagiorgi et al., arXiv:0906.1997) P(νe → νe) = 1 − 4|Ue4|2(1 − |Ue4|2) sin2 x41 ≡ 1 − sin2 2θee sin2 x41 Example Fit : ∆m2

41 = 1.78 eV2 and sin2 2θee = 0.089 using all reactor data

with new fluxes (J. Kopp et al., arXiv:1103.4570) No CPV : can’t reconcile ¯ ν (LSND, MB) and ν (MB) data

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.8/32

3+2 SBL oscillations

Add two sterile neutrinos with three active ones at the eV scale SBL approximation : ∆m2

21 ≈ ∆m2 31 ≈ 0 and xij ≡ ∆m2 ijL/4E

P(¯ νµ → ¯ νe) = 4|Ue4|2|Uµ4|2 sin2 x41 + 4|Ue5|2|Uµ5|2 sin2 x51 + 8|Ue4Uµ4Ue5Uµ5| sin x41 sin x51 cos(x54 + δ)

δ ≡ arg(U∗

e4Uµ4Ue5U∗ µ5) is the CP-phase

P(νe → νe) = 1 − 4(1 − |Ue4|2 − |Ue5|2)(|Ue4|2 sin2 x41 + |Ue5|2 sin2 x51) − 4|Ue4|2|Ue5|2 sin2 x54

∆m2

41

|Ue4| |Uµ4| ∆m2

51

|Ue5| |Uµ5| δ/π A : arXiv:1103.4570 0.47 0.128 0.165 0.87 0.138 0.148 1.64 B : arXiv:0906.1997 0.39 0.40 0.20 1.10 0.21 0.14 1.1

Global best-fit points for (3+2) model. Mass splittings are shown in eV2

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.9/32

What do we need?

We have both positive and negative hints for sterile high

∆m2 oscillation. Nothing is conclusive !!

We need powerful new experiments to have appearance and disappearance searches at high significance involving both neutrinos and anti-neutrinos

Combine powerful new multi-kiloton liquid scintil- lator, argon or water detectors with a modest power decay-at-rest neutrino source at short-baseline Observe the L/E dependence of the oscillation wave across the length scales of these detectors SKA, Patrick Huber, arXiv:1007.3228 SKA, J.M. Conrad, M.H. Shaevitz, arXiv:1105.4984

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.10/32

Stopped Pion Source

800 MeV protons from cyclotrons interact in a low-A target (C, H2O) producing π+ and, at a low level, π−

p + X → π± + X′

Low-A target is embedded in a high-A, dense material where pions are brought to rest

π− & daughter µ− captured before DIF, minimizing ¯ νe π+ decay produces mono-energetic 29.8 MeV νµ & µ+ π+ → µ+ + νµ µ+ decays at rest, providing Michel spectrum µ+ → e+ + νe + ¯ νµ

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.11/32

Decay At Rest (DAR) Source

π+ → µ+ + νµ | → e+ + νe + ¯ νµ

νµ νµ

Φ (MeV

• 1

• 1

ν

Provides an equal, high-intensity, isotropic, DAR νµ, νe and ¯

νµ

beam with tiny ¯

νe contamination (4 × 10−4)

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.12/32

Cyclotron : Proton Source

Mike Shaevitz, SBNW11, Fermilab

Cyclotrons : ideal low-cost source for low energy protons Bunch spacing ∼ few tens of ns, continuous source Average beam power, 10 - 100 kW, prototypes for DAEδALUS

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.13/32

Neutrino Source Details

4 × 1021 per year, per flavor (νµ, ¯ νµ and νe), 1.6 × 1018 per year of ¯ νe (4 × 10−4 compared to other flavors); Delivered as 100 kW average power, with 200 kW instantaneous power, (50% duty factor allowing equal beam-on and beam-off data sets); 800 MeV protons on target; ±25 cm smearing (assumed flat) on neutrino production point; 20 m distance from average production point to face of detector fiducial region.

p/π ratio uncertain : conservative 10% correlated normalization error on all flavors 20% normalization error on the π− DIF background No uncertainty in the shape of the energy spectrum

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.14/32

DAR beam interactions

g.s.

Ar K C N p n [IBD]

* −

40 40

( ) e

e ,

ν ( )

+

e

e ,

[MeV]

ν

[ cm ]

2 νe , e ( )

12 12

−

1e−43

Neutrino energy

50 45 40 35 30 25 20 15 10 1e−39 1e−40 1e−41 1e−42

Cross−section

¯ νµ → ¯ νe Appearance ¯ νe + p → e+ + n (IBD)

Free protons : Liquid scintillator oil, H2O Low kinematic threshold : 1.81 MeV Coincidence tag between prompt positron and the delayed neutron capture by a proton n + p → d + γ (2.2 MeV) after ∼ 250 µs

νe → νe Disappearance νe+12C → e−+12Ng.s. Threshold 17.33 MeV, well measured, ∼ 5 to 10% uncertainty

prompt e−, followed within a 60 ms window by e+ from β-decay of the 12Ng.s., mean τ 15.9 ms

νe +40 Ar → e− +40 K⋆ Threshold 4.24 to 5.89 MeV depending on which 40K⋆

It has the highest cross-section in the energy range of interest, excellent for Disappearance studies

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.15/32

LENA Scintillation Detector

50 kt Fiducial (Unsegmented) 100 m tall by 30 m diameter Source-to-detector-face = 20 m Low detection threshold

Excellent Vertex and Energy Resolution Clear coincidence signal for ¯ νe IBD events Deep underground location (4000 mwe) Negligible cosmic muon backgrounds

Neutrino Energy threshold

For appearance : Eν > 20 MeV For disappearance : Eν > 33 MeV

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.16/32

Appearance wave in LENA

[ With Osc/Full Transmutation ]

(3+1) (3+2) 50 kt LENA (Appearance mode)

L/E Event ratio

0.007 0.008 0.009 0.01 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0.005 [m/MeV] 0.004 0.003 0.002 0.001 0.006

Bin and fit IBD data with reconstructed L/E (3+1) fit : Karagiorgi et al., arXiv:0906.1997 ∆m2

41 = 0.57 eV2 & sin2 2θµe = 0.0097

(3+2) fit : J. Kopp et al., arXiv:1103.4570 Accessible L range : 20–120 m DAR energy range : 20–52.8 MeV SKA, J.M. Conrad, M.H. Shaevitz, arXiv:1105.4984

Oscillation wave is dramatic in the long LENA detector and can provide a powerful handle to discriminate between (3+1) and (3+2) schemes

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.17/32

Appearance Event Rates

∆m2

41

|Ue4| |Uµ4| ∆m2

51

|Ue5| |Uµ5| δ/π A : arXiv:1103.4570 0.47 0.128 0.165 0.87 0.138 0.148 1.64 B : arXiv:0906.1997 0.39 0.40 0.20 1.10 0.21 0.14 1.1 Fiducial Mass Radius Length Signal Signal Intrinsic ¯ νe (A : 1103.4570) (B : 0906.1997) Background 50 kt 13.58 m 100 m 12985 32646 1450 25 kt 10.78 m 79.37 m 7787 18356 875 10 kt 7.94 m 58.48 m 3753 7964 443 5 kt 6.3 m 46.42 m 2080 4044 261

Signal and beam background events in 5 to 50 kt LENA Total 4 × 1021 ¯

νµ (100 kW source), efficiency 90%

The intrinsic ¯

νe beam contamination is 4 × 10−4

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.18/32

DAR-LENA ¯ νµ → ¯ νe Sensitivity

22θ

sin ∆m

2

2

[eV ] −1 −4

Appearance mode

−3

10 kW (1 year)

−2

µe

1

MiniBooNE 99% CL (2 dof)

−1

+ LSND

ν

(2 dof)

σ 5

( )

10

10 kt 5 kt 50 kt DAR−LENA

10 10 10 10 10 10

25 kt

22θ

sin ∆m

2

2

[eV ] −1 −4

Appearance mode 100 kW (1 year)

−2

e µ

1 −3

MiniBooNE

−1

99% CL (2 dof) + LSND

(2 dof)

σ 5

ν

( )

10

5 kt 25 kt 50 kt DAR−LENA

10 10 10 10 10 10

10 kt

SKA, J.M. Conrad, M.H. Shaevitz, arXiv:1105.4984

5 kt LENA combined with a small 10 kW DAR source can test the LSND/MiniBooNE anti- neutrino signal at 5 σ CL in 3+1 model in 1 yr

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.19/32

Disappearance wave in LENA

50 kt LENA (Disappearance mode) (3+1) (3+2)

Event ratio [ With Osc/No Osc ] L/E

0.88 0.5 1 1.5 2 2.5 3 3.5 [m/MeV] 0.98 0.96 0.94 0.92 0.9 1

Bin and fit νe scattering data with L/E (3+1) fit : J. Kopp et al., arXiv:1103.4570 ∆m2

41 = 1.78 eV2 and sin2 2θee = 0.089

(3+2) fit : J. Kopp et al., arXiv:1103.4570 Accessible L range : 20–120 m DAR energy range : 33–52.8 MeV SKA, J.M. Conrad, M.H. Shaevitz, arXiv:1105.4984

Different shape for (3+1) and (3+2) waves. Comparison between the amplitudes of the wave in various L/E bins cancels flux uncertainties

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.20/32

Disappearance Event Rates

∆m2

41

|Ue4| |Uµ4| ∆m2

51

|Ue5| |Uµ5| δ/π A : arXiv:1103.4570 0.47 0.128 0.165 0.87 0.138 0.148 1.64 B : arXiv:0906.1997 0.39 0.40 0.20 1.10 0.21 0.14 1.1 Fiducial Mass Radius Length Evts w/ Osc Evts w/ Osc Evts, No Osc (A : 1103.4570) (B : 0906.1997) 50 kt 13.58 m 100 m 170191 139119 181672 25 kt 10.78 m 79.37 m 102726 85271 109590 10 kt 7.94 m 58.48 m 52105 43940 55439 5 kt 6.3 m 46.42 m 30874 26321 32735

CC νe scattering events on 12C in 5 to 50 kt LENA Total 4 × 1021 νe (100 kW source), efficiency 80% Eν threshold of 33 MeV and resolution 10%/

• Ee/MeV

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.21/32

DAR-LENA νe → νe Sensitivity

2

∆m

2

2

[eV ] 1 −1 −2

e

(2 dof)

e

sin θ 2

Disappearance mode 100 kW (1 year) σ 3 All reactor data (new flux)

−1

99% CL (2 dof) 10 kt 25 kt 50 kt

10 10 10 10

DAR−LENA

10

5 kt

100 kW source (4 × 1021 νe), 5 - 50 kt fiducial (3+1) model with simple 2-ν approximation Triangle & Bullet : (3+1) best-fit values for all reactor data with old & new fluxes Dashed green curve : 99% CL (2 dof) limit from reactor data with new reactor fluxes SKA, J.M. Conrad, M.H. Shaevitz, arXiv:1105.4984

10 kt LENA with a flux of 4 × 1021 νe can provide stringent test of the recent reactor anomaly at 3 σ CL (2 dof)

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.22/32

NOνA : Coming Soon

Segmented Scintillator Detector

Detector mass 14 kt CH2 Scintillator Target, 30% PVC Dimensions : 15.7 m × 15.7 m × 67 m NOνA not made for low energy signal It can only perform νe disappearance Cannot see the 2.2 MeV γ from n capture Very little shielding – 3 m of Earth Largest background : 1010 Michel electrons/year produced by stopped cosmic muon decay Michel electron events identified and vetoed by tracking the parent muon For this study, we consider 10,000 to 50,000 un-vetoed Michel background events

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.23/32

NOνA Event Rates

∆m2

41

|Ue4| |Uµ4| ∆m2

51

|Ue5| |Uµ5| δ/π A : arXiv:1103.4570 0.47 0.128 0.165 0.87 0.138 0.148 1.64 B : arXiv:0906.1997 0.39 0.40 0.20 1.10 0.21 0.14 1.1 Fiducial Length Breadth Height Evts w/ Osc Evts w/ Osc Evts, No Osc Mass 1103.4570 0906.1997 14 kt 67 m 15.7 m 15.7 m 32388 27407 34415

CC νe scattering events on 12C in 14 kt NOνA far detector Total 4 × 1021 νe (100 kW source), efficiency 50%

ν energy threshold of 38 MeV and resolution

100%/

• Ee/MeV

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.24/32

DAR-NOνA νe → νe Sensitivity

2

99% CL (2 dof)

∆m

2

2

[eV ] 1

(new flux)

−2

All reactor data

2θ sin

e e

1 MW

−1

1 year run ν 3 σ

−1

Disappearance mode

100 kW

(2 dof) 25k Bkg/100 kW 25k Bkg/1 MW 50k Bkg/100 kW DAR−NO A

10 10 10 10

50k Bkg/1 MW

10 100 kW & 1 MW average source power 25k & 50k effective Michel e− Backgrounds (3+1) model with simple 2-ν approximation Triangle & Bullet : (3+1) best-fit values for all reactor data with old & new fluxes Dashed green curve : 99% CL (2 dof) limit from reactor data with new reactor fluxes SKA, J.M. Conrad, M.H. Shaevitz, arXiv:1105.4984

100 kW machine is marginal in covering the test points and a higher-power, full DAEδALUS type machine, is needed

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.25/32

Future Liquid Argon Detector

Possible detector for νe disappearance search with DAR beam

∆m2

41

|Ue4| |Uµ4| ∆m2

51

|Ue5| |Uµ5| δ/π A : arXiv:1103.4570 0.47 0.128 0.165 0.87 0.138 0.148 1.64 B : arXiv:0906.1997 0.39 0.40 0.20 1.10 0.21 0.14 1.1 Fiducial Length Breadth Height Evts w/ Osc Evts w/ Osc Evts, No Osc Mass 1103.4570 0906.1997 5 kt 50 m 10 m 7 m 345664 288107 368880 3 kt 30 m 10 m 7 m 292723 250432 309856 1.5 kt 15 m 10 m 7 m 211483 186615 221322

CC νe scattering events on 40Ar in 1.5 to 5 kt LAr detector Total 4 × 1021 νe (100 kW source), efficiency 90%

ν energy threshold of 20 MeV and resolution

11%/√Ee+2.5%

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.26/32

DAR-LAr νe → νe Sensitivity

2

3

∆m

2

2

[eV ] 1

(2 dof)

−1

σ

e

−2

e

sin θ 2

Disappearance mode 100 kW (1 year) All reactor data (new flux) 99% CL (2 dof)

−1

1.5 kt

10 10

5 kt

10 10

DAR−LAr

10

3 kt

100 kW average source power Negligible background from cosmic muons (under 4000 mwe of shielding) (3+1) model with simple 2-ν approximation Triangle & Bullet : (3+1) best-fit values for all reactor data with old & new fluxes Dashed green curve : 99% CL (2 dof) limit from reactor data with new reactor fluxes SKA, J.M. Conrad, M.H. Shaevitz, work in progress

1.5 kt LAr detector and 100 kW source is enough to test the reactor anomaly at high significance

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.27/32

What Super-K can do?

5 sigma (2 dof)

99%CL (2 dof) MiniBooNE+LSND

0.1 0.001 0.01 0.1 Delta_m_sq (eV^2) sin^2(2*theta_emu) SK+100 kW SK+10 kW SK+5 kW 10kt+100 kW 5kt+100 kW 10 1 0.0001

EGADS + 1 MW

100 kW 10 kt 5 kt SK

Delta_m_sq (eV^2) sin^2(2*theta_ee) 0.01 1 0.1 10 0.1

SKA, J.M. Conrad, M.H. Shaevitz, work in progress 5 kW machine combined with Super-K can test the LSND/MiniBooNE anti-neutrino signal at 5 σ CL in 3+1 model in 1 yr. Super-K and 100 kW machine is more than enough to test the reactor anomaly at 3 σ

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.28/32

Conclusions

Large neutrino detectors using liquid scintillator and liquid argon will come on-line within the next decade These detectors combined with high intensity 10–100 kW cyclotron DAR neutrino sources would have unprecedented sensitivity to sterile ν

• scillations in the high ∆m2 ∼ 0.5-10 eV2 region

These experiments are an important option as a next major step to search for sterile neutrino

• scillations

Thank you

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.29/32

Number of Sterile Neutrinos

C Giunti, BEYOND3NU, LNGS

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.30/32

From Cosmology

C Giunti, BEYOND3NU, LNGS

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.31/32

β & (ββ)0ν Decay

mβ ∼ 0.12 – 0.71 eV (2 σ) mββ ∼ 0.011 – 0.15 eV (2 σ)

C Giunti, BEYOND3NU, LNGS

Sanjib K. Agarwalla, FLASY2011, Valencia, Spain, 13/07/11 – p.32/32