Sanjib Kumar Agarwalla - Nevis Laboratories · 2014-09-19 · Sanjib K. Agarwalla, FLASY2011,...

FLASY2011

Short Baseline Neutrino Anomalies

and Future Probes

Sanjib Kumar Agarwalla

([email protected])

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

Radioactiveνe/νe Source experiments(L/E ∼ 1 m/1 MeV)

Reactorνe experiments(L/E ∼ 5 m/5 MeV)

Accelerator producedν experiments(L/E ∼ 1 km/1 GeV)

Atmospheric Neutrinos in IceCube(L/E ∼ 1000 km/1 TeV)


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 atL ≃ 1 km

νe disappearance search

KARMEN and LSNDνe-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


Short-baseline ν oscillation

Recent results from short-baselineneutrino experiments hint towards

high ∆m2 ∼ 0.1–10 eV2 oscillation

Are they pointing towards Sterileneutrinos or something else?


Positive Indications

LSND : L = 30 m, < Eνµ> = 40 MeV

3.8σ excess ofνe events in a beam ofνµ

PRL 75 (1995) 2650; PRC 54 (1996) 2685; PRL 77 (1996) 3082; PRD64 (2001) 112007

MiniBooNE : L = 541 m, < Eνµ,νµ> = 700 MeV

A 2.8σ excess ofνe events in the anti-neutrino modeabove475 MeV, consistent with LSNDPRL 103 (2009) 111801; PRL 105 (2010) 181801


Positive Indications

Recent Reactor Anomaly

Reanalysis of reactor fluxes in Muelleret al.,(arXiv:1101.2663) shows 2.5% upward shift in flux

Overall reduction in predicted flux compared to existingdata can be interpreted as oscillations at baselines oforder 10–100 m (arXiv:1101.2755)

Gallium Anomaly

There is a deficit ofνe measured in the radioactive sourceexperiments of the GALLEX and SAGE detector

Suggests possibleνe disappearance at 2.7σ(arXiv:1006.3244)


Negetive Indications : Tensions

In MiniBooNE, no oscillation in theν-mode for energiesabove475 MeV

PRL 98 (2007) 231801

An unexplained3σ excess ofνe events in theν-mode ofMiniBooNE below475 MeV

PRL 102 (2009) 101802

No hint of steriles in MiniBooNEνµ/νµ disappearancePRL 103 (2009) 061802

Strong limit onνµ disappearance from CDHSPLB 134 (1984) 281

No trace of steriles in atmospheric and solar neutrino datain the required parameter rangePRD 76 (2007) 093005


3+1 SBL oscillations

Add one sterileν with three active ones at the eV scale

SBL approximation :∆m221 ≈ ∆m2

31 ≈ 0 andxij ≡ ∆m2ijL/4E

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

Example Fit :∆m2

41= 0.57 eV2 andsin2 2θµe = 0.0097 using LSND, MB-ν,

KARMEN (Karagiorgiet al., arXiv:0906.1997)

P (νe → νe) = 1 − 4|Ue4|2(1 − |Ue4|2) sin2x41 ≡ 1 − sin2 2θee sin2

x41

Example Fit :∆m2

41= 1.78 eV2 andsin2 2θee = 0.089 using all reactor data

with new fluxes (J. Koppet al., arXiv:1103.4570)

No CPV : can’t reconcileν (LSND, MB) andν (MB) data


3+2 SBL oscillations

Add two sterile neutrinos with three active ones at the eV scale

SBL approximation :∆m221 ≈ ∆m2

31 ≈ 0 andxij ≡ ∆m2ijL/4E

P (νµ → νe) = 4|Ue4|2|Uµ4|2 sin2x41 + 4|Ue5|2|Uµ5|2 sin2

x51

+ 8|Ue4Uµ4Ue5Uµ5| sinx41 sinx51 cos(x54 + δ)

δ ≡ arg(U∗

e4Uµ4Ue5U∗

µ5) is theCP -phase

P (νe → νe) = 1 − 4(1 − |Ue4|2 − |Ue5|2)(|Ue4|2 sin2x41 + |Ue5|2 sin2

x51)

− 4|Ue4|2|Ue5|2 sin2x54

∆m241 |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


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 appearanceand disappearance searches at high significance involvingboth 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


Stopped Pion Source

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

p + X → π± + X ′

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

π− & daughterµ− captured before DIF, minimizingνe

π+ decay produces mono-energetic 29.8 MeVνµ & µ+

π+ → µ+ + νµ

µ+ decays at rest, providing Michel spectrum

µ+ → e+ + νe + νµ


Decay At Rest (DAR) Source

π+ → µ+ + νµ

|→ e+ + νe + νµ

0 10 20 30 40 50 60

νµ ν

µ

Φ (M

eV-1 s

-1)

Eν (MeV)

νe

Provides an equal, high-intensity, isotropic, DARνµ, νe andνµ

beam with tinyνe contamination (4 × 10−4)


Cyclotron : Proton Source

Mike Shaevitz, SBNW11, Fermilab

Cyclotrons : ideal low-cost source for low energy protonsBunch spacing∼ few tens of ns, continuous source

Average beam power, 10 - 100 kW, prototypes for DAEδALUS


Neutrino Source Details

4 × 1021 per year, per flavor (νµ, νµ andνe),

1.6 × 1018 per year ofνe (4 × 10−4 compared to other flavors);

Delivered as 100 kW average power, with 200 kW instantaneouspower,

(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% correlatednormalization error on all flavors

20% normalization error on theπ− DIF background

No uncertainty in the shape of the energy spectrum


DAR beam interactions

g.s.

Ar K

C N

p n [IBD]

*− 4040( )ee ,ν

( )+ee ,

[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

Cro

ss−s

ectio

nνµ → 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∼ 250µs

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 the12Ng.s., meanτ 15.9 ms

νe +40 Ar → e− +40 K⋆ Threshold 4.24 to 5.89 MeV depending on which40K⋆

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


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 forνe IBD events

Deep underground location (4000 mwe)

Negligible cosmic muon backgrounds

Neutrino Energy threshold

For appearance : Eν > 20 MeV

For disappearance : Eν > 33 MeV


Appearance wave in LENA

[ With

Osc

/Ful

l Tra

nsm

utat

ion

]

(3+1)

(3+2)

50 kt LENA (Appearance mode)

L/E

Eve

nt r

atio

0

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 reconstructedL/E

(3+1) fit : Karagiorgiet al., arXiv:0906.1997

∆m241 = 0.57 eV2 & sin2 2θµe = 0.0097

(3+2) fit : J. Koppet al., arXiv:1103.4570

Accessible L range : 20–120 m

DAR energy range : 20–52.8 MeV


Oscillation wave is dramatic in the long LENA

detector and can provide a powerful handle to

discriminate between (3+1) and (3+2) schemes


Appearance Event Rates

∆m241 |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

Total4 × 1021 νµ (100 kW source), efficiency 90%

The intrinsicνe beam contamination is4 × 10−4


DAR-LENA νµ → νe Sensitivity

22θsin

∆m2

2[e

V

]

−1−4

Appearance mode

−3

10 kW (1 year)

−2

µe

1

MiniBooNE

0 99% CL (2 dof)

−1

+ LSNDν

(2 dof)σ5

( )

10

10 kt5 kt

50 kt

DAR−LENA

10

10

10

10 10 10

25 kt

22θsin

∆m2

2[e

V

]

−1−4

Appearance mode

100 kW (1 year)

−2

eµ

1

−3

0MiniBooNE

−1

99% CL (2 dof)+ LSND

(2 dof)σ5

ν( )

10

5 kt

25 kt50 kt

DAR−LENA

10

10

10

10 10 10

10 kt


5 kt LENA combined with a small 10 kW

DAR source can test the LSND/MiniBooNE anti-

neutrino signal at 5σ CL in 3+1 model in 1 yr


Disappearance wave in LENA50 kt LENA (Disappearance mode)

(3+1)

(3+2)

Eve

nt r

atio

[ 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

1Bin and fitνe scattering data withL/E


∆m241 = 1.78 eV2 andsin2 2θee = 0.089


Accessible L range : 20–120 m

DAR energy range : 33–52.8 MeV


Different shape for (3+1) and (3+2) waves.

Comparison between the amplitudes of the wave

in various L/E bins cancels flux uncertainties


Disappearance Event Rates

∆m241 |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 on12C in 5 to 50 kt LENA

Total4 × 1021 νe (100 kW source), efficiency 80%

Eν threshold of 33 MeV and resolution 10%/√

Ee/MeV


DAR-LENA νe → νe Sensitivity

2

0

∆m2

2[e

V

]1

−1−2

e

(2 dof)

esin θ2

Disappearance mode

100 kW (1 year)

σ3

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

Dashedgreencurve : 99% CL (2 dof) limit

from reactor data with new reactor fluxes


10 kt LENA with a flux of 4× 1021 νe can provide

stringent test of the recent reactor anomaly at

3σ CL (2 dof)


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 performνe disappearance

Cannot see the 2.2 MeVγ 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 theparent muon

For this study, we consider 10,000 to 50,000 un-vetoed Michel background events


NOνA Event Rates

∆m241 |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

CCνe scattering events on12C in 14 kt NOνA far detector


ν energy threshold of 38 MeV and resolution100%/

√

Ee/MeV


DAR-NOνA νe → νe Sensitivity

2

99% CL (2 dof)

∆m2

2[e

V

]1

(new flux)

−2

All reactor data

2θsin ee

1 MW

−1

1 year run

ν 3 σ

−1

Disappearance mode

0

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







100 kW machine is marginal in covering the test

points and a higher-power, full DAEδALUS type

machine, is needed


Future Liquid Argon Detector

Possible detector forνe disappearance search with DAR beam

∆m241 |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

CCνe scattering events on40Ar in 1.5 to 5 kt LAr detector


ν energy threshold of 20 MeV and resolution11%/

√Ee+2.5%


DAR-LAr νe → νe Sensitivity

2

3

∆m2

2[e

V

]1

(2 dof)

0

−1

σ

e

−2

esin θ2

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)






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


What Super-K can do?

5 sigma (2 dof)

99%CL (2 dof)

MiniBooNE+LSND

0.1

0.001 0.01 0.1

Del

ta_m

_sq

(eV

^2)

sin^2(2*theta_emu)

SK+100 kWSK+10 kWSK+5 kW

10kt+100 kW5kt+100 kW

10

1

0.0001

EGADS + 1 MW100 kW

10 kt5 kt

SK

Del

ta_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 5σ CL in 3+1 model in 1 yr. Super-K and 100 kW machine is more than enough to test

the reactor anomaly at 3σ


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

oscillations 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

oscillations

Thank you


Number of Sterile Neutrinos

C Giunti, BEYOND3NU, LNGS


From Cosmology

C Giunti, BEYOND3NU, LNGS


β & (ββ)0ν Decay

mβ ∼ 0.12 – 0.71 eV (2σ)

mββ ∼ 0.011 – 0.15 eV (2σ)C Giunti, BEYOND3NU, LNGS


Sanjib Kumar Agarwalla - Nevis Laboratories · 2014-09-19 · Sanjib K. Agarwalla, FLASY2011,...

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