Hugh Gallagher Tufts University June 15, 2004 Neutrino 2004 College de France

Hugh GallagherTufts University

June 15, 2004Neutrino 2004

College de France

OtherAtmospheric Neutrino Experiments

(past) – present – and future

H. Gallagher, Tufts University Neutrino 2004 June 15, 2004

IntroductionIn less than two decades, atmospheric neutrinos have gone from being “anomalous” to being one of our main tools for exploration of the lepton sector.

1980s – 1990s: Skepticism was rampant!

“Neutrino experiments are hard!”

“Cosmic ray experiments are hard!”

“Oscillation experiments are hard!”

Since 1998 the experimental evidence from SuperK, MACRO and Soudan 2 for atmospheric neutrino oscillations has been overwhelming.

Now that neutrino oscillations are established, is there still a role for atmospheric neutrinos to play in the experimental study of neutrino oscillations?


Experimental Goals - Present

One set of experimental questions around the goal of confirming or refuting the standard picture of neutrino oscillations.

Mixing between 3 active flavors of neutrinos through neutrino oscillations. No sterile mixing. No CPT violation.Majorana masses, small via see-saw mechanism.

Experimental goals:Confirmation with multiple independent measurementsObserving “oscillations”

Confirming through appearanceRuling out mixing to sterile neutrinosRuling out various alternative hypotheses: decoherence, neutrino decay, CPT violation in the neutrino sector, violation of Lorentz invariance…

NC detectionp p

J. Beacom and S. Palomares-Ruiz

PRD 67 (2003)


Current ExperimentsThese goals, as well as the measurement of m2

23 and sin2(2), have been the focus of the current generation of experiments.

1. Soudan 2 2. MACRO3. MINOS4. SNO

Final or “nearly final” analyses

Preliminary analyses


Soudan 2: The Detector

224 1m x 1m x 2.7 m modules963 ton total mass5.90 fiducial kton-yr exposure

The detector is surrounded by a ~1700 m2 “veto shield”which provides nearly 4 coverage for the identificationof charged particles entering / exiting the detector cavern.

The experiment is located 2340 feet underground in the Soudan UndergroundState Park in Soudan, Minnesota.


Soudan 2

Up-stopping muons < E = 6.2 GeV

Contained events<E> ~ 1 GeV

Partially contained events<E> ~ 6 GeV

“In-down” muons<E = 2.4 GeV

• 3 flavor categories (e CC, CC, NC) • 2 bins of resolution (“hi” and “low” resolution)• Data corrected for neutral backgrounds (6% in hi-resolution samples)

e quasi-elastic

multiprong


Soudan 2

€

Rν μ ν e= 0.69 ± 0.12

CEV Flavor ratio

note scale

e “NC”

1466 46 76

e 67 1337 72

NC 123 111 77

Flavor tag

Tru

e fl

avor€

R =μ − like /e − like( )DATA

μ − like /e − like( )MC

Corrected for mis-id


Soudan 2

Perform a Feldman-Cousins analysisusing unbinned maximum likelihood assuming .

Flux normalization and background amounts (7 parameters) allowed to floatat each point in (m2, sin2(2)) plane.

Nuisance Parameters:e-energy calibration: 7%-energy calibration: 3% Flux shape (1 + b E): b = 0.005 GeV-1 e/ ratio: 5%Qel/inelastic : 20%log10(m2)

sin2(2)

ln L

M. Sanchez et al, PRD 68, 113004 (2003)


Soudan 2: Results

Best Fit:

m2 = 0.0052 eV2

sin22= 0.97

f(data/mc) = 0.90

MC Bartol '96

Inclusion of systematic errorsand application of Feldman-Cousins technique substantiallyincreases the size of the 90% CL region.


Soudan 2: Upgoing Muons

A sample of 45 events entering orexiting the bottom of the detector have been isolated.

Work is underway to incorporate them into the oscillation fits.

Scan

Category

MC Truth (no osc.) Data

In-Down Up-Stop

In-down 13.3+1.4 0.7+0.2 17

Up-stop 1.9+0.5 58.4+1.9 26

Ambig’s 0.9+0.4 3.6+0.5 2


MACRO

5.3 kton detector located in the Gran Sasso laboratory~40 CR 1989 – 2000

3 atmos samples:1. Up-throughgoing 2. In-up going 3. In-down + Up-stop

Scintillator layers for timing (0.5 ns)Streamer tubes for tracking (1 cm)


MACRO: Up-going

Produced by neutrino interactions in rock below detector.

Shape of distribution known to 5%Normalization uncertain to 25%

2 independent analyses yield consistent results.

MC predictions assume oscillationswith the MACRO parameters:sin2(2) = 1 , m2 = 0.0023 eV2

Estimate E and …


MACRO: Energy CalibrationEnergy estimated from muon multipleCoulomb scattering.

Use drift time in streamers to get x ~ 3 mm.

Calibrated in test beam runs at the CERN PS and SPS.

Muon energy estimated using a neural network with 7 inputs, 1 hiddenlayer and a single output.

Global E resolution is 150%.


MACRO

InUp

Identified by topological criteriaand time-of-flight.

Expect to be fully oscillated.

UpStop + InDown

Identified by topology:UpStop fully oscillatedInDown unoscillated

FLUKA MCPrediction

(no oscillation)

Oscillations withMACRO parameters

2 low energy samples

Ratio InUp/(UpStop+InDown)

Known to 6%


MACRO

Category Ndetected Rmeas+stat R R0+0

Vertical/

Horizontal

547.3 1.38 + 0.12 1.61 2.11 + 0.13

Nlow/

Nhigh

100.5 0.85 + 0.16 1.00 1.50 + 0.25

InUp/

(InDown+UpStop)

418.4 0.60 + 0.06 0.56 0.745 + 0.06

Monte Carlo studies are carried out to find the flux normalization – independent statisticsmost senstive to oscillations.

• Vertical (cos<-0.7) / Horizontal (cos>-0.4) Upward Throughgoing muons

• Nlow (E<30 GeV) / Nhigh (E>130 GeV)• InUp / (InDown + UpStop)

Ambrosio et al, “Measurements of Atmospheric Muon Neutrino Oscillations”, submitted to EPJ.Ambrosio et al, Phys Lett. B 566, (2003) 35.Ambrosio et al, NIM A 492, (2002) 376.


MACRO

parameters normalize the data to the prediction in each category.

Absolute rate of the UpThrough events is not used because of the uncertaintyin the flux at high energy.

10 bin angular distribution of up-through events

(Nlow, Nhigh) (InDown+UpStop, InUp)

Use Feldman-Cousins procedure to account for physical boundary.

Best fit: sin2(2)=1 -- m2=0.0023 eV2

Vertical / horizontal rate sensitive to matter effects: s excluded at 99.8% CL

Suggest increase in flux normalization of:

25% at high energy12% at low energy


MINOS: Far Detector5.4 kton long baseline detector2 2.7 kton “supermodules”Fermilab beam on schedule for late 2004.

Alternating 8m octagonal planes:• 1 inch thick steel• 192 4.1 cm x 1cm plastic scintillator strips with embedded WLS fiber

Average 1.5 T magnetic field8-fold optical multiplexing atface of 16 channel Hammamatsu PMTs. Scintillator layers rotated by + 45o for 3d tracking.

…

2-ended readout

Scintillator panel veto shield


MINOS: Cosmic Ray Data

Time vs Y

Time vs Z

Y vs X

Y vs Z

y

x

z

Strip vs Plane

First detector capable of separating from interactions:

Contained events, up-going stopping muons, and neutrino-induced throughgoing muons. Muon energy determined by range or curvature, track direction from timing or curvature.


MINOS: Atmospheric Neutrinos Thursday’s MINOS talk will include results from 2 preliminary analyses ondata taken September 2002 – April 2004. • throughgoing muons • contained events (1.85 fiducial-kiloton years)

Neutrino Sky Map:

Muon direction for neutrino-induced throughgoing muons.


Sudbury Neutrino Observatory SNO: Not just a solar neutrino detector…

CR , atmospheric neutrinos, spallation products

Large overburden means thatone can look for throughgoing muonsfrom neutrino interactions from above the horizon.


SNOAnalysis of 730+ live-days data is proceeding.

Data above the horizon is unoscillated,Determines the flux normalization Powerful lever arm for an oscillation fit.

Normalization region


Experimental Goals - Future

m223 ~ 10-3 eV2 e

m212 ~ 10-5 eV2

Experimental Questions include:• Better precision on masses and mixing angles• Is sin2(223) different from unity? • Determination of sin(23 )• Measurement of non-zero 13 • Measurement of CP • “Normal” or “Inverted” mass hierarchy• Neutrino mass scales – Dirac or Majorana particles

The Future: Precision Measurements of the PMNS Matrix!


Atmospheric Neutrinos -- Future

Ue1 Ue2 Ue3

U1 U2 U3

U1 U2 U

Atmospheric neutrino experiments have sensitivity to all of the above experimental questions except those related directly to the neutrino mass.

Measurements will be of subtle effects, particularly those brought about by matter effects.

Future experiments will require reduction of experimental uncertainties through improved models of atmospheric neutrino fluxes and neutrino interaction cross sections on nuclear targets.

Future detectors will be large (100kton – Mton) andexplore multiple physics topics:• Proton decay • Long-baseline detectors • Atmospheric neutrinos…


INO: India-based Neutrino Observatory

1965 – first detection of atmospheric neutrinos in the Kolar Gold Fields

Phase I: Atmospheric neutrinosPhase II: Very long baseline detector

• 30-50 kton magnetized steel• 140 layers of 6 cm thick Fe plates• 2.5 cm air gap containing RPCs• ns timing for direction resolution• 1-1.3 T magnetic field for good momentum

resolution and charge determination• 2 sites under consideration

Explore mass hierarchy through

A possible design


UNO: Undergound Nucleon Decay and Neutrino Observatory

Proton decay at 1035 yr sensitivity Atmospheric neutrinosAstrophysical neutrino observatorySupernova relic neutrino detection Long baseline neutrino detector

Possible centerpiece for a US National Underground Lab

Scales up a proven technology:650 kton (440 fid) water Cerenkov detector.3 60 x 60 x 60 m3 optically isolated cubes.10%-40%-10% PMT coverage. Considering various underground sitesHenderson mine is leading candidate.


Future: Icarus

Muon spectrometer

T600 T1200T1200

≈3 kton of liquid Argon

An observation of atmospheric neutrino events with very high qualityAn unbiased, mostly systematic free, observation of atmospheric neutrino events

CC/NC separation, clean e/µ discrimination, all final states accessible, excellent e/π0 separation, particle identification (p/K/π) for slow particles

An excellent reconstruction of incoming neutrino properties (energy and direction)


Future: Icarus

Down-going ’s

Up-going ’s

1535 events in 5 kt y

(2 years of T3000)

1535 events in 5 kt y

(2 years of T3000)E = 370 MeV

P = 250 MeV Tp = 90 MeV

quasi-elastic interaction

90 cm

90 c

m

p e

(simulated event)


Frejus Laboratory

0 1000 2000 3000

04 0002000 6 000 8 000

102

103

104

105

106

IMB

SOUDAN

CANFRANC

KAMIOKA

BOULBY MINE

GRAN SASSO

HOMESTAKE LSM

BAKSAN MONT BLANC

SUDBURY

Depth (meters)

Depth (meters of water equivalent)

(FINLANDE)

ST GOTHARD

(WIPP)

muon

flux

per

m2

and

per

year

( FRÉJUS )

4800

Considering options including:1 Mton water Cerenkov100 kt liquid Ar

Site considerations:

• good depth (at least 4800 mwe)• good rock quality• horizontal access• good baseline for superbeam, beam• centrally located


Hyper-Kamiokande1 Mton water Cerenkov detector: follow-up to JHF SuperK with 4 MW superbeam


Conclusions

Thanks toFrancesco Ronga, Tony Mann, Mayly Sanchez,

Tom Kafka, Mark Thomson, Brian Rebel, Joe Formaggio, Flavio Cavanna, Luigi Mosca, Ed

Kearns, Josh Klein, Chang-Kee Jung,M.V.N Murthy, Luciano Moscoso, Francis Halzen

and Jerome Damet.

Soudan 2

90% CL intervals

MACRO

SuperK

Good consistency between results from SuperK, Soudan 2, and MACRO.

“Non-SuperK” atmospheric neutrinos nowin the hands of MINOS and SNO.

Future experiments will have sensitivity to more of the PMNS matrix – an independentcheck of results from future long baselinebeams with completely different systematics.

Documents

Hugh Gallagher Tufts University June 15, 2004 Neutrino 2004 College de France