A review on the long baseline A review on the long baseline neutrino experiments neutrino experiments

Pasquale MigliozziPasquale MigliozziINFN, Sezione Napoli, Italy

The PMNS matrixThe PMNS matrix

3

2

1

321

321

321

UUU

UUU

UUU eeeeanalysesreactor Solar,

100

0cossin

0sincossexperimentnew by probed Terms

cos0sin

010

sin0cosanalyses K2K c,Atmospheri

cossin0

sincos0

001

1212

1212

1313

1313

2323

2323

CPCP ii ee

• e is suppressed due to small m122

• m232 and 23 dominate

• CP is the CP violation phase

23

223

213

4

232

132

232

232

132

232

sinsincos

sinsincos

sinsinsin

P

P

P

e

e

E

kmLm

)(27.1 2

2323

Leading oscillations in vacuum

Neutrino Oscillation MassesNeutrino Oscillation Masses

Three different types of experiments three different mass ranges!

Mass range accessible tolong baseline experiments

Super-Kamiokande Super-Kamiokande atmospheric atmospheric results results

1289 days

The atmospheric neutrino The atmospheric neutrino deficitdeficit

There is an apparent deficit of atmospheric 's seen in both Cerenkov detectors and calorimeters

While the atmospheric flux has large uncertainties, the L/E dependence implies oscillations

If it is oscillations, m2~3x10-3 eV2 @sin22=1 It is likely to be - (-s oscillations are

excluded at 99% CL)

Why long baseline Why long baseline experiments?experiments?

Check atmospheric neutrino results with a controllable beam

See appearance

Measure the product |m223|x23 with ~10%

precisionMeasure e and 13

Constrain or measure s

K2K

250 km

Close Detectors (CD)Far Detector

Sensitivity of the experimentSensitivity of the experiment

Sensitive to m2 above 2x10-3 eV2!

The neutrino beamThe neutrino beam

Pion monitor

Target/Horn systemAl alloy250 kA current

Proton intensity~5.5x1012/spill

Decay pipe200 m long and filledwith Helium @1atm

Average energy<E> ~ 1.3 GeV

K2K close detectorK2K close detector

Features Good vertex resolution Good angular resolution Good momentum resolutionfor high energy muons

Aim Measure energy Measure profile

Features Similar systematics as Super-Kamiokande

Aim Measure rate Measure 0 production

Fine grained calorimeter 1kton detector

(MRD)

to SK

MRD consists Drift tubes +12 layers of Fe(10cm x4 + 20cm x8) Fiducial mass 312 ton 200k evts/2.1x1019pot

Profile and spectrum stabilityProfile and spectrum stabilitymonitored with the MRDmonitored with the MRD

Stability of the profile Stability of the spectrum

To SK

1mrad

1mrad

beam direction is stable within 1 mrad

interaction @ different interaction @ different locationslocations

Event selection at SKEvent selection at SK

Using GPS timing

TOFTTT KEKSK

require

s1.3T2.0

28 evts fully contained in the fiducial volumehave been observed

10-3 background events up to nowmainly from atmospheric events

Trigger similar to the one used for atmospheric neutrino induced events

Expected #Expected # evts at SK (1) evts at SK (1)

CD

SKSK

CDFD

CD TL

TLRNN

..

..1observedexpected

#evts expected at SK assuming null oscillations

#evts observed in the near detector

Live time correctionusing proton on target

target

target

d

d

CD

SK

CDCD

SKSK

CDFD

N

N

E

ER

Event ratio R from MC calculation but

SK and CD confirmed bypion monitor (E > 1 GeV)

Expected #Expected # evts at SK (2) evts at SK (2)

The 1kton water Cerenkov detector is used as reference CD detector same neutrino interaction target

(cross section uncertainty cancels out) same detection energy threshold same event reconstruction scheme

small systematic error

The MRD and Scifi/Water detectors are used to check the consistency of the 1kton detector results

Expected #Expected # evts at SK (3) evts at SK (3)

Main source of sys. Error Sys. error from 1kton meas. (mainly due to fid. vol.) 5% Sys. error from SK meas. 3% Sys. Error from extrapolationFar/Close 7% Statistical error 1%

From June 1999 to June 2000 (2.3x1019 pot)

Results consistent with a deficit @90% C.L.K2K is running now, energy spectrum distortion is under study

The CNGS neutrino beamThe CNGS neutrino beam

ICARUS

The beam will

start

in may 2005

The CNGS beamThe CNGS beam

Shared SPS operation

200 days/year 4.5x1019 pot / year

Nominal beam

( m-2 / pot) 7.78x10-9

CC / pot / kton 5.85x10-17

< E > ( GeV ) 17

(e + e) / 0.87 %

/ 2.1 %

prompt negligible

ICARUS liquid argon imagingICARUS liquid argon imaging

The ICARUS technique is based on the fact that ionization electrons can driftover large distances (meters) in a volume of purified liquid Argon under a strongelectric field. If a proper readout system is realized (i.e. a set of fine pitch wiregrids) it is possible to realize a massive "electronic bubble chamber", withsuperb 3-D imaging.

C.R. shower from3 ton prototype

The ICARUS T600 moduleThe ICARUS T600 module

3

Atmospheric neutrinos Large event statistics with

Detection down to production thresholdsComplete event final state reconstructionIdentification all neutrino flavors Identification of neutral currents

Excellent resolution on L/E reconstructionDirect appearance search

Neutrinos from CERNSearch for µ Search for µ e

Solar neutrinosEnergy threshold: 5 MeV Large statistics, precision measurements“Smoking gun”: CC & NC

ICARUS 5kton physics reach (I)ICARUS 5kton physics reach (I)

m232, 23

m212

m232 23 13

m212, 12

extract

extract

extract

Proton decay

Large variety of decay modes accessible

study branching ratios free of systematics

Background free searches linear gain in sensitivity with

exposure

Neutrino “factory”

Precise measurement oscillation

Matter effects, sign of m223

First observation of e

CP violation

ICARUS 5kton physics reach ICARUS 5kton physics reach (II)(II)

m232 23 13

m232>0 or m2

32<0 ?

Unitarity of mixing matrix

0?

extract

oscillations (I)oscillations (I)

Analysis of the electron sampleExploit the small intrinsic e contamination of the beam (0.8% of CC)Exploit the unique e/π0 separation

Statistical excess visible before cuts this is the main reason for performing this experiment at long baseline !

At m2=3.5x10-3 eV2 110 e events are expected

Main background from charged current interactions of e in the beam 470 events are expected

oscillations (II)oscillations (II)

Reconstructed energy

e CC

signal

Reconstructed visible energy spectrum of electron events clearly evidences excess from oscillations into tau neutrino

oscillations (III)oscillations (III)

e CC

Transverse missing PT

Kinematical selection in order to enhance S/B ratio

Can be tuned “a posteriori” depending on the actual m2

For example, with cuts listed below, reduction of background by factor 100 for a signal efficiency 33%

m232=3.5x10–3 eV2; sin2223 = 1

Search for Search for 1313≠0 (I)≠0 (I)

P( e) sin2 213sin2232

32P( )cos4 13 sin2 223

232

4 years @ CNGS

P( e) sin2 213sin2232

32P( )cos4 13 sin2 2232

32

m232=3.5x10–3 eV2; sin2223 = 1 ; sin2213 = 0.05

Transverse missing PTTotal visible energy

Search for Search for 1313≠0 (II)≠0 (II)

Sensitivity to Sensitivity to 1313 in three family- in three family-mixingmixing

Estimated sensitivity to e oscillations in presence of (three family mixing)

Factor 5 improvement on sin2213 at m2 = 3x10–3 eV2

Almost two-orders of magnitude improvement over existing limit at high m2

4 years @ CNGS

The OPERA experimental The OPERA experimental technique technique

Emulsion Cloud Chamber (ECC) Emulsions for tracking, passive material as target Basic technique works

charmed “X-particle” first observed in cosmic rays (1971) DONUT/FNAL beam-dump experiment: events observed

m2 = (1.6 - 4) x10-3 eV2 ( SuperK) Mtarget~2 kton of ECC

large detector sensitivity, complexity modular structure (“bricks”): basic performance is preserved

Ongoing developments in the emulsion technique, required by the large vertex detector mass:

industrially produced emulsion films automatic scanning microscopes with ultra high-speed

Pb

Emulsion layers

1 mm

Experience with emulsions and/or searches : E531, CHORUS, NOMAD and DONUT

~ 10

m

The detector at The detector at Gran SassoGran Sasso(modular structure, configuration with three “supermodules”(modular structure, configuration with three “supermodules”))

spectrometerMagnetised Iron Dipoles

Drift tubes and RPCs

target and decay detector

Each “supermodule” is a sequence of 24 “modules”

consisting of - a “wall” of Pb/emulsion “bricks”- planes of orthogonal scintillator

strips

scintillator strips

brick wall

module

brick(56 Pb/Em. “cells”)

8 cm (10X0)

supermodule

Detector ready by may 2005

Sensitivity to Sensitivity to oscillations oscillations

Decay mode DIS long QE long DIS short Overall

e 3.0 2.6 1.3 3.7 2.7 2.8 - 2.7 h 2.2 2.8 - 2.3Total 8.0 8.3 1.3 8.7

5 years

3 years

e h Total

Charm production 0.15 0.03 0.15 0.33

e CC and 0 0.01 - - 0.01Large scattering - 0.10 - 0.10Hadronreinteractions

- - 0.10 0.10

Total 0.16 0.13 0.25 0.54

Total 0.19 0.13 0.25 0.57

Summary of Summary of detection efficiencies detection efficiencies(in % and including BR)(in % and including BR)

Expected background(5 years data taking)

m2 = 1.2x10-3 eV2 at full mixing

sin2 (2) = 6.0x10-3 at large m2

After 5 years data taking

Full mixing

5 years with shared SPS operation (2.25x1020 pot)

Average target mass = 1.8 kton (accounting for mass reduction with time, due to brick removal for analysis)

Uncertainties on background and efficiencies accounted for in the following

Expected Expected events events

decay 1.6 2.5 4.0 b.g.e 1.9 4.7 11.8 0.19 1.5 3.5 8.8 0.13h 1.3 3.0 7.6 0.25

Total 4.7 11.2 28.2 0.57

)eV 10(m 232

Statistical significanceStatistical significance

6 events

4 discoveryEvents observed

Sig

nif

ican

ce(e

qui

vale

nt )

NN44

Poisson distribution of the expected background

#evts observedNn

Probability that the b.g. fakes the

signal: < Pn if #observed evts

Nn

P4 = 6.3x10-5

P3 = 2.7x10-3

Probability of 4Probability of 4 significance significance

Schematic view of theSK allowed region

sin22

m2 (

eV2 )

68%

22%

9%

• Simulate a large number of experiments with oscillation parameters generated according to the SuperK probability distribution

• N4 events required for a discovery at

4

• Evaluate fraction P4 of experiments observing N4 events

years P3 P4

3 94% 80%

5 97% 92%

90 % CL limits * m2 ( 10-3 eV2 )

1.6 2.5 4.0

Upper limit 2.2 3.1 4.6

Lower limit 0.9 1.8 3.4

(U - L) / (2xTrue) 41 % 26 % 15 %

OPERA90 % CL in 5 years

* assuming the observation of a number of events corresponding to those expected for the given m2

Determination of Determination of mm22

(mixing constrained by SuperK)(mixing constrained by SuperK)

The MINOS ExperimentThe MINOS Experiment

Two Detector NeutrinoOscillation Experiment

(Start 2004)

Near detector: 980 tons

Far detector: 5400 tons

Iron/ScintillatorSampling calorimeter

1 cm x 4 cm plastic scintillator+

2.5 cm iron plates

The neutrino beam The neutrino beam

Target and horn 2 are moveable the beam energy can be changed

1st oscillation maximum

Need the low energy beamwith <E> = 7.6 GeV to see1st oscillation maximum which occurs at 2 GeV

SK best fit

Osc

illat

i on

Pro

babi

lity

Physics MeasurementsPhysics Measurements

Obtain firm evidence for oscillationsCharge current (CC) interaction rate and energy

distributionNC/(CC+NC) ratio (T-test)

Measurement of oscillation parameters, m2, sin22CC energy distribution

Determination of the oscillation mode(s) or s from NC and CC energy distributions

e limits or observation by identification of electrons

Limit from the T-testLimit from the T-test

likeNClikeCC

likeCC

NN

NT

NCC-like events with identified muonNNC-like events with no muon

10 kton-yr exposure2% overall flux uncertainty2% CC effciency uncertainty2% NC trigger efficiency uncertainty

Limit from the CC Energy Limit from the CC Energy SpectrumSpectrum

10 kton-yr exposure

2% overall flux uncertainty

2% bin-to-bin flux uncertainty

2% CC efficiency uncertainty

CC Energy Spectrum for various CC Energy Spectrum for various mm22

mm22, sin, sin2222 sensitivity sensitivity

10 kton-yr exposure

2% overall flux uncertainty

2% bin-to-bin flux uncertainty

2% CC efficiency uncertainty

For m2 = 0.0035 eV2 should be able to achieve better than 10% error at 68% C.L on both m2 and sin22

Limit on Limit on ee

MINOS 10 kt-yr 90% C.L. limit

Chooz 1999

m3 > m2

Matter effects includedm2

solar = 3 10-5 eV2

12 = 23 = 45 degrees = 010% systematic error on background

Ue32 < 0.013 @ m2>3 10-3 eV2

sin2213 < 0.05 @ m2>3 10-3 eV2

Already close to systematics limited with 10% error on background

JHF-Kamioka neutrino JHF-Kamioka neutrino experimentexperiment

Approved in December 2000Construction 2001-2006

50 GeV PS machineSuper-Kamiokande as a far detectorBaseline 295 kmLow energy neutrino beam tuned at the oscillation maximum

Physics measurementsPhysics measurements

Factor 10 improvement in disappearance

(sin2223)~0.01 (m223)~2x10-4 eV2

Search for e appearance with a sensitivity 20 times better than CHOOZ limit

sin22e 0.5 x sin2213 > 0.003

Search for a small admixture of sterile neutrinos

Layout of JHF and the Layout of JHF and the beam beam

Narrow Band Beam Off Axis beams

Thin solid line shows the WBB

• A large variety of beams is available to tune the energy at the oscillation maximum• Neutrino beam energy scan possible• Energy peak around 1 GeV• Electron neutrino contamination well below 1%

disappearance disappearance

energy reconstruction for QE (red)and non-QE interactions

m2 = 0.003 eV2

sin2223 = 1

non-QE events

All events

w/o oscillations

with oscillations

The error bar is from the statistics of 5 years

disappearance sensitivitydisappearance sensitivity

Ratio of measured spectrum with oscillations to the expectedone after subtraction of non-QEevents

Final sensitivity to oscillation parameters:•Off Axis 2 beam•NBB 1.5 GeV •NBB 3 GeV

ee appearance search appearance search

• Signal: e(Far)/(Near) expected to appear at the disappearance dip• Backgrounds

• misidentification: negligible• e contamination ~0.2-03%• 0 (neutral current) background ~0.3%

Sensitivity to sin22e > 0.003 A factor 20 better than the CHOOZ limit

~ 3x1020 e yr~ 3x1020 yr

The CERN present scenario

Neutrinos from a muon Neutrinos from a muon storage ringstorage ring

A very complex acceleration and storage A very complex acceleration and storage systemsystem

Optimal baseline is around 3000 kmfor CP violation + matter effects.

Search for long-baseline detector Search for long-baseline detector laboratorieslaboratories

Physics from Physics from e e ee with a long baseline program at a Neutrino with a long baseline program at a Neutrino

FactoryFactory

disappearance

(m2) ~ 5 x 10-5 (sin2223) ~ 5 x 10-3

– e appearance sensitivity down to sin22e ~ 10-3 - 10-4

Matter effects sign of m13

CP violationHigh energy e essential and unique

Neutrino interaction rates x 10 or more w/r to present beamsVery large detectors needed

ConclusionConclusion

The existing experiment is running smootly and could give soon conclusive results

(yes or no to oscillations) Experiments foreseen in the next years will probe mixing

angles deeply(23 and 13)

Future accelerators will be able to pin down with high precision the oscillation parameters and study CP violation

( in the PMNS matrix)

There is a lot of work to do!