Pre- Factory Possibilities

Leslie Camilleri CERN, PH

Scoping Study Meeting Imperial College May 6, 2005

Plan of talk• The Past: excellent results from Solar, atmospheric, K2K and KAMLAND.• The Future: A Neutrino Factory some time in the future.

I will talk about the “bridge” between the past and the Factory. The interest: , the mass hierarchy, the CP phase

• Near Future: T2K NOvA C2GT Reactors• Intermediate Future: SPL Beta beams

But remember two persisting anomalies in physics:LSND(High mass to e oscillations) and NuTeV(3 sin2 W)

Near Future (Accelerators)T2K (Japan) 295km

C2GT (CNGS beam) ~1200km

NOA(NUMI beam) 810km

All three projects are Long Baseline Off-axis projects:Can dial energy of beamTo maximum of oscillation

They look for

~ e oscillations

by searching for

e appearance in a

beam.

Correlations: 8-fold degeneracyFrom M. Lindner:

ambiguityMass hierarchy two-fold degeneracydegeneracy: sin223 is what enters in the oscillation formula. For sin2 223, say = 0.92, 223 is 67o or 113 o and 23 is 33.5o or 56.5 (x1.5)If we just have a lower limit on sin2 223: all values in between are possible

Matter effects In vacuum and without CP violation:

P(e)vac = sin2 23 sin2 2sin2 atm

with atm= 1.27 m232 (L/E)

For m232 = 2.5 x 10-3 eV2 and for maximum oscillation:

Must have: atm = /2 L(km)/E(GeV) = 495 For L = 800km E = 1.64 GeV, For L = 295km E = 0.6 GeV

Introducing matter effects, at the first oscillation maximum:

P(e)mat = [1 +- (2E/ER)] P(e)vac

with ER = [12 GeV][m232/(2.5x10-3)][2.8 gm.cm-3/] ~ 12 GeV

+- depends on the mass hierarchy.

Matter effects grow with energy and therefore with distance.3 times larger (30%) at NOA (1.64 GeV) than at T2K (0.6 GeV)

T2K Detector

50 ktons (22.5 kton fiducial)

Reconstructed Super- K

T2K K2K

Machine

Energy

40 GeV 12 GeV

Power(MW) 0.75 0.0052

Events(5yr) 11000 ~150

Near detector at 280m to measure flux before oscillation

0.4 % intrinsic e

background at peakMust know it wellData taking

13Sensitivity, correlations

But, the limit on sin2 2 is much worse if we take into account correlations and degeneracies

Sin2 213 ~ 0.04

CP 150

T2K II: Hyper-KamiokandeOne megaton Water Cerenkov and 4MW accelerator.

0.01

0.001

+150o-150o

sin2213

Improvement by more than an order of magnitude on 13 sensitivity

All degeneracies included

T2K II: Sensitivity to CP

Definition: For each value of sin2 213:The minimum for which there is a difference Of 3 between CP and NO CP violation

Limited bystatistics

Limited because:CP violation asymmetry () decreases with increasing sin2 213

Sin2 213

0.010.0001

20o

50o

NOA DetectorGiven relatively high energy of NUMI beam, decided to optimize NOAfor resolution of the mass hierarchyDetector: 14mrad (12 km) Off-axis of the Fermilab NUMI beam (MINOS).At Ash River near Canadian border (L = 810km) : New site. Above ground.Fully active detector consisting of 15.7m long plastic cells filled with liquid scintillator: Total mass 30 ktons.Each cell is viewed by a looped WLS fibre read by an APD

760 000 cells

MINOS Near detector events, and Beam

The NUMI beam is already functional !MINOS NEAR detector has observed and reconstructed neutrino events.

E

• Expected proton intensity on target 6.5 x 1020 per year greatly helped by•cancellation of BTeV and foreseen end of collider programme in 2009.•Longer term: 8 GeV proton driver: 25 x 1020 protons per year: Phase II.

If approved in 2006, First kiloton: 2009. Full completion: 2011.

3 measurement limits for sin2 213

5 years Phase I

(NO proton driver)

m2 > 0m2

mm

T2K

NOA always MORE sensitive than T2K (about a factor of 1.4)

Mix Neutrinos and Anti neutrinosComparison with Reactor

Neutrinos and anti neutrinos mix to have a more uniform dependence of the sensitivity

on . Proton driver brings a factor of

2 more sensitivity

Comparison with reactors, shows NOA always MORE sensitive.

Resolution of mass hierarchy Fraction of over which the

mass hierarchy can be resolved at

qual amounts of neutrino and antineutrino running: 3 years each assuming Phase I.

Near the CHOOZ limit the mass hierarchy can be resolved over 50% of the range of .

T2K can only resolve the hierarchy in a region already excluded by CHOOZ.

(Because of its lower energy).

Some small improvement if we combine T2K and NOA results

CHOOZ limit

T2K

Looking further ahead With a proton driver, Phase II, the

mass hierarchy can be resolved over 75% of near the CHOOZ limit.

In addition to more protons in Phase II, to resolve hierarchy a second detector at the second oscillation maximum can be considered:

atm= 1.27 m232 (L/E) =

L/E = 1485, a factor of 3 larger than at 1st max.

For ~ the same distance, E is 3 times smaller:

matter effects are smaller by a factor of 3

50 kton detector at 710 km. 30km off axis (second max.) 6 years (3+ 3 )

Determines mass hierarchy for all values of down to sin2 213 = 0.02

CERN to Gulf of TARANTO

The CNGS beam continues SOUTH: beyond the Gran SassoGoes over the Gulf of Taranto.A detector in the Gulf would be 40km OFF-AXIS.And at a distance of ~1200km would be appropriate for the SECOND oscillation maximum.Immersed in the sea at a depth of 1000m

Required energy:0.8 GeV

Implies a modified lower energy CNGS beam Incompatible with OPERA running

CERN to Gulf of TARANTO: C2GT• Basic Unit: 380mm diameter HPD with a cube of 5 Si sensors:

• One on each of 5 faces of cube :Uniform 110o angular acceptance.

Cube 5 Sisensors

High pressure glass container

Viewing distance of ~ 20m.Fiducial mass: 1.5 Mton

Radius 150m10m x 10m

Proton intensity(rep. rate of accel.) and Flux (Proportionalto make C2GT less competitive Waiting for OPERA completion also a problem

13 with Reactors The best limit comes from a reactor experiment: CHOOZ. Energetically impossible to produce a from’s, in an appearance

experiment. Technique: anti-e disappearance experiment

Pee = 1 – sin2 213 sin2 [(m232L)/(4E)] near oscillation maximum

Advantage: NO dependence on CP or on mass hierarchy: No ambiguities.

Disadvantage: Cannot determine them!

Measured through inverse decay: e + p = e+ + nMeasure e+ and n (capture in gadolinium or scintillator): Reconstruct energy

Look for Distortion of the e energy spectrumEffects are SMALL :Must know e energy spectrum well to control systematics.

Solution: Use a FAR detector to search for oscillations (1700m) and a NEAR detector to measure spectrum BEFORE oscillations(170m).

Example: Double Chooz detector

Muons VETO(shield)Thickness = 150mm

Acrylic Gamma catcher vesselLiquid scint.(R = 1,8m,H = 4 m,t = 8mm)

LS

+ 0

,1%

Gd

LS

Acrylic Target vesselLiquid scint+Gd(R=1,2m,h=2,8m,t = 12mm)

Non-scintillatingBuffer: Water

Systematics Improvements over CHOOZ

Two detectors: Reactor power and cross sections, Energy per fission : Negligible.

Thicker non-scintillating buffer: Smaller singles rate allows e+ threshold of 0.5 MeV well below the lowest possible 1.02 MeV. No Uncertainty due to Threshold.

Target mass: Only Relative mass needed. Will be measured by weighing filling vessel Before and After fill.

Chooz DoubleChooz

Power 0.7% --------

Reactor

’ s1.9% --------

E/fission 0.6% --------

Det. eff 1.5% 0.5%

#protons 0.8% 0.2%

Total 2.7% 0.6%

Schedule and Sensitivity

Near det. ready

2003 2004 2005 2006 2007 2008 2009Site Data takingProposal Construction ?& design

Far detector starts Near detector starts

Near det. readyFar det. ready

0.02

Importance of Systematics

1%

0.4%

10 x run time only gains x 2 in sensitivity

Superconducting Proton Linac Power : 4 MW Kinetic Energy : 2.2 GeV (3.5 GeV) Repetition Rate: 50 Hz Spill Length: 11 msec. Accumulator needed to shorten

pulse length. Target: Liquid Mercury Jet to cope

with stress due to high flux. Focusing: Horn and Reflector

optimized for 600 MeV/c particles Decay Tunnel: 20m long 1m radius Neutrino energy to be at oscillation

maximum for m232 = 2.5 x 10-3 eV2

260 MeV Distance: 130km Location: New lab in Frejus tunnel Detector mass: 440 kton fiducial. Type: Water Cerenkov (Super-K)

Optimization of Proton beam energy Angle of emission ofPions (0.5 < p < 0.7 GeV/c)/s

Horn acceptance < 25o

More at 3.5.4.5 GeV. Higher flux.20% Increase in significance

Better sensitivity at 3.5, 4.5 GeV

3.5, 4.5 GeV

2.2 GeV

2.2 GeV

J.E. Campagne, A. Cazes hep-ex/0411062

Optimization of the neutrino energy

• Modify horn

• Profitable to go to

350 MeV

Instead of 260 MeV

350 MeV

Advantage of mixing neutrino and antineutrino running

• 3.5 and 4.5 GeV proton beam

• 260 and 350 MeV options

• 5 years of running.

• 2 years of running and

8 years of running

The limit IMPROVES near = 90o

Beta beams

• Idea introduced by Piero Zucchelli.

• Accelerate radioactive ions decaying via + or -.

• Because of Lorentz boost, the decay electron neutrinos or antineutrinos will be focused forward into a beam.

• Look for: Appearance of or

Advantages: “Clean” beams with no intrinsic

component.

Precisely calculable energy spectra. Energy of beam tunable through

acceleration of ions.

Accelerate protons in SPLImpinge on appropriate sourceBunch resulting ions (atmospheric ’s)Accelerate ions in PS and SPS.Store in decay ring. 8 bunches.Favourite scheme: 6He 6Li + e- + e

18Ne 18F + e+ + e

Half lives: 0.8 sec and 0.64 sec.

Stored together if (18Ne) = 1.67

(6He)Detector: Same as for SPL (Frejus)

sensitivity for = 60,100

Statistics limited

Limited becauseCP violation Asymmetry decreases with increasing

2% Syst. Unc.

2.9 x 1018 6He ions and 1.2 x 1018 18Ne ions per year decaying in straight sections

M. Mezzetto SPSC Villars

Down to 30o

Optimization of J. Burguet-Castell, hep/ph/0503021 and M. Mezetto.

Not necessary to store the 2 ion types simultaneously: 4 bunches each.Store 8 bunches of given type at a time and run each type half as long as in joint run.

Frees from (18Ne) = 1.67 (6He) constraint.Assume number of ions stored is INDEPENDENT of energy.Different schemes tried, all leading to higher energies. This is profitable because:Higher event rates because of larger cross sections.Better directionality: lower atmospheric background.Signal events are in a region of lower atmospheric rate.Fermi motion relatively less of a problem: better correlation between reconstructed and actual neutrino energy.Can analyze energy dependence of appearanceEvents instead of just counting them.

Fix baseline at Frejus• 99% CL on improves from

> 30o to > 15o for a

symmetric scheme.

• The 13 sensitivity improves

a little.

60,100 scheme

6He 18NeCC events 101263 14478413=1o, =0o 7 118

13=1o, =90o 45 64

Beam back. 0 0

Det. backs. 262 206

30o

150

= 100

13 = 8o

= 90o

Fix at maximum SPS value: 150.

• For this the optimum distance is

300 km

• The 99% CL reach can be improved

from 15o to 10o.

• and the 13 sensitivity can also be improved substantially

But no existing laboratory at this distance!

300 km

60,100 130km

150,150 300km

sin2213

L(

L(km)

Combining SPL and Beta beams

• The beam is more sensitive than an SPL beam.• The beam only requires the SPL for 10% of its up time.• Can therefore run of an SPL beam at the SAME TIME as the beams.• The combination improves over the beam alone.

SPL + km

BothSPL

Systematic uncertainties

Must be kept at the

2% level

Most important ones: Target mass difference between near and far detectors.

Uncertainty on and cross sections (will be measured by near detector)

T2K II vs Beta

T2K Phase II and beam= 150) have very similar CP reach and sin2 213 sensitivity.

sin2213

sin2213

T2K II

150

T2K II

(Personal) ConclusionsAccelerator physicists must be encouraged to produce

detailed studies of SPL and beams scenarios.

Many options are still possible. Some optimizations are only days old.

Work in progress.Double Chooz, could be first to go, but its physics is

limited.T2K, will be next, and will include the physics of the

reactor experiment.NOA, provided it gets an early approval, has the most

extensive physics reach, in particular a first look at the mass hierarchy.