pre- n factory possibilities
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Pre- n Factory Possibilities. Leslie Camilleri CERN, PH Scoping Study Meeting Imperial College May 6, 2005. Plan of talk. - PowerPoint PPT PresentationTRANSCRIPT
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.