K. Long, 2 December 2014 MICE as a step towards the Neutrino Factory 1

Contents Motivation The Neutrino Factory Muon Ionization Cooling Experiment Conclusions 2

MOTIVATION MICE as a step towards the Neutrino Factory 3

The neutrino is special Most abundant matter particle … – … and all of its properties are not yet measured The neutrino mass is much smaller than all other matter particles … – … hints at a unique and different mechanism 4

Beyond the Standard Model Neutrino oscillations imply: – Neutrino mass and that the neutrino-flavours mix – Readily described by the Standard Neutrino Model Theoretical interpretation of oscillations requires that either: – The neutrino is its own antiparticle; A new state of mater; or – Neutrinos and antineutrinos are different lepton number must be conserved; A new physical principal Tiny mass may be linked to physics at very high energy – E.g. Weinberg: Majorana-mass term first term beyond those that make up the 5

A window on the unknown Fundamental questions: – Is CP-invariance violated in neutrino oscillations? – Is the neutrino-mass spectrum normal or inverted? – Is the neutrino-mixing matrix unitary? – Are there sterile neutrinos? – Are quark and lepton flavour connected? – Is the nature of the neutrino Majorana or Dirac? – What is the absolute neutrino-mass scale? 6

The case for precision Some guidance from theory: – Sum rules in models that relate quarks and leptons Antusch, King 7

The case for precision What determines the goal for sensitivity and precision? – Sensitivity: Definitive discovery! – Must have sensitivity of “~5σ” – To resolve the LSND/miniBooNE “suite of anomalies” may set the bar higher! – Precision: Field presently led by experiment; – Too many, or too few, theories; Goal to determine parameters with a precision comparable to that with which the quark-mixing parameters are known PDG 8

THE NEUTRINO FACTORY MICE as a step towards the Neutrino Factory 9

The SνM measurement programme: Looking beyond MINOS(+), T2K, NOνA, DChooz, Daya Bay, Reno, … – θ 13 will be very well known Therefore future programme must: – Complete the “Standard Neutrino Model” (SνM): Determine the mass hierarchy Search for (and discover?) leptonic CP-invariance violation – Establish the SνM as the correct description of nature: Determine precisely the degree to which θ 23 differs from π/4 Determine θ 13 precisely Determine θ 12 precisely – Search for deviations from the SνM: Test the unitarity of the neutrino mixing matrix Search for sterile neutrinos, non-standard interactions, … 10 arXiv:

The SνM measurement programme: Looking beyond MINOS(+), T2K, NOνA, DChooz, Daya Bay, Reno, … – θ 13 will be very well known Therefore future programme must: – Complete the “Standard Neutrino Model” (SνM): Determine the mass hierarchy Search for (and discover?) leptonic CP-invariance violation – Establish the SνM as the correct description of nature: Determine precisely the degree to which θ 23 differs from π/4 Determine θ 13 precisely Determine θ 12 precisely – Search for deviations from the SνM: Test the unitarity of the neutrino mixing matrix Search for sterile neutrinos, non-standard interactions, … 11 arXiv:

CPiV: Two options: – Exploit L/E spectrum: DAEδALUS – Measure asymmetry: Large θ 13 makes discovery conceivable, but: – Places premium on the control of systematic uncertainties 12 Phys.Rev.D78:111103,2008 CERN-SPSC ; SPSC-EOI-007 Shaevitz

Neutrino Factory: Two approaches: – Optimise L and E to match detector threshold IDS-NF approach: – 1.4% signal – 20% background 13 arXiv:

Neutrino Factory: Two approaches: – Optimise L and E to match detector threshold IDS-NF approach: – Exploit LAr detector sited 1300 km from FNAL MAP/MASS approach: 14 arXiv: ; v1

Neutrino Factory: 15 IDS-NF NuMAX Bayes, Coloma

Accelerator challenges: Proton driver: – 4 MW; 5 < Ep < 15 GeV; bunch length 1—3 ns – Linac (CERN, FNAL) and ring (RAL, JPARC) options: Progress: costing based on SPL Pion-production target: – Baseline: liquid mercury jet – Options: powder jet or solid – Progress: particle shielding, magnetic lattice Muon front end: – Chicane (new) to remove secondary hadrons: Bent solenoid transport & beryllium absorber – Buncher & rotator: Progress: lattice revision in response to engineering study – Cooling: Baseline: solenoid transport, LiH absorber Options: bucked coils or high-pressure H2 Progress: lattice revision in response to engineering study Rapid acceleration: – Two options considered for acceleration to 10 GeV: Linac, RLA I and RLA II; Linac, RLA I and FFAG – Choice based on cost and performance estimates Proton driver: – Development of high-power, pulsed proton source underway at proton labs Pion-production target: – MERIT experiment at CERN proved principle of mercury jet target – Progress: particle shielding, magnetic lattice Muon front end: – Chicane (new) to remove secondary hadrons: Bent solenoid transport & beryllium absorber – MuCool programme at FNAL: Study of effect of magnetic field on high-gradient, warm, copper cavities; – MICE experiment at RAL: Proof of principle of ionization-cooling technique Progress: lattice revision in response to engineering stud Rapid acceleration: – EMMA experiment at DL: Proof of principal of non-scaling FFAG technique; – Novel technology allows circular acceleration without magnet ramp 16

MUON IONIZATION COOLING EXPERIMENT MICE as a step towards the Neutrino Factory 17

Muon front-end Optimised bunching, phase-rotator, and ionisation-cooling lattice is reduced 18 Neuffer, Rogers

Ionisation cooling Muon beam after phase rotation and bunching: – Wide —  x ~ 10(+) cm – Divergent —   ~ 150(+) mr – i.e. large normalised emittance: Cooling required: – To increase by a factor of 2—10 the number of muons in acceptance of subsequent accelerator Ionisation cooling is the only practical solution: – Muon lifetime is short (2  s at rest)

Ionisation cooling formalism Exponential decrease in normalised emittance: Competition between: – dE/dx [cooling] and MCS [heating] Optimum: – Low Z, large X 0 – Tight focus – H 2 gives best performance

21 Muon Ionization Cooling Experiment ISIS RAL MICE

MICE Muon Beam

Beam-line instrumentation

MICE Muon Beam

Characterisation of the MICE Muon Beam Iterate to determine trace-space parameters: – Initial estimate of p z from TOF – (x 0,y 0 ), (x 1,y 1 ) and M x,y (p z ) used to determine trace- space parameters – Updated estimate of p z from trace space parameters Corrections applied for energy loss in air and material

MICE trackers 350 μm scintillating-fibre tracker: – 10 p.e./mip demonstrated with cosmics – 470 μm intrinsic resolution per plane MC: delivers per-cent level emittance measurement 27

Reminder; the “cooling equation” Paraxial (and other) approximation: Emittance: – MICE Muon Beam optics and diffuser settings Material: – Absorber change (LH2; LiH); p, E and β: – Vary beam momentum, optics 28

MICE Study of material, lattice, momentum and emittance (Step IV) will start Q2 2015; Ionization cooling demonstration: – Revised configuration developed in response to P5 recommendations; – Cooling demonstration configuration complete: summer 2017 All components fabricated Essential technology demonstration imminent 29

“Step IV”; 2015/16 30

Cooling demonstration; 2017/18 31

Cooling demonstration; performance 32 Cooling Transmission

CONCLUSIONS MICE as a step towards the Neutrino Factory 33

Conclusions Muon accelerators have the potential to: – Revolutionise the study of neutrino oscillations; – Provide a route to multi-TeV lepton-antilepton collisions; MICE will provide essential demonstration of ionization cooling: – Starting 2015: Investigation of the effect of material, emittance, momentum on the cooling effect – Starting 2017: Demonstration of ionization cooling; Systematic study of factors that affect cooling perfomance Next generation of LBL experiments will make an initial survey of CPiV: – Capability to deliver the Neutrino Factory required: To study the effect in detail if CPiV is discovered; or To continue the search if it is not The MICE demonstration of ionization cooling will: – Prove the feasibility of muon beams for particle physics – Provide the essential first step in delivering the necessary capability 34