Neutrino studies at an eic proton injector
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Neutrino Studies at an EIC Proton Injector. Jeff Nelson College of William & Mary. Outline. A highly selective neutrino primer Including oscillations (what & why we believe) Neutrino sources (now & future) Beams Example concepts & proposals for next decade and beyond

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Neutrino Studies at an EIC Proton Injector

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Neutrino Studies at an EIC Proton Injector

Jeff Nelson

College of William & Mary


  • A highly selective neutrino primer

    • Including oscillations (what & why we believe)

  • Neutrino sources (now & future)

    • Beams

    • Example concepts & proposals for next decade and beyond

  • What will we be studying in 10+ years?

    • Summary of yesterday’s neutrino session

    • Short baseline

      • Neutrino properties

      • Neutrinos interactions and neutrinos as probes

    • Long baseline – oscillation physics

    • Novel beams

  • Where an EIC proton injector could fit into this future

Cliffs Notes on Neutrinos

  • There are only 3 “light” active neutrino flavors (from Z width)

    • Electron, muon, & tau types

    • Cosmological mass limits imply ∑mν< 0.7 eV (WMAP + Ly-a)

    • Oscillations imply at least one neutrino greater than 0.04 eV (more later)

  • Basic interactions => basic signatures

    • Cross sections crudely linear with energy

    • Charged current (CC)

      • The produced lepton tags the neutrino type

      • Has an energy threshold

      • Neutrino’s energy converted to “visible” energy

    • Neutral current (NC)

      • No information about the neutrino type

      • No energy threshold

      • Some energy carried away by an out-going neutrino

    • Electron scattering (ES)

Oscillation Formalism















E (GeV)

  • With 2 neutrino basis (weak force & mass) there can be flavor oscillations

  • The probability that a neutrino (e.g. nm ) will look like another variety (e.g. nt ) will be

    P(nm nt ; t)= |<nt|nm (t)>|2

  • A 2-component unitary admixture characterized by q results in

    P(nm nt ) =sin22qsin2(1.27Dm2L/E)

  • Experimental parameter

    L (km) /E (GeV)

  • Oscillation (physics) parameters

    sin22q(mixing angle)

    Dm2 = mt2 - mm2 (mass squared difference, eV2)

Dm2 = 0.003 eV2; L = 735 km

3-Flavor Oscillation Formalism

  • In 3 generations, the mixing is given by

    • Where, and

    • There are 3Dm2’s (only 2 are independent)

    • 2 independent signs of the mass differences

    • There are also 3 angles and 1 CP violating phase

  • Predicts: CPV, sub-dominate oscillations (all 3 flavors)

  • Matter effects (MSW)

    • Electron neutrinos see a different potential due to electrons in matter

How do we know what we know?

  • In the past decades there have been many oscillation experiments in many forms

  • Neutrino sources

    • Reactor neutrinos

    • Solar neutrinos

    • Supernovae

    • Atmospheric neutrinos (cosmic rays)

    • Heavy elements concentrated in the Earth’s core

    • Accelerator neutrinos

  • Luckily we are converging to just a few important facts…

Solar Neutrinos: Case Closed

  • Sun emits neutrinos while converting H to He

    • The overall neutrino production rate is well known based on the amount of light emitted by the sun

    • There are too few electron neutrinos; seen by a number of experiments

    • From SNO’s NC sample we know the overall solar flux is bang on

    • Looks like ne => nactive oscillations w/MSW

  • KamLand, a ~100 km baseline reactor experiment, confirms

  • A very consistent picture

Phys. Rev. Lett. 89, 011301 (2002)


Atmospheric Neutrinos


L ~ 20 km






L ~ 104 km


Super K

  • Consistent results

    • Super K results are the standard; other experiments are consistent

    • Electrons show no effect

      • Reactors give the best limits

    • Matter effects tell us it’s a transition to normal neutrinos

M. Ishitsuka NOON04


  • They observe a 4s excess of ne events

  • Spatial distributions as expected

  • Allowed region strongly constrained by other experiments

Phys. Rev. D 64, 112007 (2001).

Parameter Summary

  • The 3 mass signatures are not consistent with 3 neutrinos

  • Either

    • A signature is incorrect

    • Or there is another non-interacting type of neutrino (aka sterile)

    • Or CPT volation

    • Miniboone testing LSND result at Fermilab right now

Adapted from H. Murayama; PDG

Current Summary of Active Neutrino Parameters (ignoring CPT and/or sterile)

  • Mass splittings

  • Angles

K2K ExperimentMan-Made Neutrinos

  • Neutrinos from KEK to SuperK

    • Pp = 12 GeV

    • Goal of 1020 protons on target (POT)

    • 5 kW beam power

    • Baseline of 250 km

    • Running since 1999

    • 50 kT detector

  • They see 44 events

    • Based on near detector extrapolations, they expected 64 ± 6 events without oscillations

  • Results are consistent with atmospheric data but not yet statistically compelling

hep-ex/0212007 (K2K)

The Next 5 Years

  • The current generation of oscillation experiments are designed to

    • Confirm atmospheric results with accelerator n’s (K2K)

    • Resolve sterile neutrino situation (MiniBooNE; more later)

    • Demonstrate oscillatory behavior of nm’s (MINOS)

    • Refine the solar region (KamLAND)

    • Demonstrate explicitly nmnt oscillation mode by detecting nt appearance (OPERA)

    • Precise (~10%) measurement of ATM parameters (MINOS)

    • Improve limits on nmne subdominant oscillation mode, or detect it (MINOS, ICARUS)

    • Test of matter effects (SNO)

Long Baseline Example:MINOS Detectors & NuMI Beam

A 2-detector long-baseline neutrino oscillation experiment in a beam from Fermilab’s Main Injector

Near Detector: 980 tons

Far Detector: 5400 tons

On the Fermilab Site

  • 120 GeV Main Injector’s (MI) main job is stacking antiprotons and as an injector in the Tevatron

  • Most bunches are not used required for p-bar production

  • So…

    • Put them on a target and make neutrinos

  • Same thing is also done with the 8 GeV booster

Making a Neutrino Beam

Wilson Hall for Scale

Muon Monitors

Absorber Hall

Proton carrier

Target Hall

Decay volume

Near Detector Hall

NuMI Beam & Spectra

nm CC Events/kt/year

Low Medium High

470 1270 2740

nm CC Events/MINOS/2 year

Low Medium High

5080 13800 29600

4x1020 protons on target/year

4x1013 protons/2.0 seconds

0.4 MW beam power

(0.25 MW initially)

Target & Horn


  • Graphite target

  • Magnetic horn (focusing element)

    • 250 kA, 5 ms pulses

NuMI Target Hall

MINOS Charged-Current Spectrum Measurement

Status in ~5 Years

  • We will know

    • Both mass differences (Kamland, MINOS)

    • 2 of the 3 angles @ 10% (Kamland+SNO; SK+MINOS)

    • Sign of one of the mass differences (Solar MSW)

    • First tests of CPT in allowed regions (MINOS, MiniBooNE)

  • Probably still missing

    • Last angle? *

    • Confirmation of matter effects *

    • Sign of the other mass difference; mass hierarchy *

    • CP in neutrinos *

    • Absolute mass scale (double beta; cosmology)

    • Majorana or Dirac (double beta)

      * addressable with “super beam” experiments

Super Beam Rules of Thumb

  • It’s the [proton beam power] x [mass] that matters

    • Crudely linear dependence of pion production vs Eproton

    • Generally energy & cycle time are related and hence the power is conserved within a synchrotron

    • Remember that we design an experiment at constant L/E

    • The beam divergence due to the energy of the pions is balanced by the boost of the pions and the v cross section at constant L/E

Long Baseline Goals

  • Find evidence for nmne

    • One small parameter in phenomenology

  • Determine the mass hierarchy

    • Impacts model building

  • Is q23 exactly equal to 1??? – test to 1% level

  • Precision measurement of the CP-violating phase d

    • Cosmological matter imbalance significance

    • Potentially orders of magnitude stronger than in the quark sector

  • Resolve q ambiguities

    • Significant cosmological/particle model building implications

Super Beam PhasingPart of the DoE Roadmap

  • Phase I (~next 5 years)


  • Phase II (5-10 years)

    • 50kt detector & somewhat less than 1 MW

      • J2K, NOnA, super reactor experiment

  • Phase III (10+ years; super beams)

    • Larger detectors and MW+ beams

      • JPARC phase II + Hyper K (Mton ĉ)

      • NuMI + Proton driver + 2nd 100kt detector

      • CERN SPL + Frejus (0.5 Mton ĉ)

      • BNL super beam + UNO (0.5 Mton ĉ) @ NUSL

  • Phase IV (20 years ???)

    • Neutrino factory based on muon storage ring

  • Phase II e.g. Off-Axis Searches for ve Appearance

    • 2 off-axis programs

      • JPARC to Super K (T2K; Funded)

      • NuMI to NOnA (Under Review)

    • Main goal

      • Look for electron appearance <1% (30X current limits)

      • Off-axisdetector site to get a narrow-band beam

      • Fine-grain detectors to reduce NC po background below the intrinsic beam contamination

      • Statistics limited for most any foreseeable exposure


    There are matter effects visible in the 820km range

    Provides handle on CP phase, mass hierarchy but…

    Ambiguities with just a single measurement

    In addition

    If sin2(2q23) = 0.95

    sin2(q23) = 0.39 or 0.61

    Cosmology cares

    Rough equivalence of reactor & antineutrino measurements

    Eventually need 2nd energy (AKA detector position) in same beam to resolve at narrow-band beam

    Interpretation of Results

    NOnA Goal

    Phase IIIe.g. BNL Super Beam + UNO

    • Turn AGS into a MW beam

      • 10X in AGS beam power

      • Not same upgrades as eRHIC

      • Use a very long baseline

      • Wide-band or off-axis beam

      • White paper released

    • Mton-class proton decay detector called UNO envisioned at the National Underground Lab (NUSL)

      • Location not picked but any of the possibilities are compatible with this concept

      • LOI to funding agencies this year



    ~2500 km

    Very Long Baselines Somewhat Improved Reach & …

    Wide-band beam accesses a large range of the spectrum gives access to resolve all ambiguities

    Near future short baseline program

    Recent proposals

    • MINERvA @ main injector

    • FINeSSE @ Fermilab booster

    • Fine grained devices

    • Most topics will still benefit from higher Stats


    Short Baseline Neutrinos

    • Neutrino properties

      • Sterile neutrinos after MiniBooNE (few eV2 range)

        • R-process in supernovae astro-ph/0309519 hep=ph/0205029 suggests searches beyond LSND indicated region

      • Magnetic moment

        • Required if massive Dirac neutrinos

        • Suggested by beyond SM models

        • Models go from minimal BSM model of 3x10-19 µB to current limits of 6.8x10-10µB (in vµ)

    • Neutrinos as a probe of nucleon structure

      • Form factors (low energy)

        • Current generations to probe to Ds ~ ± 0.04

      • Structure Functions (higher-energy)

    Sterile Beyond LSND/MiniBooNE

    • Current proposals a more coverage for sterile neutrinos through controlling systematics with 2-detector measurements

    • An EIC class injector would allow the statistics to fully exploit this approach

      • Needs study to determine the possible reach and systematic limits

    Oscillation experiments run in the sub GeV to few GeV range

    • Extracting neutrino spectra complicated by using an energy range where a lot of things matter

      • Quasi-elastic, resonance production and DIS contribute significantly

      • Coherent mechanisms important

      • The difference between Evis and Ev due to nuclear effects, Fermi motion, rescattering …

      • Also requires a subtraction of NC events that fake low energy CC events

    • Neutrino experiments rely on MC

    • A useful collaboration between neutrino & electron scattering communities promises to be useful for both

      • NuInt conference series

        • 3rd meeting this week at Gran Sasso


    “Medium Energy” Physics

    A high-intensity neutrino beam offers new possibilities for the study of nucleon and nuclear structure.

    e.g. NuMI has very similar kinematic coverage to current generation of JLab experiments.

    A new window on many of the questions currently being explored in JLab experiments.

    Physics Goals

    • Quasi-elastic (n + n --> m-+ p, 300 K events off 3 tons CH)

      • Precision measurement of s(En) and ds/dQ important for neutrino oscillation studies.

      • Precision determination of axial vector form factor (FA), particularly at high Q2

      • Study of proton intra-nuclear scattering and their A-dependence (C, Fe and Pb targets)

    • Resonance Production (e.g. n + N ---> n /m- + D, 600 K total, 450K 1p)

      • Precision measurement of s and ds/dQfor individual channels

      • Detailed comparison with dynamic models, comparison of electro- & photo production, the resonance-DIS transition region -- duality

      • Study of nuclear effects and their A-dependence e.g. 1 p<-- > 2 p <--> 3 p final states

    • Coherent Pion Production (n + A --> n /m- + A + p, 25 K CC / 12.5 K NC)

      • Precision measurement of s(E) for NC and CC channels

      • Measurement of A-dependence

      • Comparison with theoretical models

    Physics Goals

    • Nuclear Effects (C, Fe and Pb targets)

      • Final-state intra-nuclear interactions. Measure multiplicities and Evis off C, Fe and Pb.

      • Measure NC/CC as a function of EH off C, Fe and Pb.

      • Measure shadowing, anti-shadowing and EMC-effect as well as flavor-dependent nuclear effects and extract nuclear parton distributions.

    • MINERnA and Oscillation Physics

      • MINERnA measurements enable greater precision in measure of Dm, sin2q23 in MINOS

      • MINERnA measurements important for q13 in MINOS and off-axis experiments

      • MINERnA measurements as foundation for measurement of possible CP and CPT violations in the n-sector

    • sT and Structure Functions (2.8 M total /1.2 M DIS events)

      • Precision measurement of low-energy total and partial cross-sections

      • Understand resonance-DIS transition region - duality studies with neutrinos

      • Detailed study of high-xBj region: extract pdf’s and leading exponentials over 1.2M DIS events

    • Most all of these would benefit from 10x or more statistics beyond proposals

    Physics Goals

    • Strange and Charm Particle Production (> 60 K fully reconstructed exclusive events) -

      • Exclusive channel s(En) precision measurements - importance for nucleon decay background studies.

      • Statistics sufficient to reignite theorists attempt for a predictive phenomenology

      • Exclusive charm production channels at charm threshold to constrain mc

    • Generalized Parton Distributions (few K events)

      • Provide unique combinations of GPDs, not accessible in electron scattering (e.g. C-odd, or valence-only GPDs), to map out a precise 3-dimensional image of the nucleon. MINERnA would expect a few K signature events in 4 years.

      • Provide better constraints on nucleon (nuclear) GPDs, leading to a more definitive determination of the orbital angular momentum carried by quarks and gluons in the nucleon (nucleus)

      • provide constraints on axial form factors, including transition nucleon --> N* form factors

    Beta Beam Concept

    • Goal is to make a very well understood neutrino beam (flux, spectrum, and no background)

      • Zuchelli (2002)

    • Start with radioactive ions

      • Use ions that beta decay with high Q and reasonable lifetime

      • Boost them with a  in the range 55 to 140

      • Result would be a highly collimated beam

    Beta beams recently proposed for

    • High Energy q13 & CP violation

    • Low EnergyNeutrino – nucleus interactions

    • Lowest EnergyNeutrino Magnetic Moments

    Example Design from CERN

    • Lindroos (2003)

    CP violation & q13

    • CERN vision for oscillation studies uses 200 km baseline with 0.44 Mton detector

    • For q13 = 3 deg appearance rates (10 yr)

      • 18Ne66 events (osc,)

      • 6He32 events (osc.)

    • T Violation test

      •  beam vs conventional

        ve=> vµ vµ => ve

    Neutrino-Nucleus Interactions

    • Lower energy beta beam (boosted to 10s of MeV)

    • Applications for astrophysics

      • Supernova neutrino detection

      • Supernova nucleosynthesis

      • Solar Neutrino Detection

    • Currently

      • Carbon only know to 4% - 10%

      • D, 56Fe, 127I reported with ~40% error

    • Cross sections ~ 10-41cm2

      • Can make a 10% measurement in 10 ton detector with 1015 v/s over in a reasonable run

    Volpe (2003)

    Magnetic Moment

    • Neutrinos have mass there therefore the have a magnetic moment

    • Very sensitive to physics beyond the standard model

    • Current limits vary by species but are in the range of 10-15mB (e.g. from reactor studies)

    • Would need 1015 ions/s for reasonable sensitivity

    Beam Intensity

    • Current experiments near-term experiments (next 5 years) are fraction of a MW beam power

      • Few x 1020 to 1021 protons on target

      • eLIC booster in routine use on target

        • (1-3)x1022 per year

        • Up to 4MW

      • Each generation proposes factor of 10 X in [mass] x [power]

    Current, Planned, & Dream Super Beam Facilities

    ProgramPpEvP (MW)L (km)yr



    NuMI (initial)1203.50.2573505

    NuMI (full design)1203.50.473508


    JPARC to SK 501.00.829508

    NOnA (NuMI Off-Axis)1201.50.481009


    Super Reactorn/a0.011015 yrs?

    JPARC phase II500.84295

    Fermilab Proton driver1201.81.9735/1500

    CERN SPL (proton linac) 2 0.34130

    AGS Upgrade301-722500

    eLIC injector201-542500

    Now/next couple years~5 years10-15 years

    Relationship to EIC Complexes

    To RHIC

    To Target Station

    High Intensity Source

    plus RFQ

    200 MeV Drift Tube Linac



    1.2 GeV  28 GeV

    0.4 s cycle time (2.5 Hz)

    200 MeV

    400 MeV

    Superconducting Linacs

    800 MeV

    1.2 GeV

    0.2 s

    0.2 s

    • At BNL

      • Use AGS for a neutrino program while is also feeding RHIC & eRHIC

    • At JLab

      • Use Large Booster for a neutrino program when not loading the storage ring

      • Probably cleanest best if electron and proton booster functions are separated

    What about eLIC?

    • The distance to the NuSL site is about the same for either BNL or JLab

    • Large Injector gets used for few minutes per fill of the collider

      • Rest of the time could be used for “pinging” a target

      • Beam power for eLIC proton injector competitive with other super beams

      • Implies some machine design issues

    • Needs 11o angle to hit NUSL

      • Similar ground water issues to BNL

    • Site is potentially restrictive but fortunately the beam line would run nearly parallel to Jefferson Ave (~10o)


    • Long baseline

      • T2K & hep-ex/0106019

      • NOvA

      • BNL Super beamhep-ex/0305105

      • CERN SPLCERN 2000-012

      • Beta beam

    • Short baseline

      • MINERvA

      • FINeSSEhep-ex/0402007

    • APS neutrino study; super beam working group workshop two weeks ago


      • Retreat and working group report this year


    • A rich field for investigation of neutrino oscillations using long & very long baselines

      • Considerable beyond-SM & cosmology value

    • Neutrino scattering to structure

    • Proton injector for EIC has potential to be a world class neutrino source on a competitive time scale

    • Connections between NUSL, neutrino community, and EIC promise a broad program embracing different communities with orthogonal uses of the facility

      • A potentially powerful combination

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