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Superbeams. Deborah Harris Fermilab July 26, 2004 NuFact’04 Osaka University. Outline of this Talk. Goals for the Next Steps Why Superbeams are a Challenge Beamline Strategies Detector Strategies (see Strolin tomorrow!) Prospects Near Term: T2K and NO n A

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Deborah Harris


July 26, 2004


Osaka University

Outline of this talk
Outline of this Talk

  • Goals for the Next Steps

  • Why Superbeams are a Challenge

  • Beamline Strategies

  • Detector Strategies (see Strolin tomorrow!)

  • Prospects

    • Near Term: T2K and NOnA

    • Why Two Beams are better than one…

    • Far Term: Lots of other ideas…

  • Summary

Deborah Harris, Superbeams, NuFact04

What do we want to know
What do we want to know?

  • Known:

    • Two large mixing angles, maybe one small

    • 3 independent mass splittings, one is positive

    • Absolute neutrino mass limits

  • Unknown:

    • Absolute Mass Scale

    • How many n’s are there?

    • Mass Hierarchy?

    • Is CP Violated?

    • Are n’s their own antiparticles?

Mena&Parke, hep-ph/0312131

Deborah Harris, Superbeams, NuFact04

Definition of mixing angles
Definition of Mixing Angles

  • Need to measure ne to nm transitions at Datm-scale baseline/energy

Deborah Harris, Superbeams, NuFact04

What happens when n e s pass through the earth
What happens when ne’s pass through the earth?

“Raises potential

Energy for ne’s and

Anti-ne’s separately”

Wolfenstein, PRD (1978)

electron density

in the earth

Deborah Harris, Superbeams, NuFact04

Designing a neutrino experiment
Designing a Neutrino Experiment

  • Currently: pin down or eliminate Dm2

  • Next: look for ne /nm transitions at Dm2atm

    • CP violation in absence of matter effects

    • Matter effects in absence of Dmsol2

Deborah Harris, Superbeams, NuFact04

Making a neutrino beam
Making a Neutrino Beam

  • Conventional Beam

  • Beta Beam

  • Neutrino Factory

Detector Needs

Deborah Harris, Superbeams, NuFact04

Conventional beam challenges
Conventional Beam Challenges

What is so hard about nm →ne

  • CHOOZ tells us it’s a small effect (<5%)

  • Unavoidable contamination of ne in beam

    • From m decays

    • At high enough p energies, K enters too!

      • KL→ p+ e –ne and KL→ p- e +ne

  • Can mistake

    p0, m or p± for e

Deborah Harris, Superbeams, NuFact04

Two approaches narrow and broad
Two Approaches: Narrow and Broad

  • Narrow Band Beams

    • Lower backgrounds under peak from ne and NC

    • But flux is narrower than oscillation maximum!

    • Most sensitive limits per MW*kton

    • Examples: T2K, NOnA, CNGT

  • Broad Band Beams

    • Higher event rates

    • In some cases actually measure shape of oscillations

    • Higher ne backgrounds at any one energy

    • Examples: BNL LOI, FeHo, CERN SPL

Deborah Harris, Superbeams, NuFact04

Off axis neutrino beams
“Off Axis” Neutrino Beams

  • First Suggested by Brookhaven (BNL 889)

  • Take advantage of Lorentz Boost and 2-body decays

  • Concentrate nm flux at

    one energy

  • Lower NC and ne

    backgrounds at that

    energy (3-body decays)

Deborah Harris, Superbeams, NuFact04

Detector options
Detector Options

  • Water Cerenkov

  • Scintillator Calorimetry

  • Liquid Argon TPC

Deborah Harris, Superbeams, NuFact04

Water cerenkov
Water Cerenkov

  • Excellent particle ID for single-ring events

  • Most massive n detector built to date

  • More problematic for multi-ring events

  • Multi-p events can fake single-ring events

p0or e?

SuperK event displays courtesy Mark Messier

Being considered

for higher and

higher energies

because of

low energy


(see Strolin’s talk)

Deborah Harris, Superbeams, NuFact04

Scintillator calorimetry
Scintillator Calorimetry

  • Calorimeter with <X0 sampling can do

    • e/g separation by looking for gaps after event vertex

    • e/m separation from track characteristics

  • Can see all particles, good energy reconstruction at all energies

  • Events at right: all scintillator, 1 cell equals:

    • 4.9 cm horizontal axis

    • 4.0 cm vertical axis

nm + A -> p +m-

ne+A→p p+p- e-

n + A -> p + 3p± + p0 + n

Cooper, June 2004 PAC

Deborah Harris, Superbeams, NuFact04

Liquid argon tpc
Liquid Argon TPC

  • Electronic Bubble Chamber

  • Lots of recent progress with

    event reconstruction

  • Test runs at Pavia and CERN producing lots of pretty events

  • Looking forward to seeing how detector measures CNGS beam

  • Looking to “industrialize” design








Run 939 Event 46


Rubbia, NuINT04




e-,15 GeV, pT=1.16 GeV/c

Deborah Harris, Superbeams, NuFact04

In praise of near detectors
In Praise of Near Detectors

  • To make precise measurements,need

    • Background cross sections

    • Signal (CC!) cross sections

MINERnA event display





Data compiled by G.Zeller, hep-ex/0312061


Need Dedicated Measurements in fine-grained detectors

(see D.Casper’s talk on Friday)

Deborah Harris, Superbeams, NuFact04

First step seeing if q 13 is non zero
First Step: seeing if Q13 is non-zero

  • T2K Tokai to Kamioka

    • 295km, 1st osc. maximum

    • 50kton Water Cerenkov (SK)

    • New 0.8MW proton Source: J-PARC

December, 2003




12/2003 Exp’t approved

2008 Accelerator operating

2009 n Physics Running

Deborah Harris, Superbeams, NuFact04

T2k detector suite
T2K Detector Suite

  • Several jobs,

  • several detectors:

  • Verify n beam direction

  • Measure nm and ne fluxes with high statistics

  • Measure background and signal cross sections

  • Eventually, verify background rates in “identical” detector at 2km

Hayato, n2004

Deborah Harris, Superbeams, NuFact04

T2k physics reach
T2K Physics Reach

Hayato, n2004

Deborah Harris, Superbeams, NuFact04

No n a

  • Use Existing NuMI beamline

  • New Detector 12km off axis

  • 820km shows best compromise between reach in q13 and matter effects

  • PAC recommendation

    “The Committee strongly endorses the physics case for the NOnA detector, and would like to see NOnA proceed on a fast track that maximizes its physics impact.”

  • Beam ready first—start taking data with fraction of the detector

  • New Studies show all scintillator has better reach per dollar

Assuming Dm2=2.5x10-3eV2

Messier, n2004

Deborah Harris, Superbeams, NuFact04

No n a physics reach
NOnA Physics Reach

Because of CP and matter effects, “reach” vs. sin2 2q13 will vary…

50kton baseline


50kton baseline


Feldman, Aspen PAC 2004

Deborah Harris, Superbeams, NuFact04

Oscillation probabilities
Oscillation Probabilities


  • For any one energy and baseline, you don’t get the whole story…

  • Need two energies, or two baselines, and at least one baseline needs to be long enough to see matter effects

  • First question: what do you get if you add more protons and detector to first generation experiments?

Minakata & Nunokawa JHEP 2001

Deborah Harris, Superbeams, NuFact04

What does 2 get you that 1 doesn t
What does 2 get you that 1 doesn’t?

  • J-PARC Upgrade:

    • 0.7 to 4MW proton source

      • Beamline preparations now

    • 50kton to 500kton (Hyper-K)

      • Study new light collection technology

  • NOnA Upgrade:

    • 0.25 to 2MW proton source

      • Proton Driver CD-0 Machine and Physics Study

      • Possible second detector at 710km, 30km off axis

Feldman, Aspen 2004

Deborah Harris, Superbeams, NuFact04

Cp violation at t2hyper k

4MW, 540kt

2yr for nm

6~7yr for nm

CP Violation at T2Hyper-K

CHOOZ excluded

sin22q13<[email protected]~3x10-3eV2

3s CP sensitivity :

|d|>20o for sin22q13>0.01

with 2% syst.



(signal+BG) stat only

no BG

signal stat only


T2K 3s discovery





T2K-I 90%

Kobayashi, n2004

Deborah Harris, Superbeams, NuFact04

Next steps depend on first steps
Next Steps depend on First Steps

  • LSND Confirmed by MiniBooNE?

    • Lots of new shorter baseline beamlines needed

    • CP violation in nm→ntbecomes more important

  • Both T2K and NOnA see no evidence for q13≠0?

    • Upgrade either (or both) to get most sensitive search

  • Either T2K or NOnA see a hint of q13≠0?

    • Lots of new ideas, depends on who sees what

      • Is signal in neutrinos or antineutrinos?

      • Does one see it but not the other?

  • No matter what we know we will need:

    • Need protons and targets that can accept them

    • Need better background rejection with high efficiency

Deborah Harris, Superbeams, NuFact04

Fermilab to homestake
Fermilab to Homestake


  • Based on 2MW at 120GeV, +2MW at 8GeV

  • Several off axis beams + 1 on axis beam to give broad spectrum

  • May be easiest way to get to 4MW of proton power

  • Very preliminary, more of a show of flexibility given enough protons

30 mR maximum off axis



120 GeV


8 GeV


Deborah Harris, Superbeams, NuFact04

Fermilab to homestake physics reach
Fermilab to Homestake Physics Reach

ne Appearance

Water Cerenkov

nm Disappearance

  • Considering Different Detectors

  • 500kT Water Cerenkov (shown here)

  • Liquid Argon TPC

  • All-Scintillator Detector (NOnA)

Water Cerenkov

Michael, Snowmass 2004

Deborah Harris, Superbeams, NuFact04

Brookhaven to homestake
Brookhaven to Homestake

  • 28GeV AGS upgrade to 1MW (2MW) cf current 0.1MW

  • Wide band beam (0.5~6GeV)

  • L=2,540km

  • Mton UNO (alternative option: Liquid Argon TPC)

  • ~13,000 nm CC/year/500kt

  • Cover higher osc. maxima

    Recent Progress

    AGS Upgrade path solidified

    Civil Construction Developed

    Targeting R&D

    Better WC simulations—


    ways to overcome


    (1 degree off-axis capability)

Brett Viren

Chiaki Yanagisawa

Deborah Harris, Superbeams, NuFact04

Brookhaven to homestake physics reach

But with both n and n running, CP precision much higher

Brookhaven to Homestake Physics Reach

Studies with agressive Detector MC: even with only n data,

CP violation and mass hierarchy are visible

in some regions of parameter space.

Normal hierarchy

Reversed hierarchy

Diwan, 3/2004 APS study meeting

Deborah Harris, Superbeams, NuFact04

Beta beam and spl at cern
Beta-Beam and SPL at CERN

  • 4MW 2.2GeV Superconducting Proton Linac (SPL) @ CERN

  • Low energy wide band (En~0.3GeV)

  • L=130km

  • Water Cerenkov (400kt) or LAr TPC

  • ~18,000 nm CC/year/400kt

  • SPL in R&D, UNO in conceptual design

  • Clear overlap between SPL target and neutrino factory target

Schematic of

Large detectors in

Frejus tunnel

(Mosca, CERN 2004)

Beta beam uses known

Isolde technology…

Progress on design, and

radiation shielding

Deborah Harris, Superbeams, NuFact04

Beta beam and spl physics reach
Beta-Beam and SPL Physics Reach

Results below for combining

Conventional and beta-beams

But also physics study has been done

To look at higher energy beta-beams

As well—feasibility studies to follow…

Burguet-Castel et al,hep-ph/0312068

Mezzetto, NuFact03

Deborah Harris, Superbeams, NuFact04


  • Two complementary steps

    right around the corner

    • T2K

    • NOnA

  • After that, we know we need more protons—many proton driver

    upgrade paths

    • Fermilab

    • J-PARC

    • Brookhaven

    • CERN SPL

  • Plenty of important measurements

    to make along the way

    • Cross Sections (MINERnA,K2K Scibar)

  • Next superbeam to build depends on what the first superbeams find

Deborah Harris, Superbeams, NuFact04