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Physics Opportunities at the NuMI Neutrino Beam. Physics Opportunities NuMI Beam Overview Off-axis NuMI Beam Backgrounds and Detector Issues Detector Possibilities Potential NuMI Off-axis Sensitivity Site Question Politics, Schedule, etc. Adam Para, Fermilab

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physics opportunities at the numi neutrino beam
Physics Opportunities at the NuMI Neutrino Beam
  • Physics Opportunities
  • NuMI Beam Overview
  • Off-axis NuMI Beam
  • Backgrounds and Detector Issues
  • Detector Possibilities
  • Potential NuMI Off-axis Sensitivity
  • Site Question
  • Politics, Schedule, etc

Adam Para, Fermilab

Neutrino Factory Working Group

CERN, September 10, 2002

three outstanding questions
Three outstanding questions
  • Neutrino mass pattern: This ? Or that?
  • Electron component of n3
  • Complex phase of s  CP violation in a neutrino sector
neutrino propagation in matter
Neutrino Propagation in Matter
  • Matter effects reduce mass of ne and increase mass of ne
  • Matter effects increase Dm223 for normal hierarchy and reduce Dm223 for inverted hierarchy
the key n m n e oscillation experiment
The key: nm ne oscillation experiment

A. Cervera et al., Nuclear Physics B 579 (2000) 17 – 55, expansion to second order in

  • First 2 terms are independent of the CP violating parameter d
  • The last term changes sign between n and n
  • If q13 is very small (≤ 1o) the second term (subdominant oscillation) competes with 1st
  • For small q13, the CP terms are proportional to q13; the first (non-CP term) to q132
  • The CP violating terms grow with decreasing En (for a given L)
  • CP violation is observable only if all angles ≠ 0
anatomy of bi probability ellipses
Anatomy of Bi-probability ellipses

Minakata and Nunokawa, hep-ph/0108085



  • Observables are:
  • P
  • P
  • Interpretation in terms of sin22q13, d and sign of Dm223 depends on the value of these parameters and on the conditions of the experiment: L and E



an example cp and matter effects at 730 km
An example: CP and Matter Effects at 730 km

Parameter correlation: even very precise determination of Pn leads to a large allowed range of sin22q23  need antineutrinos

what will minos do
What will MINOS do?

Two functionally identical neutrino detectors

Det. 1

Det. 2

possible result in 2005
Possible result in 2005(?)

Expected event spectrum

Observed event spectrum

Ratio: survival probability as a function of energy

Shape: disappearance mechanism . Oscillations? Decays? Other?

If oscillations => precise (~10%) measurement of the parameters




minos limits on n m to n e oscillations
MINOS Limits on nm to neOscillations

10 kton-yr exposure,

Dm2=0.003 eV2, |Ue3|2=0.01:

Signal (e = 25%) - 8.5 ev

ne background - 5.6 ev

Other (NC,CC,nt) – 34.1 ev

M. Diwan,M. Mesier, B. Viren, L. Wai, NuMI-L-714

90% CL: | Ue3|2< 0.01

Sample ofnecandidates defined using topological cuts

numi flexible neutrino beam
NuMI: Flexible Neutrino Beam

Expected CC Events Rates in Minos 5kt detector

  • High 16,000 ev/yr
  • Medium 7,000 ev/yr
  • Low 2,500 ev/yr

‘zoom’ lens:

Vary the relative distances of the source and focusing elements

status of numi tunnel
Status of NuMI Tunnel

MARCH 2002

Beam pipe is now

finished and

cast in concrete

numi horn1 testing
NuMI Horn1: testing

1st Horn under test

1 year worth of pulses

horn 2 under construction
Horn 2: under construction

Initial weld samples Final horn being electron welded

likely numi schedule
Likely NuMI Schedule
  • Surface Building and Outfitting contract has just been signed (mid-September)
  • The Underground (tunnel, caverns, and shafts) contractor should be finished in mid-November of this year (2002)
  • Outfitting should take about 1 year
  • Installation of beam technical components and Near Detector should take about 1 year
  • We expect first beam on NuMI target 11/04
receipe for a better n e appearance experiment
Receipe for a Better ne Appearance Experiment
  • More neutrinos in a signal region
  • Less background
  • Better detector (improved efficiency, improved rejection against background)
  • Bigger detector
  • Lucky coincidences:
  • distance to Soudan = 735 km, Dm2=0.025-0.035 eV2
  • Below the tau threshold! (BR(t->e)=17%)
two body decay kinematics
Two body decay kinematics

At this angle, 15 mrad, energy of produced neutrinos is 1.5-2 GeV for all pion energies  very intense, narrow band beam

‘On axis’: En=0.43Ep

off axis magic d beavis at al bnl proposal e 889
Off-axis ‘magic’ ( D.Beavis at al. BNL Proposal E-889)

1-3 GeV intense beams with well defined energyin a cone around the nominal beam direction

medium energy beam off axis detectors
Medium Energy Beam: Off-axis detectors

Neutrino event spectra at putative detectors located at different locations

Neutrinos from K decays

A. Para, M. Szleper, hep-ex/0110032

n e appearance experiment a primer
ne Appearance Experiment: a Primer
  • Know your expected flux
  • Know the beam contamination
  • Know the NC background*rejection power (Note: need to beat it down to the level of ne component of the beam only)
  • Know the electron ID efficiency
beam systematics predict the spectrum medium energy beam
Beam Systematics: Predict the Spectrum. Medium Energy Beam

Event spectra at far detectors located at different positions derived from the single near detector spectrum using different particle production models.

Four different histograms superimposed

Total flux predictable to ~1-2 %.

sources of the n e background
Sources of the ne background


ne/nm ~0.5%

At low energies the dominant background is from m+e++ne+nm decay, hence

  • K production spectrum is not a major source of systematics
  • ne background directly related to the nmspectrum at the near detector

K decays

background rejection beam detector issue
Background rejection: beam + detector issue

n spectrum

NC (visible energy), no rejection

Spectrum mismatch: These neutrinos contribute to background, but no signal

ne background

ne (|Ue3|2 = 0.01)

NuMI low energy beam

NuMI off-axis beam

These neutrinos contribute to background, but not to the signal

fighting nc background the energy resolution
Fighting NC background:the Energy Resolution

M. Messier, Harvard U.

Cut around the expected signal region to improve signal/background ratio

sensitivity dependence on n e efficiency and nc rejection
Sensitivity dependence on neefficiency and NC rejection

Major improvement of sensitivity by improving ID efficiency up to ~50%

Factor of ~ 100 rejection (attainable) power against NC sufficient

NC background not a major source of the error, but a near detector probably desirable to measure it

numi beam layout
NuMI Beam Layout

Near off-axis detector

antineutrinos are very important
Antineutrinos are very important

Antineutrinos are crucial to understanding:

  • Mass hierarchy
  • CP violation
  • CPT violation

High energy beams experience: antineutrinos are ‘expensive’.

Ingredients: s(p+)~3s(p-) (large x)

For the same number of POT

NuMI ME beam energies:

s(p+)~1.15s(p-) (charge conservation!)

Neutrino/antineutrino events/proton ~ 3

Backgrounds very similar to the neutrino case (smaller NC background)

(no Pauli exclusion ~25% at 0.7 GeV)

detector s challenge
Detector(s) Challenge
  • Surface (or light overburden)
    • High rate of cosmic m’s
    • Cosmic-induced neutrons
  • But:
    • Duty cycle 0.5x10-5
    • Known direction
    • Observed energy > 1 GeV

LoDen R&D project

  • Principal focus: electron neutrinos identification
  • Good sampling (in terms of radiation/Moliere length)
  • Large mass:
  • maximize mass/radiation length
  • cheap
numi off axis detector
NuMI Off-axis Detector
  • Different detector possibilities are currently being studied
  • The goal is an eventual 20 kt fiducial volume detector
  • The possibilities are:
    • Low Z target with RPC’s, drift tubes or scintillator
    • Liquid Argon (a large version of ICARUS)
    • Water Cherenkov counter
an example of a possible detector
An example of a possible detector

Low Z tracking calorimeter


  • absorber material (plastic? Water? Particle board?)
  • longitudinal sampling (DX0)?
  • What is the detector technology (RPC? Scintillator? Drift tubes?)
  • Transverse segmentation (e/p0)
  • Surface detector: cosmic ray background? time resolution?
  • . . .

NuMI off-axis detector workshop: January 2003

a typical signal event
A ‘typical’ signal event

Fuzzy track = electron

cc n e vs nc events in a tracking calorimeter analysis example
CC ne vs NC events in a tracking calorimeter: analysis example
  • Electron candidate:
    • Long track
    • ‘showering’ I.e. multiple hits in a road around the track
    • Large fraction of the event energy
    • ‘Small’ angle w.r.t. beam
  • NC background sample reduced to 0.3% of the final electron neutrino sample (for 100% oscillation probability)
  • 35% efficiency for detection/identification of electron neutrinos
resistive plate counters virginia tech belle
Resistive Plate Counters (Virginia Tech, BELLE)

Glass electrodes are used to apply an electric field of ~4kV/mm across a 2mm gap. The gap has a mixture of argon,isobutane and HFC123a gas. An ionizing particle initiates a discharge which capacitively induces a signal on external pickup strips.

5 years of tests in Virginia Tech, 4 years operating experience in Belle

glass spark counters monolith
Glass Spark Counters (Monolith)

It is an RPC with electrodes made of standard float glass instead of

Bakelite with a completely different design approach developed at LNGS.

(see G.Bencivenni et al. NIM A300 (1991) 572

C.Gustavino et al. To be published on NIM )

Gas Mixture : Argon/Freon/C4H10 = 48/48/4

Spacers by

injection molding

(2 mm)



Float Glass

Resistive film

End caps by

injection molding

Thermoplastic soldering

for gas sealing

Easy and fast and cheap construction

Ready for mass production.

energy resolution of digital sampling calorimeter
Energy Resolution of Digital Sampling Calorimeter
  • Digital sampling calorimeter:
    • 1/3 X0 longitudinal
    • 3 cm transverse
  • Energy = Cx(# of hits)
  • DE ~ 15% @ 2 GeV
  • DE ~ 10% 4-10 GeV
  • ~15% non-linearity @ 8 GeV, no significant non-gaussian tails
constructing the detector wall
Constructing the detector ‘wall’
  • Containment issue: need very large detector. Recall: K2K near detector – 1 kton mass, 25 tons fiducial, JHF proposal – 1 kton mass, 100 tons fiducial
  • Engineering/assembly/practical issues

Solution: Containers ?

Containers ?

J. Cooper 5/3/02


  • 90% of the world’s manufactured goods (i.e. non-bulk) moves in standardized shipping containers
  • > 14 million units exist,leading Ports handle 15 M units / year
    • The most common types are: 20’ Dry Freight (x 8’ x 8’ 6”) (6.1 m x 2.44 m x 2.59 m)

40’ High Cubes (x 8’ x 9’ 6 “) (12.2 m x 2.44 m x 2.9 m)

    • Jargon unit is the TEU (Twenty-foot Equivalent Unit)
  • 1 million new TEUs built each year
    • This is real “mass production”
    • Almost all built overseas, Balance of trade helps us

2 TEU– High Cube

container details
Container Details
  • ISO specifications
  • Corner posts take load
  • Corner blocks for rigging
  • Corrugated steel sides & top
  • Doors on one end (or more)
  • Hardwood plywood floor sealed to sides
  • Angle/channel steel support below floor, fork pockets
numi beam on and off axis
NuMI Beam: on and off-axis

Det. 2

Det. 1

  • Selection of sites, baselines, beam energies
  • Physcis/results driven experiment optimization
two most attractive sites
Two Most Attractive Sites
  • Closer site, in Minnesota
    • About 711 km from Fermilab
    • Close to Soudan Laboratory
    • Unused former mine
    • Utilities available
    • Flexible regarding exact location
  • Further site, in Canada, along Trans-Canada highway
    • About 985 km from Fermilab
    • There are two possibilities:
      • About 3 kmto the west, south of Stewart Lodge
      • About 2 km to the east, at the gravel pit site, near compressor station
location of canadian sites
Location of Canadian Sites

Stewart Lodge Beam Gravel Pit

a closer look
A Closer Look

Stewart Lodge

Compressor station


Gravel pit

sensitivity dependence on n e efficiency and nc rejection1
Sensitivity dependence on neefficiency and NC rejection

Major improvement of sensitivity by improving ID efficiency up to ~50%

Factor of ~ 100 rejection power against NC sufficient

NC background not a major source of the error, but a near detector probably desirable to measure it

Sensitivity to ‘nominal’ |Ue3|2 at the level 0.001 (phase I) and 0.0001 (phase II)

important reminder
Important Reminder
  • Oscillation Probability (or sin22qme) is not unambigously related to fundamental parameters, q13 or Ue32
  • At low values of sin22q13 (~0.01), the uncertainty could be as much as a factor of 4 due to matter and CP effects
  • Measurement precision of fundamental parameters can be optimized by a judicious choice of running time between n and n
numi of axis sensitivity for phases i and ii
NuMI Of-axis Sensitivity for Phases I and II

We take the

Phase II to have

25 times higher

POT x Detector


Neutrino energy

and detector

distance remain

the same

result driven program importance of l e flexibility
Result-driven program: importance of L, E flexibility

Phase I: run at 712 km, oscillation maximum

Where to locate Phase II detector?

Matter effects amplify the effect: increase statistics at this location

Osc. Maximum induces d=0/d=p ambiguity  move to lower/higher energy

Matter induces d=p/2 vs d=3p/2 ambiguity  move to the second maximum

on the importance of being mobile mammals vs dinosaurs
On the importance of being mobile:mammals vs dinosaurs?


Super-superbeam somewhere? Here we come!

determination of mass hierarchy
Determination of mass hierarchy

Matter effects can amplify the

effect, [sgn(Dm213=+1), d=3p/2], or reduce the effect [sgn(Dm213=+1), d=3p/2],

and induce the degeneracy at smaller values of sin22q13.

In the latter case a measurement at the location where matter effects are small (even with neutrinos only!) breaks the degeneracy and extends the hierarchy determination to lower values of sin22q13.  complementarity of NuMI vs JHF

recent initiative
Recent Initiative
  • A Letter of Intent has been submitted to Fermilab in June expressing interest in a new n effort using off-axis detector in the NuMI beam
  • This would most likely be a ~15 year long, 2 phase effort, culminating in study of CP violation
  • The LOI was considered by the Fermilab PAC at its Aspen July, 2002, meeting
fermilab official reaction
Fermilab Official Reaction

Given the exciting recent results, the eagerly anticipated results from the present and near future program, and the worldwide interest in future experiments, it is clear that the field of neutrino physics is rapidly evolving. Fermilab is already well positioned to contribute through its investment in MiniBooNE and NuMI/MINOS. Beyond this, the significant investment made by the Laboratory and NuMI could be further exploited to play an important role in the elucidation of q13 and the exciting possibility of observing CP violation in the neutrino sector.

( June 2002, PAC Recommendation)

We will encourage a series of workshops and discussions, designed to help convergence on strong proposals within the next few years. These should involve as broad a community as possible so that we can accurately guage the interest and chart our course. Understanding the demands on the accelerator complex and the need for possible modest improvements is also a goal. Potentially, an extension of the neutrino program could be a strong addition to the Fermilab program in the medium term. We hope to get started on this early in 2003.

Michael Witherell

the next steps schedule
The Next Steps/Schedule
  • R&D effort on light Z detectors is ongoing
  • Workshop on detector technology issues planned for January, 2003
  • Proposal to DOE/NSF in early 2003 for support of R&D and subsequent construction of a Near Detector in NuMI beam to be taking data by early 2005
  • Proposal for construction of a 25 kt detector in late 2004
  • Site selection, experiment approval, and start of construction in late 2005
  • Start of data taking in the Far Detector in late 2007
concluding remarks
Concluding Remarks
  • Neutrino Physics appears to be an exciting field for many years to come
  • Most likely several experiments with different running conditions will be required
  • Off-axis detectors offer a promising avenue to pursue this physics
  • NuMI beam is excellently matched to this physics in terms of beam intensity, flexibility, beam energy, and potential source-to-detector distances that could be available
  • We have great interest in forming a Collaboration that could work on these opportunities

Monday, Sept. 16, UCL London, Massey Lecture Theater, 10 am-5 pm : ‘All about NuMI off-axis’. Welcome…

do we need a dedicated near detector a k a predicting the off axis spectrum
Do we need a dedicated near detector? A.k.a predicting the off-axis spectrum.

Neutrino fluxes detected at the near and far detectorsproduced by the same parent hadron beam, hence:

every neutrino event observed at the near detector implies a certain flux(En) at the far detector.

Correlation function M depends mostly on the focusing system and the geometry of the beam line (M. Szleper, A. Para hep-exp/011001). It depends on the location of the far detector.

how to predict the off axis spectrum ii
How to predict the off-axis spectrum II

Decay angle QNQF, henceENEF.

Take as an example two neutrino energy bins:

  • Well focused, parallel beam of pions M11,M220, M12=M21=0
  • Realistic beam, far detector on axis M11,M120, M21<M11, M12~0
  • Off-axis beam M11,M22,M21~0, M120
n e appearance experiment
ne appearance experiment
  • Large number of nm oscillating away

(~ 800 per 10 kton*years)

  • Below t threshold no background
  • The only backgrounds due to
    • ne component of the beam (0.5%)
    • NC background
      • NC background as small as it can be (very small higher energy tail not contributing to the signal)
      • Total energy constraint
what if d m 2 is lower than we think
What if Dm2 is lower than we think?

Need to wait with a choice of the detector location? Why?

  • Oscillation probability varies with energy
  • Energy varies with angle (position)
  • In practice:
  • Oscillation probability varies slowly to the right of the maximum => relatively small reduction of signal
  • Low energy  large angle  significant neutrino flux reduction

Optimal experiment location fairly insensitive to the valueDm2