The Future of Neutrino Physics in a PostMiniBooNE Era

1
The Future of Neutrino Physics in a
Post-MiniBooNE Era

• H. Ray
• Los Alamos National Laboratory

2
Outline

• Introduction to neutrino oscillations
• LSND The motivation for MiniBooNE
• MiniBooNE Overview Current Status
• The Spallation Neutron Source

3
Standard Model of Physics
2/3 -1/3
0 ?1
0 -1
4
Wave-Particle Duality

• Flavor states are comprised of mass states

m1
m2
??
?e
ELECTRON
??
?e
5
Superposition of Masses
?? ? ?e
6
Neutrino Oscillations
Weak state
Mass state
cos ?
sin ?
?e
?1

??
?2
cos ?
-sin ?
??(0)gt -sin ? ?1gt cos ? ?2gt
7
Neutrino Oscillations
Weak state
Mass state
cos ?
sin ?
?e
?1

??
?2
cos ?
-sin ?
??(t)gt -sin ? ?1gt cos ? ?2gt
e-iE1t
e-iE2t
8
Neutrino Oscillations
Posc lt?e ??(t)gt2
9
Neutrino Oscillations
Distance from point of creation of neutrino beam
to detection point
?m2 is the difference of the squared masses of
the two neutrino states
Posc sin22? sin2 1.27 ?m2 L E
? Is the mixing angle
E is the energy of the neutrino beam
10
Neutrino Oscillations
11
Current Oscillation Status
Posc sin22? sin2 1.27 ?m2 L
E
?m2 ma2 - mb2
If there are only 3 ?mac2 ?mab2 ?mbc2
12
Exploring LSND
Fit to oscillation hypothesis
Backgrounds

• Want the same L/E
• Want higher statistics
• Want different systematics
• Want different signal signature and backgrounds

13
MiniBooNE
14
MiniBooNE Neutrino Beam
Fermilab

• Start with an 8 GeV beam of protons from the
  booster

15
MiniBooNE Neutrino Beam
World record for pulses pre-MB 10M MB 100M
Fermilab

• The proton beam enters the magnetic horn where it
  interacts with a Beryllium target
• Focusing horn allows us to run in neutrino,
  anti-neutrino mode
• Collected 6x1020 POT, 600,000 ? events
• Running in anti-? mode now, collected 1x1020 POT

16
MiniBooNE Neutrino Beam
Fermilab

• p Be stream of mesons (?, K)
• Mesons decay into the neutrino beam seen by the
  detector
• K / ? ? ? ??
• ? ? e ?? ?e

17
MiniBooNE Neutrino Beam
Fermilab

• An absorber is in place to stop muons and
  un-decayed mesons
• Neutrino beam travels through 450 m of dirt
  absorber before arriving at the MiniBooNE detector

18
MiniBooNE Detector

• 12.2 meter diameter sphere
• Pure mineral oil
• 2 regions
• Inner light-tight region, 1280 PMTs (10
  coverage)
• Optically isolated outer veto-region, 240 PMTs

19
Detecting Neutrinos

• Neutrinos interact with material in the detector.
  Its the outcome of these interactions that we
  look for

20
Neutrino Interactions
MeV GeV

• Elastic Scattering
• Quasi-Elastic Scattering
• Single Pion Production
• Deep Inelastic Scattering

21
Neutrino Interactions

• Target left intact
• Neutrino imparts recoil energy to target

Elastic Scattering
Quasi-Elastic Scattering
p
n

• Neutrino in, charged lepton out
• Target changes type
• Need minimum neutrino E
• Need enough CM energy to make the two outgoing
  particles

W
?e
e-
22
Observing ? Interactions

• Dont look directly for neutrinos
• Look for products of neutrino interactions
• Passage of charged particles through matter
  leaves a distinct mark
• Cerenkov effect / light
• Scintillation light

23
Cerenkov and Scintillation Light

• Charged particles with a velocity greater than
  the speed of light in the medium produce an
  E-M shock wave
• v gt c/n
• Similar to a sonic boom
• Prompt light signature

• Charged particles deposit energy in the medium
• Isotropic, delayed

24
Event Signature
25
MiniBooNE
MB ?? ? ?e LSND ?? ? ?e

• Lots of ?e in MiniBooNE beam vs no ?e in LSND
  beam
• Complicated and degenerate light sources
• Require excellent data to MC agreement in
  MiniBooNE

• Lots of ?e in MiniBooNE beam vs no ?e in LSND
  beam
• Complicated and degenerate light sources
• Require excellent data to MC agreement in
  MiniBooNE

26
The Monte Carlo
Sources of Light
Tank Effects

• Reflection
• Tank walls, PMT faces, etc.
• Scattering off of mineral oil
• Raman, Rayleigh
• PMT Properties

• Cerenkov light
• Scintillation light
• Fluorescence from Cerenkov light that is
  absorbed/re-emitted

27
Perfecting the Monte Carlo
External Measurements and Laser Calibration
Calibrate with variety of internal Physics
samples
Validate final Model through Data to Monte Carlo
comparisons
28
Quasi-Elastic ?? Events
Constrain the intrinsic ?e flux estimate -
crucial to get right!
29
MiniBooNE Current Status

• MiniBooNE is performing a blind analysis (closed
  box)
• Some of the info in all of the data
• All of the info in some of the data
• All of the info in all of the data

• MiniBooNE is performing a blind analysis (closed
  box)
• Some of the info in all of the data
• All of the info in some of the data

• MiniBooNE is performing a blind analysis (closed
  box)
• Some of the info in all of the data

Public results April 11th
30
Final Outcomes
Confirm LSND
Inconclusive
Reject LSND
31
Final Outcomes
Confirm LSND
Inconclusive
Reject LSND
Need to determine what causes oscillations
Sterile neutrinos?
32
Final Outcomes
Confirm LSND
Inconclusive
Reject LSND
Need to collect more data / perform a new
experiment
33
Final Outcomes
Confirm LSND
Inconclusive
Reject LSND
Need to determine what causes oscillations
Need to collect more data / perform a new
experiment
SNS
34
Final Outcomes
Confirm LSND
Inconclusive
Reject LSND
35
Final Outcomes
Confirm LSND
Inconclusive
Reject LSND
SNS
36
All Roads Lead to the SNS
Confirm LSND
Inconclusive
Reject LSND
Need to determine what causes oscillations
Need to collect more data / perform a new
experiment
SNS
37
What is the SNS?
Spallation Neutron Source
Accelerator based neutron source in Oak Ridge, TN
38
The Spallation Neutron Source

• 1 GeV protons
• Liquid Mercury target
• First use of pure mercury as a proton beam
  target
• 60 bunches/second
• Pulses 695 ns wide
• LAMPF 600 ?s wide,
• FNAL 1600 ns wide
• Neutrons freed by the spallation process are
  collected and guided through beam lines to
  various experiments

Hg
Neutrinos come for free!
39
The Spallation Neutron Source
?- absorbed by target
E range up to 52.8 MeV
Mono-Energetic! ?? 29.8 MeV
? DAR
Target Area
(Liquid Mercury (Hg) target)
40
The Spallation Neutron Source

• ? ? ? ??
• ? 26 ns
• ? ? e ?? ?e
• ? 2.2 ?s

• Pulse timing, beam width, lifetime of particles
  excellent separation of neutrino types

Simple cut on beam timing 72 pure ??
41
The Spallation Neutron Source
SNS

• ? ? ? ??
• ? 26 ns
• ? ? e ?? ?e
• ? 2.2 ?s

• Mono-energetic ??
• E 29.8 MeV
• ??, ?e known distributions
• end-point E 52.8 MeV

MiniBooNE
GeV
42
The Spallation Neutron Source
Neutrino spectrum in range relevant to
astrophysics / supernova predictions!
43
Proposed Experiments
Osc-SNS Sterile Neutrinos
?-SNS Supernova Cross Sections
44
Neutrino Interactions
SNS Allowed Interactions
MeV GeV

• Elastic Scattering
• Quasi-Elastic Scattering
• Single Pion Production
• Deep Inelastic Scattering

45
Neutrino Interactions _at_ SNS

• All neutrino types may engage in elastic
  scattering interactions

Sterile Neutrino Search
46
Neutrino Interactions _at_ SNS

• All neutrino types may engage in elastic
  scattering interactions
• Muon mass 105.7 MeV, Electron mass 0.511 MeV
• Muon neutrinos do not have a high enough energy
  at the SNS to engage in quasi-elastic
  interactions!

Sterile Neutrino Search
Oscillation Search
47
Neutrino Interactions _at_ SNS

• Appearance ?? ? ?e
• ?e 12C ? e- 12N
• 12N ? 12C e (8 MeV) ?e

Intrinsic ?e vs mono-energetic ?e from ??
E of e- (MeV)
E of e- (MeV)
48
Why the SNS?
Expected for LSND best fit point of sin22?
0.004 dm2 1
May be lt 500 ns!
49
Sterile Neutrinos

• Sterile neutrinos RH neutrinos, dont interact
  with other matter (LH Weak)
• Use super-allowed elastic scattering interactions
  to search for oscillations between flavor states
  and sterile neutrinos
• Disappearance ?? ? ?e
• ?? C ? ?? C
• C ? C 15.11 MeV photon
• One detector look for deficit in ?x events
• Two detectors compare overall ?x event rates

50
Sterile Neutrinos
Near Detector only
Near Far Detector
51
Sterile Neutrinos
There are several indirect astrophysical hints
in favor of sterile neutrinos at the keV scale.
Such neutrinos can explain the observed
velocities of pulsars, they can be dark matter,
and they can play a role in star formation and
reionization of the universe.
Kusenko, hep-ph/0609158
52
Sterile Neutrinos

• R-process nucleosynthesis
• Balantekin and Fuller, Astropart. Phys. 18, 433
  (2003)
• Pulsar kicks
• Kusenko, Int. J. Mod. Phys. D 13, 2065 (2004)
• Dark matter
• Asaka, Blanchet, Shaposhnikov, Phys. Lett. B 631,
  151 (2005)
• Formation of supermassive black holes
• Munyaneza, Biermann, Astron and Astrophys., 436,
  805 (2005)
• Play impt. role in Big Bang nucleosynthesis
• Smith, Fuller, Kishimoto, Abazajian,
  astro-ph/0608377

53
but thats not all!

• CPT violation (or CP sterile neutrinos) allows
  different mixing for ?, anti-?
• Possible explanation for positive LSND, null
  MiniBooNE
• Compare ?, anti-? measured oscillation
  probabilities
• CP ?? ? ?e ? ?? ? ?e
• CPT ?? ? X ? ?? ? X

54
Mass Varying Neutrinos

• All positive oscillation signals occur in matter
  (K2K, KamLAND, LSND) no direct information on
  oscillation parameters in air/vacuum
• Require a path to detector which can be
  vacated/filled with dirt to test
• Barger, Marfalia, Whisnant. Phys. Rev. D 73,
  013005 (2006)
• Schwetz, Winter. Phys. Lett. B633, 557-562 (2006)

55
Why the SNS?
Confirm LSND
Inconclusive
Reject LSND
Looking for new physics
Need much higher statistics
Need to perform analysis with anti-neutrinos
to completely rule out LSND
Precise, well-defined neutrino/anti-neutrino
beam with very high statistics and low backgrounds
56
Why the SNS?

• SNS well known E spectrum to allow precise
  measurements
• SNS simultaneous measurements in neutrino,
  anti-neutrino modes
• SNS different systematics to LSND, MB
• Second cross check of LSND
• SNS can perform beyond the standard model
  searches not open to MB
• Sterile neutrino search, CP/CPT, MaVaNus

57
The Global Picture

• The Neutrino Matrix
• APS Multi-Divisional Neutrino Study, Nov 2004
• www.aps.org/policy/reports/multidivisional/neutrin
  o/upload/main.pdf

Pg ii
58
The Global Picture

• The Neutrino Matrix
• APS Multi-Divisional Neutrino Study, Nov 2004
• www.aps.org/policy/reports/multidivisional/neutrin
  o/upload/main.pdf

Pg iii
59
The Global Picture

• The Neutrino Matrix
• APS Multi-Divisional Neutrino Study, Nov 2004
• www.aps.org/policy/reports/multidivisional/neutrin
  o/upload/main.pdf

Pg 27
60
The Global Picture

• The Neutrino Matrix
• APS Multi-Divisional Neutrino Study, Nov 2004
• www.aps.org/policy/reports/multidivisional/neutrin
  o/upload/main.pdf

Pg 27
61
Summary

• SNS is about to become the best neutrino based
  facility in the US
• DOE proposal for 2 near detectors awaiting
  funding
• Internal LANL proposal produced for far detector
• Regardless of the outcome of MiniBooNE, the
  future of precision neutrino measurements in
  the US lies at the SNS!

62
Backup Slides
63
A Brief History of Neutrinos

• 1930 Postulated by Pauli
• 1950-60 First detection by Reines-Cowan,
  inverse beta decay
• 1935 First nu mass experiments
• 1972 Bergkvist, mass upper limit
• 1980 - 85 Soviet ITEP, mass uplow limit
• Infamous 17 keV neutrino

64
Ex Beta Decay
duu 2/3
n
p
dud -1/3
W-
W- -1
?e
e-
time
65
Standard Model of Physics

• Also have 12 anti-particles (same mass
  lifetime, opposite charge)
• Gauge particles mediate or transmit forces
  between particles
• Forces that create particles also dictate which
  interactions particles can participate in
• E-M particles with electric charge
• Quarks, leptons
• Strong binds quarks together
• Quarks

66
Standard Model of Physics

• Weak force of transmutation!
• changes flavor of quarks, leptons within a family
• Only force that acts on neutrinos
• Neutral current no exchange of electric charge
  (Z)
• Charged current exchange electric charge (W,
  W-)

67
Standard Model of Physics
W
W-
68
Quark Mixing

• Problem! If Weak force only acts inside of a
  family - how do you explain lambda decay?

u
u
?
d
p
d
s
u
d
W-
?-
u
69
Quark Mixing

• Solution quark generations are rotated for the
  purposes of weak interactions
• Instead of the Weak force coupling
• It couples

u
u
d
d
70
Quark Mixing

• Where d is a linear combination of the d, s, b
  quarks

Weak state
Mass state
d
d
Vus
Vub
Vud
s
s

Vcd
b
b
Vtd
71
Quark Mixing

• States which participate in Strong interactions
  are mass states
• States which participate in Weak interactions are
  mixtures of mass states

W
W-



72
Standard Model of Physics
Neutrino Oscillations Observed
Assume Neutrinos Have Mass
Neutrino Oscillations Observed
Assume Neutrinos Have Mass
Introduce ? mass into SM via RH field (Sterile
Neutrinos) which mix w/ LH fields (SM ?)
Introduce ? mass into SM via RH field (Sterile
Neutrinos) which mix w/ LH fields (SM ?)
Use Oscillations to find Sterile Neutrinos
Use Oscillations to find Sterile Neutrinos
73
LSND

• 800 MeV proton beam H20 target, Copper beam
  stop
• 167 ton tank, liquid scintillator, 25 PMT
  coverage
• E? 20-52.8 MeV
• L 25-35 meters
• ?e p ? e n
• n p ? d ? (2.2 MeV)

74
The LSND Result

• Different from other oscillation signals
• Higher ?m2
• Smaller mixing angle
• Much smaller probability (very small signal) 0.3

75
The LSND Problem
?m2ab ma2 - mb2
Posc sin22? sin2 1.27 ?m2 L
E

• Something must be wrong!
• Flux calculation
• Measurement in the detector
• Both
• Neither

Reminiscent of the great Ray Davis Homestake
missing solar neutrino problem!
76
Confirming LSND
?m2ab ma2 - mb2
Posc sin22? sin2 1.27 ?m2 L
E

• Want the same L/E
• Want higher statistics
• Want different sources of systematic errors
• Want different signal signature and backgrounds

77
Step 1 External Measurements

• Start with external desktop measurements

IU Cyclotron 200 MeV proton beam
Extinction rate 1 / Extinction Length
78
Step 2 Internal Samples

• Identify internal samples which isolate various
  components of the OM
• UVF, Scint are both isotropic, same
  wave-shifting/time constants
• Low-E Neutral Current Elastic events below
  Cerenkov threshold

79
Step 3 Verify MC Evolution

• Examine cumulative ?2/NDF distributions across
  many physics samples, many variables

Background to CCQE Sample
Calibration Sample
Provide ?e Constraint
Mean 1.80, RMS 1.47 Mean 1.19, RMS 0.76
Mean 20.83, RMS 25.59 Mean 3.48, RMS 3.17
Mean 16.02, RMS 25.90 Mean 3.24, RMS 2.94
80
Signal Region ?e Events
PRELIMINARY
81
SNS Stats

• 17 of incident protons produce pions
• 2.3 x 10-5 ?- decay before capture
• ? stopped lt0.3 ns
• 1.3 GeV protons produce
• 0.098 ?, 0.061 ?-
• For 9.6 x 1015 protons/sec on target get 0.94 x
  1015 of each flavor ??, Anti-??, ?e
• Anti-?e / Anti-?? lt 3 x 10-4
• Flux _at_ 50 m from target 3 x 106 s-1 cm-2

82
?-SNS Near Detectors
Full proposal submitted to DOE in August, 2005

• Homogeneous, Segmented
• Primary function cross sections for
  astrophysics
• Most relevant for supernova neutrino detection
  2H, C, O, Fe, Pb

83
Osc-SNS Far Detector

• MiniBooNE/LSND-type detector
• Higher PMT coverage (25 vs 10)
• Mineral oil scintillator (vs pure oil)
• Faster electronics (200 MHz vs 10 MHz)
• 60m upstream of the beam dump/target
• Removes DIF bgd

84
Appearance Osc. Searches

• 2 oscillation searches at SNS can be performed
  with CC interactions to look for flavor change
• Appearance ?? ? ?e (ala LSND)
• ?e p ? e n
• n p ? d 2.2 MeV photon
• Appearance ?? ? ?e
• ?e 12C ? e- 12Ngs
• 12Ngs ? 12C e (8 MeV) ?e
• MiniBooNE uses ?e n ? e- p

lower E ?e vs higher E ?e
85
Sterile Neutrinos
?? C ? ?? C C ? C 15.11 MeV photon

• Near detector 2056 events/year (25 ton)
• Far detector 3702 events/year (500 ton)

Event rates only for ??
86
Event Rates per Year
250 ton detector _at_ 60 m, 100 eff
87
Lorentz Violation

• LSND, Atm, Solar oscillations explained by small
  Lorentz violation
• Size of violation consistent with size of effects
  emerging from underlying unified theory at Planck
  scale
• Kostelecky, Mewes. hep-ph/0406255 (2004)
• Oscillations depend on direction of ? propagation
• Dont need to introduce neutrino mass!
• Look for sidereal variations in oscillation
  probability

88
Neutron Background

• 109 neutrons/day pass through near detectors
• CC measurements bgd free
• neutron bgds greatly suppressed for t gt 1 ?s
  after start of beam spill
• ? production is governed by ? lifetime (2.2 ?s )

89
Near Detector Rates

• Segmented (10 ton fiducial mass)
• Iron 3200 CC/year
• Lead 14,000
• Al 3,100
• Homogeneous
• Carbon 1,000
• Oxygen 450

90
Minos

• 120 GeV proton beam
• Graphite target
• 2 movable horns
• 1.27x1020 POT
• Next up ?? ? ?e osc search

91
MINER?A

• Placed in NuMi beamline, directly upstream of
  Minos
• Segmented solid scintillator detector, use Minos
  as ? det
• C, Fe, Pb targets
• Quasi-Elastic Q2, CC Coherent ? prod. at very
  high E (6, 20 GeV)
• Construction complete by 2009
• 4 yr run plan

92
NO?A

• Off-Axis detector
• Near Far Detectors