Transcript Neutrino Flavor Oscillations at the Neutrino News from Fermilab Fermilab Main Injector Sacha E. Kopp University of Texas at Austin SMU Physics Department Seminar 22 October 2007

Neutrino
Flavor
Oscillations
at the
Neutrino
News
from Fermilab
Fermilab Main Injector
Sacha E. Kopp
University of Texas
at Austin
SMU Physics
Department
Seminar
22 October 2007
Quantum Mechanics
and
Double Slit Experiments
•
•
•
•
Particles exhibit wave interference
Indeterminacy (pattern lost if measure which slit)
One particle vs ensemble
Interpretation: probability waves
 TOT  1   2
e-
1 ?
2 ?
I ( )
2 
 cos ( )
I0
2

path d sin 


2


A Tonomura et al.,
Am. J. of Phys. 57 117-120 (1989)
•
What We Observe “at the Screen”:
Lepton Number
Why must the muon decay weakly?
 Long lifetime result of heavy W
 Lifetime t~2ms
•
m-  e- ne
nm
Lm
+1 0
0
Le
0 +1 -1
More favorable decay
m-  e- g
+1
0
Lm
Le
+1
0
Lepton
Number!
0 0
+1 0
 Electromagnetic interaction
 Should have lifetime ~10-18 sec
 Observed rate < 1.2  10-11 of all m decays
(M.L. Brooks et al, Phys. Rev. Lett. 83, 1521 (1999)
n’s Have Lepton Number
• Nuclear b decay has e, reactors produce ne
• Reines & Cowen exp’t to observe free ne
ne + p  e+ + n
Reines & Cowan, Science 124, 103
(1956), Phys. Rev. 113, 273 (1959)
• Contrast to “failed” experiment by R. Davis
ne + 37Cl  e- + 37Ar
R. Davis, Phys. Rev. 97, 766 (1955)
NOT OBSERVED
n’s Have Lepton Number (cont’d)
• In 1957, Brookhaven AGS and CERN
PS first accelerators intense enough to
make n beam
p + Be   + X,
  m n
Saw lots of…
n
• 1962: Lederman, Steinberger,
Schwartz propose experiment to see
nm + N m- + X
(Phys.Rev.Lett. 9, 36 (1962))
nm + N m- + X
Saw none of…
n
ne + N e- + X
Weak Interactions
Conserve Lepton Number
Lepton
# Conserved

m
Lepton
# Conserved
nm
nm
m-
  m nm
?
nm  N  m- + X
• Many exp’t confirmations of Lepton number conservation
(m, t decays, etc)
• Neutrino interactions conserve lepton number too.
• But what happens to the neutrino in between
creation/annihilation, while in flight?
Neutrino Double Slit Experiment
• We create and observe |nm & |ne  via weak interaction
• But suppose n’s have mass  0. Can label them by
|n1  -- the heavier mass state with m = m1.
|n2  -- the lighter mass state with m = m2.
• We do not know in which mass state the neutrino propagates
(it’s an unknown ‘slit’) – must assume both  interference!
nm
n1
n2
nm or ne?
• Suppose at t=0 have a state | (0)= |nm. Later…?
NB: sin2(x)
because now
talking about
fraction of beam
that disappears!
2t/4p]
2L/E ]
Probability{nmne}(t)  sin2[Dm
[1.27Dm
n
2
2
2
2
D
m

m
m
1
2
To see the effect, must have En/L~Dm
A Mixture of n States
• How can a quantum state produced at t=t1 appear as a
different quantum state at t=t2?
• Mass eigenstates need not coincide with
weak eigenstates (two indep. bases) nm
|ne = cos |n1 + sin |n2
|nm = - sin |n1 + cos |n2
• Reminiscent of crossed polarizers.
 n2

ne
n1
Neutrinos have 3 slits
• The nt discovered  3 lepton flavors must exist
(K. Kodama et al., Phys. Lett. B504 218 (2001)]
• Measurements of Z0 boson resonance  only 2.9830.009
lepton flavors participate in weak interaction
[S. Eidelman et al., Phys. Lett. B592, 1 (2004) ]
n1
nm
n2
n3
• With 3 n families we expect
 3 mixing probabilities between flavor i  j
 2 distinct mass splittings
ne
nm
nt
n Mixing Orthodoxy
• If you believe in flavor mixing, there must be a 33 unitary
transformation to mass states:
Is this90%C.L.
non-zero???
CHOOZ
sin13<0.22
Large@enough
to-3measure
Dm2=210
eV2
sinsolar <0.62
Phys.Lett.B466,415
CP in nm  (1999)
ne
(Smirnov, hep/0309299)

c12c13
n e 

 
n m    - s12c23 - c12 s23s13
 s s - c c s e i
n 
 t
 12 23 12 23 13
s12c13
c12c23 - s12 s23s13ei
- c12 s23 - s12c23s13ei
cij  cosij
s13e -i 

s23c13 
c23c13 
sij  sinij
Super-K
sin
23>0.58
Is the90%C.L.
mixing
angle
@ Dm2=210-3eV2
truly(hep-ex/0404034)
maximal???
• In the quarks, mixing matrix has phase 0 responsible for CP.
But hopefully this picture is wrong or incomplete!
(Peggy Lee: “Is that all there is?”)
n 1 
 
n 2 
n 
 3
Two Detector n Experiments
FNAL CCFR experiment, 1982-83
CERN CHARM/CDHS experiments, 1982-83
•Near detector predicts n energy spectrum and rate at far
detector (asssuming an absence of oscillations)
•Greatly reduces systematic uncertainties due to calculating beam flux.
Interpretation of Oscillation Results
Oscillation
Probability
E0 /5
E0 /3 2nd max
E0 1st max
Neutrino Energy
2

D
m
L
2
2

P(n m  n t )  sin 2 sin 1.27
En 

• Oscillations into
unknown flavor
causes dip in
obvserved spectrum.
magnitude of
suppresion from
sin2(2)
Dm2=0.005eV2
location of dip
from Dm2
Long Baseline n Oscillation Exp’s
• Reproduce atmospheric n effect using accelerator beam
• L ~ 100’s kilometers to match oscillation frequency
Near Detector:
980 tons
Far Detector:
5400 tons
Det. 1
735 km
Det. 2
MINOS
(Fermilab to Minnesota)
L = 735 km 2005
K2K (KEK to SuperK)
L = 250 km Concluded
CNGS (Cern to Gran Sasso, Italy)
L = 750 km tested 2006, run 2008
The Challenge of Long Baselines…
1.E+14
1.E+13
ANL
FNAL Main Ring
BNL
CERN PS
LSND
Nomad/
Chorus
Beam Dose (Joules)
CERN SPS
IHEP
1.E+12
1.E+11
MINOS
goal
LAMPF
KEK
this
analysis
FNAL Booster
FNAL NuMI
FNAL TeV
1.E+10
K2K
1.E+09
2n
flavors
Discovery
of NC’s
1.E+08
1960
MiniBooNE
1965
1970
1975
1980
S. Kopp, “Accelerator Neutrino Beams,” Physics Reports
439, 101 (2007), arXiv:hep-ex/0609129
1985
Year
1990
1995
2000
2005
2010
The NuMI Beam
Main
Injector
Accelerator
Extraction
magnets
Target Hall
Plan View
Evacuated Decay Volume
Hadron Absorber
target
focusing horns
Access Tunnel
n beam
Near Detector Hall
Muon Alcoves
Elevation View
Ground Level
Surface Building
Target Hall
V118 Bend
Carrier Tunnel
V108 Bend
Surface Building
Hadron Absorber
Service Shaft
n beam
Near Detector Hall
Muon Alcoves
Neutrinos at the Main Injector
• MI ramp time ~1.5sec
• MI is fed 1.56ms batches
from 8 GeV Booster
• Simultaneous acceleration
& dual extraction of
protons for
 Production of p
(Tevatron collider)
 Production of
neutrinos (NuMI)
Batch 2
Main Injector
Batch 1
• NuMI designed for
 8.67 ms single turn
extraction
 41013ppp @ 120 GeV
• Antiproton Production:
 Requires bunch rotation
(Dt~1.5nsec)
 Merges two Booster
batches into one batch
(“slip-stacking”)
Batch 3
½ Batch
(empty)
Batch 4
½ Batch
(empty)
Batch 6
Batch 5
Pbar
Target
NuMI
Lambertsons
Bend out of MI
NuMI Proton Beam Line
Final bend to Soudan
Target Hall
Target Hall
after
Contractor
completion
Decay pipe
Target Hall shielding installation
Target/baffle
Module installed
Focusing Horns
Main horn field between conductors
figure A. Marchionni, J. Hylen
Horn 2 suspended
from shielding module
being lowered into
shielding pit
Hall probe moving
along horn axis
MINOS Near Detector
MINOS Far Detector
magnetized Fe-scintillator calorimeter
MINOS Far Detector
segmented scint for X, Y tracking
485 planes, 8m diam, 5400 tons
Raison d’Être for a
Northern Minnesota
Experiment!
Austin American-Statesman Newspaper,
Sunday, April 18, 2004
Neutrino Beams 101:
Beam MC

B

XB
i
i
i
Focusing peak
Error (Far/Near)
Consequence: Flux Uncertainty
figure courtesy Ž. Pavlović
“Low”
Energy
Neutrino Beams 102
proton target
“High”
Energy
target
Horn 1
Horn 2
Pions with
pT=300 MeV/c and
p=5 GeV/c
p=10 GeV/c
p=20 GeV/c
Vary n beam energy
by sliding the target
in/out of the 1st horn
Horn 1
Horn 2
figure courtesy Ž. Pavlović
Opportunity: Flexible Beam Energy
M. Kostin et al,
“Proposal for ContinuouslyVariable Neutrino Beam
Energy,”
Fermilab-TM-2353-AD (2002)
figure courtesy Ž. Pavlović
Neutrino Beams 103:

to far
Detector
(stiff)
target

f
n
(soft)
Decay Pipe
• ND and FD spectra
similar, but not identical
0.43E
En 
2 2
1 g 

1 
1

Flux  2 
2 2 
L 1 g  
ND
Beam MC
LE Beam
2
figure courtesy M. Kostin
Near
Detector
Consequence: Extrapolating to the FD
Far Detector MC
Near Detector MC
(×1.2×10-6)
NiNear
• ND and FD spectra
are similar, but not
identical
• If they were
identical, (NuMI
approximating a
point source) could
say
i
i
NFar
 FN N Near
where
FN = (Znear/Zfar)2
Extrapolating to the FD (cont’d)
• The ND sees the NuMI beam as an extended line source of neutrinos, while FD
sees a point source,
Edge of
Horn 1
solid angle
weighted by
 lifetime
neck
Horn 2
neck
1
- 0.43 m z / E ct
e
dz
48m (Z FD - z ) 2
 720 m
1
- 0.43 m z / E ct
e
dz
48m (Z ND - z ) 2
720 m
FN
where En  0.43 E.
• Better than this need a MC to
evaluate FN.
 Angular correlations in decay
 Pi’s that interact before decaying
NuMI Beam MC
Decay Pipe
backgrounds
event identification
Blind Analysis Procedure
calibration
•Intensive checks of ND data
neutrino interaction identification in ND & FD
MINOS Decided to
backgrounds, efficiencies, etc.Pursue a
“Blind Analysis”
beam modeling – how well can we extrapolate flux measured in
Policy
ND to the expected flux in the FD??
beam flux
•Much to be learned from the ND Data
near-far extrapolation
•Not much statistics in the FD
Not much to learn
Opportunity to bias ourselves
fitting
interpretation
Step 1: Look at ND Data
• Hope no gross disagreements with beam MC
• See if neutrino identification is OK
ND Events Observed
First Observed Neutrino
Events in Near MINOS
Detector
January 21, 2005
nm + Fe m + X
Neutral Current nm Backgrounds
• Analysis requires an
energy spectrum
measurement.
• In nm+Fem + X
interaction, reconstruct
En=pm+EX,
• Can’t see full neutrino
energy in NC
nm+Fenm + X
interactions.
MINOS MC
CC (no osc.)
Hypothetical
MINOS Data
CC (with osc.)
NC Background
Visible Neutrino Energy (GeV)
Coping with High Intensity
• 10-20 events/spill in the ND (cf 10-4/spill in the FD!)
In one spill (51012 ppp)
In one slice
Time (msec)
Slice
Slice 3
5
2
1
4
Beam is Stable
•
•
•
•
•
•
June
July
August
September
October
November
ND Compared to Beam MC
“High” Energy
Beam Setting
“Medium” Energy
Beam Setting
“Low” Energy
Beam Setting
MINOS Data
Calculated n flux
figure courtesy P. Vahle
• These plots show the
beam spectrum as “dead
reckoned” by Fluka2005
+ our tracking MC
through the beam line.
• Errors bars from the
beam systematics
(dominated by /K
production in the target).
• Some real apparent
contradictions? MC is
low in the LE beam, but
high in the ME beam.
ND Spectra After Tuning
figure courtesy Ž. Pavlović, P. Vahle
Step 2: Decide How to Extrapolate
ND  FD
• FD Spectrum = (F/N ratio)  ND Spectrum
N
i
En , FD
 N
i
FN
i
En , ND
NEn = Number of events at given energy of neutrino in ND or FD
i = particular energy bin
• Tests on “mock data” to ensure no biases, understand systematics
Alternative
Extrapolation
“Matrix Method”
A. Para & M.
Szleper,
arXiv:hepex/0110032
Checks of
the Fitting
• MC “Mock data sets”
 100 experiments
 each 1020 POT exposure
• Studies of
 biases
 statistical precision
Best Fit
Dm2
(eV2)
Best Fit
sin2(2)
figures
courtesy
D. Petyt
Best Fit c2
Systematic Uncertainties
Shift in Δm2
(10-3 eV2)
Shift in
sin2(2θ)
Near/Far norm. (livetime, fid vol) 4%
0.065
<0.005
Absolute hadronic energy scale 10%
0.075
<0.005
NC contamination 50%
0.010
0.008
All other systematic uncertainties
0.041
<0.005
Total systematic (summed in quadrature)
0.11
0.008
Statistical error (data)
0.17
0.080
Uncertainty
Step 3: Peek at the Far Detector Data
( “Box is still closed”)
•In 2006 analysis, question was “Do n’s disappear?”
unknown “blinding function” to hide most of the data
Collaborators given free access to “open” data set
Only got to see full data set once “box was open”
•In 2007 analysis, want unbiased Dm2, sin2(2) measurement
Access to all the data, but complete blinding of all rates
Did not look at energy spectrum, so couldn’t bias Dm2
Checks on the FD Data
Track Vertex in X (m)
Track Vertex in Y (m)
Track Vertex in Z (m)
• These are all CC neutrino events
• Rates blinded – we don’t know the normalization
• MC has been scaled to agree with data
Calibration
region used for calibration
figure courtesy N. Tagg
• Calibratrions based on stopping cosmic ray m’s.
• Study ionization for 20-plane window upstream of stopping m location.
Example Events (I)
• These events taken from the “open” data sample in the FD (which we are
permitted to look at in detail).
• En = 3.0 GeV
• y = Ehad/En=0.3
Example Events (II)
• These events taken from the “open” data sample in the FD (which we are
permitted to look at in detail).
• En = 24.4 GeV
• y = Ehad/En=0.4
Example Events (III)
• These events taken from the “open” data sample in the FD (which we are
permitted to look at in detail).
• En = 10.0 GeV
• y = Ehad/En=0.3
Example Events (IV)
• These events taken from the “open” data sample in the FD (which we are
permitted to look at in detail).
• En = 2.1 GeV
• y = Ehad/En=0.1 (‘quasi-elastic’?)
Example Events (V)
• These events taken from the “open” data sample in the FD (which we are
permitted to look at in detail).
• En = 18.7 GeV
• y = Ehad/En=0.9
Example Events (VI)
• These events taken from the “open” data sample in the FD (which we are
permitted to look at in detail).
• En = 3.3 GeV
• y = Ehad/En=0.6
Example Events (VII)
• These events taken from the “open” data sample in the FD (which we are
permitted to look at in detail).
• En = 25 GeV
• y = Ehad/En=0.6
Step 4: Look at All Events
“Open the Box”
FD Events are “In time” and Uniform
Time Relative to Spill (msec)
Neutrino Energy Spectrum
Null Oscillation Hypothesis
c2 /n.d.f = 139.2/36 =3.9
Oscillation Hypothesis Fit
c2/n.d.f =41.2/34=1.2
P(c2,n.d.f)=0.18
20
| Δm32 | 2.38-00..16
10-3 eV2 / c4
2
sin 2 (2 23 )  1.00-0.08
“Accident & Substance: Two possible explanations
“Fair
andbulk
Balanced”
for the
of reality”
April 6, 2006 Inside article:
“One possible explanation for dark matter is a
group of subatomic particles called neutrinos. …
Last week, researchers working on the MINOS
experiment at Fermilab, near Chicago, confirmed
these results. …”
“The researchers created a beam of muon neutrinos
… The neutrinos then travelled 750km (450 miles)
through the Earth to a detector in a former iron
mine in Soudan, Minnesota.”
“By comparing how many muon neutrinos arrived
there with the number generated, Fermilab's
researchers were able to confirm that a significant
number of muon neutrinos had disappeared—that
is, they had changed flavour. Thus the neutrino
does, indeed, have mass and a more accurate
number can be put on it.”
Fitting into the Unphysical Region
Δm  2.26 10 eV
sin 2 2  1.07
2
-3
2
57
Compare 1.3 & 2.5 1020POT Datasets
• Reconstruction and selection method
 Changes number of events
 ~2σ change in Δm2
• Shower modeling
 Δm2 systematic decrease 0.06×10-3eV2
• New data set fluctuates down
58
Our Long-term Goal:
For Dm2 = 0.0020 eV2, sin2 223 = 1.0
Oscillated/unoscillated
ratio of number of nm
CC events in far
detector vs Eobserved
Expectation if Dm2=0.001eV2
Expectation if n Decay
Expectation if Extra Dimensions
Hypothetical MINOS Data
figure courtesy D. Petyt
.
Off-Axis Beam from NuMI
Probability (%)
Dm2>0
Baseline (km)
• Possible to measure rates P(nmne) P(nmne) due to…
 CP violation
 n’s propagating through matter
• Fermilab P929 (NOnA)
D
nmne
vacuum
nmne
ATLAS
NOnA
Competition in Japan
1st Demonstration of Off-Axis Beam

• NuMI n’s sprayed in all directions.
• Kmn and mn decays lead to
lower En at large decay angle
0.43E
En 
1  g 2 2
~110mrad to
MiniBooNE
• Opportunity to double-check our
beam flux calculations using
‘mature’ neutrino detector
MiniBooNE nm CC Events
Total Calculated NuMI Beam flux
Calculated n flux from  Decays
Calculated n from K Decays
figure courtesy Alexis
Aguilar-Arévalo
Visible Neutrino Energy (GeV)
The Fermilab Neutrino Program
• Many ideas are now being discussed/proposed/built
 MINOS – Precision oscillation parameters
 NOvA – first observation of nmne, matter effects?
 MINErVA – precision scattering cross sections
 MicroBooNE – Liquid Argon TPC R&D
 NuSOnG – weak mixing angle
 FNAL-DUSEL – CP Violation in neutrinos?
• Project X accelerator would enable diverse program
Workshop on
Physics
Opportunities
with the
Project X
Accelerator
Fermilab,
Nov 16-17, 2007
The path
forward is
crystal clear …
SMU student
Yurii Maravin,
Summer 1994
Prof. Thomas Coan, Fall 1993
…but
very
fragile
indeed.
The Blind Leading the Blind?
double-beta
“Knowing in
part may
make a fine
tale, but
wisdom
comes from
seeing the
whole.”
accelerator
direct mn
It Remains a World-Wide Effort
to Interpret Neutrino
Disappearance
and the Possibilities of
Neutrino Mass
atmospheric
LSND/MiniBooNE
solar
reactor
Conclusions
• MINOS rapidly progressing
 Construction complete after 6 years
 3.51020 POT delivered
 First result confirms n’s disappear
 Under oscillation hypothesis,
2
-3
2
Dm23
 (2.38-00..20
)

10
eV
16
sin 2 (2 23 )  1.00-0.08
• Rich program of physics ahead
 Results on oscillations vs other new
physics
 Search for rare osc. phenomena, like
nmne, nmns
 Is nmnt mixing maximal?
 Future experiments: CP violation
Backup Slides
Alternatives for nm Disappearance
“Neutrinos actually decay to
lighter states”
“Neutrinos propagating
in Extra Dimensions”
Barger et al., hep-ph/9907421
Barbieri et al., hep-ph/9907421
“SuperK effect is combination
of Dm2(solar) and
Dm2(LSND)”
Barenboim et al., hep-ph/0009247
NuMI low
energy beam
No osc.
oscillations
Barenboim
No osc.
oscillations
Neutrino decay
NuMI high
energy beam
•
Most think nmnt looks like a good explanation of the
atmospheric n depletion, but one must be open to other
possibilities given
 The 3 Dm2 problem
 Naturalness, attraction of a nsterile GUT’s
 Due skepticism of jumping to conclusions in hard
experiments
Charged Current nm Selection
MINOS MC
Track Charge
MINOS MC
MINOS MC
Track length (planes) Track length beyond Shower
Track Pulse Height / Plane Track Curvature/Resolution
Y = 1 – pm/En
• Charged current events distinguished by
 muon track
 long event length
• Probability distribution function to reduce nm-NC bckgd to nm-CC sample.
Charged Current nm Selection (cont’d)
CC-like
Near Detector Data
rejected as
NC like
Event Classification Parameter
• In LE beam, expect 89% efficiency, 98% CC purity
“Tuning” the Beam Spectra in (xF, pT)
LE10/0kA
LE10/170kA
LE10/185kA
Vary
the horn
current
LE10/200kA
LE100/200kA
LE250/200kA
Vary the
target’s
location
F/N Ratio After Tuning
• Several tunings
of the (xF, pT)
spectra were
attempted.
• All can
accommodate the
ND neutrino
spectra.
• All yield similar
tuned F/N ratio
(within 2%)
Charged Current nm Selection Variables
Track length (planes)
Track Pulse Height / Plane
Track length beyond Shower
Y = 1 – pm/En
Curvature/Resolution
Classification Parameter
Comparison with Unblinded MC
c2 /n.d.f = 30.8/20 = 1.5
Reconstructed yEhad/En
No Osc.
Osc. (Dm2=0.0024 eV2)
MINOS Data