Transcript ppt, 2.3M

Searching for New Physics with
Atmospheric Neutrinos and
AMANDA-II
John Kelley
Preliminary Exam
March 27, 2006
Questions to Answer
• Atmospheric neutrinos
– What are they? Where do they come from?
– What physics can we learn from them?
• How do we detect them?
• How can we extract the physics from the data?
Atmospheric Neutrinos
• Where do they come from? Cosmic
rays!
• Cosmic rays (p, He, etc.) interact in
upper atmosphere, produce charged
pions, kaons
“What do you get when you slam junk into junk?
You get pions!” — B. Balantekin
Figure from Los Alamos Science 25 (1997)
• These decay and produce muons and
neutrinos
Air Showers
QuickTime™ and a
Video decompressor
are needed to see this picture.
Energy Spectra
CR primary spectrum
 Resulting  flux
(uncertainties in primary flux, hadronic models)
Knee
Figure: Halzen, Bad Honnef (2004)
Figure: Gaisser, astro-ph/0502380
Oscillations: Particle Physics with
Atmospheric Neutrinos
• Evidence (SuperK, SNO) that
neutrinos oscillate flavors
(hep-ex/9807003)
• Mass and weak eigenstates not
the same (mixing angle(s))
• Implies weak states oscillate as
they propagate (governed by
energy differences)
Figures from Los Alamos Science 25 (1997)
Oscillation Probability
Three Families?
• In theory: mixing is more
complicated (3x3 matrix; 3 mixing
angles and a CP-violation phase)
• In practice: different energies and
baselines (and small 13) mean
approximate decoupling again into
two families
Standard (non-inverted) hierarchy
Atmospheric    is essentially two-family
Atmospheric Baselines
• Direction of neutrino (zenith angle) corresponds to
different propagation baselines L
L ~ O(104 km)
• Happy coincidence of Earth size, m2, and
atmospheric  energies
L ~ O(102 km)
SuperK, hep-ex/0404034
Experimental Results
atmospheric
Global oscillation fits
(Maltoni et al., hep-ph/0405172)
Beyond the Standard Model
• What is the structure of
space-time on the smallest
scales?
• Are “fundamental”
symmetries such as Lorentz
invariance preserved at high
energies?
Why Neutrinos?
• Neutrinos are already post-SM (massive)
• For E > 100 GeV and m < 1 eV*, Lorentz  > 1011
• Oscillations are a sensitive quantum-mechanical probe
Eidelman et al.: “It would be surprising if further surprises
were not in store…”
* From cosmological data, mi < 0.5 eV, Goobar et. al, astro-ph/0602155
New Physics Effects
• Violation of Lorentz invariance
(VLI) in string theory or loop
quantum gravity*

c - 1
c - 2
• Violations of the equivalence
principle (different gravitational
coupling)†
• Interaction of particles with spacetime foam  quantum decoherence
of flavor states‡
* see e.g. Carroll et al., PRL 87 14 (2001), Colladay and Kostelecký, PRD 58 116002 (1998)
† see e.g. Gasperini, PRD 39 3606 (1989)
‡ see e.g. Anchordoqui et al., hep-ph/0506168
Phenomenology
Theory
Pheno
Experiment
Current status: theories are suggestive of modifications to SM,
but cannot yet specify exact form / magnitude of effects
Amelino-Camelia on QG: “…a subject often derided as a safe haven for theorists wanting
to speculate freely without any risk of being proven wrong by experimentalists.”
Theory / pheno / experimental feedback shaping future work!
(e.g., quasar halos and loop quantum gravity, gr-qc/0508121)
VLI Phenomenology
• Modification of dispersion relation*:
• Different maximum attainable velocities ca (MAVs) for
different particles: E ~ (c/c)E
• For neutrinos: MAV eigenstates not necessarily flavor or
mass eigenstates
* Glashow and Coleman, PRD 59 116008 (1999)
VLI Oscillations
Gonzalez-Garcia, Halzen, and Maltoni, hep-ph/0502223
• For atmospheric , conventional oscillations turn off above
~50 GeV (L/E dependence)
• VLI oscillations turn on at high energy (L E dependence),
depending on size of c/c, and distort the zenith angle /
energy spectrum
Survival Probability
c/c = 10-27
Quantum Decoherence
Phenomenology
• Modify propagation through density matrix formalism:
• Solve DEs for neutrino system, get oscillation probability*:
*for more details, please see Morgan et al., astro-ph/0412628
QD Parameters
• Various proposals for how parameters
depend on energy:
simplest
preserves
Lorentz invariance
recoiling D-branes!
Survival Probability ( model)
a==
4  10-32 (E2 / 2)
How Do We Detect ?
1.
Need an interaction — small cross-section necessitates a
big target!
2.
Then detect the interaction products (say, using their
radiation)
Čerenkov
effect

Čerenkov Cone
QuickTime™ and a
Video decompressor
are needed to see this picture.
Location, Location, Location
Where on Earth could we have a huge natural
target of a transparent medium?!
Obligatory South Pole Photo
~3 km ice!
photo by J. Braun
AMANDA-II
AMANDA-II
19 strings
677 OMs
Trigger rate: 80 Hz
Data years: 2000“Up-going”
“Down-going”
(from Northern sky) (from Southern sky)
Optical Module
PMT noise: ~1 kHz
Muon Neutrino Events
• Can reconstruct muon direction to 2-3º
(timing / light propagation in ice)
QuickTime™ and a
PNG decompressor
are needed to see this picture.
• Quality cuts:
• smoothness of hits along track
• likelihood of up vs. down
• resolution of track fit
•…
• Allows rejection of large muon
background
Data Sample
2000-2003 sky map
Livetime: 807 days
3329 events (up-going)
<5% fake events
No point sources found:
pure atmospheric sample!
Adding 2004, 2005 data:
> 5000 events (before cut optimization)
Analysis
Or, how to extract the physics from the data?
detector
MC
…only in a perfect world!
Closer to Reality
Zenith angle reconstruction — still looks good
reconst.
The problem is knowing the neutrino energy!
Muon Energy Loss
-dE/dx ≈ a + b log(E)
Stochastic losses produce
mini-showers along track
Light output is a reasonable
handle on energy
Figure by T. Montaruli
Number of OMs hit
Nch (number of OMs hit): stable observable, but acts
more like an energy threshold
Other methods exist: dE/dx estimates, neural networks…
Observables
c/c = 10-25
No New Physics
Binned Likelihood Test
Poisson probability
Product over bins
Test Statistic: LLH
Testing the Parameter Space
c/c
excluded
allowed
sin(2)
Given a measurement, want to
determine values of parameters
{i} that are allowed / excluded
at some confidence level
Feldman-Cousins Recipe
• For each point in parameter space {i}, sample many times
from parent Monte Carlo distribution (MC “experiments”)
• For each MC experiment, calculate likelihood ratio:
L = LLH at parent {i} - minimum LLH at some {i,best}
• For each point {i}, find Lcrit at which, say, 90% of the MC
experiments have a lower L
• Once you have the data, compare Ldata to Lcrit at each point
to determine exclusion region
Feldman & Cousins, PRD 57 7 (1998)
1-D Examples
(all normalized to data)
Finding the Sensitivity:
Zenith Angle
2000-05 simulated
Sensitivity to c/c
• 90%: 2.1  10-26
• 95%: 2.5  10-26
• 99%: 2.9  10-26
allowed
excluded
MACRO limit:
2.5  10-26 (90%)
Sensitivity using Nch
2000-05 simulated
Sensitivity to c/c
• 90%: 2.5  10-27
• 95%: 3.0  10-27
• 99%: 3.9  10-27
Systematic Errors
• Atmospheric production uncertainties
• Detector effects (OM sensitivity)
• Ice Properties
Can be treated as nuisance parameters:
minimize LLH with respect to them
Normalization is already included!
To Do List
• 2004-05 data and Monte Carlo processing
• Optimize quality cuts
• Extend analysis capabilities
–
–
–
–
better energy estimator?
full systematic error treatment
multiple dimensions
optimize binning
• Analyze data (discover Lorentz violations)
• Write thesis
• Vacation in Papua New Guinea