Download - Raghunath Ganugapati(Newt) && Paolo Desiati
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Raghunath Ganugapati(Newt) && Paolo Desiati
Event Topology Studies for detection of prompt muons in the down going muon flux
IceCube Collaboration Meeting,March 23rd,2005,Berkeley
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Detection With AMANDA-II
• Extra Terrestrial Neutrinos• High energy spectrum hypothesis d/dE ~ E-2
• Backgrounds
• Conventional Atmospheric µ , from decay of (π± , K± ) d/dE ~ E-3.7
• Possible components from
decay of atmospheric charmed particles. d/dE ~ E-2.7
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Uncertainty in Prompt Lepton Cross Sections
• The uncertainty ~3 orders
• Need for accelerator data extrapolation
• Crossover between 40TeV and 3 PeV
ZhVd
AMANDA II (neutrinos)
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Neutrino Vs Muon Fluxes
Ref:GGV,hep-ph/0209111 v1 10 Sep 2002
Essentially same to ~100TeV at sea level
• Constraint on a prompt µ is equivalent to a constraint on prompt
Use down going muon data
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Analysis Description
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Signal Simulation Single µ with an assumed energy spectrum of prompt µ (RPQM) and isotropic in zenith and azimuth angle at the surface of the earth
Standard AMANDA codes used for propagation and detector response. Charm-D model will also be used.
Signal ,Background Simulation and Data
The conventional muons produced from the π± and K± decay is the B.G.
CORSIKA 6.02 with the QGSJET01 model of hadron interactions and decay used.
Background Data
70 days life time worth data taken by the AMANDA II during 2001 will be studied.
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Analysis levels
• L2 standard minimum bias data • L3 Zenith Angle Cut
• L4 Event Quality Cuts
• L5 Topology cut (single muon and a bundle of muons)• Early Hit (Topology1)• dE/dX method (Topology2)
• L6 Energy Cut
Strategies for separation of Signal from Background
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Zenith distribution(L3)
True track
Reco Track
Cos(zenith) B/S vs Cos(zenith)
True track(S)Reco Track(S)
Reco Track(BG)
TrueTrack(BG)
• S/B ratio improves near the horizon
• Lots of misreconstructed muon near horizon
• Angular resolution very important to see enhancement of S/B near the horizon.
Cut these out
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Quality Cuts(L4)
• Track Length(>120m) Distance between direct hits
projected on to the length of the track • Number of Direct Hit(>6) The more the number of direct hits
the better the guess track and less likely to converge to a false minimum
• Reduced Chi square(<7.3) Chisquare computed using time
residuals and divided by total number of hits
• Pre and Post hits (prehit<1.5 and posthit<1.5) Well reconstructed muon have very
few hits that arrive later or before in time (Peter Stefan's dE/dX method)
SinglesSingles(after QC)
MultiplesMultiples(after QC)
Angular Resolution
Improve from 8 to 3.5 degrees
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Muon Bundles
log10(energy at cpd) GeV
Singles
MultiplesSignal
• The multiple muon background goes with same slope as the signal
• Need to improve the sensitivityOf our instrument to prompt muon
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Topology 1 (Early Hit)(L5)
snapshot
Cherenkov cone BCD from reconstructed track propagating in time relative to the tracks.
• Limitations
•Random Noise hits (3.0 photo electron cut)
• Misreconstructed single muon ( Good angular resolution vital )
Muon1
Muon2
Early Hit
Reconstructed track
A
B
Δθ
•The hit at B is earlier by time
length(AB)/cice
C
D
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Topology 1(Eview Earlyhits)
EarlyhitAmplitude>3pe (proximity cut)(Noise Hits suppressed)
Distance<50m (proximity cut)
timedelay<-15ns
Reconstructed Track
Well reconstructed single muon should not have this
Muon Bundle Single Muon (misreco)
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Time Residuals and Convoluted Pandel
Time delay(16 PPandel) Time delay(64 CPandel)
Excess Earlyhits in MC
Data
BG MC
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EarlyHits
0 degree2 degree5 degree
Cut these out
Does retainA decent bit of single muon
Earlyhits
1 muon
234-10
10-2525-50
Cut these
Muon Multiplicity
Resolution effect on single muon track
Multiplicity effect on true tracks
Filtering Efficiency (Topology 1)
Frac
tion
ret
aine
d
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Topology 2 (Energy Deposition dE/dX)(L5)
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Hit Selection and Estimators(L5)
Quality Cuts (already discussed)
I choose only direct hits(-15ns to 75 ns)(less effected by ice properties)
Use hits with in 50m radius cylinder
around the track(less scattered)
Take only hits with amplitude greater 3.0 P.E for reconstruction.
Estimator1
B= Nphoton Observed Photon Nphoton expected from MIM
Estimator1 gives Estimator2
y = σ B/<B>
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Filtering Efficiency(L5)
Result (Reco track) True track(Ideal)
y = σ B/<B> y = σ B/<B>
Cut these out
Cut these out
Signal
BG
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Energy Cut(L6)
Nhits(Energy Observable)
2001 exp data
2001 signal(RPQM)+BG
BGSignal
Integral Spectra
Data Description
Avg Upper limit
0% sys)
10% sys
(20% sys)
(30% sys)
(40% sys)
Best Cut Nhit=310,Signal=9.4,B.G=6
MRF=0.7(30%SYS)
MRF
Data observed=16 Signal Expectation (RPQM)=9.4
B.G Expectation=6.0 Event upper limit=22.4
MRFsim=0.70 (30% SYS)
MRFdata=22.4/9.4= 2.3(very preliminary)
Nhits(Energy Observable)
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Constraining Charm Neutrino models by analysis of downgoing Muon Data
A Restrictive limit means enhanced sensitivity to diffuse neutrinos
AMANDA II(muons)
ZHVdPreliminary Limit (70days)
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BACK UP SLIDES
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Energy Correlation
Number of Hits Vs log10(energy at cpd) GeV
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Note that the distribution of less than 3.0P.E. hits remains almost flat outside 50m.
Could be noise?(Randomness)
Why than does it fall down as we come close to the track?
There is a pile up in amplitude for noise hits inside 50m from the track as the pulse from early noise hit gets smeared out with the actual hits from muons
Greater than 3.0P.E hits
Less than 3.0P.E hits
Perpendicular distance from reconstructed track for
BGMC muons(m)
Goodhits
Random Hits
~10 timesgreater
Amplitude-Perpendicular distance to the Hit space
Δt<-15ns only
Dump this space out
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Dust
Dust
Clear Ice
Reconstructed track in dataTrue track
Geometrical Effect
Reconstructed track in simulation
•The Monte Carlo tracks are reconstructed away from the true track than in the data because of various assumptions and the way the time delay is calculated.
•The tracks are reconstructed pivoted about the centre of the detector so any discrepancies in timing tend to scale roughly as the distance from the centre and hence outer strings become more susceptible to the differences than the inner ones.
Δθ
Leverarm(AB)*Δθ
A
B
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Done with all hits (not just direct hits)
SinglesMultiples
KeepThese
Filtering Efficiency(L5)
When all hits are chosen notice what happens?
Any possible separation of S-Bis destroyed by the fluctuationof ice properties
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Amplitude-Time Residual space
Amplitude(P.E) Amplitude(P.E)
Data
Background
DataBackground
A projection of the amplitude for a region of space in time residual less than –15ns is shown; there appears to be some disagreement between the data and the simulation in the low amplitude regime.
This bin(0-2 P.E) has significantly large number of hits compared with the other neighboring bins. What are these hits?Noise?
Ignore these
R2
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Ice Properties Ice properties themselves
introduce some fluctuations into the observed amplitude
Think what the optical properties of a dust layer could do to the Photo Electron recorded?
May be need to apply corrections to the PE recorded depending on the layer of ice to retrieve information in original form to undo what ice does (for Horizontal muons this gets tricky!!!)
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Dust
Dust
Clear Ice
True track
Δθ
A
B
Reco Track
Large Amplitude Seen when lower is expected from reco track hypothesis
Small Amplitude Seen when large is expected from reco track hypothesis
Reconstruction Errors
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Data Agreement(16fold-ppandel)
Number of Hits
DataB.GSignal
The Overall Agreement is not extremely good within the limit of systematics (30-40%)
A possibility to improve the scenario is to use a 64-iteration Convoluted Pandel and repeat the whole procedure described