1. Topological Study of Downgoing Muon Events for the
Separation of High Energy Single muons from Muon bundles
Raghunath Ganugapati(Newt)
&&
Paolo Desiati

2. Detection With AMANDA-II
Extra Terrestrial Neutrinos
High energy spectrum hypothesis
dF/dE œ E-2
Backgrounds
Conventional Atmospheric µ
dF/dE œ E-3.7
Conventional Atmospheric n
from decay of (π± , K± )
Possible nm components from
decay of atmospheric charmed
particles.
dF/dE œ E-2.7

3. Charm Mechanism Vs π± , K± Mechanism
The interaction of a high energy cosmic ray with air nuclei produces a D± which takes up most of the energy and momentum of the primary.
Showering effect and the production of accompanying π± and K± is negligible when required to estimate the flux at the surface of the earth.
Ref: Doctoral thesis of
Prof.Varieschi

4. Muon Bundles The multiple muon background
goes with the same slope as the
signal so the signal will be masked in the fluctuations of the multiple muon background
We need to reject this background
To improve the sensitivity
Of our instrument to prompt muon
Singles
Multiples
Signal
log10(energy at cpd) GeV

5. Timing Pattern Larger distance = > larger time delay (Pandel)
Why are we getting more early (less delayed) hits at large distances from track)?
Suggests a different time delay structure then the normal Cherenkov cone and it could possibly be exploited for identication

6. Early Hit Illustration(Idea1)
Muon2
Early Hit
Reconstructed track A B
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 ) D Δθ C
Muon1
snapshot
The hit at B is earlier by time
length(AB)/cice

7. EarlyHit From Muon Bundle
Reconstructed
Track
Earlyhit
Amplitude>3pe (proximity cut)(Noise Hits suppressed)
Distance<50m (proximity cut)
timedelay<-15ns

8. EarlyHit from Mis-Reconstructed Muon
These are earlyhits that have high penality and hence unlikely to
Occur for a Well reconstructed single muon

9. 64-Iteration Convoluted Pandel Vs 16-fold Patched Pandel
The Convoluted Pandel
Convoluting gaussian PMT noise smearing with Pandel function using Confluent Hyper geometric functions (George and Mathieu)
Much better Angular resolution and description of time delay distributions
High energy
Muon
With nhits>200
Time delay (ns) (16-fold ppandel)
“1-fold iterated Convoluted Pandel has approximately same angular resolution Of a 16-fold ppandel”
-Mathieu Ribordy
(AMANDA collaboration meeting,Mons)

10. Muon Bundle Filter Efficiency
Signal
Does retain
A decent bit of single muon
Singles
Multiples
Rejected by
Factors of 1 in 50
Nhits(true track)
Signal
Singles
Multiples
Fraction of muons that pass VS
Muon depth
Nhits(reconstructed track)

11. Systematics Of the Filter
Energy Dependence
Muon Multiplicity
Degree Of Misreconstruction

12. Mis-Reconstructed Muon
0 degree
2 degree
Notice the loss in signal as
we go from 0 to 5 degree point
Spread misreconstruction
5 degree
Cut these out
Misreconstructed single high energy muon are lost in this filter,there is a need to ensure high angular resolution for this method to work optimally
EarlyHits

13. Muon Multiplicity Cut these Earlyhits 10-25 25-50 2 3 4-10
The filter and the method works
better when there are more muons
Cut these
Earlyhits

14. Energy Dependence Signal Background Cut these Earlyhits Earlyhits
Nhits
At higher energies
We get rid of more background
while not loosing any signal
Cut these
Cut these
Earlyhits
Earlyhits

15. ENERGY LOSS There are two kinds of processes: Continuous: ionization
Energy loss vs. muon energy:
There are two kinds of processes:
Continuous: ionization
Stochastic: Pair production, bremstrahlung, photonuclear interactions
Above the critical energy (600 GeV in water) stochastic losses dominate.
Very important that this plot only shows the average muon energy loss and no mention of fluctuations

16. Multiple Muon Event

17. Single Muon Event The Amplitude in the PMT’S
In general saturates well below
this limit (the peaks appear compressed
When seen through the adc channel)
Largest Shot (Energy Release)
Still belongs to Single muon

18. NEW ESTIMATORS y = σ B/<B>
An estimator1 is defined, based on a comparison between the light produced by the muon and the light it would have produced if it was a minimum Ionizing muon:
An estimator2 is derived from estimator 1 and is
y = σ B/<B>
B=Number of Observed Photon/Number of Photons expected from MIM

19. Ice Properties
Ice properties themselves introduce some fluctuations into the observed amplitude
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!!!)

20. Reconstruction Errors
True track
Large Amplitude Seen when lower is
expected from reco track hypothesis B
Dust Δθ
Reco Track
Clear Ice A
Dust
Small Amplitude Seen when large is expected from reco track hypothesis

21. HIT AND EVENT SELECTION
To overcome some of these problems partly
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)
Require the event to have at least 6 direct hits(more direct hits means
more information to study the fluctuations )
Criteria on Track length and chi square to improve reconstruction quality
Take only hits with amplitude greater 3.0 P.E for reconstruction.
(No noise hits which will introduce some systematic fluctuations)

22. SIGNAL-BACKGROUND DISTRIBUTIONS
Singles
Multiples
Keep
These
y = σ B/<B>
y = σ B/<B>
Linear scale
Log scale
Done with Reconstructed track(Con Pandel)

23. SIGNAL-BACKGROUND DISTRIBUTIONS
Singles
Multiples
Keep
These
y = σ B/<B>
y = σ B/<B>
Lin scale
Log scale
Done with true track

24. SIGNAL-BACKGROUND DISTRIBUTIONS
Singles
When all hits are chosen
notice what happens?
Any possible separation of
signal and background through
this parameter is masked out
by the fluctuations of ice
properties
Multiples
Keep
These
y = σ B/<B>
Done with all hits (not just direct hits)

25. SYSTEMATICS Multiplicity Energy y = σ B/<B> y = σ B/<B>
2 muon
Nhits( )
3 muon
Nhits( )
5 muon
Nhits( )
5-10 muon
Nhits( )
10-25 muon
Nhits( )
Very Little
Correlation ?
Nhits( )
No correlation
Cut these
Cut these
y = σ B/<B>
y = σ B/<B>