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

Backgrounds Conventional Atmospheric dF/dE E-3.7

Conventional Atmospheric n from decay of ( , K ) dF/dE E-3.7

Possible nm components from decay of atmospheric charmed particles. dF/dE E-2.7

Uncertainty in Prompt Lepton Cross Sections The uncertainty~3 orders

Need for accelerator data extrapolation

Crossover between 40TeV and 3 PeVZhVd

Neutrino Vs Muon Fluxes

Analysis Description

Signal Simulation Single with an assumed energy spectrum of prompt (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

Levels (L2 is the standard minimum bias data)

Zenith Angle(L3)

Event Quality Related(L4)

Topology(single muon and a bundle of muons)(L5)Early Hit(Topology1)dE/dX method(Topology2)

Energy(L6)

Strategies for separation of Signal from Background

Zenith distribution(L3)True trackReco TrackCos(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

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(

Muon Bundleslog10(energy at cpd) GeV SinglesMultiplesSignal

The multiple muon background goes with same slope as the signal

Need to improve the sensitivityOf our instrument to prompt muon

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 )Muon1The hit at B is earlier by time length(AB)/cice

CD

Topology 1(Eview Earlyhits)EarlyhitAmplitude>3pe (proximity cut)(Noise Hits suppressed)

Distance

Time Residuals and Convoluted Pandel Time delay(16 PPandel)Time delay(64 CPandel)Excess Earlyhits in MCDataBG MC

Muon MultiplicityTrue Track(Ideal)Result (Reco Track) Filtering Efficiency(Topology 1)

Topology 2 (Energy Deposition dE/dX)(L5)

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 = B/

Filtering Efficiency(L5)Result (Reco track)True track(Ideal)y = B/y = B/Cut these outCut these outSignalBG

Energy Cut(L6)Nhits(Energy Observable)2001 exp data2001 signal(RPQM)+BGBGSignalIntegral SpectraData DescriptionAvg Upper limit 0% sys)10% sys

(20% sys)

(30% sys)

(40% sys)

Best Cut Nhit=310,Signal=9.4,B.G=6MRF=0.7(30%SYS) MRFData 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(preliminary)

Nhits(Energy Observable)

Constraining Charm Neutrino models by analysis of downgoing Muon Data A Restrictive limit means enhance sensitivity to diffuse neutrinosAMANDA II(muons)

ZHVd

BACK UP SLIDES

Energy CorrelationNumber of Hits Vs log10(energy at cpd) GeV

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 hitsLess than 3.0P.E hitsPerpendicular distance from reconstructed track for BGMC muons(m)GoodhitsRandom Hits~10 timesgreaterAmplitude-Perpendicular distance to the Hit spacet

DustDustClear IceReconstructed track in dataTrue trackGeometrical EffectReconstructed track in simulationThe 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. Leverarm(AB)*

AB

Filtering Efficiency(L5)Done with all hits (not just direct hits)

SinglesMultiplesKeepTheseWhen all hits are chosen notice what happens?

Any possible separation of S-Bis destroyed by the fluctuationof ice properties

Amplitude-Time Residual space

Amplitude(P.E)Amplitude(P.E)DataBackgroundDataBackgroundA 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 theseR2

Ice PropertiesIce 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!!!)

DustDustClear IceTrue trackABReco TrackLarge Amplitude Seen when lower is expected from reco track hypothesisSmall Amplitude Seen when large is expected from reco track hypothesis

Reconstruction Errors

Data Agreement(16fold-ppandel)Number of HitsDataB.GSignalThe 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