A Novel Tau Signature in Neutrino Telescopes
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August 29, 2006 Tyce DeYoung, Doug Cowen, Soeb Razzaque A Novel Tau Signature in Neutrino Telescopes 2 nd Workshop on TeV Particle Astrophysics Madison, Wisconsin (astro-ph/0608486)
description
A Novel Tau Signature in Neutrino Telescopes. (astro-ph/0608486). 2 nd Workshop on TeV Particle Astrophysics Madison, Wisconsin. Classic Tau Signature. “Double Bang” Learned & Pakvasa 1995 ν N interaction Tau lepton track ~50 m/PeV (neglecting energy loss) - PowerPoint PPT Presentation
Transcript of A Novel Tau Signature in Neutrino Telescopes
August 29, 2006
Tyce DeYoung, Doug Cowen, Soeb Razzaque
A Novel Tau Signature in Neutrino Telescopes
2nd Workshop on TeV Particle AstrophysicsMadison, Wisconsin
(astro-ph/0608486)
August 29, 2006TeV Astro II
Classic Tau SignatureClassic Tau Signature
“Double Bang”Learned & Pakvasa 1995
νN interaction
Tau lepton track ~50 m/PeV
(neglecting energy loss)
Tau decay
August 29, 2006TeV Astro II
Windows for Flavor IDWindows for Flavor ID
(supernovæ) showers vs. tracks
full flavor ID
Neutrino flavor
e
Log(ENERGY/eV)
12 18156 219
e
double bang
August 29, 2006TeV Astro II
Alternative SignatureAlternative Signature
“Lollipop” – half of a double bangBeacom, Bell, Hooper, Pakvasa & Weiler
Relatively dim track
Stops in a big cascade(starting tracks dominated by BG)
August 29, 2006TeV Astro II
Tau Decay ModesTau Decay Modes
Decay mode Branching fraction
• τ → ντ + e + νe 17.8%
• τ → ντ + X (hadronic) ~65%
• τ → ντ + μ + νμ 17.4%
double bang /lollipop
August 29, 2006TeV Astro II
Energy LossesEnergy Losses
Edx
dE
ionization stochastic losses
Particles are detected in neutrino telescopes through energy deposited in the detector
Stochastic energy loss mechanisms:
• Bremsstrahlung• pair production• Photonuclear interactions
ee
Muons are brighter than taus
τ
μ
→ track suddenly brightensCan we see it?
(D. Cowen)
August 29, 2006TeV Astro II
Muonic Tau DecayMuonic Tau Decay
τ → ντ + μ + νμ
Muon energy spectrum in the lab frame:
where
Average muon energy
E
Ex
5943
1 23 xxdx
dn
EE 35.0
(Perl 1992)
August 29, 2006TeV Astro II
dE/dx Flavor DependencedE/dx Flavor Dependence
Muons lose energy by pair production & brems
Taus lose a lot in photonuclear interactionsμ τ
Dutta, Reno, Sarcevic, and Seckel
August 29, 2006TeV Astro II
Photonuclear Loss Models
Photonuclear Loss Models
Depend on parton density f’ns, nuclear shadowing
August 29, 2006TeV Astro II
Energy Loss MechanismsEnergy Loss Mechanisms
Bremsstrahlung
Pair production
Photonuclear interactions
ll
ll
ll
γ
e+
e-
hadronicshower
( = μ,τ)l
EMshowers
August 29, 2006TeV Astro II
Hadronic Light YieldHadronic Light Yield
Hadronic showers emit 65-85% of the light of an electromagnetic shower of the same energy
M. Kowalski
August 29, 2006TeV Astro II
Put It All TogetherPut It All Together
• Fraction of tau energy carried by muon
• Relative energy loss rates for tau, muon– dE/dx roughly 7x higher for muon than for
tau, at fixed lepton energy
• Relative light yields for photonuclear energy loss vs. bremsstrahlung, pair production– Flat ratio of 75% assumed
35.0 EE
August 29, 2006TeV Astro II
Brightness RatioBrightness Ratio
typical neutrinotelescope
trackenergy
resolutionσ(log10 E) ≈ 0.3
track length
August 29, 2006TeV Astro II
Low Energy Taus?Low Energy Taus?
• 1 TeV tau “track:” 5 cm Impossible!
ντ → τ + X μ + νμ + ντ
• Two neutrinos take 2/3 the energy → dim track
• Compare energy of hadronic shower to energy of muon track?
Need to worry about NC/νe background!
MC studies in progress…
(suggestion John Beacom)
August 29, 2006TeV Astro II
Tagging Low Energy Taus?
Tagging Low Energy Taus?
Eshower
Etr
ac
k
NC and νe
ντ?νμ CC
