aspen workshop april 2007
DESCRIPTION
Upper limit on the upward-going electron-neutrino flux from the HiRes Instrument Lauren M. Scott Postdoctoral Research Associate Rutgers, the State University of New Jersey. Aspen Workshop April 2007. Outline. Motivation for looking at ν e (instead of ν μ ) - PowerPoint PPT PresentationTRANSCRIPT
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Aspen Workshop
April 2007
Upper limit on the upward-going Upper limit on the upward-going electron-neutrino flux from the HiRes Instrumentelectron-neutrino flux from the HiRes Instrument
Lauren M. ScottLauren M. ScottPostdoctoral Research AssociatePostdoctoral Research Associate
Rutgers, the State University of New JerseyRutgers, the State University of New Jersey
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Aspen Workshop
April 2007
• Motivation for looking at νe (instead of νμ)
• The search for upward-going events in the HiRes-II data.
• Landau-Pomeranchuk-Migdal effect.
• Monte-Carlo technique for modeling HiRes detector response to νe.
• Upper limit on the flux of upward-going νe and ντ
(and comparison with other experiments / theoretical limits).
• Uncertainties / assumptions.
OutlineOutline
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Aspen Workshop
April 2007
Why electron-neutrino-inducedWhy electron-neutrino-inducedshowers?showers?
• At HiRes energies (>1018 eV), interaction cross sections are high. Earth-skimming events pass through enough material. σ ≈ 10-32 cm2 (1018 eV), 10-31 cm2 (1021 eV)
• Landau-Pomeranchuk-Migdal effect bremsstrahlung, pair-production cross sections are suppressed e- (cc) : ELPM = 6 ×1014 eV (rock) ELPM = 2 ×1018 eV (air, desert floor)
LPM threshold is much higher for νμ and ντ.
• Large target volume, interactions occurring deep in the earth will be detectable at the surface.
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Aspen Workshop
April 2007
Search for upward-going showersSearch for upward-going showers
Expect events to• have small elevation angles• have long tracks• be detected mostly in the HiRes-II lower-ring mirrors (elevation from 3○ to 17○)
Summer 2006 upward-going neutrino searchmost likely candidates “up/down” cosmic-ray events
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Aspen Workshop
April 2007
Modeling the LPM effectModeling the LPM effect
for a full Monte Carlo detector simulation, must model• energy- and depth-dependence of the LPM effect• energy spectrum of particles as a function of depth• LPM effect in air for high-energy events.
Stanev, Vankov, Streitmatter, Ellsworth and Bowen, Phys. Rev. D., 1982
Kim, K. PhD Thesis, Univ. of Utah, 2002
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Aspen Workshop
April 2007
Modeling the LPM effectModeling the LPM effect
1018, 1019, 1020, 1021 eV
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Modeling the LPM effectModeling the LPM effectin rockin rock
Aspen WorkshopApril 2007
0
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K. Greisen, Progress in Cosmic Ray Physics vol. 3, 1956
Open circles : Greisen functional formClosed circles : LPM
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Aspen Workshop
April 2007
0
00
2/10
0
2
3
ln
ln2
31exp
31.0),(
t
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E
sttEN
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Modeling the LPM effectModeling the LPM effectin airin air
K. Greisen, Progress in Cosmic Ray Physics vol. 3, 1956
Open circles : Greisen functional formClosed circles : LPM
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Aspen Workshop
April 2007
Modeling the LPM effectModeling the LPM effect
Airshower from a 1020 eVelectron entering air at 50,000 g/cm2 is a super-position of air showers fromNe in each energy bin.
E0 = 1020 eVspectrum @50 kg/cm2
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Aspen Workshop
April 2007
Monte Carlo TechniqueMonte Carlo Technique
• Flat distribution of neutrino energies in log(E).• Isotropic upward-going events.• 70% CC events / 30% NC events (from ratio of cross sections)• Each event, interpolate depth in rock that gives Nmax = 107 in air.• CC : superpose LPM airshower from spectrum at point of exit from earth• NC : GH profile, unchanged from rock into air• Calculate εINTER and εINTER.• Force neutrino to interact along “interaction length.”• Run through full detector trigger simulation routine (mcru)• Find geometry, plane-fitting for events that pass trigger (rufpln)
εINTER
εTRANS
HR-II
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Aspen Workshop
April 2007
Typical MC eventTypical MC event
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Aspen Workshop
April 2007
MC : event by eventMC : event by event(deepest)(deepest)
Compare to1018 : 40 m1019 : 100 m1020 : 300 m1021 : 1200 m
Baltrusaitis et al.,Phys. Rev. D 31, 1985
Depth ~ E0.6
Open circles : Fly’s EyeClosed circles : this work
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Aspen Workshop
April 2007
HiRes-II HiRes-II ννee aperture aperture
2.1EA
thrown
intertrans
0
accep
i
N
jjj
Ei NAA
ti
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Aspen Workshop
April 2007
Dotted line: Gelmini et al., 2007.Dashed line: Semikoz & Sigl, 2004.
HiRes-II HiRes-II ννee flux limit flux limit
2.2 EdE
dN• 2.3 events over entire energy range (90% CL)
• livetime = 3638 hours
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Aspen Workshop
April 2007
Dotted line: Gelmini et al., 2007. Red : νe Black : νe + ντ Dashed line: Semikoz & Sigl, 2004. Blue : ντ
Upper limit on the flux of Upper limit on the flux of ννee and and ννττ (C.L. 90%)(C.L. 90%)
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Aspen Workshop
April 2007
SystematicsSystematics
• Uncertainty associated with cross sections (this work: pQCD CTEQ5 parameterization)
Gazizov & Kowalski, Comp. Phys. Comm, 2005.
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Aspen Workshop
April 2007
SystematicsSystematics
• Uncertainty associated with cross sections (this work: pQCD CTEQ5 parameterization).
• LPM threshold in air increases with altitude (this work: desert floor).
1018 eV• desert• 5 km• 10 km• 15 km
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Aspen Workshop
April 2007
SystematicsSystematics
1019 eV• desert• 5 km• 10 km• 15 km
• Uncertainty associated with cross sections (this work: pQCD CTEQ5 parameterization).
• LPM threshold in air increases with altitude (this work: desert floor).
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Aspen Workshop
April 2007
SystematicsSystematics
1020 eV• desert• 5 km• 10 km• 15 km
• Uncertainty associated with cross sections (this work: pQCD CTEQ5 parameterization).
• LPM threshold in air increases with altitude (this work: desert floor).
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Aspen Workshop
April 2007
SystematicsSystematics
• Large systematic uncertainty associated with cross sections (this work: pQCD CTEQ5 parameterization).
• LPM threshold in air increases with altitude (this work: desert floor).
1021 eV• desert• 5 km• 10 km• 15 km
Adjusting air showersfor altitude-dependenceof LPM effect will raisethe limit somewhat
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Aspen Workshop
April 2007
Monte Carlo TechniqueMonte Carlo Technique
1018 eV
1019 eV
1020 eV
1021 eV
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Aspen Workshop
April 2007
Closed circles : Fraction of CC events whose trajectories pass through the earth.Open circles : Fraction of MC events whose trajectories only pass through the air.
MC : event by eventMC : event by event(earth-skimming)(earth-skimming)
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Aspen Workshop
April 2007
MC : event by eventMC : event by event(furthest away)(furthest away)
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Aspen Workshop
April 2007