Requests for Online Vertical Event Filter (VEF)
Name: Jan Kunnen
Email: kunnen.jan@gmail.com Physics working group : wimp-wg
Physics working group leader and email : Carlos de los Heros (cph@fysast.uu.se), Carsten Rott (carsten.rott@gmail.com)
Overview
The Vertical Event Filter (VEF) is designed to select low energy (~10-500 GeV), vertically upgoing events. These are the events of interest in Earth WIMP searches and neutrino oscillation analyses. The filter selects STRING triggered events that are
reconstructed as upgoing, and uses the top 5 DOM layer as a veto, in order to reduce the number of misreconstructed, downgoing background events.
Though this relaxation doubles the total rate (from ~4 Hz to ~9 Hz, see table 1); this total rate is still relatively low. Also the fact that it is alright to pass the data in sDST format makes the requested bandwidth lower.
As a last remark, it should be pointed out that the filter didn’t change w.r.t. last year.
Physics Motivation
The VEF has two main physics motivations :
1. Earth WIMPs will annihilate and neutrinos will be produced in the decay of the annihilation products. The produced neutrinos will thus come from the center of the Earth and so they will be vertically up- going. Since the filter has been designed to collect low energy neutrinos (~10 - 500 GeV), the VEF is essential for the sensitivity of IceCube to the lower mass Earth WIMPs.
2. The fillter has a low enough energy reach to be sensitive to standard atmospheric neutrino oscillations. One expects a significant deficit in the up-going near-vertical νμ flux around 25GeV [3].
Filter Rates
The files that were used are :
MinBias data : /net/user/blaufuss/IC86_2_MinBias/MinBiasJuly01-?.i3.bz2
CORSIKA : /data/sim/IceCube/2011/generated/CORSIKA-in-ice/8859/00000- 00999/IC86.2011_corsika.008859.00000?.i3.bz2
Signal : /data/sim/IceCube/2011/generated/neutrino-generator/8644/00000- 00999/nugen_numu_IC86.2011.008644.*.i3.bz2
Only events with the following conditions were selected as signal : 1. Primary neutrino energy < 500 GeV
2. Primary neutrino zenith < 2.96 radians
Single String Multiple Strings
Minbias Rate (Hz) 4.15 9.14
Corsika Rate (Hz) 3.92 8.65
Signale Efficiency (%) See figure 1
Table 1 : rates and efficiencies for the Vertical Event Filter
The efficiency of VEF for signal is shown on the plot below. The efficiency is calculated as
so an efficiency of 1 would mean that all the signal events are selected by the filter
Figure 1 efficiencies of the Vertical Event Filter
Description of Filter
The filter only uses keys that are provided in the 2013 base processing script
def VEFFilter(tray, name, pulses='RecoPulses' ,singlestring = False, If=lambda f: True):
"""
This tray segment is the Vertical Event Filter segment.
"""
icetray.load("filter-2013",False)
tray.AddModule("I3FilterModule<I3VEFFilter_13>", name+"_VEFFilter", TriggerEvalList = [filter_globals.inicestringtriggered],
DecisionName = filter_globals.VEFFilter, LinefitCut = 1.2,
PoleMuonLlhFit = filter_globals.muon_llhfit, PoleMuonLinefit = filter_globals.muon_linefit, MuonLlhCut = 2.5,
DiscardEvents = False, TopLayerDOMCut = 5, RecoPulsesKey = pulses,
SingleStringRequirement = singlestring, If = If
)
In the above traysegment, 2 new names were introduced :
VEFFilter = 'VEFFilter_13'
RecoPulses = filter_globals.CleanedMuonPulses = 'CleanedMuonPulses'
Note the parameter : SingleStringRequirement = False. This is the only tunable parameter.
The filter scripts can be found add :
http://code.icecube.wisc.edu/svn/projects/filter-2013/branches/vef/
Requested bandwidth
GB/day = 86400 x (782 + 172 x < hlc >) x passing rate x 10-9 / 1.28 = 86400 x (782 + 172 x 9.5) x 10 x 10-9 / 1.28
= 1.63 GB/day
where <hlc> has been calculated by using the IC86 MinBias data files mentioned in section 1 and the passing rate in these files is ~10Hz.
A reduction of data rate of approximately 2 fold is possible by setting SingleStringRequirement = True.
As was already mentioned, the fact that it is alright to pass the data in sDST format makes the requested bandwidth lower.
References
[1] 2011 Vertical Event Filter Proposol, James Davis
https://docushare.icecube.wisc.edu/dsweb/Get/Document-56551/VEFproposal.pdf [2] The 2013filter baseprocessing script
http://code.icecube.wisc.edu/svn/projects/filter-2013/trunk/python/baseproc.py [3] ICRC2011-Atmospheric neutrino oscillations with DeepCore [ArXiv:1111.2731]
Appendix : Some more plots
Some plots to compare data (left plots) and corsika (right plots) before (black) and after (red) VEF selection
