K2K OD Event Official Plots

Please send suggestions, comments, complaints to schol@budoe.bu.edu

Event Selection Information

nomenclature.eps is a cartoon showing OD event topologies for explanation purposes. Blue arrows represent events detected as FC; green arrows represent events detected as OD-contained (ODC); and red arrows represent events detected as crossing.

The following three plots show the effect of cuts on beam MC and background. The beam MC is Nuance, and the background sample is taken from a random subrun.

For all plots, only events classificed as "OD" (nhitac>10, the standard atmpd PC criterion) are shown. In all cases, the shaded regions indicate events which are kept. The green-outline unshaded regions show events that are rejected.

• qismsk_cut.ps, qismsk_cut.eps: These show distributions of qismsk, the total ID charge in photoelectrons. High charge events are rejected. Note the different scales on the x-axis for MC and background.
• odclust_cut.ps, odclust_cut.ps: These show distributions of the number of OD clusters according the clustering algorithm ("super_cluster", a modified version of the atmpd PC2 clustering algorithm).
• nodintgood_cut.ps, nodintgood_cut.eps: These show distributions of the number of good intime tubes. "Intime" means in a sliding 500 ns time window where the number of hits is maximized. Note the different scales on the x-axis for MC and background.

K2K OD Event Summary: June 1999 to March 2000

• Page 1: list of cuts
• Page 2: list of event classification criteria
• Page 3: numbers of events of each class found, and expected numbers of background

For more detailed information, see the reports at http://hep.bu.edu/~schol/k2k/od/.

Some particular notes on the predictions:

• The details of the calculation can be found at: http://hep.bu.edu/~schol/k2k/od/expected_calc/.
• The systematic uncertainty on the ODC and crossing rates is dominated by the uncertainty on the ODC/FC and crossing/FC ratio, which depends mostly on detector simulation of light in the OD. This uncertainty was estimated using data and MC for two atmospheric neutrino samples: PC events (exiting) and upward stopping muons (entering), by examining differences in efficiency around the cut value for the number of good intime tubes cut. The same uncertainties apply to the oscillated values. Note that the systematic error is still under study.

Time Difference Distributions

june99-mar00.eps, june99-mar00.eps show distributions of time differences between the event time and the beam time, in microseconds. Three time scales are shown.

The cut is -0.2 to 1.3 microsecs to be considered inside the beam window. (note that this is different from the previous cut).

june99-mar00-5us.ps, june99-mar00-5us.eps show the same on +/- 5 microsec scale, vertical scale to match FC plot. Shaded histo represents crossers.

tdiff_cuts.ps, tdiff_cuts.eps show the time difference distribution for all events, with each of the cuts applied sequentially, for the June-Mar period. The line labeled "Events passing cuts 1,2" is really two lines, very close together (because these two cuts-- the qismsk cut and the od cluster cut -- are highly correlated). The shaded histogram is the final OD sample after all 3 cuts.

xypos_jun99-mar00.ps, xzpos_jun99-mar00.ps show positions of the OD events in two views. For the crossers, the position is the fit vertex. For the ODC events, the position is at the highest charge OD cluster position (for zero p.e. threshold clustering). The "lower" ODC positions have z<0, the "upper" ones have z>0. (Note that since cluster positions coincide with tube positions, events can "overlap" in these pictures). (I will add direction arrows to these).

OD Candidates

The events subdirectory has superscan event displays of all of the candidates found, named runxxxxxx_yyy_zzzzzzzzzz.eps, where xxxx is the run number and yyy is the subrun number and zz is the event number.

The file events/event_info_jun99-mar00.txt has information for each event, including reconstructed information for crossers.