cosmogenic background to nucleon decay

COSMOGENIC BACKGROUND TO NUCLEON

DECAYMatt RobinsonKarl Warburton

Vitaly KudryavtsevElena Korolkova

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Matt Robinson, Vitaly Kudryavtsev, Karl Warburton, Elena Korolkova

DATA• Target of 109 muons simulated now reached and

surpassed. Just over 2x109 now produced. Copies on LHC grid (LFN:/dune/user/m/matthew.robinson/mctruth/), at FNAL (/pnfs/dune/persistent/musun/mctruth) and at Sheffield.

• Small amount of grid enabled storage at Sheffield used to buffer data was sufficient as it was being continuously downloaded and deleted as jobs finished.

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ANALYSIS• Analysis runs through sim::IDE objects (idealised “Hits” from

geant4) and separates out energy depositions resulting from charged Kaon interactions, secondaries, decay products and from interactions not associated with a charged Kaon.

• Only events where a single charged Kaon appears in the detector are considered background.

• Limits of a likely real detector not properly accounted for in this approach. Likely to represent an optimal limit in what can be done.

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ANALYSIS• “Near” energy now being accounted for as in Karl’s analysis.

• Analysis module completely rewritten as it was getting rather too ugly.

• Same background event revealed with new analysis, plus one additional event from the second 109 events.

• Need to decide how to handle “near” energy in final analysis. Karl’s GENIE data will help with this.

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Charged Kaon Spectrum, 2x109 filtered muons

x=energy from kaon and secondaries


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“Near” Energy Spectrum, 2x109 filtered muons


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Proton Decay Background Candidates

y=energy from kaon and secondariesx=all other event energy including “near” but not “decay”.


NEAR ENERGY AND BACKGROUND EVENTS• Background event at

• enear = 0 MeV• kaon+secondaries = 172 MeV• other (without near) = 2.5 MeV• kaon+secondaries+enear = 172 MeV

• Background event at • enear = 0.35 MeV• kaon+secondaries = 114 MeV• other (without near) = 17 MeV• kaon+secondaries+enear = 114 MeV

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• As “Near” energy is zero in first background event it does not appear in a log plot where enear is an axis.


"Near" energy [MeV]1−10 1 10 210 310 410

ene

rgy

depo

sitio

n (in

cludi

ng s

econ

darie

s) [M

eV]

+/-

K

1

10

210

310

410 All single kaons (4985)Passing Muon cut (2477)Passing Fiducial cut (10)Inside Energy ROI (2)

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Kaon Energy vs “Near” Energy, 2x109 filtered muons


Other energy excluding "Near" [MeV]1 10 210 310 410 510

ene

rgy

depo

sitio

n (in

clud

ing

seco

ndar

ies)

[MeV

]+/

-K

1

10

210

310


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Kaon Energy vs Other energy excluding “Near”, 2x109 filtered muons


Other energy excluding "Near" [MeV]1 10 210 310 410 510

+ "N

ear"

ener

gy d

epos

ition

[MeV

]+/

-K

1

10

210

310


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Kaon + “Near” Energy vs Other Energy, 2x109 filtered muons


PRE-RECONSTRUCTION FILTER• Second filter to apply before hit reconstruction

has been finalised.Cuts events with Etotal > 3 GeV, Etotal < 10 MeV, and with energy within 10 cm of edges > 5 MeV.

• 106 muons reconstructed, 17402 passing original (muon track length) filter and of those 2310 (13% or 0.23% muons).

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HIT RECONSTRUCTION

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• Hit reconstruction, after various problems arising from collapse of IC dirac system, change in dependencies between larsoft v5 and v6 (redhat-lsb-core) and various other issues, now progressing well.

• Will not have full data set, but should have some plots for FDTF. Expecting first 109 by the end of the week.


CONCLUSIONS• Initial production phase finally complete with 2x109 muons

simulated.

• Filter finalised and hit reconstruction tested.

• Hit reconstruction progressing (finally). First 109 by the end of the week (hopefully).

• “Near” energy now being considered.

• Need to look at GENIE data and other information to improve identification of likely background events.

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• K0L produced outside detector


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• K0L converts to K+ well inside active volume• No hits from K0 so looks like proton decay


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• K+ decays as expected, pi+ produced


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• pi+ eventually decays to very low energy mu+


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K0L in from side, 168 MeV

K+, 109 MeV

pi+, 110 MeV

p, 52 MeV

Various gammas

SECOND BACKGROUND CANDIDATE

cosmogenic background to nucleon decay

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