Km3 v4r5 and the OPA

C.W.James, AWG meeting 30 Nov 2012

Development version of km3: v4r5

• Changes from v4r4 (see Bologna presentation)

- Use of Nautilus glass- Couple of minor ‘bug’ fixes (no real effect expected)- Aug25 angular acceptance now standard (not

included in official v4r4 release)- Improved version of OPA should be working properly.

• Topics for today:- Show Nautilus glass- Show current v4r5 response to numu_CC events- Discuss OPA- Discuss scattering/absorption

C.W.James, AWG telecon, 30th Nov 2012 2

Benthos Nautilus glass

• It turns out that km3 has been using Benthos glass – which was the right thing to do, back in 1998…

- Glass absorbs photons- important in modelling the optical modules.- Measurements from: ANTARES-OM-98-1

- Mistake found using comparisons with Heide’s simulations for angular efficiency

Original numbers lost to time!

C.W.James, AWG telecon, 30th Nov 2012 3

Comparison of v4r5 to rbr v2

• 40 runs, all numu_CC and anumu_CC events – cumulative distribution. Decrease due to

- angular acceptance changes- gen being placed in seawater

C.W.James, AWG telecon, 30th Nov 2012 4

Comparison of v4r5 to rbr v2

• Ratio: relative decrease wrt run-by-run v2- (all three use august 2012 angular acceptance)

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Good news!

• The simulations are no longer getting any worse! (or at least, not by very much)

• Planned release version of v4r5 (this afternoon?) predicts the same number of muons of neutrino origin as v4r4

- (perhaps very slight decrease due to Nautilus glass?)

C.W.James, AWG telecon, 30th Nov 2012 6

Part 4: Preliminary OPA results(work by M. Dentler)

C.W.James, AWG telecon, 30th Nov 2012 7

One-particle approximation (OPA)

• Principles:

• Can not account for changes in shower shape.• Use gen to run pion showers and compare photon

yields

W-/W+/Z0

q

νl

q

l/νlM. Spurio, 2008

C.W.James, AWG telecon, 30th Nov 2012 8

Preliminary results from OPA investigation• Work finished; 95% of analysis finished; 50% of

‘pretty pictures’ finished.• Shower shape ‘important’ out to ~10m distance, • Pion weights: should be O~100% above 10 GeV

C.W.James, AWG telecon, 30th Nov 2012 9

Fit

• A rather complex function…- Fit log10[number of photons at shell 15] as a function

of pion energy

- Normalise to the number of photons from an electron at energy Ee (proportional to Ee)

- Invert:

C.W.James, AWG telecon, 30th Nov 2012 10

Implementation in km3mc

• In km3: use:- INOPA 1- Converts pion energy:

• Do not call GEASIM - ever

Calls OPA only if the particle is NOT a muon

Adds momentum to calculate the mean shower axis

Gets OPA weights

C.W.James, AWG telecon, 30th Nov 2012 11

OPA Weights

• Weight = 1 for e+-, gamma, pi0, some kaons

• Weight = [complex formula] if pi+-

• Weight = 0 otherwise

C.W.James, AWG telecon, 30th Nov 2012 12

Should we use the OPA?

• Comparison by Mona:- Run full pion shower- Run electron cascade of original OPA energy (constant

weight 0.2)- Run electron cascade of new OPA energy (variable

weight)- Run pion shower, but only include direct photons

• Compare number of photons incident at each shell. What do we get?

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Should we use the OPA?

• 35 m

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Should we use the OPA?

• 4m – shower shape effect

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Should we use the OPA?

• 8m – it’s fine

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Rbr results…• (sadly, still in the queue)

• Plan to use dusj shower reco as a test of the OPA in rbr scripts

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Discussion on scattering/absorption

[insert discussion here]

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