Error handling if solving eigenvalue equation fails

[ktht]

A handful of jobs failed because of this line:

tautau-Entanglement/interface/comp_EigenVectors_and_EigenValues.h

Line 47 in d62fb80

EigenVectors = tmp.EigenVectors(EigenValues);

when calculating Rchsh. Although it's supposed to be caught whenever an exception is thrown, in practice it can trigger this line, which is delegated to signal handler. The only solution would be to ignore erros by setting gErrorAbortLevel to kBreak here:

tautau-Entanglement/bin/analyzeEntanglementNtuple.cc

Line 85 in d62fb80

gErrorAbortLevel = kError;

But then this line will cause issues:

tautau-Entanglement/interface/comp_EigenVectors_and_EigenValues.h

Line 52 in d62fb80

return std::vector<std::pair<TVectorD, double>>();

which causes all results to be nans.

I've only noticed this error when running the jobs on a subset of events (1M). It's not clear yet if it'll persist when processing the full sample. Interestingly, the only jobs that failed with this particular error are pi_a1 in startPos mode when the cut on $\cos\theta^*$ is quite relaxed.

[ktht]

So the error still persisted even after processing the full sample (of 200M events). All jobs that failed are running in startPos mode and either in rho+a1 or pi+a1 decay mode (but the former happened four times as frequently). Half of the failed jobs ran ML fit while the other half ran the summation method. Fortunately, we don't necessarily need those results for the publication.