Minos +ve /-ve error is giving zero

Dear Experts,

I am doing a fit with Minos. One parameter is showing a -ve Error at zero but my fitter show status successful. Is there any way to fix the negative error not to zero but a physical value?

Many thanks
Chandi

Hi,

Minos can fail also when your normal minimization (e.g. Migrad) works fine. The function for example could have some problematic behavior in a region at around 1 sigma from the minimum and this could cause Minos to fail and return a zero error. A scan of the function or the profiled one, could help understand the problem.
What exactly error message are you getting from Minos ?

Lorenzo

Hi @moneta
Many thanks.

I am attaching here a code which will help to understand the problem.

This is the fitter output, where you can see the status is successful but parameter 1 -ve error hitting the limit.
totalpdftoyprofile.cc (4.6 KB)

FCN=-8.17055 FROM MINOS STATUS=SUCCESSFUL 105 CALLS 1349 TOTAL
EDM=3.23899e-06 STRATEGY= 1 ERROR MATRIX ACCURATE
EXT PARAMETER PARABOLIC MINOS ERRORS
NO. NAME VALUE ERROR NEGATIVE POSITIVE
1 B1 4.24976e-07 6.06018e-01 at limit 3.04669e-01
2 Nsig 3.16763e+00 1.96455e+00 -1.71155e+00 2.37656e+00
3 Tau 1.34629e+00 7.71188e-01 -5.56776e-01 1.30872e+00
4 TauBkg2 1.61210e+00 7.71357e-01 -5.72048e-01 1.21308e+00
5 nbd1 1.16724e+00 1.99325e-01 -2.00018e-01 1.99879e-01
6 nbkg 4.78941e+00 2.35457e+00 -2.00951e+00 2.79110e+00
7 nsemi 6.32231e+00 1.54070e+00 -1.49719e+00 1.59716e+00

Do you mean if the status of minos is successful, the minos minimization is failed?

Many thanks again.
Best
Chandi

Hi,
What you are getting is normal. Your parameter value for B1 is almost zero, at the limit, so there is no Minos negative error.

Lorenzo

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.