MINOS: Invalid lower/upper error for parameter

Roofit and RooStats
1

Dear Experts,
can you please explain to me exactly what it means:

Minos: Invalid lower error for parameter AfbS
Minos: Lower error for parameter AfbS : -188.474
Minos: Invalid upper error for parameter AfbS
Minos: Upper error for parameter AfbS : 188.474

What does it mean “Invalid lower/upper error for parameter …” ?
Please, feel free to go into the details.
I need to thoroughly understand the origin of this message.

Many thanks,

  • Mauro.
2

Hi Mauro,

This means that the minimisation of the likelihood in N-1 parameters failed when running Minos. The returned error should be the parabolic error from the Hessian matrix.
It could be caused by a numerical error in the likelihood function or some intrinsic instability of the obtained fit
(e.g. very correlated parameters)

Best Regards

Lorenzo