SCIENTIFIC DATA ANALYSIS LABORATORY (a. a. 2021-2022)

Laurea Magistrale / Year-II / Semester-I

Professor: Alexis Pompili

Program/Syllabus of the course

Suggested textbooks for the theoretical part of the course:
- Cowan (ediz. 1998)
- Lista (ediz. 2020)
- Metzger (ediz. 2010)

Copyright: all the material of this course could be used only under permission of the author
        (pompili AT ba.infn.it) and with proper acknowledgment.

In order to connect to the virtual machine hosted at ReCas and dedicated to the course ("pompilicorso"):
- from a Unix/Linux machine : ssh -Y [username]@90.147.75.45
- from a Windows (10) machine you need to freely download (from https://sourceforge.net) :
  Xming X Server for Windows and /Xming-fonts/7.7.0.10 to be able to use Emacs)

ZOOM Connection Coordinates (Meeting ID): 271 574 7853

Qualche esercitazione sara' concertata con il Dr. Adriano Di Florio (che sara' anche nella commissione d'esame).

PRACTICAL CLASS 0

Introduction to the Operting System UNIX/LINUX

Introduction to the editor EMACS

Introduction to the light editor VI

Introduction to ROOT : Introduction to the use of ROOT and exercises to begin with(Practical Class 0)

Further material about the introduction to ROOT

PRACTICAL CLASS 1

Histogramming within ROOT

In this exercise you will learn, starting by a given rootuple of histograms, how to get the plots in Fig.4 (or Fig.6)
in the CMS paper JINST 7 P10002 (2012).

To understand the physics content (muon reconstruction and identification at CMS) please study the pagg. 6-14.

For the description of the code (ROOT macro) and the procedure: Esercitazione-1(pdf)

Additional code concerns how-to-do simulation-to-data ratio; proper rebinning can be suitable to make the ratio not prone to fluctuations in the distribution tails.

Exercise: try relative normalization (shape comparison) instead of absolute normalization as proposed in the main code exercise.

PRACTICAL CLASS 2

Exercise on histogram comparison (with ROOT): compatibility with other real data and with simulations

D^0 meson production cross section:
- CMS data compared with FONLL (https://arxiv.org/abs/2107.01476; Figure 5 / upper);
- CMS data compared with ALICE data (https://arxiv.org/abs/2102.13601) [ support description here ].

Learn the use of TGraphErrors and TGraphAsymErrors.

PRACTICAL CLASS 3

Exercise on hypothesis testing : observables to discriminate background from signal, ROC curves

For the description of the code (ROOT macro) and the procedure: Esercitazione-2(pdf)

PRACTICAL CLASS 4

Introduction to RooFit

First Maximum Likelihood Fit with RooFit

For the description of the code (ROOT macro) and the procedure: Exercise-3(pdf).

For the theory behind fitting with MINUIT (the minimization engine of RooFit)
[Unbinned ML fit, Binned ML fit, Extended ML fit] have a look at the Addendum.
Here is additional follow-up material about MIGRAD, HESSE, MINOS functions in MINUIT.

Exercise: enable MINOS and check the difference with the symmetric(parabolic) error estimations.

PRACTICAL CLASS 4b

Refine the fit previously performed:

For the description of the code (ROOT macro) and the procedure: Exercise-4b.
These slides introduce the single-sided CB implementation, the bin-by-bin pulls and their uncertainty.
This is the comparison between the old and the new fit (but also in the previous slides!)

Exercise: discuss why the projection of the bin-by-bin pulls should follow a standard gaussian distribution.
If not then the fit has something "pathological".

PRACTICAL CLASS 5

PRACTICAL CLASS 6

Try two different background models (Chebyshev and Exponential);
try also to use a common Alpha and N for the tails of the two Crystal Ball functions.

Warning: find a turnaround for the maximum of 9 arguments in RooArgList

PRACTICAL CLASS 10

Here is proposed a similtaneous interpolation of two variables (mass and proper time, for B+ to J/psi K+ selected candidates) SLIDES

PRACTICAL CLASS 12