PHYSTAT-Flavour 2020

Europe/Zurich
Diego Tonelli (INFN Trieste, Italy), Hans Peter Dembinski (Max-Planck-Institute for Nuclear Physics, Heidelberg), Louis Lyons (Imperial College (GB)), Matthew William Kenzie (University of Warwick (GB)), Olaf Behnke (Deutsches Elektronen-Synchrotron (DE))
Description

Zoom link

Meeting ID: 95191277014

Passcode: 318108

The virtual workshop deals with the

Statistical issues in modern flavour physics experiments

Topics to be included in the compact three afternoons workshop are                                 

  • Principal inference techniques, also near physical boundaries
  • Parameter estimation with using weighted events
  • Systematic uncertainties

The workshop will be a mixture of invited talks from physicists and statisticians. One important goal is to collect a list of open issues in statistical treatments and procedures in flavour experiments that can be addressed in a future longer workshop with onsite participation.

The homepage of PHYSTAT with a list of all workshops is at https://espace.cern.ch/phystat.

Surveys
Evaluation of PHYSTAT-Flavour workshop and ideas for a future workshop
Registration
Registration
Participants
  • Abdul Basith Kaliyar
  • Abhishek Das
  • Adriano Di Florio
  • Ahmed Abdelmotteleb
  • Aiqiang Guo
  • Alan Schwartz
  • Alberto Bragagnolo
  • Alberto Sanchez Hernandez
  • Alessandro Bertolin
  • Alessandro Calandri
  • Alessio Boletti
  • Alexander Ward
  • Alexis Pompili
  • Aman Sangal
  • Andrea Fodor
  • Andrea Merli
  • Andreas Guth
  • Andrew Fowlie
  • Andrzej Kupsc
  • André David
  • Angela Giraldi
  • Angelo Di Canto
  • Anita Lavania
  • Anja Beck
  • Apostolos Theodoridis
  • Aravindhan Venkateswaran
  • Artem Vasyukov
  • Ashutosh Bhardwaj
  • Atanu Modak
  • Atanu Nath
  • Behzad Salmassian
  • Blaise Raheem Delaney
  • Bob Cousins
  • Bogdan Malaescu
  • bolun zhang
  • Bradley Efron
  • Brunella D'Anzi
  • ByungGu Cheon
  • Candan Isik
  • Carlos Pegueros
  • Carmen Giugliano
  • Carolina Da Silva Bolognani
  • Carsten Niebuhr
  • Chandiprasad Kar
  • Changzheng YUAN
  • Chaoyi Lyu
  • Chengping Shen
  • Cheolhun Kim
  • Christoph Michael Langenbruch
  • Claire Prouve
  • Clara Matteuzzi
  • Claudia Cecchi
  • Cristina Lazzeroni
  • Dana Seman Bobulska
  • Daniel Alejandro Perez Navarro
  • Daniel Unverzagt
  • Daniele Marangotto
  • Daniele Paesani
  • Darren Price
  • Davide Zuliani
  • Debabrata Bhowmik
  • Denis Derkach
  • Devender Kumar
  • Dibyajyoti Kalita
  • Dosbol Baigarashev
  • Dylan Palo
  • Eduardo Rodrigues
  • Elena Solovieva
  • Eleonora Diociaiuti
  • Elisa Manoni
  • Elisa Minucci
  • Elisabeth Maria Niel
  • Emmanouil Vourliotis
  • Enrico Graziani
  • Enrico Lusiani
  • Eric Persson
  • Felix Metzner
  • Filippo Dattola
  • Fionn Bishop
  • Flavia Cicala
  • Francesco Brizioli
  • Francisco J Carrera
  • Francisco Matorras
  • Franco Simonetto
  • Francois Lagarde
  • Francois Le Diberder
  • Frank Porter
  • Gabriel Gomes
  • Gaetano de Marino
  • Galin Jones
  • Gayane Ghevondyan
  • Gediminas Sarpis
  • George Lovell
  • Georgios Karathanasis
  • Georgios Melachroinos
  • Gevorg Karyan
  • Gianantonio Pezzullo
  • Gianluca Inguglia
  • Giovanni Punzi
  • Giulia Tuci
  • Giulio Mezzadri
  • Govindraj Singh Virdee
  • Guglielmo De Nardo
  • Guillaume Falmagne
  • HanEol Cho
  • Hannah Wakeling
  • Hans Peter Dembinski
  • Harisree Krishnamoorthy
  • Hazaravard Ghumaryan
  • Henrikas Svidras
  • Heriberto Castilla-Valdez
  • Hevjin Yarar
  • HIDEYUKI NAKAZAWA
  • Horacio Crotte Ledesma
  • Hossein Afsharnia
  • Houbing Jiang
  • Igor Smirnov
  • Ilya Komarov
  • Irina Nasteva
  • Isabel Haide
  • Israel Kurtz
  • Ivan Lilienberg
  • Ivan Martinez Soler
  • Jacopo Pinzino
  • James Kahn
  • Jan-Marc Basels
  • Jim Libby
  • Jing-Ge Shiu
  • Jittapan Ineead
  • Jonas Eschle
  • Joseph Carmignani
  • JUan A. Cuesta-Albertos
  • Julia Manuela Silva
  • Jyotirmoi Borah
  • Ka Tung Lau
  • Kai Zhu
  • Karim Massri
  • Karol Adamczyk
  • Kate Ciampa
  • Kevin Mota Amarilo
  • Kirill Ivanov
  • Kirill Skovpen
  • Koen Lambrechts
  • Konstantinos Nikolopoulos
  • Kristina Jaruskova
  • Kyungho Kim
  • Lais Soares Lavra
  • Lakshan Ram Madhan Mohan
  • Lars Sowa
  • Leonardo Cristella
  • Letizia Peruzzo
  • Lex Greeven
  • Louis Lyons
  • Lu Cao
  • Lubos Bician
  • Lucas Martel
  • Lucas Nicholas Falcao Ferreira
  • Lukas Bierwirth
  • Mackenzie Devilbiss
  • Maharnab Bhattacharjee
  • Makoto Uchida
  • Manolis Kargiantoulakis
  • Mapse Barroso Ferreira Filho
  • Marcel Hohmann
  • Marcello Rotondo
  • Marco Scodeggio
  • Marina Artuso
  • Mario Merola
  • Martin Angelsmark
  • Matthew Kenzie
  • Maximilian Graf
  • Michael Schmelling
  • Michael Schmitt
  • Michael Wilkinson
  • Michal Koval
  • Michal Zamkovsky
  • Michele Corvino
  • Mikael Kuusela
  • Mike M
  • Mindaugas Sarpis
  • Miroslav Kubu
  • Miroslav Saur
  • Mohammad Abrar Wadud
  • Moritz Bauer
  • Muhammad Alibordi
  • Nam Tran
  • Namrata Agrawal
  • Nazım ÇABUK
  • Niladri Sahoo
  • Olaf Behnke
  • Olivier Deschamps
  • Olivier Leroy
  • Pablo Goldenzweig
  • Patrick Ecker
  • Paul Feichtinger
  • Peilian Li
  • Peter Kammel
  • Peter Stangl
  • Pietro Vischia
  • Pim Jordi Verschuuren
  • Pooja Kumari
  • Prasanna Kumar Siddireddy
  • Racha Cheaib
  • Radoslav Marchevski
  • Rahmat Rahmat
  • Rahul Tiwary
  • RAJEEV KUMAR
  • Rajesh Kumar Maiti
  • Razvan-Daniel Moise
  • Riccardo Lollini
  • Riccardo Manfredi
  • Riley Henderson
  • Roberta Volpe
  • Roger Barlow
  • Rosamaria Venditti
  • Ruiting Ma
  • Ryan Atkin
  • Samet Lezki
  • Sanqiang Qu
  • Sara Algeri
  • Sara Fiorendi
  • Sara Sellam
  • Sascha Dreyer
  • Seema Choudhury
  • Senem ÇABUK
  • Sergey Kholodenko
  • Sergey Polikarpov
  • Shalini Epari
  • Shantam Taneja
  • Shivam -
  • Shubhangi Krishan Maurya
  • Simon Wehle
  • Simone Amoroso
  • Simone Bifani
  • Simranpreet Kaur
  • Sitong An
  • Slavomira Stefkova
  • Snigdho Chakraborty
  • Soeren Prell
  • Soufiane Zerradi
  • Srishti Bhasin
  • Stefanos Leontsinis
  • Sungjin Cho
  • Svenja Granderath
  • Taeun Kwon
  • Tamaki Holly McGrath
  • Thanh Dong
  • Thomas Bache
  • Thomas Junk
  • Thomas Oeser
  • Thomas Peter Jones
  • TianYu Qi
  • Tim Philip Hucking
  • Titus Mombacher
  • Tom Browder
  • Tommaso Pajero
  • Trevor Shillington
  • Umberto Tamponi
  • Valeriia Lukashenko
  • Varvara Batozskaya
  • Viacheslav Duk
  • Vidya Sagar VOBBILISETTI
  • Vincent Alexander Croft
  • Vukan Jevtic
  • wang hongpeng
  • Weimin Song
  • William Kyle
  • Wolfgang Rolke
  • Wolfgang Walkowiak
  • Xiaodong Shi
  • Xiqing Hao
  • Yanting Fan
  • Yixiong Zhou
  • Yongkyu Kim
  • Youngjoon Kwon
  • Yuan-Ru Lin
  • Yue Pan
  • Yunxuan Song
  • Yuping Guo
  • Zhenhong Wu
  • Zijun Xu
    • 14:00 15:45
      Session 1
      Conveners: Matthew William Kenzie (University of Warwick (GB)), Olaf Behnke (Deutsches Elektronen-Synchrotron (DE))
      • 14:00
        Introduction and Welcome 5m
        Speaker: Olaf Behnke (Deutsches Elektronen-Synchrotron (DE))
      • 14:05
        Statistical issues in modern beauty and charm flavour physics experiments 30m

        We give an overview of common statistical issues discussed in the heavy flavour physics experiments LHCb and Belle. A focus will be put on limit setting in searches, the use of weighted events in inference (as computed with the sPlot technique), and the handling of systematic uncertainties.

        Speaker: Hans Peter Dembinski (Max-Planck-Institute for Nuclear Physics, Heidelberg)
      • 14:35
        Discussion time 10m
      • 14:45
        Approaches to evaluating and reporting systematic uncertainties in flavour physics 30m

        The high luminosity and large cross sections enjoyed by LHC experiments means that statistical errors are minimal, and the rigorous treatment of systematic errors becomes very important - an area which lacks the "safety net" of chi squared and other goodness-of-fit measures. This entails including all uncertainties, estimating them properly, and not to inflating the error by including the results of consistency checks. This talk surveys recent papers by ATLAS, CMS and LHCb and examines how the collaborations handle the identification and estimation of systematic errors, the extent to which this is being done correctly, and what lessons can be learned.

        Speaker: Roger Barlow (University of Huddersfield (GB))
      • 15:15
        Discussion time 15m
      • 15:30
        Virtual coffee break 15m
    • 15:45 17:15
      Session 1
      Conveners: Olaf Behnke (Deutsches Elektronen-Synchrotron (DE)), Matthew William Kenzie (University of Warwick (GB))
      • 15:45
        Testing a point null hypothesis versus a continuous alternative hypothesis 30m

        I will discuss aspects of the frequentist and Bayesian approaches to testing a point null hypothesis (say mu=0) versus a continuous alternative hypothesis (say mu>0). This test arises frequently in particle physics, where mu is the signal strength of a previously unobserved signal (within or beyond the Standard Model). The frequentist testing approach maps identically onto the frequentist theory of confidence intervals. Thus, as Feldman and Cousins eventually realized, the method advocated in their 1998 paper on confidence intervals maps identically onto the "classical" theory of likelihood ratio hypothesis tests in Kendall and Stuart (which in addition includes nuisance parameters). Meanwhile, the traditional Bayesian approach to hypothesis testing (due to Jeffreys) is completely separate from the Bayesian approach to credible intervals, with no corresponding mapping. Direct sensitivity to the prior pdf for mu, even in the asymptotic limit of large sample size, is a consequence, as is the Jeffreys-Lindley paradox (arXiv:1310.3791). My talk will draw on parts of my “Lectures on Statistics in Theory: Prelude to Statistics in Practice” (arXiv:1807.05996).

        Speaker: Robert Cousins Jr (University of California Los Angeles (US))
      • 16:15
        Discussion time 15m
      • 16:30
        Interval Estimation, and the practice of Flavour Physics 30m

        Interval estimation is one of the most common types of inference practiced by experimentalists, and the flavour sector is not less interested than high-pt physics. In fact, the physics of flavour brings to the table some quite interesting problems, with complex multi-dimensional parameter spaces, non-linearities, and significant systematic effects. While much has been written on the theoretical principles of interval estimation, oftentimes the practitioner meets with issues for which practical guidance is not easy to find. Amongst typical hurdles are the correct handling of systematic uncertainties in frequentist intervals, and optimization of data selection for "best sensitivity" in the double-sided problem of discovery vs limits. I will give a discussion of those problems in the light of real-life experience from flavour physics measurements.

        Speaker: Giovanni Punzi (Universita & INFN Pisa (IT))
      • 17:00
        Discussion time 15m
    • 14:00 15:45
      Session 2
      Conveners: Diego Tonelli (INFN Trieste, Italy), Hans Peter Dembinski (Max-Planck-Institute for Nuclear Physics, Heidelberg)
      • 14:00
        Practical concerns in statistical combinations at ATLAS and CMS 30m

        The ATLAS and CMS collaborations have produced numerous results during the first two data-taking runs of the LHC, ranging from precision measurements of SM processes to searches for exotic phenomena and the discovery of the Higgs boson. These results make use of (often complex) statistical techniques, both for the publications and during the development and review of the data analysis/ In this talk, I will cover some of the common practices and tools used at both ATLAS and CMS to produce these results, and practical considerations for performing combinations across different channels or experiments.

        Speaker: Nicholas Wardle (Imperial College (GB))
      • 14:30
        Disucssion time 15m
      • 14:45
        Informative Goodness-of-Fit for Multivariate Distributions 30m

        In any experimental science, the knowledge available on a given phenomenon is formalized into a statistical model. The latter encapsulates our understanding of its nature, its properties as well as our uncertainties. Experimental measurements are then collected and statistical tests of hypothesis are used to answer the important question: is our model valid? As a result, a variety of tests for goodness-of-fit (GOF) have been proposed in the literature to study multivariate distributions. Despite their usefulness, classical GOF methods are somehow limited by their confirmatory nature. Specifically, when the respective null hypothesis is rejected, they do not allow us to identify the underlying causes which invalidate the model postulated by the scientists, nor they give any indication on how the latter can be improved to obtain a closer representation of the true data distribution. In simple words, they do not provide any insights on what went wrong. In this talk, I will introduce an informative goodness-of-fit (iGOF) approach to study multivariate distributions and which aims to address this issue directly. Specifically, when the null model is rejected, iGOF allows us to identify the underlying sources of mismodelling and naturally equip practitioners with additional insights on the underlying data distribution.

        Speaker: Sara Algeri (University of Minnesota)
      • 15:15
        Disucssion time 15m
      • 15:30
        Virtual coffee break 15m
    • 15:45 19:15
      Session 2
      Conveners: Louis Lyons (Imperial College (GB)), Dr Hans Peter Dembinski (Max-Planck-Institute for Nuclear Physics, Heidelberg)
      • 15:45
        Look-elsewhere effect in particle physics - knowns and unknowns 30m

        The LEE, also known as multiple comparisons problem and addressed by a trials factor, has become an essential part of any analyst's toolkit in the last decade. It is much less esoteric and much more pervasive that one could naively think and we'll walking through a series of first hand recounts of appearances it has made in the LHC. We'll both discuss known techniques to deal with the effect as well as potential caveats in hitherto unseen problems. While some potential problems are related to physics, the future is highly multi-dimensional and that brings us to present-day statistics issues that, interestingly, particle physicists may end up being reasonably equipped to tackle.

        Speaker: André David (CERN)
      • 16:15
        Discussion time 45m
      • 17:00
        Afternoon Break 1h
      • 18:00
        Estimation, Accuracy and the Bootstrap 30m

        A brief introduction to boostrap estimates of accuracy, this talk does not assume familiarity with the topic. Bootstrap standard errors and confidence intervals are described using a small but genuine data set.

        Speaker: Prof. Brad Efron (Stanford University)
      • 18:30
        Discussion time 45m
    • 14:00 15:45
      Session 3
      Conveners: Olaf Behnke (Deutsches Elektronen-Synchrotron (DE)), Matthew William Kenzie (University of Warwick (GB))
      • 14:00
        Using sWeights to disentangle signal and background 30m

        When an observable density is a superposition of signal and background PDFs that each factorise in a ''discriminant'' and a ''control'' variable, sWeights allow one to determine the signal density in the control variable using information from only the discriminant variable.
        After reviewing the basics of the method and casting the formalism into the framework of orthogonal functions, the talk will address numerical aspects of the method and how to deal with weighted events or factorisation breaking.

        Speaker: Michael Schmelling (Max-Planck-Gesellschaft (DE))
      • 14:30
        Discussion time 15m
      • 14:45
        Fitting weighted events 30m

        Fits of weighted events, for example to correct for acceptance effects or to statistically subtract background events using sWeights, have recently seen increasing use in the flavour physics community. This talk will discuss the determination of parameters and their uncertainties using weighted events, with particular focus on unbinned fits of weighted data.

        Speaker: Christoph Michael Langenbruch (Rheinisch Westfaelische Tech. Hoch. (DE))
      • 15:15
        Discussion time 15m
      • 15:30
        Virtual coffee break 15m
    • 15:45 17:30
      Session 3
      Conveners: Hans Peter Dembinski (Max-Planck-Institute for Nuclear Physics, Heidelberg), Louis Lyons (Imperial College (GB))
      • 15:45
        Goodness of Fit for unbinned data 30m
        Speaker: Francois Rene Le Diberder
      • 16:15
        Discussion time 15m
      • 16:30
        Global Fits 30m

        Global fits are an indispensable tool in the search for New Physics (NP). On the one hand, they can provide interpretations of measurements that deviate from Standard Model (SM) predictions, and on the other hand, they allow using the wealth of experimental data for testing the viability of NP models. Being "global" means that these fits include hundreds of observables, whose theoretical predictions depend on a large number of nuisance parameters. Furthermore, the number of possible fit parameters in effective fields theories and explicit NP models can be huge. In this talk, I show how global fits are used in phenomenological analyses of flavour physics and other precision tests of the SM, I describe approximations that facilitate working with the large number of nuisance parameters, and I discuss issues and ambiguities related to the large number of possible fit parameters.

        Speaker: Peter Stangl (University of Bern)
      • 17:00
        Discussion time 15m
      • 17:15
        Final remarks and closing of the workshop 15m
        Speakers: Diego Tonelli (INFN Trieste, Italy), Hans Peter Dembinski (Max-Planck-Institute for Nuclear Physics, Heidelberg), Louis Lyons (Imperial College (GB)), Matthew William Kenzie (University of Warwick (GB)), Olaf Behnke (Deutsches Elektronen-Synchrotron (DE))