Changes between Version 9 and Version 10 of SRCombinations


Ignore:
Timestamp:
Feb 19, 2020, 7:58:39 PM (5 years ago)
Author:
GaelAlguero
Comment:

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  • SRCombinations

    v9 v10  
    7676
    7777After installing those packages, please try to install pyhf again.
     78
     79== Combining SR using covariance matrices with the [https://cds.cern.ch/record/2242860 simplified likelihood] method ==
     80
     81Covariance matrices provided for some CMS SUSY searches, can be used to build an approximate simplified likelihood. {{{info}}} files from the [http://madanalysis.irmp.ucl.ac.be/wiki/PublicAnalysisDatabase Public Analysis Database] can be extended with the covariance information from which MadAnalysis5 builds a simplified likelihood. This allows to compute combined CLs and combined cross-section upper limits. The standard syntax of the {{{info}}} file
     82{{{
     83<analysis id="analysis name">
     84    <region type="signal" id="region name">
     85        <nobs> ... </nobs>
     86        <nb> ... </nb>
     87        <deltanb> ... </deltanb>
     88    </region>
     89    ...
     90</analysis>
     91}}}
     92specifying, for each SR, the number of observed events {{{<nobs>}}}, expected background events {{{<nb>}}} and their uncertainty {{{<deltanb>}}}, is therefore extended by adding in each {{{<region>}}} subelement, the successive covariance values with respect to all other regions:
     93{{{
     94<analysis id="analysis name" cov_subset="combined SRs">
     95    <region type="signal" id="region name">
     96        <nobs> ... </nobs>
     97        <nb> ... </nb>
     98        <deltanb> ... </deltanb>
     99        <covariance region="first SR name">...</covariance>
     100        <covariance region="second SR name">...</covariance>
     101        ...
     102        <covariance region="last SR name">...</covariance>
     103    </region>
     104    ...
     105</analysis>
     106}}}
     107where, for each {{{<covariance>}}} element, the associated region is specified with the {{{region}}} attribute. Every missing covariance value will be interpreted as a zero element in the covariance matrix. If a {{{<region>}}} subelement does not contain any covariance values, then it won't be included in the set of combined regions. This allows to combine only a subset of signal regions. For instance, [http://cms-results.web.cern.ch/cms-results/public-results/publications/SUS-16-039/index.html CMS-SUS-16-039] only provides covariances for signal regions of type A.
     108In addition, an attribute {{{cov_subset}}} must be added to the {{{<analysis>}}} main element to store information about which SRs subset is combined. In the case of CMS-SUS-16-039, this is:
     109{{{
     110<analysis id="cms_sus_16_039" cov_subset="SRs_A">
     111}}}
     112The susbset description will be printed to the output file with the results from simplified likelihood combination, after the usual exclusion information:
     113{{{
     114<set> <tag> <cov_subset> <exp> <obs> <CLs> ||
     115}}}
     116The successive elements consist of the dataset name, the analysis name,  the description of the subset of combined SRs, the expected and observed cross section upper limits at 95% confidence level (CL), and finally the exclusion level, 1-CLs. A concrete example reads
     117{{{
     118defaultset  cms_sus_16_039  [SL]-SRs_A  10.4851515  11.1534040  0.9997  ||
     119}}}
     120where {{{[SL]}}} stands for simplified likelihood.