Springer Theses Recognizing Outstanding Ph.D. Research Béranger Dumont Higgs, Supersymmetry and Dark Matter After Run I of the LHC Springer Theses Recognizing Outstanding Ph.D. Research Aims and Scope The series “Springer Theses” brings together a selection of the very best Ph.D. theses from around the world and across the physical sciences. Nominated and endorsed by two recognized specialists, each published volume has been selected foritsscientificexcellenceandthehighimpactofitscontentsforthepertinentfield of research. For greater accessibility to non-specialists, the published versions includeanextendedintroduction,aswellasaforewordbythestudent’ssupervisor explainingthespecialrelevanceoftheworkforthefield.Asawhole,theserieswill provide a valuable resource both for newcomers to the research fields described, and for other scientists seeking detailed background information on special questions. Finally, it provides an accredited documentation of the valuable contributions made by today’s younger generation of scientists. Theses are accepted into the series by invited nomination only and must fulfill all of the following criteria (cid:129) They must be written in good English. (cid:129) ThetopicshouldfallwithintheconfinesofChemistry,Physics,EarthSciences, Engineeringandrelatedinterdisciplinary fields such asMaterials,Nanoscience, Chemical Engineering, Complex Systems and Biophysics. (cid:129) The work reported in the thesis must represent a significant scientific advance. (cid:129) Ifthethesisincludespreviouslypublishedmaterial,permissiontoreproducethis must be gained from the respective copyright holder. (cid:129) They must have been examined and passed during the 12 months prior to nomination. (cid:129) Each thesis should include a foreword by the supervisor outlining the signifi- cance of its content. 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More information about this series at http://www.springer.com/series/8790 é B ranger Dumont Higgs, Supersymmetry and Dark Matter After Run I of the LHC Doctoral Thesis accepted by the University of Grenoble, France 123 Author Supervisor Dr. BérangerDumont Dr. SabineKraml CTPU-IBS Laboratory of Subatomic Physics IBSCenter for TheoreticalPhysics &Cosmology, CNRS/IN2P3 ofthe Universe University of Grenoble Yuseong-gu,Daejeon Grenoble Korea,Republic of (SouthKorea) France ISSN 2190-5053 ISSN 2190-5061 (electronic) SpringerTheses ISBN978-3-319-44955-5 ISBN978-3-319-44956-2 (eBook) DOI 10.1007/978-3-319-44956-2 LibraryofCongressControlNumber:2016949591 ©SpringerInternationalPublishingSwitzerland2017 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpart of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission orinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodologynowknownorhereafterdeveloped. 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Printedonacid-freepaper ThisSpringerimprintispublishedbySpringerNature TheregisteredcompanyisSpringerInternationalPublishingAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland And here, poor fool! with all my lore I stand, no wiser than before Johann Wolfgang von Goethe, Faust, 1808 We shed as we pick up, like travellers who must carryeverything intheirarms, andwhat we let fall will be picked up by those behind. The procession is very long and life is very short. We die on the march. But there is nothing outside the march so nothing can be lost to it. Tom Stoppard, Arcadia, Act I, Sc. 3, 1993 ’ Supervisor s Foreword The years spent on a doctoral thesis are a very special time, even more so if they coincide with the discovery of a century and one can contribute to its under- standing. Such was the case for Béranger. Béranger set out in 2011 to do his Ph.D. in theoretical particle physics on the topicof“Darkmatterthelaboratoryandinthesky”.Hisfirstpublicationconcerned the phenomenology of a mainly right-handed sneutrino (a spin-0 partner of the neutrino in supersymmetric theories) as a candidate for the dark matter in the universe. This work consisted of a global analysis by means of Markov Chain MonteCarlosampling,includingall relevant constraints fromcollider searchesfor supersymmetric particles as well as direct and indirect dark matter searches. One of the key elements here was the careful treatment of nuclear and astrophysical uncertainties when evaluating the constraints from the XENON experiment. Two distinct cases emerged that satisfied all constraints: heavy sneutrino dark matter with mass of order 100 GeV, as well as light sneutrino dark matter with mass of about 3–6 GeV; we discussed the implications of both cases for dark matter searches, as well as for SUSY and Higgs searches at the LHC. While originally thoughttobethefoundationuponwhichtobuildthethesis,thisworkisnowjusta small part of Chap. 3 of this thesis. In2012,thediscoveryoftheHiggsbosonattheCERNLHCmarkedamilestone in particle physics. The Higgs boson was the last missing piece of the Standard Model,itsexistencebeingcrucialforthebreakingoftheelectroweaksymmetryand for giving mass to the weak gauge bosons. The most burning question after the discovery was whether we were dealing with the Higgs boson predicted by the standard theory, or whether the newly discovered particle would carry hints for a more fundamental theory. Béranger immediately took the opportunity to join my collaborationwithJohnF.Gunion,oneofthepioneersofHiggsphenomenology,to work on this problem. Mastering all the technical subtleties on his own, he developed a fitting code which thoroughly took into account all published LHC measurementsinthevariousHiggsproductionanddecaychannels.Thisenabledus to carry out a whole series of studies, including “Higgs couplings at the end of vii viii Supervisor’sForeword 2012” published in JHEP1302, 053 (2013), “Status of invisible Higgs decays” publishedinPhys.Lett.B723,340(2013)and“GlobalfittoHiggssignalstrengths and couplings, and implications for extended Higgs sectors” published in Phys. Rev. D88, 075008 (2013), which all very quickly became top-cited papers. In particular, the last one has been cited nearly 200 times by now. Based on this, in January 2013 and only in his second year of Ph.D., Béranger wasaskedtogiveaplenarytalkattheCERNworkshop“LikelihoodsfortheLHC searches” about how theorists use the Higgs results published by the experimental collaborations. This can be considered a rare honour, and Béranger gave an excellent presentation. Moreover, this set off an initiative which culminated in the document“OnthepresentationoftheLHCHiggsresults”,arXiv:1307.5865,which putforthconclusionsandsuggestionsregardingthepresentationoftheLHCHiggs results that may help to maximize their impact and their utility to the whole High Energy Physics community. The document was co-signed by 17 physicists, but Béranger’s contributions were among the most crucial ones. Of course we were not the only group to work on the theoretical understanding of the Higgs measurements. In fact, it was a highly competitive undertaking, somethinglikeagoldrushinourfield.Itwasahighlyexcitingtime,andapleasure to work with Béranger and see him develop. While most of the other groups kept their computer codes private, Béranger realised that it would be highly valuable to have a public code for fitting the Higgs data, written in a modern programming language and based on modern programming standards. Indeed the wealth of experimental results makes it quite a complex task to assess the compatibility of a nonstandard Higgs boson with all the available data. Together with a fellow Ph.D. student, Jeremy Bernon, Béranger thus set out to write such a program for public use. The outcome is Lilith, a Python library in which the Higgs likelihood in whatever model theuser feeds inisevaluatedbased onexperimental resultsstored inaneasilyextensibleXMLdatabase.Theprogram,publishedinEur.Phys.J.C75, no. 9, 440 (2015) and available from Launchpad, is easy to use and very fast. All this now forms Chap. 2 and the major part of this thesis. Very clearly and peda- gogicallywritten,itcanserveasatextbookintroductiontounderstandingtheHiggs measurements at Run 1 of the LHC. In parallel, in his final year of the Ph.D., Béranger worked on (re-)interpreting theresultsoftheLHCsearchesforsupersymmetricparticles.Tostartwith,together with authors of the MadAnalysis5 package (a C++ package for sophisticated physics analyses of Monte Carlo events) he extended the program to be able to simultaneously deal with multiple sub-analyses. Moreover, he helped devise a novel user-friendly treatment for the kinematic selection criteria. Béranger also wrote the first implementation of an LHC analysis, which then served as the template for all other analyses that now form the “MadAnalysis5 Public Analysis Database”.ThisisdescribedinthesecondpartofChap.3ofthethesis,thusclosing thecirclewithwherehestarted.Again,thechapterisveryclearlywritten,carefully explaining the subtleties involved in (re-)interpreting the LHC searches, starting from the so-called simplified-model approach all the way to full recasting of the experimental analyses. Supervisor’sForeword ix At theend,Béranger entitledhis thesis “Higgs, supersymmetry and darkmatter afterRunIoftheLHC”.Thetitleiswellchosen,ashisthesisindeeddescribesthe legacy of Run I, to which he significantly contributed on the theory side. As said before, it was a highly exciting time. Béranger brought in curiosity, dedication, a verycareful approach,andhewasnever afraidoffacingchallenges, neither onthe intellectual nor on the technical side. In his modest and softly-spoken manner he stoodhisgroundagainststrongopinions,seniorprofessors,andthehighpressureto achieve and to publish fast. Forme,thesethreeyearswerefullofdelight.WhatremainsistowishBéranger luck for his future career, and the reader joy in indulging in this thesis. Grenoble, France Dr. Sabine Kraml August 2016 Abstract Two major problems call for an extension of the Standard Model (SM): the hier- archy problem in the Higgs sector and the dark matter in the Universe. The dis- covery of a Higgs boson with mass of about 125 GeV was clearly the most significant piece of news from CERN’s Large Hadron Collider (LHC). In addition to representing the ultimate triumph of the SM, it shed new light on the hierarchy problem and opened up new ways of probing new physics. The various measure- mentsperformedatRunIoftheLHCconstraintheHiggscouplingstoSMparticles as well as invisible and undetected decays. In this thesis, the impact of the LHC Higgs results on various new physics scenarios is assessed, carefully taking into account uncertainties and correlations between them. Generic modifications of the Higgs coupling strengths, possibly arising from extended Higgs sectors or higher dimensional operators, are considered. Furthermore, specific new physics models are tested. This includes, in particular, the phenomenological Minimal SupersymmetricStandardModel.WhileaHiggs bosonhasbeenfound,nosignof beyond the SM physics was observed at Run I of the LHC in spite of the large number of searches performed by the ATLAS and CMS collaborations. The implications of the negative results obtained in these searches constitute another important part of this thesis. First, supersymmetric models with a dark matter candidateareinvestigatedinlightofthenegativesearchesforsupersymmetryatthe LHCusingaso-called“simplifiedmodel”approach.Second,toolsusingsimulated events to constrain any new physics scenario from the LHC results are presented. Moreover, during this thesis the selection criteria of several beyond the SM anal- yses have been reimplemented in the MadAnalysis 5 framework and made available in a public database. xi