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Publication

Search for flavoured leptonic decays of long-lived particles in the LHCb detector

Matthieu Philippe Luther Marinangeli
EPFL, 2020
Thèse EPFL

Résumé

New massive long-lived particles (LLP) are predicted by multiple beyond the Standard Model theories. This thesis presents the search of such long-lived particles decaying leptonically in the $e \mu \nu$ final state. The search is performed using 2.31 fb $^{-1}$ of proton-proton collisions collected by the LHCb detector at a center-of-mass energy of $\sqrt{s} = 13$ TeV, seeking for displaced vertices of electrons and muons of opposite charges.

LLPs with masses between 7 to $50$ GeV/c $^2$ , and lifetime between 2 and 50 ps, are explored in this search. Three kinds of LLP production modes are considered: the direct pair production of LLPs from quark interactions, the pair production from a Standard Model like Higgs boson with a mass of $125$ GeV/c $^2$ , and charged current production from an on-shell $W$ boson with an additional lepton.

No evidence of these long-lived states has been observed, upper limits at $95 \%$ CL on the production cross-section times branching ratio have been set on the different production mode.

Official source

https://infoscience.epfl.ch/record/279779?ln=fr

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Matthieu Philippe Luther Marinangeli
EPFL, 2020
Thèse EPFL

Résumé

No evidence of these long-lived states has been observed, upper limits at $95 \%$ CL on the production cross-section times branching ratio have been set on the different production mode.

Official source

https://infoscience.epfl.ch/record/279779?ln=fr

À propos de ce résultat

Concepts associés (17)

Concepts associés

Chargement

Publications associées (108)

Publications associées

Chargement

Searches for heavy Higgs bosons in two-Higgs-doublet models and for $t→ch$ decay using multilepton and diphoton final states in $pp$ collisions at 8 TeV

Muhammad Ahmad, Georgios Anagnostou, Konstantin Androsov, Alexandre Aubin, Giovanni Bianchi, Roberto Castello, Yixing Chen, Tian Cheng, Giuseppe Codispoti, Alessandro Degano, Charles Dietz, Milos Dordevic, Dipanwita Dutta, Matthias Finger, Francesco Fiori, Yifei Guo, Ruchi Gupta, Csaba Hajdu, Alexis Kalogeropoulos, Ji Hyun Kim, Donghyun Kim, Vineet Kumar, Ajay Kumar, Sanjeev Kumar, Ekaterina Kuznetsova, Wei Li, Ho Ling Li, Shuai Liu, Hao Liu, Werner Lustermann, Matteo Marone, Thomas Muller, Ioannis Papadopoulos, Vladimir Petrov, Quentin Python, Andrea Rizzi, Paolo Ronchese, Sourav Sen, Ashish Sharma, Varun Sharma, Lesya Shchutska, Muhammad Shoaib, Michal Simon, Gurpreet Singh, Jan Steggemann, Wei Sun, Andromachi Tsirou, Paul Turner, Joao Varela, Rui Wang, Zheng Wang, Xiao Wang, Jian Wang, Qian Wang, Matthias Weber, Matthias Wolf, Fan Yang, Yong Yang, Kai Yi, Lei Zhang, Yu Zheng

Searches are presented for heavy scalar (

\mathrm{H}

) and pseudoscalar (

\mathrm{A}

) Higgs bosons posited in the two doublet model (2HDM) extensions of the standard model (SM). These searches are based on a data sample of

\mathrm{p}\mathrm{p}

collisions collected with the CMS experiment at the LHC at a center-of-mass energy of

\sqrt{s} = 8~\mathrm{TeV}

and corresponding to an integrated luminosity of

19.5~\mathrm{fb}^{-1}

. The decays

\mathrm{H} \rightarrow \mathrm{h} \mathrm{h}

and

\mathrm{A} \rightarrow \mathrm{Z} \mathrm{h}

, where

\mathrm{h}

denotes an SM-like Higgs boson, lead to events with three or more isolated charged leptons or with a photon pair accompanied by one or more isolated leptons. The search results are presented in terms of the

\mathrm{H}

and

\mathrm{A}

production cross sections times branching fractions and are further interpreted in terms of 2HDM parameters. We place 95% CL cross section upper limits of approximately

7~\mathrm{pb}

\sigma \mathcal{B}

for

\mathrm{H} \rightarrow \mathrm{h} \mathrm{h}

and

2~\mathrm{pb}

for

\mathrm{A} \rightarrow \mathrm{Z} \mathrm{h}

. Also presented are the results of a search for the rare decay of the top quark that results in a charm quark and an SM Higgs boson,

\mathrm{t} \rightarrow \mathrm{c} \mathrm{h}

, the existence of which would indicate a nonzero flavor-changing Yukawa coupling of the top quark to the Higgs boson. We place a 95% CL upper limit of 0.56% on

\mathcal{B}(\mathrm{t} \rightarrow \mathrm{c} \mathrm{h})

2014

Search for flavoured leptonic decays of long-lived particles in the LHCb detector

Searches for heavy Higgs bosons in two-Higgs-doublet models and for $t→ch$ decay using multilepton and diphoton final states in $pp$ collisions at 8 TeV

Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs

Search for dark photons in decays of Higgs bosons produced in association with Z bosons in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

Searches for heavy Higgs bosons in two-Higgs-doublet models and for $t→ch$ decay using multilepton and diphoton final states in $pp$ collisions at 8 TeV

Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs

Search for dark photons in decays of Higgs bosons produced in association with Z bosons in proton-proton collisions at $ \sqrt{s} $ = 13 TeV