Effective Field Theories have changed our understanding of Quantum Field Theories. This thesis shows several applications of this powerful tool in the context of the Standard Model and for searches of New Physics. The thesis starts with a review of the St ...

EPFL2022

Microlens-enhanced silicon photomultiplier arrays for LHCb SciFi Tracker Upgrade Ib

Olivier Schneider, Guido Haefeli, Ettore Zaffaroni, Carina Trippl

A large-scale Scintillating Fibre Tracker has been developed and constructed for the current LHCb Upgrade 1. The high radiation by fast neutrons reduces the light yield of the detector in the course of LHC Run 3, and is challenging the tracker's hit detect ...

ELSEVIER2022

Measurement of the prompt-production cross-section ratio sigma(chi(c2))/sigma(chi(c1)) in pPb collisions at root s(NN)=8.16 TeV

Lesya Shchutska, Olivier Schneider, Aurelio Bay, Yiming Li, Guido Haefeli, Frédéric Blanc, Christoph Frei, Tatsuya Nakada, Michel De Cian, Elena Graverini

This article reports the first measurement of prompt chi(c1) and chi(c2) charmonium production in nuclear collisions at Large Hadron Collider energies. The cross-section ratio sigma(chi(c2))/sigma(chi(c1)) is measured in pPb collisions at root s(NN) = 8.16 ...

2021

Observation of New Resonances Decaying to J=Psi K plus and J=Psi phi

Lesya Shchutska, Olivier Schneider, Aurelio Bay, Yiming Li, Guido Haefeli, Frédéric Blanc, Christoph Frei, Tatsuya Nakada, Michel De Cian, Elena Graverini

The first observation of exotic states with a new quark content ccus decaying to the J/Psi K+ final state is reported with high significance from an amplitude analysis of the B+-> J/ Psi phi K+ decay. The analysis is carried out using proton-proton collisi ...

2021

Evidence of a J/psi Lambda structure and observation of excited Xi(-) states in the Xi(-)(b) -> J/psi Lambda K- decay

Lesya Shchutska, Olivier Schneider, Aurelio Bay, Yiming Li, Guido Haefeli, Frédéric Blanc, Tatsuya Nakada, Christoph Frei, Michel De Cian, Elena Graverini

First evidence of a structure in the J/psi Lambda invariant mass distribution is obtained from an amplitude analysis of Xi(-)(b) -> J/psi Lambda K- decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness with ...

2021

Branching Fraction Measurements of the Rare B-s(0) -> phi mu(+)mu(-) and B-s(0)-> f(2)' (1525)mu(+)mu(-) Decays

Lesya Shchutska, Olivier Schneider, Aurelio Bay, Yiming Li, Guido Haefeli, Frédéric Blanc, Christoph Frei, Tatsuya Nakada, Michel De Cian, Elena Graverini

The branching fraction of the rare B-s(0) -> phi mu(+)mu(-) decay is measured using data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to integrated luminosities of 1, 2, and 6 fb(-1), respectively. The bran ...

2021

First indication of the Lambda-b baryon decay to a charmless baryonic final state

Vladimir Macko

The Standard Model of particle physics provides predictions of many fundamental processes. One of them is the existence of charmless processes involving only baryons, namely charmless purely baryonic decays of baryons. Yet none of these decay modes has bee ...

EPFL2021

Search for heavy neutral leptons in W plus . mu plus mu +/- jet decays

Olivier Schneider, Aurelio Bay, Yiming Li, Guido Haefeli, Frédéric Blanc, Christoph Frei, Tatsuya Nakada, Michel De Cian, Luca Pescatore, Chitsanu Khurewathanakul

A search is performed for heavy neutrinos in the decay of a W boson into two muons and a jet. The data set corresponds to an integrated luminosity of approximately 3.0 fb-1 of proton-proton collision data at centre-of-mass energies of 7 and 8 TeV collected ...

SPRINGER2021

Search for lepton flavour violation in B meson decays at LHCb

Lino Ferreira Lopes

The current limitations of the standard model of elementary particle physics drive the search for phenomenons forbidden within that framework with the goal to unveil a more universal theory. This thesis presents the search for two lepton flavour violating ...

EPFL2021

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Effective Field Theories for New and Old Physics

Alfredo Glioti

EPFL2022

Measurement of the prompt-production cross-section ratio sigma(chi(c2))/sigma(chi(c1)) in pPb collisions at root s(NN)=8.16 TeV

Lesya Shchutska, Olivier Schneider, Aurelio Bay, Yiming Li, Guido Haefeli, Frédéric Blanc, Christoph Frei, Tatsuya Nakada, Michel De Cian, Elena Graverini

2021

B^{+}\rightarrow K^{+}\ell^{+}\ell^{-}

and

B^{0}\rightarrow K^{*0}\ell^{+}\ell^{-}

decays is performed, in two ranges of the dilepton invariant-mass squared,

q^{2}

. The analysis uses bea ...

2023