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doctoral thesis

Precision measurement of neutral charm meson mixing parameters

Pietrzyk, Guillaume Max  
2022

This thesis presents a measurement of the neutral charm meson mixing parameters $y_{C!P}^{KK} - y_{C!P}^{K\pi}$ and $y_{C!P}^{\pi\pi} - y_{C!P}^{K\pi}$ using $D^0 \rightarrow K^-K^+$, $D^0 \rightarrow \pi^-\pi^+$ and $D^0 \rightarrow K^-\pi^+$ decays. These parameters correspond to the departure from unity of the ratio of the effective decay widths of $D^0 \rightarrow K^-K^+$ or $D^0 \rightarrow \pi^-\pi^+$ decays over the effective decay width of $D^0 \rightarrow K^-\pi^+$ decays.The measurement is done with the dataset collected in the Run 2 (2015-2018) of the Large Hadron Collider (LHC) by the LHCb experiment at CERN at a centre-of-mass energy of $13\mathrm{TeV}$, and corresponding to an integrated luminosity of $6 , \mathrm{fb}^{-1}$. The $D^0$ mesons originate from $D^{\ast+}(2010) \rightarrow D^0 \pi^+$ decays. We measure \begin{equation} \begin{split} y_{C!P}^{KK} - y_{C!P}^{K\pi} & = (7.08 \pm 0.30 \pm 0.14) \times 10^{-3}, , \ y_{C!P}^{\pi\pi} - y_{C!P}^{K\pi} & = (6.57 \pm 0.53 \pm 0.16) \times 10^{-3}, , \end{split} \end{equation} where the first uncertainty is statistical while the second is systematic. Neglecting final state dependent contributions, we obtain the combination \begin{equation} y_{C!P} - y_{C!P}^{K\pi} = (6.96 \pm 0.26 \pm 0.13) \times 10^{-3} , . \end{equation} This measurement improves by a factor of four the precision of the current world average value of $y_{C!P} - y_{C!P}^{K\pi}$. In addition, the results allow for an improvement of the precision on the mixing parameter $y$ by a factor of two, where $y$ is connected to the width difference between the neutral charm meson mass eigenstates. The new world average value of $y$ is estimated to be \begin{equation} y = (6.45 \pm 0.24) \times 10^{-3} , . \end{equation} This thesis also presents the work done for the EPFL fibre mat production as part of the LHCb Scintillating Fibre (SciFi) Tracker upgrade.

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Type
doctoral thesis
DOI
10.5075/epfl-thesis-8771
Author(s)
Pietrzyk, Guillaume Max  
Advisors
Blanc, Frédéric  orcid-logo
Jury

Prof. Oleg Yazyev (président) ; Dr Frédéric Blanc (directeur de thèse) ; Prof. Klaus Kirch, Prof. Guy Wilkinson, Dr. Michael J. Morello (rapporteurs)

Date Issued

2022

Publisher

EPFL

Publisher place

Lausanne

Public defense year

2022-03-04

Thesis number

8771

Total of pages

255

Subjects

particle physics

•

LHCb

•

LHC

•

charm mixing

•

CP violation

•

tracker

•

scintillating fibres

EPFL units
LPHE3  
Faculty
SB  
School
IPHYS  
Doctoral School
EDPY  
Award

Gilbert Hausmann Award

2023
Available on Infoscience
February 21, 2022
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/185594
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