B Mesons Phenomenology to the Search of a Signal Beyond the Standard Model

Abstract : Over the last decades, the loop induced decay $bo sgamma$ has attracted a considerable amount of attention due to its potential sensitivity to new physics. In the standard model, the processes $bo sgamma_{L(R)}$ and $overline{b}o overline{s}gamma_{R(L)}$ are proportional to the Wilson coefficients $C_7(C'_7)$. The decay $Bo Kpipigamma$ provides via angular analysis a parity odd observable ($lambda$) and via $B-overline{B}$ mixing a CP odd observable ($S_{ho Kgamma}$) both sensitive to the ratio $C'_7/C_7approx m_s/m_b$. The main issue is that both $lambda$ and $S_{ho Kgamma}$ are accompanied by a dilution factor originating from the strong decay. This work is focused on the estimation and modelisation of those dilution factors.The transition $Bo Kpipigamma$ occurs as three subsequent decays. The weak process $Bo K_{res}gamma$ is followed by the strong 3-body decay of the kaonic resonance $K_{res}o Kpipi$ via three distinct intermediate states $ho K$, $K^*pi$ and $kappapi$.The observable $S_{ho Kgamma}$ is accessible with the final state $K^0pi^+pi^-gamma$, but the presence of non CP eigenstates $K^{*pm}pi^mp$ and $kappa^pmpi^mp$ induce the dilution factor $D$.To deal with this inconvenience, we derive the expression of $D$ in terms of the partial waves $ho K$, $K^*pi$ and $kappapi$ and including the koanic resonances $K_1(1270/1400), K^*(1410)$ and $K_2^*(1430)$. The partial waves can then be fitted using the final state $K^{pm}pi^{mp}pi^{pm}gamma$, where the experimental sensitivity is higher, in order the compute the dilution factor. Then we propose a new model independent method to determine $D$, which consist in extracting the dilution factor independently of $S_{ho Kgamma}$ using final states with one neutral pion such as $K^+pi^-pi^0gamma$. Exploiting existing data with $m_{Kpipi} <1.8;$GeV$/c^2$, we obtained $D=0.92pm0.17$.When considering only $K_1(1270/1400)$ and $K^*(1410)$, fitting the angular and Dalitz plot distribution allows to extract $lambda$ with an accuracy of the order of $pm 10%$ for a sample of $5.10^3$ Monte Carlo generated events. But this require a good knowledge of different quantities of importance in the strong decay such as the $K_1$ mixing angle, individual $Bo K_{res}gamma$ branching ratios and relative phases. We show that some of those parameters can simultaneously fitted with $lambda$ with a loss of accuracy of just a few percent. We derive how, using only the angular distribution, one can partially cancel contribution from the strong decay and obtain a lower bound on $|lambda|$.
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Submitted on : Wednesday, November 7, 2018 - 3:54:05 PM
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Jeremy Hebinger. B Mesons Phenomenology to the Search of a Signal Beyond the Standard Model. High Energy Physics - Phenomenology [hep-ph]. Université Paris-Saclay, 2017. English. ⟨NNT : 2017SACLS260⟩. ⟨tel-01915429⟩



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