arXiv subjects

Damir Bečirević

Publications and source records attributed to Damir Bečirević.

21 records · Page 2Linked to original sources

arXiv2017

Seeking the CP-odd Higgs via $h\rightarrow η_{c,b}\ell^+\ell^-$

We show that the decay rates of the Higgs boson to a pseudoscalar quarkonium and a pair of leptons, $h\to P\ell^+\ell^-$ ($P\in\{η_c,η_b\}$), can be substantially enhanced in a scenario with two Higgs doublets with a softly broken $\mathbb{Z}_2$ symmetry (2HDM) when the CP-odd Higgs A is light, i.e. $m_A\lesssim m_h$. Depending on the type of 2HDM the enhancement of $\mathcal{B}(h\to η_{c,b}τ^+τ^-)$ with respect to its Standard Model value can be an order of magnitude larger, i.e. $\mathcal{O}(10^{-6}\div10^{-5})$. The decays $h\to P\ell^+\ell^-$ could therefore provide an efficient channel to investigate the presence of a light CP-odd Higgs $A$ and help to disentangle among various 2HDM scenarios.

hep-ph↗

arXiv2016

Leptoquark model to explain the $B$-physics anomalies, $R_K$ and $R_D$

We show that a model with a scalar leptoquark of hypercharge $Y=1/6$ which includes the light right-handed neutrinos, can successfully describe both of the $B$-physics anomalies, $R_K^{\rm exp} < R_K^{\rm SM}$ and $R_D^{\rm exp} > R_D^{\rm SM}$. We discuss the corresponding low energy effective theory and, after using the known experimental data as constraints, we show that the model is viable and that it offers several predictions which can be tested experimentally.

hep-ph↗

arXiv2016

Lepton flavor non-universality in $b \to s \ell^+ \ell^-$ processes

We explore a scenario of New Physics entering the description of $B\to K^{(\ast )} μμ$ decay through couplings to the operators ${\cal O}_{9,10}^\prime$, satisfying $C_9^\prime = - C_{10}^\prime$. From the current data on ${\cal B}(B_s\to μμ)$ and ${\cal B}(B\to K μμ)_{[15,22] \,\mathrm{GeV}^2}$, we obtain constraints on $\mathrm{Re} C_{10}^\prime$ and $\mathrm{Im} C_{10}^\prime$ which we then assume to be lepton specific, and find $R_K= {\cal B}(B\to K μμ)/ {\cal B}(B\to K ee)_{[1,6]\,\mathrm{GeV}^2}=0.88(8)$, consistent with recent value measured at LHCb. A specific realization of this scenario is the one with a scalar leptoquark state $Δ$, in which $C_{10}^\prime$ is related to the mass of $Δ$ and its Yukawa couplings. We then show that this scenario does not make any significant impact on $B_s-\overline B_s$ mixing amplitude nor to $ {\cal B}(B\to Kν\bar ν)$. Instead, it can modify $R_{K^\ast}= {\cal B}(B\to K^\ast μμ)/ {\cal B}(B\to K^\ast ee)_{[1,6]\,\mathrm{GeV}^2}$, which will soon be experimentally measured and we find it to be $R_{K^\ast}= 1.11(8)$, while $R_{K^\ast}/R_K= 1.27(19)$. A similar ratio of forward-backward asymmetries also becomes lower than in the Standard Model.

hep-ph↗