In the aligned two-Higgs-doublet model, the alignment of Yukawa matrices in flavour space guarantees the absence of tree-level flavour-changing neutral currents, while allowing at the same time for new sources of CP violation, implying potentially large effects in many low-energy processes. In this work we study the constraints from exclusive radiative B → V γ decays, where V denotes a light vector meson. The current experimental data on the CP-averaged branching ratios and the direct CP and isospin asymmetries are analyzed. It is found that, while the branching ratios and direct CP asymmetries do not constrain the parameter space much further compared to the inclusive B → X s,d γ decays, complementary constraints can be obtained from the isospin asymmetries ∆(K * γ) and ∆(ργ). In addition, correlations between the various observables in exclusive B → V γ and inclusive B → X s,d γ decays are investigated in detail, and predictions are made for several so far unmeasured observables. Within the Standard Model (SM), flavour-changing neutral current (FCNC) interactions, which are absent at tree level, are highly suppressed due to the Glashow-Iliopoulos-Maiani mechanism [1], thereby providing a very sensitive probe of new physics (NP). In this respect, the exclusive and inclusive radiative B-meson decays induced by the quark-level FCNC transitions b → sγ and b → dγ are of particular interest; for a recent review, see e.g. [2].On the experimental side, especially the decays corresponding to b → sγ transitions are known with good accuracy, but branching ratios and even CP and isospin asymmetries have been measured for several b → dγ decays as well [3,4]. These results stem mainly from the two B-factory experiments Belle and BaBar; LHCb has however recently started to provide data as well [5,6]. On the theoretical side, while the inclusive decays can be essentially calculated perturbatively with high precision, the exclusive processes are more complicated due to the involved interplay of non-perturbative strong interaction effects [2]. The QCD factorization (QCDF) approach, which will be adopted in this paper, has provided a systematic framework for the treatment of exclusive radiative B-meson decays [7][8][9][10]. For alternative approaches, see e.g. [11][12][13][14][15]. Due to these experimental and theoretical improvements achieved in recent years, the exclusive b → s(d) γ decay channels are providing important constraints on various NP models [16,17].Due to its simplicity and being the low-energy limit of some more complete theories, the two-Higgs-doublet model (2HDM) has been regarded as a popular extension of the SM since its first proposal in the 1970s [18]. In its most general version, the model gives rise to unwanted FCNC phenomena due to the non-diagonal couplings of neutral scalars to fermions. Different ways to suppress them have been proposed, giving rise to a variety of specific implementations [19].The tree-level FCNCs can be eliminated requiring the alignment in flavour space of the Yukawa matrices coupl...
