NOTE: First draft. We welcome comments, corrections, suggestions. For missing references we kindly ask to specify in relation to which topic and at which point of the review it would be appropriate to include a citation. We will not be able to address unspecifed requests.

(2017) 'Redening the axion window.', Physical review letters., 118 (3). 031801.Further information on publisher's website:https://doi.org/10.1103/PhysRevLett.118.031801Publisher's copyright statement:Reprinted with permission from the American Physical Society: Physical Review Letters 118, 031801 c (2017) by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modied, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. A major goal of axion searches is to reach inside the parameter space region of realistic axion models. Currently, the boundaries of this region depend on somewhat arbitrary criteria, and it would be desirable to specify them in terms of precise phenomenological requirements. We consider hadronic axion models and classify the representations R Q of the new heavy quarks Q. By requiring that (i) the Q's are sufficiently short lived to avoid issues with long-lived strongly interacting relics, (ii) no Landau poles are induced below the Planck scale; 15 cases are selected which define a phenomenologically preferred axion window bounded by a maximum (minimum) value of the axion-photon coupling about 2 times (4 times) larger than is commonly assumed. Allowing for more than one R Q , larger couplings, as well as complete axion-photon decoupling, become possible.

The vector leptoquark representation, Uµ = (3, 1, 2/3), was recently identified as an exceptional single mediator model to address experimental hints on lepton flavour universality violation in semileptonic B-meson decays, both in neutral (b → sµµ) and charged (b → cτ ν) current processes. Nonetheless, it is well-known that massive vectors crave an ultraviolet (UV) completion. We present the first full-fledged UV complete and calculable gauge model which incorporates this scenario while remaining in agreement with all other indirect flavour and electroweak precision measurements, as well as, direct searches at high-pT . The model is based on a new non-abelian gauge group spontaneously broken at the TeV scale, and a specific flavour structure suppressing flavour violation in ∆F = 2 processes while inducing sizeable semileptonic transitions.

We propose a mechanism that allows for sizeable flavour violation in quark-lepton currents, while suppressing flavour changing neutral currents in quark-quark and lepton-lepton sectors. The mechanism is applied to the recently proposed "4321" renormalizable model, which can accommodate the current experimental anomalies in B-meson decays, both in charged and neutral currents, while remaining consistent with all other indirect flavour and electroweak precision measurements and direct searches at high-p T . To support this claim, we present an exhaustive phenomenological survey of this fully calculable UV complete model and highlight the rich complementarity between indirect and direct searches. A.7 Vector-fermion interactions in the mass basis 47 A.8 Tri-linear gauge boson vertices 49 A.9 Renormalisation group equations 51 A.10 SU (4) generators 524. there are very severe constraints from flavour observables in pure leptonic channels, most notably in processes violating lepton universality and lepton flavour.Since the first point clearly contrasts with the remaining ones, finding a coherent NP framework to explain all these facts remains a non-trivial challenge. However, the points above are also suggesting in a (qualitative) way their own solutions. Indeed a viable NP scenario should:1. contain a leptoquark with large flavour violating couplings in order to trigger the anomalous semileptonic decays in charged currents; *

Publisher's copyright statement:Reprinted with permission from the American Physical Society: Physical Review D 96, 075003 c 2017 by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modied, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We discuss phenomenological criteria for defining "axion windows," namely regions in the parameter space of the axion-photon coupling where realistic models live. Currently, the boundaries of this region depend on somewhat arbitrary criteria, and it would be highly desirable to specify them in terms of precise phenomenological requirements. We first focus on hadronic axion models within post-inflationary scenarios, in which the initial abundance of the new vectorlike quarks Q is thermal. We classify their representations R Q by requiring that (i) the Q are sufficiently short lived to avoid issues with long-lived strongly interacting relics, (ii) the theory remains weakly coupled up to the Planck scale. The more general case of multiple R Q is also studied, and the absolute upper and lower bounds on the axion-photon coupling as a function of the axion mass is identified. Pre-inflationary scenarios in which the axion decay constant remains bounded as f a ≤ 5 × 10 11 GeV allow for axion-photon couplings only about 20% larger. Realistic Dine-Fischler-Srednicki-Zhitnitsky type of axion models also remain encompassed within the hadronic axion window. Some mechanisms that can allow to enhance the axion-photon coupling to values sizeably above the preferred window are discussed.

Many new physics models that explain the intriguing anomalies in the b-quark flavor sector are severely constrained by B s mixing, for which the Standard Model prediction and experiment agreed well until recently. The most recent Flavour Lattice Averaging Group (FLAG) average of lattice results for the nonperturbative matrix elements points, however, in the direction of a small discrepancy in this observable Cabibbo-Kobayashi-Maskawa (CKM). Using up-to-date inputs from standard sources such as PDG, FLAG and one of the two leading CKM fitting groups to determine ΔM SM s , we find a severe reduction of the allowed parameter space of Z 0 and leptoquark models explaining the B anomalies. Remarkably, in the former case the upper bound on the Z 0 mass approaches dangerously close to the energy scales already probed by the LHC. We finally identify some model-building directions in order to alleviate the tension with B s mixing.

The constraints of gauge unification on intermediate mass scales in nonsupersymmetric SOð10Þ scenarios are systematically discussed. With respect to the existing reference studies we include the Uð1Þ gauge mixing renormalization at the one-and two-loop level, and reassess the two-loop beta coefficients. We evaluate the effects of additional Higgs multiplets required at intermediate stages by a realistic mass spectrum and update the discussion to the present day data. On the basis of the obtained results, SOð10Þ breaking patterns with up to two intermediate mass scales are discussed for potential relevance and model predictivity.

We propose a class of axion models with generation-dependent Peccei-Quinn charges for the known fermions that allow one to suppress the axion couplings to nucleons and electrons. Astrophysical limits are thus relaxed, allowing for axion masses up to O(0.1)  eV. The axion-photon coupling remains instead sizable, so that next-generation helioscopes will be able to probe this scenario. Astrophobia unavoidably implies flavor-violating axion couplings so that experimental limits on flavor-violating processes can provide complementary probes. The astrophobic axion can be a viable dark matter candidate in the heavy mass window and can also account for anomalous energy loss in stars.