Higgs bosons with large couplings to light quarks

Abstract

A common lore has arisen that beyond the Standard Model (BSM) particles, which can be searched for at current and proposed experiments, should have flavorless or mostly third-generation interactions with Standard Model quarks. This theoretical bias severely limits the exploration of BSM phenomenology, and is especially constraining for extended Higgs sectors. Such limitations can be avoided in the context of Spontaneous Flavor Violation (SFV), a robust and UV complete framework that allows for significant couplings to any up or down-type quark, while suppressing flavorchanging neutral currents via flavor alignment. In this work we study the theory and phenomenology of extended SFV Higgs sectors with large couplings to any quark generation. We perform a comprehensive analysis of flavor and collider constraints of extended SFV Higgs sectors, and demonstrate that new Higgs bosons with large couplings to the light quarks may be found at the electroweak scale. In particular, we find that new Higgses as light as 100 GeV with order ∼ 0.1 couplings to first or second generation quarks, which are copiously produced at LHC via quark fusion, are allowed by current constraints. Furthermore, the additional SFV Higgses can mix with the SM Higgs, providing strong theory motivation for an experimental program looking for deviations in the light quark-Higgs couplings. Our work demonstrates the importance of exploring BSM physics coupled preferentially to light quarks, and the need to further

Constraints on long-lived light scalars with flavor-changing couplings and the KOTO anomaly

“…We are very grateful to Daniel Egana-Ugrinovic for useful correspondence and comparison with the results in Ref. [7], which helped us correct our earlier calculations of the flavor-changing Kaon decays for the singlet scalar case, including the effective FCNC scalar couplings, the threshold for the hadron decays and the re-absorption factor. We also thank Kaladi Babu, Sabyasachi Chakraborty, Bhaskar Dutta and Taku Yamanaka for useful discussions and correspondence.…”

“…Note Added: While finalizing our manuscript, we noticed Ref. [7], which has some overlap with our SM-singlet scalar case (cf. Sec.…”

“…In Eq. (2.8), the factor D K K /b K cτ K (with K standing for both K ± and K L ) takes into account the re-absorption of Kaons before decaying [7], with K = 15.3 cm the absorption length, b K = E K /m K the Lorentz boost factor with E K 25 GeV, and τ K the total Kaon decay width. It turns out that the re-absorption factors are respectively 8.1 × 10 −4 and 2.0 × 10 −4 for K ± and K L .…”

“…But given the far-reaching consequences, we take the KOTO result (1.1) at face value and explore possible implications for some simple BSM scenarios that can be independently tested in other ongoing or future experiments. At the phenomenological level, the KOTO signal can be interpreted as the emission of a new light, long-lived scalar particle S in the two-body kaon decay K L → π 0 S, which subsequently decays outside the KOTO detector, thus mimicking the invisible νν final states in K L → π 0 νν [5][6][7]. 1 In this paper, we consider possible ultraviolet (UV)-complete model frameworks for such a new light scalar particle S with m S < m K − m π 0 and with a flavor-changing effective coupling of the form KπS so that it can be emitted in kaon decay.…”

Implication of K→πνν¯ for generic neutrino interactions in effective field theories

“…In the SM no events are expected from the above Kaon rare decays, but KOTO reported three signal events in the search of K L → π 0 νν. There exist quite a few works trying to explain these intriguing events reported by KOTO [4,[11][12][13] (or constrain particular new physics (NP) models [14,15]) and meanwhile avoid the violation of its relation with the K + → π + νν decay, that is the Grossman-Nir bound [16].…”