Probing New Physics with Isotope Shift Spectroscopy

We investigate the potential to probe physics beyond the Standard Model with isotope shift measurements of optical atomic clock transitions. We first derive the reach for generic new physics above the GeV scale at the effective field theory level, as well as estimate the limits on possible new spin-independent forces mediated by sub-GeV states coupled to electrons and neutrons. We also study the weak force and show that isotope shifts could provide strong constraints on the $Z^0$ couplings to valence quarks, which complement precision observables at LEP and atomic parity violation experiments. Finally, motivated by recent experimental hints of a new 750 GeV resonance in diphotons, we also consider the potential to probe its parity-preserving couplings to electrons, quarks and gluons with this method. In particular, combining the diphoton signal with indirect constraints from $g_e-2$ and isotope shifts in Ytterbium allows to probe the resonance coupling to electrons with unprecedented precision.Comment: 6 pages, 2 figures, 2 table

Pinning down electroweak dipole operators of the top quark

We consider hadronic top quark pair production and pair production in association with a photon or a $Z$ boson to probe electroweak dipole couplings in $t\bar{b}W$, $t\bar{t}\gamma$ and $t\bar{t}Z$ interactions. We demonstrate how measurements of these processes at the 13 TeV LHC can be combined to disentangle and constrain anomalous dipole operators. The construction of cross section ratios allows us to significantly reduce various uncertainties and exploit orthogonal sensitivity between the $t\bar{t}\gamma$ and $t\bar{t}Z$ couplings. In addition, we show that angular correlations in $t\bar{t}$ production can be used to constrain the remaining $t\bar{b}W$ dipole operator. Our approach yields excellent sensitivity to the anomalous couplings and can be a further step towards precise and direct measurements of the top quark electroweak interactions.Comment: 9 pages, 3 figures. v2: additional references, extended discussion, matches the journal versio

Electroweak constraints on flavorful effective theories

We derive model-independent constraints arising from the Z and W boson observables on dimension six operators in the effective theory beyond the Standard Model. In particular, we discuss the generic flavor structure for these operators as well as several flavor patterns motivated by simple new physics scenarios.Comment: 31 pages; v2: SILH basis constraints added, comments and clarifications added or remove

Coupling QCD-scale axion-like particles to gluons

We present a novel data-driven method for determining the hadronic interaction strengths of axion-like particles (ALPs) with QCD-scale masses. Using our method, it is possible to calculate the hadronic production and decay rates of ALPs, along with many of the largest ALP decay rate to exclusive final states. To illustrate the impact on QCD-scale ALP phenomenology, we consider the scenario where the ALP-gluon coupling is dominant over the ALP coupling to photons, electroweak bosons, and all fermions for $m_{\pi} \lesssim m_a \lesssim 3$ GeV. We emphasize, however, that our method can easily be generalized to any set of ALP couplings to SM particles. Finally, using the approach developed here, we provide calculations for the branching fractions of $\eta_c \to VV$ decays, i.e. $\eta_c$ decays into two vector mesons, which are consistent with the known experimental values.Comment: 19 pages, 7 figures; v3 Fig 4 updated to account for a small change in the limit taken from [1903.03586

Flavor Beyond the Standard Universe

We explore the possibility that the observed pattern of quark masses is the consequence of a statistical distribution of Yukawa couplings within the multiverse. We employ the anthropic condition that only two ultra light quarks exist, justifying the observed richness of organic chemistry. Moreover, the mass of the recently discovered Higgs boson suggests that the top Yukawa coupling lies near the critical condition where the electroweak vacuum becomes unstable, leading to a new kind of flavor puzzle and to a new anthropic condition. We scan Yukawa couplings according to distributions motivated by high-scale flavor dynamics and find cases in which our pattern of quark masses has a plausible probability within the multiverse. Finally we show that, under some assumptions, these distributions can significantly ameliorate the runaway behavior leading to weakless universes.Comment: 12 pages, 4 figure

Light quark Yukawa couplings from Higgs kinematics

We show that the normalized Higgs production $p_T$ and $y_h$ distributions are sensitive probes of Higgs couplings to light quarks. For up and/or down quark Yukawa couplings comparable to the SM $b$ quark Yukawa the $\bar u u$ or $\bar d d$ fusion production of the Higgs could lead to appreciable softer $p_T$ distribution than in the SM. The rapidity distribution, on the other hand, becomes more forward. We find that, owing partially to a downward fluctuation, one can derive competitive bounds on the two couplings using ATLAS measurements of normalized $p_T$ distribution at 8\,TeV. With 300 fb${}^{-1}$ at 13\,TeV LHC one could establish flavor non-universality of the Yukawa couplings in the down sector.Comment: 15 pages, 7 figures; v2: add clarifications, plot and refs. conclusion unchanged; v3: matched to the published versio

Lepton flavor universality violation without new sources of quark flavor violation

We show that new physics models without new flavor violating interactions can explain the recent anomalies in the $b\to s\ell^+\ell^-$ transitions. The $b\to s\ell^+\ell^-$ arises from a $Z'$ penguin which automatically predicts the $V-A$ structure for the quark currents in the effective operators. This framework can be realized either in a renormalizable $U(1)'$ setup or be due to new strongly interacting dynamics. The di-muon resonance searches at the LHC are becoming sensitive to this scenario since the $Z'$ is relatively light, and could well be discovered in future searches by ATLAS and CMS.Comment: 5 pages, 3 figures, correction of a mistake in eq. (16), Fig. 2 updated, conclusions unchange

Probing Atomic Higgs-like Forces at the Precision Frontier

We propose a novel approach to probe new fundamental interactions using isotope shift spectroscopy in atomic clock transitions. As concrete toy example we focus on the Higgs boson couplings to the building blocks of matter: the electron and the up and down quarks. We show that the attractive Higgs force between nuclei and their bound electrons, that is poorly constrained, might induce effects that are larger than the current experimental sensitivities. More generically, we discuss how new interactions between the electron and the neutrons, mediated via light new degrees of freedom, may lead to measurable non-linearities in a King plot comparison between isotope shifts of two different transitions. Given state-of-the-art accuracy in frequency comparison, isotope shifts have the potential of being measured with sub-Hz accuracy, thus potentially enabling the improvement of current limits on new fundamental interactions. Candidate atomic system for this measurement require two different clock transitions and four zero nuclear spin isotopes. We identify several systems that satisfy this requirement and also briefly discuss existing measurements. We consider the size of the effect related to the Higgs force and the requirements for it to produce an observable signal.Comment: 7 pages, added focus on light higgs-like mediators, electron density at the nucleus improved with effective quantum number, version accepted for publication in PR

Charming the Higgs

We show that current Higgs data permit a significantly enhanced Higgs coupling to charm pairs, comparable to the Higgs to bottom pairs coupling in the Standard Model, without resorting to additional new physics sources in Higgs production. With a mild level of the latter current data even allow for the Higgs to charm pairs to be the dominant decay channel. An immediate consequence of such a large charm coupling is a significant reduction of the Higgs signal strengths into the known final states as in particular into bottom pairs. This might reduce the visible vector-boson associated Higgs production rate to a level that could compromise the prospects of ever observing it. We however demonstrate that a significant fraction of this reduced signal can be recovered by jet-flavor-tagging targeted towards charm-flavored jets. Finally we argue that an enhanced Higgs to charm pairs coupling can be obtained in various new physics scenarios in the presence of only a mild accidental cancellation between various contributions.Comment: 8 pages, 3 figure