29 research outputs found
Phenomenology of Extra Abelian Gauge Symmetries
No full textIn the search for new physics, models of extra U(1) symmetries provide a simple but versatile theoretical framework to attenuate shortcomings of the Standard Model (SM). In an effort to systematically survey the physical prospects of such theories, we study three different phenomenological aspects of extra U(1) symmetries.
First, studying Flavor-Changing Neutral Currents (FCNC) mediated by an effective heavy Z' boson, we identify the most stringent constraints for all possible combinations of lepton and quark flavor violating couplings.In regions of parameter space where severe bounds from meson mixing are avoided, LHC resonance searches can provide the leading constraint.
Such scenarios are able to explain the observed (g-2)_\mu and tau decay anomalies.
Second, we consider the possibility that the hidden photon is the gauge boson of the anomaly-free groups U(1)_{B-L}, U(1)_{L_\mu-L_e}, U(1)_{L_e-L_\tau} or U(1)_{L_\mu-L_\tau}. Taking into account loop-induced kinetic mixing, we perform a comprehensive analysis of all hidden photon constraints in these scenarios. While generically stringent bounds arise due to neutrino couplings, for U(1)_{L_{\mu}-L_\tau} an explanation of the (g-2)_\mu anomaly is possible.
Finally, extending the previously considered U(1)_{L_\mu-L_\tau} model by a vector-like fermion \chi, we find that the (g-2)_\mu anomaly and the dark matter relic abundance can be simultaneously explained
A Consistent Theory of Kinetic Mixing and the Higgs Low-Energy Theorem
No full textExtensions of the Standard Model of particle physics with new Abelian gauge
groups allow for kinetic mixing between the new gauge bosons and the
hypercharge gauge boson, resulting in mixing with the photon. In many models
the mixing with the hypercharge gauge boson captures only part of the kinetic
mixing term with the photon, since the new gauge bosons can also mix with the
neutral component of the gauge bosons. We take these contributions
into account and present a consistent description of kinetic mixing for general
Abelian gauge groups both in the electroweak symmetric and the broken phase. We
identify an effective operator that captures the kinetic mixing with
and demonstrate how renormalisable contributions arise if the charged fields
only obtain their masses from electroweak symmetry breaking. For the first
time, a low-energy theorem for the couplings of novel Abelian gauge bosons with
the Standard Model Higgs boson is derived from the one-loop kinetic mixing
amplitudes.Comment: 6 pages, 1 figure; v2: matches published version in Phys. Rev. Lett.,
minor typos correcte
Purely flavor-changing Z ′ bosons and where they might hide
No full textAbstract A plethora of ultraviolet completions of the Standard Model have extra U(1) gauge symmetries. In general, the associated massive Z ′ gauge boson can mediate flavor-changing neutral current processes at tree level. We consider a situation where the Z ′ boson couples solely via flavor-changing interactions to quarks and leptons. In this scenario the model parameter space is, in general, quite well constrained by existing flavor bounds. However, we argue that cancellation effects shelter islands in parameter space from strong flavor constraints and that these can be probed by multipurpose collider experiments like ATLAS or CMS as well as LHCb in upcoming runs at the LHC. In still allowed regions of parameter space these scenarios may help to explain the current tension between theory and experiment of (g − 2) μ as well as a small anomaly in τ decays
How to rule out in with White Dwarf Cooling
No full textIn recent years, the gauge group has received a lot of attention since it can, in principle, account for the observed excess in the anomalous muon magnetic moment , as well as the Hubble tension. Due to unavoidable, loop-induced kinetic mixing with the SM photon and , the gauge boson can contribute to stellar cooling via decays into neutrinos. In this work, we perform for the first time an \textit{ab initio} computation of the neutrino emissivities of white dwarf stars due to plasmon decay in a model of gauged . A key result is that current observations of the early-stage white dwarf neutrino luminosity at the 30\% level exclude previously allowed regions of the parameter space favoured by a simultaneous explanation of the and anomalies. In this work, we present the relevant white dwarf cooling limits over the entire mass range. In particular, we have performed a rigorous computation of the luminosities in the resonant regime, where the mass is comparable to the white dwarf plasma frequencies.17 pages, 6 figures, 2 data files; v2: improved discussion of the cooling limit, matches journal version to appear in JHE
How to rule out (g − 2) μ in U 1 L μ − L τ with white dwarf cooling
No full textAbstract In recent years, the gauge group U 1 L μ − L τ has received a lot of attention since it can, in principle, account for the observed excess in the anomalous muon magnetic moment (g − 2) μ , as well as the Hubble tension. Due to unavoidable, loop-induced kinetic mixing with the SM photon and Z, the U 1 L μ − L τ gauge boson A ′ can contribute to stellar cooling via decays into neutrinos. In this work, we perform for the first time an ab initio computation of the neutrino emissivities of white dwarf stars due to plasmon decay in a model of gauged U 1 L μ − L τ . A key result is that current observations of the early-stage white dwarf neutrino luminosity at the 30% level exclude previously allowed regions of the parameter space favoured by a simultaneous explanation of the (g – 2) μ and H 0 anomalies. In this work, we present the relevant white dwarf cooling limits over the entire A ′ mass range. In particular, we have performed a rigorous computation of the luminosities in the resonant regime, where the A ′ mass is comparable to the white dwarf plasma frequencies
Hunting all the hidden photons
No full textAbstract We explore constraints on gauge bosons of a weakly coupled U(1) B − L , U1Lμ−Le,U1Le−LτandU1Lμ−Lτ . To do so we apply the full constraining power of experimental bounds derived for a hidden photon of a secluded U(1) X and translate them to the considered gauge groups. In contrast to the secluded hidden photon that acquires universal couplings to charged Standard Model particles through kinetic mixing with the photon, for these gauge groups the couplings to the different Standard Model particles can vary widely. We take finite, computable loop-induced kinetic mixing effects into account, which provide additional sensitivity in a range of experiments. In addition, we collect and extend limits from neutrino experiments as well as astrophysical and cosmological observations and include new constraints from white dwarf cooling. We discuss the reach of future experiments in searching for these gauge bosons
Flavor structure of anomaly-free hidden photon models
No full textExtensions of the Standard Model with an Abelian gauge group are constrained by gauge anomaly cancellation, so that only a limited number of possible charge assignments is allowed without the introduction of new chiral fermions. For flavor universal charges, couplings of the associated hidden photon to Standard Model fermions are flavor conserving at tree level. We show explicitly that even the flavor-specific charge assignments allowed by anomaly cancellation condition lead to flavor-conserving tree-level couplings of the hidden photon to quarks and charged leptons if the Cabibbo-Kobayashi-Maskawa or Pontecorvo-Maki-Nakagawa-Sakata matrix can be successfully reconstructed. Further, loop-induced flavor-changing couplings are strongly suppressed. As a consequence, the structure of the Majorana mass matrix is constrained and flavor-changing tree-level couplings of the hidden photon to neutrino mass eigenstates are identified as a means to distinguish the U(1)B−L gauge boson from any other anomaly-free extension of the Standard Model without new chiral fermions. We present a comprehensive analysis of constraints and projections for future searches for a U(1)B−L gauge boson, calculate the reach of resonance searches in B meson decays and comment on the implications for nonstandard neutrino interactions
The potential of CMS as a high energy neutrino scattering experiment
No full textWith its enormous number of produced neutrinos the LHC is a prime facility to study the behaviour of high-energy neutrinos. In this letter we propose a novel search strategy for identifying neutrino scattering via displaced appearing jets in the high granularity calorimeter (HGCAL) of the CMS endcap in the high luminosity run of the LHC. We demonstrate in a cut-and-count based analysis how the enormous hadronic background can be reduced while keeping most of the neutrino signal. This paper serves as a proof-of-principle study to illustrate the feasibility of the first direct observation of high-energetic neutrinos coming from W decay
