Kinetic Mixing Term Research Articles

Generalized Dirac duality and CP violation in a two-photon theory

A kinetic mixing term, which generalizes the duality symmetry of Dirac, is studied in a theory with two photons (visible and hidden). This theory can be either CP conserving or CP violating depending on the transformation of fields in the hidden sector. However, if CP is violated, it necessarily occurs in the hidden sector. This opens up an interesting possibility of new sources of CP violation.

Stabilization of semilocal strings by dark scalar condensates

Semilocal and electroweak strings are well-known to be unstable against unwinding by the condensation of the second Higgs component in their cores. A large class of current models of dark matter contains dark scalar fields coupled to the Higgs sector of the Standard Model (Higgs portal) and/or dark U(1) gauge fields. It is shown, that Higgs-portal-type couplings and a gauge kinetic mixing term of the dark U(1) gauge field have a significant stabilising effect on semilocal strings in the "visible" sector.

Kinetic mixing at strong coupling

A common feature of many string-motivated particle physics models is additional strongly coupled U(1)'s. In such sectors, electric and magnetic states have comparable mass, and integrating out modes also charged under U(1) hypercharge generically yields CP preserving electric kinetic mixing and CP violating magnetic kinetic mixing terms. Even though these extra sectors are strongly coupled, we show that in the limit where the extra sector has approximate N = 2 supersymmetry, we can use formal methods from Seiberg-Witten theory to compute these couplings. We also calculate various quantities of phenomenological interest such as the cross section for scattering between visible sector states and heavy extra sector states, as well as the effects of supersymmetry breaking induced from coupling to the MSSM.

Non-Abelian monopoles as the origin of dark matter

We suggest that dark matter may be partially constituted by a dilute ’t Hooft–Polyakov monopoles gas. We reach this conclusion by using the Georgi–Glashow model coupled to a dual kinetic mixing term [Formula: see text] where [Formula: see text] is the electromagnetic field and [Formula: see text] the ’t Hooft tensor. We show that these monopoles carry both (Maxwell) electric and (Georgi–Glashow) magnetic charges and the electric charge quantization condition is modified in terms of a dimensionless real parameter. This parameter could be determined from milli-charged particle experiments.

On the entanglement between interacting scalar field theories

We study "field space entanglement" in certain quantum field theories consisting of N number of free scalar fields interacting with each other via kinetic mixing terms. We present exact analytic expressions for entanglement end Renyi entropies between arbitrary number of scalar fields by which we could explore certain entanglement inequalities. Other entanglement measures such as mutual information and entanglement negativity have also been studied. We also give some comments about possible holographic realizations of such models.

Translational symmetry breaking in field theories and the cosmological constant

We argue, at a very basic effective field theory level, that higher dimension operators in scalar theories that break symmetries at scales close to their ultraviolet completion cutoff, include terms that favour the breaking of translation (Lorentz) invariance, potentially resulting in striped, chequered board or general crystal-like phases. Such descriptions can be thought of as the effective low energy description of QCD-like gauge theories near their strong coupling scale where terms involving higher dimension operators are generated. Our low energy theory consists of scalar fields describing operators such as $\bar{q} q$ and $\bar{q} F^{(2n)} q$. Such scalars can have kinetic mixing terms that generate effective momentum dependent contributions to the mass matrix. We show that these can destabilize the translationally invariant vacuum. It is possible that in some real gauge theory such operators could become sufficiently dominant to realize such phases and it would be interesting to look for them in lattice simulations. We present a holographic model of the same phenomena which includes RG running. A key phenomenological motive to look at such states is recent work that shows that the non-linear response in $R^2$ gravity to such short range fluctuations can mimic a cosmological constant. Intriguingly in a cosmology with such a Starobinsky inflation term, to generate the observed value of the present day acceleration would require stripes at the electroweak scale. Unfortunately, low energy phenomenological constraints on Lorentz violation in the electron-photon system appear to strongly rule out any such possibility outside of a disconnected dark sector.

Dark Forces Searches at KLOE-2

Direct searches of dark matter are performed at accelerator facilities. The existence of a new vector boson has been postulated in different scenarios where in the most basic scheme the coupling to the SM can be achieved via a kinetic mixing term due to the U boson. The KLOE experiment at DA$\phi$NE searched for the U boson both in Dalitz decays of the $\phi$ meson and in continuum events. For all of these searches an upper limit for the U boson coupling $\epsilon^{2}$ has been established in the mass range $50 \, \text{MeV} < m_U < 1000\,\text{MeV}$. A summary of the different models and searches along with results are presented.

Baryon and dark matter genesis from strongly coupled strings

D3-brane probes of E-type Yukawa points lead to strongly coupled nearly conformal sectors nearby the Standard Model (visible sector) which are motivated by F-theory GUTs. Realistic visible sector brane configurations induce a seesaw mass hierarchy in the hidden sector with light GUT singlets charged under a strongly coupled hidden sector U(1). Interpreting these GUT singlets as dark matter, this leads to a matter genesis scenario where the freeze out and subsequent decay of heavy mediators between the two sectors simultaneously populates comparable amounts of baryon and dark matter asymmetry. Generating a net matter asymmetry requires a generational structure in the probe sector which is absent at weak string coupling, but is automatically realized at strong string coupling via towers of dyonic bound states corresponding to multi-prong string junctions. The hidden U(1) couples to the visible sector through both electric and magnetic kinetic mixing terms, providing an efficient means to deplete the symmetric component of dark matter. The mass of the dark matter is of order ~ 10 GeV. The dark matter mass and the matter asymmetry are both controlled by the scale of conformal symmetry breaking ~ 10^(9) - 10^(13) GeV, with the precise relation between the two set by details of the visible sector brane configuration.

SU(2) KINETIC MIXING TERMS AND SPONTANEOUS SYMMETRY BREAKING

The non-Abelian generalization of the Holdom model, i.e. a theory with two gauge fields coupled to the kinetic mixing term g tr (Fμν(A)Fμν(B)) is considered. Contrarily to the Abelian case, the group structure G×G is explicitly broken to G. For SU(2) this fact implies that the residual gauge symmetry as well as the Lorentz symmetry is spontaneously broken. We show that this mechanism provides masses for the involved particles. Also, the model presents instanton solutions with a redefined coupling constant.

Simple flavor protection for the Randall-Sundrum model

We present a simple variation of warped flavor models where the hierarchies of fermion masses and mixings are still explained but dangerous flavor-violating effects in the Kaon sector are greatly reduced. The key new ingredients are two horizontal $U(1)$ symmetries. These symmetries forbid flavor violation in the down-quark sector (with the exception of IR brane localized kinetic mixing terms for the left-handed quarks) while allowing for flavor violation in the up-quark sector. The leading flavor constraints come from ${D}^{0}\ensuremath{-}{\overline{D}}^{0}$ mixing, and are safely satisfied for the Kaluza-Klein mass scale of order 3 TeV. Our analysis of the flavor constraints includes the effects of the (usually ignored) brane localized kinetic terms. We also comment on the effects of the additional $U(1)$ gauge bosons that are present if the horizontal symmetries are gauged.

Minicharges and magnetic monopoles

Minicharged particles arise naturally in extensions of the Standard Model with a kinetic mixing term between the ordinary electromagnetic U(1) and an extra “hidden sector”U(1). In this note we study the compatibility of these particles with the existence of magnetic monopoles. We find that angular momentum quantization allows only certain combinations of ordinary and hidden monopole charge. Using the example where one of the U(1)s originates from a spontaneously broken SU(2), we demonstrate that exactly the allowed types of monopoles arise as 't Hooft–Polyakov monopoles.

Probing hidden sector photons through the Higgs window

We investigate the possibility that a (light) hidden sector extra photon receives its mass via spontaneous symmetry breaking of a hidden sector Higgs boson, the so-called hidden-Higgs. The hidden-photon can mix with the ordinary photon via a gauge kinetic mixing term. The hidden-Higgs can couple to the standard model Higgs via a renormalizable quartic term---sometimes called the Higgs portal. We discuss the implications of this light hidden-Higgs in the context of laser polarization and light-shining-through-the-wall experiments as well as cosmological, astrophysical, and non-Newtonian force measurements. For hidden-photons receiving their mass from a hidden-Higgs, we find in the small mass regime significantly stronger bounds than the bounds on massive hidden sector photons alone.

The flavor of the composite pseudo-goldstone Higgs

We study the flavor structure of 5D warped models that provide a dual description of a composite pseudo-Goldstone Higgs. We first carefully re-examine the flavor constraints on the mass scale of new physics in the standard Randall-Sundrum-type scenarios, and find that the KK gluon mass should generically be heavier than about 21 TeV. We then compare the flavor structure of the composite Higgs models to those in the RS model. We find new contributions to flavor violation, which while still are suppressed by the RS-GIM mechanism, will enhance the amplitudes of flavor violations. In particular, there is a kinetic mixing term among the SM fields which (although parametrically not enhanced) will make the flavor bounds even more stringent than in RS. This together with the fact that in the pseudo-Goldstone scenario Yukawa couplings are set by a gauge coupling implies the KK gluon mass to be at least about 33 TeV. For both the RS and the composite Higgs models the flavor bounds could be stronger or weaker depending on the assumption on the value of the gluon boundary kinetic term. These strong bounds seem to imply that the fully anarchic approach to flavor in warped extra dimensions is implausible, and there have to be at least some partial flavor symmetries appearing that eliminate part of the sources for flavor violation. We also present complete expressions for the radiatively generated Higgs potential of various 5D implementations of the composite Higgs model, and comment on the 1–5 percent level tuning needed in the top sector to achieve a phenomenologically acceptable vacuum state.

Probing theZ′gauge boson with the spin configuration of top quark pair production at futuree−e+linear colliders

We explore the effects of extra neutral gauge boson involved in the supersymmetric E6 model on the spin configuration of the top quark pair produced at the polarized e- e+ collider. Generic mixing terms are considered including kinetic mixing terms as well as mass mixing. In the off-diagonal spin basis of the standard model, we show that the cross sections for the suppressed spin configurations can be enhanced with the effects of the Z' boson through the modification of the spin configuration of produced top quark pair enough to be measured in the Linear Colliders, which provides the way to observe the effects of Z' boson and discriminate the pattern of gauge group decomposition. It is pointed out that the kinetic mixing may dilute the effects of mass mixing terms, and we have to perform the combined analysis.

Leptophobic U(1)'s and the Rb-Rc anomalies.

In this paper, we investigate the possibility of explaining both the R_b excess and the R_c deficit reported by the LEP experiments through Z-Z' mixing effects. We have constructed a set of models consistent with a restrictive set of principles: unification of the Standard Model (SM) gauge couplings, vector- like additional matter, and couplings which are both generation-independent and leptophobic. These models are anomaly-free, perturbative up to the GUT scale, and contain realistic mass spectra. Out of this class of models, we find three explicit realizations which fit the LEP data to a far better extent than the unmodified SM or MSSM and satisfy all other phenomenological constraints which we have investigated. One realization, the \eta-model coming from E_6, is particularly attractive, arising naturally from geometrical compactifications of heterotic string theory. This conclusion depends crucially on the inclusion of a U(1) kinetic mixing term, whose value is correctly predicted by renormalization group running in the E_6 model given one discrete choice of spectra.

Comment on ZZ′ mixing in extended gauge theories

In gauge theories with gauge groups containing more than one U (1) gauge group, it is possible to have kinetic mixing terms for the different U (1) gauge fields in the lagrangian. The physical consequences of these mixings are studied. It is shown that electromagnetic interactions are not affected by these mixing terms. The properties of interactioms mediated by massive gauge bosons are modified however. Ways of eliminating the kinetic mixing terms are also discussed.