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2022 ◽  
Vol 137 (1) ◽  
Author(s):  
M. Kachelrieß ◽  
M. N. Malmquist

AbstractCovariant gauges lead to spurious, non-physical polarisation states of gauge bosons. In QED, the use of the Feynman gauge, $$\sum _{\lambda } \varepsilon _\mu ^{(\lambda )}\varepsilon _\nu ^{(\lambda )*} = -\eta _{\mu \nu }$$ ∑ λ ε μ ( λ ) ε ν ( λ ) ∗ = - η μ ν , is justified by the Ward identity which ensures that the contributions of non-physical polarisation states cancel in physical observables. In contrast, the same replacement can be applied only to a single external gauge boson in squared amplitudes of non-abelian gauge theories like QCD. In general, the use of this replacement requires to include external Faddeev–Popov ghosts. We present a pedagogical derivation of these ghost contributions applying the optical theorem and the Cutkosky cutting rules. We find that the resulting cross terms $$\mathcal {A}(c_1,\bar{c}_1;\ldots )\mathcal {A}(\bar{c}_1,c_1;\ldots )^*$$ A ( c 1 , c ¯ 1 ; … ) A ( c ¯ 1 , c 1 ; … ) ∗ between ghost amplitudes cannot be transformed into $$(-1)^{n/2}|\mathcal {A}(c_1,\bar{c}_1;\ldots )|^2$$ ( - 1 ) n / 2 | A ( c 1 , c ¯ 1 ; … ) | 2 in the case of more than two ghosts. Thus the Feynman rule stated in the literature holds only for two external ghosts, while it is in general incorrect.


2022 ◽  
Vol 258 ◽  
pp. 06008
Author(s):  
Eugenio Megías ◽  
Manuel Pérez-Victoria ◽  
Mariano Quirós

We study some features of a warped five-dimensional model that solves the hierarchy problem and exhibits a continuum of Kaluza-Klein (KK) modes with a mass gap at the TeV scale. We compute the propagators and spectral functions for massless bulk gauge bosons, and study how the continuum can be reached as the limit of a set of models with discrete spectrum. Finally, we study the low energy effective theory and provide explicit results for the Wilson coefficients.


Author(s):  
S. Boukaddid ◽  
R. Ahl Laamara ◽  
L. B. Drissi ◽  
E. H. Saidi ◽  
J. Zerouaoui

In this paper, we study the M-string realization of chiral [Formula: see text]-super-conformal field theory in 6 dimensions and its orbifold compactification down to three-dimensional (3D). We analyze its fractionally charged BPS particle spectrum in connection with effective 3D Chern–Simons gauge theory and the supersymmetric fractional quantum Hall effect in [Formula: see text] dimensions. We construct the set of underlying fractionally charged BPS particles in the ground state of the compactified M string and find that it contains 144 BPS states that are generated by four basic quasi-particles (two bosonic-like and two fermionic like) and their CPT conjugate. Two representations of the gauge bosons and the gauginos as condensates of the basic quasiparticles are found and explicit realizations are also given. Other features concerning generalizations are also discussed.


2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Daniele Barducci ◽  
Enrico Bertuzzo ◽  
Giovanni Grilli di Cortona ◽  
Gabriel M. Salla

Abstract Dark photons are massive abelian gauge bosons that interact with ordinary photons via a kinetic mixing with the hypercharge field strength tensor. This theory is probed by a variety of different experiments and limits are set on a combination of the dark photon mass and kinetic mixing parameter. These limits can however be strongly modified by the presence of additional heavy degrees of freedom. Using the framework of dark effective field theory, we study how robust are the current experimental bounds when these new states are present. We focus in particular on the possible existence of a dark dipole interaction between the Standard Model leptons and the dark photon. We show that, under certain assumptions, the presence of a dark dipole modifies existing supernovæ bounds for cut-off scales up to $$ \mathcal{O} $$ O (10–100 TeV). On the other hand, terrestrial experiments, such as LSND and E137, can probe cut-off scales up to $$ \mathcal{O} $$ O (3 TeV). For the latter experiment we highlight that the bound may extend down to vanishing kinetic mixing.


2021 ◽  
Author(s):  
Hani W. Maalouf

Abstract Solving for the missing masses in the Higgs resonances, it was necessary to extend, even quantitatively via an index measurable amount, the SM using a threshold related longitudinal violation procedure. The obtained expression, by being non-contributing via its non-anomalously resulting parameter, is linked to a Cauchy-Schwartz 4-scalar product ratio type of two virtual Gauge Bosons momenta in its minimal anomalous configuration, as vs. its non-anomalous internal. Changing the bounds from energy into momenta, a convexity condition appears. Such technique clarifies the perturbative e.m. fields’ extensions into perturbative and non-perturbative QCD.In applications, there is the violation of the chiral insertion by the axion into neutrinos, and the Lepton number when passing form velocity to spin resonances, such confirming the CS procedure as plus the defiance of the SM comes through their branching ratios but not their angular distributions. Further which if remaining at the same level of minimization can restore the universality of extendibility in the Higgs self-couplings.Leading into deriving the phase of K0 → π+π-, in A(∆1=2)/A(∆1=0) so a conformal skipping dynamical shift from direct CP violation of D0 → K+K- and D0 → π+π- asymmetries, in the long-short mixing concords the phase of KL → π0ννbar, solving the KOTO anomaly.


2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Hrishabh Bharadwaj ◽  
Sukanta Dutta ◽  
Ashok Goyal

Abstract We address the observed discrepancies in the anomalous magnetic dipole moments (MDM) of the muon and electron by extending the inert two Higgs Doublet Model (2HDM) with SM gauge singlet complex scalar field and singlet Vector-like Lepton (VLL) field. We obtain the allowed parameter space constrained from the Higgs decays to gauge Bosons at LHC, LEP II data and electro-weak precision measurements. The muon and electron MDM’s are then explained within a common parameter space for different sets of allowed couplings and masses of the model particles.


2021 ◽  
Vol 2105 (1) ◽  
pp. 012014
Author(s):  
A. Marantis ◽  
I. Maznas ◽  
K. Kordas ◽  
A. Leisos ◽  
A. Tsirigotis

Abstract Vector Boson Scattering (VBS) processes provide a great source of information on the structure of the Quartic Gauge Boson Couplings (QGCs). The Standard Model allows self interactions of the charged vector gauge bosons, although vertices with neutral-only bosons are forbidden. In this paper we use Monte Carlo samples containing VBS events with two Z-bosons in association with two jets, and we present preliminary studies for the setting of constraints on anomalous quartic couplings. In these studies we investigate typical kinematic variables and we classify them according to their sensitivity to aQGC effects. Finally, we evaluate the cross-section enhancement by each one of the dimension-eight QGC operators in the ZZjj channel.


Author(s):  
Wanpeng Tan

A sufficiently massive star in the end of its life will inevitably collapse into a black hole as more deconfined degrees of freedom make the core ever softer. One possible way to avoid the singularity in the end is by dimensional phase transition of spacetime. Indeed, the black hole interior, two-dimensional (2D) in nature, can be described well as a perfect fluid of free massless Majorana fermions and gauge bosons under a 2D supersymmetric mirror model with new understanding of emergent gravity from dimensional evolution of spacetime. In particular, the 2D conformal invariance of the black hole gives rise to desired consistent results for the interior microphysics and structures including its temperature, density and entropy.


2021 ◽  
Vol 104 (7) ◽  
Author(s):  
P. S. Bhupal Dev ◽  
Doojin Kim ◽  
Kuver Sinha ◽  
Yongchao Zhang

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