scholarly journals Dark moments for the Standard Model?

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Thomas G. Rizzo
Keyword(s):  
Standard Model ◽  
Magnetic Dipole ◽  
Parameter Space ◽  
Gauge Coupling ◽  
Large Mass ◽  
Mass Scale ◽  
Complex Scalar ◽  
Quantum Numbers ◽  
The Standard Model ◽  
Model Setup

Abstract If dark matter (DM) interacts with the Standard Model (SM) via the kinetic mixing (KM) portal, it necessitates the existence of portal matter (PM) particles which carry both dark and SM quantum numbers that will appear in vacuum polarization-like loop graphs. In addition to the familiar ∼ eϵQ strength, QED-like interaction for the dark photon (DP), in some setups different loop graphs of these PM states can also induce other coupling structures for the SM fermions that may come to dominate in at least some regions of parameter space regions and which can take the form of ‘dark’ moments, e.g., magnetic dipole-type interactions in the IR, associated with a large mass scale, Λ. In this paper, motivated by a simple toy model, we perform a phenomenological investigation of a possible loop-induced dark magnetic dipole moment for SM fermions, in particular, for the electron. We show that at the phenomenological level such a scenario can not only be made compatible with existing experimental constraints for a significant range of correlated values for Λ and the dark U(1)D gauge coupling, gD, but can also lead to quantitatively different signatures once the DP is discovered. In this setup, assuming complex scalar DM to satisfy CMB constraints, parameter space regions where the DP decays invisibly are found to be somewhat preferred if PM mass limits from direct searches at the LHC and our toy model setup are all taken seriously. High precision searches for, or measurements of, the e+e− → γ + DP process at Belle II are shown to provide some of the strongest future constraints on this scenario.

scholarly journals STRING SCALE GAUGE COUPLING UNIFICATION WITH VECTOR-LIKE EXOTICS AND NONCANONICAL U(1)Y NORMALIZATION

2007 ◽  
Vol 22 (32) ◽  
pp. 6203-6218 ◽  
Author(s):  
V. BARGER ◽  
JING JIANG ◽  
PAUL LANGACKER ◽  
TIANJUN LI
Keyword(s):  
Standard Model ◽  
Gauge Coupling ◽  
Independent Sets ◽  
Tree Level ◽  
New Approach ◽  
Quantum Numbers ◽  
The Standard Model

We use a new approach to study string scale gauge coupling unification systematically, allowing both the possibility of noncanonical U (1)Y normalization and the existence of vector-like particles whose quantum numbers are the same as those of the Standard Model (SM) fermions and their Hermitian conjugates and the SM adjoint particles. We first give all the independent sets (Yi) of particles that can be employed to achieve SU (3)C and SU (2)L string scale gauge coupling unification and calculate their masses. Second, for a noncanonical U (1)Y normalization, we obtain string scale SU (3)C × SU (2)L × U (1)Y gauge coupling unification by choosing suitable U (1)Y normalizations for each of the Yi sets. Alternatively, for the canonical U (1)Y normalization, we achieve string scale gauge coupling unification by considering suitable combinations of the Yi sets or by introducing additional independent sets (Zi), that do not affect the SU (3)C × SU (2)L unification at tree level, and then choosing suitable combinations, one from the Yi sets and one from the Zi sets. We also briefly discuss string scale gauge coupling unification in models with higher Kac–Moody levels for SU (2)L or SU (3)C.

scholarly journals $$U(1)_{B_3-L_2}$$ explanation of the neutral current $$B-$$anomalies

2021 ◽  
Vol 81 (1) ◽  
Author(s):  
B. C. Allanach
Keyword(s):  
Standard Model ◽  
Neutral Current ◽  
Vector Boson ◽  
Baryon Number ◽  
Higgs Bosons ◽  
Complex Scalar ◽  
Quantum Numbers ◽  
The Standard Model ◽  
Model Predictions ◽  
Rule Out

AbstractWe investigate a speculative short-distance force, proposed to explain discrepancies observed between measurements of certain neutral current decays of B hadrons and their Standard Model predictions. The force derives from a spontaneously broken, gauged $$U(1)_{B_3-L_2}$$ U ( 1 ) B 3 - L 2 extension to the Standard Model, where the extra quantum numbers of Standard Model fields are given by third family baryon number minus second family lepton number. The only fields beyond those of the Standard Model are three right-handed neutrinos, a gauge field associated with $$U(1)_{B_3-L_2}$$ U ( 1 ) B 3 - L 2 and a Standard Model singlet complex scalar which breaks $$U(1)_{B_3-L_2}$$ U ( 1 ) B 3 - L 2 , a ‘flavon’. This simple model, via interactions involving a TeV scale force-carrying $$Z^\prime $$ Z ′ vector boson, can successfully explain the neutral current $$B-$$ B - anomalies whilst accommodating other empirical constraints. In an ansatz for fermion mixing, a combination of up-to-date $$B-$$ B - anomaly fits, LHC direct $$Z^\prime $$ Z ′ search limits and other bounds rule out the domain 0.15 $$\hbox {TeV}< M_{Z^\prime }<$$ TeV < M Z ′ < 1.9 TeV at the $$95\%$$ 95 % confidence level. For more massive $$Z^\prime $$ Z ′ s, the model possesses a flavonstrahlung signal, where pp collisions produce a $$Z^\prime $$ Z ′ and a flavon, which subsequently decays into two Higgs bosons.

scholarly journals Scrutinizing vacuum stability in IDM with Type-III inverse seesaw

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Priyotosh Bandyopadhyay ◽  
Shilpa Jangid ◽  
Manimala Mitra
Keyword(s):  
Standard Model ◽  
Beta Function ◽  
Planck Scale ◽  
Gauge Coupling ◽  
Mass Scale ◽  
Dark Matter Candidate ◽  
Mass Generation ◽  
Type Iii ◽  
The Standard Model ◽  
The Stability

Abstract We consider the extension of the Standard Model (SM) with an inert Higgs doublet that also contains two or three sets of SU(2)L triplet fermions with hypercharge zero and analyze the stability of electroweak vacuum for the scenarios. The model represents a Type-III inverse seesaw mechanism for neutrino mass generation with a Dark matter candidate. An effective potential approach calculation with two-loop beta function have been carried out in deciding the fate of the electroweak vacuum. Weak gauge coupling g2 shows a different behaviour as compared to the Standard Model. The modified running of g2, along with the Higgs quartic coupling and Type-III Yukawa couplings become crucial in determining the stability of electroweak vacuum. The interplay between two and three generations of such triplet fermions reveals that extensions with two generations is favoured if we aspire for Planck scale stability. Bounds on the Higgs quartic couplings, Type-III Yukawa and number of triplet fermion generations are drawn for different mass scale of Type-III fermions. The phenomenologies of inert doublet and Type-III fermions at the LHC and other experiments are commented upon.

scholarly journals Complete leading-order standard model corrections to quantum leptogenesis

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Paul Frederik Depta ◽  
Andreas Halsch ◽  
Janine Hütig ◽  
Sebastian Mendizabal ◽  
Owe Philipsen
Keyword(s):  
Standard Model ◽  
Gauge Coupling ◽  
Thermal Bath ◽  
Leading Order ◽  
Boltzmann Equations ◽  
The Standard Model ◽  
Majorana Neutrinos ◽  
Infinite Loop ◽  
First Time ◽  
The Universe

Abstract Thermal leptogenesis, in the framework of the standard model with three additional heavy Majorana neutrinos, provides an attractive scenario to explain the observed baryon asymmetry in the universe. It is based on the out-of-equilibrium decay of Majorana neutrinos in a thermal bath of standard model particles, which in a fully quantum field theoretical formalism is obtained by solving Kadanoff-Baym equations. So far, the leading two-loop contributions from leptons and Higgs particles are included, but not yet gauge corrections. These enter at three-loop level but, in certain kinematical regimes, require a resummation to infinite loop order for a result to leading order in the gauge coupling. In this work, we apply such a resummation to the calculation of the lepton number density. The full result for the simplest “vanilla leptogenesis” scenario is by $$ \mathcal{O} $$ O (1) increased compared to that of quantum Boltzmann equations, and for the first time permits an estimate of all theoretical uncertainties. This step completes the quantum theory of leptogenesis and forms the basis for quantitative evaluations, as well as extensions to other scenarios.

scholarly journals Flavour Anomalies in a U(1) SUSY Extension of the SM

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 191
Author(s):  
Alexander Bednyakov ◽  
Alfiia Mukhaeva
Keyword(s):  
Standard Model ◽  
Parameter Space ◽  
Gauge Boson ◽  
New Physics ◽  
Low Energy ◽  
Effective Theory ◽  
The Standard Model ◽  
Meson Mixing ◽  
Additional Anomaly ◽  
Lepton Flavour

Flavour anomalies have attracted a lot of attention over recent years as they provide unique hints for possible New Physics. Here, we consider a supersymmetric (SUSY) extension of the Standard Model (SM) with an additional anomaly-free gauge U(1) group. The key feature of our model is the particular choice of non-universal charges to the gauge boson Z′, which not only allows a relaxation of the flavour discrepancies but, contrary to previous studies, can reproduce the SM mixing matrices both in the quark and lepton sectors. We pay special attention to the latter and explicitly enumerate all parameters relevant for our calculation in the low-energy effective theory. We find regions in the parameter space that satisfy experimental constraints on meson mixing and LHC Z′ searches and can alleviate the flavour anomalies. In addition, we also discuss the predictions for lepton-flavour violating decays B+→K+μτ and B+→K+eτ.

scholarly journals Characters and group invariant polynomials of (super)fields: road to “Lagrangian”

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
Upalaparna Banerjee ◽  
Joydeep Chakrabortty ◽  
Suraj Prakash ◽  
Shakeel Ur Rahaman
Keyword(s):  
Standard Model ◽  
Explicit Construction ◽  
Effective Field ◽  
Compact Groups ◽  
Group Invariant ◽  
Fundamental Particles ◽  
Quantum Numbers ◽  
The Standard Model ◽  
Mass Dimension ◽  
Complete Set

AbstractThe dynamics of the subatomic fundamental particles, represented by quantum fields, and their interactions are determined uniquely by the assigned transformation properties, i.e., the quantum numbers associated with the underlying symmetry of the model under consideration. These fields constitute a finite number of group invariant operators which are assembled to build a polynomial, known as the Lagrangian of that particular model. The order of the polynomial is determined by the mass dimension. In this paper, we have introduced an automated $${\texttt {Mathematica}}^{\tiny \textregistered }$$ Mathematica ® package, GrIP, that computes the complete set of operators that form a basis at each such order for a model containing any number of fields transforming under connected compact groups. The spacetime symmetry is restricted to the Lorentz group. The first part of the paper is dedicated to formulating the algorithm of GrIP. In this context, the detailed and explicit construction of the characters of different representations corresponding to connected compact groups and respective Haar measures have been discussed in terms of the coordinates of their respective maximal torus. In the second part, we have documented the user manual of GrIP that captures the generic features of the main program and guides to prepare the input file. We have attached a sub-program CHaar to compute characters and Haar measures for $$SU(N), SO(2N), SO(2N+1), Sp(2N)$$ S U ( N ) , S O ( 2 N ) , S O ( 2 N + 1 ) , S p ( 2 N ) . This program works very efficiently to find out the higher mass (non-supersymmetric) and canonical (supersymmetric) dimensional operators relevant to the effective field theory (EFT). We have demonstrated the working principles with two examples: the standard model (SM) and the minimal supersymmetric standard model (MSSM). We have further highlighted important features of GrIP, e.g., identification of effective operators leading to specific rare processes linked with the violation of baryon and lepton numbers, using several beyond standard model (BSM) scenarios. We have also tabulated a complete set of dimension-6 operators for each such model. Some of the operators possess rich flavour structures which are discussed in detail. This work paves the way towards BSM-EFT.

scholarly journals Exploration of Extended Higgs Sectors with Run-2 Proton–Proton Collision Data at the LHC

Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2144
Author(s):  
Arnaud Ferrari ◽  
Nikolaos Rompotis
Keyword(s):  
Standard Model ◽  
Higgs Sector ◽  
Scalar Fields ◽  
Higgs Bosons ◽  
Proton Collision ◽  
Complex Scalar ◽  
Proton Proton ◽  
The Standard Model ◽  
Extended Higgs Sectors ◽  
Proton Proton Collision

One doublet of complex scalar fields is the minimal content of the Higgs sector in order to achieve spontaneous electroweak symmetry breaking and, in turn, to generate the masses of fundamental particles in the Standard Model. However, several theories beyond the Standard Model predict a nonminimal Higgs sector and introduce additional singlets, doublets or even higher-order weak isospin representations, thereby yielding additional Higgs bosons. With its high proton–proton collision energy (13 TeV during Run-2), the Large Hadron Collider opens a new window towards the exploration of extended Higgs sectors. This review article summarises the current state-of-the-art experimental results recently obtained in searches for new neutral and charged Higgs bosons with a partial or full Run-2 dataset.

scholarly journals Gauge coupling unification in the Standard Model

2005 ◽  
Vol 624 (3-4) ◽  
pp. 233-238 ◽  
Author(s):  
V. Barger ◽  
Jing Jiang ◽  
Paul Langacker ◽  
Tianjun Li
Keyword(s):  
Standard Model ◽  
Gauge Coupling ◽  
The Standard Model

scholarly journals Constraining extended scalar sectors at the LHC and beyond

2018 ◽  
Vol 33 (10n11) ◽  
pp. 1830007 ◽  
Author(s):  
Agnieszka Ilnicka ◽  
Tania Robens ◽  
Tim Stefaniak
Keyword(s):  
Dark Matter ◽  
Higgs Boson ◽  
Standard Model ◽  
Parameter Space ◽  
Beyond The Standard Model ◽  
The Standard Model ◽  
Doublet Model ◽  
Inert Doublet Model ◽  
Scalar Sector ◽  
Scalar Singlet

We give a brief overview of beyond the Standard Model (BSM) theories with an extended scalar sector and their phenomenological status in the light of recent experimental results. We discuss the relevant theoretical and experimental constraints, and show their impact on the allowed parameter space of two specific models: the real scalar singlet extension of the Standard Model (SM) and the Inert Doublet Model. We emphasize the importance of the LHC measurements, both the direct searches for additional scalar bosons, as well as the precise measurements of properties of the Higgs boson of mass 125 GeV. We show the complementarity of these measurements to electroweak and dark matter observables.

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