RENORMALIZABILITY AND SEARCHING FOR THE ABELIAN Z′ BOSON IN FOUR-FERMION PROCESSES

2001 ◽  
Vol 16 (02) ◽  
pp. 179-188 ◽  
Author(s):  
A. V. GULOV ◽  
V. V. SKALOZUB
Keyword(s):  
Scalar Field ◽  
Z Boson ◽  
Axial Vector ◽  
Scalar Fields ◽  
Low Energy ◽  
Strongly Correlated ◽  
Absolute Value ◽  
Effective Lagrangian ◽  
The Standard Model ◽  
Model Independent

A model independent search for Abelian Z′ gauge boson in four-fermion processes is analyzed. It is based on a low energy effective Lagrangian parametrizing the Z′ interactions with the fermion and scalar fields of the Standard Model. These parameters are related due to the requirement of renormalizability (gauge invariance). It is found that the absolute value of the Z′ coupling to the axial-vector currents is the same for all fermions and it is strongly correlated with the Z′ coupling to the scalar field. On the base of these relations the dependences between the parameters of the effective Lagrangian constructed from dimension-six operators are derived.

scholarly journals Observables for model-independent detections of Z′ boson at the ILC

2015 ◽  
Vol 30 (16) ◽  
pp. 1550087
Author(s):  
V. Skalozub ◽  
I. Kucher
Keyword(s):  
Cross Section ◽  
Z Boson ◽  
Axial Vector ◽  
Effective Lagrangian ◽  
The Standard Model ◽  
Model Predictions ◽  
Model Independent ◽  
Vector Formula ◽  
Two Parameter

The integral observables for model-independent detections of Abelian Z′ gauge boson in e+e- → μ+μ-(τ+τ-) process with unpolarized beams at the ILC energies are proposed. They are based on the differential cross-section of deviations from the standard model predictions calculated with a low energy effective Lagrangian and taking into consideration the relations between the Z′ couplings to the fermions derived already. Due to these relations, the cross-section exhibits angular distribution giving a possibility for introducing one- or two-parameter observables which effectively fit the mass mZ′, the axial-vector [Formula: see text] and the product of vector couplings vevμ(vevτ). A discovery reach for the Z′ is estimated for two of introduced observables. Determination of the basic Z′ model is discussed. Comparison with other results and approaches is given.

TECHNIDILATON OR HIGGS?

1993 ◽  
Vol 08 (03) ◽  
pp. 275-283 ◽  
Author(s):  
EDI HALYO
Keyword(s):  
Standard Model ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Higgs Bosons ◽  
Low Energy ◽  
Gauge Bosons ◽  
Effective Lagrangian ◽  
The Standard Model

Interactions of the technidilaton with fermions and gauge bosons are obtained by constructing a low energy effective Lagrangian and using the fact that the technidilaton couples to the trace of the energy-momentum tensor Θµµ. Technidilaton’s interactions are compared with those of the Higgs bosons of the Standard Model with one or two scalar doublets.

scholarly journals THE EFFECT OF ELECTROMAGNETIC PROPERTIES OF NEUTRINOS ON THE PHOTON–NEUTRINO DECOUPLING TEMPERATURE

2012 ◽  
Vol 27 (32) ◽  
pp. 1250187
Author(s):  
S. C. İNAN ◽  
M. KÖKSAL
Keyword(s):  
Lagrangian Model ◽  
Electromagnetic Properties ◽  
Beyond The Standard Model ◽  
Ultrahigh Energy ◽  
Qcd Phase Transition ◽  
Effective Lagrangian ◽  
Independent Analysis ◽  
The Standard Model ◽  
Model Independent ◽  
The Impact

We examine the impact of electromagnetic properties of neutrinos on the annihilation of relic neutrinos with ultrahigh energy cosmic neutrinos for the [Formula: see text] process. For this process, photon–neutrino decoupling temperature is calculated via effective Lagrangian model beyond the standard model. We find that photon–neutrino decoupling temperature can be importantly reduced below the QCD phase transition with the model independent analysis defining electromagnetic properties of neutrinos.

scholarly journals Lepton flavor violating $$\Lambda _b\rightarrow \Lambda \ell _1\ell _2$$ decay

2019 ◽  
Vol 79 (12) ◽  
Author(s):  
Diganta Das
Keyword(s):  
Standard Model ◽  
Parameter Space ◽  
Axial Vector ◽  
Branching Ratio ◽  
Low Energy ◽  
Effective Hamiltonian ◽  
Decay Distribution ◽  
Lepton Flavor ◽  
The Standard Model ◽  
Pseudo Scalar

AbstractInspired by the recent hints of lepton flavor universality violation in $$b\rightarrow s\ell \ell $$b→sℓℓ and $$b\rightarrow c\ell \nu $$b→cℓν transitions, we study lepton flavor violating exclusive $$\Lambda _b\rightarrow \Lambda \ell _1^+\ell _2^-$$Λb→Λℓ1+ℓ2- ($$\ell _1\ne \ell _2$$ℓ1≠ℓ2) decay, which is forbidden in the Standard Model. Starting from a general effective Hamiltonian for a $$b\rightarrow s\ell _1^+\ell _2^-$$b→sℓ1+ℓ2- transition that includes vector and axial-vector operators, and scalar and pseudo-scalar operators, we derive a two-fold decay distribution of $$\Lambda _b\rightarrow \Lambda \ell _1^+\ell _2^-$$Λb→Λℓ1+ℓ2-. The distribution helps us to construct the differential branching ratio and the lepton-side forward–backward asymmetry, which are studied in a vector leptoquark model. The parameter space of the vector leptoquark model is constrained by low energy observables.

LIMITING THE MASSES AND COUPLING STRENGTHS OF THE SECOND Z BOSON

1992 ◽  
Vol 07 (21) ◽  
pp. 5155-5163
Author(s):  
T. CHHABRA ◽  
P. RAM BABU
Keyword(s):  
Experimental Data ◽  
Z Boson ◽  
Z Bosons ◽  
Low Energy ◽  
Model Independent ◽  
Coupling Strengths ◽  
The Masses

We relate the observables of [Formula: see text] scatterings, e+e−→μ+μ− and [Formula: see text] to look for the existence of new neutrinos coupling to the second Z boson. The observables in νe scattering and [Formula: see text] are sensitive to the presence of new neutrinos, and the ones in e+e−→μ+μ− are sensitive to additional Z bosons. Hence the relations between low energy observables of these reactions can be used to test the existence of new neutrinos coupling to the standard Z boson and/or the second Z boson. From available experimental data, the mass and coupling strengths of the second Z boson are constrained in a model-independent way.

scholarly journals Z lepton flavour violation as a probe for new physics at future $$e^+e^-$$ colliders

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Lorenzo Calibbi ◽  
Xabier Marcano ◽  
Joydeep Roy
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
New Physics ◽  
Effective Field ◽  
Low Energy ◽  
The Standard Model ◽  
Discovery Potential ◽  
Flavour Violation ◽  
Model Independent ◽  
Lepton Flavour

AbstractIn this work we assess the potential of discovering new physics by searching for lepton-flavour-violating (LFV) decays of the Z boson, $$Z\rightarrow \ell _i \ell _j$$ Z → ℓ i ℓ j , at the proposed circular $$e^+e^-$$ e + e - colliders CEPC and FCC-ee. Both projects plan to run at the Z-pole as a “Tera Z factory”, i.e., collecting $${\mathcal {O}}\left( 10^{12} \right) $$ O 10 12 Z decays. In order to discuss the discovery potential in a model-independent way, we revisit the LFV Z decays in the context of the Standard Model effective field theory and study the indirect constraints from LFV $$\mu $$ μ and $$\tau $$ τ decays on the operators that can induce $$Z\rightarrow \ell _i \ell _j$$ Z → ℓ i ℓ j . We find that, while the $$Z\rightarrow \mu e$$ Z → μ e rates are beyond the expected sensitivities, a Tera Z factory is promising for $$Z\rightarrow \tau \ell $$ Z → τ ℓ decays, probing New Physics at the same level of future low-energy LFV observables.

scholarly journals Charming ALPs

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Adrian Carmona ◽  
Christiane Scherb ◽  
Pedro Schwaller
Keyword(s):  
Ultra Violet ◽  
New Physics ◽  
Low Energy ◽  
Effective Theory ◽  
Tree Level ◽  
Meson Decay ◽  
Fixed Target ◽  
The Standard Model ◽  
Model Independent ◽  
Key Features

Abstract Axion-like particles (ALPs) are ubiquitous in models of new physics explaining some of the most pressing puzzles of the Standard Model. However, until relatively recently, little attention has been paid to its interplay with flavour. In this work, we study in detail the phenomenology of ALPs that exclusively interact with up-type quarks at the tree-level, which arise in some well-motivated ultra-violet completions such as QCD-like dark sectors or Froggatt-Nielsen type models of flavour. Our study is performed in the low-energy effective theory to highlight the key features of these scenarios in a model independent way. We derive all the existing constraints on these models and demonstrate how upcoming experiments at fixed-target facilities and the LHC can probe regions of the parameter space which are currently not excluded by cosmological and astrophysical bounds. We also emphasize how a future measurement of the currently unavailable meson decay D → π + invisible could complement these upcoming searches.

SUPERSTRING INSPIRED NEUTRAL GAUGE BOSON IN ELASTIC ep-ASYMMETRIES

1989 ◽  
Vol 04 (27) ◽  
pp. 2689-2699 ◽  
Author(s):  
V.A. BEDNYAKOV
Keyword(s):  
Electron Beam ◽  
Elastic Scattering ◽  
Z Boson ◽  
Low Energy ◽  
Boson Mass ◽  
Kinematic Variable ◽  
Accelerator Facility ◽  
Good Opportunity ◽  
Mixing Angle ◽  
The Standard Model

The possible manifestations of the superstring inspired extra Z′-boson in polarized electron and positron elastic scattering on protons was studied. The Z′-boson generated deviations from the Standard Model in asymmetries [Formula: see text] and [Formula: see text] were investigated as functions of the kinematic variable Q2, Z′-boson mass, Z–Z′ mixing angle in the U1η, U1χ and U1ψ low energy superstring models. These deviations vary from fractions of per cent to 20–25%, depending on the above mentioned parameters. We show that precise measurements of these asymmetries (for example, on the Continuous Electron Beam Accelerator Facility) can give a good opportunity to obtain strong restrictions on parameters of superstring E6-models.

scholarly journals A low-energy perspective on the minimal left-right symmetric model

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
W. Dekens ◽  
L. Andreoli ◽  
J. de Vries ◽  
E. Mereghetti ◽  
F. Oosterhof
Keyword(s):  
Dipole Moments ◽  
Global Analysis ◽  
Scalar Fields ◽  
Effective Field ◽  
Low Energy ◽  
Symmetric Model ◽  
Ckm Matrix ◽  
Stringent Constraint ◽  
The Standard Model ◽  
The Right

Abstract We perform a global analysis of the low-energy phenomenology of the minimal left-right symmetric model (mLRSM) with parity symmetry. We match the mLRSM to the Standard Model Effective Field Theory Lagrangian at the left-right-symmetry breaking scale and perform a comprehensive fit to low-energy data including mesonic, neutron, and nuclear β-decay processes, ∆F = 1 and ∆F = 2 CP-even and -odd processes in the bottom and strange sectors, and electric dipole moments (EDMs) of nucleons, nuclei, and atoms. We fit the Cabibbo-Kobayashi-Maskawa and mLRSM parameters simultaneously and determine a lower bound on the mass of the right-handed WR boson. In models where a Peccei-Quinn mechanism provides a solution to the strong CP problem, we obtain $$ {M}_{W_R} $$ M W R ≳ 5.5 TeV at 95% C.L. which can be significantly improved with next-generation EDM experiments. In the P-symmetric mLRSM without a Peccei-Quinn mechanism we obtain a more stringent constraint $$ {M}_{W_R} $$ M W R ≳ 17 TeV at 95% C.L., which is difficult to improve with low-energy measurements alone. In all cases, the additional scalar fields of the mLRSM are required to be a few times heavier than the right-handed gauge bosons. We consider a recent discrepancy in tests of first-row unitarity of the CKM matrix. We find that, while TeV-scale WR bosons can alleviate some of the tension found in the Vud,us determinations, a solution to the discrepancy is disfavored when taking into account other low-energy observables within the mLRSM.

scholarly journals Reconstructing effective Lagrangians embedding residual family symmetries

2021 ◽  
Vol 81 (1) ◽  
Author(s):  
Jordan Bernigaud ◽  
Ivo de Medeiros Varzielas ◽  
Jim Talbert
Keyword(s):  
Finite Groups ◽  
Low Energy ◽  
Beyond The Standard Model ◽  
Top Down ◽  
Family Symmetry ◽  
Bottom Up ◽  
Effective Lagrangian ◽  
Mass Matrices ◽  
The Standard Model ◽  
Bsm Physics

AbstractWe consider effective Lagrangians which, after electroweak- and family-symmetry breaking, yield fermionic mass matrices and/or other flavoured couplings exhibiting residual family symmetries (RFS). Thinking from the bottom up, these RFS intimately link ultraviolet (UV) Beyond-the-Standard Model (BSM) physics to infrared flavour phenomenology without direct reference to any (potentially unfalsifiable) UV dynamics. While this discussion is typically performed at the level of RFS group generators and the UV flavour groups they can close, we now also focus on the RFS-implied shape of the low-energy mass/coupling matrices. We then show how this information can be used to algorithmically guide the reconstruction of an effective Lagrangian, thereby forming top-down models realizing the typical bottom-up phenomenological conclusions. As a first application we take results from scans of finite groups capable of controlling (through their RFS) CKM or PMNS mixing within the SM alone. We then extend this to recently studied scenarios where RFS also control special patterns of leptoquark couplings, thus providing proof-in-principle completions for such ‘Simplified Models of Flavourful Leptoquarks.’

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