scholarly journals THE THIRD TYPE OF FERMION MIXING IN THE LEPTON AND QUARK INTERACTIONS WITH LEPTOQUARKS

2012 ◽  
Vol 27 (11) ◽  
pp. 1250062 ◽  
Author(s):  
A. V. KUZNETSOV ◽  
N. V. MIKHEEV ◽  
A. V. SERGHIENKO
Keyword(s):  
Lower Bound ◽  
Standard Model ◽  
Low Energy ◽  
Minimal Extension ◽  
The Third ◽  
Model Based ◽  
Mixing Parameters ◽  
The Standard Model

The low-energy manifestations of a minimal extension of the electroweak standard model based on the quark–lepton symmetry SU(4)V ⊗SU(2)L ⊗GR of the Pati–Salam-type are analyzed. Given this symmetry the third type of mixing in the interactions of the SU(4)V leptoquarks with quarks and leptons is shown to be required. An additional arbitrariness of the mixing parameters could allow, in principle, to decrease noticeably the lower bound on the vector leptoquark mass originated from the low-energy rare processes, strongly suppressed in the standard model.

scholarly journals Heavy neutrino searches at future Z-factories

2019 ◽  
Vol 79 (9) ◽  
Author(s):  
Jian-Nan Ding ◽  
Qin Qin ◽  
Fu-Sheng Yu
Keyword(s):  
Standard Model ◽  
Cross Sections ◽  
Upper Bounds ◽  
Minimal Extension ◽  
Neutrino Sector ◽  
Mixing Parameters ◽  
The Standard Model ◽  
Background Events ◽  
Sigma E ◽  
Two Jets

Abstract We analyze the capacity of future Z-factories to search for heavy neutrinos with their mass from 10 to 85 GeV. The heavy neutrinos N are considered to be produced via the process $$e^+e^-\rightarrow Z\rightarrow \nu N$$e+e-→Z→νN and to decay into an electron or muon and two jets. By means of Monte Carlo simulation of such signal events and the Standard Model background events, we obtain the upper bounds on the cross sections $$\sigma (e^+e^-\rightarrow \nu N\rightarrow \nu \ell jj)$$σ(e+e-→νN→νℓjj) given by the Z-factories with integrated luminosities of 0.1, 1 and 10 $$\hbox {ab}^{-1}$$ab-1 if no signal events are observed. Under the assumption of a minimal extension of the Standard Model in the neutrino sector, we also present the corresponding constraints on the mixing parameters of the heavy neutrinos with the Standard Model leptons, and find they are improved by at least one order compared to current experimental constraints.

scholarly journals GAUGING THE SHADOW SECTOR WITH SO(3)

2000 ◽  
Vol 15 (19) ◽  
pp. 1221-1225 ◽  
Author(s):  
G. B. TUPPER ◽  
R. J. LINDEBAUM ◽  
R. D. VIOLLIER
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Gauge Group ◽  
Cold Dark Matter ◽  
Atmospheric Neutrino ◽  
Dark Matter Particle ◽  
Low Energy ◽  
Model Based ◽  
The Standard Model

We examine the phenomenology of a low-energy extension of the Standard Model, based on the gauge group SU (3) ⊗ SU (2) ⊗ U (1)⊗ SO (3), with SO(3) operating in the shadow sector. This model offers vacuum νe → νs and νμ → ντ oscillations as the solution of the solar and atmospheric neutrino problems, and it provides a neutral heavy shadow lepton X that takes the role of a cold dark matter particle.

scholarly journals HEAVY MAJORANA NEUTRINOS IN e-e- COLLISIONS

1998 ◽  
Vol 13 (14) ◽  
pp. 2363-2381 ◽  
Author(s):  
CHRISTOPH GREUB ◽  
PETER MINKOWSKI
Keyword(s):  
Standard Model ◽  
Cross Section ◽  
Majorana Neutrino ◽  
Low Energy ◽  
Left Handed ◽  
Mixing Parameters ◽  
Heavy Majorana Neutrino ◽  
The Standard Model ◽  
Majorana Neutrinos ◽  
The Masses

We discuss the process e-e-→W-W- mediated by heavy Majorana neutrino exchange in the t- and u channel. In our model the cross section for this reaction is a function of the masses (mN) of the heavy Majorana neutrinos and mixing parameters (UeN) originating from mixing between the ordinary left-handed standard model neutrinos and additional singlet right-handed neutrino fields. Taking into account the standard model background and constraints from low energy measurements, we present discovery limits in the [Formula: see text] plane. We also discuss how to measure in principle the CP violating phases, i.e., the relative phases between the mixing parameters.

scholarly journals Effective operator bases for beyond Standard Model scenarios: an EFT compendium for discoveries

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Upalaparna Banerjee ◽  
Joydeep Chakrabortty ◽  
Suraj Prakash ◽  
Shakeel Ur Rahaman ◽  
Michael Spannowsky
Keyword(s):  
Standard Model ◽  
High Energy ◽  
Beyond The Standard Model ◽  
Minimal Extension ◽  
Effective Operator ◽  
Abelian Gauge ◽  
Gauge Symmetries ◽  
Higher Dimensional ◽  
The Standard Model ◽  
Mass Dimension

Abstract It is not only conceivable but likely that the spectrum of physics beyond the Standard Model (SM) is non-degenerate. The lightest non-SM particle may reside close enough to the electroweak scale that it can be kinematically probed at high-energy experiments and on account of this, it must be included as an infrared (IR) degree of freedom (DOF) along with the SM ones. The rest of the non-SM particles are heavy enough to be directly experimentally inaccessible and can be integrated out. Now, to capture the effects of the complete theory, one must take into account the higher dimensional operators constituted of the SM DOFs and the minimal extension. This construction, BSMEFT, is in the same spirit as SMEFT but now with extra IR DOFs. Constructing a BSMEFT is in general the first step after establishing experimental evidence for a new particle. We have investigated three different scenarios where the SM is extended by additional (i) uncolored, (ii) colored particles, and (iii) abelian gauge symmetries. For each such scenario, we have included the most-anticipated and phenomenologically motivated models to demonstrate the concept of BSMEFT. In this paper, we have provided the full EFT Lagrangian for each such model up to mass dimension 6. We have also identified the CP, baryon (B), and lepton (L) number violating effective operators.

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 Rb, Rc and New Physics: An Updated Model Independent Analysis

1997 ◽  
Vol 12 (04) ◽  
pp. 723-742 ◽  
Author(s):  
P. Bamert
Keyword(s):  
Standard Model ◽  
Neutral Current ◽  
New Physics ◽  
Low Energy ◽  
Coupling Constant ◽  
A Value ◽  
Independent Analysis ◽  
The Standard Model ◽  
Necessary And Sufficient ◽  
Do So

We analyze LEP and SLC data from the 1995 Summer Conferences as well as from low energy neutral current experiments for signals of new physics. The reasons for doing this are twofold: first to explain the deviations from the Standard Model observed in Rb and Rc and second to constrain nonstandard contributions to couplings of the Z0 boson to all fermions and to the oblique parameters. We do so by comparing the data with the Standard Model as well as with a number of test hypotheses concerning the nature of the new physics. These include nonstandard [Formula: see text]-, [Formula: see text]- and [Formula: see text]-couplings as well as the couplings of the Z0 to fermions of the entire first, second and third generations and universal corrections to all up- and down-type quark couplings (as can arise see for example in Z' mixing models). We find that nonstandard [Formula: see text] couplings are both necessary and sufficient to explain the data and in particular the Rb anomaly. It is not possible to explain Rb, Rc and a value of the strong coupling constant consistent with low energy determinations invoking only nonstandard [Formula: see text]- and [Formula: see text]-couplings. To do so one has to have also new physics contributions to the [Formula: see text] or universal corrections to all [Formula: see text] couplings.

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 η′K PUZZLE OF B MESON DECAYS AND NEW PHYSICS EFFECTS IN THE TC2 MODEL

2001 ◽  
Vol 16 (07) ◽  
pp. 441-455 ◽  
Author(s):  
ZHENJUN XIAO ◽  
WENJUN LI ◽  
GONGRU LU ◽  
LIBO GUO
Keyword(s):  
Standard Model ◽  
B Meson ◽  
New Physics ◽  
Decay Rates ◽  
Low Energy ◽  
Effective Hamiltonian ◽  
B Meson Decays ◽  
The Standard Model ◽  
Model Predictions ◽  
Input Parameters

Using the low energy effective Hamiltonian with the generalized factorization, we calculate the new physics contributions to B→π+π-, Kπ and Kη′ in the topcolor-assisted-technicolor (TC2) model, and compare the results with the available data. By using [Formula: see text] preferred by the CLEO data of B→π+π-decay, we find that the new physics enhancements to B→ Kη′ decays are significant in size, ~ 50% with respect to the standard model predictions, insensitive to the variations of input parameters and hence provide a simple and plausible new physics interpretation for the observed unexpectedly large B→ Kη′ decay rates.

scholarly journals PROBING SO(10) SYMMETRY BREAKING PATTERNS THROUGH SFERMION MASS RELATIONS

2005 ◽  
Vol 20 (18) ◽  
pp. 4241-4257 ◽  
Author(s):  
B. ANANTHANARAYAN ◽  
P. N. PANDITA
Keyword(s):  
Standard Model ◽  
Supersymmetry Breaking ◽  
Gauge Group ◽  
Low Energy ◽  
Grand Unification ◽  
The Standard Model ◽  
Scalar Mass ◽  
Mass Terms ◽  
Standard Model Gauge Group ◽  
Slepton Mass

We consider supersymmetric SO(10) grand unification where the unified gauge group can break to the Standard Model gauge group through different chains. The breaking of SO(10) necessarily involves the reduction of the rank, and consequent generation of nonuniversal supersymmetry breaking scalar mass terms. We derive squark and slepton mass relations, taking into account these nonuniversal contributions to the sfermion masses, which can help distinguish between the different chains through which the SO(10) gauge group breaks to the Standard Model gauge group. We then study some implications of these nonuniversal supersymmetry breaking scalar masses for the low energy phenomenology.

scholarly journals From old symmetries to new symmetries: Quarks, leptons and B-L

2014 ◽  
Vol 29 (29) ◽  
pp. 1430066 ◽  
Author(s):  
Rabindra N. Mohapatra
Keyword(s):  
Standard Model ◽  
Weak Interactions ◽  
Low Energy ◽  
Neutrino Masses ◽  
Beyond The Standard Model ◽  
The Standard Model ◽  
Recent Developments

The Baryon–Lepton difference (B-L) is increasingly emerging as a possible new symmetry of the weak interactions of quarks and leptons as a way to understand the small neutrino masses. There is the possibility that current and future searches at colliders and in low energy rare processes may provide evidence for this symmetry. This paper provides a brief overview of the early developments that led to B-L as a possible symmetry beyond the standard model, and also discusses some recent developments.

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