arXiv subjects

A. V. Gulov

Publications and source records attributed to A. V. Gulov.

12 recordsLinked to original sources

arXiv2009

Model independent search for Z'-boson signals

An approach to the model-independent searching for the Z' gauge boson as a virtual state in scattering processes is developed. It accounts for as a basic requirement the renormalizability of underlying unspecified in other respects model. This results in a set of relations between low energy couplings of Z' to fermions that reduces in an essential way the number of parameters to be fitted in experiments. On this ground the observables which uniquely pick out the Z' boson in leptonic processes are introduced and the data of LEP experiments analyzed. The Z' couplings to leptons and quarks are estimated at 95% confidence level. These estimates may serve as a guide for experiments at the Tevatron and/or LHC. A comparison with other approaches and results is given.

hep-ph↗

arXiv2006

Z' signal from the LEP2 data

The many-parametric fit of the LEP2 data on e^+e^-\to e^+e^-, μ^+μ^-, τ^+τ^- processes is performed to estimate signals of the Abelian Z'-boson beyond the standard model. The model-independent relations between the Z' couplings to the standard model particles allow to describe the Z' effects in lepton processes by 4 independent parameters. No signal is found by the complete LEP2 data set, and the 1.3σsignal is detected by the fit of the backward bins. The Z' couplings to the vector and axial-vector lepton currents are constrained. The comparisons with the one-parameter fits and with the LEP1 experiments are performed.

hep-ph↗

arXiv2006

Signals of Z' boson in the Bhabha process within the LEP2 data set

The LEP2 data set on the Bhabha process is analyzed with the aim to detect the signals of the heavy virtual Z' gauge bosons. The state interacting with the left-handed standard-model doublets and called the Chiral Z' is investigated. This particle was introduced already as the low-energy state allowed by the renormalizability of the model. The contribution of the Chiral Z' state to the Bhabha process is described by two parameters: the coupling to electrons and the Z-Z' mixing angle. The sign-definite one-parameter observable is proposed to measure the Z' coupling to the electron current. The one-parameter fit of the data shows no signals of the particle. The alternative two-parameter fit of the differential cross-sections is also performed. It also shows no Chiral Z' signals. The comparisons with other fits are discussed.

hep-ph↗

arXiv2004

Model-independent search for the Abelian Z' boson in the Bhabha process

Model-independent observables to pick out the Abelian Z' signal in the Bhabha process are introduced at energies >= 200 GeV. They measure separately the Z'-induced vector and axial-vector four-fermion contact couplings. The analysis of the LEP2 data constrains the value of the Z'-induced vector four-fermion coupling at the 2-sigma confidence level that corresponds to the Abelian Z' boson with the mass of order 1 TeV.

hep-ph↗

arXiv2003

Signals of the Abelian Z' boson within the analysis of the LEP2 data

The preliminary LEP data on the e^+e^- -> l^+l^- scattering are analysed to establish a model-independent search for the signals of virtual states of the Abelian Z' boson. The recently introduced observables give a possibility to pick up uniquely the Abelian Z' signals in these processes. The mean values of the observables are in accordance with the Z' existence. However, the accuracy of the experimental data is deficient to detect the signal at more than the 1σconfidence level. The results of other model-independent fits and further prospects are discussed.

hep-ph↗

arXiv2002

Signals of the Abelian Z' boson within the model independent analysis of the LEP data

The preliminary LEP data set on the total cross sections and the forward-backward asymmetries of the $e^+e^-\to\bar{f}f$ processes are analysed to establish a model-independent search for the signals of the virtual Abelian Z' boson. The recently introduced observables giving possibility to pick up uniquely the Z' signals in these processes are used. The mean values of the observables are in accordance with the Z' detection at the $1σ$ accuracy. The results of other model-independent fits and further prospects are discussed.

hep-ph↗

arXiv2001

Model-independent search for the Abelian Z' boson and the LEP data

Model-independent search for the Abelian $Z'$ gauge boson virtual state based on the new observable in the processes $e^+ e^- \to l^+ l^-$ is analyzed for the LEP data. The observable is introduced by using following from renormalizability of an underlying theory the correlations between the parameters of the low energy effective Lagrangian and kinematics of the scattering processes. The central values of the observable are in accordance with the $Z'$ existence, although no real signal is found at the $1σ$ level. Lower limits at the 95% confidence level on the corresponding contact interaction scale are derived in the range of 15.6 - 18.6 TeV. Comparisons with other fits are done.

hep-ph↗

arXiv2001

Renormalizability and searching for Z' gauge bosons

New observables for searching for Z' virtual states in processes e^+e^-\to\bar{f}f are proposed. They are based on the relations following due to renormalizability of an underlying theory between the parameters of the low-energy effective Lagrangian. Two types of the Z' interactions are considered. The observables allow to pick up uniquely the signals of both Z' bosons. The search for the Z' at future linear colliders and the treating of the LEP data are discussed.

hep-ph↗

arXiv2000

Renormalizability and model independent description of Z' signals at low energies

Model independent search for signals of heavy Z' gauge bosons in low-energy four-fermion processes is analyzed. It is shown that the renormalizability of the underlying theory containing Z', formulated as a scattering in the field of heavy virtual states, can be implemented in specific relations between different processes. Considering the two-Higgs-doublet model as the low-energy basis theory, the two types of Z' interactions with light particles are found to be compatible with the renormalizability. They are called the Abelian and the "chiral" couplings. Observables giving possibility to uniquely detect Z' in both cases are introduced.

hep-ph↗

arXiv2000

Renormalization group relations and searching for abelian Z' Boson in the four-fermionic processes

The method of searching for signals of heavy virtual particles is developed. It is based on a renormalization group equation for the low energy effective Lagrangian and the decoupling theorem. As an application, the model independent search for Abelian Z' boson in four-fermion processes is analyzed. The basic one-loop renormalization group relation for the parameters of the effective Lagrangian is derived which gives possibility to reduce the problem to the scattering of the Standard Model particles in the ``external field'' substituting heavy virtual Z' state. From the set of derived relations it is determined that the absolute value of the Z' coupling to the axial currents has to be the same for all fermions and is strongly correlated to the Z' coupling to the scalar fields. The corresponding dependences between the parameters of the effective Lagrangians are derived.

hep-ph↗

arXiv1999

Renormalizability and the model independent observables for abelian Z' search

The observables useful for the model independent search for signals of the abelian Z' in the processes e^+ e^- \to {\bar f}f are introduced. They are based on the renormalization group relations between the Z' couplings to the Standard Model particles developed recently and extend the variables suggested by Osland, Pankov and Paver. The bounds on the values of the observables at the center-of-mass energy \sqrt{s} = 500GeV are derived.

hep-ph↗

arXiv1998

Renormalization group and relations between scattering amplitudes in a theory with different mass scales

In the Yukawa model with two different mass scales the renormalization group equation is used to obtain relations between scattering amplitudes at low energies. Considering fermion-fermion scattering as an example, a basic one-loop renormalization group relation is derived which gives possibility to reduce the problem to the scattering of light particles on the "external field" substituting a heavy virtual state. Applications of the results to problems of searching new physics beyond the Standard Model are discussed.

hep-ph↗