arXiv subjects

Vladimir Cherepanov

Publications and source records attributed to Vladimir Cherepanov.

5 recordsLinked to original sources

arXiv2024

The polarimeter vector for $τ\rightarrow 3 πν_τ$ decays

The polarimeter vector of the $τ$ represents an optimal observable for the measurement of the $τ$ spin. In this paper we present an algorithm for the computation of the $τ$ polarimeter vector for the decay channels $τ^{-} \rightarrow π^{-}π^{+}π^{-}ν_τ$ and $τ^{-} \rightarrow π^{-}π^{0}π^{0}ν_τ$. The algorithm is based on a model for the hadronic current in these decay channels, which was fitted to data recorded by the CLEO experiment.

hep-ex↗

arXiv2018

Kinematic reconstruction of $Z/H \rightarrow ττ$ decay in proton-proton collisions

The knowledge of $τ$ lepton kinematic and kinematic of the $τ$ pair in the decay $Z/H \rightarrow ττ$ is essential for various analysis at LHC. However, the reconstruction of the whole kinematic of the $τ$ decay is a challenging task, since in every $τ$ decay at least one neutrino is present in the final state which escapes detection. In this paper a kinematic technique (Global Event Fit) to estimate the momentum escaped with neutrinos and hence the full momentum of the $τ$ lepton pair is described. The algorithm is based on iterative minimization of the likelihood with constrains derived from all available kinematic information on the decay. The method requires the direction of at least one $τ$ lepton to be well defined and therefore the method can be applied to the decays $Z/H \rightarrow ττ\rightarrow X + a_{1}ν$ with $a_{1}$ resonance decaying into three charged pions.

hep-ph↗

arXiv2018

Methods for a measurement of $τ$ polarization asymmetry in the decay $Z\rightarrow ττ$ at LHC and determination of the effective weak mixing angle

In this paper a general method to measure the longitudinal polarization of $τ$ lepton in the process $pp \rightarrow Z^{0} \rightarrow ττ$ is described. The method of optimal observable allows to distinguish between the $τ$ lepton helicity states with maximum possible sensitivity. The optimal observable for the main $τ$ decay modes ($e/μνν$, $πν$, $ρν$, $a_{1}ν$) that can be identified by CMS or ATLAS detectors is described. The analyzing power for $τ$ polarization can be further gained by taking into account a correlation between longitudinal spin states of $τ^{+}$ and $τ^{-}$. The theoretical systematic uncertainty on the $τ$ polarization measured using the $τ\rightarrow 3πν$ decays is estimated to be $(ΔP_τ)_{model} = (1.41 \pm 1.37)\times 10^{-4}$. This value is approximately 50 times smaller than the best uncertainty on $τ$ polarization measurement given by combination of all LEP results. An approach to propagate the measured $τ$ polarization averaged over the $Z^{0}$ lineshape and parton density functions to the electroweak parameters is also discussed.

hep-ph↗

arXiv1995

Parametric Generation of Second Sound by First Sound in Superfluid Helium

We report the first experimental observation of parametric generation of second sound (SS) by first sound (FS) in superfluid helium in a narrow temperature range in the vicinity of $T_λ$. The temperature dependence of the threshold FS amplitude is found to be in a good quantitative agreement with the theory suggested long time ago and corrected for a finite geometry. Strong amplitude fluctuations and two types of the SS spectra are observed above the bifurcation. The latter effect is quantitatively explained by the discreteness of the wave vector space and the strong temperature dependence of the SS dissipation length.

cond-mat↗

arXiv1994

How do frustrations without disorder result in the spin-glass-like behavior of the kagomé antiferromagnet?

Freezing of the classical spin liquid of the Heisenberg kagomé antiferromagnet is studied. At low temperature, the coplanar spin configurations are known to dominate among all possible three-dimensional low-energy states because of the fluctuation interaction. It is shown that the statistical weight of ${\bf q} =0$ domains is negligible. This allows one to describe coplanar states in terms of $\sqrt{3}\times \sqrt{3}$ domains with three possible spin orientations. The domain walls are mapped onto closed self-avoiding loops on the hexagonal lattice. The probability of domain formation is evaluated. It is shown that in FC (field cooled) regime a telescopic hierarchy of domains appears. The spatial and temporal behavior of the spin correlation function is estimated. The difference between FC and ZFC behavior is discussed.

cond-mat↗