Vladimir Cherepanov

We present the achievements of the last years of the experimental and theoretical groups working on hadronic cross section measurements at the low-energy e + e − colliders in Beijing, Frascati, Ithaca, Novosibirsk, Stanford and Tsukuba and on τ decays. We sketch the prospects in these fields for the years to come. We emphasise the status and the precision of the Monte Carlo generators used to analyse the hadronic cross section measurements obtained as well with energy scans as with radiative return, to determine luminosities and τ decays. The radiative corrections fully or approximately implemented in the various codes and the contribution of the vacuum polarisation are discussed.

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−→π−π+π−ντ and τ−→π−π0π0ντ. 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 [1]. Program Title: PolarimetricVectorTau2a1, version 1.0.1 CPC Library link to program files: https://doi.org/10.17632/z986tk5pyv.1 Developer's repository link: https://github.com/TTauSpin/PolarimetricVectorTau2a1 Licensing provisions: MIT Programming language: C++ 11 Nature of problem: The polarimeter vector h of the τ can be used to measure the τ spin orientation. The vector h is a function of the momenta of the particles produced in the τ decay and needs to be computed in the restframe of the τ lepton. While for the decay channels τ−→π−ντ and τ−→π−π0ντ expressions for h exist in the literature, no corresponding expressions exist for the channels τ−→π−π+π−ντ and τ−→π−π0π0ντ. Solution method: In this paper, we present an algorithm for the computation of the τ polarimeter vector h for the decay channels τ−→π−π+π−ντ and τ−→π−π0π0ντ. The algorithm is based on a model for the dynamics of hadronic interactions in these decay channels. The parameters of the model have been determined by a fit to data recorded by the CLEO experiment.

A new CMS tracker detector will be installed for operation at the High Luminosity LHC (HL-LHC). This detector comprises modules with two closely spaced parallel sensor plates and front-end ASICs capable of transmitting tracking information to the CMS Level-1 (L1) trigger at the 40 MHz beam crossing rate. The inclusion of tracking information in the L1 trigger decision will be essential for selecting events of interest efficiently at the HL-LHC. The CMS Binary Chip (CBC) has been designed to read out and correlate hits from pairs of tracker sensors, forming so-called track stubs. For the first time, a prototype irradiated module and a full-sized module, both equipped with the version 2 of the CBC, have been operated in test beam facilities. The efficiency of the stub finding logic of the modules for various angles of incidence has been studied. The ability of the modules to reject tracks with transverse momentum less than 2 GeV has been demonstrated. For modules built with irradiated sensors, no significant drop in the stub finding performance has been observed. Results from the beam tests are described in this paper.

We use experimental data on $e^{+}e^{-} \rightarrow \eta\pi^{+}\pi^{-}$ and $\tau^{-} \to \eta\pi^{-}\pi^{0}\nu_{\tau}$ to test conservation of vector current (CVC) by comparing the predicted hadronic spectrum and branching fraction with the $\tau$ decay data. Based on the corresponding $e^+e^-$ data and CVC, we also calculate the branching fraction of $\tau^{-} \to \eta^\prime\pi^{-}\pi^{0}\nu_{\tau}$ decay.

Status of \tau <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>τ</mml:mi></mml:math> lepton decay Monte Carlo generator TAUOLA, and its main recent applications are reviewed. It is underlined, that in recent efforts on development of new hadronic currents, the multi-dimensional nature of distributions of the experimental data must be taken with a great care. Studies for H \to \tau\tau ; \tau \to hadrons <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>H</mml:mi><mml:mo>→</mml:mo><mml:mi>τ</mml:mi><mml:mi>τ</mml:mi><mml:mo>;</mml:mo><mml:mi>τ</mml:mi><mml:mo>→</mml:mo><mml:mi>h</mml:mi><mml:mi>a</mml:mi><mml:mi>d</mml:mi><mml:mi>r</mml:mi><mml:mi>o</mml:mi><mml:mi>n</mml:mi><mml:mi>s</mml:mi></mml:mrow></mml:math> indeed demonstrate that multi-dimensional nature of distributions is important and available for evaluation of observables where \tau <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>τ</mml:mi></mml:math> leptons are used to constrain experimental data. For that part of the presentation, use of the TAUOLA program for phenomenology of H <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>H</mml:mi></mml:math> and Z <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Z</mml:mi></mml:math> decays at LHC is discussed, in particular in the context of the Higgs boson parity measurements with the use of Machine Learning techniques. Some additions, relevant for QED lepton pair emission and electroweak corrections are mentioned as well.

Research relevance. Studies of the causes and mechanism of hazardous production situations origin and development at coal mining enterprises have shown that their development is most often due to organizational factors, and the prerequisites for their occurrence are associated, to a greater extent, with process flow factors of mining operations, including design decisions. For this reason, it became necessary to establish specific process flow factors that are prerequisites for the emergence of hazardous production situations at a coal pit. Research objective is to establish the factors of hazardous production situations occurrence; to identify and justify indicators of hazardous production situations origin, obtained based on an assessment of the general state of mining, to take into account appropriate scenarios for preventing or avoiding the hazardous production situations in the course of development; to diagnose early signs of their occurrence and eliminate the causes of their development. Methods of research. The state of mining in the coal pit and operations on production safety were assessed from the perspective of hazardous production situations origin and development and was carried out during the process audit. Indicators of the state of the deep pit working area were formed based on the analysis of data from geographic information monitoring of mining, safety rules, as well as process flow diagrams of mining operations. Results. Based on the results of the process audit of the state of mining operations, the factors that are prerequisites for the development of hazardous production situations are determined. They became the basis for the selection of process flow and organizational indicators of hazardous production situations occurrence. The conditions for hazardous production situations occurrence are defined, depending on the presence of objective natural, process flow and organizational factors affecting the safety of work. Conclusions. Open-pit coal mining is naturally accompanied by the emergence and development of hazardous production situations. It is proposed to monitor the prerequisites of hazardous production situations by process flow and organizational indicators in order to make adequate management decisions to prevent the occurrence of hazardous incidents.

The polarimeter vector of the $\tau$ represents an optimal observable for the measurement of the $\tau$ spin. In this paper we present an algorithm for the computation of the $\tau$ polarimeter vector for the decay channels $\tau^{-} \rightarrow \pi^{-}\pi^{+}\pi^{-}\nu_{\tau}$ and $\tau^{-} \rightarrow \pi^{-}\pi^{0}\pi^{0}\nu_{\tau}$. 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.

We use experimental data on $e^{+}e^{-} \rightarrow \eta\pi^{+}\pi^{-}$ and $\tau^{-} \to \eta\pi^{-}\pi^{0}\nu_{\tau}$ to test conservation of vector current (CVC) by comparing the predicted hadronic spectrum and branching fraction with the $\tau$ decay data. Based on the corresponding $e^+e^-$ data and CVC, we also calculate the branching fraction of $\tau^{-} \to \eta^\prime\pi^{-}\pi^{0}\nu_{\tau}$ decay.

The paper presents single-flight beam diagnostic system for VEPP-2000 injection channels. The system includes two types of beam position monitors: secondary emission monitors and image current monitors. Tuning of the system, calibration of monitors, hardware and software of the diagnostic system are described. Main goal of the beam diagnostic system is providing lossless beam transport. To solve such problem one needs to tune up as guide fields as focusing fields of transportation channels. First task - trajectory correction is solved with response matrix inversion by SVD method. Second task - optic function reconstruction - is solved with help of multidimensional fitting of channel magnet structure parameters with minimization mean-square deviation of modelled response matrix from measured one. The paper presents results of practical experience with automated beam transfer and optic functions tuning of injection channels of VEPP-2000 complex.

The knowledge of $\tau$ lepton kinematic and kinematic of the $\tau$ pair in the decay $Z/H \rightarrow \tau\tau$ is essential for various analysis at LHC. However, the reconstruction of the whole kinematic of the $\tau$ decay is a challenging task, since in every $\tau$ 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 $\tau$ 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 $\tau$ lepton to be well defined and therefore the method can be applied to the decays $Z/H \rightarrow \tau\tau \rightarrow X + a_{1}\nu$ with $a_{1}$ resonance decaying into three charged pions.

Status of tau lepton decay Monte Carlo generator TAUOLA, and its main recent applications are reviewed. It is underlined, that in recent efforts on development of new hadronic currents, the multi-dimensional nature of distributions of the experimental data must be taken with a great care. Studies for H to tau tau; tau to hadrons indeed demonstrate that multi-dimensional nature of distributions is important and available for evaluation of observables where tau leptons are used to constrain experimental data. For that part of the presentation, use of the TAUOLA program for phenomenology of H and Z decays at LHC is discussed, in particular in the context of the Higgs boson parity measurements with the use of Machine Learning techniques. Some additions, relevant for QED lepton pair emission and electroweak corrections are mentioned as well.

At the LHC, τ-leptons are frequently produced in the decays of W and Z bosons. The development of an efficient and accurate reconstruction and identification of τ-leptons is therefore an important item in the CMS physics program. However, this is challenging due to neutrino in the final state. We report on the development of algorithms to identify τ-lepton decays and discuss the first CMS measurements of W and Z decays involving τ-leptons using the 7 TeV dataset from the pp-run in 2010.

The potential of the CMS detector to measure the τ - lepton polarization asymmetry in Z0 decays is studied. Using data corresponding to an integrated luminosity of 19.6 fb−1 at 8 TeV and 2.3 fb−1 at 13 TeV the τ polarization asymmetry is measured exploiting decay channels τ→ρν and τ→a1ν.

We use experimental data on e + e − → η ( η ′ ) π + π − and conservation of vector current to estimate the branching fractions of τ − decay to η ( η ′ ) π − π 0 ν τ . The obtained values are compared to the experimental results.

We use experimental data on $e^+e^- \to \eta (\eta^{\prime})\pi^+\pi^-$ and conservation of vector current to estimate the branching fractions of $\tau^-$ decay to $\eta (\eta^{\prime})\pi^-\pi^0\nu_{\tau}$. The obtained values are compared to the experimental results.

We use experimental data on $e^+e^- \to η(η^{\prime})π^+π^-$ and conservation of vector current to estimate the branching fractions of $τ^-$ decay to $η(η^{\prime})π^-π^0ν_τ$. The obtained values are compared to the experimental results.

We use experimental data on $e^+e^- \to \eta (\eta^{\prime})\pi^+\pi^-$ and conservation of vector current to estimate the branching fractions of $\tau^-$ decay to $\eta (\eta^{\prime})\pi^-\pi^0\nu_{\tau}$. The obtained values are compared to the experimental results.

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.

Status of τ lepton decay Monte Carlo generator TAUOLA, and its main recent applications are reviewed.It is underlined, that in recent efforts on development of new hadronic currents, the multi-dimensional nature of distributions of the experimental data must be taken with a great care.Studies for H → τ τ ; τ → hadrons indeed demonstrate that multi-dimensional nature of distributions is important and available for evaluation of observables where τ leptons are used to constrain experimental data.For that part of the presentation, use of the TAUOLA program for phenomenology of H and Z decays at LHC is discussed, in particular in the context of the Higgs boson parity measurements with the use of Machine Learning techniques.Some additions, relevant for QED lepton pair emission and electroweak corrections are mentioned as well.

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.