arXiv subjects

A. Drutskoy

Publications and source records attributed to A. Drutskoy.

At least 19 recordsLinked to original sources

arXiv2025

The ILD Detector: A Versatile Detector for an Electron-Positron Collider at Energies up to 1 TeV

The International Large Detector, ILD, is a detector concept for an experiment at a future high energy lepton collider. The detector has been optimised for precision physics in a range of energies from 90~GeV to about 1~TeV. ILD features a high precision, large volume combined silicon and gaseous tracking system, together with a high granularity calorimeter, all inside a central solenoidal magnetic field. The paradigm of particle flow has been the guiding principle of the design of ILD. ILD is based mostly on technologies which have been demonstrated by extensive research and test programs. The ILD concept is proposed both for linear and circular lepton collider, be it at CERN or elsewhere. The concept has been developed by a group of nearly 60 institutes from around the world, and offers a well developed and powerful environment for science and technology studies at lepton colliders. In this document, the required performance of the detector, the proposed implementation and the readiness of the different technologies needed for the implementation are discussed.

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arXiv2025

Simulation of the process $e^+e^- \rightarrow W^+W^-$ with the heavy right-handed neutrino exchange at 1 TeV future lepton colliders

We study potential contribution of the heavy right-handed neutrino exchange in the process $e^{+}e^{-} \rightarrow W^{+}W^{-}$. This process is sensitive to heavy neutrinos with masses larger than $\sqrt{s}$. The Monte Carlo simulation of the studied process is performed assuming the Seesaw type-I model, where heavy right-handed neutrinos (heavy neutral leptons, HNL) are introduced in the leptonic sector. Within the Standard Model (SM), the process has a large cross section described by diagrams with $s$-channel $Z / γ$ exchange and $t$-channel active neutrino exchange. Respectively, the $t$-channel right-handed neutrino exchange amplitude will interfere with these SM amplitudes. However, the angular distributions of the $W$ boson production and decay are different for the right-handed neutrino and SM amplitudes. That can be used to evaluate potential HNL contribution using the extended likelihood method. The simulation of the $e^{+}e^{-} \rightarrow W^{+}W^{-}$ process is performed at the 1 TeV center-of-mass energy and polarisation $P_{e^+e^-}$ of (20 %, -80 %), which is a standard option for the future linear $e^+e^-$ collider ILC. Both $W$ bosons are reconstructed from two hadronic jets. Simulation of the SM background processes is also done. The beam-induced backgrounds and the initial state radiation (ISR) effects are taken into account. The majority of background processes are effectively suppressed by the cuts on the invariant masses of two and four jets. Finally, we obtain upper limits on the mixing parameter $|V_{eN}|^2$ as a function of $M(N)$.

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arXiv2023

A possible search for Majorana neutrinos at future lepton colliders

We discuss the process $\ell^+\ell^- \to N W^{\pm} \ell^{\mp}$, where $N$ is a heavy Majorana neutrino and $\ell = e, μ$. Large cross sections are expected for these processes at high center-of-mass energies, which can be reached at future lepton-lepton colliders. The Monte Carlo simulation of the studied processes is produced within the framework of the seesaw type-I model, where the Majorana neutrinos (or heavy neutral leptons, HNL), are introduced in the standard leptonic sector. Recently the possibility to search for the direct HNL production was studied in the $\ell^+\ell^- \to N ν_{\ell}$ process with the subsequent decay $N \to W^{\pm} \ell^{\mp}$. In this paper we investigate an alternative process $\ell^+\ell^- \to N W^{\pm} \ell^{\mp} \to W^{\pm}W^{\pm}\,\ell^{\mp}\,\ell^{\mp}$ with the lepton number violation by two units. The similar processes appear in collisions with the same-sign beams, $e^-e^- \to N W^-\,e^- \to W^-\,W^-\,e^+\,e^-$ or $μ^+μ^+ \to N W^+\,μ^+ \to W^+\,W^+\,μ^+\,μ^-$. The cross sections of the processes under consideration are enhanced by the soft photon exchange in the $t$-channel. We calculate the cross sections for the signals and potential Standard Model backgrounds for the $e^+e^-$ beam collisions at the 1 TeV center-of-mass energy and the $μ^+μ^-$ collisions at 3 TeV and 10 TeV. Due to the diagrams with soft $t$-channel photons and respective interference the promptly emitted leptons are produced in the direction close to the corresponding beam. These leptons will be lost in the beam pipe or badly measured by forward detectors. However, the signal events can be well separated from backgrounds using the rest of the event containing the $WW\ell$ particles. Finally, the expected upper limits on the mixing parameters $|V_{\ell N}|^2$ as a function of M($N$) are calculated.

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arXiv2022

Measurement of ${\cal B}r(H \to Zγ)$ at the 250 GeV ILC

The $e^+e^- \to HZ$ process with the subsequent decay of the Higgs boson $H \to Zγ$ is studied, where both $Z$ bosons are reconstructed in the final states with two jets. The analysis is performed using Monte Carlo data samples obtained with detailed ILD (The International Large Detector) detector simulation assuming an integrated luminosity of 2 ab$^{-1}$, beam polarizations of ${\cal{P}}_{e^-e^+} = (-0.8, +0.3)$, and center-of-mass energy of $\sqrt{s}$ = 250 GeV. The analysis is repeated for the case of two 0.9 ab$^{-1}$ data samples with polarizations ${\cal{P}}_{e^-e^+} = (\mp0.8, \pm0.3)$. Contributions of the potential background processes are studied using all available ILD MC event samples. The largest background comes from the $e^+e^- \to W^+W^-$ process supplemented by an energetic photon produced by initial state radiation. To suppress this background we require that at least one of the $Z$ bosons decays to $b$-jets. To reduce the jet reconstruction uncertainties the $M_Δ = M(jjγ) - M(jj) + M(Z_{\rm nom})$ variable is used, where $M(Z_{\rm nom})$ = 91.2 GeV. The $M_Δ$ distributions are obtained for the studied signal and backgrounds to estimate the expected accuracy of the ${\cal B}r(H \to Zγ)$ measurement. The accuracy is 22$\%$ for the option of the single polarization sample described above and deteriorate to 24$\%$ in case of the sample with two polarizations. The proposed method can be applied at any future $e^+e^-$ collider.

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arXiv2020

Latest D0 results on exotic hadrons produced in $p\bar{p}$ collisions

Prompt and nonprompt productions of exotic multiquark states are studied using the $\sim$10.4 fb$^{-1}$ data sample collected by the D0 experiment in Tevatron $p\bar{p}$ collisions at $\sqrt{s}$ = 1.96 TeV. The recent D0 results on the prompt and nonprompt production of the $X(3872)$ and $Z_c^+(3900)$ states and the $P_c$ pentaquarks at the 4450 MeV region are reported. Signals corresponding to these states are found in the nonprompt production, whereas only the $X(3872)$ state is seen in the prompt production. The ratio of prompt to nonprompt $X(3872)$ production is about three times larger in the D0 measurement than that obtained by the ATLAS experiment at 8 TeV. Theoretically, the production, formation, coalescence, and disassociation processes are expected to be quite different for conventional mesons with a spatial size of (0.4-0.8) fm, compact multiquark states such as tetraquarks with a size of a few fm, and spatially extended molecular states with a size of (4-10) fm. They can be differently affected in prompt hadron-hadron collisions where there are many additional particles emitted from the interaction point. Consequently, the prompt to nonprompt production ratio of spatially extended exotic states can be suppressed at LHC comparing with the Tevatron conditions, because of large difference in the hadron-hadron collisions particle multiplicity. The prompt production studies provide an opportunity to better understand the nature of exotic states.

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arXiv2020

COMET Phase-I Technical Design Report

The Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of an aluminium nucleus ($μ-e$ conversion, $μ^- N \to e^- N$); a lepton flavor violating process. The experimental sensitivity goal for this process in the Phase-I experiment is $3.1\times10^{-15}$, or 90 % upper limit of branching ratio of $7\times 10^{-15}$, which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the \mue conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described.

physics.ins-det↗

arXiv2019

Experimental determination of the isospin of $Λ_c(2765)^+/Σ_c(2765)^+$

We report an experimental determination of the isospin of $Λ_c(2765)^+/Σ_c(2765)^+$ using 980 fb$^{-1}$ data in the $e^+e^-$ annihilation around $\sqrt{s} = 10.6$ GeV collected by the Belle detector located at the KEKB collider. The isospin partners are searched for in the $Σ_c(2455)^{++/0} π^{0}$ channels, and no evidence was obtained. Thus the isospin is determined to be zero, and the particle is established to be a $Λ_c$.

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arXiv2019

Measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^{\ast})$ with a semileptonic tagging method

We report a measurement of the ratios of branching fractions $\mathcal{R}(D) = {\cal B}(\bar{B} \to D τ^- \barν_τ)/{\cal B}(\bar{B} \to D \ell^- \barν_{\ell})$ and $\mathcal{R}(D^{\ast}) = {\cal B}(\bar{B} \to D^* τ^- \barν_τ)/{\cal B}(\bar{B} \to D^* \ell^- \barν_{\ell})$, where $\ell$ denotes an electron or a muon. The results are based on a data sample containing $772\times10^6$ $B\bar{B}$ events recorded at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. The analysis utilizes a method where the tag-side $B$ meson is reconstructed in a semileptonic decay mode, and the signal-side $τ$ is reconstructed in a purely leptonic decay. The measured values are $\mathcal{R}(D)= 0.307 \pm 0.037 \pm 0.016$ and $\mathcal{R}(D^{\ast})= 0.283 \pm 0.018 \pm 0.014$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $0.2$ and $1.1$ standard deviations, respectively, while their combination agrees with the Standard Model predictions within $1.2$ standard deviations.

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arXiv2019

Measurement of the $D^{\ast-}$ polarization in the decay $B^0 \to D^{\ast -}τ^+ν_τ$

We report the first measurement of the $D^{\ast -}$ meson polarization in the decay $B^0 \to D^{*-} τ^+ν_τ$ using the full data sample of 772$\times 10^6$ $B\bar{B}$ pairs recorded with the Belle detector at the KEKB electron-positron collider. Our result, $F_L^{D^\ast} = 0.60 \pm 0.08 ({\rm stat}) \pm 0.04 ({\rm sys})$, where $F_L^{D^\ast}$ denotes the $D^{\ast-}$ meson longitudinal polarization fraction, agrees within about $1.7$ standard deviations of the standard model prediction.

hep-ex↗

arXiv2018

COMET - A submission to the 2020 update of the European Strategy for Particle Physics on behalf of the COMET collaboration

The search for charged lepton flavour violation (CLFV) has enormous discovery potential in probing new physics Beyond the Standard Model (BSM). Among the muonic CLFV processes, $μ\to e$ conversion is one of the most important processes, having several advantages compared to other such processes. We describe the COMET experiment, which is searching for $μ\to e$ conversion in a muonic atom at the J-PARC proton accelerator laboratory in Japan. The COMET experiment has taken a staged approach; the first stage, COMET Phase-I, is currently under construction at J-PARC, and is aiming at a factor 100 improvement over the current limit. The second stage, COMET Phase-II is seeking another 100 improvement (a total of 10,000), allowing a single event sensitivity (SES) of $2.6 \times 10^{-17}$ with $2\times 10^{7}$ seconds of data-taking. Further improvements by one order of magnitude, which arise from refinements to the experimental design and operation, are being considered whilst staying within the originally-assumed beam power and beam time. Such a sensitivity could be translated into probing many new physics constructions up to $\mathcal{O}(10^{4})$ TeV energy scales, which would go far beyond the level that can be reached directly by collider experiments. The search for CLFV $μ\to e$ conversion is thus highly complementary to BSM searches at the LHC.

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arXiv2018

Hadronic Energy Resolution of a Combined High Granularity Scintillator Calorimeter System

This paper presents results obtained with the combined CALICE Scintillator Electromagnetic Calorimeter, Analogue Hadronic Calorimeter and Tail Catcher & Muon Tracker, three high granularity scintillator-SiPM calorimeter prototypes. The response of the system to pions with momenta between 4 GeV/c and 32 GeV/c is analysed, including the energy response, resolution, and longitudinal shower profiles. The results of a software compensation technique based on weighting according to hit energy are compared to those of a standard linear energy reconstruction. The results are compared to predictions of the GEANT4 physics lists QGSP_BERT_HP and FTFP_BERT_HP.

physics.ins-det↗

arXiv2018

Measurements of branching fraction and $CP$ asymmetry of the $\bar{B}^{0}(B^{0})\to K^{0}_{S}K^{\mp}π^{\pm}$ decay at Belle

We report the measurement of the branching fraction and $CP$ asymmetry for the $\bar{B}^{0}(B^{0})\to K^{0}_{S}K^{\mp}π^{\pm}$ decay. The analysis is performed on a data sample of 711 $\rm{fb}^{-1}$ collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. We obtain a branching fraction of $(3.60\pm0.33\pm0.15)\times10^{-6}$ and an $\mathcal{A}_{CP}$ of $(-8.5\pm8.9\pm0.2)\%$, where the first uncertainties are statistical and the second are systematic. Hints of peaking structures are also observed in the differential branching fraction as functions of Dalitz variables.

hep-ex↗

arXiv2018

Study of charmless decays $B^{\pm} \to K^{0}_{S} K^{0}_{S} h^{\pm}$ ($h=K,π$) at Belle

We report a search for charmless hadronic decays of charged $B$ mesons to the final states $K^{0}_{S} K^{0}_{S} K^{\pm}$ and $K^{0}_{S} K^{0}_{S} π^{\pm}$ . The results are based on a $711 {fb}^{-1}$ data sample that contains $772 \times 10^6$ $B \bar{B}$ pairs, and was collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. For $B^{\pm} \to K^{0}_{S} K^{0}_{S} K^{\pm}$ decays, the measured branching fraction and direct $CP$ asymmetry are $[10.64\pm0.49(stat)\pm 0.44(syst)]\times10^{-6}$ and [$-0.6\pm3.9(stat)\pm 3.4(syst)$] %, respectively. In the absence of a statistically significant signal for $B^{\pm}\to K^{0}_{S} K^{0}_{S} π^{\pm}$, we set the 90 % confidence-level upper limit on its branching fraction at $1.14 \times 10^{-6}$.

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arXiv2017

Measurement of the tau Michel parameters $\barη$ and $ξκ$ in the radiative leptonic decay $τ^- \rightarrow \ell^- ν_τ \barν_{\ell}γ$

We present a measurement of the Michel parameters of the $τ$ lepton, $\barη$ and $ξκ$, in the radiative leptonic decay $τ^- \rightarrow \ell^- ν_τ \barν_{\ell} γ$ using 711~f$\mathrm{b}^{-1}$ of collision data collected with the Belle detector at the KEKB $e^+e^-$ collider. The Michel parameters are measured in an unbinned maximum likelihood fit to the kinematic distribution of $e^+e^-\rightarrowτ^+τ^-\rightarrow (π^+π^0 \barν_τ)(\ell^-ν_τ\barν_{\ell}γ)$ $(\ell=e$ or $μ)$. The measured values of the Michel parameters are $\barη = -1.3 \pm 1.5 \pm 0.8$ and $ξκ= 0.5 \pm 0.4 \pm 0.2$, where the first error is statistical and the second is systematic. This is the first measurement of these parameters. These results are consistent with the Standard Model predictions within their uncertainties and constrain the coupling constants of the generalized weak interaction.

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arXiv2017

Search for heavy neutrinos at Belle

We report on a search for heavy neutrinos in B-meson decays. The results are obtained using a data sample that contains 772x10^6 BB-bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. No signal is observed and upper limits are set on mixing of heavy neutrinos with left-handed neutrinos of the Standard Model in the mass range 0.5 - 5.0 GeV/c^2.

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arXiv2017

Precise determination of the CKM matrix element $\left| V_{cb}\right|$ with $\bar B^0 \to D^{*\,+} \, \ell^- \, \bar ν_\ell$ decays with hadronic tagging at Belle

The precise determination of the CKM matrix element $\left| V_{cb}\right|$ is important for carrying out tests of the flavour sector of the Standard Model. In this article we present a preliminary analysis of the $\bar B^0 \to D^{*\,+} \, \ell^- \, \bar ν_\ell$ decay mode and its charge conjugate, selected in events that contain a fully reconstructed $B$-meson, using 772 million $e^+ \, e^- \to Υ(4S) \to B \bar B$ events recorded by the Belle detector at KEKB. Unfolded differential decay rates of four kinematic variables fully describing the $\bar B^0 \to D^{*\,+} \, \ell^- \, \bar ν_\ell$ decay in the $B$-meson rest frame are presented. We measure the total branching fraction $\mathcal{B}( \bar B^0 \to D^{*\,+} \, \ell^- \, \bar ν_\ell ) = \left(4.95 \pm 0.11 \pm 0.22 \right) \times 10^{-2}$, where the errors are statistical and systematic respectively. The value of $\left|V_{cb} \right|$ is determined to be $\left( 37.4 \pm 1.3 \right) \times 10^{-3}$. Both results are in good agreement with current world averages.

hep-ex↗

arXiv2017

Search for B decays to final states with the eta_c meson

We report a search for $B$ decays to selected final states with the $η_c$ meson: $B^{\pm}\to K^{\pm}η_cπ^+π^-$, $B^{\pm}\to K^{\pm}η_cω$, $B^{\pm}\to K^{\pm}η_cη$ and $B^{\pm}\to K^{\pm}η_cπ^0$. The analysis is based on $772\times 10^6$ $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We set 90\% confidence level upper limits on the branching fractions of the studied $B$ decay modes, independent of intermediate resonances, in the range $(0.6-5.3)\times 10^{-4}$. We also search for molecular-state candidates in the $D^0\bar{D}^{*0}-\bar{D}^0D^{*0}$, $D^0\bar{D}^0+\bar{D}^0D^0$ and $D^{*0}\bar{D}^{*0}+\bar{D}^{*0}D^{*0}$ combinations, neutral partners of the $Z(3900)^{\pm}$ and $Z(4020)^{\pm}$, and a poorly understood state $X(3915)$ as possible intermediate states in the decay chain, and set 90\% confidence level upper limits on the product of branching fractions to the mentioned intermediate states and decay branching fractions of these states in the range $(0.6-6.9)\times 10^{-5}$.

hep-ex↗

arXiv2016

Observation of Transverse $Λ/\barΛ$ Hyperon Polarization in $e^+e^-$ Annihilation at Belle

We report the first observation of the polarization of $Λ/\barΛ$ hyperons transverse to its production plane in $e^+e^-$ annihilation. We observe a significant polarization that rises with the fractional energy carried by the hyperon as well as its transverse momentum. To define the production plane, we use the direction of the hyperon momentum together with either the thrust axis in the event or the momentum vector of a hadron in the opposite hemisphere. Furthermore, we investigate the contributions to the hyperon polarization from the feed-down from $Σ^0/\barΣ^0$ and $Λ_c^{\pm}$ decays. This measurement uses a dataset of 800.4fb$^{-1}$ collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.

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