Super Charm-Tau Research Articles

Status of the Super Charm-Tau Detector software

The Super Charm-Tau (SCT) Factory project is actively developing in Budker Institute of Nuclear Physics, Novosibirsk. This paper presents the SCT Detector offline software framework Aurora components, status and future prospects.

R&D status of FARICH option for PID

The Super Charm-Tau Factory project is a future electron–positron colliding beam experiment with unprecedented high luminosity of 10[Formula: see text][Formula: see text]cm[Formula: see text][Formula: see text]s[Formula: see text] at the center of mass energy range from 3 to 7[Formula: see text]GeV. To perform the broad physics program, the high-performance universal detector is proposed. One of the main detector subsystems is the FARICH (Focusing Aerogel RICH) detector. The proposed FARICH scheme combined with abilities of tracking system will provide the excellent [Formula: see text]-separation for the whole operation momentum range and [Formula: see text]-separation up to momentum of 1.5[Formula: see text]GeV/c. In 2023 two multilayer focusing aerogel samples with record overall sizes [Formula: see text][Formula: see text]mm were produced in Novosibirsk. The results of the beam tests of these aerogel samples and comparison with simulation are presented. Conceptual design and some technical issues of the dedicated particle identification system based on FARICH technique are discussed as well.

Measurement of the Michel parameters in leptonic τ-decays at Super Tau-Charm facility

We present a new method for direct measurement of all Michel parameters in the [Formula: see text] decay related to the polarization of the daughter muon: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]. The method is based on the reconstruction of the muon decays-in-flight in the tracker of the [Formula: see text] collider experiments and relies on the correlation between muon spin and its daughter electron momentum. The low probability of decay-in-flight in the tracker volume is compensated by the unprecedented statistics of modern flavor factories, which ultimately leads to the possibility of achieving high accuracy. We discuss the application of the suggested method in the experiments at [Formula: see text] colliders and present a feasibility study for the future Super Charm-Tau Factory experiment. We also discuss the result of the first use of the proposed method in the Belle experiment, confirming its applicability.

Status and R & D of ASHIPH-SiPM option for PID

The ASHIPH (Aerogel, SHifter, PHotomultiplier) Cherenkov counters are considered as a particle identification system alternative option for the detector on future Super Charm-Tau factory. The ASHIPH counters have been operating successfully in the KEDR and SND experiments in Novosibirsk at the Budker Institute of Nuclear Physics. Previously in our experiments Micro Channel Plate PMTs were used for the photon detection in the ASHIPH counters. Now, we have developed a prototype of the ASHIPH counter with SiPM (Silicon PMTs) array as a photodetector. Such an upgrade will increase the number of detected photoelectrons by 2.5 times and consequently improve the quality of particle separation. The results of testing the ASHIPH counter prototype on the electron test beam facility of the VEPP-4M accelerator is presented.

Inner tracker for super Charm-Tau factory detector based on compact time projection chamber

Time Projection Chamber as Inner Tracker for Super Charm-Tau Factory Detector was simulated. Minimum required momentum for [Formula: see text]-meson to be reliably registered was determined to be 50[Formula: see text]MeV/c. Momentum resolution of a few percents was obtained for the detection of [Formula: see text]-mesons with initial momentum less than 100[Formula: see text]MeV/c.

The spatial resolution measurements on the small prototype of the Super Charm-Tau Factory drift chamber

Budker Institute of Nuclear Physics is actively evolving the Super Charm-Tau Factory project. A drift chamber with a small hexagonal cell was proposed for this collider. For experimental measurements of a spatial resolution, a drift chamber small prototype consisting of seven cells has been developed. The experiments have been carried out in He/C3H8 (60/40) and He/C2H6 (50/50) gas mixtures at different gas gains using cosmic particles. For this purpose, a calibration procedure for R(t, α) has been developed and fine-tuned, taking into account small prototype features and an angular dependence of isochrones at the edge of the cells. As a result, the average spatial resolutions are less than 100μm for gas gains greater than 5⋅104.

The result of simulation studies of a GEM-based TPC for the inner tracker of Super Charm-Tau Factory Detector at BINP

The Super Charm Tau Factory (SCTF) is a newly proposed electron-positron collider with an energy range of 2–7 GeV in the center of the mass system and luminosity of about 1035 cm-2s-1, instrumented with Super Charm-Tau Detector. The innermost part of the SCTD is the inner tracker (IT). The main tasks of IT are the extension of the lever arm of the drift chamber, detection of soft hadrons, and reconstruction of the secondary particles that decay in the IT. The main candidates for IT are silicon strip detectors, cylindrical MPGD detectors, and a time projection chamber (TPC). This paper discusses the results of simulation studies of the TPC detector in detail and the plans for the inner tracker development.

Touschek lifetime and luminosity optimization for Russian Super Charm Tau factory

Electron-positron collider Super Charm Tau factory is planned to be built in the National center for physics and mathematics, Sarov. It is a double ring collider with crab waist collision scheme operating in wide beam energy range from 1.5 GeV to 3.5 GeV with peak luminosity of 1035 cm-2s-1. The polarized electron source and three Siberian Snakes provide 80% longitudinally polarized electron beam at 2 GeV. Superconducting wigglers decrease damping times, effects of intra-beam scattering and increase Touschek beam lifetime, particularly at low energy. The paper presents the status of collider design and optimization of luminosity and beam lifetime.

Fast Simulation for the Super Charm-Tau Factory Detector

The Super Charm-Tau factory (high luminosity electron-positron collider with 3–7 GeV center of mass energy range) experiment project is under development by the consortium of Russian scientific and education organizations. The article describes the present status of the Super Charm-Tau detector fast simulation and the algorithms on which it is based, example usage and demonstration of fast simulation results.

What Machine Learning Can Do for Focusing Aerogel Detectors

Particle identification at the Super Charm-Tau factory experiment will be provided by a Focusing Aerogel Ring Imaging CHerenkov detector (FARICH). The specifics of detector location make proper cooling difficult, therefore a significant number of ambient background hits are captured. They must be mitigated to reduce the data flow and improve particle velocity resolution. In this work we present several approaches to filtering signal hits, inspired by machine learning techniques from computer vision.

Calibration and Reconstruction Algorithm for FARICH System of the Detector at Super Charm-Tau Factory

Calibration and Reconstruction Algorithm for FARICH System of the Detector at Super Charm-Tau Factory

Prospects for the Search for a Leptophilic Scalar and a Dark Photon in Experiments at the Super Charm-Tau Factory

Prospects for the Search for a Leptophilic Scalar and a Dark Photon in Experiments at the Super Charm-Tau Factory

Kinematic and vertex fitting package for the CMD-3 experiment

In this article, we discuss a new software package of kinematic and vertex fitting for the CMD-3 experiment at the VEPP-2000 electron-positron collider. The authors describe in detail the fitting algorithm, parametrization of four-momenta and trajectories of various particles and present the results of testing the fitting pakage using events of Monte Carlo simulation of various e + e - annihilation processes. The authors also provide several examples of the fitting package validation using Gaussian simulation. Although the package discussed in this article is intended for the CMD-3 experiment, it can also be used in other experiments. The authors consider the described package as their first step towards a more universal and rigorous kinematic and vertex fitting package that can be used in future e + e - experiments, such as the Super Charm-Tau factory.

Plans for novel Cherenkov detectors at the Super Charm-Tau Factory in Novosibirsk

The future e + e − Super Charm-Tau Factory (SCTF) to be built at Novosibirsk will cover an energy range of 2 – 7 GeV. The projected record luminosity of 1035 cm −2 s −1 and the longitudinal polarization of the electrons will enable a wide range of standard model precision tests and options for the discovery of flavor violating decays beyond the standard model. A 4π detector with excellent particle identification (PID) is required with challenging μ/π-separation in the range 0.2 – 1.2 GeV/c. This talk focuses on two new concepts and the first tests of novel Cherenkov detectors for SCTF, a focusing aerogel RICH (FARICH) and a focusing DIRC (fDIRC). Both require single-photon detection with good coordinate and timing resolution. The prototyping for both versions already started at BINP and Giessen. The tests include various photon detectors (MCP-PMT, SIPM, MPPC). The first results using cosmic muons at the Giessen Cosmic Station are presented.

A new method for the measurement of the Michel parameters that describe the daughter muon polarization in the τ−→ μ− overline{nu} μντ decay

This paper provides a detailed description of the method for the first direct measurement of all Michel parameters in the τ−→ μ− overline{nu} μντ decay related to the polarization of the daughter muon. An application of the suggested method in the existing and future experiments at e+e− colliders is considered. We have performed a feasibility study for the future Super Charm-Tau Factory and Belle II experiments. For the first one, the sensitivity to the Michel parameters ξ′, ξ′′, η′′, α′/A, and β′/A is estimated. For the latter, only one Michel parameter, ξ′, for which the sensitivity is maximum, is considered.

Effects of Electroweak Radiative Corrections in Polarized Low-Energy Electron–Positron Annihilation into Lepton Pairs

Complete one-loop electroweak radiative corrections to the cross section of the process {{e}^{ + }}{{e}^{ - }} to {{mu }^{ - }}{{mu }^{ + }}({{tau }^{ - }}{{tau }^{ + }}) are evaluated with the help of the SANC system. Higher-order contributions of the initial state radiation are computed in the QED structure function formalism. Numerical results are given for the center-of-mass energy range sqrt s = 5, 7 GeV for various polarization degrees of the initial particles. This study is a contribution to the research program of the Super Charm-Tau Factory project being under development in Sarov, Russia.

The central tracker of SCTF and CMD3 detectors

The CMD3 experiment has been operating at the VEPP-2000 electron-positron collider, at the Budker Institute of Nuclear Physics, since December 2010. Its main goal is to measure the hadronic cross sections necessary to evaluate the anomalous magnetic moment of the muon. The discrepancy between the theoretical calculations and the experimental results obtained at the Brookhaven experiments is approximately 3.7 σ.The comparison between the results of the new “g-2” experiment at Fermilab and the theoretical calculation with the new experimental contributions from CMD3 could confirm the discrepancy, which is a new important hint of New Physics.A key element for the success the CMD3 experiment is the tracking detector, which is a drift chamber built in the year 2009 at INFN of Lecce. Due to aging effects, its replacement is necessary, so that an innovative tracking detector, named TraPId (Tracking and Particle Identification), has been designed: an ultra-light drift chamber equipped with cluster counting/timing readout techniques, which exploits the expertise gained with the successful construction of the MEG II drift chamber. The drift chamber proposed for CMD3 will be also the prototype for the tracking system of the future Super Charm-Tau Factory detector (SCTF).In this paper, the new design of TraPId is described, with a focus on the mechanical design of the end plates, their novel tension recovery scheme and the expected performances.

Development of compact TPC for future Super Charm-Tau Factory detector

Currently, the Budker Institute of Nuclear Physics together with Novosibirsk State University are developing the detector for the future Super Charm-Tau Factory (SCTF) to be built in Russia. SCTF is an electron–positron collider with 3.5GeV per beam and a luminosity of 1035cm−2s−1. SCTF will be instrumented with a general-purpose detector (SCTD). The innermost part of the SCTD will contain the inner tracker (IT). The main task of the IT is an extension of the lever arm of the central drift chamber, efficient detection of soft hadrons and reconstruction of secondary vertices of particles that decay in the IT volume (like Ks,Λ0, etc.). The most attractive candidate for the IT is the compact time-projection chamber (CTPC). It can be made with a very thin inner wall allowing to reduce significantly the threshold for soft hadrons. In addition, CTPC can provide the dE/dx information for the discrimination of electrons from hadrons. We present recent results on the simulation of spatial resolution and drift time of CTPC as well as space charge effects induced by positive ions.

Progress and perspectives of FARICH R&D for the Super Charm-Tau Factory project

Particle identification system based on Focusing Aerogel RICH (FARICH) detector is considered as an option for the future experiments at the Super Charm-Tau Factory (Russia). We present the progress of FARICH R&D at the Budker Institute of Nuclear Physics. New samples of focusing 4-layer aerogels with maximal refractive index 1.065 were produced in 2020–2021. First beam test results with relativistic electrons demonstrate single photon resolution (SPR) of 9÷10mrad. According to simulation results, the aerogels with such SPR are able to provide μ/π-separation at the level of more than 3 standard deviations for tracks with momentum 1.5 GeV/c. The first version of electronics to readout SiPM arrays based on TDC implemented on FPGA (FPGA-TDC) was developed and manufactured.

The drift chamber project for the Super Charm-Tau Factory detector

Since recently, the design of the detector for the Super Charm-Tau Factory has been actively developed at the Budker Institute. The principal tasks of the detector tracking system are to provide efficient reconstruction of charged-particle tracks, to determine their momenta and impact parameters with high precision and to identify particles using their energy losses. This article describes various issues related to the development of the drift chamber, the main part of the tracking system.