Super Charm-Tau Factory 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.

Hyperon–nucleus/nucleon scattering at BESIII

Utilizing the large quantity of hyperons and antihyperons produced by the decay of 10 billion [Formula: see text] and 2.7 billion [Formula: see text] collected at BESIII, the cross-sections of several specific elastic or inelastic (anti-)hyperon–nucleus/nucleon reactions have been measured via the scattering between the (anti-)hyperons and the nucleus in the dense objects of BESIII detector. The novel method developed in these works extends the research field and opens a new era for the experiments at [Formula: see text] colliders. The results of such measurements will definitely benefit a lot the precise probe of the (anti-)hyperon–nucleus/nucleon interactions and provide constraints for the studies of the potential of strong interaction, the origin of color confinement, the unified model for baryon–baryon interactions, and the internal structure of neutron stars. The desirable prospects of corresponding studies in the future Super Tau-Charm Factory (STCF) are also discussed in this report.

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.

Role of the triangle singularity in the isospin breaking process J/ψ→ΛΛ¯π and the possible evidence of Σ*(12−) states

In this study, the impact of triangle singularity is investigated in the isospin breaking process J/ψ→ΛΛ¯π. The triangle singularity is found to play a significant role in the process, resulting in the creation of a resonancelike structure around 1.4 GeV in the Λπ(Λ¯π) invariant mass spectrum. To amplify the impact of this triangle singularity, the presence of two Σ*(12−) states around 1.4 GeV and 1.6 GeV is essential, yet these states have not been definitively identified in the current baryon spectrum. We recommend that experiments, particularly the Beijing Spectrometer and the future Super Tau-Charm Factory, investigate the process J/ψ→ΛΛ¯π to offer direct evidence for our predicted triangle singularity and additional evidence regarding the Σ(12−) states. Published by the American Physical Society 2024

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.

New signature of low mass Z′ in J/ψ decays* *Supported in part by the National Key Research and Development Program of China under (2020YFC2201501) and the National Natural Science Foundation of China (NSFC) (12347103, 12205063)

We explored a new approach to search for a low-mass particle through decays by identifying its existence through parity-violating phenomena in the isospin-violating final states of and the corresponding charge conjugated states of . Our investigation centered on a generation-independent and leptophobic with mass below 10 GeV. Given the present experimental conditions at Beijing Spectrometer III (BESIII) and the anticipated opportunities at the Super Tau Charm Factory (STCF), we conducted Monte-Carlo simulations to predict possible events at both facilities. Notably, we foresee a substantial enhancement in the precision of the lower limit estimation of as well as a reduction in statistical uncertainty with upcoming STCF experiments. Furthermore, it is essential to highlight that a null result in the measurement of would impose stringent constraints, requiring the couplings to be in the order of .

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.

Prospects to study hyperon-nucleon interactions at BESIII* *Supported by the National Natural Science Foundation of China (NSFC) (11935018, 11875054, 12165022), the Chinese Academy of Sciences (CAS) Key Research Program of Frontier Sciences (QYZDJ-SSW-SLH003), and the Fundamental Research Project of Yunnan Province, China (202301AT070162)

The prospects to study hyperon-nucleus/nucleon interactions at BESIII and similar colliders are analyzed in this paper. Utilizing the large quantity of hyperons produced by the decay of 10 billion and 2.7 billion collected at BESIII, the cross sections of several specific elastic and inelastic hyperon-nucleus reactions can be measured via scattering between hyperons and nucleus in the dense objects of the BESIII detector. Subsequently, the cross sections of the corresponding hyperon-nucleon interactions can be extracted from further phenomenological calculations. The interactions between antihyperons and nucleus/nucleon, including scattering and annihilation, can also be studied using the method proposed in this study. The results will definitely benefit the realization of precise probes for hyperon-nuclei/nucleus interactions and establish constraints to study the potential of strong interaction, the origin of color confinement, a unified model for baryon-baryon interactions, and the internal structure of neutron stars. In addition, the desirable prospects of corresponding studies in the future Super Tau-Charm Factory (STCF) are discussed and estimated in this study.

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.

Probing inelastic dark matter at the LHC, FASER, and STCF

In this work, we explore the potential of probing the inelastic dark matter (DM) model with an extra U(1)D gauge symmetry at the Large Hadron Collider, Forward Search Experiment, and Super Tau Charm Factory. To saturate the observed DM relic density, the mass splitting between two light dark states has to be small enough and thus leads to some distinctive signatures at these colliders. By searching for the long-lived particle, the displaced muon jets, the soft leptons, and the monophoton events, we find that the inelastic DM mass in the range of 1 MeV to 210 GeV could be tested. Published by the American Physical Society 2024

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

Prospects for ditauonium discovery at colliders

The feasibility of observing ditauonium, the bound state of two tau leptons, at e+e− colliders (BES III at s=3.78 GeV, Belle II at s=10.6 GeV, a future super tau-charm factory (STCF) at s≈2mτ, and the FCC-ee at s=91.2 GeV) as well as in hadronic and photon-photon collisions at the LHC, is studied. Cross sections and expected yields for spin-0 para- (T0) and spin-1 ortho- (T1) ditauonium are presented for nine different production and decay processes. Para-ditauonium can be observed at the FCC-ee via photon fusion in its diphoton decay (γγ→T0→γγ). Ortho-ditauonium can be observed at STCF via e+e−→T1→μ+μ−, where a threshold scan with monochromatized beams can also provide a very precise extraction of the tau lepton mass with O(25 keV) uncertainty. Observing pp →T1(μ+μ−)+X at the LHC is possible by identifying its displaced vertex with a good control of the combinatorial dimuon background. In addition, we compute the rare decay branching fractions of ditauonium into quarkonium plus a photon.

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.

SECALROC2: A Low-Noise, High-Speed, and Full Digital Outputs Front-End ASIC for STCF Electromagnetic Calorimeter With APD Detectors

In this work, a low-noise and high-rate front-end readout application-specific integrated circuit (ASIC) named SECALROC2 for the electromagnetic calorimeter (ECAL) in the super tau-charm factory (STCF) is presented. The chip is designed to process signals generated from avalanche photodiode detectors (APDs) for both energy and time measurement. The large detector capacitance and leakage current of the APD pose a great challenge to the noise and speed performance of the front-end readout circuit (ROC). A low-noise preamplifier and a fifth-order high-linearity shaper with adjustable peaking times are proposed to decrease noise induced by the 270-pF detector capacitance. A peak detect-and-hold circuit and a high-linearity differential analog buffer are adopted to convert each peak voltage of the shaper to differential voltages with sufficient driving capability. A fast shaper and a discriminator are implemented to produce trigger signals for the time of arrival (TOA) measurement. To reduce the complexity and power consumption of the ECAL system, a 12-bit 10-MS/s pipelined analog-to-digital converter (ADC) and a 16-bit three-stage time-to-digital converter (TDC) with 42-ps bin size TDC are integrated on-chip for full-digitalized outputs. This ASIC was designed and fabricated in a standard commercial 1P6M 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> mixed-signal CMOS process and the chip area occupancy is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.4\times1.6$ </tex-math></inline-formula> mm2. The experimental results show that the input charge of the ASIC ranges from 3.2 to 400 fC. The measured nonlinear error of the system is less than 2.5% with an event rate up to 400 kcps. The equivalent noise charge (ENC) is 1367 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{e}^{-}$ </tex-math></inline-formula> + 4.93 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{e}^{-}$ </tex-math></inline-formula> /pF at 800-ns peaking time. The timing resolution is better than 540 ps at an input charge of 160 fC. The measured ENC can achieve 3820 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{e}^{-}$ </tex-math></inline-formula> when the ASIC is connected to an APD detector. The effective number of bits (ENOB) of the ADC is 10.8-bit when operated at 10 MS/s.