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New physics may show itself in vector portal via the kinetic mixing of the ordinary photon with the dark one. For very light dark photon its production in particle collisions occur via oscillations with the ordinary photon. We discuss probability of light dark photon production and its possible signatures at collider experiments.
We presented new technique of the measurement cross section at $e^{+}e^{-}$ collider. This approach base on study angular distribution in laboratory frame as function of energy near threshold, when center mass system has non-zero velocity. Such technique can be used at Super Charm-Tau Factory. Super Charm-Tau Factory has Crab Waist collision scheme of the interaction point. It gives the velocity of the center mass system $\sim 0.03c$. We complied feasibility study of this technique for the $e^{+}e^{-}\to n\bar{n}$ process. In case standard way, main contribution in invariant mass resolution is beam energy spread. Our study allows one obtain invariant mass resolution from beam energy spread much smaller then gives widely used approach. On the threshold, relative resolution depend on $\delta E_{b}/E_{b}\sim10^{-3}$ for widely used approach. For new one technique relative invariant mass resolution depend as $(\delta E_{b}/E_{b})^{2}\sim10^{-6}$. We assume that contributions from other factors are large. New technique allows one reach invariant mass resolution $\delta W/W\sim10^{-4}$. This gives possibility study fine structure of the cross section near threshold.
This work is dedicated to measurement of the strong phases difference between the Cabibbo favoured and doubly Cabibbo suppressed decays of the neutral D-meson for extraction of the D0 anti-D0 mixing parameters. Key feature of this new method is the reconstruction of the neutral kaon (D0->K0 pi0) in semileptonic final state. Using this method time-dependent decay rate of the kaon can provide us with information about strong phase difference. To estimate potential accuracy we perform a feasibility study.
The large data sets a SCTF facility will produce will new opportunities for Partial-Wave Analyses (PWA) of various final states, of which we will study two example cases.
For $\tau$-events, we study the effects of the missing kinematic information due to the escaping neutrinos and their effect on the results of a PWA.
In D meson decays, how PWA can help to extract CP violating effects and introduce a method to perform such an analysis in a model-independent way, exceeding the model independence of common MIPWA approaches.
We present a feasibility study of muon polarization measurement to extract the Michel parameter $\xi’$ in tau decays. We suggest as method using the angular distribution of electron in the rest frame of decayed in the drift chamber muon, as electron momentum correlates with muon polarization. The Monte Carlo simulation of Belle detector with parameters of SCT beams was used to generate signal events. The possible background was studied and methods of its suppression were suggested. The most contribution is expected from the light mesons decayed in flight and from particles scattering. The reconstruction efficiency and statistical uncertainties were estimated depend on muon polarization.
Michel parameters (MP) determine the Lorentz structure of the charged weak interaction, they are in the list of the basic properties of every lepton. The difference of the measured MP from their Standard Model expectation will exhibit clear signature of the New Physics. Feasibility study of Michel parameters at the Super Charm-Tau factory and Belle II with polarized electron beam has been carried out. This simple generator level study allows us to estimate the statistical sensitivities to MP as a function of electron beam polarization. Two analysis techniques were tested: the unbinned maximum likelihood fit of the (tau --> lep nu nu; tau --> pi pi0 nu) events in the full nine-dimensional phase space, and unbinned maximum likelihood fit of the (tau --> lep nu nu; tau --> all) in the three-dimensional phase space. Sensitivities to MP were estimated for the whole expected Super Charm-Tau factory and Belle II tau data samples. The impact of the electron beam polarization at the Super Charm-Tau factory is discussed.
Recent results of high-statistics studies of the tau -> K pi nu decays at e+ e- B factories, Belle and BABAR, are reviewed. Complementary searches for CP symmetry violation in the tau -> K_S pi (>= 0 pi0) nu decays at BABAR and tau -> K_S pi nu at Belle are discussed. The new technique to search for CPV in tau -> K_S pi nu decay is proposed where the CPV phase is extracted in the unbinned maximum likelihood fit of the (tau -> K_S pi nu; tau -> pi pi0 nu) events in the 12-dimensional phase space. The impact of the electron beam polarization at the Super Charm-Tau factory is analyzed.
In order to guarantee an excellent PID at SCTF, two Cherenkov counters are proposed as one possible design option of the final SCTF detector. Both detectors use the method of detection of internally reflected Cherenkov light, what is called the DIRC concept. The main purpose of these DIRCs is to separate pions and muons up to a momentum of 1 GeV/c with a $4\pi$ angular coverage.
Two endcap DIRCs are proposed that cover the forward and backward regions. They consist of a thin fused silica radiator plate each, with attached focusing optics. A third DIRC detector, that will contain fused silica bars and expansion volumes, is going to be designed in a barrel shape around the $e^+e^-$ interaction point. The concept of these detectors is based on existing models that have already been developed for the PANDA detector at FAIR.
This talk will mainly cover the simulation studies that are currently ongoing, which aim to optimize the performance of these detectors with respect to the Cherenkov angle resolution and timing information. The results of these simulations will be used to identify the best optical parameters and readout systems for both detectors. According to the actual plan, silicon photomultipliers (SiPMs) with a high granularity are going to be used to measure single Cherenkov photons. Special optics is going to be required for obtaining a high detector resolution. In addition to that, it will be important to use fast readout electronics to correct for dispersion effects of the created Cherenkov light in fused silica.
We developed Aerogel RICH (ARICH) detector as a forward endcap PID detector in the Belle II spectrometer. ARICH consists of 248 aerogel tiles as radiators and 420 Hybrid Avalanche Photodetectors (HAPDs) as photon detectors. Belle II conducted the commissioning operation in 2018, and then started the physics run this year. In this presentation, the operation and experience as well as the initial performance of the ARICH detector is reported.
Modern high luminosity e+ e- factory requires fast electromagnetic calorimeter to collect the data efficiently at high trigger rates and suppress severe beam background. The prototype of the calorimeter for the Super Charm-Tau factory based on pure CsI scintillation crystals, wavelength shifters with the novel nanostructured organosilicon luminophores, and avalanche photodiodes Hamamatsu S8664-55 is discussed. The results of the beam test of the basic element of the calorimeter are reported. Simulation of the calorimeter response is also briefly discussed.
Large Area Picosecond Photodetectors (LAPPD) are a new generation of microchannel plate based photomultipliers being manufactured by Incom. These devices feature large sensitive area of 350 $cm^2$, high quantum efficiency ($\sim$20%), and tens of picosecond single photon level timing resolution. Initial devices use a stripline anode structure, allowing for high spatial resolution of 1-3 mm while minimizing the number of readout channels. These characteristics make LAPPD a very attractive option as a photodetector for collider experiments in High Energy Physics, such as future Charm-Tau Factories. In this report we present readout electronics which has been developed to be used with LAPPD devices. This electronics read out all channels of a single stripline-anode LAPPD. Waveform sampling up to 5GSPS is performed with the DRS4 switched-capacitor array ASIC. All DRS4 channels are digitized in parallel with two 32-channel ADCs. An on-board FPGA coordinates digitization and readout of waveforms, and could further be expanded to include some waveform processing. Data packages built in the FPGA are sent to a DAQ system via optical fiber, with a baseline Gigabit Ethernet interface implemented entirely on the FPGA. The electronics has different triggering options: self-triggering using DRS4 transparent mode and external triggering, making event control very flexible. Further flexibility is enhanced with embedded software for an on-FPGA soft-core processor, as well as DAQ readout and control software. This open-source ecosystem is being developed to provide full control of the device operation and an easy way to integrate it to any environment. In the report we describe the status of the electronics development along with its firmware and readout software.
A common bus tour to Moscow downtown, visit to Kremlin, Red Square and St. Basil Cathedral.
Please put on warm clothes, as part of the visit to Kremlin and Red Square involves a walk outdoors. The expected day temperature is +11°C, night temperature — +1°C.