Spherical Neutral Detector Research Articles

Measurement of the e+e\u2212 \u2192 \u03c0+\u03c0\u2212 process cross section with the SND detector at the VEPP-2000 collider in the energy region 0.525 < sqrt{s} < 0.883 GeV

The cross section of the process e+e− → π+π− has been measured in the Spherical Neutral Detector (SND) experiment at the VEPP-2000 e+e− collider VEPP-2000 in the energy region 525 < sqrt{s} < 883 MeV. The measurement is based on data with an integrated luminosity of about 4.6 pb−1. The systematic uncertainty of the cross section determination is 0.8% at sqrt{s} > 0.600 GeV. The ρ meson parameters are obtained as mρ = 775.3 ± 0.5 ± 0.6 MeV, Γρ = 145.6 ± 0.6 ± 0.8 MeV, Bρ→e+e− × Bρ→π+π− = (4.89 ± 0.02 ± 0.04) × 10−5, and the parameters of the e+e− → ω → π+π− process, suppressed by G-parity, as Bω→e+e− × Bω→π+π− = (1.32 ± 0.06 ± 0.02) × 10−6 and and ϕρω = 110.7 ± 1.5 ± 1.0 degrees.

Upgrade of the SND electromagnetic calorimeter

Current status and last results of the Spherical Neutral Detector (SND) calorimeter upgrade are described. The main part of SND detector is a three-layer spherical NaI(Tl) electromagnetic calorimeter (EMC). The total thickness of NaI(Tl) in the calorimeter is 35 cm. The vacuum phototriodes (VPT) are used as photosensitive devices for the calorimeter counters. The quantum efficiency of VPT is about 15%, the average gain is 10, and the light collection efficiency is about 10%. New spectrometric channel of EMC was designed and implemented. It consists of a NaI(Tl) crystal, a vacuum phototriode, a charge-sensitive preamplifier a shaper and digitizing modules. The digitization is performed by 6 ADCs AD9228BCPZ-40 (4 channel, 12 bits, 40 MBPS) and the data go in serial form to the SoC Xilinx Zynq-7000. This SoC is basically a combination of FPGA programmable logic and ARM processor. The special algorithm for signal waveform processing was developed to determine time of flight and amplitude with high time (1 ns) and amplitude (250 keV) resolution. The algorithm is based on the invariability of the signal waveform. The waveform calibration procedures are developed and implemented. Successful data taking run was performed with upgraded EMC in 2019.

Collider experiment SND and Precision Physics with hadronic e+e- cross sections

The Spherical Neutral Detector (SND) is an experiment for e+e− annihilation study at low energies 0.2−2 GeV. The light quark anti−quark bound states are the main subject of study at these energies. They express themselves as resonances in the e+e− hadronic cross sections. Hadronic cross sections could be recalculated to hadronic vacuum polarization (HVP). The Standard Model predictions today are limited by HVP which is not calculable with modern QCD theory. In this talk we present the review of the hadronic cross sections measurements at SND and new measurements: e+e− → π+π−, π0γ, π+π−π0, ωπ0, K+K−η, η, KsKLπ0, π+π−π0η, ωπ0η e.t.c.

Calibration of the calorimeter signal waveform in the SND detector

The new spectrometric channel for the Spherical Neutral Detector (SND) electromagnetic calorimeter (EMC) is described. It provides measurement of the calorimeter signal arrival time and amplitude with 1 ns and 250 keV resolutions, respectively. The new electronics is useful for reliable detection of low-speed anti-neutrons from the e + e − → n n ̄ reaction near threshold and needed for increasing the EMC operation rate. The algorithm of determination of signal parameters (time, amplitude) is based on invariability of the signal waveform. We present the procedure of the waveform calibration using signals from cosmic-muon and Bhabha scattering events.

SND DAQ system evolution

The spherical neutral detector (SND) takes data at the e+e- collider VEPP-2000 in Novosibirsk. We present here recent upgrades of the SND DAQ system which are mainly aimed to handle the enhanced events rate load after the collider modernization. To maintain acceptable events selection quality the electronics throughput and computational power should be increased. These goals are achieved with the new fast digitizing electronics and distributed data taking. The data flow for the most congested detector subsystems is distributed and processed separately. We describe the new distributed SND DAQ software architecture, its computational and network infrastructure.

Hadronic cross sections measurement with the SND detector at VEPP-2000 e+e− collider

The cross sections , , , , K+K−, , , have been measured with the spherical neutral detector at the VEPP-2000 e+e− collider in the energy range from 0.3 to 2.0 GeV.

New electronics of the spectrometric channel for the SND detector electromagnetic calorimeter

The Spherical Neutral Detector (SND) is intended for study of electron–positron annihilation at the VEPP-2000 e+e− collider (BINP, Novosibirsk) in the center-of-mass energy region below 2GeV. The main part of the detector is a three-layer electromagnetic calorimeter based on NaI(Tl) crystals. The physics program of the SND experiment includes a high statistics study of neutron–antineutron production near threshold, for which time measurements in the calorimeter are required. In this paper we describe new shaping and digitizing calorimeter electronics, which allow to reach a time resolution of about 1ns for 100MeV signal and an amplitude resolution of about 250keV.

Study of the e + e – → π+π–π0 process in the energy range 1.05–2.00 GeV

The cross section for the e + e – → π+π–π0 process in the energy range 1.05–2.00 GeV has been measured using the data collected in the experiment with the Spherical Neutral Detector (SND) at the VEPP-2000 e + e – collider. The obtained results on the cross section are in good agreement with previous measurements by the SND at the VEPP-2M collider and BABAR, but have a better accuracy.

Muon system of SND detector

The Spherical Neutral Detector muon system composed of proportional tubes and plastic scintillation counters is described. This system is constructed for the SND detector collecting data at VEPP-2000 e+e− collider. The results of the muons and pions detection efficiency measurements are presented. These measurements are performed using e+e−→μ+μ−, e+e−→π+π−, e+e−→π+π−π0π0, e+e−→e+e− processes and cosmic muons. Efficiency for muons is 95.5% for the energies 0.6–1.0 GeV and becomes much lower in energy range 0.45–0.60 GeV. Pions detection efficiency varies from 0 at 0.4 GeV to 56% at 1.0 GeV. Probability of the muon system hit from electon/positron is no more than 0.43%.

Spherical Neutral Detector for experiments at VEPP-2000 collider

Spherical Neutral Detector (SND) is a general purpose non-magnetic detector for experiments at VEPP-2000 e + e − collider in Novosibirsk in the energy range 2 E = 0.4 – 2.0 GeV . Charged particle track coordinates are measured using drift and proportional chambers placed in a common gas volume. Particle identification is performed using energy deposition in the drift chamber at low particle momenta p ⩽ 300 MeV and aerogel threshold counters at high particle momenta p ⩾ 300 MeV . Photon energies are measured using 3-layer spherical electromagnetic calorimeter. Muons penetrating the detector and cosmic background muons are detected by the muon system based on proportional tubes and plastic scintillator counters. At present the detector is operating at VEPP-2000.

First results of spherical neutral detector (SND) experiments at VEPP-2000

Preliminary results of the first experiments at the new VEPP-2000 e+e− collider are presented. The experiments have been carried out in the center of mass energy range 1–2 GeV with instant luminosity 1030–1031cm−2s−1 and total integrated luminosity of about 10pb−1. The main e+e− annihilation cross sections, π+π−π0π0,π+π−π0,π0π0γ,andπ+π−η, have been measured. The cross section of nucleon–antinucleon production is also presented.

Measurement of the cross section for the e + e − → ωπ0 → π0π0γ process in the energy range of 1.1–1.9 GeV

The cross section for the e+e− → ωπ0 → π0π0γ process has been measured in the energy range of 1.1–1.9 GeV. The measurement has been made with the Spherical Neutral Detector at the VEPP-2000 e+e− collider. The data in the energy range of 1.1–1.4 GeV are in agreement with the earlier measurements with the SND and CMD-2 detectors. The cross section has also been measured above 1.4 GeV.

Search for the e + e − → K ± K S π ∓ process on the VEPP-2M e + e − collider

We report on the results of the search for the e+e− → K±KSπ∓ process. Data with an integrated luminosity of 1.36 pb−1 collected in experiment with a spherical neutral detector (SND) on the VEPP-2M e+e− collider in the energy range from 1.36 to 1.38 GeV have been analyzed. The upper limits of the σ < 150 pb cross sections of the sought process have been established for an energy of 1.37 GeV at a confidence level of 90%.

The VEPP-2000 electron-positron collider: First experiments

In 2007, at the Institute of Nuclear Physics (Novosibirsk), the construction of the VEPP-2000 electron-positron collider was completed. The first electron beam was injected into the accelerator structure with turned-off solenoids of the final focus. This mode was used to tune all subsystems of the facility and to train the vacuum chamber using synchrotron radiation at electron currents of up to 150 mA. The VEPP-2000 structure with small beta functions and partially turned-on solenoids was used for the first testing of the “round beams” scheme at an energy of 508 MeV. Beam-beam effects were studied in strong-weak and strong-strong modes. Measurements of the beam sizes in both cases showed a dependence corresponding to model predictions for round colliding beams. Using a modernized SND (spherical neutral detector), the first energy calibration of the VEPP-2000 collider was performed by measuring the excitation curve of the phimeson resonance; the phi-meson mass is known with high accuracy from previous experiments at VEEP-2M. In October 2009, a KMD-3 (cryogenic magnetic detector) was installed at the VEPP-2000 facility, and the physics program with both the SND and LMD-3 particle detectors was started in the energy range of 1–1.9 GeV. This first experimental season was completed in summer 2010 with precision energy calibration by resonant depolarization.

Search for e + e − → f 0(600)γ, f 0(980)γ, f 0(1350)γ, and f 2(1270)γ processes in the energy range from 1.05 to 1.38 GeV

In the energy range from 1.05 to 1.38 GeV, the upper limits for the cross sections of e + e − → f 0(600)γ, f 0(980)γ, f 0(1350)γ, and f 2(1270)γ → π0π0γ processes have been established. Measurements are performed in accordance with the statistics gathered in experiment with a spherical neutral detector (SND) on the VEPP-2M e + e − collider. The resultant upper limits vary from 6 to 42 pb depending on the energy and the model.

New tracking system of the SND detector

A new tracking system (TS) of the Spherical Neutral Detector (SND) for experiments at the VEPP-2000 e+e− collider is described. The TS is completely assembled, mounted on the detector, and ready for collecting data from the VEPP-2000. Test experiments with cosmic-ray events and VEPP-2000 beams showed a stable operation of the system. The simulation, calibration, and reconstruction procedures were debugged by using available data.

Measurement of the e + e − → ηπ+π− cross section in the % MathType!MTEF!2!1!+- % feaagaart1ev2aaatCvAUfKttLearuqr1ngBPrgarmWu51MyVXgatC % vAUfeBSjuyZL2yd9gzLbvyNv2CaeHbd9wDYLwzYbItLDharyavP1wz % ZbItLDhis9wBH5garqqr1ngBPrgifHhDYfgasaacH8srps0lbbf9q8 % WrFfeuY-Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0-yr0RYxir-J % bba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dmeaabaqaciGacaGaae % qabaWaaqaafaaakeaadaGcaaqaaiabdohaZbWcbeaaaaa!3E0A! $$ \sqrt s $$ = 1.04–1.38-GeV energy range with a spherical neutral detector at the VEPP-2M collider

The e + e − → ηπ+π− cross section in the η → 2γ channel has been measured in the $$ \sqrt s $$ = 1.04- to 1.38-GeV energy range. The data with a total integrated luminosity of 9.05 pb−1 were collected on a spherical neutral detector at the VEPP-2M collider. The results are consistent with the BaBar and CMD2 data and have a higher statistical accuracy.

Study of the process e+e− → π+π−π0π0 at energies √s < 1 GeV

In an experiment with the Spherical Neutral Detector at VEPP-2M collider the cross section of the process e+e− → π+π−π0π0 was measured. At energies √s < 920 MeV this cross section was measured for the first time. The energy dependence of the cross section is well discribed by the vector dominance model with contributions from ρ, ρ′, ρ′′ mesons. The decay probability ρ → π +π−π0π0 was found to be Bρ = (1.60±0.74±0.18) × 10−5. The upper limit for the decay ω → π+π−π0π0 was improved by two orders of magnitude compared to the previous measurements and is Bω < 2 × 10−4 at 90% confidence level.

Searching for the process e+e- → K+K-π0 in experiments with the spherical neutral detector at VEPP-2M

We have searched for the process e+e- → K+K-π0 at energies up to 1.38 GeVin an experiment with the spherical neutral detector at the VEPP-2M e+e- collider. The upper limits of the cross sections for the processes σ(e+e →; φπ: → K+K-π0) < 0.023 nb and σ(e+e- → KK*(892) → K+K-π0) < 0.059 nb have been established at a 95% confidence level.

Study of process e + e − → π+π−π0π0 at energies √s &lt; 1 GeV with the spherical neutral detector

The cross section for the process e + e − → π+π−π0π0 has been measured in an experiment with a spherical neutral detector, with the cross section at energies √s < 920 MeV having been measured for the first time. The model of vector dominance describes well the data obtained if the ρ, ρ′, and ρ″ resonances are taken into account. The probability of the decay ρ → π+π−π0π0 is B(ρ → π+π−π0π0) = (1.60 ± 0.74 ± 0.18) × 10−5. The upper limit for the decay ω → π+π−π0π0 has been improved by two orders of magnitude compared to previous measurements and is B(ω → π+π−π0π0) < 2 × 10−4 at a 90% confidence level.