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.     

VEPP-2000 collider commissioning

Construction of the VEPP-2000 construction was completed at the end of 2006. The first beam was captured in a special regime without final focus solenoids. In this regime, all systems of power supplies and machine control were calibrated and tuned. In the same mode vacuum chamber treatment by synchrotron radiation was performed with an electron beam current of up to 150 mA. The first test of the round beam option was performed at an energy of 508 MeV with a solenoidal field of 10 T in two straight sections of interaction. The text was submitted by the author in English.     

Commissioning of the Electron-Positron Collider VEPP-2000 after the Upgrade

The VEPP-2000 electron–positron collider has been operating at BINP since 2010. Applying the concept of round colliding beams allows us to reach the record value of the beam–beam parameter, ξ ~ 0.12. The VEPP-2000 upgrade, including the connection to the new BINP Injection Complex, the improvement of the BEP booster, and the BEP–VEPP-2000 transfer channels for operation at 1 GeV, substantially increases the installation luminosity. Data collection is in progress.     

Status of Vepp-2000 BINP Electron–Positron Collider

Physics of Particles and Nuclei Letters - VEPP-2000 is the only electron–positron collider with round beams. This factor enables one to increase the beam–beam effect limit. During the...     

Recommissioning the Modernized VEPP-2000 Electron–Positron Collider

The VEPP-2000 electron–positron collider has been operating at the Budker Institute of Nuclear Physics (BINP) since 2010. Applying the concept of round colliding beams allowed the record value of the beam–beam parameter ξ ～ 0.12 to be reached. The upgrading of the VEPP-2000 complex, including the connection to the new BINP Injection Complex and modification of the electron–position booster and the BEP–VEPP-2000 transfer channels to work at 1 GeV, resulted in a significant increase in luminosity. Work on statistical data collection using detectors is in progress.     

Search for the Process $${e}^{+}{e}^{-}\to \eta^{\prime}\gamma$$ with the SND Detector

Physics of Atomic Nuclei - The results of searches for the process $$e^{+}e^{-}\to\eta^{\prime}\gamma$$ in an experiment with the SND detector at the VEPP-2000 electron–positron collider are...     

Experiments on the physics of charged particle beams at the VEPP-4M electron-positron collider

The VEPP-4M accelerator facility with a universal KEDR detector is designed to conduct experiments with colliding electron-positron beams. High-energy physics, nuclear physics, and studies using synchrotron radiation are the main directions of research with this facility. In addition, experiments on poorly explored issues in the physics of beams in the electron-positron storage ring and methodological studies to prepare an experiment aimed at testing corollaries of the CPT theorem for an electron and a positron are regularly conducted at the VEPP-4 facility. A number of works performed in recent years are described: studies to increase the accuracy of comparing the electron and positron spin precession frequencies by the resonant depolarization method; measurements of the count rate of Touschek electrons as a function of the beam energy in a wide range; comparison of the methods for measuring the beam energy spread; a study of the electron beam dynamics when a nonlinear betatron resonance is crossed.     

Measurement of the Cross Section for the Process $${e^{+}e^{-}}{\to}{K}^{{+}}{K}^{{-}}{\pi}^{{0}}$$ with the SND Detector at Collision Energies of $$\sqrt{{s}}{=}{1.3{-}2.0}$$ GeV in the Center-of-Mass Frame

Physics of Atomic Nuclei - In an experiment with the SND detector at the VEPP-2000 $$e^{+}e^{-}$$ collider, the cross sections for the processes $$e^{+}e^{-}\to K^{+}K^{-}\pi^{0}$$ and...     

Status and prospects of VEPP-2000 electron-positron collider

High energy physics experiments were started at VEPP-2000 at the end of 2010; the third experimental run was finished in July 2013. The last run was devoted to the energy range 160–510 MeV in a beam. Compton backscattering energy measurements were used for the regular energy calibration of the VEPP-2000, together with resonance depolarization and NMR methods. The conception of the round colliding beam lattice along with precise orbit and lattice correction yielded a record high peak luminosity of 1.2 × 10³¹ cm^?2 s^?1 at 510 MeV and an average luminosity of 0.9 × 10³¹ cm^?2 s^?1 per run. A total betatron tune shift of 0.174 was achieved at 392.5 MeV. This corresponds to the beam-beam parameter ξ = 0.125 in terms of the collision point. The injection system is currently modernized to allow injection of particles at the VEPP-2000 energy maximum and the elimination of the existing lack of positrons.     

The status of VEPP-4

The VEPP-4 accelerator-accumulator complex is designed for carrying out experiments with colliding electron-positron beams with the energy in the range of from 1 to 5 GeV using a VEPP-4M collider equipped with the KEDR magnetic detector. Experiments in the field of high-energy physics (HEP) using the complex in its present state have been being carried out since 2002. Science programs other than HEP programs are carried out in the VEPP-4, including experiments with synchrotron-radiation (SR) beams and studies on nuclear physics with an internal gas target, on verification of the CPT invariance, on accelerator physics, etc. The status of the complex, main results, methods used, new approaches, and long-term plans have been described.     

Energy scale calibration of the KEDR tagging system

The KEDR detector tagging system is a symmetric focusing magnetic spectrometer of small-angle electrons born in the interaction region of the VEPP-4M collider. Using this system, which is designed for studying the two-photon processes, the scattered electrons and positrons energy is measured with a resolution of ΔE/E₀= 0.03–0.6% where E₀ is the beam energy. Two different methods are employed for calibrating the tagging system energy scale: the first one involves the electron/positron tagging by the energy of the singlebremsstrahlung photon measured in the BGO calorimeter, and the second one is based on the determination of the recoil electrons spectrum edge in the Compton backscattering of monochromatic laser radiation. The technical implementation and the present status of the calibration system are discussed in this paper.     

Dynamics of η→3π0 decay

The η→3π⁰ decay was studied with the SND detector at the VEPP-2Me ⁺ e ^? collider. The parameter that describes deviation of the Dalitz plot of events from a uniform distribution was found to be α=?0.010±0.021±0.010.     

Experimental investigation of high-energy photon splitting in atomic fields

Data analysis of an experiment in which photon splitting in atomic fields was observed is presented. The experiment was performed at the tagged photon beam of the ROKK-1M facility at the VEPP-4M collider. In the energy region of 120-450 MeV, statistics of 1.6x10(9) photons incident on the BGO target was collected. About 400 candidate photon-splitting events were reconstructed. Within the attained experimental accuracy, the experimental results are consistent with the calculated exact atomic-field cross section. The predictions obtained in the Born approximation differ significantly from the experimental results.     

Proj ect for m easuri ng th e n eutro n el ectromag n etic form factor i n th e r eactio n e+ e− → n$$ \bar n $$ at th e VEPP-2000 collid er

A project aimed at measuring the neutron electromagnetic form factor in the reaction e ⁺ e ^? → n \(\bar n\) with the SND detector at the VEPP-2000 e ⁺ e ^? collider is presented. The results obtained for the time resolution of the NaI(Tl) counter using flash-ADC are reported along with estimates of the efficiency of separation of neutron-antineutron events.     

中国极化电子离子对撞机探测器设计

核子是构成宇宙可见物质的最主要成分,也是研究强相互作用的最佳实验室。对核子内部结构的研究是当前理论和实验研究的重要前沿。在核子内部结构的实验研究中,电子- 离子对撞机(Electron Ion Collider, EIC)是最理想的装置,能提供核子内部最清晰的图像,是人类认识物质世界深层次结构,特别是核子与原子核结构最理想的工具。中国极化电子离子对撞机EicC项目,设想在已开建的HIAF 高能离子束的基础上进行升级:将离子束流升级成15~20 GeV 的极化束流,建设3~5 GeV 高能极化电子束流,实现质心系能量为10~20 GeV双极化电子- 离子对撞,在海夸克能区对核子内部结构进行精细测量,并对质子质量、奇特强子态等诸多重要物理课题展开研究。在本文中,我们开发了EicC 快模拟软件,对探测器性能进行参数化模拟;通过物理模拟汇集EicC探测需求,利用探测器模拟软件进行优化并提出EicC 探测器谱仪的初步设计方案。该谱仪方案提供了接近全立体角的覆盖范围和大动量范围内的粒子鉴别能力,兼顾EicC项目丰富的物理课题。     

Direct measurement of the phi(1020) leptonic branching ratio

The process e(+)e(-)-->mu(+)mu(-) has been studied by the SND detector at the VEPP-2M e(+)e(-) collider in the phi(1020)-resonance energy region. The measured effective phi meson leptonic branching ratio B(phi-->l(+)l(-)) identical with square root of B(phi-->e(+)e(-))B(phi-->mu(+)mu(-))] = (2.89 +/- 0.10 +/- 0.06) x 10(-4) agrees well with the Particle Data Group value B(phi-->e(+)e(-)) = (2.91 +/- 0.07) x 10(-4), confirming mu-e universality. Without additional assumption of mu-e universality the branching ratio B(phi-->mu(+)mu(-)) = (2.87 +/- 0.20 +/- 0.14) x 10(-4) was obtained.     

New measurement of the ϒ-meson mass

The method of resonance depolarization has been used for the absolute energy calibration of storage ring VEPP-4. The beam polarization was measured by the up-down asymmetry of the synchrotron radiation back-scattered on the colliding beam. By scanning the ? resonance with the MD-1 detector, we obtained a massM=9460.59 ±0.12 MeV.     

Measurement of the VEPP-4M Collider Energy Spread in the Entire Energy Range

Physics of Particles and Nuclei Letters - The energy spread of the VEPP-4M electron–positron collider at the Budker Institute of Nuclear Physics was measured in the 1100–4750 MeV range...     

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 ^? ?? ???⁰ ?? ??⁰??⁰?? process has been measured in the energy range of 1.1?C1.9 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?C1.4 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.