Projects of Nuclotron modernization and Nuclotron-based ion collider facility (NICA) at JINR

One of the basic facilities at the Joint Institute for Nuclear Research (JINR) in Dubna is the 6 A GeV Nuclotron, which has replaced the old weak focusing 10-GeV proton accelerator Synchrophasotron. The first relativistic nuclear beams with the energy of 4.2 A GeV were obtained at the Synchrophasotron in 1971. Since that time, relativistic nuclear physics has been one of the main directions of the JINR research program. In the coming years, the new JINR flagship program assumes the experimental study of hot and dense strongly interacting QCD matter at the new JINR facility. This goal is proposed to be reached by (i) development of the existing Nuclotron accelerator facility as a basis for generation of intense beams over atomic mass range from protons to uranium and light polarized ions, (ii) design and construction of the Nuclotron-based heavy Ion Collider fAcility (NICA) with the maximum nucleon-nucleon center-of-mass collision energy of √s _NN = 9 GeV and averaged luminosity 10²⁷ cm⁻² s⁻¹, and (iii) design and construction of the Multipurpose Particle Detector (MPD) at intersecting beams. Realization of the project will lead to unique conditions for research activity of the world community. The NICA energy region is of major interest because the highest nuclear (baryonic) density under laboratory conditions can be reached there. Generation of intense polarized light nuclear beams aimed at investigation of polarization phenomena at the Nuclotron is foreseen. The text was submitted by the author in English.     

Status of NICA complex at JINR

New scientific program is proposed at Joint Institute for Nuclear Research (JINR) in Dubna aimed a study of hot and dense baryonic matter in the wide energy region from 2 GeV/amu to √s _NN = 11 GeV, and investigation of nucleon spin structure with polarized protons and deuterons maximum energy in the c.m. 27 GeV (for protons). To realize this program the development of JINR accelerator facility in high energy physics has started. This facility is based on the existing superconducting synchrotron—Nuclotron. The program foresees both experiments at the beams extracted from the Nuclotron, and construction of ion collider—the Nuclotron-based Ion Collider fAcility (NICA).     

Study of the MPD detector capabilities for electron-positron pair measurements at the NICA collider

One of the main tasks of the NICA/MPD physics program is a study of low-mass vector mesons ρ, ω, ? by measuring their dileptonic decay channels. In this paper, the current status of simulations of electron-positron pair measurements in MPD is presented and the detector performance for such measurements is discussed.     

Cryogenics for the future accelerator complex NICA at JINR

The NICA cryogenics will be based on the modernized liquid helium plant that was b uilt in the early 90’s for the superconducting synchrotron known as the Nuclotron. The main goals of the modernization are: increasing of the total refrigerator capacity from 4000 W to 8000 W at 4.5 K, making a new distribution system of liquid helium, and ensuring the shortest possible cool down time. These goals will be achieved by means of an additional 1000 l/hour helium liquefier and “satellite” refrigerators located near the accelerator rings. This report describes the design choices of the NICA, demonstrates helium flow diagrams with major new components and briefly informs of the liquid nitrogen system that will be used for shield cooling at 77 K and at the first stage of cooling down of three accelerator rings with the total length of about 1 km and “cold” mass of 290 tons.     

The Multi-Purpose Detector for NICA heavy-Ion Collider at JINR

The Multi-Purpose Detector (MPD) is designed to study heavy-ion collisions at the Nuclotron-based heavy Ion Collider fAcility (NICA) at JINR, Dubna. Its main components located inside a superconducting solenoid are a tracking system composed of a silicon microstrip vertex detector followed by a large volume time-projection chamber, a time-of-flight system for particle identification and a barrel electromagnetic calorimeter. A zero degree hadron calorimeter is designed specifically to measure the energy of spectators. In this paper, all parts of the apparatus are described and their tracking and particle identification parameters are discussed in some detail.     

Coherent instabilities in the NICA collider

The thresholds of coherent beam instabilities in the NICA collider are analyzed in the present work. Studies were limited on the coherent oscillations in one of the rings due to the weakness of the beam-beam interaction forces when compared to the single-beam Coulomb forces. The thresholds of the single-beam and multiple-beam instabilities are estimated for the chosen collider operation scenario. Measures that have to be taken to suppress the instabilities are discussed.     

Intense ion-beam dynamics in the NICA collider

The problems of intense ion-beam dynamics in the developed and optimized optical structure of the NICA collider are considered. Conditions for beam collisions and obtaining the required parameters of luminosity in the operation energy range are discussed. The restriction on collider luminosity is related to effects of the domination of the space charge and intrabeam scattering. Applying methods of cooling, electron and stochastic ones, will permit one to suppress these effects and reach design luminosity. The work also deals with systems of magnetic field correction and problems of calculating the dynamic aperture of the collider.     

NICA at JINR: New prospects for exploration of quark-gluon matter

A new scientific program is proposed at the Joint Institute for Nuclear Research (JINR) in Dubna aimed at studies of hot and dense baryonic matter in the wide energy range from 2 GeV/u kinetic energy in fixed target experiments to $\sqrt {s_{NN} } = 4 - 11$ GeV/u in the collider mode. To realize this program the development of the JINR accelerator facility in high-energy physics (HEP) has been started. This facility is based on the existing superconducting synchrotron??the Nuclotron. The program foresees both experiments at the beams extracted from the Nuclotron, and the construction of a heavy-ion collider??the Nuclotron-based Ion Collider fAcility (NICA) which is designed to reach the required parameters with an average luminosity of L = 10²⁷ cm^?2 s^?1.     

Intriguing aspects in baryon production at relativistic heavy-ion collider

We review experimental results on baryon production at mid-rapidity in nucleus-nucleus collisions at RHIC. Outstanding physics issues include the mechanism for baryon-anti-baryon production from thermally equilibrated partons, the dynamics of baryon number transport and the evolution dynamics of baryons during hadronic expansion before the final freeze-out. We highlight recent measurements on the production of protons, lambdas and their anti-particles in terms of these physics issues. We propose a physical mechanism of topological baryon formation through gluon junction hadronization and future measurements, which can test this hypothesis experimentally.     

Transport properties of the fluid produced at relativistic heavy-ion collider

It is by now well known that the relativistic heavy-ion collisions at RHIC, BNL have produced a strongly interacting fluid with remarkable properties, among them the lowest ever observed ratio of the coefficient of shear viscosity to entropy density. Arguments based on ideas from the string theory, in particular the AdS/CFT correspondence, led to the conjecture — now known to be violated — that there is an absolute lower limit 1/4π on the value of this ratio. Causal viscous hydrodynamics calculations together with the RHIC data have put an upper limit on this ratio, a small multiple of 1/4π, in the relevant temperature regime. Less well-determined is the ratio of the coefficient of bulk viscosity to entropy density. These transport coefficients have also been studied non-perturbatively in the lattice QCD framework, and perturbatively in the limit of high-temperature QCD. Another interesting transport coefficient is the coefficient of diffusion which is also being studied in this context. In this paper some of these recent developments are reviewed and then the opportunities presented by the anticipated LHC data are discussed, for the general nuclear physics audience.     

Estimation of electron-cloud effect on NICA collider

The preliminary results from simulating the formation of electron clouds in the NICA collider using the ECLOUD program package are presented. Requirements for the acceleration chamber of the NICA collider for a gold nuclei beam are discussed.     

Charged-particle multiplicity at mid-rapidity in Au-Au collisions at relativistic heavy-ion collider

The particle density at mid-rapidity is an essential global variable for the characterization of nuclear collisions at ultra-relativistic energies. It provides information about the initial conditions and energy density reached in these collisions. The pseudorapidity densities of charged particles at mid-rapidity in AuAu collisions at √^s _NN = 130 and 200 GeV at RHIC (relativistic heavy ion collider) have been measured with the PHENIX detector. The measurements were performed using sets of wire-chambers with pad readout in the two central PHENIX tracking arms. Each arm covers one quarter of the azimuth in the pseudorapidity interval |η| < 035. Data is presented and compared with results from proton-proton collisions and nucleus-nucleus collisions at lower energies. Extrapolations to LHC energies are discussed.     

Partonic effects on pion interferometry at the relativistic heavy-ion collider

Using a multiphase transport model that includes both initial partonic and final hadronic interactions, we study the pion interferometry at the Relativistic Heavy-Ion Collider. We find that the two-pion correlation function is sensitive to the magnitude of the parton-scattering cross section, which controls the parton density at which the transition from the partonic to hadronic matter occurs. Also, the emission source of pions is non-Gaussian, leading to source radii that can be more than twice larger than the radius parameters extracted from a Gaussian fit to the correlation function.     

Estimating the main radiation source terms for the NICA collider

The various radiation sources at the NICA collider were identified and specified. It is found that the most powerful ones are the beam catchers restricting the beam ??halo??. The double differential neutron yields from the catcher are calculated using the GEANT4 code. A simulation of the total absorbed dose in the magnet superconducting winding due to the catcher radiation is carried out for the accepted levels of beam losses. The induced radioactivity of the catcher is predicted for the collider schedule.     

Operational stochastic cooling in the relativistic heavy-ion collider

Operational stochastic cooling of 100 GeV/nucleon gold beams has been achieved in the BNL Relativistic Heavy-Ion Collider. We discuss the physics and technology of the longitudinal cooling system and present results with the beams. A simulation algorithm is described and shown to accurately model the system.     

Full-scale prototype of the circular track detector for the multipurpose detector facility at the NICA acceleration complex

The development of the NICA heavy ion collider, which is now under way, assumes the development of a Multipurpose Detector (MPD), including an end-cap tracker (EC) (which can be a wheel-type tracker based on thin-wall drift tubes (straws) similar to the inner detector of the transition radiation tracker (TRT) in the ATLAS experiment). The identical front and back tracker modules mounted behind the TPC are to ensure the detection of Au-Au ion collision products in the pseudorapidity range from 1.4 to 2.1 with good track parameters of reconstructed events. Each module will contain 60 circular straw planes and maximum straw occupancy will be no higher than 0.2 particle per collision. The NICA EC is substantially different from its analogue and requires a certain amount of R&D. The first results from applying new technology to make a full-scale prototype of the circular EC detector for NICA are presented.     

Charged particle density distributions in Au + Au collisions at relativistic heavy-ion collider energies

Charged particle pseudorapidity distributions have been measured in Au+ Au collisions using the BRAHMS detector at RHIC. The results are presented as a function of the collision centrality and the center of mass energy. They are compared to the predictions of different parton scattering models and the important role of hard scattering processes at RHIC energies is discussed. Keywords. Relativistic heavy-ion collisions; charged hadron production; pseudorapidity distributions; centrality dependence; hard scattering processes.     

Coherent instabilities in the booster and collider of the heavy ion accelerator complex NICA

In the first part some knowledge about the coherent instabilities in cyclic accelerators and storage rings necessary for the analysis of the collective effects in the heavy ion collider NICA is given. The second part discusses the possibilities for arising of coherent instabilities in the booster and in the collider of the NICA complex. Both coupling impedances and instability thresholds and growth rates have been estimated for single and coupled bunches. Parameters of the beam feedback system for damping of the instabilities have been analyzed. The investigation has been performed at the Veksler and Baldin Laboratory of High Energy Physics, JINR.