Heavy ions with the Large Hadron Collider and the ALICE detector

The Large Hadron Collider (LHC) under construction at CERN is also planned as a heavy ion collider with lead ions colliding at an energy of 2.7+2.7 ATeV. This corresponds to collisions of matter with cosmic rays of the utmost energies observed so far promising the study of new and exciting aspects of physics. Minor improvements of the newly commissioned lead ion source at the CERN SPS are necessary in order to provide a luminosity of L=2×10²⁷ cm^?2s^?1. The detector ALICE has been chosen as the third detector for the LHC and will be dedicated to the physics of these nuclear collisions and also to the large cross section physics in p+p collisions.     

Electron loss of heavy many-electron ions in relativistic collisions with neutral atoms

Electron-loss processes arising in collisions of heavy many-electron ions (like U²⁸⁺) with neutral atoms (H, N, Ar) are considered over a wide energy range including relativistic energies. Various computer codes (LOSS, LOSS-R, HERION, and RICODE), created for calculation of the electron-loss cross sections, and their capability are described. Recommended data on the electron-loss cross sections of U²⁸⁺ ions colliding with H, N, Ar targets and predicted lifetimes of U²⁸⁺ ion beams in accelerator are given. Calculated electronloss cross sections are compared with available experimental data and other calculations.     

Vector boson pair production in e−e− collisions with polarized beams

The W-boson pair production in e⁻e⁻ collisions with polarized beams is investigated. The helicity amplitudes are derived for general couplings and the conditions for a good high-energy behaviour of the cross-section are given. The results are applied to the heavy vector boson production in the context of the left-right symmetric model. The Ward identities and the equivalence theorem are also discussed.     

Intense low energy positron beams

Intense positron beams are under development or being considered at several laboratories. Already today a few accelerator based high intensity, low brightness e⁺ beams exist producing of the order of 10⁸–10⁹ e⁺/s. Several laboratories are aiming at high intensity, high brightness e⁺ beams with intensities greater than 10⁹ e⁺/s and current densities of the order of 10¹³–10¹⁴ e⁺ s^–1 cm^–2. Intense e⁺ beams can be realized in two ways (or in a combination thereof) either through a development of more efficient ⁺ moderators or by increasing the available activity of ⁺ particles. In this review we shall mainly concentrate on the latter approach. In atomic physics the main trust for these developments is to be able to measure differential and high energy cross-sections in e⁺ collisions with atoms and molecules. Within solid state physics high intensity, high brightness e⁺ beams are in demand in areas such as the re-emission e⁺ microscope, two-dimensional angular correlation of annihilation radiation, low energy e⁺ diffraction and other fields. Intense e⁺ beams are also important for the development of positronium beams, as well as exotic experiments such as Bose condensation and Ps liquid studies.     

The HFT,a Heavy Flavor Tracker for STAR

Determining the degree of termalisation of the medium created in heavy ion collisions at RHIC remains highly debated. Elliptic flow (v₂) measurements at RHIC have already suggested the development of collectivity among partons before hadronization. If heavy flavor hadrons flow with the light flavor hadrons, this indicates frequent interactions between the light (u, d ,s) and heavy (c, b) quarks. Thus, thermalization of light quarks is likely to have been reached through partonic re-scattering. Experimentally this can be probed by making a direct measurement of D-mesons v₂ with sufficient precision at low transverse momentum. Using the Heavy Flavor Tracker (HFT) detector, the STAR experiment at RHIC is proposing to both study this process and also to directly reconstruct charmed hadrons (D⁰, D⁺, D_s, Λ_C, ...), using the displaced vertices of their decay products. The HFT is the first vertex detector to use a new and promising CMOS active pixel sensor technology. It will allow to build a relatively fast, accurate and radiation tolerant detector, while keeping the material budget low (∼0.3%X₀ per layer). Detector design and physics performance simulations are presented.     

核物理研究新进展

本文介绍了国际核物理研究的趋势,核物理研究的前沿已从传统核物理转向亚核自由度变得重要的领域,讨论了在核结构、核反应、相对论性重离子碰撞、亚核自由度、放射性核束和核天体物理学等领域所获得的最新成果. It is presented the trend of the nuclear physics research in the world,the fron- tier of nuclear physics research has been moved from the traditional nuclear physics to the field in which the subnuclear freedoms become very important.New research results obtained in the fields of nuclear structures,nuclear reactions,relativistic heavy ion collisions, subnuclear freedoms,radioactive nuclear beams and nuclear astrophysics are discussed.     

LUE-75 Linear Accelerator Facility at Yerevan Physics Institute

Owing to the growing interest in the low-energy nuclear physics, it becomes relevant to enhance the potential of the experimental facilities at Yerevan Physics Institute (YerPhI). The complex unit based on the linear electron accelerator LUE-75 (ARUS synchrotron injector) for applied and fundamental experiments with electron beams, the intensity and energy of which can vary in a wide range of 10^–18–10^–5 А and 10–50 MeV, has been created. In recent years, the regimes developed at LUE-75 were applied to obtain the controllable electron beams of extremely low intensity used for calibration of detectors.     

The influence of strong magnetic fields on position production in heavy-ion collisions

The strongest magnetic fields (|B|_max≈10¹⁵G) being accessible to experimental investigations are created transiently in collisions of very heavy ions. The possible interplay of these collisional magnetic fields with detected peak structures in spectra of emitted electron-position pairs is elucidated. As basis for a dynamical treatment we computed the adiabatic phase correlation diagram which exhibits no structures to cause the striking peaks. Relativistic two-centre continuum states for non-axial symmetric vector potentials are determined.     

Results on non-SUSY searches for physics beyond standard model in pp collisions at CMS

In this paper a review of the results on searches for physics beyond the standard model in pp collisions with the CMS experiment at {ie257-1} and 8 TeV is presented. Aspects of the analyses and their achieved limits on Z′- and W′-bosons, heavy neutrino, 4 ^th generation, leptoquarks as well as extra dimensions will be covered.     

Clocking hadronization at RHIC

The RHIC accelerator collided Au on Au beams at $\sqrt {s_{NN} } = 130$ GeV in the summer of 2000. To study these collisions, the RHIC experiments have been using a number of observables. One new observable in the field of relativistic heavy ions is the balance function. The balance function can be used to measure the correlation of charged particle pairs in rapidity. The rapidity separation of a particle pair that is created at the same point indicates the time of hadronization for that pair. Preliminary balance function analyses of STAR data are reported. The calculation of a balance function for hadron gas simulations (HIJING) is also discussed in this paper. These preliminary results indicate that the balance function is a useful observable in heavy-ion collisions.     

Electromagnetic and strange probes of dense nuclear matter at NICA/MPD: a feasibility study

The main task of the NICA/MPD physics program is a study of the properties of nuclear matter under extreme conditions achieved in collisions of heavy ions. These properties can reveal themselves through different probes, the most promising among those being the lepton-antilepton pairs and strange hadrons. In this paper the MPD performance for measuring the electron-positron pairs and strange particles (Λ, Ξ^– and Ω^– hyperons and their antiparticles \(\overline \Lambda \), \({\overline \Xi ^ + }\) and \({\overline \Omega ^ + }\) as well as hypernuclei ₃ ^Λ Λ) in central Au + Au collisions at NICA energies is presented.     

Heavy quarks at RHIC and LHC within a partonic transport model

Production and space-time evolution of heavy quarks in central and non-central heavy-ion collisions at RHIC and LHC are studied with the partonic transport model Boltzmann Approach of MultiParton Scatterings (BAMPS). In addition to the initially created heavy quarks in hard parton scatterings during nucleon-nucleon collisions, secondary heavy quark production in the quark-gluon plasma is investigated and the sensitivity on various parameters is estimated. In BAMPS heavy quarks scatter with particles of the medium via elastic collisions, whose cross section is calculated with the running coupling and a more precise implementation of Debye screening. In this framework, we compute the elliptic flow and nuclear modification factor of heavy quarks and compare it to the experimental data.     

Superhorizon fluctuations and acoustic oscillations in relativistic heavy ion collisions

We focus on the initial state spatial anisotropies, originating at the thermalization stage, for central collisions in relativistic heavy-ion collisions. We argue that the physics of fluctuations at the early stages of heavy ion collisions has strong similarities with the physics of density fluctuations in the early universe which give rise to remarkable acoustic peaks in the cosmic microwave background radiation (CMBR) power spectrum. Following the method of analysis in CMBR physics, we propose that a plot of root mean square values of the flow coefficients ?{[`(v_n² )] } o v_n^rms\sqrt {\overline {v_n^2 } } \equiv v_n^{rms} , calculated in a laboratory fixed coordinate system, for a large range of n from 1 to about 30, can give non-trivial information about the initial stages of the system and its evolution. We also argue that for all wavelengths λ of the anisotropy (at the surface of the plasma region) much larger than the acoustic horizon size H_s^fr H_s^{f^r } at the freezeout stage, the resulting values of V _n ^mns should be suppressed by a factor of order 2H_s^fr /l2H_s^{f^r } /\lambda .     

High Energy Unequal-nuclei Collisions and Relaxation Time in Fokker Plank Equation

In this paper,the time evolution of high energy heavy ion collisions is described by Fokker-Planck Equation.The rapidity distribution of the final state particles is analysed with this model for ¹⁶O and ³²S particles beams of 200AGeV.The relaxation time for various systems are determined.Results comparable to the usual empirical data are obtained.     

γ-γ Physics with peripheral relativistic heavy ion collisions

The high flux of equivalent photons present in relativistic heavy ion collisions of two chargesZ ₁ andZ ₂ gives rise to the collision of two equivalent photons. The cross-sections for various processes are directly related to the correspondingγ- γ cross-sections. As compared toγ- γ physics being studied at e⁺ e^? colliders, we find that high energy states will not be so easily accessible at the existing facilities, however, the enhancement factor (Z ₁ Z ₂)² in the expression for the cross section will provide very large photon fluxes for lower energies.     

Multiple electron loss by structured heavy ions in fast collisions with complex atoms

A nonperturbative theory of multiple ionization of heavy structured ions in fast collisions with complex neutral atoms is developed. Cross sections are calculated for multiple loss of electrons (up to 15) in collisions of U¹⁰⁺ and U²⁸⁺ with argon atoms and nitrogen molecules. The results are compared with experimental data.