Experimental demonstration of colliding-beam-lifetime improvement by electron lenses

We report the successful application of space-charge forces of a low-energy electron beam for improvement of particle lifetime determined by beam-beam interaction at a high-energy collider. In our experiments, an electron lens, a novel instrument developed for the beam-beam compensation, was set on a 980-GeV proton bunch at the Fermilab Tevatron proton-antiproton collider. The proton-bunch losses due to its interaction with the antiproton beam were reduced by a factor of 2 when the electron lens was operating. We describe the principle of electron lens operation and present experimental results.     

High-voltage electron cooler project for NICA collider

A high-voltage electron cooling system (ECS) with electron energy reaching 2.5 MeV for the NICA collider is being designed at the Joint Institute for Nuclear Research. The ECS is being developed in correspondence with the available experience in manufacturing similar systems from around the world. The main feature of this design is the use of two cooling electron beams (one beam per collider ring); electrons are accelerated and decelerated by a common high-voltage generator. A conceptual project of high-voltage ECS has been developed. The cooler consists of three tanks filled with SF₆ gas under pressure. Two of them contain electron-beam forming systems; each system consists of two electron guns, two electron collectors, and accelerating-decelerating tubes placed in a longitudinal magnetic field generated by a solenoid. The third tank contains a high-voltage generator based on the voltage-multiplying circuit.     

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.     

Associated Production of a Photon with Dark Matter Pair at the ILC within the Littlest Higgs Model with T-parity

Within the context of the Littlest Higgs model with T-parity, the heavy photon (A_H) is supposed to be an ideal dark matter (DM) candidate. One direct proof of validity of the model is to produce the heavy photon at collider. In this paper, we investigate the associated production of a photon with heavy photon pair at the planned international e⁺e^- linear collider (ILC), i.e. e⁺e^- → A_HA_Hγ and show the distributions of the transverse momenta of the photon. The numerical results indicate that the heavy photon production rate could reach several fb at the low mass parameter space and the characteristic signal is a single high energetic photon and missing energy, carried by the heavy photons. All in all, it can be a good chance to observe the heavy photon via this process with the high yearly luminosity of the ILC.     

MeV- and Sub-MeV-photon Sources Based on Compton Backscattering at Spring-8 and KPSI-JAEA

Recently we have constructed two facilities for generating photon beams in the MeV and sub-MeV energy regions by means of the Compton backscattering with a laser and an electron beam at SPring-8 and at Kansai Photon Science Institute of Japan Atomic Energy Agency(KPSIJAEA).The MeV-photon source at SPring-8 consists of a continuous-wave optically-pumped far infrared laser with a wavelength of 118.8 μm and an 8 GeV stored electron beam.Present MeV-photon flux is estimated to be 1.3×10~3 photons/s.On the other hand,the sub-MeV-photon source at KPSI-JAEA consists of a pulse Nd:YAG laser with a wavelength of 1 064 nm and a 150 MeV electron beam accelerated by microtron.In the first trial of the photon production in this source,backscattered photon flux is estimated to be 20 photons/pulse.Both the Compton backscattered photon sources have possibilities to be used for new tools in various fields such as nuclear physics,materials science,and astronomy.     

Collimation with hollow electron beams

A novel concept of controlled halo removal for intense high-energy beams in storage rings and colliders is presented. It is based on the interaction of the circulating beam with a 5-keV, magnetically confined, pulsed hollow electron beam in a 2-m-long section of the ring. The electrons enclose the circulating beam, kicking halo particles transversely and leaving the beam core unperturbed. By acting as a tunable diffusion enhancer and not as a hard aperture limitation, the hollow electron beam collimator extends conventional collimation systems beyond the intensity limits imposed by tolerable losses. The concept was tested experimentally at the Fermilab Tevatron proton-antiproton collider. The first results on the collimation of 980-GeV antiprotons are presented.     

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.     

Discovering and studying bileptons with e−e− collisions

We analyze the prospects for discovering and unraveling the nature of doubly charged bileptons at a linear collider of the next generation running in its e⁻e⁻ mode. We stress the importance of initial state radiation, beam spread and polarization, and compute the discovery bounds. The gauge nature of vector bileptons can be determined by studying hard photon emission.     

Heavy quark production at the TESLA collider and its sensitivity to the gluon content in the photon

Heavy quark production is studied at the TESLA high energy linear collider (LC) both in its nominal and photon collider (PC) mode. Leading order cross-sections are calculated for the production of heavy quarks, , at high transverse momenta. The sensitivity of this process to the gluon content in the photon is studied. Received: 26 November 2001 / Published online: 21 June 2002     

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.     

Booster synchrotron of NICA accelerator complex

NICA is a new accelerator complex being constructed at the Joint Institute for Nuclear Research; the main task of this complex is to perform collider experiments for ion beams up to uranium with energies of up to 3.5 × 3.5 GeV/nucleon. This complex includes an electron string ion source, a 6 MeV/nucleon linear accelerator, a booster, the Nuclotron, and a collider with an average luminosity of 10²⁷ cm² s^?1. The main tasks of the booster are to accumulate up to 4 × 10^{9 197}Au³²⁺ ions, to accelerate to 600 MeV/nucleon (sufficient enough energy for completely stripping nuclei), to reduce the requirements of vacuum conditions for the Nuclotron, and to form the necessary beam emittance using an electron cooling system. The specific features of the NICA booster and the requirements for the basic systems of the synchrotron and their parameters are presented in this paper.     

Effects of ion motion in intense beam-driven plasma wakefield accelerators

Recent proposals for using plasma wakefield accelerators (PWFA) as a component of a linear collider have included intense electron beams with densities many times in excess of the plasma density. The beam's electric fields expel the plasma electrons from the beam path to many beam radii in this regime. We analyze here the motion of plasma ions under the beam fields, and find for a proposed PWFA collider scenario that the ions completely collapse inside of the beam. Simulations of ion collapse are presented. Implications of ion motion on the feasibility of the PWFA-based colliders are discussed.     

Design of the 2.5 MV Electron Cooling System and the Potential for Increasing NICA Collider Luminosity

The design and capabilities of the electron cooling system for the NICA collider are discussed. This system should suppress the intrabeam scattering and beam–beam interactions.     

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.     

Unparticle Effects on Top Quark Pair Production at Photon Collider

The unparticle effects on tt^- production at the future photon collider are investigated. Distributions of tt^- invariant mass and that for transverse momentum of top quark with respect to Standard Model and unparticle production are predicted. An odd valley with scalar unparticle contribution appears for some values of du, which is due to the big cancellation between the contribution from SM and that from unparticle. This character may be used to study the properties of scalar unparticle. Our investigations also show that scalar unparticle may play a significant role in tt^- production at the photon collider if it exists.     

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.     

Fixed target project AFTER at the LHC beams for heavy ion and hadron physics

High intensity proton and lead ion beams at the LHC collider allow one to use the beam halo by placing a fixed target or a bent crystal for beam extraction. The particle energy in this case is just half that at the RHIC collider, but the luminosity exceeds the collider luminosity many times. It is also possible to install a polarized target in the extracted beam. The project AFTER is aimed at investigation of rare processes, polarization phenomena, determination of the parameters required for analysis of cosmic rays and neutrino astrophysics, detailed investigation of quarkonia production and suppression depending on the phase transition of matter to the quark-gluon phase.     

Polarized deuterons and protons at NICA@JINR

The novel scheme of proton and deuteron polarization control in the NICA collider at Dubna is proposed. By means of two Siberian Shakes with solenoid magnetic field the beam spin tune is shifted to the “zero” spin resonance vicinity, whereas manipulation of the polarization is realized by “weak” field solenoids. The scheme makes it possible to obtain any desired direction of the polarization in the both MPD and SPD detectors for any sort of the particles. The possibility of the beam polarization control in the orbit plane at any azimuth of the collider magnetic arcs exists also. The last gives necessary flexibility of optimal matching the beam polarization at injection into collider and at the polarimetery monitor points.     

Measurement of electron clouds in large accelerators by microwave dispersion

Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation at high currents. Furthermore, it is difficult to probe their density over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave transmitted over a section of the accelerator and used it to measure the average electron cloud density over a 50 m section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center.