arXiv subjects
Publications and source records attributed to V. I. Telnov.
One of the interaction regions at the linear colliders should be compatible both with e+e- and gamma-gamma, gamma-electron modes of operation. In this paper, the differences in requirements and possible design solutions are discussed.
This paper is the second part of my overview on photon colliders given at the conference ``The photon: its first hundred years and the future'' (PHOTON2005 + PLC2005). The first paper describes the first 25 years of the history and evolution of photon colliders. The present paper considers the photon collider at the ILC: possible parameters, technical problems and present status.
In this invited talk at the ``historical'' session of PHOTON2005, I was asked to recount the history and the development, from its earliest days to the present, of the idea of photon colliders based on conversion of high energy electrons to high-energy photons at a future high-energy linear e+e- collider. Described in this talk are the general features and schemes of a photon collider, the evolution in understanding of what the parameters of a realistic photon collider are, possible solutions of various technical problems, the physics motivation, and the present status of photon-collider development. For a more detailed description of the photon collider at the ILC and a discussion of the associated technical issues, please refer to my talks at PLC2005, the conference that immediately followed PHOTON2005 (to be published in Acta Physica Polonica B as well).
At Snowmass2005 the Global Group 6 (Physics Options) considered the requirements and configurational issues related to possiblealternatives to the baseline e+e- collisions, including gamma-gamma, gamma-electron, electron-electron, GigaZ and fixed target experiments, and identified the potential performance parameters.
For removal of disrupted beams at the ILC linear e+e- collider it is desirable to collide beams at some crossing angle. An especially large crossing angle, of about 25 mrad, is necessary for the photon collider, where disrupted beams are softer and wider than in the e+e- case. Some complications arise due to the solenoidal magnetic field of the detector. Radiation of particles in this field can increase the vertical beam size, leading to a loss of the luminosity. In addition, in the presence of a detector magnetic field the beam trajectories are not flat. Moreover, in the case of e-e- beams, the vertical collision angle is non-zero and larger than the beam diagonal angle sigma_y/sigma_z, and this should be corrected in some way. In this paper, possible solutions of these problems are considered. It is shown that at the ILC one can have the interaction region compatible both with e+e- and gamma-gamma, gamma-e modes of operation without loss of luminosity.
At photon colliders gamma-gamma, gamma-electron high energy photons are produced by Compton scattering of laser light off the high energy electrons (or positrons) at a linear collider. At first sight, photon colliders based on e-e- or e+e- primary beams have similar properties and therefore for convenience one can use e+e- beams both for e+e- and gamma-gamma modes of operation. Below we compare these options and show that e-e- beams are much better (mandatory) because in the e+e- case low energy background gamma-gamma to hadrons is much higher and e+e- annihilation reactions present a very serious background for gamma-gamma processes.
Photon collider based on cold and warm linear collider technologies are compared from the point of view of attainable luminosities, technical feasibility of laser systems and experimental conditions.
Photon beams at photon colliders are very narrow, powerful and can not be deflected. For the beam dump at the TESLA-like collider we suggest to use a long gas (Ar) spoiler in front of the water absorber, this solves the overheating and mechanical stress problems. The neutron background at the interaction point is estimated.
A tightly focused laser beam (laser wire) is used for measurement of transverse electron beam sizes in storage rings and linear colliders. It is assumed that the laser beam does nothing with the electron beam except Compton scatterings which happen with a rather small probability. In reality, electrons crossing the laser beam get kicks (with 100 % probability) proportional to the square of the laser field and inversely proportional to the beam energy. In practical cases of beam diagnostics this effect is negligible.
Linear collider designs foresee some bends of about 5-10 mrad. The spin precession angle of one TeV electrons on 10 mrad bend is 23.2 rad and it changes proportional to the energy. Measurement of the spin direction using Compton scattering of laser light on electrons before and after the bend allows determining the beam energy with an accuracy about of 10^{-5}. In this paper the principle of the method, the procedure of the measurement and possible errors are discussed. Some remarks about importance of plasma focusing effects in the method of beam energy measurement using Moller scattering are given.
In a number of papers an attractive method of laser polarization of electrons (positrons) at storage rings or linear colliders has been proposed. We show that these suggestions are incorrect and based on errors in simulation of multiple Compton scattering and in calculation of the Compton spin-flip cross sections. We argue that the equilibrium polarization in this method is zero.
The application of the two-photon process pp -> pp + mu^+mu^- for the luminosity measurements at LHC with the ATLAS detector is considered. The expected accuracy of the absolute offline luminosity determination is 1 - 2 % for the luminosity range of 10^{33} - 10^{34} cm^-2 s^-1. The preliminary cross section estimates done for LHCb promise the same level of the luminosity measurement accuracy at L = 2 x 10^{32} cm^-2 s^-1.
In some supersymmetric extensions of the Standard Model fairly light superpartner of t-quark is predicted, which may form bound states - stoponiums. We estimate potentials of TESLA linear collider in search for stoponium, considering the basic e+e- option and the gamma-gamma option (Photon Linear Collider - PLC). It is found that PLC could be the best machine for discovery of these new narrow strong resonances. It can produce thousands stoponiums per 100 fb$^-1$ integrated luminosity in the high energy peak. In the case of scenarios when stoponium decays mainly into gluons the signal/background ratio is about 1/4. The channel S->hh into two lightest Higgs bosons could be also seen with high significance. Thus, several weeks run is sufficient for the stoponium discovery, if its mass is approximately known (e.g. from observation of direct stops production at LHC). Then, in MSSM scenarios with dominant S->hh decay PLC shows excellent possibilities to discover bound state of stops, practically immediately after beginning of operating. The e+e- option also has some prospects to observe stoponium but only in the case of scenarios with dominant decay into two lightest Higgs bosons, with tens of events per 100 $fb^{-1}$. Interesting possibility appears in the case when the resonance is seated on 0.1% width luminosity peak - one could resolve the stoponium exited states.