Beam-beam effects investigation and parameters optimization for a circular e+e- collider TLEP to study the Higgs boson

Several proposals exist for future circular electron-positron colliders designed for precise measurements of the Higgs boson characteristics and electroweak processes. At very high energies, synchrotron radiation of the particles in a strong electromagnetic field of the oncoming bunch (beamstrahlung) becomes extremely important, because of degradation of the beam lifetime and luminosity. We present theoretical calculations of beamstrahlung (including the beam lifetime reduction and the energy spread increase) which are benchmarked against quasi strong-strong computer simulation. Calculation results are used to optimize TLEP project (CERN).Comment: 17 pages, 2 tables, 9 figure

Synchrotron oscillation damping due to beam-beam collisions

In DA{\Phi}NE, the Frascati e+/e- collider, the crab waist collision scheme has been successfully implemented in 2008 and 2009. During the collision operations for Siddharta experiment, an unusual synchrotron damping effect has been observed. Indeed, with the longitudinal feedback switched off, the positron beam becomes unstable with beam currents in the order of 200-300 mA. The longitudinal instability is damped by bringing the positron beam in collision with a high current electron beam (~2A). Besides, we have observed a shift of \approx 600Hz in the residual synchrotron sidebands. Precise measurements have been performed by using both a commercial spectrum analyzer and the diagnostics capabilities of the DA{\Phi}NE longitudinal bunch-by-bunch feedback. This damping effect has been observed in DA{\Phi}NE for the first time during collisions with the crab waist scheme. Our explanation is that beam collisions with a large crossing angle produce a longitudinal tune shift and a longitudinal tune spread, providing Landau damping of synchrotron oscillations.Comment: 3 pages, 5 figures, talk presented to IPAC'10 - Kyoto - May 24-28 201

How to increase the physics output per MW.h for FCC-ee?

The efficiency of colliders for physics is largely determined by their luminosity, while most of the energy consumed by high-energy $e^+e^-$ colliders is proportional to the total beam current. Thus, the energy efficiency is mainly determined by the specific luminosity that needs to be maximized. One of the most effective ways to achieve this is by using the Crab waist collision scheme, which implies a large Piwinski angle (LPA). A distinctive feature of the FCC-ee is the great influence of beamstrahlung (radiation in the field of an opposite bunch) on beam dynamics. At low energies, this manifests itself in a significant increase in the energy spread and bunch length, at high energies, in a limitation of the beam lifetime. The collision of intense bunches with LPA and beamstrahlung can also lead to various kinds of instabilities limiting the luminosity. Here, we discuss the main aspects to consider when optimizing the parameters of the FCC-ee collider at different energies and explain the choice of basic parameters such as RF voltage, lattice functions at IP, bunch intensity, etc. We will also pay attention to open issues requiring further study and identify some key points for the next phase of this project.Comment: 6 pages, 3 figure

Aplication of Frequency Map Analysis to Beam-Beam Effects Study in Crab Waist Collision Scheme

We applied Frequency Map Analysis (FMA) - a method that is widely used to explore dynamics of Hamiltonian systems - to beam-beam effects study. The method turned out to be rather informative and illustrative in the case of a novel Crab Waist collision approach, when "crab" focusing of colliding beams results in significant suppression of betatron coupling resonances. Application of FMA provides visible information about all working resonances, their widths and locations in the planes of betatron tunes and betatron amplitudes, so the process of resonances suppression due to the beams crabbing is clearly seen.Comment: 11 pages, 10 figure

Russian Language Speakers: Some Observations on their Communicative Behavior

The paper presents the description of specific communicative practice among the Russian language speakers. This research is based on linguistic and cultural data collected in everyday speech and behavior, as well as in the Russian philosophical and literary tradition. The following elements of verbal communication were analyzed: syntactic structures, lexical units, and phonetics. Sociocultural phenomena, such as role-switching, use of background knowledge, and talk domination were observed too. Generally, the method applied here could be defined as content analysis. The findings of the present study suggest that the typical features of the communicative style in the Russian culture are straightforwardness, familiarity, gender and race intolerance, aggressiveness, rude language, irony, and emotionalityThe paper presents the description of specific communicative practice among the Russian language speakers. This research is based on linguistic and cultural data collected in everyday speech and behavior, as well as in the Russian philosophical and literary tradition. The following elements of verbal communication were analyzed: syntactic structures, lexical units, and phonetics. Sociocultural phenomena, such as role-switching, use of background knowledge, and talk domination were observed too. Generally, the method applied here could be defined as content analysis. The findings of the present study suggest that the typical features of the communicative style in the Russian culture are straightforwardness, familiarity, gender and race intolerance, aggressiveness, rude language, irony, and emotionality.  The paper presents the description of specific communicative practice among the Russian language speakers. This research is based on linguistic and cultural data collected in everyday speech and behavior, as well as in the Russian philosophical and literary tradition. The following elements of verbal communication were analyzed: syntactic structures, lexical units, and phonetics. Sociocultural phenomena, such as role-switching, use of background knowledge, and talk domination were observed too. Generally, the method applied here could be defined as content analysis. The findings of the present study suggest that the typical features of the communicative style in the Russian culture are straightforwardness, familiarity, gender and race intolerance, aggressiveness, rude language, irony, and emotionality