Analytical Study and Tracking Simulations of the Beam-Beam Compensation at Tevatron

Head-on and long-range induced tunespread of about 0.025 in the Tevatron collider at Run II (together with the increased strength of the resonances) can significantly deteriorate the {bar p} lifetime and the collider luminosity. It was proposed to employ the so-called Tevatron Electron Lenses (TEL) to compress the beam-beam footprint and eliminate completely the bunch-to-bunch tunespread (PACMAN effect) for small amplitude particles. The first lens has been recently installed and tested [1]. This report presents results of analytical studies and tracking simulations of the linear beam-beam compensation (elimination of the bunch-to-bunch tune variation). Compression of the beam-beam footprint (nonlinear compensation) is discussed in [2]

MIMO Frechet filters for hyperspectral images

Медианная фильтрация широко используется при обработке изображений, в которых пиксель представляется набором его скалярных компонент, значение пикселя заменяется медианой пикселей в окне вокруг него. В данной работе рассматриваются изображения, в которых пиксели представляются вектором в цветовом пространстве. Обработка данных изображений основывается на идее о том, что медиана – это значение пикселя, сумма расстояний до которого от остальных пикселей окна минимальна. Медиана Фреше дискретного набора векторнозначных пикселей в пространстве с метрикой является точкой минимума суммы метрических расстояний до всех пикселей. В этой статье расширяется понятие медианы Фреше до обобщенной медианы Фреше, которая является минимумом стоимостной функцией Фреше, представленной агрегационной функцией метрических расстояний, вместо обычной суммы. Кроме того, мы предлагаем использовать агрегационное расстояние вместо классической метрики расстояния. Мы используем обобщенную медиану Фреше для построения новых нелинейных многоканальных фильтров. Качество подавления шума данными фильтрами сравнивается с основными алгоритмами: медианным и усредняющим.Median filtering has been widely used in scalar-valued image processing as an edge preserving operation. The basic idea is that the pixel value is replaced by the median of the pixels contained in a window around it. In this work this idea is extended onto vector-valued images. It is based on the fact that the median is also the value that minimizes the sum of distances between all grey-level pixels in the window. The Frechet median of a discrete set of vector-valued pixels in a metric space with a metric is the point minimizing the sum of metric distances to the all sample pixels. In this paper, we extend the notion of the Frechet median to the general Frechet median, which minimizes the Frechet cost function (FCF) in the form of aggregation function of metric distances, instead of the ordinary sum. Moreover, we propose use an aggregation distance instead of classical metric distance. We use generalized Frechet median for constructing new nonlinear MIMO-filters. Noise reduction quality of the introduced method is evaluated and compared with some classic algorithms like mean and median filtering

Experimental investigation of high-energy photon splitting in atomic fields

The new data analysis of the experiment, where the photon splitting in the atomic fields has been observed for the first time, is presented. This 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, the statistics of $1.6\cdot 10^9$ photons incident on the BGO target was collected. About 400 candidates to the photon splitting events were reconstructed. Within the attained experimental accuracy, the experimental results are consistent with the cross section calculated exactly in an atomic field. The predictions obtained in the Born approximation significantly differ from the experimental results.Comment: 11 pages, 6 figures, LaTe

Tevatron Beam Halo Collimation System: Design, Operational Experience and New Methods

Collimation of proton and antiproton beams in the Tevatron collider is required to protect CDF and D0 detectors and minimize their background rates, to keep irradiation of superconducting magnets under control, to maintain long-term operational reliability, and to reduce the impact of beam-induced radiation on the environment. In this article we briefly describe the design, practical implementation and performance of the collider collimation system, methods to control transverse and longitudinal beam halo and two novel collimation techniques tested in the Tevatron.Comment: 25 p

Status of the Super-B factory Design

The SuperB international team continues to optimize the design of an electron-positron collider, which will allow the enhanced study of the origins of flavor physics. The project combines the best features of a linear collider (high single-collision luminosity) and a storage-ring collider (high repetition rate), bringing together all accelerator physics aspects to make a very high luminosity of 10$^{36}$ cm$^{-2}$ sec$^{-1}$. This asymmetric-energy collider with a polarized electron beam will produce hundreds of millions of B-mesons at the $\Upsilon$(4S) resonance. The present design is based on extremely low emittance beams colliding at a large Piwinski angle to allow very low $\beta_y^\star$ without the need for ultra short bunches. Use of crab-waist sextupoles will enhance the luminosity, suppressing dangerous resonances and allowing for a higher beam-beam parameter. The project has flexible beam parameters, improved dynamic aperture, and spin-rotators in the Low Energy Ring for longitudinal polarization of the electron beam at the Interaction Point. Optimized for best colliding-beam performance, the facility may also provide high-brightness photon beams for synchrotron radiation applications