Axion beams at HERA?

If the recently observed anomaly in the PVLAS experiment is due to the axion, then the powerful beams of synchrotron photons, propagating through high magnetic field of the HERA beamline, become strong axion sources. This gives a unique opportunity of detection of the axion-photon interactions by installing a small detector in the HERA tunnel, and to corroborate the axion hypothesis within a few days of running.Comment: 5 pages, 1 figur

Measurement of the Longitudinal Polarization of the HERA Electron Beam Using Crystals and the ZEUS Luminosity Monitor

A measurement of the longitudinal polarization of the electron beam at HERA utilizing coherent interactions of high energy photons in crystals is proposed. Modification of existing facilities would allow an independent polarization measurement and a verification of birefringence phenomena in crystals for 20--30~GeV photons. Relevant experimental issues and systematic uncertainties are also presented.Comment: 9 pages, latex, 4 figures appended as uuencoded fil

Observation of the beam-size effect at HERA

A precise measurement of the spectrum of the photons from $ep$ bremsstrahlung with the ZEUS luminosity monitor at HERA is reported. The measurement shows a reduced rate compared to the Bethe-Heitler spectrum for photon energies below 5~GeV. This suppression, called the beam-size effect, is explained by the finite transverse size of the beam overlap relative to the typical impact parameter in the process of $ep$ bremsstrahlung at HERA energies.Comment: 12 pages, late

GASTOF: Ultra-fast ToF forward detector for exclusive processes at the LHC

GASTOF (Gas Time-of-Flight) detector is a Cherenkov detector proposed for very precise (10--20 ps) arrival time measurements of forward protons at some 420 m from the central detectors of CMS and ATLAS. Such an excellent time resolution will allow by z-by-timing technique for precise measurement of the z-coordinate of the event vertex in exclusive production at the LHC, when two colliding protons are scattered at very small angles. In the paper we present first GASTOF prototype, simulations of its performance as well as first tests using a cosmic muon telescope.Comment: 6 pages, 3 figures, presented at the conference ''Physics at LHC'', Krakow, June 200

Spurious Acceleration Noise on the LISA Spacecraft Due to Solar Irradiance

The Laser Interferometer Space Antenna (LISA) is a conguration of three satellites that will very precisely measure the distance between each satellite in order to detect gravitational waves, small undulations in spacetime.[1] Therefore, the stability of LISA satellite conguration will be crucial to its ability to measure gravitational waves, as will understanding the noise introduced in the measured gravitational wave signal from various environmental accelerations. Although solar irradiance will most denitely be a great source of noise in the desired frequency band and will greatly attempt to disrupt the satellite conguration, previous research has only considered zeroth order calculations of force on the satellites by irradiance in static systems. To remedy this, we used a geometric and material based approach to calculate the force on the satellites solar arrays, the only component facing the sun. Running our simulation of LISA based on irradiance data from the VIRGO (Variability of solar IRadiance and Gravity Oscillations) experiment, we examined the Fourier transform of force to and the associated acceleration noise expected in the LISA frequency band due to solar irradiance.[2] This research will help engineers in the construction of the solar array as well as help isolate the gravitational wave signal when LISA is own

Central μ+μ−\mu^{+}\mu^{-} production via photon-photon fusion in proton-proton collisions with proton dissociation

We present a formalism which uses fluxes of equivalent photons including transverse momenta of the intermediate photons. The formalism reminds the familiar $k_t$-factorization approach used, e.g., to study the two-photon production of $c\bar{c}$ or $b\bar{b}$ pairs. The results of the new method are compared with those obtained using the code LPAIR, and a good agreement is obtained. The inclusion of the photon transverse momenta is necessary in studies of correlation observables. We present distributions for the dimuon invariant mass, transverse momentum of the muon pair and relative azimuthal angle between muons separately for elastic-elastic, elastic-inelastic, inelastic-elastic and inelastic-inelastic mechanisms. For typical experimental cuts all mechanisms give similar contributions. The results are shown for different sets of cuts relevant for the LHC experiments. The cross sections in different regions of phase space depend on $F_2$ structure function in different regions of $x$ and $Q^2$. A comment on $F_2$ is made.Comment: 24 pages, 36 figures, 2 table

High energy bremsstrahlung at the FCC-ee, FCC-eh and LHeC

Bremsstrahlung spectra will be strongly distorted due to small lateral beam sizes at future colliders. That in turn will have large consequences for the electron and positron beam lifetimes as well as for the luminosity measurements in the case of electron-hadron colliders. We discuss in detail such consequences for the Future Circular Collider and Large Hadron electron Collider cases