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A. Schiller

Publications and source records attributed to A. Schiller.

228 records · Page 13Linked to original sources
arXiv1996

Quantum effects in radiation on short bunches

The radiation caused by particles of one bunch in the collective electromagnetic field of the short oncoming bunch is studied. Quantum effects are calculated for the spectrum of radiated photons. Using this spectrum, the dependence of the relative energy loss delta on a quantum parameter kappa is dicussed. It is shown that the behaviour of delta changes considerably with the increase of that parameter. In the classical regime (kappa << 1) the energy loss is proportional to the incoming particle energy, while in the extreme quantum regime (kappa >> 1) the energy loss becomes a constant. The coherent e+e- pair production for gamma-e colliders as cross-channel to CBS is considered.

hep-ph↗
arXiv1995

A new possibility to monitor collisions of relativistic heavy ions at LHC and RHIC

We consider the radiation of particles of one bunch in the collective field of the oncoming bunch, called coherent bremsstrahlung (CBS). The main characteristics of CBS for LHC (in the Pb-Pb mode) and for RHIC are calculated. At LHC about $3.9 10^8 dE_γ/E_γ$ photons per second are expected for photon energies $E_γ\stackrel{<} {\sim} E_c= 93 $ eV. It seems that CBS can be a potential tool for optimizing collisions and for measuring beam parameters. The bunch length can be found from the critical energy of the CBS spectrum; the transverse bunch size is related to the photon rate. A specific dependence of photon rate on the impact parameter between the beams allows for a fast control over the beam displacement.

hep-ph↗
arXiv1995

$3$--Dimensional Approach to Hot Electroweak Matter for $M_{Higgs} \leq 70$ GeV

We study the electroweak phase transition by lattice simulations of an effective 3-dimensional theory, for a Higgs mass of about $70$ GeV. Exploiting a variant of the equal weight criterion of phase equilibrium, we obtain transition temperature, latent heat and surface tension and compare with $M_H \approx 35$ GeV. For the symmetric phase, bound state masses and the static force are determined and compared with results for pure $SU(2)$ theory.

hep-lat↗
arXiv1995

The equivalent photon approximation for coherent processes at colliders

We consider coherent electromagnetic processes for colliders with short bunches, in particular the coherent bremsstrahlung (CBS). CBS is the radiation of one bunch particles in the collective field of the oncoming bunch. It can be a potential tool for optimizing collisions and for measuring beam parameters. A new simple and transparent method to calculate CBS is presented based on the equivalent photon approximation for this collective field. The results are applied to the $ϕ$--factory $DAΦNE$. For this collider about $ 5 \cdot 10^{14} d E_γ/ E_γ$ photons per second are expected in the photon energy $E_γ$ range from the visible light up to 25 eV.

hep-ph↗
arXiv1995

Non-Perturbative versus Perturbative Renormalization of Lattice Operators

Our objective is to compute the moments of the deep-inelastic structure functions of the nucleon on the lattice. A major source of uncertainty is the renormalization of the lattice operators that enter the calculation. In this talk we compare the renormalization constants of the most relevant twist-two bilinear quark operators which we have computed non-perturbatively and perturbatively to one loop order. Furthermore, we discuss the use of tadpole improved perturbation theory.

hep-lat↗
arXiv1995

A Lattice Evaluation of the Deep-Inelastic Structure Functions of the Nucleon

The lower moments of the unpolarized and polarized deep-inelastic structure functions of the nucleon are calculated on the lattice. The calculation is done with Wilson fermions and for three values of the hopping parameter $κ$, so that we can perform the extrapolation to the chiral limit. Particular emphasis is put on the renormalization of lattice operators. The renormalization constants, which lead us from lattice to continuum operators, are computed perturbatively to one loop order as well as non-perturbatively.

hep-lat↗
arXiv1995

Polarized and Unpolarized Nucleon Structure Functions from Lattice QCD

We report on a high statistics quenched lattice QCD calculation of the deep-inelastic structure functions $F_1$, $F_2$, $g_1$ and $g_2$ of the proton and neutron. The theoretical basis for the calculation is the operator product expansion. We consider the moments of the leading twist operators up to spin four. Using Wilson fermions the calculation is done for three values of $κ$, and we perform the extrapolation to the chiral limit. The renormalization constants, which lead us from lattice to continuum operators, are calculated in perturbation theory to one loop order.

hep-lat↗
arXiv1995

3-D lattice simulation of the electroweak phase transition at small Higgs mass

We study the electroweak phase transition by lattice simulations of an effective 3-dimensional theory, for a Higgs mass of about $35 GeV$. In the broken symmetry phase our results on masses and the Higgs condensate are consistent with 2-loop perturbative results. However, we find a non-perturbative lowering of the transition temperature, similar to the one previously found at $m_H = 80 GeV$. For the symmetric phase, bound state masses and the static force are determined and compared with results for pure $SU(2)$ theory.

hep-lat↗