Search results for "MSS"
showing 10 items of 2513 documents
The effect of magnetic field strength on the time evolution of high energy bremsstrahlung radiation created by an electron cyclotron resonance ion so…
2009
Abstract An electron cyclotron resonance (ECR) ion source is one of the most used ion source types for high charge state heavy ion production. In ECR plasma the electrons are heated by radio frequency microwaves in order to provide ionization of neutral gases. As a consequence, ECR heating also generates very high electron energies (up to MeV region) which can produce a vast amount of bremsstrahlung radiation causing problems with radiation shielding and heating superconducting cryostat of an ECR ion source. To gain information about the time evolution of the electron energies in ECR plasma radial bremsstrahlung measurements were performed. JYFL 14 GHz ECR ion source was operated in pulsed …
Neutrino Bremsstrahlung from electrons in neutron star crusts
2001
The process of v (v) over bar Bremsstrahlung via electron scattering off nuclei in the crust of a cooling neutron star is studied within the Random Phase Approximation. We show that the electromagnetic plasma screens the vector weak coupling of electrons with the neutrino field. This screening effect takes place in both the crystalline and liquid phase of the neutron star crust, when the momentum carried out by the neutrino pair is smaller than the inverse Debye screening distance of the electrons. This condition holds in the crust volume at temperatures and densities where the electron Bremsstrahlung dominates the neutrino production. As a result, the vector weak current contribution to th…
Incoherent bremsstrahlung in nuclei
1994
We have studied the processes A(e, e′γ)X in nuclei, or incoherent bremsstrahlung, and determined expressions for the cross section in terms of the same nuclear response functions RL, RT, which appear in inclusive electron scattering (e, e′) in nuclei. Calculations of the cross sections are carried out using a Fermi gas model, complemented by the local-density approximation, to evaluate the response functions. We have carried out a study which shows that the reaction can be used to determine reliably the response functions from experimental data. On the other hand we have compared the incoherent bremsstrahlung with the coherent one in order to see the limits to the tagging technique, which p…
Electro-produced slow positrons
1989
During the last 6 years it has been demonstrated that electro-produced intense beams of slow positrons are possible. High energy electrons from an accelerator generate bremsstrahlung in a thick conversion target of high element number Z. The photons produce electronpositron pairs and a small fraction of the positrons may be moderated to thermal energies. A review is given of the existing slow positron beam lines using this technique. At accelerator energies of 100 MeV total conversion efficiencies of several slow positrons per 106 primary electrons have been obtained, resulting in average intensities of several 109 slow positrons per second or more than 105 slow positrons in pulses having a…
The selection and performance of diamond radiators used in coherent bremsstrahlung experiments
2005
The bremsstrahlung emitted as a result of scattering electrons in thin diamond crystals provides a useful source of high energy photons for use in photonuclear experiments, since the coherent bremsstrahlung produced is linearly polarized. Techniques for selecting the most favorable diamonds have been investigated. These are optical polaroid analysis, X-ray topography and rocking curve measurements. The diamonds are characterized with a view to determining their performance as radiators, and bremsstrahlung spectra from a diamond radiator used at the Mainz MAMI-B facility are presented. The changes caused by high energy electrons to the crystal properties of the diamond and to the resulting c…
Experimental study of theγp→ηpreaction with the Crystal Ball detector at the Mainz Microtron (MAMI-C)
2010
The gamma p - = W >= 1.87 GeV). Bremsstrahlung photons produced by the 1.5-GeV electron beam of the Mainz Microtron MAMI-C and momentum analyzed by the Glasgow tagging spectrometer were used for the eta-meson production. Our accumulation of 3.8 x 10(6) gamma p -< eta p -< 3 pi(0) p -< 6 gamma p events allows a detailed study of the reaction dynamics. The gamma p -< eta p differential cross sections were determined for 120 energy bins and the full range of the production angles. Our data show a dip near W = 1680 MeV in the total cross section caused by a substantial dip in eta production at forward angles. The data are compared to predictions of previous SAID and MAID partial-wave analyses a…
Physical mechanism of the linear beam-size effect at colliders
1996
We present qualitative but precise description of the linear beam-size effect predicted for the processes in which unstable but long--living particles collide with each other. We derive physically pronounced equation for the events rate which proves that the linear beam-size effect corresponds to the scattering of one beam of particles on the decay products of the other. We compare this linear beam-size effect with the known logarithmic beam-size effect measured in the experiments on a single bremsstrahlung at VEPP-4 and HERA.
Discarding a 125 GeV heavy Higgs in an MSSM model with explicit CP-violation
2016
AbstractCurrent experimental constraints prove being enough to rule out the possibility of the mh∼125 GeV Higgs found at LHC being a heavy Higgs in a general MSSM context, even with explicit CP violation in the Higgs potential. Differently than what has been done in prior studies, we perform this job analitically, with expressions related to a few observables. Te relevance of ττ production through Higgs and BR(B→Xsγ) processes is emphasized, since they are enough to erase the possibility of finding an MSSM neutral Higgs lighter than the scalar discovered at LHC.
Low-mass dileptons at high momenta in ultra-relativistic heavy-ion collisions
1992
Abstract We calculate the emission rate of low-mass dileptons at high momenta from a quark-gluon plasma. We find a large enhancement compared with the naive Born rate. Numerical estimates for relativistic heavy ions collisions at RHIC and LHC suggest, however, that the thermal signal is dominated by the background coming from meson decays and from hadronic bremsstrahlung.
Quasifree photoproduction of eta mesons off protons and neutrons
2014
Differential and total cross sections for the quasifree reactions $\ensuremath{\gamma}p\ensuremath{\rightarrow}\ensuremath{\eta}p$ and $\ensuremath{\gamma}n\ensuremath{\rightarrow}\ensuremath{\eta}n$ have been determined at the MAMI-C electron accelerator by using a liquid deuterium target. Photons were produced via bremsstrahlung from the 1.5 GeV incident electron beam and energy tagged with the Glasgow photon tagger. Decay photons of the neutral decay modes $\ensuremath{\eta}\ensuremath{\rightarrow}2\ensuremath{\gamma}$ and $\ensuremath{\eta}\ensuremath{\rightarrow}3{\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}6\ensuremath{\gamma}$ and coincident recoil nucleons were detected in a combin…