Search results for "Particle acceleration"
showing 10 items of 30 documents
Precision measurement of the structure function ratiosF 2 He /F 2 D ,F 2 C /F 2 D andF 2 Ca /F 2 D
1991
We present the structure function ratiosF2He/F2D,F2C/F2D andF2Ca/F2D measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. The kinematic range 0.0035<x<0.65 and 0.5<Q2<90 GeV2 is covered. At lowx the three ratios are significantly smaller than unity and the size of the depletion grows with decreasingx and increasing mass numberA. At intermediatex the ratios show an enhancement of about 2% above unity for C/D and Ca/D, possibly less for He/D. There are indications of someQ2 dependence in the Ca/D data. The integrals of the structure function differencesF2A−F2D are discussed.
Lifetimes of charged and neutralD mesons
1987
We have measured the lifetimes of hadronically produced charged and neutralD mesons using silicon microstrip detectors and an active silicon target in the NA32 spectrometer at the CERN SPS. We obtainτD± = (10.9±1.51.9)·10−13s andτD(−)10 = (4.2±0.5)·10−13s based on 59 and 90 fully reconstructed decays respectively, giving a ratioτD±/τD(−)10 of 2.6 ±0.5.
The evolution of the large-scale emission in Fanaroff-Riley type I jets
2011
Recent observations in X-rays and gamma-rays of nearby Fanaroff-Riley type I (FR I) radio galaxies have raised the question of the origin of the emission detected in the termination structures of their jets. The study of these structures can give information on the conditions for particle acceleration and radiation at the front shocks. In addition, an evolutionary scenario can help to disentangle the origin of the detected X-ray emission in young FR I sources, like some gigahertz peaked spectrum active galactic nuclei. This work focuses on the nature and detectability of the radiation seen from the termination regions of evolving FR I jets. We use the results of a relativistic, two-dimensio…
Parity violation correlations in light muonic atoms
1989
The 2 S -1 S transition in light muonic atoms is very sensitive to parity violation correlations induced via neutral currents. Observables depending on these transitions such as the photon polarization and the angular correlation between the emitted radiation and the atom polarization are a clear signal of weak neutral currents in atoms. We find the relation between the lepton and quark couplings and these observables emphasizing the effect of the nuclear spin. The results expected in muonic, atoms μ- 4 He and μ- 3 He are given.
$$\bar K^{0*} (892)$$ andK 0*(892) production at lowp t and the quark parton model
1990
Data on the production of the neutralK*(892) resonances at lowpt by 200 GeVK− and π− is compared with the predictions of various models based on the quark parton model of hadrons.
Modeling particle acceleration and non-thermal emission in supernova remnants
2021
According to the most popular model for the origin of cosmic rays (CRs), supernova remnants (SNRs) are the site where CRs are accelerated. Observations across the electromagnetic spectrum support this picture through the detection of non-thermal emission that is compatible with being synchrotron or inverse Compton radiation from high energy electrons, or pion decay due to proton-proton interactions. These observations of growing quantity and quality promise to unveil many aspects of CRs acceleration and require more and more accurate tools for their interpretation. Here, we show how multi-dimensional MHD models of SNRs, including the effects on shock dynamics due to back-reaction of acceler…
Optical pulsations from a transitional millisecond pulsar
2017
Weakly magnetic, millisecond spinning neutron stars attain their very fast rotation through a 1E8-1E9 yr long phase during which they undergo disk-accretion of matter from a low mass companion star. They can be detected as accretion-powered millisecond X-ray pulsars if towards the end of this phase their magnetic field is still strong enough to channel the accreting matter towards the magnetic poles. When mass transfer is much reduced or ceases altogether, pulsed emission generated by particle acceleration in the magnetosphere and powered by the rotation of the neutron star is observed, preferentially in the radio and gamma-ray bands. A few transitional millisecond pulsars that swing betwee…
3D simulations of wind-jet interaction in massive X-ray binaries
2010
High-mass microquasars may produce jets that will strongly interact with surrounding stellar winds on binary system spatial scales. We study the dynamics of the collision between a mildly relativistic hydrodynamical jet of supersonic nature and the wind of an OB star. We performed numerical 3D simulations of jets that cross the stellar wind with the code Ratpenat. The jet head generates a strong shock in the wind, and strong recollimation shocks occur due to the initial overpressure of the jet with its environment. These shocks can accelerate particles up to TeV energies and produce gamma-rays. The recollimation shock also strengthens jet asymmetric Kelvin-Helmholtz instabilities produced i…
INTEGRAL serendipitous detection of the gamma-ray microquasar LS 5039
2006
LS 5039 is the only X-ray binary persistently detected at TeV energies by the Cherenkov HESS telescope. It is moreover a gamma-ray emitter in the GeV and possibly MeV energy ranges. To understand important aspects of jet physics, like the magnetic field content or particle acceleration, and emission processes, such as synchrotron and inverse Compton (IC), a complete modeling of the multiwavelength data is necessary. LS 5039 has been detected along almost all the electromagnetic spectrum thanks to several radio, infrared, optical and soft X-ray detections. However, hard X-ray detections above 20 keV have been so far elusive and/or doubtful, partly due to source confusion for the poor spatial…
Transverse momentum distributions for exclusive $\varrho^{0}$ muoproduction
1992
We have studied transverse momentum distributions for exclusive rho(0) muoproduction on protons and heavier nuclei at 2 < Q2 < 25 GeV2. The Q2 dependence of the slopes of the p(t)2 and t' distributions is discussed. The influence of the non-exclusive background is investigated. The p(t)2-slope for exclusive events is 4.3 +/- 0.6 +/- 0.7 GeV-2 at large Q2. The p(t)2 spectra are much softer than inclusive p(t)2 spectra of leading hadrons produced in deep inelastic scattering.