5,657 research outputs found
Study of the system in the mass range up to 1200 MeV
The reaction has been studied with GAMS-2000
spectrometer in the secondary 38 GeV/c -beam of the IHEP U-70
accelerator. Partial wave analysis of the reaction has been performed in the
mass range up to 1200 MeV. The -meson is seen as a sharp
peak in S-wave. The -dependence of production cross section has
been studied. Dominant production of the at a small transfer
momentum confirms the hypothesis of Achasov and Shestakov about significant
contribution of the exchange () in the mechanism
of meson production in -channel of the reaction.Comment: 4 pages, 3 figures, talk given at HADRON'9
Search for invisible decays of sub-GeV dark photons in missing-energy events at the CERN SPS
We report on a direct search for sub-GeV dark photons (A') which might be
produced in the reaction e^- Z \to e^- Z A' via kinetic mixing with photons by
100 GeV electrons incident on an active target in the NA64 experiment at the
CERN SPS. The A's would decay invisibly into dark matter particles resulting in
events with large missing energy. No evidence for such decays was found with
2.75\cdot 10^{9} electrons on target. We set new limits on the \gamma-A' mixing
strength and exclude the invisible A' with a mass < 100 MeV as an explanation
of the muon g_\mu-2 anomaly.Comment: 6 pages, 3 figures; Typos corrected, references adde
Dark Matter Search Perspectives with GAMMA-400
GAMMA-400 is a future high-energy gamma-ray telescope, designed to measure
the fluxes of gamma-rays and cosmic-ray electrons + positrons, which can be
produced by annihilation or decay of dark matter particles, and to survey the
celestial sphere in order to study point and extended sources of gamma-rays,
measure energy spectra of Galactic and extragalactic diffuse gamma-ray
emission, gamma-ray bursts, and gamma-ray emission from the Sun. GAMMA-400
covers the energy range from 100 MeV to ~3000 GeV. Its angular resolution is
~0.01 deg(Eg > 100 GeV), and the energy resolution ~1% (Eg > 10 GeV). GAMMA-400
is planned to be launched on the Russian space platform Navigator in 2019. The
GAMMA-400 perspectives in the search for dark matter in various scenarios are
presented in this paperComment: 4 pages, 4 figures, submitted to the Proceedings of the International
Cosmic-Ray Conference 2013, Brazil, Rio de Janeir
Technical Design Report for the PANDA Solenoid and Dipole Spectrometer Magnets
This document is the Technical Design Report covering the two large
spectrometer magnets of the PANDA detector set-up. It shows the conceptual
design of the magnets and their anticipated performance. It precedes the tender
and procurement of the magnets and, hence, is subject to possible modifications
arising during this process.Comment: 10 pages, 14MB, accepted by FAIR STI in May 2009, editors: Inti
Lehmann (chair), Andrea Bersani, Yuri Lobanov, Jost Luehning, Jerzy Smyrski,
Technical Coordiantor: Lars Schmitt, Bernd Lewandowski (deputy),
Spokespersons: Ulrich Wiedner, Paola Gianotti (deputy
Constraints on New Physics in the Electron g-2 from a Search for Invisible Decays of a Scalar, Pseudoscalar, Vector, and Axial Vector
We performed a search for a new generic boson, which could be a scalar
(), pseudoscalar (), vector () or an axial vector () particle
produced in the 100 GeV electron scattering off nuclei, ,
followed by its invisible decay in the NA64 experiment at CERN. No evidence for
such process was found in the full NA64 data set of
electrons on target. We place new bounds on the coupling strengths
to electrons, and set constraints on their contributions to the electron
anomalous magnetic moment ,
for the mass region GeV. These results are an order of
magnitude more sensitive compared to the current accuracy on from the
electron experiments and recent high-precision determination of the fine
structure constant.Comment: 6 pages, 4 figure
Hunting down the X17 boson at the CERN SPS
Recently, the ATOMKI experiment has reported new evidence for the excess of
events with a mass 17 MeV in the nuclear transitions of He,
that they previously observed in measurements with Be. These observations
could be explained by the existence of a new vector boson. So far, the
search for the decay with the NA64 experiment at the
CERN SPS gave negative results. Here, we present a new technique that could be
implemented in NA64 aiming to improve the sensitivity and to cover the
remaining parameter space. If a signal-like event is detected, an
unambiguous observation is achieved by reconstructing the invariant mass of the
decay with the proposed method. To reach this goal an optimization of the
production target, as well as an efficient and accurate reconstruction of
two close decay tracks, is required. A dedicated analysis of the available
experimental data making use of the trackers information is presented. This
method provides independent confirmation of the NA64 published results [Phys.
Rev. D101, 071101 (2020)], validating the tracking procedure. The detailed
Monte Carlo study of the proposed setup and the background estimate shows that
the goal of the proposed search is feasible
Design and Performance of the GAMMA-400 Gamma-Ray Telescope for Dark Matter Searches
The GAMMA-400 gamma-ray telescope is designed to measure the fluxes of gamma-rays and cosmic-ray electrons (+) positrons, which can be produced by annihilation or decay of the dark matter particles, as well as to survey the celestial sphere in order to study point and extended sources of gamma-rays, measure energy spectra of Galactic and extragalactic diffuse gamma-ray emission, gamma-ray bursts, and gamma-ray emission from the Sun. GAMMA-400 covers the energy range from 100 MeV to 3000 GeV. Its angular resolution is approximately 0.01deg (E(sub gamma) greater than 100 GeV), the energy resolution approximately 1% (E(sub gamma) greater than 10 GeV), and the proton rejection factor approximately 10(exp 6). GAMMA-400 will be installed on the Russian space platform Navigator. The beginning of observations is planned for 2018
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