Search results for "Antimatter"
showing 10 items of 64 documents
Laser cooling of relativistic heavy-ion beams for FAIR
2015
Laser cooling is a powerful technique to reduce the longitudinal momentum spread of stored relativistic ion beams. Based on successful experiments at the experimental storage ring at GSI in Darmstadt, of which we show some important results in this paper, we present our plans for laser cooling of relativistic ion beams in the future heavy-ion synchrotron SIS100 at the Facility for Antiproton and Ion Research in Darmstadt.
Preparing single ultra-cold antihydrogen atoms for free-fall in GBAR
2014
We discuss an experimental approach allowing to prepare antihydrogen atoms for the GBAR experiment. We study the feasibility of all necessary experimental steps: The capture of incoming $\bar{\rm H}^{+}$ ions at keV energies in a deep linear RF trap, sympathetic cooling by laser cooled Be+ ions, transfer to a miniaturized trap and Raman sideband cooling of an ion pair to the motional ground state, and further reducing the momentum of the wavepacket by adiabatic opening of the trap. For each step, we point out the experimental challenges and discuss the efficiency and characteristic times, showing that capture and cooling are possible within a few seconds. We discuss an experimental approach…
A semiconductor laser system for the production of antihydrogen
2012
Laser-controlled charge exchange is a promising method for producing cold antihydrogen. Caesium atoms in Rydberg states collide with positrons and create positronium. These positronium atoms then interact with antiprotons, forming antihydrogen. Las er excitation of the caesium atoms is essential to increase the cross section of the charge-exchange collisions. This method was demonstrated in 2004 by the ATRAP collaboration by using an available copper vapour laser. For a second generation of charge-e xchange experiments we have designed a new semiconductor laser system that features several improvements compared to the copper vapour laser. We describe this new laser system and show the resul…
Towards an Improved Measurement of the Proton Magnetic Moment
2017
The BASE collaboration performed the most precise measurement of the proton magnetic moment. By applying the so-called double Penning-trap method with a single proton a fractional precision of 3.3 parts-per-billion was reached. This article describes the primary limitations of the last measurement and discusses improvements to reach the sub-parts-per-billion level.
Electromagnetic properties of neutrinos in a background of electrons.
1989
Using covariant methods we calculate the neutrino electromagnetic vertex in a gas of electrons to lowest order in a loop expansion and to the lowest order in $\frac{1}{{M}_{W}^{2}}$. The new induced terms, while they are chirality preserving, yield additional contributions to the dipole moments in the nonrelativistic limit. These are identical for particles and antiparticles and so need not vanish for Majorana neutrinos. As applications of our formulas, the expression for the $\mathrm{plasmon}\ensuremath{\rightarrow}\ensuremath{\nu}\overline{\ensuremath{\nu}}$ decay rate is rederived and the dispersion relation of a massless neutrino propagating in matter in the presence of an external magn…
Double-trap measurement of the proton magnetic moment at 0.3 parts per billion precision
2017
Precise knowledge of the fundamental properties of the proton is essential for our understanding of atomic structure as well as for precise tests of fundamental symmetries. We report on a direct high-precision measurement of the magnetic moment μp of the proton in units of the nuclear magneton μN. The result, μp = 2.79284734462 (±0.00000000082) μN, has a fractional precision of 0.3 parts per billion, improves the previous best measurement by a factor of 11, and is consistent with the currently accepted value. This was achieved with the use of an optimized double–Penning trap technique. Provided a similar measurement of the antiproton magnetic moment can be performed, this result will enable…
J/ψ production as a function of charged particle multiplicity in pp collisions at s =7 TeV
2012
The ALICE Collaboration reports the measurement of the relative J/psi yield as a function of charged particle pseudorapidity density dN(ch)/d eta in pp collisions at root s = 7 TeV at the LHC. J/psi particles are detected for p(t) > 0, in the rapidity interval vertical bar y vertical bar 0. In the highest multiplicity interval with (dN(ch)/d eta)(bin)) = 24.1, corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias J/psi yield by a factor of about 5 at 2.5 < y <4 (8 at vertical bar y vertical bar < 0.9) is observed. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
Neutron to mirror-neutron oscillations in the presence of mirror magnetic fields
2009
We performed ultracold neutron (UCN) storage measurements to search for additional losses due to neutron (n) to mirror-neutron (n') oscillations as a function of an applied magnetic field B. In the presence of a mirror magnetic field B', UCN losses would be maximal for B = B'. We did not observe any indication for nn' oscillations and placed a lower limit on the oscillation time of tau_{nn'} > 12.0 s at 95% C.L. for any B' between 0 and 12.5 uT.
Measurement of the cosmic ray antiproton/proton flux ratio at TeV energies with the ARGO-YBJ detector
2012
Cosmic ray antiprotons provide an important probe to study the cosmic ray propagation in the interstellar space and to investigate the existence of dark matter. Acting the Earth-Moon system as a magnetic spectrometer, paths of primary antiprotons are deflected in the opposite sense with respect to those of the protons in their way to the Earth. This effect allows, in principle, the search for antiparticles in the direction opposite to the observed deficit of cosmic rays due to the Moon (the so-called `Moon shadow'). The ARGO-YBJ experiment, located at the Yangbajing Cosmic Ray Laboratory (Tibet, P.R. China, 4300 m a.s.l., 606 g/cm$^2$), is particularly effective in measuring the cosmic ray …
Dynamically generatedN*andΛ*resonances in the hidden charm sector around 4.3 GeV
2011
The interactions of $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}{\ensuremath{\Sigma}}_{c}$-$\mathrm{D\ifmmode \bar{}\else \={}\fi{}}{\ensuremath{\Lambda}}_{c}$, ${\mathrm{D\ifmmode \bar{}\else \={}\fi{}}}^{*}{\ensuremath{\Sigma}}_{c}$-${\mathrm{D\ifmmode \bar{}\else \={}\fi{}}}^{*}{\ensuremath{\Lambda}}_{c}$, and related strangeness channels, are studied within the framework of the coupled-channel unitary approach with the local hidden gauge formalism. A series of meson-baryon dynamically generated relatively narrow ${N}^{*}$ and ${\ensuremath{\Lambda}}^{*}$ resonances are predicted around 4.3 GeV in the hidden charm sector. We make estimates of production cross sections of these predicted res…