Lin D.X.,Helmholtz Institute Mainz |
Lin D.X.,Johannes Gutenberg University Mainz
Nuclear and Particle Physics Proceedings | Year: 2017
The BESIII experiment is running on the double-ring symmetric collider, BEPCII, at center-of-mass energies between 2.0 and 4.6 GeV. The collected data can be analyzed to measure the baryon electromagnetic form factors in direct e+e−-annihilation and in initial state radiation processes. In this paper, results on e+e−→pp‾ and preliminary results on e+e−→ΛΛ‾ based on the data collected by BESIII in 2011 and 2012 are presented. Preliminary results on the proton electromagnetic form factors measurement are also reported based on the analysis of e+e−→pp‾γ with 7 data samples at center-of-mass energies between 3.773 and 4.6 GeV. © 2016 Elsevier B.V.
Borschevsky A.,Helmholtz Institute Mainz |
Pershina V.,Helmholtz Center for Heavy Ion Research |
Eliav E.,Tel Aviv University |
Kaldor U.,Tel Aviv University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013
The ionization potentials, excitation energies, and electron affinity of superheavy element 120 and the polarizabilities of its neutral and ionized states are calculated. Relativity is treated within the four-component Dirac-Coulomb formalism; Breit or Gaunt terms are added in some cases. Electron correlation is included via the intermediate Hamiltonian Fock-space coupled cluster method for the spectra and ionization potentials and via the single reference coupled cluster singles and doubles with perturbative triples [CCSD(T)] approach for the electron affinities and polarizabilities. To assess the accuracy of the results, the atomic properties of the lighter homologues, Ba and Ra, are also calculated. Very good agreement with available experimental values is obtained, lending credence to the predictions for element 120. The atomic properties in group 2 are largely determined by the valence ns orbital, which experiences relativistic stabilization and contraction in the heavier group-2 elements. As a result, element 120 is predicted to have a relatively high ionization potential (5.851 eV), similar to that of Sr, and rather low electron affinity (0.021 eV) and polarizability (163 a.u.), comparable to those of Ca. The adsorption enthalphy of element 120 on Teflon, which is important for possible future experiments on this atom, is estimated as 35.4 kJ/mol, the lowest among the elements considered here. © 2013 American Physical Society.
Hessberger F.P.,Helmholtz Center for Heavy Ion Research |
Hessberger F.P.,Helmholtz Institute Mainz
ChemPhysChem | Year: 2013
The search for new superheavy elements (SHEs) is at present one of the most exciting adventures in nuclear physics. Thanks to enhanced experimental techniques, the synthesis of elements Z=113 to 118 in reactions using 48Ca projectiles and targets made of isotopes of the elements neptunium to californium has been claimed. Discovery of the elements Z=114 (named flerovium) and Z=116 (named livermorium) has been accepted by the IUPAC. The others are waiting. The situation for element 113 is particular; here claims on discovery come from groups from RIKEN, Wako, Saitama, Japan and FLNR-JINR, Dubna, Russia. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Sobiczewski A.,National Center for Nuclear Research |
Sobiczewski A.,Helmholtz Institute Mainz |
Sobiczewski A.,Helmholtz Center for Heavy Ion Research |
Litvinov Y.A.,Helmholtz Center for Heavy Ion Research
Physical Review C - Nuclear Physics | Year: 2014
The accuracy of current theoretical descriptions of nuclear masses is studied. Ten theoretical models of various kinds are taken for the study: the macroscopic-microscopic, purely microscopic (self-consistent), and models of other natures. Some of them are traditional, but still widely used, while the others are very recent. The most recently evaluated experimental masses of 2012 are taken for the test of the models. Much attention is given to the dependence of the accuracy on the region of nuclei described by the models. The macroscopic-microscopic approaches are still found to be the most accurate in the description of atomic masses. However, the recently developed purely microscopic models (the Hartree-Fock-Bogoliubov approach) reach comparable accuracy. A strong dependence of the accuracy on the region of nuclei described is found, knowledge of which is crucial for a realistic description of specific nuclei. © 2014 American Physical Society.
News Article | December 12, 2016
The Physics World 2016 Breakthrough of the Year goes to "the LIGO Scientific Collaboration for its revolutionary, first-ever direct observations of gravitational waves". Nine other achievements are highly commended and cover topics ranging from nuclear physics to material science and more. Almost exactly 100 years after they were first postulated by Albert Einstein in his general theory of relativity, gravitational waves hit the headlines in 2016 as the US-based LIGO collaboration detected two separate gravitational-wave events using the Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO). The first observation was made on 14 September 2015 and was announced in February this year. A second set of gravitational waves rolled through LIGO's detectors on 26 December 2015, and this so-called "Boxing Day event" was announced in June this year. Gravitational waves are ripples in the fabric of space–time, and these observations mark the end of a decades-long hunt for these interstellar undulations. The measurements also herald the start of the era of gravitational-wave astronomy and multi-messenger astronomy, whereby gravitational-wave observations are combined with those made by optical and radio telescopes and other detectors observing the cosmos. Indeed, LIGO's twin detectors will soon be joined by a global network of gravitational-wave detectors. The gravitational waves from both events were produced by cataclysmic events in the distant universe – the collision and eventual merger of two black holes. In the first event, two black holes of 36 and 29 solar masses, respectively, merged to form a spinning, 62 solar-mass black hole, some 1.3 billion light-years away in an event dubbed GW150914. The gravitational waveform was picked up by the then newly upgraded aLIGO detectors – one in Hanford, Washington, and the other in Livingston, Louisiana. In fact, when the signal reached the observatories, both detectors were still being calibrated. Despite this, the signal from GW150914 was so strong and clear that it could be "seen" in the data by eye and was measured to a statistical certainty of 5.1σ. The waves in the Boxing Day event – dubbed GW151226 – were also generated by colliding black holes. These weighed in at 14 and 8 solar masses, and merged to form a single, spinning 21 solar-mass black hole, some 1.4 billion light-years away. In October 2015 LIGO recorded a third possible event, dubbed LVT151012. Although not statistically significant enough to be a discovery, the team believes this event also arose from two coalescing black holes. LIGO detected three events in its four months of observation, and this was no mean feat. The instruments are sensitive enough to detect a change in length less than 1000th the size of a single proton between its interferometer's arms – which is an incredible feat of engineering. LIGO has already changed our view of the universe – its observations are the first direct evidence for the existence of black holes. Also, the stellar-mass black holes that merged in both events do not fit our current understanding of black holes. Astronomers had thought that such binaries would either not form at all or, if they did, they would be too far apart to merge within the age of the universe. Also, the LIGO collaboration had expected that its first detections would come from binary neutron-star mergers rather than coupling black holes, which were thought to be rare. But the data from the recent discoveries suggest that the rate of binary-black-hole mergers is higher than expected. The top 10 breakthroughs were chosen by a panel of four Physics World editors and reporters, and the criteria for judging included: Now for our nine runner-up breakthroughs, which are listed below in no particular order. To Chen Wang, Robert Schoelkopf and colleagues at Yale University in the US and INRIA Paris-Rocquencourt in France for creating a Schrödinger's cat that lives and dies in two boxes at once. In this new twist on a much-loved quantum paradox, the boxes that hold Schrödinger's cat are two entangled microwave cavities. The cats are represented by large ensembles of photons, which exist in each cavity. These ensembles can be in one of two quantum states – alive or dead – and the team managed to put the entire system into a state in which both cats (in both boxes) are both alive and dead until a measurement is made. Besides providing a novel illustration of how Schrödinger's cat can be in two places at once, the large numbers of photons in such "cat states" could provide a robust way of storing quantum information using error-correction protocols. To Lars von der Wense, Peter Thirolf and colleagues at Ludwig Maximilian University of Munich, GSI Helmholtz Centre for Heavy Ion Research, Helmholtz Institute Mainz and the Johannes Gutenberg University Mainz for detecting the elusive thorium-229 nuclear-clock transition. It has long been a goal of some in the metrology community to produce a "nuclear clock" by locking a laser to a rare low-energy nuclear transition. Such a clock would, in principle, be much more stable than a conventional atomic clock because the nucleus is much less susceptible to interference from stray electromagnetic fields. The predicted 7.8 eV transition in thorium-229 is seen as an ideal candidate – except that physicists had been unable to actually detect it. By doing experiments involving atoms and ions of thorium-229, the team showed that the transition does indeed exist and has energy in the 6.3–18.3 eV range. The next step for the researchers is to improve their measurements so that the energy is known to millielectronvolt precision. This would then allow the transition to be studied using laser spectroscopy. To Giles Hammond and colleagues at the University of Glasgow for building a highly sensitive gravimeter that is both inexpensive and compact. Their tiny device can make very precise measurements of Earth's gravity and could be deployed in drone aircraft or in multi-sensor arrays to perform a range of tasks, including mineral exploration, civil engineering and monitoring volcanoes. While the gravimeter is not quite as sensitive as the best available sensors, it could be produced for a 1000th of the cost and is also significantly smaller and lighter than current devices. The device is based on a "proof mass", which is a piece of silicon about 10 mm long that sits on top of two flexible struts. The mass, struts and frame are all made using standard semiconductor-manufacturing processes. To Cory Dean, Avik Ghosh and colleagues at Columbia University, the University of Virginia, Cornell University, the Japanese National Institute for Materials Science, Shenyang National Laboratory for Materials Science and IBM for measuring the negative refraction of electrons in graphene. Negative refraction is a property of some artificial metamaterials and can be used to create novel optical devices such as a perfect lens. Electrons in materials can behave as waves and negative refraction should also occur at the interface between an n-type and a p-type semiconductor (a p–n junction). It has proven impossible to see this effect in conventional semiconductors because most electrons are reflected at p–n junctions. Dean and colleagues created a p–n junction in graphene and ensured that the interface was very smooth to minimize reflections – allowing them to measure the negative refraction of electrons. Negative refraction could be used to bring a diverging electron beam to a sharp focus and this could form the basis of an electronic switch that consumes very small amounts of energy. To the Pale Red Dot collaboration for finding clear evidence that a rocky exoplanet orbits within the habitable zone of Proxima Centauri, which is the nearest star to the solar system. Dubbed Proxima b, the exoplanet has a mass about 1.3 times that of the Earth and is therefore most likely a terrestrial planet with a rocky surface. Our newly found neighbour also lies within its star's habitable zone, meaning that it could, in theory, sustain liquid water on its surface, and may even have an atmosphere. Proxima Centauri is a red-dwarf star that is just 4.2 light-years away from the Sun. While Proxima b could be subject to ultraviolet and X-radiation that is far more intense than that experienced on Earth, the team says that this does not exclude the existence of an atmosphere. Whether the planet contains liquid water, and ultimately life, depends upon exactly how it formed – according to the team. To Chris Ballance and colleagues at the University of Oxford and Ting Rei Tan and colleagues at NIST in Boulder, Colorado, for creating and measuring quantum entanglement between pairs of two different kinds of ions. The work – which was done independently by the two groups – is an important step towards the creation of ion-based quantum computers based on two or more different kinds of ion. Such hybrid systems would take advantage of the fact that some ions are better than others at performing specific quantum-computing tasks. The Oxford team entangled ions of two different isotopes of the same element – calcium-40 and calcium-43 – whereas the NIST group used beryllium-9 and magnesium-25 as their ions. To Gail McConnell, Brad Amos and colleagues at the University of Strathclyde for creating a new microscope lens that offers the unique combination of a large field of view with high resolution. Called a mesolens, the device allows a confocal microscope to create 3D images of much larger biological samples than was previously possible – while providing detail at the sub-cellular level. The ability to view whole specimens in a single image could assist in the study of many biological processes and ensure that important details are not overlooked. The researchers used the lens in a customized confocal microscope to image 12.5 day-old mouse embryos. They were able to image single cells, heart-muscle fibres and sub-cellular details, not just near the surface of the sample but throughout the depth of the embryo. To Rainer Blatt and Peter Zoller of the Institute for Quantum Optics and Quantum Information Innsbruck and the University of Innsbruck, and colleagues, for simulating fundamental-particle interactions using a quantum computer. The team used four trapped ions to model the physics that describes the creation and annihilation of electron–positron pairs. While the result can be easily calculated using a conventional computer, problems that are beyond the reach of even the most powerful supercomputers could be solved by the quantum computer if it could be scaled up to include about 30 ions. The team has already built a system with that many ions, but its performance must be improved significantly before it can do practical simulations – something that could be possible within a decade. To Kilian Singer, Johannes Roßnagel and colleagues at the University of Mainz for creating an engine based on just one atom. The team's heat engine converts a difference in temperature to mechanical work by confining a single calcium atom in a funnel-shaped trap. The researchers then heated the atom using electrical noise, and as its temperature increased, its oscillations in the radial direction became larger, causing it to sample regions of higher potential, sending the particle towards the larger end of the trap. By turning the noise on and off periodically, the researchers caused the atom to oscillate between the two ends of the trap. This motion is damped to prevent the atom from escaping the trap – and the energy required to keep the atom in the trap is the work done by the engine. Their next research goal is to cool the atom further and confine it more tightly, so that it no longer behaves as a classical particle but rather as a quantum wavepacket. This could open the door to studies of the interface between thermodynamics and quantum mechanics.
Hori M.,Max Planck Institute of Quantum Optics |
Hori M.,University of Tokyo |
Walz J.,Johannes Gutenberg University Mainz |
Walz J.,Helmholtz Institute Mainz
Progress in Particle and Nuclear Physics | Year: 2013
The Antiproton Decelerator (AD) facility of CERN began operation in 1999 to serve experiments for studies of CPT invariance by precision laser and microwave spectroscopy of antihydrogen (H̄) and antiprotonic helium (p̄He+) atoms. The first 12 years of AD operation saw cold H̄ synthesized by overlapping clouds of positrons (e+) and antiprotons (p̄) confined in magnetic Penning traps. Cold H̄ was also produced in collisions between Rydberg positronium (Ps) atoms and p̄. Ground-state H̄ was later trapped for up to ∼1000 s in a magnetic bottle trap, and microwave transitions excited between its hyperfine levels. In the p̄He+ atom, deep ultraviolet transitions were measured to a fractional precision of (2.3-5)×10-9 by sub-Doppler two-photon laser spectroscopy. From this the antiproton-to-electron mass ratio was determined as Mp̄/me=1836.1526736(23), which agrees with the p value known to a similar precision. Microwave spectroscopy of p̄He+ yielded a measurement of the p̄ magnetic moment with a precision of 0.3%. More recently, the magnetic moment of a single p̄ confined in a Penning trap was measured with a higher precision, as μp̄=-2.792845(12)μnucl in nuclear magnetons. Other results reviewed here include the first measurements of the energy loss (-dE/dx) of 1-100 keV p̄ traversing conductor and insulator targets; the cross sections of low-energy (<10 keV) p̄ ionizing atomic and molecular gas targets; and the cross sections of 5 MeV p̄ annihilating on various target foils via nuclear collisions. The biological effectiveness of p̄ beams destroying cancer cells was measured as a possible method for radiological therapy. New experiments under preparation attempt to measure the gravitational acceleration of H̄ or synthesize H̄+. Several other future experiments will also be briefly described. © 2013 Elsevier B.V. All rights reserved.
Van Tilburg K.,Stanford University |
Leefer N.,Helmholtz Institute Mainz |
Bougas L.,Helmholtz Institute Mainz |
Budker D.,Helmholtz Institute Mainz |
And 2 more authors.
Physical Review Letters | Year: 2015
We report new limits on ultralight scalar dark matter (DM) with dilatonlike couplings to photons that can induce oscillations in the fine-structure constant α. Atomic dysprosium exhibits an electronic structure with two nearly degenerate levels whose energy splitting is sensitive to changes in α. Spectroscopy data for two isotopes of dysprosium over a two-year span are analyzed for coherent oscillations with angular frequencies below 1rads-1. No signal consistent with a DM coupling is identified, leading to new constraints on dilatonlike photon couplings over a wide mass range. Under the assumption that the scalar field comprises all of the DM, our limits on the coupling exceed those from equivalence-principle tests by up to 4 orders of magnitude for masses below 3×10-18eV. Excess oscillatory power, inconsistent with fine-structure variation, is detected in a control channel, and is likely due to a systematic effect. Our atomic spectroscopy limits on DM are the first of their kind, and leave substantial room for improvement with state-of-the-art atomic clocks. © 2015 American Physical Society. © 2015 American Physical Society.
Sanchez Lorente A.,Helmholtz Institute Mainz
Hyperfine Interactions | Year: 2014
Hypernuclear research will be one of the main topics addressed by the PANDA experiment at the planned Facility for Antiproton and Ion Research FAIR at Darmstadt (Germany). http://www.gsi.de, http://www.gsi.de/fair/ Thanks to the use of stored (Formula presented.) beams, copious production of double Λ hypernuclei is expected at the PANDA experiment, which will enable high precision γ spectroscopy of such nuclei for the first time, and consequently a unique chance to explore the hyperon-hyperon interaction. In particular, ambiguities of past experiments in determining the strength of the ΛΛ interaction will be avoided thanks to the excellent energy precision of a few keV (FWHM) achieved by germanium detectors. Such a resolution capability is particularly needed to resolve the small energy spacing of the order of (10–100) keV, which is characteristic from the spin doublet in hypernuclei the so -called ”hypernuclear fine structure”. In comparison to previous experiments, PANDA will benefit from a novel technique to assign the various observable γ-transitions in a unique way to specific double hypernuclei by exploring various light targets. Nevertheless, the ability to carry out unique assignments requires a devoted hypernuclear detector setup. This consists of a primary nuclear target for the production of (Formula presented.) + (Formula presented.) pairs, a secondary active target for the hypernuclei formation and the identification of associated decay products and a germanium array detector to perform γ spectroscopy. Moreover, one of the most challenging issues of this project is the fact that all detector systems need to operate in the presence of a high magnetic field and a large hadronic background. Accordingly, the need of an innovative detector concept will require dramatic improvements to fulfil these conditions and that will likely lead to a new generation of detectors. In the present talk details concerning the current status of the activities related to the detector developments for this challenging programme will be given. Among these improvements is the new concept for a cooling system for the germanium detector based on a electro-mechanical device. In the present work, the cooling efficiency of such devices has been successfully tested, showing their capability to reach liquid nitrogen temperatures and therefore the possibility to use them as a good alternative to the standard liquid nitrogen dewars. Furthermore, since the momentum resolution of low momentum particles is crucial for the unique identification of hypernuclei, an analysis procedure for improving the momentum resolution in few layer silicon based trackers is presented. © 2014, Springer International Publishing Switzerland.
Ma Y.,Helmholtz Institute Mainz
Progress in Particle and Nuclear Physics | Year: 2012
This proceeding is a summary based on the talk given at the 33rd international school of nuclear physics, Erice, Italy. An introduction following the historical development of a theoretical treatment of nucleon electromagnetic form factors will be given. A feasibility study on the time-like electromagnetic form factor at PANDA is presented based on a Monte Carlo simulation. Some recent progress on electromagnetic processes at PANDA is also given. © 2012 Elsevier B.V. All rights reserved.
Lorente A.S.,Helmholtz Institute Mainz
EPJ Web of Conferences | Year: 2015
Hypernuclear research will be one of the main topics addressed by the PANDA experiment at the planned Facility for Antiproton and Ion Research FAIR at Darmstadt (Germany). [1, 2] Thanks to the use of stored p¯ beams, copious production of double Λ hypernuclei is expected at the PANDA experiment, which will enable high precision γ spectroscopy of such nuclei for the first time, and consequently a unique chance to explore the hyperon-hyperon interaction. In particular, ambiguities of past experiments in determining the strength of the ΛΛ interaction will be avoided thanks to the excellent energy precision of a few keV (FWHM) achieved by germanium detectors. Such a resolution capability is particularly needed to resolve the small energy spacing of the order of (10-100) keV, which is characteristic from the spin doublet in hypernuclei the so -called "hypernuclear fine structure". In comparison to previous experiments, PANDA will benefit from a novel technique to assign the various observable γ-transitions in a unique way to specific double hypernuclei by exploring various light targets. Nevertheless, the ability to carry out unique assignments requires a devoted hypernuclear detector setup. This consists of a primary nuclear target for the production of Σ- + Σ pairs, a secondary active target for the hypernuclei formation and the identification of associated decay products and a germanium array detector to perform γ spectroscopy. Moreover, one of the most challenging issues of this project is the fact that all detector systems need to operate in the presence of a high magnetic field and a large hadronic background. Accordingly, the need of an innovative detector concept will require dramatic improvements to fulfil these conditions and that will likely lead to a new generation of detectors. In the present work details concerning the current status of the activities related to the detector developments for this challenging programme will be given. Among these improvements is the new concept for a cooling system for the germanium detector based on a electro-mechanical device. In the present work, the cooling efficiency of such devices has been successfully tested, showing their capability to reach liquid nitrogen temperatures and therefore the possibility to use them as a good alternative to the standard liquid nitrogen dewars. Furthermore, since the momentum resolution of low momentum particles is crucial for the unique identification of hypernuclei, an analysis procedure for improving the momentum resolution in few layer silicon based trackers is presented. © Owned by the authors, published by EDP Sciences, 2015.