Narrow Results

The Alpha Magnetic Spectrometer (AMS) is a high energy particle physics experiment in space scheduled to be installed on the International Space Station (ISS) by 2006 for a three-year mission. After a precursor flight of a prototype detector on board of the NASA Space Shuttle in June 1998, the construction of the detector in its final configuration is started and it will be completed by 2004. The purpose of this experiment is to provide a high statistics measurement of charged particles and nuclei in rigidity range 0.5 GV to few TV and to explore the high-energy (> 1 GeV) gamma-ray sky. In this paper we describe the detector layout and present an overview of the main scientific goals both in the domain of astrophysics: cosmic-ray origin, age and propagation and the exploration of the most energetic gamma-ray sources; and in the domain of astroparticle: the anti-matter and the dark matter searches.

The Alpha Magnetic Spectrometer (AMS) is a state of the art detector for the extrater-restrial study of matter, antimatter and missing matter. During the STS-91 precursor flight in may 1998 AMS collected nearly 100 millions of Cosmic Rays on Low Earth Orbit, measuring with high accuracy their composition. We review the results on the flux of proton, electron, positron and helium. Analysis of the under cutoff spectra indicates the existence of a new type of belts of energetic trapped particles characterized by a dominance of positrons versus electrons. AMS is currently being refurbished for a three year mission on the International Space Station where the its sensitivity to rare events will be increased by three to four orders of magnitude.

The PAMELA satellite-borne experiment¹, to be launched in 2005, is a powerful spectrometer including a magnetic field tracker and particle identification detectors. PAMELA science is broad and includes studies of interstellar propagation, solar modulation and search for dark matter signals.

The validity of CPT invariance in the field of “nuclear binding masses” has been studied for nuclei (antinuclei) with two and three nucleons (antinucleons): $(\mathrm{\text{d}}∕\overline{\mathrm{\text{d}}})$ and ${(}^3\mathrm{\text{He}}∕{}^3\overline{\mathrm{\text{He}}})$. It is discussed the importance of investigating the transition from the world where gluons and quarks carry their QCD colors (QGCW) to the world where gluons and quarks exist only with zero-QCD-color (QGZCW).

This paper proves, via an analytical approach, that 170 (out of 256) Boolean CA rules in a one-dimensional cellular automata (CA) are time-reversible in a generalized sense. The dynamics on each attractor of a time-reversible rule N is exactly mirrored, in both space and time, by its bilateral twin ruleN^†. In particular, all 69 period-1 rules, 17 (out of 25) period-2 rules, and 84 (out of 112) Bernoulli rules are time-reversible.

The remaining 86 CA rules are time-irreversible in the sense that N and N^† mirror their dynamics only in space, but not in time. In this case, each attractor of N defines a unique arrow of time.

A simple "time-reversal test" is given for testing whether an attractor of a CA rule is time-reversible or time-irreversible. For a time-reversible attractor of a CA rule N the past can be uniquely recovered from the future of N^†, and vice versa. This remarkable property provides 170 concrete examples of CA time machines where time travel can be routinely achieved by merely hopping from one attractor to its bilateral twin attractor, and vice versa. Moreover, the time-reversal property of some local rules can be programmed to mimic the matter–antimatter "annihilation" or "pair-production" phenomenon from high-energy physics, as well as to mimic the "contraction" or "expansion" scenarios associated with the Big Bang from cosmology.

Unlike the conventional laws of physics, which are based on a unique universe, most CA rules have multiple universes (i.e. attractors), each blessed with its own laws. Moreover, some CA rules are endowed with both time-reversible attractors and time-irreversible attractors.

Using an analytical approach, the time-τ return map of each Bernoulli στ-shift attractor of all 112 Bernoulli rules are shown to obey an ultra-compact formula in closed form, namely,.

or its inverse map.

These maps completely characterize the time-asymptotic (steady state) behavior of the nonlinear dynamics on the attractors. In-depth analysis of all but 18 global equivalence classes of CA rules have been derived, along with their basins of attraction, which characterize their transient regimes.

Above all, this paper provides a rigorous nonlinear dynamics foundation for a paradigm shift from an empirical-based approach à la Wolfram to an attractor-based analytical theory of cellular automata.

Matter–antimatter asymmetry observed in our Universe is discussed with attention to different effects which are (or may be) present in the phase diagram of matter. Some implications which can possibly be present in astrophysical objects are also discussed. They may not rely on non-equilibrium conditions. For this, spontaneous (or not) symmetry breakings expected and/or envisaged to occur in the phase diagram of matter are briefly discussed and different scenarios for particular periods of the early Universe are proposed, which can also yield aspects of relevance for formation of large structures. Issues which can also be of relevance for the Hubble's Law are raised.

PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range (protons: 80 MeV–700 GeV, electrons 50 MeV–400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV–190 GeV), positrons (50 MeV–270 GeV) and search for antimatter with a precision of the order of 10^-8). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, 15 2006 in a 350 × 600 km orbit with an inclination of 70 degrees. The detector is composed of a series of scintillator counters arranged at the extremities of a permanent magnet spectrometer to provide charge, Time-of-Flight and rigidity information. Lepton/hadron identification is performed by a Silicon-Tungsten calorimeter and a Neutron detector placed at the bottom of the device. An Anticounter system is used offline to reject false triggers coming from the satellite. In self-trigger mode the Calorimeter, the neutron detector and a shower tail catcher are capable of an independent measure of the lepton component up to 2 TeV. In this work we present some of its scientific results in its first five years of operation.

The energy dependence of the ratio for antiparticle to particle in pp collisions of high energy is studied using the parton and hadron cascade and dynamically constrained phase-space coalescence models. The yield ratios of antimatter and matter for different masses are measured at various c.m energies. It is found that the yield ratios of antimatter and matter increase with the increase of the c.m energy of pp collisions until they gradually approach to 1 after the c.m energy is more than 200 GeV. The distribution of transverse momentum also has significant dependence on the energy and mass, i.e., the average transverse momentum increases when the c.m energy of pp collisions increase. The model results are compatible with the STAR and ALICE preliminary data.

Evidence for the existence of antimatter in the Galaxy and in the cosmos as a whole is reviewed and possible explanations that have been proposed for its origin discussed.

A fundamental question in physics that has yet to be addressed experimentally is whether particles of antimatter, such as the antiproton or positron, obey the weak equivalence principle (WEP). Several theoretical arguments have been put forward arguing limits for possible violations of WEP. No direct `classical' gravitational experiment, the measurement of the free fall of an antiparticle, has been performed to date to determine if a particle of antimatter would experience a force in the gravitational potential of a normal matter body that is different from normal gravity. 30 years ago we proposed a free fall experiment using protons and antiprotons, modeled after the experiment to measure the gravitational acceleration of a free electron. At that time we gave consideration to yet another possible observation of gravitational differences between matter and antimatter based on the gravitational red shift of clocks. I will recall the original arguments and make a number of comments pertaining to the technical problems and other issues that prevented the execution of the antiproton free fall measurement. Note that a different gravitational force on antimatter in the gravitational field of matter would not constitute a violation of CPT, as this is only concerned with the gravitational acceleration of antimatter in the gravitational field of an antimatter body.

experiment's main goal is to measure the local gravitational acceleration of antihydrogen and thus perform a direct test of the weak equivalence principle with antimatter. In the first phase of the experiment the aim is to measure with 1% relative precision. This paper presents the antihydrogen production method and a description of some components of the experiment, which are necessary for the gravity measurement. Current status of the experimental apparatus is presented and recent commissioning results with antiprotons are outlined. In conclusion we discuss the short-term goals of the collaboration that will pave the way for the first gravity measurement in the near future.

The classical Weak Equivalence Principle has not yet been tested using antimatter in matter gravitational fields. The GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment, recently approved by CERN, proposes to measure the free-fall acceleration of antihydrogen. In this experiment, positive antihydrogen ions will be produced, and subsequently cooled down using laser cooled Be⁺ ions. Then, when a temperature of around 20 μK has been reached, the excess positron will be detached and the free-fall time will be measured using the antiproton annihilation products. An overview of the experiment will be given together with its present status.

The motivation of the AEgIS experiment is to test the universality of free fall with antimatter. The goal is to reach a relative uncertainty of 1% for the measurement of the earth's gravitational acceleration on an antihydrogen beam. High vertex position resolution is required for a position detector. An emulsion based detector can measure the annihilation vertex of antihydrogen atoms with a resolution of 1-2 μm, which if realized in the actual experiment will enable a 1% measurement of with less than 1000 atoms. Developments and achievements on emulsion detectors for the AEgIS experiment are presented here.

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 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 present a brief, and unfortunately incomplete, summary of the 2013 Workshop on Antimatter Gravity (WAG) held at Bern, Switzerland.

The ALPHA project at the CERN AD is testing fundamental symmetries between matter and antimatter using trapped antihydrogen atoms. The spectrum of the antihydrogen atom may be compared to ordinary hydrogen where it has been measured very precisely. CPT conservation, which underpins our current theoretical framework, requires equality of the masses and charges of matter and its antimatter partners, so antihydrogen spectroscopy presents a path to precision CPT tests.

I will discuss the techniques used by ALPHA to trap more than 8000 antihydrogen atoms in 2016, and interrogate them for 600s. The 1S-2S transition in antihydrogen has been observed for the first time, and it agrees with its hydrogen counterpart within an uncertainty of 400 kHz or 0.2 ppb. The charge of the antihydrogen atom has been bounded below $0.710^{-9}e$. A value of 1420.4 0.5MHz for the hyperfine splitting has been obtained from observation of the positron spin resonance spectrum.

The Alpha Magnetic Spectrometer, AMS, is successfully operating on the International Space Station for more than 6 years and has collected over 100 billion cosmic rays. We present the new physics results from AMS on the precision measurements of elementary particles and nuclei in the cosmic rays. Surprisingly, the spectra of both the primary cosmic rays (including proton, helium, carbon, and oxygen) and the secondary cosmic rays (including lithium, beryllium, and boron) all progressively harden above ∼200 GV. Remarkably, the boron-to-carbon flux ratio is well described by a single power law above 65 GV and consistent with the Kolmogorov turbulence model of magnetized plasma. Unexpectedly, of the four cosmic elementary particles, protons, antiprotons and positrons have nearly identical rigidity (momentum/charge) dependence from ∼60 GV to ∼500 GV, electrons have distinctly different rigidity dependence. Most importantly, AMS continues studies of complex antimatter candidates with stringent detector verification and constantly collection of data.

The Alpha Magnetic Spectrometer (AMS) is a state of the art detector for the extraterrestrial study of matter, antimatter and missing matter. During the STS-91 precursor flight in may 1998 AMS collected nearly 100 millions of Cosmic Rays on Low Earth Orbit, measuring with high accuracy their composition. We review the results on the flux of proton, electron, positron and helium. Analysis of the under cutoff spectra indicates the existence of a new type of belts of energetic trapped particles characterized by a dominance of positrons versus electrons. AMS is currently being refurbished for a three year mission on the International Space Station where the its sensitivity to rare events will be increased by three to four orders of magnitude.

PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range with the study of the antimatter component as main objective. The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, 15^th 2006 in a 350 × 600 km orbit with an inclination of 70 degrees. In this work we describe the experiment and its first results.

The Alpha Magnetic Spectrometer (AMS) is a particle physics detector designed to measure charged cosmic rays spectra up to TV region, with high energy photon detection capability up to few hundred GeV. With the large acceptance, the long duration (3 years) and the state of the art particle identification techniques, AMS will provide the most sensitive search for the existence of antimatter nuclei and for the origin of dark matter. The detector is being constructed with an eight layers Silicon Tracker inside a large superconducting magnet, providing a ~ 0.8 Tm² bending power and an acceptance of ~ 0.5 m²sr. A Transition Radiation Detector and a 3D Electromagnetic Calorimeter allow for electron, positron and photon identification, while independent velocity measurements are performed by a Time of Flight scintillating system and a Ring Image Cherenkov detector. The overall construction is due to be completed by 2008.