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CURATOR

PhD Student at École de technologie supérieure studying Carbon Nanotube MEMS.

PINBOARD SUMMARY

We know that everything on earth is comprised of matter but what about antimatter?

Where have I heard the word Antimatter before? Antimatter became famous because it played a prominent part in the plot of Dan Brown's famous book Angels and Demons;but the scientific community has known antimatter since the early 1920s when it was first proposed by Paul Dirac although it was not known by its name then. So what exactly is Antimatter? As the name suggests Antimatter is the mirror image of Matter which is comprised of electrons, protons, neutrons and the lot. Thus, the antiparticle to the electron would be a positron carrying a net positive charge. The positron was first discovered by Carl Anderson in 1932 which provided the first concrete evidence for the presence of antimatter in the universe. Theory states that right after the Big Bang both matter and antimatter were created simultaneously. However, the quantity of matter in the observable universe dwarfs the antimatter quantity. How is antimatter produced? High energy collisions between subatomic particles produce antimatter. The European Organization for Nuclear Research (CERN) runs experiments frequently to produce particles of antimatter using a Particle Accelerator. Elsewhere, high energy cosmic rays striking the earth's atmosphere produce trace amounts of Antimatter. Antiparticles like Positrons are naturally produced due to radioactivity. Why do we study Antimatter? Studying the properties of antimatter leads us to answer a question that has fascinated humanity since the dawn of time - "How was the Universe created?". We can roll back in time to find out more abut the first moments after the Big Bang. Can we actually use antimatter? Antimatter finds its use in medical imaging such as Positron Emission Tomography. Other potential applications include use as fuel for interstellar travels as fantasized in Hollywood sci-fi. Fascinating yet dangerous stuff Matter and Antimatter when in contact annihilate each other. This, unfortunately, is the law of Nature and prevents us from harnessing Antimatter's potential. The interaction between Matter and Antimatter in sufficient quantities can be cataclysmic. Technology to store antimatter has also not been discovered yet which is another obstacle. However, studying antimatter is still f major interest to particle phyisicists.

10 ITEMS PINNED

Systematic uncertainties in long-baseline neutrino-oscillation experiments

Abstract: Thanks to global efforts over the past two decades, the phenomenon of neutrino oscillations is now well established. In ongoing experiments, the parameters driving the oscillations are being determined with rapidly increasing precision. Yet there still are open issues that have implications going well beyond neutrino physics. The next two decades are expected to bring definite answers to the neutrino-mass hierarchy and violation of charge-particle (CP) symmetry in neutrino oscillations. The question of the mass hierarchy---whether the neutrino masses follow the pattern of the charged-lepton masses---is relevant for cosmology, astrophysics and unification theories. On the other hand, CP violating oscillations have the potential to give an important, or event dominant, contribution to the matter-antimatter asymmetry in the Universe. For the success of future neutrino-oscillation studies it is, however, necessary to ensure a significant reduction of uncertainties, particularly those related to neutrino-energy reconstruction. We discuss different sources of systematic uncertainties, paying special attention to those arising from nuclear effects and detector response. Analyzing nuclear effects we show the importance of developing accurate theoretical models, capable to provide truly quantitative description of neutrino cross sections, together with the relevance of their implementation in Monte Carlo generators and extensive testing against scattering data. We also point out the fundamental role of efforts aiming to determine detector response in test-beam exposures.

Pub.: 01 Sep '16, Pinned: 21 Apr '17

Matter-Antimatter Propulsion via QFT Effects from Parallel Electric and Magnetic Fields

Abstract: Matter/antimatter (MAM) pair production from the vacuum through intense electric fields has been investigated theoretically for nearly a century. This history is reviewed and proposals of MAM for intra-solar system and interstellar propulsion systems are examined. The quantum mechanical foundation of MAM production was developed by MAM production occurs when the electric field strength is above the critical value at which the fields become non-linear with self-interactions (known as the Schwinger limit).MAM production occurs when the electric field strength is above the critical value at which the fields become non-linear with self-interactions (known as the Schwinger limit). As the energy density of lasers approach the critical strength of 10^16 V/cm, the feasibility and functionality of electron-positron pair production has received growing interest. Current laser intensities are approaching within 1 order of magnitude of the Schwinger limit. Processes for lowering the critical energy density below the Schwinger limit through additional quantum mechanical effects have been explored. One under study at the U. of Connecticut and the U. of Duisburg-Essen is pulsation of inhomogeneous electric fields within a carrier wave. Another is via enhancement of quantum effects by addition of a magnetic field parallel to the electric field. Magnetic field enhancement to quark/anti-quark production through chiral symmetry breaking effects in QCD was considered by J. Preskill in the 1980's. S. Pyo and D. Page showed in 2007 that parallel magnetic fields enhance electron/positron production via an analogous QED effect. MAM production as a highly efficient fuel source for intra solar system and interstellar propulsion was proposed by D. Crow in 1983. The viability of this method of propulsion will be studied, especially from the parallel electric and magnetic field approach.

Pub.: 13 Sep '16, Pinned: 21 Apr '17

Observation of the 1S-2S transition in trapped antihydrogen.

Abstract: The spectrum of the hydrogen atom has played a central part in fundamental physics in the past 200 years. Historical examples of its significance include the wavelength measurements of absorption lines in the solar spectrum by Fraunhofer, the identification of transition lines by Balmer, Lyman et al., the empirical description of allowed wavelengths by Rydberg, the quantum model of Bohr, the capability of quantum electrodynamics to precisely predict transition frequencies, and modern measurements of the 1S-2S transition by Hänsch(1) to a precision of a few parts in 10(15). Recently, we have achieved the technological advances to allow us to focus on antihydrogen-the antimatter equivalent of hydrogen(2,3,4). The Standard Model predicts that there should have been equal amounts of matter and antimatter in the primordial Universe after the Big Bang, but today's Universe is observed to consist almost entirely of ordinary matter. This motivates physicists to carefully study antimatter, to see if there is a small asymmetry in the laws of physics that govern the two types of matter. In particular, the CPT (charge conjugation, parity reversal, time reversal) Theorem, a cornerstone of the Standard Model, requires that hydrogen and antihydrogen have the same spectrum. Here we report the observation of the 1S-2S transition in magnetically trapped atoms of antihydrogen in the ALPHA-2 apparatus at CERN. We determine that the frequency of the transition, driven by two photons from a laser at 243 nm, is consistent with that expected for hydrogen in the same environment. This laser excitation of a quantum state of an atom of antimatter represents a highly precise measurement performed on an anti-atom. Our result is consistent with CPT invariance at a relative precision of ~2 × 10(-10).

Pub.: 23 Dec '16, Pinned: 21 Apr '17

Neutrino Mass, Leptogenesis and FIMP Dark Matter in a ${\rm U}(1)_{\rm B-L}$ Model

Abstract: The Standard Model (SM) is unable to explain the origin of tiny neutrino masses, dark matter and matter-antimatter asymmetry of the Universe. In this work, we propose a model that can address all these three observations. Our model extends the SM by a local U$(1)_{\rm B-L}$ gauge symmetry, three right-handed (RH) neutrinos to cancel the gauge anomalies, and two scalars, one of which is charged under U$(1)_{\rm B-L}$ while the other is not. The U$(1)_{\rm B-L}$ symmetry is broken spontaneously when the scalar charged under this gauge group picks up a VEV. This results in making both the additional neutral gauge boson as well as the RH neutrinos massive. The light neutrino masses can be generated easily in this model by the Type I seesaw mechanism. Here we consider phenomenologically interesting TeV scale RH Majorana neutrinos and two of them are nearly degenerate, which allows us to generate a lepton asymmetry via resonant leptogenesis. This lepton asymmetry is converted to the baryon asymmetry through sphaleron processes allowing us to correctly reproduce the observed matter-antimatter asymmetry of the Universe. Finally, the second new scalar which is neutral under the SM as well as U$(1)_{\rm B-L}$ gauge group is made stable by adding a $\mathbb{Z}_2$ symmetry. We show that this particle can easily play the role of the dark matter of the Universe. Null results from direct detection experiments force us to think about the beyond thermal WIMP scenario. Thus, we consider our dark matter candidate to be very feebly interacting with the cosmic soup and hence it is called the FIMP which never attains thermal equilibrium. We study in detail the production of the dark matter via freeze-in mechanism before and after electroweak symmetry breaking and use the observed dark matter relic abundance to put constraints on relevant model parameters.

Pub.: 03 Apr '17, Pinned: 21 Apr '17

Background-free search for neutrinoless double-β decay of 76Ge with GERDA

Abstract: Many extensions of the Standard Model of particle physics explain the dominance of matter over antimatter in our Universe by neutrinos being their own antiparticles. This would imply the existence of neutrinoless double-β decay, which is an extremely rare lepton-number-violating radioactive decay process whose detection requires the utmost background suppression. Among the programmes that aim to detect this decay, the GERDA Collaboration is searching for neutrinoless double-β decay of 76Ge by operating bare detectors, made of germanium with an enriched 76Ge fraction, in liquid argon. After having completed Phase I of data taking, we have recently launched Phase II. Here we report that in GERDA Phase II we have achieved a background level of approximately 10−3 counts keV−1 kg−1 yr−1. This implies that the experiment is background-free, even when increasing the exposure up to design level. This is achieved by use of an active veto system, superior germanium detector energy resolution and improved background recognition of our new detectors. No signal of neutrinoless double-β decay was found when Phase I and Phase II data were combined, and we deduce a lower-limit half-life of 5.3 × 1025 years at the 90 per cent confidence level. Our half-life sensitivity of 4.0 × 1025 years is competitive with the best experiments that use a substantially larger isotope mass. The potential of an essentially background-free search for neutrinoless double-β decay will facilitate a larger germanium experiment with sensitivity levels that will bring us closer to clarifying whether neutrinos are their own antiparticles.

Pub.: 05 Apr '17, Pinned: 21 Apr '17