Neutrinos

A neutrino (njuːˈtriːnoʊ ; denoted by the Greek letter ν) is a fermion (an elementary particle with spin of 1 /2) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small (-ino) that it was long thought to be zero. The rest mass of the neutrino is much smaller than that of the other known elementary particles excluding massless particles. The weak force has a very short range, the gravitational interaction is extremely weak due to the very small mass of the neutrino, and neutrinos do not participate in the strong interaction. Thus, neutrinos typically pass through normal matter unimpeded and undetected. Weak interactions create neutrinos in one of three leptonic flavors: electron neutrino, _Electron neutrino muon neutrino, _Muon neutrino tau neutrino, _Tau neutrino Each flavor is associated with the correspondingly named charged lepton. Although neutrinos were long believed to be massless, it is now known that there are three discrete neutrino masses with different tiny values (the smallest of which could even be zero), but the three masses do not uniquely correspond to the three flavors: A neutrino created with a specific flavor is a specific mixture of all three mass states (a quantum superposition). Similar to some other neutral particles, neutrinos oscillate between different flavors in flight as a consequence. For example, an electron neutrino produced in a beta decay reaction may interact in a distant detector as a muon or tau neutrino. The three mass values are not yet known as of 2022, but laboratory experiments and cosmological observations have determined the differences of their squares, an upper limit on their sum (< 2.14e-37kg), and an upper limit on the mass of the electron neutrino. For each neutrino, there also exists a corresponding antiparticle, called an antineutrino, which also has spin of 1 /2 and no electric charge.

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Neutrino oscillation is a quantum mechanical phenomenon in which a neutrino created with a specific lepton family number ("lepton flavor": electron, muon, or tau) can later be measured to have a different lepton family number. The probability of measuring a particular flavor for a neutrino varies between three known states, as it propagates through space. First predicted by Bruno Pontecorvo in 1957, neutrino oscillation has since been observed by a multitude of experiments in several different contexts.

Air showers are extensive cascades of subatomic particles and ionized nuclei, produced in the atmosphere when a primary cosmic ray enters the atmosphere. When a particle of the cosmic radiation, which could be a proton, a nucleus, an electron, a photon, or (rarely) a positron, interacts with the nucleus of a molecule in the atmosphere, it produces a vast number of secondary particles, which make up the shower.

The D mesons are the lightest particle containing charm quarks. They are often studied to gain knowledge on the weak interaction. The strange D mesons (Ds) were called "F mesons" prior to 1986. The D mesons were discovered in 1976 by the Mark I detector at the Stanford Linear Accelerator Center. Since the D mesons are the lightest mesons containing a single charm quark (or antiquark), they must change the charm (anti)quark into an (anti)quark of another type to decay.

High-Speed Wireline Link Design

Hazar Yüksel

High-speed serial links are a crucial application of semiconductor technology and have been the enabler of the scaling of computing systems. The increasing data-rate requirements of these links have only been partially satisfied by advancements in process technologies. Implementing serial links operating at a data rate of more than 25 Gb/s thus requires constantly inventing smarter algorithms, architectures, power-management techniques, and new standards. The Viterbi algorithm (VA), an attractive solution for symbol detection in the presence of intersymbol interference (ISI) and noise, minimizes the error probability in detecting the whole symbol sequence, instead of a single symbol as in decision-feedback equalization. The bit-error-rate (BER) performance of the VA is thus better than that of symbol-by-symbol detectors because the VA does not cancel the ISI, but rather uses the information embedded therein to maximize the reliability of its decisions. However, implementing a maximum-likelihood sequence detector (MLSD) realizing the VA may be prohibitive because design specifications regarding area, latency, power consumption, and speed may not be satisfied concurrently. Suboptimal solutions, such as feed-forward and decision-feedback equalizers (DFEs), may therefore be chosen instead of MLSDs due to their lower implementation complexity. A reduced-state sequence detector (RSSD) reduces the implementation complexity of the MLSD with negligible performance degradation by exploiting set-partitioning principles and embedded per-survivor decision feedback. A sliding-block or systolic-array Viterbi detector (VD) breaks the speed bottleneck in sequence-detector implementations by parallelizing the operation of the VA. In this thesis, we implement a 56-Gb/s four-level pulse-amplitude-modulation (4-PAM) DFE to demonstrate the feasibility of a multi-level analog-to-digital-converter (ADC)-based symbol-by-symbol detector in terms of achievable area, BER, energy-efficiency, latency, and speed figures comparable to those of analog solutions. Furthermore, to improve the BER figures, we implement a 25.6-Gb/s 4-PAM reduced-state sliding-block VD to demonstrate the feasibility of a multi-level sequence detector in terms of achievable area, energy-efficiency, latency, and speed figures comparable to those of symbol-by-symbol detectors. Moreover, we develop a sliding-block VA with optimized unequal synchronization and survivor path memory lengths to reduce its implementation complexity, latency, and power consumption. An increase in speed is thereby achieved at the same implementation complexity, BER, latency, and power consumption. We then develop a novel VD with embedded per-survivor decision feedback, whose longest path contains only one adder, to increase its speed significantly. Next, we propose a concatenated-coding scheme using an outer Reed—Solomon code and a four-dimensional (4-D) 5-PAM inner trellis-coded-modulation (TCM) scheme to achieve signal-to-noise-ratio gains without bandwidth expansion. Finally, we implement a 70-Gb/s 4-D 5-PAM systolic-array TCM decoder with eight states, which includes an inverse Tomlinson—Harashima precoder, to demonstrate the feasibility of a multi-level ADC-based sequence decoder in terms of achievable speed figures comparable to those of sequence detectors.

EPFL2017

Baryogenesis, Dark Matter and Neutrino Oscillations from Right-Handed Neutrinos

Laurent Canetti

Our knowledge of our universe is deeply related to our understanding of physics at the sub- atomic scale. Indeed, at its early stage, our universe was so hot and so dense that the only relevant interactions were those between fundamental particles. Therefore, to improve our comprehension of the phenomena that take place over very large scales, we should improve our understanding of the physics at extremely small ones. The so-called Standard Model of particle physics (SM) provides us with a description of these fundamental particles and their interactions. Despite its enormous success, this model fails to explain several experimental evidences. In this thesis, we focus on the following three questions that are not answered by the SM. What is the so-called dark matter that is present in every galaxy? Why is our present universe made of matter with almost no trace of anti-matter? Finally, why can a neutrino of one family transform into a neutrino of another family? In this thesis, we show that the simple addition of three new neutrinos to the Standard Model allows us to answer the three questions above. The model that realizes this scenario is known as Neutrino Minimal Standard Model (νMSM). In this work, we give a comprehensive summary of all known constraints in the νMSM. We present the first complete quantitative study of the parameter space of the model where no physics beyond the νMSM is needed to simultaneously explain the three phenomena cited above. Moreover, these new particles can be looked for using current day experimental techniques and our results provide a guideline for future experimental searches.

EPFL2013

Improving the neutrino mass hierarchy identification with inelasticity measurement in PINGU and ORCA

Mathieu Ribordy

Multimegaton scale in under-ice and underwater detectors of atmospheric neutrinos with a few GeV energy threshold (PINGU, ORCA) open up new possibilities in the determination of neutrino properties, and in particular the neutrino mass hierarchy. With a dense array of optical modules it will be possible to determine the inelasticity, y, of the charged current nu(mu) events in addition to the neutrino energy E-nu and the muon zenith angle theta(mu). The discovery potential of the detectors will substantially increase with the measurement of y. It will enable (i) a partial separation of the neutrino and antineutrino signals, (ii) a better reconstruction of the neutrino direction, (iii) the reduction of the neutrino parameters degeneracy, (iv) a better control of systematic uncertainties, and (v) a better identification of the nu(mu) events. It will improve the sensitivity to the CP-violation phase. The three-dimensional (E-nu, theta(mu), y), nu(mu) oscillograms with the kinematical as well as the experimental smearing are computed. We present the asymmetry distributions in the E-nu - theta(mu) plane for different intervals of y and study their properties. We show that the inelasticity information reduces the effect of degeneracy of parameters by 30%. With the inelasticity, the total significance of establishing mass hierarchy may increase by (20-50)%, thus effectively increasing the volume of the detector by a factor of 1.5-2.

Amer Physical Soc2013

Neutrinos and Neutrino Oscillations PHYS-416: Particle physics II

Explores neutrino detection, oscillations, PMNS matrix, CP symmetries, mass hierarchies, and experimental methods.

Fermion Masses and Mixings

Explores fermion masses, chiral nature, and Yukawa couplings.

Solar Neutrinos: Experiments and Spectra PHYS-400: Selected topics in nuclear and particle physics

Explores solar neutrino detection, energy spectra, cosmic neutrinos, atmospheric neutrinos, and high-energy astroparticles.

Standard Model

The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetic, weak and strong interactions – excluding gravity) in the universe and classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists worldwide, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks.

Topics in nuclear physics

Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies the atom as a whole, including its electrons. Discoveries in nuclear physics have led to applications in many fields. This includes nuclear power, nuclear weapons, nuclear medicine and magnetic resonance imaging, industrial and agricultural isotopes, ion implantation in materials engineering, and radiocarbon dating in geology and archaeology.

Stellar astronomy

A star is an astronomical object comprising a luminous spheroid of plasma held together by self-gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations.