3,334 research outputs found

### Are Neutrinos Their Own Antiparticles?

We explain the relationship between Majorana neutrinos, which are their own
antiparticles, and Majorana neutrino masses. We point out that Majorana masses
would make the neutrinos very distinctive particles, and explain why many
theorists strongly suspect that neutrinos do have Majorana masses. The
promising approach to confirming this suspicion is to seek neutrinoless double
beta decay. We introduce a toy model that illustrates why this decay requires
nonzero neutrino masses, even when there are both right-handed and left-handed
weak currents.Comment: 8 pages, pd

### Additional time-dependent phase in the flavor-conversion formulas

In the framework of intermediate wave-packets for treating flavor
oscillations, we quantify the modifications which appear when we assume a
strictly peaked momentum distribution and consider the second-order corrections
in a power series expansion of the energy. By following a sequence of analytic
approximations, we point out that an extra time-dependent phase is merely the
residue of second-order corrections. Such phase effects are usually ignored in
the relativistic wave-packet treatment, but they do not vanish
non-relativistically and can introduce some small modifications to the
oscillation pattern even in the ultra-relativistic limit.Comment: 9 pages, 3 figure

### Flavor and chiral oscillations with Dirac wave packets

We report about recent results on Dirac wave packets in the treatment of
neutrino flavor oscillation where the initial localization of a spinor state
implies an interference between positive and negative energy components of
mass-eigenstate wave packets. A satisfactory description of fermionic particles
requires the use of the Dirac equation as evolution equation for the
mass-eigenstates. In this context, a new flavor conversion formula can be
obtained when the effects of chiral oscillation are taken into account. Our
study leads to the conclusion that the fermionic nature of the particles, where
chiral oscillations and the interference between positive and negative
frequency components of mass-eigenstate wave packets are implicitly assumed,
modifies the standard oscillation probability. Nevertheless, for
ultra-relativistic particles and sharply peaked momentum distributions, we can
analytically demonstrate that these modifications introduce correction factors
proportional to (m12/p0) square which are practically un-detectable by any
experimental analysisComment: 16 pages, 2 figure

### Exceptional Performance in Competitive Ski Mountaineering: An Inertial Sensor Case Study.

Organized biannually in the Swiss Alps since 1984, the "Patrouille des Glaciers" (PDG) is one of the most challenging long-distance ski mountaineering (skimo) team competitions in the world. The race begins in Zermatt (1,616 m) and ends in Verbier (1,520 m), covering a total distance of 53 km with a cumulated 4,386 m of ascent and 4,482 m of descent. About 4,800 athletes take part in this competition, in teams of three. We hereby present the performance analysis of the uphill parts of this race of a member (#1) of the winning team in 2018, setting a new race record at 5 h and 35 min, in comparison with two amateur athletes. The athletes were equipped with the Global Navigation Satellite System (GNSS) antenna, a heart rate monitor, and a dedicated multisensor inertial measurement unit (IMU) attached to a ski, which recorded spatial-temporal gait parameters and transition events. The athletes' GNSS and heart rate data were synchronized with the IMU data. Athlete #1 had a baseline VO <sub>2</sub> max of 80 ml/min/kg, a maximum heart rate of 205 bpm, weighed 69 kg, and had a body mass index (BMI) of 21.3 kg/m <sup>2</sup> . During the race, he carried 6 kg of gear and kept his heart rate constant around 85% of max. Spatiotemporal parameters analysis highlighted his ability to sustain higher power, higher pace, and, thus, higher vertical velocity than the other athletes. He made longer steps by gliding longer at each step and performed less kick turns in a shorter time. He spent only a cumulative 5 min and 30 s during skins on and off transitions. Skimo performance, thus, requires a high aerobic power of which a high fraction can be maintained for a prolonged time. Our results further confirm earlier observations that speed of ascent during endurance skimo competitions is a function of body weight and race gear and vertical energy cost of locomotion, with the latter function of climbing gradient. It is also the first study to provide some reference benchmarks for spatiotemporal parameters of elite and amateur skimo athletes during climbing using real-world data

### How can we test seesaw experimentally?

The seesaw mechanism for the small neutrino mass has been a popular paradigm,
yet it has been believed that there is no way to test it experimentally. We
present a conceivable outcome from future experiments that would convince us of
the seesaw mechanism. It would involve a variety of data from LHC, ILC,
cosmology, underground, and low-energy flavor violation experiments to
establish the case.Comment: 5 pages, 4 figure

### Gravitational Lensing of the SDSS High-Redshift Quasars

We predict the effects of gravitational lensing on the color-selected
flux-limited samples of z~4.3 and z>5.8 quasars, recently published by the
Sloan Digital Sky Survey (SDSS). Our main findings are: (i) The lensing
probability should be 1-2 orders of magnitude higher than for conventional
surveys. The expected fraction of multiply-imaged quasars is highly sensitive
to redshift and the uncertain slope of the bright end of the luminosity
function, beta_h. For beta_h=2.58 (3.43) we find that at z~4.3 and i*<20.0 the
fraction is ~4% (13%) while at z~6 and z*<20.2 the fraction is ~7% (30%). (ii)
The distribution of magnifications is heavily skewed; sources having the
redshift and luminosity of the SDSS z>5.8 quasars acquire median magnifications
of med(mu_obs)~1.1-1.3 and mean magnifications of ~5-50. Estimates of
the quasar luminosity density at high redshift must therefore filter out
gravitationally-lensed sources. (iii) The flux in the Gunn-Peterson trough of
the highest redshift (z=6.28) quasar is known to be f_lambda<3 10^-19
erg/sec/cm^2/Angstrom. Should this quasar be multiply imaged, we estimate a 40%
chance that light from the lens galaxy would have contaminated the same part of
the quasar spectrum with a higher flux. Hence, spectroscopic studies of the
epoch of reionization need to account for the possibility that a lens galaxy,
which boosts the quasar flux, also contaminates the Gunn-Peterson trough. (iv)
Microlensing by stars should result in ~1/3 of multiply imaged quasars in the
z>5.8 catalog varying by more than 0.5 magnitudes over the next decade. The
median equivalent width would be lowered by ~20% with respect to the intrinsic
value due to differential magnification of the continuum and emission-line
regions.Comment: 27 pages, 10 figures. Expansion on the discussion in
astro-ph/0203116. Replaced with version accepted for publication in Ap

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