119254616
Neutrino Oscillations from Cosmic Sources: A Nu Window to Cosmology
Neutrino astrophysics promises a wealth of information about neutrinos and the history of the universe through which they have traveled. In this letter, we extend the standard neutrino qoscillation discussion to neutrinos propagating through expanding curved space. This extension introduces a new cosmological parameter in the oscillation phase. The new parameter ℐ records cosmic history in much the same manner as the redshift variable z or the apparent luminosity distance DL. Measuring ℐ through neutrino oscillations may help to determine cosmological parameters and distinguish between different cosmologies.
14853773
Clustering in highest energy cosmic rays: physics or statistics?
Directional clustering can be expected in cosmic ray observations due to purely statistical fluctuations for sources distributed randomly in the sky. We develop an analytic approach to estimate the probability of random cluster configurations, and use these results to study the strong potential of the HiRes, Auger, Telescope Array and EUSO/OWL/AirWatch facilities for deciding whether any observed clustering is most likely due to non-random sources.
121147596
Dimuon production by neutrinos: Test of weak-current models
We compare predictions of weak-current models for ..mu../sup +/..mu../sup -/ production initiated by ..nu.. and anti ..nu.. with experimental x, y, p, and v distributions of the muon associated with the incident neutrino. These distributions indicate that ..nu..N dimuon production occurs dominantly off valence quarks, with a y dependence that is somewhat suggestive of (1 - y)/sup 2/, while anti ..nu..N production occurs from sea quarks. Nevertheless, the original charm model provides a viable explanation within the uncertainties of present data. An improved description of the ..nu..N dimuon distributions is obtained with a V + A charm-changing current. The dimuon data do not exhibit the characteristics expected from the production of the b-type quark of vectorlike theories. A vector-meson-dominance interpretation does not predict satisfactory x dependences. (AIP)
17703221
Lower energy consequences of an anomalous high-energy neutrino cross section
A new strong interaction has been postulated for neutrinos above {approximately}10{sup 19}eV to explain the production of highest-energy cosmic-ray events. We derive a dispersion relation relating the hypothesized high-energy cross section to the lower-energy neutrino-nucleon elastic amplitude. Remarkably, we find that the real forward amplitude becomes anomalous seven orders of magnitude lower in energy than does the total cross section. We discuss possible measurable consequences of this early onset of new neutrino physics and conclude that a significantly enhanced elastic {nu}N scattering rate may occur for the neutrino beams available at Fermilab and CERN. {copyright} {ital 1999} {ital The American Physical Society}
117398144
Oscillation and Mixing Among the Three Neutrino Flavors
With the educated, interested non-specialist as the target audience, we overview what is known and not known about contemporary neutrino physics. Theory tells us that neutrinos are the second-most common particle in the Universe, behind only the quanta of radiation called photons. Almost a trillion neutrinos per second enter each human eyeball, and yet we do not see them; these neutrinos, in roughly equal numbers, are emanations from our Sun and relics of the hot "big bang" era of the early Universe. Much of what we know about neutrinos, and hope to learn in the future, is derived from a unique feature of neutrinos -- "oscillation" among neutrino "flavor" types. An initial neutrino flavor will in general oscillate into another flavor as the neutrino propagates in space and time. Oscillations are a quantum mechanical phenomenon. One of the wonders of neutrinos is that their quantum mechanics may be observed over large distances, even astronomically large. We begin this article with neutrino phenomenology in terms of masses and mixing angles, including the matter-antimatter asymmetric "phase" that appears with three neutrino types. Next we venture into neutrino oscillations. We conclude with a discussion of model-building for the neutrino masses and mixings. Throughout this article, attention is devoted to the 2012 result that the "small" neutrino mixing angle is not so small, after all.
118630505
Baseline-dependent neutrino oscillations with extra-dimensional shortcuts
In extra-dimensional scenarios oscillations between active and sterile neutrinos can be governed by a new resonance in the oscillation amplitude. This resonance results when cancellation occurs between two phase differences, the usual kinematic one coming from the neutrino mass-squared difference, and a geometric one coming from the difference in travel times of the sterile neutrino through the bulk relative to the active neutrino confined to the brane. In this work we introduce a specific metric for the brane-bulk system, from which we explicitly derive extra-dimensional geodesics for the sterile neutrino, and ultimately the oscillation probability of the active-sterile two-state system. We find that for an asymmetrically warped metric, the resonance condition involves both the neutrino energy E and the travel distance L on the brane. In other words, the resonant energy may be viewed as baseline dependent. We show that to a good approximation, the resonance condition is not on E or on L, but rather on the product LE. The model is rich in implications, including the possibility of multiple solutions to the resonance condition, with ramifications for existing data sets, e.g., LSND and MiniBooNE. Some phenomenology with these brane-bulk resonances is discussed.
32656642
Beam loss response measurements with a LHC prototype collimator in the SPS
Beam tests with a large hadron collider (LHC) prototype collimator were performed at the super proton synchrotron (SPS) in autumn 2006. Applying a new collimator control system many new beam measurements were performed. This contribution presents results on collimator- induced beam loss measurements and their applications to beam-based alignment of collimators and measurements of the beam size and position. Interesting features of the recorded beam loss signals are illustrated and possible impacts for LHC operation are discussed.
73532792
BEAM HALO ON THE LHC TCDQ DILUTER SYSTEM AND THERMAL LOAD ON THE DOWNSTREAM SUPERCONDUCTING MAGNETS
The moveable single-jawed graphite TCDQ diluter must be positioned very close to the circulating LHC beam in order to prevent damage to downstream components in the event of an unsynchronised beam abort. A two-jawed graphite TCS.IR6 collimator forms part of the TCDQ system. The requirement to place the jaws close to the beam means that the system can intercept a substantial beam halo load. Initial investigations indicated a worryingly high heat load on the Q4 coils. This paper presents the updated load cases, shielding and simulation geometry, and the results of simulations of the energy deposition in the TCDQ system and in the downstream superconducting Q4 magnet. The implications for the operation of the LHC are discussed.
55348092
Beam dynamics aspects of crab cavities in the CERN Large Hadron Collider
Modern colliders bring into collision a large number of bunches to achieve a high luminosity. The long-range beam-beam effects arising from parasitic encounters at such colliders are mitigated by introducing a crossing angle. Under these conditions, crab cavities (CC) can be used to restore effective head-on collisions and thereby to increase the geometric luminosity. Such crab cavities have been proposed for both linear and circular colliders. The crab cavities are rf cavities operated in a transverse dipole mode, which imparts on the beam particles a transverse kick that varies with the longitudinal position along the bunch. The use of crab cavities in the Large Hadron Collider (LHC) may not only raise the luminosity, but it could also complicate the beam dynamics, e.g., crab cavities might not only cancel synchrobetatron resonances excited by the crossing angle but they could also excite new ones, they could reduce the dynamic aperture for off-momentum particles, they could influence the aperture and orbit, also degrade the collimation cleaning efficiency, and so on. In this paper, we explore the principal feasibility of LHC crab cavities from a beam dynamics point of view. The implications of the crab cavities for the LHC optics, analytical and numerical luminositymore » studies, dynamic aperture, aperture and beta beating, emittance growth, beam-beam tune shift, long-range collisions, and synchrobetatron resonances, crab dispersion, and collimation efficiency will be discussed.« less
119117884
Proceedings of the 2nd Workshop on Flavor Symmetries and Consequences in Accelerators and Cosmology (FLASY12)
Although existing theoretical models generally prefer extremely heavy right-handed neutrinos to generate light neutrino masses via the seesaw mechanism, there are several observed phenomena that point to the existence of both keVand eV-scale sterile neutrinos. We present two A4 flavor symmetry models that can accommodate light sterile neutrinos and remain compatible with neutrino data. Higher order seesaw terms and higher-dimensional operators are studied, and the phenomenological implications of light sterile neutrinos on neutrinoless double beta decay are discussed. 1.
111125409
LHC COLLIMATION EFFICIENCY DURING COMMISSIONING
The design of the LHC collimation system requires understanding and maximizing the ultimate performance with all collimators. However, for the commissioning of the LHC it is important to analyze the collimation efficiency with certain subsets of collimators, with increased collimator gaps and relaxed set-up tolerances. Special studies on halo tracking and energy deposition have been performed in order to address this question. The expected cleaning performance and intensity limits are discussed for various collimation scenarios which might be used during commissioning of the LHC.