10338502
Explaining LSND using extra‐dimensional shortcuts
We explore the possibility to explain the LSND [1] result in the context of extra‐dimensional theories. If sterile neutrinos take shortcuts through extra dimensions, this results in altered neutrino dispersion relations. Active‐sterile neutrino oscillations thus are modified and new types of resonances occur.
2745888
Bounds on relic neutrino masses in the Z-burst model
Neutrinos from far-away sources annihilating at the Z resonance on relic neutrinos may give origin to the extreme-energy cosmic rays (EECR). If “Z-bursts” are responsible for the EECR events, then we show that the non-observation of cosmic ray events at energies above 2 ×10 20 eV by the AGASA Collaboration implies a lower bound ∼ 0.3 eV on the relic neutrino mass. Since this mass exceeds the mass-squared differences inferred from oscillation physics, the bound in fact applies to all three neutrino masses. Together with the upper bound provided by comparisons of the CMB anisotropy with largescale structure, this bound leaves only a small interval for neutrino masses around 0.3 eV, if Z-bursts are to explain the existing EECR events.
119170988
Flavor Sensitivity to $\theta_{13}$ and the Mass Hierarchy for neutrinos from Solar WIMP Annihilation
The effect of the higher-energy 2nd resonance and the associated adiabatic-to-nonadiabatic transition on neutrino propagation in solar matter is presented. For WIMP-annihilation neutrinos injected with energies in the "sweet region" between 300 MeV and 10 GeV at the Sun's center, a significant and revealing dependence on the neutrino mass hierarchy and the mixing angle theta_13 down to 0.5 degrees is found in the flavor ratios arriving at Earth. In addition, the amplification of flavor ratios in the sweet region allows a better discrimination among possible annihilation modes of the solar dark matter. Under mild assumptions on WIMP properties, it is estimated that 200 neutrino events in the sweet region would be required for inferences of theta_13, the mass hierarchy, and the dominant WIMP annihilation mode. Future large-volume, low-energy neutrino detectors are likely needed if the measurement is to be made.
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)
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.
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.
107656092
Results of the studies on energy deposition in IR6 superconducting magnets from continuous beam loss on the TCDQ system
SummaryA single sided mobile graphite diluter block TCDQ, in combination with a two-sidedsecondary collimator TCS and an iron shield TCDQM, will be installed in front of thesuperconducting quadrupole Q4 magnets in IR6, in order to protect it and other downstreamLHC machine elements from destruction in the event of a beam dump that is not synchronisedwith the abort gap. The TCDQ will be positioned close to the beam, and will intercept theparticles from the secondary halo during low beam lifetime. Previous studies [1-4] haveshown that the energy deposited in the Q4 magnet coils can be close to or above the quenchlimit. In this note the results of the latest FLUKA energy deposition simulations for Beam 2are described, including an upgrade possibility for the TCDQ system with an additionalshielding device. The results are discussed in the context of the expected performance levelsfor the different phases of LHC operation. 1. Introduction The LHC beam dumping system includes a single sided mobile diluter block TCDQ [5],consisting of two blocks namely TCDQA and TCDQB, in combination with a secondarycollimator TCS and an iron shield TCDQM [6], installed in front of the superconductingquadrupole Q4 magnet in IR6, in order to protect it and other LHC machine elements fromdestruction in the event of a beam dump that is not synchronised with the abort gap [7]. TheTCDQ element should protect the LHC from damage from swept bunches under all conditions,in particular the arc aperture at 450 GeV, the low-beta triplet aperture and the tungsten tertiarycollimators at 7 TeV. The TCDQ must also prevent quenches of Q4, arising from spuriousparticles in the abort gap during a normal beam dump, and from particles lost from the beamhalo during regular operation.The two-jawed TCS collimator is located immediately after the TCDQ to precisely definethe horizontal beam position and to achieve higher precision collimation of secondary haloparticles from both sides. The TCS will receive a potentially high load from the secondary haloin the event of low beam lifetime. The nominal settings of the TCDQ and TCS are assumed tobe 8 and 7 s
55312556
Performance test of a micro-pattern stereo detector with two gas electron multipliers
Abstract We report on the performance of a large micro-pattern detector with two gas electron multiplier foils and a two-layer readout structure at ground potential. The two readout layers each have a 406 μm pitch and cross at an effective angle of 6.7°. This structure allows for two orthogonal coordinates to be determined. Using a muon beam at CERN together with a silicon tracking system, the position resolutions of the two coordinates are measured to be 50 μm and 1 mm respectively (1 standard deviation). The muon detection efficiency for the two-dimensional space points reaches 96%. The detector was found to be well operational over a wide range in the settings of the different electrical fields.
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.
17145107
APERTURES IN THE LHC BEAM DUMP SYSTEM AND BEAM LOSSES DURING BEAM ABORT
The LHC beam dumping system (LBDS) is used to dispose accelerated protons and ions in a wide energy range from 450 GeV up to 7 TeV. An abort gap of 3 μs is foreseen to avoid sweeping particles through the LHC ring aperture. This paper gives a brief overview of the critical apertures in the extraction region and the two beam dump lines. MAD-X tracking studies have been made to investigate the impact of particles swept through the aperture due to extraction kicker failures or the presence of particles within the abort gap. The issue of failures during beam abort is a major concern for machine protection as well as a critical factor for safe operation of the experiments and their detectors.
55572949
CRITICAL HALO LOSS LOCATIONS IN THE LHC
Results of simulations with all movable elements of the LHC collimation system [1] are discussed for various operation modes. Compared to previous results, the placing of additional collimators reduced the beam losses by a factor 10 in the ideal machine case, i.e. nominal collimators settings for both 450 GeV and 7 TeV beam energies. First results for Beam 2 are also reviewed. The sensitivity of the system to free orbit oscillations is addressed. These results show that it is sufficient to use a limited number of beam loss monitors (BLMs) for the setup and optimization of the LHC Collimation System.