119305743
Neutrino flavor ratios as diagnostic of solar WIMP annihilation
We consider the neutrino (and antineutrino) flavors arriving at the Earth for neutrinos produced in the annihilation of weakly interacting massive particles (WIMPs) in the sun's core. Solar-matter effects on the flavor propagation of the resulting ≥ GeV neutrinos are studied analytically within a density-matrix formalism. Matter effects, including mass-state level crossings, influence the flavor fluxes considerably. The exposition herein is somewhat pedagogical, in that it starts with adiabatic evolution of single flavors from the sun's center, with θ 13 set to zero, and progresses to fully realistic processing of the flavor ratios expected in WIMP decay, from the sun's core to the Earth. In the fully realistic calculation, nonadiabatic level crossing is included, as are possible nonzero values for θ 13 and the CP-violating phase δ. Because of resonance enhancement in matter, nonzero values of θ 13 even smaller than a degree can noticeably affect flavor propagation. Both normal and inverted neutrino-mass hierarchies are considered. Our main conclusion is that measuring flavor ratios (in addition to energy spectra) of ≥ GeV solar neutrinos can provide discrimination between WIMP models. In particular, we demonstrate the flavor differences at the Earth for neutrinos from the two main classes of WIMP final states, namely W + W ― and 95% bb + 5% τ + τ ― . Conversely, if WIMP properties were to be learned from production in future accelerators, then the flavor ratios of ≥ GeV solar neutrinos might be useful for inferring θ 13 and the mass hierarchy. From the full calculations, we find (and prove) some general features: a flavor-democratic flux produced at the sun's core arrives at the Earth still flavor democratic; for maximal θ 32 but arbitrary θ 21 and θ 13 , the replacement δ → π ― δ leaves the ν e flavor spectra unaltered but interchanges ν μ and ν τ spectra at the Earth; and, only for neutrinos in the inverted hierarchy and antineutrinos in the normal hierarchy is the dependence on the mixing phase δ not suppressed to order δm 2 21 /δm 2 32 .
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.
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.
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.
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.
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)
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
2156470
Performance reach of the "phase 1" LHC collimation system
State-of-the-art tracking tools have been developed for detailed LHC collimation and beam loss studies. This includes full chromatic treatment of both beam lines and error models. This paper reviews the main results on the performance reach of the multi-stage LHC collimation system that is being installed in the LHC. Limitations on the allowed proton loss rates and the stored intensity can be derived from the comparison of local losses with estimated quench limits for the superconducting magnets. The origins of the cleaning-related performance limitations are presented and possible improvements are discussed.
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.
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.
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