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}
118699692
Electroweak bremsstrahlung in dark matter annihilation
A conservative upper bound on the total dark matter annihilation rate can be obtained by constraining the appearance rate of the annihilation products which are hardest to detect. The production of neutrinos, via the process {chi}{chi}{yields}{nu}{nu}, has thus been used to set a strong general bound on the dark matter annihilation rate. However, standard model radiative corrections to this process will inevitably produce photons which may be easier to detect. We present an explicit calculation of the branching ratios for the electroweak bremsstrahlung processes {chi}{chi}{yields}{nu}{nu}Z and {chi}{chi}{yields}{nu}eW. These modes inevitably lead to electromagnetic showers and further constraints on the dark matter annihilation cross section. In addition to annihilation, our calculations are also applicable to the case of dark matter decay.
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)
122879516
Analytic Expressions for the Cascade Decay $W \to$ Heavy Fermion $\to$ Light Fermion, and a Signature Study of the Process $W \to$ Heavy Lepton $\to$ Electron
A covariant formalism for single-particle inclusive decay of the W and Z bosons is established. It is then applied to the cascade decay of the W to a light fermion via an intermediate fermion with an arbitrary mix of V and A coupling. Exact analytic expressions are presented for heavy-fermion production in W decay, for heavy-fermion decay, and for the complete decay chain. As a particular illustration of the cascade results, the electron signatures for W decay through the tau and through a new heavy lepton are studied in detail in the W rest frame and contrasted.
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.
120773060
QCD predictions for jet transverse momentum in leptoproduction
Abstract QCD predictions for distributions in the jet variable Σ T  [ Σ had p T |] 2 are calculated for incident ν, ν and μ. Estimates of the nonperturbative background are constructed.
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.
55454565
THE FINAL COLLIMATION SYSTEM FOR THE LHC
The LHC collimation system has been re-designed over in order to address the unprecedented challenges that are faced with the 360 MJ beams at 7 TeV. The layout of the LHC has now been frozen and a final approach for collimation and cleaning has been adopted. In total 132 pure collimator locations have been reserved in the two LHC rings and can be installed in a phased approach. Up to 88 collimators of five different types will be available for initial beam operation. The system has been fully optimized for avoiding beam-induced quenches of superconducting magnets and for sufficient survival of beamline components against radioactive dose. The phased approach for LHC collimation is described, the various collimators and their functionalities are explained, and the expected system performance is summarized. Large Hadron Collider Project
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.
17929707
Evaluation of Beam Losses And Energy Deposition for a Possible Phase II Design for LHC Collimation
The Large Hadron Collider (LHC) beams are designed to have high stability and to be stored for many hours. The nominal beam intensity lifetime is expected to be of the order of 20h. The Phase II collimation system has to be able to handle particle losses in stable physics conditions at 7 TeV in order to avoid beam aborts and to allow correction of parameters and restoration to nominal conditions. Monte Carlo simulations are needed in order to evaluate the behavior of metallic high-Z collimators during operation scenarios using a realistic distribution of losses, which is a mix of the three limiting halo cases. Moreover, the consequences in the IR7 insertion of the worst (case) abnormal beam loss are evaluated. The case refers to a spontaneous trigger of the horizontal extraction kicker at top energy, when Phase II collimators are used. These studies are an important input for engineering design of the collimation Phase II system and for the evaluation of their effect on adjacent components. The goal is to build collimators that can survive the expected conditions during LHC stable physics runs, in order to avoid quenches of the SC magnets and to protect other LHC equipments.
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.