17439400
JEM-EUSO Science Objectives
JEM-EUSO, on board of the Japanese Exploration Module of the International Space Station, is being proposed as the first space observatory devoted to UHECR. Its privileged position at 430 km above the Earth surface, combined with a large field of view, innovative optics and a high efficiency focal surface, results in an unprecedented exposure which significantly surpasses that of the largest ground observatories. The large number of events expected above the GZK threshold for photo-pion production by protons will allow the directional identification of individual sources and the determination of their spectra, i.e., doing astronomy and astrophysics through the particle channel. Similar goals can be achieved in the case of light UHECR nuclei. Furthermore, the atmospheric target volume ($\sim 10^{12}$ ton) makes the possibility of neutrino observation a highlight of the mission. Other exploratory objectives include the detection of extreme energy gammas and the study of Galactic magnetic fields as well as global observations of the earth's atmosphere, including clouds, night-glows, plasma discharges, and meteors. In this contribution we will describe the scientific objectives of JEM-EUSO.
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.
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.
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
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.
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
27473327
Transverse impendance of LHC collimators
The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.
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.