Neutrino Oscillation Physics Research Articles

Future possibilities with Fermilab neutrino beams

We will start with a brief overview of neutrino oscillation physics with emphasis on the remaining unanswered questions. Next, after mentioning near future reactor and accelerator experiments searching for a non zero θ13, we will introduce the plans for the next generation of long-baseline accelerator neutrino oscillation experiments. We will focus on experiments utilizing powerful (0.7 − 2.1 MW) Fermilab neutrino beams, either existing or in the design phase.

Neutrino factory for both large and smallθ13

An analysis of the neutrino oscillation physics capability of a low-energy neutrino factory is presented, including a first simulation of the detector efficiency and event energy threshold. The sensitivity of the physics reach to the presence of backgrounds is also studied. We consider a representative baseline of 1480 km, we use muons with 4.12 GeV energy and we exploit a very conservative estimate of the energy resolution of the detector. Our analysis suggests an impressive physics reach for this setup, which can eliminate degenerate solutions, for both large and small values of the mixing angle {theta}{sub 13}, and can determine leptonic CP violation and the neutrino mass hierarchy with extraordinary sensitivity.

Long-Baseline Neutrino Physics in the U.S.

Long-baseline neutrino oscillation physics in the U.S. is centered at the Fermi National Accelerator Laboratory (FNAL), in particular at the Neutrinos at the Main Injector (NuMI) beamline commissioned in 2004-2005. Already, the MINOS experiment has published its first results confirming the disappearance of ν μ 's across a 735 km baseline. The forthcoming NO ν A experiment will search for the transition ν μ → ν e and use this transition to understand the mass heirarchy of neutrinos. These, as well as other conceptual ideas for future experiments using the NuMI beam, will be discussed. The turn-on of the NuMI facility has been positive, with over 310 kW beam power achieved. Plans for increasing the beam intensity once the Main Injector accelerator is fully-dedicated to the neutrino program will be presented.

Recoilless resonant neutrino capture and basics of neutrino oscillations

It is shown that the experiment on recoilless resonant emission and absorption of , proposed recently by Raghavan, could have an important impact on our understanding of the physics of neutrino oscillations.

Physics with a very long neutrino factory baseline

We discuss the neutrino oscillation physics of a very long neutrino factory baseline over a broad range of lengths (between 6000 km and 9000 km), centered on the 'magic baseline' ({approx}7500 km) where correlations with the leptonic CP phase are suppressed by matter effects. Since the magic baseline depends only on the density, we study the impact of matter density profile effects and density uncertainties over this range, and the impact of detector locations off the optimal baseline. We find that the optimal constant density describing the physics over this entire baseline range is about 5% higher than the average matter density. This implies that the magic baseline is significantly shorter than previously inferred. However, while a single detector optimization requires fine-tuning of the (very long) baseline length, its combination with a near detector at a shorter baseline is much less sensitive to the far detector location and to uncertainties in the matter density. In addition, we point out different applications of this baseline which go beyond its excellent correlation and degeneracy resolution potential. We demonstrate that such a long baseline assists in the improvement of the {theta}{sub 13} precision and in the resolution of the octant degeneracy. Moreover, wemore » show that the neutrino data from such a baseline could be used to extract the matter density along the profile up to 0.24% at 1{sigma} for large sin{sup 2}2{theta}{sub 13}, providing a useful discriminator between different geophysical models.« less

Neutrino oscillation physics at an upgraded CNGS with large next generation liquid Argon TPC detectors

The determination of the missing $U_{e3}$ element (magnitude and phase) of the PMNS neutrino mixing matrix is possible via the detection of $\numu\to\nue$ oscillations at a baseline $L$ and energy $E$ given by the atmospheric observations, corresponding to a mass squared difference $E/L \sim \Delta m^2\simeq 2.5\times 10^{-3} eV^2$. While the current optimization of the CNGS beam provides limited sensitivity to this reaction, we discuss in this document the physics potential of an intensity upgraded and energy re-optimized CNGS neutrino beam coupled to an off-axis detector. We show that improvements in sensitivity to $\theta_{13}$ compared to that of T2K and NoVA are possible with a next generation large liquid Argon TPC detector located at an off-axis position (position rather distant from LNGS, possibly at shallow depth). We also address the possibility to discover CP-violation and disentangle the mass hierarchy via matter effects. The considered intensity enhancement of the CERN SPS has strong synergies with the upgrade/replacement of the elements of its injector chain (Linac, PSB, PS) and the refurbishing of its own elements, envisioned for an optimal and/or upgraded LHC luminosity programme.

Optimization of a neutrino factory oscillation experiment

We discuss the optimization of a neutrino factory experiment for neutrino oscillation physics in terms of muon energy, baselines, and oscillation channels (gold, silver, platinum). In addition, we study the impact and requirements for detector technology improvements, and we compare the results to beta beams. We find that the optimized neutrino factory has two baselines, one at about 3000 to 5000km, the other at about 7500km (``magic'' baseline). The threshold and energy resolution of the golden channel detector have the most promising optimization potential. This, in turn, could be used to lower the muon energy from about 50GeV to about 20GeV. Furthermore, the inclusion of electron neutrino appearance with charge identification (platinum channel) could help for large values of \sin^2 2 \theta_{13}. Though tau neutrino appearance with charge identification (silver channel) helps, in principle, to resolve degeneracies for intermediate \sin^2 2 \theta_{13}, we find that alternative strategies may be more feasible in this parameter range. As far as matter density uncertainties are concerned, we demonstrate that their impact can be reduced by the combination of different baselines and channels. Finally, in comparison to beta beams and other alternative technologies, we clearly can establish a superior performance for a neutrino factory in the case \sin^2 2 \theta_{13} < 0.01.

Toward precision study of atmospheric neutrino oscillations

Atmospheric neutrinos have been playing a major role in studying neutrino oscillations. Because of the unique feature of atmospheric neutrinos, future atmospheric neutrino experiments are likely to contribute to precision studies of neutrino oscillations. Possible contribution of future atmospheric neutrino experiments to the neutrino oscillation physics are discussed, including the measurements of θ 13 , the sign of Δ m 23 2 , the determination of octant of θ 23 and possibly the CP phase.

Neutrino oscillation physics with a FNAL proton driver

We discuss the need of a proton driver for the Fermilab neutrino oscillation program, as well as its role in the global context.

Summary of the Neutrino Oscillations Working Group at NuFact05

The Neutrino Oscillation Physics working group at NuFactO5 discussed the status of the present generation of experiments, the plans for the next generation, and the physics performance of the various proposed second generation facilities. The present knowledge of the parameters that govern neutrino oscillations was review and the contributions that the up-coming and future experiments can make was discussed. The status of neutrino phenomenology was also discussed and a number of non-standard theoretical descriptions of the neutrino were presented. This paper summarizes the experimental, phenomenological and theoretical contributions to the working group and the conclusions of the discussions amongst the participants.

Describing Oscillations of High Energy Neutrinos in Matter Precisely

We present a formalism for precise description of oscillation phenomena in matter at high energies or high densities, V > Delta m(2)/2E, where V is the matter-induced potential of neutrinos. The accuracy of the approximation is determined by the quantity, where is the mixing angle in matter and is a typical change of the potential over the oscillation length (). We derive simple and physically transparent formulas for the oscillation probabilities, which are valid for arbitrary matter density profiles. They can be applied to oscillations of high-energy accelerator, atmospheric, and cosmic neutrinos in the matter of the Earth, substantially simplifying numerical calculations and providing an insight into the physics of neutrino oscillations in matter. The effect of parametric enhancement of the oscillations of high-energy neutrinos is considered.

Reactor neutrinos

We review the status and the results of reactor neutrino experiments, that toe the cutting edge of neutrino research. Short baseline experiments have provided the measurement of the reactor neutrino spectrum, and are still searching for important phenomena such as the neutrino magnetic moment. They could open the door to the measurement of coherent neutrino scattering in the near future. Middle and long baseline oscillation experiments at Chooz and KamLAND have played a relevant role in neutrino oscillation physics in the last years. It is now widely accepted that a new middle baseline disappearance reactor neutrino experiment with multiple detectors could provide a clean measurement of the last undetermined neutrino mixing angle θ 13 . We conclude by opening on possible use of neutrinos for Society: the non-proliferation of nuclear materials and geophysics. To cite this article: Th. Lasserre, H.W. Sobel, C. R. Physique 6 (2005).

Plans for a Proton Driver at Fermilab

During the last several years, stunning experimental results have established that neutrinos have nonzero masses and substantial mixing. The Standard Model must be extended to accommodate neutrino mass terms. The observation that neutrino masses and mass splittings are all many orders of magnitude smaller than those of any of the other fundamental fermions suggests radically new physics, perhaps originating at the GUT or Planck Scale, or perhaps the existence of new spatial dimensions. In some sense we know that the Standard Model is broken, but we don't know how it is broken. Whatever the origin of the observed neutrino masses and mixing, it is likely to require a profound extension to our picture of the physical world. The first steps in understanding this revolutionary new physics are to pin down the measurable parameters and to address the next round of basic questions: (1) Are there only three neutrino flavors, or do light, sterile neutrinos exist? (2) If there are only three generations, there is one angle ({theta}{sub 13}) in the mixing matrix that is unmeasured. How large is it? (3) Which of the two possible orderings of the neutrino mass eigenstates applies? (4) If {theta}{sub 13} is large enough onemore » it may be possible to measure the quantum-mechanical phase {delta}. If {theta}{sub 13} and {delta} are non-zero there will be CP violation in the lepton sector. These questions can be addressed by accelerator based neutrino oscillation experiments. The answers will guide our understanding of what lies beyond the Standard Model, and whether the new physics provides an explanation for the baryon asymmetry of the Universe (via leptogenesis), or provides deep insight into the connection between quark and lepton properties (via Grand Unified Theories), or perhaps leads to an understanding of one of the most profound questions in physics: Why are there three generations of quarks and leptons? The answers may well further challenge our picture of the physical world, and will certainly have important implications for our understanding of cosmology and the evolution of the early Universe. The current Fermilab Program is an important part of the world-wide accelerator based effort to explore and understand the physics of neutrino oscillations. By early 2005, with both MINOS and MiniBooNE taking data, Fermilab will be able to answer some of the most pressing first-round questions raised by the discovery that neutrinos have mass. Fermilab's high-intensity neutrino beams are derived from 8- and 120-GeV proton beams. MiniBooNE is currently taking data using 8 GeV Protons from the Booster. The 120 GeV NuMI beam will start to operate in early 2005 using a 0.25 MW proton beam power from the Main Injector. Future neutrino programs will build on these existing facilities. New short and long baseline experiments have been proposed. There are proposals to increase the available number of protons at 8 and 120 GeV with the goal of addressing the full range of questions presented by neutrino oscillations. Key to that vision is a new intense proton source that usually is referred to as the Proton Driver.« less

Neutrino oscillation physics with a higher γ β-beam

We demonstrate the excellent physics case of a β –beam facility in which the radioactive 6 He ions producing anti-neutrinos are accelerated to γ ∼ 150 while the 18 Ne ions producing neutrinos are accelerated to γ ∼ 250 . We assume a baseline of 300 km. The interest of this scenario stands in the fact that it corresponds to the maximum acceleration that can be achieved by the SPS at CERN, and it could be realized without major technological challenges.

Decoupling supernova and neutrino oscillation physics with LAr TPC detectors

Core collapse supernovae are a huge source of all flavour neutrinos. The flavourcomposition, energy spectrum and time structure of the neutrino burst from a galacticsupernova can provide information about the explosion mechanism and the mechanisms ofproto neutron star cooling. Such data can also give information about the intrinsicproperties of the neutrino such as flavour oscillations. One important question isto understand to what extent the supernova and the neutrino physics can bedecoupled in the observation of a single supernova. On one hand, the understandingof the supernova explosion mechanism is still plagued by uncertainties whichhave an impact on the precision with which one can predict time-, energy- andflavour-dependent neutrino fluxes. On the other hand, the neutrino mixing propertiesare not fully known, since the type of mass hierarchy and the value of theθ13 angle are unknown, and in fact large uncertainty still exists on the prediction ofthe actual effect of neutrino oscillations in the event of a supernova explosion.In this paper we discuss the possibility of probing the neutrino mixing angleθ13 and the type of mass hierarchy from the detection of supernova neutrinos with a liquidargon TPC detector. Moreover, describing the supernova neutrino emission by a set of fiveparameters (average energy of the different neutrino flavours, their relative luminosity andthe total supernova binding energy), we quantitatively study how it is possible to constrainthese parameters. A characteristic feature of the liquid argon TPC is the accessibility tofour independent detection channels ((1) elastic scattering off electrons, (2) chargedneutrino and (3) antineutrino and (4) neutral currents on argon nuclei) which have differentsensitivities to electron neutrino, anti-electron neutrino and other neutrino flavours (muonand tau (anti)neutrinos). This allows us to over-constrain the five supernova andthe flavour mixing parameters and to some extent disentangle neutrino fromsupernova physics. Numerically, we find that a very massive liquid argon detector(O(100 kton)) is needed to perform accurate measurements of these parameters, speciallyin supernova scenarios where the average energies of electron and non-electronneutrinos are similar (almost degenerate neutrinos) or if no information about theθ13 mixing angle and type of mass hierarchy is available.

Neutrino oscillation physics with a higher- γβ-beam

The precision measurement and discovery potential of a neutrino factory based on boosted radioactive ions in a storage ring (“ β-beam”) is re-examined. In contrast with past designs, which assume ion γ factors of ∼100 and baselines of L=130 km, we emphasize the advantages of boosting the ions to higher γ and increasing the baseline proportionally. In particular, we consider a “medium- γ” scenario ( γ∼500, L∼730 km) and a “high- γ” scenario ( γ∼2000, L∼3000 km). The increase in statistics, which grow linearly with the average beam energy, the ability to exploit the energy dependence of the signal and the sizable matter effects at this longer baseline all increase the discovery potential of such a machine very significantly.

ExplainingΩbaryon≈0.2Ωdarkthrough the synthesis of ordinary matter from mirror matter: A more general analysis

The emerging cosmological picture is of a spatially flat universe composed predominantly of three components: ordinary baryons $({\ensuremath{\Omega}}_{B}\ensuremath{\approx}0.05),$ nonbaryonic dark matter $({\ensuremath{\Omega}}_{\mathrm{dark}}\ensuremath{\approx}0.22)$ and dark energy $({\ensuremath{\Omega}}_{\ensuremath{\Lambda}}\ensuremath{\approx}0.7).$ We recently proposed that ordinary matter was synthesized from mirror matter, motivated by the argument that the observed similarity of ${\ensuremath{\Omega}}_{B}$ and ${\ensuremath{\Omega}}_{\mathrm{dark}}$ suggests an underlying similarity between the fundamental properties of ordinary and dark matter particles. In this paper we generalize the previous analysis by considering a wider class of effective operators that nongravitationally couple the ordinary and mirror sectors. We find that while all considered operators imply ${\ensuremath{\Omega}}_{\mathrm{dark}}=\mathrm{few}\ifmmode\times\else\texttimes\fi{}{\ensuremath{\Omega}}_{B},$ only a subset quantitatively reproduce the observed ratio ${\ensuremath{\Omega}}_{B}/{\ensuremath{\Omega}}_{\mathrm{dark}}\ensuremath{\approx}0.20.$ The $\ensuremath{\sim}1\mathrm{eV}$ mass scale induced through these operators hints at a connection with neutrino oscillation physics.

ExtrinsicCPTviolation in neutrino oscillations in matter

We investigate matter-induced (or extrinsic) CPT violation effects in neutrino oscillations in matter. Especially, we present approximate analytical formulas for the CPT-violating probability differences for three flavor neutrino oscillations in matter with an arbitrary matter density profile. Note that we assume that the CPT invariance theorem holds, which means that the CPT violation effects arise entirely because of the presence of matter. As special cases of matter density profiles, we consider constant and step-function matter density profiles, which are relevant for neutrino oscillation physics in accelerator and reactor long baseline experiments as well as neutrino factories. Finally, the implications of extrinsic CPT violation on neutrino oscillations in matter for several past, present, and future long baseline experiments are estimated.

Precision neutrino oscillation physics with an intermediate baseline reactor neutrino experiment

We discuss the physics potential of intermediate $L \sim 20 \div 30$ km baseline experiments at reactor facilities, assuming that the solar neutrino oscillation parameters $\Delta m^2_{\odot}$ and $\theta_{\odot}$ lie in the high-LMA solution region. We show that such an intermediate baseline reactor experiment can determine both $\Delta m^2_{\odot}$ and $\theta_{\odot}$ with a remarkably high precision. We perform also a detailed study of the sensitivity of the indicated experiment to $\Delta m^2_{\rm atm}$, which drives the dominant atmospheric $\nu_{\mu}$ ($\bar{\nu}_{\mu}$) oscillations, and to $\theta$ - the neutrino mixing angle limited by the data from the CHOOZ and Palo Verde experiments. We find that this experiment can improve the bounds on $\sin^2\theta$. If the value of $\sin^2\theta$ is large enough, $\sin^2\theta \gtap 0.02$, the energy resolution of the detector is sufficiently good and if the statistics is relatively high, it can determine with extremely high precision the value of $\Delta m^2_{\rm atm}$. We also explore the potential of the intermediate baseline reactor neutrino experiment for determining the type of the neutrino mass spectrum, which can be with normal or inverted hierarchy. We show that the conditions under which the type of neutrino mass hierarchy can be determined are quite challenging, but are within the reach of the experiment under discussion.

Oscillation effects on supernova neutrino rates and spectraand detection of the shock breakout in a liquid argon TPC

A liquid argon TPC (ICARUS-like) has the ability to detect cleanneutrino bursts from type-II supernova collapses. In this paper, we considerfor the first time the four possible detectablechannels, namely, the elastic scattering on electrons from allneutrino species, νe charged current absorption on Ar withproduction of excited K, ν̄e charged current absorption onAr with production of excited Cl and neutral current interactionson Ar from all neutrino flavours. We compute the total rates and energy spectra of supernovaneutrino events including the effects of the three-flavour neutrinooscillation with matter effects in the propagation in the supernova. Results show a dramatic dependence onthe oscillation parameters and on the energyspectrum, especially for charged-current events. The shock breakout phase has also been investigatedusing recent simulations of the core collapse supernova. We stress the importance of the neutral current signal to decouplesupernova from neutrino oscillation physics.