Narrow Results

We consider a neutrino mass generating model which employs a scalar leptoquark and a scalar diquark. The neutrino masses are generated at the two-loop level, as in the Zee-Babu model and the scalars play the role of the doubly and singly charged scalar in the Zee-Babu model. With a moderate working assumption that the magnitudes of the six Yukawa couplings between diquark and the down type quarks are of the same order. Strong connections are found between the neutrino masses and the charged lepton flavor violating processes. In particular, we study ℓ → ℓʹγ and Z → ℓℓʹ, and find that some portions of the parameter space of this model are within the reach of the planned charged lepton flavor violating experiments. Interesting lower bounds are predicted. The type of neutrino mass hierarchy could also be determined by measuring the charged lepton flavor violating double ratios. Moreover, definite leptoquark decay branching ratios are predicted when there is no Yukawa interaction between the right handed fermions and leptoquark, which could help refine the collider search limit on the scalar leptoquark mass.

The MINOS experiment will study muon neutrino oscillations in the range of parameter space implied by the measurements with atmospheric neutrinos. The two magnetized toroidal tracking calorimeters, 1 kton at Fermilab and 5.4 kton in the Soudan Mine 735-km away, are constructed out of extruded scintillator strips and use wavelength-shifting and clear fibers read out by multi-anode photomultipliers. The far detector is now more than 3/4 completed and commenced collecting cosmic ray data. The neutrino beamline and the near detector will be finished by the end of 2004. In addition, a calibration detector was also constructed and exposed to the test beams. Over the last two years the entire project has progressed on schedule and budget and with most of the civil construction out of the way the road to this interesting physics program is finally cleared.

The recent neutrino oscillation experimental results indicate that at least one neutrino has a mass greater than 50 meV. The next generation of double-beta decay experiments will very likely have a sensitivity to an effective Majorana neutrino mass below this target. Therefore this is a very exciting time for this field of research as even null results from these experiments have the potential to elucidate the nature of the neutrino.

The existence of a neutrino magnetic moment implies contributions to the neutrino mass via radiative corrections. We derive model-independent "naturalness" upper bounds on the magnetic moments of Dirac and Majorana neutrinos, generated by physics above the electroweak scale. For Dirac neutrinos, the bound is several orders of magnitude more stringent than present experimental limits. However, for Majorana neutrinos the magnetic moment bounds are weaker than present experimental limits if μ_ν is generated by new physics at ~ 1 TeV, and surpass current experimental sensitivity only for new physics scales > 10 – 100 TeV. The discovery of a neutrino magnetic moment near present limits would thus signify that neutrinos are Majorana particles.

Latest results on 0νββ, 0νχ⁰ββ and 2νββ decays of different isotopes from NEMO-3 double beta decay experiment are presented. In particular, new limits at 90% C.L. on neurtinoless double beta decay of ¹⁰⁰Mo and ⁸²Se have been obtained, T_1/2 > 5.8 × 10²³y and T_1/2 > 2.1 × 10²³y, respectively.

Since the confirmation of neutrino oscillations it is known that neutrinos possess a non-zero rest mass. This has far reaching implications for the standard model of particle physics and for cosmology. The KArlsruhe TRitium Neutrino mass experiment, KATRIN, aims to search for the mass of the electron neutrino with a sensitivity of 0.2 eV (90% C.L.) and a detection limit of 0.35 eV (5 sigma). Even a null-result of KATRIN will exclude many theoretical models with degenerate neutrino masses and will give new input for particle astrophysics and cosmology. At KATRIN the same measurement principle is utilized as in the previous neutrino mass experiments in Mainz and Troitsk. These experiments search for a deviation in the spectrum of the electrons in the beta-decay of tritium near the endpoint, that will be caused by a non-zero neutrino mass. The beta-spectrum is measured using a MAC-E filter. KATRIN is being set up at the Forschungszentrum Karlsruhe in Germany. The principle and present status of KATRIN are presented.

It is one of the biggest challenge in particle physics and cosmology to determine the mass of neutrinos. Current neutrinoless double beta decay experiment show that the total neutrino mass is smaller than 1–6 eV.

In recent years, precise CMB data make it possible to constrain neutrino masses cosmologically. It says that the total neutrino mass is smaller than 2 eV in standard ACDM model.¹ But if there are other physical processes which affects the CMB anisotropies, such constraint may be changed. A primordial magnetic field (PMF) is one of such physical processes. In this work, we constrain the total neutrino mass from CMB anisotropies with the PMF effect.

The KArlsruhe TRItium Neutrino experiment KATRIN is designed to measure the absolute neutrino mass scale by analyzing the endpoint region of the tritium beta-decay spectrum with a sensitivity of 0.2 eV/c² (90 % C.L.). A high-luminous windowless gaseous tritium source with an activity of 1.7 · 10¹¹Bq will produce the decay electrons, their energy spectrum will be analyzed by a combination of two electrostatic retarding spectrometers with magnetic adiabatic collimation (MAC-E-filter). Fluctuations of the source column density and inelastic scattering processes within the source affect the energy distribution of the decay electrons. Hence, a precise and continuous monitoring of the source activity is necessary to correct the data taken by the main detector. A prototype of the beam monitor detector, based on a silicon drift diode, has been developed to measure an expected counting rate in the range of 10⁶/(s · mm²). The detector element shall be moveable across the complete beam in a magnetic field of 0.8 T, resulting in a beam diameter of 20 cm. A precise sensor positioning device has been designed and built to be compatible with the primary beamline vacuum of 10^-11 mbar.

The cosmological constant of nonlinear supersymmetric general relativity(NLSUSYGR) may be the origin of everything and give new insights into the origin of mass and the mysterious relations between the cosmology and the (low energy) particle physics.

Abdus Salam challenged the chiral gauge nature of the Standard Model by paving the road towards the Left-Right symmetric electro-weak theory. I describe here the logical and historical construction of this theory, by emphasising the pioneering and key role it played for neutrino mass. I show that it is a self-contained and predictive model with the Higgs origin of neutrino mass, in complete analogy with the SM situation regarding charged fermions.

We review the first fully relativistic description for the neutrinoless double-beta decay by the beyond-mean-field covariant density functional theory. The calculations of the nuclear transition matrix elements are based on a full relativistic transition operator and nuclear wave functions in which the dynamic effects of particle-number, angularmomentum, and parity conservations as well as shape fluctuations are incorporated. We find that the commonly used nonrelativistic approximation for the transition operator is justified within the mechanism of light-Majorana-neutrino exchange. We stress that reducing the discrepancies in the predicted nuclear matrix elements by different nuclear models is a major challenge in nuclear physics.

Mass spectrometry is a well-established technique for nuclear structure studies in exotic nuclei far off stability. The Penning-trap mass spectrometer SHIP-TRAP at GSI has focused on mass measurements of the heaviest elements to map shell effects around N = 152. Several upgrades are presently ongoing to extend these measurements to heavier elements. A major step was the implementation of the phase-imaging technique (PI-ICR) that has been used for mass measurements of long-lived and stable nuclides in the context of neutrino physics. In this contribution recent achievements are briefly reviewed.

Radiative neutrino mass models and the seesaw models are viewed from the unifying framework of standard model effective operators that explicitly violate lepton number by two units (ΔL = 2). After some comments on naturalness and leptogenesis in the minimal type 1 seesaw model, a full list of minimal renormalisable models that produce mass dimension-7, ΔL = 2 operators at low energies is presented. By way of example, phenomenological bounds from Run 1 LHC and lepton flavour violation data are then placed on one of these models. A possible connection between radiative neutrino mass models and the current flavour anomalies in b → c and b → s transitions is then described.

Nuclear double beta decay, an extremely rare radioactive decay process, is - in one of its variants - one of the most exciting means of research into particle physics beyond the standard model. The large progress in sensitivity of experiments searching for neutrinoless double beta decay in the last two decades - based largely on the use of large amounts of enriched source material in "active source experiments" - has lead to the observation of the occurrence of this process in nature (on a 6.4 sigma level), with the largest half-life ever observed for a nuclear decay process (2.2×10²⁵ y). This has fundamental consequences for particle physics - violation of lepton number, Majorana nature of the neutrino. These results are independent of any information on nuclear matrix elements (NME)*. It further leads to sharp restrictions for SUSY theories, sneutrino mass, right-handed W-boson mass, superheavy neutrino masses, composite-ness, leptoquarks, violation of Lorentz invariance and equivalence principle in the neutrino sector.

The masses of light-neutrinos are found to be degenerate, and to be at least 0.22±0.02eV. This fixes the contribution of neutrinos as hot dark matter to ≥4.7% of the total observed dark matter. The neutrino mass determined might solve also the dark energy puzzle.

EXO-200 (Enriched Xenon Observatory - 200kg) is an underground double-beta decay experiment that uses 200kg of Xenon isotopically enriched to 80% in Xenon-136. The Xenon is contained in an ultra-low background TPC where there is simultaneous collection of scintillation light (using Large Area Avalanche Photodiodes (LAAPD's)) and ionization charge in order to significantly enhance the energy resolution. EXO-200 should measure the, as yet unobserved, two neutrino double-beta decay mode as well as achieve competitive sensitivity for the neutrinoless double-beta decay mode of Xenon-136. EXO-200 is currently undergoing final construction and commissioning. R&D is being conducted towards the construction of a ton-class detector. A high-resolution micropattern (MicroMegas) readout system is being studied in Bern, Switzerland. The scheme offers full tracking capabilities and 3D event reconstruction for possible application in a future gas-phase EXO detector.

Neutrinoless Double Beta Decay searches are the only way to give an answer to the neutrino mass nature, Dirac or Majorana. These experiments are extremely delicate and the greatest obstacle to improve their sensitivity is the background level that can be achieved. LUCIFER is a project, financed by a ERC-AdG, that would like to build a demonstrator of a technique based on the double read-out (scintillation light + heat) of ZnSe crystals used as bolometers. The goal is to reach a background lower than 0.001 counts/kg/keV/year. Along the way we would like to learn how practical is the enrichment of Se into ⁸²Se, how efficient is the process of crystallization and how radiopure the crystals can be grown. In this talk we will discuss the properties of ZnSe crystals and sketch the layout of the project.

Neutrinoless nuclear double 0νββ decay, recently experimentally observed for ⁷⁶Ge on a confidence level of > 6 σ, has fundamental consequences for particle physics - violation of (total) lepton number, Majorana nature of the neutrino. It further leads to sharp restrictions for SUSY theories, sneutrino mass, right-handed W-boson mass, superheavy neutrino masses, compositeness, leptogenesis, violation of Lorentz violation and equivalence principle in the neutrino sector.

The masses of light neutrinos follow to be degenerate, and to be at least 0.22 ± 0.02 eV. This fixed the contribution of neutrinos as hot dark matter to ≥ 4.7% of the total observed dark matter. The neutrino mass determined might also solve the dark energy puzzle.

The observation of 0νββ decay is naturally a great challenge for future experiments, in particular also with other 0νββ - emitter isotopes. There are several important experiments under construction. Present experiments have hardly a chance to reach the sensitivity required for confirmation - although sometimes this impression is given (e.g. by unproperly comparing 1.5 σ limits (of CUORICINO etc.) with the 6σ result obtained for ⁷⁶Ge.

LUCIFER (Low-background Underground Cryogenic Installation For Elusive Rates) is a new project for the study of neutrinoless Double Beta Decay, based on the technology of the scintillating bolometers. These devices promise a very efficient rejection of the a background, opening the way to a virtually background-free experiment if candidates with a transition energy higher than 2615 keV are investigated. The baseline candidate for LUCIFER is ⁸²Se. This isotope will be embedded in ZnSe crystals grown with enriched selenium and operated as scintillating bolometers in a low-radioactivity underground dilution refrigerator. In this paper, the LUCIFER concept will be introduced and the sensitivity and the prospects related to this project will be discussed.

KATRIN is a direct neutrino mass experiment with sub-eV sensitivity for neutrino masses from tritium β decay. It is currently set up at Karlsruhe Institute of Technology (KIT), Germany, and combines a high luminosity windowless molecular tritium gas source with a high resolution electrostatic retarding spectrometer (MAC-E Filter) to investigate the β decay spectrum near the endpoint E₀ with very high precision. It will improve the neutrino mass sensitivity by one order of magnitude down to 0.2 eV, sufficient to cover the degenerate neutrino mass scenarios and the cosmologically relevant neutrino mass range.

Neutrinoless double electron capture (0νECEC) of atomic nuclei has recently attracted a lot of attention due to its potential in accessing the absolute mass scale of the neutrino. In particular, the resonant 0νECEC is interesting based on the possible huge enhancement of the corresponding decay rate by a resonance condition. Recently the mass differences of two atom pairs were measured in order to study the enhancement of the 0νECEC rates of ⁷⁴Se and ¹¹²Sn. We have evaluated the associated nuclear matrix elements by using the proton-neutron quasiparticle random-phase approximation with realistic two-body interactions. The absolute mass scale of the neutrino can also be accessed through beta decays of small decay energy. Related to this we have also studied the recently discovered rare ultra-low-Q-value beta-decay branch of ¹¹⁵In by using microscopic phonon-quasiparticle coupling schemes. Our calculations suggest that the effects of atomic origin may introduce non-negligible, even dramatic effects on this and other decays with a Q value in this extreme regime of only hundreds of eV.