55758365
Current Status and Future Perspectives of the LUCIFER Experiment
In the field of fundamental particle physics, the neutrino has become more and more important in the last few years, since the discovery of its mass. In particular, the ultimate nature of the neutrino (if it is a Dirac or a Majorana particle) plays a crucial role not only in neutrino physics, but also in the overall framework of fundamental particle interactions and in cosmology. The only way to disentangle its ultimate nature is to search for the neutrinoless double beta decay. The idea of LUCIFER is to combine the bolometric technique proposed for the CUORE experiment with the bolometric light detection technique used in cryogenic dark matter experiments. The bolometric technique allows an extremely good energy resolution while its combination with the scintillation detection offers an ultimate tool for background rejection. The goal of LUCIFER is not only to build a background-free small-scale experiment but also to directly prove the potentiality of this technique. Preliminary tests on several detectors containing different interesting DBD emitters have clearly demonstrated the excellent background rejection capabilities that arise from the simultaneous, independent, double readout of heat and scintillation light.
62170783
Terra Incognita 2: Exploring and Modeling Absolute Masses
After drawing the context of discussion of this parallel session, we offer a summary of the various contributions, and comment on future perspectives. We include only the few references that are useful for the discussion, and refer to the individual contributions for a complete bibliography on the related subjects.
118915062
Dark matter search with innovative techniques
55610143
From Cuoricino to CUORE: Investigating the inverted hierarchy region of neutrino mass
Cuoricino is a Double Beta Decay experiment operating deep underground, in the Laboratori Nazionali del Gran Sasso, Italy; at a depth of about 3500 m.w.e. The search for the 0νββ of 130Te is carried out with the bolometric technique and an upper limit of 3×1024 y (@ 90%C.L.) is set for this process. Cuoricino represents not only the most sensitive DBD Experiment presently operating but also a prototype for a next generation experiment, CUORE (Cryogenic Underground Observatory for Rare Events). The expected performance and sensitivity, based on Monte Carlo simulations and extrapolations of the present Cuoricino results, indicate that CUORE will be able to test the 0.02-0.05 eV region for the effective neutrino mass, having a high discovery potential in the inverted hierarchy region of the neutrino mass pattern.
121148985
Neutrinoless Double-Beta Decay
This paper introduces the neutrinoless double-beta decay (the rarest nuclear weak process) and 
describes the status of the research for this transition, both from the point of view of theoretical 
nuclear physics and in terms of the present and future experimental scenarios. Implications of this 
phenomenon on crucial aspects of particle physics are briefly discussed. The calculations of the nuclear 
matrix elements in case of mass mechanisms are reviewed, and a range for these quantities is proposed 
for the most appealing candidates. After introducing general experimental concepts—such as the 
choice of the best candidates, the different proposed technological approaches, and the sensitivity—we make the point on the experimental situation. Searches running or in preparation are described, providing an organic presentation which picks up similarities and differences. A critical comparison of 
the adopted technologies and of their physics reach (in terms of sensitivity to the effective Majorana 
neutrino mass) is performed. As a conclusion, we try to envisage what we expect round the corner 
and at a longer time scale.
203744172
How to improve the sensitivity of future neutrino mass experiments with thermal calorimeters
In this paper we discuss the perspectives for a new generation of neutrino mass experiments using thermal detectors to reach interesting sensitivities before and after the KATRIN experiment. By scaling the performance of the present Milano neutrino mass experiment with Monte Carlo simulations, we show how a new experiment can validate the present limit of few eV set by spectrometers before the KATRIN experiment starts. We also show how such a result can be used to design a very large thermal detector experiment to reach sensitivities beyond the KATRIN expected one. r 2003 Elsevier B.V. All rights reserved. PACS: 14.60.Pq; 23.40.Bw; 29.90.þr; 02.70.Uu
29885643
Anomalous Behavior in an Effective Model of Graphene with Coulomb Interactions
We analyze by exact Renormalization Group (RG) methods the infrared properties of an effective model of graphene, in which two-dimensional (2D) massless Dirac fermions propagating with a velocity smaller than the speed of light interact with a 3D quantum electromagnetic field. The fermionic correlation functions are written as series in the running coupling constants, with finite coefficients that admit explicit bounds at all orders. The implementation of Ward Identities in the RG scheme implies that the effective charges tend to a line of fixed points. At small momenta, the quasi-particle weight tends to zero and the effective Fermi velocity tends to a finite value. These limits are approached with a power law behavior characterized by non-universal critical exponents.
14496666
Lattice gauge theory model for graphene
The effects of the electromagnetic (em) electron-electron interactions in half-filled graphene are investigated in terms of a lattice gauge theory model. By using exact renormalization group methods and lattice Ward identities, we show that the em interactions amplify the responses to the excitonic pairings associated to a Kekule distortion and to a charge-density wave. The effect of the electronic repulsion on the Peierls-Kekule instability, usually neglected, is evaluated by deriving an exact non BCS gap equation, from which we find evidence that strong em interactions among electrons facilitate the spontaneous distortion of the lattice and the opening of a gap.
119295233
The ground state construction of the two-dimensional Hubbard model on the honeycomb lattice
In these lectures I consider the half-filled two-dimensional (2D) Hubbard model on the honeycomb lattice and I review the rigorous construction of its ground state properties by making use of constructive fermionic Renormalization Group methods.
337931
The Scaling limit of the energy correlations in non integrable Ising models
We obtain an explicit expression for the multipoint energy correlations of a non solvable two-dimensional Ising models with nearest neighbor ferromagnetic interactions plus a weak finite range interaction of strength �, in a scaling limit in which we send the lattice spacing to zero and the temperature to the critical one. Our analysis is based on an exact mapping of the model into an interacting lattice fermionic theory, which generalizes the one originally used by Schultz, Mattis and Lieb for the nearest neighbor Ising model. The interacting model is then analyzed by a multiscale method first proposed by Pinson and Spencer. If the lattice spacing is finite, then the correlations cannot be computed in closed form: rather, they are expressed in terms of infinite, convergent, power series in �. In the scaling limit, these infinite expansions radically simplify and reduce to the limiting energy correlations of the integrable Ising model, up to a finite renormalization of the parameters. Explicit bounds on the speed of convergence to the scaling limit are derived.
55458894
Lattice quantum electrodynamics for graphene
Abstract The effects of gauge interactions in graphene have been analyzed up until now in terms of effective models of Dirac fermions. However, in several cases lattice effects play an important role and need to be taken consistently into account. In this paper, we introduce and analyze a lattice gauge theory model for graphene, which describes tight binding electrons hopping on the honeycomb lattice and interacting with a three-dimensional quantum U ( 1 ) gauge field. We perform an exact renormalization group analysis, which leads to a renormalized expansion that is finite at all orders. The flow of the effective parameters is controlled thanks to Ward identities and a careful analysis of the discrete lattice symmetry properties of the model. We show that the Fermi velocity increases up to the speed of light and Lorentz invariance spontaneously emerges in the infrared. The interaction produces critical exponents in the response functions; this removes the degeneracy present in the non interacting case and allows us to identify the dominant excitations. Finally, we add mass terms to the Hamiltonian and derive by a variational argument the correspondent gap equations, which have an anomalous non-BCS form, due to the non trivial effects of the interaction.