2157347
On electromagnetic contributions in WIMP quests
The effect pointed out by A. B. Migdal in 1940's (hereafter named Migdal effect) has so far been usually neglected in the direct searches for WIMP Dark Matter candidates. This effect consists in the ionization and the excitation of bound atomic electrons induced by the recoiling atomic nucleus. In the present paper the related theoretical arguments are developed and some consequences of the proper accounting for this effect are discussed by some examples of practical interest.
118311956
DAMA investigations on Dark Matter at Gran Sasso: results and perspectives
The DAMA/NaI experiment (≃ 100 kg highly radiopure NaI(Tl)) at the Gran Sasso National Laboratory of the I.N.F.N. had the unique feature to effectively investigate the presence of Dark Matter particles in the galactic halo by exploiting the model independent annual modulation signature. A total exposure of more than 105 kg × day, collected over seven annual cycles, has pointed out at 6.3 σ C.L. an effect which satisfies all the many peculiarities of the signature. Neither systematics nor side reactions able to account for the observed effect were found. No experiment whose result can be directly compared in a model independent way with the experimental one of DAMA/NaI is available so far. Searches in space experiments are not in contradiction with DAMA/NaI. Several (but still few with respect to the possibilities) corollary model dependent quests for the candidate particle have also been carried out; others are in progress. At present the second generation DAMA/LIBRA set‐up (≃ 250 kg highly radiopure NaI(...
119701812
Signals from dark Universe: DAMA/LIBRA at LNGS
The DAMA/LIBRA set-up (about 250 kg highly radiopure NaI(Tl) sensitive mass) is running at the Gran Sasso National Laboratory of the INFN. The first DAMA/LIBRA results point out the presence of a dark matter particle component in the galactic halo, as well as the former DAMA/NaI set-up; cumulatively the data support such evidence at 8.2σ CL and satisfy all the peculiarities of the dark matter annual modulation signature.
124862840
DIRECT DETECTION OF DARK MATTER PARTICLES
17766827
Investigating electron interacting dark matter
Some extensions of the standard model provide dark matter candidate particles which can have a dominant coupling with the lepton sector of the ordinary matter. Thus, such dark matter candidate particles (chi(0)) can be directly detected only through their interaction with electrons in the detectors of a suitable experiment, while they are lost by experiments based on the rejection of the electromagnetic component of the experimental counting rate. These candidates can also offer a possible source of the 511 keV photons observed from the galactic bulge. In this paper this scenario is investigated. Some theoretical arguments are developed and related phenomenological aspects are discussed. Allowed intervals and regions for the characteristic phenomenological parameters of the considered model and of the possible mediator of the interaction are also derived considering the DAMA/NaI data.
117048271
First DAMA/LIBRA Results and Beyond
The DAMA project is an observatory for rare processes and it is operative deep underground at the Gran Sasso National Laboratory of the I.N.F.N. Its main apparatus is the DAMA/LIBRA set-up, consisting of ≃250 kg highly radiopure NaI(Tl) detectors. Its first results — obtained by exploiting over four annual cycles the model independent annual modulation signature for Dark Matter (DM) particles — confirm by those of the former DAMA/NaI, supporting the evidence for Dark Matter presence in the galactic halo at 8.2 σ C.L.. The DAMA/NaI and DAMA/LIBRA data, in fact, satisfy all the many peculiarities of the DM annual modulation signature. Neither systematic effects nor side reactions able to account for the observed modulation amplitude and to contemporaneously satisfy all the several requirements of the DM signature are available. Future perspectives are also addressed.
119221143
Octahedral symmetry with geometrical breaking: New prediction for neutrino mixing angle theta(13) and CP violation
We propose octahedral group O-h as the family symmetry of the neutrino-lepton sector. We find that O-h contains subgroups Z(2)(mu tau) circle times Z(2)(s) and Z(4)(l) for realizing the bimaximal (BM) mixings theta(23) = theta(12) = 45 degrees, where Z(2)(mu tau) circle times Z(2)(s) and Z(4)(l) serve as the residual symmetries of neutrinos and charged leptons, respectively. We present geometric interpretations of BM mixing in the octahedron, and construct natural geometrical breaking of Z(4)(l), leading to nontrivial deviations from the BM mixings. Our theory makes truly simple predictions of a relatively large reactor angle, theta(13) similar or equal to 45 degrees - theta(12) = 7.5 degrees-13.7 degrees(3 sigma), the nearly maximal atmospheric angle and the approximate maximal Dirac CP violation. These agree well with the current neutrino data, and will be further probed by the on-going and upcoming oscillation experiments.
13928631
Multigauge-boson vertices and chiral Lagrangian parameters in Higgsless models with ideal fermion delocalization
Higgsless models with fermions whose $SU(2)$ properties are ``ideally delocalized,'' such that the fermion's probability distribution is appropriately related to the $W$ boson wave function, have been shown to minimize deviations in precision electroweak parameters. As contributions to the $S$ parameter vanish to leading order, current constraints on these models arise from limits on deviations in multi-gauge-boson vertices. We compute the form of the triple and quartic gauge-boson vertices in these models and show that these constraints provide lower bounds only of the order of a few hundred GeV on the masses of the lightest $KK$ resonances. Higgsless models with ideal fermion delocalization provide an example of extended electroweak gauge interactions with suppressed couplings of fermions to extra gauge bosons, and these are the only models for which triple-gauge-vertex measurements provide meaningful constraints. We relate the multigauge couplings to parameters of the electroweak chiral Lagrangian, and the parameters obtained in these $SU(2)\ifmmode\times\else\texttimes\fi{}SU(2)$ models apply equally to the corresponding five-dimensional gauge theory models of QCD. We also discuss the collider phenomenology of the $KK$ resonances in models with ideal delocalization. These resonances are found to be fermiophobic, therefore traditional direct collider searches are not sensitive to them and measurements of gauge-boson scattering will be needed to find them.
102507809
Natural electroweak symmetry breaking from scale invariant Higgs mechanism
We construct a minimal viable extension of the standard model (SM) with classical scale symmetry. Its scalar sector contains a complex singlet in addition to the SM Higgs doublet. The scale-invariant and CP-symmetric Higgs potential generates radiative electroweak symmetry breaking ` a la Coleman-Weinberg, and gives a natural solution to the hierarchy problem, free from fine-tuning. Besides the 125 GeV SM-like Higgs particle, it predicts a new CP-even Higgs (serving as the pseudo-Nambu-Goldstone boson of scale symmetry breaking) and a CP-odd scalar singlet (providing the dark matter candidate) at weak scale. We systematically analyze experimental constraints from direct LHC Higgs searches and electroweak precision tests, as well as theoretical bounds from unitarity, triviality and vacuum stability. We demonstrate the viable parameter space, and discuss implications for new Higgs and dark matter (DM) searches at the upcoming LHC runs and for the on-going direct detections of DM.
6798711
Deconstructed Higgsless models with one-site delocalization
In this note we calculate the form of electroweak corrections in deconstructed Higgsless models for the case of a fermion whose weak properties arise from two adjacent $SU(2)$ groups on the deconstructed lattice. We show that, as recently proposed in the continuum, it is possible for the value of the electroweak parameter $\ensuremath{\alpha}S$ to be small in such a model. In addition, by working in the deconstructed limit, we may directly evaluate the size of off-$Z$-pole electroweak corrections arising from the exchange of Kaluza-Klein modes; this has not been studied in the continuum. The size of these corrections is summarized by the electroweak parameter $\ensuremath{\alpha}\ensuremath{\delta}$. In one-site delocalized Higgsless models with small values of $\ensuremath{\alpha}S$, we show that the amount of delocalization is bounded from above, and must be less than 25% at 95% C.L. We discuss the relation of these calculations to our previous calculations in deconstructed Higgsless models, and to models of extended technicolor. We present numerical results for a four-site model, illustrating our analytic calculations.
14324310
Minimal schemes for large neutrino mixings with inverted hierarchy
Abstract Existing oscillation data point to non-zero neutrino masses with large mixings. We analyze the generic features of the neutrino Majorana mass matrix with inverted hierarchy and construct realistic minimal schemes for the neutrino mass matrix that can explain the large (but not maximal) ν e – ν μ mixing of MSW-LAM as well as the nearly maximal ν μ – ν τ mixing and the small (or negligible) ν e → ν τ transition. These minimal schemes are quite unique and turn out to be extremely predictive. Implications for neutrinoless double beta decay, tritium beta decay and cosmology are analyzed.