arXiv subjects

A. Bottino

Publications and source records attributed to A. Bottino.

At least 73 records · Page 4Linked to original sources

arXiv1999

Dark Matter and its Particle Candidates

In these lectures we first briefly review the main observational facts which imply that most part of matter in the Universe is not visible and some recent intriguing experimental data which would point to a significant contribution to Omega due to a cosmological constant. We subsequently discuss some particle candidates for dark matter, with particular emphasis for the neutralino. We present the main properties of this particle, also in the light of the most recent experimental results in direct search for relic particles; furthermore, we discuss the perspectives for their indirect searches.

hep-ph↗

arXiv1999

Extending the DAMA annual-modulation region by inclusion of the uncertainties in the astrophysical velocities

The original annual-modulation region, singled out by the DAMA/NaI experiment for direct detection of WIMPs, is extended by taking into account the uncertainties in the galactic astrophysical velocities. Also the effect due to a possible bulk rotation for the dark matter halo is considered. We find that the range for the WIMP mass becomes 30 GeV < m_chi < 130 GeV at 1-sigma C.L. with a further extension in the upper bound, when a possible bulk rotation of the dark matter halo is taken into account. We show that the DAMA results, when interpreted in the framework of the Minimal Supersymmetric extension of the Standard Model, are consistent with a relic neutralino as a dominant component of cold dark matter (on the average in our universe and in our galactic halo). It is also discussed the discovery potential for the relevant supersymmetric configurations at accelerators of present generation.

hep-ph↗

arXiv1998

Combining the data of annual modulation effect in WIMP direct detection with measurements of WIMP indirect searches

In previous papers we showed that the data of the DAMA/NaI experiment for WIMP direct detection, which indicate a possible annual modulation effect, are widely compatible with an interpretation in terms of a relic neutralino as the major component of dark matter in the Universe. In the present note we discuss the detectability of the relevant supersymmetric neutralino configurations by two of the most promising methods of indirect search for relic particles: measurement of cosmic-ray antiprotons and measurement of neutrino fluxes from Earth and Sun.

hep-ph↗

arXiv1998

Neutralino properties in the light of a further indication of an annual modulation effect in WIMP direct search

We demonstrate that the further indication of a possible annual modulation effect, singled out by the DAMA/NaI experiment for WIMP direct detection, is widely compatible with an interpretation in terms of a relic neutralino as the major component of dark matter in the Universe. We discuss the supersymmetric features of this neutralino in the Minimal Supersymmetric extension of the Standard Model (MSSM) and their implications for searches at accelerators.

hep-ph↗

arXiv1998

Compatibility of the new DAMA/NaI data on an annual modulation effect in WIMP direct search with a relic neutralino in supergravity schemes

Recent results of the DAMA/NaI experiment for WIMP direct detection point to a possible annual modulation effect in the detection rate. We show that these results, when interpreted in terms of a relic neutralino, are compatible with supergravity models. Together with the universal SUGRA scheme, we also consider SUGRA models where the unification condition in the Higgs mass parameters at GUT scale is relaxed.

hep-ph↗

arXiv1998

Which fraction of the measured cosmic-ray antiprotons might be due to neutralino annihilation in the galactic halo?

We analyze the data of low-energy cosmic-ray antiproton spectrum, recently published by the BESS Collaboration, in terms of newly calculated fluxes for secondary antiprotons and for a possible contribution of an exotic signal due to neutralino annihilation in the galactic halo. We single out the relevant supersymmetric configurations and discuss their explorability with experiments of direct search for particle dark matter and at accelerators. We discuss how future measurements with the Alpha Magnetic Spectrometer (AMS) on the Shuttle flight may disentangle the possible neutralino-induced contribution from the secondary one.

astro-ph↗

arXiv1997

Extending a previous analysis on a possible modulation effect in WIMP direct search

In this note we present an extension of our previous analysis of some preliminary experimental results of the DAMA/NaI Collaboration which might be indicative of a yearly modulation effect. Here we present a direct way for obtaining from the experimental data the relevant cosmological implications for relic neutralinos. We find that some of the configurations singled out by the DAMA/NaI results would have cosmological properties compatible with a neutralino as a dominant component of cold dark matter (on the average in the Universe and in our galactic halo).

hep-ph↗

arXiv1997

Pinning down neutralino properties from a possible modulation signal in WIMP direct search

We analyze the properties of neutralino under the hypothesis that some preliminary experimental results of the DAMA/NaI Collaboration may be indicative of a yearly modulation effect. We examine which supersymmetric configurations would be singled out by the DAMA/NaI data. We also discuss the possibility to investigate these configurations by means of experimental searches for relic neutralinos other than direct searches. We finally discuss the possibility to probe these configurations by accelerator searches.

hep-ph↗

arXiv1996

Exploring the supersymmetric parameter space by direct search for WIMPs

It is shown that the new data of the DAMA/NaI detector, combined with recent calculations of nuclear structure functions, provide the most stringent upper bounds on the WIMP-nucleon cross-section both for spin-dependent and for scalar interactions. It is proved that, for the first time, data from an experiment of direct search for WIMPs allow the exploration of a region of the supersymmetric parameter space not yet fully investigated at accelerators.

hep-ph↗

arXiv1996

Neutralino Dark Matter

We examine the main properties of relic neutralinos in the context of the Minimal Supersymmetric extension of the Standard Model. We present a whole set of results obtained for the relic abundance and for detection rates with a model constrained according to the latest accelerator data. Predicted detection rates for relic neutralinos are compared to the present experimental bounds. A comparison with results obtained with more sophisticated theoretical schemes with unification assumptions at M_{GUT} is presented too. We also briefly discuss some properties of a Higgsino-like neutralino which has recently been suggested in connection with a supersymmetric interpretation of a single event at the Fermilab Tevatron.

astro-ph↗

arXiv1996

Perspectives for Detection of a Higgsino-like Relic Neutralino

It has been conjectured by Ambrosanio, Kane, Kribs, Martin and Mrenna (AKM) that the CDF event $p \bar p \to e^+ e^- γγ+ missing E_T$ is due to a decay chain involving two neutralino states (the lightest and the next-to-lightest ones). The lightest neutralino ($χ_{AKM}$) has been further considered by Kane and Wells as a candidate for cold dark matter. In this paper we examine the properties of relic $χ_{AKM}$'s in their full parameter space, and examine the perspectives for detection by comparing theoretical predictions to sensitivities of various experimental searches. We find that for most regions of the parameter space the detectability of a relic $χ_{AKM}$ would require quite substantial improvements in current experimental sensitivities. The measurements of neutrino fluxes from the center of the Earth and of an excess of $\bar{p}/p$ in cosmic rays are shown to offer some favorable perspectives for investigating a region of the $χ_{AKM}$ parameter space around the maximal $\tan β$ value allowed by the model.

astro-ph↗

arXiv1996

On neutralino stars as microlensing objects

The microlensing objects, Machos, recently observed in the halo of our Galaxy, can be interpreted as dense neutralino objects, neutralino stars, produced by the gravitational instability of neutralino gas. Taking the mass and radius of these objects from microlensing observations we calculated the diffuse gamma-ray flux produced in neutralino--neutralino annihilation inside the objects. The resulting flux is many orders of magnitude higher than the observed one.

astro-ph↗

arXiv1996

Relic neutralinos in a best-fitted MSSM

We examine the properties of relic neutralinos in the regions of the parameter space selected by recent fits to all the electroweak observables within the Minimal Supersymmetric Standard Model. We discuss the relic neutralino cosmic abundance and the direct detection rates for these most likely supersymmetric configurations. We employ the relevant experimental bounds to constrain the set of the best-fit configurations and discuss the discovery potential of the direct search for relic neutralinos.

hep-ph↗

arXiv1996

Searching for Relic Neutralinos using Neutrino Telescopes

Neutrino telescopes of large area offer the possibility of searching for indirect signals of relic neutralinos in the galactic halo, due to annihilations in the Sun or the Earth. Here we investigate the sensitivity, using a supergravity scheme where the soft scalar mass terms are not constrained by universality conditions at the grand unification scale. We first discuss in which regions of the supersymmetric parameter space the neutralino may be considered as a good candidate for cold dark matter. The discovery potential of the search using neutrino telescopes is then compared to that of the direct search for relic neutralinos.

hep-ph↗

arXiv1996

Short-baseline neutrino oscillations and neutrinoless double-beta decay in the framework of three neutrino mixing and a mass hierarchy

We have analyzed the results of the latest terrestrial neutrino oscillation experiments in the framework of a model with mixing of three massive neutrinos and a neutrino mass hierarchy ($ m_1 << m_2 << m_3 $). In this model, oscillations of the terrestrial neutrinos are characterized by three parameters, $ Δm^2 = m_3^2 - m_1^2 $ and the squared moduli of the two mixing matrix elements $U_{e3}$ and $U_{\mu3}$. Using the results of disappearance experiments and solar neutrino experiments, it is shown that only two regions of possible values of $|U_{e3}|^2$ and $|U_{\mu3}|^2$ are allowed: I. $|U_{e3}|^2$ and $|U_{\mu3}|^2$ are both small and II. $|U_{e3}|^2$ is small and $|U_{\mu3}|^2$ is large. If the mixing parameters are in the region I, $ ν_μ<-> ν_e $ oscillations are suppressed. In this case the LSND indication in favor of $ ν_μ<-> ν_e $ oscillations is not compatible with the negative results of all other experiments. If the mixing parameters are in the region II, $ ν_e <-> ν_τ$ oscillations are strongly suppressed. If massive neutrinos are Majorana particles, our analysis shows that neutrinoless double-beta decay could be observed in the experiments of the next generation only if the mixing parameters are in the region I.

hep-ph↗

arXiv1996

Non--Baryonic Dark Matter

The best particle candidates for non--baryonic cold dark matter are reviewed, namely, neutralino, axion, axino and Majoron. These particles are considered in the context of cosmological models with the restrictions given by the observed mass spectrum of large scale structures, data on clusters of galaxies, age of the Universe etc.

astro-ph↗

arXiv1995

Limits on the Neutrino Mass and Mixing Angle from Pion and Lepton Decays

Motivated by a recent rather surprising conclusion based on the 1992 PDG data on the pion, kaon and lepton decays that if three generations of neutrinos are assumed to be massive and mixed, the heaviest neutrino, $ν_3$, could have a mass in the range, $155~\mbox{MeV} \lsim m_3 \lsim 225~\mbox{MeV}$, we have analyzed the latest 1995 data on the leptonic decays of pion, $μ$ and $τ$ with the assumption that three generations of neutrinos are massive and mixed. It is shown that when the radiative corrections are included and the constraint {}from partial decay widths is imposed, the 1995 data are consistent with three massless neutrinos with no mixing. Various limits on the neutrino mass and mixing angle implied by the 1995 data are presented together with a critique of the previous analysis.

hep-ph↗

arXiv1995

Neutrino oscillations with three-generation mixings and mass hierarchy

We have analyzed the results of reactor and accelerator neutrino oscillation experiments in a model with mixing of three neutrino fields and a neutrino mass hierarchy. It is shown that $ ν_μ\leftrightarrows ν_e $ oscillations with $ 0.6 \le Δm^2 \le 100 \, \mathrm{eV}^2 $ and amplitude larger than $ 2 \times 10^{-3} $ are not compatible with the existing limits on neutrino oscillations if the non-diagonal elements of the mixing matrix are small. Thus, if the excess of positron events recently observed in the LSND experiment is due to $ \barν_μ\to \barν_e $ oscillations, the mixing in the lepton sector is basically different from the CKM mixing of quarks.

hep-ph↗