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J. A. Grifols

Publications and source records attributed to J. A. Grifols.

26 records · Page 2Linked to original sources
arXiv1996

New Astrophysical Constraints on the Mass of the Superlight Gravitino

In some supergravity models, the superlight gravitino is accompanied by a light weakly coupled scalar (S) and pseudo-scalar (P) particle. The coupling of these particles to matter is inversely proportional to the product of the gravitino mass and the Planck mass. As a result, their emission from the stars and supernovae via the photon electron scattering reaction for certain ranges of the gravitino mass can become the dominant energy loss mechanism in contradiction with observations thereby ruling out those mass values for the gravitino. For scalar and/or pseudo-scalar masses between 10 MeV and a keV, the SN1987A observations exclude the gravitino mass range from 0.03 eV to 30 eV whereas if the S/P masses are less than a keV, constraints of stellar energy loss can exclude the gravitino masses ranging from $3\times 10^{-6}$ eV to 50 eV for the photino mass of 100 GeV. We also find that for S/P mass less than an MeV, Big Bang Nucleosynthesis constraints imply a gravitino mass larger than one eV. These are the most stringent bounds to date on the gravitino mass in this class of models.

hep-ph↗
arXiv1996

Leptonic Photons and Nucleosynthesis

Should $U(1)$ long-range forces be associated to electron, muon and/or tau quantum number then their ''fine structure constants" are seen to be bound by nucleosynthesis data to be less than about $1.7 \times 10^{-11}$. For $τ$ and $μ$ this is the best upper limit up to date

astro-ph↗
arXiv1996

Astrophysical bounds on superlight gravitinos

We derive the allowed mass range for the superlight gravitino present in a large class of supersymmetric models from the observed luminosity from Supernova 1987A. We find that for photino masses of order 100 GeV, the mass range $2.6\times 10^{-6} eV \leq m_{\tilde{g}} \leq 2.2\times 10^{-8} eV$ for the gravitino $\tilde{g}$ is excluded by SN1987A observations. Unlike the bounds on $m_{\tilde{g}}$ from nucleosynthesis, the bounds in the present paper do not depend critically on the uncertainties of the observational input.

hep-ph↗
arXiv1996

Gamma Rays from SN1987A due to Pseudoscalar Conversion

A light pseudoscalar coupled to two photons would be copiously emitted by the core of a supernova. Part of this flux would be converted to $γ-$rays by the galactic magnetic field. Measurements on the SN1987A $γ-$ray flux by the Gamma-Ray Spectrometer on the Solar Maximum Mission satellite already imply a bound on the coupling $g < 3 \times 10^{-12}$ GeV$^{-1}$. The improved generation of satellite-borne detectors, like EGRET or the project GLAST, could be able to detect a pseudoscalar-to-photon signal from a nearby supernova, for allowed values of $g$.

astro-ph↗
arXiv1995

Bound states of scalar bosons in extensions of the Standard Model

We explore systematically, in a general two Higgs doublet model, the possibility, that bound systems of scalar bosons do exist. We find a wide region of parameter space in the scalar potential for which S-wave bound states of Higgs bosons do indeed exist. On the contrary we show that the Minimal Supersimmetric Standard Model does not admit such bound systems.

hep-ph↗
arXiv1994

Residual long-range pseudoscalar forces between unpolarised macroscopic bodies

In this paper we survey the effects of residual long-range forces associated to $γ_5$-spin dependent-couplings of fermions to massless bosons exerted by unpolarised bulk matter over macroscopic distances. We establish that such forces with behaviour proportional to $R^{-6}$ do indeed exist. They arise as a quantum mechanical effect due to simultaneous exchange of two quanta. We explore their presence in existing astronomical as well as laboratory data on non-newtonian components of the force between macroscopic bodies. Since no limits on their real existence could be found, we conclude that residual long-range pseudoscalar attractive and composition dependent forces between neutral unpolarised bulk matter extending over macroscopic distances are very efficiently shielded over a huge range of distances: from astronomical scales down to the micron scale.

hep-ph↗