arXiv subjects

Graciela B. Gelmini

Publications and source records attributed to Graciela B. Gelmini.

At least 73 records · Page 4Linked to original sources

arXiv2012

Halo independent comparison of direct dark matter detection data

We extend the halo-independent method of Fox, Liu, and Weiner to include energy resolution and efficiency with arbitrary energy dependence, making it more suitable for experiments to use in presenting their results. Then we compare measurements and upper limits on the direct detection of low mass ($\sim10$ GeV) weakly interacting massive particles with spin-independent interactions, including the upper limit on the annual modulation amplitude from the CDMS collaboration. We find that isospin-symmetric couplings are severely constrained both by XENON100 and CDMS bounds, and that isospin-violating couplings are still possible at the lowest energies, while the tension of the higher energy CoGeNT bins with the CDMS modulation constraint remains. We find the CRESST II signal is not compatible with the modulation signals of DAMA and CoGeNT.

hep-ph↗

arXiv2012

Fits to Light WIMPs

We review fits to "light WIMPs" since the region was first mentioned relative to the DAMA collaboration data in 2003 to the present, analyzing the compatibility of potential signals and bounds in this region. We include dark halo independent data comparisons.

hep-ph↗

arXiv2012

Aberration features in directional dark matter detection

The motion of the Earth around the Sun causes an annual change in the magnitude and direction of the arrival velocity of dark matter particles on Earth, in a way analogous to aberration of stellar light. In directional detectors, aberration of weakly interacting massive particles (WIMPs) modulates the pattern of nuclear recoil directions in a way that depends on the orbital velocity of the Earth and the local galactic distribution of WIMP velocities. Knowing the former, WIMP aberration can give information on the latter, besides being a curious way of confirming the revolution of the Earth and the extraterrestrial provenance of WIMPs. While observing the full aberration pattern requires extremely large exposures, we claim that the annual variation of the mean recoil direction or of the event counts over specific solid angles may be detectable with moderately large exposures. For example, integrated counts over Galactic hemispheres separated by planes perpendicular to Earth's orbit would modulate annually, resulting in Galactic Hemisphere Annual Modulations (GHAM) with amplitudes larger than the usual non-directional annual modulation.

astro-ph.CO↗

arXiv2012

Ring-like features in directional dark matter detection

We discuss a novel dark matter signature relevant for directional detection of Weakly Interacting Massive Particles (WIMPs). For heavy enough WIMPs and low enough recoil energies, the maximum of the recoil rate is not in the direction of the average WIMP arrival direction but in a ring around it at an angular radius that increases with the WIMP mass and can approach 90 degrees at very low energies. The ring is easier to detect for smaller WIMP velocity dispersion and larger average WIMP velocities relative to the detector. In principle the ring could be used as an additional indication of the WIMP mass range.

astro-ph.CO↗

arXiv2012

Recoiling Ion-Channeling in Direct Dark Matter Detectors

The channeling of the recoiling nucleus in crystalline detectors after a WIMP collision would produce a larger scintillation or ionization signal in direct detection experiments than otherwise expected. I present estimates of channeling fractions obtained using analytic models developed from the 1960's onwards to describe channeling and blocking effects. We find the fractions to be too small to affect the fits to potential WIMP candidates. I also examine the possibility of detecting a daily modulation of the dark matter signal due to channeling.

astro-ph.CO↗

arXiv2011

Gamma-Ray Constraints on Maximum Cosmogenic Neutrino Fluxes and UHECR Source Evolution Models

The dip model assumes that the ultra-high energy cosmic rays (UHECRs) above 10$^{18}$ eV consist exclusively of protons and is consistent with the spectrum and composition measure by HiRes. Here we present the range of cosmogenic neutrino fluxes in the dip-model which are compatible with a recent determination of the extragalactic very high energy (VHE) gamma-ray diffuse background derived from 2.5 years of Fermi/LAT data. We show that the largest fluxes predicted in the dip model would be detectable by IceCube in about 10 years of observation and are within the reach of a few years of observation with the ARA project. In the incomplete UHECR model in which protons are assumed to dominate only above 10$^{19}$ eV, the cosmogenic neutrino fluxes could be a factor of 2 or 3 larger. Any fraction of heavier nuclei in the UHECR at these energies would reduce the maximum cosmogenic neutrino fluxes. We also consider here special evolution models in which the UHECR sources are assumed to have the same evolution of either the star formation rate (SFR), or the gamma-ray burst (GRB) rate, or the active galactic nuclei (AGN) rate in the Universe and found that the last two are disfavored (and in the dip model rejected) by the new VHE gamma-ray background.

astro-ph.CO↗

arXiv2011

Direct Dark Matter Searches: Fits to WIMP Candidates

After a brief introduction to dark matter in general and to WIMPs as candidates, we review recent results of direct dark matter searches. We concentrate on older and more recent hints pointing to light WIMP's with mass below 10 GeV.

hep-ph↗

arXiv2011

Daily modulation due to channeling in direct dark matter crystalline detectors

The channeling of the ion recoiling after a collision with a WIMP in direct dark matter crystalline detectors produces a larger scintillation or ionization signal than otherwise expected. Channeling is a directional effect which depends on the velocity distribution of WIMPs in the dark halo of our Galaxy and could lead to a daily modulation of the signal. Here we compute upper bounds to the expected amplitude of daily modulation due to channeling using channeling fractions that we obtained with analytic models in prior work. After developing the general formalism, we examine the possibility of finding a daily modulation due to channeling in the data already collected by the DAMA/NaI and DAMA/LIBRA experiments. We find that even the largest daily modulation amplitudes (of the order of 10% in some instances) would not be observable for WIMPs in the standard halo in the 13 years of data taken by the DAMA collaboration. For these to be observable the DAMA total rate should be 1/40 of what it is or the total DAMA exposure should be 40 times larger. The daily modulation due to channeling will be difficult to measure in future experiments. We find it could be observed for light WIMPs in solid Ne, assuming no background.

astro-ph.CO↗

arXiv2011

Channeling in solid Xe, Ar and Ne direct dark matter detectors

The channeling of the ion recoiling after a collision with a WIMP changes the ionization signal in direct detection experiments, producing a larger scintillation or ionization signal than otherwise expected. We give estimates of the fraction of channeled recoiling ions in solid Xe, Ar and Ne crystals using analytic models produced since the 1960's and 70's to describe channeling and blocking effects.

astro-ph.CO↗

arXiv2010

Ion-Channeling in Direct Dark Matter Crystalline Detectors

hep-ph↗

arXiv2010

Channeling in direct dark matter detection I: channeling fraction in NaI (Tl) crystals

The channeling of the ion recoiling after a collision with a WIMP changes the ionization signal in direct detection experiments, producing a larger signal than otherwise expected. We give estimates of the fraction of channeled recoiling ions in NaI (Tl) crystals using analytic models produced since the 1960's and 70's to describe channeling and blocking effects. We find that the channeling fraction of recoiling lattice nuclei is smaller than that of ions that are injected into the crystal and that it is strongly temperature dependent.

astro-ph.CO↗

arXiv2010

Channeling in direct dark matter detection II: channeling fraction in Si and Ge crystals

The channeling of the ion recoiling after a collision with a WIMP changes the ionization signal in direct detection experiments, producing a larger signal than otherwise expected. We give estimates of the fraction of channeled recoiling ions in Si and Ge crystals using analytic models produced since the 1960's and 70's to describe channeling and blocking effects. We used data obtained to avoid channeling in the implantation of dopants in Si crystals to test our models.

astro-ph.CO↗

arXiv2010

Channeling in direct dark matter detection III: channeling fraction in CsI crystals

The channeling of the ion recoiling after a collision with a WIMP changes the ionization signal in direct detection experiments, producing a larger signal scintillation or ionization than otherwise expected. We give estimates of the fraction of channeled recoiling ions in CsI crystals using analytic models produced since the 1960's and 70's to describe channeling and blocking effects.

astro-ph.CO↗

arXiv2009

Inert-Sterile Neutrino: Cold or Warm Dark Matter Candidate

In usual particle models, sterile neutrinos can account for the dark matter of the Universe only if they have masses in the keV range and are warm dark matter. Stringent cosmological and astrophysical bounds, in particular imposed by X-ray observations, apply to them. We point out that in a particular variation of the inert doublet model, sterile neutrinos can account for the dark matter in the Universe and may be either cold or warm dark matter candidates, even for masses much larger than the keV range. These Inert-Sterile neutrinos, produced non-thermally in the early Universe, would be stable and have very small couplings to Standard Model particles, rendering very difficult their detection in either direct or indirect dark matter searches. They could be, in principle, revealed in colliders by discovering other particles in the model.

hep-ph↗

arXiv2009

Relevance of Ion-Channeling for Direct DM Detection

The channeling of the recoiling nucleus in crystalline detectors after a WIMP collision would produce a larger scintillation or ionization signal in direct detection experiments than otherwise expected. I present estimates of the importance of this effect for the total direct detection rate and the daily modulation of the signal using analytic models produced in the 1960's and 70's to describe the effects of channeling and blocking in crystals.

hep-ph↗

arXiv2009

Experimental signatures of non-standard pre-BBN cosmologies

If detected, dark matter particles such as WIMPs and sterile neutrinos will be the earliest relics we can study, the first coming from before Big Bang Nucleosynthesis, an epoch from which we have no data so far. Here we discuss how different pre-BBN cosmological models affect the properties of these particles, and how these properties could thus allow to determine the evolution of the Universe before BBN.

hep-ph↗

arXiv2009

High energy cosmic rays

I review here some of the physics we are learning and expect to learn in the near future through the observation of cosmic rays. The study of cosmic rays involves a combination of data from accelerators, ground arrays, atmospheric fluorescence detectors and balloon and satellite experiments. I will discuss the data of the Pierre Auger Observatory, PAMELA, ATIC and FST among other experiments.

astro-ph.HE↗

arXiv2008

Search for Dark Matter

The search for dark matter is a very wide an active field of research, and I necessarily concentrate here only in some aspects of it. I will review the prospects for direct and indirect dark matter searches of Weakly Interacting Massive Particles in the dark halo of our galaxy and focus in particular on the data of GLAST, PAMELA and DAMA.

hep-ph↗