arXiv subjects

Boris Panes

Publications and source records attributed to Boris Panes.

12 recordsLinked to original sources

arXiv2021

Identification of point sources in gamma rays using U-shaped convolutional neural networks and a data challenge

At GeV energies, the sky is dominated by the interstellar emission from the Galaxy. With limited statistics and spatial resolution, accurately separating point sources is therefore challenging. Here we present the first application of deep learning based algorithms to automatically detect and classify point sources from gamma-ray data. For concreteness we refer to this approach as AutoSourceID. To detect point sources, we utilized U-shaped convolutional networks for image segmentation and {\it k}-means for source clustering and localization. We also explored the Centroid-Net algorithm, which is designed to find and count objects. The training data are based on 9.5 years of exposure from The Fermi Large Area Telescope (Fermi-LAT) and we used source properties of active galactic nuclei (AGNs) and pulsars (PSRs) from the fourth Fermi-LAT source catalog (4FGL) in addition to several models of background interstellar emission. The results of the localization algorithm are fed into a classification neural network that is trained to separate the three general source classes (AGNs, PSRs, and FAKE sources). We compared our localization algorithms qualitatively with traditional methods and find them to have similar detection thresholds. We also demonstrate the robustness of our source localization algorithms to modifications in the interstellar emission models, which presents a clear advantage over traditional methods. The classification network is able to discriminate between the three classes with typical accuracy of $\sim$ 70%, as long as balanced data sets are used in classification training. In https://github.com/bapanes/AutoSourceID, we publish our training data sets and analysis scripts and invite the community to join the data challenge aimed to improve the localization and classification of gamma-ray point sources.

astro-ph.HE↗

arXiv2020

Probing the anomalous positron fraction origin with fully leptonic decaying gravitino dark matter candidates

The flux of electron and positron cosmic rays measured by the space-based experiments PAMELA, AMS-02, CALET, DAMPE and Fermi-LAT shows an unexpected behaviour at high energies, in comparison with expectations from standard astrophysical sources. In particular, AMS-02 observations provide compelling evidence for a new source of positrons and electrons whose origin is still unknown. Plausible scenarios include either the contribution of dark matter or unresolved astrophysical sources, such as nearby pulsars. It has been shown that explanations based mostly on dark matter, tend to overproduce gamma-rays, entering in conflict with measurements of the extra-galactic gamma-ray background (EGB). Although this situation seems to be quite generic, it ultimately depends on the properties of the dark matter candidate. In this work we revisit a model in which the gravitino is a dark matter candidate decaying to SM particles through R-parity violating couplings. We show that decay channels allowed by trilinear couplings produce more electrons and positrons and fewer photons in comparison to channels allowed by bilinear couplings. Indeed, when considering AMS-02 data alone we find that the trilinear model is compatible with EGB constraints. However, this result may change when DAMPE or CALET measurements of the sum of electrons and positrons fluxes are considered instead of AMS-02 data. Therefore, in order to evaluate this model further, discrepancies between the data collected by these experiments need to be clarified

hep-ph↗

arXiv2018

Seeking leptoquarks in IceCube

We investigate the sensitivity of IceCube(-Gen2) to a scalar leptoquark scenario with couplings only to heavy quark flavors which may be connected to solving discrepancies in $B$-meson semileptonic decays. We take into account, for the first time, the non-negligible neutrino-gluon cross section induced by leptoquarks, and we systematically account for indirect and direct constraints which have been overlooked in previous studies. We conclude that IceCube(-Gen2) can only probe the light LQ regime, already disfavored by the combination of flavor physics constraints, electroweak precision data and the direct searches at the LHC.

hep-ph↗

arXiv2016

How Unequal Fluxes of High Energy Astrophysical Neutrinos and Antineutrinos can Fake New Physics

Flavor ratios of very high energy astrophysical neutrinos, which can be studied at the Earth by a neutrino telescope such as IceCube, can serve to diagnose their production mechanism at the astrophysical source. The flavor ratios for neutrinos and antineutrinos can be quite different as we do not know how they are produced in the astrophysical environment. Due to this uncertainty the neutrino and antineutrino flavor ratios at the Earth also could be quite different. Nonetheless, it is generally assumed that flavor ratios for neutrinos and antineutrinos are the same at the Earth, in fitting the high energy astrophysical neutrino data. This is a reasonable assumption for the limited statistics for the data we currently have. However, in the future the fit must be performed allowing for a possible discrepancy in these two fractions in order to be able to disentangle different production mechanisms at the source from new physics in the neutrino sector. To reinforce this issue, in this work we show that a wrong assumption about the distribution of neutrino flavor ratios at the Earth may indeed lead to misleading interpretations of IceCube results.

hep-ph↗

arXiv2015

Confronting recent AMS-02 positron fraction and Fermi-LAT Extragalactic Gamma-Ray Background measurements with gravitino dark matter

Recent positron flux fraction measurements in cosmic-rays (CR) made by the AMS-02 satellite confirm and extends the evidence on the existence of a new (yet unknown) source of high energy positrons. To explain this excess, we use the gravitino of bilinear R-parity violating SUSY models as a decaying Dark Matter candidate, as the source of those high energy particles. Being a long lived weak-interacting and spin 3/2 particle, it offers several particularities which makes it an attractive candidate. We compute the electron, positron and $γ$-ray\ fluxes produced by each gravitino decay channel at the Earth. Combining the flux from the different decay modes we can fit AMS-02 measurements of the positron fraction, as well as the electron and positron fluxes, with a gravitino mass in the range $1-2$ TeV and lifetimes of $\sim 1.0-0.8\times 10^{26}$ s. . Then, we study the viability of these scenarios through their implications in $γ$-ray observations. We set limits on the gravitino lifetime using the Extragalactic $γ$-ray Background recently reported by the {\it Fermi}-LAT Collaboration and a state-of-the-art model of its known contributors. These limits exclude the gravitino parameter space which provides an acceptable explanation of the AMS-02 data. Therefore, we conclude that the gravitino of bilinear R-parity violating models is ruled out as the unique primary source of electrons and positrons needed to explain the rise in the positron fraction.

hep-ph↗

arXiv2015

Possible Interpretations of IceCube High-Energy Neutrino Events

We discuss possible interpretations of the 37 high energy neutrino events observed by the IceCube experiment in the South Pole. We examine the possibility to explain the observed neutrino spectrum exclusively by the decays of a heavy long-lived particle of mass in the PeV range. We compare this with the standard scenario, namely, a single power-law spectrum related to neutrinos produced by astrophysical sources and a viable hybrid situation where the spectrum is a product of two components: a power-law and the long-lived particle decays. We present a simple extension of the Standard Model that could account for the heavy particle decays that are needed in order to explain the data. We show that the current data equally supports all above scenarios and try to evaluate the exposure needed in order to falsify them in the future.

hep-ph↗

arXiv2014

Gravitino Dark Matter in Split Supersymmetry with Bilinear R-Parity Violation

In Split-SUSY with BRpV we show that the Gravitino DM solution is consistent with experimental evidence on its relic density and life time. We arrive at this conclusion by performing a complete numerical and algebraic study of the parameter space, including constraints from the recently determined Higgs mass, updated neutrino physics, and BBN constraints on NLSP decays. The Higgs mass requires a relatively low Split-SUSY mass scale, which is naturally smaller than usual values for reheating temperature, allowing the use of the standard expression for the relic density. We include restrictions from neutrino physics with three generations, and notice that the gravitino decay width depends on the atmospheric neutrino mass scale. We calculate the neutralino decay rate and find it consistent with BBN. We mention some implications on indirect DM searches.

hep-ph↗

arXiv2014

A survey for low stau yields in the MSSM

We study the implications of LHC results for the abundance of long-lived staus after freeze-out from thermal equilibrium in a super-WIMP dark matter scenario. We classify regions in the MSSM parameter space according to the stau yield, considering all possible co-annihilation effects as well as the effects of resonances and large Higgs-sfermion couplings. Afterwards, we examine the viability of these regions after imposing experimental and theoretical constraints, in particular a Higgs mass around 125 GeV and null-searches for heavy stable charged particles (HSCP) at the LHC. We work in a pMSSM framework and perform a Monte Carlo scan over the parameter space. To interpret the HSCP searches in our scenario, we consider all potentially important superparticle production processes, developing a fast estimator for NLO cross sections for electroweak and strong production at the LHC. After applying all constraints, we find that stau yields below 10^-14 occur only for resonant annihilation via a heavy Higgs in combination with either co-annihilation or large left-right stau mixing. We encounter allowed points with yields as low as 2x10^-16, thus satisfying limits from big bang nucleosynthesis even for large stau lifetimes.

hep-ph↗

arXiv2012

Minimum Length - Maximum Velocity

We study a framework where the hypothesis of a minimum length in space-time is complemented with the notion of reference frame invariance. It turns out natural to interpret the action of the obtained reference frame transformations in the context of doubly special relativity. As a consequence of this formalism we find interesting connections between the minimum length properties and the modified velocity-energy relation for ultra-relativistic particles. For example we can predict the ratio between the minimum lengths in space and time using the results from OPERA about superluminal neutrinos.

hep-ph↗

arXiv2009

Radiative Neutralino Decay in Split Supersymmetry

Radiative neutralino decay $χ^0_2 -> χ^0_1γ$ is studied in a Split Supersymmetric scenario, and compared with mSUGRA and MSSM. This 1-loop process has a transition amplitude which is often quite small, but has the advantage of providing a very clear and distinct signature: electromagnetic radiation plus missing energy. In Split Supersymmetry this radiative decay is in direct competition with the tree-level three-body decay $χ^0_2 -> χ^0_1 f\overline f$, and we obtain large values for the branching ratio $B(χ^0_2 -> χ^0_1γ)$ which can be close to unity in the region $M_2 \sim M_1$. Furthermore, the value for the radiative neutralino decay branching ratio has a strong dependence on the split supersymmetric scale $\widetilde{m}$, which is otherwise very difficult to infer from experimental observables.

hep-ph↗

arXiv2009

Gravity Effects on Neutrino Masses in Split Supersymmetry

The mass differences and mixing angles of neutrinos can neither be explained by R-Parity violating split supersymmetry nor by flavor blind quantum gravity alone. It is shown that combining both effects leads, within the allowed parameter range, to good agreement with the experimental results. The atmospheric mass is generated by supersymmetry through mixing between neutrinos and neutralinos, while the solar mass is generated by gravity through flavor blind dimension five operators. Maximal atmospheric mixing forces the tangent squared of the solar angle to be equal to 1/2. The scale of the quantum gravity operator is predicted within a 5% error, implying that the reduced Planck scale should lie around the GUT scale. In this way, the model is very predictive and can be tested at future experiments.

hep-ph↗

arXiv2008

Collider Phenomenology of Gauge-Higgs Unification Scenarios in Warped Extra Dimensions

We compute the couplings of the zero modes and first excited states of gluons, $W$'s, $Z$ gauge bosons, as well as the Higgs, to the zero modes and first excited states of the third generation quarks, in an RS Gauge-Higgs unification scenario based on a bulk $SO(5)\times U(1)_X$ gauge symmetry, with gauge and fermion fields propagating in the bulk. Using the parameter space consistent with electroweak precision tests and radiative electroweak symmetry breaking, we study numerically the dependence of these couplings on the parameters of our model. Furthermore, after emphasizing the presence of light excited states of the top quark, which couple strongly to the Kaluza Klein gauge bosons, the associated collider phenomenology is analyzed. In particular, we concentrate on the possible detection of the first excited state of the top, $t^1$, which tends to have a higher mass than the ones accessible via regular QCD production processes. We stress that the detection of these particles is still possible due to an increase in the pair production of $t^1$ induced by the first excited state of the gluon, $G^1$.

hep-ph↗