Search

Dark matter is one of the most important open problems in particle physics and cosmology. Weakly interacting massive particles (WIMPs) appear as an appealing solution, providing the right relic density with a cross-section at the electroweak scale, however, no WIMP signals were observed until now. Secluded models are good alternatives to the standard ones. In this case, instead of a direct annihilation to the standard model (SM) particles, the dark matter annihilates into mediators which subsequently decay into SM particles. In this way, secluded models may avoid the stringent limits from direct searches, and, at the same time, be probed by indirect detection experiments. Motivated by the appearance of secluded dark matter in several model building endeavors, in this talk, we will present the sensitivity of several gamma-ray instruments (current and prospects), including Fermi-LAT, H.E.S.S., CTA, and SWGO, to secluded dark matter annihilations in the inner galactic halo, and in the dwarf spheroidal galaxies, covering a wide range dark matter masses, from tens of GeV to hundreds of TeV., Comment: 8 pages, 3 figures, talk presented at the 37th ICRC

Meson decays offer a good opportunity to probe new physics. The rare kaon decay K+→π+νν¯ is one of the cleanest of them and, for this reason, is rather sensitive to new physics, in particular, vector mediators. The NA62 Collaboration, running a fixed-target experiment at CERN, recently reported an unprecedented sensitivity to this decay, namely a branching fraction of BR(K+→π+νν¯)=(11-3.5+4.0)×10-11 at 68% C.L. Vector mediators that couple to neutrinos may yield a sizeable contribution to this decay. Motivated by the new measurement, we interpret this result in the context of a concrete Z′ model, and put our findings into perspective with the correlated KL→π0νν¯ decay measured by the KOTO Collaboration, current, and future colliders, namely the High-Luminosity and High-Energy Large Hadron Collider. Meson decays offer a good opportunity to probe new physics. The rare kaon decay $K^+ \rightarrow \pi^+ \nu\bar{\nu}$ is one of the cleanest of them and, for this reason, is rather sensitive to new physics, in particular, vector mediators. NA62 collaboration, running a fixed-target experiment at CERN, recently reported an unprecedented sensitivity to this decay, namely a branching fraction of $BR(K^+ \rightarrow \pi^+ \nu\bar{\nu}) = (11^{+4.0}_{-3.5})\times 10^{-11}$ at 68% C.L. Vector mediators that couple to neutrinos may yield a sizeable contribution to this decay. Motivated by the new measurement, we interpret this result in the context of a concrete $Z^\prime$ model, and put our findings into perspective with the correlated $K_L \rightarrow \pi^0 \nu \bar{\nu}$ decay measured by KOTO collaboration, current, and future colliders, namely the High-Luminosity and High-Energy LHC.

Right-handed neutrinos appear in several extensions beyond the Standard Model, specially in connection to neutrino masses. Motivated by this, we present a model of right-handed neutrino dark matter that interacts with Standard Model particles through a new gauge symmetry as well as via mass mixing between the new vector field and the Z boson, and investigate different production mechanisms. We derive the dark matter relic density when the Hubble rate is faster than usual, when dark matter decouples in a matter domination epoch, and when it decouples in a radiation domination regime, which is then followed by a matter domination era. The direct detection rate features a spin-independent but velocity suppressed operators, as well as a spin-dependent operator when the mass mixing is correctly accounted for. We put all these results into perspective with existing flavor physics, atomic parity violation, and collider bounds. Lastly, we outline the region of parameter space in which a weak scale right-handed neutrino dark matter stands as a viable dark matter candidate., Comment: 15 pages, 8 figures

We investigate simplified models involving an inert scalar triplet and vector-like leptons that can account for the muon $g-2$ anomaly. These simplified scenarios are embedded in a model that features W' and Z' bosons, which are subject to stringent collider bounds. The constraints coming from the muon $g-2$ anomaly are put into perspective with collider bounds, as well as bounds coming from lepton flavor violation searches. The region of parameter space that explains the $g-2$ anomaly is shown to be within reach of lepton flavor violation probes and future colliders such as HL-LHC and HE-LHC., 8 pages, 6 figures. Version accepted for publication in PRD

We explore the dark matter phenomenology of a weak-scale right-handed neutrino in the context of a Two Higgs Doublet Model. The expected signal at direct detection experiments is different from the usual spin-independent and spin-dependent classification since the scattering with quarks depends on the dark matter spin. The dark matter relic density is set by thermal freeze-out and in the presence of non-standard cosmology, where an Abelian gauge symmetry is key for the dark matter production mechanism. We show that such symmetry allows us to simultaneously address neutrino masses and the flavor problem present in general Two Higgs Doublet Model constructions. Lastly, we outline the region of parameter space that obeys collider, perturbative unitarity and direct detection constraints., Comment: 27 pages, 3 figures. Matches the version accepted for publication in JCAP

We have witnessed in the past decade the observation of a puzzling cosmic-ray excess at energies larger than $10$ GeV. The AMS-02 data published this year has new ingredients such as the bump around $300$ GeV followed by a drop at $800$ GeV, as well as smaller error bars. Adopting the background used by the AMS-02 collaboration in their analysis, one can conclude that previous explanations to the new AMS-02 such as one component annihilating and decaying dark matter as well as pulsars seem to fail at reproducing the data. Here, we show that in the right-handed neutrino portal might reside the answer. We discuss a decaying two-component dark matter scenario where the two-body decay products are right-handed neutrinos that have their decay pattern governed by the type I seesaw mechanism. This setup provides a very good fit to data, for example, for a conservative approach including just statistical uncertainties leads to $\chi^2/d.o.f \sim 2.3$ for $m_{DM_1}=2150$ GeV with $\tau_{1}=3.78 \times 10^{26}$ s and $m_{DM_2}=300$ with $\tau_{2}=5.0 \times 10^{27}$ s for $M_N=10$ GeV, and, in an optimistic case, including systematic uncertainties, we find $\chi^2/d.o.f \sim 1.12$, for $M_N = 10$ GeV, with $m_{DM_1}=2200$ GeV with $\tau_{1}=3.8 \times 10^{26}$ s and $m_{DM_2}=323$ GeV with $\tau_{2}=1.68 \times 10^{27}$ s., Comment: 9 pages, 10 figures; Accepted for publication in PRD

There is convincing observational evidence for an increasing cosmic-ray positron-to-electron ratio at energies larger than $\sim 10$~GeV, at odds with expectations from secondary positron production. The most recent AMS-02 data exhibit an interesting spectral feature consisting of a bump at an energy around $300$~GeV followed by a drop around $\sim 800$~GeV. A possible explanation to the most recent data is that the excess positron originates from decaying dark matter. Here, we show that models consisting of two dark matter particle species contributing equally to the global cosmological dark matter density provide strikingly good fits to the data. The favored models, with a best-fit with $\chi^2/d.o.f \sim 0.5$ consist of a first species weighing $750$~GeV decaying with a lifetime $\tau_{\chi}\sim 10^{26}$~s to $\tau$ lepton pairs (or to a pair of vector bosons subsequently decaying to a $\tau$ pair each), and a second species with a mass around 2.3 TeV decaying to $\mu$ lepton pairs. We provide a few possible concrete realizations for this scenario., Comment: 6 pages, 2 figures

Short-lived mediators are often used to describe dark matter interactions with Standard Model particles. When the dark matter mass is heavier than the mass of the mediator, it may self-annihilate into short-lived mediators, and in some cases this might be the dominant annihilation channel. This scenario is known as secluded dark matter. We use Fermi-LAT observations of dwarf spheroidal galaxies, H.E.S.S. data from the Galactic center, and Planck measurements of the Cosmic Microwave Background to constrain secluded dark matter. We explore the interplay between these experiments and we assess the impact of the mediator mass on our bounds, an often overlooked yet very important point. In particular, we exclude pair -annihilation cross-sections greater or on the order of $\sigma v \sim 4 \times 10^{-27} {\rm cm^3/s}$ for dark matter masses around $10$~GeV and greater or on the order of $\sigma v \sim \times 10^{-25} {\rm cm^3/s}$ for dark matter masses around a TeV. Our findings supersede previous constraints which use Fermi-LAT data, and constitute the first limits on secluded dark sectors using the H.E.S.S. telescope. We also show that one can fit TeV gamma-ray observations from H.E.S.S. with secluded dark matter annihilations, with the mediator mass impacting the best-fit dark matter particle mass. Our findings indicate that any assessment of secluded dark sectors in the context of indirect detection significantly depends on the choice of the mediator mass., Comment: 29 pages, 12 figures. References included and H.E.S.S. limits updated

We discuss the phenomenology of an MeV-scale Dirac fermion coupled to the Standard Model through a dark photon with kinetic mixing with the electromagnetic field. We compute the dark matter relic density and explore the interplay of direct detection and accelerator searches for dark photons. We show that precise measurements of the temperature and polarization power spectra of the Cosmic Microwave Background Radiation lead to stringent constraints, leaving a small window for the thermal production of this MeV dark matter candidate. The forthcoming MeV gamma-ray telescope e-ASTROGAM will offer important and complementary opportunities to discover dark matter particles with masses below 10 MeV. Lastly, we discuss how a late-time inflation episode and freeze-in production could conspire to yield the correct relic density while being consistent with existing and future constraints., 27 pages, 7 figures. It matched published version

Dark matter annihilations have been fiercely restricted by the non-observation of excess events in indirect detection probes. Typically the interactions that dictate annihilation are also present in the dark matter-nucleon scattering cross section, also severely constrained by direct detection experiments. Semi-annihilations arise as a possible way to ameliorate the tension and even change the standard dark matter relic density calculation. In this work, we derive indirect detection bounds for several semi-annihilation channels including gauge bosons, the Higgs, leptophilic and leptophobic scalars. Our analysis is based on the gamma-ray observations in the direction of Dwarf Spheroidal Galaxies (Fermi-LAT) and the Galactic Center (H.E.S.S.), and Planck measurements of Cosmic Background Radiation. In addition, we derive the prospects for the Cherenkov Telescope Array (CTA) sensitivity to all these semi-annihilation modes., 18 pages, 8 figures, version accepted for publication in JCAP

A puzzling excess in gamma-rays at GeV energies has been observed in the center of our galaxy using Fermi-LAT data. Its origin is still unknown, but it is well fitted by Weakly Interacting Massive Particles (WIMPs) annihilations into quarks with a cross section around $10^{-26}{\rm cm^3 s^{-1}}$ with masses of $20-50$~GeV, scenario which is promptly revisited. An excess favoring similar WIMP properties has also been seen in anti-protons with AMS-02 data potentially coming from the Galactic Center as well. In this work, we explore the possibility of fitting these excesses in terms of semi-annihilating dark matter, dubbed as semi-Hooperon, with the process ${\rm WIMP\, WIMP \rightarrow WIMP\, X}$ being responsible for the gamma-ray excess, where X=h,Z. An interesting feature of semi-annihilations is the change in the relic density prediction compared to the standard case, and the possibility to alleviate stringent limits stemming from direct detection searches. Moreover, we discuss which models might give rise to a successful semi-Hooperon setup in the context of $\mathcal{Z}_3$,$\mathcal{Z}_4$ and extra "dark" gauge symmetries., Comment: 8 pages, 3 figures, version published in Phys. Lett. B

This work deals with right handed sneutrino as thermal cold dark matter candidate. This scalar emerges in a supersymmetric version of $SU(3)_c \otimes SU(3)_L \otimes U(1)_X$ gauge model where right handed neutrinos are a natural component of leptonic chiral scalar supermultiplets. We first consider the issue of a $125$~GeV Higgs boson mass in this model, showing that constraints on stop mass and trilinear soft coupling are considerably alleviated compared to MSSM. Then we investigate the region of parameter space that is consistent with right handed sneutrino as thermal cold dark matter, under the light of Planck results on the relic abundance and direct detection from LUX experiment. This sneutrino mainly annihilates through an extra neutral gauge boson, $Z^\prime$, and Higgs exchange, so that the physics of dark matter is somewhat related to the parameters determining Higgs and $Z^\prime$ masses. We then obtain that right handed sneutrino in this model must be heavier than $400$~GeV to conform with Planck and LUX, simultaneously constraining the $Z^\prime$ mass to be above 2400~GeV, which is in perfect agreement with LHC searches in a non-supersymmetric version of this model., Minor changes, references added, 20 pages, 4 figures and 1 table