Search

The operation of the next generation of gamma-ray observatories will lead to a great advance in dark matter searches. In this paper, we use the hidden sectors hypothesis within the so-called secluded models to calculate the capabilities of the Southern Wide-field Gamma-ray Observatory (SWGO) to detect gamma-ray signatures produced by dark matter particles concentrated in the Sun. We assume the dark matter particle annihilates into metastable mediators which decay into $\gamma\gamma$, $e^+e^-$, $\tau^+\tau^-$, and $\bar{b}b$ outside the Sun. We found that the SWGO will be able to probe a spin-dependent cross-section of about $10^{-46}$ cm$^2$ for dark matter masses smaller than 5 TeV. This result shows an unprecedented sensitivity surpassing the current instruments by more than one order of magnitude., Comment: 15 pages, 3 figures

The detection of gravitational waves from a binary neutron star merger by Advanced LIGO and Advanced Virgo (GW170817), along with the discovery of the electromagnetic counterparts of this gravitational wave event, ushered in a new era of multimessenger astronomy, providing the first direct evidence that BNS mergers are progenitors of short gamma-ray bursts (GRBs). Such events may also produce very-high-energy (VHE, > 100GeV) photons which have yet to be detected in coincidence with a gravitational wave signal. The Cherenkov Telescope Array (CTA) is a next-generation VHE observatory which aims to be indispensable in this search, with an unparalleled sensitivity and ability to slew anywhere on the sky within a few tens of seconds. New observing modes and follow-up strategies are being developed for CTA to rapidly cover localization areas of gravitational wave events that are typically larger than the CTA field of view. This work will evaluate and provide estimations on the expected number of of gravitational wave events that will be observable with CTA, considering both on- and off-axis emission. In addition, we will present and discuss the prospects of potential follow-up strategies with CTA., Comment: Presented at the 38th International Cosmic Ray Conference (ICRC 2023), 2023 (arXiv:2309.08219)

The dark matter relic density may be governed by the presence of new mediators that connect the dark matter field with the Standard Model particles. When the dark matter particle mass is larger than the mediator's, the pair production of mediators is kinematically open. This setup is known in the literature as secluded dark matter. Motivated by the appearance of secluded dark matter in several model building endeavours, we investigate the sensitivity of TeV gamma-ray instruments in the Southern Hemisphere namely, H.E.S.S., CTA, and SWGO to secluded dark matter annihilating in the Galactic Halo. We exploit the complementarity aspects of these detectors to find restrictive bounds on the annihilation cross-section for different annihilation channels. In particular, for a dark matter particle mass of $2$~TeV, H.E.S.S. is able to constraint $\langle \sigma v \rangle \geq 4 \times 10^{-26}\,\, {\rm cm}^3\, {\rm s}^{-1}$ at 95\% confidence level for the $4q$ and $4\tau$ channel, while CTA will be sensitive to $\langle \sigma v \rangle \geq 7 \times 10^{-27}\,\, {\rm cm}^3\, {\rm s}^{-1}$ and SWGO $\langle \sigma v \rangle \geq 6 \times 10^{-27}\,\, {\rm cm}^3\, {\rm s}^{-1}$ for the $4\tau$ channel, both well below the thermal relic cross-section. In fact, the combination of CTA and SWGO will be able to probe cross-sections below the thermal relic value for dark matter particles in the whole mass range between 100 GeV and 100 TeV in the $4q$ and $4\tau$ channels, and between 100 GeV and $\sim$40 TeV in the $4b$ channel., Comment: 20 pages

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 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

Secluded dark matter is one of the most popular dark matter models, where dark matter annihilations go into particles that belong to a dark sector. An interesting way to probe such models is via indirect detection. In particular, gamma-ray observations are rather promising. Taking into account $1\%$ level of systematics, in this work we show that the Cherenkov Telescope Array (CTA) will place the most stringent bounds on the dark matter annihilation cross section, surpassing existing probes based on H.E.S.S., Fermi-LAT, and Planck data, for dark matter masses above $400$ GeV, independently of the channel and choosing the Einasto profile. We consider scenarios of secluded annihilations into leptophilic, leptophobic scalars and Higgs-like particles being able to exclude an annihilation cross section of $1.7 \times 10^{-25}$ cm$^3 \,$s$^{-1}$ for $m_{DM}=5000$ GeV, for $\phi \to e^+e^-$ channel, for example, exceeding the current limits by one order of magnitude., Comment: 9 pages, 14 figures. Matches version published in PLB

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., Comment: 18 pages, 8 figures, version accepted for publication in JCAP

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., Comment: 27 pages, 7 figures. It matched published version

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

It is imperative that any proposal of new physics possesses a Higgs-like boson with 125 GeV of mass and couplings with the standard particles that recover the branching ratios and signal strengths as measured by CMS and ATLAS. We address this issue within the supersymmetric version of the minimal 3-3-1 model. For this we develop the Higgs potential with focus on the lightest Higgs provided by the model. Our proposal is to verify if it recovers the properties of the standard Higgs. With respect to its mass, we calculate it up to one loop level by taking into account all contributions provided by the model. In regard to its couplings, we restrict our investigation to couplings of the Higgs-like boson with the standard particles, only. We then calculate the dominant branching ratios and the respective signal strengths and confront our results with the recent measurements of CMS and ATLAS. As distinctive aspects, we remark that our Higgs-like boson intermediates flavor changing neutral processes and then argue that its signature is the decay $t \rightarrow h+c$. We calculate its branching ratio and compare it with current bounds. We also show that the potential is stable for the region of parameter space employed in our calculations., Comment: 20 pages, 10 figures

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

Within the context of vector mediators, is a new signal observed in flavor changing interactions, particularly in the neutral mesons systems $K^{0}-\bar{K}^{0}$, $D^{0}-\bar{D}^{0}$ and $B^0-\bar{B^0}$, consistent with dilepton resonance searches at the LHC? In the attempt to address this very simple question, we discuss the complementarity between flavor changing neutral current (FCNC) and dilepton resonance searches at the LHC run 2 at $13$TeV with $3.2\, {\rm fb^{-1}}$ of integrated luminosity, in the context of vector mediators at tree level. Vector mediators, are often studied in the flavor changing framework, specially in the light of the recent LHCb anomaly observed at the rare B decay. However, the existence of stringent dilepton bound severely constrains flavor changing interactions, due to restrictive limits on the $Z^{\prime}$ mass. We discuss this interplay explicitly in the well motivated framework of a 3-3-1 scheme, where fermions and scalars are arranged in the fundamental representation of the weak SU(3) gauge group. Due to the paucity of relevant parameters, we conclude dilepton data leave little room for a possible new physics signal stemming from these systems, unless a very peculiar texture parametrization is used in the diagonalization of the CKM matrix. In other words, if a signal is observed in such flavor changing interactions, it is unlikely comes from a 3-3-1 model., Comment: 8 pages, 9 figures, Matches version accepted 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., Comment: Minor changes, references added, 20 pages, 4 figures and 1 table

We revisit the muon magnetic moment (g-2) in the context of Composite Higgs models and Technicolor, and provide general analytical expressions for computing the muon magnetic moment stemming from new fields such as, neutral gauge bosons, charged gauge bosons, neutral scalar, charged scalars, and exotic charged leptons type of particles. Under general assumptions we assess which particle content could address the $g-2_{\mu}$ excess. Moreover, we take a conservative approach and derive stringent limits on the particle masses in case the anomaly is otherwise resolved and comment on electroweak and collider bounds. Lastly, for concreteness we apply our results to a particular Technicolor model., Comment: 9 pages, 5 figures