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Daniel E. Lopez-Fogliani

Publications and source records attributed to Daniel E. Lopez-Fogliani.

At least 19 recordsLinked to original sources

Insights into Dark Matter Direct Detection Experiments: Decision Trees versus Deep Learning

The detection of Dark Matter (DM) remains a significant challenge in particle physics. This study exploits advanced machine learning models to improve detection capabilities of liquid xenon time projection chamber experiments, utilizing state-of-the-art transformers alongside traditional methods like Multilayer Perceptrons and Convolutional Neural Networks. We evaluate various data representations and find that simplified feature representations, particularly corrected S1 and S2 signals as well as a few shape-related features including the time difference between signals, retain critical information for classification. Our results show that while transformers offer promising performance, simpler models like XGBoost can achieve comparable results with optimal data representations. We also derive exclusion limits in the cross-section versus DM mass parameter space, showing minimal differences between XGBoost and the best performing deep learning models. The comparative analysis of different machine learning approaches provides a valuable reference for future experiments by guiding the choice of models and data representations to maximize detection capabilities.

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Phenomenological implications of sterile neutrinos in the $μν$SSM and dark matter

We analyze the role of sterile neutrinos in the framework of the $μν$SSM, where the presence of right-handed neutrinos provides a simultaneous solution to $μ$- and $ν$-problems in supersymmetry. We adopt a minimalistic approach, reproducing light neutrino masses and mixing angles at tree level using just two right-handed neutrinos as part of the seesaw mechanism. A third right-handed neutrino does not contribute significantly to the mass of the three active ones, behaving as a sterile neutrino with a mass in the range keV$-$MeV. Furthermore, a sterile neutrino of about $10$ keV can be a good candidate for dark matter with a lifetime larger than the age of the Universe. In particular, the three-body decay to active neutrinos gives the dominant contribution to its lifetime. The one-loop decay to gamma and active neutrino is subdominant, but relevant for observations such as astrophysical X-rays. We find regions of the parameter space of the $μν$SSM, with different values of the sterile neutrino mass, fulfilling not only these constraints but also collider constraints from the Higgs sector.

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Right-handed sneutrino and gravitino multicomponent dark matter in light of neutrino detectors

We investigate the possibility that right-handed (RH) sneutrinos and gravitinos can coexist and explain the dark matter (DM) problem. We compare extensions of the minimal supersymmetric standard model (MSSM) and the next-to-MSSM (NMSSM) adding RH neutrinos superfields, with special emphasis on the latter. If the gravitino is the lightest supersymmetric particle (LSP) and the RH sneutrino the next-to-LSP (NLSP), the heavier particle decays to the former plus left-handed (LH) neutrinos through the mixing between the scalar partners of the LH and RH neutrinos. However, the interaction is suppressed by the Planck mass, and if the LH-RH sneutrino mixing parameter is small, $\ll O(10^{-2})$, a long-lived RH sneutrino NLSP is possible even surpassing the age of the Universe. As a byproduct, the NLSP to LSP decay produces monochromatic neutrinos in the ballpark of current and planned neutrino telescopes like Super-Kamiokande, IceCube and Antares that we use to set constraints and show prospects of detection. In the NMSSM+RHN, assuming a gluino mass parameter $M_3 = 3$ TeV we found the following lower limits for the gravitino mass $m_{3/2} \gtrsim 1-600$ GeV and the reheating temperature $T_R \gtrsim 10^5 - 3 \times 10^7$ GeV, for $m_{\tildeν_R} \sim 10-800$ GeV. If we take $M_3=10$ TeV, then the limits on $T_R$ are relaxed by one order of magnitude.

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The new $(g-2)_μ$ and Right-Handed Sneutrino Dark Matter

In this paper we investigate the $(g-2)_μ$ discrepancy in the context of the R-parity conserving next-to-minimal supersymmetric Standard Model plus right-handed neutrinos superfields. The model has the ability to reproduce neutrino physics data and includes the interesting possibility to have the right-handed sneutrino as the lightest supersymmetric particle and a viable dark matter candidate. Since right-handed sneutrinos are singlets, no new contributions for $δa_μ$ with respect to the MSSM and NMSSM are present. However, the possibility to have the right-handed sneutrino as the lightest supersymmetric particle opens new ways to escape Large Hadron Collider and direct detection constraints. In particular, we find that dark matter masses within $10 \lesssim m_{\tildeν_{R}} \lesssim 600$ GeV are fully compatible with current experimental constraints. Remarkably, not only spectra with light sleptons are needed, but we obtain solutions with $m_{\tildeμ} \gtrsim 600$ GeV in the entire dark matter mass range that could be probed by new $(g-2)_μ$ data in the near future. In addition, dark matter direct detection experiments will be able to explore a sizable portion of the allowed parameter space with $m_{\tildeν_{R}} \lesssim 300$ GeV, while indirect detection experiments will be able to probe a much smaller fraction within $200 \lesssim m_{\tildeν_{R}} \lesssim 350$ GeV.

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Dark matter candidates in the NMSSM with RH neutrino superfields

R-parity conserving supersymmetric models with right-handed (RH) neutrinos are very appealing since they could naturally explain neutrino physics and also provide a good dark matter (DM) candidate such as the lightest supersymmetric particle (LSP). In this work we consider the next-to-minimal supersymmetric standard model (NMSSM) plus RH neutrino superfields, with effective Majorana masses dynamically generated at the electroweak scale (EW). We perform a scan of the relevant parameter space and study both possible DM candidates: RH sneutrino and neutralino. Especially for the case of RH sneutrino DM we analyse the intimate relation between both candidates to obtain the correct amount of relic density. Besides the well-known resonances, annihilations through scalar quartic couplings and coannihilation mechanisms with all kind of neutralinos, are crucial. Finally, we present the impact of current and future direct and indirect detection experiments on both DM candidates.

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Explaining muon $g-2$ data in the $μν$SSM

We analyze the anomalous magnetic moment of the muon $g-2$ in the $μν$SSM. This $R$-parity violating model solves the $μ$ problem reproducing simultaneously neutrino data, only with the addition of right-handed neutrinos. In the framework of the $μν$SSM, light left muon-sneutrino and wino masses can be naturally obtained driven by neutrino physics. This produces an increase of the dominant chargino-sneutrino loop contribution to muon $g-2$, solving the gap between the theoretical computation and the experimental data. To analyze the parameter space, we sample the $μν$SSM using a likelihood data-driven method, paying special attention to reproduce the current experimental data on neutrino and Higgs physics, as well as flavor observables such as $B$ and $μ$ decays. We then apply the constraints from LHC searches for events with multi-leptons + MET on the viable regions found. They can probe these regions through chargino-chargino, chargino-neutralino and neutralino-neutralino pair production. We conclude that significant regions of the parameter space of the $μν$SSM can explain muon $g-2$ data.

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Searching for Supersymmetry: The $μν$SSM

We review the role played by the '$μ$ from $ν$' supersymmetric standard model ($μν$SSM) in the search for supersymmetry. First, we discuss its theoretical motivation, that is the simultaneous solution of $μ$- and $ν$-problems through the introduction of right-handed neutrinos. The latter produces $R$-parity violation (RPV), giving rise to interesting signals of new physics. As by-products, in the $μν$SSM there are dark matter candidates, and electroweak baryogenesis can be realized. Then, we survey signals by which the model could be tested at the large hadron collider (LHC). In addition to the enlarged Higgs sector with sneutrinos, we put special emphasis in analyzing the intimate connection between the lightest supersymmetric particle (LSP) lifetime and the size of neutrino Yukawa couplings. Displaced vertices and/or multileptons are some of the interesting signatures that can be probed. Finally, we discuss possible extensions of the $μν$SSM such as the inclusion in the superpotential of the conventional trilinear lepton-number violating couplings, the addition of an extra $U(1)'$ gauge group to the symmetry of the standard model, or the reinterpretation of the Higgs doublets as a fourth family of leptons superfields motivating the existence of a fourth family of vector-like quark doublet superfields.

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MeV-GeV $γ$-ray telescopes probing gravitino LSP with coexisting axino NLSP as dark matter in the $μν$SSM

In $R$-parity violating supersymmetry, the gravitino as the lightest supersymmetric particle (LSP) is a good candidate for dark matter, with the interesting characteristic to be detectable through $γ$-ray telescopes. We extend this analysis considering an axino next-to-LSP (NLSP) as a coexisting dark matter particle contributing with a detectable signal in the $γ$-ray spectrum. The analysis is carried out in the framework of the $μν$SSM, which solves the $μ$ problem reproducing simultaneously neutrino data only with the addition of right-handed neutrinos. We find that important regions of the parameter space can be tested by future MeV-GeV $γ$-ray telescopes through the line signal coming from the decay of the axino NLSP into photon-neutrino. In a special region, a double-line signal from axino NLSP and gravitino LSP is possible with both contributions detectable.

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MeV-GeV $γ$-ray telescopes probing axino LSP/gravitino NLSP as dark matter in the $μν$SSM

Axino and gravitino are promising candidates to solve the dark matter (DM) problem in the framework of supersymmetry. In this work, we assume that the axino is the lightest supersymmetric particle (LSP), and therefore contributes to DM. In the case of R-parity violating models, the axino can decay into a neutrino-photon pair with a lifetime much longer than the age of the Universe, yielding a potentially detectable signal. Interestingly, a gravitino next-to-LSP (NLSP) can live enough as to contribute to the relic density. We study both scenarios, only axino LSP as DM, and axino LSP with gravitino NLSP as DM. We carry out the analysis in the context of the $μν$SSM, which solves the $μ$ problem and reproduces neutrino data, only adding couplings involving right-handed neutrinos. In particular, we perform a complete analysis of the relevant parameter space of the model considering constraints from neutrino physics, cosmological observations, and $γ$-ray detection. We find that the axino or the gravitino can produce a signal detectable by future MeV-GeV $γ$-ray telescopes. In addition, in a parameter region where we get a well-tempered mixture of both particles, a double-line signal arises as a smoking gun.

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Sampling the $μν$SSM for displaced decays of the tau left sneutrino LSP at the LHC

Within the framework of the $μν$SSM, a displaced dilepton signal is expected at the LHC from the decay of a tau left sneutrino as the lightest supersymmetric particle (LSP) with a mass in the range $45 - 100$ GeV. We compare the predictions of this scenario with the ATLAS search for long-lived particles using displaced lepton pairs in $pp$ collisions, considering an optimization of the trigger requirements by means of a high level trigger that exploits tracker information. The analysis is carried out in the general case of three families of right-handed neutrino superfields, where all the neutrinos get contributions to their masses at tree level. To analyze the parameter space, we sample the $μν$SSM for a tau left sneutrino LSP with proper decay length $cτ> 0.1$ mm using a likelihood data-driven method, and paying special attention to reproduce the current experimental data on neutrino and Higgs physics, as well as flavor observables. The sneutrino is special in the $μν$SSM since its couplings have to be chosen so that the neutrino oscillation data are reproduced. We find that important regions of the parameter space can be probed at the LHC run 3.

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Electroweak superpartners scrutinized at the LHC in events with multi-leptons

We analyze a multi-lepton signal plus missing transverse energy from neutrinos expected at the LHC for a Bino-like neutralino as the lightest supersymmetric particle (LSP), when the left sneutrino is the next-to-LSP and hence a suitable source of Binos. The discussion is carried out in the framework of the $μν$SSM, where the presence of $R$-parity violating (RPV) couplings involving right-handed neutrinos solves the $μ$ problem and can reproduce simultaneously the neutrino data. Left sneutrinos/sleptons are pair produced at $pp$ collisions decaying to Binos, with the latter decaying via RPV to $W\ell$ or $Zν$. This signal can be compared with LHC searches for electroweak superpartners through chargino-neutralino production. The reduced cross section of the sneutrino/slepton production in comparison with the one of the latter process, limits the sensitivity of the searches to small sneutrino/slepton masses. Although the resulting compressed spectrum typically evades the aforementioned searches, we show that analyses using recursive jigsaw reconstruction are sensitive to these scenarios. As a by-product, we find that the region of Bino masses $110-120$ GeV and sneutrino masses $120-140$ GeV can give rise to a tri-lepton signal compatible with the local excess recently reported by ATLAS.

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Looking for the left sneutrino LSP with displaced-vertex searches

We analyze a displaced dilepton signal expected at the LHC for a tau left sneutrino as the lightest supersymmetric particle with a mass in the range $45$-$100$ GeV. The sneutrinos are pair produced via a virtual $W$, $Z$ or $γ$ in the $s$ channel and, given the large value of the tau Yukawa coupling, their decays into two dileptons or a dilepton plus missing transverse energy from neutrinos can be significant. The discussion is carried out in the $μν$SSM, where the presence of $R$-parity violating couplings involving right-handed neutrinos solves the $μ$ problem and can reproduce the neutrino data. To probe the tau left sneutrinos we compare the predictions of the $μν$SSM with the ATLAS search for long-lived particles using displaced lepton pairs in $pp$ collisions at $\sqrt s= 8$ TeV, allowing us to constrain the parameter space of the model. We also consider an optimization of the trigger requirements used in existing displaced-vertex searches by means of a High Level Trigger that exploits tracker information. This optimization is generically useful for a light metastable particle decaying into soft charged leptons. The constraints on the sneutrino turn out to be more stringent. We finally discuss the prospects for the $13$ TeV LHC searches as well as further potential optimizations.

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Searching for left sneutrino LSP at the LHC

We analyze relevant signals expected at the LHC for a left sneutrino as the lightest supersymmetric particle (LSP). The discussion is carried out in the `$μ$ from $ν$' supersymmetric standard model ($μν$SSM), where the presence of $R$-parity breaking couplings involving right-handed neutrinos solves the $μ$ problem and reproduces neutrino data. The sneutrinos are pair produced via a virtual $W$, $Z$ or $γ$ in the $s$ channel. From the prompt decay of a pair of left sneutrinos LSPs of any family, a significant diphoton signal plus missing transverse energy (MET) from neutrinos can be present in the mass range 118-132 GeV, with 13 TeV center-of-mass energy and an integrated luminosity of 100 fb$^{-1}$. In addition, in the case of a pair of tau left sneutrinos LSPs, given the large value of the tau Yukawa coupling diphoton plus leptons and/or multileptons can appear. We find that the number of expected events for the multilepton signal, together with properly adopted search strategies, is sufficient to give a significant evidence for a sneutrino of mass in the range 130-310 GeV, even with the integrated luminosity of 20 fb$^{-1}$. In the case of the signal producing diphoton plus leptons, an integrated luminosity of 100 fb$^{-1}$ is needed to give a significant evidence in the mass range 95-145 GeV. Finally, we discuss briefly the presence of displaced vertices and the associated range of masses.

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On a reinterpretation of the Higgs field in supersymmetry and a proposal for new quarks

In the framework of supersymmetry, when $R$-parity is violated the Higgs doublet superfield $H_d$ can be interpreted as another doublet of leptons, since all of them have the same quantum numbers. Thus Higgs scalars are sleptons and Higgsinos are leptons. We argue that this interpretation can be extended to the second Higgs doublet superfield $H_u$, when right-handed neutrinos are assumed to exist. As a consequence, we advocate that this is the minimal construction where the two Higgs doublets can be interpreted in a natural way as a fourth family of lepton superfields, and that this is more satisfactory than the usual situation in supersymmetry where the Higgses are `disconnected' from the rest of the matter and do not have a three-fold replication. On the other hand, in analogy with the first three families where for each lepton representation there is a quark counterpart, we propose a possible extension of this minimal model including a vector-like quark doublet representation as part of the fourth family. We also discuss the phenomenology of the associated new quarks.

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Search for sharp and smooth spectral signatures of $μν$SSM gravitino dark matter with Fermi-LAT

The $μν$SSM solves the $μ$ problem of supersymmetric models and reproduces neutrino data, simply using couplings with right-handed neutrinos $ν$'s. Given that these couplings break explicitly $R$ parity, the gravitino is a natural candidate for decaying dark matter in the $μν$SSM. In this work we carry out a complete analysis of the detection of $μν$SSM gravitino dark matter through $γ$-ray observations. In addition to the two-body decay producing a sharp line, we include in the analysis the three-body decays producing a smooth spectral signature. We perform first a deep exploration of the low-energy parameter space of the $μν$SSM taking into account that neutrino data must be reproduced. Then, we compare the $γ$-ray fluxes predicted by the model with Fermi-LAT observations. In particular, with the 95$\%$ CL upper limits on the total diffuse extragalactic $γ$-ray background using 50 months of data, together with the upper limits on line emission from an updated analysis using 69.9 months of data. For standard values of bino and wino masses, gravitinos with masses larger than about 4 GeV, or lifetimes smaller than $10^{28}$ s, produce too large fluxes and are excluded as dark matter candidates. However, when limiting scenarios with large and close values of the gaugino masses are considered, the constraints turn out to be less stringent, excluding masses larger than 17 GeV and lifetimes smaller than $4\times 10^{25}$ s.

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Hunting physics beyond the standard model with unusual $W^\pm$ and $Z$ decays

Nonstandard on-shell decays of $W^\pm$ and $Z$ bosons are possible within the framework of extended supersymmetric models, i.e., with singlet states and/or new couplings compared to the minimal supersymmetric standard model. These modes are typically encountered in regions of the parameter space with light singlet-like scalars, pseudoscalars, and neutralinos. In this letter we emphasize how these states can lead to novel signals at colliders from $Z$- or $W^\pm$-boson decays with prompt or displaced multileptons/tau jets/jets/photons in the final states. These new modes would give distinct evidence of new physics even when direct searches remain unsuccessful. We discuss the possibilities of probing these new signals using the existing LHC run-I data set. We also address the same in the context of the LHC run-II, as well as for the future colliders. We exemplify our observations with the "$μ$ from $ν$" supersymmetric standard model, where three generations of right-handed neutrino superfields are used to solve shortcomings of the minimal supersymmetric standard model. We also extend our discussion for other variants of supersymmetric models that can accommodate similar signatures.

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Probing the $μν$SSM with light scalars, pseudoscalars and neutralinos from the decay of a SM-like Higgs boson at the LHC

The "$μ$ from $ν$" supersymmetric standard model ($μν$SSM) can accommodate the newly discovered Higgs-like scalar boson with a mass around 125 GeV. This model provides a solution to the $μ$-problem and simultaneously reproduces correct neutrino physics by the simple use of right-handed neutrino superfields. These new superfields together with the introduced $R$-parity violation can produce novel and characteristic signatures of the $μν$SSM at the LHC. We explore the signatures produced through two-body Higgs decays into the new states, provided that these states lie below in the mass spectrum. For example, a pair produced light neutralinos depending on the associated decay length can give rise to displaced multi-leptons/taus/jets/photons with small/moderate missing transverse energy. In the same spirit, a Higgs-like scalar decaying to a pair of scalars/pseudoscalars can produce final states with prompt multi-leptons/taus/jets/photons.

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Probing the "$μ$ from $ν$" supersymmetric standard model with displaced multileptons from the decay of a Higgs boson at the LHC

The "$μ$ from $ν$" supersymmetric standard model ($μν$SSM) cures the $μ$-problem and concurrently reproduces measured neutrino data by using a set of usual right-handed neutrino superfields. Recently, the LHC has revealed the first scalar boson which naturally makes it tempting to test $μν$SSM in the light of this new discovery. We show that this new scalar while decaying to a pair of unstable long-lived neutralinos, can lead to a distinct signal with non-prompt multileptons. With concomitant collider analysis we show that this signal provides an unmistakable signature of the model, pronounced with light neutralinos. Evidence of this signal is well envisaged with sophisticated displaced vertex analysis, which deserves experimental attention.

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