arXiv subjects

Yann Mambrini

Publications and source records attributed to Yann Mambrini.

At least 73 records · Page 4Linked to original sources

arXiv2018

XENON1T Takes a Razor to a Dark $E_6$-Inspired Model

Motivated by the recent result of XENON1T collaboration with full exposure, 279 life days, that sets the most stringent limit on the spin-independent dark matter-nucleon scattering cross section we discuss a dark $E_6$-inspired model that features the presence of a $U(1)_{d-u}$ gauge symmetry. The dark matter candidate is a Dirac fermion that interacts with Standard Model fermions via a massive Z' that preserves the quantum number assignments of this symmetry. We compute the spin-independent scattering cross section off xenon nucleus and compare with the XENON1T limit; find the LHC bound on the Z' mass as well as the projection sensitivity of high-energy and luminosity LHC; and derive the Fermi-LAT bounds on the dark matter annihilation cross section based on the observation of gamma-rays in the direction of Dwarf Spheroidal galaxies. We exploit the complementarity between these datasets to conclude that the new bound from XENON1T severely constrain the model, which combined with the LHC upgrade sensitivity rules out this WIMP realization setup below 5 TeV.

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arXiv2018

Moduli Portal Dark Matter

We show that moduli fields as mediators between the Standard Model and the dark sector can naturally lead to the observed relic abundance. Indeed, even if moduli are very massive, the nature of their couplings with matter and gauge fields allows producing a sufficiently large amount of dark matter in the early Universe through the freeze-in mechanism. Moreover, the complex nature of the moduli fields whose real and imaginary part couple differently to the thermal bath gives an interesting and unusual phenomenology compared to other freeze-in models of that type.

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arXiv2018

Freezing-in dark matter through a heavy invisible $Z'$

We demonstrate that in a class of the $U(1)'$ extension of the Standard Model (SM), under which all the Standard Model matter fields are uncharged and the additional neutral gauge boson $Z'$ couples to a set of heavy nonstandard fermions, dark matter (DM) production mediated by $Z'$ can proceed through the generation of generalized Chern-Simons (GCS) couplings. The origin of the GCS terms is intimately connected to the cancellation of gauge anomalies. We show that the DM production cross section triggered by GCS couplings is sufficient even for an intermediate scale $Z'$ . A large range of DM and Z masses is then allowed for reasonably high reheating temperature ($T_\rh \gtrsim 10^{10}~\text{GeV}$). This type of scenario opens up a new paradigm for unified models. We also study the UV completion of such effective field theory constructions, augmenting it by a heavy fermionic spectrum. The latter, when integrated out, generates the GCS-like terms and provides a new portal to the dark sector. The presence of a number of derivative couplings in the GCS-like operators induces a high temperature dependence to the DM production rate. The mechanism has novel consequences and leads to a new reheating dependence of the relic abundance.

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arXiv2018

Gravitino Decay in High Scale Supersymmetry with R-parity Violation

We consider the effects of R-parity violation due to the inclusion of a bilinear $μ^\prime L H_u$ superpotential term in high scale supersymmetric models with an EeV scale gravitino as dark matter. Although the typical phenomenological limits on this coupling (e.g. due to lepton number violation and the preservation of the baryon asymmetry) are relaxed when the supersymmetric mass spectrum is assumed to be heavy (in excess of the inflationary scale of $3 \times 10^{13}$ GeV), the requirement that the gravitino be sufficiently long-lived so as to account for the observed dark matter density, leads to a relatively strong bound on $μ^\prime \lesssim 20$ GeV. The dominant decay channels for the longitudinal component of the gravitino are $Z ν, W^\pm l^\mp$, and $hν$. To avoid an excess neutrino signal in IceCube, our limit on $μ'$ is then strengthened to $μ' \lesssim 50$ keV. When the bound is saturated, we find that there is a potentially detectable flux of mono-chromatic neutrinos with EeV energies.

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arXiv2018

Spin-2 Portal Dark Matter

We generalize models invoking a spin-2 particle as a mediator between the dark sector and the Standard Model. We show that a massive spin-2 messenger can efficiently play the role of a portal between the two sectors. The dark matter is then produced via a freeze-in mechanism during the reheating epoch. In a large part of the parameter space, production through the exchange of a massive spin-2 mediator dominates over processes involving a graviton with Planck suppressed couplings. We perform a systematic analysis of such models for different values of the spin-2 mass relative to the maximum and the final temperature attained at reheating.

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arXiv2017

$Z'$ portal to Chern-Simons Dark Matter

We study the phenomenological credibility of a vectorial dark matter, coupled to a $Z'$ portal through Chern-Simons interaction. We scrutinize two possibilities of connecting a $Z'$ with the Standard Model: (1) through kinetic mixing and (2) from a second Chern-Simons interaction. Both scenarios are characterized by suppressed nuclear recoil scatterings, rendering direct detection searches not promising. Indirect detection experiments, on the other hand, furnish complementary limits for TeV scale masses, specially with the CTA. Searches for mono-jet and dileptons signals at the LHC are important to partially probe the kinetic mixing setup. Finally we propose an UV completion of the Chern-Simons Dark Matter framework.

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arXiv2017

Vector SIMP dark matter

Strongly Interacting Massive Particles (SIMPs) have recently been proposed as light thermal dark matter relics. Here we consider an explicit realization of the SIMP mechanism in the form of vector SIMPs arising from an $SU(2)_X$ hidden gauge theory, where the accidental custodial symmetry protects the stability of the dark matter. We propose several ways of equilibrating the dark and visible sectors in this setup. In particular, we show that a light dark Higgs portal can maintain thermal equilibrium between the two sectors, as can a massive dark vector portal with its generalized Chern-Simons couplings to the vector SIMPs, all while remaining consistent with experimental constraints.

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arXiv2017

Inflation and High-Scale Supersymmetry with an EeV Gravitino

We consider inflation and supersymmetry breaking in the context of a minimal model of supersymmetry in which the only "low" energy remnant of supersymmetry is the gravitino with a mass of order an EeV. In this theory, the supersymmetry breaking scale is above the inflaton mass, m ~ 3 x 10^{13} GeV, as are all sfermion and gaugino masses. In particular, for a no-scale formulation of Starobinsky-like inflation using the volume modulus T, we show that inflation can be accommodated even when the supersymmetry breaking scale is very large. Reheating is driven through a gravitational coupling to the two Higgs doublets and is enhanced by the large mu-parameter. This leads to gravitino cold dark matter where the mass is constrained to be in the range 0.1 EeV $\lesssim m_{3/2} \lesssim 1000$ EeV.

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arXiv2017

Enhancement of the Dark Matter Abundance Before Reheating: Applications to Gravitino Dark Matter

In the first stages of inflationary reheating, the temperature of the radiation produced by inflaton decays is typically higher than the commonly defined reheating temperature $T_{RH} \sim (Γ_ϕM_P)^{1/2}$ where $Γ_ϕ$ is the inflaton decay rate. We consider the effect of particle production at temperatures at or near the maximum temperature attained during reheating. We show that the impact of this early production on the final particle abundance depends strongly on the temperature dependence of the production cross section. For $\langle σv \rangle \sim T^n/M^{n+2}$, and for $n < 6$, any particle produced at $T_{\rm max}$ is diluted by the later generation of entropy near $T_{RH}$. This applies to cases such as gravitino production in low scale supersymmetric models ($n=0$) or NETDM models of dark matter ($n=2$). However, for $n\ge6$ the net abundance of particles produced during reheating is enhanced by over an order of magnitude, dominating over the dilution effect. This applies, for instance to gravitino production in high scale supersymmetry models where $n=6$.

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arXiv2017

The Case for an EeV Gravitino

We consider the possibility that supersymmetry is broken above the inflationary mass scale and that the only "low" energy remnant of supersymmetry is the gravitino with mass of order the EeV scale. The gravitino in this class of models becomes a candidate for the dark matter of the Universe. To avoid the over-production of gravitinos from the decays of the next-to-lightest supersymmetric particle we argue that the supersymmetric spectrum must lie above the inflationary mass scale ($M_{\rm SUSY} > 10^{-5} M_{\rm P} \sim 10^{13}$ GeV). Since $m_{3/2} \simeq M_{\rm SUSY}^2/M_{\rm P}$, we expect $m_{3/2} \gtrsim 0.2$ EeV. Cosmological constraints then predict a relatively large reheating temperature between $10^{10}$ and $10^{12}$ GeV.

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arXiv2017

GUT Models at Current and Future Hadron Colliders and Implications to Dark Matter Searches

Grand Unified Theories (GUT) offer an elegant and unified description of electromagnetic, weak and strong interactions at high energy scales. A phenomenological and exciting possibility to grasp GUT is to search for TeV scale observables arising from Abelian groups embedded in GUT constructions. That said, we use dilepton data (ee and $μμ$) that has been proven to be a golden channel for a wide variety of new phenomena expected in theories beyond the Standard Model to probe GUT-inspired models. Since heavy dilepton resonances feature high signal selection efficiencies and relatively well-understood backgrounds, stringent and reliable bounds can be placed on the mass of the $Z^{\prime}$ gauge boson arising in such theories. In this work, we obtain 95\% C.L. limits on the $Z^{\prime}$ mass for several GUT-models using current and future proton-proton colliders with $\sqrt{s}= 13~{\rm TeV},\, 33~{\rm TeV},\,{\rm and}\, 100$~TeV, and put them into perspective with dark matter searches in light of the next generation of direct detection experiments.

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arXiv2017

A Minimal Model of Gravitino Dark Matter

Motivated by the absence of signals of new physics in both searches for new particles at LHC and for a Weakly Interacting Massive Particle (WIMP) dark matter candidate, we consider a scenario where supersymmetry is broken at a scale above the reheating temperature. The low energy particle content consists then only in Standard Model states and a gravitino. We investigate the possibility that the latter provides the main component of dark matter through a freeze in mechanism from annihilation of thermalized Standard Model particles. We focus on the case where its production through scattering in the thermal plasma is well approximated by the non-linear supersymmetric effective Lagrangian of the associated goldstino and identify the parameter space allowed by the cosmological constraints, allowing the possibility of large reheating temperature compatible with leptogenesis scenarios, alleviating the so called "gravitino problem".

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arXiv2017

The Waning of the WIMP? A Review of Models, Searches, and Constraints

Weakly Interacting Massive Particles (WIMPs) are among the best-motivated dark matter candidates. In light of no conclusive detection signal yet despite an extensive search program that combines, often in a complementary way, direct, indirect, and collider probes, we find it timely to give a broad overview of the WIMP paradigm. In particular, we review here the theoretical foundations of the WIMP paradigm, discuss status and prospects of various detection strategies, and explore future experimental challenges and opportunities.

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arXiv2016

Augury of Darkness: The Low-Mass Dark Z' Portal

Dirac fermion dark matter models with heavy $Z^{\prime}$ mediators are subject to stringent constraints from spin-independent direct searches and from LHC bounds, cornering them to live near the $Z^{\prime}$ resonance. Such constraints can be relaxed, however, by turning off the vector coupling to Standard Model fermions, thus weakening direct detection bounds, or by resorting to light $Z^{\prime}$ masses, below the Z pole, to escape heavy resonance searches at the LHC. In this work we investigate both cases, as well as the applicability of our findings to Majorana dark matter. We derive collider bounds for light $Z^{\prime}$ gauge bosons using the $CL_S$ method, spin-dependent scattering limits, as well as the spin-independent scattering rate arising from the evolution of couplings between the energy scale of the mediator mass and the nuclear energy scale, and indirect detection limits. We show that such scenarios are still rather constrained by data, and that near resonance they could accommodate the gamma-ray GeV excess in the Galactic center.

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arXiv2016

Scrutinizing a di-photon resonance at the LHC through Moscow zero

The ATLAS and CMS collaborations have recently released their new analyses of the diphoton searches. We look in detail the consequences of their results deriving strong constraints on models where a scalar resonance $s$ decays into two light pseudoscalars which in turn decay into two pairs of collimated photons, mis-identified with two real photons. In our construction, all mass terms are generated dynamically, and only one pair of vector-like fermions generate couplings which will be probed using the upcoming LHC data. Moreover, we show that a stable dark matter candidate, respecting the cosmological constraints, is naturally affordable in the model.

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arXiv2016

Multicomponent Dark Matter from Gauge Symmetry

The composition of Dark Matter (DM) remains an important open question. The current data do not distinguish between single- and multi-component DM, while in theory constructions it is often assumed that DM is composed of a single field. In this work, we study a hidden sector which naturally entails multicomponent DM consisting of spin-1 and spin-0 states. This UV complete set-up is based on SU(3) hidden gauge symmetry with the minimal scalar field content to break it spontaneously. The presence of multiple DM components is a result of a residual Z_2 x Z'_2 symmetry which is part of an unbroken global U(1) x Z'_2 inherent in the Yang-Mills systems. We find that the model exhibits various parametric regimes with drastically different DM detection prospects. In particular, we find that the direct detection cross section is much suppressed in large regions of parameter space as long as the Standard Model Higgs mixes predominantly with a single scalar from the hidden sector. The resulting scattering rate is often beyond the level of sensitivity of XENON1T, while still being consistent with the thermal WIMP paradigm.

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arXiv2016

Dark Matter and Global Symmetries

General considerations in general relativity and quantum mechanics are known to potentially rule out continuous global symmetries in the context of any consistent theory of quantum gravity. Assuming the validity of such considerations, we derive stringent bounds from gamma-ray, X-ray, cosmic-ray, neutrino, and CMB data on models that invoke global symmetries to stabilize the dark matter particle. We compute up-to-date, robust model-independent limits on the dark matter lifetime for a variety of Planck-scale suppressed dimension-five effective operators. We then specialize our analysis and apply our bounds to specific models including the Two-Higgs-Doublet, Left-Right, Singlet Fermionic, Zee-Babu, 3-3-1 and Radiative See-Saw models. {Assuming that (i) global symmetries are broken at the Planck scale, that (ii) the non-renormalizable operators mediating dark matter decay have $O(1)$ couplings, that (iii) the dark matter is a singlet field, and that (iv) the dark matter density distribution is well described by a NFW profile}, we are able to rule out fermionic, vector, and scalar dark matter candidates across a broad mass range (keV-TeV), including the WIMP regime.

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arXiv2016

Re-opening dark matter windows compatible with a diphoton excess

We investigate a simple setup in which an excess in the di-photon invariant mass distribution around $750$ GeV, as seen by the ATLAS and CMS collaborations, is originated through a pair of collimated photon pairs. In this framework a scalar state $s$ decays into two light pseudo-Goldstone bosons $a$, each of which subsequently decays into a pair of collimated photons which are misidentified as a single photon. In a minimal context of spontaneous symmetry breaking, we show that coupling a complex scalar field $Φ=(s+ia)/\sqrt{2}$ to a fermionic dark matter candidate $χ$, also responsible for generating its mass, allows for the correct relic density in a large region of the parameter space, while not being excluded by the direct or indirect detection experiments. Moreover, the correct relic abundance can naturally co-exist with a relatively large width for the resonant field $s$.

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