Probing light dark scalars with future experiments
Enrico Bertuzzo, Marco Taoso
备注：
25 pages, 2 appendices, 6 figures. v2: version accepted for publication. Several clarifications added, Figs. 3-5 modified to take into account the heaviest state decay length. Conclusions unchanged
We investigate a dark sector containing a pair of light non-degenerate scalar particles, with masses in the MeV-GeV range, coupled to the visible sector through heavier mediators. The heaviest dark state is long-lived, and its decays offer new testable signals. We analyze the prospects for detection with the proposed beam-dump facility SHiP, and the proposed LHC experiments FASER and MATHUSLA. Moreover, we consider bounds from the beam-dump experiment CHARM and from colliders (LEP, LHC and BaBar). We present our results both in terms of an effective field theory, where the heavy mediators have been integrated out, and of a simplified model containing a vector boson mediator, which can be heavy $\gtrsim\mathcal{O}(1)$ TeV, or light $\mathcal{O}(10)$ GeV. We show that future experiments can test large portions of the parameter space currently unexplored, and that they are complementary to future High-Luminosity LHC searches.
The cosmological phase transition with Q-balls production mechanism can explain the baryogenesis and dark matter simultaneously, where constraints on dark matter masses and reverse dilution are significantly relaxed. We study how to probe this scenario by collider signals at QCD next-to-leading order and gravitational wave signals.
In the standard model extended by a single complex scalar boson with a softly broken global U(1) symmetry, a pseudo Nambu-Goldstone boson becomes a candidate for dark matter. In this paper, we discuss the direct detection of the pseudo Nambu-Goldstone boson dark matter. Since the tree-level amplitude for dark matter-nucleon scattering vanishes, higher order quantum corrections for the amplitude should be taken into account. We perform the calculation at the next-to-leading order in QCD in a systematic manner.
We have analyzed the prospect of probing a non-universal gaugino mass model of mixed bino-higgsino dark matter at the current 7 TeV run of LHC. It provides cosmologically compatible dark matter relic density over two broad bands of parameters, corresponding to $m_{\gl} < m_{\sq}$ and $m_{\gl} \sim m_{\sq}$. The SUSY spectrum of this model has two distinctive features : (i) an approximate degeneracy among the lighter chargino and neutralino masses, and (ii) an inverted mass hierarchy of squark masses. We find that these features can be exploited to obtain a viable signal upto $m_{\gl} \sim$ 800…
Vector boson fusion (VBF) processes at the Large Hadron Collider (LHC) provide a unique opportunity to search for new physics with electroweak couplings. A feasibility study for the search of supersymmetric dark matter in the final state of two VBF jets and large missing transverse energy is presented at 14 TeV. Prospects for determining the dark matter relic density are studied for the cases of Wino and Bino-Higgsino dark matter. The LHC could probe Wino dark matter with mass up to approximately 600 GeV with a luminosity of 1000 fb$^{-1}$.
We show that the economical 3-3-1 model has a dark mater candidate. It is a real scalar H_1^0 in which main part is bilepton (with lepton number 2) and its mass is in the range of some TeVs. We calculate the relic abundance of H_1^0 dark matter by using micrOMEGAs 2.4 and figure out parameter space satisfying the WMAP constraints. Direct and indirect searches are studied for a special choice of parameters in the WMAP - allowed region.
We analyze the oscillations of Rydberg atoms in the framework of quantum field theory and we reveal non-trivial vacuum energy which has the equation of state of the dark matter. This energy is similar to that expected for mixed neutrinos and affects the thermal capacity of the gas. Therefore, the deflection of the thermal capacity of Rydberg atoms could prove the condensate structure of vacuum for mixing fermions and open new scenarios in the study of the dark components of the universe.
The flavor structure in unified theory is probed with superparticle mass spectrum observed in future particle experiments. A key ingredient is the generation dependence of scalar mass non-degeneracy. The observed non-degeneracy in low-energy regime is shown to provide a direct imprint of flavor structure in high-energy fundamental theory. The implication from flavor-violating rare process is also discussed.
The direct detection of Dark Matter particles with mass below the GeV-scale is hampered by soft nuclear recoil energies and finite detector thresholds. For a given maximum relative velocity, the kinematics of elastic Dark Matter nucleus scattering sets a principal limit on detectability. Here we propose to bypass the kinematic limitations by considering the inelastic channel of photon emission in the nuclear recoil. Our proposed method allows to set the first limits on Dark Matter below 500 MeV in the plane of Dark Matter mass and cross section with nucleons. In situations where a Dark Matter-…
Pseudo-Goldstone dark matter coupled to the Standard Model via the Higgs portal offers an attractive framework for phenomenologically viable pseudo-scalar dark matter. It enjoys natural suppression of the direct detection rate due to the vanishing of the relevant (tree level) Goldstone boson vertex at zero momentum transfer, which makes light WIMP-like dark matter consistent with the strong current bounds. In this work, we explore prospects of detecting pseudo-Goldstone dark matter at the LHC, focusing on the vector boson fusion (VBF) channel with missing energy. We find that, in substantial r…
Due to the very large mass of the top-quark, probing the flavor changing top-charm-scalar vertex is clearly very important. Fortunately the largeness of $m_t$ endows a unique signature to the resulting reaction i.e., $e^+e^-\to t\bar c (\bar t c)$ that should be helpful in identification of such events. A two Higgs doublet model, without natural flavor conservation, is used to give an illustrative estimate for the rate for these reactions.
Rare leptonic kaon and pion decays $K^+(π^+) \to μ^+\, ν_μ\, e^+ e^-$ can be used to probe a dark photon of mass ${\cal O}(10)$~MeV, with the background coming from the mediation of a virtual photon. This is most relevant for the 16.7-MeV dark photon proposed to explain a 6.8$σ$ anomaly recently observed in $^8$Be transitions by the Atomki Collaboration. We evaluate the reach of future experiments for different scenarios of how the dark photon couples with the standard model particles, and show that a great portion of the preferred 16.7-MeV dark photon parameter space can be decisively probed.…
In this paper we consider loop corrections to the spin-independent WIMP-nucleon scattering cross section in bottom-quark flavored scalar-type dark matter models. We focus on two scenarios: (a) a complex scalar dark matter with a scalar particle as the mediator; and (b) a real scalar dark matter with a vector boson as the mediator. In both scenarios, the direct detection cross sections are either spin-dependent or kinematically forbidden at the tree-level. Corrections induced by the WIMP-gluon effective operator, scalar-type WIMP-quark effective operator, and the twist-2 effective operator are …
We propose a new search for Dark Matter at the LHC, characteristic of scenarios beyond the Standard Model with a pseudoscalar portal between the visible and dark sectors. This search, leading to a $\bar{b} b Z( \rightarrow \ell\ell) + E_{T} \hspace{-4mm}/\hspace{2mm}$ final state, reaches large regions of parameter space not probed by Dark Matter searches via multi-jet $+ E_{T} \hspace{-4mm}/\hspace{2mm}$, searches for new scalars and flavour bounds. We show that this search could be used to test the Dark Matter origin of the gamma ray Galactic Centre excess with LHC Run 2 data.
Within the context of a generalized linear sigma model that includes two nonets of scalar mesons (a two-quark nonet and a four-quark nonet) and two nonets of pseudoscalar mesons (a two-quark nonet and a four-quark nonet) a collective description of scalar and pseudoscalar mesons below and above 1 GeV is studied. The quark contents of these states are probed; estimates on their quark components are extracted; and prediction for pi pi scattering amplitude is made. An overview of these studies is presented here.
We study possible deviations from the Standard Model in the reaction $e^+e^- \to Zϕ$, where $ϕ$ denotes a spinless neutral boson. We show how the $Z$ decay angular correlation can be used to extract detailed information on the $ϕ$ couplings, such as the parity of $ϕ$, radiatively induced form factor effects and possible CP violation in the scalar sector.
Although theoretically well-motivated as a minimal consistent Dark Matter (DM) model, the Inert Doublet Model (IDM) fell short in explaining the existence of DM in the intermediate mass region ($100-500$ GeV). We try to address this problem by introducing an additional vector dark matter. We show that the relic density of inert dark matter candidate can be enhanced significantly with new interactions in the intermediate mass region $100-500$ GeV in the multicomponent dark matter model when compared with the usual single component inert doublet model. We also show that we can get a reasonable e…
We investigate a dark matter model involving an inert $\mathrm{SU}(2)_\mathrm{L}$ quadruplet scalar with hypercharge 1/2. After the electroweak symmetry breaking, the dark sector contains one doubly charged, two singly charged, and two neutral scalars. The lighter neutral scalar can be a viable dark matter candidate. Electroweak production of these scalars at the Large Hadron Collider leads to potential signals in the $\text{monojet} + /\!\!\!\!E_\mathrm{T}$ and $\text{soft-leptons} + \text{jets} + /\!\!\!\!E_\mathrm{T}$ channels. We thus derive constraints on the model by reinterpreting recen…
Dark matter particles can be captured by the sun with rates that depend on the dark matter mass and the DM-nucleon cross section. However, for masses below $\sim 3.3$ GeV, the captured dark matter particles evaporate, leading to an equilibrium where the rate of captured particles is equal to the rate of evaporating ones. Unlike dark matter particles from the halo, the evaporating dark matter particles have velocities that are not limited to values below the escape velocity of the galaxy. Despite the fact that high velocities are exponentially suppressed, I demonstrate here that current undergr…
We study a pseudoscalar dark-matter model arising from a complex singlet extension of the standard model (SM), and show that the dark-matter--nucleon scattering is suppressed when two CP-even scalars are degenerate. In such a degenerate-scalar scenario we explore the model parameter space which satisfies constraints from the direct detection experiments and the relic density of dark matter. In addition, we discuss a possibility to verify such a scenario by using the recoil mass technique at the International Linear Collider. We find that a pair of states separated by 0.2 GeV can be distinguish…
We present cosmological perturbation theory in neutrino probe interacting dark-energy models, and calculate cosmic microwave background anisotropies and matter power spectrum. In these models, the evolution of the mass of neutrinos is determined by the quintessence scalar field, which is responsible for the cosmic acceleration today. We consider several types of scalar field potentials and put constraints on the coupling parameter between neutrinos and dark energy. Assuming the flatness of the universe, the constraint we can derive from the current observation is $\sum m_ν < 0.87 eV$ at the 95…
Collider searches for long-lived particles yield a promising avenue to probe the freeze-in production of Dark Matter via the decay of a parent particle. We analyze the prospects of probing the parameter space of Dark Matter freeze-in from the decay of neutral parent particles at the LHC and beyond, taking as a case study a freeze-in Dark Matter scenario via the Standard Model Higgs. We obtain the projected sensitivity of the proposed MATHUSLA surface detector (for MATHUSLA100 and MATHUSLA200 configurations) for long-lived particle searches to the freeze-in Dark Matter parameter space, and stud…
With the primary motivation of probing the quark substructure of scalar mesons, a generalized linear sigma model for the lowest and the next-to-lowest scalar and pseudoscalar mesons is employed to investigate several semi-leptonic decays of $D$ mesons. The free parameters of the model (in its leading approximation) have been previously determined from fits to mass spectra and various low-energy parameters. With these fixed parameters, the model has already given encouraging predictions for different low-energy decays and scattering, as well as for semileptonic decay channels of $D_s^+$ that in…
We study possible deviations from the Standard Model in the reaction $e^+e^- \to Zϕ$, where $ϕ$ denotes a spinless neutral boson. We show how the $Z$ decay angular correlation can be used to extract detailed information on the $ϕ$ couplings, such as the parity of $ϕ$, radiatively induced form factor effects and possible CP violation in the scalar sector. Consequences of gauge invariant dimension six operators are discussed as an example.
LHC has found hints for a Higgs particle of 125 GeV. We investigate the possibility that such a particle is a mixture of scalar and pseudoscalar states. For definiteness, we concentrate on a two Higgs doublet model with explicit CP violation and soft Z2 violation. Including all Higgs production mechanisms, we determine the current constraints obtained by comparing h -> gamma gamma with h -> V V*, and comment on the information which can be gained by measurements of h -> b \bar{b}. We find bounds |s_2| < 0.83 at one sigma, where |s_2|=0 (|s_2|=1) corresponds to a pure scalar (pure pseudoscalar)…
I investigate a class of models with scalar and pseudoscalar solutions to the g-2 anomaly in the mass range between 1 MeV and 40 GeV. In particular, I investigate the constraints from BaBar, beam dump experiments and from Z decay measured quantities. I find that most of the favored region in this mass range is excluded except for a small window between ~30 MeV and 200 MeV. This open window is expected to be covered by the proposed NA64 experiment. The results can be readily applied to other proposed solutions of the anomaly, such as solutions with Z0 or with the dark photon.
We discuss experimental probes of isospin-violating dark matter (IVDM), including direct and indirect detection strategies. We point out the important role which IVDM plays in understanding recent data regarding low-mass dark matter, and describe strategies for finding evidence of IVDM at current and upcoming experiments.
We study the production processes $e^+e^-\to H^0_iZ$, $H^0_iH^0_j$ and $H^0_iν_e\overline ν_e$ in the context of the CP violating MSSM. In a given channel we show that the cross-section for all i (=1,2,3) can be above 0.1 fb provided $M_{H_{2,3}}\la 300$ GeV. This should be detectable at a Next Linear Collider and would provide evidence for scalar-pseudoscalar mixing.
Recent results from PAMELA and ATIC hint that O(TeV) dark matter (DM) is annihilating, in our galactic neighborhood, predominantly to leptons. The annihilation rate is much larger now than during freeze-out, one possible explanation of this is a low-velocity enhancement of the annihilation cross section. In a model independent fashion, we show that in this case the rate of neutrino emission from the Earth, due to DM annihilation, may be greatly enhanced while the rate from the Sun is unaltered. There is potential for IceCube to see these earthborn neutrinos while the same parameter space will …
We have explored the prospect of probing a neutral scalar ($H$) produced in association with one $b$-quark and decaying either invisibly or into a pair of $b$-quarks at the LHC with centre of mass energy $\sqrt s = 14$ TeV. In this regard, we adopt an effective theory approach to parameterize a $Hb\bar bg$ vertex arising from a dimension six operator that encompasses the effect of some new physics setting in at a high scale. We concentrate solely on the five-flavor scheme to ascertain the sensitivity of the 14 TeV LHC in probing such an effective coupling as a function of the scalar mass at th…
We examine the sensitivity at a future 100 TeV proton-proton collider to compressed dark sectors whose decay products are invisible due to below-threshold energies and/or small couplings to the Standard Model. This scenario could be relevant to models of WIMP dark matter, where the lightest New Physics state is an (isolated) electroweak multiplet whose lowest component is stable on cosmological timescales. We rely on the additional emission of a hard on-shell $Z$-boson decaying to leptons, a channel with low background systematics, and include a careful estimate of the real and fake background…
We study the sensitivity to sub-GeV dark sectors of high energy ($ \geq100$ GeV) proton fixed target experiments such as the Main Injector and the future Long-Baseline Neutrino Facility (LBNF). We focus on off-axis detectors since they have been shown to be the ideal location to reduce the neutrino background. We consider MiniBooNE as an off-axis detector for the NuMI facility and a hypotetical detector for LBNF located 200 m away from the target and 6.5 degrees off-axis. We find that with the existing data, MiniBoone can explore new regions of the parameter space for leptophobic dark forces i…
We consider associated production of dark matter with single top quark, in a simplified dark matter model with spin-0 mediators. The produced top quark is polarized and the polarization depends on the CP of the mediator. We calculate both the cross-section and top polarization for these processes. We compute angular asymmetries which demonstrate the difference between the polarization expected for the scalar or pseudoscalar mediator. Both the cross section and top polarization are sensitive to the CP property of the mediator, depending on the mediator mass. We find that these polarization asym…
Dark Matter (DM) is omnipresent in our universe. Despite its abundance, the microscopic identity of DM still remains a mystery. Primordial black holes (PBHs), possibly formed via gravitational collapse of large density perturbations in the early universe, are one of the earliest proposed and viable DM candidates. Recent studies indicate that PBHs can make up a large or even entire fraction of the DM density for a wide range of masses. Here, we briefly review the observational constraints on PBHs as DM, concentrating on the ultra-light mass window. Ultra-light PBHs emit particles via Hawking ra…
We constrain the Higgs-portal model employing the vector-boson fusion channel at the LHC. In particular, we include the phenomenologically interesting parameter region near the Higgs resonance, where the Higgs-boson mass is close to the threshold for dark-matter production and a running-width prescription has to be employed for the Higgs-boson propagator. Limits for the Higgs-portal coupling as a function of the dark-matter mass are derived from the CMS search for invisible Higgs-boson decays in vector-boson fusion at 13 TeV. Furthermore, we perform projections for the 14 TeV HL-LHC and the 27…
When dark matter candidate and its parent particles are nearly degenerate, it would be difficult to probe them at the Large Hadron Collider directly. We propose to explore their quantum loop effects at the CEPC through the golden channel process $e^+e^-\to μ^+μ^-$. We use a renormalizable toy model consisting of a new scalar and a fermion to describe new physics beyond the Standard Model. The new scalar and fermion are general multiplets of the $SU(2)_L\times U(1)_Y$ symmetry, and couple to the muon lepton through Yukawa interaction. We calculate their loop contributions to anomalous $γμ^+μ^-$…
Dark photon not only provides a portal linking dark sector particles and ordinary matter but also is a well-motivated dark matter candidate. We propose to detect the dark photon dark matter through the inverse Compton-like scattering process $p+γ^\prime \to p+γ$. Thanks to the ultra-high energy primary cosmic rays, we find that such a method is able to probe the dark photon mass from $10^{-2}$ eV down to $10^{-19}$ eV with the expected sensitivity of eROSITA $X$-ray telescope, which can extend the current lower limit of dark photon mass from Jupiter's magnetic fields experiment by about three …
This paper investigates the collider phenomenolgy of a minimal nonthermal dark matter model with a 1-GeV dark matter candidate, which naturally explain baryongensis. Since the light dark matter is not parity-protected, it can be singly produced at the LHC. This leads to large missing energy associated with an energetic jet whose transverse momentum distribution is featured by a Jacobian-like shape. The monojet, dijet, paired dijet and 2 jets + missing energy channels are studied. Currently existing data at Tevatron and LHC offer significant bounds on our model.
Gravitational lensing observations of galaxy clusters have identified dark matter ``blobs'' with remarkably low baryonic content. We use such a system to probe the particle nature of dark matter with X-ray observations. We also study high resolution X-ray grating spectra of a cluster of galaxies. From these grating spectra we improve the conservative constraints on a particular dark matter candidate, the sterile neutrino, by more than one order of magnitude. Based on these conservative constraints obtained from Cosmic X-ray observations alone, the low mass (m_s < 10keV) and low mixing angle (s…
We propose a new scenario of using the dark axion portal at one-loop level to explain the recently observed muon anomalous magnetic moment by the Fermilab Muon g-2 experiment. Both axion/axion-like particle (ALP) and dark photon are involved in the same vertex with photon. Although ALP or dark photon alone cannot explain muon $g-2$, since the former provides only negative contribution while the latter has very much constrained parameter space, dark axion portal can save the situation and significantly extend the allowed parameter space. The observed muon anomalous magnetic moment provides a ro…
From measurements of the cosmic microwave background (CMB), the effective number of neutrino is found to be close to the standard model value Neff = 3.046 for the \LambdaCDM cosmology. One can obtain the same CMB angular power spectrum as that of \LambdaCDM for the different value of Neff by using the different dark energy model (i.e. for the different value of w). This degeneracy between Neff and w in CMB can be broken from future galaxy survey using the matter power spectrum.
Recent cosmological observations indicate the existence of extra light species, i.e., dark radiation. In this paper we show that signatures of the dark radiation are imprinted in the spectrum of inflationary gravitational waves. If the dark radiation is produced by the decay of a massive particle, high frequency mode of the gravitational waves are suppressed. In addition, due to the effect of the anisotropic stress caused by the dark radiation, a dip in the gravitational wave spectrum may show up at the frequency which enters the horizon at the time of the dark radiation production. Once the g…
Distance measurements to Type Ia supernovae (SNe Ia) indicate that the Universe is accelerating and that two-thirds of the critical energy density exists in a dark-energy component with negative pressure. Distance measurements to SNe Ia can be used to distinguish between different possibilities for the dark energy, and if it is an evolving scalar field, to reconstruct the scalar-field potential. We derive the reconstruction equations and address the feasibility of this approach by Monte-Carlo simulation.
The hypothesis of dark matter interacting with the standard model uniquely via the Higgs portal is severely challenged by experiments. However, if dark matter is a fermion, the Higgs-portal interaction implies the presence of mediators, which can change the phenomenology significantly. This article discusses the impact of weakly-interacting mediators on the dark-matter relic abundance, direct detection, and collider searches. At the LHC, a typical signature of Higgs-portal fermion dark matter features soft leptons and missing energy, similarly to gaugino production in models with supersymmetry…
We propose an unified model of dark matter and baryon asymmetry in a lepto-philic world above the electroweak scale. We provide an example where the inflaton decay products subsequently generate a lepton asymmetry and a dark matter abundance with an unique coupling in the early universe, while the present day decay of the dark matter through the same coupling gives rise the observed cosmic ray anomalies at PAMELA and Fermi Large Area Telescope.
We investigate the interplay between early universe cosmology and dark matter direct detection, considering axion models with naturally suppressed couplings to photons. In the context of the cosmological relaxation of the electroweak scale, we focus on a scenario of \emph{Relaxion Dark Matter}, in which the relaxion field constitutes all the observed dark matter relic density and its allowed mass range is fixed to a few $\mathrm{keV}$ by construction. In particular, we show that a relaxion particle with mass $m_ϕ= 3.0 \,\mathrm{keV}$ which couples to electrons with $g_{ϕ, e}= 6.8 \times 10^{-1…
If dark matter particles are not perfectly stable, their decay products might be seen in the cosmic-ray fluxes. A natural candidate for decaying dark matter is the gravitino in R-parity violating scenarios. In the relevant GeV-TeV energy range, the Fermi Large Area Telescope (LAT) is now measuring cosmic gamma-ray fluxes with an unprecedented precision. We use the Fermi LAT gamma-ray data to search for signatures from gravitino dark matter particles, concentrating on gamma-ray lines and galaxy cluster observations. Implications of our results for the decay length of the next-to-lightest superp…
