The production and decay of a new heavy vector boson, a chromophilic $Z'$ vector boson, is described. The chromophilic $Z'$ couples only to two gluons, but its two-body decays are absent, leading to a dominant decay mode of $Z'\rightarrow q\bar{q}g$. The unusual nature of the interaction predicts a cross-section which grows with $m_{Z'}$ for a fixed coupling and an accompanying gluon with a coupling that rises with its energy. We study the $t\bar{t}g$ decay mode, proposing distinct reconstruction techniques for the observation of an excess and for the measurement of $m_{Z'}$. We estimate the sensitivity of current experimental datasets.
We study a model with $U(1)_{L_μ- L_τ}$ gauge symmetry and discuss collider searches for a scalar boson, which breaks $U(1)_{L_μ- L_τ}$ symmetry spontaneously, decaying into light $Z'$ gauge boson. In this model, the new gauge boson, $Z'$, with a mass lighter than $\mathcal{O}(100)$ MeV, plays a role in explaining the anomalous magnetic moment of muon via one-loop contribution. For the gauge boson to have such a low mass, the scalar boson, $ϕ$ with $\mathcal{O}(100)$ GeV mass appears associated with the symmetry breaking. We investigate experimental constraints on $U(1)_{L_μ- L_τ}$ gauge coupl…
We present a search for a new heavy vector boson $Z'$ that decays to gluons. Decays to on-shell gluons are suppressed, leading to a dominant decay mode of $Z' \rightarrow g^*g$. We study the case where the off-shell gluon $g^*$ converts to a pair of top quarks, leading to a final state of $t\bar{t}g$. In a sample of events with exactly one charged lepton, large missing transverse momentum and at least five jets, corresponding to an integrated luminosity of 8.7 fb$^{-1}$ collected by the CDF II detector, we find the data to be consistent with the standard model. We set upper limits on the produ…
We analyze the decays to muons of a light dilaton produced via vector boson fusion at the LHC. We investigate models in which the electroweak symmetry breaking is triggered by a spontaneously broken, approximately conformal sector. Taking into account the possibility of shifts in the dilaton Yukawa couplings to muons, we find a rather promising scenario for the conformal model search in the channel, with the possibility for a dilaton discovery at a delivered luminosity of 100 fb-1 at the LHC or, alternatively, for an extension of the exclusion zone in the model parameter space, until now fixed…
Clear methods to differentiate between decaying and annihilating dark matter (DM) scenarios are still by and large unavailable. In this note, we study the potential astrophysical signatures of a new class of hidden sector decaying DM models, which can address the recent cosmic ray measurements. Such models may produce primary photons and/or neutrinos at large rates, correlated with the leptonic production. The photon and neutrino spectra will then contain sharp features at the TeV scale. We demonstrate the discovery potential for upcoming and future measurements by FERMI, HESS, AGIS and IceCub…
The purpose of line-intensity mapping (IM), an emerging tool for extragalactic astronomy and cosmology, is to measure the integrated emission along the line of sight from spectral lines emitted from galaxies and the intergalactic medium. The observed frequency of the line then provides a distance determination allowing the three-dimensional distribution of the emitters to be mapped. Here we discuss the possibility to use these measurements to seek radiative decays or annihilations from dark-matter particles. The photons from monoenergetic decays will be correlated with the mass distribution, w…
The `$μ$ from $ν$' supersymmetric standard model ($μν$SSM) solves the $μ$ problem of supersymmetric models and reproduces neutrino data, simply using couplings with the three families of right-handed neutrinos $ν$'s. Novel signatures of supersymmetry at the LHC are expected through these new states, and couplings breaking $R$ parity. All supersymmetric particles are potential candidates for the lightest one, which is not stable leading to prompt or displaced vertices and producing final states with multi-leptons/taus/jets/photons and missing energy. Besides, a decaying gravitino turns out to b…
We analyze the possibility of detection of cosmological relic neutrinos via neutrino capture on beta decaying nuclei. This reaction has no threshold in neutrino energy, which is crucial for searching for relic neutrinos possessing very low energies. We focus on tritium (3H) and rhenium (187Re) beta radioactive isotopes to be used in KATRIN and MARE experiments dedicated to measurement of the electron neutrino mass at sub-eV scale. We examine these experiments from the viewpoint of searching for the cosmological neutrinos via neutrino capture. We conclude that even with possible gravitational c…
We explore the phenomenology of scalar fields in the adjoint representation of SM gauge groups. We write a general set of dimension 5 effective operators in which SM adjoint scalars couple to pairs of standard model bosons. Using these effective operators, we explore new possible decay channels of a scalar color octet into a gluon and a Z boson/ gluon and a photon. We recast several analyses from Run I of the LHC to find constraints on an a scalar octet decaying into these channels, and we project the discovery potential of color octets in our gluon+photon channel for the 14 TeV run of LHC.
We study a simplified model of the SM Higgs boson decaying to a degenerate pair of scalars which travel a macroscopic distance before decaying to SM particles. This is the leading signal for many well-motivated solutions to the hierarchy problem that do not propose additional light colored particles. Bounds for displaced Higgs decays below $10$ cm are found by recasting existing tracker searches from Run I. New tracker search strategies, sensitive to the characteristics of these models and similar decays, are proposed with sensitivities projected for Run II at $\sqrt{s} = 13 $ TeV. With 20 fb$…
We present results of a search for the 3.5 keV emission line in our recent very long (~ 1.4 Ms) XMM-Newton observation of the Draco dwarf spheroidal galaxy. The astrophysical X-ray emission from such dark matter-dominated galaxies is faint, thus they provide a test for the dark matter origin of the 3.5 keV line previously detected in other massive, but X-ray bright objects, such as galaxies and galaxy clusters. We do not detect a statistically significant emission line from Draco; this constrains the lifetime of a decaying dark matter particle to tau > (7-9) x 10^27 s at 95% CL (combining all …
LHC run-II has a great potential to search for new resonances in the diphoton channel. Latest 13 TeV data already put stringent limits on the cross sections in the diphoton channel assuming the resonance is produced through the gluon-gluon fusion. Many beyond the Standard Model (SM) theories predict TeV-scale scalars, which copiously decay to diphotons. Apart from the gluon-gluon fusion production, these scalars can also be dominantly produced in other ways too at the LHC namely through the quark-quark fusion or the gauge boson fusions like the photon-photon, photon-$Z$, $WW$ or $ZZ$ fusions. …
We consider interpretations of the recent $\sim 3 σ$ reports by the CMS and ATLAS collaborations of a possible $X(\sim 750~{\rm GeV})$ state decaying into $γγ$ final states. We focus on the possibilities that this is a scalar or pseudoscalar electroweak isoscalar state produced by gluon-gluon fusion mediated by loops of heavy fermions. We consider several models for these fermions, including a single vector-like charge $2/3$ T quark, a doublet of vector-like quarks $(T, B)$, and a vector-like generation of quarks, with or without leptons that also contribute to the $X \to γγ$ decay amplitude. …
The abundant $ψ'$ events have been collected at the Beijing Electron Positron Collider-II (BEPCII) that could undoubtedly provide us with a great opportunity to study the more attractive charmonium decays. As has been noticed before, in the process of $J/ψ$ decaying to the baryonic final states, $p K^- \barΛ$, the evident $Λ^*$ and $N^*$ bands have been observed. Similarly, by using the product of $χ_{cJ}$ from $ψ'$ radiative decay, we may confirm it or find some extra new resonances. $χ_{c0}$'s data samples will be more than $χ_{c1,2}$ taking into account the larger branching ratio of $ψ'\toγ…
In this paper we propose to use convolutional neural networks (CNNs) to improve the precision measurement of the Higgs boson-gluon effective coupling at lepton colliders. The CNN is employed to recognize the Higgs boson and a $Z$ boson associated production process, with the Higgs boson decaying to a gluon pair and the $Z$ boson decaying to a lepton pair at the center-of-mass energy 250 GeV and integrated luminosity 5 ab$^{-1}$. By using CNNs, the uncertainty of the effective coupling measurement can be decreased from $1.94\%$ to about $1.28\%$ using the PYTHIA data and from $1.82\%$ to about …
We pursue a scenario where the lighter top squark (stop) mass is accessible for the Large Hadron Collider (LHC) in the near future, while gluinos and first two generation squarks are heavier. At $\sqrt{s} = 8$ TeV, we investigate the identification of stops which decay predominantly into a top quark and the stable lightest supersymmetric particle. We use a simple kinematical variable, $M3$, to reconstruct two top quarks which are pair-produced from the stops, in the fully hadronic channel. The dominant Standard Model (SM) background for this signal stems from $t\bar t$ plus jets, with one top …
High-luminosity experiments are able to search for new physics at low energies, which could have evaded detection thus far due to very weak couplings to the Standard Model. The DarkLight experiment at Jefferson Lab is designed to search for a new U(1) vector boson A' in the mass range 10-100 MeV through its decay A' -> e+ e-. In this paper, we demonstrate that DarkLight is also sensitive to an A' decaying to invisible final states. We analyze the DarkLight reach for invisible A' bosons assuming a nominal two month running time, including the possibility of augmenting the DarkLight design to in…
We consider the effects in the production via gluon fusion in LHC collisions of one or two spin-zero new resonant particles $Φ$ that decay into a top quark pair. We revisit previous analyses of the interferences between the heavy-fermion loop-induced $gg \rightarrow Φ\rightarrow t\bar{t}$ signal and the continuum QCD background $gg \rightarrow t\bar{t}$. We show that in the presence of standard model fermions only in the $gg \rightarrow Φ$ loops, the interference effect is destructive causing a dip in the $t \bar t$ mass distribution. Including New Physics such as additional vector-like quarks…
The $U(1)$ extensions of the Standard Model contain a heavy neutral gauge boson $Z^\prime$. If leptophobic, the boson can evade the stringent bounds from the dilepton resonance searches. We consider two theoretically well-motivated examples of leptophobic $U(1)$ extensions in which the $Z'$ decays to right-handed neutrinos (RHNs) with substantial branchings. The coexistence of a leptophobic $Z^\prime$ and the RHNs opens up a new possibility of searching for these particles simultaneously through the production of a $Z^\prime$ at the LHC and its decay to a RHN pair. For this decay to occur, the…
In this paper we briefly review the LHC discovery potential of a light pseudoscalar Higgs boson of the NMSSM, $a_1$, produced in the gluon fusion $gg\to a_1$ , bottom-quark fusion $b\bar b\to a_1$ and bottom-gluon fusion $bg\to ba_1$. We also review the LHC discovery potential of the next-to-lightest CP-even Higgs boson $h_2$ being the non-SM-like Higgs, decaying either into two light CP-odd Higgs bosons $a_1 a_1$ or into a light $a_1$ and the $Z$ gauge boson through the gluon fusion $gg \to h_2$ in the 4$τ$ final state. We find that the light $a_1$ can be detected at the LHC in a variety of p…
We investigate the prospects for the discovery of massive color-octet vector bosons at the CERN Large Hadron Collider with $\sqrt{s} = 14$ TeV. A phenomenological Lagrangian is adopted to evaluate the cross section of a pair of colored vector bosons (colorons, $\tildeρ$) decaying into four colored scalar resonances (hyper-pions, $\tildeπ$), which then decay into eight gluons. We include the dominant physics background from the production of $8g,7g1q, 6g2q$, and $5g3q$, and determine the masses of $\tildeπ$ and $\tildeρ$ where discovery is possible. For example, we find that a 5$σ$ signal can b…
We demonstrate that not only the production of virtual photons decaying into low-mass lepton pairs, but also the one of weak bosons at large transverse momenta is dominated by quark-gluon scattering. Measurements of these processes at the LHC can therefore provide useful constraints on the parton densities in the proton, in particular the one of the gluon, and their nuclear modifications.
We reemphasise the usefulness of angular correlations in LHC searches for missing transverse energy ($E_T^{\mathrm{miss}}$) signatures that involve jet $(j)$ pairs with large invariant mass. For the case of mono-jet production via gluon-fusion, we develop a realistic analysis strategy that allows to split the dark matter (DM) signal into distinct one jet-like and two jet-like event samples. By performing state-of-the-art Monte Carlo simulations of both the mono-jet signature and the standard model background, it is shown that the dijet azimuthal angle difference $Δϕ_{j_1 j_2}$ in $2 j +E_T^{\m…
ATLAS and CMS recently show the first results from run 2 of the Large Hadron Collider (LHC) at $\sqrt{s}=13$ TeV. A resonant bump at a mass of around 750 GeV in the diphoton invariant mass spectrum is indicated and the corresponding diphoton production cross section is around 3-10 fb. Motivated by the LHC diphoton excess, we propose that the possible resonance candidate is a Higgs singlet. To produce the Higgs singlet via gluon-gluon fusion process, we embed the Higgs singlet in the framework of vector-like triplet quark (VLTQ) model. As a result, the Higgs singlet decaying to diphoton final s…
The neutrinoless double beta decay is analyzed using a general Lorentz invariant effective Lagrangian for various decaying nuclei of current experimental interest: $^{76}$Ge, $^{82}$Se, $^{100}$Mo, $^{130}$Te, and $^{136}$Xe. We work out the half-lives and angular correlation coefficients of the outgoing electrons in several scenarios for new physics: the left-right symmetric models, the R-parity-violating SUSY and models with leptoquarks. The theoretical uncertainty in the nuclear matrix elements is discussed.
In this paper we propose to use the measurement of the thermal Quark-Gluon Plasma (QGP) dilepton spectra in the Intermediate Mass Region (IMR) of heavy-ion collisions, as a new method to search for GeV-scale dark gauge bosons (gamma' or Z'). Such light mediators are a common feature of light (i.e. low mass) dark matter scenarios, which have been invoked to explain puzzling signals in dark matter indirect and direct detection experiments. First we show that a light gamma' or Z' will generate a resonant enhancement of the dilepton spectrum produced thermally by the QGP, at an energy correspondin…
We study the search for electroweakinos at the 13 TeV LHC in the case of heavy scalar superpartners. We consider both the direct production mode and the one associated with the decay of heavy Higgs bosons, and concentrate on the case of light Higgsinos and Binos. In this case, the direct production searches becomes more challenging than in the light Wino scenario. In the direct production mode, we use the current experimental searches to set the reach for these particles at larger luminosities, and we emphasize the relevance of considering both the neutral gauge boson and the neutral Higgs dec…
We propose a strategy for searching for theoretically-unanticipated new physics which avoids a large trials factor by focusing on experimental strengths. Searches for resonances decaying into pairs of visible particles are experimentally very powerful due to the localized mass peaks and have a rich history of discovery. Yet, due to a focus on subsets of theoretically-motivated models, the landscape of such resonances is far from thoroughly explored. We survey the existing set of searches, identify untapped experimental opportunities and discuss the theoretical constraints on models which would…
We extend the standard model to include a weak-triplet and color-octet scalar. This `octo-triplet' field consists of three particles, two charged and one neutral, whose masses and renormalizable interactions depend only on two new parameters. The charged octo-triplet decay into a W boson and a gluon is suppressed by a loop factor and an accidental cancellation. Thus, the main decays of the charged octo-triplet may occur through higher-dimensional operators, mediated by a heavy vectorlike fermion, into quark pairs. For an octo-triplet mass below the t\bar{b} threshold, the decay into Wb\bar{b} …
