scholarly journals Soft displaced leptons at the LHC

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Freya Blekman ◽  
Nishita Desai ◽  
Anastasiia Filimonova ◽  
Abanti Ranadhir Sahasransu ◽  
Susanne Westhoff
Keyword(s):  
Neural Network ◽  
Dark Matter ◽  
Transverse Momentum ◽  
Standard Model ◽  
Comprehensive Analysis ◽  
Weak Scale ◽  
The Standard Model ◽  
Lepton Decays ◽  
Relic Abundance ◽  
Large Background

Abstract Soft displaced leptons are representative collider signatures of compressed dark sectors with feeble couplings to the standard model. Prime targets are dark matter scenarios where co-scattering or co-annihilation sets the relic abundance upon freeze-out. At the LHC, searches for soft displaced leptons are challenged by a large background from hadron or tau lepton decays. In this article, we present an analysis tailored for displaced leptons with a low transverse momentum threshold at 20 GeV. Using a neural network, we perform a comprehensive analysis of the event kinematics, including a study of the expected detection efficiencies and backgrounds at small momenta. Our results show that weak-scale particles decaying into soft leptons with decay lengths between 1 mm and 1 m can be probed with LHC Run 2 data. This motivates the need for dedicated triggers that maximize the sensitivity to displaced soft leptons.

scholarly journals Stealth decaying spin-1 dark matter

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Cédric Delaunay ◽  
Teng Ma ◽  
Yotam Soreq
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Direct Detection ◽  
Gauge Coupling ◽  
Indirect Detection ◽  
Cosmological Time ◽  
Electron Neutrinos ◽  
The Standard Model ◽  
Lepton Decays ◽  
Relic Abundance

Abstract We consider models of decaying spin-1 dark matter whose dominant coupling to the standard model sector is through a dark-Higgs Yukawa portal connecting a TeV-scale vector-like lepton to the standard model (right-handed) electron. Below the electron-positron threshold, dark matter has very slow, loop-suppressed decays to photons and (electron) neutrinos, and is stable on cosmological time-scale for sufficiently small gauge coupling values. Its relic abundance is set by in-equilibrium dark lepton decays, through the freeze-in mechanism. We show that this model accommodates the observed dark matter abundance for natural values of its parameters and a dark matter mass in the ∼ 5 keV to 1 MeV range, while evading constraints from direct detection, indirect detection, stellar cooling and cosmology. We also consider the possibility of a nonzero gauge kinetic mixing with the standard model hypercharge field, which is found to yield a mild impact on the model’s phenomenology.

scholarly journals Search for dark matter in association with an energetic photon in pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Dark Matter ◽  
Transverse Momentum ◽  
Standard Model ◽  
Confidence Level ◽  
Axial Vector ◽  
Beyond The Standard Model ◽  
Proton Proton ◽  
Missing Transverse Momentum ◽  
Upper Limits ◽  
The Standard Model

Abstract A search for dark matter is conducted in final states containing a photon and missing transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV. The data, collected during 2015–2018 by the ATLAS experiment at the CERN LHC, correspond to an integrated luminosity of 139 fb−1. No deviations from the predictions of the Standard Model are observed and 95% confidence-level upper limits between 2.45 fb and 0.5 fb are set on the visible cross section for contributions from physics beyond the Standard Model, in different ranges of the missing transverse momentum. The results are interpreted as 95% confidence-level limits in models where weakly interacting dark-matter candidates are pair-produced via an s-channel axial-vector or vector mediator. Dark-matter candidates with masses up to 415 (580) GeV are excluded for axial-vector (vector) mediators, while the maximum excluded mass of the mediator is 1460 (1470) GeV. In addition, the results are expressed in terms of 95% confidence-level limits on the parameters of a model with an axion-like particle produced in association with a photon, and are used to constrain the coupling gaZγ of an axion-like particle to the electroweak gauge bosons.

scholarly journals Resurrecting low-mass axion dark matter via a dynamical QCD scale

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Lucien Heurtier ◽  
Fei Huang ◽  
Tim M.P. Tait
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Temperature Dependent ◽  
Axion Field ◽  
Wide Range ◽  
The Standard Model ◽  
Low Mass ◽  
Higher Temperature ◽  
Relic Abundance ◽  
Dependent Mass

Abstract In the framework where the strong coupling is dynamical, the QCD sector may confine at a much higher temperature than it would in the Standard Model, and the temperature-dependent mass of the QCD axion evolves in a non-trivial way. We find that, depending on the evolution of ΛQCD, the axion field may undergo multiple distinct phases of damping and oscillation leading generically to a suppression of its relic abundance. Such a suppression could therefore open up a wide range of parameter space, resurrecting in particular axion dark-matter models with a large Peccei-Quinn scale fa ≫ 1012 GeV, i.e., with a lighter mass than the standard QCD axion.

scholarly journals Flipped U(1) extended standard model and Majorana dark matter

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Cao H. Nam
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Boson Mass ◽  
Type I ◽  
Seesaw Mechanism ◽  
Gauge Symmetries ◽  
The Standard Model ◽  
Gauge Boson Mass ◽  
The Right ◽  
Relic Abundance

AbstractWe propose a general flavor-independent extension of the Standard Model (SM) with the minimal particle content, based on the symmetry $$SU(3)_C\times SU(2)_L\times U(1)_{Y'}\times U(1)_X\times Z_2$$ S U ( 3 ) C × S U ( 2 ) L × U ( 1 ) Y ′ × U ( 1 ) X × Z 2 . In this scenario, the charge operator is identified in terms of the charges of two U(1) gauge symmetries. The light neutrino masses are generated via Type-I seesaw mechanism only with two heavy right-handed neutrinos acquiring their Majorana masses through the $$U(1)_{Y'}\times U(1)_X$$ U ( 1 ) Y ′ × U ( 1 ) X symmetry breaking. We study various experimental constraints on the parameters of the model and investigate the phenomenology of the right-handed neutrino dark matter (DM) candidate assigned a $$Z_2$$ Z 2 -odd parity. We find that the most important constraints are the observed DM relic abundance, the current LHC limits, and the ambiguity of the SM neutral gauge boson mass.

scholarly journals Anomalous leptonic U(1) symmetry: Syndetic origin of the QCD axion, weak-scale dark matter, and radiative neutrino mass

2018 ◽  
Vol 33 (03) ◽  
pp. 1850024 ◽  
Author(s):  
Ernest Ma ◽  
Diego Restrepo ◽  
Óscar Zapata
Keyword(s):  
Dark Matter ◽  
Large Hadron Collider ◽  
Standard Model ◽  
Neutrino Mass ◽  
Hadron Collider ◽  
Neutrino Masses ◽  
Weak Scale ◽  
The Standard Model

The well-known leptonic U(1) symmetry of the Standard Model (SM) of quarks and leptons is extended to include a number of new fermions and scalars. The resulting theory has an invisible QCD axion (thereby solving the strong CP problem), a candidate for weak-scale dark matter (DM), as well as radiative neutrino masses. A possible key connection is a color-triplet scalar, which may be produced and detected at the Large Hadron Collider.

DIRECT VERSUS INDIRECT SEARCHES FOR NEUTRALINO DARK MATTER

1992 ◽  
Vol 07 (09) ◽  
pp. 733-747 ◽  
Author(s):  
A. BOTTINO ◽  
V. DE ALFARO ◽  
N. FORNENGO ◽  
A. MORALES ◽  
J. PUIMEDÓN ◽  
...  
Keyword(s):  
Experimental Data ◽  
Dark Matter ◽  
Standard Model ◽  
Coupling Strength ◽  
Supersymmetric Extension ◽  
Set Constraints ◽  
The Standard Model ◽  
Search Data ◽  
Relic Abundance ◽  
Minimal Supersymmetric Extension

Direct search for neutralino dark matter is analyzed in the framework of the minimal supersymmetric extension of the standard model, using a realistic evaluation of the neutralino relic abundance which also includes radiative corrections to the Higgs masses. Relevance of the present (Ge detectors) experimental data to set constraints on the parameters of the model is discussed and expectations for future experiments which involve neutralino-nucleus coherent processes are investigated. These results are compared to those obtained in a previous paper from indirect search data. In the present analysis particular attention is paid to the theoretical uncertainties due to the different estimates of the Higgs-nucleon coupling strength.

scholarly journals Forbidden dark matter annihilations into Standard Model particles

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Raffaele Tito D’Agnolo ◽  
Di Liu ◽  
Joshua T. Ruderman ◽  
Po-Jen Wang
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Relevant Parameter ◽  
Annihilation Rate ◽  
High Luminosity ◽  
Muon Mass ◽  
Electron Positron ◽  
Dark Matter Mass ◽  
The Standard Model ◽  
Relic Abundance

Abstract We present kinematically forbidden dark matter annihilations into Standard Model leptons. This mechanism precisely selects the dark matter mass that gives the observed relic abundance. This is qualitatively different from existing models of thermal dark matter, where fixing the relic density typically leaves open orders of magnitude of viable dark matter masses. Forbidden annihilations require the dark matter to be close in mass to the particles that dominate its annihilation rate. We show examples where the dark matter mass is close to the muon mass, the tau mass, or the average of the tau and muon masses. We find that most of the relevant parameter space can be covered by the next generation of proposed beam-dump experiments and future high-luminosity electron positron colliders. Forbidden dark matter predicts large couplings to the Standard Model that can explain the observed value of (g − 2)μ.

scholarly journals Exploring direct detection suppressed regions in a simple 2-scalar mediator model of scalar dark matter

2021 ◽  
Vol 81 (5) ◽  
Author(s):  
Jérôme Claude ◽  
Stephen Godfrey
Keyword(s):  
Dark Matter ◽  
Simple Model ◽  
Standard Model ◽  
Parameter Space ◽  
Cross Sections ◽  
Direct Detection ◽  
Detection Limits ◽  
Interference Effects ◽  
The Standard Model ◽  
Relic Abundance

AbstractWe explore regions of parameter space that give rise to suppressed direct detection cross sections in a simple model of scalar dark matter with a scalar portal that mixes with the standard model Higgs. We found that even this simple model allows considerable room in the parameter space that has not been excluded by direct detection limits. A number of effects leading to this result have been previously noted. Our main new result explores interference effects between different contributions to DM annihilation when the DM mass is larger than the scalar portal mass. New annihilation channels open up and the parameters of the model need to compensate to give the correct DM relic abundance, resulting in smaller direct detection cross sections. We find that even in a very simple model of DM there are still sizeable regions of parameter space that are not ruled out by experiment.

scholarly journals Two-component Dark Matter in the vectorlike hypercolor extension of the Standard Model

2019 ◽  
Vol 201 ◽  
pp. 09001 ◽  
Author(s):  
Vitaly Beylin ◽  
Maxim Bezuglov ◽  
Vladimir Kuksa
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Bound States ◽  
Model Framework ◽  
Component Structure ◽  
Neutral Particles ◽  
Quark Sector ◽  
The Standard Model ◽  
Two Component ◽  
Relic Abundance

We consider a minimal vectorlike extension of the Standard Model that naturally contains two types of stable neutral particles. They can be interpreted as the Dark Matter candidates. Here, the SM is supplemented by a new fermion (H-quark) sector that is in confilnement providing by the SU(2)HC gauge group. H-quarks interact with the SM particles via standard electroweak bosons. In analogy with the conventional QCD, H-quarks can form bound states, H-hadrons, that emerge in the σ− model framework. Along with the stable neutral H-pion, there is one more pseudo-goldstone (diquark) state, B0, which is stable and also can be a component of the DM. Mass splittings both for components of the H-pion triplet and for neutral H-pion and B0 have been calculated, it is shown that this splittings can be small. The relic abundance for this composition of the DM is analyzed as well as the DM particles scattering off nucleons. A feature of this scenario is that Dark Matter turns out to consist of particles which are close in mass but have different origin and interact differently with ordinary matter. So, the model predicts two-component structure of the DM together with some specifilc manifestations of it.

scholarly journals FIMP Dark Matter in Clockwork/Linear Dilaton extra-dimensions

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Nicolás Bernal ◽  
Andrea Donini ◽  
Miguel G. Folgado ◽  
Nuria Rius
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Parameter Space ◽  
Extra Dimensions ◽  
Scalar Fields ◽  
The Standard Model ◽  
Linear Dilaton ◽  
Warped Extra Dimensions ◽  
Relic Abundance ◽  
Significant Region

Abstract We study the possibility that Dark Matter (DM) is made of Feebly Interacting Massive Particles (FIMP) interacting just gravitationally with the Standard Model particles in the framework of a Clockwork/Linear Dilaton (CW/LD) model. We restrict here to the case in which the DM particles are scalar fields. This paper extends our previous study of FIMP’s in Randall-Sundrum (RS) warped extra-dimensions. As it was the case in the RS scenario, also in the CW/LD model we find a significant region of the parameter space in which the observed DM relic abundance can be reproduced with scalar DM mass in the MeV range, with a reheating temperature varying from 10 GeV to 109 GeV. We comment on the similarities of the results in both extra-dimensional models.

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