Anomaly-mediated Supersymmetry Breaking Research Articles

Electroweak loop contributions to the direct detection of wino dark matter

Electroweak loop corrections to the matrix elements for the spin-independent scattering of cold dark matter particles on nuclei are generally small, typically below the uncertainty in the local density of cold dark matter. However, as shown in this paper, there are instances in which the electroweak loop corrections are relatively large, and change significantly the spin-independent dark matter scattering rate. An important example occurs when the dark matter particle is a wino, e.g., in anomaly-mediated supersymmetry breaking (AMSB) and pure gravity mediation (PGM) models. We find that the one-loop electroweak corrections to the spin-independent wino LSP scattering cross section generally interfere constructively with the tree-level contribution for AMSB models with negative Higgsino mixing, mu < 0, and in PGM-like models for both signs of mu , lifting the cross section out of the neutrino fog and into a range that is potentially detectable in the next generation of direct searches for cold dark matter scattering.

On s-confining SUSY-QCD with anomaly mediation

In this work, we present a comprehensive study of the phase diagram of supersymmetric QCD with Nf = Nc + 1 flavors perturbed by Anomaly Mediated Supersymmetry Breaking (AMSB). We extend the previous analyses on s-confining ASQCD theories in three different directions. We show that the existence of the QCD-like vacuum is independent of the size of the SUSY breaking parameter. We further expand the analysis of these models by including two and three-loop contributions to investigate the robustness and limitations of the results. Finally, we include the leading effect of higher-order Kähler terms to investigate the stability of the phase diagram as we approach the confining energy scale. The analysis with higher order Kähler terms is also extended for Nc = 2 for which AMSB alone gives inconclusive results.

Explaining the Muon g − 2 Anomaly in Deflected AMSB for NMSSM

We propose to embed the General NMSSM (Next-to-Minimal Supersymmetric Standard Model) into the deflected AMSB (Anomaly Mediated Supersymmetry Breaking) mechanism with Yukawa/gauge deflection contributions. After the integration of the heavy messenger fields, the analytical expressions of the relevant soft SUSY breaking spectrum for General NMSSM at the messenger scale can be calculated. We find that successful EWSB (Electroweak Symmetry Breaking) and realistic low energy NMSSM spectrum can be obtained in some parameter regions. In addition, we find that the muon g−2 anomaly and electron g−2 anomaly (for positive central value electron g−2 experimental data) can be jointly explained to 1σ and 2σ range, respectively. The Z3 invariant NMSSM, which corresponds to ξF=0 in our case, can also jointly explain the muon and electron anomaly to 1σ and 2σ range, respectively.

Guide to anomaly-mediated supersymmetry-breaking QCD

We present a careful study of the chiral symmetry breaking minima and the baryonic directions in supersymmetric QCD ($SU({N}_{c})$ with ${N}_{f}$ flavors) perturbed by anomaly mediated supersymmetry breaking (AMSB). For the s-confining case of ${N}_{f}={N}_{c}+1$ and most of the free-magnetic phase (${N}_{f}\ensuremath{\le}1.43{N}_{c}$) we find that naive tree level baryonic runaways are stabilized by loop effects. Runaways are present, however, for the upper end of the free magnetic phase (${N}_{f}\ensuremath{\gtrsim}1.43{N}_{c}$) and into conformal window, signaling the existence of incalculable minima at large field values of $\mathcal{O}(\mathrm{\ensuremath{\Lambda}})$. Nevertheless, the chiral symmetry breaking points are locally stable, and are expected to continuously connect to the vacua of QCD for large SUSY breaking. The case of ${N}_{f}={N}_{c}$ requires particular care due to the inherently strongly coupled nature of the quantum modified moduli space. Due to the incalculability of critical K\"ahler potential terms, the stability of the chiral symmetry breaking point along baryonic directions cannot be determined for ${N}_{f}={N}_{c}$. With the exception of this case, all theories to which AMSB can be applied (${N}_{f}&lt;3{N}_{c}$) possess stable chiral symmetry breaking minima, and all theories with ${N}_{f}\ensuremath{\lesssim}1.43{N}_{c}$ (aside from ${N}_{f}={N}_{c}$) are protected from runaways to incalculable minima.

More exact results on chiral gauge theories: The case of the symmetric tensor

We study dynamics of $SU(N\ensuremath{-}4)$ gauge theories with fermions in rank-2 symmetric tensor and $N$ antifundamental representations, by perturbing supersymmetric theories with anomaly-mediated supersymmetry breaking. We find the $SU(N)\ifmmode\times\else\texttimes\fi{}U(1)$ global symmetry is dynamically broken to $SO(N)$ for $N\ensuremath{\ge}17$, a different result from conjectures in the literature. For $N&lt;17$, the theory initially flows to a superconformal fixed point, but is diverted by the soft masses, which act as a relevant perturbation.

Demonstration of Confinement and Chiral Symmetry Breaking in SO(Nc) Gauge Theories

We demonstrate that $SO(N_{c})$ gauge theories with matter fields in the vector representation confine due to monopole condensation and break the $SU(N_{F})$ chiral symmetry to $SO(N_{F})$ via the quark bilinear. Our results are obtained by perturbing the ${\cal N}=1$ supersymmetric theory with anomaly-mediated supersymmetry breaking.

Mixed modulus and anomaly mediation in light of the muon g \u2212 2 anomaly

The new measurement of the anomalous magnetic moment of muon at the Fermilab Muon g− 2 experiment has strengthened the significance of the discrepancy between the standard model prediction and the experimental observation from the BNL measurement. If new physics responsible for the muon g− 2 anomaly is supersymmetric, one should consider how to obtain light electroweakinos and sleptons in a systematic way. The gauge coupling unification allows a robust prediction of the gaugino masses, indicating that the electroweakinos can be much lighter than the gluino if anomaly-mediated supersymmetry breaking is sizable. As naturally leading to mixed modulus-anomaly mediation, the KKLT scenario is of particular interest and is found capable of explaining the muon g− 2 anomaly in the parameter region where the lightest ordinary supersymmetric particle is a bino-like neutralino or slepton.

Some exact results in chiral gauge theories

We analyze dynamics of chiral gauge theories based on the $SU(N)$ gauge group with one antisymmetric tensor $A$ and ($N\ensuremath{-}4$) antifundamentals ${F}_{i}$ when $N$ is odd. Based on the continuity to the supersymmetric gauge theories with anomaly-mediated supersymmetry breaking, we claim that the global $SU(N\ensuremath{-}4)$ symmetry is spontaneously broken to $Sp(N\ensuremath{-}5)$. There are $N\ensuremath{-}5$ massless fermions as a fundamental representation of $Sp(N\ensuremath{-}5)$, and another massless fermion, together saturating the anomaly matching conditions. When $N$ is even, the unbroken flavor symmetry is $Sp(N\ensuremath{-}4)$ while there are no massless fermions. Our result is different from the dynamics suggested by tumbling where the full $SU(N\ensuremath{-}4)$ symmetry is unbroken, but the tumbling picture can be modified via the addition of a second condensate to produce the symmetry breaking pattern predicted from our method.

Some Exact Results in QCD-like Theories.

I propose a controlled approximation to QCD-like theories with massless quarks by employing supersymmetric QCD perturbed by anomaly-mediated supersymmetry breaking. They have identical massless particle contents. Thanks to the ultraviolet insensitivity of anomaly mediation, dynamics can be worked out exactly when m≪Λ, where m is the size of supersymmetry breaking and Λ the dynamical scale of the gauge theory. I demonstrate that chiral symmetry is dynamically broken for N_{f}≤3/2N_{c} while the theories lead to nontrivial infrared fixed points for larger number of flavors. While there may be a phase transition as m is increased beyond Λ, qualitative agreements with expectations in QCD are encouraging and suggest that two limits m≪Λ and m≫Λ may be in the same universality class.

Search for disappearing tracks in proton-proton collisions at [formula omitted

A search is presented for long-lived charged particles that decay within the volume of the silicon tracker of the CMS experiment. Such particles can produce events with an isolated track that is missing hits in the outermost layers of the silicon tracker, and is also associated with little energy deposited in the calorimeters and no hits in the muon detectors. The search for events with this “disappearing track” signature is performed in a sample of proton-proton collisions recorded by the CMS experiment at the LHC with a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 101fb−1 recorded in 2017 and 2018. The observation of 48 events is consistent with the estimated background of 47.8−2.3+2.7(stat)±8.1(syst) events. Upper limits are set on chargino production in the context of an anomaly-mediated supersymmetry breaking model for purely wino and higgsino neutralino scenarios. At 95% confidence level, the first constraint is placed on chargino masses in the higgsino case, excluding below 750 (175) GeV for a lifetime of 3 (0.05)ns. In the wino case, the results of this search are combined with a previous CMS search to produce a result representing the complete LHC data set recorded in 2015–2018, the most stringent constraints to date. At 95% confidence level, chargino masses in the wino case are excluded below 884 (474) GeV for a lifetime of 3 (0.2)ns.

Search for disappearing tracks as a signature of new long-lived particles in proton-proton collisions at sqrt{s}=13 TeV

A search is presented for long-lived charged particles that decay within the CMS detector and produce the signature of a disappearing track. A disappearing track is an isolated track with missing hits in the outer layers of the silicon tracker, little or no energy in associated calorimeter deposits, and no associated hits in the muon detectors. This search uses data collected with the CMS detector in 2015 and 2016 from proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, corresponding to an integrated luminosity of 38.4 fb−1. The results of the search are interpreted in the context of the anomaly-mediated supersymmetry breaking model. The data are consistent with the background-only hypothesis. Limits are set on the product of the cross section for direct production of charginos and their branching fraction to a neutralino and a pion, as a function of the chargino mass and lifetime. At 95% confidence level, charginos with masses below 715 (695) GeV are excluded for a lifetime of 3 (7) ns, as are charginos with lifetimes from 0.5 to 60 ns for a mass of 505 GeV. These are the most stringent limits using a disappearing track signature on this signal model for chargino lifetimes above ≈0.7 ns.

Anomaly-mediated SUSY breaking model retrofitted for naturalness

Anomaly-mediated supersymmetry breaking (AMSB) models seem to have become increasingly implausible due to 1. difficulty in generating a Higgs mass m(h)~125 GeV, 2. typically unnatural superparticle spectra characterized by a large superpotential mu term and 3. the possibility of a wino-like lightest SUSY particle (LSP) as dark matter now seems to be excluded. In the present paper we propose some minor modifications to the paradigm model which solve these three issues. Instead of adding a universal bulk scalar mass to avoid tachyonic sleptons, we add distinct Higgs and matter scalar soft masses which then allow for light higgsinos. To gain accord with the measured Higgs mass, we also include a bulk trilinear soft term. The ensuing natural generalized AMSB (nAMSB) model then has a set of light higgsinos with mass nearby the weak scale m(W,Z,h)~100 GeV as required by naturalness while the winos populate the several hundred GeV range and gluinos and squarks occupy the multi-TeV range. For LHC searches, the wino pair production followed by decay to same-sign diboson signature channel offers excellent prospects for discovery at high luminosity LHC along with higgsino pair production leading to soft dileptons plus jet(s)+MET. A linear e^+e^- collider operating above higgsino pair production threshold should be able to distinguish the AMSB gaugino spectra from unified or mirage unified scenarios. Dark matter is expected to occur as a higgsino-like WIMP plus axion admixture.

Seesaw-deflected Anomaly Mediation and the 125 GeV Higgs Boson

We investigate the phenomenology of a class of model that at the same time solves the tachyonic slepton problem of the pure anomaly mediated supersymmetry breaking (AMSB) model and generates neutrino masses. We introduce heavy fields in the seesaw mechanism that are the messengers in the deflected AMSB scenario. Various theoretical and phenomenological constraints have been taken into account, especially the Higgs mass limits. The viable parameter regions have been specified, and the properties of dark matter candidate have been studied. We point out that the type III seesaw with three generations of 24-messenger is excluded, while the type II seesaw and type III seesaw with two generations of 24-messenger are still allowed. The sparticle masses are heavy as in usual SUSY models. The spin-independent crosssection of the scattering between the lightest neutralino and proton show the possibility to see evidences of new physics from future dark matter search experiments. We find that the lepton flavor violation effects caused by the Yukawa mediation are suppressed due to the electroweak symmetry breaking condition.

Mirage models confront the LHC. III. Deflected mirage mediation

We complete the study of a class of string-motivated effective supergravity theories in which modulus-induced soft supersymmetry breaking is sufficiently suppressed in the observable sector so as to be competitive with anomaly-mediated supersymmetry breaking. Here we consider deflected mirage mediation (DMM), where contributions from gauge mediation are added to those arising from gravity mediation and anomaly mediation. We update previous work that surveyed the rich parameter space of such theories, in light of data from the CERN Large Hadron Collider (LHC) and recent dark matter detection experiments. Constraints arising from LHC superpartner searches at $\sqrt{s} = 8\,{\rm TeV}$ are considered, and discovery prospects at $\sqrt{s} = 14\,{\rm TeV}$ are evaluated. We find that deflected mirage mediation generally allows for SU(3)-charged superpartners of significantly lower mass (given current knowledge of the Higgs mass and neutralino relic density) than was found for the `pure' mirage mediation models of Kachru et al. Consequently, discovery prospects are enhanced for many combinations of matter multiplet modular weights. We examine the experimental challenges that will arise due to the prospect of highly compressed spectra in DMM, and the correlation between accessibility at the LHC and discovery prospects at large-scale liquid xenon dark matter detectors.

Constraints on the pMSSM, AMSB model and on other models from the search for long-lived charged particles in proton-proton collisions at [Formula: see text

Stringent limits are set on the long-lived lepton-like sector of the phenomenological minimal supersymmetric standard model (pMSSM) and the anomaly-mediated supersymmetry breaking (AMSB) model. The limits are derived from the results presented in a recent search for long-lived charged particles in proton–proton collisions, based on data collected by the CMS detector at a centre-of-mass energy of 8 TeV at the Large Hadron Collider. In the pMSSM parameter sub-space considered, 95.9 % of the points predicting charginos with a lifetime of at least 10 ns are excluded. These constraints on the pMSSM are the first obtained at the LHC. Charginos with a lifetime greater than 100 ns and masses up to about 800 GeV in the AMSB model are also excluded. The method described can also be used to set constraints on other models.

Search for disappearing tracks in proton-proton collisions at s = 8 $$ \sqrt{s}=8 $$ TeV

A search is presented for long-lived charged particles that decay within the CMS detector and produce the signature of a disappearing track. Disappearing tracks are identified as those with little or no associated calorimeter energy deposits and with missing hits in the outer layers of the tracker. The search uses proton-proton collision data recorded at sqrt(s) = 8 TeV that corresponds to an integrated luminosity of 19.5 inverse femtobarns. The results of the search are interpreted in the context of the anomaly-mediated supersymmetry breaking (AMSB) model. The number of observed events is in agreement with the background expectation, and limits are set on the cross section of direct electroweak chargino production in terms of the chargino mass and mean proper lifetime. At 95% confidence level, AMSB models with a chargino mass less than 260 GeV, corresponding to a mean proper lifetime of 0.2 ns, are excluded.

Self-interacting dark matter from a non-Abelian hidden sector

There is strong evidence in favor of the idea that dark matter is self interacting, with the cross section-to-mass ratio $\ensuremath{\sigma}/m\ensuremath{\sim}1\text{ }\text{ }{\mathrm{cm}}^{2}/\mathrm{g}\ensuremath{\sim}1\text{ }\text{ }\mathrm{barn}/\mathrm{GeV}$. We show that viable models of dark matter with this large cross section are straightforwardly realized with non-Abelian hidden sectors. In the simplest of such models, the hidden sector is a pure gauge theory, and the dark matter is composed of hidden glueballs with a mass around 100 MeV. Alternatively, the hidden sector may be a supersymmetric pure gauge theory with a $\ensuremath{\sim}10\text{ }\text{ }\mathrm{TeV}$ gluino thermal relic. In this case, the dark matter is largely composed of glueballinos that strongly self interact through the exchange of light glueballs. We present a unified framework that realizes both of these possibilities in anomaly-mediated supersymmetry breaking, where, depending on a few model parameters, the dark matter may be composed of hidden glueballinos, hidden glueballs, or a mixture of the two. These models provide simple examples of multicomponent dark matter, have interesting implications for particle physics and cosmology, and include cases where a subdominant component of dark matter may be extremely strongly self interacting, with interesting astrophysical consequences.

(Non-)decoupled supersymmetric field theories

We study some consequences of coupling supersymmetric theories to (super)gravity. To linear order, the couplings are determined by the energy-momentum supermultiplet. At higher orders, the couplings are determined by contact terms in correlation functions of the energy-momentum supermultiplet. We focus on the couplings of one particular field in the supergravity multiplet, the auxiliary field $M$. We discuss its linear and quadratic (seagull) couplings in various supersymmetric theories. In analogy to the local renormalization group formalism, we provide a prescription for how to fix the quadratic couplings. They generally arise at two-loops in perturbation theory. We check our prescription by explicitly computing these couplings in several examples such as mass-deformed ${\cal N}$ = 4 and in the Coulomb phase of some theories. These couplings affect the Lagrangians of rigid supersymmetric theories in curved space. In addition, our analysis leads to a transparent derivation of the phenomenon known as Anomaly Mediation. In contrast to previous approaches, we obtain both the gaugino and scalar masses of Anomaly Mediation by relying just on classical, minimal supergravity and a manifestly local and supersymmetric Wilsonian point of view. Our discussion naturally incorporates the connection between Anomaly Mediation and supersymmetric $AdS_4$ Lagrangians. This note can be read without prior familiarity with Anomaly Mediated Supersymmetry Breaking (AMSB).

Search for charginos nearly mass degenerate with the lightest neutralino based on a disappearing-track signature inppcollisions at(s)=8 TeVwith the ATLAS detector

A search is presented for direct chargino production based on a disappearing-track signature using 20.3 fb-1 of proton-proton collisions at sqrt(s) = 8 TeV collected with the ATLAS experiment at the LHC. In anomaly-mediated supersymmetry breaking (AMSB) models, the lightest chargino is nearly mass-degenerate with the lightest neutralino and its lifetime is long enough to be detected in the tracking detectors by identifying decays that result in tracks with no associated hits in the outer region of the tracking system. Some models with supersymmetry also predict charginos with a significant lifetime. This analysis attains sensitivity for charginos with a lifetime between 0.1 ns and 10 ns, and significantly surpasses the reach of the LEP experiments. No significant excess above the background expectation is observed for candidate tracks with large transverse momentum, and constraints on chargino properties are obtained. In the AMSB scenarios, a chargino mass below 270 GeV is excluded at 95% confidence level.

Positively deflected anomaly mediation in the light of the Higgs boson discovery

Anomaly-mediated supersymmetry breaking (AMSB) is a well-known mechanism for flavor-blind transmission of supersymmetry breaking from the hidden sector to the visible sector. However, the pure AMSB scenario suffers from a serious drawback, namely, the tachyonic slepton problem, and needs to be extended. The so-called (positively) deflected AMSB is a simple extension to solve the problem and also provides us with the usual neutralino lightest superpartner as a good candidate for dark matter in the Universe. Motivated by the recent discovery of the Higgs boson at the Large Hadron Collider (LHC) experiments, we perform the parameter scan in the deflected AMSB scenario by taking into account a variety of phenomenological constraints, such as the dark matter relic density and the observed Higgs boson mass around 125--126 GeV. We identify the allowed parameter region and list benchmark mass spectra. We find that in most of the allowed parameter regions, the dark matter neutralino is Higgsino-like and its elastic scattering cross section with nuclei is within the future reach of the direct dark matter search experiments, while (colored) sparticles are quite heavy and their discovery at the LHC is challenging.