arXiv subjects

Csaba Balázs

Publications and source records attributed to Csaba Balázs.

52 records · Page 3Linked to original sources

arXiv2017

Sensitivity of the Cherenkov Telescope Array to the detection of a dark matter signal in comparison to direct detection and collider experiments

Imaging atmospheric Cherenkov telescopes (IACTs) that are sensitive to potential $γ$-ray signals from dark matter (DM) annihilation above $\sim50$ GeV will soon be superseded by the Cherenkov Telescope Array (CTA). CTA will have a point source sensitivity an order of magnitude better than currently operating IACTs and will cover a broad energy range between 20 GeV and 300 TeV. Using effective field theory and simplified models to calculate $γ$-ray spectra resulting from DM annihilation, we compare the prospects to constrain such models with CTA observations of the Galactic center with current and near-future measurements at the Large Hadron Collider (LHC) and direct detection experiments. For DM annihilations via vector or pseudoscalar couplings, CTA observations will be able to probe DM models out of reach of the LHC, and, if DM is coupled to standard fermions by a pseudoscalar particle, beyond the limits of current direct detection experiments.

astro-ph.HE↗

arXiv2017

Electroweak baryogenesis in the Z3-invariant NMSSM

We calculate the baryon asymmetry of the Universe in the Z3-invariant Next-to-Minimal Supersymmetric Standard Model where the interactions of the singlino provide the necessary source of charge and parity violation. Using the closed time path formalism, we derive and solve transport equations for the cases where the singlet acquires a vacuum expectation value (VEV) before and during the electroweak phase transition. We perform a detailed scan to show how the baryon asymmetry varies throughout the relevant parameter space. Our results show that the case where the singlet acquires a VEV during the electroweak phase transition typically generates a larger baryon asymmetry, although we expect that the case where the singlet acquires a VEV first is far more common for any model in which parameters unify at a high scale. Finally, we examine the dependence of the baryon asymmetry on the three-body interactions involving gauge singlets.

hep-ph↗

arXiv2016

Dark matter properties implied by gamma ray interstellar emission models

We infer dark matter properties from gamma ray residuals extracted using eight different interstellar emission scenarios proposed by the Fermi-LAT Collaboration to explain the Galactic Center gamma ray excess. Adopting the most plausible simplified ansatz, we assume that the dark matter particle is a Majorana fermion interacting with standard fermions via a scalar mediator. Using this theoretical hypothesis and the Fermi residuals we calculate Bayesian evidences, including Fermi-LAT exclusion limits from 15 dwarf spheroidal galaxies as well. Our Bayes factors single out four of the Fermi scenarios as compatible with the simplified dark matter model. In the most preferred scenario the dark matter (mediator) mass is in the 100-500 (1-200) GeV range and its annihilation is dominated by top quark final state. Less preferred but still plausible is annihilation into b\bar{b} and tau^+tau^- final states with an order of magnitude lower dark matter mass. Our conclusion is that the properties of dark matter extracted from gamma ray data are highly sensitive to the modeling of the interstellar emission.

hep-ph↗

arXiv2016

Semi-analytic techniques for calculating bubble wall profiles

We present semi-analytic techniques for finding bubble wall profiles during first order phase transitions with multiple scalar fields. Our method involves reducing the problem to an equation with a single field, finding an analytic solution and perturbing around it. The perturbations can be written in a semi-analytic form. We argue that our technique lacks convergence problems and demonstrate the speed of convergence on an example potential.

hep-ph↗

arXiv2016

AMS-02 fits Dark Matter

In this work we perform a comprehensive statistical analysis of the AMS-02 electron, positron fluxes and the antiproton-to-proton ratio in the context of a simplified dark matter model. We include known, standard astrophysical sources and a dark matter component in the cosmic ray injection spectra. To predict the AMS-02 observables we use propagation parameters extracted from observed fluxes of heavier nuclei and the low energy part of the AMS-02 data. We assume that the dark matter particle is a Majorana fermion coupling to third generation fermions via a spin-0 mediator, and annihilating to multiple channels at once. The simultaneous presence of various annihilation channels provides the dark matter model with additional flexibility, and this enables us to simultaneously fit all cosmic ray spectra using a simple particle physics model and coherent astrophysical assumptions. Our results indicate that AMS-02 observations are not only consistent with the dark matter hypothesis within the uncertainties, but adding a dark matter contribution improves the fit to the data. Assuming, however, that dark matter is solely responsible for this improvement of the fit, it is difficult to evade the latest CMB limits in this model.

hep-ph↗

arXiv2015

Interpreting the Fermi-LAT gamma ray excess in the simplified framework

We test the plausibility that a Majorana fermion dark matter candidate with a scalar mediator explains the gamma ray excess from the Galactic center. Assuming that the mediator couples to all third generation fermions we calculate observables for dark matter abundance and scattering on nuclei, gamma, positron, and anti-proton cosmic ray fluxes, radio emission from dark matter annihilation, and the effect of dark matter annihilations on the CMB. After discarding the controversial radio observation the rest of the data prefers a dark matter (mediator) mass in the 10-100 (3-1000) GeV region and weakly correlated couplings to bottom quarks and tau leptons with values of 10^{-3}-1 at the 68\% credibility level.

hep-ph↗

arXiv2014

Simplified Dark Matter Models Confront the Gamma Ray Excess

Inspired by the excess of gamma rays from the Galactic Center, we confront a number of simplified dark matter models with experimental data. Assuming a single dark matter particle coupled to standard matter via a spin-0 mediator, we compare model evidences for Majorana fermion, real scalar and real vector dark matter candidates. We consider dark matter annihilation into various fermionic final states contributing to the observed differential gamma ray flux. Our likelihood function also includes the dark matter relic density, its elastic scattering cross section with nuclei, and collider limits. Using Bayesian inference we confine the mass and couplings strengths of the dark matter and mediator particle. Our results show that, if the gamma ray excess is due to dark matter the above parameters are well constrained by the observations. We find that the Majorana fermion dark matter model is supported the most by the data.

hep-ph↗

arXiv2014

Bayesian naturalness of the CMSSM and CNMSSM

The recent discovery of the 125.5 GeV Higgs boson at the LHC has fueled interest in the next-to-minimal supersymmetric standard model (NMSSM) as it may require less fine-tuning than the minimal model to accommodate such a heavy Higgs. To this end we present Bayesian naturalness priors to quantify fine-tuning in the (N)MSSM. These priors arise automatically as Occam razors in Bayesian model comparison and generalize the conventional Barbieri-Giudice measure. In this paper we show that the naturalness priors capture features of both the Barbieri-Giudice fine-tuning measure and a simple ratio measure that has been used in the literature. We also show that according to the naturalness prior the constrained version of the NMSSM is less tuned than the CMSSM.

hep-ph↗

arXiv2014

Thermal dark matter implies new physics not far above the weak scale

In this work we complete a model independent analysis of dark matter constraining its mass and interaction strengths with data from astro- and particle physics experiments. We use the effective field theory framework to describe interactions of thermal dark matter particles of the following types: real and complex scalars, Dirac and Majorana fermions, and vector bosons. Using Bayesian inference we calculate posterior probability distributions for the mass and interaction strengths for the various spin particles. The observationally favoured dark matter particle mass region is 10-100 GeV with effective interactions that have a cut-off at 0.1-1 TeV. This mostly comes from the requirement that the thermal abundance of dark matter not exceed the observed value. Thus thermal dark matter coupled with present data implies new physics most likely under 10 TeV.

hep-ph↗

arXiv2013

Should we still believe in constrained supersymmetry?

We calculate Bayes factors to quantify how the feasibility of the constrained minimal supersymmetric standard model (CMSSM) has changed in the light of a series of observations. This is done in the Bayesian spirit where probability reflects a degree of belief in a proposition and Bayes' theorem tells us how to update it after acquiring new information. Our experimental baseline is the approximate knowledge that was available before LEP, and our comparison model is the Standard Model with a simple dark matter candidate. To quantify the amount by which experiments have altered our relative belief in the CMSSM since the baseline data we compute the Bayes factors that arise from learning in sequence the LEP Higgs constraints, the XENON100 dark matter constraints, the 2011 LHC supersymmetry search results, and the early 2012 LHC Higgs search results. We find that LEP and the LHC strongly shatter our trust in the CMSSM (with $M_0$ and $M_{1/2}$ below 2 TeV), reducing its posterior odds by a factor of approximately two orders of magnitude. This reduction is largely due to substantial Occam factors induced by the LEP and LHC Higgs searches.

hep-ph↗

arXiv2013

Peccei-Quinn violating minimal supergravity and a 126 GeV Higgs

In a Peccei-Quinn extension of supergravity the h --> γγdetection rate can be significantly enhanced due to the reduction of the total Higgs decay width. To assess the viability of various Peccei-Quinn extensions of minimal supergravity we perform a Bayesian analysis on three such scenarios. The main constraints on these models come from the currently observed Higgs boson like state by the Large Hadron Collider and from the WMAP observation of dark matter abundance. Our comparative study reveals that under these constraints the PQ violating scenarios with axino dark matter are clearly preferred over the minimal supegravity model with the lightest neutralino as a dark matter candidate.

hep-ph↗

arXiv2012

Extracting the size of the cosmic electron-positron anomaly

We isolated the anomalous part of the cosmic electron-positron flux within a Bayesian likelihood analysis. Using 219 recent cosmic ray spectral data points, we inferred the values of selected cosmic ray propagation parameters. In the context of the propagation model coded in GalProp, we found a significant tension between the electron positron related and the rest of the fluxes. Interpreting this tension as the presence of an anomalous component in the electron-positron related data, we calculated background predictions for PAMELA and Fermi-LAT based on the non-electron-positron related fluxes. We found a deviation between the data and the predicted background even when uncertainties, including systematics, were taken into account. We identified this deviation with the anomalous electron-positron contribution. We briefly compared this model independent signal to some theoretical results predicting such an anomaly.

astro-ph.HE↗

arXiv2011

SU(7) Unification of SU(3)_CSU(4)_W U(1)_{B-L}

We propose the SUSY SU(7) unification of the SU(3)_C* SU(4)_W* U(1)_{B-L} model. Such unification scenario has rich symmetry breaking chains in a five-dimensional orbifold. We study in detail the SUSY SU(7) symmetry breaking into SU(3)_C* SU(4)_W* U(1)_{B-L} by boundary conditions in a Randall-Sundrum background and its AdS/CFT interpretation. We find that successful gauge coupling unification can be achieved in our scenario. Gauge unification favors low left-right and unification scales with tree-level \sin^2θ_W=0.15. We use the AdS/CFT dual of the conformal supersymmetry breaking scenario to break the remaining N=1 supersymmetry. We employ AdS/CFT to reproduce the NSVZ formula and obtain the structure of the Seiberg duality in the strong coupling region for 3/2N_c<N_F<3N_C. We show that supersymmetry is indeed broken in the conformal supersymmetry breaking scenario with a vanishing singlet vacuum expectation value.

hep-ph↗

arXiv2010

Radio and gamma-ray constraints on dark matter annihilation in the Galactic center

We determine upper limits on the dark matter (DM) self-annihilation cross section for scenarios in which annihilation leads to the production of electron--positron pairs. In the Galactic centre (GC), relativistic electrons and positrons produce a radio flux via synchroton emission, and a gamma ray flux via bremsstrahlung and inverse Compton scattering. On the basis of archival, interferometric and single-dish radio data, we have determined the radio spectrum of an elliptical region around the Galactic centre of extent 3 degrees semi-major axis (along the Galactic plane) and 1 degree semi-minor axis and a second, rectangular region, also centered on the GC, of extent 1.6 degrees x 0.6 degrees. The radio spectra of both regions are non-thermal over the range of frequencies for which we have data: 74 MHz -- 10 GHz. We also consider gamma-ray data covering the same region from the EGRET instrument (about GeV) and from HESS (around TeV). We show how the combination of these data can be used to place robust constraints on DM annihilation scenarios, in a way which is relatively insensitive to assumptions about the magnetic field amplitude in this region. Our results are approximately an order of magnitude more constraining than existing Galactic centre radio and gamma ray limits. For a DM mass of m_χ=10 GeV, and an NFW profile, we find that the velocity-averaged cross-section must be less than a few times 10^-25 cm^3 s^-1.

hep-ph↗

arXiv2009

Stochastic resolution of the LHC inverse problem

In this work the LHC inverse problem is quantified in the Bayesian context by clarifying the relation between the mapping from the theory parameter space to experimental signature space and the inverse map. We demonstrate that, after complementing the LHC data by existing astrophysical, collider, and low energy measurements, a simple likelihood analysis is able to significantly reduce the inverse problem. The presented approach offers a robust, economic, and extendable way to extract theoretical parameters from the LHC, and other experimental, data.

hep-ph↗

arXiv2008

Guaranteed discovery of the NmSuGra model

We analyze the discovery potential of the next-to-minimal supergravity motivated model: NmSuGra. This model is an extension of mSuGra by a gauge singlet, and contains only one additional parameter: lambda, the Higgs-singlet-Higgs coupling. NmSuGra solves the mu-problem and reduces the fine tuning of mSuGra. After identifying parameter space regions preferred by present experimental data, we show that these regions of NmSuGra are amenable to detection by the combination of the Large Hadron Collider and an upgraded Cryogenic Dark Matter Search. This conclusion holds strictly provided that the more than three sigma discrepancy in the difference of the experimental and the standard theoretical values of the anomalous magnetic moment of the muon prevails in the future.

hep-ph↗