Search

The gamma-ray excess observed by the Fermi-LAT in the Galactic Center can be interpreted by the dark matter annihilation to bb via a light pseudoscalar in the next-to-minimal supersymmetric standard model (NMSSM). It is interesting to note that the corresponding singlet scalar is useful to achieve a strongly firstorder phase transition required by the electroweak baryogenesis. In this paper, we investigate the possibility that the NMSSM model can simultaneously accommodate these two issues. The phase transition strength can be characterized by the vacua energy gap at zero temperature and be sufficiently enhanced by the treelevel effect in the NMSSM. We find that the annihilation of singlino/Higgsino dark matter (DM) particles occurring close to the light pseudoscalar resonance is favored by the Galactic Center excess and the observed DM relic density, and some resulting regions in the parameter space with a small κ/λ and a negative Aκ can simultaneously account for a successful strongly first-order electroweak phase transition. [ABSTRACT FROM AUTHOR]

We study the prospect of dark matter (DM) searches in the monojet channel at future pp colliders with center-of-mass energies of 33, 50, and 100 TeV. We consider a class of simplified models in which a vector boson connecting DM particles to quarks is introduced. Comparing with studies in the effective field theory, the present framework gives more reasonable production rates and kinematics of the DM signatures. We estimate the sensitivities of future colliders with an integrated luminosity of 3 ab-1 to the DM-induced monojet signature and show the parameter space that can be explored. The constraints from direct and indirect DM detection experiments are compared with the future collider sensitivities. We find that the future collider detection will be much more sensitive than the indirect detection for the vector interaction and have better sensitivities than those of the direct detection by several orders of magnitude for the axial vector interaction. [ABSTRACT FROM AUTHOR]

Motivated by the Galactic Center gamma-ray excess in the Fermi-LAT data, we study the signatures of a class of tau portal dark matter (DM) models where DM particles preferentially couple to tau leptons at the LHC. We consider the constraints from the DM direct detection and investigate the sensitivity of the LHC to di-tau plus missing energy signatures. We find that the LHC with a high luminosity of 3000 f b-1 can test the tau portal DM models with fermionic mediators in the mass range of 120 ~ 450 GeV. [ABSTRACT FROM AUTHOR]

We explore the mono-Z signature for dark matter searches at future high energy e+e- colliders. In the context of effective field theory, we consider two kinds of contact operators describing dark matter interactions with electroweak gauge bosons and with electron/positron, respectively. For five benchmark models, we propose kinematic cuts to distinguish signals from backgrounds for both charged leptonic and hadronic decay modes of the Z boson. We also present the experimental sensitivity to cutoff scales of effective operators and compare it with that of the Fermi-LAT indirect search and demonstrate the gains in significance for the several configurations of polarized beams. [ABSTRACT FROM AUTHOR]

In this work, we study the constraints on the scenario of light stops and sbottoms in the next-to-minimal supersymmetric standard model (NMSSM), especially by a 125 GeV Higgs boson discovery and the LHC bounds on supersymmetry. The constraints from dark matter detections are also taken into account. From the parameter scan, we find that the NMSSM can well accommodate a light Higgs boson around 125 GeV and decay patterns. We would like to stress that the LHC direct supersymmetry searches with b tagging are very powerful and can set strong bounds on many NMSSM parameter points with light stops and sbottoms. We find t- → bχ1+ is a very promising channel for light stop detection if the mass splitting between χ1+ and χ10 is very small. It is also pointed out that in order to close the parameter space of light stops and sbottoms, new search strategies for signal channels such as pp →t~ltt~l → tt~ χt~10χt~10 and pp → b~lb~l → tt~W+W- χ~10χ~10 may be necessary. [ABSTRACT FROM AUTHOR]

In this paper we study the Breit-Wigner enhancement of dark matter (DM) annihilation considering the kinetic decoupling in the evolution of DM freeze-out at the early Universe. Since the DM temperature decreases much faster (as \/R2) after kinetic decoupling than that in kinetic equilibrium (as 1/R2), we find the Breit-Wigner enhancement of the DM annihilation rate after the kinetic decoupling will affect the DM relic density significantly. Focusing on the model parameters that try to explain the anomalous cosmic positron/electron excesses observed by PAMELA/Fermi/ATIC, we find the elastic scattering Xf → Xf is not efficient in keeping dark matter in kinetic equilibrium, and the kinetic decoupling temperature Tkd is comparable to the chemical decoupling temperature Tf ∼ O(10) GeV. The reduction of the relic density after Tkd is significant and leads to a limited enhancement factor ∼O(102). Therefore, it is difficult lo explain the anomalous positron/electron excesses in cosmic rays by DM annihilation and give the correct DM relic density simultaneously in the minimal Breit-Wigner enhancement model. We also mention that if the nonthermal DM velocity distribution after kinetic decoupling or new scattering processes are considered, this constraint could be changed. [ABSTRACT FROM AUTHOR]

In this work, we study the light stop pair signals at the LHC. We explore the supersymmetry parameter space with nonuniversal gaugino and third-generation masses at the grand unified theory scale. Recent LHC supersymmetry search results based on 35 pb-1 and 1 fb-1 of data are implemented to put the limits on stop pair events. The dark matter relic density and direct detection constraints are also taken into account. Detailed simulations on the signals and background for some benchmark points are performed, and it is found that the stop pair signals usually escape the LHC search if the present cut conditions are used. We also explore the potential and sensitivity of ILC to probe such scenarios. It is found that the ILC can detect them with an integrated luminosity of a few tens of fb-1. [ABSTRACT FROM AUTHOR]

As a well-motivated dark matter candidate, axions can be detected through the axion-photon resonant conversion in the magnetospheres of magnetic white dwarf stars or neutron stars. In this work, we utilize Omega Centauri, which is the largest globular cluster in the Milky Way and is suggested to be the remnant core of a dwarf galaxy, to probe the axion dark matter through radio signals that originate from all the neutron stars and magnetic white dwarf stars in it. With 100 h of observation, the combination of the radio telescopes Square Kilometer Array phase 1 and Low-Frequency Array can effectively probe the parameter space of the axion-photon coupling gaγ up to 10-14~10-15 GeV-1 for the axion mass range of 0.1~30 µeV. Depending on the choice of neutron star evolution model, this limitation is 2 or 3.5 orders of magnitude higher than that of the single neutron star or magnetic white dwarf. [ABSTRACT FROM AUTHOR]

Axion as one of the promising dark matter candidates can be detected through narrow radio lines emitted from the magnetic white dwarf stars. Due to the existence of the strong magnetic field, the axion may resonantly convert into the radio photon (Primakoff effect) when it passes through a narrow region in the corona of the magnetic white dwarf, where the plasma frequency is equal to the axion mass. We show that for the magnetic white dwarf WD 2010+310, the future experiment SKA phase 1 with 100 hours of observation can effectively probe the parameter space of the axion-photon coupling gaγ up to ~10-12 GeV-1 for the axion mass range of 0.2~3.7 µeV. Note that in the low mass region (ma≲1.5 µeV), the WD 2010+310 could give greater sensitivity than the neutron star RX J0806.4-4123. [ABSTRACT FROM AUTHOR]

We investigate the significance of a dark matter (DM) signal from the AMS-02 cosmic antiproton flux. Global fits to the data are performed under different propagation and hadronic interaction models. The uncertainties from the injection spectrum, propagation effects, and solar modulation of the cosmic rays are taken into account comprehensively. Since we need to investigate extended parameter regions with multiple free parameters in the fit, the machine learning method is adopted to maintain a realistic time cost. We find that a DM signal with DM mass ∼100  GeV or above 1 TeV would possibly be required. A comprehensive discussion is performed to clarify how are these uncertainties affecting the two kinds of DM signals. The low-energy DM signal is significant for the case with diffusive reacceleration propagation model + charge-independent solar modulation configuration. However, it is severely affected by the propagation and solar modulation effects. On the other hand, the high-energy DM signal is mainly influenced by the hadronic interaction model. Most of the hadronic interaction models do not indicate a significant high-energy DM signal except that the EPOS-LHC interaction model always requires a high-energy DM signal with a significance more than 5σ. [ABSTRACT FROM AUTHOR]

We study the time-dependent modulation effect and derive the local interstellar spectra (LIS) for the cosmic ray (CR) proton, helium, boron, and carbon. A two-dimensional modulation model including the variation of the interplanetary environment with time is adopted to describe the modulation process. The propagation equation of CRs in the heliosphere is numerically solved by the package Solarprop. We derive the LIS by fitting the latest results of several experiments, including Voyager 1, PAMELA, BESS-POLARII, and ACE, during low solar activity periods. We further study the modulation in the polarity reversal periods with the PAMELA proton data. We find that the rigidity dependence of the diffusion coefficient is critical to explain the modulation effect during reversal periods. Our results also indicate a power law relation between the diffusion coefficient and the magnitude of the heliospheric magnetic field at the Earth. [ABSTRACT FROM AUTHOR]

We investigate the effect of fermionic electroweak multiplet dark matter models on the stability of the electroweak vacuum using two-loop renormalization group equations (RGEs) and one-loop matching conditions. Such a treatment is crucial to obtain reliable conclusions, compared with one-loop RGEs and tree-level matching conditions. In addition, we find that the requirement of perturbativity up to the Planck scale would give strong and almost mass-independent constraints on the Yukawa couplings in the dark sector. We also evaluate these models via the idea of finite naturalness for the Higgs mass fine-tuning issue. [ABSTRACT FROM AUTHOR]

We study natural supersymmetry in the generalized minimal supergravity (GmSUGRA). For the parameter space with low energy, electroweak fine-tuning measures less than 50, we are left with only the Z-pole, Higgs-pole, and Higgsino LSP scenarios for dark matter (DM). We perform the focused scans for such parameter space and find that it satisfies various phenomenological constraints and is compatible with the current direct detection bound on neutralino DM reported by the LUX experiment. Such parameter space also has solutions with correct DM relic density besides the solutions with DM relic density smaller or larger than 5σ WMAP9 bounds. We present five benchmark points as examples. In these benchmark points, the gluino and the first two generations of squarks are heavier than 2 TeV, stop ̅t1,2 are in the mass range [1, 2] TeV, while sleptons are lighter than 1 TeV. Some part of the parameter space can explain the muon anomalous magnetic moment within 3σ as well. We also perform the collider study of such solutions by implementing and comparing with relevant studies done by the ATLAS and CMS Collaborations. We find that the points with Higgsino dominant ̅χ02/̅χ±1 mass up to 300 GeV are excluded in Z-pole scenario while for Higgs-pole scenario, the points with ̅χ02 mass up to 460 GeV are excluded. We also notice that the Higgsino LSP points in our present scans are beyond the reach of present LHC searches. Next, we show that for both the Z-pole and Higgs-pole scenarios, the points with electroweak fine-tuning measures around 20 do still survive. [ABSTRACT FROM AUTHOR]

Searching for γ rays from dwarf spheroidal galaxies (dSphs) is a promising approach to detect dark matter (DM) due to the high DM densities and low baryon components in dSphs. The Fermi-LAT observations from dSphs have set stringent constraints on the velocity independent annihilation cross section. However, the constraints from dSphs may change in velocity dependent annihilation scenarios because of the different velocity dispersions in galaxies. In this work, we study how to set constraints on the velocity dependent annihilation cross section from the combined Fermi-LAT observations of dSphs with the kinematic data. In order to calculate the γ ray flux from the dSph, the correlation between the DM density profile and velocity dispersion at each position should be taken into account. We study such correlation and the relevant uncertainty from kinematic observations by performing a Jeans analysis. Using the observational results of three ultrafaint dSphs with large J-factors, including Willman 1, Reticulum II, and Triangulum II, we set constraints on the p-wave annihilation cross section in the Galaxy as an example. [ABSTRACT FROM AUTHOR]

We study the impact of fermionic dark matter (DM) on projected Higgs precision measurements at the Circular Electron Positron Collider (CEPC), including the one-loop effects on the e+e-→Zh cross section and the Higgs boson diphoton decay, as well as the tree-level effects on the Higgs boson invisible decay. As illuminating examples, we discuss two UV-complete DM models, whose dark sector contains electroweak multiplets that interact with the Higgs boson via Yukawa couplings. The CEPC sensitivity to these models and current constraints from DM detection and collider experiments are investigated. We find that there exist some parameter regions where the Higgs measurements at the CEPC will be complementary to current DM searches. [ABSTRACT FROM AUTHOR]

We study the signatures of the triplet-quadruplet dark matter model at the LHC and future colliders, including the 100 TeV Super Proton-Proton Collider and the 240 GeV Circular Electron Positron Collider. The dark sector in this model contains one fermionic electroweak triplet and two fermionic quadruplets, which have two kinds of Yukawa couplings to the Higgs doublet. Electroweak production signals of the dark sector fermions in the monojet+ET, disappearing track, and multilepton+ET channels at the LHC and the Super Proton-Proton Collider are investigated. Moreover, we study the loop effects of this model on the Circular Electron Positron Collider precision measurements of e+e-→Zh and h→γγ. We find that most of the parameter regions allowed by the observed dark matter relic density will be well explored by such direct and indirect searches at future colliders. [ABSTRACT FROM AUTHOR]

The AMS-02 collaboration has published the measurement of the cosmic antiproton to proton ratio p/p and the p flux with a high precision up to ∼450 GeV. In this work, we perform a systematic analysis of the secondary antiproton flux generated by the cosmic ray interaction with the interstellar gas. The uncertainties of the prediction from the cosmic ray propagation process and the hadronic interaction models are analyzed. We find the two effects may interplay with each other in the prediction. In some combinations of the propagation and hadronic interaction models the secondary p predictions give quite good fit to the AMS-02 data and thus set very stringent constraint on the dark matter annihilation cross section, while in some cases the predictions would deviate from the data. Especially, we find that the epos lhc hadronic model, which can fit the collider data very well, predicts a slightly lower p/p ratio than the AMS-02 data at the high energy end. [ABSTRACT FROM AUTHOR]

Growing evidence reveals universal hardening on various cosmic ray spectra, e.g., proton, positron, as well as antiproton fractions. Such universality may indicate they have a common origin. In this paper, we argue that these widespread excesses can be accounted for by a nearby supernova remnant surrounded by a giant molecular cloud. Secondary cosmic rays (p, e+) are produced through the collisions between the primary cosmic-ray nuclei from this supernova remnant and the molecular gas. Different from the background, which is produced by the ensemble of a large number of sources in the Milky Way, the local injected spectrum can be harder. The time-dependent transport of particles would make the propagated spectrum even harder. Under this scenario, the anomalies of both primary (p, e-) and secondary (e+, p/p) cosmic rays can be properly interpreted. We further show that the TeV to sub-PeV anisotropy of the proton is consistent with the observations if the local source is relatively young and lying at the anti-Galactic center direction. [ABSTRACT FROM AUTHOR]

Mass measurement of a particle whose decay products including invisible particles is a challenging task at colliders. For a new physics model involving a dark matter candidate N and a Z2 symmetry that stabilizes it, a typical new process at e+e- colliders is the pair production e+e-→YY followed by decay processes Y→aN and Y→bN, where a and b are visible but N is invisible. In this work, we propose a new method to measure the physical masses in this topology by making use of the kinematic equations given by momentum-energy conservation and on-shell conditions. For each event, the solvability of these equations determines a limited region on the trial mY-mN plane. The edge of this region can be used to define two variables, medgeY and medgeN, whose distributions are utilized to derive the measurement values of mY and mN. The measurement deviations and uncertainties are also estimated after including detector effects and background contamination. [ABSTRACT FROM AUTHOR]

We propose an interesting framework for asymmetric scalar dark matter (ADM), which has novel collider phenomenology in terms of an unstable ADM bound state (ADMonium) produced via Higgs portals. ADMonium is a natural consequence of the basic features of ADM: the (complex scalar) ADM is charged under a dark local U(1)d symmetry which is broken at a low scale and provides a light gauge boson X. The dark gauge coupling is strong and then ADM can annihilate away into X-pair effectively. Therefore, the ADM can form a bound state due to its large self-interaction via X mediation. To explore the collider signature of ADMonium, we propose that ADM has a two-Higgs doublet portal. The ADMonium can have a sizable mixing with the heavier Higgs boson, which admits a large cross section of ADMonium production associated with bb. The resulting signature at the LHC depends on the decays of X. In this paper we consider a case of particular interest: p p → bb + ADMonium followed by ADMonium → 2 X → 2 e+e- where the electrons are identified as (un)converted photons. It may provide a competitive explanation to heavy di-photon resonance searches at the LHC. [ABSTRACT FROM AUTHOR]

We study a simplified scenario in the next-to-minimal supersymmetric standard model with a split electroweak spectrum, in which only the singlino and Higgsinos are light and other superpartners are decoupled. Serving as a dark matter candidate, a singlino-dominated neutralino χ01 should have either resonant annihilation effects or sizable Higgsino components to satisfy the observed relic abundance. The sensitivities of LHC searches and dark matter detection experiments are investigated. With an integrated luminosity of 30(300) fb-1, 3l+ET and 2l+ET searches at the 13 (14) TeV LHC are expected to reach up to mχ01∼150(230) GeV and mχ02,χ±1∼320(480) GeV. Near future dark matter direct and indirect detection experiments are promising to cover the parameter regions where collider searches lose their sensitivities. [ABSTRACT FROM AUTHOR]

The Alpha Magnetic Spectrometer (AMS-02) has just published the unprecedentedly precise measurement of the cosmic electron and positron spectra. In this paper, we try to give a quantitative study on the AMS-02 results by a global fitting to the electron and positron spectra, together with the updated positron fraction data. The Markov chain Monte Carlo algorithm is adopted to do the fitting. The primary electron spectrum and the parameters for pulsars or dark matter that contribute extra positrons are determined simultaneously. We find that there is a hardening of the primary electron spectrum at ~60 GeV. With such a new feature at the background spectrum, both the pulsars and dark matter can explain the AMS-02 results very well. The dark matter scenario shows a drop at the positron fraction at ~300 GeV but suffers very strong constraints from Fermi γ-ray observations. The fitting results also suggest that the propagation model with convection may be more favored by the lepton data than the reacceleration model. [ABSTRACT FROM AUTHOR]

Recently, the PAMELA collaboration published the cosmic nuclei and electron spectra with high precision, together with the cosmic antiproton data updated, and the Fermi-LAT collaboration also updated the measurement of the total e++e- spectrum to lower energies. In this paper we develop a Markov Chain Monte Carlo (MCMC) package CosRayMC, based on the Galactic Propagation (GALPROP) cosmic ray propagation model to study the implications of these new data. It is found that if only the background electrons and secondary positrons are considered, the fit is very bad with X2red &ap; 3.39. Taking into account the extra e+ e- sources of pulsars or dark matter annihilation we can give much better fit to these data, with the minimum X2red &ap; 1.04. This means the extra sources are necessary with a very high significance in order to lit the data. However, the data show little difference between pulsar and dark matter scenarios. Both the background and extra source parameters are well constrained with this MCMC method. The antiproton data can further constrain the branching ratio of dark matter annihilation into quarks to be Bq < 0.5% at 2σ confidence level. The possible systematical uncertainties of the present study are discussed. [ABSTRACT FROM AUTHOR]

Recent cosmic ray (CR) experiments discovered that the CR spectra experience a remarkable hardening for rigidity above several hundred GV. We propose that this is caused by the superposition of the CR energy spectra of many sources that have a dispersion in the injection spectral indices. Adopting similar parameters as those of supernova remnants derived from the Fermi γ-ray observations, we can reproduce the observational CR spectra of different species well. This may be interpreted as evidence to support the supernova remnant origin of CRs below the knee. We further propose that the same mechanism may explain the "ankle" of the ultra high energy CR spectrum. [ABSTRACT FROM AUTHOR]

The energy spectra of primary and secondary cosmic rays (CRs) generally harden at several hundreds of GeV, a finding which can be naturally interpreted by means of propagation effects. We adopt a spatially dependent CR propagation model to fit the spectral hardening, where a slow-diffusion disk (SDD) is assumed near the galactic plane. We aim to constrain the propagation parameters with a Bayesian parameter estimation based on a Markov chain Monte Carlo sampling algorithm. The latest precise measurements of carbon spectrum and B/C ratio are adopted in the Bayesian analysis. The 10Be/9Be and Be/B ratios are also included to break parameter degeneracies. The fitting result shows that all the parameters are well constrained. Especially, the thickness of the SDD is limited to 0.4-0.5 kpc above and below the galactic plane, which could be the best constraint for the slow-diffusion region among similar works. The p/p ratio and the amplitude of CR anisotropy predicted by the SDD model are consistent with the observations, while the predicted high-energy electron and positron fluxes are slightly and significantly lower than the observations, respectively, indicating the necessity of extra sources. [ABSTRACT FROM AUTHOR]

LHAASO J0621+3755 is a TeV gamma-ray halo newly identified by LHAASO-KM2A. It is likely to be generated by electrons trapped in a slow-diffusion zone around PSR J0622+3749 through inverse Compton scattering. However, when the gamma-ray spectrum of LHAASO-KM2A is fitted, the GeV fluxes derived by the commonly used one-zone normal diffusion model for electron propagation are significantly higher than the upper limits of Fermi-LAT. In this work, we try to solve the contradiction by adopting a more generalized propagation model, i.e., the superdiffusion model or the two-zone diffusion model. For the superdiffusion scenario, we find that a model with superdiffusion index α≲1.2 can meet the constraints of Fermi-LAT observation. For the two-zone diffusion scenario, the size of the slow-diffusion zone is required to be smaller than ∼50  pc, which is consistent with theoretical expectations. Future precise measurements of the Geminga halo may further distinguish between these two scenarios for the electron propagation in pulsar halos. [ABSTRACT FROM AUTHOR]

In this work, we investigate the axionlike particle (ALP)-photon oscillation effect in the spectra of the blazar Markarian 421 (Mrk 421) using 4.5 years of the Astrophysical Radiation with Ground-based Observatory at YangBaJing (ARGO-YBJ) and Fermi Large Area Telescope (Fermi-LAT) data. These data are collected during the common operation time, which cover ten activity phases of Mrk 421. No significant ALP-photon oscillation effect is confirmed. On the other hand, not all the observations of the ten phases can be individually used to set the 95% confidence level (C.L.) constraint on the ALP parameter space. However, the constraint can be significantly improved if the analyses for the ten phases are combined. We find that the upper limit at 95% C.L. on the ALP-photon coupling gaγ set by the ARGO-YBJ and Fermi-LAT observations of Mrk 421 is within ~[2×10-11, 6×10-11] GeV-1 for the ALP mass of ~5×10-10 eV≲ma ≲ 5×10-7eV. [ABSTRACT FROM AUTHOR]

Cosmic-ray (CR) propagation in the interstellar medium (ISM) of the Galaxy might be a superdiffusion process, rather than the commonly adopted normal diffusion. The spatial distribution of CRs around a pointlike source can be adopted to test the real picture that describes the CR propagation. The TeV γ-ray halo around the Geminga pulsar is an ideal target, where the spatial distribution of the escaped electrons and positrons can be derived from the morphology of the halo. In this work, we test the superdiffusion model in the ISM around the Geminga pulsar by fitting it to the surface brightness profile of the Geminga halo measured by HAWC. Our results show that the chi-square statistic monotonously increases as α decreases from 2 to 1, where α is the characteristic index of superdiffusion describing the degree of fractality of the ISM and α=2 corresponds to the normal diffusion model. We find that a model with α<1.32 (using the data within 4° around the pulsar) or α<1.4 (using the data within 6° around the pulsar) is disfavored at 95% confidence level. A superdiffusion model with α close to 2 can well explain the morphology of the Geminga halo, while it predicts much higher positron flux at Earth than the normal diffusion model. This has important implication for the interpretation of the CR positron excess. [ABSTRACT FROM AUTHOR]

In this work we use the newly reported boron-to-carbon ratio (B/C) from AMS-02 and the time-dependent proton fluxes from PAMELA and AMS-02 to constrain the source and propagation parameters of cosmic rays in the Milky Way. A linear correlation of the solar modulation parameter with solar activities is assumed to account for the time-varying cosmic ray fluxes. A comprehensive set of propagation models, with or without reacceleration or convection, has been discussed and compared. We find that only the models with reacceleration can self-consistently fit both the proton and B/C data. The rigidity dependence slope of the diffusion coefficient, δ, is found to be about 0.38-0.50 for the diffusion-reacceleration models. The plain diffusion and diffusion-convection models fit the data poorly. We compare different model predictions of the positron and antiproton fluxes with the data. We find that the diffusion-reacceleration models overproduce low energy positrons, while nonreacceleration models give better fit to the data. As for antiprotons, reacceleration models tend to underpredict low energy antiproton fluxes, unless a phenomenological modification of the velocity dependence of the diffusion coefficient is applied. Our results suggest that there could be important differences of the propagation for nuclei and leptons, in either the Milky Way or the solar heliosphere. [ABSTRACT FROM AUTHOR]

The AMS-02 Collaboration has just published a high-precision measurement of the cosmic positron fraction e+/(e-+e+), which rises with energy from ~5 GeV to ~350 GeV. The result indicates the existence of primary electron/positron sources to account for the positron excess. In this work, we investigate the possibility that the nearby mature pulsars with ages of O(105) yr are the primary positron sources. By fitting the data we find that the positrons from a single nearby pulsar, such as Geminga or Monogem, with the spectral index α~2 can interpret the AMS-02 result. We also investigate the possibility that high-energy positrons are generated by multiple known pulsars in the ATNF catalogue. Such a scenario can also fit the AMS-02 data well. Future precise measurements of fine structures in the positron spectrum would be a support to the pulsar scenario. [ABSTRACT FROM AUTHOR]