Search

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 hours of observation, the combination of SKA phase 1 and LOFAR can effectively probe the parameter space of the axion-photon coupling $g_{a\gamma}$ up to $10^{-14}\sim 10^{-15}~\text{GeV}^{-1}$ for the axion mass range of $0.1\sim 30 ~\mu\text{eV}$. Depending on the choice of neutron star evolution model, this limitation is two or three and a half orders of magnitude higher than that of the single neutron star or magnetic white dwarf., Comment: 22 pages, 8 figs, and 2 tables; Phys Rev D accepted version

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.

In this work, we investigate the axion-like 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 ($\rm C.L.$) 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% $\rm C.L.$ on the ALP-photon coupling $g_{a\gamma}$ set by the ARGO-YBJ and Fermi-LAT observations of Mrk 421 is within $\sim [2\times 10^{-11}, \ 6\times 10^{-11}] \rm \, GeV^{-1}$ for the ALP mass of $\sim 5\times 10^{-10}$ eV $\lesssim m_a \lesssim 5\times 10^{-7}\, \rm eV$., Comment: 10 pages, 8 figures

The TeV $\gamma$-ray halo around the Geminga pulsar is an important indicator of cosmic-ray (CR) propagation in the local zone of the Galaxy as it reveals the spatial distribution of the electrons and positrons escaping from the pulsar. Considering the intricate magnetic field in the interstellar medium (ISM), it is proposed that superdiffusion model could be more realistic to describe the CR propagation than the commonly used normal diffusion model. In this work, we test the superdiffusion model in the ISM around the Geminga pulsar by fitting to the surface brightness profile of the Geminga halo measured by HAWC. Our results show that the chi-square statistic monotonously increases as $\alpha$ decreases from 2 to 1, where $\alpha$ is the characteristic index of superdiffusion describing the degree of fractality of the ISM and $\alpha=2$ corresponds to the normal diffusion model. We find that model with $\alpha, Comment: 11 pages, 4 figures, 1 table

The hardening and softening features in the DAMPE proton spectrum are very likely to be originated from a nearby supernova remnant (SNR). The proton spectrum from the nearby SNR is required to be very hard below $\approx10$ TeV. To reproduce this feature, we illustrate that anomalously slow-diffusion zone for cosmic rays (CRs) must be existed in the local interstellar medium (ISM) after also taking the dipole anisotropy of CRs into account. Assuming that the diffusion coefficient is homogeneous in the nearby ISM, we show that the diffusion coefficient is constrained to the magnitude of $10^{26}$ cm$^2$ s$^{-1}$ when normalized to 1 GeV, which is about 100 times smaller than the average value in the Galaxy. We further discuss the spatial distribution of the slow diffusion and find two distinct possibilities. In one case, the SNR is several hundred of parsecs away from the solar system, meanwhile both the SNR and the solar system are required to be included in a large slow-diffusion zone. The homogeneous diffusion belongs to this case. In the other case, the SNR is very close with a distance of $\sim50$ pc and the slow-diffusion zone is only limited around the SNR. The required diffusion coefficient is further smaller in the latter case. This work provides a new way of studying the CR diffusion in the local ISM., 8 pages, 5 figures, 1 table

We investigate the axion like particle (ALP)-photon oscillation effect in the high energy $\gamma$-ray spectra of PG 1553+113 and PKS 2155-304 measured by Fermi-LAT and H.E.S.S.. The choice of extragalactic background light (EBL) model, which induces the attenuate effect in observed $\gamma$-ray spectra, would affect the ALP implication. For the ordinary EBL model that prefers a null hypothesis, we set constraint on the ALP-photon coupling constant at 95% C.L. as $g_{a\gamma}\lesssim 5\times 10^{-11} ~\rm{GeV}^{-1}$ for the ALP mass $\sim 10$ neV. We also consider the CIBER observation of the cosmic infrared radiation, which shows an excess at the wave wavelength of $\sim 1~\mu$m after the substraction of foregrounds. The high energy gamma-rays from extragalactic sources at high redshifts would suffer from a more significant attenuate effect caused by this excess. In this case, we find that the ALP-photon oscillation would improve the fit to the observed spectra of PKS 2155-304 and PG 1553+113 and find a favored parameter region at 95% C.L.., Comment: 8 pages, 7 figures, 1 table

The Fermi-LAT detects no significant anisotropy of the cosmic-ray (CR) electrons and positrons ($e^-+e^+$) with seven years of data, which provides the strongest restriction to the $e^-+e^+$ anisotropy up to now. As next generation CR observatory, HERD is expected to have a better capability of anisotropy detection than Fermi-LAT. In this paper, we discuss several models aimed to explain the AMS-02 data by the present and future anisotropy measurements. We find that the upper limits of Fermi-LAT disfavor Vela SNR as the dominant source in sub-TeV, while other cases that remain safe under the constraint of Fermi-LAT are expected to be distinguished from each other by HERD. We then discuss the possibilities of remarkable TeV spectral features, and test the corresponding anisotropies. We find the conditions under which the TeV model can have a prominent spectral feature and avoid the constraint of Fermi-LAT at the same time. Furthermore, the expected performance of HERD is sensitive enough to detect the anisotropies of all these TeV models, and even for the case of a featureless TeV spectrum. Thus HERD may play a crucial part in the study of the origin of cosmic electrons and positrons., 12 pages, 8 figures, 4 tables, accepted for publication in MNRAS

The Large High Altitude Air Shower Observatory (LHAASO) is a next-generation observatory for high-energy gamma rays and cosmic rays with wide field of view. It will detect gamma rays with high sensitivity in the energy range from 300 GeV to 1 PeV. Therefore, it is promising for LHAASO to search for the high-energy gamma rays induced by dark matter (DM) self-annihilation in dwarf spheroidal satellite galaxies (dSphs), which are ideal objects for the DM indirect detection. In this work, we investigate the LHAASO sensitivity to DM self-annihilation signatures for 19 dSphs and take the uncertainties on the spatial DM distribution of dSphs into account. We perform a joint likelihood analysis for the 19 dSphs and find that the LHAASO sensitivity to the DM annihilation cross section will reach $\mathcal{O}({10}^{\ensuremath{-}24})\ensuremath{\sim}\mathcal{O}({10}^{\ensuremath{-}25})\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ at the mass scale above tera-electron-volts for several annihilation modes, which is larger than the canonical thermal relic cross section by a factor of 10--100.

The Large High Altitude Air Shower Observatory (LHAASO) is a next generation observatory for high energy gamma-rays and cosmic rays with a wide field of view, which is sensitive to gamma-rays from 300 GeV to 1 PeV. LHAASO is an ideal experiment to explore the gamma-ray signatures induced by annihilation of heavy dark matter(DM) particles in dwarf spheroidal satellite galaxies(dSphs). In this study, we investigate the LHAASO sensitivity to the DM annihilation at DM masses above 1TeV. We consider nineteen dSphs with large J−factors and incorporate the statistical uncertainties of the J−factor in a combined analysis. Comparing with current limits, we find that LHAASO is sensitive to the annihilation signatures for DM masses from several TeV up to 100 TeV.

HAWC measured the angular profile of the TeV $\gamma$-ray halo around Geminga, which indicates an anomalously slow diffusion for the cosmic electrons and positrons (electrons hereafter) in this halo region. The origin of the slow-diffusion region is a fresh and intriguing problem. We first check the self-confined scenario, that is, the electrons released by Geminga induce Alfven waves through streaming instability, and they are then trapped by the Alfven waves. Considering the proper motion of Geminga pulsar, however, we find that Geminga cannot provide enough electrons in the late age to account for the so slow diffusion. Then we propose another scenario in which the slow-diffusion region is preexisting. Geminga may still be inside the turbulent region left by its parent SNR. The SNR injects energy to the magnetic field turbulence of the background medium, which can be adequate to explain the observed slow diffusion. Some other TeV halos could also be understood under this scenario.

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 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 (HMF) at the Earth., 23 pages,12 figures

We investigate the implications on the 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 all the effects considered in the fitting process interplay with each other, among which the hadronic interaction model is the most important factor affecting the result. In most hadronic interaction and CR propagation models no DM signal is found with significance larger than $2\sigma$ except that the EPOS-LHC interaction model requires a more than $3\sigma$ DM signal with DM mass around $1\,\mathrm{TeV}$. For the diffusive reacceleration propagation model there is a highly significant DM signal with mass around $100\,\mathrm{GeV}$. However, the signal becomes less than $1\sigma$ if we take a charge dependent solar modulation potential in the analysis., Comment: 25 pages, 6 figures

As a next-generation complex extensive air shower array with a large field of view, the large high altitude air shower observatory (LHAASO) is very sensitive to the very high energy gamma-rays from $\sim$ 300 GeV to 1 PeV, and may thus serve as an important probe for the heavy dark matter (DM) particles. In this study, we make a forecast for the LHAASO sensitivities to the gamma-ray signatures resulting from DM decay in dwarf spheroidal satellite galaxies (dSphs) within the LHAASO field of view. Both individual and combined limits for 19 dSphs incorporating the uncertainties of the DM density profile are explored. Owing to the large effective area and strong capability of the photon-proton discrimination, we find that LHASSSO is sensitive to the signatures from decaying DM particles above $\mathcal{O}(1)$ TeV. The LHAASO sensitivity to the DM decay lifetime reaches $\mathcal{O} (10^{26}) \sim \mathcal{O} (10^{28})$ s for several decay channels at the DM mass scale from 1 TeV to 100 TeV., Comment: 9 pages, 2 figures, 2 table, accepted for publication in Chinese Physics C

Geminga pulsar is surrounded by a multi-TeV $\gamma$-ray halo radiated by the high energy electrons and positrons accelerated by the central pulsar wind nebula (PWN). The angular profile of the $\gamma$-ray emission reported by HAWC indicates an anomalously slow diffusion for the cosmic-ray electrons and positrons in the halo region around Geminga. In the paper we study the possible mechanism for the origin of the slow diffusion. At first, we consider the self-generated Alfv\'en waves due to the streaming instability of the electrons and positrons released by Geminga. However, even considering a very optimistic scenario for the wave growth, we find this mechanism DOES NOT work to account for the extremely slow diffusion at the present day if taking the proper motion of Geminga pulsar into account. The reason is straightforward as the PWN is too weak to generate enough high energy electrons and positrons to stimulate strong turbulence at the late time. We then propose an assumption that the strong turbulence is generated by the shock wave of the parent supernova remnant (SNR) of Geminga. Geminga may still be inside the SNR, and we find that the SNR can provide enough energy to generate the slow-diffusion circumstance. The TeV halos around PSR B0656+14, Vela X, and PSR J1826-1334 may also be explained under this assumption., Comment: 7 pages, 5 figures, accepted by MNRAS

The precise measurements of energy spectra of cosmic ray positrons and/or electrons by recent experiments show clear excesses above 10 GeV. Moreover, a potential sharp spectral feature was suggested by the Dark Matter Particle Explorer (DAMPE) data. These results inspire quite a number of discussions on the connection with either the annihilation/decay of dark matter (DM) or the astrophysical origins. Here we discuss a DM scenario in which DM particles could annihilate and decay into standard model particle pairs simultaneously. In this model, the peak structure is due to the DM annihilation in a nearby subhalo and the broad positron/electron excesses are due to the decay of DM in the Milky Way. This model can reasonably explain the DAMPE and AMS-02 data of the total $e^+e^-$ spectra and the positron fraction, with model parameters being consistent with existing constraints. A simple realization of such a DM model is the spin-1 vector DM model., 17 pages, 5 figures; JCAP in press

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 t˜1,2 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 χ˜20/χ˜1± mass up to 300 GeV are excluded in Z-pole scenario while for Higgs-pole scenario, the points with χ˜20 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.

Searching for gamma 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 gamma 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., Comment: 10 pages, 13 figures

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 $e^+e^-\to Zh$ 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., Comment: 30 pages, 14 figures; minor revisions to match the published version

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., Comment: 29 pages, 10 figures; published version

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 $\text{monojet}+/\!\!\!\!E_\mathrm{T}$, disappearing track, and $\text{multilepton}+/\!\!\!\!E_\mathrm{T}$ 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 $e^+e^-\to Zh$ and $h\to\gamma\gamma$. 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., Comment: 30 pages, 11 figure

The cosmic-ray (CR) $e^\pm$ excess observed by AMS-02 can be explained by dark matter (DM) annihilation. However, the DM explanation requires a large annihilation cross section which is strongly disfavored by other observations, such as the Fermi-LAT gamma-ray observation of dwarf galaxies and the Planck observation of the cosmic microwave background (CMB). Moreover, the DM annihilation cross section required by the CR $e^\pm$ excess is also too large to generate the correct DM relic density with thermal production. In this work we use the Breit-Wigner mechanism with a velocity dependent DM annihilation cross section to reconcile these tensions. If DM particles accounting for the CR $e^\pm$ excess with $v\sim \mathcal{O}(10^{-3})$ are very close to a resonance in the physical pole case, their annihilation cross section in the Galaxy reaches a maximal value. On the other hand, the annihilation cross section would be suppressed for DM particles with smaller relative velocities in dwarf galaxies and at recombination, which may affect the gamma-ray and CMB observations, respectively. We find a proper parameter region that can simultaneously explain the AMS-02 results and the thermal relic density, while satisfying the Fermi-LAT and Planck constraints., Comment: 15 pages, 5 figures

Many studies have shown that either the nearby astrophysical source or dark matter (DM) annihilation/decay is required to explain the origin of high energy cosmic ray (CR) $e^\pm$, which are measured by many experiments, such as PAMELA and AMS-02. Recently, the Dark Matter Particle Explorer (DAMPE) collaboration has reported its first result of the total CR $e^\pm$ spectrum from $25 \,\mathrm{GeV}$ to $4.6 \,\mathrm{TeV}$ with high precision. In this work, we study the DM annihilation and pulsar interpretations of the DAMPE high energy $e^\pm$ spectrum. In the DM scenario, the leptonic annihilation channels to $\tau^+\tau^-$, $4\mu$, $4\tau$, and mixed charged lepton final states can well fit the DAMPE result, while the $\mu^+\mu^-$ channel has been excluded. In addition, we find that the mixed charged leptons channel would lead to a sharp drop at $\sim$ $\mathrm{TeV}$. However, these DM explanations are almost excluded by the observations of gamma-ray and CMB, unless some complicated DM models are introduced. In the pulsar scenario, we analyze 21 nearby known pulsars and assume that one of them is the primary source of high energy CR $e^\pm$.Considering the constraint from the Fermi-LAT observation of the $e^\pm$ anisotropy, we find that two pulsars are possible to explain the DAMPE data. Our results show that it is difficult to distinguish between the DM annihilation and single pulsar explanations of high energy $e^\pm$ with the current DAMPE result., Comment: 25 pages,6 figures

Recently, many new dwarf spheroidal satellites (dSphs) have been discovered by the Dark Energy Survey (DES). These dSphs are ideal candidates for probing for gamma-ray emissions from dark matter (DM) annihilation. However, no significant signature has been found by the Fermi-LAT dSph observations. In this work, we reanalyze the Fermi-LAT Pass 8 data from the direction of Reticulum II, where a slight excess has been reported by some previous studies. We treat Reticulum II (DES J0335.6-5403) as a spatially extended source, and and that no significant gamma-ray signature is observed. Based on this result, we set upper-limits on the DM annihilation cross section., Comment: 7 pages, 5 figures

Recently the AMS-02 collaboration has published the measurement of the cosmic antiproton to proton ratio $\bar{p}/p$ and the $\bar{p}$ flux with a high precision up to $\sim 450\,\mathrm{GeV}$. In this work, we perform a systematic analysis of the secondary antiproton flux generated by the cosmic ray interaction with the interstellar gas. The uncertainty of the prediction originates from the cosmic ray propagation process and the hadronic interaction models. Although the cosmic ray propagation parameters have been well controlled by the AMS-02 $B/C$ ratio data for a specified model, different propagation models can not be discriminated by the $B/C$ data. The $\bar{p}$ flux is also calculated for several hadronic interaction models, which are generally adopted by the cosmic ray community. However, the results for different hadronic models do not converge. We find the EPOS LHC model, which seems to fit the collider data very well, predicts a slightly lower $\bar{p}/p$ ratio than the AMS-02 data at the high energy end. Finally we derive the constraints on the dark matter annihilation cross section from the AMS-02 $\bar{p}/p$ ratio for different propagation and hadronic interaction models., 21 pages, 11 figures, 2 tables. arXiv admin note: text overlap with arXiv:1504.07230

As the TeV halos around Geminga and PSR B0656+14 have been confirmed by HAWC, slow diffusion of cosmic rays could be general around pulsars, and the cosmic positron spectrum from pulsars could be significantly changed. As a consequence, the most likely pulsar source of the positron excess, Geminga, is no more a viable candidate under the additional constraint from Fermi-LAT. Moreover, the latest measurement by AMS-02 shows a clear cutoff in the positron spectrum, which sets a strict constraint on the age of the pulsar source. Considering these new developments we reanalyze the scenario in this work. By checking all the observed pulsars under the two-zone diffusion scenario, we propose for the first time that PSR B1055-52 is a very promising source of the positron excess. B1055-52 can well reproduce both the intensity and the high-energy cut of the AMS-02 positron spectrum, and may also explain the H.E.S.S $e^-+e^+$ spectrum around 10 TeV. Moreover, if the slow diffusion is universal in the local interstellar medium, B1055-52 will be the unique reasonable source of the AMS-02 positron spectrum among the observed pulsars., Comment: 12 pages, 3 figures, 1 table

The precise spectrum of electrons and positrons at high energies plays an important role in understanding their origin. DArk Matter Particle Explorer has reported their first measurement of the spectrum from 25 GeV to 4.6 TeV. This spectrum reveals a tentative peak at ~1.4 TeV, which requires a nearby source of . In this work, we study the properties of a large nearby dark matter subhalo that accouns for this spectral peak, such as its mass and distance from Earth, for different concentration models. We compare spectra of the sources in 3FGL with that from DM annihilation in the subhalo, and find ten candidates that have comparable gamma-ray spectra. However, according to the N-body simulation, the probability that such a large subhalo is close enough to Earth is less than 0.1%.

In this review we do not try to cover all the aspects of physics beyond the standard model (BSM), instead our latest understanding on the BSM will be presented: i) The Higgs sector is likely related to BSM, which can be confirmed at current running large hadron collider (LHC) or the future colliders. Furthermore we pointed out that spontaneous CP violation can be closely related to the lightness of the Higgs boson. ii) Top quark forward-backward asymmetry, which was measured by Tevatron, might be the sign of BSM. We proposed a new color-octet particle ZC to account for the observation and ZC can be further studied at the LHC. iii) If dark matter (DM) is utilized to accommodate astrophysical observations, it ought to be observed at the high energy LHC and DM produced at colliders should be the smoking gun signal. iv) Lithium puzzle might also be the sign of the BSM. We briefly review the newly proposed solution to Lithium puzzle, i.e., the existence of non-thermal component during the big bang nuclei-synthesis (BBN). The possible origins of the non-thermal component can be dark matter or the new accelerating mechanism of normal particles.

Growing evidence reveals universal hardening on various cosmic ray spectra, e.g. proton, positron, as well as antiproton fraction. 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 ($\rm p$, $\rm e^+$) 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 large amount 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 ($\rm p$, $\rm e^-$) and secondary ($\rm e^+$, $\rm \bar{p}/p$) cosmic rays can be properly interpreted. We further show that the TeV to sub-PeV anisotropy of proton is consistent with the observations if the local source is relatively young and lying at the anti-Galactic center direction., 10 pages, 6 figures

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 $Z_2$ symmetry that stabilizes it, a typical new process at $e^+e^-$ colliders is the pair production $e^+e^- \to Y\bar{Y}$ followed by decay processes $Y\to aN$ and $\bar{Y}\to b\bar{N}$, 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 $m_Y$-$m_N$ plane. The edge of this region can be used to define two variables, $m_Y^\mathrm{edge}$ and $m_N^\mathrm{edge}$, whose distributions are utilized to derive the measurement values of $m_Y$ and $m_N$. The measurement deviations and uncertainties are also estimated after including detector effects and background contamination., 23 pages, 15 figures, 2 tables. V2, method improved, figures and discussions added

We study the collider phenomenology of the electroweak phase transition and electroweak baryogenesis in the framework of the effective field theory. Our study shows that the effective theory using the dimension-6 operators can enforce strong first order phase transition and provide sizable CP violation to realize a successful electroweak baryogenesis. Such dimension-6 operators can induce interesting Higgs phenomenology that can be verified at colliders such as the LHC and the planning CEPC. We then demonstrate that this effective theory can originate from vector-like quarks and the triplet Higgs., Comment: 18 pages, 14 figures;version published in Phys.Rev.D

The $\ensuremath{\gamma}$-ray observation of dwarf spheroidal satellites (dSph's) is an ideal approach for probing the dark matter (DM) annihilation signature. The latest Fermi-LAT dSph searches have set stringent constraints on the velocity independent annihilation cross section in the small DM mass range, which gives very strong constraints on the scenario to explain the AMS-02 positron excess by DM annihilation. However, the dSph constraints would change in the velocity dependent annihilation scenarios, because the velocity dispersion in the dSph's varies from that in the Milky Way. In this work, we use a likelihood map method to set constraints on the velocity dependent annihilation cross section from the Fermi-LAT observation of six dSph's. We consider three typical forms of the annihilation cross section, i.e. p-wave annihilation, Sommerfeld enhancement, and Breit-Wigner resonance. For the p-wave annihilation and Sommerfeld enhancement, the dSph limits would become much weaker and stronger compared with those for the velocity independent annihilation, respectively. For the Breit-Wigner annihilation, the dSph limits would vary depending on the model parameters. We show that the scenario to explain the AMS-02 positron excess by DM annihilation is still viable in the velocity dependent cases.

Although the standard model (SM) is extremely successful, there are various motivations for considering the physics beyond the SM. For example, the SM includes neither dark energy nor dark matter, which has been confirmed through astrophysical observations. Examination of the dark sector, which contains new, light, weakly-coupled particles at the GeV scale or lower, is well motivated by both theory and dark-matter detection experiments. In this mini-review, we focus on one particular case in which these new particles can interact with SM particles through a kinematic mixing term between U(1) gauge bosons. The magnitude of the mixing can be parameterized by a parameter є. Following a brief overview of the relevant motivations and the constraints determined from numerous experiments, we focus on the light dark sector phenomenology at low-energy high-luminosity e + e − colliders. These colliders are ideal for probing the new light particles, because of their large production rates and capacity for precise resonance reconstruction. Depending on the details of a given model, the typical observed signatures may also contain multi lepton pairs, displaced vertices, and/or missing energy. Through the use of extremely large data samples from existing experiments, such as KLOE, CLEO, BABAR, Belle, and BESIII, the magnitude of the mixing can be parameterized by a parameter є < 10−4–10−3 constraint can be obtained. Obviously, future experiments with larger datasets will provide opportunities for the discovery of new particles in the dark sector, or for stricter upper limits on є. Once the light dark sector is confirmed, the particle physics landscape will be changed significantly.

In this work we study the constraints on dark matter (DM) annihilation/decay from the Fermi-LAT Isotropic Gamma-Ray Background (IGRB) observation. We consider the contributions from both extragalactic and galactic DM components. For DM annihilation, the evolutions of extragalactic DM halos are taken into account. We find that the IGRB constraints under some DM subhalo models can be comparable to those derived from the observations of dwarf spheroidal galaxies. We also use the IGRB results to constrain the parameter regions accounting for the latest AMS-02 electron-positron anomaly. We find that the majority of DM annihilation/decay channels are strongly disfavored by the latest Fermi-LAT IGRB observation; only DM annihilation/decay to $\mu^+\mu^-$ may be valid., Comment: 27 pages, 6 figures

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 $\tilde{\chi}_1^0$ 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 $30 (300) \mathrm{fb}^{-1}$, $3l + E_\mathrm{T} \!\!\!\!\!\!\!/ \;\;\;$and $2l + E_\mathrm{T} \!\!\!\!\!\!\!/ \;\;\;$ searches at the 13 (14) TeV LHC are expected to reach up to $m_{\tilde{\chi}_1^0}\sim 150 (230) \mathrm{GeV}$ and $m_{\tilde{\chi}_2^0,\tilde{\chi}_1^{\pm}}\sim 320 (480) \mathrm{GeV}$. Near future dark matter direct and indirect detection experiments can cover some parameter regions where collider searches lose their sensitivities., Comment: 23 pages, 8 figures. v2:parameter points added

The OPERA collaboration has recently reported the superluminal neutrinos with velocity of (vν - c)/c ~ 2.5 × 10-5. This result can be explained in the Lorentz invariance violation (LIV) models. The modified dispersion relation of neutrino lead to modified kinematics of the processes the neutrinos involved. For processes that neutrinos in the final states the processes are suppressed. We find to allow the neutrino production process π → μ + νμ, the neutrino energy should be less than about 5 GeV if taking a large LIV parameter ~ O(10-5) implied by OPERA data. For the processes that neutrinos in the initial states new processes that are forbidden in the LI scenario may open, such as the ν → ν + γ or ν → ν + e+ + e-, which lead neutrinos to lose energy quickly. As the atmospheric neutrino spectrum agrees well with expectation without LIV we find it can constrain the neutrino LIV parameter to ~ O(10-12), which is 7 orders smaller than the value measured at OPERA. We further propose to study the astrophysical neutrino spectra, which can constrain the neutrino LIV parameter down to O(10-15).

The Fermi $\gamma$-ray space telescope reported the observation of several Galactic supernova remnants recently, with the $\gamma$-ray spectra well described by hadronic $pp$ collisions. The possible neutrino emissions from these Fermi detected supernova remnants are discussed in this work, assuming the hadronic origin of the $\gamma$-ray emission. The muon event rates induced by the neutrinos from these supernova remnants on typical km$^3$ neutrino telescopes, such as the IceCube and the KM3NeT, are calculated. The results show that for most of these supernova remnants the neutrino signals are too weak to be detected by the on-going or up-coming neutrino experiment. Only for the TeV bright sources RX J1713.7-3946 and possibly W28 the neutrino signals can be comparable with the atmospheric background in the TeV region, if the protons can be accelerated to very high energies. The northern hemisphere based neutrino telescope might detect the neutrinos from these two sources., Comment: 16 pages with elsarticle style, 4 figures, 1 table. Minor revisions, accepted for publication in Astroparticle Physics

The recent HAWC observations of very-high-energy $\gamma$-ray halo around Geminga and Monogem indicate a very slow diffusion of cosmic rays, which results in tiny contribution of positrons from these two pulsars to the local flux. This makes the cosmic positron excess anomaly observed by PAMELA and AMS-02 even more puzzling. However, from the Boron-to-Carbon ratio data one can infer that the average diffusion coefficient in the Galaxy should be much larger. In this work we propose a two-zone diffusion model that the diffusion is slow only in a small region around the source, outside of which the propagation is as fast as usual. We find that such a scenario can naturally explain the positron excess data with parameters even more reasonable than that in the conventional one-zone diffusion model. The reason is that during the life time of Geminga ($\sim 300$ kyr) the electrons/positrons have propagated too far away with a fast diffusion and lead to a low local flux. The slow diffusion region in the two-zone model helps to confine the electrons/positrons for a long time and lead to an enhancement of the local flux. So under the constraint of the HAWC observations, pulsars are still the probable origin of the cosmic-ray positron excess., Comment: 10 pages, 4 figures, Accepted for publication in ApJ

The DArk Matter Particle Explorer (DAMPE), a space-based high precision cosmic ray detector, has just reported the new measurement of the total electron plus positron energy spectrum up to 4.6 TeV. A notable feature in the spectrum is the spectral break at $\sim 0.9$ TeV, with the spectral index softening from $-3.1$ to $-3.9$. Such a feature is very similar to the knee at the cosmic nuclei energy spectrum. In this work we propose that the knee-like feature can be explained naturally by assuming that the electrons are accelerated at the supernova remnants (SNRs) and released when the SNRs die out with lifetime around $10^5$ years. The cut-off energy of those electrons have already decreased to several TeV due to radiative cooling, which may induce the observed TeV spectral break. Another possibility is that the break is induced by a single nearby old SNR. Such a scenario may bring a large electron flux anisotropy that is observable by the future detectors. We also show that a minor part of electrons escaping during the acceleration in young and nearby SNRs are able to contribute to several TeV or higher energy region of the spectrum., Comment: 23 pages, 4 figures, 2 tables

The $ O(GeV)$ extra $ U(1)$ gauge boson named U-boson, has been proposed to mediate the interaction among leptons and dark matter (DM), in order to account for the observations by PAMELA and ATIC. In such kind of models, the extra U(1) gauge group can be chosen as $U(1)_{L_i-L_j}$ with $L_i$ the $i-$th generation lepton number. This anomaly-free model provides appropriate dark matter relic density and boost factor required by experiments. In this work the observability of such kind of U-boson at BESIII detector is investigated through the processes $ e^ + e^ - \to U\gamma$, followed by $U\to e^+e^-$, $U\to \mu^+\mu^-$ and $U\to \nu\overline{\nu}$. In the invisible channel where U-boson decays into neutrinos, BESIII can measure the coupling of the extra $ U(1)$ down to $ O(10^{- 4}) \sim O(10^{- 5})$ because of the low Standard Model backgrounds. In the visible channel where U-boson decays into charged lepton pair, BESIII can only measure the coupling down to $ O(10^{- 3}) \sim O(10^{- 4})$ due to the large irreducible QED backgrounds., Comment: 7pages, 9figures; V2: SecIII corrected, discussions added

The gamma-ray excess observed by the Fermi-LAT in the Galactic Center can be interpreted by the dark matter annihilation to $b\bar{b}$ via a light pseudoscalar in the NMSSM. It is interesting to note that the corresponding singlet scalar is useful to achieve a strongly first order 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 tree-level effect in the NMSSM. We find that the annihilation of Singlino/Higgsino DM particles occurring close to the light pseudoscalar resonance is favored by the galactic center excess and the observed DM relic density, and a resulting small $\kappa/\lambda$ and a negative $A_\kappa$ can also lead to a successful strongly first order electroweak phase transition., Comment: 18 pages,3 figures, comments are welcomed

The recent reported 750 GeV diphoton excess at the 13 TeV LHC is explained in the framework of effective field theory assuming the diphoton resonance is a scalar (pseudoscalar) particle. It is found that the large production rate and the broad width of this resonance are hard to simultaneously explain if only visible final states are considered. Therefore an invisible decay channel to dark matter (DM) is strongly favored by the diphoton excess with a broad width, given a large coupling of the new scalar to DM. We set constraints on the parameter space in this scenario using the results from LHC Run 1, DM relic density, and DM direct and indirect detection experiments. We find that the DM searches can exclude a large portion of the parameter regions accounting for the diphoton excess with a broad width., Comment: 26 pages, 8 figures. v2,references added. v3, figures updated. v4, discussions and figures added. v5, discussions added

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 fb$^{-1}$ can test the tau portal DM models with fermionic mediators in the mass range of $120\sim450$ GeV., 10 pages, 5 figures

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.

The detection of dark matter has made great progresses in recent years. We give a brief review on the status and progress in dark matter detection, including the progresses in direct detection, collider detection at LHC and focus on the indirect detection. The results from PAMELA, ATIC, Fermi-LAT and relevant studies on these results are introduced. Then we give the progress on indirect detection of gamma rays from Fermi-LAT and ground based Cerenkov telescopes. Finally the detection of neutrinos and constraints on the nature of dark matter are reviewed briefly., Comment: 33 pages, invited review

We investigate the sensitivity to the effective operators describing interactions between dark matter particles and photons at future high energy e+e(-) colliders via the gamma + is not an element of channel. Such operators could be useful to interpret the potential gamma-ray line signature observed by the Fermi-LAT. We find that these operators can be further tested at e(+)e(-) colliders by using either unpolarized or polarized beams. We also derive a general unitarity condition for 2 -> n processes and apply it to the dark matter production process e(+)e(-) -> chi chi gamma.

The AMS-02 collaboration has just published a high precision measurement of the cosmic positron fraction $e^+/(e^- + e^+)$, which rises with energy from $\sim 5$ GeV to $\sim 350$ 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 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 $\alpha \sim 2$ 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., Comment: 8 pages, 6 figures

A Comment on the Letter by U. Das and B. Mukhopadhyay, Phys. Rev. Lett. 110, 071102 (2013). The authors of the Letter offer a Reply.

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 $\tilde {t}\to b\tilde{\chi}^+_1$ is a very promising channel for light stop detection if the mass splitting between $\tilde{\chi}^+_1$ and $\tilde{\chi}^0_1$ 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 $p p \to {\tilde t_1} {\tilde t_1} \to t {\bar t} h h \tilde{\chi}^0_1 \tilde{\chi}^0_1$ and $p p \to {\tilde b_1} {\tilde b_1} \to t {\bar t} W^+ W^- \tilde{\chi}^0_1 \tilde{\chi}^0_1$ may be necessary., Comment: 43 pages, 18 figs

It was recently reported that there may exist monochromatic $\gamma$-ray emission at $\sim 130$ GeV from the Galactic center in the Fermi Large Area Telescope data, which might be related with dark matter (DM) annihilation. In this work we carry out a comprehensive check of consistency of the results with the DM annihilation scenario, using the 3.7 yrs Fermi observation of the inner Galaxy, Galactic halo, clusters of galaxies and dwarf galaxies. The results found are as follows. 1) Very strong constraints on the DM annihilation into continuous $\gamma$-rays from the Galactic center are set, which are as stringent as the "natural" scale assuming thermal freeze-out of DM. Such limit sets strong constraint on the DM models to explain the line emission. 2) No line emission from the Galactic halo is found in the Fermi data, and the constraints on line emission is marginally consistent with the DM annihilation interpretation of the $\sim 130$ GeV line emission from the inner Galaxy. 3) No line emission from galaxy clusters and dwarf galaxies is detected, although possible concentration of photons from clusters in 120-140 GeV is revealed. The constraints from clusters and dwarf galaxies are weak and consistent with the DM annihilation scenario to explain the $\sim 130$ GeV line emission., Comment: 16 pages (JHEP style), 6 figures and 1 table; added discussion on the continuous background for line search; accepted by JCAP