Majorana Dark matter with B+L gauge symmetry

We present a new model that extends the Standard Model (SM) with the local B+L symmetry, and point out that the lightest new fermion $\zeta$, introduced to cancel anomalies and stabilized automatically by the B+L symmetry, can serve as the cold dark matter candidate. We study constraints on the model from Higgs measurements, electroweak precision measurements as well as the relic density and direct detections of the dark matter. Numerical results reveal that the pseudo-vector coupling of $\zeta$ with $Z$ and the Yukawa coupling with the SM Higgs are highly constrained by the latest results of LUX, while there are viable parameter space that could satisfy all the constraints and give testable predictions.Comment: 17 pages, 4 figures, minor revision, more references adde

Using LISA-like Gravitational Wave Detectors to Search for Primordial Black Holes

Primordial black hole (PBH), which can be naturally produced in the early universe, remains a promising dark matter candidate . It can merge with a supermassive black hole (SMBH) in the center of a galaxy and generate gravitational wave (GW) signals in the favored frequency region of LISA-like experiments. In this work, we initiate the study on the event rate calculation for such extreme mass ratio inspirals (EMRI). Including the sensitivities of various proposed GW detectors, we find that such experiments offer a novel and outstanding tool to test the scenario where PBH constitutes (fraction of) dark matter. The PBH energy density fraction of DM ($f_\text{PBH}$) could potentially be explored as small as $10^{-3} \sim 10^{-4}$. Further, LISA has the capability to search for PBH mass upto $10^{-2} \sim 10^{-1} M_\odot$. Other proposed GW experiments can probe lower PBH mass regime.Comment: 8 pages, 2 figure

Resonant Di-Higgs Production at Gravitational Wave Benchmarks: A Collider Study using Machine Learning

We perform a complementarity study of gravitational waves and colliders in the context of electroweak phase transitions choosing as our template the xSM model, which consists of the Standard Model augmented by a real scalar. We carefully analyze the gravitational wave signal at benchmark points compatible with a first order phase transition, taking into account subtle issues pertaining to the bubble wall velocity and the hydrodynamics of the plasma. In particular, we comment on the tension between requiring bubble wall velocities small enough to produce a net baryon number through the sphaleron process, and large enough to obtain appreciable gravitational wave production. For the most promising benchmark models, we study resonant di-Higgs production at the high-luminosity LHC using machine learning tools: a Gaussian process algorithm to jointly search for optimum cut thresholds and tuning hyperparameters, and a boosted decision trees algorithm to discriminate signal and background. The multivariate analysis on the collider side is able either to discover or provide strong statistical evidence of the benchmark points, opening the possibility for complementary searches for electroweak phase transitions in collider and gravitational wave experiments.Comment: 22 pages, 6 figures, 3 tables. Version published in JHE

O(αsv2)O(\alpha_s v^2) Corrections to Hadronic and Electromagnetic Decays of 1S0^1S_0 Heavy Quarkonium

We study $O(\alpha_sv^2)$ corrections to decays of $^1S_0$ heavy quarkonium into light hadrons and two photons within the framework of nonrelativistic QCD, and find these $O(\alpha_sv^2)$ corrections to have significant contributions especially for the decay into light hadrons. With these new results, experimental measurements of the hadronic width and the $\gamma\gamma$ width of $\eta_c$ can be described more consistently. By fitting experimental data, we find the long-distance matrix elements of $\eta_c$ to be $|\mathcal{R}_{\eta_c}(0)|^2=0.834^{+0.281}_{-0.197}\ \textrm{GeV}^3$ and $< \bm{v}^2 >_{\eta_c}=0.232^{+0.121}_{-0.098}$. Moreover, $\eta_c(2S)$ is also discussed and the $\gamma\gamma$ decay width is predicted to be $3.34^{+2.06}_{-2.10}\ \textrm{KeV}$.Comment: Version published in PRD, 22 pages, 7 figures, references adde

Electron Flavored Dark Matter

In this paper we investigate the phenomenology of the electron flavored Dirac dark matter with two types of portal interactions. We analyze constraints from the electron magnetic moment anomaly, LHC searches of singly charged scalar, dark matter relic abundance as well as direct and indirect detections. Our study shows that the available parameter space is quite constrained, but there are parameter space that is compatible with the current data. We further show that the DAMPE cosmic ray electron excess, which indicates cosmic ray excess at around 1.5 TeV, can be interpreted as the annihilation of dark matter into electron positron pairs in this model.Comment: 6 pages, 5 figure