Inspired by the string axiverse idea, it has been suggested that the recent transition from decelerated to accelerated cosmic expansion is driven by an axion-like quintessence field with a sub-Planckian decay constant. The scenario requires that the axion field be rather near the maximum of its potential but is less finely tuned than other explanations of cosmic acceleration. The model is parametrized by an axion decay constant $f$, the axion mass $m$, and an initial misalignment angle $|{\theta }_i|$ which is close to $\pi$. In order to determine the $m$ and ${\theta }_i$ values consistent with observations, these parameters are mapped onto observables: the Hubble parameter $H(z)$ at an angular-diameter distance $d_A(z)$ to redshift $z=0.57$, as well as the angular sound horizon of the cosmic microwave background (CMB). Measurements of the baryon acoustic oscillation (BAO) scale at $z\simeq 0.57$ by the BOSS survey and Planck measurements of CMB temperature anisotropies are then used to probe the $\{m,f,{\theta }_i\}$ parameter space. With current data, CMB constraints are the most powerful, allowing a fraction of only $\sim 0.2$ of the parameter-space volume. Measurements of the BAO scale made using the SPHEREx or SKA experiments could go further, observationally distinguishing all but $\sim {10}^{-2}$ or $\sim {10}^{-5}$ of the parameter-space volume (allowed by simple priors) from the $\mathrm{\Lambda }\mathrm{CDM}$ model.

We consider two Higgs doublet models with a softly broken U(1) symmetry, for various limiting values of the scalar mixing angles $\alpha$ and $\beta$. These correspond to the Standard Model Higgs particle being the lighter $CP$-even scalar (alignment) or the heavier $CP$-even scalar (reverse alignment), and also the limit in which some of the Yukawa couplings of this particle are the opposite sign of the vector boson couplings (wrong sign). In these limits we impose a criterion for naturalness by demanding that quadratic divergences cancel at one loop. We plot the allowed masses of the remaining physical scalars based on naturalness, stability, perturbative unitarity, and constraints coming from the $\rho$ parameter. We also calculate the $h\to \gamma \gamma$ decay width in the wrong sign limit.

We combine and extend the analyses of effective scalar, vector, Majorana and Dirac fermion Higgs portal models of dark matter (DM), in which DM couples to the Standard Model (SM) Higgs boson via an operator of the form ${\mathcal{O}}_{\mathrm{DM}}{H}^{†}H$. For the fermion models, we take an admixture of scalar $\overline{\psi }\psi$ and pseudoscalar $\overline{\psi }i{\gamma }_5\psi$ interaction terms. For each model, we apply constraints on the parameter space based on the Planck measured DM relic density and the LHC limits on the Higgs invisible branching ratio. For the first time, we perform a consistent study of the indirect detection prospects for these models based on the WMAP7/Planck observations of the cosmic microwave background, a combined analysis of 15 dwarf spheroidal galaxies by Fermi-LAT and the upcoming Cherenkov Telescope Array (CTA). We also perform a correct treatment of the momentum-dependent direct search cross section that arises from the pseudoscalar interaction term in the fermionic DM theories. We find, in line with previous studies, that current and future direct search experiments such as LUX and XENON1T can exclude much of the parameter space, and we demonstrate that a joint observation in both indirect and direct searches is possible for high mass weakly interacting massive particles. In the case of a pure pseudoscalar interaction of a fermionic DM candidate, future gamma-ray searches are the only class of experiment capable of probing the high mass range of the theory.

We study a three-loop-induced neutrino mass model with exotic vectorlike isospin doublet leptons which contain a dark matter candidate. Then we explore lepton flavor violations and dark matter physics in a coannihilation system. In this paper, the nearly degenerate Majorana fermion dark matter can naturally be achieved at the two-loop level, while the mass splitting can be larger than $\mathcal{O}(200)\mathrm{keV}$ which is required from the constraint of the direct detection search with spin-independent inelastic scattering through the $Z\text{-boson}$ portal. As a result, a monochromatic photon excess, with threshold energy greater than $\mathcal{O}(200)\mathrm{keV}$, is predicted in our model and could be measured through indirect detection experiments such as INTEGRAL.

We present the bare one-, two-, and three-loop form factors in massless quantum chromodynamics as linear combinations of finite master integrals. Using symbolic integration, we compute their $\epsilon$ expansions and thereby reproduce all known results with an independent method. Remarkably, in our finite basis, only integrals with a less-than-maximal number of propagators contribute to the cusp anomalous dimensions. We report on indications of this phenomenon at four loops, including the result for a finite, irreducible, twelve-propagator form factor integral. Together with this article, we provide our automated software setup for the computation of finite master integrals.

This paper provides a superfield based approach to constructing a collinear slice of $\mathcal{N}=1$ superspace. The strategy is analogous to integrating out anticollinear fermionic degrees-of-freedom as was developed in the context of soft-collinear effective theory. The resulting Lagrangian can be understood as an integral over collinear superspace, where half the supercoordinates have been integrated out. The application to $\mathcal{N}=1$ super Yang-Mills is presented. Collinear superspace provides the foundation for future explorations of supersymmetric soft-collinear effective theory.

An intense 120 GeV proton beam incident on an extremely long iron target generates enormous numbers of light-mass particles that also decay within that target. If one of these particles decays to a final state with a hidden gauge boson, or if such a particle is produced as a result of the initial collision, then that weakly interacting hidden-sector particle may traverse the remainder of the target and be detected downstream through its possible decay to an $e^{+}{e}^{-}$, ${\mu }^{+}{\mu }^{-}$, or ${\pi }^{+}{\pi }^{-}$ final state. These conditions can be realized through an extension of the SeaQuest experiment at Fermilab, and in this initial investigation we consider how it can serve as an ultrasensitive probe of hidden vector gauge forces, both Abelian and non-Abelian. A light, weakly coupled hidden sector may well explain the dark matter established through astrophysical observations, and the proposed search can provide tangible evidence for its existence—or, alternatively, constrain a “sea” of possibilities.

We present a determination of the $P$-wave $\pi \pi \to \pi {\gamma }^{\star }$ transition amplitude from lattice quantum chromodynamics. Matrix elements of the vector current in a finite volume are extracted from three-point correlation functions, and from these we determine the infinite-volume amplitude using a generalization of the Lellouch-Lüscher formalism. We determine the amplitude for a range of discrete values of the $\pi \pi$ energy and virtuality of the photon and observe the expected dynamical enhancement due to the $\rho$ resonance. Describing the energy dependence of the amplitude, we are able to analytically continue into the complex energy plane and from the residue at the $\rho$ pole extract the $\rho \to \pi {\gamma }^{\star }$ transition form factor. This calculation, at $m_{\pi }\approx 400\mathrm{MeV}$, is the first to determine the form factor of an unstable hadron within a first principles approach to QCD.

Multiplicity, rapidity and transverse momentum distributions of hadrons produced both in inelastic and nondiffractive $pp$ collisions at energies from $\sqrt{s}=200\mathrm{GeV}$ to 14 TeV are studied within the Monte Carlo quark-gluon string model. Good agreement with the available experimental data up to $\sqrt{s}=13\mathrm{TeV}$ is obtained, and predictions are made for the collisions at top LHC energy $\sqrt{s}=14\mathrm{TeV}$. The model indicates that Feynman scaling and extended longitudinal scaling remain valid in the fragmentation regions, whereas strong violation of Feynman scaling is observed at midrapidity. The Koba-Nielsen-Olesen (KNO) scaling in multiplicity distributions is violated at LHC also. The origin of both maintenance and violation of the scaling trends is traced to short range correlations of particles in the strings and interplay between the multistring processes at ultrarelativistic energies.

We provide a detailed study of prompt double $J/\psi$ production within the nonrelativistic QCD (NRQCD) framework in proton-proton collisions at the LHC. We confront the recent LHC data with the results obtained at leading order (LO) in the NRQCD framework within two approaches of the collinear factorization and the $k_T$-factorization. We show that the LHCb data are consistent with the $k_T$-factorized LO NRQCD results. We show that the full LO NRQCD formalism cannot describe the recent CMS data, with about one order of magnitude discrepancy. If the CMS data are confirmed, this indicates rather large higher-order corrections for prompt double $J/\psi$ production. We provide various predictions which can further test the NRQCD-based approach at the LHC in a kinematic region that LO contributions dominate. We also investigate long-range in rapidity double $J/\psi$ correlations. We found no evidence of a ridge-like structure for double $J/\psi$ production in proton-proton collisions at the LHC up to subleading ${\alpha }_s^6$ accuracy.

Muon-neutrino elastic scattering on electrons is an observable neutrino process whose cross section is precisely known. Consequently a measurement of this process in an accelerator-based ${\nu }_{\mu }$ beam can improve the knowledge of the absolute neutrino flux impinging upon the detector; typically this knowledge is limited to $\sim 10\%$ due to uncertainties in hadron production and focusing. We have isolated a sample of $135\pm 17$ neutrino-electron elastic scattering candidates in the segmented scintillator detector of MINERvA, after subtracting backgrounds and correcting for efficiency. We show how this sample can be used to reduce the total uncertainty on the NuMI ${\nu }_{\mu }$ flux from 9% to 6%. Our measurement provides a flux constraint that is useful to other experiments using the NuMI beam, and this technique is applicable to future neutrino beams operating at multi-GeV energies.

Originally designed as a new nuclear reactor monitoring device, the Nucifer detector has successfully detected its first neutrinos. We provide the second-shortest baseline measurement of the reactor neutrino flux. The detection of electron antineutrinos emitted in the decay chains of the fission products, combined with reactor core simulations, provides a new tool to assess both the thermal power and the fissile content of the whole nuclear core and could be used by the International Agency for Atomic Energy to enhance the safeguards of civil nuclear reactors. Deployed at only 7.2 m away from the compact Osiris research reactor core (70 MW) operating at the Saclay research center of the French Alternative Energies and Atomic Energy Commission, the experiment also exhibits a well-suited configuration to search for a new short baseline oscillation. We report the first results of the Nucifer experiment, describing the performances of the $\sim 0.85{\mathrm{m}}^3$ detector remotely operating at a shallow depth equivalent to $\sim 12\mathrm{m}$ of water and under intense background radiation conditions. Based on 145 (106) days of data with the reactor on (off), leading to the detection of an estimated $40760{\overline{\nu }}_e$, the mean number of detected antineutrinos is $281\pm 7(\mathrm{stat})\pm 18(\mathrm{syst}){\overline{\nu }}_e/\mathrm{day}$, in agreement with the prediction of $277\pm 23{\overline{\nu }}_e/\mathrm{day}$. Because of the large background, no conclusive results on the existence of light sterile neutrinos could be derived, however. As a first societal application we quantify how antineutrinos could be used for the Plutonium Management and Disposition Agreement.

We construct supersymmetric Janus solutions using four-dimensional $N=3$ gauged supergravity with $SO(3)\times SU(3)$ gauge group. The $N=3$ supersymmetric ${\mathrm{AdS}}_4$ vacuum with unbroken $SO(3)\times SU(3)$, identified with the compactification of eleven-dimensional supergravity on ${\mathrm{AdS}}_4\times N^{010}$, provides a gravity dual of supersymmetric $N=3$ Chern-Simons-Matter theory in three dimensions with $SU(3)$ flavor symmetry. The Janus solutions accordingly describe supersymmetric conformal interfaces within this Chern-Simons-Matter theory via the $\mathrm{AdS}/\mathrm{CFT}$ holography. We find two classes of Janus solutions preserving respectively (2,1) and (0,1) supersymmetry on the ($1+1$)-dimensional conformal defects. The solution with (2,1) supersymmetry preserves $SO(2)\times SO(2)\times SO(2)\subset SO(3)\times SU(3)$ symmetry while the (0,1) supersymmetric solution is invariant under a larger $SO(2)\times SU(2)\times SO(2)$ symmetry.

In this paper, we show the existence of static and rotating universal horizons and black holes in gravitational theories with broken Lorentz invariance. We pay particular attention to the ultraviolet regime, and show that universal horizons and black holes exist not only in the low energy limit but also at the ultraviolet energy scales. This is realized by presenting various static and stationary exact solutions of the full theory of the projectable Hořava gravity with an extra U(1) symmetry in ($2+1$)-dimensions, which, by construction, is power-counting renormalizable.

We study the possibility of a heavy scalar or pseudoscalar in TeV-scale beyond the Standard Model scenarios being the inflaton of the early universe in light of the recent $\mathcal{O}(750)\mathrm{GeV}$ diphoton excess at the LHC. We consider a scenario in which the new scalar or pseudoscalar couples to the Standard Model gauge bosons at the loop level through new massive Standard Model charged vectorlike fermions with or without dark fermions. We calculate the renormalization group running of both the Standard Model and the new scalar couplings, and present two different models that are perturbative, with a stabilized vacuum up to near the Planck scale. Thus, the Standard Model Higgs and this possible new resonance may still preserve the minimalist features of Higgs inflation.

Neutrino-dominated accretion flows (NDAFs) around rotating stellar-mass black holes (BHs) have been theorized as the central engine of relativistic jets launched in massive star core collapse events or compact star mergers. In this work, we calculate the electron neutrino/antineutrino spectra of NDAFs by fully taking into account the general relativistic effects, and investigate the effects of viewing angle, BH spin, and mass accretion rate on the results. We show that even though a typical NDAF has a neutrino luminosity lower than that of a typical supernova (SN), it can reach ${10}^{50}–{10}^{51}\mathrm{erg}{\mathrm{s}}^{-1}$ peaking at $\sim 10\mathrm{MeV}$, making NDAFs potentially detectable with the upcoming sensitive MeV neutrino detectors if they are close enough to Earth. Based on the observed gamma-ray burst (GRB) event rate in the local universe and requiring that at least three neutrinos are detected to claim a detection, we estimate a detection rate up to $\sim (0.10–0.25)$ per century for GRB-related NDAFs by the Hyper-Kamiokande (Hyper-K) detector if one neglects neutrino oscillation. If one assumes that all type Ib/c SNe have an engine-driven NDAF, the Hyper-K detection rate would be $\sim (1–3)$ per century. By considering neutrino oscillations, the detection rate may decrease by a factor of 2–3. Detecting one such event would establish the observational evidence of NDAFs in the Universe.

In this work we construct a chiral SU(3) Lagrangian with $D$ mesons of spin $J^P=0^{-}$ and $J^P=1^{-}$ and charmed baryons of spin $J^P=1/2^{+}$ and $J^P=3/2^{+}$. There are 42 leading two-body counterterms involving two charmed baryon fields and two $D$ meson fields in the constructed Lagrangian. The heavy-quark spin symmetry leads to 35 sum rules, while the large-$N_c$ operator analysis predicts 29 at the next-to leading order of the $1/N_c$ expansion. The combination of the sum rules from both the heavy-quark symmetry and the large-$N_c$ analysis results in 38 independent sum rules, which reduces the number of free parameters in the chiral Lagrangian to only four. This is a remarkable result demonstrating the consistency of the heavy-quark symmetry and large-$N_c$ operator analysis.

Motivated by what is possibly the first sign of new physics seen at the LHC, the diphoton excess at 750 GeV in ATLAS and CMS, we present a model that provides naturally the necessary ingredients to explain the resonance. The simplest phenomenological explanation for the diphoton excess requires a new scalar state, $X(750)$, as well as additional vectorlike (VL) fermions introduced in an ad-hoc way in order to enhance its decays into a pair of photons and/or increase its production cross section. We show that the necessary VL quarks and their couplings can emerge naturally from a complete framework based on the $SU(3{)}_L\otimes U(1{)}_{\mathcal{X}}$ gauge symmetry.