We present first results on the calculation of fermionic spectral functions from analytically continued flow equations within the functional renormalization group approach. Our method is based on the same analytic continuation from imaginary to real frequencies that was developed and used previously for bosonic spectral functions. In order to demonstrate the applicability of the method also for fermionic correlations we apply it here to the real-time quark propagator in the quark-meson model and calculate the corresponding quark spectral functions in the vacuum.

We compute the $O({\alpha }_s{\alpha }^2)$ and $O({\alpha }_s^2\alpha )$ contributions to the production cross section of a $Z$ boson with one $b$ jet at the Large Hadron Collider (LHC) and study their phenomenological relevance for LHC physics. The accurate prediction of hadronic $Z+b$-jet production is needed to control a background that greatly affects both the measurement of Higgs-boson properties and the searches of new physics at the LHC. At the same time it could enable the first precise measurement of the $b$-quark parton distribution function. In this context $b$-quark mass effects become relevant and need to be studied with care, both at the level of the hard process and at the level of the initial- and final-state parton evolution. It is the aim of this paper to explore some of these issues in the framework of a massive five-flavor scheme and to assess the need for the inclusion of both electroweak corrections, in addition to QCD corrections, and $b$-quark mass effects in the prediction of total and differential cross sections for hadronic $Z+b$-jet production.

In this paper, we generalize the concept of an effective $\mathrm{\Delta }{m}_{ee}^2$ for ${\nu }_e/{\overline{\nu }}_e$ disappearance experiments, which has been extensively used by the short baseline reactor experiments, to include the effects of propagation through matter for longer baseline ${\nu }_e/{\overline{\nu }}_e$ disappearance experiments. This generalization is a trivial, linear combination of the neutrino mass squared eigenvalues in matter and thus is not a simple extension of the usually vacuum expression, although, as it must, it reduces to the correct expression in the vacuum limit. We also demonstrated that the effective $\mathrm{\Delta }{m}_{ee}^2$ in matter is very useful conceptually and numerically for understanding the form of the neutrino mass squared eigenstates in matter and hence for calculating the matter oscillation probabilities. Finally, we analytically estimate the precision of this two-flavor approach and numerically verify that it is precise at the subpercent level.

The growth rate of cosmic structure is a powerful cosmological probe for extracting information on the gravitational interactions and dark energy. In the late-time Universe, the growth rate becomes nonlinear and is usually probed by measuring the two-point statistics of galaxy clustering in redshift space up to a limited scale, retaining the constraint on the linear growth rate $f$. In this paper, we present an alternative method to analyze the growth of structure in terms of local densities, i.e., $f(\mathrm{\Delta })$. Using $N$-body simulations, we measure the function of $f(\mathrm{\Delta })$ and show that structure grows faster in high-density regions and slower in low-density regions. We demonstrate that $f(\mathrm{\Delta })$ can be modeled using a log-normal Monte Carlo random walk approach, which provides a means to extract cosmological information from $f(\mathrm{\Delta })$. We discuss prospects for applying this approach to galaxy surveys.

We consider the doublet-triplet fermionic model in the scheme of the custodial limit when the dark matter (DM) candidate is pure doublet and lies at the electroweak scale. This scheme, despite being an appealing and promising DM model, is severely constrained by the interplay between the DM relic density constraint and the LHC measurement of the Higgs diphoton decay rate. In this work, the DM relic density is considered to arise from either a nonstandard cosmology scenario or as a part of a larger sector encompassing other DM particles in order to saturate the observed relic abundance. For these scenarios we investigate the impact of the new sector in different collider observables, and study constraints coming from direct detection and indirect detection of gamma-rays both in the diffuse and linelike spectrum. As a result, we find that in the nonstandard cosmology scenario most experiments impose, up to a certain point, restrictions, though large portions of the parameter space are still viable. For the multi-component case, only direct detection imposes constraints.

We have performed the most comprehensive resonance-model fit of ${\pi }^{-}{\pi }^{-}{\pi }^{+}$ states using the results of our previously published partial-wave analysis (PWA) of a large data set of diffractive-dissociation events from the reaction ${\pi }^{-}+p\to {\pi }^{-}{\pi }^{-}{\pi }^{+}+p_{\text{recoil}}$ with a $190\mathrm{GeV}/c$ pion beam. The PWA results, which were obtained in 100 bins of three-pion mass, $0.5<m_{3\pi }<2.5\mathrm{GeV}/c^2$, and simultaneously in 11 bins of the reduced four-momentum transfer squared, $0.1<t^{\prime }<1.0(\mathrm{GeV}/c{)}^2$, are subjected to a resonance-model fit using Breit-Wigner amplitudes to simultaneously describe a subset of 14 selected waves using 11 isovector light-meson states with $J^{PC}=0^{-+}$, $1^{++}$, $2^{++}$, $2^{-+}$, $4^{++}$, and spin-exotic $1^{-+}$ quantum numbers. The model contains the well-known resonances $\pi (1800)$, $a_1(1260)$, $a_2(1320)$, ${\pi }_2(1670)$, ${\pi }_2(1880)$, and $a_4(2040)$. In addition, it includes the disputed ${\pi }_1(1600)$, the excited states $a_1(1640)$, $a_2(1700)$, and ${\pi }_2(2005)$, as well as the resonancelike $a_1(1420)$. We measure the resonance parameters mass and width of these objects by combining the information from the PWA results obtained in the 11 $t^{\prime }$ bins. We extract the relative branching fractions of the $\rho (770)\pi$ and $f_2(1270)\pi$ decays of $a_2(1320)$ and $a_4(2040)$, where the former one is measured for the first time. In a novel approach, we extract the $t^{\prime }$ dependence of the intensity of the resonances and of their phases. The $t^{\prime }$ dependence of the intensities of most resonances differs distinctly from the $t^{\prime }$ dependence of the nonresonant components. For the first time, we determine the $t^{\prime }$ dependence of the phases of the production amplitudes and confirm that the production mechanism of the Pomeron exchange is common to all resonances. We have performed extensive systematic studies on the model dependence and correlations of the measured physical parameters.

A search for pair production of the supersymmetric partners of the Higgs boson (higgsinos $\tilde{H}$) in gauge-mediated scenarios is reported. Each higgsino is assumed to decay to a Higgs boson and a gravitino. Two complementary analyses, targeting high- and low-mass signals, are performed to maximize sensitivity. The two analyses utilize LHC $pp$ collision data at a center-of-mass energy $\sqrt{s}=13\mathrm{TeV}$, the former with an integrated luminosity of $36.1{\mathrm{fb}}^{-1}$ and the latter with $24.3{\mathrm{fb}}^{-1}$, collected with the ATLAS detector in 2015 and 2016. The search is performed in events containing missing transverse momentum and several energetic jets, at least three of which must be identified as $b$-quark jets. No significant excess is found above the predicted background. Limits on the cross section are set as a function of the mass of the $\tilde{H}$ in simplified models assuming production via mass-degenerate higgsinos decaying to a Higgs boson and a gravitino. Higgsinos with masses between 130 and 230 GeV and between 290 and 880 GeV are excluded at the 95% confidence level. Interpretations of the limits in terms of the branching ratio of the higgsino to a $Z$ boson or a Higgs boson are also presented, and a 45% branching ratio to a Higgs boson is excluded for $m_{\tilde{H}}\approx 400\mathrm{GeV}$.

A search for physics beyond the standard model is performed using a sample of high-mass diphoton events produced in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$. The data sample was collected in 2016 with the CMS detector at the LHC and corresponds to an integrated luminosity of $35.9{\mathrm{fb}}^{-1}$. The search is performed for both resonant and nonresonant new physics signatures. At 95% confidence level, lower limits on the mass of the first Kaluza-Klein excitation of the graviton in the Randall-Sundrum warped extra-dimensional model are determined to be in the range of 2.3 to 4.6 TeV, for values of the associated coupling parameter between 0.01 and 0.2. Lower limits on the production of scalar resonances and model-independent cross section upper limits are also provided. For the large extra-dimensional model of Arkani-Hamed, Dimopoulos, and Dvali, lower limits are set on the string mass scale $M_{\mathrm{S}}$ ranging from 5.6 to 9.7 TeV, depending on the model parameters. The first exclusion limits are set in the two-dimensional parameter space of a continuum clockwork model.

The multicenter solutions of four-dimensional $\mathcal{N}=2$ supergravity contain a subset of scaling solutions with vanishing total angular momentum. In a near limit those solutions are asymptotically locally ${\mathrm{AdS}}_2\times {\mathrm{S}}^2$, but we show that a higher moment of angular momentum contributes a subtle twist, rotating the ${\mathrm{S}}^2$ with time. This provides some potential hair distinguishing the asymptotics of these scaling solutions from the near-horizon geometry of an extremal Bogomol’nyi-Prasad-Sommerfield black hole.

We consider the renormalization of four-fermion operators in the critical QED and $SU(N_c)$ version of the Gross-Neveu-Yukawa model in noninteger dimensions. Since the number of mixing operators is infinite, the diagonalization of an anomalous dimension matrix becomes a nontrivial problem. At leading order, the construction of eigenoperators is equivalent to solving certain three-term recurrence relations. We find analytic solutions of these recurrence relations that allow us to determine the spectrum of anomalous dimensions and study their properties.

We develop a cosmological model based on action-dependent Lagrangian theories. The main feature here is the nonconservation of the energy momentum tensor due to the nontrivial geometrical construction of the theory. We provide the basic set of equations necessary to study both the cosmological background expansion as well as the linear matter perturbation growth. We show that the simplest realization of the Universe as described by only one component is not viable as expected from the existing correspondence between this model and the case of viscous cosmological fluids. However, modeling the energy content of the Universe as composed by two pressureless fluids, i.e., one a typical cold dark matter fluid and the other a pressureless “dark energy” fluid which is responsible for driving the late-time acceleration expansion, is qualitatively compatible with observational data.

Neutrinos emitted from a supernova may undergo flavor conversions almost immediately above the core, with possible consequences for supernova dynamics and nucleosynthesis. However, the precise conditions for such fast conversions can be difficult to compute and require knowledge of the full angular distribution of the flavor-dependent neutrino fluxes that is not available in typical supernova simulations. In this paper, we show that the overall flavor evolution is qualitatively similar to the growth of a so-called “zero mode” determined by the background matter and neutrino densities, which can be reliably predicted using only the second angular moments of the electron lepton number distribution, i.e., the difference in the angular distributions of the ${\nu }_e$ and ${\overline{\nu }}_e$ fluxes. We propose that this zero mode, which neither requires computing the full Green’s function nor detailed knowledge of the angular distributions, may be useful for a preliminary diagnosis of possible fast flavor conversions in supernova simulations with modestly resolved angular distributions.

This study investigates a multilayer high reflector with new coating materials for next-generation laser interferometer gravitational wave detectors operated at cryogenic temperatures. We use the plasma-enhanced chemical vapor deposition method to deposit amorphous silicon nitride and silica quarter-wave high-reflector stacks and studied the properties pertinent to the coating thermal noise. Room- and cryogenic-temperature mechanical loss angles of the silicon nitride and silica quarter-wave bilayers are measured using the cantilever ring-down method. We show, for the first time, that the bulk and shear loss angles of the coatings can be obtained from the cantilever ring-down measurement, and we use the bulk and shear losses to calculate the coating thermal noise of silicon nitride and silica high-reflector coatings. The mechanical loss angle of the silicon nitride and silica bilayer is dispersive with a linear weakly positive frequency dependence, and, hence, the coating thermal noise of the high reflectors show a weakly positive frequency dependence in addition to the normal $1/\sqrt{f}$ dependence. The coating thermal noise of the silicon nitride and silica high-reflector stack is compared to the lower limit of the coating thermal noise of the end test mirrors of ET-LF, KAGRA, LIGO Voyager, and the directly measured coating thermal noise of the current coatings of Advanced LIGO. The optical absorption of the silicon nitride and silica high reflector at 1550 nm is 45.9 ppm. Using a multimaterial system composed of seven pairs of ion-beam-sputter deposited $\mathrm{Ti}:{\mathrm{Ta}}_2{\mathrm{O}}_5$ and silica and nine pairs of silicon nitride and silica on a silicon substrate, the optical absorption can be reduced to 2 ppm, which meets the specification of LIGO Voyager.

We present a simple $U(1{)}_{B_3-3L_2}$ gauge standard model extension that can easily account for the anomalies in $R(K)$ and $R(K^{*})$ reported by LHCb. The model is economical in its setup and particle content. Among the standard model fermions, only the third generation quark family and the second generation leptons transform nontrivially under the new $U(1{)}_{B_3-3L_2}$ symmetry. This leads to lepton nonuniversality and flavor changing neutral currents involving the second and third quark families. We discuss the relevant experimental constraints and some implications.

In this paper, we examine the sensitivity of the three top quark production at the LHC to the top quark flavor-changing neutral currents (FCNC) as well as the sensitivity of the four top production to the strong and weak dipole moments of the top quark. Upper limits at 95% CL on the branching fractions of $\mathcal{B}(t\to qX)$, where $X=g$, $Z$, $\gamma$, $H$ and $q=u$, $c$, are set by performing an analysis on three top events in the same-sign dilepton channel. We consider the main sources of the background processes and a realistic detector simulation is performed at the center-of-mass energy of 14 TeV. In the second part of this work, based on the recent upper limits which have been set on the four top quark cross section by the ATLAS and CMS collaborations from 13 TeV data, we constrain the top quark strong and weak dipole moments. The bounds on the top quark dipole moments are presented using the future LHC prospects for four top quark cross section measurement.

We predict the rate for exclusive double-charmonium production in electron-positron annihilation $e^{+}{e}^{-}\to J/\psi +{\eta }_c$ using pQCD and the NRQCD framework for hard, heavy-quarkonium exclusive processes. The cross sections measured at the $B$-factories Belle and BABAR at $\sqrt{s}=10.6\mathrm{GeV}$ disagree with the pQCD leading-order predictions by an order of magnitude. The predictions at next-to-leading order are, however, very sensitive to the choice of the renormalization scale, resulting in an apparent discrepancy between the theoretical prediction and the data. We show that this discrepancy can in fact be eliminated by applying the principle of maximum conformality (PMC) to set the renormalization scale. By carefully applying the PMC to different topologies of the annihilation process, one achieves precise pQCD predictions, together with improved perturbative convergence. We also observe that the single-photon-fragmentation QED correction is important, an effect that increases the total cross section by about 10%. The scale-fixed, scheme-independent cross section predicted by the PMC is ${\sigma }_{\text{tot}}{|}_{\text{PMC}}=20.35_{-3.8}^{+3.5}\mathrm{fb}$, where the uncertainties come from the squared average of the errors due to the value of the charm mass and the uncertainty from the quarkonium wave functions at the origin. We find that the typical momentum flow of the process is 2.30 GeV, which explains the guessed choice of 2–3 GeV using conventional scale setting. The scale-fixed $e^{+}{e}^{-}\to J/\psi +{\eta }_c$ cross section predicted by the PMC shows agreement with the Belle and BABAR measurements.

This is a collection of notes about spectral form factors of standard ensembles in random matrix theory, written for the practical usage of the current study of late time quantum chaos. More precisely, we consider the Gaussian unitary ensemble, the Gaussian orthogonal ensemble, the Gaussian symplectic ensemble, the Wishart-Laguerre unitary ensemble, the Wishart-Laguerre orthogonal ensemble, and the Wishart-Laguerre symplectic ensemble. These results and their physics applications cover a threefold classification of late time quantum chaos in terms of spectral form factors.

In this paper, we propose a new mechanism with a warped extra dimension to solve the hierarchy problem, which is parallel to the Randall-Sundrum (RS) brane scenario. Different from the RS scenario, the fundamental scale is TeV scale, and the four-dimensional Planck scale is generated from the exponential warped extra dimension at size of a few ${\mathrm{TeV}}^{-1}$. The experimental consequences of this scenario are very different from that of the RS scenario. In the explicit realization in the nonlocal gravity theory, there is a tower of spin-2 excitations with mass gap ${10}^{-4}\mathrm{eV}$, and they are coupled with the gravitational scale to the standard model particles. We further discuss the possible generalizations in other modified gravity theories. The experimental consequences are similar to a ($4+N$)-dimensional large extra dimension, but $N$ can be a noninteger, which satisfies the experimental constraints more easily than the integer large extra-dimension model.

We study the shadows cast by near-extremal Kerr-modified gravity (MOG) black holes for different values of the parameter in modified gravity. In particular, we consider an isotropic emitter orbiting near such black holes and analytically compute the positions, fluxes and redshift factors of their images. The size of the shadow decreases when the modified parameter is increased. For each shadow, the images of the emitter appear on a special part of the shadow which has a rich structure. The primary image and secondary images are similar to those produced for the near-extremal (high-spin) Kerr black hole, but the near-extremal Kerr-MOG black hole can have a spin ($\widehat{J}/M_{\alpha }^2$) which is finitely lower than 1. When the modified parameter is varied, the typical positions of the corresponding images do not change, nor does the typical redshift factor associated with the primary image. However, another typical redshift factor associated with the secondary image increases when the modified parameter is increased. We also find that the fluxes increase in that case. These images appear periodically with periods greater than that of Kerr. This provides an alternative signature away from the Kerr case which may be tested by the Event Horizon Telescope.

In this work, we study Berwald spacetimes and their vacuum dynamics, where the latter are based on a Finsler generalization of Einstein’s equations derived from an action on the unit tangent bundle. In particular, we consider a specific class of spacetimes that are nonflat generalizations of the very special relativity (VSR) line element, which we call “very general relativity” (VGR). We derive necessary and sufficient conditions for the VGR line element to be of Berwald type. We present two novel examples with the corresponding vacuum field equations: a Finslerian generalization of vanishing scalar invariant (VSI) spacetimes in Einstein’s gravity as well as the most general homogeneous and isotropic VGR spacetime.