Production of the $\mathrm{{\rm Y}}(1\mathrm{S})$ meson in association with a vector boson is a rare process in the standard model with a cross section predicted to be below the sensitivity of the Tevatron. Observation of this process could signify contributions not described by the standard model or reveal limitations with the current nonrelativistic quantum-chromodynamic models used to calculate the cross section. We perform a search for this process using the full Run II data set collected by the CDF II detector corresponding to an integrated luminosity of $9.4{\mathrm{fb}}^{-1}$. The search considers the $\mathrm{{\rm Y}}\to \mu \mu$ decay and the decay of the $W$ and $Z$ bosons into muons and electrons. In these purely leptonic decay channels, we observe one $\mathrm{{\rm Y}}W$ candidate with an expected background of $1.2\pm 0.5$ events, and one $\mathrm{{\rm Y}}Z$ candidate with an expected background of $0.1\pm 0.1$ events. Both observations are consistent with the predicted background contributions. The resulting upper limits on the cross section for $\mathrm{{\rm Y}}+W/Z$ production are the most sensitive reported from a single experiment and place restrictions on potential contributions from non-standard-model physics.

We measure the ratio of cross sections, $\sigma (p\overline{p}\to Z+2b\text{jets})/\sigma (p\overline{p}\to Z+2\text{jets})$, for associated production of a $Z$ boson with at least two jets with transverse momentum $p_T^{\text{jet}}>20\mathrm{GeV}$ and pseudorapidity $|{\eta }^{\text{jet}}|<2.5$. This measurement uses data corresponding to an integrated luminosity of $9.7{\mathrm{fb}}^{-1}$ collected by the D0 experiment in Run II of Fermilab’s Tevatron $p\overline{p}$ Collider at a center-of-mass energy of 1.96 TeV. The measured integrated ratio of $0.0236\pm 0.0032(\text{stat})\pm 0.0035(\text{syst})$ is in agreement with predictions from next-to-leading-order perturbative QCD and the Monte Carlo event generators pythia and alpgen.

We use the worldline numerics technique to study a cylindrically symmetric model of magnetic flux tubes in a dense lattice and the nonlocal Casimir forces acting between regions of magnetic flux. Within a superconductor the magnetic field is constrained within magnetic flux tubes and if the background magnetic field is on the order the quantum critical field strength, $B_k=\frac{m^2}{e}=4.4\times {10}^{13}$ Gauss, the magnetic field is likely to vary rapidly on the scales where QED effects are important. In this paper, we construct a cylindrically symmetric toy model of a flux tube lattice in which the nonlocal influence of QED on neighboring flux tubes is taken into account. We compute the effective action densities using the worldline numerics technique. The numerics predict a greater effective energy density in the region of the flux tube, but a smaller energy density in the regions between the flux tubes compared to a locally constant-field approximation. We also compute the interaction energy between a flux tube and its neighbors as the lattice spacing is reduced from infinity. Because our flux tubes exhibit compact support, this energy is entirely nonlocal and predicted to be zero in local approximations such as the derivative expansion. This Casimir-Polder energy can take positive or negative values depending on the distance between the flux tubes, and it may cause the flux tubes in neutron stars to form bunches. In addition to the above results we also discuss two important subtleties of determining the statistical uncertainties within the worldline numerics technique. Firstly, the distributions generated by the worldline ensembles are highly non-Gaussian, and so the standard error in the mean is not a good measure of the statistical uncertainty. Secondly, because the same ensemble of worldlines is used to compute the Wilson loops at different values of $T$ and $x_{\mathrm{cm}}$, the uncertainties associated with each computed value of the integrand are strongly correlated. We recommend a form of jackknife analysis which deals with both of these problems.

We elaborate on the radiative behavior of tree-level scattering amplitudes in the soft regime. We show that the subleading soft term in single-gluon emission of quark-gluon amplitudes in QCD is controlled by differential operators, whose universal form can be derived from both on-shell recursion and gauge invariance, as it was shown to hold for graviton and gluon scattering.

In arbitrary dimension, we consider the Einstein-Maxwell Lagrangian supplemented by the more general quadratic-curvature corrections. For this model, we derive four classes of charged Lifshitz black hole solutions for which the metric function is shown to depend on a unique integration constant. The masses of these solutions are computed using the quasilocal formalism based on the relation established between the off-shell Abbott-Deser-Tekin and Noether potentials. Among these four solutions, three of them are interpreted as extremal in the sense that their masses vanish identically. For the last family of solutions, both the quasilocal mass and the electric charge are shown to depend on the integration constant. Finally, we verify that the first law of thermodynamics holds for each solution and a Smarr formula is also established for the four solutions.

Current cosmological data puts increasing pressure on models of dark energy in the freezing class, e.g. early dark energy or those with equation of state $w$ substantially different from $-1$. We investigate to what extent data will distinguish the thawing class of quintessence from a cosmological constant. Since thawing dark energy deviates from $w=-1$ only at late times, we find that deviations $1+w\lesssim 0.1$ are difficult to see even with next generation measurements; however, modest redshift drift data can improve the sensitivity by a factor of two. Furthermore, technical naturalness prefers specific thawing models.

In the coming years, the gravitational-wave community will be optimizing detector performance to target a variety of astrophysical sources which make competing demands on detector sensitivity in different frequency bands. In this paper we describe a number of technologies that are being developed as anticipated upgrades to the Advanced LIGO detectors and quantify the potential sensitivity improvement they offer. Specifically, we consider squeezed light injection for the reduction of quantum noise, detector design and materials changes which mitigate thermal noise and mirrors with significantly increased mass. We explore how each of these technologies impacts the detection of the most promising gravitational-wave sources and suggest an effective progression of upgrades which culminates in a twofold improvement in broadband sensitivity.

We propose a general method for the numerical evaluation of operator product expansion coefficients in three dimensional conformal field theories based on the study of the conformal perturbation of two point functions in the vicinity of the critical point. We test our proposal in the three dimensional Ising model, looking at the magnetic perturbation of the $⟨\sigma (\mathbf{r})\sigma (0)⟩$, $⟨\sigma (\mathbf{r})\epsilon (0)⟩$ and $⟨\epsilon (\mathbf{r})\epsilon (0)⟩$ correlators from which we extract the values of $C_{\sigma \epsilon }^{\sigma }=1.07(3)$ and $C_{\epsilon \epsilon }^{\epsilon }=1.45(30)$. Our estimate for $C_{\sigma \epsilon }^{\sigma }$ agrees with those recently obtained using conformal bootstrap methods, while $C_{\epsilon \epsilon }^{\epsilon }$, as far as we know, is new and could be used to further constrain conformal bootstrap analyses of the 3d Ising universality class.

We consider the finite temperature phase diagram of holographic QCD in the Veneziano limit ($N_c\to \infty$, $N_f\to \infty$ with $x_f=N_f/N_c$ fixed) and calculate one string loop corrections to the free energy in certain approximations. Such corrections, especially due to the pion modes, are unsuppressed in the Veneziano limit. We find that under some extra assumptions the first order transition following from classical gravity solutions can become second order. If stringy asymptotics are of a special form and there are residual interactions, it may even become of third order. Operationally these computations imply modeling the low temperature chiral symmetry breaking phase with a hadron gas containing $N_f^2$ massless Goldstone bosons and an exponential spectrum of massive hadrons. A third order transition is possible only if repulsive hadron interactions via the excluded volume effect are included.

Considering the generalized minimal supergravity model in the minimal supersymmetric Standard Model, we study the electroweak supersymmetry, in which the squarks and/or gluino are heavy around a few TeVs while the sleptons, sneutrinos, bino, winos, and/or Higgsinos are light within 1 TeV. We resolve the $(g-2{)}_{\mu }/2$ discrepancy for the muon anomalous magnetic moment in the Standard Model successfully and identify a parameter space in which such solutions also have the electroweak fine-tuning measures ${\mathrm{\Delta }}_{\mathrm{EW}}$ 16.5 (6%) and ${\mathrm{\Delta }}_{\mathrm{EW}}$ 25 (4%) without and with the Wilkinson Microwave Anisotropy Probe (WMAP) bounds, respectively. We find that the allowed mass ranges, which are consistent within $3\sigma$ of the $g-2$ discrepancy, for the lightest neutralino, charginos, stau, stau neutrinos, and first two-family sleptons are [44, 390], [100, 700], [100, 700], [52, 800], and [150, 800]  GeV, respectively. Moreover, our solutions satisfy the latest bounds reported by the ATLAS and CMS collaborations on electroweakinos and sleptons. The colored sparticles such as light stop, gluinos, and the first the first two generations of squark masses have been found in the mass ranges of [500, 3000], [1300, 4300], and [1800, 4200] GeV, respectively. To obtain the observed dark matter relic density for the lightest supersymmetric particle (LSP) neutralino, we have the bino-wino, LSP neutralino-stau, and LSP neutralino-tau sneutrinos coannihilation scenarios and the resonance solutions such as the $A$ pole, Higgs pole, and $Z$ pole. We identify the Higgsino-like LSP neutralino and display its spin-independent and spin-dependent cross sections with nucleons. We present ten benchmark points that can be tested at the up coming collider searches as well.

We examine the Kogut-Susskind formulation of lattice gauge theories under the light of fermionic and bosonic degrees of freedom that provide a description useful to the development of quantum simulators of gauge-invariant models. We consider both discrete and continuous gauge groups and adopt a realistic multicomponent Fock space for the definition of matter degrees of freedom. In particular, we express the Hamiltonian of the gauge theory and the Gauss law in terms of Fock operators. The gauge fields are described in two different bases based on either group elements or group representations. This formulation allows for a natural scheme to achieve a consistent truncation of the Hilbert space for continuous groups, and provides helpful tools to study the connections of gauge theories with topological quantum double and string-net models for discrete groups. Several examples, including the case of the discrete $D_3$ gauge group, are presented.

The single top-quark final state provides sensitivity to new heavy resonances produced in proton-proton collisions at the Large Hadron Collider. Particularly, the single top plus quark final state appears in models with heavy charged bosons or scalars, or in models with flavor-changing neutral currents involving the top quark. The cross sections and final-state kinematics distinguish such models from each other and from standard model backgrounds. Several models of resonances decaying to a single top-quark final state are presented and their phenomenology is discussed.

We investigate the possibility of detecting Majorana neutrinos at the Large Hadron-electron Collider, an electron-proton collision mode at CERN. We study the $l_j^{+}+3\text{jets}$ ($l_j\equiv e,\mu ,\tau$) final states that are, due to leptonic number violation, a clear signature for intermediate Majorana neutrino contributions. Such signals are not possible if the heavy neutrinos have Dirac nature. The interactions between Majorana neutrinos and the Standard Model particles are obtained from an effective Lagrangian approach. We present our results for the total cross section as a function of the neutrino mass, the effective couplings, and the new physics scale. We also show the discovery region as a function of the Majorana neutrino mass and the effective couplings. Our results show that the Large Hadron-electron Collider may be able to discover Majorana neutrinos with masses lower than 700 and 1300 GeV for electron beams settings of $E_e=50\mathrm{GeV}$ and $E_e=150\mathrm{GeV}$, respectively.

The T2K experiment has performed a search for ${\nu }_e$ disappearance due to sterile neutrinos using $5.9\times 10^{20}$ protons on target for a baseline of 280 m in a neutrino beam peaked at about 500 MeV. A sample of ${\nu }_e$ CC interactions in the off-axis near detector has been selected with a purity of 63% and an efficiency of 26%. The p-value for the null hypothesis is 0.085 and the excluded region at 95% C.L. is approximately ${\sin }^{2}2{\theta }_{\text{ee}}>0.3$ for $\mathrm{\Delta }{m}_{\text{eff}}^2>7{\mathrm{eV}}^2/{\mathrm{c}}^4$.

We examine the local conformal invariance (Weyl invariance) in tensor-scalar theories used in recently proposed conformal cosmological models. We show that the Noether currents associated with Weyl invariance in these theories vanish. We assert that the corresponding Weyl symmetry does not have any dynamical role.

Lattice QCD results for the coefficient $c_2$ appearing in the Taylor expansion of the pressure show that this quantity increases with the temperature towards the Stefan-Boltzmann limit. On the other hand, model approximations predict that when a vector repulsion, parametrized by $G_V$, is present this coefficient reaches a maximum just after $T_c$ and then deviates from the lattice predictions. Recently, this discrepancy has been used as a guide to constrain the (presently unknown) value of $G_V$ within the framework of effective models at large $N_c$ (LN). In the present investigation we show that, due to finite $N_c$ effects, $c_2$ may also develop a maximum even when $G_V=0$ since a vector repulsive term can be dynamically generated by exchange-type radiative corrections. Here we apply the optimized perturbation theory (OPT) method to the two-flavor Polyakov–Nambu–Jona-Lasinio model (at $G_V=0$) and compare the results with those furnished by lattice simulations and by the LN approximation at $G_V=0$ and also at $G_V\ne 0$. The OPT numerical results for $c_2$ are impressively accurate for $T\lesssim 1.2T_c$ but, as expected, they predict that this quantity develops a maximum at high $T$. After identifying the mathematical origin of this extremum we argue that such a discrepant behavior may naturally arise within this type of effective quark theories (at $G_V=0$) whenever the first $1/N_c$ corrections are taken into account. We then interpret this hypothesis as an indication that beyond the large-$N_c$ limit the correct high-temperature (perturbative) behavior of $c_2$ will be faithfully described by effective models only if they also mimic the asymptotic freedom phenomenon.

In this paper, we explore the effects of neutrino flavor oscillations on supernova nucleosynthesis and on the neutrino signals. Our study is based on detailed information about the neutrino spectra and their time evolution from a spherically symmetric supernova model for an $18M_{\odot }$ progenitor. We find that collective neutrino oscillations are not only sensitive to the detailed neutrino energy and angular distributions at emission, but also to the time evolution of both the neutrino spectra and the electron density profile. We apply the results of neutrino oscillations to study the impact on supernova nucleosynthesis and on the neutrino signals from a Galactic supernova. We show that in our supernova model, collective neutrino oscillations enhance the production of rare isotopes ${}^{138}\mathrm{La}$ and ${}^{180}\mathrm{Ta}$ but have little impact on the $\nu \mathrm{p}$-process nucleosynthesis. In addition, the adiabatic Mikheyev-Smirnov-Wolfenstein flavor transformation, which occurs in the $\mathrm{C}/\mathrm{O}$ and He shells of the supernova, may affect the production of light nuclei such as ${}^7\mathrm{Li}$ and ${}^{11}\mathrm{B}$. For the neutrino signals, we calculate the rate of neutrino events in the Super-Kamiokande detector and in a hypothetical liquid argon detector. Our results suggest the possibility of using the time profiles of the events in both detectors, along with the spectral information of the detected neutrinos, to infer the neutrino mass hierarchy.

We present a comprehensive numerical study of dynamical mass generation for unquenched QED in four dimensions, in the absence of four-fermion interactions, using the Dyson-Schwinger approach. We begin with an overview of previous investigations of criticality in the quenched approximation. To this we add an analysis using a new fermion-antifermion-boson interaction ansatz, the Kızılersü-Pennington (KP) vertex, developed for an unquenched treatment. After surveying criticality in previous unquenched studies, we investigate the performance of the KP vertex in dynamical mass generation using a renormalized fully unquenched system of equations. This we compare with the results for two hybrid vertices incorporating the Curtis-Pennington vertex in the fermion equation. We conclude that the KP vertex is as yet incomplete, and its relative gauge variance is due to its lack of massive transverse components in its design.