${\Omega }_b\to {\Omega }_c^{(*)}$ semileptonic decays are studied in details. Relevant helicity amplitudes are written down. Both unpolarized and polarized ${\Omega }_b$ cases are considered. Decay angular distributions, asymmetry parameters and semileptonic decay rates are calculated, with numerical results using leading order results of the large $N_c$ heavy quark effective theory.

Supersymmetric grand unification usually provides unification of the bottom quark and the tau lepton Yukawa couplings at the scale of the grand unified theory (GUT). In the constrained minimal supersymmetric standard model this can be realized only for a very particular choice of parameters. In this paper we study the GUT scale ratio $y_{\tau }/y_b$ for less peculiar parameters in the large $\tan \beta$ regime and identify one parameter region preferred by current experimental data. In this region, which is well within the reach of the LHC, the ratio is very close to the recently proposed value of $3/2$.

Domain wall formation is quite generic in spontaneous left-right parity ($D$-parity) breaking models. Since they are in conflict with cosmology, we need some mechanisms to remove them. Planck scale suppressed effects have been considered to be quite successful for this purpose. We study this possibility in the minimal supersymmetric left-right model originally proposed by Kuchimanchi et al. [R. Kuchimanchi and R. N. Mohapatra, Phys. Rev. D 48, 4352 (1993).] where both $D$-parity and $R$-parity $(R_p=(-1{)}^{3(B-L)+2s})$ are spontaneously broken. We find that Planck scale suppressed terms allowed for the specific particle content of this model can successfully remove the domain walls provided the $D$-parity breaking scale is relatively low $(\le {10}^5–{10}^7\mathrm{GeV})$. However, demanding this theory to be part of a grand unified theory such as $SO(10)$ forces the $D$-parity breaking scale to be very high $(\ge {10}^{14}\mathrm{GeV})$ and hence is in conflict with the constraint from domain wall removal. We also find another class of $R$-parity violating supersymmetric left-right models where both these constraints can be simultaneously satisfied.

Partial split supersymmetry with bilinear R-parity violation allows one to reproduce all neutrino mass and mixing parameters. The viable dark matter candidate in this model is the gravitino. We study the hypothesis that both possibilities are true: partial split supersymmetry explains neutrino physics and dark matter is actually composed of gravitinos. Since the gravitino has a small but nonzero decay probability, its decay products could be observed in astrophysical experiments. Combining bounds from astrophysical photon spectra with the bounds coming from the mass matrix in the neutrino sector we derive a stringent upper limit for the allowed gravitino mass. This mass limit is in good agreement with the results of direct dark matter searches.

We examine the taste structure of eigenvectors of the staggered-fermion Dirac operator. We derive a set of conditions on the eigenvectors of modes with small eigenvalues (near-zero modes), such that staggered fermions reproduce the ’t Hooft vertex in the continuum limit. We also show that, assuming these conditions, the correlators of flavor-singlet mesons are free of contributions singular in $1/m$, where $m$ is the quark mass. This conclusion holds also when a single flavor of sea quark is represented by the fourth root of the staggered-fermion determinant. We then test numerically, using the highly improved staggered-quark action, whether these conditions hold on realistic lattice gauge fields. We find that the needed structure does indeed emerge.

We propose an axigluon with mass between 400 and 450 GeV and flavor-universal couplings to quarks to explain the Tevatron $t$ - $\overline{t}$ forward-backward asymmetry. The model predicts a small negative asymmetry for $t$ - $\overline{t}$ pairs with invariant mass below 450 GeV and a large positive asymmetry above 450 GeV. The asymmetry arises from interference between $s$-channel gluon and axigluon diagrams and requires a relatively weakly coupled axigluon ($g_a=g_{qcd}/3$). Axigluon-gluon interference does not contribute to the $t$ - $\overline{t}$ cross section. New contributions to the cross section arise only at fourth order in the axigluon coupling and are very small for a sufficiently broad axigluon. Dijet measurements do not significantly constrain the axigluon couplings. We propose several possible UV completions of the phenomenological axigluon which explain the required small couplings and large width. Such UV completions necessarily contain new colored fermions or scalars below the axigluon mass and predict multijet events with large cross sections at the Tevatron and LHC.

We present a two-flavor linear sigma model with global chiral symmetry and (axial-)vector mesons as well as an additional glueball degree of freedom. We study the structure of the well-established scalar resonances $f_0(1370)$ and $f_0(1500)$: by a fit to experimentally known decay widths we find that $f_0(1370)$ is predominantly a $\overline{q}q$ state and $f_0(1500)$ is predominantly a glueball state. The overall phenomenology of these two resonances can be well described. Other assignments for our mixed quarkonium-glueball states are also tested, but turn out to be in worse agreement with the phenomenology. As a by-product of our analysis, the gluon condensate is determined.

The quark-gluon string model reproduces well the global characteristics of the $pp$ collisions at energies of $\sqrt{s}=200\mathrm{GeV}$ (RHIC) and $\sqrt{s}=900\mathrm{GeV}$ (LHC). In present paper the quark-gluon string model is employed for the description of femtoscopic characteristics of identical pions produced in the aforementioned reactions. The study is concentrated on the low multiplicity and multiplicity averaged events, where no collective effects are expected. The different procedures for fitting the one-dimensional correlation functions of pions are studied and compared with the space-time distributions extracted directly from the model. Particularly, it is shown that the double-Gaussian fit reveals the contributions coming separately from resonances and from directly produced particles. The comparison of model results with the experimental data favors a decrease in particle formation time with rising collision energy.

A $\sim 5\mathrm{GeV}$ “dark baryon” with a cosmic asymmetry similar to that of baryons is a natural candidate for the dark matter. We study the possibility of generating such a state through dynamical electroweak symmetry breaking, and show that it can share the relic baryon asymmetry via sphaleron interactions, even though it has no electroweak interactions. The scattering cross section on nucleons, estimated in analogy to QCD, is within reach of underground direct detection experiments.

We present a new class of oscillons in the ($1+1$)-dimensional signum-Gordon model. The oscillons periodically move to and fro in space. They have finite total energy, finite size, and are strictly periodic in time. The corresponding solutions of the scalar field equation are explicitly constructed from the second order polynomials in the time and position coordinates.

We present an on-shell graphical framework for superamplitudes in super Yang-Mills theory with arbitrary supersymmetry. Our diagrammatic procedure is derived through manipulations of the full $\mathcal{N}=4$ superamplitude and illustrated by a number of explicit examples.

We evaluate the Wald Noether charge entropy for a black hole in generalized theories of gravity. Expanding the Lagrangian to second order in gravitational perturbations, we show that contributions to the entropy density originate only from the coefficients of two-derivative terms. The same considerations are extended to include matter fields and to show that arbitrary powers of matter fields and their symmetrized covariant derivatives cannot contribute to the entropy density. We also explain how to use the linearized gravitational field equation rather than quadratic actions to obtain the same results. Several explicit examples are presented that allow us to clarify subtle points in the derivation and application of our method.

Creation of cold dark matter (CCDM) can macroscopically be described by a negative pressure, and, therefore, the mechanism is capable to accelerate the Universe, without the need of an additional dark energy component. In this framework, we discuss the evolution of perturbations by considering a Neo-Newtonian approach where, unlike in the standard Newtonian cosmology, the fluid pressure is taken into account even in the homogeneous and isotropic background equations (Lima, Zanchin, and Brandenberger, MNRAS 291, L1, 1997). The evolution of the density contrast is calculated in the linear approximation and compared to the one predicted by the $\Lambda \mathrm{CDM}$ model. The difference between the CCDM and $\Lambda \mathrm{CDM}$ predictions at the perturbative level is quantified by using three different statistical methods, namely: a simple ${\chi }^2$-analysis in the relevant space parameter, a Bayesian statistical inference, and, finally, a Kolmogorov-Smirnov test. We find that under certain circumstances, the CCDM scenario analyzed here predicts an overall dynamics (including Hubble flow and matter fluctuation field) which fully recovers that of the traditional cosmic concordance model. Our basic conclusion is that such a reduction of the dark sector provides a viable alternative description to the accelerating $\Lambda \mathrm{CDM}$ cosmology.

Electroweak baryogenesis (EWBG) in extensions of the standard model will be tested quantitatively in upcoming nuclear and particle physics experiments, but only to the extent that theoretical computations are robust. Currently there exist orders-of-magnitude discrepancies between treatments of charge transport dynamics during EWBG performed by different groups, each relying on different sets of approximations. In this work, we introduce a consistent power-counting scheme (in ratios of length scales) for treating systematically the dynamics of EWBG: $CP$-asymmetric flavor oscillations, collisions, and diffusion. Within the context of a simplified model of EWBG, we derive the relevant Boltzmann equations using nonequilibrium field theory, and solve them exactly without ansatz for the functional form of the density matrices. We demonstrate the existence of a resonant enhancement in charge production when the flavor oscillation length is comparable to the wall thickness. We compare our results with the existing treatment of EWBG by Konstandin, Prokopec, Schmidt, and Seco (KPSS) who previously identified the importance of flavor oscillations in EWBG. We conclude: (i) the power counting of KPSS breaks down in the resonant regime, and (ii) this leads to substantial underestimation of the charge generated in the unbroken phase, and potentially of the final baryon asymmetry.

We employ a variational basis with a number of $\overline{q}q$ and $\pi \pi$ lattice interpolating fields with quantum numbers of the $\rho$ resonance to extract the discrete energy spectrum in a finite volume. In the elastic region, this spectrum is related to the phase shift of the continuum scattering amplitude by Lüscher’s formula, and the relation allows the extraction of resonance parameters from the spectrum calculation. The simulations are performed at three different total momenta of the coupled $\overline{q}q-\pi \pi$ system, which allows us to extract the $p$-wave scattering phase at five values of pion relative momenta near the resonance region. The effective range formula describes the phase-shift dependence nicely, and we extract the resonance mass $m_{\rho }=792(7)(8)\mathrm{MeV}$ and the coupling $g_{\rho \pi \pi }=5.13(20)$ at our $m_{\pi }\simeq 266\mathrm{MeV}$. The coupling $g_{\rho \pi \pi }$ is directly related to the width of the $\rho$ meson, and our value is close to the value derived from the experimental width. The simulations are performed using dynamical gauge configurations with two mass-degenerate flavors of tree-level improved clover-Wilson fermions. Correlation functions are calculated using the recently proposed distillation method with Laplacian-Heaviside smearing of quarks, which enables flexible calculations, in many cases with unprecedented accuracy.

Motivated by the duality with thermalization in field theory, we study gravitational collapse of a minimally coupled massless scalar field in Einstein gravity with a negative cosmological constant. We investigate the system numerically and establish that for small values of the initial amplitude of the scalar field there is no black hole formation, rather, the scalar field performs an oscillatory motion typical of geodesics in Anti de Sitter. For large enough values of the amplitude of the scalar field, we find black hole formation, which we detect numerically as the emergence of an apparent horizon. Using the time of formation as an estimate for thermalization in the field theory, we conclude that thermalization occurs very rapidly, close to the causal bound for a very wide range of black hole masses. We further study the thermalization time in more detail as a function of the amplitude and the width of the initial Gaussian scalar field profile and detect a rather mild structure.

We present an analysis of Brownian force noise from residual gas damping of reference test masses as a fundamental sensitivity limit in small force experiments. The resulting acceleration noise increases significantly when the distance of the test mass to the surrounding experimental apparatus is smaller than the dimension of the test mass itself. For the Advanced LIGO interferometric gravitational wave observatory, where the relevant test mass is a suspended 340 mm diameter cylindrical end mirror, the force noise power is increased by roughly a factor 40 by the presence of a similarly shaped reaction mass at a nominal separation of 5 mm. The force noise, of order $20\mathrm{fN}/{\mathrm{Hz}}^{1/2}$ for $2\times {10}^{-6}\mathrm{Pa}$ of residual ${\mathrm{H}}_2$ gas, rivals quantum optical fluctuations as the dominant noise source between 10 and 30 Hz. We present here a numerical and analytical analysis for the gas damping force noise for Advanced LIGO, backed up by experimental evidence from several recent measurements. Finally, we discuss the impact of residual gas damping on the gravitational wave sensitivity and possible mitigation strategies.

We discuss two striking Large Hadron Collider (LHC) signatures of the constrained version of the exceptional supersymmetric standard model, based on a universal high-energy soft scalar mass $m_0$, soft trilinear coupling $A_0$ and soft gaugino mass $M_{1/2}$. The first signature we discuss is that of light exotic color triplet charge $1/3$ fermions, which we refer to as $D$-fermions. We calculate the LHC production cross section of $D$-fermions, and discuss their decay patterns. Secondly we discuss the $E_6$ type $U(1{)}_N$ spin-1 $Z^{\prime }$ gauge boson and show how it may decay into exotic states, increasing its width and modifying the line shape of the dilepton final state. We illustrate these features using two representative exceptional supersymmetric standard model benchmark points, including an “early LHC discovery” point, giving the Feynman rules and numerical values for the relevant couplings in order to facilitate further studies.

In the Higgsless models, there are extra gauge bosons which keep the perturbative unitarity of a longitudinally polarized gauge boson. The three-site Higgsless model is a minimal Higgsless model and contains three extra gauge bosons, $W^{\prime \pm }$ and $Z^{\prime }$. In this paper, we report the discovery potential of the $Z^{\prime }$ gauge boson via Drell-Yan production with $Z^{\prime }$ $(\mathrm{\text{mass}}=380,500,600\mathrm{GeV})\to WW\to \ell \nu qq$ ($\ell =e$, $\mu$) at the LHC ($\sqrt{s}=14\mathrm{TeV}$).

We study the quark mass dependence of the finite temperature QCD phase transition in the heavy quark region using an effective potential defined through the probability distribution function of the average plaquette. Performing a simulation of SU(3) pure gauge theory, we first confirm that the distribution function has two peaks indicating that the phase transition is of first order in the heavy quark limit, while the first-order transition turns into a crossover as the quark mass decreases from infinity, where the mass dependence of the distribution function is evaluated by the reweighting method combined with the hopping parameter expansion. We determine the endpoint of the first-order transition region for $N_f=1$, 2, 3 and $2+1$ cases. The quark mass dependence of the latent heat is also evaluated in the first-order transition region.