Final states with four tops appear in various extensions of the standard model. Alas, top reconstruction faces combinatorial issues as they show up as large multiplicity events. In this paper, we present a new procedure to determine whether new physics is in fact due to a new source for tops. We establish the use of this procedure to separate the signal from background (primarily $t\overline{t}+\mathrm{\text{jets}}$). Our analysis is model independent, in that it does not use any details of the four top production (such as possible missing energy), and does not require $b$-tagging.

We study nucleon structure with positive and negative parities using a parity-doublet model endowed with hidden local symmetry with the objective to probe dense baryonic matter. The model—that we shall refer to as the “parity-doublet hidden local symmetry model” for short—allows a chiral-invariant mass of the nucleons unconnected to spontaneously broken chiral symmetry, which comes out to be $m_0\sim 200\mathrm{MeV}$ at tree level, from fitting to the decay width of the parity doubler, N(1535), to nucleon-pion and nucleon axial coupling $g_A=1.267$. The presence of a substantial $m_0$ that remains nonvanishing at chiral restoration presents a deep issue for the origin of the nucleon mass and will affect nontrivially the equation of state for dense baryonic matter relevant for compact stars. We construct a chiral perturbation theory at one-loop order and explore the phase structure of the model using renormalization group equations. We find a fixed point that we identify with the “dilaton limit” at which the hidden local symmetry vector mesons decouple from the nucleons. We suggest that the cold baryonic system will flow to this limit either before or at reaching the vector manifestation fixed point of hidden local symmetry theory as density increases toward that of chiral restoration.

We propose a new way for determining the $CP$ violation angle $\gamma$ without any hadronic uncertainty. The suggested method is to use the two triangles formed by the decay amplitudes of $B^{\pm }\to (D^0,{\overline{D}}^0,D_{CP}^0)K_{0(2)}^{*\pm }(1430)$. The advantages are that large $CP$ asymmetries are expected in these processes and only singly Cabibbo-suppressed $D$ decay modes are involved. Measurements of the branching fractions of the neutral $B_d$ decays into $D{K}_{0(2)}^{*}(1430)$ and the time-dependent $CP$ asymmetries in $B_s\to (D^0,{\overline{D}}^0)M$ ($M=f_0(980)$, $f_0(1370)$, $f_2^{\prime }(1525)$, $f_1(1285)$, $f_1(1420)$, $h_1(1180)$) provide an alternative way to extract the angle $\gamma$, which will increase the statistical significance.

Three-dimensional Gödel black hole is a solution to Einstein-Maxwell-Chern-Simons theory with a negative cosmological constant. We have studied the hidden conformal symmetry for massive scalar field without any additional condition in the background of three-dimensional nonextremal and extremal Gödel black holes. This conformal symmetry is uncovered by the observation that the radial wave equations in both cases can all be rewritten in the form of $SL(2,R)$ Casimir operators through introducing two sets of conformal coordinates to write the $SL(2,R)$ generators. At last, we give the holographic dual descriptions of Bekenstein-Hawking entropies of nonextremal and extremal black holes from Cardy formula of conformal field theory.

We calculate the critical exponent $\nu$ of the $O(N)$ symmetric ${\phi }^4$ model within the $1/N$ expansion of the two-particle-irreducible effective action, which provides us with a self-consistent approximation scheme for the correlation function. The exponent $\nu$ controls the behavior of a two-point function $⟨\phi \phi ⟩$ near the critical point $T\ne T_c$ through the correlation length $\xi \sim |T-T_c{|}^{-\nu }$, but we notice that it appears also in the scaling form of the three-point vertex function ${\Gamma }^{(2,1)}\sim ⟨\phi \phi {\phi }^2⟩$ at the critical point $T=T_c$; in the momentum space, ${\Gamma }^{(2,1)}\sim k^{2-\eta -1/\nu }$. We derive a self-consistent equation for ${\Gamma }^{(2,1)}$ from the two-particle-irreducible effective action including the skeleton diagrams up to the next-leading-order in the $1/N$ expansion, and solve it to the leading-log accuracy (i.e., keeping the leading $\ln k$ terms) to obtain $\nu$. Our results turn out to improve those obtained in the standard one-particle-irreducible calculation at the next-leading-order.

We consider the polarization tensor of a color charged gluon field in SU(2) in the background of a homogeneous color magnetic field and calculate its projection onto the lower (tachyonic) state. We obtain a quite simple representation of the polarization tensor in terms of double parametric integral. We provide examples for the numerical evaluation of the polarization tensor in this case. Also, we consider the corresponding expressions at high temperature and calculate the charged gluon magnetic mass in this limit. We conclude that radiation corrections stabilize the ground state. Applications of the results obtained are discussed.

By 2015 the advanced versions of the gravitational-wave detectors Virgo and LIGO will be online. They will collect data in coincidence with enough sensitivity to potentially deliver multiple detections of gravitation waves from inspirals of compact-object binaries. This work is focused on understanding the effects introduced by uncertainties in the calibration of the interferometers. We consider plausible calibration errors based on estimates obtained during LIGO’s fifth and Virgo’s third science runs, which include frequency-dependent amplitude errors of $\sim 10\%$ and frequency-dependent phase errors of $\sim 3\mathrm{degrees}$ in each instrument. We quantify the consequences of such errors estimating the parameters of inspiraling binaries. We find that the systematics introduced by calibration errors on the inferred values of the chirp mass and mass ratio are smaller than 20% of the statistical measurement uncertainties in parameter estimation for 90% of signals in our mock catalog. Meanwhile, the calibration-induced systematics in the inferred sky location of the signal are smaller than $\sim 50\%$ of the statistical uncertainty. We thus conclude that calibration-induced errors at this level are not a significant detriment to accurate parameter estimation.

We use one-dimensional numerical simulations to study spherical collapse in the $f(R)$ gravity models. We include the nonlinear self-coupling of the scalar field in the theory and use a relaxation scheme to follow the collapse. We find an unusual enhancement in density near the virial radius which may provide observable tests of gravity. We also use the estimated collapse time to calculate the critical overdensity ${\delta }_c$ used in calculating the mass function and bias of halos. We find that analytical approximations previously used in the literature do not capture the complexity of nonlinear spherical collapse.

We show that a stacking approach to galaxy clusters can improve current limits on decaying dark matter by a factor $\gtrsim 5-100$, with respect to a single source analysis, for all-sky instruments such as Fermi-LAT. Based on the largest sample of x-ray-selected galaxy clusters available to date (the MCXC, Meta-Catalog of X-Ray Detected Clusters), we provide all the astrophysical information, in particular, the astrophysical term for decaying dark matter, required to perform an analysis with current instruments.

We present a theory of the generation of magnetic fields in bubble collisions during the electroweak phase transition, which may be first order in various extensions of the standard model, for example, the minimal supersymmetric standard model. Using the equations of motion determined from an effective minimal supersymmetric standard model Lagrangian, we derive the magnetic field using a model of gentle collisions of the electroweak phase transition bubbles, discussed in our earlier work. Solutions of the relevant equations of motion for the magnetic field are examined in O(1,2) space-time symmetry with boundary conditions applied at the time of collision. These solutions indicate that the magnetic fields evolving from our equations of motion are somewhat larger in magnitude and extend more uniformly through the available volume of the bubble than those found in the Abelian Higgs model. The magnetic fields so produced might possibly seed galactic and extragalactic magnetic fields observed today.

Supersymmetry-breaking sectors generically have an approximate global $U(1)$ $R$ symmetry. Thermal effects tend to restore the $R$ symmetry in the reheated early universe. We revisit the gravitino generation from the thermal plasma, and we argue that an $R$-symmetric phase suppresses the gaugino masses and thereby the production of the helicity $\pm 1/2$ gravitino component. For reasonable values of the hidden sector parameters, the gravitino can account for the dark matter of the Universe with a relic abundance characterized by a remarkable insensitivity to the reheating temperature.

We investigate theta-vacuum effects on the QCD phase diagram for the realistic $2+1$ flavor system, using the three-flavor Polyakov-extended Nambu-Jona-Lasinio (PNJL) model and the entanglement PNJL model as an extension of the PNJL model. The theta-vacuum effects make the chiral transition sharper. For large theta-vacuum angle the chiral transition becomes first order even if the quark number chemical potential is zero, when the entanglement coupling between the chiral condensate and the Polyakov loop is taken into account. We finally propose a way of circumventing the sign problem on lattice QCD with finite theta.

In SUSY models with heavy squarks and gaugino mass unification, the gaugino pair production reaction $pp\to {\tilde{W}}_1^{\pm }{\tilde{Z}}_2$ dominates gluino pair production for $m_{\tilde{g}}\gtrsim 1\mathrm{TeV}$ at LHC with $\sqrt{s}=14\mathrm{TeV}$ (LHC14). For this mass range, the two-body decays ${\tilde{W}}_1\to W{\tilde{Z}}_1$ and ${\tilde{Z}}_2\to h{\tilde{Z}}_1$ are expected to dominate the chargino and neutralino branching fractions. By searching for $\ell b\tilde{b}+{\mathrm{E̸}}_T$ events from ${\tilde{W}}_1^{\pm }{\tilde{Z}}_2$ production, we show that LHC14 with $100{\mathrm{fb}}^{-1}$ of integrated luminosity becomes sensitive to chargino masses in the range $m_{{\tilde{W}}_1}\sim 450–550\mathrm{GeV}$ corresponding to $m_{\tilde{g}}\sim 1.5–2\mathrm{TeV}$ in models with gaugino mass unification. For ${10}^3{\mathrm{fb}}^{-1}$, LHC14 is sensitive to the $Wh$ channel for $m_{{\tilde{W}}_1}\sim 300–800\mathrm{GeV}$, corresponding to $m_{\tilde{g}}\sim 1–2.8\mathrm{TeV}$, which is comparable to the reach for gluino pair production followed by cascade decays. The $Wh+{\mathrm{E̸}}_T$ search channel opens up a new complementary avenue for SUSY searches at LHC, and serves to point to SUSY as the origin of any new physics discovered via multijet and multilepton $+{\mathrm{E̸}}_T$ channels.

We employ the ATLAS search results for events containing jets and large missing transverse momentum, corresponding to an integrated luminosity of $1{\mathrm{fb}}^{-1}$, to investigate the constrained minimal supersymmetric model with $b-\tau$ Yukawa coupling unification. In this scenario, one of the stops is the next-to-lightest supersymmetric particle (NLSP), which coannihilates with the lightest (LSP) neutralino to yield the desired dark matter relic abundance. The NLSP stop, here taken to be lighter than the top quark, is slightly ($\lesssim 20\%–30\%$) heavier than the LSP neutralino, and it primarily decays into the LSP and a charm quark. We find that the multijets and monojet ATLAS searches are sensitive to this scenario if the stop pair production is accompanied by a hard QCD jet. The excluded limit for the NLSP stop mass from the ATLAS data can reach 160 GeV in the coannihilation region, with mass below 140 GeV essentially excluded. A significant region of the parameter space corresponding to large $m_0$ values, $8\mathrm{TeV}\lesssim m_0\lesssim 16\mathrm{TeV}$, is excluded by our analysis. For LSP neutralino mass $\sim 100\mathrm{GeV}$, the LHC constraints in some cases on the spin-dependent (spin-independent) neutralino-nucleon cross section are significantly more stringent than the current and expected bounds from Xenon, CDMS, and IceCube.

We study the effect of color octet scalars on the high transverse momenta four-jet cross section at the LHC. We consider both weak singlet and doublet scalars, concentrating on the case of small couplings to quarks. We find that a relatively early discovery at the LHC is possible for a range of scalar masses.

In this article, we revisit the Type II seesaw mechanism based on the addition of a weak triplet scalar to the standard model. We perform a comprehensive study of its phenomenology at the LHC energies, complete with the electroweak precision constraints. We pay special attention to the doubly-charged component, object of collider searches for a long time, and show how the experimental bound on its mass depends crucially on the particle spectrum of the theory. Our study can be used as a roadmap for future complete LHC studies.

The extension of the concept of generalized parton distributions leads to the introduction of baryon to meson transition distribution amplitudes (TDAs), nondiagonal matrix elements of the nonlocal three quark operator between a nucleon and a meson state. We present a general framework for modeling nucleon to pion ($\pi N$) TDAs. Our main tool is the spectral representation for $\pi N$ TDAs in terms of quadruple distributions. We propose a factorized Ansatz for quadruple distributions with input from the soft-pion theorem for $\pi N$ TDAs. The spectral representation is complemented with a $D$-term like contribution from the nucleon exchange in the cross channel. We then study backward pion electroproduction in the QCD collinear factorization approach in which the nonperturbative part of the amplitude involves $\pi N$ TDAs. Within our two component model for $\pi N$ TDAs, we update previous leading-twist estimates of the unpolarized cross section. Finally, we compute the transverse target single spin asymmetry as a function of skewness. We find it to be sizable in the valence region and sensitive to the phenomenological input of our $\pi N$ TDA model.

The flavor-conserving nonleptonic weak interaction can be studied experimentally through the observation of parity violation in nuclear and few-body systems. At hadronic scales, matrix elements of parity-violating four-quark operators ultimately give rise to the parity-violating couplings between hadrons, and such matrix elements can be calculated nonperturbatively using lattice QCD. In this work, we investigate the running of isovector parity-violating operators from the weak scale down to hadronic scales using the renormalization group. We work at next-to-leading order in the QCD coupling, and include both neutral-current and charged-current interactions. At this order, results are renormalization-scheme dependent, and we utilize ’t Hooft-Veltman dimensional regularization. The evolution of Wilson coefficients at leading and next-to-leading order is compared. Next-to-leading-order effects are shown to be non-negligible at hadronic scales.

We present a novel analysis of the $\pi N$ scattering amplitude in Lorentz covariant baryon chiral perturbation theory renormalized in the extended-on-mass-shell scheme. This amplitude, valid up to $\mathcal{O}(p^3)$ in the chiral expansion, systematically includes the effects of the $\Delta (1232)$ in the $\delta$-counting, has the right analytic properties, and is renormalization-scale independent. This approach overcomes the limitations that previous chiral analyses of the $\pi N$ scattering amplitude had, providing an accurate description of the partial wave phase shifts of the Karlsruhe-Helsinki and George-Washington groups up to energies just below the resonance region. We also study the solution of the Matsinos group which focuses on the parameterization of the data at low energies. Once the values of the low-energy constants are determined by adjusting the center-of-mass energy dependence of the amplitude to the scattering data, we obtain predictions on different observables. In particular, we extract an accurate value for the pion-nucleon sigma term, ${\sigma }_{\pi N}$. This allows us to avoid the usual method of extrapolation to the unphysical region of the amplitude. Our study indicates that the inclusion of modern meson-factory and pionic-atom data favors relatively large values of the sigma term. We report the value ${\sigma }_{\pi N}=59(7)\mathrm{MeV}$ and comment on implications that this result may have.