We investigate the properties of charmonia in a thermal medium, showing that with increasing temperature the decay widths of these mesons behave in a nontrivial way. Our analysis is based on a potential model with interaction potential extracted from thermal lattice QCD calculations of the free-energy of a static quark-antiquark pair. We find that in the crossover region some decay widths are extremely enhanced. In particular, at temperatures $T\sim T_c$ the decay widths of the $J/\Psi$ that depend on the value of the wave function at the origin are enhanced with respect to the values in vacuum by about a factor 2. In the same temperature range the decay width of the process ${\chi }_{cJ}\to J/\Psi +\gamma$ is enhanced by approximately a factor 6 with respect to the value in vacuum. At higher temperatures the charmonia states dissociate and the widths of both decay processes become vanishing small.

With the advent of high precision neutrino scattering experiments comes the need for improved radiative corrections. We present a phenomenological analysis of some contributions to the production of photons in neutrino neutral current scattering that are relevant to experiments subsuming the 1% level of accuracy.

We have used the Collider Detector at Fermilab (CDF-II) to search for the flavor-changing neutral-current (FCNC) top-quark decay $t\to Zc$ using a technique employing ratios of $W$ and $Z$ production, measured in $p\overline{p}$ data corresponding to an integrated luminosity of $1.52{\mathrm{fb}}^{-1}$. The analysis uses a comparison of two decay chains, $p\overline{p}\to t\overline{t}\to WbWb\to \ell \nu bjjb$ and $p\overline{p}\to t\overline{t}\to ZcWb\to \ell \ell cjjb$, to cancel systematic uncertainties in acceptance, efficiency, and luminosity. We validate the modeling of acceptance and efficiency for lepton identification over the multiyear data set using another ratio of $W$ and $Z$ production, in this case the observed ratio of inclusive production of $W$ to $Z$ bosons. To improve the discrimination against standard model backgrounds to top-quark decays, we calculate the top-quark mass for each event with two leptons and four jets assuming it is a $t\overline{t}$ event with one of the top quarks decaying to $Zc$. For additional background discrimination we require at least one jet to be identified as originating from a $b$ quark. No significant signal is found and we set an upper limit on the FCNC branching ratio $\mathrm{Br}(t\to Zc)$ using a likelihood constructed from the $\ell \ell cjjb$ top-quark mass distribution and the number of $\ell \nu bjjb$ events. Limits are set as a function of the helicity of the $Z$ boson produced in the FCNC decay. For 100% longitudinally-polarized $Z$ bosons we find limits of 8.3% and 9.3% (95% C.L.) depending on the assumptions regarding the theoretical top-quark pair production cross section.

We present the first measurement of the mass of the top quark in a sample of $t\overline{t}\to \ell \overline{\nu }b\overline{b}q\overline{q}$ events (where $\ell =e,\mu$) selected by identifying jets containing a muon candidate from the semileptonic decay of heavy-flavor hadrons (soft muon $b$ tagging). The $p\overline{p}$ collision data used correspond to an integrated luminosity of $2{\mathrm{fb}}^{-1}$ and were collected by the CDF II detector at the Fermilab Tevatron Collider. The measurement is based on a novel technique exploiting the invariant mass of a subset of the decay particles, specifically the lepton from the $W$ boson of the $t\to Wb$ decay and the muon from a semileptonic $b$ decay. We fit template histograms, derived from simulation of $t\overline{t}$ events and a modeling of the background, to the mass distribution observed in the data and measure a top quark mass of $180.5\pm 12.0(\mathrm{stat})\pm 3.6(\mathrm{syst})\mathrm{GeV}/c^2$, consistent with the current world average value.

Rotational excitations of compact $Q$-balls in the complex signum-Gordon model in $2+1$ dimensions are investigated. We find that almost all such spinning $Q$-balls have the form of a ring of strictly finite width. In the limit of large angular momentum $M_z$, their energy is proportional to $|M_z{|}^{1/5}$.

We consider $C{P}^{N-1}$ models in $d+1$ dimensions around Lifshitz fixed points with dynamical critical exponent $z$, in the large-$N$ expansion. It is shown that these models are asymptotically free and dynamically generate a mass for the $C{P}^{N-1}$ fields for all $d=z$. We demonstrate that, for $z=d=2$, the initially nondynamical gauge field acquires kinetic terms in a way similar to usual $C{P}^{N-1}$ models in $1+1$ dimensions. Lorentz invariance emerges generically in the low-energy electrodynamics, with a nontrivial dielectric constant given by the inverse mass gap and a magnetic permeability which has a logarithmic dependence on scale. At a special multicritical point, the low-energy electrodynamics also has $z=2$, and an essentially singular dependence of the effective action on $B={ϵ}_{ij}{\partial }_i{A}_j$.

We show that adding a vacuum expectation value to a gauge field left over from a dimensional reduction of three-dimensional pure supersymmetric Yang-Mills theory generates mass terms for the fundamental fields in the two-dimensional theory while supersymmetry stays intact. This is similar to the adjoint mass term that is generated by a Chern-Simons term in this theory. We study the spectrum of the two-dimensional theory as a function of the vacuum expectation value and of the Chern-Simons coupling. Apart from some symmetry issues a straightforward picture arises. We show that at least one massless state exists if the Chern-Simons coupling vanishes. The numerical spectrum separates into (almost) massless and very heavy states as the Chern-Simons coupling grows. We present evidence that the gap survives the continuum limit. We display structure functions and other properties of some of the bound states.

Dynamical Chern-Simons modified gravity is an attractive, yet relatively unexplored, candidate to an alternative theory of gravity. The dynamical Chern-Simons correction couples a dynamical scalar field to the gravitational field. In this framework, we analyze the perturbation formalism and stability properties of spherically symmetric black holes. Assuming that no background scalar field is present, gravitational perturbations with polar and axial parities decouple. We find no effect of the Chern-Simons coupling on the polar sector, while axial perturbations couple to the Chern-Simons scalar field. The axial sector can develop strong instabilities if the coupling parameter $\beta$, associated to the dynamical coupling of the scalar field, is small enough; this yields a constraint on $\beta$ which is much stronger than the constraints previously known in the literature.

There is a deep cosmological mystery: although dependent on very different underlying physics, the time scales of structure formation, of galaxy cooling (both radiatively and against the CMB), and of vacuum domination do not differ by many orders of magnitude, but are all comparable to the present age of the universe. By scanning four landscape parameters simultaneously, we show that this quadruple coincidence is resolved. We assume only that the statistical distribution of parameter values in the multiverse grows towards certain catastrophic boundaries we identify, across which there are drastic regime changes. We find order-of-magnitude predictions for the cosmological constant, the primordial density contrast, the temperature at matter-radiation equality, the typical galaxy mass, and the age of the universe, in terms of the fine structure constant and the electron, proton and Planck masses. Our approach permits a systematic evaluation of measure proposals; with the causal patch measure, we find no runaway of the primordial density contrast and the cosmological constant to large values.

Supersymmetric extensions of the standard model of particle physics assuming the gravitino to be the lightest supersymmetric particle (LSP), and with the next-to-LSP (NLSP) decaying to the gravitino during big bang nucleosynthesis (BBN), are analyzed. Particular emphasis is laid on their potential to solve the “${}^7\mathrm{Li}$ problem,” observations leading to an apparent 2 to 4 overproduction of ${}^7\mathrm{Li}$ with respect to standard big bang nucleosynthesis predictions, their production of cosmologically important amounts of ${}^6\mathrm{Li}$, as well as the resulting gravitino dark matter densities in these models. The study includes several improvements compared to prior studies concerning NLSP hadronic branching ratios, the evaluation of hadronic NLSP decays on BBN, BBN catalytic effects, updated nuclear reaction rates, and relies on a complete calculation of the NLSP thermal abundance, interfacing state-of-the-art computer packages. Heavy gravitinos in the constrained minimal supersymmetric standard model are reanalyzed, whereas light gravitinos in gauge-mediated supersymmetry breaking scenarios are studied for the first time in the context of the “lithium problems.” It is confirmed that decays of NLSP staus to heavy gravitinos, while producing all the dark matter, may at the same time resolve the ${}^7\mathrm{Li}$ problem. For NLSP decay times $\approx {10}^3\sec$, such scenarios also lead to cosmologically important ${}^6\mathrm{Li}$ (and possibly ${}^9\mathrm{Be}$) abundances. However, as such scenarios require heavy $\gtrsim 1\mathrm{TeV}$ staus they are likely not testable at the LHC. It is found that decays of NLSP staus to light gravitinos may lead to significant ${}^6\mathrm{Li}$ (and ${}^9\mathrm{Be}$) abundances, whereas NLSP neutralinos decaying into light gravitinos may solve the ${}^7\mathrm{Li}$ problem. Though both scenarios are testable at the LHC they may not lead to the production of the bulk of the dark matter. A section of the paper outlines particle properties required to significantly reduce the ${}^7\mathrm{Li}$ abundance, and/or enhance the ${}^6\mathrm{Li}$ (and possibly ${}^9\mathrm{Be}$) abundances, by the decay of an arbitrary relic particle.

We characterize the nonlinear evolution of the baryon acoustic feature as traced by the dark matter and halos, using a combination of perturbation theory and $N$-body simulations. We confirm that the acoustic peak traced by the dark matter is both broadened and shifted as structure forms, and that this shift is well described by second-order perturbation theory. These shifts persist for dark matter halos, and are a simple function of halo bias, with the shift (mostly) increasing with increasing bias. Extending our perturbation theory results to halos with simple two parameter bias models (both in Lagrangian and Eulerian space) quantitatively explains the observed shifts. In particular, we demonstrate that there are additional terms that contribute to the shift that are absent for the matter. At $z=0$ for currently favored cosmologies, the matter shows shifts of $\sim 0.5\%$, $b=1$ halos shift the acoustic scale by $\sim 0.2\%$, while $b=2$ halos shift it by $\sim 0.5\%$; these shifts decrease by the square of the growth factor $D(z)$ at higher redshifts. These results are easily generalized to galaxies within the halo model, where we show that simple galaxy models show marginally larger shifts than the correspondingly biased halos, due to the contribution of satellites in high mass halos. While our focus here is on real space, our results make specific predictions for redshift space. For currently favored cosmological models, we find that the shifts for halos at $z=0$ increase by $\sim 0.3\%$; at high $z$, they increase by $\sim 0.5\%D^2$. Our results demonstrate that these theoretical systematics are smaller than the statistical precision of upcoming surveys, even if one ignored the corrections discussed here. Simple modeling, along the lines discussed here, has the potential to reduce these systematics to below the levels of cosmic variance limited surveys.

We present a correlated analysis for the $\Delta B=1$, 2 processes which occur via $b\to s$ transitions within models with a family nonuniversal $U(1{)}^{\prime }$. We take a model-independent approach and only require family universal charges for the first and second generations and small fermion mixing angles. The results of our analysis show that within this class of models, the anomalies in $B_s-{\overline{B}}_s$ mixing and the time-dependent $CP$ asymmetries of the penguin-dominated $B_d\to (\pi ,\varphi ,{\eta }^{\prime },\rho ,\omega ,f_0)K_S$ decays can be accommodated.

We study a simple extension of the minimal supersymmetric standard model in which the Abelian sector of the theory consists of $B-L$ and right-handed isospin. In the minimal model this Abelian gauge structure is broken to the standard model hypercharge gauge group by nonvanishing vacuum expectation values of the right-handed sneutrinos, resulting in spontaneous $R$-parity violation. This theory can emerge as a low energy effective theory of a left-right symmetric theory realized at a high scale. We determine the mass spectrum of the theory, and discuss the generation of neutrino masses and $R$-parity violating interactions. The possibility of distinguishing between $R$-parity violating models with a gauged $U(1{)}_{B-L}$ broken at the TeV scale at the Large Hadron Collider is discussed.

We study nucleon-to-delta electromagnetic transition form factors and relations between them within the framework of the holographic dual model of QCD proposed by Sakai and Sugimoto. In this setup, baryons appear as topological solitons of the five-dimensional holographic gauge theory that describes a tower of mesons and their interactions. We find a relativistic extension of the nucleon-delta-vector meson interaction vertices and use these to calculate transition form factors from holographic QCD. We observe that at low momentum transfer, magnetic dipole, electric and Coulomb quadrupole form factors, and their ratios follow the patterns expected in the large $N_c$ limit. Our results at this approximation are in reasonable agreement with experiment.

We discuss a notion of gluon-glueball duality analogous to quark-hadron duality. We apply this idea to the radiative decay of heavy orthoquarkonium, $Q\overline{Q}\to \gamma gg$, which has been used to search for glueballs. The duality is first introduced in two simplified contexts: (i) a hypothetical version of QCD without any light quarks and (ii) QCD in the large-$N_c$ limit. We then discuss how an approximate form of this duality could hold in real QCD, based on a hierarchy of time scales in the temporal evolution of the $gg$ subsystem in radiative orthoquarkonium decay. We apply this notion of gluon-glueball duality to suggest a method that could be useful in experimental searches for glueballs.

We construct a new realization of type-II seesaw for neutrino masses and baryon asymmetry by extending the standard model with one light and two heavy singlet scalars besides one Higgs triplet. The heavy singlets pick up small vacuum expectation values to give a suppressed trilinear coupling between the triplet and doublet Higgs bosons after the light singlet drives the spontaneous breaking of lepton number. The Higgs triplet can thus remain light and be accessible at the LHC. The lepton-number conserving decays of the heavy singlets can generate a lepton asymmetry stored in the Higgs triplet to account for the matter-antimatter asymmetry in the Universe. We further introduce stable gauge bosons from a hidden sector, which obtain masses and annihilate into the Higgs triplet after spontaneous breaking of the associated non-Abelian gauge symmetry. With Breit-Wigner enhancement, the stable gauge bosons can simultaneously explain the relic density of dark matter and the cosmic positron/electron excesses.

We report measurements of charmless hadronic $B^0$ decays into the ${\pi }^{+}{\pi }^{-}{K}^{+}{\pi }^{-}$ final state. The analysis uses a sample of $657\times {10}^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider at the resonance. The decay $B^0\to {\rho }^0{K}^{+}{\pi }^{-}$ is observed for the first time; the significance is $5.0\sigma$ and the corresponding partial branching fraction for $M_{K\pi }\in (0.75,1.20)\mathrm{GeV}/c^2$ is $[2.8\pm 0.5(\mathrm{stat})\pm 0.5(\mathrm{syst})]\times {10}^{-6}$. We also obtain the first evidence for $B^0\to f_0(980)K^{+}{\pi }^{-}$ with $3.5\sigma$ significance and for $B^0\to {\pi }^{+}{\pi }^{-}{K}^{*0}$ with $4.5\sigma$ significance. For the two-body decays $B^0\to {\rho }^0{K}^{*0}$ and $B^0\to f_0(980)K^{*0}$, the significances are $2.7\sigma$ and $2.5\sigma$, respectively, and the upper limits on the branching fractions are $3.4\times {10}^{-6}$ and $2.2\times {10}^{-6}$ at 90% confidence level.

Characterizing the propagation of particles in an external non-Abelian field only in terms of invariants constructed from its field tensor is not always sufficient, especially, in many analytically tractable and phenomenologically interesting cases.

Spin induced precessional modulations of gravitational wave signals from supermassive black hole binaries can improve the estimation of luminosity distance to the source by space based gravitational wave missions like the Laser Interferometer Space Antenna (LISA). We study how this impacts the ability of LISA to do cosmology, specifically, to measure the dark energy equation of state (EOS) parameter $w$. Using the $\Lambda \mathrm{CDM}$ model of cosmology, we show that observations of precessing binaries with mass ratio $10:1$ by LISA, combined with a redshift measurement, can improve the determination of $w$ up to an order of magnitude with respect to the nonprecessing case depending on the total mass and the redshift.

We show that the squared speed of sound $v_s^2$ is bounded from above at high temperatures by the conformal value of $1/3$ in a class of strongly coupled four-dimensional field theories, given some mild technical assumptions. This class consists of field theories that have gravity duals sourced by a single-scalar field. There are no known examples to date of field theories with gravity duals for which $v_s^2$ exceeds $1/3$ in energetically favored configurations. We conjecture that $v_s^2=1/3$ represents an upper bound for a broad class of four-dimensional theories.