The OPERA Collaboration has reported the observation of superluminal muon neutrinos, whose speed $v_{\nu }$ exceeds that of light $c$, with $(v_{\nu }-c)/c\simeq 2.5\times {10}^{-5}$. In a recent work, Cohen and Glashow have refuted this claim by noting that such neutrinos will lose energy, by pair emission of particles, at unacceptable rates. Following the Cohen and Glashow arguments, we point out that pair emissions consistent with the OPERA anomaly can lead to detectable signals for neutrinos originating from decays of highly boosted top quarks at the LHC, allowing an independent test of the superluminal neutrino hypothesis.

We show that bound states moving in a finite periodic volume have an energy correction which is topological in origin and universal in character. The topological volume corrections contain information about the number and mass of the constituents of the bound states. These results have broad applications to lattice calculations involving nucleons, nuclei, hadronic molecules, and cold atoms. We illustrate and verify the analytical results with several numerical lattice calculations.

Collinear and soft divergences in perturbative quantum gravity are investigated to arbitrary orders in amplitudes for wide-angle scattering, using methods developed for gauge theories. We show that collinear singularities cancel when all such divergent diagrams are summed over, by using the gravitational Ward identity that decouples unphysical polarizations from the S-matrix. This analysis generalizes a result previously demonstrated in the eikonal approximation. We also confirm that the only virtual graviton corrections that give soft logarithmic divergences are of the ladder and crossed ladder types.

Building on an insight due to Avramidi, we provide a system of transport equations for determining key fundamental bitensors, including derivatives of the world function, $\sigma (x,x^{\prime })$, the square root of the Van Vleck determinant, ${\Delta }^{1/2}(x,x^{\prime })$, and the tail term, $V(x,x^{\prime })$, appearing in the Hadamard form of the Green function. These bitensors are central to a broad range of problems from radiation reaction to quantum field theory in curved spacetime and quantum gravity. Their transport equations may be used either in a semi-recursive approach to determining their covariant Taylor series expansions, or as the basis of numerical calculations. To illustrate the power of the semi-recursive approach, we present an implementation in Mathematica, which computes very high order covariant series expansions of these objects. Using this code, a moderate laptop can, for example, calculate the coincidence limit $[a_7(x,x)]$ and $V(x,x^{\prime })$ to order $({\sigma }^a{)}^{20}$ in a matter of minutes. Results may be output in either a compact notation or in xTensor form. In a second application of the approach, we present a scheme for numerically integrating the transport equations as a system of coupled ordinary differential equations. As an example application of the scheme, we integrate along null geodesics to solve for $V(x,x^{\prime })$ in Nariai and Schwarzschild spacetimes.

Using a well-established effective interaction in a rainbow-ladder truncation model of QCD, we fix the remaining model parameter to the bottomonium ground-state spectrum in a covariant Bethe-Salpeter equation approach and find surprisingly good agreement with the available experimental data including the $2^{--}$ ${\rm Y}(1D)$ state. Furthermore, we investigate the consequences of such a fit for charmonium and light-quark ground states.

We study the high speed collision and reconnection of Abrikosov–Nielsen–Olesen cosmic strings in the type-II regime of the Abelian Higgs model, that is, scalar-to-gauge mass ratios larger than 1. Qualitatively, new phenomena such as multiple reconnections and clustering of small-scale structure have been observed in the deep type-II regime and reported in a previous paper, as well as the fact that the previously observed “loop” that mediates the second intercommutation is only a loop for sufficiently large mass ratios. Here we give a more detailed account of our study, which involves 3D numerical simulations with the parameter $\beta =m_{\mathrm{scalar}}^2/m_{\mathrm{gauge}}^2$ in the range $1\le \beta \le 64$, the largest value simulated to date, as well as 2D simulations of vortex-antivortex head-on collisions to understand their possible relation to the new 3D phenomena. Our simulations give further support to the ideas that Abelian Higgs strings never pass through each other, even at ultrarelativistic speeds, unless this is the result of a double reconnection; and that the critical velocity for double reconnection goes down with increasing mass ratio, but energy conservation suggests a lower bound around 0.77 c. We discuss the qualitative change in the intermediate state observed for large mass ratios. We relate it to a similar change in the outcome of 2D vortex-antivortex collisions in the form of radiating bound states, whereas we find no evidence of the back-to-back reemergence reported in previous studies. In the deep type-II regime the angular dependence of the critical speed for double reconnection does not seem to conform to the semianalytic predictions based on the Nambu-Goto approximation. We can model the high angle collisions reasonably well by incorporating the effect of core interactions, and the torque they produce on the approaching strings, into the Nambu-Goto description of the collision. An interesting, counterintuitive aspect is that the effective collision angle is smaller (not larger) as a result of the torque. Our results suggest differences in network evolution and radiation output with respect to the predictions based on Nambu-Goto or $\beta =1$ Abelian Higgs dynamics.

We expose simple and practical relations between the integrated four- and five-point one-loop amplitudes of $\mathcal{N}\ge 4$ supergravity and the corresponding (super-)Yang-Mills amplitudes. The link between the amplitudes is simply understood using the recently uncovered duality between color and kinematics that leads to a double-copy structure for gravity. These examples provide additional direct confirmations of the duality and double-copy properties at loop level for a sample of different theories.

We investigate the effect of matter density fluctuations on supernova collective neutrino flavor oscillations. In particular, we use full multiangle, three-flavor, self-consistent simulations of the evolution of the neutrino flavor field in the envelope of an O-Ne-Mg core-collapse supernova at shock breakout (neutronization neutrino burst) to study the effect of the matter density “bump” left by the He-burning shell. We find a seemingly counterintuitive increase in the overall ${\nu }_{\mathrm{e}}$ survival probability created by this matter density feature. We discuss this behavior in terms of the interplay between the matter density profile and neutrino collective effects. While our results give new insights into this interplay, they also suggest an immediate consequence for supernova neutrino burst detection: it will be difficult to use a burst signal to extract information on fossil burning shells or other fluctuations of this scale in the matter density profile. Consistent with previous studies, our results also show that the interplay of neutrino self-coupling and matter fluctuation could cause a significant increase in the ${\nu }_{\mathrm{e}}$ survival probability at very low energy.

We study the generalization of QED synchrotron radiation to the QCD case with a chromomagnetic field using the Schwinger et al. source method. It is shown that the QED case can be obtained as a special limit. The comparison with the path integral approach of Zakharov has shown consistent results.

We study the stability and chaos of three compact objects using post-Newtonian (PN) equations of motion derived from the Arnowitt-Deser-Misner-Hamiltonian formulation. We include terms up to 2.5 PN order in the orbital part and the leading order in spin corrections. We performed numerical simulations of a hierarchical configuration of three compact bodies in which a binary system is perturbed by a third, lighter body initially positioned far away from the binary. The relative importance of the different PN orders is examined. The basin boundary method and the computation of Lyapunov exponent were employed to analyze the stability and chaotic properties of the system. The 1 PN terms produced a small but noticeable change in the stability regions of the parameters considered. The inclusion of spin or gravitational radiation does not produce a significant change with respect to the inclusion of the 1 PN terms.

Gamma rays from the annihilation of dark matter particles in the Galactic halo provide a particularly promising means of indirectly detecting dark matter. Here, we demonstrate that pronounced spectral features at energies near the dark matter particles’ mass, which are a generic prediction for most models, can significantly improve the sensitivity of gamma-ray telescopes to dark matter signals. We derive projected limits on such features (including the traditionally looked-for line signals) and show that they can be much more efficient in constraining the nature of dark matter than the model-independent broad spectral features expected at lower energies.

We investigate thermal leptogenesis in a supersymmetric neutrinophilic Higgs model by taking phenomenological constraints into account, where, in addition to the minimal supersymmetric standard model, we introduce an extra Higgs field with a tiny vacuum expectation value which generates neutrino masses. Thanks to this tiny vacuum expectation value of the neutrinophilic Higgs, our model allows us to reduce the mass of the lightest right-handed (s)neutrino to be $\mathcal{O}({10}^5)\mathrm{GeV}$, keeping sufficiently large $CP$ asymmetry in its decay. Therefore, the reheating temperature after inflation is not necessarily high; hence this scenario is free from the gravitino problem.

We revisit the cosmological evolution of domain wall networks, taking advantage of recent improvements in computing power. We carry out high-resolution field theory simulations in two, three and four spatial dimensions to study the effects of dimensionality and damping on the evolution of the network. Our results are consistent with the expected scale-invariant evolution of the network, which suggests that previous hints of deviations from this behavior may have been due to the limited dynamical range of those simulations. We also use the results of very large (${1024}^3$) simulations in three cosmological epochs to provide a calibration for the velocity-dependent one-scale model for domain walls: we numerically determine the two free model parameters to have the values $c_w=0.5\pm 0.2$ and $k_w=1.1\pm 0.3$.

One distinguishes between “true” $CP$-violating triple-product (TP) asymmetries which require no strong phases and “fake” asymmetries which are due to strong phases but require no $CP$ violation. So far a single true TP asymmetry has been measured in $K_L\to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$. A general discussion is presented for $T$-odd TP asymmetries in four-body decays. It is shown that TP asymmetries vanish for two identical and kinematically indistinguishable particles in the final state. Two examples are $D^0\to K^{-}{\pi }^{+}{\pi }^{-}{\pi }^{+}$ and $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}{\pi }^0$. A nonzero TP asymmetry can be expected when nontrivial kinematic correlations exist, as in the decay $K_L\to e^{+}{e}^{-}{e}^{+}{e}^{-}$. Triple-product asymmetries measured in charmed particle decays indicate an interesting pattern of final-state interactions. We reiterate a discussion of TP asymmetries in $B$ meson decays to two vector mesons each decaying to a pseudoscalar pair, extending results to decays where one vector meson decays into a lepton pair. We derive expressions for time-dependent TP asymmetries for neutral $B$ decays to flavorless states in terms of the neutral $B$ mass difference $\Delta m$ and the width-difference $\Delta \Gamma$. Time-integrated true $CP$-violating asymmetries, measurable for untagged $B_s$ decays, are shown to be suppressed by neither ${\Gamma }_s/\Delta m_s$ nor $\Delta {\Gamma }_s/{\Gamma }_s$ if transversity amplitudes for $CP$-even and $CP$-odd states involve different weak phases. In contrast, fake asymmetries require flavor tagging and are suppressed by the former ratio when time integrated. We apply our results to $B\to K^{*}\varphi$ and $B_s\to \varphi \varphi$ data and suggest an application for $B_s\to J/\psi \varphi$.

This paper seeks to demonstrate that many of the existing mass-measurement variables proposed for hadron colliders ($m_T$, $m_{\mathrm{eff}}$, $m_{T2}$, missing ${\overrightarrow{p}}_T$, $h_T$, ${\sqrt{\widehat{s}}}_{\min }$, etc.) are far more closely related to each other than is widely appreciated, and indeed can all be viewed as a common mass-bound specialized for a variety of purposes. A consequence of this is that one may understand better the strengths and weaknesses of each variable, and the circumstances in which each can be used to best effect. In order to achieve this, we find it necessary first to revisit the seemingly empty and infertile wilderness populated by the subscript “$T$” (as in “${\mathrm{p̸}}_T$”) in order to remind ourselves what this process of transversification actually means. We note that, far from being simple, transversification can mean quite different things to different people. Those readers who manage to battle through the barrage of transverse notation distinguishing “$\top$” from “$\vee$” or from “$\circ$,” and “early projection” from “late projection,” will find their efforts rewarded towards the end of the paper with (i) a better understanding of how collider mass variables fit together, (ii) an appreciation of how these variables could be generalized to search for things more complicated than supersymmetry, (iii) will depart with an aversion to thoughtless or naïve use of the so-called transverse methods of any of the popular computer Lorentz-vector libraries, and (iv) will take care in their subsequent papers to be explicit about which of the 61 identified variants of the “transverse mass” they are employing.

Particle physics models with more than one Higgs boson occur in many frameworks for physics beyond the standard model, including supersymmetry, technicolor, composite Higgs, and “little Higgs” models. If the Higgs sector contains couplings stronger than electroweak gauge couplings, there will be heavy Higgs particles that decay to lighter Higgs particles plus heavy particles such as $W$, $Z$, and $t$. This motivates searches for final states involving multiple $W$, $Z$, $t$, and $\overline{b}b$ pairs. A two Higgs doublet model with custodial symmetry is a useful simplified model to describe many of these signals. The model can be parameterized by the physical Higgs masses and the mixing angles $\alpha$ and $\beta$, so discovery or exclusion in this parameter space has a straightforward physical interpretation. We illustrate this with a detailed analysis of the process $gg\to A$ followed by $A\to hZ$ and $h\to WW$. For $m_A\simeq 330\mathrm{GeV}$, $m_h\simeq 200\mathrm{GeV}$ we can get a $4.5\sigma$ signal with $1{\mathrm{fb}}^{-1}$ of integrated luminosity at the Large Hadron Collider.

One of the main channels which allows for a large rate of neutralino dark matter annihilation in the early Universe is via the pseudoscalar Higgs $A$-resonance. In this case, the measured dark matter abundance can be obtained in the minimal supergravity (mSUGRA) model when $\tan \beta \sim 50$ and $2m_{{\tilde{Z}}_1}\sim m_A$. We investigate the reaction $pp\to b\varphi \to b{\mu }^{+}{\mu }^{-}+X$ (where $\varphi =A$ or $H$) at the CERN LHC where requiring the tag of a single $b$-jet allows for amplification of the signal-to-background ratio. The rare but observable Higgs decay to muon pairs allows for a precise measurement of the Higgs boson mass and decay width. We evaluate signal and background using CalcHEP, with muon energy smearing according to the CMS detector. We find that the Higgs width (${\Gamma }_A$) can typically be determined with the accuracy up to $\sim 8\%$ ($\sim 17\%$) for $m_A\sim 400(600)\mathrm{GeV}$ assuming ${10}^3{\mathrm{fb}}^{-1}$ of integrated luminosity. Therefore, the $pp\to b\varphi \to b{\mu }^{+}{\mu }^{-}+X$ process provides a unique possibility for direct ${\Gamma }_A$ measurement at the LHC. While the Higgs width is correlated with the parameter $\tan \beta$ for a given value of $m_A$, extracting $\tan \beta$ is complicated by an overlap of the $A$ and $H$ peaks, radiative corrections to the $b$ and $\tau$ Yukawa couplings, and the possibility that SUSY decay modes of the Higgs may be open. In the case where a dilepton mass edge from ${\tilde{Z}}_2\to {\ell }^{+}{\ell }^{-}{\tilde{Z}}_1$ is visible, it should be possible to test the relation that $2m_{{\tilde{Z}}_1}\sim m_A$.

The fate of R-parity in the context of the minimal supersymmetric standard model is a central issue which has profound implications for particle physics and cosmology. In this article, we discuss the possibility of testing the mechanism responsible for the stability of the lightest supersymmetric particle at the Large Hadron Collider (LHC). The simplest theoretical framework where R-parity conservation can be explained dynamically allows for two types of B-L models. In the first scenario the new Higgses decay mainly into two right-handed neutrinos, giving rise to exotic lepton number violating signals together with displaced vertices. In the second model, one could have peculiar channels with multileptons and/or multiphotons in the final state. In both cases, the local B-L gauge symmetry is broken at the TeV scale and the discovery of the new Higgs bosons may be possible at the LHC. We investigate in detail the production mechanisms for the Higgs bosons relevant for the LHC and the key decays which would shed light on how R-parity is conserved. These results may help to understand the link between the cold dark matter of the universe and the missing energy that could be observed at the LHC if supersymmetry is realized in nature.

We perform a lattice QCD study of the $\rho$ meson decay from the $N_f=2+1$ full QCD configurations generated with a renormalization group improved gauge action and a nonperturbatively $O(a)$-improved Wilson fermion action. The resonance parameters, the effective $\rho \to \pi \pi$ coupling constant and the resonance mass, are estimated from the $P$-wave scattering phase shift for the isospin $I=1$ two-pion system. The finite size formulas are employed to calculate the phase shift from the energy on the lattice. Our calculations are carried out at two quark masses, $m_{\pi }=410\mathrm{MeV}$ ($m_{\pi }/m_{\rho }=0.46$) and $m_{\pi }=300\mathrm{MeV}$ ($m_{\pi }/m_{\rho }=0.35$), on a ${32}^3\times 64$ ($La=2.9\mathrm{fm}$) lattice at the lattice spacing $a=0.091\mathrm{fm}$. We compare our results at these two quark masses with those given in the previous works using $N_f=2$ full QCD configurations and the experiment.

We show that simultaneous precision measurements of the $CP$-violating phase in time-dependent $B_s\to J/\psi \varphi$ study and the $B_s\to {\mu }^{+}{\mu }^{-}$ rate, together with measuring $m_{t^{\prime }}$ by direct search at the LHC, would determine $V_{t^{\prime }s}^{*}{V}_{t^{\prime }b}$ and therefore the $b\to s$ quadrangle in the four-generation standard model. The forward–backward asymmetry in $B\to K^{*}{\ell }^{+}{\ell }^{-}$ provides further discrimination.