The physical pole and running masses of squarks and gluinos have recently been related at two-loop order in a mass-independent renormalization scheme. I propose a general method for improvement of such formulas, and argue that better accuracy results. The improved version gives an imaginary part of the pole mass that agrees exactly with the direct calculation of the physical width at next-to-leading order. I also find the leading three-loop contributions to the gluino pole mass in the case that squarks are heavier, using effective field theory and renormalization-group methods. The efficacy of these improvements for the gluino and squarks is illustrated with numerical examples. Some necessary three-loop results for gauge coupling and fermion mass beta functions and pole masses in theories with more than one type of fermion representation, which are not directly accessible from the published literature, are presented in an Appendix.

Based on lattice simulations with two flavors of dynamical, $\mathcal{O}(a)$-improved Wilson fermions we present results for the first two moments of the distribution amplitudes of pseudoscalar mesons at several values of the valence quark masses. By extrapolating our results to the physical masses of up/down and strange quarks, we find the first two moments of the $K^{+}$ distribution amplitude and the second moment of the ${\pi }^{+}$ distribution amplitude. We use nonperturbatively determined renormalization coefficients to obtain results in the $\overline{\mathrm{MS}}$ scheme. At a scale of $4{\mathrm{GeV}}^2$ we find $a_2^{\pi }=0.201(114)$ for the second Gegenbauer moment of the pion’s distribution amplitude, while for the kaon, $a_1^K=0.0453(9)(29)$ and $a_2^K=0.175(18)(47)$.

We consider single-inclusive forward pion production in high-energy proton-proton collisions at RHIC energies. A good baseline description of the transverse momentum distributions at high rapidity is obtained within Mueller’s dipole formalism with an anomalous dimension incorporating an “extended geometric scaling” window between the saturation and DGLAP regimes. We then formulate pion production for transversely polarized projectiles within the same approach. We assume that an azimuthal, spin-dependent asymmetry arises from the so-called Sivers effect and investigate the single transverse-spin asymmetry $A_N$ at 200 GeV and 500 GeV center-of-mass energy. A simple parametrization of the Sivers functions from the literature compares reasonably well with the high-energy STAR data if the overall normalization is scaled up by at least a factor of 2. The STAR data might therefore indicate that the Sivers effect is significantly stronger than thought so far. We also analyze higher-twist contributions to $A_N$ and find that they largely cancel.

We study elementary particle reactions that result from the interaction of an atomic system with a very intense laser wave of circular polarization. As a specific example, we calculate the rate for the laser-driven reaction $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$, where the electron and positron originate from a positronium atom or, alternatively, from a nonrelativistic $e^{+}{e}^{-}$ plasma. We distinguish accordingly between the coherent and incoherent channels of the process. Apart from numerical calculations, we derive by analytical means compact formulas for the corresponding reaction rates. The rate for the coherent channel in a laser field of circular polarization is shown to be damped because of the destructive interference of the partial waves that constitute the positronium ground-state wave packet. Conditions for the observation of the process via the dominant incoherent channel in a circularly polarized field are pointed out.

We present a simultaneous analysis, within an impact parameter dependent saturated dipole model, of exclusive diffractive vector meson ($J/\psi$, $\varphi$, and $\rho$) production, deeply virtual Compton scattering and the total ${\gamma }^{*}p$ cross section data measured at HERA. Various cross sections measured as a function of the kinematic variables $Q^2$, $W$ and $t$ are well described, with little sensitivity to the details of the vector meson wave functions. We determine the properties of the gluon density in the proton in both longitudinal and transverse dimensions, including the impact parameter dependent saturation scale. The overall success of the description indicates universality of the emerging gluon distribution and proton shape.

Within the LO QCD parton model of Semi-Inclusive Deep Inelastic Scattering, $\ell N\to \ell hX$, with unintegrated quark distribution and fragmentation functions, we study the ${\mathit{P}}_{hT}$ dependence of the double longitudinal-spin asymmetry $A_{LL}$. We include $1/Q$ kinematic corrections, which induce an azimuthal modulation of the asymmetry, analogous to the Cahn effect in unpolarized SIDIS. We show that a study of $A_{LL}$ and of the weighted DSA $A_{LL}^{\cos {\varphi }_h}$ allows to extract the transverse momentum dependence of the unintegrated helicity distribution function $g_{1L}^q(x,k_{\perp })$ [or $\Delta q(x,k_{\perp })]$. Predictions, based on some models for the unknown functions, are given for ongoing COMPASS, HERMES and JLab experiments.

The exclusive production of pairs of vector mesons with $J^{PC}=1^{--}$ in $e^{+}{e}^{-}$ collisions can proceed through $e^{+}{e}^{-}$ annihilation into two virtual photons. At energies much greater than the meson masses, the cross section is dominated by the independent fragmentation of the virtual photons into the vector mesons. The fragmentation approximation is used to calculate the cross sections and angular distributions for pairs of vector mesons that can be produced at the $B$ factories. The predicted cross sections for ${\rho }^0+{\rho }^0$ and ${\rho }^0+\varphi$ production agree with recent measurements by the BABAR Collaboration. For the production of two charmonium vector mesons, the nonfragmentation corrections to the cross sections are calculated by using the NRQCD factorization formalism. The predicted cross sections for $J/\psi +J/\psi$ and $J/\psi +\psi (2S)$ production are compatible with upper limits set by the Belle Collaboration.

We present a search for the decay of a $B^0$ or ${\overline{B}}^0$ meson to a ${\overline{K}}^{*0}{K}^0$ or $K^{*0}{\overline{K}}^0$ final state, using a sample of approximately $232\times {10}^6$ $B\overline{B}$ events collected with the BABAR detector at the PEP-II asymmetric energy $e^{+}{e}^{-}$ collider at SLAC. The measured branching fraction is $\mathcal{B}(B^0\to {\overline{K}}^{*0}{K}^0)+\mathcal{B}(B^0\to K^{*0}{\overline{K}}^0)=({0.2}_{-0.8-0.3}^{+0.9+0.1})\times {10}^{-6}$. We obtain the following upper limit for the branching fraction at 90% confidence level: $\mathcal{B}(B^0\to {\overline{K}}^{*0}{K}^0)+\mathcal{B}(B^0\to K^{*0}{\overline{K}}^0)<1.9\times {10}^{-6}$. We use our result to constrain the standard model prediction for the deviation of the $CP$ asymmetry in $B^0\to \varphi K^0$ from $\sin 2\beta$.

We present a measurement of the inclusive jet cross section in $p\overline{p}$ interactions at $\sqrt{s}=1.96\mathrm{TeV}$ using $385{\mathrm{pb}}^{-1}$ of data collected with the CDF II detector at the Fermilab Tevatron. The results are obtained using an improved cone-based jet algorithm (Midpoint). The data cover the jet transverse momentum range from 61 to $620\mathrm{GeV}/c$, extending the reach by almost $150\mathrm{GeV}/c$ compared with previous measurements at the Tevatron. The results are in good agreement with next-to-leading order perturbative QCD predictions using the CTEQ6.1M parton distribution functions.

The decay of highly excited massive string states in compactified heterotic string theories is discussed. We calculate the decay rate and spectrum of states carrying momentum and winding in the compactified direction. The longest lived states in the spectrum are near Bogomol’nyi-Prasad-Sommerfield (BPS) states whose decay is dominated by a single decay channel of massless radiation which brings the state closer to being BPS.

We discuss the general question of which conformal field theories have dual descriptions in terms of quantum gravity theories on anti-de Sitter space. We analyze in detail the case of a deformed product of $n$ conformal field theories (each of which has a gravity dual), and we claim that the dual description of this is by a quantum gravity theory on a union of $n$ anti-de Sitter spaces, connected at their boundary (by correlations between their boundary conditions). On this union of spaces, ($n-1$) linear combinations of gravitons obtain a mass, and we compute this mass both from the field theory and from the gravity sides of the correspondence, finding the same result in both computations. This is the first example in which a graviton mass in the bulk of anti-de Sitter space arises continuously by varying parameters. The analysis of these deformed product theories leads us to suggest that field theories may be generally classified by a “connectivity index,” corresponding to the number of components (connected at the boundary) in the space-time of the dual gravitational background. In the field theory this index roughly counts the number of independent gauge groups, but we do not have a precise general formula for the index.

We calculate the one loop amplitudes for the two gluon scattering process in light cone gauge with fermions and scalars circulating in the loop. This extends the work of [D. Chakrabarti, J. Qiu, and C. B. Thorn, Phys. Rev. D 72, 065022 (2005)., D. Chakrabarti, J. Qiu, and C. B. Thorn, Phys. Rev. D 74, 045018 (2006)], in which only the gluon circulates the loop. By putting all fields in the adjoint representation with $N_f=2$, $N_s=6$, the scattering amplitude of gluon by gluon in the special case of $\mathcal{N}=4$ super Yang-Mills can be obtained. The massive fermion and scalar with arbitrary representations are also considered.

We compute the bulk viscosity $\zeta$ of high-temperature QCD to leading order in powers of the running coupling ${\alpha }_{\mathrm{s}}(T)$. We find that it is negligible compared to shear viscosity $\eta$ for any ${\alpha }_{\mathrm{s}}$ that might reasonably be considered small. The physics of bulk viscosity in QCD is a bit different than in scalar ${\varphi }^4$ theory. In particular, unlike in scalar theory, we find that an old, crude estimate of $\zeta \simeq 15(\frac{1}{3}-v_{\mathrm{s}}^2{)}^2\eta$ gives the correct order of magnitude, where $v_{\mathrm{s}}$ is the speed of sound. We also find that leading-log expansions of our result for $\zeta$ are not accurate except at very small coupling.

We construct a field theoretic version of 2T physics including interactions in an action formalism. The approach is a Becchi-Rouet-Stora-Tyutin (BRST) formulation based on the underlying $\mathrm{Sp}(2,R)$ gauge symmetry and shares some similarities with the approach used to construct string field theory. In our first case of spinless particles, the interaction is uniquely determined by the BRST gauge symmetry, and it is different than the Chern-Simons type theory used in open string field theory. After constructing a BRST gauge invariant action for 2T physics field theory with interactions in $d+2$ dimensions, we study its relation to standard 1T physics field theory in $(d-1)+1$ dimensions by choosing gauges. In one gauge we show that we obtain the Klein-Gordon field theory in $(d-1)+1$ dimensions with unique $\mathrm{SO}(d,2)$ conformal invariant self interactions at the classical field level. This $\mathrm{SO}(d,2)$ is the natural linear Lorentz symmetry of the 2T field theory in $d+2$ dimensions. As indicated in Fig. 1, in other gauges we expect to derive a variety of $\mathrm{SO}(d,2)$ invariant 1T physics field theories as gauge fixed forms of the same 2T field theory, thus obtaining a unification of 1T dynamics in a field theoretic setting, including interactions. The BRST gauge transformation should play the role of duality transformations among the 1T physics holographic images of the same parent 2T field theory. The availability of a field theory action opens the way for studying 2T physics with interactions at the quantum level through the path integral approach.

In this paper it will be shown that the standard model in $3+1$ dimensions is a gauge fixed version of a 2T physics field theory in $4+2$ dimensions, thus establishing that 2T physics provides a correct description of nature from the point of view of $4+2$ dimensions. The 2T formulation leads to phenomenological consequences of considerable significance. In particular, the higher structure in $4+2$ dimensions prevents the problematic $F*F$ term in QCD. This resolves the strong $CP$ problem without a need for the Peccei-Quinn symmetry or the corresponding elusive axion. Mass generation with the Higgs mechanism is less straightforward in the new formulation of the standard model, but its resolution leads to an appealing deeper physical basis for mass, coupled with phenomena that could be measurable. In addition, there are some brand new mechanisms of mass generation related to the higher dimensions that deserve further study. The technical progress is based on the construction of a new field theoretic version of 2T physics including interactions in an action formalism in $d+2$ dimensions. The action is invariant under a new type of gauge symmetry which we call 2T-gauge symmetry in field theory. This opens the way for investigations of the standard model directly in $4+2$ dimensions, or from the point of view of various embeddings of $3+1$ dimensions, by using the duality, holography, symmetry, and unifying features of 2T physics.

We examine the question of finding the supersymmetric completion of the $R^4$ term in M-theory. Using superfield methods, we present an eight-derivative action in eight dimensions that has 32 preserved supersymmetries. We show also that this action has a hidden 11-dimensional Lorentz invariance. It can thus be uplifted to give the complete set of bosonic terms in the M-theory eight-derivative action.

In this paper we study noncommutative black holes. We use a diffeomorphism between the Schwarzschild black hole and the Kantowski-Sachs cosmological model, which is generalized to noncommutative minisuperspace. Through the use of the Feynman-Hibbs procedure we are able to study the thermodynamics of the black hole, in particular, we calculate the Hawking’s temperature and entropy for the noncommutative Schwarzschild black hole.

We perform numerical simulations of black-hole binaries to study the exchange of spin and orbital angular momentum during the last, highly nonlinear, stages of the coalescence process. To calculate the transfer of angular momentum from orbital to spin, we start with two quasicircular configurations, one with initially nonspinning black holes, the other with corotating black holes. In both cases the binaries complete almost two orbits before merging. We find that, during these last orbits, the specific spin ($a/m$) of each horizon increases by only 0.012 for the initially nonspinning configuration, and by only 0.006 for the initially corotating configuration. By contrast, the corotation value for the specific spin should increase from 0.1 at the initial proper separation of $10M$ to 0.33 when the proper separation is $5M$. Thus the spin-orbit coupling is far too weak to tidally lock the binary to a corotating state during the late-inspiral phase. We also study the converse transfer from spin into orbital motion. In this case, we start the simulations with parallel, highly-spinning nonboosted black holes. As the collision proceeds, the system acquires a non-head-on orbital motion, due to spin-orbit coupling, that leads to the radiation of angular momentum. We are able to accurately measure the energy and angular momentum losses and model their dependence on the initial spins.

It is believed that soon after the Planck era, space-time should have a semiclassical nature. According to this, the escape from the general relativity theory is unavoidable. Two geometric counterterms are needed to regularize the divergences which come from the expected value. These counterterms are responsible for a higher derivative metric gravitation. Starobinsky’s idea was that these higher derivatives could mimic a cosmological constant. In this work numerical solutions are considered for general Bianchi I anisotropic space-times in this higher derivative theory. The approach is “experimental” in the sense that there is no attempt for an analytical investigation of the results. It is shown that for zero cosmological constant $\Lambda =0$, there are sets of initial conditions which form basins of attraction that asymptote Minkowski space. The complement of this set of initial conditions form basins which are attracted to some singular solutions. It is also shown, for a cosmological constant $\Lambda >0$, that there are basins of attraction to a specific de Sitter solution. This result is consistent with Starobinsky’s initial idea. The complement of this set also forms basins that are attracted to some type of singular solution. Because the singularity is characterized by curvature scalars, it must be stressed that the basin structure obtained is a topological invariant, i.e., coordinate independent.

Violations of Lorentz invariance that appear via operators of dimension four or less are completely parametrized in the Standard Model Extension (SME). In the pure photonic sector of the SME, there are 19 dimensionless, Lorentz-violating parameters. Eighteen of these have experimental upper bounds ranging between ${10}^{-11}$ and ${10}^{-32}$; the remaining parameter, ${\tilde{k}}_{\mathrm{tr}}$, is isotropic and has a much weaker bound of order ${10}^{-4}$. In this Brief Report, we point out that ${\tilde{k}}_{\mathrm{tr}}$ gives a significant contribution to the anomalous magnetic moment of the electron and find a new upper bound of order ${10}^{-8}$. With reasonable assumptions, we further show that this bound may be improved to ${10}^{-14}$ by considering the renormalization of other Lorentz-violating parameters that are more tightly constrained. Using similar renormalization arguments, we also estimate bounds on Lorentz-violating parameters in the pure gluonic sector of QCD.