We compute the beta functions for the three gauge couplings of the Standard Model in the minimal subtraction scheme to three loops. We take into account contributions from all sectors of the Standard Model. The calculation is performed using both Lorenz gauge in the unbroken phase of the Standard Model and background field gauge in the spontaneously broken phase. Furthermore, we describe in detail the treatment of ${\gamma }_5$ and present the automated setup which we use for the calculation of the Feynman diagrams. It starts with the generation of the Feynman rules and leads to the bare result for the Green’s function of a given process.

In this paper we carried out a nonperturbative analysis of a thermal quasifermion in the chiral symmetric thermal QCD/QED medium by studying its self-energy function through the Dyson-Schwinger equation with the hard-thermal-loop resummed improved ladder kernel. Our analysis reveals several interesting results, two in some of which may force us to change the image of thermal quasifermions: (1) The thermal mass of a quasifermion begins to decrease as the strength of the coupling gets stronger and finally disappears in the strong coupling region, thus showing a property of a massless particle, and (2) its imaginary part (i.e., the decay width) persists to have $O(g^{2}T\log (1/g))$ behavior. These results suggest that in the recently produced strongly coupled quark-gluon plasma, the thermal mass of a quasiquark should vanish. Taking into account the largeness of the imaginary part, it seems very hard for a quark to exist as a qausiparticle in the strongly coupled quark-gluon plasma phase. Other important findings are as follows: (3) The collective plasmino mode disappears also in the strongly coupled system, and (4) there exists an ultrasoft third peak in the quasifermion spectral density at least in the weakly coupled QED/QCD plasma, indicating the existence of the ultrasoft fermionic mode.

We study the implications of light third generation sparticles on the production cross section and decay widths of a light $CP$-even Higgs boson. For simplicity, we consider scenarios in which only one of the sfermions from the third generation is light. For each case, we attempt to explain the apparently large enhancement in the Higgs production and decay in the diphoton channel with small deviations in the $ZZ$ channel. In the minimal supersymmetric standard model (MSSM) framework we find that only a light stau can explain these observations while keeping the lightest $CP$-even Higgs boson mass in the interval $123\mathrm{GeV}\lesssim m_h\lesssim 127\mathrm{GeV}$. For the light stop scenario, the observations related to the diphoton and $ZZ$ channel can be accommodated but, in order to satisfy the Higgs mass bound, one needs to go beyond the MSSM. In particular, we invoke vectorlike particles with masses around a TeV. These new particles preserve gauge coupling unification and provide additional contributions to the Higgs mass. With these new contributions a 126 GeV Higgs mass is easily achieved. We also find that with only a light sbottom quark, the above mentioned excess is hard to accommodate.

We consider a renormalizable messenger sector with magic messenger fields instead of the usual SU(5) complete multiplets. We derive the soft supersymmetry breaking terms and show that the gaugino sector can be parametrized by only two parameters. These parameters can be chosen appropriately to obtain various patterns of gaugino masses and different ratios among them. The sfermion sector can also be characterized by two independent parameters which can be adjusted to change the relative masses of squarks and sleptons. A judicious choice of parameters also allows us to achieve the lightest Higgs boson mass, about 125 GeV. In this paper we focus on a scenario where a comparatively large hierarchy exists between the U(1) and SU(2) gaugino mass parameters. In such a case, the lightest Higgs boson originating from the decay of the next-to-lightest neutralino, following the direct production of a chargino neutralino pair, can be considerably boosted. We show that a boosted supersymmetric Higgs signal with a decent signal-to-background ratio can be obtained using the jet substructure technique at the LHC with 8 TeV (14 TeV) center-of-mass energy and an integrated luminosity of about $30{\mathrm{fb}}^{-1}$ ($15{\mathrm{fb}}^{-1}$).

We study the D-term effect on runaway directions of the F-term scalar potential. A minimal renormalizable model is presented where supersymmetry is broken without any pseudomoduli. The model is applied to the hidden sector of gauge mediation for spontaneously breaking $R$ symmetry and generating nonvanishing gaugino masses at the one-loop order.

Transverse single-spin asymmetries in inclusive deep inelastic lepton-nucleon scattering can be generated through multiphoton exchange between the leptonic and the hadronic part of the process. Here we consider the two-photon exchange and mainly focus on the transverse target spin asymmetry. In particular, we investigate the case where two photons couple to different quarks. Such a contribution involves a quark-photon-quark correlator in the nucleon, which has a (model-dependent) relation to the Efremov-Teryaev-Qiu-Sterman quark-gluon-quark correlator $T_F$. Using different parametrizations for $T_F$ we compute the transverse target spin asymmetries for both a proton and a neutron target and compare the results to recent experimental data. In addition, potential implications for our general understanding of single-spin asymmetries in hard scattering processes are discussed.

Nucleon magnetic moments display a rich nonanalytic dependence on the quark mass in both quenched and full QCD. They provide a forum for a detailed examination of the connection between quenched and full QCD made possible through the formalism of finite-range regularized chiral effective field theory. By defining meson-cloud and core contributions through the careful selection of a regularization scale, one can correct the meson cloud of quenched QCD to make full QCD predictions. Whereas past success is based on unquenching the leading-order loop contributions, here we extend and test the formalism including next-to-leading-order loop contributions. We discuss the subtleties associated with working at next-to-leading order and illustrate the role of higher-order corrections.

Within a nuclear model where the deuteron has $NN$ and $\pi NN$ components, we derive a convolution formula for investigating the Drell-Yan process in proton-deuteron ($pd$) reactions. The contribution from the $\pi NN$ component is expressed in terms of a pion momentum distribution that depends sensitively on the $\pi NN$ form factor. With a $\pi NN$ form factor determined by fitting the $\pi N$ scattering data up to invariant mass $W=1.3\mathrm{GeV}$, we find that the pion-exchange and nucleon Fermi-motion effects can change significantly the ratios between the proton-deuteron and proton-proton Drell-Yan cross sections, $R_{pd/pp}={\sigma }^{pd}/(2{\sigma }^{pp})$, in the region where the partons emitted from the target deuteron are in the Bjorken $x_2\gtrsim 0.4$ region. The calculated ratios $R_{pd/pp}$ at 800 GeV agree with the available data. Predictions at 120 GeV for analyzing the forthcoming data from Fermilab are presented.

Pairs of top and antitop quarks are produced at the LHC to a large extent in association with a hard jet. We investigate the charge asymmetry in $t\overline{t}+j$ production in quantum chromodynamics (QCD) and with additional massive color-octet vector bosons. The total charge asymmetry at the LHC is suppressed by the large charge-symmetric background from gluon-gluon fusion. We show to what extent the asymmetry can be enhanced by suitable phase space cuts and, in particular, elaborate on the kinematics of the hard jet in the $t\overline{t}+j$ final state. We demonstrate that in QCD, the asymmetry amounts to 1.5% for central jets without an excessive reduction of the cross section. By applying additional kinematical cuts, the asymmetry can be enhanced to 4%, but at the cost of a strong reduction of the cross section. Massive color-octet states can generate sizeable effects in $t\overline{t}+j$ production, both on the charge asymmetry and on the cross section. The charge asymmetry probes both vector and axial-vector couplings to quarks. We show that massive color octets can generate asymmetries up to $\pm 10\%$ for moderate and up to $\pm 30\%$ for strong kinematical cuts to be used in experimental analyses at the LHC. Jet kinematics can be used to obtain further information about the nature of the couplings and thereby to discriminate between different models.

Introducing $n$ right-handed neutrinos to the Standard Model yields, in general, massive active neutrinos. We give explicit parametrizations for the involved mixing and coupling matrices in terms of physical parameters for both the top-down and the bottom-up approach for arbitrary $n$. Bounds on the complex mixing angles in the bottom-up approach from perturbativity of the Yukawa couplings to charged lepton flavor violation are discussed. As a novel illustration of possible effects from $n\ne 3$, we extend the neutrino anarchy framework to arbitrary $n$; we show that while the anarchic mixing angles are insensitive to the number of singlets, the observed ratios of neutrino masses prefer small $n$ for the simplest linear measure.

We present a study of ${\tau }^{-}\to {\pi }^{-}{K}_S^0{K}_S^0({\pi }^0){\nu }_{\tau }$ and ${\tau }^{-}\to K^{-}{K}_S^0{K}_S^0({\pi }^0){\nu }_{\tau }$ decays using a data set of 430 million $\tau$ lepton pairs, corresponding to an integrated luminosity of $468{\mathrm{fb}}^{-1}$, collected with the BABAR detector at the PEP-II asymmetric energy $e^{+}{e}^{-}$ storage rings. We measure branching fractions of $(2.31\pm 0.04\pm 0.08)\times {10}^{-4}$ and $(1.60\pm 0.20\pm 0.22)\times {10}^{-5}$ for the ${\tau }^{-}\to {\pi }^{-}{K}_S^0{K}_S^0{\nu }_{\tau }$ and ${\tau }^{-}\to {\pi }^{-}{K}_S^0{K}_S^0{\pi }^0{\nu }_{\tau }$ decays, respectively. We find no evidence for ${\tau }^{-}\to K^{-}{K}_S^0{K}_S^0{\nu }_{\tau }$ and ${\tau }^{-}\to K^{-}{K}_S^0{K}_S^0{\pi }^0{\nu }_{\tau }$ decays and place upper limits on the branching fractions of $6.3\times {10}^{-7}$ and $4.0\times {10}^{-7}$ at the 90% confidence level.

We present a measurement of the branching fraction and time-dependent $CP$ violation parameters in $B^0\to a_1^{\pm }(1260){\pi }^{\mp }$ decays. The results are obtained from the final data sample containing $772\times {10}^6$ $B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We obtain the product branching fraction $\mathcal{B}(B^0\to a_1^{\pm }(1260){\pi }^{\mp })\times \mathcal{B}(a_1^{\pm }(1260)\to {\pi }^{\pm }{\pi }^{\mp }{\pi }^{\pm })=(11.1\pm 1.0(\mathrm{stat})\pm 1.4(\mathrm{syst}))\times {10}^{-6}$ and an upper limit on the product branching fraction for a possible decay with the same final state $\mathcal{B}(B^0\to a_2^{\pm }(1320){\pi }^{\mp })\times \mathcal{B}(a_2^{\pm }(1320)\to {\pi }^{\pm }{\pi }^{\mp }{\pi }^{\pm })<2.2\times {10}^{-6}\mathrm{\text{at}}90\%\mathrm{CL}$. In a time-dependent measurement to extract $CP$ asymmetries, we obtain the $CP$ violation parameters ${\mathcal{A}}_{CP}=-0.06\pm 0.05(\mathrm{stat})\pm 0.07(\mathrm{syst})$, ${\mathcal{C}}_{CP}=-0.01\pm 0.11(\mathrm{stat})\pm 0.09(\mathrm{syst})$, ${\mathcal{S}}_{CP}=-0.51\pm 0.14(\mathrm{stat})\pm 0.08(\mathrm{syst})$, representing time- and flavor-integrated direct, flavor-dependent direct and mixing-induced $CP$ violation, respectively. Simultaneously, we also extract the $CP$-conserving parameters $\Delta \mathcal{C}=+0.54\pm 0.11(\mathrm{stat})\pm 0.07(\mathrm{syst})$, $\Delta \mathcal{S}=-0.09\pm 0.14(\mathrm{stat})\pm 0.06(\mathrm{syst})$, which, respectively, describe a rate difference and strong phase difference between the decay channels where the $a_1^{\pm }$ does not contain the spectator quark and those where it does. We find first evidence of mixing-induced $CP$ violation in $B^0\to a_1^{\pm }(1260){\pi }^{\mp }$ decays with $3.1\sigma$ significance. The rate where the $a_1^{\pm }$ does not contain the spectator quark from the $B$ meson is found to dominate the rate where it does at the $4.1\sigma$ level. However, there is no evidence for either time- and flavor-integrated direct $CP$ violation or flavor-dependent direct $CP$ violation.

We investigate the decay $B_s^0\to J/\psi K^{+}{K}^{-}$ for invariant masses of the $K^{+}{K}^{-}$ pair in the range $1.35<M(K^{+}{K}^{-})<2\mathrm{GeV}$. The data sample corresponds to an integrated luminosity of $10.4{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ accumulated with the D0 detector at the Fermilab Tevatron collider. From the study of the invariant mass and spin of the $K^{+}{K}^{-}$ system, we find evidence for the two-body decay $B_s^0\to J/\psi f_2^{\prime }(1525)$ and measure the relative branching fraction of the decays $B_s^0\to J/\psi f_2^{\prime }(1525)$ and $B_s^0\to J/\psi \varphi$ to be $R_{f_2^{\prime }/\varphi }=0.19\pm 0.05(\mathrm{stat})\pm 0.04(\mathrm{syst})$.

This paper presents a search for a new heavy particle produced in association with a top or antitop quark. Two models in which the new heavy particle is a color singlet or a color triplet are considered, decaying, respectively, to $\overline{t}q$ or $tq$, leading to a resonance within the $t\overline{t}+\mathrm{\text{jets}}$ signature. The full 2011 ATLAS $pp$ collision data set from the LHC ($4.7{\mathrm{fb}}^{-1}$) is used to search for $t\overline{t}$ events produced in association with jets, in which one of the $W$ bosons from the top quarks decays leptonically and the other decays hadronically. The data are consistent with the Standard Model expectation, and a new particle with mass below 430 Gev for both $W^{\prime }$ boson and color triplet models is excluded at 95% confidence level, assuming unit right-handed coupling.

We combine the next-to-next-to-leading order QCD corrections to lepton-pair production through the Drell-Yan mechanism with the next-to-leading order (NLO) electroweak corrections within the framework of the Fully Exclusive W and Z Production (FEWZ) simulation code. Control over both sources of higher-order contributions is necessary for measurements where percent-level theoretical predictions are crucial and in phase-space regions where the NLO electroweak corrections grow large. The inclusion of both corrections in a single simulation code eliminates the need to separately incorporate such effects as final-state radiation and electroweak Sudakov logarithms when comparing many experimental results to theory. We recalculate the NLO electroweak corrections in the complex-mass scheme for both massless and massive final-state leptons, and modify the QCD corrections in the original FEWZ code to maintain consistency with the complex-mass scheme to the lowest order. We present phenomenological results for LHC studies that include both next-to-next-to-leading order QCD and NLO electroweak corrections. In addition, we study several interesting kinematics features induced by experimental cuts in the distribution of photon radiation at the LHC.

Through the AdS/CFT correspondence, Lifshitz spacetimes describe field theories with dynamical scaling ($z\ne 1$). Although curvature invariants are small, the Lifshitz metric exhibits a null singularity in the IR with a large tidal force that excites string oscillator modes. However, Lifshitz is not a vacuum solution of the Einstein equations—the metric is supported by nontrivial matter content which must be taken into account in analyzing the propagation of test objects. In this paper, we consider the interaction of a string with a D0-brane density in the IR which supports a class of UV-complete $z=2$ Lifshitz constructions. We show that string/D-brane scattering in the Regge limit slows the string significantly, preventing divergent mode production and resolving the would-be singularity in string propagation.

We investigate the properties of holographic fermions in charged Lifshitz black holes at finite temperature through the AdS/CFT correspondence. In the charged Lifshitz background with the dynamical exponent $z=2$, we find that the dispersion relation is linear. The scaling behavior of the imaginal part of the Green function relative to $k_{\perp }=k-k_F$ is also discussed. We find, although the system has a linear dispersion relation and quadratic quasiparticle width, it does not satisfy Luttinger’s theorem. We also find that the variation of the scaling parameters $\alpha$ and $\beta$ is small as the charge $q$ varies. Furthermore, we also discuss the effect of the dynamical exponent $z$ by considering the cases $z=4$ and $z=6$ and show that $\mathrm{Im}{G}_{ii}$ become smooth when the dynamical exponent $z$ increases.

We consider the four-dimensional quantum electrodynamics extended with Myers-Pospelov Lorentz-violating dimension-five operators to investigate 4D-2D projection. In projecting out the 4D theory down to a 2D theory, we get analogs of these operators. Namely, we obtain a new two-dimensional theory with corresponding scalar and fermionic 2D Myers-Pospelov Lorentz-violating dimension-three operators. New defect structures can also be found from this new projected-out 2D scalar sector. Furthermore, we also show that this 2D scalar sector can also be radiatively induced through the new 2D fermionic sector.

In this article we considered models of particles living in a three-dimensional space-time with a nonstandard noncommutativity induced by shifting canonical coordinates and momenta with generators of a unitary irreducible representation of the Lorentz group. The Hilbert space gets the structure of a direct product with the representation space, where we are able to construct operators which realize the algebra of Lorentz transformations. We study the modified Landau problem for both Schrödinger and Dirac particles, whose Hamiltonians are obtained through a kind of non-Abelian Bopp’s shift of the dynamical variables from the ones of the usual problem in the normal space. The spectrum of these models are considered in perturbation theory, both for small and large noncommutativity parameters. We find no constraint between the parameters referring to noncommutativity in coordinates and momenta but they rather play similar roles. Since the representation space of the unitary irreducible representations $SL(2,\mathbb{R})$ can be realized in terms of spaces of square-integrable functions, we conclude that these models are equivalent to quantum mechanical models of particles living in a space with an additional compact dimension.

In the context of noncommutative geometries, we develop a group Fourier transform for the Lie group SU(2). Our method is based on the Schwinger representation of the Lie algebra $\mathfrak{s}\mathfrak{u}(2)$ in terms of spinors. It allows us to prove that the noncommutative ${\mathbb{R}}^3$ space dual to the SU(2) group is in fact of the Moyal type and endowed with the Voros star product when expressed in the spinor variables. Finally, from the perspective of quantum gravity, we discuss the application of these new tools to group field theories for spinfoam models and their interpretation as noncommutative field theories with quantum-deformed symmetries.