We revisit the effects of QCD instantons in semi-inclusive deep inelastic scattering. We show that large single spin asymmetry (SSA) effects can be induced in longitudinally and transversely polarized proton targets. The results are in agreement with most of the reported data for pion and kaon production. The same effects are found to be important in polarized proton on proton scattering for both charged and chargeless pion productions. The results agree with the reported data in a wide range of $\sqrt{s}=19.4–200\mathrm{GeV}$. We predict the SSA for ${\pi }^{\pm }$ production in $p_{\uparrow }p$ in the collider range of $\sqrt{s}=62.4–500\mathrm{GeV}$. The backward ${\pi }^{\pm }$ and ${\pi }^0$ productions for the SSA in $p_{\uparrow }p$ collisions are predicted to coincide at large $\sqrt{s}$.

In this article we use the Schwinger–Dyson equations to compute the nonperturbative modifications caused to the infrared finite gluon propagator (in the Landau gauge) by the inclusion of a small number of quark families. Our basic operating assumption is that the main bulk of the effect stems from the “one-loop dressed” quark loop contributing to the full gluon self-energy. This quark loop is then calculated, using as basic ingredients the full quark propagator and quark-gluon vertex; for the quark propagator we use the solution obtained from the quark-gap equation, while for the vertex we employ suitable Ansätze, which guarantee the transversality of the answer. The resulting effect is included as a correction to the quenched gluon propagator, obtained in recent lattice simulations. Our main finding is that the unquenched propagator displays a considerable suppression in the intermediate momentum region, which becomes more pronounced as we increase the number of active quark families. The influence of the quarks on the saturation point of the propagator cannot be reliably computed within the present scheme; the general tendency appears to be to decrease it, suggesting a corresponding increase in the effective gluon mass. The renormalization properties of our results, and the uncertainties induced by the unspecified transverse part of the quark-gluon vertex, are discussed. Finally, the gluon propagator is compared with the available unquenched lattice data, showing rather good agreement.

We investigate the “scaling Ansatz” in the neutrino sector within the framework of a type-I seesaw mechanism with diagonal charged lepton and right-handed Majorana neutrino mass matrices ($M_R$). We also assume the four zero texture of Dirac neutrino mass matrices ($m_D$) which severely constrain the phenomenological outcomes of such schemes. The scaling Ansatz and the present neutrino data allow only six such matrices out of 126 four zero Yukawa matrices. In this scheme, in order to generate large ${\theta }_{13}$, we break the scaling Ansatz in $m_D$ through a perturbation parameter and we also show that our breaking scheme is radiatively stable. We further investigate $CP$ violation and baryogenesis via leptogenesis in those surviving textures.

We present a measurement of the elastic differential cross section $d\sigma (p\overline{p}\to p\overline{p})/dt$ as a function of the four-momentum-transfer squared $t$. The data sample corresponds to an integrated luminosity of $\approx 31{\mathrm{nb}}^{-1}$ collected with the D0 detector using dedicated Tevatron $p\overline{p}$ Collider operating conditions at $\sqrt{s}=1.96\mathrm{TeV}$ and covers the range $0.26<|t|<1.2{\mathrm{GeV}}^2$. For $|t|<0.6{\mathrm{GeV}}^2$, $d\sigma /dt$ is described by an exponential function of the form $A{e}^{-b|t|}$ with a slope parameter $b=16.86\pm 0.10(\mathrm{stat})\pm 0.20(\mathrm{syst}){\mathrm{GeV}}^{-2}$. A change in slope is observed at $|t|\approx 0.6{\mathrm{GeV}}^2$, followed by a more gradual $|t|$ dependence with increasing values of $|t|$.

The first dedicated search for ultrahigh-energy (UHE) tau neutrinos of astrophysical origin was performed using the IceCube detector in its 22-string configuration with an instrumented volume of roughly $0.25{\mathrm{km}}^3$. The search also had sensitivity to UHE electron and muon neutrinos. After application of all selection criteria to approximately 200 live-days of data, we expect a background of $0.60\pm 0.19(\mathrm{stat})\genfrac{}{}{0ex}{}{+0.56}{-0.58}(\mathrm{syst})$ events and observe three events, which after inspection, emerge as being compatible with background but are kept in the final sample. Therefore, we set an upper limit on neutrinos of all flavors from UHE astrophysical sources at 90% C.L. of $E_{\nu }^2{\Phi }_{90}({\nu }_{\mathrm{x}})<16.3\times {10}^{-8}\mathrm{GeV}{\mathrm{cm}}^{-2}{\mathrm{sr}}^{-1}{\mathrm{s}}^{-1}$ over an estimated primary neutrino energy range of 340 TeV to 200 PeV.

Naive dimensional analysis (NDA) is a widely used ansatz to estimate coupling constants among composite states emerging from dynamics of a strongly coupled gauge theory. However, the validity of NDA is still unclear because of the difficulty in calculating these quantities in strongly coupled theories. We examine the NDA ansatz using gauge/string duality, by estimating glueball coupling constants from gravitational description. The NDA scaling rule for coupling constants of some types of glueballs is verified and extended by both generic estimation and numerical calculations. The scaling rule verified in this article can be applied to some class of quiver gauge theories as well, not just to gauge theories with a single gauge group $SU(Nc)$.

We use gauge/gravity duality to study deeply virtual Compton scattering (DVCS) in the limit of high center of mass energy at fixed momentum transfer, corresponding to the limit of low Bjorken $x$, where the process is dominated by the exchange of the Pomeron. Using conformal Regge theory we review the form of the amplitude for Pomeron exchange, at both strong and weak ’t Hooft coupling. At strong coupling, the Pomeron is described as the graviton Regge trajectory in anti–de Sitter (AdS) space, with a hard wall to mimic confinement effects. This model agrees with HERA data in a large kinematical range. The behavior of the DVCS cross section for very high energies, inside saturation, can be explained by a simple AdS black disk model. In a restricted kinematical window, this model agrees with HERA data as well.

We study the implications at the LHC for a recent class of noncustodial warped extra-dimensional models where the ${\mathrm{AdS}}_5$ metric is modified near the infrared brane. Such models allow for TeV Kaluza-Klein excitations without conflict with electroweak precision tests. We discuss both the production of electroweak and strong Kaluza-Klein gauge bosons. As we will show, only signals involving the third generation of quarks seem to be feasible in order to probe this scenario.

In 2011, the XENON100 experiment has set unprecedented constraints on dark matter-nucleon interactions, excluding dark matter candidates with masses down to 6 GeV if the corresponding cross section is larger than ${10}^{-39}{\mathrm{cm}}^2$. The dependence of the exclusion limit in terms of the scintillation efficiency (${\mathcal{L}}_{\mathrm{eff}}$) has been debated at length. To overcome possible criticisms XENON100 performed an analysis in which ${\mathcal{L}}_{\mathrm{eff}}$ was considered as a nuisance parameter and its uncertainties were profiled out by using a Gaussian likelihood in which the mean value corresponds to the best fit ${\mathcal{L}}_{\mathrm{eff}}$ value (smoothly extrapolated to 0 below 3 keVnr). Although such a method seems fairly robust, it does not account for more extreme types of extrapolation nor does it enable us to anticipate how much the exclusion limit would vary if new data were to support a flat behavior for ${\mathcal{L}}_{\mathrm{eff}}$ below 3 keVnr, for example. Yet, such a question is crucial for light dark matter models which are close to the published XENON100 limit. To answer this issue, we use a maximum likelihood ratio analysis, as done by the XENON100 Collaboration, but do not consider ${\mathcal{L}}_{\mathrm{eff}}$ as a nuisance parameter. Instead, ${\mathcal{L}}_{\mathrm{eff}}$ is obtained directly from the fits to the data. This enables us to define frequentist confidence intervals by marginalizing over ${\mathcal{L}}_{\mathrm{eff}}$.

We investigate a potential of discovering lepton flavor violation (LFV) at the Large Hadron Collider. A sizeable LFV in low energy supersymmetry can be induced by massive right-handed neutrinos, which can explain neutrino oscillations via the seesaw mechanism. We investigate a scenario where the distribution of an invariant mass of two hadronically decaying taus (${\tau }_{\mathrm{h}}{\tau }_{\mathrm{h}}$) from ${\tilde{\chi }}_2^0$ decays is the same in events with or without LFV. We first develop a transfer function using this ditau mass distribution to model the shape of the non-LFV ${\tau }_{\mathrm{h}}\mu$ invariant mass. We then show the feasibility of extracting the LFV ${\tau }_{\mathrm{h}}\mu$ signal. The proposed technique can also be applied for a LFV ${\tau }_{\mathrm{h}}e$ search.

We study the properties of charmonium states at finite temperature in quenched QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above $T_c$. Our analysis suggests that both $S$ wave states ($J/\psi$ and ${\eta }_c$) and $P$ wave states (${\chi }_{c0}$ and ${\chi }_{c1}$) disappear already at about $1.5T_c$. The charm diffusion coefficient is estimated through the Kubo formula and found to be compatible with zero below $T_c$ and approximately $1/\pi T$ at $1.5T_c\lesssim T\lesssim 3T_c$.

Sizable amounts of heavy quarkonium events can be produced through $W$ boson decays at the LHC. Such channels will provide a suitable platform to study the properties of heavy quarkonium. The “improved trace technology,” which disposes the amplitude $\mathcal{M}$ at the amplitude level, is helpful for deriving compact analytical results for complex processes. As an important new application, in addition to the production of the lower-level Fock states $|(Q{\overline{Q}}^{\prime })[1S]⟩$ and $|(Q{\overline{Q}}^{\prime })[1P]⟩$, we make a further study on the production of higher excited $|(Q{\overline{Q}}^{\prime })⟩$ quarkonium Fock states $|(Q{\overline{Q}}^{\prime })[2S]⟩$, $|(Q{\overline{Q}}^{\prime })[3S]⟩$, and $|(Q{\overline{Q}}^{\prime })[2P]⟩$. Here $|(c\overline{c})⟩$ stands for charmonium, $|(c\overline{b})⟩$ for quarkonium, and $|(b\overline{b})⟩$ for bottomonium. We show that sizable amounts of events for those higher excited states can also be produced at the LHC. Therefore, we need to take them into consideration for a sound estimation. Assuming all excited heavy quarkonium states decay to the ground spin-singlet $[1^1{S}_0]$ wave state with $100\%$ efficiency via electromagnetic or hadronic interactions, we can obtain the total decay width by adding all of the mentioned Fock states together. As a result, at the LHC with the luminosity $\mathcal{L}\propto {10}^{34}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ and the center-of-mass energy $\sqrt{S}=14\mathrm{TeV}$, we observe that $8.7\times {10}^6$ ${\eta }_c$ and $J/\Psi$, $4.3\times {10}^5$ $B_c$ and $B_c^{*}$, $1.4\times {10}^3$ ${\eta }_b$ and ${\rm Y}$ events per year can be obtained through $W^{+}$ decays.

We calculate the scattering amplitudes of Goldstone bosons off the pseudoscalar $D$ mesons in the unitarized heavy meson chiral approach. The low energy constants appearing in the $\mathcal{O}(p^2)$ chiral Lagrangian are determined by fitting lattice simulations on $S$-wave scattering lengths. $D_{s0}^{*}(2317)$ is obtained as a bound state in the $(S,I)=(1,0)$ $DK$ channel. Possible bound states or resonance states in other channels are investigated as well. The quark mass dependence of the mass and binding energy of $D_{s0}^{*}(2317)$ is also investigated, which indicates predominately $DK$ molecular nature.

The central diffractive production of mesons $f_0(980)$ and $f_2(1270)$ at the energy of CERN-Large Hadron Collider experiment on proton-proton collisions is investigated. The processes initiated by quasireal photon-photon collisions and by central diffraction processes are considered. The role played by the photon-Odderon production channel is also studied. The cross sections for these distinct production channels are compared and analyzed.

The QCD evolution of the unpolarized transverse momentum dependent (TMD) distribution functions and of the Sivers functions have been discussed in recent papers. Following such results we reconsider previous extractions of the Sivers functions from semi-inclusive deep inelastic scattering data and propose a simple strategy which allows to take into account the $Q^2$ dependence of the TMDs in comparison with experimental findings. A clear evidence of the phenomenological success of the TMD-evolution equations is given, mostly, by the newest COMPASS data off a transversely polarized proton target.

We have just entered an era of precision measurements for $B_s$-decay observables. A characteristic feature of the $B_s$-meson system is $B_s^0\mathrm{\text{−}}{\overline{B}}_s^0$ mixing, which exhibits a sizable decay width difference. The latter feature leads to a subtle complication for the extraction of branching ratios of $B_s$ decays from untagged data samples, leading to systematic biases as large as $\mathcal{O}(10\%)$ that depend on the dynamics of the considered decay. We point out that this effect can only be corrected for using information from a time-dependent analysis and suggest the use of the effective $B_s$ decay lifetime, which can already be extracted from the untagged data sample, for this purpose. We also address several experimental issues that can play a role in the extraction of effective lifetimes at a hadron collider, and advocate the use of the $B_s$ branching ratios, as presented in this note, for consistent comparisons of theoretical calculations and experimental measurements in particle listings.

We consider a spin-0 unparticle and calculate its contribution to the weak properties of a fermion, which in the proper limit reduce to previously reported results for the electromagnetic properties. We then obtain an estimate for the electromagnetic and weak properties of the $\tau$ lepton. For the unparticle parameters, we consider the most recent bounds from the lepton flavor-violating decay $\tau \to 3\mu$, the muon anomalous magnetic moment, and the data for monojet production plus missing transverse energy at the LHC. In the most promising scenario, it is found that the unparticle contributions to the $\tau$ electromagnetic properties can be larger than the contributions predicted by the standard model and some of its extensions, such as the seesaw model and extensions of the minimal supersymmetric standard model with a mirror fourth generation and vectorlike multiplets. As for the contributions to the weak properties, they are larger than the standard model contributions but are much smaller than the current experimental limits. We also discuss the case of the electromagnetic and weak properties of the bottom and top quarks.

We study the processes $e^{+}{e}^{-}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}\gamma$, $K^{+}{K}^{-}{\pi }^0{\pi }^0\gamma$, and $K^{+}{K}^{-}{K}^{+}{K}^{-}\gamma$, where the photon is radiated from the initial state. About 84 000, 8000, and 4200 fully reconstructed events, respectively, are selected from $454{\mathrm{fb}}^{-1}$ of BABAR data. The invariant mass of the hadronic final state defines the $e^{+}{e}^{-}$ center-of-mass energy, so that the $K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}\gamma$ data can be compared with direct measurements of the $e^{+}{e}^{-}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}$ reaction. No direct measurements exist for the $e^{+}{e}^{-}\to K^{+}{K}^{-}{\pi }^0{\pi }^0$ or $e^{+}{e}^{-}\to K^{+}{K}^{-}{K}^{+}{K}^{-}$ reactions, and we present an update of our previous result based on a data sample that is twice as large. Studying the structure of these events, we find contributions from a number of intermediate states and extract their cross sections. In particular, we perform a more detailed study of the $e^{+}{e}^{-}\to \varphi (1020)\pi \pi \gamma$ reaction and confirm the presence of the $Y(2175)$ resonance in the $\varphi (1020)f_0(980)$ and $K^{+}{K}^{-}{f}_0(980)$ modes. In the charmonium region, we observe the $J/\psi$ in all three final states and in several intermediate states, as well as the $\psi (2S)$ in some modes, and measure the corresponding products of branching fraction and electron width.

The Julia-Toulouse mechanism is used to show that the topological Abelian BF term may be induced by the condensation of electric charges. As an application, we discuss the subtle question of including consistently magnetic defects in the Maxwell-BF theory as a way to avoid the usual problems of current conservation, charge quantization, Elitzur’s theorem violation, and the reality of the Dirac brane produced by nonminimal coupling. We also discuss a new way of obtaining Dirac’s veto, which is based on the so-called Dirac brane symmetry.

The probability generating function of the number of electron-positron pairs produced in a uniform electric field is constructed. The mean and variance of the numbers of pairs are calculated, and analytical expressions for the probability of low numbers of electron-positron pairs are given. A recursive formula is derived for evaluating the probability of any number of pairs. In electric fields of supercritical strength $|eE|>\pi m^2/\ln 2$, where $e$ is the electron charge, $E$ is the electric field, and $m$ is the electron mass, a branch point singularity of the probability generating function penetrates the unit circle $|z|=1$, which leads to the asymptotic divergence of the cumulative probability. This divergence indicates a failure of the continuum limit approximation. In the continuum limit and for any field strength, the positive definiteness of the probability is violated in the tail of the distribution. Analyticity, convergence, and positive definiteness are restored upon the summation over discrete levels of electrons in the normalization volume.