An energy independent scaling of the near-side ridge yield at a given multiplicity has been observed by the ATLAS and the CMS collaborations in $p+p$ collisions at $\sqrt{s}=7$ and 13 TeV. Such a striking feature of the data can be successfully explained by approaches based on initial state momentum space correlation generated due to gluon saturation. In this paper, we try to examine if such a scaling is also an inherent feature of the approaches that employ strong final state interaction in $p+p$ collisions. We find that hydrodynamical modeling of $p+p$ collisions using EPOS 3 shows a violation of such scaling. The current study can, therefore, provide important new insights on the origin of long-range azimuthal correlations in high multiplicity $p+p$ collisions at the LHC energies.

We discuss prompt production of $J/\psi$ mesons in proton-proton collisions at the LHC within the NRQCD $k_t$-factorization approach using Kimber-Martin-Ryskin (KMR) unintegrated gluon distributions (UGDF). We include both direct color-singlet production ($gg\to J/\psi g$) as well as a feed down from ${\chi }_c\to J/\psi \gamma$ and ${\psi }^{\prime }\to J/\psi X$ decays. The production of the decaying mesons (${\chi }_c$ or ${\psi }^{\prime }$) is also calculated within the NRQCD $k_t$-factorization approach. The corresponding matrix elements for $gg\to J/\psi \mathrm{g}$, $gg\to {\psi }^{\prime }g$ and $gg\to {\chi }_c$ include parameters of the nonrelativistic space wave functions of the quarkonia at $r=0$, which are taken from potential models in the literature. We get the ratio of the corresponding cross section ratio for ${\chi }_c(2)$-to-${\chi }_c(1)$ at midrapidities much closer to experimental data than obtained in a recent analysis. Differential distributions in rapidity and transverse momentum of $J/\psi$ and ${\psi }^{\prime }$ are calculated and compared with experimental data of the ALICE and LHCb Collaborations. We discuss a possible onset of gluon saturation effects in the production of $J/\psi$ and ${\chi }_c$ mesons at forward/backward rapidities. We show that it is necessary to modify the standard KMR UGDF to describe ALICE and LHCb data. A mixed UGDF scenario was proposed. Then, we can describe the experimental data for $J/\psi$ production within model uncertainties with a color-singlet component only. Therefore, our theoretical results leave only relatively small room for the color-octet contributions. We discuss relations to other models in the literature. The results for the so-called hybrid model are compared to the results of the original $k_t$-factorization approach.

We calculate the one- and two-point correlation functions of the energy density and the divergence of the Chern-Simons current in the nonequilibrium glasma state formed in a high-energy nuclear collision. We show that the latter depends on the difference of the total and linearly polarized gluon transverse momentum distributions. Since the divergence of the Chern-Simons current provides the source of axial charge, we infer information about the statistical properties of axial charge production at early times. We further develop a simple phenomenological model to characterize axial charge distributions in terms of distributions of the energy density.

We derive an explicit analytical expression for the magnetic dipole moment of the $\rho$ meson, ${\mu }_{\rho }$, in a relativistic constituent-quark model. We adopt our relativistic approach to composite systems, modified instant-form (mIF) relativistic quantum mechanics (RQM), that we used particularly to construct a unified $\pi \&\rho$ model [Phys. Rev. D 93, 036007 (2016)] describing electroweak properties of light mesons. This model provides a parameter-free calculation to give ${\mu }_{\rho }=2.16\pm 0.03$ $[e/2M_{\rho }]$ which is in accordance with the conventional experimental data. The magnetic, quadrupole, and charge form factors also are derived and presented. We consider the small uncertainty of our value of the magnetic moment as one of the undoubted advantages of the method. A comparison is made with recent lattice QCD results and previous calculations using a variety of methods.

Neutrino induced coherent charged pion production on nuclei, ${\overline{\nu }}_{\mu }A\to {\mu }^{\pm }{\pi }^{\mp }A$, is a rare inelastic interaction in which the four-momentum squared transferred to the nucleus is nearly zero, leaving it intact. We identify such events in the scintillator of MINERvA by reconstructing $|t|$ from the final state pion and muon momenta and by removing events with evidence of energetic nuclear recoil or production of other final state particles. We measure the total neutrino and antineutrino cross sections as a function of neutrino energy between 2 and 20 GeV and measure flux integrated differential cross sections as a function of $Q^2$, $E_{\pi }$, and ${\theta }_{\pi }$. The $Q^2$ dependence and equality of the neutrino and antineutrino cross sections at finite $Q^2$ provide a confirmation of Adler’s partial conservation of axial current hypothesis.

The process $e^{+}{e}^{-}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ is studied using data samples at $\sqrt{s}=2.2324$, 2.400, 2.800 and 3.080 GeV collected with the BESIII detector operating at the BEPCII collider. The Born cross section is measured at $\sqrt{s}=2.2324\mathrm{GeV}$, which is 1.0 MeV above the $\mathrm{\Lambda }\overline{\mathrm{\Lambda }}$ mass threshold, to be $305\pm 45_{-36}^{+66}\mathrm{pb}$, where the first uncertainty is statistical and the second systematic. The cross section near threshold is larger than that expected from theory, which predicts the cross section to vanish at threshold. The Born cross sections at $\sqrt{s}=2.400$, 2.800 and 3.080 GeV are measured and found to be consistent with previous experimental results, but with improved precision. Finally, the corresponding effective electromagnetic form factors of $\mathrm{\Lambda }$ are deduced.

The characteristics of tree-level scattering amplitudes in theories with nonlinear (super)symmetries were recently proposed by Kallosh to be encoded in a simple way directly from the action, based on a background field method. We check this conjecture to lowest nontrivial order in the Volkov-Akulov theory, where the local 6-point diagram cancels and the results up to 6 points indeed are in agreement with $S$-matrix computations.

Class-$\mathcal{S}$ theories are four-dimensional $\mathcal{N}=2$ supersymmetric field theories constructed by the reduction of a (2,0) six-dimensional theory on a punctured Riemann surface $C$ (called the UV curve). A basic degeneration limit of the surface $C$ is when several punctures are brought close to each other. As this happens, a long tube appears in $C$ and a weakly coupled gauge group emerges. When the corresponding gauge coupling is turned off, we are left with two surfaces. This decoupling leads to a unique result. We explain how to fix the gauge group that becomes weakly coupled and the resulting two theories, in terms of the types of punctures on the surface $C$. Each of the resulting theories is given in terms of a class-$\mathcal{S}$ theory (plus possibly additional free hypermultiplets). Many other more complicated degeneration limits can be described by repeatedly using this specification. For questions about weak coupling limits in such theories, it is useful to consider the set of punctures that can appear at the end of a tube. These are the punctures that are created in the resulting surfaces when the gauge coupling is taken to be extremely weak. Not any puncture can be formed in a decoupling process, and this set is described. Each such puncture can be found diagrammatically in terms of the other punctures on $C$ in a particular decoupling limit. The relation of the gauge group to the symmetry associated with this puncture is discussed. We discuss the relation of such degeneration limits of large $N$ theories, through the AdS/CFT correspondence, to decoupled field theories on ${\mathrm{AdS}}_5$.

Coleman and De Luccia (CDL) showed that gravitational effects can prevent the decay by bubble nucleation of a Minkowski or AdS false vacuum. In their thin-wall approximation this happens whenever the surface tension in the bubble wall exceeds an upper bound proportional to the difference of the square roots of the true and false vacuum energy densities. Recently it was shown that there is another type of thin-wall regime that differs from that of CDL in that the radius of curvature grows substantially as one moves through the wall. Not only does the CDL derivation of the bound fail in this case, but also its very formulation becomes ambiguous because the surface tension is not well defined. We propose a definition of the surface tension and show that it obeys a bound similar in form to that of the CDL case. We then show that both thin-wall bounds are special cases of a more general bound that is satisfied for all bounce solutions with Minkowski or AdS false vacua. We discuss the limit where the parameters of the theory attain critical values and the bound is saturated. The bounce solution then disappears and a static planar domain wall solution appears in its stead. The scalar field potential then is of the form expected in supergravity, but this is only guaranteed along the trajectory in field space traced out by the bounce.

We develop a formalism to help calculate in quantum field theory the departures from the description of a system by classical field equations. We apply the formalism to a homogeneous condensate with attractive contact interactions and to a homogeneous self-gravitating condensate in critical expansion. In their classical descriptions, such condensates persist forever. We show that in their quantum description, parametric resonance causes quanta to jump in pairs out of the condensate into all modes with wave vector less than some critical value. We calculate, in each case, the time scale over which the homogeneous condensate is depleted and after which a classical description is invalid. We argue that the duration of classicality of inhomogeneous condensates is shorter than that of homogeneous condensates.

In the context of a binary inspiral of mixed neutron star–black hole systems, we investigate the excitation of the neutron star oscillation modes by the orbital motion. We study generic eccentric orbits and show that tidal interaction can excite the $f$-mode oscillations of the star by computing the amount of energy and angular momentum deposited into the star by the orbital motion tidal forces via closed form analytic expressions. We study the $f$-mode oscillations of cold neutron stars using recent microscopic nuclear equations of state, and we compute their imprint into the emitted gravitational waves.

Using only global symmetries of QCD, we set up an effective model of quarks at finite temperature near the crossover, including all possible terms up to dimension-6. We first treat this in mean field theory. Then we investigate low-energy fluctuations around it up to one-loop order in fermions below the crossover. Static correlation functions of pions and the crossover temperature, both measured on the lattice, completely suffice to fix all parameters of the theory. We examine predictions of this theory, including those for thermodynamic quantities. The results are encouraging.

Conventionally, one adopts typical momentum flow of a physical observable as the renormalization scale for its perturbative QCD (pQCD) approximant. This simple treatment leads to renormalization scheme-and-scale ambiguities due to the renormalization scheme and scale dependence of the strong coupling and the perturbative coefficients do not exactly cancel at any fixed order. It is believed that those ambiguities will be softened by including more higher-order terms. In the paper, to show how the renormalization scheme dependence changes when more loop terms have been included, we discuss the sensitivity of pQCD prediction on the scheme parameters by using the scheme-dependent $\{{\beta }_{m\ge 2}\}$-terms. We adopt two four-loop examples, $e^{+}{e}^{-}\to \text{hadrons}$ and $\tau$ decays into hadrons, for detailed analysis. Our results show that under the conventional scale setting, by including more-and-more loop terms, the scheme dependence of the pQCD prediction cannot be reduced as efficiently as that of the scale dependence. Thus a proper scale-setting approach should be important to reduce the scheme dependence. We observe that the principle of minimum sensitivity could be such a scale-setting approach, which provides a practical way to achieve optimal scheme and scale by requiring the pQCD approximate be independent to the “unphysical” theoretical conventions.

We present a version of the twin Higgs mechanism with minimal symmetry structure and particle content. The model is built upon a composite Higgs theory with global $SO(6)/SO(5)$ symmetry breaking. The leading contribution to the Higgs potential, from the top sector, is solely canceled via the introduction of a standard model neutral top partner. We show that the inherent $Z_2$ breaking of this construction is under control and of the right size to achieve electroweak symmetry breaking, with a fine-tuning at the level of 5%–10%, compatibly with the observed Higgs mass. We briefly discuss the particular phenomenological features of this scenario.

We study the three-body radiative decays $B\to \varphi (\rho )K\gamma$ induced by a flavor-changing neutral current in the perturbative QCD approach. Pseudoscalar-vector ($PV$) distribution amplitudes (DAs) are introduced for the final-state $\varphi K$ ($\rho K$) pair to capture important infrared dynamics in the region with a small $PV$-pair invariant mass. The dependence of these $PV$ DAs on the parton momentum fraction is parametrized in terms of the Gegenbauer polynomials, and the dependence on the meson momentum fraction is derived through their normalizations to timelike $PV$ form factors. In addition to the dominant electromagnetic penguin, the subleading chromomagnetic penguin, quark-loop and annihilation diagrams are also calculated. After determining the $PV$ DAs from relevant branching-ratio data, the direct $CP$ asymmetries and decay spectra in the $PV$-pair invariant mass are predicted for each $B\to \varphi (\rho )K\gamma$ mode.

An effective relativistic kinetic theory has been constructed for an interacting system of quarks, antiquarks and gluons within a quasiparticle description of hot QCD medium at finite temperature and baryon chemical potential, where the interactions are encoded in the gluon and quark effective fugacities with nontrivial energy dispersions. The local conservations of stress-energy tensor and number current require the introduction of a mean field term in the transport equation which produces non-vanishing contribution to the first order transport coefficients. Such contribution has been observed to be significant for the temperatures which are closer to the QCD transition temperature, however, induces negligible contributions beyond a few times the transition temperature. As an implication, impact of the mean field contribution on the temperature dependence of the shear viscosity, bulk viscosity and thermal conductivity of a hot QCD medium in the presence of binary, elastic collisions among the constituents, has been investigated. Visible effects have been observed for the temperature regime closer to the QCD transition temperature.

The parton quasidistribution functions (QDFs) of Ji have been found by Radyushkin to be directly related to the transverse momentum distributions (TMDs), to the pseudodistributions, and to the Ioffe-time distributions (ITDs). This makes the QDF results at finite longitudinal momentum of the hadron interesting in their own right. Moreover, the QDF-TMD relation provides a gateway to the pertinent QCD evolution, with respect to the resolution scale $Q$, for the QDFs. Using the Kwieciński evolution equations and well established parametrizations at a low initial scale, we analyze the QCD evolution of quark and gluon QDF components of the proton and the pion. We discuss the resulting breaking of the longitudinal-transverse factorization and show that it has little impact on QDFs at the relatively low scales presently accessible on the lattice, but the effect is visible in reduced ITDs at sufficiently large values of the Ioffe time. Sum rules involving derivatives of ITDs and moments of the parton distribution functions (PDFs) are applied to the European Twisted Mass Collaboration lattice data. This allows us for a lattice determination of the transverse-momentum width of the TMDs from QDF studies.

Under the assignment of $a_0(1450)$ as the ground isovector scalar meson, the strong decays of $a_0(1950)$ and $a_0(2020)$ are evaluated in the ${}^3{P}_0$ model. Our calculations suggest that $a_0(1950)$ and $a_0(2020)$ can be regarded as the same resonance referring to $a_0(3{}^3{P}_0)$. The masses and strong decays of $a_0(2{}^3{P}_0)$ and $a_0(4{}^3{P}_0)$ are also predicted, which can be useful in the search for radially excited scalar mesons in the future.

We report on a precision measurement of the cross section for the reaction $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ in the mass range $0.30<M_{\pi \pi }<1.00\mathrm{GeV}/c^2$ with the initial state radiation (ISR) method, using $817{\mathrm{pb}}^{-1}$ of data at $e^{+}{e}^{-}$ center-of-mass energies near 3.77 GeV and $586{\mathrm{pb}}^{-1}$ of data at $e^{+}{e}^{-}$ center-of-mass energies near 4.17 GeV, collected with the CLEO-c detector at the CESR $e^{+}{e}^{-}$ collider at Cornell University. The integrated cross sections in the range $0.30<M_{\pi \pi }<1.00\mathrm{GeV}/c^2$ for the process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ are determined with a statistical uncertainty of 0.7% and a systematic uncertainty of 1.6%. The leading-order hadronic contribution to the muon anomalous magnetic moment calculated using these measured $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ cross sections in the range $M_{\pi \pi }=0.30$ to $1.00\mathrm{GeV}/c^2$ is calculated to be $(500.6\pm 3.6(\mathrm{stat})\pm 8.0(\mathrm{syst}))\times {10}^{-10}$.

In this paper, the study of collisions between kinks arising in the family of MSTB models is addressed. Phenomena such as elastic kink reflection, mutual annihilation, kink-antikink transmutation and inelastic reflection are found and depend on the impact velocity.