We show how a new hidden gauge symmetry responsible for neutrino mass as well as dark matter in the Universe can be discovered through scalar mediators responsible for breaking the new symmetry. The new force mediator ($Z^{\prime }$) may be lighter than the Standard Model gauge bosons but cannot be observed in traditional searches for new gauge bosons. We highlight a novel way of discovering such a symmetry at the Large Hadron Collider by incorporating an existing ATLAS analysis on four-lepton final states which include the Higgs resonance. In addition, we show that the hidden sector also introduces flavor violation in the lepton sector, which can become a significant channel of discovery for the new force.

We compute the topological susceptibility slope ${\chi }^{\prime }$, related to the second moment of the two-point correlator of the topological charge density, of $2d$ ${\mathrm{CP}}^{N-1}$ models for $N=5$, 11, 21 and 31 from lattice Monte Carlo simulations. Our strategy consists in performing a double limit: first, we take the continuum limit of ${\chi }^{\prime }$ at fixed smoothing radius in physical units; then, we take the zero-smoothing-radius limit. Since the same strategy can also be applied to $4d$ gauge theories and full QCD, where ${\chi }^{\prime }$ plays an intriguing theoretical and phenomenological role, this work constitutes a step toward the lattice investigation of this quantity in such models.

We investigate full off-shell effects in $t\overline{t}b\overline{b}$ production in the dilepton channel at the LHC with the center-of-mass energy $\sqrt{s}=13\mathrm{TeV}$. Specifically, we compute next-to-leading-order (NLO) QCD corrections to the $pp\to e^{+}{\nu }_e{\mu }^{-}{\overline{\nu }}_{\mu }b\overline{b}b\overline{b}+X$ process and provide a prescription for $b$-jet identification to distinguish prompt $b$ jets from $b$ jets originating from the decay of the top quarks. As an important irreducible background to $pp\to t\overline{t}H(H\to b\overline{b})$, $t\overline{t}$ production in association with two prompt $b$ jets is a primary source of uncertainty in the measurement of $t\overline{t}H(H\to b\overline{b})$. In quantifying full off-shell effects, we perform comparisons between the state-of-the-art full off-shell computation and the calculation in the narrow width approximation. The former includes all double-, single- and nonresonant Feynman diagrams, interferences as well as finite-width effects of the top quarks and $W$ gauge bosons. The latter restricts the unstable top quarks and $W$ gauge bosons to on-shell states and includes for the first time NLO QCD corrections to both production and decays. We observe that full off-shell effects are subdominant compared to the scale uncertainties for the integrated fiducial cross section and for the majority of differential observables in the phase-space regions that we investigated. However, for a number of observables related to beyond the Standard Model searches, full off-shell effects are significant. Furthermore, with our $b$-jet labeling prescription, the prompt $b$ jets and the $b$ jets from top-quark decays can be successfully disentangled.

Heavy-quark spin symmetry (HQSS) implies that in the direct decay of a heavy quarkonium with spin $S$, only lower lying heavy quarkonia with the same spin $S$ can be produced. However, this selection rule, expected to work very well in the $b$-quark sector, can be overcome if multiquark intermediate states are involved in the decay chain, allowing for transitions to the final-state heavy quarkonia with a different spin $S^{\prime }$. In particular, the measured decays $\mathrm{\Upsilon }(10860)\to \pi Z_b^{(\prime )}\to \pi \pi \mathrm{\Upsilon }(nS)$ ($n=1$, 2, 3) and $\mathrm{\Upsilon }(10860)\to \pi Z_b^{(\prime )}\to \pi \pi h_b(mP)$ ($m=1$, 2) appear to have nearly equal strengths, which is conventionally explained by a simultaneous presence of both $S_{b\overline{b}}=0$ and $S_{b\overline{b}}=1$ components in the wave functions of the $Z_b\mathrm{s}$ in equal shares. Meanwhile, the destructive interference between the contributions of the $Z_b$ and $Z_b^{\prime }$ to the decay amplitude for a $\pi \pi h_b$ final state kills the signal to zero in the strict HQSS limit. In this paper, we discuss how the HQSS violation needs to be balanced by the narrowness of the $Z_b^{(\prime )}$ states in the physical case to allow for equal transition strengths into final states with different total heavy quark spins, and how spin symmetry is restored as a result of a subtle interplay of the scales involved, when the mass of a heavy quark becomes infinite. Moreover, we demonstrate how similar branching fractions of the decays into $\pi \pi h_b$ and $\pi \pi \mathrm{\Upsilon }$ can be obtained and how the mentioned HQSS breaking can be reconciled with the dispersive approach to the $\pi \pi /K\overline{K}$ interaction in the final state and matched with the low-energy chiral dynamics in both final states.

The Standard Model can be defined quantitatively by running parameters in a mass-independent renormalization scheme at a fixed reference scale. We provide a set of simple interpolation formulas that give the fundamental Lagrangian parameters in the $\overline{\mathrm{MS}}$ scheme at a renormalization scale of 200 GeV, safely above the top-quark mass and suitable for matching to candidate new physics models at very high mass scales using renormalization group equations. These interpolation formulas take as inputs the on-shell experimental quantities and use the best available calculations in the pure $\overline{\mathrm{MS}}$ scheme. They also serve as an accounting of the parametric uncertainties for the short-distance Standard Model Lagrangian. We also include an interpolating formula for the $W$-boson mass. This paper is based on results obtained with the publicly available computer program smdr.

We study the radiative and weak nonleptonic decays of vector $B$ mesons within the covariant confined quark model developed in our previous papers. First, we calculate the matrix elements and decays widths of the radiative decays $B^{*}\to B\gamma$. The obtained results are compared with those obtained in other approaches. Then, we consider the nonleptonic decays $B^{*}\to D^{*}V$ which proceed via tree-level quark diagrams. We show that the analytical expressions for the amplitudes correspond to the factorization approach. In the framework of our model we calculate the leptonic decay constants and the form factors of the $B^{*}\to D^{*}(V)$ transitions in the entire physical region of the momentum transfer squared. Finally, we calculate the two-body decay widths and compare our results with other models.

A measurement of the inclusive cross section of in-flight electron-positron annihilation to photons, $e^{+}{e}^{-}\to \gamma \gamma$, is presented using the PADME detector at the Laboratori Nazionali di Frascati. A beam of 430 MeV positrons, corresponding to a center-of-mass energy of 20 MeV, strikes a thin diamond target. The two photons produced in the interaction are detected by an electromagnetic calorimeter made of BGO crystals. The measurement is the first based on direct detection of the photon pair and one of the most precise for positron energies below 1 GeV. It represents an intermediate step in the ultimate PADME goal of searching for dark sector particles and mediators weakly coupled to photons and electrons, with masses ranging from 1 to 20 MeV. The final value, ${\sigma }_{e^{+}{e}^{-}\to \gamma \gamma }=(1.977\pm 0.018(\mathrm{stat})\pm 0.119(\mathrm{syst}))\mathrm{mb}$, agrees with next-to-leading-order QED predictions within the 6% experimental uncertainty.

We present a search for electron-recoil signatures from the charged-current absorption of fermionic dark matter using the EXO-200 detector. We report an average electron-recoil background rate of $6.8\times {10}^4\mathrm{cts}{\mathrm{kg}}^{-1}{\mathrm{yr}}^{-1}{\mathrm{keV}}^{-1}$ above 4 MeV and find no statistically significant excess over our background projection. Using a total ${}^{136}\mathrm{Xe}$ exposure of 234.1 kg yr, we exclude new parameter space for the charged-current absorption cross section for dark matter masses between $m_{\chi }=2.6–11.6\mathrm{MeV}$ with a minimum of $6\times {10}^{-51}{\mathrm{cm}}^2$ at 8.3 MeV at the 90% confidence level.

We develop a systematic renormalization procedure for QFT in anti-de Sitter spacetime. UV infinities are regulated using a geodesic point-splitting method, which respects AdS isometries, while IR infinities are regulated by cutting off the radial direction (as in holographic renormalization). The renormalized theory is defined by introducing $Z$ factors for all parameters in the Lagrangian and the boundary conditions of bulk fields (sources of dual operators), and a boundary counterterm action, $S_{\mathrm{ct}}$, such that the limit of removing the UV and IR regulators exists. The results are in general scheme dependent (mirroring the analogous result in flat space) and require renormalization conditions. These may be provided by the dual CFT (or by string theory in AdS). Our analysis amounts also to a first principles derivation of the Feynman rules regarding Witten diagrams. The presence and treatment of IR divergences is essential for correctly accounting for anomalous dimensions of dual operators. We apply the method to scalar ${\mathrm{\Phi }}^4$ theory and obtain the renormalized two-point function of the dual operator to two loops, and the renormalized four-point function to one-loop order, for operators of any dimension $\mathrm{\Delta }$ and bulk spacetime dimension up to $d+1=7$.

When massless particles are involved, the traditional scattering matrix ($S$ matrix) does not exist: It has no rigorous nonperturbative definition and has infrared divergences in its perturbative expansion. The problem can be traced to the impossibility of isolating single-particle states at asymptotic times. On the other hand, the troublesome nonseparable interactions are often universal: In gauge theories, they factorize so that the asymptotic evolution is independent of the hard scattering. Exploiting this factorization property, we show how a finite “hard” $S$ matrix, $S_H$, can be defined by replacing the free Hamiltonian with a soft-collinear asymptotic Hamiltonian. The elements of $S_H$ are gauge invariant and infrared finite and exist even in conformal field theories. One can interpret elements of $S_H$ alternatively 1) as elements of the traditional $S$ matrix between dressed states, 2) as Wilson coefficients, or 3) as remainder functions. These multiple interpretations provide different insights into the rich structure of $S_H$.

A large number of studies, all using Bayesian parameter inference from Markov chain Monte Carlo methods, have constrained the presence of a decaying dark matter component. All such studies find a strong preference for either very long-lived or very short-lived dark matter. However, in this paper, we demonstrate that this preference is due to parameter volume effects that drive the model towards the standard $\mathrm{\Lambda }\mathrm{CDM}$ model, which is known to provide a good fit to most observational data. Using profile likelihoods, which are free from volume effects, we instead find that the best-fitting parameters are associated with an intermediate regime where around 3% of cold dark matter decays just prior to recombination. With two additional parameters, the model yields an overall preference over the $\mathrm{\Lambda }\mathrm{CDM}$ model of $\mathrm{\Delta }{\chi }^2\approx -2.8$ with Planck and BAO and $\mathrm{\Delta }{\chi }^2\approx -7.8$ with the SH0ES $H_0$ measurement, while only slightly alleviating the $H_0$ tension. Ultimately, our results reveal that decaying dark matter is more viable than previously assumed, and illustrate the dangers of relying exclusively on Bayesian parameter inference when analyzsing extensions to the $\mathrm{\Lambda }\mathrm{CDM}$ model.

We revisit the constraint from the recently reported cosmic birefringence on axionlike particles with a general decay constant. Particular attention is paid to the naturalness of the model parameter space, which has been overlooked in the literature. We show that the observed cosmic birefringence is naturally explained by the electroweak axion with a string-theory inspired decay constant $F_A\simeq {10}^{16}\mathrm{GeV}$.

Drell-Yan production is one of the precision cornerstones of the LHC, serving as calibration for measurements such as the $W$-boson mass. Its extreme precision at the level of 1% challenges theory predictions at the highest level. We present the first independent calculation of Drell-Yan production at order ${\alpha }_s^3$ in transverse-momentum ($q_T$) resummation improved perturbation theory. Our calculation reaches the state-of-the-art through inclusion of the recently published four loop rapidity anomalous dimension and three loop massive axial-vector contributions. We compare to the most recent data from CMS with fiducial and differential cross-section predictions and find excellent agreement at the percent level. Our resummed calculation including the matching to $Z+\text{jet}$ production at NNLO is publicly available in the upcoming cute-mcfm 10.3 release and allows for theory-data comparison at an unprecedented level.

We impose $U$-spin symmetry [$SU(2{)}_{\text{Uspin}}$] on the Hamiltonian for $B$ decays. As expected, we find the equality of amplitudes related by the exchange $d\leftrightarrow s$. We also find that the amplitudes for the $\mathrm{\Delta }S=0$ processes $B^0\to {\pi }^{+}{\pi }^{-}$, $B_s^0\to {\pi }^{+}{K}^{-}$, and $B^0\to K^{+}{K}^{-}$ form a $U$-spin triangle relation. The amplitudes for $B_s^0\to K^{+}{K}^{-}$, $B^0\to {\pi }^{-}{K}^{+}$, and $B_s^0\to {\pi }^{+}{\pi }^{-}$ form a similar $\mathrm{\Delta }S=1$ triangle relation. And these two triangles are related to one another by $d\leftrightarrow s$. We perform fits to the observables for these six decays. If perfect $U$ spin is assumed, then the fit is very poor. If $U$-spin-breaking contributions are added, then we find many scenarios that can explain the data. However, in all cases, 100% $U$-spin breaking is required, considerably larger than the naive expectation of $\sim 20\%$. This is the $U$-spin puzzle; it may be strongly hinting at the presence of new physics.

Recent LHCb amplitude analysis on $B^{+}\to J/\psi \varphi K^{+}$ suggests the existence of exotic $X$ and $Z_{cs}$ hadrons, based on an assumption that Breit-Wigner resonances describe all the peak structures. However, all the peaks and also dips in the spectra are located at relevant meson-meson thresholds where threshold kinematical cusps might cause such structures. This points to the importance of an independent amplitude analysis with due consideration of the kinematical effects, and this is what we do in this work. Our model fits well $J/\psi \varphi$, $J/\psi K^{+}$, and $K^{+}\varphi$ invariant mass distributions simultaneously, demonstrating that all the $X$, $Z_{cs}$, and dip structures can be well described with the ordinary $s$-wave threshold cusps. Spin-parity of the $X(4274)$ and $X(4500)$ structures are respectively $0^{-}$ and $1^{-}$ from our model, as opposed to $1^{+}$ and $0^{+}$ from the LHCb model. With all relevant threshold cusps considered, the number of fitting parameters seems to be significantly reduced. The LHCb data requires $D_s^{(*)}{\overline{D}}^{*}$ scattering lengths in our model to be consistent with zero, disfavoring $D_s^{(*)}{\overline{D}}^{*}$ molecule interpretations of $Z_{cs}(4000)$ and $Z_{cs}(4220)$ and, via the SU(3) relation, being consistent with previous lattice QCD results.

The path-integral measure of a gauge-invariant fermion theory is transformed under the chiral transformation and leads to an elegant derivation of the anomalous chiral Ward-Takahashi identities, as we know from the seminal work of Fujikawa. We present in this work an alternative and illuminating way to calculate the Jacobian in the path-integral measure from the covariant derivative expansion technique used in effective field theory. We present several ways to customize the crucial regularization such that the anomaly is located in the desired current, which is unprecedented within the path integral approach. We are then able to derive, in a transparent and unified way, the covariant, consistent, gravitational, and scale anomalies.

Brane observers executing appropriate motion through a partially compactified Lorentz invariant bulk spacetime, such as $M_4\times S^1$, can send signals along the brane that are instantaneous or even travel backward in time. Nevertheless, causality in the braneworld remains intact. We establish these results, which follow from superluminal signal propagation reported in Greene et al. [Superluminal propagation on a moving braneworld, Phys. Rev. D 106, 085001 (2022).], through classical analysis and then extend our reasoning by examining quantum mechanical microcausality. One implication is the capacity for real time communication across arbitrarily large distances.

The $R+R^2$ model of gravity with the corresponding shallow potential in the Einstein frame is consistent with the observations. Recently, many efforts have been made to generalize the $R+R^2$ (Starobinsky) model of inflation or use other shallow potentials to construct a model for the early Universe. We revise the question about the shallow potential. We propose a model in which the Starobinsky model can emerge through a dynamical mechanism. We show that the absence of ghost modes results to constraints on the parameters of the Starobinsky model. We obtain the scalar spectral index and the tensor-to-scalar ratio of the extended model and study the three-point correlation function of the curvature perturbation to estimate the primordial non-Gaussianities of the proposed model.

We present the results of the first Machine Learning Gravitational-Wave Search Mock Data Challenge. For this challenge, participating groups had to identify gravitational-wave signals from binary black hole mergers of increasing complexity and duration embedded in progressively more realistic noise. The final of the 4 provided datasets contained real noise from the O3a observing run and signals up to a duration of 20 s with the inclusion of precession effects and higher order modes. We present the average sensitivity distance and run-time for the 6 entered algorithms derived from 1 month of test data unknown to the participants prior to submission. Of these, 4 are machine learning algorithms. We find that the best machine learning based algorithms are able to achieve up to 95% of the sensitive distance of matched-filtering based production analyses for simulated Gaussian noise at a false-alarm rate (FAR) of one per month. In contrast, for real noise, the leading machine learning search achieved 70%. For higher FARs the differences in sensitive distance shrink to the point where select machine learning submissions outperform traditional search algorithms at FARs $\ge 200$ per month on some datasets. Our results show that current machine learning search algorithms may already be sensitive enough in limited parameter regions to be useful for some production settings. To improve the state-of-the-art, machine learning algorithms need to reduce the false-alarm rates at which they are capable of detecting signals and extend their validity to regions of parameter space where modeled searches are computationally expensive to run. Based on our findings we compile a list of research areas that we believe are the most important to elevate machine learning searches to an invaluable tool in gravitational-wave signal detection.

The quadrupole normal-mode oscillation frequency $f_n$ of a multiquark star are computed for $n=1–5$. At the transition from low to high density multiquark in the core region, the first two modes jump to larger values, a distinctive signature of the presence of the high-density core. When the star oscillation couples with spacetime, gravitational waves (GW) will be generated and the star will undergo damped oscillation. The quasinormal modes (QNMs) of the oscillation are computed using two methods, direct scan and WKB, for QNMs with small and large imaginary parts respectively. The small imaginary QNMs have frequencies 1.5–2.6 kHz and damping times 0.19–1.7 secs for a multiquark star with mass $M=0.6–2.1M_{\odot }$ (solar mass). The WKB QNMs with large imaginary parts have frequencies 5.98–9.81 kHz and damping times 0.13–0.46 ms for $M\simeq 0.3–2.1M_{\odot }$. They are found to be the fluid $f-\mathrm{modes}$ and spacetime curvature $w-\mathrm{modes}$, respectively.