Scalar-tensor theories with screening mechanisms come with nonlinearities that make it difficult to study setups of complex geometry without resorting to numerical simulations. In this paper, we use the femtoscope code that we introduced in a previous work in order to compute the fifth force arising in the chameleon model in the Earth orbit. We go beyond published works by introducing a departure from spherical symmetry—embodied by a mountain on an otherwise spherical Earth—as well as by implementing several atmospheric models, and quantify their combined effect on the chameleon field. Building on the numerical results thus obtained, we address the question of the detectability of a putative chameleon fifth force by means of space geodesy techniques and, for the first time, quantitatively assess the backreaction created by the screening of a satellite itself. We find that although the fifth force has a supposedly measurable effect on the dynamics of an orbiting spacecraft, the imprecise knowledge of the mass distribution inside the Earth greatly curtails the constraining power of such space missions. Finally, we show how this degeneracy can be lifted when several measurements are performed at different altitudes.

We study the implications of the stringy spacetime uncertainty relation (STUR) for inflationary cosmology. By demanding that no fluctuation modes that exit the Hubble radius are affected by the nonlocality resulting from the STUR, we find an upper bound on the number of e-foldings of inflation. The bound is a factor of 2 weaker than what results from the trans-Planckian censorship criterion (TCC). By demanding that the inflationary phase is simultaneously consistent with STUR and sufficiently long for inflation to provide a causal explanation of structure on the scale of the current Hubble radius, we find an upper bound on the energy scale of inflation. The bound is less restrictive than what follows from the TCC, but it remains in conflict with canonical single-field inflation models.

New observational data measured with high degree of accuracy of compact isolated neutron stars and binary stars in gravitational wave remnants have the potential to explore the strong field gravity. Within the framework of energy-momentum squared gravity (EMSG) theory, we study its impact on several properties of neutron stars and plausible modifications from the predictions of general relativity. Based on a representative set of relativistic nuclear mean field models, nonrelativistic Skyrme-Hartree-Fock models, and microscopic calculations, we show deviations of neutron star mass-radius sequence in EMSG theory as compared to general relativity. The variation in the effective nuclear equation of state in EMSG results in distinct magnitudes in the reduced pressure, speed of sound, and maximum compactness at the center of neutron stars. We perform extensive correlation analysis of the nuclear model parameters with the neutron star observables in light of the new observational bounds. Perceptible modifications in the correlations are found in the models of gravity that provide different estimates of the slope and curvature of nuclear matter symmetry energy. The available neutron star data, however, do not impose stringent enough constraints for a clear evidence of deviations from general relativity.

Matter in compact stars is dense enough that transient events within the star could have sufficiently high energies to produce detectable gravitational waves (GWs). These GWs could be used to constrain the equation of state (EOS) for matter in the star and could reveal that there is more than one type of EOS at play in the population, implying that multiple types of compact stars exist. One of these types could be quark stars, composed almost entirely of stable quark matter, and observing GWs is a way to test for the strange matter EOS. Here we explore the possibility that, if fundamental ($f$-) mode oscillations in pulsars are induced by a pulsar glitch, then these oscillations might produce detectable GWs. We use the existing population of pulsars and their glitches, as well as a much larger synthesized population, along with 15 EOSs (eight for neutron stars and seven for quark stars) to generate frequencies, damping times, and GW strengths for each. We find that of the EOSs examined, all quark star EOSs produce narrower distributions of $f$-mode frequency than neutron star EOSs. This result, along with other elements of the data, could be used to differentiate between GWs (or other signals from $f$ modes) originating from neutron stars and quark stars and thus could confirm the existence of quark stars. We also find that GW astronomy is a potentially viable method for detecting a larger population of pulsars which are not observable electromagnetically and that future GW observatories have the possibility to greatly expand this capability.

The study of the rare decays $B\to K^{(*)}\nu \overline{\nu }$ offers a window into the dynamics operating at the electroweak scale, allowing studies of the Standard Model and searches for heavy new physics. However, the analysis of these decays is also potentially sensitive to the on shell production of new light bosons $X$ through the process $B\to K^{(*)}X$. In particular, Belle II has recently measured $B^{+}\to K^{+}\nu \overline{\nu }$, finding a $2.8\sigma$ excess under the assumption of heavy new physics. Since this excess is rather localized in the kaon energy, a fit that includes the decay mode $B^{+}\to K^{+}X$ to the kinematic distributions prefers $m_X\approx 2\mathrm{GeV}$ with branching fraction $\mathrm{Br}[B\to KX]=(8.8\pm 2.5)\times {10}^{-6}$ and a significance of $\approx 3.6\sigma$. However, no excess was found in the BABAR measurements of $B\to K^{(*)}\nu \overline{\nu }$, and a global analysis of the Belle II and BABAR data leads to $\mathrm{Br}[B\to KX]=(5.1\pm 2.1)\times {10}^{-6}$ with a reduced significance of $\approx 2.4\sigma$. We then study various simplified dark-flavored models and present a possible UV completion based on a gauged $B_3-L_3$ symmetry, highlighting the discovery potential of dedicated searches for $B\to K^{(*)}X$ at Belle II.

We study phenomenology of a light scalar dark matter (DM). In the model, there is an inert doublet scalar and a singlet Dirac fermion $\psi$, both charged under a global $Z_2$ symmetry. The mass of the lightest inert scalar $H$ can be lighter than 10 GeV by imposing appropriate relations between three scalar quartic couplings. The lightest $Z_2$ odd particle is stable and DM. In this paper, focusing on the parameter space where $H$ is lighter than $\psi$ and is DM, we discuss DM physics related to relic density, direct detection, indirect detection, collider searches, and other cosmological observations. We clarify differences from the case where $\psi$ is instead DM, which has been focused on in previous works.

The Belle II experiment recently observed the decay $B^{+}\to K^{+}\nu \nu$ for the first time, with a measured value for the branching ratio of $(2.3\pm 0.7)\times {10}^{-5}$. This result exhibits a $\sim 3\sigma$ deviation from the Standard Model (SM) prediction. The observed enhancement with respect to the Standard Model could indicate the presence of invisible light new physics. In this paper, we investigate whether this result can be accommodated in a minimal Higgs portal model, where the SM is extended by a singlet Higgs scalar that decays invisibly to dark sector states. We find that current and future bounds on invisible decays of the 125 GeV Higgs boson completely exclude a new scalar with a mass $\gtrsim 10\mathrm{GeV}$. On the other hand, the Belle II results can be successfully accommodated if the new scalar is lighter than $B$ mesons but heavier than kaons. We also investigate the cosmological implications of the new states and explore the possibility that they are part of an Abelian Higgs extension of the SM. Future Higgs factories are expected to place stringent bounds on the invisible branching ratio of the 125 GeV Higgs boson, and will be able to definitively test the region of parameter space favored by the Belle II results.

We reanalyze the effective field theory (EFT) approach for the scenario in which the particles that account for the dark matter (DM) in the universe are vector states that interact only through the Standard Model-like Higgs boson. These DM particles are searched for in direct and indirect detection in astrophysical experiments and in invisible Higgs decays at the LHC. The constraints obtained in these two search types are complementary and correlated. In recent years, it has been advocated that the EFT approach is problematic for small DM mass and that it does not capture all the aspects of vector DM; one should thus rather interpret the searches in ultraviolet complete theories that are more realistic. In this paper, we show that a more appropriate definition of the EFT with the introduction of an effective new physics scale parameter, can encompass such issues. We illustrate this by matching the EFT to two examples of ultraviolet completions for it: the U(1) model with a dark photon and a model that was recently adopted by the LHC experiments in which vectorlike fermions generate an effective interaction between the Higgs and the DM states at the one-loop level. Additionally, we find that the region of parameter space that is relevant for DM phenomenology is well inside the range of validity of the EFT. It thus provides a general parametrization of the effects of any ultraviolet model in the regime under exploration, making it the ideal framework for model-independent analyses of the vector DM Higgs-portal.

In addition to anomalies associated with the muon $g-2$ and the branching ratio (BR) of $B\to D^{(*)}\tau \overline{\nu }$, Belle II recently observed an unexpectedly large BR in the $B^{+}\to K^{+}\nu \overline{\nu }$ decay. To resolve the anomalous excesses in these observables, we propose a framework involving a leptoquark, denoted by $S_1$, which has the feature that down-type quarks merely couple to neutrinos but not the charged leptons, avoiding the strict constraint from the $B_s\to {\mu }^{-}{\mu }^{+}$ decay. With the introduction of the $U(1{)}_{L_{\mu }-L_{\tau }}$ gauge symmetry, the $Z^{\prime }$ with light mass not only resolves the muon $g-2$ anomaly, but also ensures that $S_1$ couples exclusively to the third-generation leptons so that only $\tau {\overline{\nu }}_{\tau }$ and $\tau$-neutrino modes are involved in the processes $b\to c\ell \overline{\nu }$ and $b\to s\nu \overline{\nu }$, respectively. Under the dominant constraints from $|\mathrm{\Delta }F|=2$ processes, we find that the $S_1$ contributions to the BRs of $B\to K^{(*)}\nu \overline{\nu }$ and $K_L\to {\pi }^0\nu \overline{\nu }$ can be factorized into the same multiplicative factor multiplying the standard model predictions, and the enhancement can be up to a factor of 2. In particular, $\mathcal{B}(K^{+}\to {\pi }^{+}\nu \overline{\nu })$ can reach the upper $1\sigma$ error of the experimental value, i.e., $\simeq 15.4\times {10}^{-11}$. We also show that the model can fit the new world averages of $R(D^{(*)})$ and contribute significantly to the $\tau$ polarization in the $B\to D\tau \overline{\nu }$ decay and $\mathcal{B}(B_c\to \tau \overline{\nu })$.

We study the correlator of temporal Wilson lines at nonzero temperature in $2+1$ flavor lattice QCD with the aim to define the heavy quark-antiquark potential at nonzero temperature. For temperatures $153\mathrm{MeV}\le T\le 352\mathrm{MeV}$ the spectral representation of this correlator is consistent with a broadened peak in the spectral function, position, or width of which then defines the real or imaginary parts of the heavy quark-antiquark potential at nonzero temperature, respectively. We find that the potential’s real part is not screened contrary to the widely held expectations. We comment on how this fact may modify the picture of quarkonium melting in the quark-gluon plasma.

In this paper, we calculate the decay widths and branching fractions for the decays $Z\to H+\gamma$ up to $\mathcal{O}({\alpha }_s{v}^2)$ accuracy within the framework of nonrelativistic QCD, where $H$ stands for the $S$-wave quarkonium ${\eta }_c$, $J/\psi$, ${\eta }_b$, or $\mathrm{\Upsilon }$, respectively. To compare with the leading-order terms, those corrections show good perturbative behavior as expected. It is found that contributions from the next-to-leading order QCD correction $\mathcal{O}({\alpha }_s{v}^0)$, the relativistic correction $\mathcal{O}({\alpha }_s^0{v}^2)$ and their joint correction $\mathcal{O}({\alpha }_s{v}^2)$ are sizable and comparable to each other, especially for the charmonium case. Thus we need to take all of them into consideration for a sound estimation. For a high luminosity electron-positron collider running around the $Z$ pole, due to $Z$-boson resonance effect, sizable events could be produced from those rare decay channels.

The $P$-wave charmonium electromagnetic Dalitz decays $h_c\to {\eta }^{(\prime )}{\ell }^{+}{\ell }^{-}$ $(\ell =e,\mu )$ with large recoil momentum are investigated in the framework of perturbative QCD, and the contributions from the small-recoil-momentum region are described by the overlap of soft wave functions. The transition form factors $f_{h_c{\eta }^{(\prime )}}(q^2)$ and the normalized transition form factors $F_{h_c{\eta }^{(\prime )}}(q^2)$ in full kinematic region are derived for the first time. It is noticed that there are no IR divergences at the one-loop level, and the transition form factors with the relativistic corrections from the internal momentum of $h_c$ are insensitive to both the shapes of ${\eta }^{(\prime )}$ distribution amplitudes and the invariant mass of the lepton pair in the large-recoil-momentum region. Intriguingly, unlike the situation in the $S$-wave charmonium decays $J/\psi \to {\eta }^{(\prime )}{\ell }^{+}{\ell }^{-}$, we find that the contributions from the small-recoil-momentum region are comparable with those from the large-recoil-momentum region in the $P$-wave charmonium decays $h_c\to {\eta }^{(\prime )}{\ell }^{+}{\ell }^{-}$. By employing the obtained $F_{h_c{\eta }^{(\prime )}}(q^2)$, we give predictions of the branching ratios $\mathcal{B}(h_c\to {\eta }^{(\prime )}{\ell }^{+}{\ell }^{-})$, which may come within the range of measurement of present or near-future experiments.

We carry out a systematic analysis of the Cabibbo-favored and singly-Cabibbo-suppressed decays of $D^0\to VV$, and demonstrate that the long-distance mechanism due to the final-state interactions can provide a natural explanation for these mysterious polarization puzzles observed in $D^0\to VV$ in experiments. More observables, which can be measured at BESIII, and possibly at LHCb, are also suggested.

We introduce the novel approach of using the superscaling variable as an observable and an analysis tool in the context of charged current neutrino-nucleus interactions. We study the relation between the superscaling variable and the removal energy, in addition to other fundamental parameters of the neutrino-nucleus interaction models. In the second half of the paper, we discuss the experimental viability of this measurement following a study of neutrino energy and missing momentum reconstruction. We show that the superscaling variable is measurable in neutrino interaction experiments provided that the proton is detected in the final state. We discuss the resolution of this measurement, and the limitation imposed by the proton’s detection threshold.

Recent measurements of charm-baryon production in hadronic collisions have questioned the universality of charm-quark fragmentation across different collision systems. In this work the fragmentation of charm quarks into charm baryons is probed, by presenting the first measurement of the longitudinal jet momentum fraction carried by ${\mathrm{\Lambda }}_c^{+}$ baryons, $z_{\parallel }^{\mathrm{ch}}$, in hadronic collisions. The results are obtained in proton-proton ($pp$) collisions at $\sqrt{s}=13\mathrm{TeV}$ at the LHC, with ${\mathrm{\Lambda }}_c^{+}$ baryons and charged (track-based) jets reconstructed in the transverse momentum intervals of $3\le p_T^{{\mathrm{\Lambda }}_c^{+}}<15\mathrm{GeV}/c$ and $7\le p_T^{\text{jet ch}}<15\mathrm{GeV}/c$, respectively. The $z_{\parallel }^{\mathrm{ch}}$ distribution is compared to a measurement of ${\mathrm{D}}^0$-tagged charged jets in $pp$ collisions as well as to pythia 8 simulations. The data hints that the fragmentation of charm quarks into charm baryons is softer with respect to charm mesons, in the measured kinematic interval, as predicted by hadronization models which include color correlations beyond leading-color in the string formation.

A search for the production of a top quark in association with a photon and additional jets via flavor changing neutral current interactions is presented. The analysis uses proton-proton collision data recorded by the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$. The search is performed by looking for processes where a single top quark is produced in association with a photon, or a pair of top quarks where one of the top quarks decays into a photon and an up or charm quark. Events with an electron or a muon, a photon, one or more jets, and missing transverse momentum are selected. Multivariate analysis techniques are used to discriminate signal and standard model background processes. No significant deviation is observed over the predicted background. Observed (expected) upper limits are set on the branching fractions of top quark decays: $\mathcal{B}(t\to u\gamma )<0.95\times {10}^{-5}$ ($1.20\times {10}^{-5}$) and $\mathcal{B}(t\to c\gamma )<1.51\times {10}^{-5}$ ($1.54\times {10}^{-5}$) at 95% confidence level, assuming a single nonzero coupling at a time. The obtained limit for $\mathcal{B}(t\to u\gamma )$ is similar to the current best limit, while the limit for $\mathcal{B}(t\to c\gamma )$ is significantly tighter than previous results.

A search has been performed for the semileptonic decays $D^0\to K_S^0{K}^{-}{e}^{+}{\nu }_e$, $D^{+}\to K_S^0{K}_S^0{e}^{+}{\nu }_e$, and $D^{+}\to K^{+}{K}^{-}{e}^{+}{\nu }_e$, using $7.9{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ annihilation data collected at the center-of-mass energy $\sqrt{s}=3.773\mathrm{GeV}$ by the BESIII detector operating at the BEPCII collider. No significant signals are observed, and upper limits are set at the 90% confidence level of $2.13\times {10}^{-5}$, $1.54\times {10}^{-5}$, and $2.10\times {10}^{-5}$ for the branching fractions of $D^0\to K_S^0{K}^{-}{e}^{+}{\nu }_e$, $D^{+}\to K_S^0{K}_S^0{e}^{+}{\nu }_e$, and $D^{+}\to K^{+}{K}^{-}{e}^{+}{\nu }_e$, respectively.

Recent progress in string theory has unveiled the discovery of Neveu Schwarz-Neveu Schwarz couplings in bosonic and heterotic effective actions at order ${\alpha }^{\prime 2}$, which were achieved by imposing $O(1,1)$ symmetry on the circle reduction of classical effective actions. While the bosonic theory features 25 couplings, the heterotic theory encompasses 24 parity-even and 3 parity-odd couplings, excluding the pure gravity couplings. In this study, we redefine the even-parity couplings in the bosonic and heterotic theories through the application of appropriate field redefinitions, resulting in 10 and 8 couplings, respectively. To establish the validity of these couplings, a cosmological reduction is conducted, demonstrating that the cosmological couplings in the heterotic theory vanish, subject to one-dimensional field redefinitions that include the lapse function and total derivative terms. Additionally, it is observed that the cosmological couplings in the bosonic theory can be expressed as $\mathrm{tr}({\dot{\mathcal{S}}}^6)$. These results are consistent with existing literature, where such behavior is attributed to the pure gravity component of the couplings. Furthermore, the consistency of the obtained couplings with 4-point string theory S-matrix elements is confirmed.

We study generic matter coupled to a $D$-dimensional supergravity using a formulation of double field theory (DFT), where all the fields are encoded in $\mathrm{O}(D,D)$ multiplets. We study both the case when the matter comes from a variational principle, as well as the case where the matter comes from a statistical or thermodynamic approach. For the latter, we construct the distribution function for the perfect fluid and its entropy current, which is a conserved quantity. We then include general viscous and elastic terms in the generalized energy-momentum tensor which, in the general case, lead to entropy production. We consistently deform the conservation law of the generalized entropy current and identify a particular nondissipative deformation. Using the generalized fluid model, we revisit the issue of noncovariance of perfect fluids under T-dualities and we show how to resolve it in our DFT model with matter.

We present a new model of $\mathcal{N}=8$ mechanics with semidynamic supermultiplets. The model is constructed as an interaction of $\mathcal{N}=4$ supermultiplets which carry an implicit $\mathcal{N}=4$ supersymmetry. The initial field content consists of three dynamical $(\mathbf{1},\mathbf{4},\mathbf{3})$ multiplets: one bosonic and two fermionic. To ensure implicit $\mathcal{N}=4$ supersymmetry, we introduce the superfields describing three semidynamical $(\mathbf{4},\mathbf{4},\mathbf{0})$ multiplets: one fermionic and two bosonic. To avoid the second-order Lagrangian for fermions from the fermionic $(\mathbf{1},\mathbf{4},\mathbf{3})$ multiplets, we convert their velocities into new auxiliary fields. After conversion, these multiplets turn into semidynamical mirror $(\mathbf{4},\mathbf{4},\mathbf{0})$ multiplets without noncanonical terms in the $\mathcal{N}=8$ Lagrangian at the component level. The final $\mathcal{N}=8$ multiplet content is $(\mathbf{1},\mathbf{8},\mathbf{7})\oplus (\mathbf{8},\mathbf{8},\mathbf{0})$. As a first step to the ultimate $\mathcal{N}=4$ superfield formulation of the model, we recall a natural description of the standard and mirror $(\mathbf{4},\mathbf{4},\mathbf{0})$ multiplets in the framework of $\mathcal{N}=4,d=1$ biharmonic superspace.