This paper presents a thorough study of the local and nonlocal amplitudes in $B^+ \to K^+\mu^+\mu^-$ transitions through an amplitude analysis of the dimuon mass spectrum of the decay. The analysis is based on $pp$ collision data corresponding to an integrated luminosity of 8.4fb$^{-1}$ collected by the LHCb experiment. This measurement employs a model that describes both one-particle and two-particle nonlocal amplitudes across the entirety of the dimuon mass spectrum, enabling the determination of both short- and long-distance contributions to the decay. The compatibility of the Wilson coefficient combinations $C_9+C_9'$ and $C_{10}+C_{10}'$ with the Standard Model prediction is found to vary between $1.6\,\sigma$ and $4\,\sigma$, depending on the choice of local form factors.

Quantum Tomography of tau lepton pairs produced at a Higgs Factory collider will enable measurements of their spin correlations arising from quantum entanglement. Such measurements rely on the ability to measure the components of and correlations between the taus' spins. We present a method to fully reconstruct the kinematics of tau pair events at an electron-positron Higgs factory collider, making use of measured particles' momenta and impact parameters. This procedure results in several consistent solutions per event, which can be assigned weights according to various event properties. Full kinematic reconstruction allows the optimal extraction of the taus' spin orientation via polarimeters. We estimate the precision with which polarimeters can be reconstructed in an ideal detector, and quantify the effects of more realistic detector performance. We conclude that for this analysis, achieving a photon angular resolution of around 1~mrad is the most crucial aspect of detector performance, while photon energy resolution and vertex detector performance are significantly less important.

The LEGEND Experiment searches for the neutrinoless double beta (0$\nu\beta\beta$) decay of $^{76}$Ge employing active high purity germanium detectors enriched in $^{76}$Ge beyond 86%. LEGEND's experimental program is articulated in two phases: LEGEND-200, currently ongoing, and LEGEND-1000, the next generation development. LEGEND-200 started operating in 2023 at Laboratori Nazionali del Gran Sasso (LNGS) and ran in a stable physics data taking regime for about one year with 142.5 kg of detectors installed. With a target background index of $2 \cdot 10^{-4} $ counts/(keV kg yr) at Q$_{\beta\beta} \sim$ 2039 keV and a final exposure of 1000 kg yr, LEGEND-200 aims to reach a 3$\sigma$ discovery sensitivity for a 0$\nu\beta\beta$ half-life of $10^{27}$ yr. In this contribution, the LEGEND-200 experiment will be presented, with a focus on its current status and on the results obtained with the first year of data. In particular, the employed analysis routines will be introduced, the signal identification and background suppression performance will be discussed, and the background appearing in the region of interest around $Q_{\beta\beta}$ will be analyzed. The performed analysis of LEGEND-200 data finds no evidence for a 0$\nu\beta\beta$ signal: a lower limit to its half-life is set instead, $T_{1/2}^{0\nu} > 0.5 \cdot 10^{26}$ yr, at 90% CL. A joint GERDA + MAJORANA Demonstrator + LEGEND-200 analysis provides a limit of $T_{1/2}^{0\nu} > 1.9 \cdot 10^{26}$ yr, at 90% CL. This work is supported by the U.S. DOE and the NSF, the LANL, ORNL and LBNL LDRD programs; the European ERC and Horizon programs; the German DFG, BMBF, and MPG; the Italian INFN; the Polish NCN and MNiSW; the Czech MEYS; the Slovak RDA; the Swiss SNF; the UK STFC; the Canadian NSERC and CFI; the LNGS and SURF facilities.

The spectral function of the charged pion form factor was extracted from two data sets. The difference between the two sets is based on the presence or absence of the recent measurement of the $\pi^+ \pi^-$ production by CMD3. Although the CMD3 data are largely incompatible with other recent measurements, it was found to provide no excess when used for analytical continuation to spacelike region. Consequently, there is evidence for incompatibility when it is compared to the spacelike pion form factor obtained by the JLaB-$\pi$ experiment. Furthermore, the extracted pionic spectral function was used to obtain the QED running charge. It was then compared with the KLOE2 experiment for radiative return $\mu^{-}\mu^{+}$ production at $ \omega/\rho $ meson energy. For this purpose the hadronic vacuum polarization has been extracted from exclusive hadronic productions in $e^+e^-$ collisions via the dispersion relation using combined data with and without the CMD3 data set included in.

Recent measurements of electroweak phenomena from the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider are summarized. The standard model of particle physics was tested through highly precise determinations of its key electroweak parameters and through measurements of electroweak processes in proton-proton collisions at unprecedented center-of-mass energies of up to $13.6 \, \mathrm{TeV}$. The performance of the CMS experiment establishes its key role in the study of electroweak physics, with many measurements performed either for the first time or with the best precision at a proton-proton collider, in some cases reaching or even surpassing the precision of legacy results from lepton colliders. Recent electroweak results from the CMS experiment include: measurements of the W and Z bosons production cross sections; high-precision measurements of the forward-backward asymmetry in Drell-Yan production and of the effective leptonic electroweak mixing angle; measurements of tau lepton properties and of multiboson production and vector boson scattering rates.

This paper presents the first search for non-resonant Higgs boson pair production in association with a top-quark pair ($t\bar{t}HH$) using proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. The data sample corresponds to an integrated luminosity of 196 fb$^{-1}$, comprising 140 fb$^{-1}$ at a centre-of-mass energy of $\sqrt{s}=13$ TeV and 56 fb$^{-1}$ at 13.6 TeV. The search targets three distinct final states expected from $t\bar{t}HH$ decays: (i) one lepton (electron or muon) with at least five $b$-quarks, (ii) at least two $b$-quarks accompanied by two leptons with the same electric charges or multiple leptons, and (iii) at least three $b$-quarks with two photons. The $t\bar{t}HH$ production cross-section, relative to its Standard Model prediction, is measured to be $\mu_{t\bar{t}HH}=-3^{+11}_{-12}$. This result corresponds to a 95$\% $ confidence-level upper limit of 20 times the Standard Model prediction for the $t\bar{t}HH$ production cross-section, with an expected limit of 21. The Higgs effective field theory Wilson coefficient $c_{t\bar{t}HH}$ is also constrained at the same confidence level to the range of $-3.9<c_{t\bar{t}HH}<3.3$, compared with the expected range of $-4.0<c_{t\bar{t}HH}<3.5$.

A flavor-tagged time-dependent analysis of $B^{0}\rightarrow K_{S}^{0}\mu^{+}\mu^{-}$ decays is performed across the full dimuon mass range excluding the $J/\psi$ and $\psi(2S)$ resonance regions. The analysis uses proton-proton collision data collected by the LHCb experiment in 2011--2018 at center-of-mass energies of 7, 8 and 13TeV, corresponding to an integrated luminosity of 9$fb^{-1}$. The CP violation parameters are determined to be $C=-0.13 \pm 0.32 \pm 0.04$ and $S= +0.82\pm 0.29 \pm 0.05$, where the first uncertainties are statistical and the second are this http URL results are consistent with the Standard Model prediction. This is the first experimental study of time-dependent CP violation in $b\rightarrow sl^{+}l^{-}$ processes.

The identification of hadronic final states plays a crucial role in the physics programme of the ATLAS Experiment at the CERN LHC. Sophisticated artificial intelligence (AI) algorithms are employed to classify jets according to their origin, distinguishing between quark- and gluon-initiated jets, and identifying hadronically decaying heavy objects such as W bosons and top quarks. This contribution summarises recent developments in constituent-based tagging architectures, including graph neural networks (GNNs) and transformer-based approaches, their performance in simulated and real data, and future perspectives towards data-driven optimisation and model-independent tagging strategies.

Accurate predictions for dark matter-electron scattering in solids require an all-electron treatment together with a faithful description of dielectric screening beyond simple approximations. In particular, local field effects, arising from microscopic inhomogeneities of the electronic response, can significantly modify scattering rates across relevant momentum and energy scales. We present an all-electron framework for computing dark matter-electron scattering rates that incorporates dielectric screening at the random-phase approximation (RPA) level, including local field effects. Using crystalline silicon as a benchmark, we show that local field effects play an important role both at large momentum transfers, spanning multiple Brillouin zones, and at low momentum near the plasmon resonance. We compute electron recoil spectra and projected sensitivities for non-relativistic halo dark matter and for boosted dark matter or other dark-sector particles, which are sensitive to the impact of local field effects in these high and low momentum regimes, respectively. We further present RPA dielectric functions including local field effects for Ge, GaAs, SiC, and diamond, enabling a systematic comparison across target materials. These developments are implemented in the open source code QCDark2.

We propose a novel test of the unitarity of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix at collider experiments. Our approach exploits the incomplete cancellation between $t$-channel neutrino exchange and $s$-channel gauge-boson contributions that arises in the presence of violation of the flavor-diagonal PMNS unitarity conditions, leading to an anomalous growth of the cross section with energy. Such effects are generic in extensions of the Standard Model in which light neutrinos mix with heavier states, and can manifest at colliders as long as the characteristic energy of the process remains below the mass threshold of the new degrees of freedom. After briefly reviewing these scenarios, we employ our strategy to derive model-independent bounds on flavor diagonal unitarity-violating effects using LEP-II data. We then present sensitivity projections for future lepton and hadron colliders, demonstrating that they are well suited to probe the unitarity of the neutrino mixing matrix with this method.

A photon linear collider, the two-photon collision mode of an $e^+e^-$ linear collider, uses high-energy laser photons backscattered off the incoming electrons and positrons. The colliding-photon polarization is fully controllable through the polarizations of the initial electron and positron beams and laser photons. We investigate the impact of colliding-photon polarization on the observability of quantum entanglement in top-quark pair production at a photon linear collider. Constructing the spin density matrix of the $t\bar{t}$ two-qubit system from the helicity amplitudes, we demonstrate that a photon linear collider is an ideal machine to probe quantum entanglement and Bell nonlocality across the broad phase space of the process.

Ring Imaging Cherenkov (RICH) detectors are a key component of particle identification systems in many particle, nuclear and astroparticle physics experiments. Their ultimate performance depends not only on detector design and hardware implementation, but also crucially on the quality of pattern recognition and data analysis algorithms used to reconstruct Cherenkov ring images and to perform particle identification. In recent years, significant advances have been made both in traditional reconstruction approaches, such as likelihood-based methods and Hough-transform techniques, and in the application of modern machine learning tools. This contribution reviews the current state of RICH reconstruction algorithms, highlights representative use cases from operating experiments, and discusses emerging trends including global particle identification strategies and generative machine learning approaches for fast simulation and reconstruction.

The Migdal effect in semiconductors, prompt ionization from a primary nuclear scattering event, can be described across all kinematic regimes using an effective field theory that encodes the complex vibrational and electronic degrees of freedom of the crystal in measurable structure factors. Simultaneously, general dark matter-nucleus interactions can be systematically described using non-relativistic effective field theory operators. We combine these two effective field theory frameworks to calculate the Migdal effect in semiconductors for all ten dimension-six non-relativistic operators. From the effective Hamiltonian, we find that DM-nucleus scattering factorizes from the ionization and vibrational excitation signal as it does in the free-atom case. Using data from EDELWEISS that was taken with a germanium detector, we derive new experimental bounds on each operator and compare these limits to other direct-detection constraints in the literature. We find the accessible parameter space to be disfavored by bounds on heavy mediators contained in simple UV completions that generate the effective operators.

We report on a search using the IceCube Neutrino Observatory for MeV neutrinos from compact binary mergers detected through gravitational waves during the LIGO-Virgo-KAGRA (LVK) O1, O2, and O3 observing runs. The search focuses on events involving at least one candidate neutron star, such as binary neutron star (BNS) and neutron star--black hole (NSBH) mergers, which may produce a burst of thermal neutrinos due to the hot and dense conditions created during the merger. We looked for short-time increases in IceCube's detector activity around each gravitational-wave event, using four time windows centered on the merger time. We also performed a binomial test for two populations, those with and without at least one neutron star. No significant excess of neutrinos was found. We set upper limits on the MeV neutrino flux for each event, and we place constraints on MeV neutrino emission from mergers that have at least one neutron star. We showcase upper limits for GW170817, the first confirmed BNS merger, providing one of the strongest limits to date on MeV neutrino emission from such sources.

Axion dark matter (DM) is predicted to convert into radio waves in neutron star magnetospheres. We assess the detectability of this signal using a 5 m radio telescope to be installed at the Fan Mountain Observatory, operating in the UHF, L- and S-bands from 0.5 to 4~GHz. We demonstrate that such a telescope can search new parameter space for axion-like particles over a broad range from $2\,\mu\text{eV}<m_a<17\,\mu\text{eV}$ for axion-photon couplings $g_{a\gamma\gamma} \gtrsim 2\times 10^{-12}\text{ GeV}^{-1}$ with a three year observing period assuming the standard halo model -- improving neutron star observations by more than an order of magnitude. The search is broadband and is thus complementary to other techniques in the same frequency range. We describe in detail our neutron star population model, noise model, and proposed observing strategy. Most constraining power comes from neutron stars at the Galactic centre, where the smooth DM halo is densest. If a DM spike exists at the Galactic centre, the search is sensitive in the QCD axion model band. UHF and L-band observations (0.5 to 2~GHz) represent the pathfinder phase of a wider program we call ``Axion Search with Telescope for Radio Astronomy'' (ASTRA). Future higher mass searches aimed at discovery potential for the post-inflation axion require further hardware development to cover S, C, X and Ku bands (2 to 18~GHz).

We present a track-finding algorithm for the Belle II experiment that specifically targets so-called kinks: signatures of charged particles decaying or scattering in-flight in the detector material, resulting in a sudden and significant change of the particle's flight direction. Our benchmark studies of this Kink Finder show that the reconstruction efficiency for such signatures is about 40%, compared to a value of around 11% for the standard Belle II track-finding algorithm. Our studies also show that the Kink Finder significantly improves the resolution of the secondary track parameters, suppresses the number of cloned tracks, and reduces the PID misidentification rates for kaon and pions.

We report the first searches for charged-lepton-flavor violation in decays of $\chi_{bJ}(1P)$ ($J=0, 1,$ and $2$) to a pair of charged leptons using 158 million $\Upsilon(2S)$ decays collected with the Belle detector in $e^+e^-$ collisions at the KEKB collider. No significant signal is observed, and we set upper limits on the branching fractions for $\chi_{bJ}(1P)$ decays to $e^\pm\mu^\mp$ at the level of $10^{-6}$ and to $e^\pm\tau^\mp$ or $\mu^\pm\tau^\mp$ at the level of $10^{-5}$. Limits on $\chi_{b0}(1P)$ decays are translated into bounds on the corresponding Wilson coefficients of scalar operators that mediate charged-lepton-flavor violation.

As a free, intensive, weakly interacting, and well directional messenger, solar neutrinos have been driving both solar physics and neutrino physics developments for more than half a century. Since more extensive and advanced neutrino experiments are under construction, being planned or proposed, we are striving toward an era of precise and comprehensive measurement of solar neutrinos in the next decades. In this article, we review recent theoretical and experimental progress achieved in solar neutrino physics. We present not only an introduction to neutrinos from the standard solar model and the standard flavor evolution, but also a compilation of a variety of new physics that could affect and hence be probed by solar neutrinos. After reviewing the latest techniques and issues involved in the measurement of solar neutrino spectra and background reduction, we provide our anticipation on the physics gains from the new generation of neutrino experiments.

The Standard Model (SM) of particle physics fails to explain the observed hierarchy in fermion masses or the origin of fermion-flavor structure. We construct a model to explain these observations in the quark sector. We introduce a spectrum of new particles consisting of six of each -- massive singlet vector-like quarks (VLQs), singlet scalars, and SU(2)-doublet scalars. SM quark masses are generated when the neutral components of the SU(2)-doublet scalars acquire non-zero vacuum expectation values (VEVs). We impose global symmetries to ensure that Yukawa couplings stay roughly flavor diagonal and democratic (of the same order), as well as to suppress tree-level flavor-changing neutral currents. Quark-mass hierarchy then follows from a hierarchy in scalar VEVs. The singlet scalars also acquire weak-scale VEVs. Together with the VLQs, they act as messengers between different generations of quarks in the SM. These messenger particles are responsible for generating the elements of the Cabibbo-Kobayashi-Masakawa (CKM) matrix which depend on the ratios of the singlet VEVs and VLQ masses. Constructed this way, the CKM matrix is found to be \emph{independent} of the SM fermion masses. Using the measured values of the CKM matrix elements and assuming order-one couplings, we derive constraints on the masses of the VLQs and discuss prospects for probing our model in the near future.

The hint of a pseudoscalar toponium state at the Large Hadron Collider (LHC) opens a new avenue for studying a novel class of QCD (quasi-)bound states with comparable formation and decay times. Compared with charmonium and bottomonium, toponium is a quasi-bound state, resembling a hydrogen atom of the strong interaction, although it appears as a broader resonance. We compute the masses and annihilation decay widths of the lowest $S$-wave ($\eta_t$, $\psi_t$) and $P$-wave ($\chi_{t0}$, $\chi_{t1}$) toponium states, and assess their discovery prospects at the High-Luminosity LHC (HL-LHC) and future lepton colliders, such as the $e^+e^-$ stage of the Future Circular Collider (FCC-ee). Detecting the vector $\psi_t$ state at the HL-LHC is hindered by the Landau-Yang theorem and the gluon-dominated production environment of the collider, whereas lepton colliders offer promising sensitivity through both constituent and two-body decays. A more precise measurement of the $\eta_t$ mass, approximately equal to that of $\psi_t$, at the LHC could help determine the optimal $t\bar{t}$ threshold center-of-mass energy for FCC-ee. The $P$-wave states remain challenging to observe at both the HL-LHC and future lepton colliders. We also discuss how toponium measurements can be used to probe top-quark properties and to conduct indirect searches for new physics, including light scalars that couple to the top quark.

We propose a novel method to probe gluon linear polarization via energy correlations in hard scattering processes. This approach exploits the characteristic $\cos 2\phi$ azimuthal modulation in single- and two-point energy correlations within jets initiated by polarized gluons. In contrast to conventional techniques that rely on $k_t$ resummation or intricate jet substructure observables, our method offers a theoretically robust and experimentally accessible avenue for gluon polarimetry. We perform an all-order analysis within the Ciafaloni-Catani-Fiorani-Marchesini (CCFM) formalism, incorporating coherent branching effects to achieve improved precision. Our predictions can be tested at current and future facilities, including the LHC, RHIC, HERA, and the EIC.

The Krauss-Nasri-Trodden (KNT) model provides a unified framework for addressing the smallness of neutrino masses (by a three-loop radiative mechanism) and the dark matter abundance (via thermal freeze-out) simultaneously. In this work, we investigate the implications of renormalization group effects on the model's parameter space. To this end, we perform a Markov Chain Monte Carlo analysis to identify the viable regions of parameter space that is consistent with all the relevant experimental and theoretical constraints at low energies. We show that a significant portion of the low-energy viable region is incompatible with the vacuum stability conditions once the renormalization group effects are taken into account. Most of the remaining parameter space of the model can be probed in future charged lepton flavor violating experiments.