The isospin doublet scalar field with hypercharge $3/2$ is introduced in some new physics models such as tiny neutrino masses. Detecting the doubly charged scalar bosons from the doublet field can be a good probe of such models. However, their collider phenomenology has not been examined sufficiently. We investigate collider signatures of the doubly and singly charged scalar bosons at the LHC for the high-luminosity upgraded option (HL-LHC) by looking at transverse mass distributions etc. With the appropriate kinematical cuts we demonstrate the background reduction in the minimal model in the following two cases depending on the mass of the scalar bosons. (1) The main decay mode of the singly charged scalar bosons is the tau lepton and missing (as well as charm and strange quarks). (2) That is into a top bottom pair. In the both cases, we assume that the doubly charged scalar boson is heavier than the singly charged ones. We conclude that the scalar doublet field with $Y=3/2$ is expected to be detectable at the HL-LHC unless the mass is too large.

Using an artificial neural network, we explore the parameter space of supergravity grand unified models consistent with the combined Fermilab E989 and Brookhaven E821 data on $(g-2{)}_{\mu }$. Within an extended mSUGRA model with nonuniversal gaugino masses, the analysis indicates that the region favored by the data is the one generated by gluino-driven radiative breaking of the electroweak symmetry ($\tilde{g}\mathrm{SUGRA}$). This region naturally leads to a split sparticle spectrum with light sleptons and weakinos but heavy squarks, with the stau and the chargino as the lightest charged particles. We show that if the entire deviation from the Standard Model $(g-2{)}_{\mu }$ arises from supersymmetry, then supersymmetry is discoverable at HL-LHC and HE-LHC via production and decay of sleptons and sneutrinos within the optimal integrated luminosity of HL-LHC and with a smaller integrated luminosity at HE-LHC. The effect of $CP$ phases on the muon anomaly is investigated, and the parameter space of $CP$ phases excluded by the Fermilab constraint is exhibited.

We show how one may classify all semisimple algebras containing the $\mathfrak{s}\mathfrak{u}(3)\oplus \mathfrak{s}\mathfrak{u}(2)\oplus \mathfrak{u}(1)$ symmetry of the Standard Model and acting on some given matter sector, enabling theories beyond the Standard Model with unification (partial or total) of symmetries (gauge or global) to be cataloged. With just a single generation of Standard Model fermions plus a singlet neutrino, the only gauge symmetries correspond to the well-known algebras $\mathfrak{su}(5)$, $\mathfrak{so}(10)$, and $\mathfrak{su}(4)\oplus \mathfrak{su}(2)\oplus \mathfrak{su}(2)$, but with two or more generations a limited number of exotic symmetries mixing flavor, color, and electroweak degrees of freedom become possible. We provide a complete catalog in the case of three generations or fewer and outline how our method generalizes to cases with additional matter.

Partial quenching allows one to consider correlation functions and amplitudes that do not arise in the corresponding unquenched theory. For example, physical $s$-wave pion scattering can be decomposed into $I=0$ and 2 amplitudes, while, in a partially-quenched extension, the larger symmetry group implies that there are more than two independent scattering amplitudes. It has been proposed that the finite-volume quantization condition of Lüscher holds for the correlation functions associated with each of the two-particle amplitudes that arise in partially-quenched theories. Using partially-quenched chiral perturbation theory, we show that this proposal fails for those correlation functions for which the corresponding one-loop amplitudes do not satisfy $s$-wave unitarity. For partially-quenched amplitudes that, while being unphysical, do satisfy one-loop $s$-wave unitarity, we argue that the proposal is plausible. Implications for previous work are discussed.

We study the chiral separation effect (CSE) in two-color and two-flavor QCD to delineate quasiparticle pictures in dense matter from low to high temperatures. Both massless and massive quarks are discussed. We particularly focus on the high density domain where diquarks form a color-singlet condensate with the electric charge $1/3$. The condensate breaks the baryon number and $U(1{)}_A$ axial symmetry, and induces the electromagnetic Meissner effects. Within a quark quasiparticle picture, we compute the chiral separation conductivity at one-loop. We have checked that Nambu-Goldstone modes, which should appear in the improved vertices as required by the Ward-Takahashi identities, do not contribute to the chiral-separation conductivity due to their longitudinal natures. In the static limit, the destructive interferences in the particle-hole channel, as in the usual Meissner effects, suppress the conductivity (in the chiral limit, to $1/3$ of that of the normal phase). This locally breaks the universality of the CSE coefficients, provided quasiparticle pictures are valid in the bulk matter.

We use QCD sum rules to study the mass spectra of $P$-wave charmed baryons of the $SU(3)$ flavor ${\mathbf{6}}_F$. We also use light cone sum rules to study their $S$- and $D$-wave decays into ground-state charmed baryons together with light pseudoscalar and vector mesons. We work within the framework of heavy quark effective theory, and we also consider the mixing effect. Our results can explain many excited charmed baryons as a whole, including the ${\mathrm{\Sigma }}_c(2800{)}^0$, ${\mathrm{\Xi }}_c(2923{)}^0$, ${\mathrm{\Xi }}_c(2939{)}^0$, ${\mathrm{\Xi }}_c(2965{)}^0$, ${\mathrm{\Omega }}_c(3000{)}^0$, ${\mathrm{\Omega }}_c(3050{)}^0$, ${\mathrm{\Omega }}_c(3066{)}^0$, ${\mathrm{\Omega }}_c(3090{)}^0$, and ${\mathrm{\Omega }}_c(3119{)}^0$. Their masses, mass splittings within the same multiplets, and decay properties are extracted for future experimental searches.

In this work, we propose the $4S\text{−}3D$ mixing scheme to assign the $\mathrm{\Upsilon }(10753)$ into the conventional bottomonium family. Under this interpretation, we further study its hidden-bottom hadronic decays with a ${\eta }^{(\prime )}$ or $\omega$ emission, which include $\mathrm{\Upsilon }(10753)\to \mathrm{\Upsilon }(1S){\eta }^{(\prime )}$, $\mathrm{\Upsilon }(10753)\to h_b(1P)\eta$, and $\mathrm{\Upsilon }(10753)\to {\chi }_{bJ}\omega$ ($J=0$, 1, 2) processes. Since the $\mathrm{\Upsilon }(10753)$ is above the $B\overline{B}$ threshold, the coupled-channel effect cannot be ignored; thus, when calculating partial decay widths of these $\mathrm{\Upsilon }(10753)$ hidden-bottom decays, we apply the hadronic loop mechanism. Our result shows that these discussed decay processes own considerable branching fractions with an order of magnitude of ${10}^{-4}–{10}^{-3}$, which can be accessible at Belle II and other future experiments.

In this work, the branching ratio $\mathcal{B}[B\to K{\chi }_{c0}(2P)]$ is extracted for the first time through the fit fractions in the newly measured $B\to KD\overline{D}$ process by LHCb. With the rescattering mechanism, this extracted branching ratio is reproduced well. Our study further enforces the role of the newly measured $B\to KD\overline{D}$ process to establish the ${\chi }_{c0}(2P)$ charmonium state, which is a crucial step when constructing the charmonium family.

Partial wave analysis is performed, with effective potentials as dynamical inputs, to scrutinize the recent LHCb data on the di-$J/\psi$ invariant mass spectrum. Coupled-channel effects are incorporated in the production amplitude via final state interactions. The LHCb data can be well described. A dynamically generated pole structure, which can be identified as the $X(6900)$ state, is found. Our analysis also provides hints for the existence of three other possible states: a bound state $X(6200)$, a broad resonant state $X(6680)$ and a narrow resonant state $X(7200)$. The $J^{PC}$ quantum numbers of the $X(6680)$ and $X(6900)$ states should be $2^{++}$, while the $X(6200)$ and $X(7200)$ states prefer $0^{++}$. To determine the above states more precisely, more experimental data for the channels, such as $J/\psi \psi (2S)$, $J/\psi \psi (3770)$, di-$\psi (2S)$, are required.

The BESIII Collaboration has observed a candidate for a $c\overline{c}s\overline{u}$ tetraquark $Z_{cs}$ at $({3982.5}_{-2.6}^{+1.8}\pm 2.1)\mathrm{MeV}$ and width $({12.8}_{-4.4}^{+5.3}\pm 3.0)\mathrm{MeV}$, while the LHCb Collaboration has observed a $Z_{cs}$ candidate in the $J/\psi K^{-}$ channel with mass of $(4003\pm 6_{-14}^{+4})\mathrm{MeV}$ and width $(131\pm 15\pm 26)\mathrm{MeV}$. In this paper, we examine the possibility that these two states are distinct eigenstates of a mixing process similar to that which gives rise to two axial-vector mesons labeled by the Particle Data Group [P. Zyla et al., Prog. Theor. Exp. Phys. 6, 083C01 (2020)] $K_1(1270)$ and $K_1(1400)$. The main point is that on top of a $\overline{c}c$ pair the $Z_{cs}$ states have the same light quark content as the $K_1$-s. In the compact tetraquark picture, this implies several additional states, analogous to members of the $K_1$ nonet. These states have not yet been observed; nor are they required in the molecular approach. Thus, experimental discovery or exclusion of these extra states will be a critical test for competing models of exotic mesons with hidden charm.

We show that under current experimental bounds of the decays $e_a\to e_b\gamma$, the recent experimental data of the muon anomalous magnetic dipole moment $(g-2{)}_{\mu }$ can be explained in the framework of the $3-3-1$ model with right-handed neutrinos. In addition, all of these branching ratios can reach closely the recent experimental upper bounds.

A search for pair production of bottom squarks in events with hadronically decaying $\tau$-leptons, $b$-tagged jets, and large missing transverse momentum is presented. The analyzed dataset is based on proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ delivered by the Large Hadron Collider and recorded by the ATLAS detector from 2015 to 2018, and corresponds to an integrated luminosity of $139{\mathrm{fb}}^{-1}$. The observed data are compatible with the expected Standard Model background. Results are interpreted in a simplified model where each bottom squark is assumed to decay into the second-lightest neutralino ${\tilde{\chi }}_2^0$ and a bottom quark, with ${\tilde{\chi }}_2^0$ decaying into a Higgs boson and the lightest neutralino ${\tilde{\chi }}_1^0$. The search focuses on final states where at least one Higgs boson decays into a pair of hadronically decaying $\tau$-leptons. This allows the acceptance and thus the sensitivity to be significantly improved relative to the previous results at low masses of the ${\tilde{\chi }}_2^0$, where bottom-squark masses up to 850 GeV are excluded at the 95% confidence level, assuming a mass difference of 130 GeV between ${\tilde{\chi }}_2^0$ and ${\tilde{\chi }}_1^0$. Model-independent upper limits are also set on the cross section of processes beyond the Standard Model.

A search is presented for lepton-flavor violating decays of the Higgs boson to $\mu \tau$ and $e\tau$. The dataset corresponds to an integrated luminosity of $137{\mathrm{fb}}^{-1}$ collected at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. No significant excess has been found, and the results are interpreted in terms of upper limits on lepton-flavor violating branching fractions of the Higgs boson. The observed (expected) upper limits on the branching fractions are, respectively, $\mathcal{B}(H\to \mu \tau )<0.15(0.15)\%$ and $\mathcal{B}(H\to e\tau )<0.22(0.16)\%$ at 95% confidence level.

Parton distributions can be defined in terms of the entropy of entanglement between the spatial region probed by deep inelastic scattering and the rest of the proton. For very small $x$, the proton becomes a maximally entangled state. This approach leads to a simple relation $S=\ln N$ between the average number $N$ of color-singlet dipoles in the proton wave function and the entropy of the produced hadronic state $S$. At small $x$, the multiplicity of dipoles is given by the gluon structure function, $N=xG(x,Q^2)$. Recently, the H1 collaboration analyzed the entropy of the produced hadronic state in deep inelastic scattering, and studied its relation to the gluon structure function; poor agreement with the predicted relation was found. In this paper we argue that a more accurate account of the number of color-singlet dipoles in the kinematics of H1 experiment (where hadrons are detected in the current fragmentation region) is given not by $xG(x,Q^2)$ but by the sea quark structure function $x\mathrm{\Sigma }(x,Q^2)$. Sea quarks originate from the splitting of gluons, so at small $x$ $x\mathrm{\Sigma }(x,Q^2)\sim xG(x,Q^2)$, but in the current fragmentation region this proportionality is distorted by the contribution of the quark-antiquark pair produced by the virtual photon splitting. In addition, the multiplicity of color-singlet dipoles in the current fragmentation region is quite small, and one needs to include $\sim 1/N$ corrections to $S=\ln N$ asymptotic formula. Taking both of these modifications into account, we find that the data from the H1 collaboration in fact agree well with the prediction based on entanglement.

Leptoquarks extending the Standard Model (SM) have attracted increased attention in the recent literature. Hence, the identification of four-dimensional (4D) SM-like models and the classification of allowed leptoquarks from strings is an important step in the study of string phenomenology. We perform the most extensive search for SM-like models from the nonsupersymmetric heterotic string $\mathrm{SO}(16)\times \mathrm{SO}(16)$, resulting in more than 170 000 inequivalent promising string models from 138 Abelian toroidal orbifolds. We explore the 4D massless particle spectra of these models in order to identify all exotics beside the three generations of quarks and leptons. Hereby, we learn which leptoquark can be realized in this string setup. Moreover, we analyze the number of SM Higgs doublets which is generically larger than one. Then, we identify SM-like models with a minimal particle content. These so-called almost SM models appear most frequently in the orbifold geometries ${\mathbb{Z}}_2\times {\mathbb{Z}}_4(2,4)$ and (1,6). Finally, we apply machine learning to our data set in order to predict the orbifold geometry where a given particle spectrum is most likely to be found.

An impressive effort is being pursued in order to develop new strategies that allow an efficient computation of multi-loop multi-leg Feynman integrals and scattering amplitudes, with a particular emphasis on removing spurious singularities and numerical instabilities. In this article, we describe an innovative geometric approach based on graph theory to unveil the causal structure of any multi-loop multi-leg amplitude in quantum field theory. Our purely geometric construction reproduces faithfully the manifestly causal integrand-level behavior of the loop-tree duality representation. We find that the causal structure is fully determined by the vertex matrix, through a suitable definition of connected partitions of the underlying diagrams. Causal representations for a given topological family are obtained by summing over subsets of all the possible causal entangled thresholds that originate connected and oriented partitions of the underlying topology. These results are compatible with Cutkosky rules. Moreover, we find that diagrams with the same number of vertices and multi-edges exhibit similar causal structures, regardless of the number of loops.

In many realizations of beyond the Standard Model theories, new massive particles are introduced, leading to a multiscale system with widely separated energy scales. In this setting the Coleman-Weinberg effective potential, which describes the vacuum of the theory at the quantum level, has to be supplemented with a prescription to handle the hierarchy in mass scales. In any quantum field theory involving scalar fields and multiple, highly differing mass scales, it is, in general, not possible to choose a single renormalization scale that will remove all the large logarithms in the effective potential. In this paper, we focus on the so-called decoupling method, which freezes the effects of heavy particles on the renormalization group running of the light degrees of freedom at low energies. We study this for a simple two-scalar theory and find that, while the decoupling method leads to an acceptable and convergent effective potential, the method does not solve the fine-tuning problem that is inherent to the hierarchy problem of multiscale theories. We also consider an alternative implementation of the decoupling approach, which gives different results for the shape of the potential, but still leads to similar conclusions on the amount of fine-tuning in the model. We suggest a way to avoid running into this fine-tuning problem by adopting a prescription on how to fix parameters in such decoupling approaches.

We study leptonic $CP$ and flavor violations in supersymmetric grand unified theory with right-handed neutrinos, paying attention to the renormalization group effects on the slepton mass matrices due to the neutrino and grand unified theory Yukawa interactions. In particular, we study in detail the impacts of the so-called Casas-Ibarra parameters on $CP$ and flavor violating observables. The renormalization group effects induce $CP$ and flavor violating elements of the supersymmetric breaking scalar mass squared matrices, which may result in sizable leptonic $CP$ and flavor violating signals. Assuming a seesaw formula for the active neutrino masses, the renormalization group effects have been often thought to be negligible as the right-handed neutrino masses become small. With the most general form of the neutrino Yukawa matrix, i.e., taking into account the Casas-Ibarra parameters; however, this is not the case. We found that the maximal possible sizes of signals of leptonic $CP$ and flavor violating processes are found to be insensitive to the mass scale of the right-handed neutrinos and that they are as large as (or larger than) the present experimental bounds irrespective of the right-handed neutrino masses.

There are broadly three channels to probe axionlike particles (ALPs) produced in the laboratory: through their subsequent decay to Standard Model (SM) particles, their scattering with SM particles, or their subsequent conversion to photons. Decay and scattering are the most commonly explored channels in beam-dump type experiments, while conversion has typically been utilized by light-shining-through-wall (LSW) experiments. A new class of experiments, dubbed PASSAT (particle accelerator helioscopes for slim axionlike-particle detection), has been proposed to make use of the ALP-to-photon conversion in a novel way: ALPs, after being produced in a beam-dump setup, turn into photons in a magnetic field placed near the source. It has been shown that such hybrid beam-dump-helioscope experiments can probe regions of parameter space that have not been investigated by other laboratory-based experiments, hence providing complementary information; in particular, they probe a fundamentally different region than decay or LSW experiments. We propose the implementation of PASSAT in future neutrino experiments, taking a DUNE-like experiment as an example. We demonstrate that the magnetic field in the planned DUNE multipurpose detector is already capable of probing the ALP-photon coupling down to $g_{a\gamma \gamma }\sim \mathrm{few}\times {10}^{-5}{\mathrm{GeV}}^{-1}$ for ALP masses $m_a\lesssim 10\mathrm{eV}$. The implementation of a CAST or BabyIAXO-like magnet would improve the sensitivity down to $g_{a\gamma \gamma }\sim {10}^{-6}{\mathrm{GeV}}^{-1}$.

The LHC may produce light, weakly interacting particles that decay to dark matter, creating an intense and highly collimated beam of dark matter particles in the far-forward direction. We investigate the prospects for detecting this dark matter in two far-forward detectors proposed for a future forward physics facility: $\mathrm{FASER}\nu 2$, a 10-ton emulsion detector, and FLArE, a 10- to 100-ton LArTPC. We focus here on nuclear scattering, including elastic scattering, resonant pion production, and deep inelastic scattering, and devise cuts that efficiently remove the neutrino-induced background. In the invisibly decaying dark photon scenario, DM-nuclear scattering probes new parameter space for dark matter masses $5\mathrm{MeV}\lesssim m_{\chi }\lesssim 500\mathrm{MeV}$. When combined with the DM-electron scattering studied previously, $\mathrm{FASER}\nu 2$ and FLArE will be able to discover dark matter in a large swath of the cosmologically favored parameter space with $\mathrm{MeV}\lesssim m_{\chi }\lesssim \mathrm{GeV}$.