We discuss a simple theory predicting the existence of a Dirac dark matter candidate from gauge anomaly cancellation. In this theory, the spontaneous breaking of the local baryon number at the low scale can be understood. We show that the constraint from the dark matter relic abundance implies an upper bound on the theory of a few tens of TeV. We study the correlation between the dark matter constraints and the prediction for the electric dipole moment of the electron. We point out the implications for the diphoton decay width of the Standard Model Higgs boson. Furthermore, we study the decays of the new Higgs boson presented in the theory, and we show that the branching ratio into two photons can be large. We also discuss the correlation between the dark matter constraints and the properties of the new Higgs boson decays. This theory could be tested at current or future experiments by combining the results from dark matter, collider, and electric dipole moment experiments.

Ever since the discovery of neutrinos, we have wondered if neutrinos are their own antiparticles. One remarkable possibility is that neutrinos have a pseudo-Dirac nature, predicting a tiny mass difference between active and sterile states. We analyze the neutrino data from SN1987A in the light of active-sterile oscillations and find a mild preference ($\mathrm{\Delta }{\chi }^2\approx 3$) for $\delta m^2=6.31\times {10}^{-20}{\mathrm{eV}}^2$. Notably, the same data is able to exclude $\delta m^2\sim [2.55,3.01]\times {10}^{-20}{\mathrm{eV}}^2$ with $\mathrm{\Delta }{\chi }^2>9$, the tiniest mass differences constrained so far. We further consider the next-generation of experiments and demonstrate their sensitivity exploring the nature of the neutrino mass.

We study the lepton flavor violating decays such as $\mu \to e\gamma$, $\tau \to e\gamma$, $\tau \to \mu \gamma$ in the three-loop radiative seesaw model proposed by Krauss, Nasri, and Trodden. In this model, the relevant coupling constants are larger for the heavier scalars that run inside loop diagrams to generate the appropriate magnitude of neutrino masses. Imposing a criterion that all the coupling constants must be small enough to be treated perturbatively, we find an upper bound on the mass of one of the scalars. By combining it with neutrino mass parameters, we derive lower bounds on the branching ratios of the lepton flavor violating processes. In a case with the inverted mass ordering and best-fit neutrino oscillation parameters, one of the lower bounds is $\mathrm{Br}(\mu \to e\gamma )>1.1\times {10}^{-13}$, which is within the reach of the MEG II experiment.

Motivated by the fact that naturalness arguments strongly suggest that the supersymmetry (SUSY)-preserving Higgsino mass parameter $\mu$ cannot be too far above the weak scale, we reexamine Higgsino pair production in association with a hard QCD jet at the High Luminosity LHC. We focus on ${\ell }^{+}{\ell }^{-}+{\cancel{E}}_T+j$ events from the production and subsequent decay, ${\tilde{\chi }}_2^0\to {\tilde{\chi }}_1^0{\ell }^{+}{\ell }^{-}$, of the heavier neutral Higgsino. The novel feature of our analysis is that we suggest angular cuts to reduce the important background from $Z(\to \tau \tau )+j$ events more efficiently than the $m_{\tau \tau }^2<0$ cut that has been used by the ATLAS and CMS Collaborations. Other cuts, needed to reduce backgrounds from $t\overline{t}$, $WWj$, and $W/Z+\ell \overline{\ell }$ production, are also delineated. We plot out the reach of LHC14 for 300 and $3000{\mathrm{fb}}^{-1}$ and also show distributions that serve to characterize the Higgsino signal, noting that Higgsinos may well be the only superpartners accessible at LHC14 in a well-motivated class of natural SUSY models.

The P2 experiment aims at high-precision measurements of the parity-violating asymmetry in elastic electron-proton and electron-${}^{12}\mathrm{C}$ scatterings with longitudinally polarized electrons. We discuss here the sensitivity of P2 to leptoquarks, which within the P2 energy range can be described in the language of Standard Model effective field theory (SMEFT). We give the expected P2 limits on the SMEFT operators and on the leptoquark parameters, which will test energy scales up to 15 TeV. In many cases those limits exceed current constraints from LHC and atomic parity violation (APV) experiments. We also demonstrate that degeneracies of different SMEFT operators can partially be resolved by use of APV experiments and different targets (protons and ${}^{12}\mathrm{C}$) at P2. Moreover, we show that P2 could confirm or resolve potential tensions between the theoretical and experimental determinations of the weak charge of ${}^{133}\mathrm{Cs}$.

In this paper, both the unpolarized and the polarized $\rho$ meson generalized parton distributions are investigated in the framework of the Nambu–Jona-Lasinio model using the proper time regularization scheme. The symmetry properties of $\rho$ meson generalized parton distributions are checked. The three independent distribution functions in deep inelastic scattering, $F_1(x)$, $b_1(x)$, and $g_1(x)$, and the Sachs-like charge, magnetic, and quadruple form factors $G_C(t)$, $G_M(t)$, and $G_Q(t)$, which are the first Mellin moments of unpolarized generalized parton distributions, are obtained. In addition, the $u$ quark axial vector form factors ${\tilde{F}}_1^u(t)$ and ${\tilde{F}}_2^u(t)$ related to the axial currents from the polarized generalized parton distributions are studied. The impact parameter dependent parton distribution functions, which are the two-dimensional Fourier transform of generalized parton distributions are studied, too. The obtained $\rho$ meson generalized parton distributions satisfy the required properties well.

We calculate the next-to-leading order (NLO) QCD corrections to $\gamma +\gamma \to {\eta }_c+c+\overline{c}$, $\gamma +\gamma \to {\eta }_b+b+\overline{b,}$ and $\gamma +\gamma \to B_c+b+\overline{c}$ processes in the framework of nonrelativistic QCD factorization formalism. The cross sections at the SuperKEKB electron-positron collider, as well as the future collider like the Circular Electron Positron Collider, are evaluated. Numerical results indicate that the NLO corrections are significant, and the uncertainties in theoretical predictions with NLO corrections are reduced as expected. Due to the high luminosity of the SuperKEKB collider, the ${\eta }_c+c+\overline{c}$ production is hopefully observable in the near future.

Three decades ago, heavy-flavor-conserving (HFC) weak decays of heavy baryons such as ${\mathrm{\Xi }}_Q\to {\mathrm{\Lambda }}_Q\pi$ and ${\mathrm{\Omega }}_Q\to {\mathrm{\Xi }}_Q\pi$ for $Q=c$, $b$ had been studied within the framework that incorporates both heavy quark and chiral symmetries. It was pointed out that if the heavy quark in the HFC process behaves as a spectator, then the $P$-wave amplitude of ${\mathcal{B}}_{\overline{3}}\to {\mathcal{B}}_{\overline{3}}+\pi$, with ${\mathcal{B}}_{\overline{3}}$ being an antitriplet heavy baryon, will vanish in the heavy quark limit. Indeed, this is the case for ${\mathrm{\Xi }}_b\to {\mathrm{\Lambda }}_b\pi$ decays. For ${\mathrm{\Xi }}_c\to {\mathrm{\Lambda }}_c\pi$ decays, they receive additional nonspectator contributions arising from the $W$-exchange diagrams through the $cs\to dc$ transition. Spectator and nonspectator $W$-exchange contributions to the $S$-wave amplitude of ${\mathrm{\Xi }}_c\to {\mathrm{\Lambda }}_c\pi$ are destructive, rendering the $S$-wave contribution even smaller. However, the nonspectator effect on the $P$-wave amplitude was overlooked in all the previous model calculations until a very recent investigation within the framework of a constituent quark model in which the parity-conserving pole terms were found to be dominant in ${\mathrm{\Xi }}_c\to {\mathrm{\Lambda }}_c\pi$ decays. Since the pion produced in the HFC process is soft, we apply current algebra to study both $S$- and $P$-wave amplitudes and employ the bag and diquark models to estimate the matrix elements of four-quark operators. We confirm that ${\mathrm{\Xi }}_c\to {\mathrm{\Lambda }}_c\pi$ decays are indeed dominated by the parity-conserving transition induced from nonspectator $W$-exchange and that they receive largest contributions from the intermediate ${\mathrm{\Sigma }}_c$ pole terms. We also show that the $S$-wave of ${\mathrm{\Omega }}_b\to {\mathrm{\Xi }}_b\pi$ decays vanishes in the heavy quark limit, while ${\mathrm{\Omega }}_c\to {\mathrm{\Xi }}_c\pi$ receive additional $W$-exchange contributions via $cs\to dc$ transition. The $P$-wave contribution to ${\mathrm{\Omega }}_c\to {\mathrm{\Xi }}_c\pi$ is enhanced by the ${{\mathrm{\Xi }}^{\prime }}_c$ pole, though it is not so dramatic as in the case of ${\mathrm{\Xi }}_c\to {\mathrm{\Lambda }}_c\pi$. The asymmetry parameter $\alpha$ is found to be positive, of order 0.70 and 0.74 for ${\mathrm{\Xi }}_c^0\to {\mathrm{\Lambda }}_c^{+}{\pi }^{-}$ and ${\mathrm{\Xi }}_c^{+}\to {\mathrm{\Lambda }}_c^{+}{\pi }^0$, respectively. The predicted branching fraction is of order $5\times {10}^{-4}$ for ${\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}_c^{+}{\pi }^{-}$ and $3\times {10}^{-4}$ for ${\mathrm{\Omega }}_c^0\to {\mathrm{\Xi }}_c^0{\pi }^0$ both with the asymmetry parameter close to $-1$.

We compute and compare the effective potential and phase structure for the quark-meson model in an extended mean-field approximation when vacuum one-loop quark fluctuations are included and the model parameters are fixed using different renormalization prescriptions. When the quark one-loop vacuum divergence is regularized under the minimal subtraction scheme, the fixing of the model parameters using the curvature masses of the scalar and pseudoscalar mesons has been termed as the quark-meson model with the vacuum term (QMVT). However, this prescription becomes inconsistent when we notice that the curvature mass is akin to defining the meson mass by the self-energy evaluation at vanishing momentum. In this work, we apply the recently reported exact prescription of the on-shell parameter fixing to that version of quark-meson model where the two quark flavors are coupled to the eight mesons of the $S{U}_L(2)\times S{U}_R(2)$ linear sigma model with isosinglet $\sigma$ ($\eta$), isotriplet $\overrightarrow{a_0}$ ($\overrightarrow{\pi }$) scalar (pseudoscalar) mesons. The model then becomes the renormalized quark-meson (RQM) model where physical (pole) masses of mesons and pion decay constant are put into the relation of the running mass parameter and couplings by using the on-shell and the minimal subtraction renormalization schemes. The vacuum effective potential plots, the phase diagrams and the order parameter temperature variations for both the RQM model and the QMVT model are exactly identical for the $m_{\sigma }=616\mathrm{MeV}$. The vacuum effective potential, when the $m_{\sigma }<616\mathrm{MeV}$, is deepest for the QMVT model. An interesting trend reversal is observed for the $m_{\sigma }>616\mathrm{MeV}$ when the effective potential of the RQM model becomes deepest. We find similar $m_{\sigma }$ dependent differences in the nature of the RQM and QMVT model phase diagrams and the order parameter temperature variations. Furthermore, $S{U}_A(2)$ chiral and $U_A(1)$ axial symmetry breaking/restoration and their interplay can also be investigated in this framework.

The dynamical entropy of dense gluonic states in proton-proton collisions at high energies is studied by using phenomenological models for the unintegrated gluon distribution. The corresponding transverse momentum probability distributions are evaluated in terms of rapidity. The dynamical entropy density is obtained in the rapidity range relevant for the collisions at the Large Hadron Collider. The total entropy density for the dense system is computed as a function of the rapidity evolution $\mathrm{\Delta }Y=Y-Y_0$ given an initial rapidity $Y_0$. The theoretical uncertainties are investigated, and a comparison with related approaches in literature is done.

Neutrino telescopes allow powerful probes of high-energy astrophysics and particle physics. Their power is increased when they can isolate different event classes, e.g., by flavor, though that is not the only possibility. Here we focus on a new event class for neutrino telescopes: dimuons, two energetic muons from one neutrino interaction. We make new theoretical and observational contributions. For the theoretical part, we calculate dimuon-production cross sections and detection prospects via deep-inelastic scattering (DIS; where we greatly improve upon prior work) and $W$-boson production (WBP; where we present first results). We show that IceCube should have $\simeq 130$ dimuons ($\simeq 6$ from WBP) in its current data and that IceCube-Gen2, with a higher threshold but a larger exposure, could detect $\simeq 620$ dimuons ($\simeq 30$ from WBP) in 10 years. These dimuons are almost all produced by atmospheric neutrinos. For the observational part, we perform a simple but conservative analysis of IceCube public data, finding 19 candidate dimuon events. Subsequent to our paper appearing, visual inspection of these events by the IceCube Collaboration revealed that they are not real dimuons, but instead arise from an internal reconstruction error that identifies some single muons crossing the dust layer as two separate muons. To help IceCube and the broader community with future dimuon searches, we include the updated full details of our analysis. Together, these theoretical and observational contributions help open a valuable new direction for neutrino telescopes, one especially important for probing high-energy QCD and new physics.

We consider the resonant production and detection of charged mesons in existing and near-future neutrino scattering experiments with $E_{\nu }\lesssim 1\mathrm{TeV}$, characteristic of high-energy atmospheric neutrinos or collider-sourced neutrino beams. The most promising candidate is the reaction ${\overline{\nu }}_e{e}^{-}\to {\rho }^{-}\to {\pi }^{-}{\pi }^0$. We discuss detection prospects at $\mathrm{FASER}\nu$, the LHC’s forward physics facility with nuclear emulsion ($\mathrm{FASER}\nu 2$) and liquid argon detectors (FLArE), and we estimate the number of expected resonance-mediated events in the existing data set of IceCube. We also outline possible detection strategies for the different experimental environments. We predict dozens of events at the forward physics facility and identify cuts with order-one signal efficiency that could potentially suppress backgrounds at $\mathrm{FASER}\nu$, yielding a signal-to-background ratio larger than 1. Antineutrino-induced $s$-channel meson resonances are yet unobserved Standard Model scattering processes which offer a realistic target for near-term experiments.

We prove that, for any theory defined over a space-time with boundary, the symplectic form derived in the covariant phase space is equivalent to the one derived from the canonical formalism.

We derive an explicit form of the dilaton potential in improved holographic QCD (IHQCD) from the experimental data of the $\rho$ meson spectrum. For this purpose, we make use of the emergent bulk geometry obtained by deep learning from the hadronic data in the work by Akutagawa et al. [Phys. Rev. D 102, 026020 (2020)]. Requiring that the geometry is a solution of an IHQCD derives the corresponding dilaton potential backward. This determines the bulk action in a data-driven way, which enables us at the same time to ensure that the deep learning proposal is a consistent gravity. Furthermore, we find that the resulting potential satisfies the requirements normally imposed in IHQCD, and that the holographic Wilson loop for the derived model exhibits quark confinement.

Expanding edge experiments are promising to open new physics windows of quantum Hall systems. In a static edge, the edge excitation, which is described by free fields decoupled with the bulk dynamics, is gapless, and the dynamics preserve conformal symmetry. When the edge expands, such properties need not be preserved. We formulate a quantum field theory in $1+1$-dimensional curved spacetimes to analyze the edge dynamics. We propose methods to address the following questions using edge waveforms from the expanding region: Does the conformal symmetry survive? Is the nonlinear interaction of the edge excitations induced by edge expansion? Do the edge excitations interact with the bulk excitations? We additionally show that the expanding edges can be regarded as expanding universe simulators of two-dimensional dilaton-gravity models, including the Jackiw-Teitelboim gravity model. As an application, we point out that our theoretical setup might simulate emission of analog Hawking radiation with the Gibbons-Hawking temperature from the future de Sitter horizon formed in the expanding-edge region.

We show how the theory of characters can be used to analyze an anomaly corresponding to chiral fermions carrying an arbitrary representation of a gauge group that is finite, but otherwise arbitrary. By way of example, we do this for some groups of relevance for the study of quark and lepton masses and mixings.

Tree-level scattering amplitudes for gravitons, gluons, and Goldstone particles in any dimensions are strongly constrained by basic principles, and they are intimately related to each other via various relations. We study two types of “universal expansions” with respect to gauge bosons and Goldstone bosons; the former expresses tree amplitudes in Einstein gravity (Yang-Mills) as linear combinations of single-trace Einstein-Yang-Mills (Yang-Mills-${\varphi }^3$) amplitudes with coefficients given by Lorentz products of polarizations and momenta, and the latter expresses tree amplitudes in nonlinear sigma model, (Dirac-)Born-Infeld and a special Galileon theory, as linear combinations of single-trace mixed amplitudes with particles of lower “degree of Adler’s zero” and coefficients given by products of Mandelstam variables. We trace the origin of gauge-theory expansions to the powerful uniqueness theorem based on gauge invariance, and expansions in effective field theories can be derived from gauge-theory ones via a special dimension reduction.