High Energy Physics - Phenomenology (hep-ph)

Abstract: The invisible axion is a hypothetical particle that arises from the Peccei-Quinn mechanism proposed to resolve the CP problem in quantum chromodynamics, and is considered one of the most favoured candidates for cold dark matter. Dish antennas can provide a useful scheme for sensitive search for dark matter axions. The conversion power through axion-photon couplings is proportional to the surface area of the metal plate, rather than the volume of the available magnetic field. To maximize the effect, we propose an advanced concept of haloscope that involves an array of horn antennae to increase the axion-induced photons and a reflector to focus them onto a photo sensor. Compared to other proposed schemes, this configuration can significantly improve the experimental sensitivity, especially in the terahertz region.

Abstract: There exists a puzzling disagreement between the results for the neutron lifetime obtained in experiments using the beam technique versus those relying on the bottle method. A possible explanation of this discrepancy postulates the existence of a beyond-Standard-Model decay channel of the neutron involving new particles in the final state, some of which can be dark matter candidates. We review the current theoretical status of this proposal and discuss the particle physics models accommodating such a dark decay. We then elaborate on the efforts undertaken to test this hypothesis, summarizing the prospects for probing neutron dark decay channels in future experiments.

Abstract: We consider the full genuine next-to-leading order SUSY-QCD corrections to the charged Higgs decays into quarks supplemented by the NNLO corrections to the effective top and bottom Yukawa couplings. The NNLO corrections to the effective top Yukawa coupling are a new ingredient of our analysis. We arrive at an approximate NNLO prediction for MSSM charged Higgs decays after including the N$^4$LO QCD corrections for large charged Higgs masses. The residual uncertainties are in the percent range or below, depending on the particular MSSM scenario.

Abstract: We investigate the Crewther relation at high loop order in a variety of renormalization schemes and gauges. By examining the properties of the relation in schemes other than modified minimal subtraction (MSbar) at the fixed points of Quantum Chromodynamics we propose a generalization of the Crewther relation that extends the MSbar construction of Broadhurst and Kataev. A derivation based on the properties of the renormalization group equation is provided for the generalization which is tested in various scenarios.

Abstract: We study a neutrino mass model with $A_4$ flavor symmetry using a type-I seesaw mechanism. The inclusion of extra flavons in our model leads to the deviations from exact tribimaximal mixing pattern resulting in a nonzero $\theta_{13}$ consistent with the recent experimental results and a sum rule for light neutrino masses is also obtained. In this framework, a connection is established among the mixing angles ($\theta_{13}$, $\theta_{12}$, $\theta_{13}$) and the Dirac CP-violation phase $\delta_{CP}$. This model also allows us a prediction of Jarlskog parameter $J_{CP}$ and the octant of the mixing angle $\theta_{23}$. We use the parameter space of our model of neutrino masses to study the neutrinoless double beta decay parameter $m_{ee}$.

Abstract: The impact of the CPT-Odd electroweak gauge sector of the Standard Model Extension on the anomalous magnetic moment of charged leptons is studied. This gauge sector is characterized by the $(k_1)_\mu$ and $(k_2)_\mu$ Lorentz coefficients, which have positive mass dimension because they are associated with a $U_Y(1)$-invariant and with an $SU_L(2)$-invariant dimension-three operators, respectively. They belong to the category of relevant interactions, which have strong effects on low-energy observables. We find that the contribution to the anomalous magnetic dipole moment of the electron can be up to fourteen orders of magnitude greater than that of the muon and up to sixteen orders greater than that of the tau. Using the experimental data for the electron, we obtain an upper bound of $\left|k^2_1-0.79 k_1\cdot k_2 +0.27 k^2_2\right|<1.31\times 10^{-19} m^2_e $. The Lorentz coefficient $(k)_{AF}$ of the Carroll-Field-Jackiw's QED is given by a linear combination of the $(k_1)_\mu$ and $(k_2)_\mu$ vectors. Assuming that $|k^2_1|, |k^2_2|\gg |k^2_{AF}|$ and taking $(k)_{AF}=0$, which implies that $(k_1)_\mu$ and $(k_2)_\mu$ are collinear, we obtain upper bounds of $|k_1^2|<7.2\times 10^{-21}m^2_e$ and $|k_2^2|<3.2\times 10^{-19}m^2_e$.

Abstract: We study perturbative unitarity constraints on generic interactions between fermion and vector fields, which are allowed to have generic quantum numbers under a $\prod_i SU(N_i) \otimes U(1)$ group. We derive compact expressions for the bounds on the couplings for the cases where the fields transform under the trivial, fundamental or adjoint representation of the various, considering both the case of a complex vector arbitrary interactions with fermionic current and also the case of vectors arising as gauge fields. We apply our results to some specific NP models showing the constraints that can be derived using the tool of perturbative unitarity.

Abstract: The failure of observing the $e^+ e^- \to J/\psi+J/\psi$ events at $B$ factories to date is often attributed to the significant negative order-$\alpha_s$ correction. In this work we compute the ${\cal O}(\alpha^2_s)$ correction to this process for the first time. The magnitude of the next-to-next-to-leading order (NNLO) perturbative correction is substantially negative so that the standard NRQCD prediction would suffer from an unphysical, negative cross section. This dilemma may be traced in the fact that the bulk contribution of the fixed-order radiative corrections stems from the perturbative corrections to the $J/\psi$ decay constant. We thus implement an improved NRQCD factorization framework, by decomposing the amplitude into the photon-fragmentation piece and the non-fragmentation piece. With the measured $J/\psi$ decay constant as input, which amounts to resumming a specific class of radiative and relativistic corrections to all orders, the fragmentation-induced production rate can be predicted accurately and serves a benchmark prediction. The non-fragmentation type of the amplitude is then computed through NNLO in $\alpha_s$ and at lowest order in velocity. Both the ${\cal O}(\alpha_s)$ and ${\cal O}(\alpha^2_s)$ corrections in the interference term become positive and exhibit a decent convergence behavior. Our finest prediction is $\sigma(e^+ e^- \to J/\psi+J/\psi)= 2.13^{+0.30}_{-0.06}$ fb at $\sqrt{s}=10.58$ GeV. With the projected integrated luminosity of 50 ${\rm ab}^{-1}$, the prospect to observe this exclusive process at \texttt{Belle} 2 experiment appears to be bright.

Abstract: Earth can act as a transducer to convert ultralight bosonic dark matter (axions and hidden photons) into an oscillating magnetic field with a characteristic pattern across its surface. Here we describe the first results of a dedicated experiment, the Search for Non-Interacting Particles Experimental Hunt (SNIPE Hunt), that aims to detect such dark-matter-induced magnetic-field patterns by performing correlated measurements with a network of magnetometers in relatively quiet magnetic environments (in the wilderness far from human-generated magnetic noise). Our experiment constrains parameter space describing hidden-photon and axion dark matter with Compton frequencies in the 0.5-5.0 Hz range. Limits on the kinetic-mixing parameter for hidden-photon dark matter represent the best experimental bounds to date in this frequency range.

Abstract: In this paper, we study the implications of the Dark Large Mixing Angle (DLMA) solutions of $\theta_{12}$ in the context of the IceCube data. We study the consequences in the measurement of the neutrino oscillation parameters namely $\theta_{23}$ and $\delta_{\rm CP}$ in light of both Large Mixing Angle (LMA) and DLMA solutions of $\theta_{12}$. We find that it will be impossible for IceCube to determine the $\delta_{\rm CP}$ and the true nature of $\theta_{12}$ i.e., LMA or DLMA at the same time. This is because of the existence of an intrinsic degeneracy at the Hamiltonian level between these parameters. Apart from that, we also identify a new degeneracy between $\theta_{23}$ and two solutions of $\theta_{12}$ for a fixed value of $\delta_{\rm CP}$. We perform a chi-square fit using three different astrophysical sources, i.e., $\mu$ source, $\pi$ source, and $n$ source to find that both $\mu$ source and $\pi$ source are allowed within $1 \sigma$ whereas the $n$ source is excluded at $2 \sigma$. It is difficult to make any conclusion regarding the measurement of $\theta_{23}$, $\delta_{\rm CP}$ for $\mu$ source. However, The $\pi$ ($n$) source prefers higher (lower) octant of $\theta_{23}$ for both LMA and DLMA solution of $\theta_{12}$. The best-fit value of $\delta_{\rm CP}$ is around $180^\circ$ ($0^\circ/360^\circ$) for LMA (DLMA) solution of $\theta_{12}$ whereas for DLMA (LMA) solution of $\theta_{12}$, the best-fit value is around $0^\circ/360^\circ$ ($180^\circ$) for $\pi$ ($n$) source. If we assume the current best-fit values of $\theta_{23}$ and $\delta_{\rm CP}$ to be true, then the $\mu$ and $\pi$ source prefer the LMA solution of $\theta_{12}$ whereas the $n$ source prefers the DLMA solution of $\theta_{12}$.

Abstract: In this paper, we propose a dedicated forward detector, FOREHUNT (FORward Experiment for HUNdred TeV), for 100 TeV FCC-hh for the detection of light long-lived particles (LLP) coming from $B$-meson decay. We calculate the signal acceptance as a function of mass and proper decay length of the LLP for 100 TeV and interpret our result in terms of model parameters for models of dark Higgs scalar and heavy neutral leptons. We also compare the sensitivity with proposed transverse detectors like MATHUSLA, CODEX-b for HL-LHC, and DELIGHT (Detector for long-lived particles at high energy of 100 TeV) for FCC-hh. Our analysis reveals that if the LLP has low decay length < 10 m, a forward detector like FOREHUNT is the best option to look for the decaying LLP, while DELIGHT is preferable for higher decay lengths.

Abstract: We discuss axion-like particles (ALPs) within the framework of Higgs Effective Field Theory, targeting instances of close alignment of ALP physics with a custodial singlet character of the Higgs boson. We tension constraints arising from new contributions to Higgs boson decays against limits from high-momentum transfer processes that become under increasing control at the LHC. Going beyond leading-order approximations, we highlight the importance of multi-top and multi-Higgs production for the pursuit of searches for physics beyond the Standard Model extensions.

Abstract: Spontaneous breaking of the $SU(2)_{L}\times U(1)_{Y}$ electroweak symmetry of the Standard Model (SM) sets the constraints on triple gauge couplings and quartic gauge couplings. Therefore, the measurement of multiboson production in $e^{-} e^{+}$ collisions allows us to directly examine the SM predictions and perform indirect investigations of new physics beyond the SM. In this paper, we concentrate the process $e^{-} e^{+} \to e^{-} Z\gamma e^{+}$ with $Z$ boson decaying to neutrinos to investigate the anomalous quartic gauge couplings using the effective Lagrangian approach at the Compact Linear Collider (CLIC). We obtain the sensitivities on the anomalous $ f_ {Ti}/\Lambda^4$ ($i=0,2,5,6,7,8,9$) couplings taking into account the systematic uncertainties of $3, 5 \%$ at $95\%$ Confidence Level for the CLIC with $\sqrt{s}=3$ TeV. Our results show that the sensitivities on some anomalous couplings without systematic errors are up to two orders of magnitude better than the current experimental limits. Considering a realistic systematic uncertainty such as $5 \%$ from possible experimental sources, the sensitivity of all anomalous quartic couplings gets worse by about $10\%$ compared to those without systematic uncertainty for the CLIC.