High Energy Physics - Phenomenology (hep-ph)

Abstract: We proposed a model-independent analysis of near-threshold enhancements using independent S-matrix poles. In this formulation, we constructed a Jost function with controllable zeros to ensure that no poles are generated on the physical Riemann sheet. We show that there is a possibility of misinterpreting the observed near-threshold signals if one utilized a limited parametrization and restrict the analysis to only one element of the S-matrix. Specifically, there is a possibility of the emergence of ambiguous pair of poles which are singularities of the full S-matrix but may not manifest in one of its elements. We apply our method to the analysis of $P_\psi^N(4312)^+$ and found that the compact pentaquark interpretation cannot be ruled out.

Abstract: We introduce the notion of cumulative activity for inelastic events generated under hadron collisions, discuss its energy dependence and connection with the reflective scattering mode. These issues are relevant for enlightening the asymptotic dynamics in view of the LHC measurements.

Abstract: The center-of-mass energies available at modern accelerators, such as the Large Hadron Collider (LHC), and at forthcoming generation accelerators, such as the Electron-Ion Collider (EIC), offer us a unique opportunity to investigate hadronic matter under the most extreme conditions ever reached. In particular, we can access the Regge-Gribov regime of QCD, described by the Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach along with its non-linear generalizations (the set of B-JIMWLK equations). The aim of these approaches is to resum large-energy logarithmic corrections which spoil the convergence of perturbative series at high-energy. The aforementioned approaches are theoretically developed both in the leading (LL) and the next-to-leading (NLL) approximation, but precise full NLL predictions still remains an open challenge. Furthermore, extending BFKL beyond the NLL approximation has been an open problem for more than twenty years. We face the task of hunting precision in this field from different perspectives. In particular, within the BFKL approach, we calculate the next-to-leading order (NLO) impact factor for the Higgs boson production. This is the necessary ingredient to study the inclusive forward emissions of a Higgs boson in association with a backward identified jet. Moreover, by using already known NLO impact factors, we propose a series of new semi-hard reactions that can be used to investigate BFKL dynamics at the LHC within NLL accuracy. We consider also the problem of extending BFKL beyond the NLL approximation and compute one of the ingredients entering the BFKL kernel at the next-to-NLL (NNLL) accuracy. Finally, in the saturation (non-linear) framework, we calculate the diffractive double hadron photo- or electroproduction cross sections with full NLL accuracy, useful to detect saturation effects, at both the future EIC or already at LHC (via Ultra Peripheral Collisions).

Abstract: The Dalitz decays of the positive parity $D_{sJ}^{(*)}$ charmed mesons, $D_{sJ}^{(*)} \to D_s^{(*)} \ell^+ \ell^-$ with $J=0,1,2$ and $\ell=e, \mu$, are important processes to investigate the nature of the $D_{sJ}^{(*)}$ states. We analyze the full set of decays, considering the four lightest $D_{sJ}^{(*)}$ mesons as belonging to the heavy quark spin doublets $\displaystyle s_\ell^P=\frac{1}{2}^+$ and $\displaystyle \frac{3}{2}^+$, with $s_\ell^P$ the spin-parity of the light degrees of freedom in mesons. The description implies relations among the observables in various modes. We study the decay distributions in the dilepton invariant mass squared and the distributions in the angle between the charged lepton momentum and the momentum of the produced meson, which are expressed in terms of universal form factors and of effective strong couplings. Such measurements are feasible at the present facilities.

Abstract: Many theories about dark matter have emerged due to its strong theoretical appeal in explaining astrophysical phenomena. However, experimental and theoretical particle physics have yet not provided evidence that dark matter is part of the observable Universe. Our work aims to investigate the interaction between Standard Model (SM) fermions and different species of dark matter (DM) particles in high-energy collisions through interaction of a new massive vector mediator, Z'. The production of scalar and fermion DM pairs via fermion annihilation into the new vector boson is investigated near a resonance, where a SM signal from hard photon emission is considered as initial state radiation, namely a mono-photon production. Values of coupling constants between the DM and the SM particles are mapped in contrast to the Planck satellite data for thermal relic density DM computed in the correct framework for the relic density near a resonance, where a weaker suppression of the relic density is expected. We show for the CLIC and LHC kinematic regimes that certain mass ranges and coupling constants of these DM particles are in agreement with the expected relic density near a resonance and are not excluded by collider and astrophysical limits.

Abstract: In this work, we investigate how multinucleon enhancement and RPA (Random Phase Approximation) suppression can affect the measurement of three unknown neutrino oscillation parameters - the CP-violating phase $\delta_{CP}$, the octant of the atmospheric mixing angle $\theta_{23}$, and the determination of the mass hierarchy, in the appearance channel of the NO$\nu$A experiment. We include the presence of the detector effect as well in the analysis, which is crucial for capturing realistic experimental scenarios. It is found that the analysis using our comprehensive model (QE(+RPA)+2p2h) exhibits significantly enhanced sensitivity compared to the pure QE interaction process, in all the cases. Also, the higher octant of $\theta_{23}$, the lower half plane of $\delta_{CP}$, and the normal mass hierarchy (HO-LHP-NH) exhibit improved sensitivity, enabling a more precise determination of the corresponding parameters. Furthermore, it is also noted that improving the performance of the detector also improves the results. Thus, including multinucleon effects and improving detector efficiency have the potential to enhance the capabilities of the NO$\nu$A (and other long baseline) experiment in conducting precise parameter studies.

Abstract: We explore how quantum gravity effects, manifested through the breaking of discrete symmetry responsible for both Dark Matter and Domain Walls, can have observational effects through CMB observations and gravitational waves. To illustrate the idea we consider a simple model with two scalar fields and two $\mathcal{Z}_2$ symmetries, one being responsible for Dark Matter stability, and the other spontaneously broken and responsible for Domain Walls, where both symmetries are assumed to be explicitly broken by quantum gravity effects. We show the recent gravitational wave spectrum observed by several pulsar timing array projects can help constrain such effects.

Abstract: Experimental bounds on the neutrino lifetime depend on the nature of the neutrinos and the details of the potentially new physics responsible for neutrino decay. In the case where the decays involve active neutrinos in the final state, the neutrino masses also qualitatively impact how these manifest themselves experimentally. In order to further understand the impact of nonzero neutrino masses, we explore how observations of solar neutrinos constrain a very simple toy model. We assume that neutrinos are Dirac fermions and there is a new massless scalar that couples to neutrinos such that a heavy neutrino - $\nu_2$ with mass $m_2$ - can decay into a lighter neutrino - $\nu_1$ with mass $m_1$ - and a massless scalar. We find that the constraints on the new physics coupling depend, sometimes significantly, on the ratio of the daughter-to-parent neutrino masses, and that, for large enough values of the new physics coupling, the "dark side" of the solar neutrino parameter space - $\sin^2\theta_{12}\sim 0.7$ - provides a reasonable fit to solar neutrino data. Our results generalize to other neutrino-decay scenarios, including those that mediate $\nu_2\to\nu_1\bar{\nu}_3\nu_3$ when the neutrino mass ordering is inverted mass and $m_2>m_1\gg m_3$, the mass of $\nu_3$.

Abstract: Diffusion generative models are promising alternatives for fast surrogate models, producing high-fidelity physics simulations. However, the generation time often requires an expensive denoising process with hundreds of function evaluations, restricting the current applicability of these models in a realistic setting. In this work, we report updates on the CaloScore architecture, detailing the changes in the diffusion process, which produces higher quality samples, and the use of progressive distillation, resulting in a diffusion model capable of generating new samples with a single function evaluation. We demonstrate these improvements using the Calorimeter Simulation Challenge 2022 dataset.

Abstract: We present the universal one-loop effective action up to dimension eight after integrating out heavy fermion(s) using the Heat-Kernel method. We have discussed how the Dirac operator being a weak elliptic operator, the fermionic operator still can be written in the form of a strong elliptic one such that the Heat-Kernel coefficients can be used to compute the fermionic effective action. This action captures the footprint of both the CP conserving as well as violating UV interactions. As it does not rely on the specific forms of either UV or low energy theories, can be applicable for a very generic action. Our result encapsulates the effects of heavy fermion loops only.

Abstract: We briefly discuss some results obtained recently about dynamical gluon mass generation. We comment that this mass provides a natural QCD infrared cutoff and also implies an infrared finite coupling constant. We also discuss the phenomenological applications of these results and how they can be treated in the context of the so-called Dynamical Perturbation Theory.