High Energy Physics - Phenomenology (hep-ph)

Abstract: Doubly-charged Higgs bosons have extensively been searched at the LHC. In this work, we study the sensitivity reach of the doubly-charged scalar ($H^{\pm\pm}$) in muon collider for the well-known Type-II seesaw scenario. First, we perform a cut-based analysis to predict the discovery prospect in the muon collider operating with 3 TeV center of mass energy. In addition to this, we have also performed a multivariate analysis and compare the cut-based result with the result obtained from the multivariate analysis. We find that the cut-based analysis is more significant as compared to the multivariate analysis in the large doubly-charged scalar mass region. We predict that a doubly-charged scalar mass, $M_{H^{\pm\pm}}$, upto 1450 GeV can be probed with $5\sigma$ significance for center of mass $\sqrt{s}= 3$ TeV and integrated luminosity $\mathcal{L} = 1000\,\textrm{fb}^{-1}$.

Abstract: We investigate the hydrodynamic helicity polarization of $\Lambda$ hyperons, defined as the projection of the spin polarization vector along the directions of particle momenta, at RHIC-BES energies by utilizing the relativistic (3+1)D CLVisc hydrodynamics framework with SMASH initial conditions. As opposed to local spin polarization at high energy collisions, our hydrodynamic simulations demonstrate that the helicity polarization induced by the kinetic vorticity dominates over other contributions at intermediate and low collision energies. Our findings provide an opportunity to probe the fine structure of local kinetic vorticity as a function of azimuthal angle at intermediate and low collision energies by mapping our predictions to the future measurements in experiments.

Abstract: We perform a complete calculation of the pion-kaon scattering amplitude in Chiral Perturbation Theory at finite temperature, paying particular attention to the analytic structure of the amplitude and the main differences with respect to the zero temperature case. We also extend the Inverse Amplitude Method at finite temperature for unequal-mass scattering processes, which allows us to unitarize the amplitude and obtain the thermal evolution of the $K_0^*(700)$ and $K^*(892)$ pole parameters. As a direct application of our analysis, we show that the thermal evolution of the $K_0^*(700)$ resonance is crucial to explain the behavior of the scalar susceptibility for isospin $I=1/2$, which in turn, is directly connected with chiral and $U(1)_A$ restoration properties of the QCD phase diagram.

Abstract: In a quasi-particle model of QCD matter at finite temperature with thermal masses for quarks and gluons from hard thermal loops, the equation of state (EOS) can be described by an effective temperature dependence of the strong coupling $g(T)$. Assuming the same effective coupling between the exchanged gluon and thermal partons, the EOS can also be related to parton energy loss.} Based on the quasi-particle linear Boltzmann transport (QLBT) model coupled to a (3+1)-dimensional viscous hydrodynamic model of the quark-gluon plasma (QGP) evolution and a hybrid fragmentation-coalescence model for heavy quark hadronization, we perform a Bayesian analysis of the experimental data on $D$ meson suppression $R_{\rm AA}$ and anisotropy $v_2$ at RHIC and the LHC. We achieve a simultaneous constraint on the QGP EOS and the heavy quark transport coefficient, both consistent with the lattice QCD results.

Abstract: We study the possibility of constraining a scenario with high scale first order phase transition (FOPT) responsible for the cogenesis of baryon and dark matter using gravitational wave (GW) (non)-observations. While the FOPT at high scale is responsible for generating baryon asymmetry through leptogenesis and dark matter via the \textit{mass-gain} mechanism, the resulting GW spectrum falls within the ongoing LIGO-VIRGO experimental sensitivity. The dark matter is preferred to be in the non-thermal ballpark with sub-GeV masses and the criteria of successful dark matter relic rules out a large portion of the parameter space consistent with high scale FOPT and successful leptogenesis. Some part of the parameter space allowed from dark matter and leptogenesis criteria also gives rise to a large signal-to-noise ratio at ongoing experiments and hence can be disfavoured in a conservative way from the non-observation of such stochastic GW background. Future data from ongoing and planned experiments will offer a complementary and indirect probe of the remaining parameter space which is typically outside the reach of any direct experimental probe.

Abstract: The framework of trans-Planckian asymptotic safety has been shown to generate phenomenological predictions in the Standard Model and in some of its simple new physics extensions. A heuristic approach is often adopted, which bypasses the functional renormalization group by relying on a parametric description of quantum gravity with universal coefficients that are eventually obtained from low-energy observations. Within this approach, a few simplifying approximations are typically introduced, including the computation of matter renormalization group equations at 1~loop, an arbitrary definition of the position of the Planck scale at $10^{19}$ GeV, and an instantaneous decoupling of gravitational interactions below the Planck scale. In this work we systematically investigate, both analytically and numerically, the impact of dropping each of those approximations on the predictions for certain particle physics scenarios. In particular we study two extensions of the Standard Model, the gauged $B-L$ model and the leptoquark $S_3$ model, for which we determine a set of irrelevant gauge and Yukawa couplings. In each model, we present numerical and analytical estimates of the uncertainties associated with the predictions from asymptotic safety.

Abstract: We consider the Heavy Quark Expansion (HQE) for the nonleptonic decay rates of heavy hadrons, and compute the NLO QCD corrections to power terms up to order $1/m_Q^2$. We neglect the masses of the final-state quarks, so the application of our result is mainly for charmed hadrons. Our result can be applied also to bottomed hadrons as they constitute the main effect to this order up to corrections of $\mathcal{O}(m_c/m_b)$ and contributions due to penguin operators. We discuss the impact of our result for the lifetimes of heavy hadrons.

Abstract: Momentum distributions of quarks/gluons inside a light baryon in a hard exclusive process are encoded in the light-cone distribution amplitudes (LCDAs). In this work, we point out that the leading twist LCDAs of a light baryon can be obtained through a simulation of a quasi-distribution amplitude calculable on lattice QCD within the framework of the large-momentum effective theory. We calculate the one-loop perturbative contributions to LCDA and quasi-distribution amplitudes and explicitly demonstrate the factorization of quasi-distribution amplitudes at the one-loop level. Based on the perturbative results, we derive the matching kernel in the $\overline{\rm MS}$ scheme and regularization-invariant momentum-subtraction scheme. Our result provides a first step to obtaining the LCDA from first principle lattice QCD calculations in the future.

Abstract: We present the full next-to-leading order (NLO) prediction for the jet-gap-jet cross section at the LHC within the BFKL approach. We implement, for the first time, the NLO impact factors in the calculation of the cross section. We provide results for differential cross sections as a function of the difference in rapidity and azimuthal angle betwen the two jets and the second leading jet transverse momentum. The NLO corrections of the impact factors induce an overall reduction of the cross section with respect to the corresponding predictions with only LO impact factors. We note that NLO impact factors feature a logarithmic dependence of the cross section on the total center of mass energy which formally violates BFKL factorization. We show that such term is one order of magnitude smaller than the total contribution, and thus can be safely included in the current prediction without a need of further resummation of such logarithmic terms. Fixing the renormalization scale $\mu_R$ according to the principle of minimal sensitivity, suggests $\mu_R$ about 4 times the sum of the transverse jet energies and provides smaller theroretical uncertainties with respect to the leading order case.

Abstract: Glueballs are the most straightforward prediction of QCD, yet while they have likely been produced, none has been unequivocally identified. We pursue a backdoor approach through anomalies, and singularly the $\eta$ and $\eta$' which brings light to this irritating situation. In particular, we advocate to consider the full decay chain $J/\psi \rightarrow X \gamma , X \rightarrow \eta \eta'$ (into glue-rich states followed by glue-rich decays). We also suggest new BES III searches, namely for the $\pi_1$ into $\eta(') \pi^0$, (this would be the partner of their recently observed $\eta_1(1855)$). Another useful investigation would be for other channels (or semi-inclusive) $f_0 (1500)$ decays (see last section)