High Energy Physics - Phenomenology (hep-ph)

Abstract: The study of exclusive processes in ultraperipheral collisions at the Large Hadron Collider (LHC) has allowed us to test several aspects of the Standard Model and to search for New Physics. In this letter, we investigate the possibility of using these processes to improve our understanding of the quarkonium production mechanism through the study of the exclusive $J/\Psi$ plus jet associate production in ultraperipheral $PbPb$ collisions. We estimate the transverse - momentum and rapidity distributions considering that the $\gamma \gamma \rightarrow J/\Psi + X$ ($X = \gamma, \, g$) subprocess is described by the Non - Relativistic QCD (NRQCD) formalism and present predictions for the rapidity ranges covered by central and forward detectors. The experimental separation of these events is discussed and the results indicate that a future experimental analysis is, in principle, feasible in future runs of the LHC and the Future Circular Collider (FCC).

Abstract: Quark flavour physics is the study of hadrons, their properties, and their decays into other particles. As a discipline it simultaneously catalogues the nature of physical states within the Standard Model of particle physics, and in doing so tests the consistency and completeness of the Standard Model's description of reality. Following the discovery of the Higgs field, it is more essential than ever to critically examine the Standard Model's own coherence. Precision studies of quark flavour are one of the most sensitive experimental instruments for this task. I give a brief and necessarily selective overview of recent developments in quark flavour physics and discuss prospects for the next generation of experiments and facilities, with an emphasis on the energy scales of beyond Standard Model physics probed by these types of measurements.

Abstract: The production of fully-heavy tetraquark states in proton-proton ($pp$) and proton-nucleus ($pA$) collisions at the center-of-mass energies of the Large Hadron Collider (LHC) and at the Future Circular Collider (FCC) is investigated considering that these states are produced through the double parton scattering mechanism. We estimate the cross sections for the $T_{4c}$, $T_{4b}$ and $T_{2b2c}$ states and present predictions for $pp$, $pCa$ and $pPb$ collisions considering the rapidity ranges covered by central and forward detectors. We demonstrate that the cross sections for $pA$ collisions are enhanced in comparison to the $pp$ predictions scaled by the atomic number. Moreover, our results indicate that a search of these exotic states is, in principle, feasible in the future runs of the LHC and FCC.

Abstract: Various models of tetraquark generation in the reaction $K^{+} p \rightarrow T (us; \bar{s}\bar{s})X$ are considered. The predictions for corresponding inclusive spectra were evaluated at the energy 32 and 250 GeV.

Abstract: We examine possible experimental signatures that may be exploited to search for stable supermassive particles with electric charges of $O(1)$ in future underground experiments, and the upcoming JUNO experiment in particular. The telltale signal would be a correlated sequence of three or more nuclear recoils along a straight line, corresponding to the motion of a non-relativistic ($\beta <10^{-2}$) particle that could enter the detector from any direction. We provide some preliminary estimates for the expected event rates.

Abstract: In this study, we comprehensively investigate the production of isovector scalar meson $a_{0}(1817)$ using the effective Lagrangian approach. Specifically, we employ the Reggeized $t$-channel Born term to calculate the total and differential cross sections for the reaction $K^{-}p \rightarrow a_{0}(1817)\Lambda$. Our analysis reveals that the optimal energy range for detecting the $a_{0}(1817)$ meson lies between $W=3.4$ MeV and $W=3.6$ MeV, where the predicted total cross section reaches a minimum value of 112 nb. Notably, the $t$ channel, as predicted by the Regge model, significantly enhances the differential cross sections, particularly at extreme forward angles. Furthermore, we investigate the Dalitz processes of $2\rightarrow 3$ and discuss the feasibility of detecting the $a_{0}(1817)$ meson in experiments such as J-PARC.

Abstract: In this paper we consider the collective modes of a momentum-space anisotropic quark-gluon plasma taking into account the effect of collisions between the plasma constituents. Our analysis is carried out using a collisional kernel of Bhatnagar-Gross-Krook form and extends prior analyses in the literature by considering all possible angles of propagation of the gluonic modes relative to the momentum-anisotropy axis. We extract both the stable and unstable modes as a function of the collision rate and confirm prior findings that gluonic unstable modes can be eliminated from the spectrum if the collision rate is sufficiently large. In addition, we discuss the conditions necessary for the existence of unstable modes and present evidence that unstable mode growth rates are maximal for modes with momentum along the anisotropy direction. Finally, we demonstrate that when there is a finite collisional rate, gluonic unstable modes are absent from the spectrum at both small and large momentum anisotropy. These results pave the way for understanding the impact of collisions on a variety of non-equilibrium quark-gluon plasma observables.

Abstract: We investigate the elastic photon-proton and photon-photon scattering in a holographic QCD model, focusing on the Regge regime. Considering contributions of the Pomeron and Reggeon exchange, the total and differential cross sections are calculated. While our model involves several parameters, by virtue of the universality of the Pomeron and Reggeon, for most of them the values determined in the preceding study on the proton-proton and proton-antiproton scattering can be employed. Once the two adjustable parameters, the Pomeron-photon and Reggeon-photon coupling constant, are determined with the experimental data of the total cross sections, predicting the both cross sections in a wide kinematic region, from the GeV to TeV scale, becomes possible. We show that the total cross section data can be well described within the model, and our predictions for the photon-proton differential cross section are consistent with the data.

Abstract: In this work we study the hybrid kind of dark matter(DM) production mechanism where both thermal and non-thermal contribution at two different epochs set the DM relic abundance. This hybrid set up in turn shifts the parameter space of DM in contrast to pure thermal DM scenario. We review such production mechanism in the context of the $SU(2)_L$ lepton doublet dark matter ($\Psi$) augmented with an additional singlet dark scalar ($S$). The neutral component of the dark doublet can serve as a stable DM candidate and in pure thermal scenario, it is under-abundant as well as excluded from direct detection constraints due to its strong gauge interactions in the sub-TeV mass regime. However, in addition to the thermal contribution, the late time non-thermal DM production from the decay of the long-lived dark scalar $S$ helps to fulfill the deficit in DM abundance. On the other hand, the strong gauge mediated direct detection constraint can be evaded with the help of a $SU(2)_L$ triplet scalar(with $Y=2$), resulting a pseudo-Dirac DM. To realize our proposed scenario we impose a discrete $\mathcal{Z}_2$ symmetry under which both $\Psi$ and $S$ are odd while rest of the fields are even. We find the lepton doublet pseudo-Dirac DM with mass $\sim 550-1200$ GeV, compatible with the observed relic density, direct, indirect, and existing collider search constraints.

Abstract: We elaborate the possibility of using the atomic radiative emission of neutrino pair (RENP) to probe the neutrino electromagnetic properties, including magnetic and electric dipole moments, charge radius, and anapole. With the typical O(eV) momentum transfer, the atomic RENP is sensitive to not just the tiny neutrino masses but also very light mediators to which the massless photon belongs. The neutrino EM properties introduce extra contribution besides the SM one induced by the heavy W/Z gauge bosons. Since the associated photon spectrum is divided into several sections whose boundaries are determined by the final-state neutrino masses, it is possible to identify the individual neutrino EM form factor elements. Most importantly, scanning the photon spectrum inside the particular section with deviation from the SM prediction once observed allows identification of the neutrino EM form factor type. The RENP provides an ultimate way of disentangling the neutrino EM properties to go beyond the current experimental searches or observations.

Abstract: We point out that a soliton such as an oscillon or boson star inevitably decays into gravitons through gravitational interactions. These decay processes exist even if there are no apparent self-interactions of the constituent field, scalar or vector, since they are induced by gravitational interactions. Hence, our results provide a strict upper limit on the lifetime of oscillons and boson stars including the dilute axion star. We also calculate the spectrum of the graviton background from decay of solitons.

Abstract: The inclusive probability to record an electron in elastic electromagnetic scattering of an electron by a spin one-half hadron is obtained, the initial quantum states of the electron and the hadron being described by the density matrices of a general form. Contrary to the Rosenbluth formula for the differential cross-section for this process, the first nontrivial contribution to the inclusive probability turns out to be of order $\alpha$ and not $\alpha^2$. This contribution describes the interference between the trivial contribution to the $S$-matrix and the leading contribution to its connected part. The explicit expression for this interference terms is derived. It is shown that the same interference term arises when the electron is scattered by the classical electromagnetic field produced by the hadron electromagnetic current averaged with respect to the free evolving density matrix of the hadron, even in the case of a single hadron. The interference term describes coherent scattering of the electron by the hadron wave packet and is immune to the quantum recoil experienced by a hadron due to scattering. The effective electron mass operator is found on the mass-shell.

Abstract: We perform the first global quantum chromodynamics (QCD) analysis of dihadron production for a comprehensive set of data in electron-positron annihilation, semi-inclusive deep-inelastic scattering, and proton-proton collisions, from which we extract simultaneously the transversity distributions of the nucleon and $\pi^+\pi^-$ dihadron fragmentation functions. We incorporate in our fits known theoretical constraints on transversity, namely, its small-$x$ asymptotic behavior and the Soffer bound. We furthermore show that lattice-QCD results for the tensor charges can be successfully included in the analysis. This resolves the previously reported incompatibility between the tensor charges extracted from dihadron production data and lattice QCD. We also find agreement with results for the transversity and tensor charges obtained from measurements on single-hadron production. Overall, our work demonstrates for the first time the universal nature of all available information for the transversity distributions and the tensor charges of the nucleon.

Abstract: In this paper we study a near-continuum dark matter model, in which dark sector consists of a tower of closely spaced states with weak-scale masses. We construct a five-dimensional model which naturally realizes this spectrum. The dark matter is described by a bulk field, which interacts with the brane-localized Standard Model sector via a Z portal. We then study collider signatures of this model. Near-continuum dark matter states produced in a collider undergo cascade decays, resulting in events with high multiplicity of jets and leptons, large missing energy, and displaced vertices. A custom-built Monte Carlo tool described in this paper allows for detailed simulation of the signal events. We present results of such simulations for the case of electron-positron collisions.

Abstract: We investigate the impact of the new measurement of the antineutrino-proton scattering cross-section from the MINERvA Collaboration on the generalized parton distributions (GPDs), especially of polarized GPDs $ \widetilde{H}^q $. To this aim, we perform some QCD analyses of the MINERvA data in addition to all available data of the proton axial form factors (FFs) $ F_A $. We show that the MINERvA data are in a good consistency with the other related experimental data which confirms the universality of GPDs in turn. Our results indicate that the MINERvA data can put new constrains on GPDs, especially $ \widetilde{H}^q $. The present study can be considered as a guideline for performing a new and comprehensive QCD global analysis of GPDs including the MINERvA measurements like as Phys. Rev. D \textbf{107}, 096005 (2023).

Abstract: Predictivity of many non-thermal dark matter (DM) models is marred by the gravitational production background. This problem is ameliorated in models with lower reheating temperature $T_R$, which allows for dilution of gravitationally produced relics. We study the freeze-in dark matter production mechanism in the thermal bath with the electroweak scale temperature. The process is Boltzmann-suppressed if the dark matter mass is above $T_R$. In this case, the coupling to the thermal bath has to be significant to account for the observed dark matter relic density. As a result, the direct DM detection experiments already probe such freeze-in models, excluding significant parts of parameter space. The forthcoming experiments will explore this framework further, extending to lower couplings and higher reheating temperatures.

Abstract: Non-perturbative results in QCD-like theories can be derived employing positivity of the Euclidean path integral measure, as pioneered by Weingarten, Vafa, Witten. We show that positivity of the measure can be generalized to parity-invariant theories with Yukawa couplings to fundamental scalars, provided the fermions are Dirac and carry a real representation of the gauge group. This result allows us to extend the proof of parity and vector-like flavor symmetries conservation to such theories, as well as to derive exact inequalities among hadrons' masses.