High Energy Physics - Phenomenology

Kronheim, B.; Kadhim, A. Al; Kuchera, M. P.; Prosper, H. B.; Ramanujan, R.

doi: 10.1088/2632-2153/ad9884pmid: N/A

Abstract:The ability to model and sample from conditional densities is important in many physics applications. Implicit quantile networks (IQN) have been successfully applied to this task in domains outside physics. In this work, we illustrate the potential of IQNs as components of emulators using the simulation of jets as an example. Specifically, we use an IQN to map jets described by their 4-momenta at the generation level to jets at the event reconstruction level. The conditional densities emulated by our model closely match those generated by $\texttt{Delphes}$, while also enabling faster jet simulation.

Hurtado-Silva, J. S.; Toscano, J. J.; Vázquez-Hernández, O.

doi: 10.1088/1361-6471/ad961fpmid: N/A

Abstract:The impact of the CPT-Odd electroweak gauge sector of the Standard Model Extension on the electromagnetic properties of charged leptons is studied. This gauge sector is characterized by the $(k_1)_\mu$ and $(k_2)_\mu$ Lorentz violation (LV) 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. We present a comprehensive study on the impact of this sector on the magnetic dipole moment (MDM) and the electric dipole moment (EDM) of charged leptons, up to second order in these LV coefficients, both at the tree and one-loop this http URL contributions of $O(k_i)$ to the MDM are found to be suppressed relative to the corresponding contributions to the EDM by approximately three orders of magnitude. Using a recent experimental limit on the electron EDM the $|(k_2)_0-|\mathbf{k_2}|\cos\theta_\gamma|<0.86\, m_e$ bound was obtained. As far as the contributions of $O(k^2_i)$ are concerned, we find that the tree-level contributions are suppressed with respect to the one-loop ones by at least a factor of $\left(m^2_l/m^2_Z\right)$. We find that the contribution to the electron MDM is by far the dominant one, as it can be up to four and seven orders of magnitude greater than those of the muon and tau, respectively. The Lorentz coefficient $(k_{AF})_\mu$ of the Carroll-Field-Jackiw's QED is given by a linear combination of $(k_1)_\mu$ and $(k_2)_\mu$. Assuming that $|k^2_1|, |k^2_2|\gg |k^2_{AF}|$ and taking $(k_{AF})_\mu=0$, which implies that $(k_1)_\mu$ and $(k_2)_\mu$ are collinear, we obtain an upper bound of $\left|\frac{ k^2_2}{m^2_e} \right|<4.36\times 10^{-10}$. The fact that $k^2_2$ is an observer Lorentz invariant allows us to introduce a new-physics scale through $\sqrt{k^2_2}=\Lambda_{CPT}$, for which we obtain the upper limit $\Lambda_{CPT}< 2.08 \times 10^{-5}\, m_e$.

Rossia, Alejo N.; Thomas, Marion O. A.; Vryonidou, Eleni

doi: 10.1007/jhep11(2023)132pmid: N/A

Abstract:Precision measurements of diboson production at the LHC is an important probe of the limits of the Standard Model. The gluon-fusion channel of this process offers a connection between the Higgs and top sectors. We study in a systematic way gluon-induced diboson production in the Standard Model Effective Field Theory. We compute the amplitudes of double Higgs, double $Z/W$ and associated $ZH$ production at one loop and with up to one insertion of a dimension-6 operator. We study their high-energy limit and identify to which operators each channel could be most sensitive. To illustrate the relevance of these processes, we perform a phenomenological study of associated $ZH$ production. We show that for some top operators the gluon-induced channel can offer competitive sensitivity to constraints obtained from top quark production processes.

Barik, Anjan Kumar; Dey, Atri; Samui, Tousik

doi: 10.48550/arxiv.2306.10540pmid: N/A

Abstract:The search for lepton flavor violation (LFV) is a powerful probe to look for new physics beyond the Standard Model. We explored the possibility of searches for LFV $Z$ boson couplings to electron and muon pairs at the upcoming electron-proton colliders, namely the Large Hadron Electron Collider (LHeC) and the Future Circular lepton-hadron Collider (FCC-eh). We employed the study via a single muon plus an associated jet channel to search for the LFV signal. We used a multivariate technique to obtain an improved signal-background analysis. By using the condition on nonobservation of any significant deviation of the signal over the expected background, we provide an upper limit on the LFV $Z$ boson coupling and corresponding branching ratio. We find that an upper limit of $2.0\times 10^{-7}$ and $9.7 \times 10^{-8}$ can be set on BR($Z\to e \mu$) at 95% C.L. with one year run of LHeC and FCC-eh, respectively, if the LFV coupling is governed by vector or axial-vector coupling. For tensor or axial-tensor coupling, these limits can be improved to $6.2\times 10^{-8}$ and $2.2\times 10^{-8}$ for LHeC and FCC-eh machines, respectively. The projected numbers improve significantly over the existing limit of $2.62\times 10^{-7}$ set by ATLAS.

Chen, Xun; Yu, Bo; Chu, Peng-Cheng; Li, Xiao-Hua; Fujita, Mitsutoshi

doi: 10.48550/arxiv.2306.00682pmid: N/A

Abstract:The effect of gluon condensate on the holographic entanglement entropy is investigated in an Einstein-Dilaton model at zero and finite temperature. There is a critical length for the difference of entanglement entropy between the connected and disconnected surfaces in this model, which is often regarded as a signal of phase transition. With the increase of gluon condensate, the critical length becomes small, which means the confinement becomes strong at zero temperature. Moreover, an entropic C-function suddenly jumps to zero at the critical length, where there are expected to be no entangled states. At finite temperatures, results show that the effect of gluon condensate on the critical length is qualitatively consistent with the case of zero temperature. We find that the entropic C-function increases as a function of $l$ at finite temperature, while it has competitive behaviors with large gluon condensate.

Yang, Jing; Xie, Ning; Huang, Fa Peng

doi: 10.1088/1475-7516/2024/11/045pmid: N/A

Abstract:Recently, the Hellings Downs correlation has been observed by different pulsar timing array (PTA) collaborations, such as NANOGrav, European PTA, Parkes PTA, and Chinese PTA. These PTA measurements of the most precise pulsars within the Milky Way show the first evidence for the stochastic gravitational wave background of our Universe. We study the ultralight axion interpretation of the new discovery by investigating the gravitational wave from axion transitions between different energy levels of the gravitational atoms, which are composed of cosmic populated Kerr black holes and their surrounding axion clouds formed through the superradiant process. By Bayesian analysis, we demonstrate that this new observation naturally admits an ultralight axion interpretation around $10^{-21}$eV, which is consistent in magnitude with the typical mass of fuzzy dark matter.

Dekker, Ariane; Holst, Ian; Hooper, Dan; Leone, Giovani; Simon, Emily; Xiao, Huangyu

doi: 10.1103/physrevd.109.083026pmid: N/A

Abstract:The LHAASO Collaboration has recently reported a measurement of the diffuse gamma-ray emission from the Galactic Plane at energies between 10 TeV and 1 PeV. While this emission is brighter than that expected from cosmic-ray interactions in the interstellar medium alone, we show that the intensity, spectrum, and morphology of this excess are in good agreement with that predicted from the "TeV halos" which surround the Milky Way's pulsar population. These results support the conclusion that TeV halos dominate the ultra-high-energy sky, and that these objects convert $\sim 5\%$ of their total spindown power into very-high and ultra-high-energy photons.