Gluon-gluon to photon-photon scattering $gg \to γγ$ offers to the LHC experiments a uniquely powerful probe of dimension-8 operators in the Standard Model Effective Field Theory (SMEFT) that are quadratic in both the electromagnetic and gluonic field-strength tensors, such as would appear in the Born-Infeld extension of the Standard Model (SM). We use 13-TeV ATLAS data on the production of isolated photon pairs to set lower limits on the scales of dimension-8 operators $M \gtrsim 1$~TeV, and discuss the prospective sensitivities of possible future hadron colliders.
We study a typical complete gluonic phase (LGP) in two-flavor color superconductivity (2SC) by calculating the essential cubic and quartic interfering term between the gluonic condensates $<A^{(8)}_{z}>$ and $<A^{(6)}_{z}>$ with a gauged NJL model. It is proven that the coefficient of the cubic interfering term and the vacuum contributions of the cubic and quartic interfering term are all equal to zeroes. The coefficients of the quartic interfering term and the $<A^{(6)}_{z}>$'s quartic self-interaction term at stationary points of LOFF phase are calculated. Comparisons among the effective pot…
We present an analysis of constraints on two types of CP-odd electron-gluonic operators $(\bar{e}iγ^5 e)G_{μν}^a G^{aμν}$ and $(\bar{e}e)G_{μν}^a \tilde{G}^{aμν}$ from current and future electric dipole moment (EDM) experiments. The recent result from the ACME experiment using ThO molecules is used to derive an impressive lower bound on the effective scale for $(\bar{e}iγ^5 e)G_{μν}^a G^{aμν}$ at 8 TeV, assuming a QCD one-loop factor and no helicity suppression from new physics. One interesting aspect is that $(\bar{e}iγ^5 e)G_{μν}^a G^{aμν}$ contributes to the observable EDM in ThO experiment…
Lepton flavor-violating processes offer interesting possibilities to probe new physics at multi-TeV scale. We discuss those in the framework of effective field theory, emphasizing the role of gluonic operators. Those operators are obtained by integrating out heavy quarks that are kinematically inaccessible at the scale where low-energy experiments take place and make those experiments sensitive to the couplings of lepton flavor changing neutral currents to heavy quarks. We discuss constraints on the Wilson coefficients of those operators from the muon conversion $μ^- + (A,Z) \to e^- + (A,Z)$ a…
We study the indirect constraints on the quartic Higgs self-coupling that arise from double-Higgs production at future hadron colliders. To this purpose, we calculate the two-loop contributions to the $gg \to hh$ amplitudes that involve a modified $h^4$ vertex. Based on our results, we estimate the reach of a $pp$ collider operating at $27 \, {\rm TeV}$ and $100 \, {\rm TeV}$ centre-of-mass energy in constraining the cubic and quartic Higgs self-couplings by measurements of double-Higgs and triple-Higgs production in gluon-fusion.
We apply a fully automated extension of the $R^*$-operation capable of calculating higher-loop anomalous dimensions of n-point Green's functions of arbitrary, possibly non-renormalisable, local Quantum Field Theories. We focus on the case of the CP-violating Weinberg operator of the Standard Model Effective Field Theory whose anomalous dimension is so far known only at one loop. We calculate the two-loop anomalous dimension in full QCD and the three-loop anomalous dimensions in the limit of pure Yang-Mills theory. We find sizeable two-loop and large three-loop corrections, due to the appearanc…
Effective field theory techniques provide us important tools to probe for physics beyond the Standard Model in a relatively model-independent way. In this work, we revisit the CP-even dimension-6 purely gluonic operator to investigate the possible constraints on it by studying its effect on top-pair production at the LHC, in particular the high $p_T$ and $m_{t\bar{t}}$ tails of the distribution. Cut-based analysis reveals that the scale of New Physics when this operator alone contributes to the production process is greater than 3.4 TeV at 95% C.L., which is a much stronger bound compared to t…
We derive one loop constraints on the anomalous quartic gauge couplings using a general non-forward dispersion relation for the elastic scattering amplitude of two longitudinally polarized vector bosons. We compare this result with another one derived by the assumption that the underlying theory satisfies the causality principle of Special Relativity and show that this latter is more constraining.
We investigate the constraints on the leptoquark Yukawa couplings and Higgs-leptoquark quartic couplings for scalar doublet leptoquark $\tilde{R}_2$, scalar triplet leptoquark $\vec S_3$ and their combination with both three generations and one generation from perturbative unitarity and vacuum stability. Perturbative unitarity of all the dimensionless couplings have been studied via one- and two-loop beta-functions. Introduction of new $SU(2)$ multiplets in terms of these leptoquarks fabricate Landau poles at two-loop level in the gauge coupling $g_2$ at $10^{19.7}$ GeV and $10^{14.4}$ GeV, re…
We present an extension of the JHUGen and MELA framework, which includes an event generator and library for the matrix element analysis. It enables simulation, optimal discrimination, reweighting techniques, and analysis of a bosonic resonance and the triple and quartic gauge boson interactions with the most general anomalous couplings. The new features, which become especially relevant at the current stage of LHC data taking, are the simulation of gluon fusion and vector boson fusion in the off-shell region, associated $ZH$ production at NLO QCD including the $gg$ initial state, and the simul…
We study the constraints that can be placed on anomalous $τ$-lepton couplings at the LHC. We use an effective Lagrangian description for physics beyond the standard model which contains the $τ$-lepton anomalous magnetic moment, electric dipole moment and weak dipole moments in two operators of dimension six. We include in our study two additional operators of dimension eight that directly couple the $τ$-leptons to gluons and are therefore enhanced at the LHC. We consider the two main effects from these couplings: modifications to the Drell-Yan cross-section and to the $τ$-lepton pair productio…
We confront the warm inflation observational predictions directly with the latest CMB data. We focus on a linear temperature (T) dissipative coefficient combined with the simplest model of inflation, a quartic chaotic potential. Although excluded in its standard cold inflation version, dissipation reduces the tensor-to-scalar ratio and brings the quartic chaotic model within the observable allowed range. We will use the CosmoMC package to derive constraints on the model parameters: the combination of coupling constants giving rise to dissipation, the effective number of relativistic degrees of…
We study Higgs + jet production at hadron colliders in order to look for new physics residual effects possibly described by the $dim=6$ operators $Ø_{GG}$ and ${\widetildeØ}_{GG}$ which induce anomalous $Hgg$ and $Hggg$ couplings. Two ways for constraining these operators at LHC may be ~useful. The first is based on the total Higgs boson production rate induced by gluon-gluon fusion, in which the main cause of limitations are due to theoretical uncertainties leading to sensitivities of $|d_G|\simeq 3.\times 10^{-4}$ and $|\widetilde{d}_G|\simeq 1.4\times 10^{-3}$ for the corresponding anomalou…
Quartic vertices provide a window into one of the most important problems in particle physics; the understanding of electroweak symmetry breaking. I survey the various processes that have been proposed to study quartic gauge boson couplings at future $e^+e^-$, $eγ$, $γγ$, $e^-e^-$, and $pp$ colliders. For the lowest dimension operators that do not include photons, it appears that the LHC will provide the most constraining measurements. However, precision measurements at high energy $e^+e^-$ colliders involving $W^+W^-$ rescattering are also quite sensitive to the effects of a strongly interact…
We study the sensitivity to the shape of the Higgs potential of single, double, and triple Higgs production at future $e^+e^-$ colliders. Physics beyond the Standard Model is parameterised through the inclusion of higher-dimensional operators $(Φ^\dagger Φ- v^2/2)^n/Λ^{(2n-4)}$ with $n=3,4$, which allows a consistent treatment of independent deviations of the cubic and quartic self couplings beyond the tree level. We calculate the effects induced by a modified potential up to one loop in single and double Higgs production and at the tree level in triple Higgs production, for both $Z$ boson ass…
We derive the first systematic observational constraints on reheating in models of inflation where an additional light scalar field contributes to primordial density perturbations and affects the expansion history during reheating. This encompasses the original curvaton model but also covers a larger class of scenarios. We find that, compared to the single-field case, lower values of the energy density at the end of inflation and of the reheating temperature are preferred when an additional scalar field is introduced. For instance, if inflation is driven by a quartic potential, which is one of…
Constraining the Higgs potential using multi-Higgs production
School of Physics, Shandong University（山东大学物理学院）；Department of Physics and Enrico Fermi Institute, University of Chicago（芝加哥大学物理系与恩里科·费米研究所）；Max Planck Institute for Physics（马克斯·普朗克物理研究所）；Physikalisches Institut, Universität Freiburg（弗赖堡大学物理研究所）；INFN, Sezione di Bologna（意大利国家核物理研究所博洛尼部分所）；Dipartimento di Fisica G. Occhialini, Università degli Studi di Milano-Bicocca and INFN, Sezione di Milano-Bicocca（米兰比可卡大学G.奥恰利尼物理系及意大利国家核物理研究所米兰比可卡分所）；Indian Institute of Science Education and Research（印度科学教育与研究学院）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙物理学研究所）
We study the effects of thermal fluctuations of gluons and the diquark pairing field on the superconducting-to-normal state phase transition in a three-flavor color superconductor, using the Ginzburg-Landau free energy. At high baryon densities, where the system is a type I superconductor, gluonic fluctuations, which dominate over diquark fluctuations, induce a cubic term in the Ginzburg-Landau free energy, as well as large corrections to quadratic and quartic terms of the order parameter. The cubic term leads to a relatively strong first order transition, in contrast with the very weak first …
The GammeV experiment has constrained the couplings of chameleon scalar fields to matter and photons. Here we present a detailed calculation of the chameleon afterglow rate underlying these constraints. The dependence of GammeV constraints on various assumptions in the calculation is studied. We discuss GammeV--CHASE, a second-generation GammeV experiment, which will improve upon GammeV in several major ways. Using our calculation of the chameleon afterglow rate, we forecast model-independent constraints achievable by GammeV--CHASE. We then apply these constraints to a variety of chameleon mod…
Gravitational-wave (GW) detections of binary neutron star coalescences play a crucial role to constrain the microscopic interaction of matter at ultrahigh density. Similarly, if boson stars exist in the universe their coalescence can be used to constrain the fundamental coupling constants of a scalar field theory. We develop the first coherent waveform model for the inspiral of boson stars with quartic interactions. The waveform includes coherently spin-induced quadrupolar and tidal-deformability contributions in terms of the masses and spins of the binary and of a single coupling constant of …
The mass of a scalar field mediating a fifth force is tightly constrained by experiments. We show, however, that adding a quartic self-interaction for such a scalar makes most tests much less constraining: the non-linear equation of motion masks the coupling of the scalar to matter through the chameleon mechanism. We discuss consequences for fifth force experiments. In particular, we find that, with quartic coupling of order unity, a gravitational strength interaction with matter is allowed by current constraints. We show that our chameleon scalar field results in experimental signatures that …
Our current measurements of the Standard Model parameters imply that the Higgs field resides in a metastable electroweak vacuum, where the vacuum can decay to a lower ground state, with cataclysmic repercussions for our Universe. According to our observations, no such event has happened in the observable universe, in spite of the various energetic processes that could have triggered it. This work serves as an overview of a method that uses the metastability of the false vacuum during cosmological inflation to provide constraints on the Higgs curvature coupling $ξ$. Considering also the effects…
The positivity bounds, derived from the axiomatic principles of quantum field theory (QFT), constrain the signs of Wilson coefficients and their linear combinations in the Standard Model Effective Field Theory (SMEFT). The precise determination of these bounds, however, can become increasingly difficult as more and more SM modes and operators are taken into account. We study two approaches that aim at obtaining the full set of bounds for a given set of SM fields: 1) the traditional elastic positivity approach, which exploits the elastic scattering amplitudes of states with arbitrarily superpos…
The Higgs quartic coupling has now been indirectly measured at the electroweak scale. Assuming no new low-scale physics, its running is known and, together with gauge and Yukawa couplings, it is a crucial new piece of information constraining UV completions of the Standard Model. In particular, supersymmetry broken at an intermediate or high energy scale with tan(beta)=1 (i.e. lambda=0) is consistent with present data and has an independent theoretical appeal. We analyze the possible string-theoretic motivations for tan(beta)=1 (including both the shift-symmetry and the more economical variant…
