Search

Precise information on the Higgs boson self-couplings provides the foundation for unveiling the electroweak symmetry breaking mechanism. Due to the scarcity of Higgs boson pair events at the LHC, only loose limits have been obtained. This is based on the assumption that the cross section is a quadratic function of the trilinear Higgs self-coupling in the $\kappa$ framework. However, if higher-order corrections of virtual Higgs bosons are included, the function form would dramatically change. In particular, new quartic and cubic power dependence on the trilinear Higgs self-coupling would appear. To get this new function form, we have performed a specialized renormalization procedure suitable for tracking all the Higgs self-couplings in each calculation step. Moreover, we introduce renormalization of the scaling parameter in the $\kappa$ framework to ensure the cancellation of all ultraviolet divergences. With the new function forms of the cross sections in both the gluon-gluon fusion and vector boson fusion channels, the upper limit of $\kappa_{\lambda_3}=\lambda_{\rm 3H}/\lambda_{\rm 3H}^{\rm SM}$ by the ATLAS (CMS) collaboration is reduced from 6.6 (6.49) to 5.4 (5.37). However, it is still hard to extract a meaningful constraint on the quartic Higgs self-coupling $\lambda_{\rm 4H}$ from Higgs boson pair production data. We also present the invariant mass distributions of the Higgs boson pair at different values of $\kappa_{\lambda}$, which could help to set optimal cuts in the experimental analysis., Comment: 12 pages, 4 figures

The Higgs boson pair production at the LHC provides a probe to the Higgs boson self-coupling. The higher-order QCD corrections in this process are sizable and must be taken into account in comparison with data. Due to the small cross section, it is necessary to consider at least one of the Higgs bosons decaying to bottom quarks. The QCD corrections to the decay processes would also be important in such cases. We present a full calculation of the total and differential cross sections for the $b\bar{b}\gamma\gamma$ final state with next-to-leading order (NLO) QCD corrections. After applying typical kinematic cuts in the final state, we find that QCD NLO corrections in the decay decrease the LO result by $19\%$ and reduce the scale uncertainties by a factor of two. The QCD corrections to the invariant mass $m_{jj\gamma\gamma}$ distribution, the transverse momentum spectra of the leading bottom quark jet and photon are significant and can not be approximated by a constant factor., Comment: 19 pages, 4 figures

The finite mass of the heavy quark suppresses the collimated radiations, which is generally referred to as the dead cone effect. In this paper, we study the distribution of hadron multiplicity over the hadron opening angle with respect to the jet axis in various flavors of jets. The corresponding measurement can be the most straightforward and simplest to explore the dynamical evolution of the radiations in the corresponding jet, which can expose the mass effect. We also propose the transverse energy-weighted angular distribution which sheds light on the interplay between perturbative and nonperturbative effects in the radiation. With Monte-Carlo simulations, our calculation shows that the dead cone effect can be clearly seen by taking the ratio between the b jet and the light-quark (inclusive) jet, promising to be measured at the LHC in the future., Comment: 7 pages, 4 figures; published version in CPC

We present the complete spectrum for the Bjorken $x$ weighted Energy-Energy Correlation in the deep inelastic scattering (DIS) process, from the target fragmentation region to the current fragmentation region, in the Breit frame. The corresponding collinear and transverse momentum-dependent logarithms are resummed to all orders with the accuracy of NLL and N$^3$LL, respectively. And the results in the full region are matched with ${\cal O}(\alpha^2_s)$ fixed-order calculation. The final numerical predictions are presented for both EIC and CEBAF kinematics., Comment: 14 pages, 8 figures

We present the first analytic results of N$^3$LO QCD corrections to the top-quark decay width. We focus on the dominant leading color contribution, which includes light-quark loops. At NNLO, this dominant contribution accounts for 95% of the total correction. By utilizing the optical theorem, the N$^3$LO corrections are related to the imaginary parts of the four-loop self-energy Feynman diagrams, which are calculated with differential equations. The results are expressed in terms of harmonic polylogarithms, enabling fast and accurate evaluation. The third-order QCD corrections decrease the LO decay width by 0.667%, and the scale uncertainty is reduced by half compared to the NNLO result. The most precise prediction for the top-quark width is now 1.321 GeV for $m_t=172.69$ GeV. Additionally, we obtain the third-order QCD corrections to the dilepton invariant mass spectrum and decay width in the semileptonic $b\to u$ transition., Comment: 11 pages, 2 figures

We outline the physics opportunities provided by the Electron Ion Collider (EIC). These include the study of the parton structure of the nucleon and nuclei, the onset of gluon saturation, the production of jets and heavy flavor, hadron spectroscopy and tests of fundamental symmetries. We review the present status and future challenges in EIC theory that have to be addressed in order to realize this ambitious and impactful physics program, including how to engage a diverse and inclusive workforce. In order to address these many-fold challenges, we propose a coordinated effort involving theory groups with differing expertise is needed. We discuss the scientific goals and scope of such an EIC Theory Alliance., Comment: 44 pages, ReVTeX, White Paper on EIC Theory Alliance

Discriminating the Higgs production mechanisms plays a crucial role in directly measuring the couplings of Higgs to gauge bosons for probing the nature of the electroweak symmetry breaking. We propose a novel method to distinguish the Higgs production mechanisms at the LHC by utilizing the jet charge asymmetry of the two leading forward jets in Higgs plus two jets production. This novel observable provides a way to disentangle the $W$-fusion from the $Z$-fusion and gluon fusion processes for the first time, due to the electric charge correlation of the two leading jets in the events. We show that the Higgs couplings to gauge bosons can be well constrained and its conclusion does not depend on the other possible new physics effects which modify the Higgs total or partial width. We also discuss the complementary roles between the proposed jet charge asymmetry measurement and the Higgs signal strength measurements at the HL-LHC in determining the Higgs couplings., Comment: 6 pages, 5 figures, version accepted by PRL

We present the first full analytic results of next-to-next-to-leading order (NNLO) QCD corrections to the top-quark decay width $\Gamma(t\to Wb)$ by calculating the imaginary part of three-loop top-quark self-energy diagrams. The results are all expressed in terms of harmonic polylogarithms and valid in the whole region $0\le m_W^2\le m_t^2$. The expansions in the $m_W^2\to 0$ and $m_W^2\to m_t^2$ limits coincide with previous studies. Our results can also be taken as the exact prediction for the lepton invariant mass spectrum in semileptonic $b\to u$ decays. We also analytically compute the decay width including the off-shell $W$ boson effect up to NNLO in QCD for the first time. Combining these contributions with electroweak corrections and the finite $b$-quark mass effect, we determine the most precise top-quark width to be 1.331 GeV for $m_t=172.69$ GeV. The total theoretical uncertainties including those from renormalization scale choice, top-quark renormalization scheme, input parameters, and missing higher-order corrections are scrutinized and found to be less than $1\%$., Comment: 8 pages, 3 figures; v2: matching the published version in PRD

We propose to utilize the average jet charge weighted single-spin asymmetry $A_e^{bQ}$ in the neutral current DIS scattering with one $b$-tagged jet produced at the EIC to probe the $Zb\bar{b}$ interactions. This novel observable is sensitive to the axial-vector component of the $Zb\bar{b}$ coupling and is complementary to the single-spin asymmetry measurement at the EIC and the $gg\to Zh$ cross section measurement at the HL-LHC in the determination of the $Zb\bar{b}$ couplings. We show that the apparent degeneracy of the $Zb\bar{b}$ couplings, implied by the LEP and SLC precision electroweak data, can be broken by the $A_e^{bQ}$ measurement at the EIC. With a large enough integrated luminosity collected at the EIC, the measurement of $A_e^{bQ}$ could also resolve the long-standing discrepancy of $A_{\rm FB}^b$ at the LEP, strongly dependent on the $b$-tagging efficiency., Comment: 6 pages, 4 figures, published version

Deep inelastic scattering on nuclei at the Electron-Ion Collider will open new opportunities to investigate the structure of matter. Heavy flavor-tagged jets are complementary probes of the partonic composition and transport coefficients of large nuclei, but introduce a new mass scale that modifies the structure of parton showers and must be carefully accounted for in perturbative calculations. In the framework of soft-collinear effective theory with Glauber gluon interactions, we present the first calculation of inclusive charm-jet and bottom-jet cross sections in electron-nucleus collisions at next-to-leading order and compare them to the reference electron-proton case. We also show predictions for the heavy flavor-tagged jet momentum sharing distributions to further clarify the correlated in-medium modification of jet substructure., Comment: 13 pages, 5 figures; v2: references added, typos corrected, to appear in Phys.Lett.B

We outline a new technique for the fully-differential matching of final-state parton showers to NNLO calculations, focussing here on the simplest case of leptonic collisions with two final-state jets. The strategy is facilitated by working in the antenna formalism, making use of NNLO antenna subtraction on the fixed-order side and the sector-antenna framework on the shower side. As long as the combined real-virtual and double-real corrections do not overcompensate the real-emission term in the three-jet region, negative weights can be eliminated from the matching scheme. We describe the implementation of all necessary components in the VINCIA antenna shower in PYTHIA 8.3., Comment: Version submitted to PLB

The energy-energy correlator (EEC) is an event shape observable which probes the angular correlations of energy depositions in detectors at high energy collider facilities. It has been investigated extensively in the context of precision QCD. In this work, we introduce a novel definition of EEC adapted to the Breit frame in deep-inelastic scattering (DIS). In the back-to-back limit, the observable we propose is sensitive to the universal transverse momentum dependent (TMD) parton distribution functions and fragmentation functions, and it can be studied within the traditional TMD factorization formalism. We further show that the new observable is insensitive to experimental pseudorapidity cuts, often imposed in the Laboratory frame due to detector acceptance limitations. In this work the singular distributions for the new observable are obtained in soft collinear effective theory up to $\mathcal{O}(\alpha_s^3)$ and are verified by the full QCD calculations up to $\mathcal{O}(\alpha_s^2)$. The resummation in the singular limit is performed up to next-to-next-to-next-to-leading logarithmic accuracy. After incorporating non-perturbative effects, we present a comparison of our predictions to PYTHIA 8 simulations., Comment: 12 pages, 6 figures; version as published

We perform a study of $W$-boson production in polarized proton-proton collisions through next-to-next-to-leading order (NNLO) in perturbative QCD. This calculation is required to extend the extraction of polarized parton distribution functions to NNLO accuracy. We present differential distributions at $\sqrt{s}=510$ GeV, relevant for comparison to measurements from the Relativistic Heavy Ion Collider (RHIC). The NNLO QCD corrections significantly reduce the scale dependence of the cross section. We compare the longitudinal single-spin asymmetries as a function of lepton pseudorapidity to RHIC data. The asymmetries exhibit excellent stability under perturbative QCD corrections., Comment: discussions expanded and references added; published version

Understanding the Higgs potential by measuring its self-interactions is fundamental in answering several big questions, such as electroweak symmetry breaking, electroweak baryogenesis, electroweak phase transition, and electroweak vacuum stability. The most promising way to probe the Higgs potential is to detect Higgs boson pair final state at high-energy colliders. In this talk, we report a recent perturbative calculation for the di-Higgs gluon-fusion process by taking into account N$^3$LO QCD radiative corrections in the approximation of infinite top quark mass limit. Finite top quark mass effects are also incorporated with several approximate schemes, which are known to be crucial in phenomenological applications. We show a very good asymptotic perturbative convergence at $\mathcal{O}(\alpha_s^5)$, and demonstrate that the remaining scale uncertainty is only at percent level., Comment: 7 pages, 2 figures, accepted contribution to proceedings of 40th International Conference on High Energy physics (ICHEP2020), July 28 - August 6, 2020, Prague, Czech Republic (virtual meeting); v2: update references

Jet production and jet substructure in reactions with nuclei at future electron-ion colliders will play a preeminent role in the exploration of nuclear structure and the evolution of parton showers in strongly-interacting matter. In the framework of soft-collinear effective theory, generalized to include in-medium interactions, we present the first theoretical study of inclusive jet cross sections and the jet charge at the EIC. Predictions for the modification of these observables in electron-gold relative to electron-proton collisions reveal how the flexible center-of-mass energies and kinematic coverage at this new facility can be used to enhance the signal and maximize the impact of the electron-nucleus program. Importantly, we demonstrate theoretically how to disentangle the effects from nuclear parton distribution functions and the ones that arise from strong final-state interactions between the jet and the nuclear medium., Comment: Figures updated, references added, version to appear in PRL

An important part of the physics program at the future electron-ion collider is to understand the nature of hadronization and the transport of energy and matter in large nuclei. Open heavy flavor production in deep inelastic scattering provides a new tool to address these critical questions. We present the first calculation of D-mesons and B-meson cross sections in electron-nucleus collisions at the EIC by including both next-to-leading order QCD corrections and cold nuclear matter effects. Our formalism employs generalized DGLAP evolution to include the contribution of in-medium parton showers, and is based on methods developed in soft-collinear effective theory with Glauber gluons that describe inclusive hadron production in reactions with nucleons and nuclei. The comprehensive study summarized here allows us to identify the optimal observables, center-of-mass energies, and kinematic regions most sensitive to the physics of energy loss and hadronization at the EIC., Comment: 11 pages, 6 figures, 1 table, v2: journal version. Figure panels, references, and discussion added

Event shape observables have been widely used for precision QCD studies at various lepton and hadron colliders. We present the most accurate calculation of the transverse-energy-energy correlation event shape variable in deep-inelastic scattering. In the framework of soft-collinear effective theory the cross section is factorized as the convolution of the hard function, beam function, jet function and soft function in the back-to-back limit. A close connection to TMD factorization is established, as the beam function when combined with part of the soft function is identical to the conventional TMD parton distribution function, and the jet function is the second moment of the TMD fragmentation function matching coefficient. We validate our framework by comparing the obtained LO and NLO leading singular distributions to the full QCD calculations in the back-to-back limit. We report the resummed transverse-energy-energy correlation distributions up to N$^3$LL accuracy matched with the NLO cross section for the production of a lepton and two jets. Our work provides a new way to precisely study TMD physics at the future Electron-Ion Collider., Comment: 14 pages, 5 figures; Matched published version

The Higgs boson pair production via gluon fusion at high-energy hadron colliders, such as the LHC, is vital in deciphering the Higgs potential and in pinning down the electroweak symmetry breaking mechanism. We carry out the next-to-next-to-next-to-leading order (N$^3$LO) QCD calculations in the infinite top-quark mass limit and present predictions for both the inclusive and differential cross sections, albeit the differential distributions other than the invariant mass distribution of the Higgs boson pair are approximated at N$^3$LO. Such corrections are indispensable in stabilising the perturbative expansion of the cross section in the strong coupling $\alpha_s$. At the inclusive level, the scale uncertainties are reduced by a factor of four compared with the next-to-next-to-leading order (NNLO) results. Given that the inclusion of the top-quark mass effects is essential for the phenomenological applications, we use several schemes to incorporate the N$^3$LO results in the infinite top-quark mass limit and the next-to-leading order (NLO) results with full top-quark mass dependence, and present theoretical predictions for the (differential) cross sections in the proton-proton collisions at the centre-of-mass energies $\sqrt{s}=13,14,27$ and $100$ TeV. Our results provide one of the most precise theoretical inputs for the analyses of the Higgs boson pair events., Comment: 51 pages, 23 figures, 4 tables. v2: journal version (minor corrections wrt v1)

We present next-to-next-to-next-to-leading order (N$^3$LO) QCD predictions for the Higgs boson pair production via gluon fusion at hadron colliders in the infinite top-quark mass limit. Besides the inclusive total cross sections at various collision energies, we also provide the invariant mass distribution of the Higgs boson pair. Our results show that the N$^3$LO QCD corrections enhance the next-to-next-to-leading order cross section by $3.0\%$ ($2.7\%$) at $\sqrt{s}=13~(100)$ TeV, while the scale uncertainty is reduced substantially below $3\%$ ($2\%$). We also find that a judicious scale choice can significantly improve the perturbative convergence. For the invariant mass distribution, our calculation demonstrates that the N$^3$LO corrections improve the scale dependence but almost do not change the shape., Comment: 8 pages, 5 figures, published version in PLB

Jet production and jet substructure modification in heavy-ion collisions have played an essential role in revealing the in-medium evolution of parton showers and the determination of the properties of strongly-interacting matter under extreme conditions. It is imperative to extend these studies to include flavor tagging and to devise observables that are sensitive to the partonic origin of jets. The average jet charge, defined as the momentum-weighted sum of the electric charges of particles inside the jet, is a proxy of the electric charge of the quark or gluon that initiates the jet. We demonstrate how the factorization framework of soft-collinear effective theory can be generalized to evaluate the jet charge in a dense strongly-interacting matter environment, such as the one produced in nuclear reactions at collider energies. Observables that can separate the contribution of in-medium branching from the trivial isospin effects are identified and their connection to established jet quenching effects is elucidated. We present predictions for the transverse momentum dependence of the jet charge distribution in nucleus-nucleus collisions and its modification relative to the proton case., Comment: 11 pages, 5 figures, as published in PRD

The past several years have witnessed important developments in the QCD theory of jet production and jet substructure in hadronic collisions. In the framework of soft-collinear effective theory, semi-inclusive jet functions and semi-inclusive fragmenting jet functions have allowed us to combine higher order calculations with resummation of potentially large logarithms of the jet radius, $\ln R$. Very recently, the semi-inclusive jet functions for partons fragmenting into heavy flavor jets were computed by Dai, Kim and Leibovich. In this paper we show how the formalism can be extended to c-jet and b-jet production in heavy ion collisions. The semi-inclusive jet functions for heavy flavor jets in a QCD medium are evaluated up to the next-to-leading order in $\alpha_s$ and first order in opacity. For phenomenological applications, we also consider the inclusion of the cold nuclear matter effects and the jet energy dissipation due to collisional interactions in matter. We present the numerical predictions for the cross sections and the corresponding nuclear modification factors in proton-nucleus and nucleus-nucleus collisions and compare our results to data from the Large Hadron Collider., Comment: 22 pages, 7 figures, as published in JHEP

The mass of heavy quarks, such as charm and bottom, plays an important role in the formation of parton showers. This effect is apparently not well understood when parton showers evolve in a strongly interacting quark-gluon plasma. We propose a new experimental measurement in relativistic heavy ion collisions, based on a two-prong subjet structure inside a reconstructed heavy flavor jet, which can place stringent constraints on the mass dependence of in-medium splitting functions. We identify the region of jet transverse momenta where parton mass effects are leading and predict a unique reversal of the mass hierarchy of jet quenching effects in heavy ion relative to proton collisions. Namely, the momentum sharing distribution of prompt $b$-tagged jets is more strongly modified in comparison to the one for light jets. Our work is useful in guiding experimental efforts at the Large Hadron Collider and the Relativistic Heavy Ion Collider in the near future., Comment: 7 pages, 5 figures, matches published version

We present a fully differential next-to-next-to-leading order calculation of the Higgs pair production in association with a $Z$ boson, which is important for probing the trilinear Higgs self-coupling. The next-to-next-to-leading-order corrections enhance the next-to-leading order total cross sections by a factor of $1.2\sim 1.5$, depending on the collider energy, and change the shape of next-to-leading order kinematic distributions. We discuss how to determine the trilinear Higgs self-coupling using our results., Comment: 6 pages, 7 figures, published version in PRD

To clarify the electroweak symmetry breaking mechanism, we need to probe the Higgs self-couplings, which can be measured in Higgs pair productions. The associated production with a vector boson is special due to a clear tag in the final state. We perform a fully differential next-to-next-to-leading-order calculation of the Higgs pair production in association with a $W$ boson at hadron colliders, and present numerical results at the 14 TeV LHC and a future 100 TeV hadron collider., Comment: 7 pages, 7 figures, matched to the published version in PLB

We present a precise theoretical prediction for the signal-background interference process of $gg(\to h^*) \to ZZ$, which is useful to constrain the Higgs boson decay width and to measure Higgs couplings to the SM particles. The approximate NNLO $K$-factor is in the range of $2.05-2.45$ ($1.85-2.25$), depending on $M_{ZZ}$, at the 8 (13) TeV LHC. And the soft gluon resummation can increase the approximate NNLO result by about $10\%$ at both the 8 TeV and 13 TeV LHC. The theoretical uncertainties including the scale, uncalculated multi-loop amplitudes of the background and PDF$+\alpha_s$ are roughly $\mathcal{O}(10\%)$ at ${\rm NNLL'}$. We also confirm that the approximate $K$-factors in the interference and the pure signal processes are the same., Comment: 18 pages, 9 figures; v2 published in JHEP

We present a detailed study of the same-sign top pair production mediated by a non-universal $Z^\prime$ including production and decay at the Large Hadron Collider (LHC) at the QCD next-to-leading order (NLO) level, using the narrow width approximation and helicity amplitudes method. We find that the QCD NLO corrections can loose the constraint on the model parameters and reduce the dependence of the total cross sections on the factorization scale significantly. We also study the signature and backgrounds of the process at the NLO level. In order to suppress the backgrounds, we further investigate the difference between the production rates of the positively and negatively charged dilepton at the LHC, and find that the same-sign dilepton signal of the new physics could be discovered more easily., Comment: 24 pages, 14 figures, 2 table. final version in PRD. arXiv admin note: text overlap with arXiv:1103.5122

We improve the resummation calculations in the ResBos program for the Higgs boson production via gluon-gluon fusion by including the NNLO Wilson coefficient functions and G-functions. The improvement leads to increasing the total cross section predictions of the new ResBos program, dubbed as ResBos2, for Higgs boson production by about 8% and 6% at the Tevatron and the LHC, respectively, as compared to the old ResBos program. Furthermore, the improved predictions are compared with those from the programs HNNLO and HqT2. We find that they agree well for the total cross sections but differ slightly for the transverse momentum $Q_T$ distributions. With ResBos2, we present the distributions of the two variables $a_T$ and $\phi^{*}$, which can have better experimental resolutions than $Q_T$, for the process of Higgs boson decaying into a photon pair. Theoretical uncertainties of the ResBos2 predictions are also discussed., Comment: 15 pages, 8 figures, 2 tables