arXiv subjects

Satyajit Seth

Publications and source records attributed to Satyajit Seth.

At least 19 recordsLinked to original sources

arXiv2025

NLP threshold corrections to W+jet production

We perform a detailed computation of the helicity-dependent next-to-leading power leading logarithms in W+jet production, originating from next-to-soft gluon radiation and soft (anti-)quark emissions. These contributions are systematically captured via helicity-sensitive spinor shifts and soft quark operators. The resulting expressions exhibit full agreement with a recently proposed universal structure of NLP corrections for processes involving the production of an arbitrary massive colourless final state in association with a jet.

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arXiv2025

Universality at next-to-leading power for jet associated processes

The study of cross-sections in the threshold limit at next-to-leading power has been a subject of sustained interest for many years. We demonstrate the universality of leading logarithms at next-to-leading power for the production of arbitrary massive colourless particles in association with a jet, contingent upon the identification of appropriate combination of helicity configurations.

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arXiv2024

On Higgs+jet production at next-to-leading power accuracy

We present computation of the next-to-leading power corrections for Higgs plus one jet production in a hadron collider via gluon fusion channel. Shifting of spinors in the helicity amplitudes without additional radiation captures the leading next-to-soft radiative behaviour and makes the calculation tractable. We establish the connection between the shifted dipole spinors and the colour ordered radiative amplitudes. We find that next-to-maximal helicity violating amplitudes do not play a role in this correction. Compact analytic expressions of next-to-leading power leading logarithms coming from different helicity configurations are shown.

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arXiv2024

Soft quark effects on H+jet production at NLP accuracy

We define soft quark operators that enable construction of colour-ordered helicity amplitudes out of the non-radiative ones. We explore these operators for Higgs plus one jet production in a hadron collider and study the next-to-leading power corrections on all partonic channels involving quark(s) and/or anti-quark(s). We also investigate the effect of next-to-soft gluon radiation in these channels employing the technique illustrated in \cite{Pal:2023vec}. Analytical expressions of next-to-leading power leading logarithms thus obtained are simple and compact in nature. Further, we discuss the connection of such logarithms with that of the pseudo-scalar Higgs plus one jet production.

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arXiv2023

Precise probing and discrimination of third-generation scalar leptoquarks

We explore the pair production of third-generation scalar leptoquark at the Large Hadron Collider to next-to-leading order accuracy in QCD, matched to parton shower for a precise probing of the stemming model. We propose to tag two boosted top-like fatjets produced from the decay of heavy leptoquarks in association with notably large missing transverse momentum and consider them as the potential signal. Such a signal demonstrates the capability of a robust discovery prospect in the multivariate analysis with different high-level observables, including jet substructure variables. Various scalar leptoquark models predict different chirality of the top quark appearing from the decay of the leptoquark carrying same electromagnetic charge. We make use of the polarization variables sensitive to the top quark polarization in order to identify the underlying theory.

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arXiv2023

Jet-veto resummation at N$^3$LL$_\text{p}$+NNLO in boson production processes

Vetoing energetic jet activity is a crucial tool for suppressing backgrounds and enabling new physics searches at the LHC, but the introduction of a veto scale can introduce large logarithms that may need to be resummed. We present an implementation of jet-veto resummation for color-singlet processes at the level of N$^3$LL$_\text{p}$ matched to fixed-order NNLO predictions. Our public code MCFM allows for predictions of a single boson, such as $Z/γ^*$, $W^{\pm}$ or $H$, or with a pair of vector bosons, such as $W^+W^-$, $W^{\pm} Z$ or $ZZ$. The implementation relies on recent calculations of the soft and beam functions in the presence of a jet veto over all rapidities, with jets defined using a sequential recombination algorithm with jet radius $R$. However one of the ingredients that is required to reach full N$^3$LL accuracy is only known approximately, hence N$^3$LL$_\text{p}$. We describe in detail our formalism and compare with previous public codes that operate at the level of NNLL. Our higher-order predictions improve significantly upon NNLL calculations by reducing theoretical uncertainties. We demonstrate this by comparing our predictions with ATLAS and CMS results.

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arXiv2022

Transverse momentum resummation at N3LL+NNLO for diboson processes

Diboson processes are one of the most accessible and stringent probes of the Standard Model's electroweak gauge structure at the LHC. They will be probed at the percent level at the high-luminosity LHC, challenging current theory predictions. We present transverse momentum resummed calculations at N3LL+NNLO for the processes $ZZ$, $WZ$, $WH$ and $ZH$, compare our predictions with most recent LHC data and present predictions at 13.6 TeV including theory uncertainty estimates. For $W^+W^-$ production we further present jet-veto resummed results at N3LLp+NNLO. Our calculations will be made publicly available in the upcoming MCFM release and allow future analyses to take advantage of improved predictions.

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arXiv2022

Non-local slicing approaches for NNLO QCD in MCFM

We present the implementation of several processes at Next-to-Next-to Leading Order (NNLO) accuracy in QCD in the parton-level Monte Carlo program MCFM. The processes treated are $pp\to H$, $W^\pm$, $Z$, $W^\pm H$, $ZH$, $W^\pmγ$, $Zγ$ and $γγ$ and, for the first time in the code, $W^+W^-$, $W^\pm Z$ and $ZZ$. Decays of the unstable bosons are fully included, resulting in a flexible fully differential Monte Carlo code. The NNLO corrections have been calculated using two non-local slicing approaches, isolating the doubly unresolved region by cutting on the zero-jettiness, ${\cal T}_0$, or on $q_T$, the transverse momentum of the colour singlet final-state particles. We find that for most, but not all processes the $q_T$ slicing method leads to smaller power corrections for equal computational burden.

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arXiv2022

Precise probing of the inert Higgs-doublet model at the LHC

The inert Higgs-doublet model provides a simple framework to accommodate a viable Higgs portal scalar dark matter candidate, together with other heavier scalars of mass 100 GeV or more. We study the effect of next-to-leading order (NLO) QCD corrections in this scenario in the context of the Large Hadron Collider. ${\cal{O}}(α_s)$ corrections to the gluon-gluon-Higgs effective coupling have been taken into account in this study wherever appropriate. We find such corrections have a significant impact on various kinematic distributions and reduce scale uncertainties substantially. Fixed order NLO results are matched to the {\sc Pythia8} parton shower (PS) and the di-fatjet signal associated with the missing transverse momentum is analyzed, as this channel has the ability to explore its entire parameter space during the next phase of the LHC run. A closer look at the NLO+PS computation indicates a sizable NLO effect together with a subdued contribution from associated production of the heavy scalar compared to the pair production, thereby leading to a refined analysis strategy during the multivariate analysis of this signal.

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arXiv2022

The one-loop amplitudes for Higgs + 4 partons with full mass effects

We present compact analytic formulae for the one-loop amplitudes for Higgs + 4 parton scattering, $0 \to g g g g h$, $0 \to \bar{q} q gg h$ and $0\to \bar{q} q \bar{q}^\prime q^\prime h$, mediated by a loop of massive coloured quarks. We exploit the correspondence with a theory in which a massive coloured scalar circulates in the loop to avoid a proliferation in the number of terms in the result. In addition, we use momentum twistors and high precision numerical evaluations to simplify the expressions. The analytic results in this paper, in terms of spinor products, allow construction of an efficient numerical program to calculate the amplitude.

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arXiv2021

The $pp\to W(\to lν)+γ$ process at next-to-next-to-leading order

We present details of the calculation of the $pp\to W(\to lν) γ$ process at next-to-next-to-leading order in QCD, calculated using the jettiness slicing method. The calculation is based entirely on analytic amplitudes. Because of the radiation zero, the NLO QCD contribution from the $gq$ channel is as important as the contribution from the Born $q\bar{q}$ process, disrupting the normal counting of leading and sub-leading contributions. We also assess the importance of electroweak (EW) corrections, including the EW corrections to both the six-parton channel $0\to \bar{u} d νe^+γg$ and the five-parton channel $0\to \bar{u} d νe^+ γ$. Previous experimental results have been shown to agree with theoretical predictions, taking into account the large experimental errors. With the advent of run II data from the LHC, the statistical errors on the data will decrease, and will be competitive with the error on theoretical predictions for the first time. We present numerical results for $\sqrt{s}=7$ and 13 TeV. Analytic results for the one-loop six-parton QCD amplitude and the tree-level seven-parton QCD amplitude are presented in appendices.

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arXiv2020

Towards the ultimate differential SMEFT analysis

We obtain SMEFT bounds using an approach that utilises the complete multi-dimensional differential information of a process. This approach is based on the fact that at a given EFT order, the full angular distribution in the most important electroweak processes can be expressed as a sum of a fixed number of basis functions. The coefficients of these basis functions - the so-called angular moments - and their energy dependance, thus form an ideal set of experimental observables that encapsulates the complete multi-dimensional differential information of the process. This approach is generic and the observables constructed allow to avoid blind directions in the SMEFT parameter space. While this method is applicable to many of the important electroweak processes, as a first example we study the $pp \to V(\ell\ell)h(bb)$ process ($V \equiv Z/W^{\pm}, \; \ell\ell \equiv \ell^+\ell^-/\ell^\pmν$), including QCD NLO effects, differentially. We show that using the full differential data in this way plays a crucial role in simultaneously and maximally constraining the different vertex structures of the Higgs coupling to gauge bosons. In particular, our method yields bounds on the $h V_{μν}V^{μν}$, $h V_{μν}\tilde{V}^{μν}$ and $h Vff$ ($ff \equiv f\bar{f}/f\bar{f}'$) couplings, stronger than projected bounds reported in any other process. This matrix-element-based method can provide a transparent alternative to complement machine learning techniques that also aim to disentangle correlations in the SMEFT parameter space.

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arXiv2020

Analytic results for scalar-mediated Higgs boson production in association with two jets

We present compact analytic formulae for all one-loop amplitudes representing the production of a Higgs boson in association with two jets, mediated by a colour triplet scalar particle. Many of the integral coefficients present for scalar mediators are identical to the case when a massive fermion circulates in the loop, reflecting a close relationship between the two theories. The calculation is used to study Higgs boson production in association with two jets in a simplified supersymmetry (SUSY) scenario in which the dominant additional contributions arise from loops of top squarks. The results presented here facilitate an indirect search for top squarks in this channel, by a precision measurement of the corresponding cross-section. However, we find that the potential for improved discrimination between the SM and SUSY cases suggested by the pattern of results in the 1- and 2-jet samples is unlikely to be realized due to the loss in statistical power compared to an inclusive analysis.

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arXiv2019

Infrared structure of $\mathcal{N}$ = 4 SYM and leading transcendentality principle in gauge theory

We present a detailed study on the infrared structure of $\mathcal{N}=4$ SYM and its connection to QCD. Calculation of collinear splitting functions helps to understand the structure and thus one can get infrared safe cross sections. We also demonstrate the factorization property that soft plus virtual part of the cross section satisfies and through factorization, we calculate soft distribution function up to third order in perturbation theory. We show that the soft distribution function is process independent that includes operators as well as external legs. In addition to this we compare our findings against the known results in QCD through principle of maximum transcendentality (PMT). We extend our analysis further for the case of three-point form factors involving stress tensor and find that it violates the PMT while comparing with the corresponding quantity in the standard model, observed for the first time at the level of form factor.

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arXiv2019

H+1 jet production revisited

We revisit the next-to-next-to-leading order (NNLO) calculation of the Higgs boson+1~jet production process, calculated in the $m_t \to \infty$ effective field theory. We perform a detailed comparison of the result calculated using the jettiness slicing method, with published results obtained using subtraction methods. The results of the jettiness calculation agree with the two previous subtraction calculations at benchmark points. The performance of the jettiness slicing approach is greatly improved by adopting a definition of 1-jettiness that accounts for the boost of the Born system. Nevertheless, the results demonstrate that power corrections in the jettiness slicing method remain significant. At large transverse momentum the effect of power corrections is much reduced, as expected.

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arXiv2019

Second order splitting functions and infrared safe cross sections in $\mathcal{N}=4$ SYM theory

We report our findings on the perturbative structure of ${\cal N}=4$ supersymmetric Yang-Mills (SYM) theory in the infrared sector by computing inclusive scattering cross sections of on-shell particles. We use half-BPS, energy-momentum tensor and Konishi operators to produce singlet states in the scattering processes to probe the soft and the collinear properties of the cross sections. By appropriately defining the infrared safe observables, we obtain collinear splitting functions up to second order in the perturbation theory. The splitting functions and the infrared finite cross sections demonstrate several interesting connections with those in the perturbative QCD. We also determine the process independent soft distribution function up to third order in the perturbation theory and show that it is universal {\it i.e.} independent of the operators as well as the external states. Interestingly, the soft distribution function in ${\cal N}=4$ SYM theory matches exactly with the leading transcendental part of the corresponding one in the QCD. This enables us to predict the third order soft plus virtual cross section for the production of the on-shell singlet states.

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arXiv2018

On Higgs boson plus gluon amplitudes at one loop

We present analytic results for one-loop Higgs boson + $n$-gluon amplitudes for $n\le 5$ in the full theory including all dependence on the (top) quark mass. In this paper we consider only the case where the gluons all have the same helicity. The amplitudes are expressed in simple formula and display similar structure. Their limiting behaviour in small Higgs momentum and large top mass is studied.

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arXiv2017

Finite remainders of the Konishi at two loops in ${\cal N}=4$ SYM

We present three point form factors (FF) in ${\cal N}=4$ Super Yang Mills theory for both the half-BPS and the Konishi operators at two loop level in the `t Hooft coupling using Feynman diagrammatic approach. We have chosen on shell final states consisting of $g ϕϕ$ and $ϕλλ$, where $ϕ,λ, g$ are scalar, Majorana fermion and gauge fields respectively. The computation is done both in the modified dimensional reduction as well as in the four dimensional helicity scheme. We have studied the universal structure of infrared (IR) singularities in these FFs using Catani's IR subtraction operators. Exploiting the factorisation property of the IR singularities and following BDS like ansatz for the IR sensitive terms in FFs, we determine the finite remainders of them. We find that the finite remainders of FFs of the half-BPS for both the choices of final states give not only identical results but also contain terms of uniform transcendentality of weight two and four at one and two loop levels, respectively. In the case of the Konishi operator, the finite remainders depend on the external states and do not exhibit uniform transcendentality. However, surprisingly, the leading transcendental terms for $g ϕϕ$ agree with that of the half-BPS. We have demonstrated the role of on shell external states for the FFs in the context of maximum transcendentality principle.

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