Articoli di riviste: "Next-to-next-to-leading order (NNLO)"

1

CONTOGOURIS, A. P., e Z. MEREBASHVILI. "APPROXIMATE NEXT-TO-LEADING ORDER AND NEXT-TO-NEXT-TO-LEADING ORDER CORRECTIONS". International Journal of Modern Physics A 18, n. 06 (10 marzo 2003): 957–66. http://dx.doi.org/10.1142/s0217751x03013983.

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For processes involving structure functions and/or fragmentation functions, arguments that over a range of a proper kinematic variable, there is a part that dominates the next-to-leading order (NLO) corrections, are briefly reviewed. The arguments are tested against more recent NLO and in particular complete next-to-next-to-leading order (NNLO) calculations. A critical examination of when these arguments may not be useful is also presented.

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Carloni Calame, Carlo M., Mauro Chiesa, Guido Montagna, Oreste Nicrosini e Fulvio Piccinini. "Muon-electron scattering at next-to-leading order accuracy". EPJ Web of Conferences 212 (2019): 05002. http://dx.doi.org/10.1051/epjconf/201921205002.

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The next-to-leading order electro-weak radiative corrections to the µ±e- → µ±e- process are reviewed and their relevance is discussed for the MUonE experiment, proposed at CERN. The aim of MUonE is the high precision measurement of the QED running coupling constant in the space-like region, from which the full hadronic contribution can be extracted and used to provide a new and independent determination of the leading-order hadronic correction to the muon g − 2. In this context, the required accuracy demands that radiative corrections are accounted for at the highest level of precision and implemented into a Monte Carlo event generator for data analysis. The first step towards the final goal of theoretical precision, which will require the full set of NNLO corrections and resummation of higher orders, is the inclusion of NLO electro-weak corrections.

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3

Hermansson-Truedsson, Nils. "Chiral Perturbation Theory at NNNLO". Symmetry 12, n. 8 (30 luglio 2020): 1262. http://dx.doi.org/10.3390/sym12081262.

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Chiral perturbation theory is a much successful effective field theory of quantum chromodynamics at low energies. The effective Lagrangian is constructed systematically order by order in powers of the momentum p2, and until now the leading order (LO), next-to leading order (NLO), next-to-next-to leading order (NNLO) and next-to-next-to-next-to leading order (NNNLO) have been studied. In the following review we consider the construction of the Lagrangian and in particular focus on the NNNLO case. We in addition review and discuss the pion mass and decay constant at the same order, which are fundamental quantities to study for chiral perturbation theory. Due to the large number of terms in the Lagrangian and hence low energy constants arising at NNNLO, some remarks are made about the predictivity of this effective field theory.

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4

Kardos, A., S. Kluth, G. Somogyi, Z. Tulipánt e A. Verbytskyi. "Precise determination of αS( $ m_{Z^0 } $ ) from a global fit of energy-energy correlations to NNLO+NNLL predictions". EPJ Web of Conferences 206 (2019): 05002. http://dx.doi.org/10.1051/epjconf/201920605002.

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We present a determination of the strong coupling constant αS( $ m_{Z^0 } $ ) using a global fit of theory predictions in next-to-next-next-leading-order (NNLO) combined with resummed predictions at the next-to-next-leading-log level (NNLL) [bibrR11]. The predictions are compared to distributions of energy-energy correlations measured in e+e−annihilation to hadronic final states by experiments at the e+e−colliders LEP, PETRA, TRISTAN and PEP. The predictions are corrected for hadronisation eﬀects using the modern generator programs Sherpa 2.2.4 and Herwig 7.1.1.

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Ogul, Hasan, Kamuran Dilsiz, Emrah Tiras, Ping Tan, Yasar Onel e Jane Nachtman. "High Order QCD Predictions for Inclusive Production ofWBosons inppCollisions ats=13 TeV". Advances in High Energy Physics 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/7865689.

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Predictions of fiducial cross sections, differential cross sections, and lepton charge asymmetry are presented for the production ofW±bosons with leptonic decay up to next-to-next-to-leading order (NNLO) in perturbative QCD. Differential cross sections ofW±bosons andWboson lepton charge asymmetry are computed as a function of lepton pseudorapidity for a defined fiducial region inppcollisions ats=13 TeV. Numerical results of fiducialW±cross section predictions are presented with the latest modern PDF models at next-to-leading order (NLO) and NNLO. It is found that the CT14 and NNPDF 3.0 predictions with NNLO QCD corrections are about 4% higher than the NLO CT14 and NNPDF 3.0 predictions while MMHT 2014 predictions with NLO QCD corrections are smaller than its NNLO QCD predictions by approximately 6%. In addition, the NNLO QCD corrections reduce the scale variation uncertainty on the cross section by a factor of 3.5. The prediction of central values and considered uncertainties are obtained using FEWZ 3.1 program.

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KIDONAKIS, NIKOLAOS. "A UNIFIED APPROACH TO NNLO SOFT AND VIRTUAL CORRECTIONS IN ELECTROWEAK, HIGGS, QCD, AND SUSY PROCESSES". International Journal of Modern Physics A 19, n. 11 (30 aprile 2004): 1793–821. http://dx.doi.org/10.1142/s0217751x04018294.

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I present a unified approach to calculating the next-to-next-to-leading order (NNLO) soft and virtual QCD corrections to cross-sections for electroweak, Higgs, QCD, and SUSY processes. I derive master formulas that can be used for any of these processes in hadron–hadron and lepton–hadron collisions. The formulas are based on a unified threshold resummation formalism and can be applied to both total and differential cross-sections for processes with either simple or complex color flows and for various factorization schemes and kinematics. As a test of the formalism, I rederive known NNLO results for Drell–Yan and Higgs production, deep inelastic scattering, and W+γ production, and I obtain expressions for several two-loop anomalous dimensions and other quantities needed in next-to-next-to-leading-logarithm (NNLL) resummations. I also present new results for the production of supersymmetric charged Higgs bosons; massive electroweak vector bosons; photons; heavy quarks in lepton–hadron and hadron–hadron collisions and in flavor-changing neutral current processes; jets; and squarks and gluinos. The NNLO soft and virtual corrections are often dominant, especially near threshold, and they reduce the scale dependence of the cross-section. Thus, a unified approach to these corrections is important in the search for new physics at present and future colliders.

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Ocalan, Kadir. "Accurate prediction of the Drell-Yan ϕη* distribution in wide dilepton mass and rapidity ranges in pp collisions through NNLO+N³LL". Physica Scripta 96, n. 12 (1 dicembre 2021): 125323. http://dx.doi.org/10.1088/1402-4896/ac3e19.

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Abstract This paper presents high-accuracy predictions for the differential cross ss as a function of the key observable ϕ η * of the neutral-current Drell-Yan (DY) dilepton production in proton-proton (pp) collisions. The differential distributions for the ϕ η * are presented by using the state-of-the-art predictions from the combined calculations of fixed-order perturbative quantum chromodynamics (QCD) corrections at next-to-next-to-leading order (NNLO) accuracy and resummation of large logarithmic terms at next-to-next-to-leading logarithmic (NNLL) and next-to-NNLL (N3LL) accuracies, i.e., NNLO+NNLL and NNLO+N3LL, respectively. The predicted distributions are reported for a thorough set of the DY dilepton invariant mass m ll ranges, spanning a wide kinematic region of 50 < m ll < 1000 GeV both near and away from the Z-boson mass peak, and rapidity y ll ranges in the central detector acceptance region of ∣y ll ∣ < 2.4. The differential ϕ η * distributions in the wide m ll and y ll ranges offer stringent tests to assess the reliability of the predictions, where the m ll and y ll are closely correlated with the parton distribution functions (PDFs) of the incoming partons. The matched predictions through NNLO+N3LL are observed to provide good description of the 13 TeV pp collision data for the ϕ η * (including the dilepton transverse momentum p T ll as well) distributions in almost the entire m ll and y ll ranges, apart from the intermediate- to high- ϕ η * region in the lowest mass range 50–76 GeV which is assessed to constitute a challenge for the presented predictions. The predictions at NNLO+N3LL are also reported at 14 TeV for the upcoming high-luminosity running era of the Large Hadron Collider (LHC), in which increasing amount of data is expected to require more accurate and precise theoretical description. The most recent PDF models MSHT20 and CT18, in addition to the NNPDF3.1, are tested for the first time for the matched predictions of the ϕ η * distribution. The differential distributions by the combined predictions through NNLO QCD+NLO EW are finally provided to enable assessment of the impact of the EW corrections for the ϕ η * .

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8

KIDONAKIS, NIKOLAOS, e RAMONA VOGT. "THEORETICAL STATUS OF THE TOP QUARK CROSS SECTION". International Journal of Modern Physics A 20, n. 14 (10 giugno 2005): 3171–73. http://dx.doi.org/10.1142/s0217751x05026054.

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We discuss the most recent calculations of the top quark total cross section and transverse momentum distributions at the Tevatron and the LHC. These calculations include the soft-gluon corrections at next-to-next-to-leading order (NNLO). The soft NNLO corrections stabilize the scale dependence of the cross section.

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9

FERROGLIA, ANDREA. "QCD CORRECTIONS TO THE RADIATIVE DECAY $\bar{B}\to X_s\gamma$". Modern Physics Letters A 23, n. 37 (7 dicembre 2008): 3123–40. http://dx.doi.org/10.1142/s021773230802879x.

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In this short review, the calculation of the next-to-next-to-leading order QCD corrections to the inclusive radiative decay [Formula: see text] is described. We summarize the salient features of the calculational framework adopted, discuss the results obtained in the last few years, and indicate the technical tools that made the NNLO calculations possible. We conclude by comparing the current NNLO theoretical estimate for the branching ratio with the experimental measurement and by briefly discussing the size and origin of the residual theoretical uncertainty.

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10

Ogul, Hasan, e Kamuran Dilsiz. "Cross Section Prediction for Inclusive Production of Z Boson in pp Collisions at s=14 TeV: A Study of Systematic Uncertainty due to Scale Dependence". Advances in High Energy Physics 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/8262018.

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Prediction of Z→l+l- production cross section (where l±=e±,μ±) in proton-proton collisions at s=14 TeV is estimated up to next-to-next-to-leading order (NNLO) in perturbative QCD including next-to-leading order (NLO) electroweak (EW) corrections. The total inclusive Z boson production cross section times leptonic branching ratio, within the invariant mass window 66<mll<116 GeV, is predicted using NNLO HERAPDF2.0 at NNLO QCD and NLO EW as σZTot=2111.69-26.92+26.31 (PDF) ±11 (αs) ±17 (scale) -30.98+57.41 (parameterization and model). Theoretical prediction of the fiducial cross section is further computed with the latest modern PDF models (CT14, MMHT2014, NNPDF3.0, HERAPDF2.0, and ABM12) at NNLO for QCD and NLO for EW. The central values of the predictions are based on DYNNLO 1.5 program and the uncertainties are extracted using FEWZ 3.1 program. In addition, the cross section is also calculated as functions of μR and μF scales. The choice of μR and μF for scale variation uncertainty is further discussed in detail.

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11

TIMÓTEO, VARESE S., TOBIAS FREDERICO, LAURO TOMIO e ANTONIO DELFINO. "RENOMALIZATION OF THE NN INTERACTION AT NNLO: UNCOUPLED PERIPHERAL WAVES". International Journal of Modern Physics E 16, n. 09 (ottobre 2007): 2822–25. http://dx.doi.org/10.1142/s0218301307008495.

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12

Ronca, Jonathan. "NNLO QED contribution to the µe → µe elastic scattering". EPJ Web of Conferences 234 (2020): 01015. http://dx.doi.org/10.1051/epjconf/202023401015.

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We present the current status of the Next-to-Next-to-Leading Order QED contribution to the µescattering. Particular focus is given to the techniques involved to tackle the virtual amplitude and their automatic implementation. Renormalization of the amplitude will be also discuss in details.

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13

Baishya, R., e J. K. Sarma. "Solution of singlet and non-singlet unpolarized DGLAP evolution equations in next-to-next-to-leading order (NNLO) by method of characteristics". Indian Journal of Physics 86, n. 2 (febbraio 2012): 145–50. http://dx.doi.org/10.1007/s12648-012-0022-5.

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14

WANG, JIAN, GUOMING CHEN e WEIMIN WU. "THE IMPACT OF LO, NLO AND NNLO FOR THE HIGGS SEARCHING AT $\sqrt{s} = 7$ TeV OF LHC". Modern Physics Letters A 25, n. 36 (30 novembre 2010): 3027–31. http://dx.doi.org/10.1142/s0217732310034146.

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Most of current Monte Carlo studies on the Higgs searching are based on LO, or NLO calculation. However, in recent years, the next-to-next-to-leading order (NNLO) corrections have been computed for some physics process, and found that the cross section increases the kinematics changes. As the results, the analysis results could be impacted by these high order QCD corrections. We use standard Monte Carlo generator for LO, as well as MC@NLO for NLO and ResBos for NNLO at 7 TeV of LHC to evaluate this impact for physics channel of the Higgs, mass at 165 GeV, to WW, then W decay to lepton and neutrino as the final states. We found the signal rate could be effected by ratio of 1:2.6:3.4 for LO, NLO and NNLO using the same standard H→WW→lνlν searching analysis process.6

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15

Boussaha, Bouzid, Farida Iddir e Lahouari Semlala. "Predictions for the Isolated Diphoton Production through NNLO in QCD and Comparison to the 8 TeV ATLAS Data". Advances in High Energy Physics 2018 (7 agosto 2018): 1–7. http://dx.doi.org/10.1155/2018/4174602.

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We present cross-section predictions for the isolated diphoton production in next-to-next-to-leading order (NNLO) QCD using the computational framework MATRIX. Both the integrated and the differential fiducial cross-sections are calculated. We found that the arbitrary setup of the isolation procedure introduces uncertainties with a size comparable to the estimation of the theoretical uncertainties obtained with the customary variation of the factorization and renormalization scales. This fact is taken into account in the final result.

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Dilsiz, Kamuran, e Emrah Tiras. "Inclusive W boson QCD predictions and lepton charge asymmetry in proton–proton collisions at = 14 TeV". Canadian Journal of Physics 96, n. 9 (settembre 2018): 1029–33. http://dx.doi.org/10.1139/cjp-2017-0635.

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Inclusive W ([Formula: see text]) boson QCD predictions and lepton charge asymmetry in proton–proton collisions at [Formula: see text] = 14 TeV is performed in this study. Total and fiducial cross section predictions are obtained up to next to next to leading order (NNLO) QCD corrections using Monte Carlo for FeMtobarn processes (MCFM) MC generator. To validate the predictions, a detailed comparison of NNLO QCD calculations with 8 TeV CMS results is performed. To discuss the advantage of the higher order QCD predictions on the scale uncertainty, a scale dependence study is presented based on the choice of renormalization (μR) and factorization (μF) scale variations. W boson – lepton charge asymmetry and differential cross section as a function of lepton pseudorapidity at [Formula: see text] = 14 TeV are further performed in 11 |η| regions.

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KREBS, H., E. EPELBAUM e ULF-G. MEIßNER. "CHIRAL EFFECTIVE POTENTIAL WITH DELTA DEGREES OF FREEDOM". International Journal of Modern Physics A 24, n. 02n03 (30 gennaio 2009): 511–14. http://dx.doi.org/10.1142/s0217751x09043961.

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Using chiral effective field theory (EFT) with explicit Δ degrees of freedom we calculated nuclear forces up to next-to-next-to-leading order (NNLO). We found much better convergence of the chiral expansion in all peripheral partial waves. We also observe strong cancellations between charge-symmetry-breaking (CSB) contributions due to nucleon- and Δ-mass splittings in the two-pion-exchange potentials. The CSB potentials appear to be weaker in the Δ-full theory.

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NEMATOLLAHI, H., M. M. YAZDANPANAH e A. MIRJALILI. "NNLO LONGITUDINAL PROTON STRUCTURE FUNCTION, BASED ON THE MODIFIED χQM". Modern Physics Letters A 27, n. 31 (4 ottobre 2012): 1250179. http://dx.doi.org/10.1142/s0217732312501799.

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We compute the longitudinal structure function of the proton (FL) at the next-to-next-to-leading order (NNLO) approximation. For this purpose, we should know the flavor-singlet, non-singlet and gluon distribution functions of the proton. We use the chiral quark model (χQM) to determine these distributions. Finally, we compare the results of FL with the recent ZEUZ and H1 experimental data and some fitting parametrizations. Our results are in good agreement with the data and the related fittings.

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Eskola, K. J., V. J. Kolhinen, P. V. Ruuskanen e R. L. Thews. "Effects of Shadowing on Drell–Yan Dilepton Production in High Energy Nuclear Collisions". International Journal of Modern Physics E 12, n. 02 (aprile 2003): 197–209. http://dx.doi.org/10.1142/s0218301303001260.

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We compute cross sections for the Drell–Yan process in nuclear collisions at next-to-leading order (NLO) in αs. The effects of shadowing on the normalization and on the mass and rapidity dependence of these cross sections are presented. An estimate of higher order corrections is obtained from next-to-next-to-leading order (NNLO) calculation of the rapidity-integrated mass distribution. Variations in these predictions resulting from choices of parton distributions sets are discussed. Numerical results for mass distributions at NLO are presented for RHIC and LHC energies, using appropriate rapidity intervals. The shadowing factors in the dilepton mass range 2 < M < 10 GeV are predicted to be substantial, typically 0.5 - 0.7 at LHC, 0.7 - 0.9 at RHIC, and approximately independent of the choice of parton distribution sets and the order of calculation.

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20

Ocalan, Kadir. "EW radiative corrections to theory predictions of charge asymmetry for W-boson hadroproduction". Physica Scripta 97, n. 7 (23 giugno 2022): 075305. http://dx.doi.org/10.1088/1402-4896/ac789a.

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Abstract The higher-order predictions of the lepton charge asymmetry A η l (the W-boson charge asymmetry A y W ) for the leptonic final state of the W-boson hadroproduction in proton–proton (pp) collisions are presented. The predictions from the state-of-the-art computations are reported for achieving adequate description of the A η l by including next-to-leading order (NLO) electroweak (EW) radiative corrections in combination with next-to-NLO (NNLO) quantum chromodynamics (QCD) radiative corrections. The combined predictions NNLO QCD+NLO EW and NNLO QCD × NLO EW, based on standard additive and factorised combination prescriptions in turn, are provided in the fiducial phase space of the pseudorapidity of the decay lepton (of the rapidity of the W-boson), comprising both central and forward detector acceptance regions as η l ≤ 4.5 (y W ≤ 4.5). The inclusion of the NLO EW effects for the A η l ( A y W ) constitutes additional input for the relative u- and d-quark densities in the proton, which is also of high importance in the domain of the high-precision studies. The predicted A η l distributions are compared with the actual measurements by CERN Large Hadron Collider (LHC) experiments at 8 TeV pp collisions energies. The combined predictions for the A η l ( A y W ) distributions are also provided in comparisons with the NNLO QCD predictions at both 13 TeV and 14 TeV energies. The impact of the NLO EW corrections for the A η l ( A y W ) distributions is extensively assessed by means of relative correction factor analysis with respect to the NNLO QCD predictions, in addition to a detailed K-factor analysis with respect to the leading order (LO) accuracy. The predicted results show that the NLO EW effects have larger impact in the forward η l region of the A η l contrary to the central η l region, and is sizable in some of the y W ranges of the A y W . The paper suggests inclusion of the presented EW corrections at NLO to have explicit accounting for the EW effects for the A η l ( A y W ) in phenomenological studies.

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Vafaee, A., e K. Javidan. "NNLO compatibility between pQCD theory and phenomenology in determination of the b-quark pole and MS¯ running masses". Modern Physics Letters A 35, n. 30 (6 agosto 2020): 2050253. http://dx.doi.org/10.1142/s0217732320502533.

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This contribution attempts to determine the [Formula: see text]-quark pole mass [Formula: see text] and [Formula: see text] running mass [Formula: see text] with two different approaches at the next-to-next-to-leading order (NNLO) corrections. At the first approach, we derive a relation between the [Formula: see text]-quark pole mass [Formula: see text] and its [Formula: see text] running mass [Formula: see text] at the NNLO corrections based on the perturbative Quantum Chromo Dynamics (pQCD) predictions. At the second approach, we extract numerical values of the [Formula: see text]-quark pole and [Formula: see text] running masses based on the NNLO phenomenology of H1 and ZEUS Collaborations combined beauty vertex production experimental data. Then we discuss about the compatibility between the pQCD theory results and phenomenology approach in determination of the [Formula: see text]-quark pole and [Formula: see text] running masses at the NNLO corrections. Also, we investigate the role and influence of the [Formula: see text]-quark mass as an extra degree of freedom added to the input parameters of the Standard Model Lagrangian, on the improvement of the uncertainty band of the proton parton distribution functions (PDFs) and particularly on the gluon distribution.

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Chekelian, Vladimir. "Determination of αs in NNLO QCD using H1 jet cross section measurements". EPJ Web of Conferences 206 (2019): 01002. http://dx.doi.org/10.1051/epjconf/201920601002.

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Measurements of jet cross sections in neutral current deep-inelastic scattering (NC DIS) using data taken with the H1 detector at HERA are accomplished by the precision measurement of double-diﬀerential inclusive jet, dijet and trijet cross sections at low photon virtualities 5.5 < Q2 < 80 GeV2, and by extending previous inclusive jet measurements in the range 150 < Q2 < 15000 GeV2 to low transverse jet momenta 5 < PT < 7 GeV. The strong coupling constant at the Z-boson mass, αs(mZ), is determined in next-to-next-to-leading order (NNLO) QCD using H1 inclusive jet and dijet cross section measurements. Complementary, αs(mZ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The running of the strong coupling is tested at diﬀerent values of the renormalisation scale and the results are found to be in agreement with the QCD expectations.

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Mondini, Roberto, e Ciaran Williams. "Bottom-induced contributions to Higgs plus jet at next-to-next-to-leading order". Journal of High Energy Physics 2021, n. 5 (maggio 2021). http://dx.doi.org/10.1007/jhep05(2021)045.

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Abstract We present a next-to-next-to-leading order (NNLO) QCD calculation of the bottom-induced contributions to the production of a Higgs boson plus a jet, i.e. the process pp → H + j to $$ \mathcal{O}\left({y}_b^2{\alpha}_s^3\right) $$ O y b 2 α s 3 . We work in the five-flavor scheme (5FS) in which the bottom quark mass is retained only in the coupling to the Higgs boson. Our calculation uses N-jettiness slicing to regulate infrared divergences, allowing for fully-differential predictions for collider observables. After extensively validating the methodology, we present results for the 13 TeV LHC. Our NNLO predictions show a marked improvement in the overall renormalization and factorization scale dependence, the latter of which proves to be particularly troublesome for 5FS calculations at lower orders. In addition, using the same methodology we present a NNLO computation of $$ b\overline{b} $$ b b ¯ → H. Our results are implemented into MCFM.

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Huang, Xu-Dong, Bin Gong e Jian-Xiong Wang. "Next-to-next-to-leading-order QCD corrections to J/ψ plus ηc production at the B factories". Journal of High Energy Physics 2023, n. 2 (6 febbraio 2023). http://dx.doi.org/10.1007/jhep02(2023)049.

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Abstract In this paper, we calculate the next-to-next-to-leading-order (NNLO) QCD corrections to e+e− → J/ψ + ηc at the B factories. After including the NNLO corrections, the cross section of e+e−→ J/ψ +ηc is enhanced by about 17%, and the perturbative series of the prediction shows the convergent behavior. It is also found that the contributions from bottom quark starts at the $$ {\alpha}_s^3 $$ α s 3 -order, which is about 2.4% of the total prediction. The renormalization scale μR dependence of the cross section is reduced at the NNLO level, but the prediction is sensitive to the charm quark mass mc. By considering the uncertainties caused by renormalization scale μR, charm quark mass mc and the NRQCD factorization scale μΛ, our prediction shows agreement with the BABAR and BELLE measurements within errors.

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Meng, Rui-Qing, Sheng-Quan Wang, Ting Sun, Chao-Qin Luo, Jian-Ming Shen e Xing-Gang Wu. "QCD improved top-quark decay at next-to-next-to-leading order". European Physical Journal C 83, n. 1 (23 gennaio 2023). http://dx.doi.org/10.1140/epjc/s10052-023-11224-4.

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AbstractWe analyse the top-quark decay at the next-to-next-to-leading order (NNLO) in QCD by using the Principle of Maximum Conformality (PMC) which provides a systematic way to eliminate renormalization scheme and scale ambiguities in perturbative QCD predictions. The PMC renormalization scales of the coupling constant $$\alpha _s$$ α s are determined by absorbing the non-conformal $$\beta $$ β terms that govern the behavior of the running coupling by using the Renormalization Group Equation (RGE). We obtain the PMC scale $$Q_\star =15.5$$ Q ⋆ = 15.5 GeV for the top-quark decay, which is an order of magnitude smaller than the conventional choice $$\mu _r=m_t$$ μ r = m t , reflecting the small virtuality of the QCD dynamics of the top-quark decay process. Moreover, due to the non-conformal $$\beta $$ β terms disappear in the pQCD series, there is no renormalon divergence and the NLO QCD correction term is greatly increased while the NNLO QCD correction term is suppressed compared to the conventional results obtained at $$\mu _r=m_t$$ μ r = m t . By further including the next-to-leading (NLO) electroweak corrections, the finite W boson width and the finite bottom quark mass, we obtain the top-quark total decay width $$\Gamma ^{\textrm{tot}}_t=1.3112^{+0.0190}_{-0.0189}$$ Γ t tot = 1 . 3112 - 0.0189 + 0.0190 GeV, where the error is the squared averages of the top-quark mass $$\Delta m_t=\pm 0.7$$ Δ m t = ± 0.7 GeV, the coupling constant $$\Delta \alpha _s(M_Z)=\pm 0.0009$$ Δ α s ( M Z ) = ± 0.0009 and the estimation of unknown higher-order terms using the PAA method with [N/M]=[1/1]. The PMC improved predictions for the top-quark decay are complementary to the previous PMC calculations for top-quark pair production and helpful for detailed studies of properties of the top-quark.

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Sang, Wen-Long, Feng Feng e Yu Jia. "Next-to-next-to-leading-order radiative corrections to e+e− → χcJ + γ at B factory". Journal of High Energy Physics 2020, n. 10 (ottobre 2020). http://dx.doi.org/10.1007/jhep10(2020)098.

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Abstract Within the nonrelativistic QCD (NRQCD) factorization framework, we have computed the $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections to the exclusive production of P-wave spin-triplet charmonia χcJ (J = 0, 1, 2) accompanied with a hard photon at B factory. For the first time, we have explicitly verified the validity of NRQCD factorization for exclusive P-wave quarkonium production to two-loop order. Unlike the χcJ electromagnetic decays, the $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections are found to be smaller than the $$ \mathcal{O} $$ O (αs) corrections in all three channels e+e− → χc0,1,2 + γ. In particular, the $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections appear moderate for χc1 + γ case, and marginal for χc0 + γ. Moreover, the predictions in next-to-next-to-leading order (NNLO) accuracy for the production rates of χc0,1 + γ are insensitive to the renormalization and factorization scales. All these features may indicate that perturbative expansion in these two channels exhibits a decent convergence behavior. By contrast, both the $$ \mathcal{O} $$ O (αs) and $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 corrections to the χc2 + γ production rate are sizable, which reduce the Born order cross section by one order of magnitude after including the NNLO perturbative corrections. Taking the values of the long-distance NRQCD matrix elements from nonrelativistic potential model, our prediction to χc1 + γ production rate is consistent with the recent Belle measurement. The NNLO predictions to the χc0,2 + γ production rates are much smaller than that for χc1 + γ, which seems to naturally explain why the e+e− → χc0,2 + γ channels have escaped experimental detection to date.

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27

van Beekveld, Melissa, Eric Laenen, Jort Sinninghe Damsté e Leonardo Vernazza. "Next-to-leading power threshold corrections for finite order and resummed colour-singlet cross sections". Journal of High Energy Physics 2021, n. 5 (maggio 2021). http://dx.doi.org/10.1007/jhep05(2021)114.

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Abstract (sommario):

Abstract We study next-to-leading-power (NLP) threshold corrections in colour-singlet production processes, with particular emphasis on Drell-Yan (DY) and single-Higgs production. We assess the quality of the partonic and hadronic threshold expansions for each process up to NNLO. We determine numerically the NLP leading-logarithmic (LL) resummed contribution in addition to the leading-power next-to-next-to-leading logarithmic (LP NNLL) resummed DY and Higgs cross sections, matched to NNLO. We find that the inclusion of NLP logarithms is numerically more relevant than increasing the precision to N3LL at LP for these processes. We also perform an analytical and numerical comparison of LP NNLL + NLP LL resummation in soft-collinear effective theory and direct QCD, where we achieve excellent analytical and numerical agreement once the NLP LL terms are included in both formalisms. Our results underline the phenomenological importance of understanding the NLP structure of QCD cross sections.

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28

Zanoli, Silvia, Mauro Chiesa, Emanuele Re, Marius Wiesemann e Giulia Zanderighi. "Next-to-next-to-leading order event generation for VH production with H → $$ b\overline{b} $$ decay". Journal of High Energy Physics 2022, n. 7 (luglio 2022). http://dx.doi.org/10.1007/jhep07(2022)008.

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Abstract (sommario):

Abstract We consider the Higgsstrahlung process in hadronic collisions and present the computation of next-to-next-to-leading order predictions matched to parton showers for both production and H → $$ b\overline{b} $$ b b ¯ decay employing the MiNNLOPS method. We present predictions for ZH and W±H production including spin correlations and off-shell effects by calculating the full processes pp → ℓ+ℓ−H → ℓ+ℓ−$$ b\overline{b} $$ b b ¯ , pp → $$ {\nu}_{\ell }{\overline{\nu}}_{\ell }H $$ ν ℓ ν ¯ ℓ H → $$ {\nu}_{\ell }{\overline{\nu}}_{\ell }b\overline{b} $$ ν ℓ ν ¯ ℓ b b ¯ and pp → ℓ±νℓH → $$ {\ell}^{\pm }{\overline{\nu}}_{\ell }b\overline{b} $$ ℓ ± ν ¯ ℓ b b ¯ in the narrow-width approximation for the Higgs boson. For the W±H process, NNLO+PS accuracy in production and decay is achieved for the first time. Our calculations are validated against earlier simulations in the NNLOPS approach that includes NNLO corrections via multi-differential reweighting. The new MiNNLOPS generators for these processes, which evaluate NNLO corrections on-the-fly in the event generation, will supersede those earlier calculations. Our predictions are in good agreement with recent measurements of the Higgsstrahlung cross sections.

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29

Abt, I., R. Aggarwal, V. Andreev, M. Arratia, V. Aushev, A. Baghdasaryan, A. Baty et al. "Impact of jet-production data on the next-to-next-to-leading-order determination of HERAPDF2.0 parton distributions". European Physical Journal C 82, n. 3 (marzo 2022). http://dx.doi.org/10.1140/epjc/s10052-022-10083-9.

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Abstract (sommario):

AbstractThe HERAPDF2.0 ensemble of parton distribution functions (PDFs) was introduced in 2015. The final stage is presented, a next-to-next-to-leading-order (NNLO) analysis of the HERA data on inclusive deep inelastic ep scattering together with jet data as published by the H1 and ZEUS collaborations. A perturbative QCD fit, simultaneously of $$\alpha _s(M_Z^2)$$ α s ( M Z 2 ) and the PDFs, was performed with the result $$\alpha _s(M_Z^2)= 0.1156 \pm 0.0011~\mathrm{(exp)}~ ^{+0.0001}_{-0.0002}~ \mathrm{(model}$$ α s ( M Z 2 ) = 0.1156 ± 0.0011 ( exp ) - 0.0002 + 0.0001 ( model $$\mathrm{+ parameterisation)}~ \pm 0.0029~\mathrm{(scale)}$$ + parameterisation ) ± 0.0029 ( scale ) . The PDF sets of HERAPDF2.0Jets NNLO were determined with separate fits using two fixed values of $$\alpha _s(M_Z^2)$$ α s ( M Z 2 ) , $$\alpha _s(M_Z^2)=0.1155$$ α s ( M Z 2 ) = 0.1155 and 0.118, since the latter value was already chosen for the published HERAPDF2.0 NNLO analysis based on HERA inclusive DIS data only. The different sets of PDFs are presented, evaluated and compared. The consistency of the PDFs determined with and without the jet data demonstrates the consistency of HERA inclusive and jet-production cross-section data. The inclusion of the jet data reduced the uncertainty on the gluon PDF. Predictions based on the PDFs of HERAPDF2.0Jets NNLO give an excellent description of the jet-production data used as input.

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30

Ajjath, A. H., Pooja Mukherjee, V. Ravindran, Aparna Sankar e Surabhi Tiwari. "Next-to SV resummed Drell–Yan cross section beyond leading-logarithm". European Physical Journal C 82, n. 3 (marzo 2022). http://dx.doi.org/10.1140/epjc/s10052-022-10174-7.

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Abstract (sommario):

AbstractWe present the resummed predictions for inclusive cross section for Drell–Yan (DY) production up to next-to-next-to leading logarithmic ($${{\overline{\mathrm{NNLL}}}}$$ NNLL ¯ ) accuracy taking into account both soft virtual (SV) and next-to SV (NSV) threshold logarithms. We restrict ourselves to resummed contributions only from quark anti-quark ($$q {{\bar{q}}}$$ q q ¯ ) initiated channels. The resummation is performed in Mellin-N-space. We derive the N-dependent coefficients and the N-independent constants to desired accuracy for our study. The resummed results are matched through the minimal prescription procedure with the fixed-order results. We find that the resummation, taking into account the NSV terms, appreciably increases the cross section while decreasing the sensitivity to renormalisation scale. We observe that, at 13 TeV LHC energies, the SV + NSV resummation at $${\overline{\mathrm{NLL}}} ({{\overline{\mathrm{NNLL}}}})$$ NLL ¯ ( NNLL ¯ ) gives about 8% (2%) corrections respectively to the NLO (NNLO) results for the considered Q range: 150–3500 GeV. In addition, the absence of quark gluon initiated contributions to NSV part in the resummed terms leaves large factorisation scale dependence indicating their importance at NSV level. We also study the numerical impact of N-independent constants and explore the ambiguity involved in exponentiating them. Finally we present our predictions for the neutral Drell–Yan process at various center of mass of energies.

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31

Boroun, G. R., e B. Rezaei. "Decoupling of the DGLAP evolution equations at next-to-next-to-leading order (NNLO) at low-x". European Physical Journal C 73, n. 5 (maggio 2013). http://dx.doi.org/10.1140/epjc/s10052-013-2412-z.

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32

Alvarez, Manuel, Josu Cantero, Michal Czakon, Javier Llorente, Alexander Mitov e Rene Poncelet. "NNLO QCD corrections to event shapes at the LHC". Journal of High Energy Physics 2023, n. 3 (17 marzo 2023). http://dx.doi.org/10.1007/jhep03(2023)129.

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Abstract (sommario):

Abstract In this work we perform the first ever calculation of jet event shapes at hadron colliders at next-to-next-to leading order (NNLO) in QCD. The inclusion of higher order corrections removes the shape difference observed between data and next-to-leading order predictions. The theory uncertainty at NNLO is comparable to, or slightly larger than, existing measurements. Except for narrow kinematical ranges where all-order resummation becomes important, the NNLO predictions for the event shapes considered in the present work are reliable. As a prime application of the results derived in this work we provide a detailed investigation of the prospects for the precision determination of the strong coupling constant and its running through TeV scales from LHC data.

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33

Ma, Liang, Yi Pang e H. Lü. "Higher derivative contributions to black hole thermodynamics at NNLO". Journal of High Energy Physics 2023, n. 6 (15 giugno 2023). http://dx.doi.org/10.1007/jhep06(2023)087.

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Abstract (sommario):

Abstract In an effective theory of gravity, thermodynamic quantities of black holes receive corrections from the infinite series of higher derivative terms. At the next to leading order, these can be obtained by using only the leading order solution. In this paper, we push forward this property to the next to next to leading order. We propose a formula which yields the Euclidean action of asymptotically flat black holes at the next to next to leading order using only the solution up to and including the next to leading order. Other conserved quantities are derived from the Euclidean action via standard thermodynamic relation. We verify our formula in examples of D-dimensional pure gravity and Einstein-Maxwell theory extended by 4- and 6-derivative terms. Based on our formula, we also prove that for asymptotically flat black holes, the physical quantities are invariant under field redefinitions.

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34

Andreev, V., A. Baghdasaryan, K. Begzsuren, A. Belousov, V. Bertone, A. Bolz, V. Boudry et al. "Erratum to: Determination of the strong coupling constant $${{\varvec{\alpha _{\mathrm{s}} (m_{\mathrm{Z}})}}}$$ in next-to-next-to-leading order QCD using H1 jet cross section measurements". European Physical Journal C 81, n. 8 (agosto 2021). http://dx.doi.org/10.1140/epjc/s10052-021-09394-0.

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Abstract (sommario):

AbstractThe determination of the strong coupling constant $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}})$$ α s ( m Z ) from H1 inclusive and dijet cross section data [1] exploits perturbative QCD predictions in next-to-next-to-leading order (NNLO) [2–4]. An implementation error in the NNLO predictions was found [4] which changes the numerical values of the predictions and the resulting values of the fits. Using the corrected NNLO predictions together with inclusive jet and dijet data, the strong coupling constant is determined to be $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}}) =0.1166\,(19)_{\mathrm{exp}}\,(24)_{\mathrm{th}}$$ α s ( m Z ) = 0.1166 ( 19 ) exp ( 24 ) th . Complementarily, $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}})$$ α s ( m Z ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value $$\alpha _{\mathrm{s}} (m_{\mathrm{Z}}) =0.1147\,(25)_{\mathrm{tot}}$$ α s ( m Z ) = 0.1147 ( 25 ) tot obtained is consistent with the determination from jet data alone. Corrected figures and numerical results are provided and the discussion is adapted accordingly.

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35

Andreev, V., A. Baghdasaryan, K. Begzsuren, A. Belousov, A. Bolz, V. Boudry, G. Brandt et al. "Erratum to: Measurement of jet production cross sections in deep-inelastic ep scattering at HERA". European Physical Journal C 81, n. 8 (agosto 2021). http://dx.doi.org/10.1140/epjc/s10052-021-09370-8.

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Abstract (sommario):

AbstractThe measurement of the jet cross sections by the H1 collaboration had been compared to various predictions including the next-to-next-to-leading order (NNLO) QCD calculations which are corrected in this erratum for an implementation error in one of the components of the NNLO calculations. The jet data and the other predictions remain unchanged. Eight figures, one table and conclusions are adapted accordingly, exhibiting even better agreement between the corrected NNLO predictions and the jet data.

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36

Gehrmann, T., A. Huss, J. Mo e J. Niehues. "Second-order QCD corrections to event shape distributions in deep inelastic scattering". European Physical Journal C 79, n. 12 (dicembre 2019). http://dx.doi.org/10.1140/epjc/s10052-019-7528-3.

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Abstract (sommario):

AbstractWe compute the next-to-next-to-leading order (NNLO) QCD corrections to event shape distributions and their mean values in deep inelastic lepton–nucleon scattering. The magnitude and shape of the corrections varies considerably between different variables. The corrections reduce the renormalization and factorization scale uncertainty of the predictions. Using a dispersive model to describe non-perturbative power corrections, we compare the NNLO QCD predictions with data from the H1 and ZEUS experiments. The newly derived corrections improve the theory description of the distributions and of their mean values.

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37

Monni, Pier Francesco, Emanuele Re e Marius Wiesemann. "MiNNLO$$_{\text {PS}}$$: optimizing $$2\rightarrow 1$$ hadronic processes". European Physical Journal C 80, n. 11 (novembre 2020). http://dx.doi.org/10.1140/epjc/s10052-020-08658-5.

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Abstract (sommario):

AbstractWe consider the MiNNLO$$_\mathrm{PS}$$ PS method to consistently combine next-to-next-to-leading order (NNLO) QCD calculations with parton-shower simulations. We identify the main sources of differences between MiNNLO$$_\mathrm{PS}$$ PS and fixed-order NNLO predictions for inclusive observables due to corrections beyond NNLO accuracy and present simple prescriptions to either reduce or remove them. Refined predictions are presented for Higgs, charged- and neutral-current Drell Yan production. The agreement with fixed-order NNLO calculations is considerably improved for inclusive observables and scale uncertainties are reduced. The codes are released within the POWHEG-BOX.

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38

Lansberg, Jean-Philippe, Maxim Nefedov e Melih A. Ozcelik. "Matching next-to-leading-order and high-energy-resummed calculations of heavy-quarkonium-hadroproduction cross sections". Journal of High Energy Physics 2022, n. 5 (maggio 2022). http://dx.doi.org/10.1007/jhep05(2022)083.

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Abstract (sommario):

Abstract The energy dependence of the total hadroproduction cross section of pseudoscalar quarkonia is computed via matching Next-to-Leading Order (NLO) Collinear-Factorisation (CF) results with resummed higher-order corrections, proportional to $$ {\alpha}_s^n{\ln}^{n-1} $$ α s n ln n − 1 (1/z), to the CF hard-scattering coefficient, where z = M2/$$ \hat{s} $$ s ̂ with M and $$ \hat{s} $$ s ̂ being the quarkonium mass and the partonic center-of-mass energy squared. The resummation is performed using High-Energy Factorisation (HEF) in the Doubly-Logarithmic (DL) approximation, which is a subset of the leading logarithmic ln(1/z) approximation. Doing so, one remains strictly consistent with the NLO and NNLO DGLAP evolution of the PDFs. By improving the treatment of the small-z asymptotics of the CF coefficient function, the resummation cures the unphysical results of the NLO CF calculation. The matching is directly performed in the z-space and, for the first time, by using the Inverse-Error Weighting (InEW) matching procedure. As a by-product of the calculation, the NNLO term of the CF hard-scattering coefficient proportional to $$ {\alpha}_s^2 $$ α s 2 ln(1/z) is predicted from HEF.

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39

Broggio, Alessandro, Sebastian Jaskiewicz e Leonardo Vernazza. "Next-to-leading power two-loop soft functions for the Drell-Yan process at threshold". Journal of High Energy Physics 2021, n. 10 (ottobre 2021). http://dx.doi.org/10.1007/jhep10(2021)061.

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Abstract (sommario):

Abstract We calculate the generalized soft functions at $$ \mathcal{O} $$ O ($$ {\alpha}_s^2 $$ α s 2 ) at next-to-leading power accuracy for the Drell-Yan process at threshold. The operator definitions of these objects contain explicit insertions of soft gauge and matter fields, giving rise to a dependence on additional convolution variables with respect to the leading power result. These soft functions constitute the last missing ingredient for the validation of the bare factorization theorem to NNLO accuracy. We carry out the calculations by reducing the soft squared amplitudes into a set of canonical master integrals and we employ the method of differential equations to evaluate them. We retain the exact d-dimensional dependence of the convolution variables at the integration boundaries in order to regulate the fixed-order convolution integrals. After combining the soft functions with the relevant collinear functions, we perform checks of the results at the cross-section level against the literature and expansion-by-regions calculations, at NNLO and partly at N3LO, finding agreement.

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40

Lombardi, Daniele, Marius Wiesemann e Giulia Zanderighi. "Advancing MıNNLOPS to diboson processes: Zγ production at NNLO+PS". Journal of High Energy Physics 2021, n. 6 (giugno 2021). http://dx.doi.org/10.1007/jhep06(2021)095.

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Abstract (sommario):

Abstract We consider Zγ production in hadronic collisions and present the first computation of next-to-next-to-leading order accurate predictions consistently matched to parton showers (NNLO+PS). Spin correlations, interferences and off-shell effects are included by calculating the full process pp → ℓ+ℓ−γ. We extend the recently developed MiNNLOPS method to genuine 2 → 2 hard scattering processes at the LHC, which paves the way for NNLO+PS simulations of all diboson processes. This is the first 2 → 2 NNLO+PS calculation that does not require an a-posteriori multi-differential reweighting. We find that both NNLO corrections and matching to parton showers are crucial for an accurate simulation of the Zγ process. Our predictions are in very good agreement with recent ATLAS data.

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41

Kollatzsch, Sophie, e Yannick Ulrich. "Lepton pair production at NNLO in QED with EW effects". SciPost Physics 15, n. 3 (20 settembre 2023). http://dx.doi.org/10.21468/scipostphys.15.3.104.

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Abstract (sommario):

We present a fully differential calculation of lepton pair production, taking into account the dominant next-to-next-to-leading order QED corrections as well as next-to-leading order electroweak and polarisation effects. We include all lepton masses, hard photon emission, as well as non-perturbative hadronic corrections. The corresponding matrix elements are implemented in the Monte Carlo framework McMule. In order to obtain a numerically stable implementation, we extend next-to-soft stabilisation, a universal technique based on a next-to-leading-power expansion, to calculations with polarised leptons. As an example, we show results tailored to the Belle II detector with the current setup as well as a potential future configuration that includes polarised beams.

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42

Das, Goutam, M. C. Kumar e Kajal Samanta. "Precision QCD phenomenology of exotic spin-2 search at the LHC". Journal of High Energy Physics 2021, n. 4 (aprile 2021). http://dx.doi.org/10.1007/jhep04(2021)111.

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Abstract (sommario):

Abstract The complete next-to-next-to leading order (NNLO) QCD correction matched with next-to-next-to leading logarithm (NNLL) has been studied for Drell-Yan production via spin-2 particle at the Large hadron collider (LHC). We consider generic spin-2 particle which couples differently to quarks and gluons (non-universal scenario). The threshold enhanced analytical coefficient has been obtained up to third order using the universal soft function and the process dependent form factors at the same order. We performed a detailed phenomenological analysis and gave a prediction for the 13 TeV LHC for the search of such BSM signature. We found that the resummed result gives sizeable corrections over a wide range of invariant mass of the lepton pair. The scale variation also stabilizes at this order and reduces to 4%. As a by-product, we also provide ingredients for third-order soft-virtual (SV) prediction as well as resummation and study the impact on LHC searches.

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43

Bell, Guido, Kevin Brune, Goutam Das e Marcel Wald. "The NNLO quark beam function for jet-veto resummation". Journal of High Energy Physics 2023, n. 1 (16 gennaio 2023). http://dx.doi.org/10.1007/jhep01(2023)083.

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Abstract (sommario):

Abstract We consider the quark beam function that describes collinear initial-state radiation that is constrained by a veto on reconstructed jets. As the veto is imposed on the transverse momenta of the jets, the beam function is subject to rapidity divergences, and we use the collinear-anomaly framework to extract the perturbative matching kernels to next-to-next-to-leading order (NNLO) in the strong-coupling expansion. Our calculation is based on a novel framework that automates the computation of beam functions in Mellin space and it provides the ingredients to extend jet-veto resummations for quark-initiated processes to NNLL′ accuracy.

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44

Gehrmann, Thomas, e Robin Schürmann. "NNLO photon fragmentation within antenna subtraction". SciPost Physics Proceedings, n. 7 (22 giugno 2022). http://dx.doi.org/10.21468/scipostphysproc.7.042.

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Abstract (sommario):

We report on our recent progress towards including the photon fragmentation contribution in next-to-next-to-leading order (NNLO) QCD predictions for photon production cross sections. This extension to previous NNLO calculations requires the identification of the photon in singular parton-photon collinear limits. We discuss how these limits can be subtracted within antenna subtraction using fragmentation antenna functions and we outline their integration.

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45

Alekhin, S., A. Kardos, S. Moch e Z. Trócsányi. "Precision studies for Drell–Yan processes at NNLO". European Physical Journal C 81, n. 7 (luglio 2021). http://dx.doi.org/10.1140/epjc/s10052-021-09361-9.

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Abstract (sommario):

AbstractWe present a detailed comparison of the fixed-order predictions computed by four publicly available computer codes for Drell–Yan processes at the LHC and Tevatron colliders. We point out that while there is agreement among the predictions at the next-to-leading order accuracy, the predictions at the next-to-next-to-leading order (NNLO) differ, whose extent depends on the observable. The sizes of the differences in general are at least similar, sometimes larger than the sizes of the NNLO corrections themselves. We demonstrate that the neglected power corrections by the codes that use global slicing methods for the regularization of double real emissions can be the source of the differences. Depending on the fiducial cuts, those power corrections become linear, hence enhanced as compared to quadratic ones that are considered standard.

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46

Braun-White, Oscar, Nigel Glover e Christian T. Preuss. "A general algorithm to build real-radiation antenna functions for higher-order calculations". Journal of High Energy Physics 2023, n. 6 (13 giugno 2023). http://dx.doi.org/10.1007/jhep06(2023)065.

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Abstract (sommario):

Abstract The antenna subtraction method has been successfully applied to a wide range of processes relevant for the Large Hadron Collider at next-to-next-to-leading order in αs (NNLO). We propose an algorithm for building antenna functions for any number of real emissions from an identified pair of hard radiator partons directly from a specified list of unresolved limits. We use the algorithm to explicitly build all single- and double-real QCD antenna functions and compare them to the previous antenna functions, which were extracted from matrix elements. The improved antenna functions should be more easily applicable to NNLO subtraction terms. Finally, we match the integration of the antenna functions over the final-final unresolved phase space to the previous incarnation, serving as an independent check on our results.

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47

Catani, Stefano, Ignacio Fabre, Massimiliano Grazzini e Stefan Kallweit. "$${t {{\bar{t}}}H}$$ production at NNLO: the flavour off-diagonal channels". European Physical Journal C 81, n. 6 (giugno 2021). http://dx.doi.org/10.1140/epjc/s10052-021-09247-w.

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Abstract (sommario):

AbstractWe consider QCD radiative corrections to the associated production of a heavy-quark pair ($$Q{{\bar{Q}}}$$ Q Q ¯ ) with a generic colourless system F at hadron colliders. We discuss the resummation formalism for the production of the $$Q{{\bar{Q}}}F$$ Q Q ¯ F system at small values of its total transverse momentum $$q_T$$ q T . We present the results of the corresponding resummation coefficients at next-to-leading and, partly, next-to-next-to-leading order. The perturbative expansion of the resummation formula leads to the explicit ingredients that can be used to apply the $$q_T$$ q T subtraction formalism to fixed-order calculations for this class of processes. We use the $$q_T$$ q T subtraction formalism to perform a fully differential perturbative computation for the production of a top-antitop quark pair and a Higgs boson. At next-to-leading order we compare our results with those obtained with established subtraction methods and we find complete agreement. We present, for the first time, the results for the flavour off-diagonal partonic channels at the next-to-next-to-leading order.

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48

Alioli, Simone, Georgios Billis, Alessandro Broggio, Alessandro Gavardi, Stefan Kallweit, Matthew A. Lim, Giulia Marinelli, Riccardo Nagar e Davide Napoletano. "Double Higgs production at NNLO interfaced to parton showers in GENEVA". Journal of High Energy Physics 2023, n. 6 (29 giugno 2023). http://dx.doi.org/10.1007/jhep06(2023)205.

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Abstract (sommario):

Abstract In this work, we study the production of Higgs boson pairs at next-to-next-to-leading order in QCD matched to parton showers, using the Geneva framework and working in the heavy-top-limit approximation. This includes the resummation of large logarithms of the zero-jettiness $$ \mathcal{T} $$ T 0 up to the next-to-next-to-next-to-leading-log accuracy. This process features an extremely large momentum transfer, which makes its study particularly relevant for matching schemes such as that employed in Geneva, where the resummation of a variable different from that used in the ordering of the parton shower is used. To further study this effect, we extend the original shower interface designed for Pythia8 to include other parton showers, such as Dire and Sherpa.

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49

Hu, YaLu, ChuanLe Sun, XiaoMin Shen e Jun Gao. "Hadronic decays of Higgs boson at NNLO matched with parton shower". Journal of High Energy Physics 2021, n. 8 (agosto 2021). http://dx.doi.org/10.1007/jhep08(2021)122.

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Abstract (sommario):

Abstract We present predictions for hadronic decays of the Higgs boson at next-to-next-to-leading order (NNLO) in QCD matched with parton shower based on the POWHEG framework. Those include decays into bottom quarks with full bottom-quark mass dependence, light quarks, and gluons in the heavy top quark effective theory. Our calculations describe exclusive decays of the Higgs boson with leading logarithmic accuracy in the Sudakov region and next-to-leading order (NLO) accuracy matched with parton shower in the three-jet region, with normalizations fixed to the partial width at NNLO. We estimated remaining perturbative uncertainties taking typical event shape variables as an example and demonstrated the need of future improvements on both parton shower and matrix element calculations. The calculations can be used immediately in evaluations of the physics performances of detector designs for future Higgs factories.

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50

Catani, Stefano, Simone Devoto, Massimiliano Grazzini e Javier Mazzitelli. "Soft-parton contributions to heavy-quark production at low transverse momentum". Journal of High Energy Physics 2023, n. 4 (28 aprile 2023). http://dx.doi.org/10.1007/jhep04(2023)144.

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Abstract (sommario):

Abstract We consider QCD radiative corrections to the production of a heavy-quark pair in hadronic collisions. We present the computation of the soft-parton contributions at low transverse momentum of the heavy-quark pair up to second order in the QCD coupling αS. These results complete the evaluation at the next-to-next-to-leading order (NNLO) of the transverse-momentum resummation formula for this process. Moreover, they give all the ingredients that are needed for the NNLO implementation of the qT subtraction formalism for heavy-quark production. We discuss the details of the computation and we provide a code that can be used to obtain the relevant results in numerical form.

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