A major ingredient in Higgs searches at the Tevatron and LHC is the elimination of backgrounds with jets. In current H -> WW -> lnulnu searches, jet algorithms are used to veto central jets to obtain a 0-jet sample, which is then analyzed to discover the Higgs signal. Imposing this tight jet veto induces large double logarithms which significantly modify the Higgs production cross section. These jet-veto logarithms are presently only accounted for at fixed order or with the leading-logarithmic summation from parton-shower Monte Carlos. Here we consider Higgs production with an inclusive event-shape variable for the jet veto, namely beam thrust Tau_cm, which has a close correspondence with a traditional p_T jet veto. Tau_cm allows us to systematically sum the large jet-veto logarithms to higher orders and to provide better estimates for theoretical uncertainties. We present results for the 0-jet Higgs production cross section from gluon fusion at next-to-next-to-leading-logarithmic order (NNLL), fully incorporating fixed-order results at next-to-next-to-leading order (NNLO). At this order the scale uncertainty is 15-20%, depending on the cut, implying that a larger scale uncertainty should be used in current Tevatron bounds on the Higgs.
We present new results for the jet-veto efficiency and zero-jet cross section in Higgs production through gluon fusion. We incorporate the N$^3$LO corrections to the total cross section, the NNLO corrections to the 1-jet rate, NNLL resummation for the jet $p_t$ and LL resummation for the jet radius dependence. Our results include known finite-mass corrections and are obtained using the jet-veto efficiency method, updated relative to earlier work to take into account what has been learnt from the new precision calculations that we include. For 13 TeV collisions and using our default choice for …
We present the inclusive transverse momentum distribution for Higgs bosons produced in bottom quark annihilation at the LHC. The results are obtained in the five-flavor scheme. The soft and collinear terms at small $p_T$ are resummed through NNLL accuracy and matched to the NNLO transverse momentum distribution at large $p_T$. We find that the theoretical uncertainty, derived from a variation of the unphysical scales entering the calculation, is significantly reduced with respect to lower orders.
The rapidity-dependent jet veto observables $\mathcal{T}_{Bj}$ and $\mathcal{T}_{Cj}$ provide a tight jet veto at central rapidity, gradually transitioning to a loose veto at forward rapidities. They divide the phase space into exclusive jet bins in a different way to the traditional jet veto observable $p_{Tj}$, and are advantageous to use under harsh pile-up conditions. We obtain predictions for the $0$-jet gluon-fusion (ggF) Higgs cross section using both of these veto observables at NNLL$'+$NNLO, and compare these predictions to the prior state-of-the-art of NLL$'+$NLO. A significant reduc…
We present results for the Higgsstrahlung process within the GENEVA Monte Carlo framework. We combine the fully differential NNLO calculation with the higher-order resummation in the 0-jettiness resolution variable (beam-thrust). The resulting parton-level events are further showered and hadronised by Pythia8. The beam-thrust resummation is carried out to NNLL$'$ accuracy, which consistently incorporates all singular virtual and real NNLO corrections. It thus provides a natural perturbative connection between the NNLO calculation and the parton shower regime, including a systematic assessment …
I present recent NNLO-NNLL results for top quark hadroproduction at the Tevatron. The total cross section as well as transverse momentum and rapidity distributions are shown.
The QCD coupling $α_s$ is extracted from the energy evolution of the first two moments (multiplicity and mean) of the parton-to-hadron fragmentation functions at low fractional hadron momentum $z$. Comparisons of the experimental $e^+e^-$ and deep-inelastic $e^\pm$p jet data to our NNLO$^*$+NNLL predictions, allow us to obtain $α_s(m_{_{\rm Z}})$ = 0.1205$\pm$0.0010$^{+0.0022}_{-0.0000}$, in excellent agreement with the current world average determined using other methods at the same level of accuracy.
We present predictions for Higgs production via gluon fusion with a p_T veto on jets and with the resummation of jet-veto logarithms at NNLL'+$NNLO order. These results incorporate explicit O(alphas^2) calculations of soft and beam functions, which include the dominant dependence on the jet radius R. In particular the NNLL' order accounts for the correct boundary conditions for the N3LL resummation, for which the only unknown ingredients are higher-order anomalous dimensions. We use scale variations in a factorization theorem in both rapidity and virtuality space to estimate the perturbative u…
We describe predictions for top-quark pair differential distributions at hadron colliders, which combine state-of-the-art NNLO QCD calculations and NLO electroweak corrections together with double resummation at NNLL$'$ accuracy of threshold logarithms and small-mass logarithms. This is the first time that such a combination has appeared in the literature. Numerical results are presented for the invariant-mass distribution, the transverse-momentum distribution as well as rapidity distributions.
We construct predictions for top quark pair differential distributions at hadron colliders that combine state-of-the-art NNLO QCD calculations with double resummation at NNLL' accuracy of threshold logarithms arising from soft gluon emissions and of small mass logarithms. This is the first time a resummed calculation at full NNLO+NNLL' accuracy in QCD for a process with non-trivial color structure has been completed at the differential level. Of main interest to us is the stability of the M_{tt} and top-quark p_T distributions in the boosted regime where fixed order calculations may become str…
Using methods of effective field theory, we derive the first all-order factorization theorem for the Higgs-boson production cross section with a jet veto, imposed by means of a standard sequential recombination jet algorithm. Like in the case of small-q_T resummation in Drell-Yan and Higgs production, the factorization is affected by a collinear anomaly. Our analysis provides the basis for a systematic resummation of large logarithms log(m_H/p_T^veto) beyond leading-logarithmic order. Specifically, we present predictions for the resummed jet-veto cross section and efficiency at next-to-next-to…
We present results for Drell-Yan production from the GENEVA Monte-Carlo framework. We combine the fully-differential NNLO calculation with higher-order resummation in the 0-jettiness resolution variable. The resulting parton-level events are further combined with parton showering and hadronization provided by PYTHIA8. The 0-jettiness resummation is carried out to NNLL', which consistently incorporates all singular virtual and real NNLO corrections. It thus provides a natural perturbative connection between the NNLO calculation and the parton shower regime, including a systematic assessment of …
The resummed transverse-momentum distribution for Higgs bosons produced via bottom-quark annihilation at the LHC is presented. Our results are obtained in the five-flavor scheme to NNLO+NNLL accuracy. We present a theoretical prediction which consistently matches the cross section at small and large transverse momenta. Theoretical uncertainties are derived from a variation of the unphysical scales entering the calculation. Their size is significantly reduced with respect to lower orders.
Les Houches study on inclusive jet production at NNLO+NNLL
Cavendish Laboratory, University of Cambridge（剑桥大学卡文迪许实验室）；Michigan State University（密歇根州立大学）；Argonne National Laboratory（阿贡国家实验室）；Yale University（耶鲁大学）；Institute of Nuclear Physics（核物理研究所）；Massachusetts Institute of Technology（麻省理工学院）
At the LHC and Tevatron strong initial-state radiation (ISR) plays an important role. It can significantly affect the partonic luminosity available to the hard interaction or contaminate a signal with additional jets and soft radiation. An ideal process to study ISR is isolated Drell-Yan production, pp -> X l+l- without central jets, where the jet veto is provided by the hadronic event shape beam thrust tau_B. Most hadron collider event shapes are designed to study central jets. In contrast, requiring tau_B << 1 provides an inclusive veto of central jets and measures the spectrum of ISR. For t…
The complete next-to-next-to leading order (NNLO) QCD correction has been studied to the di-lepton invariant mass distribution within the Randall-Sundrum (RS) framework. In addition, the soft-virtual (SV) cross-section at next-to-next-to-next-to leading order (N$^3$LO) as well as threshold resummation to next-to-next-to leading logarithms (NNLL) level have been presented. The analytical coefficient for SV production has been obtained up to three loops very recently along with the process-dependent coefficients needed to perform resummation up to NNLL. These coefficients are universal for any u…
The invariant mass of a jet is a benchmark variable describing the structure of jets at the LHC. We calculate the jet mass spectrum for Higgs plus one jet at the LHC at next-to-next-to-leading logarithmic (NNLL) order using a factorization formula. At this order, the cross section becomes sensitive to perturbation theory at the soft m_jet^2/p_T^jet scale. Our calculation is exclusive and uses the 1-jettiness global event shape to implement a veto on additional jets. The dominant dependence on the jet veto is removed by normalizing the spectrum, leaving residual dependence from non-global logar…
In electroweak-boson production processes with a jet veto, higher-order corrections are enhanced by logarithms of the veto scale over the invariant mass of the boson system. In this paper, we resum these Sudakov logarithms at next-to-next-to-leading logarithmic (NNLL) accuracy and match our predictions to next-to-leading order (NLO) fixed-order results. We perform the calculation in an automated way, for arbitrary electroweak final states and in the presence of kinematic cuts on the leptons produced in the decays of the electroweak bosons. The resummation is based on a factorization theorem fo…
We propose a new approach to the resummation of the transverse-momentum distribution of a high-mass colour-singlet system in hadronic collisions. The resummation is performed in momentum space and is free of kinematic singularities at small transverse momentum. We derive a formula accurate at the next-to-next-to-leading-logarithmic level, and present the first matched predictions to next-to-next-to-leading order for Higgs-boson production in gluon fusion at the LHC. This method can be adapted to all observables featuring kinematic cancellations in the infrared region.
We present a comparison of the computation of energy-energy correlation in $e^{+}e^{-}$ collisions in the back-to-back region at next-to-next-to-leading logarithmic accuracy matched with the next-to-next-to-leading order perturbative prediction to LEP, PEP, PETRA, SLC and TRISTAN data. With these predictions we perform an extraction of the strong coupling constant taking into account non-perturbative effects modelled with Monte Carlo event generators. The final result at NNLO+NNLL precision is $α_{S}(M_{Z})=0.11750\pm 0.00018 {\text( exp.)}\pm 0.00102{\text(hadr.)}\pm0.00257{\text(ren.)}\pm 0.…
We present the resummed predictions for inclusive cross section for the production of Higgs boson at next-to-next-to leading logarithmic ($\rm \overline {NNLL}$) accuracy taking into account both soft-virtual ($\rm SV$) and next-to SV ($\rm NSV$) threshold logarithms. We derive the $N$-dependent coefficients and the $N$-independent constants in Mellin-$N$ space for our study. Using the minimal prescription we perform the inverse Mellin transformation and match it with the corresponding fixed order results. We report in detail the numerical impact of $N$-independent part of resummed result and …
We present a formalism that resums threshold-enhanced logarithms to all orders in perturbative QCD for the rapidity distribution of any colorless particle produced in hadron colliders. We achieve this by exploiting the factorization properties and K+G equations satisfied by the soft and virtual parts of the cross section. We compute for the first time compact and most general expressions in two-dimensional Mellin space for the resummed coefficients. Using various state-of-the-art multiloop and multileg results, we demonstrate the numerical impact of our resummed results up to next-to-next-to-l…
We consider Higgs boson production through gluon--gluon fusion in hadron collisions, when a veto is applied on the transverse momenta of the accompanying hard jets. We compute the QCD radiative corrections to this process at NLO and NNLO. The NLO calculation is complete. The NNLO calculation uses the recently evaluated NNLO soft and virtual QCD contributions to the inclusive cross section. We find that the jet veto reduces the impact of the NLO and NNLO contributions, the reduction being more sizeable at the LHC than at the Tevatron.
In this article we have studied the transverse momentum distribution of the pseudo-scalar Higgs boson at the Large Hadron Collider (LHC). The small $\pt$ region which provides the bulk of the cross section is not accessible to fixed order perturbation theory due to the presence of large logarithms in the series. Using the universal infrared behaviour of the QCD we resum these large logarithms up to next-to-next-to-leading logarithmic (NNLL) accuracy. We observe a significant reduction in theoretical uncertainties due to the unphysical scales at NNLL level compared to the previous order. We pre…
We consider the transverse-momentum ($p_T$) distribution of $ZZ$ and $W^+W^-$ boson pairs produced in hadron collisions. At small $p_T$, the logarithmically enhanced contributions due to multiple soft-gluon emission are resummed to all orders in QCD perturbation theory. At intermediate and large values of $p_T$, we consistently combine resummation with the known fixed-order results. We exploit the most advanced perturbative information that is available at present: next-to-next-to-leading logarithmic resummation combined with the next-to-next-to-leading fixed-order calculation. After integrati…
We present the computation of energy-energy correlation in $e^+e^-$ collisions in the back-to-back region at next-to-next-to-leading logarithmic accuracy matched with the next-to-next-to-leading order perturbative prediction. We study the effect of the fixed higher order corrections in a comparison of our results to LEP and SLC data. The next-to-next-to-leading order correction has a sizable impact on the extracted value of $α_{\mathrm S}(M_Z)$, hence its inclusion is mandatory for a precise measurement of the strong coupling using energy-energy correlation.
We present first results on the resummation of Next-to-Soft Virtual (NSV) logarithms for the threshold production of pseudoscalar Higgs boson through gluon fusion at the LHC. These results are presented after resumming the NSV logarithms of the kind ${\log}^{i}(1-z)$ to $\overline{\text{NNLL}}$ accuracy and matching them systematically to the fixed order NNLO cross-sections. These results are obtained using collinear factorization, renormalization group invariance and recent developments in the NSV resummation techniques. The phenomenological implications of these NSV resummed results for 13 T…
Total and fiducial top pair ($t\bar{t}$) production cross sections in proton-lead (pPb) collisions at $\sqrt{s_{NN}}$ = 8.16 TeV are computed at next-to-next-to-leading-order (NNLO) accuracy including next-to-next-to-leading-log (NNLL) gluon resummation, using the CT14 and CT10 proton parton distribution functions (PDF), and the EPPS16 and EPS09 nuclear PDF parametrizations for the lead ion. The total cross sections amount to $σ(pPb\to t\bar{t}+X) = 59.0 \pm 5.3$(CT14+EPPS16)$\,^{+1.6}_{-2.1}$(scale) nb, and $57.5 \pm \,^{+4.3}_{-3.3}$(CT10+EPS09)$\,^{+1.5}_{-2.0}$(scale) nb, with small modifi…
The production of high-mass, color-singlet particles in hadron colliders is universally accompanied by initial state QCD radiation that is predominantly soft with respect to the hard process scale $Q$ and/or collinear with respect to the beam axis. At TeV-scale colliders, this is in contrast to top quark and multijet processes, which, by definition, are hard and central. Consequently, vetoing events with jets possessing transverse momenta above $p_T^{\rm Veto}$ in searches for new color-singlet states can efficiently reduce non-singlet backgrounds, thereby increasing experimental sensitivity. …
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…
This paper presents a phenomenological study for the differential cross section of the forward Z boson production in leptonic decay channels as a function of the angular variable $ϕ^{*}_η$ in proton-proton collisions. The $ϕ^{*}_η$ distribution is predicted for the forward pseudorapidity region $2.0 < η_{l} < 4.5$ of the decay leptons at center-of-mass energies 8, 13, and 14 TeV. Accurate prediction of the $ϕ^{*}_η$ distribution is achieved by means of the state-of-the-art calculations including fixed-order perturbative QCD and large logarithmic corrections. The predicted distributions are obt…
We present a general framework that allows to compute the resummed transverse-momentum distribution of a system of colorless particles. The implementation is fully differential in the degrees of freedom of the final-state system. As a first application, we consider the transverse-momentum spectrum of ZZ and WW boson pairs produced in hadron collisions, where we resum the logarithmically enhanced contributions due to multiple soft-gluon emission at small transverse momenta to all orders in perturbation theory. We exploit the most advanced perturbative information for the ZZ and WW production pr…
I discuss threshold resummation at NNLL accuracy in the standard moment-space approach in perturbative QCD for top-pair and single-top production. For top quark pair production I present new approximate NNLO results for the total cross section and for the top quark transverse momentum and rapidity distributions at 8 TeV LHC energy. I discuss the accuracy of the soft-gluon approximation and show that the NLO and NNLO approximate results from resummation are practically indistinguishable from exact NLO and partial NNLO results. For single top production I present new approximate NNLO results for…
We compute the resummed on-shell $W^+ W^-$ production cross section under a jet-veto at the LHC to partial N$^3$LL order matched to the fixed order NNLO result. Differential NNLO cross sections are obtained from an implementation of $q_T$ subtraction in Sherpa. The two-loop virtual corrections to the $q \bar q \rightarrow W^+ W^-$ amplitude, used in both fixed order and resummation predictions, are extracted from the public code {\tt qqvvamp}. We perform resummation using soft collinear effective theory (SCET), with approximate beam functions where only the logarithmic terms are included at tw…
Effects from a finite top quark mass on the H+n-jet cross section through gluon fusion are studied for $n=0/n\ge 1$ at NNLO/NLO QCD. For this purpose, sub-leading terms in $1/m_t$ are calculated. We show that the asymptotic expansion of the jet-vetoed cross section at NNLO is very well behaved and that the heavy-top approximation is valid at the five permille level up to jet-veto cuts of 300 GeV. For the inclusive Higgs+jet rate, we introduce a matching procedure that allows for a reliable prediction of the top-mass effects using the expansion in $1/m_t$. The quality of the effective field the…
If supersymmetry near the TeV scale is realized in Nature, the pair production of scalar top squarks is expected to be observable at the Large Hadron Collider. Recently, effective field-theory methods were employed to obtain approximate predictions for the cross section for this process, which include soft-gluon emission effects up to next-to-next-to-leading order (NNLO) in perturbation theory. In this work we employ the same techniques to resum soft-gluon emission effects to all orders in perturbation theory and with next-to-next-to-logarithmic (NNLL) accuracy. We analyze the effects of NNLL …
We consider the production of pairs of lepton through the Drell-Yan process at the LHC and present the most accurate prediction on their rapidity distribution. While the fixed order prediction is already known to next-to-next-to-leading order in perturbative QCD, the resummed contribution coming from threshold region of phase space up to next-to-next-to-leading logarithmic (NNLL) accuracy has been computed in this article. The formalism developed in [1-3] has been used to resum large threshold logarithms in the two dimensional Mellin space to all orders in perturbation theory. We have done a d…
Using the technology of the CAESAR approach to resummation, we examine the jet-veto efficiency in Higgs-boson and Drell-Yan production at hadron colliders and show that at next-to-leading logarithmic (NLL) accuracy the resummation reduces to just a Sudakov form factor. Matching with NNLO calculations results in stable predictions for the case of Drell-Yan production, but reveals substantial uncertainties in gluon-fusion Higgs production, connected in part with the poor behaviour of the perturbative series for the total cross section. We compare our results to those from POWHEG with and without…
The next-to-leading order (NLO) QCD radiative corrections to W+W- production at hadron colliders are well understood. We combine NLO perturbative QCD calculations with soft-gluon resummation of threshold logarithms to find a next-to-next-to leading logarithmic (NNLL) prediction for the total cross section and the invariant mass distribution at the LHC. We also obtain approximate next-to-next-to-leading order (NNLO) results for the total W+W- cross section at the LHC which includes all contributions from the scale dependent leading singular terms. Our result for the approximate NNLO total cross…
I present the next-to-next-to-leading-logarithm (NNLL) resummation of soft and collinear gluon corrections to single top quark production in the s channel. Attaining NNLL accuracy involves the calculation of the two-loop soft anomalous dimension for the partonic subprocesses. Finite-order expansions of the resummed cross section are calculated through next-to-next-to-leading order (NNLO). Numerical results are presented for s-channel single top quark production at the Tevatron and the LHC, including the dependence of the cross sections on the top quark mass and the uncertainties in the theoret…
Using the recently derived NNLO cross sections \cite{Czakon:2013goa}, we provide NNLO+NNLL theoretical predictions for top quark pair production based on all the available NNLO PDF sets, and compare them with the most precise LHC and Tevatron data. In this comparison we study in detail the PDF uncertainty and the scale, $m_t$ and $α_s$ dependence of the theoretical predictions for each PDF set. Next, we observe that top quark pair production provides a powerful direct constraint on the gluon PDF at large $x$, and include Tevatron and LHC top pair data consistently into a global NNLO PDF fit. W…
We present new results for W-boson production at large transverse momentum at the LHC and the Tevatron. The contribution of soft-gluon corrections is derived from NNLL resummation and added to the exact NLO result. Numerical results and their uncertainties for the approximate NNLO W-boson transverse momentum distributions are derived and compared to recent data from the LHC.
We present predictions for the total cross sections for pair production of squarks and gluinos at the LHC including a combined NNLL resummation of soft and Coulomb gluon effects. We derive all terms in the NNLO cross section that are enhanced near the production threshold, which include contributions from spin-dependent potentials and so-called annihilation corrections. The NNLL corrections at $\sqrt{s}=13$ TeV range from up to $20\%$ for squark-squark production to $90\%$ for gluino pair production relative to the NLO results and reduce the theoretical uncertainties of the perturbative calcul…
We have recently derived a factorization formula for the Higgs-boson production cross section in the presence of a jet veto, which allows for a systematic resummation of large Sudakov logarithms of the form alpha_s^n ln^m(p_T^veto/m_H), along with the large virtual corrections known to affect also the total cross section. Here we determine the ingredients entering this formula at two-loop accuracy. Specifically, we compute the dependence on the jet-radius parameter R, which is encoded in the two-loop coefficient of the collinear anomaly, by means of a direct, fully analytic calculation in the …
