26 research outputs found

    High Energy Resummation of Jet Observables

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    In this paper we investigate the extension of high energy resummation at LLx accuracy to jet observables. In particular, we present the high energy resummed expression of the transverse momentum distribution of the outgoing parton in the general partonic process g(q)+g(q)→g(q)+Xg(q) + g(q) \to g(q) + X. In order to reach this result, several new ideas are introduced and exploited. First we prove that LLx resummation is achieved by dressing with hard radiation an off-shell gluon initiated LO process even if its on-shell limit is vanishing or trivial. Then we present a gauge-invariant framework where these calculations can be performed by using the modern helicity techniques. Finally, we show a possible way to restore gluon indistinguishability in the final state, which is otherwise lost in the resummation procedure, at all orders in αs\alpha_s at LLx. All partonic channels are then resummed and cross-checked against fixed-order calculations up to O(αs3)\mathcal{O}(\alpha_s^3)Comment: 31 pages, 6 figure

    High energy resummation of transverse momentum distributions:Higgs in gluon fusion

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    We derive a general resummation formula for transverse-momentum distributions of hard processes at the leading logarithmic level in the high-energy limit, to all orders in the strong coupling. Our result is based on a suitable generalization of high-energy factorization theorems, whereby all-order resummation is reduced to the determination of the Born-level process but with incoming off-shell gluons. We validate our formula by applying it to Higgs production in gluon fusion in the infinite top mass limit. We check our result up to next-to-leading order by comparison to the high energy limit of the exact expression and to next-to-next-to leading by comparison to NNLL order trasverse momentum (Sudakov) resummation, and we predict the high-energy behaviour at next3^3-to-leading order. We also show that the structure of the result in the small transverse momentum limit agrees to all orders with general constraints from Sudakov resummation.Comment: 28 pages, 6 figures, Final version published in JHEP: several typos corrected (including in equations

    On the Higgs cross section at N3^3LO+N3^3LL and its uncertainty

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    We consider the inclusive production of a Higgs boson in gluon-fusion and we study the impact of threshold resummation at next-to-next-to-next-to-leading logarithmic accuracy (N3^3LL) on the recently computed fixed-order prediction at next-to-next-to-next-to-leading order (N3^3LO). We propose a conservative, yet robust way of estimating the perturbative uncertainty from missing higher (fixed- or logarithmic-) orders. We compare our results with two other different methods of estimating the uncertainty from missing higher orders: the Cacciari-Houdeau Bayesian approach to theory errors, and the use of algorithms to accelerate the convergence of the perturbative series. We confirm that the best convergence happens at μR=μF=mH / 2\mu_R=\mu_F=m_H\,/\,2, and we conclude that a reliable estimate of the uncertainty from missing higher orders on the Higgs cross section at 13 TeV is approximately ±4\pm4%.Comment: 27 pages, 6 figures. Version to be published in JHE

    Top Quark Pair Production beyond NNLO

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    We construct an approximate expression for the total cross section for the production of a heavy quark-antiquark pair in hadronic collisions at next-to-next-to-next-to-leading order (N3^3LO) in αs\alpha_s. We use a technique which exploits the analyticity of the Mellin space cross section, and the information on its singularity structure coming from large N (soft gluon, Sudakov) and small N (high energy, BFKL) all order resummations, previously introduced and used in the case of Higgs production. We validate our method by comparing to available exact results up to NNLO. We find that N3^3LO corrections increase the predicted top pair cross section at the LHC by about 4% over the NNLO.Comment: 34 pages, 9 figures; final version, to be published in JHEP; reference added, minor improvement

    Combined threshold and transverse momentum resummation for inclusive observables

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    We present a combined resummation for the transverse momentum distribution of a colorless final state in perturbative QCD, expressed as a function of transverse momentum pT and the scaling variable x. Its expression satisfies three requirements: it reduces to standard transverse momentum resummation to any desired logarithmic order in the limit pT \ue2\u86\u92 0 for fixed x, up to power suppressed corrections in pT; it reduces to threshold resummation to any desired logarithmic order in the limit x \ue2\u86\u92 1 for fixed pT, up to power suppressed correction in 1 \ue2\u88\u92 x; upon integration over transverse momentum it reproduces the resummation of the total cross cross at any given logarithmic order in the threshold x \ue2\u86\u92 1 limit, up to power suppressed correction in 1 \ue2\u88\u92 x. Its main ingredient, and our main new result, is a modified form of transverse momentum resummation, which leads to threshold resummation upon integration over pT, and for which we provide a simple closed-form analytic expression in Fourier-Mellin (b, N) space. We give explicit coefficients up to NNLL order for the specific case of Higgs production in gluon fusion in the effective field theory limit. Our result allows for a systematic improvement of the transverse momentum distribution through threshold resummation which holds for all pT, and elucidates the relation between transverse momentum resummation and threshold resummation at the inclusive level, specifically by providing within perturbative QCD a simple derivation of the main consequence of the so-called collinear anomaly of SCET

    Enhanced Carotid Plaque Echolucency Is Associated with Reduced Cognitive Performance in Elderly Patients with Atherosclerotic Disease Independently on Metabolic Profile

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    Vulnerable carotid atherosclerotic plaques are related to an increased risk of cognitive impairment and dementia in advanced age. In this study, we investigated the relationship between the echogenicity of carotid plaques and cognitive performance in patients with asymptomatic carotid atherosclerotic plaques. We enrolled 113 patients aged 65 years or more (72.4 ± 5.9 years) who underwent carotid duplex ultrasound to evaluate plaque echogenicity by grey-scale median (GSM) and neuropsychological tests to assess cognitive function. The GSM values at baseline were inversely correlated with the number of seconds required to complete Trail Makin Test (TMT) A (rho: -0.442; p < 0.0001), TMT B (rho: -0.460; p < 0.0001) and TMT B-A (rho: -0.333; p < 0.0001) and directly correlated with Mini Mental State Examination (MMSE) and Verbal Fluency Test (VFT) score (rho: 0.217; p = 0.021 and rho: 0.375; p < 0.0001, respectively) and the composite cognitive z-score (rho: 0.464; p < 0.0001). After a mean period of 3.5 ± 0.5 years, 55 patients were reevaluated according to the same baseline study protocol. Patients with baseline GSM value higher than the median value of 29 did not show any significant variation in the z-score. Instead, those with GSM ≤ 29 showed a significant worsening of z-score (-1.2; p = 0.0258). In conclusion, this study demonstrates the existence of an inverse relationship between the echolucency of carotid plaques and cognitive function in elderly patients with atherosclerotic carotid disease. These data suggest that the assessment of plaque echogenicity if used appropriately, might aid in identifying subjects at increased risk for cognitive dysfunction

    High energy resummation of transverse momentum distributions: Higgs in gluon fusion

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