Article

# Next-to-Leading Order QCD Corrections to the Production of Two Bottom-Antibottom Pairs at the LHC

Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
(Impact Factor: 7.51). 09/2011; 107(10):102002. DOI: 10.1103/PhysRevLett.107.102002
Source: PubMed

ABSTRACT We report the results of a computation of the full next-to-leading order QCD corrections to the production of two bb pairs at the LHC. This calculation at the parton level provides predictions for well separated b jets. The results show that the next-to-leading order corrections lead to an enhancement of the cross section for the central scale choice by roughly 50% with respect to the leading order result. The theoretical uncertainty estimated by variation of the renormalization and factorization scales is strongly reduced by the inclusion of next-to-leading order corrections.

### Full-text

Available from: Alberto Guffanti, Aug 11, 2015
0 Followers
·
152 Views
• Source
• "Recent breakthrough in one-loop calculational techniques, sometimes referred to as " the unitary revolution " [16] [17] [18] [19], together with great improvement in more traditional methods, have led to a tremendous progress in the calculation of multi-leg processes at hadron colliders. This is exemplified by the calculation of the following 2 → 4 processes: pp(p¯ p) → t ¯ tb ¯ b+X [20] [21] [22] [23], pp(p¯ p) → t ¯ tjj +X [24] [25], pp(p¯ p) → W + W − b ¯ b+X [26] [27], pp → b ¯ bb ¯ b+X [28], pp(p¯ p) → W + W − jj + X [29] [30], pp → W + W + jj + X [31] [32], pp(p¯ p) → W + 3j + X [33] [34], p¯ p → Z/γ * + 3j + X [35], pp → W γγj + X [36] and pp → 4j + X [37]. In addition, the first NLO QCD corrections to 2 → 5 processes, i.e. pp → W + 4j + X and pp → Z/γ * + 4j + X have recently been completed [38] [39]. "
##### Article: Constraining BSM physics at the LHC: Four top final states with NLO accuracy in perturbative QCD
[Hide abstract]
ABSTRACT: Many theories, from Supersymmetry to models of Strong Electroweak Symmetry Breaking, look at the production of four top quarks as an interesting channel to evidentiate signals of new physics beyond the Standard Model. The production of four-top final states requires large partonic energies, above the 4mt threshold, that are available at the CERN Large Hadron Collider and will become more and more accessible with increasing energy and luminosity of the proton beams. A good theoretical control on the Standard Model background is a fundamental prerequisite for a correct interpretation of the possible signals of new physics that may arise in this channel. In this paper we report on the calculation of the next-to-leading order QCD corrections to the Standard Model process pp -> tttt + X. As it is customary for such studies, we present results for both integrated and differential cross sections. A judicious choice of a dynamical scale allows us to obtain nearly constant K-factors in most distributions.
Journal of High Energy Physics 06/2012; 2012(7). DOI:10.1007/JHEP07(2012)111 · 6.22 Impact Factor
• Source
• "In practice, the massive scheme amounts to employ an effective theory with n l light quarks, where the heavy quarks are decoupled and do not enter in the computation of the running coupling constant and in the evolution of the PDFs. There are many (differential) calculations available at NLO in QCD performed in this scheme relevant for hadron collider phenomenology, including among the most important ones, pp → bb + X [1] [2], pp → 4b + X [3], pp → ttbb + X [4] [5], pp → tbj + X [6], pp → H ± tb + X [7], pp → φbb + X with φ = H, A [8] [9] [10] [11], and pp → V bb + X with V = W, Z [12] [13] [14] [15] [16] [17] [18]. However, no prediction at NNLO in QCD for any process of relevance at the LHC is available in this scheme to date. "
##### Article: b-Initiated processes at the LHC: a reappraisal
[Hide abstract]
ABSTRACT: Several key processes at the LHC in the standard model and beyond that involve $b$ quarks, such as single-top, Higgs, and weak vector boson associated production, can be described in QCD either in a 4-flavor or 5-flavor scheme. In the former, $b$ quarks appear only in the final state and are typically considered massive. In 5-flavor schemes, calculations include $b$ quarks in the initial state, are simpler and allow the resummation of possibly large initial state logarithms of the type $\log \frac{{\cal Q}^2}{m_b^2}$ into the $b$ parton distribution function (PDF), ${\cal Q}$ being the typical scale of the hard process. In this work we critically reconsider the rationale for using 5-flavor improved schemes at the LHC. Our motivation stems from the observation that the effects of initial state logs are rarely very large in hadron collisions: 4-flavor computations are pertubatively well behaved and a substantial agreement between predictions in the two schemes is found. We identify two distinct reasons that explain this behaviour, i.e., the resummation of the initial state logarithms into the $b$-PDF is relevant only at large Bjorken $x$ and the possibly large ratios ${\cal Q}^2/m_b^2$'s are always accompanied by universal phase space suppression factors. Our study paves the way to using both schemes for the same process so to exploit their complementary advantages for different observables, such as employing a 5-flavor scheme to accurately predict the total cross section at NNLO and the corresponding 4-flavor computation at NLO for fully exclusive studies.
Journal of High Energy Physics 03/2012; 2013(4). DOI:10.1007/JHEP04(2013)095 · 6.22 Impact Factor
• Source
##### Article: Introducing an interface between WHIZARD and FeynRules
[Hide abstract]
ABSTRACT: While Monte Carlo event generators like WHIZARD have become indispensable tools in studying the impact of new physics on collider observables over the last decades, the implementation of new models in such packages has remained a rather awkward and error-prone process. Recently, the FeynRules package was introduced which greatly simplifies this process by providing a single unified model format from which model implementations for many different Monte Carlo codes can be derived automatically. In this note, we present an interface which extends FeynRules to provide this functionality also for the WHIZARD package, thus making WHIZARD's strengths and performance easily available to model builders.
European Physical Journal C 10/2010; 72(5). DOI:10.1140/epjc/s10052-012-1990-5 · 5.44 Impact Factor