scholarly journals Parton distributions in the SMEFT from high-energy Drell-Yan tails

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Admir Greljo ◽  
Shayan Iranipour ◽  
Zahari Kassabov ◽  
Maeve Madigan ◽  
James Moore ◽  
...  
Keyword(s):  
Cross Sections ◽  
Neutral Current ◽  
Light Quark ◽  
High Energy ◽  
New Physics ◽  
Effective Field ◽  
Distribution Functions ◽  
High Mass ◽  
Parton Distribution Functions ◽  
The Impact

Abstract The high-energy tails of charged- and neutral-current Drell-Yan processes provide important constraints on the light quark and anti-quark parton distribution functions (PDFs) in the large-x region. At the same time, short-distance new physics effects such as those encoded by the Standard Model Effective Field Theory (SMEFT) would induce smooth distortions to the same high-energy Drell-Yan tails. In this work, we assess for the first time the interplay between PDFs and EFT effects for high-mass Drell-Yan processes at the LHC and quantify the impact that the consistent joint determination of PDFs and Wilson coefficients has on the bounds derived for the latter. We consider two well-motivated new physics scenarios: 1) electroweak oblique corrections ($$ \hat{W},\hat{Y} $$ W ̂ , Y ̂ ) and 2) four-fermion interactions potentially related to the LHCb anomalies in R(K(*)). We account for available Drell-Yan data, both from unfolded cross sections and from searches, and carry out dedicated projections for the High-Luminosity LHC. Our main finding is that, while the interplay between PDFs and EFT effects remains moderate for the current dataset, it will become a significant challenge for EFT analyses at the HL-LHC.

scholarly journals nNNPDF2.0: quark flavor separation in nuclei from LHC data

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Rabah Abdul Khalek ◽  
Jacob J. Ethier ◽  
Juan Rojo ◽  
Gijs van Weelden
Keyword(s):  
Cross Sections ◽  
Good Description ◽  
Neutral Current ◽  
High Energy ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Nuclear Dynamics ◽  
Monte Carlo Techniques ◽  
Rapidity Distributions ◽  
Nuclear Modifications

Abstract We present a model-independent determination of the nuclear parton distribution functions (nPDFs) using machine learning methods and Monte Carlo techniques based on the NNPDF framework. The neutral-current deep-inelastic nuclear structure functions used in our previous analysis, nNNPDF1.0, are complemented by inclusive and charm-tagged cross-sections from charged-current scattering. Furthermore, we include all available measurements of W and Z leptonic rapidity distributions in proton-lead collisions from ATLAS and CMS at $$ \sqrt{s} $$ s = 5.02 TeV and 8.16 TeV. The resulting nPDF determination, nNNPDF2.0, achieves a good description of all datasets. In addition to quantifying the nuclear modifications affecting individual quarks and antiquarks, we examine the implications for strangeness, assess the role that the momentum and valence sum rules play in nPDF extractions, and present predictions for representative phenomenological applications. Our results, made available via the LHAPDF library, highlight the potential of high-energy collider measurements to probe nuclear dynamics in a robust manner.

Investigating the impact of the partonic structure on the description of hadronic collisions at high energies

2020 ◽  
Vol 35 (22) ◽  
pp. 2050127
Author(s):  
M. Broilo ◽  
V. P. Gonçalves ◽  
P. V. R. G. Silva
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Proton Proton ◽  
High Energies ◽  
High Energy Behavior ◽  
Energy Behavior ◽  
The Impact ◽  
Hadronic Collisions

The impact of the partonic structure on the description of the hadronic cross-sections is investigated considering a multichannel eikonal model based on the Good–Walker approach. The total, elastic and single diffractive cross-sections are estimated considering different parametrizations for the parton distribution functions and the predictions are compared with the experimental data for proton–proton [Formula: see text] and antiproton–proton [Formula: see text] collisions. We show that the description of the high-energy behavior of the hadronic cross-sections is sensitive to the partonic structure.

Accurate prediction of the Drell-Yan φ∗ η distribution in wide dilepton mass and rapidity ranges in pp collisions through NNLO+N3LL

2021 ◽  
Author(s):  
Kadir Ocalan
Keyword(s):  
Cross Sections ◽  
Good Description ◽  
Neutral Current ◽  
Mass Range ◽  
Theoretical Description ◽  
Distribution Functions ◽  
Boson Mass ◽  
Pp Collisions ◽  
Parton Distribution Functions ◽  
Central Detector

Abstract This paper presents high-accuracy predictions for the differential cross sections 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 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 mll ranges, spanning a wide kinematic region of 50 < mll< 1000 GeV both near and away from the Z-boson mass peak, and rapidity yll ranges in the central detector acceptance region of |yll| < 2.4. The differential φ*η distributions in the wide mll and yll ranges offer stringent tests to assess the reliability of the predictions, where the mll and yll are closely correlated with the parton distribution functions (PDFs) of the incoming partons. The merged 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 pll T as well) distributions in almost the entire mll and yll 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 merged predictions at NNLO+N3LL are also reported at 14 TeV for the upcoming high-luminosity running era of the 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 are tested for the first time in addition to the NNPDF3.1 exploiting the merged φ*η predictions.

scholarly journals Determination of αs in NNLO QCD using H1 jet cross section measurements

2019 ◽  
Vol 206 ◽  
pp. 01002
Author(s):  
Vladimir Chekelian
Keyword(s):  
Strong Coupling ◽  
Cross Section ◽  
Cross Sections ◽  
Neutral Current ◽  
Distribution Functions ◽  
Boson Mass ◽  
Parton Distribution Functions ◽  
Inclusive Jet ◽  
Using Data ◽  
Jet Cross Sections

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.

scholarly journals SQUARK AND GLUINO HADROPRODUCTION

2011 ◽  
Vol 26 (16) ◽  
pp. 2637-2664 ◽  
Author(s):  
WIM BEENAKKER ◽  
SILJA BRENSING ◽  
MICHAEL KRÄMER ◽  
ANNA KULESZA ◽  
ERIC LAENEN ◽  
...  
Keyword(s):  
Cross Sections ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Proton Proton ◽  
Proton Collisions ◽  
Numerical Predictions ◽  
Theoretical Status ◽  
Higher Order Corrections ◽  
The Impact ◽  
Proton Proton Collisions

We review the theoretical status of squark and gluino hadroproduction and provide numerical predictions for all squark and gluino pair-production processes at the Tevatron and at the LHC, with a particular emphasis on proton–proton collisions at 7 TeV. Our predictions include next-to-leading order supersymmetric QCD corrections and the resummation of soft gluon emission at next-to-leading-logarithmic accuracy. We discuss the impact of the higher-order corrections on total cross-sections, and provide an estimate of the theoretical uncertainty due to scale variation and the parton distribution functions.

scholarly journals The present and future of four top operators

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Giovanni Banelli ◽  
Ennio Salvioni ◽  
Javi Serra ◽  
Tobias Theil ◽  
Andreas Weiler
Keyword(s):  
Top Quark ◽  
High Energy ◽  
New Physics ◽  
Effective Field ◽  
Proton Proton ◽  
Strongly Coupled ◽  
Composite Higgs ◽  
Electron Positron ◽  
Energy Frontier ◽  
The Impact

Abstract We study the phenomenology of a strongly-interacting top quark at future hadron and lepton colliders, showing that the characteristic four-top contact operators give rise to the most significant effects. We demonstrate the extraordinary potential of a 100 TeV proton-proton collider to directly test such non-standard interactions in four-top production, a process that we thoroughly analyze in the same-sign dilepton and trilepton channels, and explore in the fully hadronic channel. Furthermore, high-energy electron-positron colliders, such as CLIC or the ILC, are shown to exhibit an indirect yet remarkable sensitivity to four-top operators, since these constitute, via renormalization group evolution, the leading new-physics deformations in top-quark pair production. We investigate the impact of our results on the parameter space of composite Higgs models with a strongly-coupled (right-handed) top quark, finding that four-top probes provide the best sensitivity on the compositeness scale at the future energy frontier. In addition, we investigate mild yet persisting LHC excesses in multilepton plus jets final states, showing that they can be consistently described in the effective field theory of such a new-physics scenario.

scholarly journals Higher-order corrections for tW production at high-energy hadron colliders

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Nikolaos Kidonakis ◽  
Nodoka Yamanaka
Keyword(s):  
Cross Sections ◽  
Top Quark ◽  
High Energy ◽  
Higher Order ◽  
Distribution Functions ◽  
Soft Gluon ◽  
Parton Distribution Functions ◽  
Proton Proton ◽  
Rapidity Distributions ◽  
Higher Order Corrections

Abstract We discuss cross sections for tW production in proton-proton collisions at the LHC and at higher-energy colliders with energies of up to 100 TeV. We find that, remarkably, the soft-gluon corrections are numerically dominant even at very high collider energies. We present results with soft-gluon corrections at approximate NNLO and approximate N3LO matched to complete NLO results. These higher-order corrections are large and need to be included for better theoretical accuracy and smaller scale dependence. Total cross sections as well as top-quark and W-boson transverse-momentum and rapidity distributions are presented using various recent sets of parton distribution functions.

scholarly journals $$ t\overline{t}b\overline{b} $$ at the LHC: on the size of corrections and b-jet definitions

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Giuseppe Bevilacqua ◽  
Huan-Yu Bi ◽  
Heribertus Bayu Hartanto ◽  
Manfred Kraus ◽  
Michele Lupattelli ◽  
...  
Keyword(s):  
Cross Sections ◽  
Top Quark ◽  
Decay Channel ◽  
Parton Density ◽  
Accurate Estimate ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Shell Effects ◽  
Quark Decay ◽  
The Impact

Abstract We report on the calculation of the next-to-leading order QCD corrections to the production of a $$ t\overline{t} $$ t t ¯ pair in association with two heavy-flavour jets. We concentrate on the di-lepton $$ t\overline{t} $$ t t ¯ decay channel at the LHC with $$ \sqrt{s} $$ s = 13 TeV. The computation is based on pp → e+νeμ−$$ \overline{\nu} $$ ν ¯ μ$$ b\overline{b}b\overline{b} $$ b b ¯ b b ¯ matrix elements and includes all resonant and non-resonant diagrams, interferences and off-shell effects of the top quark and the W gauge boson. As it is customary for such studies, results are presented in the form of inclusive and differential fiducial cross sections. We extensively investigate the dependence of our results upon variation of renormalisation and factorisation scales and parton distribution functions in the quest for an accurate estimate of the theoretical uncertainties. We additionally study the impact of the contributions induced by the bottom-quark parton density. Results presented here are particularly relevant for measurements of $$ t\overline{t}H $$ t t ¯ H (H → $$ b\overline{b} $$ b b ¯ ) and the determination of the Higgs coupling to the top quark. In addition, they might be used for precise measurements of the top-quark fiducial cross sections and to investigate top-quark decay modelling at the LHC.

Trace of nonperturbative charm content of the nucleon on Z + c-jet production

2017 ◽  
Vol 32 (16) ◽  
pp. 1750095
Author(s):  
S. Rostami ◽  
A. Khorramian
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Center Of Mass ◽  
Distribution Functions ◽  
Mass Energy ◽  
Parton Distribution Functions ◽  
Jet Production ◽  
Center Of Mass Energy ◽  
Intrinsic Charm ◽  
The Impact

We perform a comparison of the impact of different intrinsic charm (IC) models, based on the prediction of the differential cross-sections of [Formula: see text]-boson and [Formula: see text]-jet production in [Formula: see text] collision. It is shown that regardless of choosing the model, considering nonperturbative intrinsic charm component increases the magnitude of the cross-section when the [Formula: see text] transverse momentum grows or at large rapidity [Formula: see text] of the [Formula: see text]. Moreover, to evaluate the effect of different parton distribution functions (PDFs), we also compare the results of two PDF sets in prediction of production [Formula: see text]-jet in [Formula: see text] at a center-of-mass energy of 13 TeV with taking into account the intrinsic charm contribution in the proton. It is shown that the various PDF sets give some difference in the description of the [Formula: see text]-jet cross-section.

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