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.

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 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 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 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.

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.

scholarly journals Heavy-flavor hadro-production with heavy-quark masses renormalized in the $$ \overline{\mathrm{MS}} $$, MSR and on-shell schemes

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
M. V. Garzelli ◽  
L. Kemmler ◽  
S. Moch ◽  
O. Zenaiev
Keyword(s):  
Heavy Quark ◽  
Cross Sections ◽  
Top Quark ◽  
Quark Mass ◽  
Production Cross ◽  
Hadron Collider ◽  
Distribution Functions ◽  
Heavy Flavor ◽  
Parton Distribution Functions ◽  
Heavy Quark Mass

Abstract We present predictions for heavy-quark production at the Large Hadron Collider making use of the $$ \overline{\mathrm{MS}} $$ MS ¯ and MSR renormalization schemes for the heavy-quark mass as alternatives to the widely used on-shell renormalization scheme. We compute single and double differential distributions including QCD corrections at next-to-leading order and investigate the renormalization and factorization scale dependence as well as the perturbative convergence in these mass renormalization schemes. The implementation is based on publicly available programs, MCFM and xFitter, extending their capabilities. Our results are applied to extract the top-quark mass using measurements of the total and differential $$ t\overline{t} $$ t t ¯ production cross-sections and to investigate constraints on parton distribution functions, especially on the gluon distribution at low x values, from available LHC data on heavy-flavor hadro-production.

scholarly journals Z-boson production in p-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 8.16 TeV and Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
S. Acharya ◽  
◽  
D. Adamová ◽  
A. Adler ◽  
J. Adolfsson ◽  
...  
Keyword(s):  
Z Boson ◽  
Decay Channel ◽  
Theoretical Calculations ◽  
Center Of Mass ◽  
Laboratory Frame ◽  
Distribution Functions ◽  
Boson Production ◽  
Free Nucleon ◽  
Parton Distribution Functions ◽  
Nuclear Modifications

Abstract Measurement of Z-boson production in p-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 8.16 TeV and Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV is reported. It is performed in the dimuon decay channel, through the detection of muons with pseudorapidity −4 < ημ< −2.5 and transverse momentum $$ {p}_{\mathrm{T}}^{\mu } $$ p T μ > 20 GeV/c in the laboratory frame. The invariant yield and nuclear modification factor are measured for opposite-sign dimuons with invariant mass 60 < mμμ< 120 GeV/c2 and rapidity 2.5 <$$ {y}_{\mathrm{cms}}^{\mu \mu} $$ y cms μμ < 4. They are presented as a function of rapidity and, for the Pb-Pb collisions, of centrality as well. The results are compared with theoretical calculations, both with and without nuclear modifications to the Parton Distribution Functions (PDFs). In p-Pb collisions the center-of-mass frame is boosted with respect to the laboratory frame, and the measurements cover the backward (−4.46 <$$ {y}_{\mathrm{cms}}^{\mu \mu} $$ y cms μμ < −2.96) and forward (2.03 <$$ {y}_{\mathrm{cms}}^{\mu \mu} $$ y cms μμ < 3.53) rapidity regions. For the p-Pb collisions, the results are consistent within experimental and theoretical uncertainties with calculations that include both free-nucleon and nuclear-modified PDFs. For the Pb-Pb collisions, a 3.4σ deviation is seen in the integrated yield between the data and calculations based on the free-nucleon PDFs, while good agreement is found once nuclear modifications are considered.

scholarly journals HIGGS PRODUCTION IN ASSOCIATION WITH BOTTOM QUARKS AT HADRON COLLIDERS

2006 ◽  
Vol 21 (02) ◽  
pp. 89-109 ◽  
Author(s):  
S. DAWSON ◽  
C. B. JACKSON ◽  
L. REINA ◽  
D. WACKEROTH
Keyword(s):  
Standard Model ◽  
Cross Sections ◽  
Hadron Collider ◽  
Distribution Functions ◽  
Bottom Quarks ◽  
Final States ◽  
Leading Order ◽  
Hadron Colliders ◽  
Parton Distribution Functions ◽  
Model Case

We review the present status of the QCD corrected cross-sections and kinematic distributions for the production of a Higgs boson in association with bottom quarks at the Fermilab Tevatron and CERN Large Hadron Collider. Results are presented for the Minimal Supersymmetric Standard Model where, for large tan β, these production modes can be greatly enhanced compared to the Standard Model case. The next-to-leading order QCD results are much less sensitive to the renormalization and factorization scales than the lowest order results, but have a significant dependence on the choice of the renormalization scheme for the bottom quark Yukawa coupling. We also investigate the uncertainties coming from the Parton Distribution Functions and find that these uncertainties can be comparable to the uncertainties from the remaining scale dependence of the next-to-leading order results. We present results separately for the different final states depending on the number of bottom quarks identified.

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