scholarly journals Photons as Probes of Gluon Saturation in DiluteDense Collisions

Proceedings ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 33
Author(s):  
Sanjin Benić ◽  
Kenji Fukushima ◽  
Oscar Garcia-Montero ◽  
Raju Venugopalan
Keyword(s):  
Cross Section ◽  
Center Of Mass ◽  
Effective Field ◽  
Photon Production ◽  
Color Glass ◽  
Leading Order ◽  
Small X ◽  
Gluon Saturation ◽  
Gluon Distributions ◽  
Good Agreement

We use the Color Glass Condensate (CGC) effective field theory (EFT) to calculate inclusive photon production to leading order q g → q γ , (LO), and next-to leading order g g → q q ¯ γ (NLO) at LHC energies. These processes dominate the photon production at small-x , where x ≲ 0 . 01 in the target and projectile protons. We show that the NLO contribution dominates at values of x typical at the LHC, since its cross-section is sensitive to the gluon distributions in both protons. We perform a comparison of our results to the available inclusive photon data, from ATLAS and CMS at center-of-mass energies of 2 . 76 and 7 TeV . This data lies in the range k ⊥ > 20 GeV . We show that for this range, the k ⊥ -factorized cross-section converges to the full CGC EFT result, and can be used for the comparison. We find that it gives good agreement with experimental results. Our results are to be considered as a first step towards constraining unintegrated gluon distributions, which will be continued for larger systems, where coherent scatterings are enhanced.

scholarly journals TMD gluon distributions at small x in the CGC theory

2018 ◽  
Vol 27 (05) ◽  
pp. 1830003 ◽  
Author(s):  
Elena Petreska
Keyword(s):  
Transverse Momentum ◽  
Recent Progress ◽  
Effective Theory ◽  
Color Glass ◽  
Color Glass Condensate ◽  
Transverse Momentum Dependent ◽  
Small X ◽  
Gluon Saturation ◽  
Gluon Distributions ◽  
Domain Of Validity

In this paper, we review recent progress in the description of unpolarized transverse-momentum-dependent (TMD) gluon distributions at small [Formula: see text] in the color glass condensate (CGC) effective theory. We discuss the origin of the nonuniversality of TMD gluon distributions in the TMD factorization framework and in the CGC theory and the equivalence of the two approaches in their overlapping domain of validity. We show some applications of this equivalence, including recent results on the behavior of TMD gluon distributions at small [Formula: see text], and on the study of gluon saturation. We discuss recent advances in the unification of the TMD evolution and the nonlinear small-[Formula: see text] evolution of gluon distributions.

scholarly journals Studies of Deuteron–Proton Collisions at 100 MeV

2021 ◽  
Vol 62 (4) ◽  
Author(s):  
I. Skwira-Chalot ◽  
N. Kalantar-Nayestanaki ◽  
St. Kistryn ◽  
A. Kozela ◽  
E. Stephan
Keyword(s):  
Cross Section ◽  
Effective Field Theory ◽  
Beam Energy ◽  
Effective Field ◽  
Breakup Reaction ◽  
Low Energy ◽  
Chiral Effective Field Theory ◽  
Proton Collisions ◽  
Realistic Potentials ◽  
Good Agreement

AbstractDifferential cross section for the $$^1H(d,pp)n$$ 1 H ( d , p p ) n reaction is sensitive to various dynamical ingredients and allows for thorough tests of theoretical potentials describing the interaction in the three nucleon systems. The analysis of the experimental data collected for the breakup reaction at the beam energy of 100 MeV has been performed and the first cross section results for selected configurations are presented in this paper. They are in good agreement with calculations based on the realistic potentials. Studies at this relatively low energy will also be important for examining awaited calculations within the Chiral Effective Field Theory.

scholarly journals Drell-Yan angular lepton distributions at small x from TMD factorization.

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Ian Balitsky
Keyword(s):  
Transverse Momentum ◽  
Pair Production ◽  
Cross Section ◽  
Z Boson ◽  
Equation Of Motion ◽  
Leading Order ◽  
Small X ◽  
Mulders Function

Abstract The Drell-Yan process is studied in the framework of TMD factorization in the Sudakov region s » Q2 » $$ {q}_{\perp}^2 $$ q ⊥ 2 corresponding to recent LHC experiments with Q2 of order of mass of Z-boson and transverse momentum of DY pair ∼ few tens GeV. The DY hadronic tensors are expressed in terms of quark and quark-gluon TMDs with $$ \frac{1}{Q^2} $$ 1 Q 2 and $$ \frac{1}{N_c^2} $$ 1 N c 2 accuracy. It is demonstrated that in the leading order in Nc the higher-twist quark-quark-gluon TMDs reduce to leading-twist TMDs due to QCD equation of motion. The resulting hadronic tensors depend on two leading-twist TMDs: f1 responsible for total DY cross section, and Boer-Mulders function $$ {h}_1^{\perp } $$ h 1 ⊥ . The corresponding qualitative and semi-quantitative predictions seem to agree with LHC data on five angular coefficients A0− A4 of DY pair production. The remaining three coefficients A5− A7 are determined by quark-quark-gluon TMDs multiplied by extra $$ \frac{1}{N_c} $$ 1 N c so they appear to be relatively small in accordance with LHC results.

scholarly journals Azimuthal correlations of high transverse momentum jets at next-to-leading order in the parton branching method

2022 ◽  
Vol 82 (1) ◽  
Author(s):  
M. I. Abdulhamid ◽  
M. A. Al-Mashad ◽  
A. Bermudez Martinez ◽  
G. Bonomelli ◽  
I. Bubanja ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Parton Shower ◽  
Good Description ◽  
Leading Order ◽  
High Transverse Momentum ◽  
Azimuthal Correlation ◽  
Azimuthal Correlations ◽  
The Matrix ◽  
Good Agreement

AbstractThe azimuthal correlation, $$\Delta \phi _{12}$$ Δ ϕ 12 , of high transverse momentum jets in pp collisions at $$\sqrt{s}=13$$ s = 13  TeV is studied by applying PB-TMD distributions to NLO calculations via MCatNLO together with the PB-TMD parton shower. A very good description of the cross section as a function of $$\Delta \phi _{12}$$ Δ ϕ 12 is observed. In the back-to-back region of $${\Delta \phi _{12}}\rightarrow \pi $$ Δ ϕ 12 → π , a very good agreement is observed with the PB-TMD Set 2 distributions while significant deviations are obtained with the PB-TMD Set 1 distributions. Set 1 uses the evolution scale while Set 2 uses transverse momentum as an argument in $$\alpha _\mathrm {s}$$ α s , and the above observation therefore confirms the importance of an appropriate soft-gluon coupling in angular ordered parton evolution. The total uncertainties of the predictions are dominated by the scale uncertainties of the matrix element, while the uncertainties coming from the PB-TMDs and the corresponding PB-TMD shower are very small. The $$\Delta \phi _{12}$$ Δ ϕ 12 measurements are also compared with predictions using MCatNLO together Pythia8, illustrating the importance of details of the parton shower evolution.

scholarly journals Forward particle production in proton-nucleus collisions at next-to-leading order

2018 ◽  
Vol 192 ◽  
pp. 00014
Author(s):  
D.N. Triantafyllopoulos
Keyword(s):  
Cross Section ◽  
Particle Production ◽  
Eikonal Approximation ◽  
High Energy ◽  
Fine Tuning ◽  
Color Glass ◽  
Leading Order ◽  
Energy Evolution ◽  
The Impact ◽  
Correct Size

We consider the next-to-leading order (NLO) calculation of single inclusive particle production at forward rapidities in proton-nucleus collisions and in the framework of the Color Glass Condensate (CGC). We focus on the quark channel and the corrections associated with the impact factor. In the first step of the evolution the kinematics of the emitted gluon is kept exactly (and not in the eikonal approximation), but such a treatment which includes NLO corrections is not explicitly separated from the high energy evolution. Thus, in this newly established “factorization scheme”, there is no “rapidity subtraction”. The latter suffers from fine tuning issues and eventually leads to an unphysical (negative) cross section. On the contrary, our reorganization of the perturbation theory leads by definition to a well-defined cross section and the numerical evaluation of the NLO correction is shown to have the correct size.

Modeling $\bar{p}p$ and recent LHC pp total cross-sections

2014 ◽  
Vol 29 (08) ◽  
pp. 1450044 ◽  
Author(s):  
Amr Radi ◽  
Esraa El-Khateeb
Keyword(s):  
Neural Network ◽  
Total Cross Section ◽  
Cross Section ◽  
Cross Sections ◽  
Hadron Collider ◽  
Center Of Mass ◽  
High Energy ◽  
Ann Model ◽  
Predicted Values ◽  
Good Agreement

New technique is presented for modeling total cross-section of both pp and [Formula: see text] collisions from low to ultra high energy regions using an efficient artificial neural network (ANN). We have used the input (center-of-mass energy, [Formula: see text], and type of particle P) and output (total cross-section σ tot ) data to build a prediction model by ANN. The neural network has been trained to produce a function that studies the dependence of σ tot on [Formula: see text] and P. The trained ANN model shows a good performance in matching the trained distributions, predicts cross-sections that are not presented in the training set. The general trend of the predicted values shows a good agreement with the recent Large Hadron Collider (LHC) measurements, where the total cross-section at [Formula: see text] and 8 TeV are measured to be 98.6 mb and 101.7 mb, respectively. The predicted values of the total cross-section at [Formula: see text] and 14 TeV are found to be 105.8 mb and 111.7 mb, respectively. Those predictions are in good agreement with Block, Cudell and Nakamura.

QCD ANALYSIS OF DEEP INELASTIC LEPTON-NUCLEON SCATTERING DATA

1992 ◽  
Vol 07 (25) ◽  
pp. 2307-2315
Author(s):  
S. I. BILENKAYA ◽  
D. B. STAMENOV
Keyword(s):  
Cross Section ◽  
Scale Parameter ◽  
Structure Functions ◽  
Mass Scale ◽  
Scattering Data ◽  
Nucleon Structure ◽  
Leading Order ◽  
Parton Distributions ◽  
Qcd Analysis ◽  
Good Agreement

A combined next-to-leading order QCD analysis of BCDMS µ H 2 ( D 2) and CDHS [Formula: see text] scattering data is presented. The nucleon structure functions are given in terms of parton distributions. Unlike most of the papers on this subject, the cross-section scattering data (not the values for the nucleon structure functions extracted from these data by additional extrapolations and assumptions) are fitted. A very good agreement of the data with the predictions of QCD for the parton distributions is observed. The QCD mass scale parameter Λ is determined from these data both in a flavor nonsinglet approximation and with a complete flavor singlet and non-singlet treatment. These two fits to the data give consistent results for Λ.

scholarly journals Dijet impact factor in DIS at next-to-leading order in the Color Glass Condensate

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Paul Caucal ◽  
Farid Salazar ◽  
Raju Venugopalan
Keyword(s):  
Impact Factor ◽  
Wilson Line ◽  
Effective Field ◽  
Color Glass ◽  
Inelastic Electron ◽  
Color Glass Condensate ◽  
Leading Order ◽  
Dijet Production ◽  
Discovery Potential ◽  
The Impact

Abstract We compute the next-to-leading order impact factor for inclusive dijet production in deeply inelastic electron-nucleus scattering at small xBj. Our computation, performed in the framework of the Color Glass Condensate effective field theory, includes all real and virtual contributions in the gluon shock wave background of all-twist lightlike Wilson line correlators. We demonstrate explicitly that the rapidity evolution of these correlators, to leading logarithmic accuracy, is described by the JIMWLK Hamiltonian. When combined with the next-to-leading order JIMWLK Hamiltonian, our results for the impact factor improve the accuracy of the inclusive dijet cross-section to $$ \mathcal{O} $$ O ($$ {\alpha}_s^2 $$ α s 2 ln(xf/xBj)), where xf is a rapidity factorization scale. These results are an essential ingredient in assessing the discovery potential of inclusive dijets to uncover the physics of gluon saturation at the Electron-Ion Collider.

scholarly journals Measurement of the inclusive and differential t$$ \overline{t} $$γ cross sections in the single-lepton channel and EFT interpretation at $$ \sqrt{s} $$ = 13 TeV

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
◽  
A. Tumasyan ◽  
W. Adam ◽  
J. W. Andrejkovic ◽  
T. Bergauer ◽  
...  
Keyword(s):  
Standard Model ◽  
Cross Section ◽  
Cross Sections ◽  
Top Quark ◽  
Production Cross ◽  
Center Of Mass ◽  
Effective Field ◽  
Data Set ◽  
The Standard Model ◽  
Direct Limits

Abstract The production cross section of a top quark pair in association with a photon is measured in proton-proton collisions at a center-of-mass energy of 13 TeV. The data set, corresponding to an integrated luminosity of 137 fb−1, was recorded by the CMS experiment during the 2016–2018 data taking of the LHC. The measurements are performed in a fiducial volume defined at the particle level. Events with an isolated, highly energetic lepton, at least three jets from the hadronization of quarks, among which at least one is b tagged, and one isolated photon are selected. The inclusive fiducial t$$ \overline{\mathrm{t}} $$ t ¯ γ cross section, for a photon with transverse momentum greater than 20 GeV and pseudorapidity |η| < 1.4442, is measured to be 798 ± 7(stat) ± 48(syst) fb, in good agreement with the prediction from the standard model at next-to-leading order in quantum chromodynamics. The differential cross sections are also measured as a function of several kinematic observables and interpreted in the framework of the standard model effective field theory (EFT), leading to the most stringent direct limits to date on anomalous electromagnetic dipole moment interactions of the top quark and the photon.

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