scholarly journals Factorization and transverse phase-space parton distributions

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Bin Wu
Keyword(s):  
Phase Space ◽  
Cross Section ◽  
Impact Parameter ◽  
Fourier Transforms ◽  
Distribution Functions ◽  
Glauber Model ◽  
Effective Theory ◽  
Factorization Formula ◽  
Parameter Dependent ◽  
The Impact

Abstract We first revisit impact-parameter dependent collisions of ultra-relativistic particles in quantum field theory. Two conditions sufficient for defining an impact-parameter dependent cross section are given, which could be violated in proton-proton collisions. By imposing these conditions, a general formula for the impact-parameter dependent cross section is derived. Then, using soft-collinear effective theory, we derive a factorization formula for the impact-parameter dependent cross section for inclusive hard processes with only colorless final-state products in hadron and nuclear collisions. It entails defining thickness beam functions, which are Fourier transforms of transverse phase-space parton distribution functions. By modelling non-perturbative modes in thickness beam functions of large nuclei in heavy-ion collisions, the factorization formula confirms the cross section in the Glauber model for hard processes. Besides, the factorization formula is verified up to one loop in perturbative QCD for the inclusive Drell-Yan process in quark-antiquark collisions at a finite impact parameter.

scholarly journals TACHYON DYNAMICS OF THE BLACK DISC LIMIT IN THE HARD SMALL x PROCESSES IN QCD

2006 ◽  
Vol 21 (07) ◽  
pp. 549-558 ◽  
Author(s):  
B. BLOK ◽  
L. FRANKFURT
Keyword(s):  
Cross Section ◽  
Impact Parameter ◽  
High Energy ◽  
Black Disk ◽  
Black Disc ◽  
Energy Behavior ◽  
Small X ◽  
The Cross ◽  
The Impact ◽  
Black Disc Limit

We investigate the effective field theory (EFT) which gives the approximate description of the scattering of two hard small dipoles in the small x processes in QCD near the black disc limit (BDL). We argue that the perturbative QCD approaches predict the existence of tachyon and visualize it in the approximation where α′P=0. We demonstrate that the high energy behavior of the cross-section depends strongly on the diffusion law in the impact parameter plane. On the other hand, almost threshold behavior of the cross section of the hard processes and multiplicities, i.e. fast increase of cross sections (color inflation), melting of ladders into color network and softening of the longitudinal distributions of hadrons are qualitatively insensitive to the value of diffusion in the impact parameter space. We evaluate α′P near the black disk limit and find significant α′P as the consequence of the probability conservation.

Dynamically Screened Elastic Collisions in Nonideal Plasmas

2006 ◽  
Vol 61 (7-8) ◽  
pp. 330-334
Author(s):  
Dong-Man Chang ◽  
Won-Seok Chang ◽  
Young-Dae Jung
Keyword(s):  
Cross Section ◽  
Impact Parameter ◽  
Thermal Energy ◽  
Collision Energy ◽  
Debye Length ◽  
Parameter Analysis ◽  
Ion Collisions ◽  
Dynamic Screening ◽  
Nonideal Plasmas ◽  
The Impact

The dynamic screening effects on elastic electron-ion collisions are investigated in nonideal plasmas. The second-order eikonal method with the impact parameter analysis is employed to obtain the eikonal phase as a function of the impact parameter, collision energy, thermal energy, and Debye length. The result shows that the eikonal phase decreases with increasing the thermal energy. It is also found that the dynamic screening effects on the eikonal phase are more significant for large impact parameters. The total eikonal cross section is also found to be decreased with increasing the thermal energy. It is important to note that the eikonal cross section and the eikonal phase including the dynamic screening effects are found to be greater than those including the static screening effects.

scholarly journals Analysis of combined HERA data in the impact-parameter dependent saturation model

2013 ◽  
Vol 87 (3) ◽  
Author(s):  
Amir H. Rezaeian ◽  
Marat Siddikov ◽  
Merijn Van de Klundert ◽  
Raju Venugopalan
Keyword(s):  
Impact Parameter ◽  
Hera Data ◽  
Saturation Model ◽  
Parameter Dependent ◽  
The Impact

scholarly journals Subleading EW corrections and spin-correlation effects in $$t\bar{t}W$$ multi-lepton signatures

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Rikkert Frederix ◽  
Ioannis Tsinikos
Keyword(s):  
Phase Space ◽  
Cross Section ◽  
Top Quark ◽  
Spin Correlation ◽  
Top Quarks ◽  
Correlation Effects ◽  
Spin Correlations ◽  
Decay Products ◽  
Theoretical Predictions ◽  
The Impact

AbstractRecently a slight tension between data and predictions has been reported in $$t\bar{t}W$$ t t ¯ W production by both the CMS and ATLAS collaborations. We revisit the theoretical predictions for this process, focussing on the following two effects. We disentangle various effects that lead to asymmetries among the leptonic decay products of the (anti-)top quarks and W bosons, for which we find that the spin correlations in the top-quark pair are the dominant source. We also discuss the impact of the large, formally subleading, electroweak corrections to $$t\bar{t}W$$ t t ¯ W production at the LHC. We find that this effect changes the $$t\bar{t}W$$ t t ¯ W cross section significantly in the signature phase-space regions, and should therefore be included differentially in the theory to data comparisons.

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