scholarly journals Multi-partonic medium induced cascades in expanding media

2022 ◽  
Vol 82 (1) ◽  
Author(s):  
Souvik Priyam Adhya ◽  
Carlos A. Salgado ◽  
Martin Spousta ◽  
Konrad Tywoniuk
Keyword(s):  
Path Length ◽  
Degrees Of Freedom ◽  
Evolution Equations ◽  
Measured Data ◽  
Distribution Functions ◽  
Jet Quenching ◽  
Parton Distribution Functions ◽  
Nuclear Modification ◽  
Different Types ◽  
Rapidity Dependence

AbstractGoing beyond the simplified gluonic cascades, we introduce both gluon and quark degrees of freedom for partonic cascades inside the medium. We then solve the set of coupled evolution equations numerically with splitting kernels calculated for static, exponential, and Bjorken expanding media to arrive at medium-modified parton spectra for quark and gluon initiated jets. Using these, we calculate the inclusive jet $$R_\mathrm {AA}$$ R AA where the phenomenologically driven combinations of quark and gluon jet fractions are included. Then, the rapidity dependence of the jet $$R_\mathrm {AA}$$ R AA is examined. We also study the path-length dependence of jet quenching for different types of expanding media by calculating the jet $$v_2$$ v 2 . Additionally, we study the sensitivity of observables on effects from nuclear modification of parton distribution functions, vacuum-like emissions in the plasma, and the time of the onset of the quenching. All calculations are compared with recently measured data.

scholarly journals Impact of scale, nuclear PDF and temperature variations on the interpretation of medium-modified jet production data from the LHC

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
A. Andronic ◽  
J. Honermann ◽  
M. Klasen ◽  
C. Klein-Bösing ◽  
J. Salomon
Keyword(s):  
Distribution Functions ◽  
Production Data ◽  
Crossover Temperature ◽  
Parton Distribution Functions ◽  
Temperature Variations ◽  
Nuclear Modification Factor ◽  
Nuclear Modification ◽  
Modification Factor ◽  
The Impact ◽  
Jet Structure

Abstract In this paper we present a study of in-medium jet modifications performed with JEWEL and PYTHIA 6.4, focusing on the uncertainties related to variations of the perturbative scales and nuclear parton distribution functions (PDFs) and on the impact of the initial and crossover temperature variations of the medium. The simulations are compared to LHC data for the jet spectrum and the nuclear modification factor. We assess the interplay between the choice of nuclear PDFs and different medium parameters and study the impact of nuclear PDFs and the medium on the jet structure via the Lund plane.

OVERVIEW OF EXPERIMENTAL RESULTS FROM HERMES

2012 ◽  
Vol 20 ◽  
pp. 19-28
Author(s):  
MARCO CONTALBRIGO
Keyword(s):  
Degrees Of Freedom ◽  
Distribution Functions ◽  
Real Photon ◽  
Final States ◽  
Spin Orbit ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Hermes Experiment ◽  
Electrons And Positrons ◽  
Azimuthal Asymmetries

The investigation of the partonic degrees of freedom beyond collinear approximation (3D description) has been gained increasing interest in the last decade. At the HERMES experiment, azimuthal asymmetries in hard exclusive reactions and in semi-inclusive deep-inelastic scattering of electrons and positrons off a (polarized) hydrogen and deuterium target have been measured. Such asymmetries provide new insights on crucial aspects of the parton dynamics. By measuring various hadron types in the initial and final states, flavor sensitivity is achieved. Non zero signals are reported for azimuthal asymmetries with respect the transverse target polarization in real-photon exclusive-electroproduction, which are related (still in a model dependent way) to the elusive quark orbital motion. Evidence is reported of the poorly known transversity function and of naive-T-odd transverse-momentum-dependent parton distribution functions related to spin-orbit effects. Evidence of spin-orbit effects in quark fragmentation is also observed, which are opposite in sign for favored and disfavored processes.

scholarly journals Parton Distribution Functions and Tensorgluons

Universe ◽  
2020 ◽  
Vol 6 (7) ◽  
pp. 88
Author(s):  
Roland Kirschner ◽  
George Savvidy
Keyword(s):  
Parton Distribution ◽  
Evolution Equations ◽  
Distribution Functions ◽  
Parton Distribution Functions

We derive the regularised evolution equations for the parton distribution functions that include tensorgluons.

scholarly journals Quark sivers function at small x: spin-dependent odderon and the sub-eikonal evolution

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Yuri V. Kovchegov ◽  
M. Gabriel Santiago
Keyword(s):  
Evolution Equations ◽  
Wilson Line ◽  
Distribution Functions ◽  
Coupling Constant ◽  
Parton Distribution Functions ◽  
Transverse Momentum Dependent ◽  
Sivers Function ◽  
Small X ◽  
Dipole Scattering ◽  
Line Operator

Abstract We apply the formalism developed earlier [1, 2] for studying transverse momentum dependent parton distribution functions (TMDs) at small Bjorken x to construct the small-x asymptotics of the quark Sivers function. First, we explicitly construct the complete fundamental “polarized Wilson line” operator to sub-sub-eikonal order: this object can be used to study a variety of quark TMDs at small x. We then express the quark Sivers function in terms of dipole scattering amplitudes containing various components of the “polarized Wilson line” and show that the dominant (eikonal) term which contributes to the quark Sivers function at small x is the spin-dependent odderon, confirming the re- cent results of Dong, Zheng and Zhou [3]. Our conclusion is also similar to the case of the gluon Sivers function derived by Boer, Echevarria, Mulders and Zhou [4] (see also [5]). We also analyze the sub-eikonal corrections to the quark Sivers function using the constructed “polarized Wilson line” operator. We derive new small-x evolution equations re-summing double-logarithmic powers of αs ln2(1/x) with αs the strong coupling constant. We solve the corresponding novel evolution equations in the large-Nc limit, obtaining a sub-eikonal correction to the spin-dependent odderon contribution. We conclude that the quark Sivers function at small x receives contributions from two terms and is given by$$ {f}_{1T}^{\perp q}\left(x,{k}_T^2\right)={C}_O\left(x,{k}_T^2\right)\frac{1}{x}+{C}_1\left({k}_T^2\right){\left(\frac{1}{x}\right)}^0+\cdots $$ f 1 T ⊥ q x k T 2 = C O x k T 2 1 x + C 1 k T 2 1 x 0 + ⋯ with the function CO(x,$$ {k}_T^2 $$ k T 2 ) varying slowly with x and the ellipsis denoting the subasymptotic and sub-sub-eikonal (order-x) corrections.

scholarly journals Applications of a nonlinear evolution equation I: The parton distributions in the proton

2014 ◽  
Vol 23 (10) ◽  
pp. 1450057 ◽  
Author(s):  
Xurong Chen ◽  
Jianhong Ruan ◽  
Rong Wang ◽  
Pengming Zhang ◽  
Wei Zhu
Keyword(s):  
Evolution Equation ◽  
Evolution Equations ◽  
Nonlinear Evolution ◽  
Distribution Functions ◽  
Dglap Evolution ◽  
Parton Distribution Functions ◽  
High Scale ◽  
Parton Distributions ◽  
Free Parameters ◽  
Quark Models

The nonlinear Dokshitzer–Gribov–Lipatov–Altarelli–Parisi (DGLAP) evolution equations with parton recombination corrections are used to dynamically evaluate the proton's parton distribution functions starting from a low scale μ2, where the nucleon consists of valence quarks. We find that the resulting negative nonlinear corrections can improve the perturbative stability of the QCD evolution equation at low Q2. Our resulting parton distributions, with four free parameters, are compatible with the existing databases. This approach provides a powerful tool to connect the quark models of the hadron and various nonperturbative effects at the scale μ2 with the measured structure functions at the high scale Q2 ≫ μ2.

scholarly journals PION AND KAON PRODUCTION IN NUCLEON–NUCLEON COLLISIONS

2007 ◽  
Vol 22 (02n03) ◽  
pp. 582-586
Author(s):  
MARTA TICHORUK ◽  
ANTONI SZCZUREK
Keyword(s):  
Degrees Of Freedom ◽  
Inclusive Cross Section ◽  
Nucleon Nucleon ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Kaon Production ◽  
Factorization Approach ◽  
Proton Proton ◽  
Proton Collisions ◽  
Proton Proton Collisions

Inclusive cross section for pion production in proton - proton collisions are calculated based on unintegrated parton distribution functions (uPDFs). In addition to purely gluonic terms the present approach includes also quark degrees of freedom. Phenomenological fragmentation functions from the literature are used. The new mechanisms are responsible for π+ - π- asymmetry. In contrast to standard collinear approach, application of 2 → 1 kt - factorization approach can be extended towards much lower transverse momenta, both at mid and forward rapidity region. The results of the calculation are compared with SPS and RHIC data.

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