scholarly journals J/ψ meson production in SIDIS: matching high and low transverse momentum

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Daniël Boer ◽  
Umberto D’Alesio ◽  
Francesco Murgia ◽  
Cristian Pisano ◽  
Pieter Taels
Keyword(s):  
Transverse Momentum ◽  
Meson Production ◽  
Distance Matrix ◽  
Inelastic Electron ◽  
High Transverse Momentum ◽  
Shape Functions ◽  
Long Distance ◽  
Collinear Factorization ◽  
Transverse Momentum Dependent ◽  
Gluon Distributions

Abstract We consider the transverse momentum spectrum and the cos 2ϕ azimuthal distribution of J/ψ mesons produced in semi-inclusive, deep-inelastic electron-proton scattering, where the electron and the proton are unpolarized. At low transverse momentum, we propose factorized expressions in terms of transverse momentum dependent gluon distributions and shape functions. We show that our formulae, at the order αs, correctly match with the collinear factorization results at high transverse momentum. The latter are computed at the order $$ {\alpha}_s^2 $$ α s 2 in the framework of nonrelativistic QCD (NRQCD), with the inclusion of the intermediate $$ {}^3{S}_1^{\left[1\right]} $$ 3 S 1 1 color-singlet Fock state, as well as the subleading color-octet ones that are relatively suppressed by a factor v4 in the NRQCD velocity parameter v. We show that the $$ {}^1{S}_0^{\left[8\right]} $$ 1 S 0 8 and $$ {}^3{P}_J^{\left[8\right]} $$ 3 P J 8 (J = 0, 1, 2) contributions diverge in the small transverse momentum region and allow us to determine the perturbative tails of the shape functions, which carry the same quantum numbers. These turn out to be identical, except for the overall magnitude given by the appropriate NRQCD long distance matrix element.

scholarly journals Quarkonium TMD fragmentation functions in NRQCD

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Miguel G. Echevarria ◽  
Yiannis Makris ◽  
Ignazio Scimemi
Keyword(s):  
Transverse Momentum ◽  
Phenomenological Study ◽  
Light Quark ◽  
Distance Matrix ◽  
Gluon Fusion ◽  
Coupling Constant ◽  
Long Distance ◽  
Transverse Momentum Dependent ◽  
Quarkonium Production ◽  
Fragmentation Functions

Abstract We study the transverse-momentum spectrum of quarkonium production from single light-parton fragmentation mechanism. In the case of semi-inclusive deep inelastic scattering, we observe that there are two possible initiating processes, namely photon-gluon fusion and light-quark fragmentation. For the second case we derive the factorization theorem, which involves a new hadronic quantity: the quarkonium transverse-momentum-dependent fragmentation functions in NRQCD. We calculate their matching onto the non-perturbative long distance matrix elements at the lowest order in the strong-coupling constant, $$ \mathcal{O}\left({\alpha}_s^2\right) $$ O α s 2 . Focusing on the case of the electron-ion collider, we make a comparative phenomenological study of the two production mechanisms and find the regions of the phase space where one is dominant over the other.

Transverse Single-Spin Asymmetries in Proton-Proton Collisions Within Collinear Factorization

2015 ◽  
Vol 37 ◽  
pp. 1560033
Author(s):  
Daniel Pitonyak ◽  
Koichi Kanazawa ◽  
Yuji Koike ◽  
Andreas Metz
Keyword(s):  
Transverse Momentum ◽  
Heavy Ion ◽  
High Transverse Momentum ◽  
Relativistic Heavy Ion Collider ◽  
Collinear Factorization ◽  
Transverse Momentum Dependent ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Single Spin Asymmetries ◽  
Azimuthal Asymmetries

We provide a new analysis within collinear factorization of transverse single-spin asymmetries (TSSAs) in high transverse momentum charged and neutral pion production in pp collisions at the Relativistic Heavy Ion Collider (RHIC). This study incorporates the so-called twist-3 fragmentation term and shows that one can describe RHIC data through this mechanism. Moreover, by fixing other non-perturbative inputs through extractions of transverse momentum dependent functions in e+e- → h1h2X and semi-inclusive deep-inelastic scattering (SIDIS), we provide for the first time a consistency between certain spin/azimuthal asymmetries in all three reactions (i.e., pp, e+e-, and SIDIS).

BESSEL-WEIGHTED ASYMMETRIES AND TRANSVERSE SPIN EFFECTS

2012 ◽  
Vol 20 ◽  
pp. 168-176
Author(s):  
LEONARD GAMBERG
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Parton Distribution ◽  
Evolution Equations ◽  
Distribution Functions ◽  
Transverse Spin ◽  
High Transverse Momentum ◽  
Transverse Momentum Dependent ◽  
Fragmentation Functions ◽  
The Cross

We consider the cross section for semi-inclusive deep inelastic scattering in Fourier space, conjugate to the outgoing hadron's transverse momentum, where convolutions of transverse momentum dependent parton distribution functions and fragmentation functions become simple products. Individual asymmetric terms in the cross section can be projected out by means of a generalized set of weights involving Bessel functions. Advantages of employing these Bessel weights are that they suppress (divergent) contributions from high transverse momentum and that soft factors cancel in (Bessel-) weighted asymmetries. Also, the resulting compact expressions immediately connect to previous work on evolution equations for transverse momentum dependent parton distribution and fragmentation functions and to quantities accessible in lattice QCD. Bessel-weighted asymmetries are thus model independent observables that augment the description and our understanding of correlations of spin and momentum in nucleon structure.

scholarly journals Relating transverse-momentum-dependent and collinear factorization theorems in a generalized formalism

2016 ◽  
Vol 94 (3) ◽  
Author(s):  
J. Collins ◽  
L. Gamberg ◽  
A. Prokudin ◽  
T. C. Rogers ◽  
N. Sato ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Collinear Factorization ◽  
Transverse Momentum Dependent

scholarly journals The gluon structure of hadrons and nuclei from lattice QCD

2018 ◽  
Vol 175 ◽  
pp. 01015
Author(s):  
Phiala Shanahan
Keyword(s):  
Transverse Momentum ◽  
Lattice Qcd ◽  
Degrees Of Freedom ◽  
Form Factors ◽  
Light Nuclei ◽  
Transverse Momentum Dependent ◽  
Gluon Distributions

I discuss recent lattice QCD studies of the gluon structure of hadrons and light nuclei. After very briefly highlighting new determinations of the gluon contributions to the nucleon’s momentum and spin, presented by several collaborations over the last year, I describe first calculations of gluon generalised form factors. The generalised transversity gluon distributions are of particular interest since they are purely gluonic; they do not mix with quark distributions at leading twist. In light nuclei they moreover provide a clean signature of non-nucleonic gluon degrees of freedom, and I present the first evidence for such effects, based on lattice QCD calculations. The planned Electron-Ion Collider, designed to access gluon structure quantities, will have the capability to test this prediction, and measure a range of gluon observables including generalised gluon distributions and transverse momentum dependent gluon distributions, within the next decade.

scholarly journals Intrinsic charm in the nucleon and charm production at large rapidities in collinear, hybrid and kT-factorization approaches

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Rafał Maciuła ◽  
Antoni Szczurek
Keyword(s):  
Transverse Momentum ◽  
High Energy ◽  
Charm Production ◽  
Leading Order ◽  
Collinear Factorization ◽  
Factorization Approach ◽  
High Energies ◽  
Neutrino Production ◽  
Intrinsic Charm ◽  
Gluon Distributions

Abstract We discuss the role of intrinsic charm (IC) in the nucleon for forward production of c-quark (or $$ \overline{c} $$ c ¯ -antiquark) in proton-proton collisions for low and high energies. The calculations are performed in collinear-factorization approach with on-shell partons, kT-factorization approach with off-shell partons as well as in a hybrid approach using collinear charm distributions and unintegrated (transverse momentum dependent) gluon distributions. For the collinear-factorization approach we use matrix elements for both massless and massive charm quarks/antiquarks. The distributions in rapidity and transverse momentum of charm quark/antiquark are shown for a few different models of IC. Forward charm production is dominated by gc-fusion processes. The IC contribution dominates over the standard pQCD (extrinsic) gg-fusion mechanism of $$ c\overline{c} $$ c c ¯ -pair production at large rapidities or Feynman-xF. We perform similar calculations within leading-order and next-to-leading order kT-factorization approach. The kT-factorization approach leads to much larger cross sections than the LO collinear approach. At high energies and large rapidities of c-quark or $$ \overline{c} $$ c ¯ -antiquark one tests gluon distributions at extremely small x. The IC contribution has important consequences for high-energy neutrino production in the Ice-Cube experiment and can be, to some extent, tested at the LHC by the SHIP and FASER experiments by studies of the ντ neutrino production.

scholarly journals The transverse momentum spectrum of low mass Drell–Yan production at next-to-leading order in the parton branching method

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
A. Bermudez Martinez ◽  
P. L. S. Connor ◽  
D. Dominguez Damiani ◽  
L. I. Estevez Banos ◽  
F. Hautmann ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Hadron Collider ◽  
Center Of Mass ◽  
High Energy ◽  
Leading Order ◽  
Collinear Factorization ◽  
Transverse Momentum Dependent ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Low Mass

Abstract It has been observed in the literature that measurements of low-mass Drell–Yan (DY) transverse momentum spectra at low center-of-mass energies $$\sqrt{s}$$s are not well described by perturbative QCD calculations in collinear factorization in the region where transverse momenta are comparable with the DY mass. We examine this issue from the standpoint of the Parton Branching (PB) method, combining next-to-leading-order (NLO) calculations of the hard process with the evolution of transverse momentum dependent (TMD) parton distributions. We compare our predictions with experimental measurements at low DY mass, and find very good agreement. In addition we use the low mass DY measurements at low $$\sqrt{s}$$s to determine the width $$q_s$$qs of the intrinsic Gauss distribution of the PB-TMDs at low evolution scales. We find values close to what has earlier been used in applications of PB-TMDs to high-energy processes at the Large Hadron Collider (LHC) and HERA. We find that at low DY mass and low $$\sqrt{s}$$s even in the region of $$p_\mathrm{T}/m_\mathrm{DY}\sim 1$$pT/mDY∼1 the contribution of multiple soft gluon emissions (included in the PB-TMDs) is essential to describe the measurements, while at larger masses ($$m_\mathrm{DY}\sim m_{{\mathrm{Z}}}$$mDY∼mZ) and LHC energies the contribution from soft gluons in the region of $$p_\mathrm{T}/m_\mathrm{DY}\sim 1$$pT/mDY∼1 is small.

scholarly journals Prompt $$J/\psi $$ photoproduction within the non-relativistic QCD framework at the CEPC

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Xi-Jie Zhan ◽  
Jian-Xiong Wang
Keyword(s):  
Transverse Momentum ◽  
Total Cross Section ◽  
Cross Section ◽  
Hadron Collider ◽  
Distance Matrix ◽  
Matrix Elements ◽  
Long Distance ◽  
Color Octet ◽  
Electron Positron ◽  
The Future

Abstract The prompt $$J/\psi $$J/ψ photoproduction within the non-relativistic QCD (NRQCD) framework at the future Circular Electron Positron Collider (CEPC) is studied, including the contributions from both direct and resolved photons. Employing different sets of long distance matrix elements, the total cross section is dominated by the color-octet channel. We present different kinematic distributions of $$J/\psi $$J/ψ production and the results show there will be about 50 $$J/\psi $$J/ψ events when the transverse momentum of $$J/\psi $$J/ψ is up to 20 GeV. It renders that the $$J/\psi $$J/ψ photoprodution at the CEPC is a well laboratory to test the NRQCD and further clarify the universality problem in NRQCD between electron positron collider and hadron collider.

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