scholarly journals DOUBLE PARTON FRAGMENTATION FUNCTION AND ITS EVOLUTION IN QUARKONIUM PRODUCTION

2014 ◽  
Vol 25 ◽  
pp. 1460040
Author(s):  
ZHONG-BO KANG
Keyword(s):  
Fragmentation Function ◽  
Evolution Equations ◽  
Heavy Quarkonia ◽  
Large Transverse Momentum ◽  
Heavy Quark Mass ◽  
Qcd Factorization ◽  
Factorization Formalism ◽  
Quarkonium Production ◽  
Large Enhancement ◽  
Fragmentation Functions

We summarize the results of a recent study on a new perturbative QCD factorization formalism for the production of heavy quarkonia of large transverse momentum pT at collider energies. Such a new factorization formalism includes both the leading power (LP) and next-to-leading power (NLP) contributions to the cross section in the [Formula: see text] expansion for heavy quark mass mQ. For the NLP contribution, the so-called double parton fragmentation functions are involved, whose evolution equations have been derived. We estimate fragmentation functions in the non-relativistic QCD formalism, and found that their contribution reproduce the bulk of the large enhancement found in explicit NLO calculations in the color singlet model. Heavy quarkonia produced from NLP channels prefer longitudinal polarization, in contrast to the single parton fragmentation function. This might shed some light on the heavy quarkonium polarization puzzle.

scholarly journals Spin-dependent fragmentation functions of gluon splitting into heavy quarkonia considering three different scenarios

2015 ◽  
Vol 30 (32) ◽  
pp. 1550179 ◽  
Author(s):  
S. Mohammad Moosavi Nejad ◽  
Mahdi Delpasand
Keyword(s):  
Heavy Quark ◽  
Bound State ◽  
Heavy Quarkonia ◽  
Heavy Quarkonium ◽  
Heavy Quark Mass ◽  
Spin Singlet ◽  
Fragmentation Probability ◽  
Spin Triplet ◽  
Fragmentation Functions ◽  
Heavy Quark Pair

Heavy quarkonium production is a powerful implement to study the strong interaction dynamics and QCD theory. Fragmentation is the dominant production mechanism for heavy quarkonia with large transverse momentum. With the large heavy quark mass, the relative motion of the heavy quark pair inside a heavy quarkonium is effectively nonrelativistic and it is also well known that their fragmentation functions can be calculated in the perturbative QCD framework. Here, we analytically calculate the process-independent fragmentation functions for a gluon to split into the spin-singlet and spin-triplet [Formula: see text]-wave heavy quarkonia using three different scenarios. We will show that the fragmentation probability of the gluon into the spin-triplet bound-state is the biggest one.

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 Back-to-Back Isolated Photon-Quarkonium Production at the LHC and the Transverse-Momentum-Dependent Distributions of the Gluons in the Proton

2016 ◽  
Vol 40 ◽  
pp. 1660015 ◽  
Author(s):  
J. P. Lansberg
Keyword(s):  
Transverse Momentum ◽  
Experimental Determination ◽  
Heavy Quarkonia ◽  
Proton Proton ◽  
Transverse Momentum Dependent ◽  
Proton Collisions ◽  
Quarkonium Production ◽  
Linearly Polarized ◽  
Proton Proton Collisions

The study of isolated heavy quarkonia, such as [Formula: see text] and [Formula: see text], produced in association with a photon in proton-proton collisions at the LHC, is probably the optimal way to get right away a first experimental determination of two gluon transverse-momentum-dependent distribution (TMDs) in an unpolarized proton, [Formula: see text] and [Formula: see text], the latter giving the distribution of linearly polarized gluons. To substantiante this, we calculate the transverse-momentum-dependent effects that arise in the process under study and discuss the feasibility of their measurements.

scholarly journals NRQCD: Fundamentals and Applications to Quarkonium Decay and Production

2006 ◽  
Vol 21 (04) ◽  
pp. 785-792 ◽  
Author(s):  
Geoffrey T. Bodwin
Keyword(s):  
Current Status ◽  
Experimental Measurements ◽  
Factorization Formalism ◽  
Quarkonium Production

I discuss NRQCD and, in particular, the NRQCD factorization formalism for quarkonium production and decay. I also summarize the current status of the comparison between the predictions of NRQCD factorization and experimental measurements.

scholarly journals SUSY-like relation of the splitting functions in evolution of gluon and quark jet multiplicities

2018 ◽  
Vol 191 ◽  
pp. 04006
Author(s):  
Anatoly Kotikov
Keyword(s):  
Evolution Equations ◽  
Dglap Evolution ◽  
Leading Order ◽  
Logarithmic Order ◽  
World Data ◽  
Charged Hadrons ◽  
Anomalous Dimensions ◽  
The World ◽  
Fragmentation Functions ◽  
Gluon Fragmentation

We show the new relationship [1] between the anomalous dimensions, resummed through next-to-next-to-leading-logarithmic order, in the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations for the first Mellin moments Dq,g(μ2) of the quark and gluon fragmentation functions, which correspond to the average hadron multiplicities in jets initiated by quarks and gluons, respectively. So far, such relationships have only been known from supersymmetric (SUSY) QCD. Exploiting available next-to-nextto- next-to-leading-order (NNNLO) information on the ratio D+g (μ2)=D+q (μ2) of the dominant plus components, the fit of the world data of Dq,g(μ2) for charged hadrons measured in e+e- annihilation leads to α(5)s (MZ) = 0:1205 +0:0016 -0:0020.

scholarly journals The renormalization scale problem and novel perspectives for QCD

2015 ◽  
Vol 39 ◽  
pp. 1560108
Author(s):  
Stanley J. Brodsky
Keyword(s):  
Renormalization Scale ◽  
High Transverse Momentum ◽  
Proton Proton ◽  
Direct Production ◽  
Proton Collisions ◽  
Qcd Factorization ◽  
Quarkonium Production ◽  
Proton Proton Collisions ◽  
Principle Of Maximum

I discuss a number of novel tests of QCD, measurements which can illuminate fundamental features of hadron physics. These include the origin of the “ridge” in proton-proton collisions; the production of the Higgs at high [Formula: see text]; the role of digluon-initiated processes for quarkonium production; flavor-dependent anti-shadowing; the effect of nuclear shadowing on QCD sum rules; direct production of hadrons at high transverse momentum; and leading-twist lensing corrections; and the breakdown of perturbative QCD factorization. I also review the “Principle of Maximum Conformalit” (PMC) which systematically sets the renormalization scale order-by-order in pQCD, independent of the choice of renormalization scheme, thus eliminating an unnecessary theoretical uncertainty.

scholarly journals NEXT-TO-LEADING ORDER CALCULATION OF THE COLOR-OCTET 3S1 GLUON FRAGMENTATION FUNCTION FOR HEAVY QUARKONIUM

2001 ◽  
Vol 16 (supp01a) ◽  
pp. 229-231
Author(s):  
JUNGIL LEE
Keyword(s):  
Fragmentation Function ◽  
Short Distance ◽  
Feynman Diagrams ◽  
Heavy Quarkonium ◽  
Leading Order ◽  
Light Cone Gauge ◽  
Color Octet ◽  
Feynman Gauge ◽  
Fragmentation Functions ◽  
Gluon Fragmentation

Next-to-leading order corrections to fragmentation functions in a light-cone gauge are discussed. This gauge simplifies the calculation by eliminating many Feynman diagrams at the expense of introducing spurious poles in loop integrals. As an application, the short-distance coefficients for the color-octet 3S1 term in the fragmentation function for a gluon to split into polarized heavy quarkonium states are re-calculated to order [Formula: see text]. We show that the ill-defined spurious poles cancel and the appropriate prescriptions for the remaining spurious poles can be determined by calculating a subset of the diagrams in the Feynman gauge. Our answer agrees with the recent calculation of Braaten and Lee in the Feynman gauge, but disagrees with another previous calculation.

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