Hyperon polarization in unpolarized scattering processes

Zhou, Jian; Yuan, Feng; Liang, Zuo-tang

doi:10.1103/physrevd.78.114008

Cited by 59 publications

(63 citation statements)

References 46 publications

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“…This implies that the nonderivative terms vanish identically, which is consistent with what was found by direct calculation in [13]. This way we finally obtained the following result:…”

Section: Pos(dis2016)222supporting

confidence: 80%

“…In this contribution, a parton coming from the proton with the momentum p ′ has a momentum x ′ p ′ and a quark fragmenting into the final Λ ↑ has a momentum p c = P h /z. Twist-3 quark-gluon correlation function contributes from the proton with the momentum p. The SGP contribution was calculated in the previous studies [12,13] and it was shown that the non-derivative term vanishes [13], which is in contrast to the case of p ↑ p → πX. In this section, we develop a master formula for this contribution, which has an advantage that it can simplify the actual calculation and make clear the origin of the vanishing nonderivative term.…”

Section: Sgp Contributionmentioning

confidence: 99%

“…The SGP contribution appears as derivative and nonderivative terms of the SGP function E a F (x, x). These were calculated in the previous studies [12,13] and it was shown that only the derivative term contributes. The SFP contribution appears only as a nonderivative term, but has not been calculated yet.…”

Section: Introductionmentioning

confidence: 99%

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Twist-3 approach to hyperon polarization in unpolarized proton-proton collision

Yabe¹,

Koike²,

Yoshida³

2016

Proceedings of XXIV International Workshop on Deep-Inelastic Scattering and Related Subjects — PoS(DIS2016)

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We study the transverse polarization of hyperons produced in high-energy unpolarized protonproton collisions in the framework of the collinear factorization. This phenomenon is a twist-3 observable which receives contributions from a twist-3 distribution and a twist-3 fragmentation function. We focus on the former contribution and derive the corresponding leading-order cross section. For the soft-gluon-pole contribution, we develop the "master formula" which reduces the partonic cross section to a certain 2 → 2 parton scattering cross section and thus simplifies the calculation greatly. We also calculate the soft-fermion-pole contribution for the first time and show that it vanishes in all channels.

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“…This implies that the nonderivative terms vanish identically, which is consistent with what was found by direct calculation in [13]. This way we finally obtained the following result:…”

Section: Pos(dis2016)222supporting

confidence: 80%

Section: Sgp Contributionmentioning

confidence: 99%

See 1 more Smart Citation

Twist-3 approach to hyperon polarization in unpolarized proton-proton collision

Yabe¹,

Koike²,

Yoshida³

2016

Proceedings of XXIV International Workshop on Deep-Inelastic Scattering and Related Subjects — PoS(DIS2016)

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“…It indicates that f ⊥ (1) 1T (x) evolves logarithmically with Q 2 just like f 1 (x), only falling off faster at a given x value as Q 2 increases. The evolution has also been calculated for moments of other TMD PDFs such as h ⊥ (1) 1 [44,48,49] and is similar to that of f ⊥(1)…”

Section: Jhep10(2011)021mentioning

confidence: 99%

Bessel-weighted asymmetries in semi-inclusive deep inelastic scattering

Boer

Gamberg

Musch

et al. 2011

J. High Energ. Phys.

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The concept of weighted asymmetries is revisited for semi-inclusive deep inelastic scattering. We consider the cross section 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.

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“…In analogy to the T-odd quark TMDs [44][45][46], all three T-odd gluon TMDs can be perturbatively calculated in the collinear twist-3 formalism at large transverse momentum. The hard coefficients entering in these expressions are usually different for different gauge links appearing in the gluon matrix element given in Eq.…”

Section: Tmentioning

confidence: 99%

Single Spin Asymmetries from a Single Wilson Loop

et al. 2016

Self Cite

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We study the leading-power gluon transverse momentum dependent distributions (TMDs) of relevance to the study of asymmetries in the scattering off transversely polarized hadrons. Next-to-leading-order perturbative calculations of these TMDs show that at large transverse momentum they have common dynamical origins, but that in the limit of small longitudinal momentum fraction x only one origin remains. We find that in this limit only the dipole-type gluon TMDs survive and become identical to each other. At small x they are all given by the expectation value of a single Wilson loop inside the transversely polarized hadron, the so-called spin-dependent odderon. This universal origin of transverse spin asymmetries at small x is of importance to current and future experimental studies, paving the way to a better understanding of the role of gluons in the three-dimensional structure of spin-polarized protons.Scattering off protons in high energy particle collisions such as performed at RHIC and LHC, can be described as scattering off quarks and gluons inside the proton. As the energy of the scattering process increases, the gluons play an increasingly important role, as reflected by a fast growing gluon density inside the proton. The limit of high gluon density is the one in which the gluons carry only a very small fraction, x, of the longitudinal momentum of the proton. It is expected on theoretical grounds that the gluon density will not increase without bound towards small x, but rather that it will saturate. Because of the dominance of gluons over quarks and the expected gluon saturation, the description of scattering processes considerably simplifies in the small-x limit. A complication that remains in this limit though, is that gluonic effects do not manifest themselves in the same way in all processes.It has recently become clear that the transverse momentum distribution of gluons inside the proton is not a unique quantity. Different processes may probe different distributions and thus yield different answers. This has become apparent from studies of the unpolarized gluon distribution in the small-x regime [1-3] and, independently, from studies of spin effects in high-energy scattering processes. Scattering experiments involving a spin-polarized proton exhibit large asymmetries in the production of final state particles [4][5][6][7][8][9][10][11][12]. Theoretical studies of these still largely ununderstood single spin asymmetries (SSA) led to the insight that TMDs of both quarks and gluons are sensitive to the flow of the color charge of quarks and gluons in a process and hence that they are in general process specific, i.e. nonuniversal [13]. TMD studies of the color flow dependence are generally not performed in the high gluon density region. In [2,3], the two types of treatments were connected for the case in which neither the proton nor the gluons are spin-polarized. For transversely polarized protons the connection between the TMD and small-x formalisms has so far not been made. This is our aim here.We wil...

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Hyperon polarization in unpolarized scattering processes

Cited by 59 publications

References 46 publications

Twist-3 approach to hyperon polarization in unpolarized proton-proton collision

Twist-3 approach to hyperon polarization in unpolarized proton-proton collision

Bessel-weighted asymmetries in semi-inclusive deep inelastic scattering

Single Spin Asymmetries from a Single Wilson Loop

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