Spin dependence of the inclusive reaction p + p (polarized) → π0 + X at 24 GeV/c for high-pT π0 produced in the central region

Antille, J.; Dick, L.; Madansky, L.; Perret-Gallix, D.; Werlen, M.; Gonidec, A.; Kuroda, K.; Kyberd, P.

doi:10.1016/0370-2693(80)90933-8

Cited by 79 publications

(34 citation statements)

References 26 publications

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“…In contrast to expectations based upon collinear perturbative quantum chromodynamics (pQCD) at leading twist [7], transverse single-spin asymmetries for inclusive hadron production at forward pseudorapidity from polarizedproton collisions have long been observed to be sizable, with asymmetries of a few percent persisting to transverse momentum (p T ) values as high as several GeV=c [8][9][10][11][12][13][14]. Moreover, the size of the asymmetries appears to be independent of center-of-mass energy, across a range of over an order of magnitude.…”

Section: Introductionmentioning

confidence: 96%

Azimuthal transverse single-spin asymmetries of inclusive jets and charged pions within jets from polarized-proton collisions at s=500 GeV

Adamczyk¹,

Adams²,

Adkins³

et al. 2018

Phys. Rev. D

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We report the first measurements of transverse single-spin asymmetries for inclusive jet and jet þ π AE production at midrapidity from transversely polarized proton-proton collisions at ffiffi ffi s p ¼ 500 GeV. The data were collected in 2011 with the STAR detector sampled from 23 pb −1 integrated luminosity with an average beam polarization of 53%. Asymmetries are reported for jets with transverse momenta 6 < p T < 55 GeV=c and pseudorapidity jηj < 1. Presented are measurements of the inclusive-jet azimuthal transverse single-spin asymmetry, sensitive to twist-3 initial-state quark-gluon correlators; the Collins asymmetry, sensitive to quark transversity coupled to the polarized Collins fragmentation function; and the first measurement of the "Collins-like" asymmetry, sensitive to linearly polarized gluons. Within the present statistical precision, inclusive-jet and Collins-like asymmetries are small, with the latter allowing the first experimental constraints on gluon linear polarization in a polarized proton. At higher values of jet transverse momenta, we observe the first nonzero Collins asymmetries in polarized-proton collisions, with a statistical significance of greater than 5σ. The results span a range of x similar to results from semi-inclusive deep-inelastic scattering but at much higher Q 2 . The Collins results enable tests of universality and factorization breaking in the transverse momentum-dependent formulation of perturbative quantum chromodynamics.

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Section: Introductionmentioning

confidence: 96%

Azimuthal transverse single-spin asymmetries of inclusive jets and charged pions within jets from polarized-proton collisions at s=500 GeV

Adamczyk¹,

Adams²,

Adkins³

et al. 2018

Phys. Rev. D

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“…The role of intrinsic transverse momentum and spin distribution of partons inside the hadrons in explaining the azimuthal asymmetries arising in experiments involving polarized beams [1][2][3] has been a subject of keen interest during the past decade. Transverse Single Spin Asymmetries (TSSA's), measured in meson production in hadronic collisions as well as in semi inclusive deep inelastic scattering (SIDIS) experiments, provide useful information towards understanding the transverse dynamics of partons inside the hadrons.…”

Section: Introductionmentioning

confidence: 99%

Transverse single spin asymmetry in p+p↑→J/ψ+X

Godbole¹,

Kaushik²,

Sonawane³

et al. 2017

Phys. Rev. D

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We present estimates of transverse single spin asymmetry (TSSA) in p + p ↑ → J/ψ + X within the colour evaporation model of charmonium production in a generalized parton model (GPM) framework, using the recently obtained best fit parameters for the gluon Sivers function (GSF) extracted from PHENIX data on TSSA in p+p ↑ → π 0 +X at midrapidity. We calculate asymmetry at √ s = 200 GeV, and compare the results with PHENIX data on TSSA in the process p + p ↑ → J/ψ+X. We also present estimates for asymmetry at √ s = 115 GeV corresponding to the proposed fixed target experiment AFTER@LHC and at √ s = 500 GeV corresponding to the higher RHIC energy. Finally, we investigate the effect of the transverse momentum dependent (TMD) evolution of the densities involved, on the asymmetry.

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“…This has become apparent from studies of the unpolarized gluon distribution in the small-x regime [1][2][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.…”

mentioning

confidence: 99%

Single Spin Asymmetries from a Single Wilson Loop

et al. 2016

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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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Spin dependence of the inclusive reaction p + p (polarized) → π0 + X at 24 GeV/c for high-pT π0 produced in the central region

Cited by 79 publications

References 26 publications

Azimuthal transverse single-spin asymmetries of inclusive jets and charged pions within jets from polarized-proton collisions at s=500 GeV

Azimuthal transverse single-spin asymmetries of inclusive jets and charged pions within jets from polarized-proton collisions at s=500 GeV

Transverse single spin asymmetry in p+p↑→J/ψ+X

Single Spin Asymmetries from a Single Wilson Loop

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